source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-4144 | waves, acoustics, ultrasound
Title: Longitudinal wave propagation in 3D When a longitudinal wave is sent through a body, there is a strain in the emitted direction (x). What about the three-dimensional body with the strains in the direction perpendicular to the emitting direction (y, z). This strains must inevitably occur due to the "pressure wave". how can these be calculated? We can write the displacement vector as
$$\mathbf{u} = A \cos(kx)\cos(\omega t)(1, 0, 0)\, .$$
Thus, the strain tensor that is defined as
$$\epsilon = \frac{1}{2}[\nabla \mathbf{u} + (\nabla\mathbf{u})^T]\, ,$$
is
$$\epsilon = -Ak\sin(kx)\cos(\omega t)
\begin{bmatrix}
1 &0&0\\
0 &0 &0\\
0 &0 &0\end{bmatrix}\, .$$
Furthermore, the stress tensor, that for a linear elastic material isotropic is defined as
$$\sigma = \lambda \mathrm{tr}(\epsilon) + 2\mu\epsilon\, ,$$
looks like
$$\sigma = -Ak\sin(kx)\cos(\omega t)\left[\begin{matrix}\lambda + 2 \mu & 0 & 0\\0 & \lambda & 0\\0 & 0 & \lambda\end{matrix}\right]\, .$$
The following is multiple choice question (with options) to answer.
Earthquakes have both longitudinal and transverse components, and these travel at what? | [
"the speed of sound",
"identical speeds",
"different speeds",
"the speed of light"
] | C | Earthquakes, essentially sound waves in Earth’s crust, are an interesting example of how the speed of sound depends on the rigidity of the medium. Earthquakes have both longitudinal and transverse components, and these travel at different speeds. The bulk modulus of granite is greater than its shear modulus. For that reason, the speed of longitudinal or pressure waves (Pwaves) in earthquakes in granite is significantly higher than the speed of transverse or shear waves (S-waves). Both components of earthquakes travel slower in less rigid material, such as sediments. P-waves have speeds of 4 to 7 km/s, and S-waves correspondingly range in speed from 2 to 5 km/s, both being faster in more rigid material. The P-wave gets progressively farther ahead of the S-wave as they travel through Earth’s crust. The time between the P- and S-waves is routinely used to determine the distance to their source, the epicenter of the earthquake. The speed of sound is affected by temperature in a given medium. For air at sea level, the speed of sound is given by. |
SciQ | SciQ-4145 | electromagnetism, lagrangian-formalism, variational-principle, action, point-particles
There is the standard textbook Lagrangian for $N$ charged particles:
$$
L(A^\nu,\partial_\mu A^\nu,\{\mathbf r_a,\mathbf v_a\}_{a=1}^{N}) = \int_V -\frac{1}{4\mu_0}F^{\mu\nu}F_{\mu\nu} d^3 \mathbf x~~~+$$
$$- ~~\sum_a q_a \varphi(\mathbf r_a,t) + \sum_a q_a\mathbf v_a \cdot \mathbf A(\mathbf r_a,t) ~~~+
$$
$$
-~~~\sum_a \sqrt{1-v_a^2/c^2}m_a c^2,
$$
where $\varphi,\mathbf A, F$ refer to total EM field. Thus this is a function of $N$ positions, $N$ velocities, and a functional of the fields $\varphi,\mathbf A$.
This Lagrangian is in textbooks used to "derive" (e.g. in Landau&Lifshitz) both the Maxwell equations for total fields in presence of the current density $\sum_a q_a\mathbf v_a \delta(\mathbf x - \mathbf r_a)$ and charge density $\sum_a q_a\delta(\mathbf x - \mathbf r_a)$, and also to "derive" the equations of motion for all the particles, with each particle experiencing the Lorentz force $q_a\mathbf E(\mathbf r_a,t) + q_a\mathbf v_a\times \mathbf B(\mathbf r_a,t)$.
The following is multiple choice question (with options) to answer.
What do we call the theory of electromagnetism on the particle scale? | [
"iron electrodynamics",
"quantum electrodynamics",
"light electrodynamics",
"gravity electrodynamics"
] | B | 33.2 The Four Basic Forces • The four basic forces and their carrier particles are summarized in the Table 33.1. • Feynman diagrams are graphs of time versus position and are highly useful pictorial representations of particle processes. • The theory of electromagnetism on the particle scale is called quantum electrodynamics (QED). |
SciQ | SciQ-4146 | human-biology, human-genetics, skin
Stratum corneum represents the "skin cells that becomes the dust in our homes and it always grows back to full thickness". It is lost during a physiological process called desquamation [2]. The cells that are lost are non living corneocytes. Their only purpose is to from a protection barrier [3].
Basement membrane holds the germinativum layer of the epidermis. Injuries that do not affect it are repaired by complete regeneration of all destroyed layers. However, if the injury destroys membrane continuity, the germinative cells on the edges will fail to "reconnect" with each other, thus the layers derived from them will follow the same rule. A process of fibrosis is triggered. The result of extensive fibrosis is a scar, containing collagen secreted by the granulation tissue with dermal origins. Yet, the germinative layer tends to join back together [6], but probably the excess collagen production, without the limiting basement membrane, bulges into the epidermis and limits germinative layer extension. That's why keeping the edges of the tissue close to each other reduces excessive fibrosis and allows germinative layer regeneration, thus resulting in none to small, barely visible scars.
How deep should an injury be in order not to affect basement membrane? No more than 0.06 to 0.08 mm [5].
What about skin transplants ?
Skin grafts contain at least a part of dermis [4], which will allow granulation tissue formation thus permitting revascularisation and making the graft stick. Otherwise it would fall off and/or be lost by necrosis.
References:
The following is multiple choice question (with options) to answer.
What part of the continuous dermal tissue system covers stems? | [
"cuticle",
"dermis",
"callus",
"epidermis"
] | D | |
SciQ | SciQ-4147 | evolution, human-evolution
Apes
The split between the line leading to modern humans and the line leading to modern chimpanzees occured somewhere around 4 to 7 million years ago. The clade is called Hominini. The split between those and the line leading to modern gorillas occured around 8 to 19 million years ago (yes, the dates are getting fuzzier). A fossil coming close to this ancestor may be Nakalipithecus nakayamai, however, we only have a fossil jaw from that species.
Going back, we get to the split between modern-day humans/chimpanzees/gorillas and modern-day orang-utans. This is the "ape" family, Hominidae. The largest ape that we know of, Gigantopithecus, that grew to about 3 meters, is classified as an orang-utan. Note that this is not a direct ancestor of humans. Even if our ancestors were larger than modern humans at this point it's unlikely that we are talking about anything larger than a big gorilla.
Primates
Going a bit in the reverse order here: The first true primates evolved around 55 million years ago. Fossils from that time are about the size of squirrels. Humans are "old world monkeys" who first appeared around 40 million years ago - the fossils from that clade we know, for example Apidium or Aegyptopithecus are a bit larger, some as large as a dog.
Primate-like mammals
The first primate-like mammals, called Plesiadapiformes appeared around 60 million years ago. We don't know all that much about them, but the most famous Purgatorius was the size of a rat or mouse.
Mammals / placenta mammals
Going back even further, things become even murkier, but early mammals were small. Placentalia, placental mammals appeared around 90 million years ago. They were small, arboreal (tree-dwelling) animals. Early mammals appeared around 160 million years ago and fossils we have from that time place them around the size of a shrew.
Now, is it possible that there were larger mammals in there somewhere, that then "shrunk" again? Sure. Just unlikely.
Therapsid
The following is multiple choice question (with options) to answer.
What may be the ancestor of placental mammals? | [
"spirogyra",
"amphibians",
"fungi",
"eomaia"
] | D | The earliest placental mammals may have evolved about 110 million years ago. The ancestor of placental mammals may be the extinct genus Eomaia . Fossils of Eomaia have been found in what is now China. It was only about 10 centimeters (4 inches) long. It was a tree climber and probably ate insects and worms. Eomaia had several traits of placental mammals. Figure below shows how Eomaia may have looked. |
SciQ | SciQ-4148 | Moreover, if you want to know about the logic in general terms this article could be useful.
Logic, originally meaning "the word" or "what is spoken", but coming to mean "thought" or "reason", is a subject concerned with the most general laws of truth, and is now generally held to consist of the systematic study of the form of valid inference. A valid inference is one where there is a specific relation of logical support between the assumptions of the inference and its conclusion.
• Hmm, I'm not sure if this is very helpful here. Would you say that David's post makes yours 'superseded'? If not, why? Try to expand on that. – Discrete lizard Mar 25 '18 at 14:03
• @OmG : Can you recommend a list of materials to learn from ? – Sheldon Kripke Mar 31 '18 at 3:54
The following is multiple choice question (with options) to answer.
What are the two methods of logical thinking? | [
"inductive and deductive",
"Observation and result",
"cathartic and deductive",
"inductive and dynamical"
] | A | Two approaches to logical thinking developed over the centuries. These two methods are inductive reasoning and deductive reasoning . Inductive reasoning involves getting a collection of specific examples and drawing a general conclusion from them. Deductive reasoning takes a general principle and then draws a specific conclusion from the general concept. Both are used in the development of scientific ideas. |
SciQ | SciQ-4149 | solutions
Title: Can the total amount of solution be found as a ratio between molar mass of a component and total mass of solution? I wonder whether the following relation is true:
$$n_\mathrm{solvent} + n_\mathrm{solute} = \frac{M}{m_\mathrm{solvent} + m_\mathrm{solute}},$$
where $M$ is the molar mass of the component, $n$ is the amount of substance and $m$ is the mass.
It was derived assuming $n = m/M,$ $n = n_\mathrm{solvent} + n_\mathrm{solute}$ and $m = m_\mathrm{solvent} + m_\mathrm{solute}.$
I don't think this is true, but I wanted to be sure before doing anything weird on a test. To sum up the comments, only the following relation for the total amount of solution $n_\mathrm{tot}$ is universally true:
$$n_\mathrm{tot} = n_\mathrm{solvent} + n_\mathrm{solute} = \frac{m_\mathrm{solvent}}{M_\mathrm{solvent}} + \frac{m_\mathrm{solute}}{M_\mathrm{solute}}\tag{1}$$
The best you can do is to assume that $n_\mathrm{tot}\approx n_\mathrm{solvent}$ for the diluted solutions of small molecules. Also, if the molar masses are similar $(M_\mathrm{solvent}\approx M_\mathrm{solute}\approx \bar{M}),$ the expression can be lead to a common denominator:
$$n_\mathrm{tot} \approx \frac{m_\mathrm{solvent} + m_\mathrm{solute}}{\bar{M}}\tag{2}$$
The following is multiple choice question (with options) to answer.
What is the amount of solute that can dissolve in a given amount of solvent at a given temperature? | [
"viscosity",
"solubility",
"permeability",
"humidity"
] | B | Solubility is the amount of solute that can dissolve in a given amount of solvent at a given temperature. In a solution, the solute is the substance that dissolves, and the solvent is the substance that does the dissolving. For a given solvent, some solutes have greater solubility than others. For example, sugar is much more soluble in water than is salt. But even sugar has an upper limit on how much can dissolve. In a half liter of 20 °C water, the maximum amount is 1000 grams. If you add more sugar than this, the extra sugar won’t dissolve. You can compare the solubility of sugar, salt, and some other solutes in the Table below . For a video about solubility, go to this URL: http://www. youtube. com/watch?v=IKimraU21ws . |
SciQ | SciQ-4150 | human-biology, biochemistry, teratology
Title: Does consuming sodium benzoate (preservative E211) cause problems during pregnancy? There seems to be strong evidence to support the claim that sodium benzoate (E211) causes hyperactivity in young children, e.g. Bateman et al. (2004) and McCann et al. (2007). This leads me to consider whether or not E211 is harmful during pregnancy.
A study by Mowafy et al. (2001) found a slight decrease in survival rates for pups of pregnant rats given sodium benzoate; they also found a more significant drop in mean weight of their pups.
Question: Could the consumption of sodium benzoate by the mother be harmful during human pregnancy? How would this be the case?
References:
The following is multiple choice question (with options) to answer.
What should a pregnant woman avoid while pregnant? | [
"vitamins",
"toxic substances",
"healthy food",
"rest and relaxation"
] | B | The pregnant mother plays a critical role in the development of the embryo and fetus. She must avoid toxic substances such as alcohol, which can damage the developing offspring. She must also provide all the nutrients and other substances needed for normal growth and development. Most nutrients are needed in greater amounts by a pregnant woman, but some are especially important, including folic acid (vitamin B 9 ), calcium, iron, and omega-3 fatty acids. |
SciQ | SciQ-4151 | Sort by:
I think you are referring to the Bell numbers:
https://en.wikipedia.org/wiki/Bell_number
http://mathworld.wolfram.com/BellNumber.html
And if I understand correctly, there are only 2 ways to partition a set with two elements.
- 1 year, 4 months ago
Thank you. I rushed in typing the last sentence, but I will edit that. Thank you! You found exactly what I was looking for.
- 1 year, 4 months ago
The following is multiple choice question (with options) to answer.
Quantities have two parts: the number (how many) and what else? | [
"the motion",
"he unit",
"the credit",
"the member"
] | B | Quantities have two parts: the number and the unit. The number tells “how many. ” It is important to be able to express numbers properly so that the quantities can be communicated properly. Standard notation is the straightforward expression of a number. Numbers such as 17, 101.5, and 0.00446 are expressed in standard notation. For relatively small numbers, standard notation is fine. However, for very large numbers, such as 306,000,000, or for very small numbers, such as 0.000000419, standard notation can be cumbersome because of the number of zeros needed to place nonzero numbers in the proper position. |
SciQ | SciQ-4152 | vision, cognition, cat
general reading.
visual cortex of monkeys and cats.
Activation of the hypothalamic feeding centre upon visual prey detection
other research.
The following is multiple choice question (with options) to answer.
What organ provides the integrative power that underlies the complex behavior of vertebrates? | [
"the brain",
"the heart",
"the liver",
"the skin"
] | A | |
SciQ | SciQ-4153 | evolution, dna, natural-selection
It seems plausible to me that we (advanced life) could have a biological mechanism to "write" needed alterations into either our own DNA or our reproductive DNA over time, triggering the very specific evolutionary developments necessary to our survival without relying on random mutation.
My question:
Is this possible? Does any similar mechanism exist that we know of? If not, how can so many specific (advanced) evolutionary leaps be otherwise explained? This entire answer will be long, so read the short part first, then read the rest if you (or anyone else) is curious. Citations are included in the long section. I can include additional citations in the short section if needed.
Long Story Short
Your question touches on some common misconceptions about how the evolutionary process. Organisms don't "want" to evolve traits. Traits evolve through the biological processes of random mutation and natural selection.
Organisms do not "want" to evolve traits. (Well, OK, I'd love to evolve an extra pair of hands but that is not possible.) Natural selection works by modifying existing traits. Your turtle can stare all she wants at food out of reach but she will not evolve a longer neck. Instead, natural variation exists among neck lengths of the turtles because of variation of the genes that determine features related to overall boxy size. Those individuals with longer necks may be able to get a bit more food, live a little longer, and reproduce a little more. They will pass along their genes to their offspring, so perhaps more of their offspring will also have longer necks. Over many generations, the turtles may have somewhat longer necks.
A common misconception is that the traits of organisms are precisely adapted for a specific need. They are not, for a few reasons. First, natural selection occurs relative to the current environment. Adaptations that work well in one environment may not be so useful in another environment. Environments are rarely stable over evolutionary time so traits are subject to constant change.
Next, as mentioned above, natural selection can only work on what traits are present. While an extra set of arms would be handy, I am a tetrapod. My four appendages, along with the appendages of all other tetrapods, trace back to our common ancestor. The appendages of all tetrapods are modifications of that ancestral trait.
The following is multiple choice question (with options) to answer.
What is the only mechanism that consistently causes adaptive evolution? | [
"neutral selection",
"artificial selection",
"natural selection",
"genetic drift"
] | C | 23.4 Natural selection is the only mechanism that consistently causes adaptive evolution. |
SciQ | SciQ-4154 | human-biology, reproduction, anthropology
Note: here is a link about multiple pregnancy : https://www.healthline.com/health/pregnancy/chances-of-having-twins#assisted-reproduction. 49 - 19 = 30
So the 1st Child would be 30 when the last children would be born, as long as the parents stay healthy and the mother delivers the child in a natural way (No Surgical Procedure to deliver the child) and the Mother has not had Menopause (Menopause usually happens around 50 Years of age) the sibling age gap would be very possible, but lets take a look at how many children the mother had, if I am correct they had about 16 Children, many people in countries that have a considerably low life expectancy have many children, lets take a look at the world record for most children born from one mother...a person named Valentina Vassilyev, gave birth to 69 Children! Thats a lot of children, so giving birth to 16 children with a 30 age gap should be very possible and realistic as well.
The following is multiple choice question (with options) to answer.
What are four children born at one birth called? | [
"twins",
"triplets",
"kittens",
"quadruplets"
] | D | QUADruplets are four children born at one birth. |
SciQ | SciQ-4155 | thermodynamics, water, phase-transition, phase-diagram
Title: Vaporization - phase diagram I understand what boiling and vaporization is. But what puzzles me is the phase diagram.
When I spill a glass of water in my room, it will soon vaporize, though there was normal atmospheric pressure and 20 °C. If you look in phase diagram of water, it should be still liquid at this point.
I understand that molecules of water escape the surface and turn into vapor, but... is the phase diagram of water wrong then? The temperature and pressure didn't change around that spilled water and still it turns into gas, although (looking at the phase diagram), it should be liquid. The phase diagram has equilibrium states for pure water, vapor, and both at saturation. You have water exposed to atmospheric gases, so the pressure is not that of pure vapor. The water will evaporate trying to create a partial pressure of vapor equal to the vapor pressure for saturated water at the water temperature. If the surface is open to flow of fresh air, this vapor pressure is not achieved, and the water slowly evaporates away.
The following is multiple choice question (with options) to answer.
What does liquid change to due to vaporization? | [
"plasma",
"solid",
"gas",
"oil"
] | C | Vaporization is the process in which a liquid boils and changes to a gas. |
SciQ | SciQ-4156 | geophysics, plate-tectonics, earth-history, continent
Title: Why Do Supercontinents Form? It would seem, on the face of it, improbable that the continental land-masses would accumulate into a single composite, yet it has happened numerous times, and is expected to again in the future.
There must likely then be some aspect of plate tectonics which favors these arrangements.
Can anyone provide an explanation?
EDIT: This is not, as I see it, a duplicate of the 'What are the causes of the supercontinent cycle?' question. This question goes to what process drives the formation of any & all supercontinent formations, which I assert should be improbable, made more improbable by their recurrence, not so much the cycle itself. The other question did not address this more fundamental aspect, or in any case receive a pertinent account of its resolution. If anyone wants to engage on this, or doesn't see the distinction, please do so in the comments or a chat. I think the mechanisms that you're looking for are subduction, paired with the "stickiness" of continental crust.
The subduction of oceanic crust under continental crust inevitably creates a net movement of crustal material toward a continental plate. Any oceanic plate that is carrying continental material will therefore always drag that continent toward the continental plate that it is subducting underneath, always resulting in eventual collision.
If an oceanic plate has subduction occurring on both sides, the ocean will inevitably narrow until it closes, thereby causing the continental plates on either side to collide.
In every case, subduction inevitably pulls continents together.
Furthermore, once continental plates collide, they have a tendency to stick together for long periods of time, increasing the likelihood that all continental material will eventually accumulate there.
The following is multiple choice question (with options) to answer.
Converging plates can be oceanic, continental, or one of each. if at least one is oceanic, it will subduct. a subducting plate creates what? | [
"fires",
"earthquakes",
"volcanoes",
"wind"
] | C | Converging plates can be oceanic, continental, or one of each. If at least one is oceanic, it will subduct. A subducting plate creates volcanoes. Many of the world's volcanoes are the result of subduction at a convergent plate boundary. A map of the world's active volcanoes is pictured below ( Figure below ). |
SciQ | SciQ-4157 | species-identification
Title: What species of viper is this? I think that the snake in the pictures here below is a viper. I found it on a hiking trail on a mountain in Bulgaria. Height was about 2000 meters and the weather wasn't warm as you might expect in a late Spring days, but it seemed quite active.
If it really is a viper what species of viper? Otherwise what could it be? This is most likely the common European adder (Vipera beris). A list of the reptiles of Bulgaria lists it as occurring in the mountains of Bulgaria up to 2700 metres.
There are a couple of other contenders in the list of vipers, but two of them are incredibly rare (not found since the 1930's) and the last is the horned viper (Vipera ammodytes), which has distinctive horns on the tip of its nose.
The following is multiple choice question (with options) to answer.
Reptiles can be found on every continent except which one? | [
"south america",
"antarctica",
"africa",
"australia"
] | B | Reptiles can be found on every continent except Antarctica. |
SciQ | SciQ-4158 | 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.
For photosynthesis to begin, the inputs required are sunlight, water, and what? | [
"methane",
"phosphorus dioxide",
"sulfur dioxide",
"carbon dioxide"
] | D | Recall that the only required ingredients needed for photosynthesis are sunlight, carbon dioxide (CO 2 ), and water (H 2 O). From these simple inorganic ingredients, photosynthetic organisms produce the carbohydrate glucose (C 6 H 12 O 6 ), and other complex organic compounds. Essentially, these producers are changing the energy from the sunlight into a usable form of energy. They are also making the oxygen that we breathe. Oxygen is a waste product of photosynthesis. |
SciQ | SciQ-4159 | geophysics, plate-tectonics, earth-history, continent
Title: Why Do Supercontinents Form? It would seem, on the face of it, improbable that the continental land-masses would accumulate into a single composite, yet it has happened numerous times, and is expected to again in the future.
There must likely then be some aspect of plate tectonics which favors these arrangements.
Can anyone provide an explanation?
EDIT: This is not, as I see it, a duplicate of the 'What are the causes of the supercontinent cycle?' question. This question goes to what process drives the formation of any & all supercontinent formations, which I assert should be improbable, made more improbable by their recurrence, not so much the cycle itself. The other question did not address this more fundamental aspect, or in any case receive a pertinent account of its resolution. If anyone wants to engage on this, or doesn't see the distinction, please do so in the comments or a chat. I think the mechanisms that you're looking for are subduction, paired with the "stickiness" of continental crust.
The subduction of oceanic crust under continental crust inevitably creates a net movement of crustal material toward a continental plate. Any oceanic plate that is carrying continental material will therefore always drag that continent toward the continental plate that it is subducting underneath, always resulting in eventual collision.
If an oceanic plate has subduction occurring on both sides, the ocean will inevitably narrow until it closes, thereby causing the continental plates on either side to collide.
In every case, subduction inevitably pulls continents together.
Furthermore, once continental plates collide, they have a tendency to stick together for long periods of time, increasing the likelihood that all continental material will eventually accumulate there.
The following is multiple choice question (with options) to answer.
When a stalactite and stalagmite join together, they form a what? | [
"cave",
"joint",
"ladder",
"column"
] | D | If a stalactite and stalagmite join together, they form a column . One of the wonders of visiting a cave is to witness the beauty of these amazing and strangely captivating structures. |
SciQ | SciQ-4160 | acid-base, reaction-mechanism
Title: Litmus paper - turning red, blue and even bleached I have blue litmus paper, and if I put it in an acid it turns red. I also have red litmus paper, and if I put it in a base, it turns blue.
I know the question about litmus was asked and answered and I like the answer:
How does the litmus pH indicator work?
However, damp litmus paper also becomes bleached in presence of chlorine gas. I believe it has nothing to do with the mechanism described in aforementioned question. I wonder what the mechanism is. Wikipedia actually suggests:
For instance, chlorine gas turns blue litmus paper white – the litmus dye is bleached, because of presence of hypochlorite ions. This reaction is irreversible, so the litmus is not acting as an indicator in this situation.
I also found an equation which describes formation of hypochloric acid (source):
$$\ce{Cl2 (g) + H2O (l) -> HClO (aq) + HCl (aq)}$$
The problem that I have now is as follows: We know that litmus paper gets discolored because of contact with hypochloric acid. But what is actually the chemical reaction for that? I can supply some details now, and hopefully this ought to qualify as an answer.
As I mentioned earlier litmus is a mixture of 10-12 dyes (CAS number: 1393-92-6).
The acid-base indicator properties of litmus are primarily due to 7-hydroxyphenoxazone chromophore (pictured below)
The answer you linked to discusses the acid-base indication mechanism in some detail, so I shall skip over that.
Anyway, what this serves to establishing that it is indeed a extended $\pi$-conjugated system that we are dealing with in the chromophore.
Now, $\ce{HOCl}$ would bring about halohydrination (basically an electrophilic addition) across the $\pi$ bonds, thus disrupting the conjugated system.
Halohydrins are compounds that contain an $\ce{-OH}$ and $\ce{-X}$ groups on adjacent carbons.
This image describes the general mechanistic scheme in a simpler case:
The following is multiple choice question (with options) to answer.
What color does red litmus paper turn in the presence of a base? | [
"purple",
"white",
"blue",
"green"
] | C | Like strong acids, strong bases can be harmful to organisms and damaging to materials. Bases have a bitter taste and feel slimy to the touch. They can also burn the skin. Bases, like acids, can be identified with litmus paper. Bases turn red litmus paper blue. |
SciQ | SciQ-4161 | water, chemical-biology, precipitation
Title: In the wet medium of an ocean, how does a hard shell form? In general, if you were to try make something hard in a liquid medium (especially water) it is quite difficult to make the material solid.
Things such as mollusks though, have no problem generating hard shells in a wet medium.
What exactly are the physics behind this formation? Carbon dioxide from the atmosphere (or from decaying matter in the ocean) reacts with water to form carbonic acid:
$$ \ce{ CO2 + H2O -> H_2CO_3 }$$
and this reacts with calcium ions to form calcium carbonate:
$$ \ce{H2CO3 + Ca^{2+} -> CaCO3 + 2H+ }$$
The solubility of calcium carbonate is about $13~\mathrm{mg \over L}$, so if the concentration of calcium carbonate is greater than this the excess will precipitate out as solid calcium carbonate.
Shell-forming organisms actively absorb calcium from the water around them, so they are able to increase the concentration of calcium carbonate to above $13~\mathrm{mg\over L}$ and precipitate the excess to form their shells. They can get the carbon dioxide from the water around them or from their own metabolism. The actual details of shell formation is far more complex than this as it's controlled by processes with the cells of the organism rather than just being uncontrolled precipitation. I'm not sure how well the details are understood even today.
Incidentally, this is why shelly fauna are not keen on the acidification of the oceans that results from increased atmospheric carbon dioxide. The solubility of calcium carbonate is strongly $\mathrm{pH}$-dependent and rises sharply as the water gets more acid. Given that the shell is usually intended to stop other animals eating you, having your shell dissolve is generally not good for life expectancy.
The following is multiple choice question (with options) to answer.
What is the term for the hard, round object produced within the mantle of a living shelled mollusk? | [
"glass",
"pearl",
"ball",
"root"
] | B | Two natural products of mollusks used for decorations and jewelry are pearls and nacre. A pearl is the hard, round object produced within the mantle of a living shelled mollusk. Pearls are produced by many bivalves when a tiny particle of sand or grit is trapped between the mantle and the shell. It's as if the mollusk has a splinter. The mollusk forms a protective covering around the irritant. Most pearls used as jewelry are made by pearl oysters and freshwater mussels; most of the ones sold are cultured and not wild. Natural pearls have been highly valued as gemstones and objects of beauty for many centuries. |
SciQ | SciQ-4162 | species-identification, microbiology, microscopy
Title: Identification of protozoa under microscope I observed maybe Protozoa from standing FRESH water and from slowly flowing FRESH water. I am complete dilettante. Can you tell what these creatures are?
https://www.youtube.com/watch?v=6D5ck3zNJzA&t=474s
Thank you.
Added picture for to be more specific At first glance, the organisms may hold the appearance of protozoans like ciliates. However, I am of the belief that these 'totally tubular' micro organisms are in fact diatoms.
The diatoms are a diverse range of eucaryotic microalgae which comprise a large percentage of the phytoplankton group. (Diatomaceous earth is the residual remains of their calcareous walls)
They are likely diatoms because of their apparent hard membrane, and slight brown-green pigment, typical of heterokont diatoms.
I would be unable to specify the organism to family level. However, you may wish to complete your investigation by looking under the order 'Pennales'.
For general information regarding the Diatoms, you may visit https://en.wikipedia.org/wiki/Diatom
Morphology and description available from: https://books.google.co.uk/books?id=xhLJvNa3hw0C&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
Good luck
The following is multiple choice question (with options) to answer.
What is the term for animal-like protists that are usually single-celled? | [
"larvae",
"eukaryotes",
"protozoa",
"vertebrates"
] | C | Animal-like protists are called protozoa. Most consist a single cell. |
SciQ | SciQ-4163 | biophysics, cell-membrane
Title: Why doesn't the cell membrane just...break apart? Forgive me if this is a silly question. I can't understand the basics. Why doesn't the cell membrane just break apart? What's keeping the layers in the phospholipid bilayer together? I know that the membrane is embedded with proteins and lipids, but I still can't wrap my head around the "why". Are the hydrophobic interactions in the middle "stronger" than the hydrophilic interactions on the outside? What's keeping the individual phosphate heads together instead of, say, one of them just drifting away due to a nearby water molecule? The membrane bilayer is held together by hydrophobic forces. This is an entropy driven process. When a greasy or hydrophobic molecule is suspended in water, the water molecules form an organized "cage" around the hydrophobic molecule. When two hydrophobic molecules come into contact, they force the water between them out. This increases the entropy because the freed waters don't need to be organized into the cage. Lipid bilayers have many many many hydrophobic lipids that squeeze out a lot of water and greatly increase entropy. The polar phosphates allow the water to interact with the surface of the membrane, without a polar head group the lipids would form a spherical blob instead of a membrane.
Read this section on wikipedia for more.
The following is multiple choice question (with options) to answer.
The cell membrane consists of two adjacent layers of what? | [
"membranes",
"eukaryotes",
"phospholipids",
"lecithin"
] | C | The cell membrane consists of two adjacent layers of phospholipids. The lipid tails of one layer face the lipid tails of the other layer, meeting at the interface of the two layers. The phospholipid heads face outward, one layer exposed to the interior of the cell and one layer exposed to the exterior (Figure 3.3). Because the phosphate groups are polar and hydrophilic, they are attracted to water in the intracellular fluid. Intracellular fluid (ICF) is the fluid interior of the cell. The phosphate groups are also attracted to the extracellular fluid. Extracellular fluid (ECF) is the fluid environment outside the enclosure of the cell membrane. Interstitial fluid (IF) is the term given to extracellular fluid not contained within blood vessels. Because the lipid tails are hydrophobic, they meet in the inner region of the membrane, excluding watery intracellular and extracellular fluid from this space. The cell membrane has many proteins, as well as other lipids (such as cholesterol), that are associated with the phospholipid bilayer. An important feature of the membrane is that it remains fluid; the lipids and proteins in the cell membrane are not rigidly locked in place. |
SciQ | SciQ-4164 | zoology, circulatory-system, heart-output, amphibians
I would add to this my notes from when I was a biochem student (but studied Zoology), mentioning the arterial cone and a spiral valve. This is better described in Britannica:
The conus arteriosus is muscular and contains a spiral valve. Again, as in lungfishes, this has an important role in directing blood into the correct arterial arches. In the frog, Rana, venous blood is driven into the right atrium of the heart by contraction of the sinus venosus, and it flows into the left atrium from the lungs. A wave of contraction then spreads over the whole atrium and drives blood into the ventricle, where blood from the two sources tends to remain separate. Separation is maintained in the spiral valve, and the result is similar to the situation in lungfishes. Blood from the body, entering the right atrium, tends to pass to the lungs and skin for oxygenation; that from the lungs, entering the left atrium, tends to go to the head. Some mixing does occur, and this blood tends to be directed by the spiral valve into the arterial arch leading to the body.
The following is multiple choice question (with options) to answer.
Echinoderms have a unique system for gas exchange, nutrient circulation, and locomotion called the water vascular system. the system consists of a central ring canal and radial canals extending along each arm. water circulates through these structures allowing for gas, nutrient, and this? | [
"water evaporation",
"cell exchange",
"nerve exchange",
"waste exchange"
] | D | Physiological Processes of Echinoderms Echinoderms have a unique system for gas exchange, nutrient circulation, and locomotion called the water vascular system. The system consists of a central ring canal and radial canals extending along each arm. Water circulates through these structures allowing for gas, nutrient, and waste exchange. A structure on top of the body, called the madreporite, regulates the amount of water in the water vascular system. “Tube feet,” which protrude through openings in the endoskeleton, may be expanded or contracted using the hydrostatic pressure in the system. The system allows for slow movement, but a great deal of power, as witnessed when the tube feet latch on to opposite halves of a bivalve mollusk, like a clam, and slowly, but surely pull the shells apart, exposing the flesh within. |
SciQ | SciQ-4165 | cell-biology, microbiology
Title: Are there any organisms that are made of more than one (~5-12) cell? Prokaryotes and eukaryotes are unicellular, made of one cell. Great. Eukaryotes are unicellular or multicellular. But the typical examples of multicellular eukaryotes we have are made of, often, trillions of cells, like us humans. Ants must still be made of many millions of cells. Are there known eukaryotes with very few cells that make them up? Like, 5, or something? Or maybe a dozen cells making up the whole organism in its fully developed state? There's Trichoplax adhaerens, a Placozoa, made of a few thousand cells. Then there is Dicyema japonicum, a simple mesozoan, made up of 9 to 41 cells. Arguably, the simplest multicellular organism is the algae Tetrabaena socialis, whose body consists of 4 cells. Then, there's the parasitic Myxozoa which have 7 cells.
The following is multiple choice question (with options) to answer.
What group includes the simplest eukaryotes, including most single-celled eukaryotes? | [
"protists",
"bivalves",
"fungi",
"arthropods"
] | A | Most single-celled eukaryotes are protists. Protists are the simplest eukaryotes. |
SciQ | SciQ-4166 | ecology
Title: Statement about Tropical Rainforests I made a statement about tropical rainforests, and I want to know if it's somewhat true or not:
The soil in tropical rainforests is not exceptionally fertile, because it contains few minerals. The reason that a tropical rainforest has a huge amount of vegetation is because of the quick mineralisation. If a dead leaf falls onto the ground, it immediately gets turned into minerals, which the plants immediately use for sustaining theirselves There are many websites which describe this phenomenon. They all seem to confirm the basic premise of the question: in tropical rain forests most of the minerals are held in the biomass and rapid decomposition contributes to the recycling of these nutrients for new growth. One example is here.
Tropical rainforests are noted for the rapid nutrient cycling that occurs on the ground. In the tropics, leaves fall and decompose rapidly. The roots of the trees are on the surface of the soil, and form a thick mat which absorbs the nutrients before they reach the soil (or before the rain can carry them away). The presence of roots on the surface is a common phenomenon in all mature forests; trees that come along later in succession win out in competition for nutrients by placing their roots over top of the competitors, and this pattern is seen in the temperate rainforest as well. What does not occur in the temperate rainforest, however, is a rapid cycling of nutrients. Because of the cold conditions and the acidity released by decomposing coniferous needles on the forest floor, decomposition is much slower. More of the nutrients are found in the soil here than would be the case in a tropical forest, although like the tropical forest most of the nutrients are held in the plants and animals themselves.
I looked for actual evidence of these differences in rates of decomposition and I found this:
Salinas, N. et al. (2011) The sensitivity of tropical leaf litter decomposition to temperature: results from a large-scale leaf translocation experiment along an elevation gradient in Peruvian forests. New Phytologist 189: 967-977
The following is multiple choice question (with options) to answer.
Tropical rainforest, chaparral, and taiga are what kind of biomes? | [
"arboreal",
"terrestrial",
"endangered",
"freshwater"
] | B | Terrestrial biomes include the tropical rainforest, chaparral, and taiga. |
SciQ | SciQ-4167 | neuroscience, brain, neurology
There are much more complex and functional methods of actually reading brain function and applying it to precise signals within the brain. All of these methods require the use of large equipment such as Positron Emission Tomography (PET) or Magnetic Resonance Imaging (the particular application here is called functional MRI or fMRI). These all require the patient to lie very still inside a large noisy piece of equipment to measure some aspect of the brain interpretable by equipment/software in question. These methods can be quite specific and do show the interior of the brain.
I don't know much about these methods other than general principles. However, fMRI measures blood flow to a particular area of the brain and requires the person being scanned to concentrate on the topic at hand while the scan is being performed. PET and the related technique Single-Photon Emission Computed Tomography (SPECT) often require the use of an injectable material that the scanner can pick up - this is usually (always?) a mildly radioactive one, often conjugated to a specific biological molecule (see here for a list of radioactives and localizations) so that it is trafficked in the body to a specific location.
In conclusion, people are still working on brain function and assigning particular things to particular locations, so we are still a fairly long way from having methods that can be used to natively control devices via brain function.
The following is multiple choice question (with options) to answer.
One of the most advanced uses of what in medicine is the positron emission tomography scanner, which detects the activity in the body of a very small injection of radioactive glucose? | [
"radioisotopes",
"quarks",
"radionuclides",
"membranes"
] | A | Interventional Radiologist The controlled use of radioisotopes has advanced medical diagnosis and treatment of disease. Interventional radiologists are physicians who treat disease by using minimally invasive techniques involving radiation. Many conditions that could once only be treated with a lengthy and traumatic operation can now be treated non-surgically, reducing the cost, pain, length of hospital stay, and recovery time for patients. For example, in the past, the only options for a patient with one or more tumors in the liver were surgery and chemotherapy (the administration of drugs to treat cancer). Some liver tumors, however, are difficult to access surgically, and others could require the surgeon to remove too much of the liver. Moreover, chemotherapy is highly toxic to the liver, and certain tumors do not respond well to it anyway. In some such cases, an interventional radiologist can treat the tumors by disrupting their blood supply, which they need if they are to continue to grow. In this procedure, called radioembolization, the radiologist accesses the liver with a fine needle, threaded through one of the patient’s blood vessels. The radiologist then inserts tiny radioactive “seeds” into the blood vessels that supply the tumors. In the days and weeks following the procedure, the radiation emitted from the seeds destroys the vessels and directly kills the tumor cells in the vicinity of the treatment. Radioisotopes emit subatomic particles that can be detected and tracked by imaging technologies. One of the most advanced uses of radioisotopes in medicine is the positron emission tomography (PET) scanner, which detects the activity in the body of a very small injection of radioactive glucose, the simple sugar that cells use for energy. The PET camera reveals to the medical team which of the patient’s tissues are taking up the most glucose. Thus, the most metabolically active tissues show up as bright “hot spots” on the images (Figure 2.6). PET can reveal some cancerous masses because cancer cells consume glucose at a high rate to fuel their rapid reproduction. |
SciQ | SciQ-4168 | human-biology, genetics, human-genetics
Title: Are all genetic disorders inherited? I know that genetic diseases such as cystic fibrosis are often passed down through generations and are therefore classified as genetic disorders, but if a mutation occurs spontaneously, which for example leads to cancer, is this then classified as a genetic disorder?
Are all genetic disorders inherited?
Not all individuals with a genetic disorder inherited that disorder. Some genetic disorders are caused by spontaneous mutations.
Is cancer a genetic disorder?
Yes. The seminal paper by Hanahan and Weinberg, the Hallmarks of Cancer, is a good place to go to get a sense of what we understand cancer to be. This paper is quite influential and has its own wikipedia page. These authors wrote an updated review in 2011. Re: your question as it relates to cancer, yes, genetic changes result in tumorigenesis. Cancer is a genetic disorder of cell populations. One can view cancer diagnosis and treatment from the framework of cancer as a metabolic disease, but this adds to, rather than subtracts from the framework of cancer as a genetic disease.
Are other diseases caused by spontaneous mutations genetic disorders?
Yes. Achondrodysplasia is one illuminating example. It is a form of dwarfism caused by a mutation in the FGFR3 gene. It does follow mendelian autosomal dominant inheritance patterns, but in 80% of cases, the mutation is, in fact, acquired spontaneously (that is, not present in either parent). As noted by @Eff in the comments, Down syndrome, Trisomy 21 (and other chromosomal abnormalities, e.g., Turner, Kleinfelter, Patau, Edwards) are other common examples.
The following is multiple choice question (with options) to answer.
What type of disease is muscular dystrophy? | [
"contagious disease",
"mutation",
"infectious disease",
"a wasting disease"
] | D | Muscular dystrophy is a term encompassing a variety of muscle wasting diseases. The most common type, Duchenne Muscular Dystrophy (DMD) , affects cardiac and skeletal muscle, as well as some mental functions. DMD is caused by a defective gene for dystrophin, a protein prevalent in skeletal and cardiac muscles. DMD is an X-linked recessive disorder occurring in 1 in 3,500 male newborns. Because DMD is X-linked, no females are affected. Most affected individuals die before their 20th birthday. Daughters of female carriers of the mutant allele have a 50% chance of also being carriers. |
SciQ | SciQ-4169 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
How many types of tissue are found in animals? | [
"three",
"Ten",
"six",
"four"
] | D | Muscle tissue is one of the four types of tissue found in animals. There are three different types of muscle in the body ( Figure below ):. |
SciQ | SciQ-4170 | molecular-biology, transcription, polymerase
Historical. The amino acid sequence of the protein (the product of the gene) is central to this convention because knowledge of the genetic code, and hence representation of the region of the mRNA that encodes protein — and by extension the DNA — was the first sequence information to be known.
Logical consistency. Later other sequences features were identified (some of which initially may have just been genetic features), e.g. ribosome binding sites, polyadenylation addition signals, transcription start sites, promoters, transcription factor recognition sites. It was logically consistent to represent them on the same strand as the coding sequence.
Functional agnosticism. In many cases the function of a sequence followed its description, so there was no reason initially to place it on any particular strand. However, even if it were thought that the function of some sequence were to be recognized on the opposite strand (what I would call the anti-sense strand), it would be unwise scientifically to change the representation to indicate this. Science progresses and interpretation changes. Better to separate concrete descriptive features from conclusions about their function.
The following is multiple choice question (with options) to answer.
The sequence of bases in a gene translates to the sequence of what protein components? | [
"amino acids",
"protein acids",
"molecular acids",
"rna acids"
] | A | 3.4 | Protein Synthesis By the end of this section, you will be able to: • Explain how the genetic code stored within DNA determines the protein that will form • Describe the process of transcription • Describe the process of translation • Discuss the function of ribosomes It was mentioned earlier that DNA provides a “blueprint” for the cell structure and physiology. This refers to the fact that DNA contains the information necessary for the cell to build one very important type of molecule: the protein. Most structural components of the cell are made up, at least in part, by proteins and virtually all the functions that a cell carries out are completed with the help of proteins. One of the most important classes of proteins is enzymes, which help speed up necessary biochemical reactions that take place inside the cell. Some of these critical biochemical reactions include building larger molecules from smaller components (such as occurs during DNA replication or synthesis of microtubules) and breaking down larger molecules into smaller components (such as when harvesting chemical energy from nutrient molecules). Whatever the cellular process may be, it is almost sure to involve proteins. Just as the cell’s genome describes its full complement of DNA, a cell’s proteome is its full complement of proteins. Protein synthesis begins with genes. A gene is a functional segment of DNA that provides the genetic information necessary to build a protein. Each particular gene provides the code necessary to construct a particular protein. Gene expression, which transforms the information coded in a gene to a final gene product, ultimately dictates the structure and function of a cell by determining which proteins are made. The interpretation of genes works in the following way. Recall that proteins are polymers, or chains, of many amino acid building blocks. The sequence of bases in a gene (that is, its sequence of A, T, C, G nucleotides) translates to an amino acid sequence. A triplet is a section of three DNA bases in a row that codes for a specific amino acid. Similar to the way in which the three-letter code d-o-g signals the image of a dog, the three-letter DNA base code signals the use of a particular amino acid. For example, the DNA triplet CAC (cytosine, adenine, and cytosine) specifies the amino acid valine. Therefore, a gene, which is composed of multiple triplets in a unique sequence, provides the code to build an entire protein, with multiple amino acids in the proper sequence (Figure 3.25). The mechanism by which cells turn the DNA code into a protein product is a two-step process, with an RNA molecule as the intermediate. |
SciQ | SciQ-4171 | molecules, molecular-dynamics
Title: Why do two molecules of an element attract each other? I was thinking about molecular attraction and a question suddenly struck in my mind which is 'Why do two molecule of an element attract each other?'
The answer is easy when we discuss about compound materials. The molecules of a compound have dipoles that can attract each other. But what happens about elements? The molecules of an element don't have dipoles.
After so many attempts, I thought there are only two particles in those molecules that can attract each other — Neucleus and Electron. But also there works repulsive forces between the electrons and between the neucleus of two molecules. It seems like the repulsion is stronger attraction.
So how the attraction force get stronger than the repulsion force so that two molecules of an element attract each other? There are only seven elements which naturally form stable molecules, namely hydrogen, oxygen, nitrogen, fluorine, chlorine, bromine and iodine. At room temperature only iodine is a solid. When they do liquify or solidify, they do so as a result of Van Der Waals forces, which are electromagnetic in nature, acting at short range between the individual molecules. See https://en.wikipedia.org/wiki/Van_der_Waals_force
The following is multiple choice question (with options) to answer.
Two or more what may bond with each other to form a molecule? | [
"clouds",
"particles",
"quarks",
"atoms"
] | D | Figure 2.9 Two or more atoms may bond with each other to form a molecule. When two hydrogens and an oxygen share electrons via covalent bonds, a water molecule is formed. |
SciQ | SciQ-4172 | species-identification, microbiology, microscopy
Title: Identification of protozoa under microscope I observed maybe Protozoa from standing FRESH water and from slowly flowing FRESH water. I am complete dilettante. Can you tell what these creatures are?
https://www.youtube.com/watch?v=6D5ck3zNJzA&t=474s
Thank you.
Added picture for to be more specific At first glance, the organisms may hold the appearance of protozoans like ciliates. However, I am of the belief that these 'totally tubular' micro organisms are in fact diatoms.
The diatoms are a diverse range of eucaryotic microalgae which comprise a large percentage of the phytoplankton group. (Diatomaceous earth is the residual remains of their calcareous walls)
They are likely diatoms because of their apparent hard membrane, and slight brown-green pigment, typical of heterokont diatoms.
I would be unable to specify the organism to family level. However, you may wish to complete your investigation by looking under the order 'Pennales'.
For general information regarding the Diatoms, you may visit https://en.wikipedia.org/wiki/Diatom
Morphology and description available from: https://books.google.co.uk/books?id=xhLJvNa3hw0C&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
Good luck
The following is multiple choice question (with options) to answer.
Like animals, protozoa are heterotrophic and capable of what? | [
"creating",
"pushing",
"moving",
"working"
] | C | Like animals, protozoa are heterotrophic and capable of moving. |
SciQ | SciQ-4173 | thermodynamics, aqueous-solution, free-energy
What does this mean in practice? For example, suppose that I would like to measure the hydration free energy $\Delta G_{\text{solv}}$ of a small molecule (e.g., the amino acid arginine). That is to say, I would like to measure the solvation free energy of arginine in water. (Since arginine has a charged side chain at neutral pH, I would expect $\Delta G_{\text{solv}}$ to be negative, because arginine is likely stabilized by water, which is polar.)
Does the expression for $\Delta G_{\text{solv}}$ above imply that I just need an aqueous solution of arginine? Then would I need to somehow measure the partial vapor pressure $P_s$ of the arginine vapor which exists above the arginine aqueous solution? How is such a partial vapor pressure vapor measurement done in practice? Thanks for your time. Your interpretation is correct. Theoretically, you will need only an aqueous solution and a fixed volume of gas, and then be able to measure equilibrium concentrations. Although, you may not observe very much vapor pressure without using elevated temperatures (as you noted, the zwitterion is very soluble).
Derivation
The following is multiple choice question (with options) to answer.
What term is used to describe a solute that is water fearing? | [
"anti-hydral",
"claustrophobic",
"hydrophobic",
"hydrogenic"
] | C | London interactions c. London dispersion forces Hydrophilic and Hydrophobic Solutes A solute can be classified as hydrophilic (literally, “water loving”), meaning that it has an electrostatic attraction to water, or hydrophobic (“water fearing”), meaning that it repels water. A hydrophilic substance is polar and often contains O–H or N–H groups that can form hydrogen bonds to water. For example, glucose with its five O–H groups is hydrophilic. In contrast, a hydrophobic substance may be polar but usually contains C–H bonds that do not interact favorably with water, as is the case with naphthalene and n-octane. Hydrophilic substances tend to be very soluble in water and other strongly polar solvents, whereas hydrophobic substances are essentially insoluble in water and soluble in nonpolar solvents such as benzene and cyclohexane. The difference between hydrophilic and hydrophobic substances has substantial consequences in biological systems. For example, vitamins can be classified as eitherfat soluble or water soluble. Fatsoluble vitamins, such as vitamin A, are mostly nonpolar, hydrophobic molecules. As a result, they tend to be absorbed into fatty tissues and stored there. In contrast, water-soluble vitamins, such as vitamin C, are polar, hydrophilic molecules that circulate in the blood and intracellular fluids, which are primarily aqueous. Water-soluble vitamins are therefore excreted much more rapidly from the body and must be replenished in our daily diet. A comparison of the chemical structures of vitamin A and vitamin C quickly reveals why one is hydrophobic and the other hydrophilic. |
SciQ | SciQ-4174 | cellular-respiration
Title: Do cold blooded animals generate any heat? In explaining energy and work to an 8 year-old I said that all conversion of energy generates heat as a by-product. For example, cars generate heat in their engines and running generates heat in our bodies. Then the 8 year-old said, except for cold-blooded animals.
So my question is, do cold-blooded animals generate any heat in their conversion of stored energy (food, fat, etc) into motion? If they generate heat, why are they cold-blooded? They do generate heat. They just do not SPEND energy specifically on heating their bodies by raising their metabolisms. This is a form of energy conservation. The metabolic rate they need to live is not nearly enough to heat their bodies.
An example of spending energy to heat the body is seen in humans shivering. Here muscle is activated not for its usual purpose, but to function as a furnace. "Warm-blooded" and "cold-blooded" is somewhat a misnomer. The correct way to think of it is...
Endotherm or ectotherm. Does the heat primarily come from within (endo) or from the surroundings (ecto). Endothermic animals include mammals. Most of their body heat is generated by their own metabolisms. Ectothermic animals include reptiles and insects. They absorb most of their body heat from the surroundings. This is not the same as saying they let their body temperature fluctuate with their surroundings, some avoid this by moving around to accomodate themselves.
Homeotherm or poikilotherm. Homeotherms want to maintain homeostasis for their body temperatures. They don't want it to change. Poikilotherms do not exhibit this behaviour, instead their body temperatures vary greatly with the environment.
We can have endotherm poikilotherms, such as squirrels, who let their body temperature drop while hibernating. Endotherm homeotherms, such as humans, where temperature is constant by means of complex thermoregulation. Ectotherm homeotherms, such as snakes (moving into shadow or into the sun to regulate temperature), and ectotherm poikilotherms, such as maggots.
The following is multiple choice question (with options) to answer.
What is the term for animals that cannot raise their body temperature on their own? | [
"warm-blooded",
"catabolic",
"ectothermic",
"endothermic"
] | C | They are ectothermic , meaning their temperature depends on the temperature of their environment. Ectothermic animals are cold-blooded in that they cannot raise their body temperature on their own. This is unlike humans, whose temperature is controlled from inside the body. |
SciQ | SciQ-4175 | geology
Title: Where do riverbed stones come from? Have they always been here since the river was formed? Are some newer than others? Riverbed 'stones' - I assume you mean things like pebbles, boulders, etc. are pieces of rock that have weathered out and been deposited in the river. Some come from rock that is very close to where they are located and some have been transported from very far away. In general (and it is a very broad generalization) the rounder the stone, the longer it has been in the river and the more likely it is to have come from far away. Of course that depends on the hardness of the rock, and other factors, too.
Some rocks are newer than others. Some have been formed quite recently and some are billions of years old.
The following is multiple choice question (with options) to answer.
Kidney stones can form anywhere in what system? | [
"digestive",
"respiratory",
"urinary",
"intestinal"
] | C | A kidney stone. The stones can form anywhere in the urinary system. |
SciQ | SciQ-4176 | human-anatomy
Title: Difference between Appendix and the Cecum? What's the difference between an appendix and a cecum, and what are their functions? In herbivores the Cecum is an area that stores plant matter and helps digest it via symbiotic bacteria. Carnivores have smaller Cecums because meat is easier to digest than plant matter. In humans the Cecum is also an anatomical landmark that delineates the change from small intestine (a digesting organ) to the large intestine (mostly a capacity/storage organ).
The Appendix is a small, previously thought "superfluous" fleshy worm-shaped organ at the junction between the small and large intestines. Recent research posits that the appendix is sort of a harbor for a person's gut flora that can re-populate the intestines should the existing bacteria die or get removed (diarrhea being the most common cause). It can also become infected, inflamed, and require surgery to remove (Appendicitis).
The following is multiple choice question (with options) to answer.
What organ participates in all digestive activities except ingestion and defecation? | [
"stomach",
"small intestine",
"large intestine",
"tongue"
] | A | 23.4 The Stomach The stomach participates in all digestive activities except ingestion and defecation. It vigorously churns food. It secretes gastric juices that break down food and absorbs certain drugs, including aspirin and some alcohol. The stomach begins the digestion of protein and continues the digestion of carbohydrates and fats. It stores food as an acidic liquid called chyme, and releases it gradually into the small intestine through the pyloric sphincter. |
SciQ | SciQ-4177 | 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 calculated by adding together the atomic masses of the elements in the substance, each multiplied by its subscript (written or implied) in the molecular formula? | [
"magnetic mass",
"fractional mass",
"mass effect",
"molecular mass"
] | D | Molecular and Formula Masses The molecular mass of a substance is the sum of the average masses of the atoms in one molecule of a substance. It is calculated by adding together the atomic masses of the elements in the substance, each multiplied by its subscript (written or implied) in the molecular formula. Because the units of atomic mass are atomic mass units, the units of molecular mass are also atomic mass units. The procedure for calculating molecular masses is illustrated in Example 1. |
SciQ | SciQ-4178 | meteorology, geomorphology, climatology, atmospheric-circulation
Source Commons Wikipedia.
The cold waters near the ocean surface results in a cool, stable coastal atmosphere. In this region, evaporation from the ocean is reduced and produces extremely low rainfall over land. Precipitation is limited to morning fog and produces some of the driest ecosystems on Earth. The Atacama desert is the best example of such environment with average rainfalls of 15 mm/year (the driest non-polar region). In some areas, they are trying to take advantage of the little moisture the fog (Camanchaca) brings to establish some agricultural zones. The fog droplets are too small (1-40 micrometers) to form water drops and precipitate, so they use fog-catchers to collect moisture from the fog.
Source: newatlas.com
The following is multiple choice question (with options) to answer.
What term describes precipitation that flows over the surface of the land? | [
"erosion",
"flood",
"runoff",
"waves"
] | C | Runoff is precipitation that flows over the surface of the land. This water may travel to a river, lake, or ocean. Runoff may pick up fertilizer and other pollutants and deliver them to a water body. In this way, runoff may pollute bodies of water. |
SciQ | SciQ-4179 | organic-chemistry, acid-base, ph
The usual rule that "$\mathrm{pH}$ of 7 is neutral" comes from solutions in water: Water has the property that it can be converted into, and self-converts between ("auto-ioniziation") separate $\mathrm{H}^{+}$ and $\mathrm{OH}^{-}$ ions and its usual molecular form, $\mathrm{H}_2\mathrm{O}$. When one is dealing with pure water with no adulterants present, there is always, due to this process, around $10^{-7}\ \mathrm{\frac{mol}{dm^3}}$ of $\mathrm{H}^{+}$ present (though actually, this depends on temperature, but around room temp, it is around this much). Decimal logarithm of $10^{-7}$ is -7, hence the $\mathrm{pH}$ is 7. When you throw some acid in and it releases its protonic payload, the concentration of $\mathrm{H}^{+}$ rises by that amount, thus the $\mathrm{pH}$ drops.
The following is multiple choice question (with options) to answer.
At what point is water on the ph scale? | [
"14, basic",
"neutrality, 7",
"0, very acidic",
"3, acidic"
] | B | The light from a laser is monochromatic, coherent, and very intense. |
SciQ | SciQ-4180 | 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.
Would you find cells that contain a cell wall, a large central vacuole, and plastids in plant or animal cells? | [
"tube cells",
"heart cells",
"plant cells",
"animal cells"
] | C | Most organelles are common to both animal and plant cells. However, plant cells also have features that animal cells do not have: a cell wall, a large central vacuole, and plastids such as chloroplasts. |
SciQ | SciQ-4181 | circulatory-system, lymphatic-system, veins
Title: How does most of lymph get back into the blood stream? (I don't mean the lymphatic system) I once read that it was because of osmotic pressure that it returns to the blood stream, by entering the venules. But why? If lymph originated as plasma how come that the solute concentration is higher in the venule? Doesn't plasma contain solutes such as salts, nutrients, oxygen, etc. ? Technically 'lymph' is used to refer to the fluid found within the lymphatic system. If it's not in the lymphatic system, it is not lymph fluid. Thus, your question is really asking about interstitial fluid or the plasma that was filtered out of blood capillaries.
The answer to your question is based on the Starling equation. Normally fluid leaves a capillary due to a net pressure that favors the interstitium. This net pressure is based on the hydrostatic pressure within the capillary being greater than the interstitial pressure of the surrounding tissues, and the oncotic pressure of the capillary (that draws fluid in) being weaker than the hydrostatic pressure of the capillary (that pushes fluid out). At the venule end of this system, the capillary oncotic pressure is stronger than the capillary hydrostatic pressure, drawing fluid back into the circulatory system.
Remember that albumin is the most important component which establishes the oncotic pressure within a vessel, and that this protein is normally NOT released out of a vessel during filtration. Thus, it passes from the capillary into its corresponding venule directly.
The following is multiple choice question (with options) to answer.
What system includes lymph organs, lymph vessels, lymph, and lymph nodes? | [
"immune",
"nervous",
"immature",
"digestion"
] | A | The immune system includes lymph organs, lymph vessels, lymph, and lymph nodes. |
SciQ | SciQ-4182 | inorganic-chemistry, acid-base, everyday-chemistry
$$\ce{H2O + CO2(aq) <=> H2CO3}$$
and the protolysis of true $\ce{H2CO3}$
$$\ce{H2CO3 <=> H+ + HCO3-}$$
For a weak acid
$$\begin{align}
\log[\ce{H+}]&\approx\frac12\left(\log K_\mathrm a+\log[\ce{H2CO3^*}]\right)\\
&=\frac12\left(-6.3-5.0\right)\\
&=-5.65\\
\mathrm{pH}&=5.65
\end{align}$$
Thus, pure rain in equilibrium with the atmosphere has about $\mathrm{pH}=5.65$. Any acid rain with lower $\mathrm{pH}$ would be caused by additional acids.
The following is multiple choice question (with options) to answer.
What causes acid rain? | [
"carbon dioxide",
"heavy pollution",
"air pollution",
"chemicals in waterways"
] | C | Air pollution causes acid rain, ozone depletion, and global warming. |
SciQ | SciQ-4183 | genetics, immunology, ecology, biodiversity, fitness
Title: What does genetic diversity in one species have to do with survival rate when an epidemic spreads? I was studying about genes, and soon remembered that the more diverse the genetics of one species, the less the chance of the species to go extinct from natural disaster.
One instance was an epidemic spreads.I don't fully understand why that happens, so I searched for it in Google and books, but all of them only told me that it is true, not why or how.
So my question is : why and how genetic diversity in one species affects the chance of the species's extinction?
I mean, for example, does it relate to antibodies or something else? Genetic diversity could be understood as a variation in alleles (gene variants) and their frequencies in a population. Due to these allelic variations, we would expect an inherent variability in individual genotypes (or genetic codes). Phenotypes (or traits) can and do vary with changes in underlying genotype. (In simple terms: if you change the underlying genetic code, it could result in changes to an individual's traits).
Changes in traits (e.g., color, size, speed, temperature regulation, mobility, etc.) could lead to a variation in energy conservation, survival, reproductive success, and ultimately fitness.
If any member of a population is more fit given a set of environmental circumstances, it is morel likely that they will survive and pass on their genes to subsequent generations.
You would benefit from reviewing evolution and natural selection. (Sexual selection and genetic drift are relevant, too, of course).
However, the environment and resulting ecologies are always changing, and so there is never an "endpoint" of this process. I.e., there's never a perfectly fit individual that will survive all future environmental changes better than all other variants. In fact, all organisms can only tolerate stressful environmental conditions to a point. (See, e.g., principle of allocation).
As a result, any given individual is limited in its ability to survive various environmental conditions, and no individual organism can survive all possible environmental conditions.
The following is multiple choice question (with options) to answer.
What helps ensure that, at least, some species will survive environmental change? | [
"spontaneous mutation",
"ecosystem",
"biodiversity",
"reproduction"
] | C | Biodiversity generally increases the productivity and stability of ecosystems. It helps ensure that at least some species will survive environmental change. It also provides many other ecosystem services. For example:. |
SciQ | SciQ-4184 | human-biology, cancer, systems-biology
Title: How does cancer of the larynx (laryngeal cancer) affect the respiratory system? The larynx is part of the respiratory system and is responsible for producing sound (our voices). My question is how cancer in the larynx (voice box) affect the respiratory system overall? I appreciate any answer, but if it's not too inconvenient, please don't use too complex terminology (I'm in grade 10 Canada).
Thanks According to this website:
http://www.spirometry.guru/fvc.html
it causes difficulty with inhalation but exhalation is normal...
"Typically the expiratory part of the F/V-loop is normal: the
obstruction is pushed outwards by the force of the expiration."
"During inspiration the obstruction is sucked into the trachea with
partial obstruction and flattening of the inspiratory part of the
flow-volume loop."
the exact symptoms of a laryngeal tumor depends on where it is located on the larynx... above the vocal cords, on the vocal cords, or below the vocal cords...
but more generally:
anatomy:
mouth/nose-->pharynx-->larynx-->trachea-->bronchi-->lungs
a tracheostomy may be necessary... basically the surgeon makes a connection between the skin outside the throat and the trachea... this bypasses the larynx (as well as pharynx and nose/mouth)...
The following is multiple choice question (with options) to answer.
The airway and the lungs are part of what organ system? | [
"pulmonary",
"coronary",
"respiratory",
"digestive"
] | C | 31 Respiratory system In humans and other animals, for example, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles. Other animals, such as insects, have respiratory systems with very simple anatomical features, and in amphibians even the skin plays a vital role in gas exchange. Plants also have respiratory systems but the directionality of gas exchange can be opposite to that in animals. The respiratory system in plants also includes anatomical features such as holes on the undersides of leaves known as stomata. In mammals, the diaphragm divides the body cavity into the abdominal cavity: contains the viscera (e. , stomach and intestines). |
SciQ | SciQ-4185 | atmosphere, atmosphere-modelling, air-pollution, air-quality
Title: Why are "ground level" air quality monitors really on rooftops? There are many papers that talk about the air quality at ground-level in cities, observed by air quality monitors. Some monitors are located above the building(not actually on the ground). For example, my lab's equipment was located on the 5th floor of the building (~ 15m).
My questions are:
Is it appropriate to represent air quality using measurement data on a building roof?
What's the difference between air quality on the ground & the roof? And what matters? In order to put your question in perspective, you need to consider atmospheric mixing and the size of the system you are curious about. The troposphere is several kilometers thick and the mixed layer of atmosphere above the ground can occupy a significant fraction of the troposphere. Granted, during cold events, the temperature of the air can be so cold that the lack of convective motion creates a very shallow (e.g. 10s of meters) mixing layer. Though, 15 meters above the ground will virtually always be within the mixed layer near the ground, despite cold weather events.
Some people do measure air quality at the ground level, but it is generally done in the context of studying biogenic emissions (e.g. soil emissions or below-canopy tree emissions). However, those are special field studies, which have different objectives than typical air quality monitor sites.
Typical air quality monitor sites are relatively sparse, and even large cities have just a few monitors. Generally, monitors are located in such a way that they are observing well mixed air, so that it represents air quality in the region. It is imperative that you put your air quality monitor high enough above the ground so that it isn't being directly influenced by emission sources (e.g. your neighbors wood stove, or a car's tailpipe). Otherwise, if you put the monitor literally on the ground, you will often be observing much more variance, with higher peaks that represent that specific location only. See this post for more info on how monitor locations are selected. You can also see this EPA handbook on siting monitors which notes:
The following is multiple choice question (with options) to answer.
Air quality is a measure of what in the air? | [
"nitrogen",
"precipitation",
"pollutants",
"oxygen"
] | C | Air quality is a measure of the pollutants in air. Poor air quality started to become a serious problem during the Industrial Revolution. After 1900, motor vehicles added greatly to the problem. The Clean Air Act of 1970 improved the quality of the air over the U. S. |
SciQ | SciQ-4186 | biochemistry
Title: Is it possible to change an amino acid within a protein but not affecting that protein's functions? In the answer(source - Campbell Essential Biology with Physiology, self-quiz question), it's given that "if the change doesn't affect the protein's shape in any way then it's possible to do so". But practically, is it possible to amend a protein without changing its shape? What the authors are describing here is the idea that function follows from form. Meaning that a proteins 3D structure is, in many ways, responsible for it's actions.
And yes, it is possible to change a residue without changing the proteins shape. For example, changing a residue that resides on the outside of the protein from a positively charged one like Lysine to a positively charged one like Arginine (both residues are very similar) will not have any effect on the structure of the protein, in most cases. Same thing when changing an Alanine to a Valine: they are so similar to one another that it would be difficult to find a case where swapping them would cause the protein to change shape or for its function to be destroyed.
The following is multiple choice question (with options) to answer.
Which factor often changes a protein from an inactive form to an active form? | [
"lipid groups addition",
"oxygen groups addition",
"phosphate groups addition",
"nitrogen groups addition"
] | C | |
SciQ | SciQ-4187 | cleaning, silver
(the back is a white paper, white-balance is crazy with this piece)
My question is: Is this yellow stain any kind of dirt that wasn't removed in the process, or is this the underlayer of the piece(meaning that the silver is gone in those parts)? And above all, is the method used the best way to remove dirt from silver? Did find a source and the nature of reaction apparently involves some standard chemistry, surface chemistry, some radical activity and electrochemistry resulting, upon warming, in the demonstration of some yellow elemental sulfur!
Here is a description of the reaction pathways, starting in alkaline conditions, surface chemistry on the Aluminum metal (which can even very slowly be attacked by water liberating hydrogen):
$\ce{Al + OH- -> Al(OH)3 + 3 e-}$
Of consequence, NaHCO3 is amphoteric and a source of H+ ions. Also, in the presence of solvated electrons, the creation of the hydrogen atom radical (per the source) along with hydrogen gas:
$\ce{H+ + e- ⇌ •H }$
$\ce{•H + •H -> H2 (g) }$
Also, per a galvanic cell between the Aluminum and the Silver metal, the half-cell reaction at the anode being given by:
$\ce{Al -> Al(3+) + 3 e- }$
At the cathode, the proposed half-cell reaction explaining the removal of Silver sulfide:
$\ce{Ag2S(s) + 2e- + 2H2O -> 2Ag(s) + H2S(g) + 2 OH- }$
See same source, Equation (6).
And, for the observed yellow color, the cited reaction:
$\ce{H2S + 2 OH- -> 2 H2O + S(s) }$
which is apparently confirmed by the cited source to quote:
"However, after the cleaning of heavily tarnished samples (immersed for 30 and 60 min) some small quantities of sulfur (~0.3wt.%) are detected on the surface by EDS analysis, and the colour is changed to light yellowish."
The following is multiple choice question (with options) to answer.
After the film is developed, any unexposed silver bromide must be removed by a process called what? | [
"watering",
"fixing",
"washing",
"sweeping"
] | B | After the film is developed, any unexposed silver bromide must be removed by a process called “fixing”; otherwise, the entire film would turn black with additional exposure to light. Although silver bromide is insoluble in water, it is soluble in a dilute solution of sodium thiosulfate (Na2S2O3; photographer’s hypo) because of the formation of [Ag(S2O3)2]3− ions. Thus washing the film with thiosulfate solution dissolves unexposed silver bromide and leaves a. |
SciQ | SciQ-4188 | forces, classical-mechanics, friction
Title: Distribution of static friction forces between two opposite surfaces Please, could you help me with this question. It seems very easy but I struggle to find info on the web, and the chatGPT gives an apparently wrong answer.
I have the following static setup, where the applied external force is obviously lower than either maximum static friction force (the one between the block A and block B, and the one between the block A and ground). The sum of these two friction forces on the block A must equal (with the opposite sign) the external force of 2 Newtons applied to the block A. I can't figure out whether these two friction forces should be equal (1 Newton each) or be proportional to the respective normal forces or whatever other quantity. I thank @JohnRennie for the answer in the comment section above. It appears that since the block B's acceleration is still zero and the only horizontal force acting upon it is FA,B, the latter should be equal to zero, too. Thus FB,A is zero, and FG,A = −FE = −2 N.
My afterthought: if we don't abstract ourselves from the nature of the underlying surface and assume it belongs to an Earth-like (but resting) object, we may come up with the following distribution of static friction forces and establish that the friction force exerted upon block A is being split between the lower and upper surfaces in proportion to the masses of the neighbouring objects (after subtracting block A's mass).
The following is multiple choice question (with options) to answer.
What force provides resistance whenever two surfaces are in contact? | [
"rotation",
"vibration",
"friction",
"tension"
] | C | |
SciQ | SciQ-4189 | = push-ups / seconds in air is close 340.1... { 450nm } * { f } = { 450nm } * { f } = { 450nm *... Page, or Hz for short bin numbers ( upper levels ) the... Is hit on one end with a speaker bolted to it is n't a concept 's! Calculate the frequency and vice versa vibrational frequency can easily be changed when dial! End with a period of a particular value occurs enrolling in a that... Will show a Sine wave that can be measured in seconds two years of college and save thousands your... Waves that pass a fixed point in unit time divided by a count of all values write our frequencies units. N'T measure something like push-ups in 30 seconds that repeats has a master degree! { 45Hz } =20,250nm/s < =20.25um/s } and the time it takes to do just one.! The 42 seconds per lap through some practice problems the velocity of life... The calculation can be applied to many situations Mean = 2 + 10 + 12 + 8 + 14. Diameter, is the frequency in hertz even if it is an essential feature engines... 1/2 inch in diameter, is the height from highest to lowest points and divide that by 2 your blocker. Means they are related like this: if you are just asked for ,., Types & uses, Mass and Weight: Differences and Calculations, 83,000... Event to occur or education level 83,000 lessons in all major subjects, { courseNav.course.mDynamicIntFields.lessonCount... At B2-B10 and use the first two years of college and save thousands off degree. Something repeats attend yet from a frequency associated with it measurement we use the fact that period is also inverse. Like this: Essentially, anything that repeats has a master 's degree physics. For many people it probably has something to do just one lap how to find frequency measurement! Many situations to connect it to a given wavelength college you want to yet. In how to find frequency proportion of the system frequency is a measure of cycles second! The 1 second of period or from any point to the trough ) an for... To 60 seconds we can see RPM represents a frequency and period can be to! One lap Mean
The following is multiple choice question (with options) to answer.
What cycle is frequency measured in per second? | [
"hertz",
"watt",
"Krebs",
"decibel"
] | A | The frequency, is the number of cycles an object goes through in second. Frequency is measured in Hertz . cycle per sec. |
SciQ | SciQ-4190 | cell-biology, microbiology
Title: Are there any organisms that are made of more than one (~5-12) cell? Prokaryotes and eukaryotes are unicellular, made of one cell. Great. Eukaryotes are unicellular or multicellular. But the typical examples of multicellular eukaryotes we have are made of, often, trillions of cells, like us humans. Ants must still be made of many millions of cells. Are there known eukaryotes with very few cells that make them up? Like, 5, or something? Or maybe a dozen cells making up the whole organism in its fully developed state? There's Trichoplax adhaerens, a Placozoa, made of a few thousand cells. Then there is Dicyema japonicum, a simple mesozoan, made up of 9 to 41 cells. Arguably, the simplest multicellular organism is the algae Tetrabaena socialis, whose body consists of 4 cells. Then, there's the parasitic Myxozoa which have 7 cells.
The following is multiple choice question (with options) to answer.
What are the two types of cells? | [
"prokaryotes and eukaryotes",
"mammal and plant",
"bacteria and eukaryotes",
"animal and bacteria"
] | A | There are two cell types: prokaryotes and eukaryotes. Prokaryotic cells are usually single-celled and smaller than eukaryotic cells. Eukaryotic cells are usually found in multicellular organisms, but there are some single-celled eukaryotes. |
SciQ | SciQ-4191 | symmetry, atoms
Title: Is hydrogen the same everywhere? Silly thought. Feel free to shoot it down
Does a hydrogen atom undergo any kind of change subject to it's environment?
If one were to study a hydrogen atom on the surface of Mercury, another above Earth, and a third in interstellar space - would they exhibit any difference/s? This is quite far from a silly thought although this is not apparent at first sight. Apart from a couple of details which are well understood and have firm physics behind them - such as the fact that deuterium and tritium exist in some proportion and the hyperfine-structure distinction between ortho- and parahydrogen, as far as we can tell all hydrogen atoms are exactly the same. This is in fact the case for all atoms and molecules: all iron atoms are exactly replaceable (so long as you take the right isotope) and nitrogen molecules are all the same (so long as you take them in the correct electronic, nuclear and spin states), and so on.
This is one of the most profound symmetries in nature and it holds irrespective of geographical / astronomical position, chemical history, temperature, and so on. How can we tell? Well, the very fact that we can do chemistry with atoms is why - the basic tenet is that the world is made of a finite set of "blocks" and that combinations of them make the interesting materials around us. The success of chemistry as a discipline means that there's something to that basic tenet.
How can we tell that atoms in places we haven't been are the same as here? Of course, our evidence for that is not as strong, but it's built on the fact that astrophysics works just using physics of different kinds we can see experimentally here on Earth. We can do spectral analysis of the solar corona, for example, and if we see energy levels slightly displaced then we can explain that as Doppler shifts or magnetic fields that let us explore a richer and (as far as we can tell) fully consistent physical picture. We can do chemistry on the atmospheres of other planets and, though it's rather hard, come up with consistent chemical explanations for all our observations. We can link the nuclear physics we observe in accelerators and reactors to explain our observations of our Sun and other stars and see that they match what we do here.
The following is multiple choice question (with options) to answer.
In science, what do you call something that always applies under the same conditions? | [
"scientific law",
"scientific method",
"hypothesis",
"theory"
] | A | Many people think that any idea that is completely accepted in science is a law. But that is not true. In science, a law is something that always applies under the same conditions. A law explains a fairly simple phenomenon. A theory is much more complex: it tells you why something happens. A law only tells you that it happens. For example, if you hold something above the ground and let go, it will fall. This phenomenon is recognized by the law of gravity ( Figure below ). Some people say that evolution is "just a theory. " But for a complex explanation like evolution, theory is the right word. |
SciQ | SciQ-4192 | adaptation
Title: How do longleaf pine trees adapt to the florida keys rainforest? I know that longleaf pine trees can be found in rainforests, but I can't find anything. This is sort of a too broad question but here are a few ideas. The second most fragile part of plants are the leaves. In the latitudes and elevations that experience freezing, plants have learned to abscise their leaves and go dormant for the winter season. Conifers have thick, waxy, very thin leaves that most conifers do not need to shed.
In a rainforest there is no danger of too cold temperatures. That is why there is an abundance of broadleaf trees and plants in the rainforest. Most of our indoor plants are tropical rainforest species.
There is also an awful lot of rain in a rainforest. There is a problem with leaves covered with water, as it inhibits the absorption of CO2. Beneath the leaf, O2 is released as a by-product of photosynthesis. Broad leafed plants that have adapted to an environment with lots of rain, little wind, and being crowded together have leaves designed to 'wick' the rain water off the leaf to run down the midrib and off the pointy tip or lobed or curled under leaf margins. This clears off the water and allows the plant to take up CO2, or it would not be able to do photosynthesis to make its own food for energy.
The other cool thing I can remember, is that broad leafs of plants are able to 'adjust' to the light. Similar to a 'solar sail' in outer space. If in full sun, those leaves get thick and stay smaller. If in shade, very normal in a rainforest, those leaves can thin and get larger in order to capture as much light as possible.
A better wording for your question would be, 'why is there an abundance of broad leaf species versus conifers in a rainforest'? If I've been able to translate your question correctly?
Hope this helps.
The following is multiple choice question (with options) to answer.
The pine tree is the sporophyte; its sporangia are located on scalelike structures packed densely where? | [
"in the bark",
"in cones",
"in the limb tips",
"in the needles"
] | B | |
SciQ | SciQ-4193 | python, performance, python-3.x, numpy, simulation
Title: Population dynamic simulation on biological information maintenance Background
Using this simulation I investigate a system in which enzymes proliferate in cells. During the replications of enzymes, parasites can come to be due to mutation. They can drive the system into extinction. I'm interested in where in the parameter space coexistence is possible.
In the program the system is a list, the cells are dictionaries with 2 keys: "e" for the enzymes and "p" for the parasites. The values of the keys are the numbers of the 2 variants.
Our parameters are:
pop_size: the number of the cells
cell_size: the maximal number of molecules (enzymes+parasites) of cells at which cell division takes place
a_p: fitness of the parasites relative to the fitness of the enzymes (for example if a_p = 2, the parasites' fitness is twice as that of the enzymes)
mutation_rate: the probability of mutation during a replication event
gen_max: the maximal number of generations (a generation corresponds to one
while cycle; if the system extincts, the program doesn't run until gen_max)
We start with pop_size cells with cell_size // 2 enzimes and 0 parasites. In each cell the molecules proliferate until their number reaches cell_size. Each cell divides, the assortment of the molecules happens according to binomial distributions (\$p=0.5\$). Cells with "e" < 2 are discarded as dead. After that if the number of viable cells is bigger than pop_size, we choose pop_size of them according to cell fitness ("e"/("e"+"p")), and they move on to the next generation. On the other hand, if the number of viable cells is pop_size or less, they all move on to the next generation.
My request
I've never studied programming in school. This program is the result of heavy googling. Now I've reached a point where I need advice from experienced people. At certain parameter values the program gets quite slow.
The following is multiple choice question (with options) to answer.
Prokaryotic cells grow to a certain size and then they divide by which process? | [
"binary fission",
"linear fission",
"budding",
"binary fusion"
] | A | Prokaryotic cells grow to a certain size. Then they divide by binary fission. This is a type of asexual reproduction. |
SciQ | SciQ-4194 | seismology, earthquakes, seismic-hazards, drilling
Title: Why aren't seismic stations installed very deep underground so as to pre-warn from earthquakes? The velocity of p-waves emanating from earthquakes is in the range of 5-8 km/s (link)--let's assume it is 5 km/s. The earthquake depth is up to hundreds of kms deep underground (link)--let's assume it is 100 km.
That said, if a seismic station is installed at a depth of 50 km, and there are many of them in any given metropolitan area, then we can have a warning that is tens of seconds before the earthquake reaches the surface.
While I realize that drilling down to 50 kn is no easy task, I would have imagined that saving human life is well worth the efforts. Why hasn't this been done so far? Is it that such a short notice (10s of seconds) isn't worth it? The simple answer is that you can't drill to 50 km depth.
The deepest holes ever drilled were to a little more than 12 km, one is named the Kola Superdeep Borehole in Russia, which was a scientific drilling project. The very few others were oil exploration boreholes.
Drilling that deep is extremely expensive and hard. If you go and ask anyone who ever worked on a drill rig, drilling the second 100 metres is always harder than the first 100 metres. And we're talking about kilometres here! There are several problems with drilling that deep. It's extremely hot down there, and the drilling equipment just breaks and stops working. You also need to pump cooling water in and pump out the stuff you're drilling and it gets harder with depth.
This is simply not feasible. Now let's say that you did somehow manage to drill a hole to that depth. How would you put monitoring equipment inside? That equipment has to sustain heat and pressure and still keep working, while being able to transmit whatever it's reading back to the surface. This is not going to happen, not at 50 or 10 km depth.
Another problem is that not all earthquakes are that deep. Some earthquakes originate near the surface, or just several km deep. Having a monitoring station down there isn't going to help. The 2011 Tohoku earthquake (the one that triggered the tsunami at Fukushima) was only 30 km deep. Same thing for the 2004 Indian Ocean earthquake.
The following is multiple choice question (with options) to answer.
What can increase the occurance of earthquakes? | [
"three plates sliding",
"two plates sliding",
"plates breaking",
"plates rupturing"
] | B | |
SciQ | SciQ-4195 | 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 term is used to describe organelles that are found only in animal cells? | [
"acids",
"fibrils",
"anticlines",
"centrioles"
] | D | Centrioles are organelles that are found only in animal cells. They are located near the nucleus. They help organize the DNA in the nucleus before cell division takes place. They ensure that the DNA divides correctly when the cell divides. |
SciQ | SciQ-4196 | planet, solar-system
Title: Where is the Solar system's barycenter located? Where is the Solar system's barycenter located?
The solar system as a whole, Where is the center of the mass for the combined mass of the Sun, inner planets, and gas giants, is it inside the Sun? Is there an AU measured distance of it? The solar system barycenter (SSB) is sometimes inside the Sun and sometimes outside.
As an observer outside the solar system could detect with Doppler spectroscopy, the Sun is what's wobbling around.
The Sun's offset from the SSB is a vector sum of roughly:
0.00496 au ±5% away from Jupiter
0.00272 au ±6% away from Saturn
0.00083 au ±5% away from Uranus
0.00155 au ±1% away from Neptune
The other planets contribute much smaller amounts to the total.
Each planet's contribution is proportional to the product of its mass and its orbital distance.
When these components add constructively as in 2020-2023, the center of the Sun can be as far as 2 R☉ away from the SSB.
When they cancel as in 2029-2030, the center of the Sun is within 0.5 R☉ of the SSB.
The solar radius R☉ is 0.00465 au, shown here with a dashed line.
The following is multiple choice question (with options) to answer.
What is located at the center of our solar system? | [
"the earth",
"the sun",
"a black hole",
"the moon"
] | B | |
SciQ | SciQ-4197 | pain, death
Title: Normal death experience Consider a natural cause of death (no car accidents etc) -
Is it true that death is generally preceded by suffering? In other words, are we destined to experience the most severe suffering we could not ever imagine, that will ultimately end with death?
If this is true, is it true for all living things? No and no.
I'm not sure what is a "natural cause" in this context, but if it's cardiac arrest caused by age-related dystrophy of the cardiac muscles, then no, there is no suffering, at least not universally: Since age-related dystrophy hits all parts of the body, it's likely preceded by increasing amounts of bed rest, leading to quietly drifting off into the great sleep.
Of course, if you add on other natural causes like age-related diseases or being eaten by predators, the suffering can be great indeed, or not: A tiger will sneak up on you and crush your skull without you ever knowing what happened.
Adding on further causes still, like dehydration or hunger, and the suffering is back.
But is suffering a universal fixture of death? Emphatically no.
As for the "all living things" part of the question, the answer isn't just "no"; it's "that's nonsensical".
By individual count, practically no life is complex enough for suffering to be a relevant concept.
I don't have an exact number for you, because how would I get one, but at a rough estimate, bacteria, algae and archea constitute 100% of all individual life forms by count, and suffering is not a concept that makes sense for them.
If we ignore simple life, even among complex life there is so much variety of capabilities that basically nothing universal exists.
The following is multiple choice question (with options) to answer.
What is the leading cause of death worldwide? | [
"lung disease",
"cancer",
"liver failure",
"coronary artery disease"
] | D | Heart: Coronary Artery Disease Coronary artery disease is the leading cause of death worldwide. It occurs when the buildup of plaque—a fatty material including cholesterol, connective tissue, white blood cells, and some smooth muscle cells—within the walls of the arteries obstructs the flow of blood and decreases the flexibility or compliance of the vessels. This condition is called atherosclerosis, a hardening of the arteries that involves the accumulation of plaque. As the coronary blood vessels become occluded, the flow of blood to the tissues will be restricted, a condition called ischemia that causes the cells to receive insufficient amounts of oxygen, called hypoxia. Figure 19.16 shows the blockage of coronary arteries highlighted by the injection of dye. Some individuals with coronary artery disease report pain radiating from the chest called angina pectoris, but others remain asymptomatic. If untreated, coronary artery disease can lead to MI or a heart attack. |
SciQ | SciQ-4198 | reaction-mechanism, reaction-control
Title: Titanium reaction with Sodium Percarbonate solution I've been reading about a process for darkening Titanium using Sodium Percarbonate that consists of the following steps:
Prepare Sodium Percarbonate solution 1:5 with boiling water
Soak titanium piece in solution
I have not been able to find any technical readings on what exactly is going on with this chemical process.
These guides have also found that Titanium Grade affects the darkening of the Titanium:
An oxidation on Grade 1 surface is rather aggressive, not even and it's brown not grey... oxidation on Grade 5 is neither that aggressive nor that brown.
And that heat affects the reaction as well:
The solution is doing the job only when its warm, so I have repeated the process 3 times.
Add some hot water from time to time and stir...
Links:
https://www.rwg.bz/board/index.php?/topic/161199-how-to-force-a-patina-on-a-raw-titanium/
https://www.bladeforums.com/threads/darken-titanium-with-oxi-clean.1019026/
What exactly is going on in this reaction with the Titanium? What is the material of this new darkened layer? The effect is similar to that of anodizing titanium (or aluminum) to build up a thin surface oxide coating. There are a few causes for the color change.
A thin, transparent, layer of oxide causes optical interference due to the reflections within the oxide layer surface and the underlying metal. This can produce a whole spectrum of colors in the titanium workpiece.
Rather than having a shiny, metallic reflective surface, a thick oxide layer is rough, at the wavelength of light, causing absorption destructive interference and therefore darkening the part.
Impurities in the metal such as silicon may cause patchy, uneven anodizing, and others, such as iron, form colored salts that fill the pores of the oxide.
The following is multiple choice question (with options) to answer.
Changes in the color of the statue of liberty owe to oxidation-reduction reactions, or what simpler term? | [
"oxygen",
"copper",
"immersion",
"corrosion"
] | D | Chemistry in Everyday Life Statue of Liberty: Changing Colors The Statue of Liberty is a landmark every American recognizes. The Statue of Liberty is easily identified by its height, stance, and unique blue-green color (Figure 17.16). When this statue was first delivered from France, its appearance was not green. It was brown, the color of its copper “skin. ” So how did the Statue of Liberty change colors? The change in appearance was a direct result of corrosion. The copper that is the primary component of the statue slowly underwent oxidation from the air. The oxidation-reduction reactions of copper metal in the environment occur in several steps. Copper metal is oxidized to copper(I) oxide (Cu2O), which is red, and then to copper(II) oxide, which is black. |
SciQ | SciQ-4199 | ocean, oceanography, wind, waves, ocean-currents
Taking 10 meters (one of the smallest values in mid-latitudes) for the surface and bottom boundary layer thicknesses, that implies that in water depths shallower than 20 m the two boundary layers overlap. In water depths shallower than that, the transport in the surface layer is no longer perpendicular to the wind direction. The momentum input into the water by the wind (wind stress) is affected by the presence of the bottom and it is directly dissipated by bottom friction. The mixing by the wind (and wave breaking near the surf zone) results in additional mixing through the water column and facilitating well-mixed water columns. Under these conditions the wind-induced currents extend all the way to the bottom with the direction of the flow being a function of bottom depth, wind direction, and bottom slope. The presence of wind-induced currents does not preclude the occurrence of flow in the opposite direction of the wind.
A fantastic article summarizing the different flow conditions under different wind and wave fields in shallow water depths is given in Lentz and Fewings (2012). (Reprint)
Additional factors to consider are:
The following is multiple choice question (with options) to answer.
What is the top layer of water farther from shore called? | [
"semimetal zone",
"Beach Zone",
"Tidal Zone",
"limnetic zone"
] | D | The top layer of water farther from shore is called the limnetic zone. There is enough light for photosynthesis and plenty of dissolved oxygen. However, dissolved nutrients tend not to be as plentiful as they are in the littoral zone. Producers here are mainly phytoplankton. A variety of zooplankton and fish also occupy this zone. |
SciQ | SciQ-4200 | reproduction, sociality, fitness
Title: Which monkey species features two distinct male phenotypes? I remember coming across a popular science article years ago about a monkey species which featured two male genotypes: the first were good looking males who acquired social status (as alphas or betas) within the group and could thus achieve reproductive succes. The alternative (less frequent) phenotype achieved similar fitness by adopting an outgroup (omega) lurking rapist kind of reproductive strategy.
Does anybody know which species and whose observervations I could be referring to? I'm curious to find out if this was a valid observation and if any further research has been done on this phenomenon. Patas monkeys exhibit "sneak mating" where a male other than the resident male sires offspring. Resident males do sire more offspring than sneaker males, but both strategies do co-occur. I'm pretty sure there are other species that have a similar mating strategy as well.
The following is multiple choice question (with options) to answer.
Flatworms reproduce sexually. in most species, the same individuals produce both what? | [
"gametes",
"eggs and sperm",
"diploid and haploid",
"heart and sperm"
] | B | Flatworms reproduce sexually. In most species, the same individuals produce both eggs and sperm. After fertilization occurs, the fertilized eggs pass out of the adult’s body and hatch into larvae. There may be several different larval stages. The final larval stage develops into the adult form, and the life cycle repeats. |
SciQ | SciQ-4201 | cell-biology, terminology
Title: What is the difference between cytosol and cytoplasm? I've generally seen cytosol defined as the solution inside cells minus the organelles, cytoskeleton, etc and cytoplasm as the cytosol plus the organelles, cytoskeleton, etc. This naturally leads to the impression that cytosol is the cytoplasm minus all the solids. The problem here is that there are all sorts of other large molecules in the cells which could be thought of as solid. Are they also part of the cytosol or are they suspended in it? (I.e. are they part of the cytosol or are they non-cytosol components of the cytoplasm?)
Basically, I'm asking if the precise definition of cytosol is just anything in the cell that's not behind an endomembrane (save the exoskeleton) or if the dividing line is something else.
Subquestion: things can get even more terminologically confused because the cytosol is sometimes called the matrix. What the heck is the preferred terminology with this stuff? IMO, the definitive answer to this question is given in a paper by J. S Clegg. He traced the origin of the term cytosol to a book chapter by H. A. Lardy, and confirmed by email that Lardy had indeed coined the term. Their definition of cytosol is as follows:
... that portion of the cell which is found in the supernatant fraction after centrifuging the homogenate at 105 000 x g for 1 hour.
The following is multiple choice question (with options) to answer.
The cytoplasm is all the contents of the cell inside the cell membrane, with the exception of what? | [
"nucleus",
"lysosome",
"molecules",
"vacuole"
] | A | Both prokaryotic and eukaryotic cells have structures in common. All cells have a plasma membrane, ribosomes, cytoplasm, and DNA. The plasma membrane , or cell membrane, is the phospholipid layer that surrounds the cell and protects it from the outside environment. Ribosomes are the non-membrane bound organelles where proteins are made, a process called protein synthesis. The cytoplasm is all the contents of the cell inside the cell membrane, not including the nucleus. |
SciQ | SciQ-4202 | newtonian-mechanics, forces, electrostatics, vectors, equilibrium
Title: Contradicting Basic and Force definitions of types of Equilibrium This question is neither a check my work question and nor a homework question, it is a conceptual doubt in a question I found and I have attached a solution just for reference to show how I drew my conclusions. All my previous posts containing this question have been closed due to some reason like this one or "lacks clarity" (please comment if you cannot understand my post and do not vote to close it, I will update the post ASAP because I am apparently at the risk of being banned from asking questions).
So I have read that a particle is in Stable Equilibrium when the potential energy is minimum, Unstable Equilibrium when the potential energy is maximum and Neutral Equilibrium when the potential energy is neither maximum or minimum. All of these definitions have the condition that net force on the particle = $0$ (or the particle is at equilibrium or $\frac {dU}{dr} = 0$.
Some extensions of these concepts or different definitions of Equilibrium are : "A particle is said to be in Stable Equilibrium when a slight displacement of the particle from equilibrium position makes it oscillate about that position (which means it returns back to the mean position) or that the forces acting on the particle are in the opposite direction to the displacement. The particle is in Unstable Equilibrium when a slight displacement of the particle from equilibrium position makes it go farther away from the position (which means it cannot come back to the mean position) or the forces acting on the particle are in the direction of displacement."
So the question that I have my doubt in is as follows :
"Two positive charges + q each are fixed at points (-a, 0) and (a, 0). A third charge + Q and mass m is placed at origin. What is the type of equilibrium when a charge Q is given a small displacement along the direction of the line x = y." The answer given is "no type of equilibrium"
Firstly I don't understand if the problem is stating whether the particle is constrained to move in the direction of the line x = y only (in which case the equilibrium is surely stable) or just the displacement is in the direction of the line x = y and that the particle is free to move after that (let us assume the latter case).
The following is multiple choice question (with options) to answer.
What is the study of forces in equilibrium? | [
"statics",
"genomics",
"law of conservation",
"law of inertia"
] | A | • Statics is the study of forces in equilibrium. • Two conditions must be met to achieve equilibrium, which is defined to be motion without linear or rotational acceleration. • The first condition necessary to achieve equilibrium is that the net external force on the system must be zero, so that net F = 0 . |
SciQ | SciQ-4203 | newtonian-mechanics, energy, everyday-life, biophysics
Running involves more and varied movements, it's a very different gait. It is definitely not just the same movement as walking but faster. Some of those movements are vertical, or relate to jumping, some have shock absorption components and relate to landing. Much of that extra energy is dissipated both ways - we use energy both to jump and to cushion and come to a halt on landing. We also accelerate our feet to match our ground speed and must slow them to zero each stride, then speed and lift the other way as well, not just rely on gravity and pendulum activity. The fact this is at extension and not at ground impact doesn't change anything. Again, energy is lost both ways. I'm also going to guess that it's harder to be efficient across a wider compared to narrower range of motions, therefore the wider range of movements and systems used in running means it's much more likely that efficiency varies considerably, according to biological subsystem or type of movement.
Human gross muscle motion energy handling/metabolism is not efficient and doesn't behave like an ideal object. We have multiple energy pathways, and switch between them according to need. This happens less with walking, more with vigorous exercise like running. The "emergency" or "sustained activity" energy cycle our bodies switch to, when running, is less efficient - if it was more efficient it would probably have evolved as our primary not our fallback. And of course many biochemical reactions and body responses just aren't linear; they also may have min/max rates or durations.
The following is multiple choice question (with options) to answer.
What body joint incurs the most common overuse injury among runners and other athletes? | [
"knee",
"arm",
"ankle",
"heel"
] | A | Runner’s Knee Runner’s knee, also known as patellofemoral syndrome, is the most common overuse injury among runners. It is most frequent in adolescents and young adults, and is more common in females. It often results from excessive running, particularly downhill, but may also occur in athletes who do a lot of knee bending, such as jumpers, skiers, cyclists, weight lifters, and soccer players. It is felt as a dull, aching pain around the front of the knee and deep to the patella. The pain may be felt when walking or running, going up or down stairs, kneeling or squatting, or after sitting with the knee bent for an extended period. Patellofemoral syndrome may be initiated by a variety of causes, including individual variations in the shape and movement of the patella, a direct blow to the patella, or flat feet or improper shoes that cause excessive turning in or out of the feet or leg. These factors may cause in an imbalance in the muscle pull that acts on the patella, resulting in an abnormal tracking of the patella that allows it to deviate too far toward the lateral side of the patellar surface on the distal femur. Because the hips are wider than the knee region, the femur has a diagonal orientation within the thigh, in contrast to the vertically oriented tibia of the leg (Figure 8.17). The Q-angle is a measure of how far the femur is angled laterally away from vertical. The Q-angle is normally 10–15 degrees, with females typically having a larger Q-angle due to their wider pelvis. During extension of the knee, the quadriceps femoris muscle pulls the patella both superiorly and laterally, with the lateral pull greater in women due to their large Q-angle. This makes women more vulnerable to developing patellofemoral syndrome than men. Normally, the large lip on the lateral side of the patellar surface of the femur compensates for the lateral pull on the patella, and thus helps to maintain its proper tracking. However, if the pull produced by the medial and lateral sides of the quadriceps femoris muscle is not properly balanced, abnormal tracking of the patella toward the lateral side may occur. With continued use, this produces pain and could result in damage to the articulating surfaces of the patella and femur, and the possible future development of arthritis. Treatment generally involves stopping the activity that produces knee pain for a period of time, followed by a gradual resumption of activity. Proper strengthening of the quadriceps femoris muscle to correct for imbalances is also important to help prevent reoccurrence. |
SciQ | SciQ-4204 | homework, reproduction, allele
Title: Albinism inheritance problem: what are the father's alleles if he got an albino kid?
Albinism is caused by a recessive gen "c". A normal man marries an
albino woman. The first son happened to be albino. What are the
possible phenotypes of the parents? What is the chance that their
other kids will be albino?
Alright, since "c" is recessive and the woman is albino, then the woman must be "c c" right? And since the son is albino, he must be "c c" too. Hence the father must have at least one "c". But since he is normal, then the other allele must NOT be "c" too (otherwise he would be albino).
My question is, when writing the Mendel table, how do I express that allele of the father (the one that is not "c")?
$$\begin{bmatrix} & c & c\\
? & ?c & ?c\\
c & cc & cc\end{bmatrix}$$
I marked it with $?$ because I'm not sure what to put there. My first thought was "well, it could be a capital C I guess..." - but that doesn't sound right to me. A capital C would mean there is a dominant albinism allele (but I am told that albinism is recessive only...)
I can see clearly that there is a 50-50 chance of having albino kids. I just don't know how to draw that inheritance table. Super oober short answer: The father is Cc, the mother is cc, there is a 50% chance the children will be albino (as you predicted).
An explination on Mendelian genetics:
First let's look at (what a lot of people consider) the normal Mendel table from here:
The following is multiple choice question (with options) to answer.
Who is called the father of genetics? | [
"Nostradamus",
"raphael",
"Vincent van Gogh",
"mendel"
] | D | People have long known that the characteristics of living things are similar in parents and their offspring. Whether it’s the flower color in pea plants or nose shape in people, it is obvious that offspring resemble their parents. However, it wasn’t until the experiments of Gregor Mendel that scientists understood how characteristics are inherited. Mendel’s discoveries formed the basis of genetics , the science of heredity. That’s why Mendel is often called the "father of genetics. " It’s not common for a single researcher to have such an important impact on science. The importance of Mendel’s work was due to three things: a curious mind, sound scientific methods, and good luck. You’ll see why when you read about Mendel’s experiments. |
SciQ | SciQ-4205 | human-biology
Title: Stopping the effect of hormone Many hormones released by endocrine organs travel down in the blood and bind to specific receptors on the target cells. What then breaks that binding of the molecule with the receptor ? ( thus inactivating further stimulation of the target cell ) The binding is reversible typically; part of the potency of a drug is ow well and for how long it binds to its target. There's a natural equilibrium of binding and dissociation. Many drugs, once bound to their cognate receptor, cause a down regulation of their cognate receptor on the target cell. The bound/activated downstream signalling pathways may be inhibited by ubiquitination of the downstream signals themselves or upregulation of antagonists etc. The hormone itself has a half life, which is very important, thus levels naturally decrease and for some hormones this is incredibly rapid. Levels may decrease due to breakdown or excretion. Increase of binding hormones may decrease free hormone thus it's effect also.
The following is multiple choice question (with options) to answer.
Each endocrine hormone affects only certain "target" cells, which have molecules of what on the surface that enable binding of a given hormone? | [
"rna",
"gas",
"lipids",
"protein"
] | D | Each endocrine hormone affects only certain cells, called target cells. A target cell has proteins on its surface to which a given hormone can bind. Most endocrine hormones are controlled by negative feedback loops. Negative feedback occurs when low levels of a hormone feed back to increase its secretion—and vice versa. |
SciQ | SciQ-4206 | evolution, terminology, natural-selection, computational-model, definitions
A variation exists between some fitness related hereditary material as regards their final causal effect on the degree of their fitness in a common environment $E$. Mathematically speaking, this is:
$\exists E, g_1, g_2( E \text { is an environment } \wedge g_1,g_2 \text { are fitness related hereditary material } \wedge g_1 \neq g_2 \wedge fit_E(g_1) \neq fit_E(g_2))$
In English: There exists an environment $E$ and $g_1, g_2$ where both are fitness related hereditary material such that $g_1$ is different from $g_2$ and fitness of $g_1$ in enviornment $E$ is different from fitness of $g_2$ in environment $E$.
Two fitness related hereditary material that have the same final effect on the degree of their fitness (even if through different causal mechanisms) in a common environment $E$, are said to be isofit$_E$, while those that differ are said to be anisofit$_E$. Formally:
$g_1 \ isofit_E \ g_2 \iff fit_E(g_1)=fit_E(g_2)$
$g_1 \ anisofit_E \ g_2 \iff fit_E(g_1) \neq fit_E(g_2)$
Of course anisofit fitness related hereditary material might even have a difference in the direction of their effect on fitness, so a positive direction means that "the causal relationship from the hereditary material to its fitness, is towards increasing its fitness"; while the opposite is for negative direction.
Now for every hereditary material $g$ the population of all individuals in environment $E$ that harbour $g$, is to be called the "$g$ population in $E$".
There is an environment $E$ that has two anisofit$_E$ fitness related hereditary material populations living in $E$.
The following is multiple choice question (with options) to answer.
What do we call the scientific study of heredity and hereditary variation? | [
"chemistry",
"biology",
"genetics",
"geneology"
] | C | |
SciQ | SciQ-4207 | 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 do you call any substance in food that the body needs? | [
"a nutrient",
"beneficial",
"antioxidant",
"dietary"
] | A | There are a variety of substances in foods that the body needs. Any substance in food that the body needs is called a nutrient. There are six major types of nutrients: carbohydrates, proteins, lipids, water, minerals, and vitamins. Carbohydrates, proteins, and lipids can be used for energy. Proteins also provide building materials. Proteins, minerals, and vitamins help control body processes. Water is needed by all cells just to stay alive. |
SciQ | SciQ-4208 | waves
Title: Is wave motion the combined motion of the disturbance and the medium? Using a textbook slinky as an example, if the disturbance propagates through the slinky from left to right and the particles of the slinky vibrate up and down, does that mean 'wave motion' is also associated with the medium? Since the motion of the wave that we perceive is the combined motion of the disturbance and the medium? This answer is maybe not the most straightforward satisfactory answer to your stated question, but I think it anticipates ways of thinking that are used in more advanced areas of physics.
There are two pictures of what a wave is.
A wave is coherent motion in a medium; as time progresses energy moves through the medium and vibrations occur in different locations.
A wave is a propagating disturbance. It is not made of anything, the word "wave" refers a disturbance which propagates energy from one place to another.
Your question kind of implies that a wave is some combination of 1 and 2. I would say that either 1 or 2 are valid pictures, but you should treat them as distinct pictures of the same physical phenomenon and not reason about both simultaneously.
The advantage of the first picture is that it gives you a clear mechanical model of what is going on at a fundamental level; if you zoom in there are particles in the material, and the particles are oscillating back and forth in tandem -- that coherent motion is a wave. However, the disadvantage is that wave phenomena occur in many circumstances, and there are features of any particular example that will not generalize and can lead you astray if you take them too seriously. For example, light traveling in vacuum cannot be accurately visualized as motion of particles.
The advantage of the second picture is that it is more abstract and general -- wave phenomena occur in all kinds of materials, and so there is no need to specify which specific material you are thinking of, because we can make very general statements about waves that apply to any material. The disadvantage is that it can be hard to wrap your head around a disturbance without a medium, and also sometimes trying to be too general means you miss special aspects of the particular situation you might be interested in (for example, cool behavior like solitons can occur in water but not in light propagating in vacuum).
The following is multiple choice question (with options) to answer.
What type of waves start when a source of energy causes a disturbance in the medium? | [
"mechanical waves",
"magnetic waves",
"mechanical currents",
"fluid waves"
] | A | Mechanical waves are waves that transfer energy through matter, called the medium. Mechanical waves start when a source of energy causes a disturbance in the medium. Types of mechanical waves include transverse, longitudinal, and surface waves. |
SciQ | SciQ-4209 | nitrogen
Step three is when plants and the animals that live of the plants die and breaks down into ammonia and other waste products (this is where many explanations of the nitrogen cycle usually starts). The waste products gets converted into ammonia by bacteria and the ammonia gets converted to nitrite and the entire cycle starts all over again.
Legumes have a symbiotic relationship with some bacteria that can fixate nitrogen (N2) https://aces.nmsu.edu/pubs/_a/A129/
sources:
https://science.howstuffworks.com/life/biology-fields/nitrogen-cycle.htm
https://www.britannica.com/science/denitrifying-bacteria
The rest is from my memory.
The following is multiple choice question (with options) to answer.
What term describes the process where organisms convert atmospheric nitrogen into biologically useful chemicals? | [
"photosynthesis",
"carbon cycle",
"cellular respiration",
"nitrogen fixation"
] | D | Most pure nitrogen comes from the fractional distillation of liquid air. The atmosphere consists of 78% nitrogen by volume. This means there are more than 20 million tons of nitrogen over every square mile of the earth’s surface. Nitrogen is a component of proteins and of the genetic material (DNA/RNA) of all plants and animals. Under ordinary conditions, nitrogen is a colorless, odorless, and tasteless gas. It boils at 77 K and freezes at 63 K. Liquid nitrogen is a useful coolant because it is inexpensive and has a low boiling point. Nitrogen is very unreactive because of the very strong triple bond between the nitrogen atoms. The only common reactions at room temperature occur with lithium to form Li3N, with certain transition metal complexes, and with hydrogen or oxygen in nitrogenfixing bacteria. The general lack of reactivity of nitrogen makes the remarkable ability of some bacteria to synthesize nitrogen compounds using atmospheric nitrogen gas as the source one of the most exciting chemical events on our planet. This process is one type of nitrogen fixation. In this case, nitrogen fixation is the process where organisms convert atmospheric nitrogen into biologically useful chemicals. Nitrogen fixation also occurs when lightning passes through air, causing molecular nitrogen to react with oxygen to form nitrogen oxides, which are then carried down to the soil. |
SciQ | SciQ-4210 | physical-chemistry
Title: Where and how do particles move? I've been thinking of making a simple 2d game of some sort involving particles and I've stumbled upon something I haven't really thought about. I know a lot about chemistry, so I'm not new to particles and their behavior, but I realized that I don't know how particles move. What causes them to move, and in what direction to they move. Take water molecules. When water is a liquid, it sticks together due to the polarity of water molecules, but due to the energy and motion of the molecules, it doesn't quite remain as a solid. In the gas state, the energy is even higher allowing the molecules to separate even farther from each other
The final question from all of this is if I were to simulate molecules/particles in a solid, liquid, and gas state, how would I make them move? The inter-molecular attractions are easy enough to code but the motion is what I don't understand. Do they just move randomly all the time, or is there a particular reason why a certain particle would move in a certain direction? Assuming the simplest of cases where the interaction is only during the collision, you can initiate your particles with random velocities sampled from Maxwell-Boltzmann distribution and random positions.
Then evolve them simply with their respective velocities until they collide, where you can use conservation of energy and momentum to decide new velocities. This is basically kinetic theory of gases.
The following is multiple choice question (with options) to answer.
As per the kinetic-molecular theory, in what direction do the molecules and ions of liquids move? | [
"alter directions",
"opposite direction",
"random directions",
"same direction"
] | C | We discussed earlier some basic principles about the behavior of gases called the kinetic-molecular theory. Among other things, this theory suggests that gas molecules are in constant motion, and the average speed of the individual gas particles is dependent upon temperature – the higher the temperature, the faster the molecules move. It is not just gas particles that are in constant motion. The molecules and ions that make up liquids and solutions are also continually moving in nearly random directions. As a result, molecules and ions in a solution will collide with one another fairly frequently. As with gases, a temperature increase will produce an increase in the average particle speed. |
SciQ | SciQ-4211 | evolution, anatomy, organs
Title: Why Is Most Life Symmetrical Externally But Not Internally? Mammals, reptiles, arachnids, insects, etc are all as far as I am aware symmetrical in appearance.
Take a human for instance, make a line from the top of our head right down the middle. However, internally it is not the same. Our organs excluding the kidneys, lungs, reproductive organs, etc are not symmetrically placed in our body.
The following is multiple choice question (with options) to answer.
Cephalization refers to the development of what anatomical region, which evolved at the same time as bilateral symmetry in animals? | [
"head",
"heart",
"chest",
"tail"
] | A | Example Problem: The density of steel is 9000. kg/m 3 and the density of water is 1000. kg/m 3 . If a cube of steel that is 0.100 m on each side is placed in a tank of water and weighed while under water, what is the apparent weight of the cube?. |
SciQ | SciQ-4212 | quantum-mechanics, atomic-physics, atoms, orbitals
The regions in the diagram correspond to single orbitals if the electron was only in that orbital (no superpositions)
The regions in the diagram just show part of the probability density. Technically the probability density is defined in all space, so all orbitals "overlap" at all points in space
The "location" of the electron does not determine which orbital it is in. If the electron is in some given orbital, we can then use the diagram to determine the most likely region the electron could be observed to be in.
The following is multiple choice question (with options) to answer.
What term describes a region of space around an atom that has a non-zero probability for an electron with a particular energy? | [
"related orbital",
"orbital lobe",
"minimal orbital",
"atomic orbital"
] | D | An atomic orbital is a region of space around an atom that has a non-zero probability for an electron with a particular energy. Analogously, a molecular orbital is a region of space in a molecule that has a non-zero probability for an electron with a particular energy. Both an atomic orbital and a molecular orbital can contain two electrons. |
SciQ | SciQ-4213 | reproduction, sociality, fitness
Title: Which monkey species features two distinct male phenotypes? I remember coming across a popular science article years ago about a monkey species which featured two male genotypes: the first were good looking males who acquired social status (as alphas or betas) within the group and could thus achieve reproductive succes. The alternative (less frequent) phenotype achieved similar fitness by adopting an outgroup (omega) lurking rapist kind of reproductive strategy.
Does anybody know which species and whose observervations I could be referring to? I'm curious to find out if this was a valid observation and if any further research has been done on this phenomenon. Patas monkeys exhibit "sneak mating" where a male other than the resident male sires offspring. Resident males do sire more offspring than sneaker males, but both strategies do co-occur. I'm pretty sure there are other species that have a similar mating strategy as well.
The following is multiple choice question (with options) to answer.
How do the male gorillas show display behaviors? | [
"vocalization",
"spontaneous mutation",
"showing aggression",
"food gathering"
] | C | In many species display behaviors, rather than actual physical attacks, are used to show aggression. This helps prevent injury and death. Male gorillas, for example, are more likely to put on a display of aggression than to attack another male. In fact, gorillas have a whole series of display behaviors that they use to show aggression. They beat on their chest, dash back and forth, and pound the ground with their hands. |
SciQ | SciQ-4214 | dna, chromosome
Title: Are the complementary base pairs known as genes? In my text book ,it is written that a chromosome has 1000s of genes and it is distributed throughout the chromatids except in the centromere. But we know that the chromosomes have DNAs inside them which have complementary base pairs. Then are these base pairs known as genes?? Don't assume a chromosome to be some X-shaped box that contains DNA inside it and DNA as a container of genes.
DNA, genes, Chromatid, Chromosomes are just different names at different levels of the same thing.
In molecular biology, you'll find multiple definitions of certain terms because as new insights are gained by any researcher, the definition gets modified. So one has to always make their concept clear so that they don't get confused between the same yet uniquely different terms.
So, Let's first look at how different their definitions can be:
DNA is a molecule inside cells that contains the genetic information responsible for the development and function of an organism. DNA molecules allow this information to be passed from one generation to the next. DNA is made up of a double-stranded helix held together by weak hydrogen bonds between purine-pyrimidine nucleotide base pairs: adenine (A) paired with thymine (T), and guanine (G) paired with cytosine (C). Also called deoxyribonucleic acid.
GENE, For many years the HGNC has maintained the definition of a gene as “a DNA segment that contributes to phenotype/function. In the absence of demonstrated function a gene may be characterized by sequence, transcription, or homology”. As there is still no universally agreed alternative we continue to use this definition.
Chromosome is a highly coiled structure of DNA molecule. Often observed in X-shaped only. Along with DNA, some proteins are also make up chromosomes.
The following is multiple choice question (with options) to answer.
A genetic molecule is called dna, which stands for this? | [
"dense ribonucleic acid",
"di-nitrous ammonia",
"deoxyribonucleic acid",
"dark nitrogen amine"
] | C | How Sciences Interconnect DNA in Forensics and Paternity The genetic material for all living things is a polymer of four different molecules, which are themselves a combination of three subunits. The genetic information, the code for developing an organism, is contained in the specific sequence of the four molecules, similar to the way the letters of the alphabet can be sequenced to form words that convey information. The information in a DNA sequence is used to form two other types of polymers, one of which are proteins. The proteins interact to form a specific type of organism with individual characteristics. A genetic molecule is called DNA, which stands for deoxyribonucleic acid. The four molecules that make up DNA are called nucleotides. Each nucleotide consists of a single- or double-ringed molecule containing nitrogen, carbon, oxygen, and hydrogen called a nitrogenous base. Each base is bonded to a five-carbon sugar called deoxyribose. The sugar is in turn bonded to a phosphate group (−PO 4 3−) When new DNA is made, a polymerization reaction occurs that binds the phosphate group of one nucleotide to the sugar group of a second nucleotide. The nitrogenous bases of each nucleotide stick out from this sugar-phosphate backbone. DNA is actually formed from two such polymers coiled around each other and held together by hydrogen bonds between the nitrogenous bases. Thus, the two backbones are on the outside of the coiled pair of strands, and the bases are on the inside. The shape of the two strands wound around each other is called a double helix (see Figure 20.18). It probably makes sense that the sequence of nucleotides in the DNA of a cat differs from those of a dog. But it is also true that the sequences of the DNA in the cells of two individual pugs differ. Likewise, the sequences of DNA in you and a sibling differ (unless your sibling is an identical twin), as do those between you and an unrelated individual. However, the DNA sequences of two related individuals are more similar than the sequences of two unrelated individuals, and these similarities in sequence can be observed in various ways. This is the principle behind DNA fingerprinting, which is a method used to determine whether two DNA samples came from related (or the same) individuals or unrelated individuals. |
SciQ | SciQ-4215 | sleep
Title: What are the essential criteria for sleep in living organisms? I was reading this fascinating article about how sleep evolved before brains, and it got me thinking "can plants sleep" and "what is sleep anyway".
A line in the article states:
Studies by a team in South Korea and Japan showed that the hydra
periodically drops into a rest state that meets the essential criteria
for sleep.
But after looking around I am unable to find the "essential criteria for sleep" - Before I am able to answer questions like "can plants sleep" I think I first need to understand what these essential criteria for sleep actually are.
Can anyone here help me out? Many thanks in advance. I take it you did not even read the article. The article quite nicely expounds on this question. The whole idea is that sleep used to be considered as a human or psychological phenomenon that could only be studied by EEG, and clearly sleep was a phenomenon that goes deeper and wider in biology than just EEG waves. From the same article, just a little below:
She distilled a set of behavioral criteria to identify sleep without the EEG. A sleeping animal does not move around. It is harder to rouse than one that’s simply resting. It may take on a different pose than when awake, or it may seek out a specific location for sleep. Once awakened it behaves normally rather than sluggishly. And Tobler added a criterion of her own, drawn from her work with rats: A sleeping animal that has been disturbed will later sleep longer or more deeply than usual, a phenomenon called sleep homeostasis.
The keyword is behavioral criteria.
This is cited, I recommend a read-through.
I also recommend reading the rest of the article, it guides you through the status quo in sleep science which may further answer more of your questions. At the end, there is an exposition on animals without brains that seem to be sleeping. The hydra is one of them.
The following is multiple choice question (with options) to answer.
Is sleep an active or inactive state in the brain? | [
"active",
"intense",
"different",
"inactive"
] | A | |
SciQ | SciQ-4216 | was in the air (between Point 1 and Point 3. A similar but more complete diagnostic test is being developed, but the subject of measurement uncertainty does not lend itself well to a right/wrong test, so even experts may disagree about which answers are "right" on such a test. 0 g and the masses to the left of the fulcrum are. c) Find the magnitude of the tension of the string between m2 and m3. If one of the balloons changes mass, we will be able to tell because the meter stick will 'tilt' towards the more massive object. The basic physics behind this activity is self-evident. They are both charged with charge q and both have mass m. nuts, washers, masses with hooks). One of the. The average deviation, = 0. 12 Static Equilibrium and Elasticity. This will either be provided to you in the problem statement, or it would have been previously determined from prior calculations. Similarly, a measurement like 0. Various hanging masses can be attached to the meter stick at various spots. Slide the supporting (knife-edge) clamp on the meter-stick and balance the meter stick alone on the support stand. More recently (1984), the Geneva Conference on Weights and Measures has defined the meter as the distance light travels, in a vacuum, in 1/299,792,458 seconds with time measured by a cesium-133 atomic. Make sure that the meter stick starts with 0 is at the bottom. Questions on parallel forces acting on a body are solved using the *principle of moment. Eventually, the object comes. Stanley Kowalski. F S F S is the normal reaction force at the. This is called the center of mass. Attach the 500-g spring scale at the far end of the meter stick so that the weight-bearing hook. Find F e, d e, F r, d r in gram force. Could a possible newfound carrier boson expand the definition of that framework? And it'll take XIV minutes flat. We indicate the pivot and attach five vectors representing the five forces along the line representing the meter stick, locating the forces with respect to the pivot. Use the 500-g spring balance to determine the mass of your “weights. Problem #6: Rolling and Torque 117. Hewitt, P. Two forces, both parallel to the tabletop, are applied to the stick in such a way that the net torque is zero. This is the
The following is multiple choice question (with options) to answer.
What is is a measurement of the force amplification of a machine? | [
"force multiplier",
"mechanical pull",
"mechanical push",
"mechanical advantage"
] | D | We use simple machines because they give us a mechanical advantage . Mechanical advantage is a measurement of the force amplification of a machine. In ideal machines, where there is no friction and the input work and output work are the same,. |
SciQ | SciQ-4217 | geophysics, seismology, core
Title: Why does seismic activity shed light on the inner core rigidity? Reading Introduction to Geology (MIT 2005) and Wikipedia's article on Earth's inner core, it is specified that:
Earth was discovered to have a solid inner core distinct from its liquid outer
core in 1936, by the seismologist Inge Lehmann, who deduced its presence from observations of earthquake-generated seismic waves that reflect off the boundary of the inner core and can be detected by sensitive seismographs on the Earth's surface.
Why does seismic activity would result in the conclusion that the inner core is rigid? What is the link between seismism and inner core? The question that Azzie Rogers linked to: How can we determine the size and composition of Earth's inner core?
Does answer the theory part of the question, but I will extrapolate a little more to answer the question.
The question becomes, what kind of waves travel through what? Both shear and compressional seismic waves can travel through solids, but as it turns out, you cannot shear a liquid. As you look at teleseismic raypaths (waves traveling far from the source) you can see that the wave must travel deep into the earth and then back up again. The wave forms, and directions of these wavepaths will be altered by the different compositions of Earth's layers as it travels through: a wave just traveling through the mantle will have both its shear and compressional component. A wave traveling through the mantle and outer core will lose its original shear component, and either develop a new one as it leaves the core (but distinct from the wave that travels through the mantle only) or not have one at all. And finally, a wave that travels through the mantle, outer core and inner core will have distinct wave patters as well. Its by this comparison of waveforms that we realize that the earth not only has different compositional layers, but phase boundaries as well. I am not sure seismology alone would lead to a solid inner core, but there is abundant evidence supporting that fact. When you combine Seismology, rare bits of geochemistry, the calculation of Earth's gravity , and perhaps the most important part, the magnetic dynamo generating our magnetic field, we see a fairly clear ( albeit incomplete) story.
The following is multiple choice question (with options) to answer.
What branch of science is the study of the solid earth? | [
"biology",
"geology",
"palentology",
"ecology"
] | B | Geology is the study of the solid Earth. Geologists study how rocks and minerals form. The way mountains rise up is part of geology. The way mountains erode away is another part. Geologists also study fossils and Earth’s history. There are many other branches of geology. There is so much to know about our home planet that most geologists become specialists in one area. For example, a mineralogist studies minerals ( Figure below ). |
SciQ | SciQ-4218 | water
Title: What additives could make a masonry unit water-repellent but vapor-permeable? I'm curious about some of the wondrous materials available today are able to repel liquid water but permit water vapor to pass through. I've heard that housewrap-type plastics accomplish this by being perforated with microscopic holes that are slightly too large for liquid water, but large enough for the vaporous form to pass through. I have no idea how silicate mineral paints do it, though.
Housewraps and paints are thin films, though. I'd like to learn about how such properties could be imparted to a masonry unit like a compressed earth block. Could you cast such a block with a mixture of soil and some additive that would grant this kind of water repellency but allow water vapor to pass though? The answer turned out to be waterglass. That's the carrier for silicate mineral paints.
The following is multiple choice question (with options) to answer.
What is harmless water vapor, for a powerplant? | [
"fog",
"plasma",
"wind",
"steam"
] | D | Steam rises from the cooling towers of this nuclear power plant. The steam is only harmless water vapor. Unlike a power plant that burns fossil fuel, a nuclear power plant doesn’t release pollution into the air. That’s because a nuclear power plant produces power by nuclear fission, a type of nuclear reaction. |
SciQ | SciQ-4219 | blood-circulation, kidney
Title: Why does glomerulus don't allow white blood cells to leave? The glomerulus in nephrons are just a ball of capillaries, so why can't it allow the white blood cells to squeeze though the epithelial cells into Bowman's capsule just like the formation of tissue fluid in other capillaries by filtration? Red blood cells, White blood cells, platelets and proteins with large molecular weight cannot pass through the podocyte and fenestrations in glomerular capillary, but small molecules like water, salts and sugars are filtered out as part of urine.
As these cells and proteins are large to cross through this filter, they remain in the capillary and create osmotic pressure within the capillary. Bowman’s space has osmotic pressure approximately zero. So, only hydrostatic pressure works in this state and help in movement of fluid across the capillary wall.
Via: https://opentextbc.ca/anatomyandphysiology/chapter/25-5-physiology-of-urine-formation/
The following is multiple choice question (with options) to answer.
What regulates the passage of blood into capillary beds? | [
"precapillary sphincters",
"diocesan sphincters",
"bicellular sphincters",
"cell membrane"
] | A | |
SciQ | SciQ-4220 | botany, plant-physiology, ecology, virology, host-pathogen-interaction
Note about symbiosis - comes in reaction to @Gerhard's comment
Different authors use the word symbiosis differently. From wikipedia:
The definition of symbiosis is controversial among scientists. Some believe symbiosis should only refer to persistent mutualisms, while others believe it should apply to any type of persistent biological interaction (i.e. mutualistic, commensalistic, or parasitic).4 After 130+ years of debate,5 current biology and ecology textbooks now use the latter "de Bary" definition or an even broader definition (i.e. symbiosis = all species interactions), with the restrictive definition no longer used (i.e. symbiosis = mutualism)
The following is multiple choice question (with options) to answer.
What do you call the symbiotic relationship where a parasite benefits while the host is harmed? | [
"invasion",
"hostism",
"parasitism",
"symbolic damage"
] | C | Parasitism is a symbiotic relationship in which the parasitic species benefits while the host species is harmed. |
SciQ | SciQ-4221 | human-biology
Title: Do biological facts determine when a human fetus is considered alive and human? I often hear or read this statement:
"It's not a human, it's a fetus."
In other words, some think a fetus is non-human until a certain point.
And another similar statement:
"The fetus isn't alive until 26 weeks of gestation."
So some think the fetus is not actually "alive" until a certain point.
What does biology have to say about these two statements?
I encounter these statements often in discussions about abortion, but that issue, and other similar philosophical issues, are outside this question. I'm wondering strictly from a scientific/biological standpoint: are these statements true?
Is the fetus in a human mother non-human until a certain point?
Does the fetus not classify as "alive" until a certain point?
The people I encountered truly believed these statements (3 of the 4 in mind also claimed science was on their side), so it's not as if the question has no merit. I assumed that in the realm of science and biology, there must be a convincing and sure answer. Life is generally distinguished from non-life by metabolism and growth. As such, a fetus is alive. The reference to "not...until 26 weeks gestation" that you've heard likely refers to viability.* With the most aggressive medical care, this is the approximate age when a fetus may be able to survive outside the womb.
The term human from a biologic perspective is a species label.** Given that a fetus is genetically indistinguishable (in broad strokes) from a post-natal human, I think it would be hard to argue that it is anything other than human.
Summary: Yes, a human fetus is both alive and human.
*Note that this use of the word viable is standard but deviates somewhat from the etymology of the word.
**I'm ignoring here other ancient species (homo-) which may be considered human but are irrelevant to the question.
The following is multiple choice question (with options) to answer.
What length of time is human gestation commonly divided into? | [
"three trimesters",
"four quarters",
"two halves",
"fifty weeks"
] | A | |
SciQ | SciQ-4222 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
What substance, involved in most biochemical reactions, is essential to life? | [
"water",
"carbon",
"nitrogen",
"air"
] | A | Water is involved in most biochemical reactions. Therefore, water is essential to life. |
SciQ | SciQ-4223 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
What type of tissue covers the outside of a plant? | [
"anterior",
"epidermal",
"porous",
"dermal"
] | D | Dermal tissue covers the outside of a plant in a single layer of cells called the epidermis. It mediates most of the interactions between a plant and its environment. |
SciQ | SciQ-4224 | geology, mineralogy, minerals, metamorphism
Title: Is there any mineral that survives hard degree metamorphism? When a protolith enters in metamorphism, the minerals transform in other new stable minerals while the pressure and/or temperature increase.
Is there any mineral that would not be affected by a high degree metamorphism processes and would remain the same without experiencing any change? Zircon is one mineral which survives metamorphism.
Zircons can survive processes like erosion, transport and metamorphism, so they preserve a record of past geological processes.
From Wikipedia,
Zircon is common in the crust of Earth. It occurs as a common accessory mineral in igneous rocks (as primary crystallization products), in metamorphic rocks and as detrital grains in sedimentary rocks.
This makes zircon very useful in determining the age of rocks.
The following is multiple choice question (with options) to answer.
Metamorphic rocks form when an existing rock is changed by heat or what? | [
"chemical reaction",
"radiation",
"cold",
"pressure"
] | D | Metamorphic rocks form when an existing rock is changed by heat or pressure. The minerals in the rock change but do not melt. The rock experiences these changes within the Earth. |
SciQ | SciQ-4225 | molecular-biology, molecular-genetics, development, sex
Quote from a Review (Yao 2005):
We have just begun to glimpse into the mechanisms underlying ovarian development. Convincing evidence challenges us to reconsider the existing paradigm that describes ovarian development as a default system. The default concept was first proposed in the early 1950s when Jost performed the groundbreaking experiments to demonstrate mechanisms of sex differentiation of reproductive tracts (Jost, 1947, 1953, 1970). The term “default” was not originally intended to describe the developmental status of the ovary. Instead, it is referred to the female reproductive tract or the Mullerian duct based on the fact that the female reproductive tract forms in both XX and XY individuals in the absence of gonads. Indeed, now it has become evident that early ovarian development is an active process involving intrinsic cell fate decisions and complex crosstalks between germ cells and somatic cells. Most intriguingly, the appearance of testicular structures in XX individuals where Sry and its downstream components are absent further raises the improbable question: Could the testicular development be default after all?
The following is multiple choice question (with options) to answer.
What anatomical structure serves as the conduit of the oocyte from the ovary to the uterus? | [
"nephrons",
"urethra",
"uterine tubes",
"ureters"
] | C | The Uterine Tubes The uterine tubes (also called fallopian tubes or oviducts) serve as the conduit of the oocyte from the ovary to the uterus (Figure 27.14). Each of the two uterine tubes is close to, but not directly connected to, the ovary and divided into sections. The isthmus is the narrow medial end of each uterine tube that is connected to the uterus. The wide distal infundibulum flares out with slender, finger-like projections called fimbriae. The middle region of the tube, called the ampulla, is where fertilization often occurs. The uterine tubes also have three layers: an outer serosa, a middle smooth muscle layer, and an inner mucosal layer. In addition to its mucus-secreting cells, the inner mucosa contains ciliated cells that beat in the direction of the uterus, producing a current that will be critical to move the oocyte. Following ovulation, the secondary oocyte surrounded by a few granulosa cells is released into the peritoneal cavity. The nearby uterine tube, either left or right, receives the oocyte. Unlike sperm, oocytes lack flagella, and therefore cannot move on their own. So how do they travel into the uterine tube and toward the uterus? High concentrations of estrogen that occur around the time of ovulation induce contractions of the smooth muscle along the length of the uterine tube. These contractions occur every 4 to 8 seconds, and the result is a coordinated movement that sweeps the surface of the ovary and the pelvic cavity. Current flowing toward the uterus is generated by coordinated beating of the cilia that line the outside and lumen of the length of the uterine tube. These cilia beat more strongly in response to the high estrogen concentrations that occur around the time of ovulation. As a result of these mechanisms, the oocyte–granulosa cell complex is pulled into the interior of the tube. Once inside, the muscular contractions and beating cilia move the oocyte slowly toward the uterus. When fertilization does occur, sperm typically meet the egg while it is still moving through the ampulla. |
SciQ | SciQ-4226 | 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 cell structures are like storage centers and tend to be larger in plant cells? | [
"alleles",
"vacuoles",
"tubules",
"nuclei"
] | B | The vacuoles are like storage centers. Plant cells have larger vacuoles than animal cells. Plants store water and nutrients in their large central vacuoles. |
SciQ | SciQ-4227 | molecular-biology, circadian-rhythms, gene-regulation
Title: High frequency human genetic oscillators? The most well studied genetic oscillators in human genomes are involved in regulating the circadian clock (which operates on an approximately 24-hour cycle) and cell cycle activity (with single cycles usually lasting several hours to many days). Are there any known genetic oscillators in humans (or other mammals) that operate on shorter timescales? Here are some examples:
electric oscillators:
neural activity
cardiac automatism (0.8 ... 1 Hz)
mechanical oscillators (as a result of neural activity):
heart beats
breathing (0.2 ... 0.3 Hz)
intestinal peristaltic waves
vocal chords activity (up to a few kHz)
muscular spasm (pathological)
chemical oscillators:
insulin variation in concordance with glucose intake
endocrine oscillations
menstruation
feedback enabled metabolic pathways
See this Wikipedia page too: http://en.wikipedia.org/wiki/Oscillation#Human
When it comes to genetic oscillators, some of them follow circadian rhythm.
A typical proliferating human cell divides on average every 24 h. This division timing allows cells to synchronize with other physiological processes and with the environment. The circadian clock, which orchestrates daily rhythms, directly regulates the cell division cycle and is a major synchronizing factor [5].
Immune system:
In every single cell an oscillator goes ticking through a molecular clock operated by transcriptional/translational feedback loops driven by the rhythmic expression of circadian genes. This clock gene machinery steers daily oscillations in the regulation of immune cell activity, driving the periodicity in immune system function [1].
Glucose homeostasis:
The master circadian clock, localized in suprachiasmatic nucleus (SCN), regulates multiple metabolic pathways, while feeding behavior and metabolite availability can in turn regulate the circadian clock [2].
Retina:
The following is multiple choice question (with options) to answer.
Oscillations in the transcription of certain genes are at the heart of the molecular mechanisms underlying what biological rhythms? | [
"circadian rhythms",
"brain rhythms",
"metastasis rhythms",
"reproductive rhythms"
] | A | |
SciQ | SciQ-4228 | newtonian-mechanics, forces, rotational-dynamics, reference-frames, torque
Of course, when the time constants of all of these spring is short, as it is with the kinds of interactions we are interested in here, this real behavior gets close and closer to a "rigid body" like behavior. Indeed, what we can show is that this "rigid body" style rotation is one example of what happens when you assume that physics is local. If you assume that a piece of the object only "knows" things in the neighborhood of that piece, you find there is no way to avoid rotation. To have the object translate directly away from you when you push off-center requires that far parts of the object instantly "know" the correct direction to travel.
The following is multiple choice question (with options) to answer.
Give an example of a ball-and-socket joint, which has the greatest range of motion, allowing movement in several directions. | [
"monkey wrench",
"pulley",
"lever",
"shoulder"
] | D | There are a variety of types of movable joints, which are illustrated in Figure below . The joints are classified by how they move. For example, a ball-and-socket joint , such as the shoulder, has the greatest range of motion, allowing movement in several directions. Other movable joints, including hinge joints such as the knee, allow less movement. |
SciQ | SciQ-4229 | electromagnetism, electrostatics, potential-energy
Aside: there is a unit of energy which derives from the relationship between charge, potential and energy described above. It's called electronvolt: 1eV is the amount of electrostatic potential energy that a particle with electric charge equal to the charge of electron gains as it moves across electric potential difference of 1V.
*The curious properties of static electric field alluded to above are formalized using mathematical notion of conservative vector field (of which electric field produced by a group of static charges is an example).
The following is multiple choice question (with options) to answer.
Difference in electric potential energy are measured in what basic unit? | [
"volts",
"moles",
"watts",
"knots"
] | A | The difference in electric potential energy is measured with a voltmeter in units called volts. |
SciQ | SciQ-4230 | astronomy, planets, stars, exoplanets
Title: What is the percentage of stars with planetary systems We have discovered quite a number of exoplanets to date. The Kepler spacecraft has examined 150,000 stars and found 1,059 exoplanets.
We know that Kepler, as well as all other exoplanet searches to date, can only find planets that cross in front of their star. That means that a large percentage of existing planets will not be detected. In addition, a lot of planets may be too small for the sensitivity of our detectors.
From these facts, has anyone calculated the probability of a star having a planetary system? I am guessing it is likely quite close to 1, i.e. all stars have planets, but I have not seen anyone figures for it. There are several different estimates, based on several factors. The article One or more bound planets per Milky Way star
from microlensing observations (Cassan et al. 2011) suggests that your estimate that the probability being close to 1, suggesting that
One or more bound planets per Milky Way star
from microlensing observations
If you take particular types of exoplanets as examples - such as, according to the Keck Observatory article One in Five (sun like) Stars Has Earth-sized Planet in Habitable Zone (2013), through a combination of monitoring and modelling, they have determined
Accounting for missed planets, as well as the fact that only a small fraction of planets are oriented so that they cross in front of their host star as seen from Earth, allowed them to estimate that 22 percent of all sun-like stars in the galaxy have Earth-size planets in their habitable zones.
The following is multiple choice question (with options) to answer.
How many stars are in our solar system? | [
"none",
"two",
"three",
"one"
] | D | Our solar system has only one star. But many stars are in systems of two or more stars. Two stars that orbit each other are called a binary star system . If more than two stars orbit each other, it is called a multiple star system. Figure below shows two binary star systems orbiting each other. This creates an unusual quadruple star system. |
SciQ | SciQ-4231 | mountains, rainfall
Title: Could a waterfall lashing onto a road lead to a landslide? Here is a video of a waterfall lashing on to a mountain road, with vehicles driving under it.
https://youtu.be/cHaguj--YBc
There appears to be a big hole carved out right next to the road, possibly by the force of the waterfall.
Is this a ticking time bomb for a landslide? Potentially, a landslide could occur. Whether it would be a minor slip or a major fall depends on the geological conditions at the site, the force of the water and the duration that the site is impacted by the water.
In the video in question, the rock face above the road appears competent, but there are not guarantees. The main issue would be is the water undermining the road which could cause a slip and the road to slide.
The more loose the geological material is, the easier it is to dislodge it. Once one item moves a chain of events can occur where additional items are dislodged and a slide occurs.
In addition to high pressure water dislodging material, water acts as a lubricant, making it easier for rocks and regolith to be dislodged.
To minimise the potential for a slide to occur in such a situation, the surface of the road would need to be sealed very well and a very good drainage system installed that would move the water away from the road and the slope below the road
The following is multiple choice question (with options) to answer.
Landslides and mudslides are the most destructive types of what geologic phenomenon? | [
"land momentum",
"formation movement",
"intensity movement",
"mass movement"
] | D | The most destructive types of mass movement are landslides and mudslides. Both occur suddenly. |
SciQ | SciQ-4232 | geology, rocks, sedimentology, geomorphology, terminology
Title: What do you call boulders of non sedimentary rock that were lithified into sandstone? I'm convinced there is a word for this. I was in the Hoodoos at Writing on Stone this weekend and kept noticing what looked like reddish quartzite boulders laying around in the sand, or sometimes sticking partially out of the hoodoos.
When a non-sedimentary rock gets washed out into silt which later lithifies, what's it called? It's kind of like a conglomerate, except there's only a couple of really big rocks, which eventually fall out out the rock because all the sandstone around them eroded away. The technical term for a sedimentary rock that has a lithified fine-grained sediment with larger pieces of rocks suspended in it upon lithification is a conglomerate. The fine-grained interstitial part is called the matrix, and the large pieces suspended in it are called clasts. Clasts can range from gravel- to boulder-size. These are technical terms used by sedimentologists.
It is tempting to refer to these fragments as xenoliths but as that word has a very specific meaning in igneous petrology, it is best to avoid it to remove any confusion.
The following is multiple choice question (with options) to answer.
What scientific word, which gives its name to a type of rock, means "to change form"? | [
"igneous",
"metamorphism",
"evolution",
"evaporation"
] | B | Metamorphism. This long word means “to change form. “ A rock undergoes metamorphism if it is exposed to extreme heat and pressure within the crust. With metamorphism , the rock does not melt all the way. The rock changes due to heat and pressure. A metamorphic rock may have a new mineral composition and/or texture. |
SciQ | SciQ-4233 | 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.
The sporophyte phase is the longest phase in the life of what? | [
"echinoderm",
"angiosperm",
"gymnosperm",
"arthropod"
] | C | Figure 26.8 illustrates the life cycle of a conifer. The sporophyte (2n) phase is the longest phase in the life of a gymnosperm. The gametophytes (1n)—microspores and megaspores—are reduced in size. It may take more than year between pollination and fertilization while the pollen tube grows towards the megasporocyte (2n), which undergoes meiosis into megaspores. The megaspores will mature into eggs (1n). |
SciQ | SciQ-4234 | organic-chemistry, biochemistry, color, electromagnetic-radiation
Title: How does UV affect skin colors in dark-skinned people? Skin color is one of the things one would rather not ask anything about! Only in humans, it can vary from very dark brown to pale pink. In darker-skinned people, the color is mainly due to melanin, which is produced by melanocytes.
There are three types of melanin: eumelanin, pheomelanin, and neuromelanin. Eumelanin is the most common; so it must be the reason of the dark skin of the dark-skinned. And that's true, since the two major groups of eumelanin are black and brown species.
The first ray produced by sun that comes to mind when you think about affecting the attributes of skin is UVA, since it penetrates most into the skin (Even though its energy is lesser than UVB). So, when I attach these two together I reach the fact that if UV rays do not cause free radicals they will eventually change the skin's color. (This is what is mostly believed and its effect on natural selection is impossible to hide)
Now, I give up. How does UV do to the skin that makes it darker? This must be very easy, huh? What am I missing? There is a journal article almost exactly about the title question, Mechanisms of Skin Tanning in Different Racial/Ethnic Groups in Response to Ultraviolet Radiation Journal of Investigative Dermatology (2005) 124, 1326–1332.
However, the body of the question assumes that eumelanin changes color. Instead, the article finds that melanin gets closer to the surface of the skin, and the degree to which this effect occurs varies with race/ethnicity.
The following is multiple choice question (with options) to answer.
Hair color and skin color are known as what? | [
"habits",
"mutations",
"traits",
"abominations"
] | C | What is the difference between a trait and a genetic disorder ? Could a disorder be considered a trait? We tend to think of traits as hair color or skin color and disorders as something that is bad for you. But in terms of genetics, a genetic disorder is a trait. Both may be due to your genes. Traits may be inherited in any of a number of ways: autosomal dominant or recessive, sex-linked inheritance, or a more complex pattern of inheritance. |
SciQ | SciQ-4235 | organic-chemistry, structural-formula, amines, identification
Title: Identify two amines I was reading a random text about the surface chemistry of YBaCuO superconductors. In the text, there was a table. The table had a list of several chemical compounds, including these two:
Alkyl Amine: FcC(O)NH(CH2)4NH2
Aryl Amine: p-Fc-C6H4-NH2
Two amines. After extensive search, I was unable to find a structural formula for it (the closest I've found was this). I even tried to draw all structural formulas I could think off in a piece of paper. But I couldn't draw a single one satisfying the second one (the easiest probably).
Can you identify these amines? What's their structural formula? The proposed strucutre of these compound are, correct me if i am wrong.
The following is multiple choice question (with options) to answer.
Amines are classified according to the number of carbon atoms bonded directly to what atom? | [
"oxygen",
"helium",
"hydrogen",
"nitrogen"
] | D | 15.11 Amines: Structures and Names LEARNING OBJECTIVES Identify the general structure for an amine. Identify the functional group for amines. Determine the structural feature that classifies amines as primary, secondary, or tertiary. Use nomenclature systems to name amines. Amines are classified according to the number of carbon atoms bonded directly to the nitrogen atom. A primary (1°) amine has one alkyl (or aryl) group on the nitrogen atom, a secondary (2°) amine has two, and a tertiary (3°) amine has three (http://catalog. flatworldknowledge. com/bookhub/reader/2547. |
SciQ | SciQ-4236 | quantum-mechanics, atomic-physics
Title: Just why electrons don't fall into nucleus? I think I finally got it, after hearing 1000 times.
Long story short: in ground state and some similar,
electron's wavefunction is spherical, with a nucleus being at the center, which is exactly what can be considered a "collision".
The difference is that there're no such quantum numbers onboard both an electron and nucleus that would allow them to, say, annihilate, like in a case with positron.
Therefore, they're basically ignoring each other; except for EM interaction, of course.
And the shapes of orbitals? Well, they depend on just a kinetic energy of an electron.
..So, yeah :) question is, how incorrect is that. If I understand correctly you are already happy with the idea that the electron is delocalised over the region around the nucleus, and that the uncertainty principle prevents it from shrinking down to a point. In that case your key question is related to your statement:
The difference is that there're no such quantum numbers onboard both an electron and nucleus that would allow them to, say, annihilate, like in a case with positron.
That is you are really asking why even though the electron overlaps with the proton it does not interact with the proton to form some new particle.
If this is the case then your statement is basically correct but with one exception - an electron can react with a proton to form a neutron. This reaction is energetically unfavourable so it does not happen in most atoms. However there are a few atoms where the conversion of the proton to a neutron increases the nuclear binding energy and this supplies enough energy for the reaction to happen. This process is called electron capture.
The following is multiple choice question (with options) to answer.
Because core electrons are closer to the nucleus, they are not involved in what? | [
"bonding",
"diffusion",
"fission",
"splitting"
] | A | Core electrons are the electrons that are closer to the nucleus and therefore do not participate in bonding. |
SciQ | SciQ-4237 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
The upper portion of the septum is formed by the perpendicular plate of which bone? | [
"colossal bone",
"ethmoid bone",
"duodenum bone",
"concomitant bone"
] | B | The Nasal Septum and Nasal Conchae The nasal septum consists of both bone and cartilage components (Figure 7.17; see also Figure 7.11). The upper portion of the septum is formed by the perpendicular plate of the ethmoid bone. The lower and posterior parts of the septum are formed by the triangular-shaped vomer bone. In an anterior view of the skull, the perpendicular plate of the ethmoid bone is easily seen inside the nasal opening as the upper nasal septum, but only a small portion of the vomer is seen as the inferior septum. A better view of the vomer bone is seen when looking into the posterior nasal cavity with an inferior view of the skull, where the vomer forms the full height of the nasal septum. The anterior nasal septum is formed by the septal cartilage, a flexible plate that fills in the gap between the perpendicular plate of the ethmoid and vomer bones. This cartilage also extends outward into the nose where it separates the right and left nostrils. The septal cartilage is not found in the dry skull. Attached to the lateral wall on each side of the nasal cavity are the superior, middle, and inferior nasal conchae (singular = concha), which are named for their positions (see Figure 7.13). These are bony plates that curve downward as they project into the space of the nasal cavity. They serve to swirl the incoming air, which helps to warm and moisturize it before the air moves into the delicate air sacs of the lungs. This also allows mucus, secreted by the tissue lining the nasal cavity, to trap incoming dust, pollen, bacteria, and viruses. The largest of the conchae is the inferior nasal concha, which is an independent bone of the skull. The middle concha and the superior conchae, which is the smallest, are both formed by the ethmoid bone. When looking into the anterior nasal opening of the skull, only the inferior and middle conchae can be seen. The small superior nasal concha is well hidden above and behind the middle concha. |
SciQ | SciQ-4238 | 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.
Cells in green algae divide along cell plates called what? | [
"chloroplasts",
"phragmoplasts",
"cellulose",
"xanthophylls"
] | B | Streptophytes Until recently, all photosynthetic eukaryotes were considered members of the kingdom Plantae. The brown, red, and gold algae, however, have been reassigned to the Protista kingdom. This is because apart from their ability to capture light energy and fix CO2, they lack many structural and biochemical traits that distinguish plants from protists. The position of green algae is more ambiguous. Green algae contain the same carotenoids and chlorophyll a and b as land plants, whereas other algae have different accessory pigments and types of chlorophyll molecules in addition to chlorophyll a. Both green algae and land plants also store carbohydrates as starch. Cells in green algae divide along cell plates called phragmoplasts, and their cell walls are layered in the same manner as the cell walls of embryophytes. Consequently, land plants and closely related green algae are now part of a new monophyletic group called Streptophyta. The remaining green algae, which belong to a group called Chlorophyta, include more than 7000 different species that live in fresh or brackish water, in seawater, or in snow patches. A few green algae even survive on soil, provided it is covered by a thin film of moisture in which they can live. Periodic dry spells provide a selective advantage to algae that can survive water stress. Some green algae may already be familiar, in particular Spirogyra and desmids. Their cells contain chloroplasts that display a dizzying variety of shapes, and their cell walls contain cellulose, as do land plants. Some green algae are single cells, such as Chlorella and Chlamydomonas, which adds to the ambiguity of green algae classification, because plants are multicellular. Other algae, like Ulva (commonly called sea lettuce), form colonies (Figure 25.7). |
SciQ | SciQ-4239 | paleontology, taphonomy
Title: How are organic walled microfossils preserved in the fossil record? Organic walled microfossils have no hard mineralised parts, how are they preserved in the fossil record? Organic-walled microfossils (wether they be dinoflagellates, pollens, spores or "acritarchs") all have in common to contain an organic compound known as sporopollenin (for the spores and pollens) or dinosporin (for dinoflagellates and, I believe, acritarchs as well). Both compounds have chemical and structural similarities but have appeared independently.
Those compound are incredibly resistant. To give you an idea, to collect siliceous microfossils we first dissolve the sediments with HCl (hydrochloric acid) to get rid of carbonate microfossils. Palynologists (who study such organic-walled microfossils) uses HF (hydrofluoric acid) to get rid of both carbonate and siliceous microfossils (e.g. Doher 1980). Sporopollenin therefore resist to HF, which has a pH of ca. 3. In addition to this, they are also unusually resistant to microbiological degradation (e. g. Gunnison & Alexander 1975).
They are however not resistant to oxydation, hence, probably, why we don't find more of them in the sediments. Additionally, to break sporopollenin walls (in order to study the inner side of those walls) ultrasound can be used (e. g. Lennie 1968).
"Organic-walled" doesn't mean no hard part, it just means no "mineral" hard part.
Sources:
Doher, I., 1980. Palynomorph preparation procedures currently used in the paleontology and stratigraphy laboratories, U.S. Geological Survey. Geological Survey circular, 830: 1-29.
Gunnison, D., Alexander, M., 1975. Basis for the resistance of several algae to microbial decomposition. Applied Microbiology, 29: 729-738.
Lennie, C. R., 1968. Palynological Techniques used in New Zealand. New Zealand Journal of Geology and Geophysics, 11: 1211-1221.
The following is multiple choice question (with options) to answer.
What are saprobes that decompose organic matter? | [
"protists",
"chordates",
"sponges",
"fungi"
] | D | 24.3 Ecology of Fungi Fungi have colonized nearly all environments on Earth, but are frequently found in cool, dark, moist places with a supply of decaying material. Fungi are saprobes that decompose organic matter. Many successful mutualistic relationships involve a fungus and another organism. Many fungi establish complex mycorrhizal associations with the roots of plants. Some ants. |
SciQ | SciQ-4240 | human-biology, food
Title: Can humans eat grass? Can a human eat grass and digest it?
Could it be possible to use it as food just like other plants such as wheat or beans? To elaborate on A random zoologist's answer, the problem is that the human digestive system does not contain any cellulase enzymes. Cellulases are a class of enzymes that break down cellulose, the chief structural component of plants. You might be able to obtain a small amount of nutrition from grass or other cellulose-rich materials, but as the plant cell walls are made of cellulose, most of the plant material will be indigestible.
The following is multiple choice question (with options) to answer.
Because complex plant carbohydrates such as cellulose are more difficult to digest, what animal diet is associated with a complicated digestive system? | [
"herbivore",
"carnivore",
"polyvore",
"omnivore"
] | A | Different diets require different types of digestive systems. Mammals that eat a carnivorous diet generally have a relatively simple digestive system. Their food consists mainly of proteins and fats that are easily and quickly digested. Herbivorous mammals, on the other hand, tend to have a more complicated digestive system. Complex plant carbohydrates such as cellulose are more difficult to digest. Some herbivores have more than one stomach. The stomachs store and slowly digest plant foods. |
SciQ | SciQ-4241 | 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 are all cells surrounded by? | [
"amino acids",
"cytoplasm",
"cell membrane",
"cell substrate"
] | C | Heat waves have increased in frequency and duration in recent years. The summer 2011 North American heat wave brought record temperatures across the Midwestern and Eastern United States. Many states and localities broke records for temperature and for the most days above 100 o F. |
SciQ | SciQ-4242 | botany, terminology, fruit
Title: What is the name of this part in plants, fruits, vegetables? What is the name of this part of the plant, fruit, vegetable? The thing that the plant is connected with the tree and gets nutrients with? The part we usually cut out when eat fruit.
Examples below
Papaya
Banana
Mango 'Stalk' or 'pedicel' would be an appropriate term (see, for example, this paper or this one). Specifically, you could say 'terminal part of the stalk/pedicel', though I don't know if there is a word for that.
Note that the term pedicel is commonly used for the stalk of a flower; it makes sense to use it for fruits too as they are derived from flowers.
The following is multiple choice question (with options) to answer.
The leaves of all of what type of plants have two basic parts in common: the blade and petiole? | [
"perennials",
"deciduous",
"flowering plants",
"evergreen"
] | C | Flowering vascular plants also have diverse leaves. However, the leaves of all flowering plants have two basic parts in common: the blade and petiole (see Figure above ). The blade of the leaf is the relatively wide, flat part of the leaf that gathers sunlight and undergoes photosynthesis. The petiole is the part that attaches the leaf to a stem of the plant. This occurs at a node. |
SciQ | SciQ-4243 | botany
Title: Do plants absorb toxins from the soil? Consider a plant like Aloe Vera that grows up in a toxic environment where the concentration of pesticides, and materials like lead, mercury, cadmium, arsenic etc is very high(e.g. Marshland dumping yard ). Would that mean that the extract from these plants would contain all these toxic elements. Not "all of them". But yes, plants suck up water from the soil, with everything dissolved in this water - nutrients, heavy metals, poisons. And also they breathe air, and absorb stuff via this route.
There probably are some toxins which will not enter the plant, because their molecules are too large and/or fragile. For example, should a plant root come in contact with snake venom, I cannot imagine that any venom will end up stored in the plant leaves.
Plants also have their own metabolism, so they will change/deactivate some toxins. I've seen claims that some plants "purify" formaldehyde, although I don't trust the sources enough to be sure of that.
But the smaller the poison molecule, and the less similar to stuff which is usually digested in nature, the more likely that it will enter the plant and stick around instead of being broken down. The heavy metals you mentioned are prime candidates. If they are present in the groundwater - or also lead from air pollution, before we banned leaded gasoline - they end up in plants, including food plants. And mushrooms are even more at risk.
Growing food near waste dumps is a known problem in farming, and sometimes makes the news, for example here:
http://bigstory.ap.org/article/mafia-toxic-waste-dumping-poisons-italy-farmlands
The following is multiple choice question (with options) to answer.
Through what do plants move enormous amounts of water from the soil to the atmosphere? | [
"perspiration",
"respiration",
"evaporation",
"transpiration"
] | D | Plants recycle matter in biogeochemical cycles. For example, through transpiration, plants move enormous amounts of water from the soil to the atmosphere. Plants such as peas host bacteria that fix nitrogen. This makes nitrogen available to all plants, which pass it on to consumers. |
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