source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-3044 | bond, ionic-compounds
Title: Determining whether a compound is ionic or molecular in nature
$\ce{HCl}$ is a molecular compound because there is a covalent bond between $\ce{H+}$(a proton) and $\ce{Cl-}$ (a chloride ion)
$\ce{NH4NO3}$ is an ionic compound because there is an ionic bond between $\ce{NH4+}$ (an ammonium ion) and $\ce{NO3-}$ (a nitrate ion) even though all the atoms comprising the molecule are non-metal.
Then, which of the following is true?
$\ce{H3C-COOH}$ is an ionic compound because there is an ionic bond between $\ce{C2H3O-}$ (an acetate ion) and $\ce{H+}$ (a proton)? OR
$\ce{H3C-COOH}$ is a molecular compound because there is a covalent bond between $\ce{C2H3O2-}$ (an acetate ion) and $\ce{H+}$ (a proton)?
The following is multiple choice question (with options) to answer.
What type of compound is hydrogen chloride? | [
"polar",
"ionic",
"covalent",
"metal"
] | C | The largest, most complex covalent molecules have thousands of atoms. Examples include proteins and carbohydrates, which are compounds in living things. The smallest, simplest covalent compounds have molecules with just two atoms. An example is hydrogen chloride (HCl). It consists of one hydrogen atom and one chlorine atom, as you can see in the Figure below . You can watch an animation of hydrogen chloride forming at the following URL. |
SciQ | SciQ-3045 | volcanology, paleontology, volcanic-hazard, archaeology, pyroclastic-flows
Title: Are Pompeii and Herculaneum unique? Has anyone ever found or gone looking for similar locations, i.e. volcanic eruption sites in which unfortunate victims – human and non-human – have been entombed in the volcanic ash, with the possibility of revealing their forms by producing casts from the voids? Such sites, if they exist, could reveal exciting new knowledge about ancient peoples and animals. Probably the best known is more recent, the 1902 eruption of Mt. Pelée on Martinique, where 30,000 people were killed by pyroclastic flows. I don't know the extent of burial - it appears that the city may have been destroyed more by the ash cloud than the dense part of the flow.
The following is multiple choice question (with options) to answer.
What kind of volcanic eruptions are less deadly? | [
"non-dormant",
"serial eruptions",
"non-explosive",
"explosive"
] | C | Some volcanic eruptions are non-explosive ( Figure below ). This happens when there is little or no gas. The lava is thin, fluid and runny. It flows over the ground like a river. People generally have a lot of warning before a lava flow like this reaches them, so non-explosive eruptions are much less deadly. They may still be destructive to property, though. Even when we know that a lava flow is approaching, there are few ways of stopping it!. |
SciQ | SciQ-3046 | botany, ecology, energy
Title: Why do plants create enough energy for the entire ecosystem? In my environmental class, we were recently learning about the $10\%$ law that basically says only $10\%$ of the energy goes from one trophic level to the next.
This got me thinking about why energy flows from one level to the next. Specifically, why do plants create enough energy for the entire ecosystem? Wouldn't they do fine without us, and wouldn't that save them the work of creating all that excess energy? Plants collect energy for themselves via photosynthesis, not for others.
It is used for it's own growth and survival.
It's energy is then redistributed to other organisms when either the plant dies and decomposes or when it is consumed. Many organism cannot collect their energy like plants do, and thus must feed on organisms (like plants) that are able to collect and store energy. This is in many cases detrimental to the plant (it should be intuitive why being eaten might be bad), and many, many plants do have traits to discourage other organisms from eating them (plants with toxins, thorns, etc.).
The following is multiple choice question (with options) to answer.
Where do most ecosystems get their energy from? | [
"earth",
"water",
"heat",
"sun"
] | D | Most ecosystems get their energy from the Sun. Only producers can use sunlight to make usable energy. Producers convert the sunlight into chemical energy or food. Consumers get some of that energy when they eat producers. They also pass some of the energy on to other consumers when they are eaten. In this way, energy flows from one living thing to another. |
SciQ | SciQ-3047 | aqueous-solution, solubility, phase
Whereas the IUPAC Gold Book defines a chemical reaction as:
A process that results in the interconversion of chemical species.
One aspect of solvation vs. reaction that may seem confusing is the solubility of ionic species. Even though $\ce{NaCl}$ becomes $\ce{Na+}$ and $\ce{Cl-}$ in an aqueous solution, this does not constitute a chemical reaction as defined above, and we say that $\ce{NaCl}$ is soluble in water. The same is true of your example of $\ce{H2SO4}$; even though it dissociates in water, it is not converted to a new chemical compound. One way to think of this is if you remove the solvent, the solute should typically resume to it's original form. From our previous example, if we evaporate the water from our aqueous solution of $\ce{Na+}$ and $\ce{Cl-}$, we just get the solid $\ce{NaCl}$ back.
Your examples of solubility in hydrochloric acid are a bit complex because that is a two-component system of water and $\ce{HCl}$. All of the compounds you discuss are water soluble and it doesn't matter if the $\ce{HCl}$ is there or not. One slight exception in your examples is ethylamine. Ethylamine itself is miscible with water, but many higher molecular weight amines are not water soluble, but are soluble in hydrochloric acid. In this case, the $\ce{H+}$ from $\ce{HCl}$ protonates the amine, making the hydrochloride salt. This is still an example of solubility however, as once you remove the solvent, you are left with the original compound, in this case the amine.
The following is multiple choice question (with options) to answer.
When a solute dissolves into a solvent what is that called? | [
"solubility",
"viscosity",
"enthalpy",
"mixing"
] | C | Enthalpy changes also occur when a solute undergoes the physical process of dissolving into a solvent. Hot packs and cold packs (see Figure below ) use this property. Many hot packs use calcium chloride, which releases heat when it dissolves according to the equation below. |
SciQ | SciQ-3048 | # Identity element of the operation $x*y = \min\{x+1, y+1\}$ on $\mathbb R$?
The following is an operation $*$ on $\mathbb R$.
$$x*y= \min\{x+1, y+1\}$$
Explain whether or not $\mathbb R$ has an identity element with respect to $*$.
This question also had two other parts, asking to explain whether it is commutative and associative. I said that it is commutative but not associative.
As for the identity element, I am confused because $\mathbb R$ goes to $-\infty$ so won't we always be able to find an element that is smaller than $x+1$?
I feel like there cannot be a neutral element because the operation $*$ is defined on $\mathbb R$ and I feel like you will always be able to find a smaller element than $x+1$.
Plus, the neutral element has to be unique so how could this operation have a unique neutral element?
Thank you for any help!
• What is $x*x{}$? – Angina Seng Sep 20 '17 at 16:56
• But that isn't unique for the operation? – JxxYsde3 Sep 20 '17 at 16:57
• It's true, though. – Professor Vector Sep 20 '17 at 17:05
• It is equivalent to you operation, JxxYsde3. I simply thought looking at what the operation is actually doing might be helpful. – amWhy Sep 20 '17 at 17:07
• The operation isn't interesting, I bet it isn't even associative. And there isn't a neutral element, naturally, exactly for the reason you doubt it: it would mean $x*e=x$ for all $x$, but if $x<e$, you have $x*e=x+1\neq x$. – Professor Vector Sep 20 '17 at 17:11
The operation $x*y = \min(x+1, y+1)$, for $x, y \in \mathbb R$, is equivalent to the following:
The following is multiple choice question (with options) to answer.
The smallest part of an element that maintains the identity of that element is called what? | [
"lattice",
"neutron",
"atom",
"nucleus"
] | C | Note Sometimes the word pure is added to substance, but this is not absolutely necessary. By definition, any single substance is pure. The smallest part of an element that maintains the identity of that element is called an atom. Atoms are extremely tiny; to make a line 1 inch long, you would need 217 million iron atoms. The smallest part of a compound that maintains the identity of that compound is called a molecule. Molecules are composed of atoms that are attached together and behave as a unit. Scientists usually work with millions and millions of atoms and molecules at a time. When a scientist is working with large numbers of atoms or molecules at a time, the scientist is studying the macroscopic view of the universe. However, scientists can also describe chemical events on the level of individual atoms or molecules, which is referred to as the microscopic viewpoint. We will see examples of Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-3049 | statistical-mechanics, atmospheric-science, density
A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which dissolved carbon dioxide (CO2) suddenly erupts from deep lake waters, forming a gas cloud that can suffocate wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water. Scientists believe earthquakes, volcanic activity, or explosions can be a trigger for such phenomenon. Lakes in which such activity occurs may be known as limnically active lakes or exploding lakes.
Picture 1: one of a number of cattle killed by a limnic eruption at Lake Nyos, Cameroon.
We can occasionally prevent the buildup of carbon dioxide by degassing the body of water.
Picture 2: a siphon used by French scientists to de-gas Lake Nyos. The carbon dioxide emerges from its deposits and bubbles into the water, floating to the top.
The following is multiple choice question (with options) to answer.
Varves form in lakes covered by what? | [
"coral reef",
"ice",
"soot",
"bridges"
] | B | Varves form in lakes covered by ice. Varves are useful to scientists for understanding climate. |
SciQ | SciQ-3050 | 1. Let total distance=X.
1st distance =30x/100.Speed=20kmph
2nd distance=60x/100 Speed=40kmph
3rd distance=10x/100Speed=10kmph
T1=1/20*30x/100 = 3x/200
T2=1/40*60x/100 =3x/200
T3=1/10*10x/100 =X/100
Applying S=D/T Formula
30x/100+60x/100+10x/100
______________________________
3x/200+ 3x/200+ X/100.
=100x*200/8x*100
=25
2. Thank you so much
3. excellent
4. Palal,post your calculation so we can rectify. It may consist a calculation error. Otherwise, answer would be same.
5. if we have taken x instead of 100, why answer doesnt comes the same way
Related Questions on Speed Time and Distance
The following is multiple choice question (with options) to answer.
Speed takes distance and what else into account? | [
"energy",
"time",
"matter",
"gravity"
] | B | Speed just takes distance and time into account. How might direction be considered as well?. |
SciQ | SciQ-3051 | physiology, neurophysiology, respiration, breathing, pulmonology
Title: Is breathing a reflex action or is it an intrinsic process? The process of breathing is controlled by respiratory centers in the brain stem. Do these centers have an innate activity, i.e., just send out signals to breathing muscles intrinsically, and have the rate and manner in which they do so modified by various regulatory factors?
Or are they driven by imbalances (in levels of oxygen, carbon dioxide, hydrogen ions) like a reflex? Let's say that hypothetically these levels remain static in an acceptable state such that this reflex is no longer needed, would breathing stop since there's no longer a driving motive or would it continue because the respiratory centers have an intrinsic activity? While the ultimate purpose of breathing could be considered to be the maintainance of a balance of the substances you are referring to (such as blood oxygen, carbon dioxide, and hydrogen ions), the blood levels of these substances do not directly control the production of action potentials within the motor neurons that promote the contraction of the diaphragm and intercostal muscles.
The propagation of these action potentials is initiated by signals from the medullary respiratory center, specifically the neurons in the dorsal respiratory group (DRG) and the ventral respiratory group (VRG). In the VRG, a complex of neurons known pre-Bötzinger complex is responsible for generating the signals that cause the rhythmic muscle contractions involved in breathing:
The respiratory rhythm generator is located in the pre-Bötzinger complex of neurons in the upper part of the VRG. This rhythm generator appears to be composed of pacemaker cells and a complex neural network that, acting together, set the basal respiratory rate.
The following is multiple choice question (with options) to answer.
Which division of the autonomic nervous system controls processes like digestion, heartbeat, and breathing? | [
"parasympathetic",
"synaptic",
"dopaminergic",
"endocrine"
] | A | The parasympathetic division controls internal organs and glands during the rest of the time. It controls processes like digestion, heartbeat, and breathing when there is not an emergency. |
SciQ | SciQ-3052 | reproduction
Excerpts from the references that lead to the short answer above:
In the developing female fetus, oogonia become primary oocytes that begin the first division of meiosis. However, this division is not completed and the primary oocytes remain “frozen” in the prophase stage of the first meiotic division.
At birth, oogonia are no longer present. Each primary oocyte is surrounded by a single layer of squamous epithelial cells called follicular cells. The primary oocyte together with its follicular cells is called a primordial follicle. There are about two million primordial follicles with their primary oocytes in the ovaries at birth suspended in the first division of meiosis.
As the female grows, primary oocytes begin to die and disappear with their follicular cells. This process continues until puberty when there are only about 400,000 primordial follicles left in the ovaries. The primary oocytes continue the process of oogenesis after puberty begins.[Source]
The total number of primary oocytes at birth is estimated to vary from 700,000 to2 million. During childhood most oocytes become atretic; only approximately400,000 are present by the beginning of puberty, and fewer than 500 will be ovulated.[Source]
Primary oocytes reach their maximum development at ~20[6] weeks of gestational age, when approximately seven million primary oocytes have been created; however, at birth, this number has already been reduced to approximately 1-2 million.Recently, however, two publications have challenged the belief that a finite number of oocytes are set around the time of birth.[Source]
In the human embryo, the thousand or so oogonia divide rapidly from the second to the seventh month of gestation to form roughly 7 million germ cells.[Source]
REFERENCES:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0008772
The following is multiple choice question (with options) to answer.
What does the ovule develop into after fertilization? | [
"germ",
"pollen",
"seed",
"zygote"
] | C | An ovule is a female reproductive structure in seed plants. It contains a tiny female gametophyte. The gametophyte produces an egg cell. After the egg is fertilized by sperm, the ovule develops into a seed. |
SciQ | SciQ-3053 | The population of a culture of bacteria, P(t), where t is time in days, is growing at a rate that is proportional to the population itself and the growth rate is 0.3. The initial population is 40. (1) What is the population after
6. ### calculus
The population of a certain community is increasing at a rate directly proportional to the population at any time t. In the last yr, the population has doubled. How long will it take for the population to triple? Round the answer
7. ### Maths
The population P of a particular city, Metropia, is growing at a rate proportional to the current population. The population at time t years is modelled by the equation P=Ae^kt where A and k are constants. With the aid of
8. ### Maths B - Population Growth
The population P of a particular city, Metropia, is growing at a rate proportional to the current population. The population at time t years is modelled by the equation P=¡¼Ae¡½^kt where A and k are constants. With the aid of
9. ### Maths B question - population
The population P of a particular city, Metropia, is growing at a rate proportional to the current population. The population at time t years is modelled by the equation P = Aekt where A and k are constants. (a) With the aid of
10. ### Population growth
The population P of a particular city, Metropia, is growing at a rate proportional to the current population. The population at time t years is modelled by the equation P = Aekt where A and k are constants. (a) With the aid of
More Similar Questions
The following is multiple choice question (with options) to answer.
What is a key factor in the growth of populations? | [
"immigration",
"legislation",
"gentrification",
"assimilation"
] | A | Moving into an area, or immigration, is a key factor in the growth of populations. Shown above is actual vintage luggage left by some of the millions of immigrants who came through Ellis Island and into the United States. |
SciQ | SciQ-3054 | temperature, weather, humidity
Title: Why does relative humidity appear limited for temperatures above 80°F? I recently compiled ten years of NOAA local climatological data. I noticed that the maximum relative humidity dropped linearly from 100% at about 80°F to 20% at about 110°F. Nothing obvious comes to mind that explained this observation.
Here is my scatterplot:
Here is graph showing the edge of interest:
I would have expected to see relative humidity values at or near 100%, even for temperatures near 100°F. Obviously, that's not what I see. Maybe this has something to do with a limit of absolute humidity or density?
Nothing obvious comes to mind that explained this observation.
Consider a simple model with the following aspects/assumptions:
The coastal regions of large bodies of water on Earth are at most as hot as about 80°F. (Some exceptions exist, such as the Persian Gulf. If the data are taken from weather stations near areas of human occupancy, such as airports, note also that regions with a wet-bulb temperature much greater than about 80°F are generally hazardous to humans.)
Water enters the atmosphere predominantly through evaporation from these large bodies of water, up to the maximum relative humidity at that maximum temperature. That fixes one point of the line you observed: 100% relative humidity at 80°F (300 K).
The vapor pressure $P_\text{vapor}$ of water increases with increasing temperature $T$; a simple model of this exponential relation is the August equation $P_\text{vapor}\approx\exp\left(20- \frac{5100}{T}\right)$, with $T$ measured in kelvins.
The relative humidity corresponds to the actual partial pressure of water vapor relative to the saturation vapor pressure at that temperature. We characterize this behavior in part through psychrometric charts.
Therefore, we should expect a downward-sloping maximum relative humidity with increasing temperature as the saturated vapor is transported inland to regions over land that may be hotter. The maximum mass of water vapor remains the same, as does the maximum absolute humidity, but the maximum relative humidity drops with increasing temperature.
The following is multiple choice question (with options) to answer.
Air is said to reach what point, a term used by meteorologists, when humidity increases or temperature decreases? | [
"freezing point",
"its dew point",
"bubble point",
"its dip point"
] | B | Air reaches its dew point when humidity increases or temperature decreases. |
SciQ | SciQ-3055 | neuroscience, biophysics, neurophysiology
Title: Why are potassium channels slower than sodium channels? I am relatively new in the subject of biology. I have a strong mathematical background and in order to get into the field of computational neuroscience, I am trying to get some biological background.
I am reading about the general mechanism of action potentials in neurons.
I understand that an action potential starts with a fast entrance of sodium into the postsynaptic cell. Since the potassium channels are slower than the sodium channels, potassium starts flowing out of the cell only around the peak of the action potential, thereby hyperpolarizing the cell's membrane potential.
What is the mechanism that causes the potassium channels to activate slower than the sodium channels? Does it involve differences in the behavior of the suitable neurotransmitters? Because I didn't manage to find transmitters or couples of transmitters and receptors which activate potassium channels, but not sodium channels (or sodium channels and not potassium channels). Short answer
The activation kinetics of Na+ channels are faster than K+ channels.
Background
Voltage-dependent channel gating basically occurs through three possible states of the channel: open, closed and inactivated (Fig. 1).
Fig. 1. Gating of a voltage-activated sodium channel. Source: Balseiro Institute.
Basically, ion channels are protein pores in the membrane. Upon depolarization, the pore opens, which is a process with fast kinetics in Na+ channels and slower kinetics in K+ channels (Lacroix et al, 2013). K+ channel activation is in the order of 6 times slower than Na+ channel activation. The slower inactivation of K+ channels allows sufficient Na+ to flow in the cell for the depolarization phase of the action potential to develop (Fig. 2).
The following is multiple choice question (with options) to answer.
In neurons, what often involves gated sodium channels? | [
"depolarization",
"polarization",
"fermentation",
"excitation"
] | A | |
SciQ | SciQ-3056 | visualization, data-analysis
One may also note on this graph that there is some kind of underlying discrete distribution of the values: very clearly for values 0 and 1, but also from all the white horizontal lines which show that some values seldom exist in the data.
The following is multiple choice question (with options) to answer.
Line graphs are especially useful for showing changes over what? | [
"energy",
"time",
"velocity",
"space"
] | B | Line graphs are especially useful for showing changes over time. The line graph in Figure below shows how distance from school changed over time when some students went on a class trip. |
SciQ | SciQ-3057 | volcanology, volcanic-hazard, volcanic-eruption
Title: Would a Yellowstone eruption destroy global agriculture? Someone recently claimed in my hearing that if the Yellowstone caldera were to erupt, the resulting ash cloud would end all agriculture for a year or two. (The speaker is not a scientist, and neither am I.)
Is that accurate?
Are there reasonable scenarios (i.e., not this) worked out for the effects of a supervolcano eruption?
I did see this question, where one of the commenters points out that such an event would be unprecedented, so our ability to predict is limited, but I'm still curious about whatever we do know at this stage. An eruption of the Yellowstone super volcano would cause agricultural disaster over a very large area. Its global effect would be significant, but not totally devastating.
The resulting climate cooling could last up to a decade. The temporary climate shift could alter rainfall patterns, and, along with severe frosts, cause widespread crop losses and famine.
But a Yellowstone megablast would not wipe out life on Earth. There were no extinctions after its last three enormous eruptions, nor have other supereruptions triggered extinctions in the last few million years.
Eruption of super volcanoes is rare which makes it difficult to ascertain what exactly would happen when the Yellowstone super volcano eventually erupts - which won't be any time soon.
Yellowstone last erupted 174 000 years ago, which was a minor eruption. Lava from Yellowstone won't be the problem, but the ash and gases will be.
The last major eruption, 630 000 years ago, covered much of western and central United States with ash. The maximum thickness of the ash from that eruption is 660 ft. The eruption was a double eruption, 170 years apart. The amount of ash thrown into the atmosphere with each eruption caused the ocean to cool by 3 degrees Celsius with each eruption.
The following is multiple choice question (with options) to answer.
After a massive eruption what will a mountain collapsing above an empty chamber create? | [
"cavern",
"valley",
"caldera",
"crater"
] | C | During a massive eruption all of the material may be ejected from a magma changer. Without support, the mountain above the empty chamber may collapse. This produces a huge caldera . Calderas are generally round, bowl-shaped formations like the picture in Figure below . |
SciQ | SciQ-3058 | human-biology, human-anatomy, terminology, anatomy, etymology
Title: Why is the opposite of plantar flexion called "dorsiflexion"? Why is the action of flexing the foot so that the toes move anteriorly/superiorly (i.e. in the direction opposite that which they move during plantar flexion) described as "dorsiflexion?" In the same vein, why is the top surface of the foot called the "dorsal surface?"
If anything, the action opposite to plantar flexion moves the foot in the ventral direction, doesn't it? And surely if you've ever seen a human in the anatomical position, you can see that there's nothing dorsal about the top surface of the foot - it's superior, perhaps, but by no means dorsal. Anatomical terms must be able to fit a wide variety of organisms, from insects to fish, dogs, horses, chimpanzees to humans. That's why the terms are sometimes confusing to people who are thinking only of bipedal humans.
In anatomy, the dorsum is the upper side of animals that typically run fly, swim or crawl in a horizontal position. In vertebrates the dorsum contains the backbone. In such an animal the "ground side" is the ventrum.
Due to varied orientation on quadrupedal mammals (where the term is more appropriately used) the "back"-side of the hand, the "top"-side of the foot and the upper surface of the tongue are referred to by the term dorsum.
Does this picture help? Note the dorsal surfaces of the body, muzzle, feet.
In anatomy, the sole of the foot is called the plantar surface. The top of the foot is called the dorsum of the foot. (Imagine us walking on all fours like apes.) Therefore when you extend your foot, it's called plantar flexion; when you flex your foot upwards towards your head, it's called dorsiflexion.
Similarly, the arteries feeding the bottom of your foot form the plantar arch. Those feeding the top are the dorsal artery (or the dorsalis pedis).
Because anatomy must describe other animals than ourselves with other orientations, it must be consistent. In a quadruped, the dorsum of the tongue and the feet do actually point to it's "back" surface. See the picture below:
The following is multiple choice question (with options) to answer.
The posterior half of the foot is formed by seven tarsal bones. the most superior of these bones is called? | [
"metatarsal",
"talus",
"patella",
"calcareous"
] | B | Tarsal Bones The posterior half of the foot is formed by seven tarsal bones (Figure 8.19). The most superior bone is the talus. This has a relatively square-shaped, upper surface that articulates with the tibia and fibula to form the ankle joint. Three areas of articulation form the ankle joint: The superomedial surface of the talus bone articulates with the medial malleolus of the tibia, the top of the talus articulates with the distal end of the tibia, and the lateral side of the talus articulates with the lateral malleolus of the fibula. Inferiorly, the talus articulates with the calcaneus (heel bone), the largest bone of the foot, which forms the heel. Body weight is transferred from the tibia to the talus to the calcaneus, which rests on the ground. The medial calcaneus has a prominent bony extension called the sustentaculum tali (“support for the talus”) that supports the medial side of the talus bone. |
SciQ | SciQ-3059 | neuroscience, brain, brain-stem
On the contrary, if the ARAS is working normally but the consciousness neural process is not, there can be alertness without, with minimal, or with some awareness. The degree of impairment of awareness depends on how much the consciousness neural process is dysfunctional. For example, in the case of damages to the consciousness neural process from diffuse cerebral hypoxia, extensive bilateral cerebral infarcts, or diffuse cerebral cortical injury, the results can be various abnormal conscious awareness’s states that range in severity of abnormal conscious awareness, depending on how much the consciousness neural process is impaired, such as (from mild to severe) acute confusional state, akinetic mutism, minimally conscious state (MCS), and vegetative state (VS). In the latter two categories, which are severe conditions, the patients can open eyes and have some reflex responses, such as blinking, chewing, and yawning, but show no (in VS) or minimal (in MCS) signs of conscious awareness of self and the environment (by clinical testing or by special investigations such as EEG, evoked potentials, and fMRI) [2].
The following is multiple choice question (with options) to answer.
What helps to regulate consciousness, arousal, and sleep states? | [
"thalamus",
"hippocampus",
"cerebral cortex",
"hypothalamus"
] | A | Basal Ganglia Interconnected brain areas called the basal ganglia (or basal nuclei), shown in Figure 35.20b, play important roles in movement control and posture. Damage to the basal ganglia, as in Parkinson’s disease, leads to motor impairments like a shuffling gait when walking. The basal ganglia also regulate motivation. For example, when a wasp sting led to bilateral basal ganglia damage in a 25-year-old businessman, he began to spend all his days in bed and showed no interest in anything or anybody. But when he was externally stimulated—as when someone asked to play a card game with him—he was able to function normally. Interestingly, he and other similar patients do not report feeling bored or frustrated by their state. Thalamus The thalamus (Greek for “inner chamber”), illustrated in Figure 35.24, acts as a gateway to and from the cortex. It receives sensory and motor inputs from the body and also receives feedback from the cortex. This feedback mechanism can modulate conscious awareness of sensory and motor inputs depending on the attention and arousal state of the animal. The thalamus helps regulate consciousness, arousal, and sleep states. A rare genetic disorder called fatal familial insomnia causes the degeneration of thalamic neurons and glia. This disorder prevents affected patients from being able to sleep, among other symptoms, and is eventually fatal. |
SciQ | SciQ-3060 | species-identification, marine-biology
Title: help identify this fish
I came across this washed up fish in Panama City, Florida in November 2015. I'm guessing it's a puffer fish but I can't find anything like it online.
Thanks. This is a kind of trunkfish. (They have different names, this could be a smooth or spotted trunkfish.). It's really a lovely and comical little fish when observed alive in coral reefs. It has the ability to change its coloration depending on whether it's excited or calm, or to minimize its contrast to the background. It is related to puffer fish.
It has a boxy, triangular body shape, and propels itself with relatively tiny, delicate fins. Like pufferfish, they are toxin producers.
In death, the body shape and coloration are different, of course. Never saw a dead one before; sad. The juveniles are adorable:
Members of this family occur in a variety of different colors, and are notable for the hexagonal or "honeycomb" patterns on their skin. - Wikipedia
The following is multiple choice question (with options) to answer.
Some fish will be over-fished to the point that their species ceases to exist, which is also known as what? | [
"extinction",
"endangered",
"abundance",
"accumulation"
] | A | will inevitably make it more difficult and costly to grow food. The world’s growing human population faces significant challenges in the increasing costs and other difficulties associated with producing food. Wild Food Sources In addition to growing crops and raising food animals, humans obtain food resources from wild populations, primarily wild fish populations. For about one billion people, aquatic resources provide the main source of animal protein. But since 1990, production from global fisheries has declined. Despite considerable effort, few fisheries on Earth are managed sustainability. Fishery extinctions rarely lead to complete extinction of the harvested species, but rather to a radical restructuring of the marine ecosystem in which a dominant species is so over-harvested that it becomes a minor player, ecologically. In addition to humans losing the food source, these alterations affect many other species in ways that are difficult or impossible to predict. The collapse of fisheries has dramatic and long-lasting effects on local human populations that work in the fishery. In addition, the loss of an inexpensive protein source to populations that cannot afford to replace it will increase the cost of living and limit societies in other ways. In general, the fish taken from fisheries have shifted to smaller species and the larger species are overfished. The ultimate outcome could clearly be the loss of aquatic systems as food sources. |
SciQ | SciQ-3061 | evolution, natural-selection, ornithology
Title: The evolutionary process in bird wings, especially with regard to winglets In this answer on aviation.SE a comparison is made between the shapes of airplanes wings and the shapes of birds wings. It concludes with the following remark:
After all, no bird has winglets. Not a single one.
In addition to be a disputable assertion (the wing tips such as the eagle's could be considered akin to a "winglet" of the fanned type) this has stricken me as based on a quite wrong assumption of how evolution works.
I tried to make my point in the comments only to reach this point:
So you consider evolved wings as not mature. The winglet modification is just waiting to happen? Nature never tried it, in >100 million years of biological flight? Could be, yes. But is extremely unlikely. That settles it for me.
Am I correct in identifying this in a wrong interpretation of the evolutionary process?
As I understand the evolutionary process, the current bird wings are not necessarily perfect, are simply the version that so far has given the best advantage. The lack of "winglets" in birds cannot then be explained simply by assuming that they do not improve the wing, but it could also be that there has never been an evolutionary pressure to evolve them or that since birds flap their wings they would be detrimental instead of beneficial or whatever other reason.
Is my understanding of the evolutionary process correct? if not, where am I at fault?
As a small addendum, another user cited the "Spandrels" in comparison to the above debate, could someone explain what could have been the meaning of the comparison? I looked up winglets so I had context for this answer. I'm interpreting winglets as the vertical tips at the end of airplane wings. If so, then you are correct. The spread primary feathers of soaring birds like eagles function as winglets (Tucker 1993). Airbus has a biomimicry web page devoted to some of the biological designs, including winglets, they incorporated into their airplane designs. Some studies suggest airplant winglets do increase efficiency (e.g., Hossain et al. 2011), but there is still some debate.
From the aviation.se answer:
The following is multiple choice question (with options) to answer.
Not surprisingly, what is the function of the most developed part of a bird's brain? | [
"controlling digestion",
"controlling breeding",
"controlling thought",
"controlling flight"
] | D | Birds have a large brain relative to the size of their body. Not surprisingly, the part of the brain that controls flight is the most developed part. The large brain size of birds is also reflected by their high level of intelligence and complex behavior. In fact, birds such as crows and ravens may be more intelligent than many mammals. They are smart enough to use objects such as twigs for tools. They also demonstrate planning and cooperation. Most birds have a poor sense of smell, but they make up for it with their excellent sense of sight. Predatory birds have especially good eyesight. Hawks, for example, have vision that is eight times sharper than human vision. |
SciQ | SciQ-3062 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
What type of roots enable a plant to grow on another plant? | [
"endemic",
"epiphytic",
"mites",
"Sickness"
] | B | Epiphytic roots enable a plant to grow on another plant. For example, the epiphytic roots of orchids develop a spongy tissue to absorb moisture. The banyan tree (Ficus sp. ) begins as an epiphyte, germinating in the branches of a host tree; aerial roots develop from the branches and eventually reach the ground, providing additional support (Figure 30.20). In screwpine (Pandanus sp. ), a palm-like tree that grows in sandy tropical soils, aboveground prop roots develop from the nodes to provide additional support. |
SciQ | SciQ-3063 | coordinate, positional-astronomy
Title: What is the connection between declination and latitude? The celestial equator is a projection of the terrestrial equator on the celestial sphere. So doesn't that mean the geographical latitude and the declination will be "exactly" equal, as they are measured from the same reference point (Celestial Equator = Geographical Equator)?
$$\lambda = \delta \pm (90° - \rm{Altitude})$$
latitude = the star's declination ± its zenith distance
= the star's declination ± (90° - the star's altitude)
Source : https://cseligman.com/laboratory/navcalc.htm
So what is the meaning of this formula as Latitude = Declination?
Also I'm unable to understand that plus-or-minus sign (north of zenith and south of zenith). It may be easier to visualize the formula by calculating the altitude based on the observer's latitude (lat) and the object's declination ($\delta$), and then re-arranging the equation to find the observer's latitude. First, the equation is only true when the object is on the meridian. Here is a diagram through the meridian (for an observer at a northern latitude):
The following is multiple choice question (with options) to answer.
What is the distance north or south of the equator called? | [
"circumference",
"elevation",
"latitude",
"longitude"
] | C | Latitude is the distance north or south of the Equator. It is expressed as a number between 0° and 90° north or south. |
SciQ | SciQ-3064 | histology
Title: Why can't plasma proteins migrate from capillaries? Why can't plasma proteins shift from capillaries to connective tissue but WBCs can be very rich in connective tissue even though obviously the WBCs had to go through capillaries. Another example: in alveolar sacs neutrophils are there in the lumen despite the presence of epithelia of alveolar sacs, and it can only reach there via capillaries. So, how can they get into lumen despite the epithelia lining? Histology textbooks say that no plasma proteins can enter or leave capillaries, but WBCs (which are much larger than proteins) can move to connective tissue via capillaries? Cells of the endothelium are joined by tight cell junctions which are impermeable or selectively permeable. Generally, proteins can only migrate through the endothelium via active transcytosis.
Leukocytes (specifically neutrophils, lymphocytes and monocytes) express various adhesion molecules and cytokine receptors which allow them to interact with endothelial cells and facilitate their movement (diapedesis) either between (paracellular) or through (transcellular) the cells. The process of leukocytes leaving the endothelial lumen is known as extravasation.
Carman CV. 2009. Mechanisms for transcellular diapedesis: probing and pathfinding by `invadosome-like protrusions'. J Cell Sci 122:3025-3035.
(C,D) The process of diapedesis, whether during intravasation or extravasation, can occur by two distinct pathways: paracellular or transcellular. (C) Paracellular diapedesis. Leukocytes and endothelial cells coordinately disassemble endothelial cell-cell junctions and open up a gap between two or more endothelial cells (Muller, 2003). (D) Transcellular diapedesis. Leukocytes migrate directly through individual endothelial cells via a transient transcellular pore that leaves endothelial cell-cell junctions intact. Note that the two individual endothelial cells in C and D are distinguished by different shades of pink.
The following is multiple choice question (with options) to answer.
In response to a cut, mast cells secrete histamines that cause nearby capillaries to do what? | [
"dilate",
"narrow",
"harden",
"constrict"
] | A | Figure 42.5 In response to a cut, mast cells secrete histamines that cause nearby capillaries to dilate. Neutrophils and monocytes leave the capillaries. Monocytes mature into macrophages. Neutrophils, dendritic cells and macrophages release chemicals to stimulate the inflammatory response. Neutrophils and macrophages also consume invading bacteria by phagocytosis. |
SciQ | SciQ-3065 | ionic-compounds
As ionic solids are added to water, water molecules proceed to surround each ion on the surface of the solid, forming a sphere of hydration. In the process, ions are separated from each other.
The $\delta^-$ charge on the oxygen atoms of water are attracted to cations and inversely, repels the $\delta^+$ hydrogen atoms. Thus, for cations, the oxygens of water point inward, and for anions, the hydrogens face inward respectively. The most important thing is that the ion-dipole interactions and separation of ions with little change in energy.
We can relate the potential energy of the ions to the two partial charges of a polar molecule like water:
$$ E_p \propto - \frac{|z|\mu}{r^2}$$
Z is the charge number of the ion and $\mu$ is the dipole moment of the polar molecule. Potential energy is lowered by the interaction between the solvent molecules and the ion. The $r^2$ term indicates that the interaction between ions and dipoles depends more on distance than the charges between two ions.
Thus, for hydration to occur, ion-dipole interactions must occur at the surface of the ion, and thus, ion-dipole interactions are strong for small, highly charged ions such as $\ce{Mg^{2+}}$, $\ce{Li^{2+}}$ etc.
$\ce{AgCl}$ is very slightly soluble in water and will not dissociate into it's ions. $\ce{HF}$ is a weak acid thus it does not deprotonate easily.
The following is multiple choice question (with options) to answer.
What is the term for an ionic compound that produces positive hydrogen ions when dissolved in water? | [
"hydrocarbon",
"base",
"acid",
"sulfur"
] | C | An acid is an ionic compound that produces positive hydrogen ions when dissolved in water. Acids taste sour and turn blue litmus paper red. |
SciQ | SciQ-3066 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
The stems of all vascular plants get longer through primary growth. this occurs in primary meristem at the tips and ______ of the stems. | [
"bottoms",
"layers",
"edges",
"nodes"
] | D | The stems of all vascular plants get longer through primary growth. This occurs in primary meristem at the tips and nodes of the stems. Most stems also grow in thickness through secondary growth. This occurs in secondary meristem, which is located in and around the vascular tissues. Secondary growth forms secondary vascular tissues and bark. In many trees, the yearly growth of new vascular tissues results in an annual growth ring like the one in Figure below . When a tree is cut down, the rings in the trunk can be counted to estimate the tree’s age. |
SciQ | SciQ-3067 | waves, electromagnetic-radiation
(Image Credit: https://www4.uwsp.edu/physastr/kmenning/Phys202/Lect16.html)
The following is multiple choice question (with options) to answer.
What kind of waves are electromagnetic waves? | [
"amplitude",
"inverse",
"transverse",
"curved"
] | C | In this lesson, you learned that electromagnetic waves are transverse waves. Like other transverse waves, electromagnetic waves have certain properties. |
SciQ | SciQ-3068 | 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.
What process is involved in the formation of a waterfall, when a stream flows from an area of harder to softer rock? | [
"erosion",
"calcification",
"evaporation",
"migration"
] | A | Mountain streams may erode waterfalls. A waterfall forms where a stream flows from an area of harder to softer rock ( Figure below ). The water erodes the softer rock faster than the harder rock. This causes the stream bed to drop down, like a step. This creates a waterfall. As erosion continues, the waterfall gradually moves upstream. |
SciQ | SciQ-3069 | human-anatomy, terminology, bio-mechanics
Title: Why metacarpus is considered hand proper? This textbook states
The hand (or manus) consists of the following parts: (a) wrist or carpus, (b) hand proper (or metacarpus), and (c) digits (thumb and fingers).
How could I justify why are digits not considered as hand proper? Hand is a prehensile organ and digits are of primary importance for prehension. So then how could metacarpus be considered as hand proper? Proper in this instance means the main body of the hand, the part that has no other identifier. the fingers and wrist have other terms to identify them, the hand proper does not. If I say the the hand you are not sure whether I mean the hand as a whole or that part in particular so it is called the hand proper. Its an old usage of the word, but that is common in anatomy text.
From webster it is the 6th definition. Proper: strictly limited to a specified thing, place, or idea
The following is multiple choice question (with options) to answer.
Meissner’s corpuscles are not as plentiful in the palms as they are in the what other part of the hand? | [
"fingernails",
"fingertips",
"bones",
"cuticles"
] | B | Which of the following statements about mechanoreceptors is false? a. Pacini corpuscles are found in both glabrous and hairy skin. Merkel’s disks are abundant on the fingertips and lips. Ruffini endings are encapsulated mechanoreceptors. Meissner’s corpuscles extend into the lower dermis. Meissner’s corpuscles, (shown in Figure 36.6) also known as tactile corpuscles, are found in the upper dermis, but they project into the epidermis. They, too, are found primarily in the glabrous skin on the fingertips and eyelids. They respond to fine touch and pressure, but they also respond to low-frequency vibration or flutter. They are rapidly adapting, fluid-filled, encapsulated neurons with small, well-defined borders and are responsive to fine details. Like Merkel’s disks, Meissner’s corpuscles are not as plentiful in the palms as they are in the fingertips. |
SciQ | SciQ-3070 | geology, crust, geobiology
Title: Does crustal thickness have anything to do with how life existed and sustained on Earth? The original question that was put on hold "If the crust were the thickest layer of Earth, what effect would its thickness have on organisms?" was actually one of those 'counterfactual question' found on my science book, and it was really just a 'reflect upon' question. And it's actually a hard one for me to answer since it's 'what if?'s. So by revising, it would still confuse some poeple, but I guess it's already specific on its own. But I still find it hard.
Follow up question:
And what if it ever was thicker than the mantle or the rest of Earth's layers, can the planet still sustain biological life? If the crust were the thickest layer or Earth, several things would happen:
It wouldn't be a "crust" any more, by definition. Because this is what a "crust" is: a thin layer on the exterior of something. However, if we assume that the mechanical properties of the crust (being cold and brittle etc) would extend deeper in the Earth, the following applies.
No mantle convection, or at least mantle convection weak enough to probably not affect the surface. Therefore, no volcanoes, no mountain building, no subduction, no recycling of volatile elements, no sub-seafloor hydrothermal vents.
If it's cold enough, the core probably solidified and there is no magnetic field.
A good example would be Mars. A planet hypothesised to have tectonic activity in the past, but not any more. The crust of Mars isn't the thickest layer (again - think of definitions), but it is thicker in absolute and relative terms when compared to Earth. I will leave the implications of "Marsifying" Earth on organisms for you to figure out.
The following is multiple choice question (with options) to answer.
What are the two types of earth crust? | [
"oceanic and continental",
"micro and continental",
"amorphous and continental",
"reflective and continental"
] | A | The crust is less than 1% of Earth by mass. The two types are oceanic crust and continental crust. |
SciQ | SciQ-3071 | energy, waves, energy-conservation, interference
Title: Energy in Destructive interference of waves Let's consider two waves on a string, having equal frequency, wavelength and amplitude. The phase difference between the two travelling waves is π. As a result, they interfere destructively, and the resultant amplitude is zero. The question is, where does the energy of the waves go? It will depend on how the waves are created on the string and applying the energy conservation conditions. In the example here the 180 degree phase difference is introduced on the string by a reflection on the wall, and it is the wall that takes up the energy.
If there are two sources from the two ends of the string I expect heat would take up the balance of energy, i.e. the atoms and molecules of the string vibrating strongly and radiating, but I guess also the two sources could react mechanically taking up energy.
(In complicated laser interference experiments itis seen that the energy is returned to the source.)
The following is multiple choice question (with options) to answer.
What is determined by the energy of the disturbance that causes the wave? | [
"Ohm",
"wave amplitude",
"frequency",
"wavelength"
] | B | Wave amplitude is determined by the energy of the disturbance that causes the wave. A wave caused by a disturbance with more energy has greater amplitude. |
SciQ | SciQ-3072 | geology, mineralogy, minerals, mining
In the Eocene, some of the laterite was eroded and deposited as alluvial bauxite ore as the sea slowly filled in.
Both the original laterite and the alluvial deposits have been mined for aluminum.
Your assertion that there are no other bauxite deposits in the US is not true; other deposits formed in similar conditions in the southeastern US, and there is also bauxite in Montana
The following is multiple choice question (with options) to answer.
What is made from the minerals in rocks known as bauxite? | [
"aluminum",
"titanium",
"glass",
"coins"
] | A | Aluminum is made from the minerals in rocks known as bauxite. |
SciQ | SciQ-3073 | 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 is a defining feature of deformed sedimentary rocks? | [
"not solid",
"only horizontal",
"not horizontal",
"not magnetic"
] | C | Sedimentary rocks that are not horizontal have been deformed. |
SciQ | SciQ-3074 | evolution, taxonomy
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves, but do not breed freely with members of another species in the wild.
That last part takes care of the ligers and tiglons. But what if we consider plants? Under the definition I just gave, most grasses (around 11,000 species) would have to be considered as one species. In the wild, most grasses will freely pollinate related species and produce hybrid seed, which germinates. You might then think we could just modify the definition to specify that the offspring must be fertile (i.e. able to reproduce with one another)...
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves, but do not breed freely with members of another species in the wild to produce fertile progeny.
Unfortunately, the situation is still more complicated (we've barely started!). Often wild hybridisation events between plants lead to healthy, fertile offspring. In fact common wheat (Triticum aestivum) is a natural hybrid between three related species of grass. The offspring are able to breed freely with one another.
Perhaps we could account for this by taking into account whether the populations usually interbreed, and whether they form distinct populations...
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of populations or meta-populations of related individuals that resemble one another, are able to breed among themselves, but do tend not to breed freely with members of another species in the wild to produce fertile progeny.
The following is multiple choice question (with options) to answer.
Resemblance to other species can serve as protection to what category of species? | [
"predator",
"producer",
"prey",
"consumer"
] | C | |
SciQ | SciQ-3075 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
What type of cells make up the epidermis of a leaf? | [
"endothermic cells",
"dermal cells",
"chloroplasts",
"mesophyll"
] | B | The epidermis of the leaf consists of a single layer of tightly-packed dermal cells. They secrete waxy cuticle to prevent evaporation of water from the leaf. The epidermis has tiny pores called stomata (singular, stoma) that control transpiration and gas exchange with the air. For photosynthesis, stomata must control the transpiration of water vapor and the exchange of carbon dioxide and oxygen. Stomata are flanked by guard cells that swell or shrink by taking in or losing water through osmosis . When they do, they open or close the stomata (see Figure below ). |
SciQ | SciQ-3076 | ocean, thermohaline-circulation, salinity
Title: Thermohaline Circulation in the Oceans I'm slightly confused by how thermohaline circulation works in the Earth's oceans. Is it different for surface water as opposed to deep water? I thought that warm water from the equator is transported to the poles, cools down, and then returns to lower latitudes. Is my thinking incorrect? Isn't water denser near the equator because of higher salinity? How does this impact the ocean circulation?
Thanks! Salinity and temperature both affects the density of sea water. When water with a fixed salinity cools down, it becomes heavier and sinks. In the same way, when vapor or ice removes water from sea water, the remains is more saline and heavier.
Thermohaline circulation can work as you describe. Surface water in the tropics is saline, due to evaporation, but warm due to high temperature in the atmosphere and therefor low density. As it reach colder climate (less solar energy per area), it cools down and the high salinity makes it sink. Surface water in polar regions also get heavier as ice is formed of water and leave the salt behind in the sea.
This is very simplified model, you can read more on the topic here and here.
The following is multiple choice question (with options) to answer.
What carries warm or cold water throughout the world’s oceans? | [
"earth rotation",
"ocean currents",
"pipes",
"gravity"
] | B | Ocean currents carry warm or cold water throughout the world’s oceans. They help to even out the temperatures in the oceans. This also affects the temperature of the atmosphere and the climate around the world. Currents that are near shore have a direct impact on climate. They may make the climate much colder or warmer. You can see examples of this in Figure below . |
SciQ | SciQ-3077 | operating-systems
Theoretically possible? Sure. Reasonable, NO. Instead of trying to use that time "lost" during a context switch, innovations focus on classifying different degrees of context switches. Basically, if you have a lightweight switch between a process, or perhaps a thread, the entire processor is not held up while doing so. For more reading, I suggest: https://en.wikipedia.org/wiki/Light-weight_process to see the difference in process types.
Clarification: The scheduler is a kernel space process.
The following is multiple choice question (with options) to answer.
What type of resource cannot be replaced as easily as it is consumed? | [
"renewable",
"biological",
"untapped",
"nonrenewable"
] | D | A nonrenewable resource is one that cannot be replaced as easily as it is consumed. Fossil fuels are an example of nonrenewable resources. They take millions of years to form naturally, and so they cannot be replaced as fast as they are consumed. To take the place of fossil fuel use, alternative energy resources are being developed. These alternative energy sources often utilize renewable resources. The following are examples of sustainable alternative energy resources:. |
SciQ | SciQ-3078 | 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 substances are involved in most of the chemical reactions that take place in organisms, including digestion? | [
"vitamins",
"hormones",
"proteins",
"enzymes"
] | D | Enzymes are involved in most of the chemical reactions that take place in organisms. About 4,000 such reactions are known to be catalyzed by enzymes, but the number may be even higher. In animals, an important function of enzymes is to help digest food. Digestive enzymes speed up reactions that break down large molecules of carbohydrates, proteins, and fats into smaller molecules the body can use. Without digestive enzymes, animals would not be able to break down food molecules quickly enough to provide the energy and nutrients they need to survive. |
SciQ | SciQ-3079 | immunology, virology
Title: Why do people dying of immune deficiency diseases appear sick? Please forgive the obviously silly appearance of this question, and/or of the tenor which may come across as flippant or dismissive of real world suffering. My intention is none of the above.
As a layperson, I have always understood that the expression of our various colds/flus etc, while frequently mis-understood as being caused by the virus, are actually just manifestations of our own immunity fighting same. In other words, all the snot, and fever and inflammation are not caused *by the virus, they are a reaction *to the virus, as we fight it off.
My question then is why do people with AIDS (or similar immunity destroying affliction) appear sick? If they have weak or non-existent immune systems, following the above logic, would one expect to see them passing away while looking entirely healthy? Many of the symptoms of disease are indeed related to inflammation, but inflammation depends heavily (though not solely) on the innate immune response. Patients with AIDS and some of the other immunodeficiencies lose their adaptive immune response, not their innate response. Therefore they are capable of mounting an inflammatory response that is not effective in clearing pathogens (because it doesn't have help from the adaptive immune system) but can still cause symptoms.
More importantly, many symptoms of disease are not caused by the inflammatory response, but are related to organ and tissue damage caused by the infection. A patient with pneumonia may have a reduced inflammatory response but will still have difficulty breathing and signs of reduced oxygen supply simply because the lung tissue has been damaged by the pathogen.
The following is multiple choice question (with options) to answer.
What occurs when the immune system is not working properly? | [
"cancer",
"allergy",
"anemia",
"immunodeficiency"
] | D | Immunodeficiency occurs when the immune system is not working properly. As a result, it cannot fight off pathogens that a normal immune system would be able to resist. Rarely, the problem is caused by a defective gene. More often, it is acquired during a person’s lifetime. Immunodeficiency may occur for a variety of reasons:. |
SciQ | SciQ-3080 | newtonian-mechanics, electromagnetism, forces, free-body-diagram
Title: Forces acting on a magnet and paper clip Suppose a paper clip is stuck to a surface, with tape for example. A magnet is placed close to the clip, and starts moving towards it. Now, there is a force acting on the clip from the magnet, but is there a force acting on the magnet from the clip? Does Newton's third law apply literally here? Absolutely yes, third Newton's law is satisfied in this case too. Maybe when you think in a magnet heavier than the clip you may think that there are no forces acting in the magnet, but you can think in a little magnet close to a heavy metal object, the object doesn't move and the magnet moves in the object's direction. Because of the magnetic field the clip gets magnetized, that means that the clip gets a magnetic induction field in the direction of the magnet's field and that creates a new magnetic field that attracts other magnetic objects, included the initial magnet.
The following is multiple choice question (with options) to answer.
The force that a magnet exerts on certain materials is called what? | [
"magnetic force",
"velocity force",
"stellar force",
"centripetal force"
] | A | The force that a magnet exerts on certain materials, including other magnets, is called magnetic force . The force is exerted over a distance and includes forces of attraction and repulsion. North and south poles of two magnets attract each other, while two north poles or two south poles repel each other. A magnet can exert force over a distance because the magnet is surrounded by a magnetic field . In the Figure below , you can see the magnetic field surrounding a bar magnet. Tiny bits of iron, called iron filings, were placed under a sheet of glass. When the magnet was placed on the glass, it attracted the iron filings. The pattern of the iron filings shows the lines of force that make up the magnetic field of the magnet. The concentration of iron filings near the poles indicates that these areas exert the strongest force. You can also see how the magnetic field affects the compasses placed above the magnet. To see an animated magnetic field of a bar magnet, go to this URL: http://micro. magnet. fsu. edu/electromag/java/magneticlines/. |
SciQ | SciQ-3081 | fluid-dynamics, differential-equations
Title: Flow around a rock in a river: which differential equation? I'm a canoist, so I know that when I go with my kayak behind a rock in a river, I feel a current that is opposite to the river current.
I'm also I student mathematician, so I would like to see this phenomenon from equations. But I don't know anything about the equations that govern fluid dynamic.
So my problem is: let be $W = \mathbb{R} \times [-2, 2]$ the river and $R = B_1(0)$ the rock (a ball inside the river). Let be $M = W \backslash R$ the river without the rock, i.e. where the water could flow. Let be $\phi: \mathbb{R} \times M \to M$ a function such that $\phi(t, x)$ is the position at time $t$ of the fluid particle that at time $t = 0$ was in position $x$. Let be the water flow from left to right. My question is: what differential equation for $\phi$ I have to solve? And does this equation predict the correct flow behind the rock? The simplest model that fits is potential flow around a cylinder (or a circle in 2D). This assumes an an inviscid, incompressible fluid with no vorticity, which is too simple to model the backflow. The backflow occurs because of viscosity produces boundary layer separation.
I think the second simplest model possible would be to solve the steady-state Navier Stokes equations for an incompressible fluid. Then it is just $$(\mathbf{v}\cdot \nabla)\mathbf{v}-\nu\nabla^2\mathbf{v}=-\nabla w$$ $$\nabla\cdot \mathrm{v}=0$$ where $\nu$ is the viscosity and $\nabla w=(\nabla p)/\rho$ is the pressure term (or other forces expressed as hydraulic head). Since you are interested in the 2D case it can also be turned into an equation for stream functions that leaves out the pressure term.
The following is multiple choice question (with options) to answer.
What is applied to a rock to make it bend and flow? | [
"acid",
"stress",
"phosphorus",
"weathering"
] | B | The amount of stress on a rock may be greater than the rock’s strength. In that case, the rock will change and deform ( Figure below ). Deep within the Earth, the pressure is very great. A rock behaves like a stretched rubber band. When the stress stops, the rock goes back to its original shape. If more stress is applied to the rock, it bends and flows. It does not return to its original shape. Near the surface, if the stress continues, the rock will fracture and break. |
SciQ | SciQ-3082 | photosynthesis, chloroplasts
Title: Chloroplasts in an animal cell What would happen if we inject a chloroplast organelle into an animal cell?
Will the animal cell destroy it? Or is it possible that the chloroplast will somehow survive, and even replicate? Could there be photosynthesis in such a cell, or will some of the necessary mechanisms be missing? To answer your bigger question:
Yes, most of this is possible - under some conditions -, and animals and animal cells can acquire chloroplasts, and use them.
E.g.: see Elysia chlorotica whose cells actively take up chloroplasts and use them, and keep them alive (though not replicating). - Though some genes of algae are also contained in the Elysia chlorotica genome - which may be considered as partial replication.
Also there are salamanders that have replicating algae within them (since embryogenesis) - even algae (with chloroplasts) within animal cells - though here the algae might be rather understood as symbionts or "cell types", and the animal cells don't have the chloroplasts by themselves.
The following is multiple choice question (with options) to answer.
What is the function of chloroplasts that are found in plant and algal cells? | [
"mitosis",
"spermatogenesis",
"glycolysis",
"photosynthesis"
] | D | Actually, almost all organisms obtain their energy from photosynthetic organisms. For example, if a bird eats a caterpillar, then the bird gets the energy that the caterpillar gets from the plants it eats. So the bird indirectly gets energy that began with the glucose formed through photosynthesis. Therefore, the process of photosynthesis is central to sustaining life on Earth. In eukaryotic organisms, photosynthesis occurs in chloroplasts . Only cells with chloroplasts—plant cells and algal (protist) cells—can perform photosynthesis. Animal cells and fungal cells do not have chloroplasts and, therefore, cannot photosynthesize. That is why these organisms, as well as the non-photosynthetic protists, rely on other organisms to obtain their energy. These organisms are heterotrophs. |
SciQ | SciQ-3083 | human-biology, surgery
Title: Is there a simple incision that would render a man impotent? I’m writing a novel in which two women (one of whom is a doctor) take revenge on a rapist by performing surgery on him.
What would be the simplest but most effective way of causing permanent and total erectile dysfunction?
I assume cutting one or more nerves but there are several up for contention:
The Dorsal nerve
Pudendal nerve
Inferior rectal nerve
Perineal nerve
Posterior scrotal nerves
Ideally, I’d like the surgery to be so minimally invasive that he wouldn’t even be aware that it had been done to him. You want to somehow damage the cavernous nerves of the penis. If you damage the preganglionic root of the cavernous nerves (the pelvic splanchnic nerve), you'll create all kinds of other problems.
You might also consider using a chemical agent instead of surgery; this will allow for increased discretion and ease of administration. I discuss this after the break in my answer.
Erection is driven by the parasympathetic nervous system; ejaculation is driven by the sympathetic nervous system. Since you're looking for "permanent and total erectile dysfunction," you want to disrupt parasympathetic innervation to the penis. The candidates you've mentioned (dorsal nerve, pudendal nerve, inferior rectal nerve, perineal nerve, posterior scrotal nerves) won't work since none of them provide parasympathetic innervation to the penis. Rather, the dorsal nerve of the penis is a branch of the pudendal nerve and provides sympathetic (ejaculation) and sensory innervation; the inferior rectal nerves are also branches of the pudendal nerve and provide purely somatic innervation to the anus (these lie below the pectinate line, which marks the boundary we use to define internal and external hemorrhoids); the posterior scrotal nerves are a sensory branch of the perineal nerve, which itself is a branch of the pudendal nerve. This plate from Gray's will help you visualize these relationships.
The following is multiple choice question (with options) to answer.
What passes through the prostate gland immediately inferior to the bladder before passing below the pubic symphysis? | [
"urethra",
"cerebellum",
"rectum",
"vagina"
] | A | Male Urethra The male urethra passes through the prostate gland immediately inferior to the bladder before passing below the pubic symphysis (see Figure 25.3b). The length of the male urethra varies between men but averages 20 cm in length. It is divided into four regions: the preprostatic urethra, the prostatic urethra, the membranous urethra, and the spongy or penile urethra. The preprostatic urethra is very short and incorporated into the bladder wall. The prostatic urethra passes through the prostate gland. During sexual intercourse, it receives sperm via the ejaculatory ducts and secretions from the seminal vesicles. Paired Cowper’s glands (bulbourethral glands) produce and secrete mucus into the urethra to buffer urethral pH during sexual stimulation. The mucus neutralizes the usually acidic environment and lubricates the urethra, decreasing the resistance to ejaculation. The membranous urethra passes through the deep muscles of the perineum, where it is invested by the overlying urethral sphincters. The spongy urethra exits at the tip (external urethral orifice) of the penis after passing through the corpus spongiosum. Mucous glands are found along much of the length of the urethra and protect the urethra from extremes of urine pH. Innervation is the same in both males and females. |
SciQ | SciQ-3084 | evolution, mammals
Title: Why haven't land animals evolved beyond urination? It occurred to me (while urinating) that this would seem to be selected against because water is a scarce resource. Why are we constantly losing water we don't need to through urination? What is it about the chemistry of urine and the waste products eliminated that make urination necessary as opposed to eliminating them through defecation and recovering the water on the way out? It is probably true that toilets and other resting-ish area are always a great place to think about biology, I agree $\ddot \smile$.
Why do we urinate?
In short, urine contains the waste from our blood while defecation is just the stuff that we haven't digested. Kidneys are the organs responsible for draining wastes (mostly nitrogen-containing, or nitrogenous, wastes) from our blood.
Trade-off: energy cost vs. water loss
You're correct that the loss of water through urination is a considerable cost for an organism (especially those living in dry environments). But the amount of water used to excrete nitrogenous wastes is negatively correlated with the energy it costs to perform this excretion. In other words, there is a trade-off between water and energy loss during nitrogen excretion. Also, the question of toxicity is important.
Three ways to excrete nitrogenous wastes
Animals basically have three choices to excrete nitrogenous wastes:
Uric acid (excreted by uricotelic organisms)
Solid (crystal) with low water solubility
Low toxicity
Little water is needed
Lots of energy is needed
Ammonia (excreted by aminotelic organisms)
Highly soluble in water
High toxicity
Lots of water is needed to dilute it because of the toxicity
Not much energy is needed
Urea (excreted by ureotelic organisms)
Solid but highly soluble in water
"medium" amount of water is needed
"medium" toxicity
"medium" amount of energy is needed
The following is multiple choice question (with options) to answer.
Terrestrial animals lose water by evaporation from their skin and which surfaces? | [
"anaerobic",
"pulmonary",
"digestive",
"respiratory"
] | D | |
SciQ | SciQ-3085 | immunology, lab-techniques, flow-cytometry, cell-sorting
Without lysis, the RBCs overwhelm the cytometer, as they make up around 95% of the cells in human whole blood. White blood cells (leukocytes), on the other hand, only make up 0.1-0.2% of cells, and lymphocytes between about 15 to 50% of leukocytes.
The cell mixture is then analyzed on a cell sorter such as a BD FACSAria.
From: https://commons.wikimedia.org/wiki/File:Fluorescence_Assisted_Cell_Sorting_%28FACS%29_B.jpg
The cells pass in single file past one or more laser beams, which excite the dyes and cause them to fluoresce at a certain wavelength. The user can then use gating to select the combination and intensity of colors they are interested in, and when a cell meets the criteria, it is given an electrical charge, and electro magnets direct it into a collection container.
The following is multiple choice question (with options) to answer.
What color are leukocytes blood cells? | [
"white",
"red",
"black",
"blue"
] | A | The chemicals that trigger an inflammatory response attract leukocytes to the site of injury or infection. Leukocytes are white blood cells. Their role is to fight infections and get rid of debris. Leukocytes may respond with either a nonspecific or a specific defense. |
SciQ | SciQ-3086 | computer-architecture, memory-hardware
They're universal -- i.e. "good enough" in the broadest possible sense: they are Turing complete and sufficiently close to some theoretical models such as the TM itself or the URM; it is safe to assume that the ubiquity of the Von Neumann machine has influenced developement of theory as well.
They're tolerably easy to reason about and very well understood by engineers and developers
They work very well for existing industrial workloads that drive the demand for hardware R&D; there is 60 years' worth of algorithms and software for Von Neumann machines.
Von Neumann closed under copper cable?
Finally - and only partly tongue-in-cheek: do note that it is very easy to obtain a decidedly non-Von Neumann machine from off-the-shelf parts: just buy two laptops and connect them with an UTP cable and you have a very strange machine where you don't have uniform, synchronized access to a single mutable storage or a single clock.
The following is multiple choice question (with options) to answer.
What is something that all machines must overcome? | [
"work",
"friction",
"stress",
"temperature"
] | B | The mechanical advantage of a simple machine such as a pulley is the factor by which the machine changes the force applied to it. The ideal mechanical advantage of a machine is its mechanical advantage in the absence of friction. All machines must overcome friction, so the ideal mechanical advantage is always somewhat greater than the actual mechanical advantage of the machine as it is used in the real world. |
SciQ | SciQ-3087 | reference-frames, momentum, energy-conservation, conservation-laws, collision
Title: Conservation of momentum and energy: what is considered to be the system? In an inelastic collision where mechanical energy is not conserved, momentum is still conserved. Should the Earth or the ground be considered as part of the system in order to account for the conservation of momentum? Since there is friction in a collision, is it appropriate to include the ground as part of the system to analyze the conservation of momentum?
Are air particles considered to be a part of this isolated system?
To clarify I am specifically talking about two vertically-moving objects colliding. Momentum is conserved in an isolated system. An isolated system has no (important) net external forces acting on it. You get to choose what constitutes the system, and therefore what forces are external and whether the system is isolated.
See Clarification about what makes a system isolated for more.
Example: You drop a rock which hits the earth in an inelastic collision.
You take the rock as your system. The rock and earth exert gravitational and collision forces on each other. The forces on the rock come from outside the system. They are external forces. Momentum is not conserved. First it increases and then decreases back to its starting value. The forces on the earth are forces on a different system.
You the the rock and the earth as your system. The rock and the earth exert the same forces as before. Now they are all forces one part of the system exerts on another part. They are internal forces. The sum of such forces must add to $0$. While different parts of the system gain and lose momentum, the total momentum of the rock + earth stays constant.
The following is multiple choice question (with options) to answer.
The conservation of momentum principle can be applied to systems as different as a comet striking earth and a gas containing huge numbers of atoms and these? | [
"particles",
"protons",
"molecules",
"ions"
] | C | The conservation of momentum principle can be applied to systems as different as a comet striking Earth and a gas containing huge numbers of atoms and molecules. Conservation of momentum is violated only when the net external force is not zero. But another larger system can always be considered in which momentum is conserved by simply including the source of the external force. For example, in the collision of two cars considered above, the two-car system conserves momentum while each one-car system does not. Making Connections: Take-Home Investigation—Drop of Tennis Ball and a Basketball Hold a tennis ball side by side and in contact with a basketball. Drop the balls together. (Be careful!) What happens? Explain your observations. Now hold the tennis ball above and in contact with the basketball. What happened? Explain your observations. What do you think will happen if the basketball ball is held above and in contact with the tennis ball?. |
SciQ | SciQ-3088 | dna, terminology
Title: Is a DNA molecule a single strand of polynucleotide or two of them linked together? Our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds. The thing is, until now, I always thought a DNA molecule was composed of two strands, those being polynucleotides, both of them being linked together. I can't find a link which is saying the same as my teacher, even if it seems technically correct to call a double helix a dimer of two DNA molecules.
I was curious to know what was the exact terminology. As you pointed out, though this may be basic biology, seeking clarification when receiving conflicting information is a good thing. Don't feel embarrassed for asking. :)
.. our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds.
Respectfully, your teacher is incorrect. A single, double-stranded DNA molecule is comprised of two helical shaped polynucleotides, and are connected together via hydrogen bonding.
Highlight of each polynucleotide
Highlight of hydrogen bonding
And just for further validation, according to Molecular Biology of the Cell, 4th ed., by Alberts B, Johnson A, Lewis J, et al.:
A DNA molecule consists of two long polynucleotide chains composed of four types of nucleotide subunits. Each of these chains is known as a DNA chain, or a DNA strand. Hydrogen bonds between the base portions of the nucleotides hold the two chains together.
So, it would seem that your teacher is referring to each polynucleotide, a.k.a. DNA strand, as a DNA molecule. Instead, she should use the verbiage: a single DNA molecule is composed of two DNA strands, which are helical-shaped polynucleotides.
The following is multiple choice question (with options) to answer.
What are the small units that comprise nucleic acids? | [
"nucleotides",
"chromosomes",
"genes",
"filaments"
] | A | DNA and RNA are nucleic acids. Nucleic acids are built of small units called nucleotides. |
SciQ | SciQ-3089 | identification, minerals
Title: How can chemists distinguish pure chemical element specimens that look almost "the same" as well as what deposit is what in a multimineral mined rock? As a non chemist I am most often charmed when visiting Wikipedia articles of chemical elements and see images of very pure specimens of element after element, proton by proton, and often also metal cube specimen made from smithing similar pure deposits.
The wiki article Periodic table allows me to do so easily; here are some elements I found looking almost the same and don't think I personally could distinguish between them without some instrument:
molybdenum and manganase
titanium and chromium
rutenium and cadmium
sodium and aluminium
silicone and germanium
The following is multiple choice question (with options) to answer.
Minerals that are not pure elements are made of what? | [
"noble gases",
"isotopes",
"chemical compounds",
"metalloids"
] | C | Minerals that are not pure elements are made of chemical compounds. For example, the mineral quartz is made of the compound silicon dioxide, or SiO 2 . This compound has one atom of the element silicon for every two atoms of the element oxygen. |
SciQ | SciQ-3090 | organic-chemistry, carbonyl-compounds
Title: Counting number of acidic-H in a molecule In a recent exam, following question was asked:
Number of acidic hydrogen present in X are:
I've found 8 of them as shown:
7 of them (marked with numerals) were correct according to solution, but 8th one (pointing with red arrow) was not. Is it because of the fact that the carbon was bridge-headed or something else? An aldehyde or a ketone with an alpha hydrogen forms a carbanion that resonates to enolate form. This leads to two canonical structures that are in resonance. The example below is a polyphenol compound extracted from turmeric, called curcumin.
source: Biomaterials. 2010 May;31(14):4179-85. doi: 10.1016/j.biomaterials.2010.01.142. Epub 2010 Feb 23. (https://www.ncbi.nlm.nih.gov/pubmed/20181392)
The hydrogens between two keto groups are most acidic. This is due to formation of two equivalent enol structures stabilized by hydrogen bonding. The structural requirement would be planarity of atoms involved in hydrogen bonding.
Below are 3-D structures of the given compound in the question above.
Structure without hydrogens
Bridgehead carbon is 4. Keto groups are at 2 , 5 and 8 (shaded in grey). Keto groups on 5 and 8 are not in the same plane . Hence Hydrogen on 4 , 22 (see figure with hydrogens) does not form stable hydrogen bonded enol structures as discussed in the above example.
Therefore, hydrogen at 8th one (pointing with red arrow) may not be acidic.
Note: 3-D structures have been drawn on Chem3Dpro
Structure with hydrogens
Structure with hydrogens (2nd view)
The following is multiple choice question (with options) to answer.
What can be classified as monoprotic or polyprotic based on the number of acidic hydrogens they contain? | [
"ions",
"salts",
"acids",
"cations"
] | C | Acids can be classified as monoprotic or polyprotic based on the number of acidic hydrogens they contain. |
SciQ | SciQ-3091 | biochemistry, photosynthesis
Title: When is Water Produced During Photosynthesis? The formula for photosynthesis is: $$6CO_2+12H_2O \rightarrow C_6H_{12}O_6+6O_2+6H_2O$$
I can count the carbons, the waters on the reactant side, the oxygens, and the glucose, but I cannot seem to locate where in either light or dark reaction 6 water molecules were produced again. Where and when were they produced? Some of the water that's split is regenerated when the hydroxyl radicals (reactive oxygen species) are converted to hydrogen peroxide, water, etc. by superoxide dismutases and antioxidative mechanisms in the chloroplast (peroxisomes/catalases, etc. take care of this). There's also some evidence that the presence of mannitol, ascorbate and glutathione protect against ROS produced in chloroplasts as well. So you input water, and in an effort to avoid oxidative damage, you do get some water generated. However, the balanced equation doesn't reflect this because it's not an actual product of photosynthesis.
About ROS and protective elements
Extra Reading on ROS in photosynthetic systems
I think that's a very obscure fact, and despite the reality of things, it's actually difficult to query the literature. Good question.
The following is multiple choice question (with options) to answer.
What is the top part of water able to receive enough sunlight for photosynthesis called? | [
"thymic zone",
"photic zone",
"synthesis zone",
"fantasmic zone"
] | B | Only the top 200 meters or so of water receive enough sunlight for photosynthesis. This part of the water is called the photic zone. Below 200 meters, there is too little sunlight for photosynthesis to take place. This part of the water is called the aphotic zone. In this zone, food must come from other sources. It may be made by chemosynthesis, in which microorganisms use energy in chemicals instead of sunlight to make food. Or, food may drift down from the water above. |
SciQ | SciQ-3092 | radiation, x-rays, cosmic-rays
Wouldn't those different types of waves have different properties?
Matter responds differently to the different wavelengths of photons, due to the increasing energy they carry which is proportional to their frequency and inversely proportional to their wavelength.
The column on the far right gives the energy of the photon. A micron wavelength is in the electron Volt range and can affect molecular distances and cohesion and living matter. Below that the interaction with matter is in bulk, not individual molecules and cells after the Ultraviolet level. The electromagnetic radiation that can affect health is ultraviolet and smaller wavelengths. The smaller the wavelength the larger the possibility of destruction of living cells which is the study of health physics: by, as the frequency increases, heating in depth,breaking of chemical bonds, ionizing, and finally destroying complete cell structures when going to MeV energies.
The following is multiple choice question (with options) to answer.
Different media affect what property of light? | [
"density",
"color",
"speed",
"temperature"
] | C | The speed of light is different in different media. |
SciQ | SciQ-3093 | eyes, sensation, senses
Title: What is the direction of the processing of light by the (human) retina and how does it happen? Quoting Textbook of Medical Physiology by Guyton and Hall, 2016, page 647,
...the functional components of the retina, which are arranged in layers from the outside to the inside as follows:
(1) pigmented layer, (2) layer of rods and cones projecting to the pigment, (3) outer nuclear layer containing the cell bodies of
the rods and cones, (4) outer plexiform layer, (5) inner nuclear layer, (6) inner plexiform layer, (7) ganglionic layer, (8) layer of optic nerve fibers, and (9) inner limiting membrane.
After light passes through the lens system of the eye and then through the vitreous humor, it enters the retina from the inside of the eye (see Figure 51-1); that is, it passes first through the ganglion cells and then through the plexiform and nuclear layers before it finally reaches the layer of rods and cones located all the way on the outer edge of the retina. This distance is a thickness of several hundred micrometers; visual acuity is decreased by this passage through such nonhomogeneous tissue. However, in the central foveal region of the retina, as discussed subsequently, the inside layers are pulled aside to decrease this loss of acuity.
I have attached Figure 51-1 for people who would like to see it.
My questions are: How does light travel to the inner parts of the retina first even when there are so many impeding layers preceding it? Why does it not stimulate the photoreceptors first? What is the pathway of the light after it travels to the the innermost retinal layer? Are the photoreceptors the first to be stimulated by the light?
The following is multiple choice question (with options) to answer.
Signals from rods and cones can follow several different pathways in what structure of the eye? | [
"aperture",
"lens",
"retina",
"aqueous humor"
] | C | |
SciQ | SciQ-3094 | sleep, hearing, perception
Title: What is the term for awareness of or inclusion of real sounds within a dream? I fell asleep while listening to a podcast, and I am sure I was dreaming but I could also still hear the podcast.
The podcast played an important role in the dream, I was searching for the source of the voice, wondering if others in the dream could hear the same voice. I started to feel a bit panicky and woke up as the podcast also happened to end. I rewound the show and confirmed that it was all there, exactly as I had heard in my dream!
I would like to read more about this type of experience, but I am having trouble finding the right words to search. Is there a name for this phenomenon? Is there anything that contributes to experiences like these? I know it wasn't lucid dreaming, because I wasn't aware of being asleep. I think I found a good expression : "sensory incorporation in dreams"
https://www.psychologytoday.com/blog/dream-factory/201409/sensory-incorporation-in-dreams
It doesn't seem reflected in a Google Scholar search however, and I don't find a consistent terminology in the papers that do seem to be about the subject. That article can be a good starting point though.
EDIT: other good one: "influence of external stimuli on dreams".
https://journals.ub.uni-heidelberg.de/index.php/IJoDR/article/view/15754
The following is multiple choice question (with options) to answer.
What is the term for getting used to something after being consistently exposed to it? | [
"habituation",
"acceptance",
"dissociation",
"modification"
] | A | One of the simplest ways of learning that occurs in just about all animals is habituation. Habituation means learning to get used to something after being exposed to it repeatedly. It usually involves getting used to something that is frightening or annoying but not dangerous. |
SciQ | SciQ-3095 | nuclear-engineering
Title: How do nuclear power plants prevent fuel rods from depleting nonuniformaly? Power output of nuclear reactors is controlled by control rods that sit in between the fuel rods:
These are pulled out to increase fission rates - and lowered to decrease them.
The control rods are made from neutron absorbing materials - such as cadmium.
When lowered completely, so many neutrons are absorbed, that no chain reaction is maintained. Pulling them out increases the neutrons that are available for fission.
My question:
The lower tips of the fuel rods will almost always be exposed to neutrons, so these should burn down much faster (have their uranium fissioned) than the upper parts that rarely have the control rods removed from them. Is there some engineering going on to have the fuel rods burn down at the same rate along their whole length? I'm going to answer this for a LWR, since I guess that's what you're thinking of.
First of all, the premise of the question is not quite correct. The power distribution of an LWR is generally sinusoidal, with a peak towards the middle of the fuel. This is true with or without control rods inserted. The most common power reactor design in operation--a conventional PWRs operating in full-power baseload operation--does not have control rods deeply inserted into the core for any significant amount of time. This shape is driven by a few factors: first, fast neutrons tend to 'leak' out of the core without thermalizing more towards the extremities. Additionally, because the top of the fuel has a higher moderator temperature (or maybe even some voids!), this also leads to less thermalization there. So, because of the shape of the power distribution, the tops and bottoms of the fuel assembly have far less power (and therefore less relative depletion) than the 'middle' of the fuel.
The following is multiple choice question (with options) to answer.
What element do nuclear power plants use in fuel rods? | [
"boron",
"uranium",
"plutonium",
"magnesium"
] | B | Nuclear power plants use uranium in fuel rods. The fuel rods become nuclear waste. Nuclear waste can be dangerous for hundreds of thousands of years. |
SciQ | SciQ-3096 | life, extremophiles
Title: How close to Earth's core can organisms live? We don't to know much about organisms living deep below the Earth's crust. Recently a team led by S. Giovanni discovered some microbes 300 m below the ocean floor. The microbes were found to be a completley new and exotic species and apparently they feed off hydrocarbons like methane and benzene. Scientists speculate that life may exist in our Solar System far below the surface of some planets or moons. This raises some questions:
What is the theoretical minimum distance from Earth's core where life can still exist. Please explain how you came up with this number. For example, there are temperature-imposed limits on many biochemical processes.
Is there the potential to discover some truly alien life forms in the Earth's mantle (by this I mean, life which is not carbon based, or life which gets its energy in ways we have not seen before, or non DNA-based life, or something along these lines)?
What is the greatest distance below the Earth's crust that life has been discovered? I believe it is the 300 m I cited above, but I am not 100% sure. There's a lot we don't know about life in deep caves, but we can bound the deepest living organism to at least 3.5 kilometers down, and probably not more than 30 kilometers down.
The worms recovered from deep mining boreholes are not particularly specifically adapted to live that far down: they have similar oxygen/temperature requirements as surface nematodes.
The Tau Tona mine is about 3.5 kilometers deep and about 60˚ C at the bottom. Hydrothermal vent life does just fine up to about 80˚C, and the crust gets warmer at "about" 25˚C per kilometer. It's entirely reasonable to expect life to about 5 kilometers down, but further than that is speculation.
Increasing pressure helps to stabilize biological molecules that would otherwise disintegrate at those temperatures, so it's not impossible there could be life even deeper. It may even be likely, given that the Tau Tona life breathes oxygen.
I am certain no life we might recognize as life exists in the upper mantle.
The following is multiple choice question (with options) to answer.
Where on earth do bacteria live? | [
"all environments",
"water",
"skin",
"blood"
] | A | Prokaryotes include Bacteria and Archaea. An individual prokaryote consists of a single cell without a nucleus. Bacteria live in virtually all environments on Earth. Archaea live everywhere on Earth, including extreme environments. |
SciQ | SciQ-3097 | waves, electromagnetic-radiation
(Image Credit: https://www4.uwsp.edu/physastr/kmenning/Phys202/Lect16.html)
The following is multiple choice question (with options) to answer.
What type of waves radiate energy out from an earthquake's focus? | [
"seismic",
"abnormal",
"Microwaves",
"volcanic"
] | A | Geologists study earthquake waves to “see” Earth's interior. Waves of energy radiate out from an earthquake’s focus. These are called seismic waves ( Figure below ). Seismic waves change speed as they move through different materials. This causes them to bend. Some seismic waves do not travel through liquids or gases. Scientists use all of this information to understand what makes up the Earth’s interior. |
SciQ | SciQ-3098 | pathophysiology, kidney
Title: To diagnose osteomyelitis of vertebral column in chronic kidney failure Assume you suspect amyloidosis because of the history of the patient: problem with vertebral column and "purulent" (serous, fibrous, or hemorrhagic) inflammation when patient very young.
Now, the patient has a chronic renal failure.
Is there any other method to diagnose the fracture of some bone than röntgen?
Assume you do not know where the fracture is exactly. Osteomyelitis can be diagnosed with the following imaging techniques [1]:
first of all: radiography to view the anatomy of the bone
the sonography can be used to diagnose fluid collections, periosteal involvement. It is also the most useful procedure for kidney assessment [2].
CT is also useful to detect early osseous erosion, but is less sensitive when it comes to bone infection
MRI is the most sensitive and specific for osteomyelitis
Nuclear imaging can be used to identify multifocal osseous involvement.
References:
Carlos Pineda et al., Radiographic Imaging in Osteomyelitis: The Role of Plain Radiography, Computed Tomography, Ultrasonography, Magnetic Resonance Imaging, and Scintigraphy
American College of Radiology, Renal failure
The following is multiple choice question (with options) to answer.
What is a popular treatment for kidney failure? | [
"psychotherapy",
"electrolysis",
"metastasis",
"dialysis"
] | D | Uncontrolled diabetes may damage capillaries of nephrons. As a result, the kidneys lose much of their ability to filter blood. This is called kidney failure . The only cure for kidney failure is a kidney transplant, but it can be treated with dialysis. Dialysis is a medical procedure in which blood is filtered through a machine (see Figure below ). |
SciQ | SciQ-3099 | hematology
Title: Is Hemoglobin binding to oxygen the same as Adsorption I have recently been reading about Hemoglobin and came across how it binds to oxygen. This seems very similar to Adsorption. Is the process of Hemoglobin binding to oxygen through Adsorption ? From the Wikipedia article you cite the answer to your question is clearly NO. They seem very different: absorption is described as a surface phenomenon, whereas oxygen binding occurs in a single internal pocket in each globin subunit and forms a specific bond to an Fe(II) atom. The chemical nature of this pocket is quite different from that of the surface of the protein.
The Wikipedia article states:
Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface.[1] This process creates a film of the adsorbate on the surface of the adsorbent.
and
Similar to surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent, or metallic) of the constituent atoms of the material are filled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates.
However if you consult a text-book which describes the biochemistry of haemoglobin, such as Berg et al. you will find the specific chemical nature of the binding clearly described, as indicated by this extract:
The iron atom lies in the center of the protoporphyrin, bonded to the four pyrrole nitrogen atoms. Under normal conditions, the iron is in the ferrous (Fe2+) oxidation state. The iron ion can form two additional bonds, one on each side of the heme plane. These binding sites are called the fifth and sixth coordination sites. In hemoglobin, the fifth coordination site is occupied by the imidazole ring of a histidine residue from the protein. In deoxyhemoglobin, the sixth coordination site remains unoccupied...The binding of the oxygen molecule at the sixth coordination site of the iron ion substantially rearranges the electrons within the iron so that the ion becomes effectively smaller, allowing it to move into the plane of the porphyrin (Figure 10.19).
The following is multiple choice question (with options) to answer.
What is critical for the formation of hemoglobin? | [
"salts",
"proteins",
"iron ions",
"platelets"
] | C | Minerals Minerals in food are inorganic compounds that work with other nutrients to ensure the body functions properly. Minerals cannot be made in the body; they come from the diet. The amount of minerals in the body is small—only 4 percent of the total body mass—and most of that consists of the minerals that the body requires in moderate quantities: potassium, sodium, calcium, phosphorus, magnesium, and chloride. The most common minerals in the body are calcium and phosphorous, both of which are stored in the skeleton and necessary for the hardening of bones. Most minerals are ionized, and their ionic forms are used in physiological processes throughout the body. Sodium and chloride ions are electrolytes in the blood and extracellular tissues, and iron ions are critical to the formation of hemoglobin. There are additional trace minerals that are still important to the body’s functions, but their required quantities are much lower. Like vitamins, minerals can be consumed in toxic quantities (although it is rare). A healthy diet includes most of the minerals your body requires, so supplements and processed foods can add potentially toxic levels of minerals. Table 24.5 and Table 24.6 provide a summary of minerals and their function in the body. |
SciQ | SciQ-3100 | endocrinology, glucose, homeostasis, insulin, hypothalamus
Title: Role of the Hypothalmus in the control of Blood Sugar In homeostatic regulation of blood glucose, the receptor and effector is the Pancreas, but how does the control centre — the Hypothalamus — connect and link into this process? Your question doesn’t make it clear whether you think that the pancreas must be under the control of the hypothalmus, or whether you are asking whether it has an influence on the pancreas in relation to the secretion of insulin and glucagon, which control the concentration of blood glucose.
First, it has been long known that secretion of insulin can be influenced by the concentration of glucose in isolated pancreatic islets in vitro, so it can not be true that the effects must involve the hypothalmus. This is implicit in most book or general information articles you might find on the web, but for an original reference a review by W.J. Malaisse in Diabetologia 9, 167–173 (1973) seems highly cited.
I know almost nothing about physiology, but on searching the web for the role of the hypothalmus in glucose homeostasis, found a most readable prize-winning postgraduate essay on the topic by Syed Hussein of Imperial College London. I trust that it is in order to append an edited extract of this:
The following is multiple choice question (with options) to answer.
Which hormones work together to control the level of glucose in the blood? | [
"insulin and estrogen",
"serotonin and glucagon",
"insulin and glucagon",
"testosterone and insulin"
] | C | The pancreas is located near the stomach. Its hormones include insulin and glucagon. These two hormones work together to control the level of glucose in the blood. Insulin causes excess blood glucose to be taken up by the liver, which stores the glucose as glycogen. Glucagon stimulates the liver to break down glycogen into glucose and release it back into the blood. The pancreas also secretes digestive enzymes into the digestive tract. |
SciQ | SciQ-3101 | botany, plant-physiology, plant-anatomy
Title: Sporophyte and gametophyte
My textbook says that in both groups of seedless plants (vascular plants, non-vascular plants) the gametophyte is a free-living plant, independent of the sporophyte.
I don't understand this statement and am now wondering if the sporophyte and gametophyte are stages in a plant's lifecycle, or are they individual parts of the plant, or are the sporophyte and the gametophyte different plants altogether? Secondly, does this differ depending on the organism?
Different plants or different structures that make up the same organism? The sporophtye is the diploid stage in the life cycle. In comparison, with humans, you and I would be sporophytes.
The Gametophyte is the haploid stage in the life cycle. In comparison, with humans, spermatozoids and ovules are gametophytes.
The following is multiple choice question (with options) to answer.
What are the two basic parts that all flowering plants have in common? | [
"stalk and petiole",
"blade and petiole",
"metal and petiole",
"leaf and petiole"
] | B | Flowering vascular plants also have diverse leaves. However, the leaves of all flowering plants have two basic parts in common: the blade and petiole. 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-3102 | physiology
Title: Why does dehydration lead to low blood pressure I understand that the two leading causes of death from dehydration is imbalance in electrolytes and loss of blood pressure. I'm trying to understand what role water is playing in these cases and how the loss of it causes these imbalances, focusing for now on the blood pressure angle.
While I understand that blood is made up heavily of water, I'm still a little confused why dehydration so quickly leads to drop in blood pressure. Why can't the body continue to pump the already existing blood through the body, where is it using the water to keep the blood pressure up and what vital function is no longer being performed that causes that pressure to drop? The blood pressure is the exertion of force upon the blood vessels by the blood fluids. Thus having less fluids will results in decreased pressure.
The following is multiple choice question (with options) to answer.
Salts are important in maintaining what balance of the blood? | [
"homeostasis",
"kinetic",
"osmotic",
"pulmonary"
] | C | |
SciQ | SciQ-3103 | botany, plant-physiology, plant-anatomy
Title: How do plants grow year after year even though they die? How do plants grow, die, and then grow again? For instance, when my plants die during the winter, how do they grow again next year? Does it have something to do with the root system? Or do they even die? It depends on the type of plant, but basically not all of the plant dies. Plants have evolved a number of strategies for winter* dormancy. These are common ones, but probably not an exhaustive list.
Deciduous trees and bushes simply drop their leaves in the fall, and so may look "dead" to the unskilled eye - though with practice, it's usually easy to distinguish between dead and dormant. Then when the weather warms in the spring, new leaves grow.
Other perennial plants may lose some or all of their top growth, even dying back to ground level, but the roots will be alive, and will start growing when the ground warms.
Still other plants have developed specialized underground structures like bulbs & rhizomes - think daffodils, tulips, irises, and similar. The rest of the plant dies, only to grow again from the bulb when conditions are right.
It's worth noting that most, if not all, of these are used for propagation as well, often naturally, and frequently with a bit of human help. Bulbs and rhizomes multiply: the daffodil bulb you planted a few years ago may now be a dozen bulbs, each of which can be moved to grow new ones. Many perennials can be increased by dividing the root mass into pieces, each of which will become a new plant. And cuttings from many trees & bushes can be induced to form new root systems, and become new plants.
Or summer, dry season, &c. For simplicity, I'll just say "winter".
The following is multiple choice question (with options) to answer.
What do some animals grow to protect themselves in winter? | [
"scales",
"thicker fur",
"antennae",
"thin skin"
] | B | |
SciQ | SciQ-3104 | meteorology, mesoscale-meteorology
In a sense, the fact pressure at one elevation induces changes\motion in another elevation maybe shouldn't seem any less weird than the fact that a low-level low pressure system can affect the wind and weather hundreds of miles away from it horizontally. This isn't spooky action at a distance, this is a continuous fluid where changes to one part of it causes impacts on another part.
The following is multiple choice question (with options) to answer.
What weather phenomenon can raise sea level as much as 25 feet when low pressure pulls water upward? | [
"cloud formation",
"storm rise",
"storm surge",
"earthquake surge"
] | C | Some of the damage done by storms is from storm surge . Low pressure in a storm pulls water upward. Water piles up at a shoreline as storm winds push waves into the coast. Storm surge may raise sea level as much as 7.5 m (25 ft). This can be devastating in a shallow land area when winds, waves, and rain are intense. |
SciQ | SciQ-3105 | energy, visible-light, photons, sun, interactions
Title: What are the physical processes involved in feeling warm from the sunlight? Suppose a human is lying on a beach. He/she starts to feel warm after exposing his/her skin to the sunlight. I assume that feeling is due to the ability of the human body of "measuring" the increasing in temperature of the skin.
Now I want to understand what are the physical processes involved in this increasing in temperature.
Imagine a group of photons impinging on the skin in a certain interval of time. I tried to list the possible interactions from a particle physics perspective between photons and the human tissue and I concluded that the possible interactions may be:
Photoionization
Compton scattering
Rayleigh scattering
Pair production
The first 3 seems to be reasonable, but the fourth one requires an energy threshold too high: there are no incident photons that may have that energy. I conclude that by looking at the spectrum of sunlight that actually reaches the earth's surface below the atmosphere. So I think that the pair production does not play a role in this situation.
Are there any other interaction processes between photons and tissue molecules involved in the increasing of temperature of the human tissue?
After listing the processes I wonder what actually increases the temperature: is the temperature increasing because the photons-molecules interactions lead to a transition of molecules to excited vibrational states? or maybe transitions to excited rotational states?
I thought that another possibility is that the photons interactions are increasing the kinetic energy of the water molecules in the skin or maybe are increasing the lattice vibration of other tissue (skin, bones or others). Are this processes happening simultaneously? One of this processes (for example transition to rotational excited states) is dominant over the others ?
I'm looking to a qualitative answer, without going into too much details of the Biology of the human body. I just want to create an approximate picture of this situation in my mind. I want to create a mental "video" from the instant in which a photon or a group of photons impinges in the skin to the moment in which tissue molecules are affected and the temperature starts rising up.
I thank in advance anyone who answers this question. You forgot garden-variety absorption! Here, light promotes electrons from lower energy states to higher energy states. However, skin is made of many small particles, so scattering is important as well.
Here’s the mental video:
The following is multiple choice question (with options) to answer.
The action of sunlight on the skin triggers the body to produce what vitamin? | [
"vitamin d",
"Vitamin A",
"tissue d",
"metabolic d"
] | A | Milk and other dairy foods are not the only sources of calcium. This important nutrient is also found in green leafy vegetables, broccoli, and intact salmon and canned sardines with their soft bones. Nuts, beans, seeds, and shellfish provide calcium in smaller quantities. Except for fatty fish like salmon and tuna, or fortified milk or cereal, vitamin D is not found naturally in many foods. The action of sunlight on the skin triggers the body to produce its own vitamin D (Figure 6.22), but many people, especially those of darker complexion and those living in northern latitudes where the sun’s rays are not as strong, are deficient in vitamin D. In cases of deficiency, a doctor can prescribe a vitamin D supplement. |
SciQ | SciQ-3106 | acoustics, air, displacement
\end{align}$$
That is a Very Loud Pop - about 80 dB. Even if we argue that only a small fraction of this pressure ends up in the audible range there is no doubt in my mind you would hear "something".
So yes, you can hear that parchment disappearing. No problem. Even if some of my approximations are off by a factor 10 or greater. We have about 5 orders of magnitude spare.
AFTERTHOUGHT
If you have ever played with a "naked" loudspeaker (I mean outside of the enclosure, so something like this one from greatplainsaudio.com):
The following is multiple choice question (with options) to answer.
What is heard when sound waves bounce back from a surface that they can't pass through? | [
"loop",
"radio",
"ultrasound",
"echo"
] | D | Did you ever hear an echo of your own voice? An echo occurs when sound waves bounce back from a surface that they can’t pass through. The woman pictured here is trying to create an echo by shouting toward a large building. When the sound waves strike the wall of the building, most of them bounce back toward the woman, and she hears an echo of her voice. An echo is just one example of how waves interact with matter. |
SciQ | SciQ-3107 | hydrology, mountains, rivers
Title: Why do rivers have 'wells' in mountains? Why/how can rivers have sources in places high above the sea level? The presence of water underground has nothing to do with sea level in mountainous country.
When rain fails on a mountain, or snow falls on a mountain and the snow eventually melts, the water from the rain or snow melt mostly travels downhill via rivers to the sea.
In getting to a river some of the water will fall on the ground. In places where the ground is covered by soil, water can travel through the soil via the pore spaces between the grains of soil. Similarly if porous rock, such as sandstone lies beneath the soil water can travel through the pores in the rock.
If a layer of impervious rock lies under the porous rock or soil, the water cannot move downwards, due to gravity, any further. This can lead to water accumulating in the soil or porous rock and saturating the soil or rock. In such situations an aquifer can form. The top of the saturated zone in an aquifer is called a water table.
The ground beneath a river is saturated and the surface of the river shows the water table exposed to atmosphere. Thus in mountainous regions the ground beneath rivers will be saturated and capable of supporting a well developed from the bank of a river.
The following is multiple choice question (with options) to answer.
What is hole that is dug or drilled through the ground down to an aquifer? | [
"well",
"big hole",
"cave",
"elevator"
] | A | Many people get their freshwater from an aquifer. They obtain the water through a well. A well is a hole that is dug or drilled through the ground down to an aquifer. |
SciQ | SciQ-3108 | physiology, herpetology, poison, amphibians
+
0.002 mg/L will fatally damage the sensitive skin on tadpoles, frogs, salamanders and other amphibians.
another source:
Free chlorine (Cl2) is a greenish gas that is well known for its
highly toxic properties as can be attested to by the thousands of
soldiers that died and were severely injured from chlorine exposure
during World War I. In water, chlorine is the most toxic substance
that we will discuss. Ironically for the amphibian keeper, it is this
toxic nature of chlorine and its ability to denature proteins, which
makes its encounter inevitable. Chlorine is generally used as an
antibacterial agent in municipal water supplies and may be present in
concentrations of over 9 mg/1 in some tap water (measured in Houston,
Texas as an example, although levels were generally lower). The
concentration of chlorine in municipal water supplies can vary greatly
from day to day, or even hour to hour, depending on conditions at the
water treatment facilities. Concentrations as low as 0.0034 mg/1 have
been noted to reduce reproduction in fathead minnows with 72 hour
LC100 (lethal concentration for 100% kill) at 0.15 mg/1 (Arthur and
Eaton,1971). LC50 (96 hour) for the shiners (Notemigonus chrysoleucas)
was as low as 0.19 mg/1 (Esvelt et al., 1971). The concentrations
found in municipal water supplies are many times greater than the
minimum lethal concentrations for many aquatic life forms.
Thus, the well being of the frog in the water of the swimming pool depends on the time the frog spends in the water. Eventually, with extended exposure the chlorine concentration will exceed the one compatible will life and the frog will die. This time is multifactorial variable, thus cannot be assessed easily - the weight and the skin surface area and skin permeability will affect the frog survival in a great degree.
The following is multiple choice question (with options) to answer.
What protective substance covers the skin of most reptiles? | [
"feathers",
"pores",
"hairs",
"scales"
] | D | Reptiles are a class of tetrapod vertebrates that produce amniotic eggs. They include crocodiles, alligators, lizards, snakes, and turtles. The reptile class is one of the largest classes of vertebrates. It consists of all amniotes except birds and mammals. Reptiles have several adaptations for living on dry land that amphibians lack. For example, as shown in Figure below , the skin of most reptiles is covered with scales. The scales, which are made of very tough keratin , protect reptiles from injury and prevent them from losing water. |
SciQ | SciQ-3109 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
What step, involving placement of a substance on the stigma, precedes fertilization? | [
"pollination",
"mitosis",
"hibernation",
"spawning"
] | A | |
SciQ | SciQ-3110 | meteorology, weather-forecasting, tornado, thunderstorm
Title: Could a large burst of super-heated or super-cooled air cause tornadoes to fall apart? We know how tornadoes form: when areas of hot air and cold air mingle, causing rotation. We can even see them form on the radar.
Yet, for all of our technology, we can't stop such events from happening - even though we can cause it to rain by seeding clouds.
But if someone were at the area that a tornado was about to form and was able to introduce an area of super-heated or super-cooled air into the potential tornado, would it destabilize the formation of the destructive whirlwind? Or would doing such a thing cause more of them to form or for them to form more quickly and/ or be more damaging? Changing air currents is very difficult and energy intensive. You'd need to alter an entire weather system - no easy feat. If you heated a very large region of cool air you might prevent the spiraling that causes tornadoes to form, but you'd need to warm at least few states worth of upper atmosphere. It would be an enormous undertaking.
There's also the logistical problem of how would you go about doing it? Heating in principal can be done faster than cooling, presumably sending up a whole lot of hydrogen in a few hundred balloons and igniting it forming hot water-vapor, which as it condenses, would further heat the atmosphere. Cooling warm air is harder as there's no quick and easy method to cool an enormous volume of air, so I think heating the high cold air would be easier than cooling the low moist air, but it would still be an enormous effort and probably cost more in prevention than the tornadoes are likely to do in total damage.
http://images.slideplayer.com/22/6379142/slides/slide_22.jpg
There's no neat and tidy technological trick to get it done that I can think of.
The following is multiple choice question (with options) to answer.
What weather phenomenon is caused by strong warm updrafts from heated ground? | [
"earthquakes",
"thunderstorms",
"currents",
"eruptions"
] | B | Thunderstorms form when the ground is really hot ( Figure below ). The air near the ground becomes very warm and humid. This is true in some locations in late afternoon or early evening in spring and summer. The warm air rises rapidly, which creates strong updrafts. When the rising air cools, its water vapor condenses. The updrafts create tall cumulonimbus clouds. Winds blow the cloud top sideways. This makes the well-known anvil shape of a cloud known as a thunderhead ( Figure below ). Water droplets and ice fly up through the cloud. When these droplets get heavy enough, they fall. This starts a downdraft. A convection cell develops within the cloud. A mature thunderstorm produces gusty winds, lightning, heavy rain, and hail. |
SciQ | SciQ-3111 | homework, plant-physiology, plant-anatomy
and 'Vascular Plants = Winning! - Crash Course Biology #37'
https://youtu.be/h9oDTMXM7M8?t=373
[5] Osmosis (water compensating solutes) "In Da Club - Membranes & Transport: Crash Course Biology #5"
https://youtu.be/dPKvHrD1eS4?list=PL3EED4C1D684D3ADF&t=148
Ian (and dad <= all errors and approximations are his :) ).
The following is multiple choice question (with options) to answer.
The older parts of what structures anchor the plant and transport water and solutes between the soil and shoots? | [
"roots",
"leaves",
"cells",
"bark"
] | A | |
SciQ | SciQ-3112 | botany, plant-physiology, plant-anatomy
*No others are known, but could definitely exist.
Bibliography
Crafts, A. S. “Phloem Anatomy, Exudation, and Transport of Organic Nutrients in Cucurbits.” Plant Physiology 7, no. 2 (1932): 183–225.
Fischer, A. “Das Siebröhrensystem von Cucurbita.” Berichte Deutsche Botanische Gesell 1 (1883): 276–279.
Fischer, A. “Neue Beiträge Zur Kenntniss Der Siebröhren.” Berichte Über Die Verhandlungen Der Königlich-Sächsischen Gesellschaft Der Wissenschaften Zu Leipzig, Mathematisch-Physische Klasse 38 (1886): 291–336.
Fischer, A. Untersuchungen Über Das Siebröhren System Der Cucurbitaceen. Berlin, 1884.
Turgeon, R. and Oparka, K. “The Secret Phloem of Pumpkins.” Proceedings of the National Academy of Sciences 107, no. 30 (2010): 13201 –13202.
Walz, C. and Giavalisco, P. and Schad, M. and Juenger, M. and Klose, J. and Kehr, J. “Proteomics of Curcurbit Phloem Exudate Reveals a Network of Defence Proteins.” Phytochemistry 65, no. 12 (2004): 1795–1804.
Zhang, B. and Tolstikov, V. and Turnbull, C. and Hicks, L. M. and Fiehn, O. “Divergent Metabolome and Proteome Suggest Functional Independence of Dual Phloem Transport Systems in Cucurbits.” Proceedings of the National Academy of Sciences 107, no. 30 (2010): 13532.
The following is multiple choice question (with options) to answer.
What do you call a specialized type of plant tissue that transports water and nutrients throughout the plant? | [
"vascular tissue",
"chloroplasm",
"thermal tissue",
"cambrium layer"
] | A | Vascular seedless plants have vascular tissue, a specialized tissue that transports water and nutrients throughout the plant. |
SciQ | SciQ-3113 | physiology, nutrition, organic-chemistry
Title: How is it known that there are only three macronutrients: proteins carbohydrates and lipids? It is stated here that in human nutrition, micronutrients are nutrients required generally in less than 100 mg daily quantities whereas macronutrients are required in gram quantities. It is widely stated that our macronutrients are carbohydrates, lipids, and proteins. How was it shown that these are the human macronutrients and that we don't have other macronutrients?
One answer to this similar question on Quora suggests that ethanol or ketones could be considered macronutrients. Ethanol is mentioned in this article, though ketones are not. Other sources I saw didn't clarify. Summary
The question is based on the misconception that the term “macronutrient” originated as a scientific definition, to which entities satisfying this definition were assigned. In fact it was a default term used as a distinction from compounds falling into the earlier category, “micronutrient”, and was used initially to encompass the three specific classes of food that had been established to be sources of energy through decades of nutritional research. Hence there was no question of whether there “should” be more macronutrients. The term is not a scientific definition, and today is used in different ways so that anyone using the term needs to clarify what it should be taken to mean in that particular context.
Food Energy and the history of Nutrition
Scientific studies of nutrition, dating the late 18th century, were initially concerned with chemical structure, metabolic fate and energy produced by different foods, and this is described in a short readable article by Ned Stafford in Nature (2010) 468, S16–17.
By the end of the 19th century protein, fat and carbohydrate had been established as the chemical fuels that supplied energy from the diet, and the energy values (in terms of the, now obsolete, calorie) had been established by Atwood, using his respiration calorimeter.
Micronutrients
The following is multiple choice question (with options) to answer.
The major fuel for the brain is which carbohydrate? | [
"glucose",
"insulin",
"glutamate",
"sucrose"
] | A | The brain is a marvelous organ. And it’s a hungry one, too. The major fuel for the brain is the carbohydrate glucose. The average adult brain represents about 2% of our body’s weight, but uses 25% of the glucose in the body. Moreover, specific areas of the brain use glucose at different rates. If you are concentrating hard, (taking a test, for example) certain parts of the brain need a lot of extra glucose while other parts of the brain only use their normal amount. Something to think about. |
SciQ | SciQ-3114 | meteorology, tornado
into
... because F6 or stronger tornadoes are not expected to occur on the
earth, they will be called Inconceivable tornadoes should they ever
occur. [1981 paper]
Very importantly, the Fujita scales are damage scales, simply because it's very difficult to directly measure the speeds of a tornado. As such we base tornado ratings by analyzing the degree which it damaged objects; SPC's Fujita scale page lists the 28 damage indicators currently available as of 2017. The highest wind speed matched with any of them, found when significant structural deformation is done to a high-rise building (over 20 stories tall), would only indicate an upper bound of 290 mph.
That does not indicate that wind speeds aren't higher than that, only that we have no structures that can withstand any higher wind speeds. Thus there would not be any potential for an F6 rating unless building methods are substantially changed to withstand stronger speeds, those buildings became prevalent enough that engineering testing were done and were able to verify its strength, and then such an extreme tornado ever hit them. Not something we're going to see anytime soon it appears.
So back to the question of whether tornadoes have winds stronger than those listed for an (E)F5? Measurement of the wind speed appears our only real hope of noting such. In-situ instruments such as anemometers generally fail well before winds reach such speeds, and typical radars cannot offer the resolution to diagnose such speeds. Only mobile Doppler radars offer much hope. There are numerous issues with utilizing such measurements, such as the fact they scan significantly above the ground layer, their sampling areas\timescales that make analyzing suction vortices difficult, and they contain uncertainties due to Nyquist frequencies, variations in reflective objects, and statistical distributions.
Such tornadoes are very rare to encounter. But in the past couple decades we have indeed managed to attain a handful of close-proximity estimated measurements of strong tornadoes. But I am not aware of any peak estimated wind speed reaching beyond the (E)F5 range. Here are the most notable ones I'm aware of:
The following is multiple choice question (with options) to answer.
How do they classify tornadoes? | [
"wind temperature",
"amount of destruction",
"wind speed",
"wind density"
] | C | The winds of a tornado can reach very high speeds. The faster the winds blow, the greater the damage they cause. Wind speed and damage are used to classify tornadoes ( Table below ). |
SciQ | SciQ-3115 | metabolism, human-anatomy, pharmacology, liver
Title: Circulation through the liver in light of drug metabolism I have a lingering question which stems from an answer that I gave to What hydrolyses aspirin within the digestive tract and blood stream?
When a drug or any other substance is absorbed into the bloodstream in the stomach or small intestine, it ultimately passes through the hepatic portal vein and into the liver sinusoids, where it is processed by hepatocytes and introduced into the general circulation via the vena cava. In terms of metabolism, this is what causes a "first-pass" effect for drugs that are ingested.
For drugs that are delivered either by intravenous, intramuscular, or sub-lingually (as in the other Biology.SE question), this first-pass effect is avoided, and the drug is introduced into the general circulation without being metabolized by the liver first.
Even though the first pass is avoided, the blood in the body still makes its way back through the liver eventually via the hepatic artery, which is a branch off of the celiac artery.
The issue I still have is, does the incoming blood from the hepatic artery merge with the blood from the hepatic portal vein? If not, does the blood from the hepatic artery still interact with the hepatocytes in some way? (it makes sense that it does, and I have also read that one of the main functions of the hepatic artery was to deliver blood supply for the liver's metabolic needs) If this is not the case, where in the body would these drugs that were introduced via IV, etc., be metabolized? Yes, the blood from the hepatic artery (proper) and the portal vein mix in the sinusoids of the liver. The hepatic vein supplies about 75% of the blood to the liver, and the hepatic artery the remaining 25%. Because the portal vein provides such a large part of the blood supply to the liver, then any disease that causes the blood to build up can cause portal hypertension.
The hepatic artery carries oxygen-rich blood from the heart. The portal vein is part of the portal system and connects the capillary beds of the gastrointestinal tract to those of the liver. Because of the larger volume through the portal vein, I think that each vessel carries about half the oxygen supply to the liver.
The following is multiple choice question (with options) to answer.
What part of the body does hepatitis b effect? | [
"liver",
"heart",
"joints",
"kidney"
] | A | Hepatitis B is a disease of the liver. It is caused by a virus called hepatitis B, which can be passed through sexual activity. Hepatitis B causes vomiting. It also causes yellowing of the skin and eyes. The disease goes away on its own in some people. Other people are sick for the rest of their lives. In these people, the virus usually damages the liver. It may also lead to liver cancer. Medicines can help prevent liver damage in these people. There is also a vaccine to protect against hepatitis B. |
SciQ | SciQ-3116 | electromagnetic-radiation, atmospheric-science, climate-science
The point between the 2 peaks is approximately 2.5 µm
A comparison between the size fractions and other small entities is shown below, just to gain some perspective:
Image source: clinicalgate.com
Studying the effects of all aerosols, particularly particulate matter on incoming solar radiation has been of major interest to atmospheric sciences as it constitutes a major source of uncertainty in radiative models. The research in how PM affects the UV (both UVA and UVB) has been, in part, a focus of many (like me) who are involved with photobiology.
There are several complications with PM, some species are emitted at a certain size, but due to chemical and other processes, they can grow into much larger secondary particulates. Additionally, some species have differing absorption of specific wavebands in the UV (and other wavelengths of light). So, this answer will concentrate on the size of the particles and their effect on the incoming UV radiation.
A key point made by the MTSU webpage (linked above) provides a general answer to one of your main questions ("Would the attenuation be mainly due to scattering?"):
Light scattering is caused by all atmospheric particles, but particles very near the same diameter as the wavelength of light scatter photons most effectively.
The MTSU webpage provides a comparison chart between electromagnetic radiation and some common types of aerosol/PM - of particular interest for this question is the solar radiation in the UV:
It is important to realise that scattering refers to light received by a particle and re-radiated at the same wavelength.
This relates to the main part of your question, whether aerosol particulate matter attenuates more in the UVA than in the UVB - (essentially wavelengths of about 295 nm and above and divided at 315 or 320 nm depending on what reference you refer to (IARC Working Group Monograph - Solar and Ultraviolet Radiation)).
Essentially, a general answer is - it depends on the size of the particulate aerosol present. The process is summarised nicely by the MTSU webpage as:
The following is multiple choice question (with options) to answer.
In the radiative zone, light particles called what can only travel a few millimeters before they hit another particle? | [
"electrons",
"photons",
"positrons",
"neutrons"
] | B | The radiative zone is the next layer out. It has a temperature of about 4 million °C. Energy from the core travels through the radiative zone. The energy travels at an extremely slow rate. Light particles are called photons . In the radiative zone, photons can only travel a few millimeters before they hit another particle. The particles are absorbed and then released again. It may take 50 million years for a photon to travel all the way through the radiative zone. |
SciQ | SciQ-3117 | geology, oceanography, geochemistry, mineralogy
Title: Will the sea get saltier forever? The sea wasn't always salty. It's been getting saltier over millions of years as minerals dissolve.
Is there a natural limit to this process, or the will the sea keep getting saltier forever?
Is there a natural process which removes salt from the sea at a significant rate?
How long would it take for the sea to get too salty to support life as we know it? No there are natural processes that remove salt as well.
as sea level changes water gets trapped in basins and evaporates leaving the salt behind, this is where many of the salt formation on earth came from. whenever sea levels fall the salinity of the ocean drops. Tectonically isolated basin can remove salt in the same way. The process can even happen repeatedly in the same basin as sea level changes.
There are biological processes that remove it as well the formation of shells and limestone remove some of the ocean salts.
Can it increase yes, but it can also decrease, over earths history there have been saltier and less salty periods.
The following is multiple choice question (with options) to answer.
What natural resource can be damaged by the accumulation of too much salt? | [
"mineral",
"soil",
"forests",
"sediment"
] | B | Soils may also remain in place but become degraded. Soil is contaminated if too much salt accumulates. Soil can also be contaminated by pollutants. |
SciQ | SciQ-3118 | human-anatomy, language
Title: Why are we using upper teeth and lower lip on labiodental sounds? I came to wonder this when studying language (as well as other same theme question posted just few ago). For example the word "fantastic" we use upper teeth and lower lip to produce F sound, instead of using lower teeth and upper lip, which would work as well with a small practice. The alternative articulation, called dentolabial, is more difficult to articulate, so it is very rarely used in human language. However, it apparently is common enough in disordered speech to be allocated an ExtIPA diacritic.
The reason labiodentals are easier: Humans normally have a slight overbite.
When the jaw and lips are in a "neutral" position, the lower lip is close to or touching the upper teeth, so with a small vertical movement of the jaw (together with tensing the lip) one can articulate a labiodental. Articulating a dentolabial requires moving the jaw a fair distance forward, to go around the upper teeth before reaching the upper lip. As Ben pointed out in the comments, front-back jaw movement is unusual, a less "common movement in terms of other vocalisations and eating".
Furthermore, since labial articulations are directly visible to observers, learners are especially likely to imitate others' exact articulation. Thus even though labiodentals and dentolabials sound similar, everyone in the population of speakers uses the same articulation (rather than having both articulations in free variation).
Perhaps dentolabials would instead be more common if most people were like this:
The following is multiple choice question (with options) to answer.
What secures teeth in the mouth? | [
"cartilage",
"socket",
"plug",
"muscles"
] | B | Anatomy of a Tooth The teeth are secured in the alveolar processes (sockets) of the maxilla and the mandible. Gingivae (commonly called the gums) are soft tissues that line the alveolar processes and surround the necks of the teeth. Teeth are also held in their sockets by a connective tissue called the periodontal ligament. The two main parts of a tooth are the crown, which is the portion projecting above the gum line, and the root, which is embedded within the maxilla and mandible. Both parts contain an inner pulp cavity, containing loose connective tissue through which run nerves and blood vessels. The region of the pulp cavity that runs through the root of the tooth is called the root canal. Surrounding the pulp cavity is dentin, a bone-like tissue. In the root of each tooth, the dentin is covered by an even harder bone-like layer called cementum. In the crown of each tooth, the dentin is covered by an outer layer of enamel, the hardest substance in the body (Figure 23.11). Although enamel protects the underlying dentin and pulp cavity, it is still nonetheless susceptible to mechanical and chemical erosion, or what is known as tooth decay. The most common form, dental caries (cavities) develops when colonies of bacteria feeding on sugars in the mouth release acids that cause soft tissue inflammation and degradation of the calcium crystals of the enamel. The digestive functions of the mouth are summarized in Table 23.4. |
SciQ | SciQ-3119 | reproduction, asexual-reproduction
Title: can self-fertilization in flowers be called asexual reproduction? Suppose a flower having both male and female reproductive parts is self-fertilized then can this be called asexual reproduction...?I'm quite confused cause in this case the fusion of male and female gametes do take place but again the gametes are from the same parent....please help. According to this article from Berkeley, asexual reproduction is:
Any reproductive process that does not involve meiosis or syngamy
Using this definition of asexual reproduction and knowing self-fertilization involves meiosis and syngamy, it is not asexual.
The following is multiple choice question (with options) to answer.
What is the production of offspring without gamete fusion called? | [
"ideal reproduction",
"organic reproduction",
"asexual reproduction",
"sexual reproduction"
] | C | |
SciQ | SciQ-3120 | geophysics, plate-tectonics
Title: Equatorial bulge and tectonic plates It is well known that the Earth is not a sphere, but rather it bulges at the equator. Also it is well known that the Earth's crust is composed of 7 or 8 (depending on definition) major tectonic plates, which are able to move on top of the asthenosphere, the upper layer of the Earth's mantle.
Due to the equatorial bulge, it would seem as though plates near the equator should not be able to drift away from the equator, and plates away from the equator should not be able to drift near the equator, since they will not be of the right shape to fit over these portions of the Earth. So how are the plates able to drift to and from the equator when the surface of the Earth is shaped differently there? The plates are not as rigid as you think. You seem to be imagining the situation as something like this: I boil an egg and take the shell off in pieces, but I can't take a piece of shell from the end and make it lay flat on the side of the egg. However, rock is not that rigid on scales of thousands of kilometres and millions of years (I don't think there exists any material which would be that rigid). Also, Earth's equatorial bulge is tiny relative to its diameter -- less than 50km. Tectonic plates move very slowly, and there is plenty of time for them to deform as they move.
The following is multiple choice question (with options) to answer.
What causes continents to drift closer to the poles or the equator? | [
"sediment movements",
"plate movements",
"tidal pull",
"wind"
] | B | Plate movements cause continents to drift closer to the poles or the Equator. Ocean currents also shift when continents drift. All these changes can affect Earth’s temperature. |
SciQ | SciQ-3121 | biochemistry, mitochondria, bioenergetics, chloroplasts
A hypothesis is an assumption made before any research has been done.
It is formed so that it can be tested to see if it might be true. A
theory is a principle formed to explain the things already shown in
data. Because of the rigors of experiment and control, it is much more
likely that a theory will be true than a hypothesis.
But is this dogmatism justified, and how does it apply to the current problem? Mitchell’s proposal was made to be tested (as in a hypothesis) but it was intended to explain the observed phenomenon (as in a theory) of oxidative phosphorylation.
An extensive article in Wikipedia begins with a more modest statement:
A hypothesis (plural hypotheses) is a proposed explanation for a
phenomenon.
And chemi-osmosis is a proposed explanation for the phenomenon of ATP synthesis in double-membrane systems; so by this token Mitchell’s choice of words seems justified.
Major dictionaries record how words are or were used in practice. In some contexts there are sharp distinctions in usage of particular words, where in others the same words are used interchangeably. In modern biological science, unlike philosophy, logic or the numerical sciences, laws, theories and hypotheses are generally of no great concern, and the writers quoted may merely feel that the word ‘theory’ (‘Einstein’s’ theory, ‘Darwin’s theory’) has more gravitas than ‘hypothesis’, a word they perhaps use to describe ideas about relatively humble scientific problems of their own.
…or they may just find it easier to spell.
The following is multiple choice question (with options) to answer.
What does a hypothesis become after many experiments provide results supporting it? | [
"a study",
"a model",
"a theory",
"a fact"
] | C | The scientific method is employed by scientists around the world, but it is not always conducted in the order above. Sometimes, hypothesis are formulated before observations are collected; sometimes observations are made before hypothesis are created. Regardless, it is important that scientists record their procedures carefully, allowing others to reproduce and verify the experimental data and results. After many experiments provide results supporting a hypothesis, the hypothesis becomes a theory . Theories remain theories forever, and are constantly being retested with every experiment and observation. Theories can never become fact or law . |
SciQ | SciQ-3122 | mineralogy, petrology
Title: How do you use the streckeisen (QAPF) classification ternary diagram to identify igneous rocks based on chemical rock composition? I have been given the following diagrams:
and
and a database that is structured like this:
ROCK NAME |SIO2 |TIO2| AL2O3| CR2O3| FEOT| CAO| MGO| MNO| K2O| NA2O| P2O5|
WEHRLITE |45.42| 0.17| 2.57| 0.32| 11.3384| 7.54| 31.93| 0.17| 0.01| 0.24| 0.01|
I want to know how to normalize the data and use these diagrams to identify the rock name based on the IUGS specification. I then am tasked to write a program that will do this automatically meaning that I have to come up with some semi-mathematically-based process to identify these rocks. Any ideas? Why you should not do it
The QAPF and related diagrams are intended for classification of rocks in the field, or preliminary classification with modal proportions as seen in the optical microscope. They are not designed with the chemical composition of the rocks in the mind. Furthermore, these diagrams are merely descriptive and not genetic. They do not take into account many factors affecting the various characteristics of the rocks. While doing something like this may be interesting for homework exercise, it is not something I would expect to see in a recent research article.
If you want to do it anyway
Your solution should consist of two steps.
The following is multiple choice question (with options) to answer.
Geologists group rocks based on how they what? | [
"dissove",
"move",
"look",
"form"
] | D | Geologists group rocks based on how they form. There are three major rock types. Each will be described in more detail in the coming concepts. |
SciQ | SciQ-3123 | genetics, dna, dna-sequencing, human-genetics
Title: Do eukaryote cells contain DNA that isn't part of a chromosome or located in the mitochondria? I specify eukaryote in the title, but I'm also interested if this question isn't applicable to eukaryote cells in general but is to humans. I was reading "RNA-seq: An assessment of technical reproducibility and comparison with gene expression arrays" (John Marioni 2008).
In the results it states
"By these criteria, 40% of reads mapped uniquely to a genomic location, and of these, 65% mapped to autosomal or sex chromosomes (the remainder mapped almost exclusively to mitochondrial DNA)."
I couldn't help but notice the "almost exclusively to mitochondrial DNA". Almost exclusively? Can DNA be found in places other than chromosones or mitochondria? Perhaps I'm interpreting the sentence wrong. Any pointers would be appreciated
Thanks In plants, chloroplasts and other plastids contain DNA, but I suppose you are more interested in humans. Quoting from wikipedia,
In many cells cytoplasmic DNA is also found, which is different from
nuclear DNA, both in methylation levels (cytoplasmic has less), and in
sequence. EccDNA or extrachromosomal circular DNA is present in all
eukaryotic cells, derived from genomic DNA and consists of repetitive
sequences of DNA found in both coding and non-coding regions of
chromosomes. EccDNA can vary in size from less than 2000 more than
20,000 base pairs. In animals, eccDNA molecules have been shown to
contain repetitive sequences that are seen in satellite DNA, 5S
ribosomal DNA and telomere DNA. The function of eccDNA has not been widely studied, but it has been proposed that the production of elements of eccDNA from genomic DNA sequences adds to the plasticity of the eukaryotic genome and can influence genome stability, cell aging and the evolution of chromosomes
The following is multiple choice question (with options) to answer.
What organelle contains the genetic material of the cell? | [
"nucleus",
"fetus",
"gamete",
"meiosis"
] | A | The nucleus contains the genetic material of the cell. |
SciQ | SciQ-3124 | waves
Title: Can a wave propagate in any substance? Aren't there any prerequisites? We see waves propagate in air, water, through the cristal of a metal and along a rope.
Isn't a wave a wonder of Nature, or is it just a simple phenomenon?
Are homogeneity and isotropy necessary properties for the correct propagation of waves?
Update
are a rope, water and space/EM field elastic in the same way? A wave can propagate in any medium that is:
a) elastic
b) less than critically damped
Neither homogeneity nor isotropy are necessary.
Any elastic system will return to it's original state when deformed, the question is just whether the deformation can propagate, and this is down to how quickly the energy of the deformation is dissipated. If the damping is high enough, this is critical damping, the material will return to its original state with a $e^{-\alpha t}$ dependance on time and no wave will propagate.
For example, in water common experience tells a gravity wave (i.e. a wave) propagates just fine, and a longitudinal wave (i.e. sound) propagates just fine. However shear waves will not propagate because they are too rapidly damped.
The following is multiple choice question (with options) to answer.
What kind of waves travel through liquids and solids as well as air? | [
"light waves",
"radio waves",
"sound waves",
"mind waves"
] | C | Sound waves can travel through many different kinds of matter. Most of the sounds we hear travel through air, but sounds can also travel through liquids such as water and solids such as glass and metal. If you swim underwater — or even submerge your ears in bathwater — any sounds you hear have traveled to your ears through water. You can tell that sounds travel through glass and other solids because you can hear loud outdoor sounds such as sirens through closed windows and doors. |
SciQ | SciQ-3125 | photosynthesis, cellular-respiration, energy, sugar
Basically, points 4-7 convey that Calvin-Benson cycle not only produces sugar but what it actually does is fix inorganic carbon (as CO2) to organic form (in the form of sugar). So, most (practically all) of the carbon that a photosynthetic plant has, comes from this carbon fixation process and that's how plants are photoautotrophic.
The following is multiple choice question (with options) to answer.
What is made by trees and other plants during photosynthesis? | [
"oxygen",
"nitrogen",
"carbon dioxide",
"methane"
] | A | Oxygen is made by trees and other plants during photosynthesis. We know that we need oxygen to live. But why? This oxygen is an essential component for the optimal production of usable energy - which occurs through cellular respiration. |
SciQ | SciQ-3126 | general-relativity, gravity, visible-light, electromagnetic-radiation, photons
Title: Is the Light REALLY bent? I've learned that always, the light go straight. The as Einstein's gravitation therory, the light can be bent in bented space-I mean, curved space.
Actullay, I think that if we in the space which interrupted by gravity, we can SEE a straight light. (The direction can be choosed by observer)
So, what is right?? Well this matter is probably mostly quibbling about fine definitions, but light follows so-called lightlike geodesics in spacetime, so as a matter of principle I would say that it follows "straight lines". A geodesic is simply the notion of a straight line generalized to the case where the geometry in question does not fulfill Euclid's parallel postulate. You can't do any better that this to generalize the notion of a straight line in Euclidean geometry.
Now, this generalization does not have all the properties of a Euclidean straight line - we've lost the parallel postulate, after all. In particular, the geometric distortion means that it can "look" bent from the point of view of a distant observer (in the sense that its projection onto a distant, inertial astronomer's field of view is a curved line). And it is no good defining "straight" to be something that projects onto a straight line on this astronomer's field of view, because that definition would be observer dependent. You can't conserve any more of the notion of straightness in non-Euclidean geometry than what is encapsulated in the definition of the notion of geodesic.
A minor pedantic point: the principle that light travels in straight lines only holds if the wavelength / frequency is much smaller than the length scale over which spacetime deviates significantly from flatness. Otherwise, diffraction effects become significant.
The following is multiple choice question (with options) to answer.
Regardless of the mode, light is modeled as traveling in straight lines called what? | [
"rays",
"waves",
"arrows",
"electrons"
] | A | 25.1 The Ray Aspect of Light There are three ways in which light can travel from a source to another location. (See Figure 25.3. ) It can come directly from the source through empty space, such as from the Sun to Earth. Or light can travel through various media, such as air and glass, to the person. Light can also arrive after being reflected, such as by a mirror. In all of these cases, light is modeled as traveling in straight lines called rays. Light may change direction when it encounters objects (such as a mirror) or in passing from one material to another (such as in passing from air to glass), but it then continues in a straight line or as a ray. The word ray comes from mathematics and here means a straight line that originates at some point. It is acceptable to visualize light rays as laser rays (or even science fiction depictions of ray guns). Ray The word “ray” comes from mathematics and here means a straight line that originates at some point. |
SciQ | SciQ-3127 | zoology, species-identification, ornithology, behaviour
Title: What is this crow eating, and is it a common part of the corvid diet? Here's a picture (by Rob Curtis) of a crow carrying and eating the corpse of what looks a bit like a small hawk or falcon:
Other pictures clearly show the crow is eating the dead bird. This image shows the underside of the head and beak; this one shows its legs, which are grayish.
What bird is being eaten?
Is this bird a usual part of the corvid diet? Or did the crow just opportunistically scavenge a dead bird? Crows are omnivorous, and will eat almost anything they find or can kill.
In this case the prey looks like a Yellow-Shafted Flicker.
The following is multiple choice question (with options) to answer.
What are organisms called, like the red-winged blackbird, that eat many different types of food? | [
"carniverous",
"specalist",
"omniverous",
"generalists"
] | D | Birds may be specialists or generalists in terms of what they eat. Generalists are organisms that eat many different types of food. Birds that are generalists include the red-winged blackbird in Figure below . It has a basic beak that can eat many different foods. Red-winged blackbirds are omnivores. They may eat a wide variety of seeds as well as insects and other small animals such as snails and frogs. |
SciQ | SciQ-3128 | evolution, terminology, classification
Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time.
Any node in a (fully bifurcating) tree that is an ancestor to more than two tips will necessarily contain tips that are also descended from some other node.
OP is correct that "there is a common ancestor at some point," and there is strong evidence that all cellular life arose by common descent from our most recent common ancestor.
In practice, the term is usually limited by context. For example, many more relevant comparisons can be made between roses and apples, than between roses and dogs, even though the ancestor of animals and plants did once exist. In a conversation about energy procurement it wouldn't make sense to reference the common descent between roses and dogs; but in a conversation about, say mitosis, it might.
The term "related" suffers similar ambiguity.
As the figure shows, two species can share many "common ancestors," so it may be necessary to specify the "most recent common ancestor." In the figure, both A and B are common ancestors of 1 and 2, but A is their most recent common ancestor.
B is the most recent common ancestor of 1,3, 2,3, and 1,2,3.
The thick black line coming down from B in the figure represents the connection to B's ancestors. All of those ancestors are common ancestors of 1,2,3, but none are the most recent common ancestor of 1,2,3.
The most recent common ancestor of cellular life is the last universal common ancestor.
OP may want to review the term clade for a slightly more precise way to talk about related species. A clade is a group composed of an ancestor plus all and only its descendants.
In the figure:
1 and 2 form a clade with A.
1, 2, 3, A, and B form a clade.
1 and 3 (excluding 2) do not form a clade.
The following is multiple choice question (with options) to answer.
What is a common name for the descriptive hypothesis that help to understand patterns of descent? | [
"gene mapping",
"evolutionary trees",
"genetic trees",
"genetic order"
] | B | |
SciQ | SciQ-3129 | thermodynamics, physical-chemistry, chemical-potential, combustion
Title: How to thermodynamically understand process of burning a piece of coal? Let's imagine that I have a match in hand and nugget of coal on my desk. Then I light up the match and place it for few seconds near the coal so a tiny piece of nugget catches fire.
Then another piece catches fire, then another and soon all the nugget is burnt down.
How did it happen? I gave the nugget just enough heat to burn the first piece. Where does come energy to burn the rest of nugget from? It is called combustion, and it happens in materials which have a lower energy content when their component molecules join with the oxygen in the atmosphere, than when in a solid/liquid structure. When energy is given to start the fire the piece of coal burns and releases energy with excess enough to sustain the reaction and leave heat energy for use.
Combustion is a high-temperature exothermic chemical reaction between a fuel and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke.
The following is multiple choice question (with options) to answer.
Exemplified by a lit match bursting into flame or the process that forms fossil fuels, chemical reactions vary greatly in terms of what? | [
"duration",
"speed",
"density",
"power"
] | B | Chemical reactions vary widely in the speeds with which they occur. Some reactions occur very quickly. If a lighted match is brought in contact with lighter fluid or another flammable liquid, it erupts into flame instantly and burns fast. Other reactions occur very slowly. A container of milk in the refrigerator will be good to drink for weeks before it begins to turn sour. Millions of years were required for dead plants under Earth’s surface to accumulate and eventually turn into fossil fuels such as coal and oil. |
SciQ | SciQ-3130 | water, pressure, building-physics
Title: Water flushed down, water pumped up (in buildings) I live in a tall building (20 floors) on a mountain. Because the water pressure from the water company is not enough, there is a water pump at the last floor which is activated each time someone is using fresh water in his apartment.
To me, that's a big waste of energy, and I think that in theory it would be possible to reuse the used water which is going down to pump some fresh water up.
I wonder if such device already exist on the market, and I would like to know how such device would be called. Would there be a problem to operate with such a height difference? In theory, yes, this could be done. Pretty much exactly as much gravitational energy is lost by the water coming down as is gained by the water going up, so you could then supply the water while hardly using any energy at all. (Just enough to offset the heat generated by friction in the pipes.)
One way in which it can be done in theory is simply to connect two gear pumps with a solid axel. Water from the down pipe will force the axel to turn, which then drives the up pump. Water can be made to flow by applying just a little bit of extra torque to the axel.
However, in practice I don't think this would be done. I imagine there would be a lot of practical issues involved in passing waste water through a pump - it would at least have to be filtered first - and as EnergyNumbers points out in a comment, the energy needed to pump water up 20 floors is pretty small in comparision to (for example) heating the apartments.
The following is multiple choice question (with options) to answer.
What is the best room in the home to start saving water? | [
"the kitchen",
"the basement",
"the bathroom",
"the bedroom"
] | C | It’s easy to save water at home. If you save even a few gallons a day you can make a big difference in the long run. The best place to start saving water is in the bathroom. Toilet flushing is the single biggest use of water in the home. Showers and baths are the next biggest use. Follow the tips below to save water at home. |
SciQ | SciQ-3131 | temperature, sun, light, equator, insolation
Title: Why does the intensity of sunlight depend on your latitude? People at the equator get to bask in more sunlight than Santa Clause and other inhabitants of the arctic regions. Not quite as pronounced, but they get more than me too.
Why is the sunlight more intense closer to the equator and less intense farther away from it?
When I posted this question, I was not thinking about the possible ambiguities, such as "Are you talking about the exposure across a surface area with some non-perpendicular angle to the sun," or "Are you talking about the light gathered by an optic facing the sun?" There is a difference. Since "basking in sunlight" was the example use case, let us assume exposure across a surface area which is lying on the ground. As noted in the comments, this answer applies to things like sun-bathing and solar panels, but it does not apply so much to a specific point-receptor like an eyeball. If all objects in question are pointing directly at the sun, then the angle of incidence is equal for all of them and this answer does not apply.
For an optic facing its target, the amount of atmosphere that the light passes through is a very large influencer. At higher latitudes, the sun is not directly overhead, and so the light is not coming straight down through the path of least atmosphere. Instead, it comes in at an angle, passing through more of the atmosphere before it gets to you.
For sun-bathers, solar panels, and the ground in general, the sunlight absorbed and reflected does depend very much on what is described in this answer. For that reason, more expensive solar panels are mounted on devices which alter their angle to face the sun for increased light exposure. And a sun-bather could likewise increase their exposure by mounting their platform at an angle. This is the direction the rest of the answer will take.
The answer is similar to the answer to some other questions, such as "Why does the solar power intensity change with the season?" and "Why does the solar intensity change with the height of the sun in the sky (ie: with the time of day)?"
The very short, non-technical version (tl;dr)
Each unit (think "beam of sunlight") is spread over a larger area.
That might not seem intuitive at first, but that is the answer in a nutshell. To see why, continue to the long version.
The following is multiple choice question (with options) to answer.
Latitude affects the amount of which radiation a place receives? | [
"thermal",
"molecular",
"solar",
"surface"
] | C | Latitude affects the amount of solar radiation a place receives. |
SciQ | SciQ-3132 | physical-chemistry, phase
Title: Properties of plasmas In chemistry one can recognize that the four states of matter are solid, liquid, gas and plasma. The first is rigid, and has a definite shape and volume. The second doesn't have a shape, and assumes the shape of its container, but it has a fixed volume. The third doesn't have either a shape or a fixed volume and assumes the volume and shape of its container. What about the fourth one (plasma)? Plasma is made up of ionized gas, so molecules have a positive electric charge and valency electrons are totally or partially separated by their nuclei.
Plasma is different from a gas since it has a high temperature and is radiation emitting; think of the Sun and other stars, which are made up of plasma and show both these properties.
Plasma hasn't got a proper volume, like gases; e.g. stars can expand or contract under the opposite effects of gravity and nuclear fusion. For example, this property is important to comprehend the formation of white dwarfs and neutron stars, process caused by high pression due to gravity.
Little trivia: there is also a fifth state of matter, whose name is Bose-Einstein Condensate (BEC).
The following is multiple choice question (with options) to answer.
What physical property of matter reflects how closely packed the particles are? | [
"volume",
"strength",
"density",
"diameter"
] | C | Density is an important physical property of matter. It reflects how closely packed the particles of matter are. Density is calculated from the amount of mass in a given volume of matter, using the formula:. |
SciQ | SciQ-3133 | standard-model, quantum-chromodynamics, quarks
These properties were so odd that for a number of years it was not
clear whether quarks actually existed or were simply a useful
mathematical fiction. For example, quarks must have charges of + 2/3e
or - 1/3e, which should be very easy to spot in certain kinds of
detectors; but intensive searches, both in cosmic rays and using
particle accelerators, have never revealed any convincing evidence for
fractional charge of this kind. By the mid-1970s, however, 10 years
after quarks were first proposed, scientists had compiled a mass of
evidence that showed that quarks do exist but are locked within the
individual hadrons in such a way that they can never escape as single
entities.
This evidence resulted from experiments in which beams of electrons,
muons, or neutrinos were fired at the protons and neutrons in such
target materials as hydrogen (protons only), deuterium, carbon, and
aluminum. The incident particles used were all leptons, particles that
do not feel the strong binding force and that were known, even then,
to be much smaller than the nuclei they were probing. The scattering
of the beam particles caused by interactions within the target clearly
demonstrated that protons and neutrons are complex structures that
contain structureless, pointlike objects, which were named partons
because they are parts of the larger particles. The experiments also
showed that the partons can indeed have fractional charges of + 2/3e
or - 1/3e and thus confirmed one of the more surprising predictions of
the quark model.
While it is true that we cannot seperate a single quark from a proton due to the color confinement property of the strong color force, it turns out that another property of the strong color force, asymptotic freedom, allows very high energy deep inelastic scattering to probe the properties of "free" quarks. These deep inelastic scattering experiments of electrons on protons established that there really were point like constituents of protons that had fractional electric charge and thus validated the quark model of hadrons.
The following is multiple choice question (with options) to answer.
What is the force of attraction between fundamental particles called quarks, called. | [
"strong nuclear force",
"magnetism",
"weak nuclear force",
"gravity"
] | A | The strong nuclear force is a force of attraction between fundamental particles called quarks, which have a type of charge called color charge. The strong nuclear force is transferred between quarks by fundamental force-carrying particles called gluons. Both protons and neutrons consist of quarks. The exchange of gluons holds quarks together within a proton or neutron. Excess, or residual, strong force holds together protons and neutrons in the nucleus. The strong nuclear force is strong enough to overcome the electromagnetic force of repulsion pushing protons apart. Both forces are represented in the Figure below . |
SciQ | SciQ-3134 | gravity, momentum, earth, rocket-science, centrifugal-force
Title: What forces carry hovering objects around the earth with its rotation? My questions are:
a) What significant forces “carry” flying objects around with the rotation of the earth,
b) How do each of those forces contribute to that “carrying”, and
c) How relatively significant is each of those forces?
d) If any of the 5 forces below are not significant contributors, please state why not.
For example, if an aircraft was to take off, thrust directly upwards and hover at say 30,000 feet for 12 hours, then come directly down again, I think we'd generally agree that it would land in the same city it took off from, not half way around the earth. The forces we have considered are:
Gravity
Centrifugal force
Centripetal force
Momentum (or is it inertia?) of the object before it left earth
The atmosphere's rotation with the earth
Any other significant contributors?
I have my opinion on which of the above are relevant, but I didn’t do much Physics at university (30 years ago), and I’d like to know what you think and why. because a friend and I disagree. You don't need a complicated answer. The answer is the fact that we are moving too.
How can this bird swoop down and catch the worm if the ground and the worm are rotating so quickly? The answer is because the ground, the air, and the tree are all moving at the same rate. The same applies to flying objects. So the forces involved are the same forces that keep everything else rotating: mainly momentum and gravity (momentum is inertia in motion).
We should remember (or learn now) that momentum only works in a straight line. Gravity forces your flying object to follow the same course that it would on earth.
The green arrows are gravity. The blue lines are momentum. They add to form a curved line. The same line you are following, the bird is following, and the worm is following.
The following is multiple choice question (with options) to answer.
The force that pulls objects toward the earth is what? | [
"Friction",
"gravity",
"Tension",
"Magnetic force"
] | B | |
SciQ | SciQ-3135 | We can keep this up, but we'll never really know the exact answer if we simply compute more and more examples. Let's instead look at a "typical'' approximation. Suppose we divide the time into $$n$$ equal intervals, and imagine that on each of these the object travels at a constant speed. Over the first time interval we approximate the distance traveled as $$(0.0)(1/n)=0$$, as before. During the second time interval, from $$t=1/n$$ to $$t=2/n$$, the object travels approximately $$3(1/n)(1/n)=3/n^2$$ centimeters. During time interval number $$i$$, the object travels approximately $$(3(i-1)/n)(1/n)=3(i-1)/n^2$$ centimeters, that is, its speed at time $$(i-1)/n$$, $$3(i-1)/n$$, times the length of time interval number $$i$$, $$1/n$$. Adding these up as before, we approximate the distance traveled as $$(0){1\over n}+3{1\over n^2}+3(2){1\over n^2}+ 3(3){1\over n^2}+\cdots+3(n-1){1\over n^2}$$ centimeters. What can we say about this? At first it looks rather less useful than the concrete calculations we've already done. But in fact a bit of algebra reveals it to be much more useful. We can factor out a 3 and $1/n^2$ to get $${3\over n^2}(0+1+2+3+\cdots+(n-1)),$$ that is, $$3/n^2$$ times the sum of the first $$n-1$$ positive integers. Now we make use of a fact you may have run across before: $$1+2+3+\cdots+k={k(k+1)\over2}.$$ In our case we're interested in
The following is multiple choice question (with options) to answer.
What is the distance something travels in a given amount of time called? | [
"revolution",
"speed",
"circulation",
"coverage"
] | B | A snail might travel 2 centimeters in a minute. A cheetah might travel 2 kilometers in the same amount of time. The distance something travels in a given amount of time is its speed. |
SciQ | SciQ-3136 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
One type of tissue, called brown fat, is made up of cells packed full of what? | [
"proteins",
"chromosomes",
"mitochondria",
"Atoms"
] | C | |
SciQ | SciQ-3137 | eeg, terminology
Now, the brain is a lump of neurons. Different types of neurons that are there for different types of tasks. Some of them respond to electrical activity (from the nervous system) by propagating or inhibiting electrical activity. We can see this in the lab, by observing how does one single neuron behaves but to date it has been impossible to observe what EACH neuron is doing in-vivo in a functioning brain. This is the "promise" of Neuroimaging.
So, when it comes to electroencephalography, an electrical activity (of the brain) is sensed by an instrument (the EEG aparratus). Actually, in this case, a ridiculously small number of electrodes (a few tenths) is used to sense the combined functioning of a ridiculously large number of neurons (a few billions).
Because of this "imbalance" we see patterns in the electroencephalography measurements that, macroscopically, correspond to brain function. We don't really know what is happening at the neuron level, but we can observe waves of electrical activity spreading throughout the surface of the brain and we hypothesize that this is probably because of the brain's properties of segregation and specialisation (and this, go through the introduction, at least once).
In other words, certain parts of the brain are devoted to certain functions and they "connect" together to exchange information as the brain functions.
Because of this, certain "states" of cognition can be cross referenced with certain electrical patterns.
For example:
The following is multiple choice question (with options) to answer.
Abnormal electrical activity in the brain is the cause of what disease associated with seizures? | [
"anemia",
"epilepsy",
"Alzheimer's",
"malaria"
] | B | Epilepsy is a disease in which seizures occur. A seizure is a period of lost consciousness that may include violent muscle contractions. It is caused by abnormal electrical activity in the brain. Epilepsy may result from an infection, injury, or tumor. In many cases, however, the cause can’t be identified. There is no known cure for epilepsy, but the seizures often can be prevented with medicine. Sometimes children with epilepsy outgrow it by adulthood. |
SciQ | SciQ-3138 | atoms, terminology
Title: What is a neutral atom? I was told that an atom's atomic number is defined as follows:
The number of electrons or protons present in a neutral atom is called atomic number. It is represented by Z.
What does neutral mean here? Why isn't it just "..present in an atom..."? Electrons and protons are charged particles. The electrons have negative charge, while protons have positive charge. A neutral atom is an atom where the charges of the electrons and the protons balance. Luckily, one electron has the same charge (with opposite sign) as a proton.
Example: Carbon has 6 protons. The neutral Carbon atom has 6 electrons. The atomic number is 6 since there are 6 protons.
The following is multiple choice question (with options) to answer.
Because atoms are always electrically neutral, for each added proton, one of what is also added? | [
"ion",
"electron",
"quark",
"neutron"
] | B | From left to right across the periodic table, each element has one more proton than the element to its left. Because atoms are always electrically neutral, for each added proton, one electron is also added. Electrons are added first to the lowest energy level possible until that level is full. Only then are electrons added to the next higher energy level. |
SciQ | SciQ-3139 | prokaryotes
Title: Are chromosomal and plasmid DNA in the nucleoid? I know plasmid DNA is not part of the chromosome, according to my textbook, but can you still class it as being part of the nucleoid?
Also is chromosomal DNA in the nucleoid? "Nucleoid" (literally means nucleus-like), is a quite old term for "bacterial chromosome" (Better to write prokaryotic chromosome since in both type of prokaryotes i.e. Archaea (former archaebacteria) and bacteria (former eubacteria) the structure is similar).
Nucleoid structurally normally excludes the plasmid-DNA (the plasmid DNA is like additional or accessory). However sometimes a plasmid DNA could go through recombination with prokaryotic chromosome 's DNA (As seen in Hfr strain of Escherichia coli)
"Chromosome" in very brief means a structure made of DNA + Protein. In case of "bacterial-chromosome", it contains both DNA and Protein; and if you take away the protein from bacterial chromosome; what you get, is the chromosomal DNA.
Reference:
Microbiology / Pelczar, Chan and Noel/ Edition-5;
Part 2: Bactria,
Chapter 5 (Morphology and fine structure of bacteria)
"Because it is not discrete nucleus, this nebulous structure has been designated by such terms as the nucleoid , the chromatin body, the nuclear equivalent, even the bacterial chromosome"
General Microbiology / Hans G. Schlegel / Edition-7:
Chapter-2 ; The cell and its structure:
2.2 The prokaryotic cell (protocyte) -> 2.2.1: The bacterial 'nucleus'
" Plasmids : In addition to chromosomal DNA, many bacteria contain extrachromosomal DNA in closed, circular, double stranded form. These autonomously replicating DNA elements are called plasmids. Linear plasmids have been found in some bacteria"
The following is multiple choice question (with options) to answer.
What is the group of single-celled organisms lacking a nucleus that have a single piece of circular dna in the nucleoid area of the cell? | [
"algae",
"chromosomes",
"prokaryotes",
"eukaryotes"
] | C | 22.2 Structure of Prokaryotes Prokaryotes (domains Archaea and Bacteria) are single-celled organisms lacking a nucleus. They have a single piece of circular DNA in the nucleoid area of the cell. Most prokaryotes have a cell wall that lies outside the boundary of the plasma membrane. Some prokaryotes may have additional structures such as a capsule, flagella, and pili. Bacteria and Archaea differ in the lipid composition of their cell membranes and the characteristics of the cell wall. In archaeal membranes, phytanyl units, rather than fatty acids, are linked to glycerol. Some archaeal membranes are lipid monolayers instead of bilayers. The cell wall is located outside the cell membrane and prevents osmotic lysis. The chemical composition of cell walls varies between species. Bacterial cell walls contain peptidoglycan. Archaean cell walls do not have peptidoglycan, but they may have pseudopeptidoglycan, polysaccharides, glycoproteins, or protein-based cell walls. Bacteria can be divided into two major groups: Gram positive and Gram negative, based on the Gram stain reaction. Gram-positive organisms have a thick cell wall, together with teichoic acids. Gram-negative organisms have a thin cell wall and an outer envelope containing lipopolysaccharides and lipoproteins. |
SciQ | SciQ-3140 | waves, electromagnetic-radiation
(Image Credit: https://www4.uwsp.edu/physastr/kmenning/Phys202/Lect16.html)
The following is multiple choice question (with options) to answer.
What are electromagnetic waves created by? | [
"oscillating charges",
"particle charges",
"gravitational charges",
"Static Charges"
] | A | 24.2 Production of Electromagnetic Waves • Electromagnetic waves are created by oscillating charges (which radiate whenever accelerated) and have the same frequency as the oscillation. • Since the electric and magnetic fields in most electromagnetic waves are perpendicular to the direction in which the wave moves, it is ordinarily a transverse wave. • The strengths of the electric and magnetic parts of the wave are related by. |
SciQ | SciQ-3141 | biochemistry
Alright so this is the oxidation of one mole of glucose equation (Without the ATPs) but till now I don't exactly know the correct answer for this question, but to not create any confusion this question is related to the Aerobic respiration (Glycolysis, Krebs Cycle and Electron transport chain).
Here's how I approached this question:
(a) is obviously not correct because the products of glycloysis are 2 pyruvate molecules and 2 ATP molecules so I checked off this choice.
(b) However seems correct because the products of 2 Krebs cycle is 4 CO2 and there is already 2CO2 when the pyruvate acid formed the 2 acetyl CoA molecules so in total that's 6CO2, but still what about the 6 Water molecules?
(c) is a very debating choice because when there is a "Complete occurrence of oxidative phosphorylation process" so that means 2 Krebs cycles had already occurred and formed the 6CO2, and during the oxidative phosphorylation process Water molecules are formed. and ATPs too? I don't exactly know about the ATPs, but aren't they supposed to be in the equation's products in order for this choice to be correct?
(d) This choice indicates to Krebs cycle but the water molecules only are formed during oxidative phosphorylation only.
So basically all the choices seems very debating and confusing and if I were to choose then I'll go with (C) because it's the only choice that makes sense for the water molecules (and the question asks for water), but I want someone to please answer this question with a brief explanation to why he chose this answer,
Thanks :) This reaction only means complete oxidation of glucose to 6 molecules of carbon dioxide and 6 molecules of water.
Reaction presented in question is very generalized, but the presence of six water molecules only means complete cellular respiration. Check out the actual biochemical pathways which take place to oxidize one glucose molecule.
And other options do not represent the complete cellular respiration, so there will not be formation of six water molecules, only option C means complete oxidation of glucose.
The following is multiple choice question (with options) to answer.
What is the first stage of cellular respiration? | [
"electron transport",
"photosynthesis",
"glycolysis",
"Krebs cycle"
] | C | The first stage of cellular respiration is glycolysis . It takes place in the cytosol of the cytoplasm. |
SciQ | SciQ-3142 | species-identification, botany, ecology
Title: Algae or Lichen identification. Coastal BC, Canada I have tried all books and internet resources I know of, but I still have no idea what this might be — a lichen or something else.
At first glimpse, I thought it was something man-made and unnatural, but then I looked closer and saw how it appears to be attached and growing. It grows on exposed rocks well above the high tide. The photo is taken in late March, on northern Vancouver Island. It's loosely attached to the rock.
It was somewhat abundant around the general area (within of a few km), but I haven't seen it elsewhere - although I'm not from BC so there might be a lot of this around.
The water droplet in the lower right corner give a rough sense of scale.
Edit:
Adding another photo in which I just noticed a streak of white, which I included in original resolution. I want to propose you expand your search to a broader taxonomic scope. Specifically, I think you might be looking at a species of "red" green algae (family: Trentepohliaceae).
From Nelson et al. (2011):
All Trentepohliaceae have filamentous growth forms and often contain large amounts of carotenoid pigments (ß-carotene and hematochrome), causing the algae to appear yellow orange in color (Thompson and Wujek 1997, Lo´pez-Bautista et al. 2002).
The Trentepohliaceae contains five genera: (Trentepohlia, Printzina, Phycopeltis, Cephaleuros and Stomatochroon) and 70+ species worldwide.
For example, the following algae (picture from England) looks fairly similar to your specimen:
Trentepohlia aurea
Source: David Fenwick
If your specimen is a species in this family of algae, it is most likely in the Trentepohlia genus (or possibly Printzina genus).
Trentepohlia is a genus of filamentous chlorophyte green algae in the family Trentepohliaceae.
Typically orange or yellow in color.
Live on tree trunks and wet rocks or symbiotically in lichens.
Here's a picture of a free-living Trentepohlia species from coastal Oregon, USA:
Source: Richard C. Hoyer (2015)
The following is multiple choice question (with options) to answer.
Red algae and green algae are the closest relatives of what? | [
"water plants",
"transfer plants",
"arctic plants",
"land plants"
] | D | 28.5 Red algae and green algae are the closest relatives of land plants. |
SciQ | SciQ-3143 | human-biology, human-anatomy
Title: Difference between the spinal cord and vertebrae column What is the difference between the spinal cord and the vertebrae column, they both run through from the head to the abdomen. Does any one have any idea. The vertebral column is a bony, segmented structure that supports the torso/head and thorax. The spinal cord is a bundle of nerves that runs inside the structure of the vertebral column. So - they run together, but are completely separate.
The following is multiple choice question (with options) to answer.
The axial skeleton forms the vertical, central axis of the body and includes all bones of the head, neck, chest, and back. it serves to protect the brain, spinal cord, heart, and what else? | [
"ovaries",
"intestines",
"knees",
"lungs"
] | D | The Axial Skeleton The skeleton is subdivided into two major divisions—the axial and appendicular. The axial skeleton forms the vertical, central axis of the body and includes all bones of the head, neck, chest, and back (Figure 7.2). It serves to protect the brain, spinal cord, heart, and lungs. It also serves as the attachment site for muscles that move the head, neck, and back, and for muscles that act across the shoulder and hip joints to move their corresponding limbs. The axial skeleton of the adult consists of 80 bones, including the skull, the vertebral column, and the thoracic cage. The skull is formed by 22 bones. Also associated with the head are an additional seven bones, including the hyoid bone and the ear ossicles (three small bones found in each middle ear). The vertebral column consists of 24 bones, each called a. |
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