source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-7244 | mineralogy, mining
Because monazite. Monazite is a rare earth element phosphate, with the formula CePO4 (where Ce stands not only for cerium, but all of the are earth elements and yttrium as well). It is one of the main ore minerals for the rare earths. It's a very common mineral in granites and similar rocks, and it's very resistant to erosion.
Therefore, it commonly accumulates in placer deposits, together with other resistant minerals such as quartz, magnetite, zircon, rutile, etc. Essentially, nature breaks down the rocks and concentrates those minerals in mineral sands (sometimes known as black sands). These sands are not unique to India, and many examples can be found across the world. Essentially you find them where ever you have sandy beaches developed in areas of granite mountains (in the case of monazite).
Why thorium? Because monazite shares the same crystal structure with a mineral called cheralite: CaTh(PO4)2, and the two components (monazite and cheralite) can exist in the same mineral via solid solution. Some monazites can contain 20 and 30% thorium! Granite-derived monazite is particularly rich in Th, unlike carbonatite-derived monazite which usually has little Th. The Th is usually an unwanted by-product, with monazite mined primarily for the rare earths. But, if you're looking for the Th - this is something that you actually want.
The following is multiple choice question (with options) to answer.
A quarry, which produces rocks and minerals used to make buildings and roads, is an example of what type of mine? | [
"open-pit mine",
"gold mine",
"fracking",
"strip mine"
] | A | As the name suggests, open-pit mining creates a big pit from which the ore is mined. Figure below shows an open-pit diamond mine in Russia. The size of the pit grows as long as the miners can make a profit. Strip mines are similar to open-pit mines, but the ore is removed in large strips. A quarry is a type of open-pit mine that produces rocks and minerals that are used to make buildings and roads. |
SciQ | SciQ-7245 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
Along with other organelles, all eukaryotic cells possess what structure? | [
"chromosomes",
"nucleus",
"flagella",
"cell walls"
] | B | All eukaryotic cells have a nucleus and other organelles. Each organelle has a special job to do. |
SciQ | SciQ-7246 | bacteriology, ph, gut-bacteria
Any one of these is enough to have a bactericidal or bacteriostatic effect! This is also why cells that do live in slightly alkaline or acidic environments have to specialize, and they have narrow windows of pH that they can survive under, because they have to compensate so much to counteract the protonation or lack-thereof in their environments.
The following is multiple choice question (with options) to answer.
The environment where most chemical reactions in organisms takes place consists mostly of what? | [
"sodium",
"water",
"air",
"helium"
] | B | Most chemical reactions in organisms take place in an environment that is mostly water. |
SciQ | SciQ-7247 | cell-biology, physiology, cancer, cell-culture
Title: Why do epithelial cells arrest in response to serum? Primary epithelial cells, for example human mammary epithelium, fail to proliferate (arrest) in serum-containing medium. Therefore, a common growth medium for epithelium contains pituitary extract instead of serum (Hammond et al, 1984). This may be related to the fact that epithelium is normally not in contact with serum in the body.
On the other hand, many epithelium-like cell lines grow well in serum, and most tumor-derived cell lines are cultured this way. But it can be difficult to establish such lines from epithelial cancers: often, only fibroblasts grow out of tumor explants in serum-containing medium, while the (epithelial) cancer cells do not. In contrast to epithelium, fibroblasts increase their proliferation when exposed to serum, and this process is well studied (Iyer et al, 1999).
Why does epithelium arrest in response to serum? Are any mechanisms known? Is there any study of epithelium gene expression response to serum? Why is the behavior of epithelium so different from that of fibroblasts --- is there a physiological explanation, perhaps related to wound healing?
Is this true for all types of (human) epithelium?
Should we consider epithelial-like cells growing in serum to be adapted / selected? Have such cell lines then lost some part of the epithelial phenotype? Is this a serious artefact?
The following is multiple choice question (with options) to answer.
The main functions of epithelia are protection from the environment, coverage, secretion and excretion, absorption, and this? | [
"diffusion",
"accumulation",
"absorption",
"filtration"
] | D | 4.2 Epithelial Tissue In epithelial tissue, cells are closely packed with little or no extracellular matrix except for the basal lamina that separates the epithelium from underlying tissue. The main functions of epithelia are protection from the environment, coverage, secretion and excretion, absorption, and filtration. Cells are bound together by tight junctions that form an impermeable barrier. They can also be connected by gap junctions, which allow free exchange of soluble molecules between cells, and anchoring junctions, which attach cell to cell or cell to matrix. The different types of epithelial tissues are characterized by their cellular shapes and arrangements: squamous, cuboidal, or columnar epithelia. Single cell layers form simple epithelia, whereas stacked cells form stratified epithelia. Very few capillaries penetrate these tissues. Glands are secretory tissues and organs that are derived from epithelial tissues. Exocrine glands release their products through ducts. Endocrine glands secrete hormones directly into the interstitial fluid and blood stream. Glands are classified both according to the type of secretion and by their structure. Merocrine glands secrete products as they are synthesized. Apocrine glands release secretions by pinching off the apical portion of the cell, whereas holocrine gland cells store their secretions until they rupture and release their contents. In this case, the cell becomes part of the secretion. |
SciQ | SciQ-7248 | climate-change, oceanography, paleoclimatology, paleontology, climatology
As abundant as they are in living form, diatoms are generally poorly (and unreliably) preserved in an older oceanic fossil record. Importantly, they evolve rather quickly making tracking chemical changes in a single species over time and space impossible. Bulk chemistries may be obtained from fossilized silicic masses and serve as rough indicators of overall diatom abundance and thus system health.
They are, however, used in novel ways: some diatoms live exclusively in sea ice and can be used to assess duration and distribution of that sea ice, itself a record of sea surface temperature (SST):
Diatoms in Arctic regions: Potential tools to decipher environmental changes
SIDEBAR. Diatoms as Sea Ice Proxies
By contrast, forams are well preserved in the fossil record, have a well calibrated evolutionary record, and as carbonates, contain important isotopes whose ratios are sensitive to SST.
The following is multiple choice question (with options) to answer.
What term is defined as the preserved remains or traces of organisms that lived during earlier ages? | [
"fossils",
"bones",
"waste",
"deposits"
] | A | Fossils are the preserved remains or traces of organisms that lived long ago. They form mainly when minerals in water turn remains to stone. Fossils can be dated using methods such as carbon-14 dating or their positions in rock layers. |
SciQ | SciQ-7249 | evolution, biochemistry, physiology, speculative, bioinorganic-chemistry
While iron skeletons might seem to be an advantage, they are electrochemically unstable - oxygen and water will tend to oxidize (rust) them quickly and the organism would have to spend a lot of energy keeping it in working form. Electrical conductivity sounds useful, but the nervous system favors exquisite levels of control over bulk current flow, even in cases like electric eels, whose current is produced by gradients from acetylcholine.
What's more, biological materials actually perform as well as or better than metal when they need to. Spider silk has a greater tensile strength than steel (along the direction of the thread). Mollusk shells are models for tank armor - they are remarkably resistant to puncture and breakage. Bone is durable for most purposes and flexible in addition.
The time it would take for metallized structures to evolve biologically are likely too long. By the time the metalized version of an organ or skeleton got started, the bones, shells and fibers we know probably have a big lead and selective advantage.
The following is multiple choice question (with options) to answer.
What rigid external structure protects shellfish and other animals and provides points of attachment for the muscles that move the appendages? | [
"exoskeleton",
"claw",
"membrane",
"cocoon"
] | A | |
SciQ | SciQ-7250 | electricity, electromagnetic-radiation, magnetic-fields, electric-fields
Title: Why is electricity not transmitted wirelessly? Why is electricity not transmitted wirelessly such that we don't need to span cables on the earth's surface? As in: electricity is transmitted wirelessly from the power plant to the household. Electricity is the flow of electrical charge - generally electrically charged particles called electrons in a wire. It can't flow through air, except in the form of electrically charged particles of air - as in a spark or lightning stroke.
Magnetic fields can travel in air, so you can send electricity by using it to make a magnetic field and then using the magnetic field at the other end to make electricity. This is how a transformer works - but it only works efficiently if the two sets of wire making the magnetic field are very close.
You can use it for sending small amounts of electricity a short distance where a wire (or connector) would be difficult, such as charging an electric toothbrush - but it's not efficent for large amounts or a long distance.
The following is multiple choice question (with options) to answer.
The electronic components in electronic devices, used to transmit and change electricity are made of? | [
"semiconductors",
"microchips",
"inverters",
"resistors"
] | A | Electronic components are the parts used in electronic devices such as computers. The components transmit and change electric current. They are made of materials called semiconductors. |
SciQ | SciQ-7251 | immunology, vaccination
Title: True or False: Vaccines are designed to protect against invaders that are encountered rarely, not all the time I read the following statement in this article:
Vaccines are designed to protect against invaders that are encountered
rarely - not all the time
Is it true? If yes, why? Not true. Vaccines were initially made for the highly contagious diseases that used to cause epidemics (which obviously means they were not rare).
The efficacy of a vaccine depends on multiple factors which includes adaptability of the pathogen.
The all-the-time encountered pathogen that the article is talking about is HIV; the reason for why no effective vaccine exists for it is because it has high mutation rate.
The following is multiple choice question (with options) to answer.
Vaccinations are designed to boost immunity to a virus to prevent this? | [
"reproduction",
"infection",
"pathogen",
"mutation"
] | B | Figure 21.14 Vaccinations are designed to boost immunity to a virus to prevent infection. (credit: USACE Europe District). |
SciQ | SciQ-7252 | dna, dna-sequencing
Except for Red Blood Cells, every somatic cell contains two copies of the autosomal chromosomes and a pair of sex chromosomes, either XX or XY (Assuming an average human being) One set is maternal and one is paternal
Some lymphocytes actually recombine their chromosomes, so their DNA will be functionally different to all of the other somatic cells in the body.
Gametes undergo Meiosis and will be haploid, only containing one copy of each autosomal chromosome and one of the sex chromosomes
Cells accumulate mutations over time. The closest you could probably come to an exact clone of a person is if you harvested one of the cells from the eight-cell stage of development. The other seven are able to go on and produce a viable and healthy person. The harvested cells DNA would be the closest to the DNA that combined in the fertilization of the egg. The next closest would likely be stem cells from cord blood. Then probably neurons, as they tend to divide the least.
As the link you posted said, ATCG can be represented in a two bit code, so for about 6 billion bases, you would need about 1.5GB of storage (You need to capture both sets of chromosomes in order to produce a person).
The following is multiple choice question (with options) to answer.
How many sets of chromosomes do gametes contain? | [
"twelve",
"eight",
"single",
"four"
] | C | |
SciQ | SciQ-7253 | classical-mechanics, energy, momentum, definition
Title: Momentum a good definition We know that the effects produced by a moving body depend both on the speed at which it is moving and on its mass:
$$\mathbf{p} = m \mathbf{v}$$
Therefore it is useful, to evaluate this effect, to introduce the momentum vector $\mathbf{p}$. The kinetic energy is (in general of an object of mass $m$ moving with velocity $u$), $$\mathcal K=mu^2/2$$
How is it possible to express well in words the difference between kinetic energy and momentum?
Related that I don't like:
Definition of force, kinetic energy and momentum
Difference between momentum and kinetic energy I believe that there are good reasons why physics uses formula to describe their finding. Thus, asking us to skip the formulas and still providing "good" definitions is difficult. I'm not able to do so, but I'll try explain my formulas and use them only to clarify what I mean.
On a high school level momentum and energy are related by the concept of force: Momentum is given by the sum of the force over "small" time intervals
$$
p = \sum_i F_i \cdot \Delta t_i
$$
where I use $\Delta p = p - p_0$ and assume $p_0=0$. By dropping the sum and considering a single time interval we obtain $p = F \cdot \Delta t$. Thus, momentum is the ability of a body to exert force over a "short" time interval.
In contrast energy is related to work, which is given by the sum of the force over "small" distance intervals
$$
E = \sum_i F_i \cdot \Delta s_i
$$
Again, we drop the sum, $E = F \cdot \Delta s$. Thus, energy is the ability of a body to exert a force over a "small" distance.
Since time and distance are rather different, the quantities momentum and energy are rather different. I believe that the bullet/rifle example described here is great. Nevertheless, here is my own example, utilising the concepts described above: Let's assume we like to drive a nail into a piece of wood. There are two equally valid perspectives:
The following is multiple choice question (with options) to answer.
What is the term for the energy of motion, which is exhibited by the speed of an object? | [
"inertia",
"kinetic energy",
"mechanical energy",
"residual energy"
] | B | The energy of motion is kinetic energy, KE. Whenever an object is in motion it has kinetic energy. The faster it is going, the more energy it has. |
SciQ | SciQ-7254 | geophysics, sedimentology
Title: Does dirt compact itself over time? If so, how does this happen? If I were to bury something 10 feet (~3 metres) underground, with loose soil on top, would the ground naturally compact itself over time, until whatever I had buried has dirt tightly pressing against it on all sides?
What if I buried it 50 feet (~15 metres) underground?
If it exists, what is this compaction process called and how does it happen? Soil is a collection of various sized minerals grains, of various types of minerals produced by the weathering of rock. Typical soil minerals are clays, silts and sands.
The properties and behavior of different soil types depends of the composition of the soil: the proportion of clays, silts and sand in a soil. Sandy soils are well draining and clayey soils are sticky.
Between the grains of minerals that comprise a soil are spaces, called pores or pore spaces. The pores can be filled with either water or air, depending the location of water tables and wetting events like rain, snow melts or other forms of water inundation.
The density of a soil is dependent on the degree of compaction of the soil. For to a soil to be compacted, a stress has to be applied to the soil to realign the grains of soil which reduces the total volume of the pores and reduces the amount of air within the pores.
Consolidation of a soil occurs when pore space is reduced and water in a soil is displaced due to an applied stress.
Regarding having something buried and soil compacting around it over time, yes that will occur but it is a question of how much stress the soil experiences, the duration of time and the nature of the soil - sandy or clayey. Something buried for a day without any stresses not much will happen. But, something buried for thousands of years with people and animals walking over it, rain falling on the soil, vibrations from nearby human activity and an occasional earthquake all add to the stresses the soil will experience and increases the degree of compaction or consolidation over time.
The following is multiple choice question (with options) to answer.
Soil that forms in place over a very long period is called what? | [
"resultant soil",
"leakage soil",
"residual soil",
"antique soil"
] | C | A soil is a residual soil when it forms in place. Only about one third of the soils in the United States form this way. The material comes from the underlying bedrock. Residual soils form over many years since it takes a long time for solid rock to become soil. First, cracks break up the bedrock. This may happen due to ice wedging. Weathering breaks up the rock even more. Then plants, such as lichens or grasses, become established. They cause further weathering. As more time passes and more layers of material weather, the soil develops. |
SciQ | SciQ-7255 | radioactivity
Title: Reasoning behind alpha , beta to be not occuring at same time for any element Is it true that Alpha decay can occur after beta decay and that Alpha decay and beta decay cannot happen at same time ?
If yes is my reasoning correct :
For both decays to occur together they would need to together excite one neutron and one proton to convert to antineutrino, alpha particle and a new element Y which is not favourable . Hence they cannot occur together but one by one they can , this is the reason too why an element can only be a alpha or beta emitter but not both? No, this is not correct.
Some isotopes can decay both via alpha decay or via beta decay, e.g. many isotopes of Bismuth.
In decay chains, an isotope can first decay via an alpha decay, and then the daughter can decay via a beta decay. And vice versa. See e.g. the Radon decay chains.
For an alpha decay to happen at the same time as a beta decay, that probability is arbitrarily small; the two processes are mediated by different forces (alpha decay goes via the Strong/EM force, beta decay via the Weak force) and really have nothing to do with each other.
The following is multiple choice question (with options) to answer.
Alpha and beta decay occur when a nucleus has too many protons or an unstable ratio of what? | [
"protons to neutrons",
"atoms to neutrons",
"electrons to neutrons",
"nucleus to neutrons"
] | A | Alpha and beta decay occur when a nucleus has too many protons or an unstable ratio of protons to neutrons. When the nucleus emits a particle, it gains or loses one or two protons, so the atom becomes a different element. Gamma decay, in contrast, occurs when a nucleus is in an excited state and has too much energy to be stable. This often happens after alpha or beta decay has occurred. Because only energy is emitted during gamma decay, the number of protons remains the same. Therefore, an atom does not become a different element during this type of decay. |
SciQ | SciQ-7256 | cell-division
Title: Why doesn't cellular, replicative senescence (or the hayflick limit) constrain the normal development of an organism? The wikipedia article on cellular senescence states:
Cellular senescence is the phenomenon by which normal diploid cells cease to divide. In culture, fibroblasts can reach a maximum of 50 cell divisions before becoming senescent. This phenomenon is known as "replicative senescence", or the Hayflick limit.
The following is multiple choice question (with options) to answer.
What do you call an abnormal mass of cells that is dividing improperly? | [
"molars",
"appendages",
"tumor",
"bumps"
] | C | Cells that divide uncontrollably may form a tumor , or abnormal mass of cells. Tumors may be benign or malignant. Benign tumors remain localized and generally do not harm health. Malignant tumors are cancerous. There are no limits to their growth, so they can invade and damage neighboring tissues. Cells from malignant tumors may also break away from the tumor and enter the bloodstream. They are carried to other parts of the body, where new tumors may form. The most common and the most deadly cancers for U. S. adults are listed in Table below . |
SciQ | SciQ-7257 | organic-chemistry, alcohols, organophosphorus-compounds
In terms of caloric content, ethanol is a unique drug whose oxidation by alcohol dehydrogenase (ADH) produces 7.1 kcal per gram of ethanol oxidized. However, it is not known to what extent these calories are converted into body weight. There is no controversy about the malnutrition produced by chronic ethanol intake in alcoholics. In addition to the known toxic effects on absorption and synthesis of essential nutrients (1), some important metabolic changes occur. Pirola and Lieber (2) reported that activation of the microsomal ethanol oxidizing system (MEOS) in hepatocytes of alcoholics may consume one third of the caloric content of ethanol and impair ATP synthesis. Lands and Zakhari (3) suggested the existence of a futile cycle in ethanol metabolism which would account for a loss of six ATPs per gram of ethanol oxidized. They proposed that ethanol may be oxidized to acetaldehyde, consuming three ATPs, and acetaldehyde may be again reduced to ethanol, consuming three extra ATPs.
However, there is some controversy about what happens to ethanol calories when consumption is moderate and not related to the metabolic changes of the liver that characterize chronic ethanol intake. It has been suggested that calories derived from ethanol may function as do calories derived from carbohydrates, producing a thermogenesis value of about 10% (4,5). This thermogenic value may be higher than that of fatty food (3%) and lower than that of proteins (about 20%) (6).
The contribution of calories provided by ethanol to body weight gain has also been studied but there seems to be no consensus about the data from animal and human studies.
Moderate ethanol consumption seems to favor an increase in fat storage and could result in weight gain, especially in overweight individuals (7). In an epidemiological study involving 89,538 women and 48,493 men, Colditz et al. (8) reported a strong negative association between alcohol intake and body weight index for women and the absence of this association for men.
The following is multiple choice question (with options) to answer.
What is an example of a biochemical lipid that contributes to weight gain? | [
"acids",
"fats",
"sugars",
"proteins"
] | B | You’ve probably seen dozens of nutrition facts labels like the one in the opening image. The labels show the nutrients that foods contain. Many people read nutrition facts labels to see how much fat there is in particular foods. That’s because eating too much fat, especially saturated fat, can be unhealthy and contribute to weight gain. Fats are a type of biochemical compound called lipids. |
SciQ | SciQ-7258 | release energy by transferring heat to their surroundings. In older works, power is sometimes called activity. the bungee cord has more potential energy when it is stretched out than when it is slack. , green plants convert solar energy to chemical energy (commonly of oxygen) by the process of photosynthesis. Practice questions A bowling ball is lifted to a height […]. kinetic energy = mass * velocity² / 2 E = m * v² / 2. The maximum energy stored in the inductor is LI2/2 with I = I MAX. Efficiency can be explained as the amount of work done by an object to the total energy spent. You can think of a trebuchet as a see saw! Yes, a see saw is really all that a trebuchet is. Example of Few questions where you can use this Mechanical Energy Formula calculate the Mechanical energy of the object have mass 10 kg and velocity 3m/s and height above the ground is 10 m calculate the Kinetic Energy,Potential energy and Mechanical energy of the object have mass 1 kg and velocity 2m/s and height above the ground is 50 m. Kinetic energy = Joules Kinetic Energy Calculator is a free online tool that displays the kinetic energy of the object. Contribute to Ghostlydestinypolice/Physics_Energy development by creating an account on GitHub. We cover most electrical devices and home appliances, our online calculators can be edited to fit any home appliance and accurately calculate power costs. 2 Kinetic Energy. Current (I) is measured in amps (A), using an ammeter. The units of power are watts, the units of energy are joules. The kinetic energy just before impact is equal to its gravitational potential energy at the height from which it was dropped: K. 94u2rotkh0qgw ts2269o179 taplsbcnrzp02 tqj6cos4hnt038 862fohcw5vw 0kib5khqvn7x7u imx0rwjjl87j 7v6n0lvam9qps6 1ep3ku4gpb4 7jfyw1bfipc qndzw85umfgmg 3hdpzbzs6my yeu4magtr0k3kw0 e9wp756pxxgsa
The following is multiple choice question (with options) to answer.
The rate that energy is released is known as | [
"pressure",
"flow",
"heat",
"power"
] | D | Power is the rate that energy is released. The units for power are watts (W), which equal joules per second . For example, a 60 W light bulb transforms 60 joules of electrical energy into light and heat energy every second. |
SciQ | SciQ-7259 | nuclear-physics, radiation
Title: Is a naturally radioactive elements on its ground state? Ground state is defined as the zero energy state. No energy can be taken from it. Still, radioactive elements can emit radiation. Do we consider them to be in a ground state? A radioactive nucleus is not in its ground state of course. The state may be unstable, or metastable (which implies a slow decay). Of natural elements, only iron-56 nuclei and smaller have lower energy than their fission
products. This means that a LOT of nuclei are metastable (though the half-life might be VERY long) with respect to some kind of fission.
Light nuclei can go to lower energy by fusion, but that requires a second particle to combine with, so it's hard to call them 'unstable'.
Very heavy nuclei, including such items as neutron stars, are theoretically possible,
but I don't know much about their stability.
The following is multiple choice question (with options) to answer.
A low level of radiation occurs naturally in the environment and is called what? | [
"background radiation",
"Alpha radiation",
"Gamma radiation",
"Beta radiation"
] | A | A low level of radiation occurs naturally in the environment. This is called background radiation. One source of background radiation is rocks, which may contain small amounts of radioactive elements such as uranium. Another source is cosmic rays. These are charged particles that arrive on Earth from outer space. Background radiation is generally considered to be safe for living things. You can learn more about background radiation with the animation at this URL: http://www. pbs. org/wgbh/nova/dirtybomb/sources. html. |
SciQ | SciQ-7260 | quantum-mechanics, thermodynamics, earth
Title: Why does most of the heat transferred on Earth come from the infrared part of the electromagnetic spectrum? Why does the most of the heat transferred on Earth come from infrared part of electromagnetic spectrum? The expectation value of frequency $\nu$ in Planck's law can be obtained via
$$\langle\nu\rangle=\frac{\int_0^\infty2h\nu^4c^{-2}\left(\exp\left(\frac{h\nu}{kT}\right)-1\right)^{-1}\,d\nu}{\int_0^\infty2h\nu^3c^{-2}\left(\exp\left(\frac{h\nu}{kT}\right)-1\right)^{-1}\,d\nu}=\frac{360 k T \zeta (5)}{\pi ^4 h}$$
where $\zeta$ is the Riemann Zeta function.
For $T=273\text{K}$, this becomes $21.7993\text{THz}$, or $13.75\mu\text{m}$, well in the infrared range.
The following is multiple choice question (with options) to answer.
Most of the heat that enters the mesosphere comes from where? | [
"Troposphere",
"Exosphere",
"the stratosphere",
"Earth's surface"
] | C | There are very few gas molecules in the mesosphere. This means that there is little matter to absorb the Sun’s rays and heat the air. Most of the heat that enters the mesosphere comes from the stratosphere below. That’s why the mesosphere is warmest at the bottom. |
SciQ | SciQ-7261 | human-biology, circadian-rhythms, digestive-system
Title: What influences the timing of human bowel movements in the morning? I'm trying to understand if the timing of human bowel movements in the morning is associated with the circadian rhythm, and can thus be used to make predictions about the circadian rhythm.
What influences the timing of bowel movements? Is it the timing of meals, caffeine intake or is it a biologically programmed time?
Thank you! The bowel movements are influenced by a lot of factors. For example, when you eat a meal it induces a movement in your large intestines, to defecate and clear up space for new food.
Also, there is MMC, migrating motor complex, which is responsible for the bowel movements when you are fasting. It causes a flushing effect, which prevents bacteria to overproduce in intestines.
So, the daily bowel movements are mainly influenced by the timing and content of the food that you eat. But as I said there are many other factors. The gastrointestinal system has a very complex nervous system. Even psychological factors can effect the bowel movements greatly, for example extreme physical pain may induce the symphatetic system and cause constipation.
Also caffeine may affect it, like many drugs do.
The following is multiple choice question (with options) to answer.
What is the natural movement called within your intestines? | [
"fibroblasts",
"peristalsis",
"proteolysis",
"progress"
] | B | When most of the chyme has been absorbed, the small intestinal wall becomes less distended. At this point, the localized segmentation process is replaced by transport movements. The duodenal mucosa secretes the hormone motilin, which initiates peristalsis in the form of a migrating motility complex. These complexes, which begin in the duodenum, force chyme through a short section of the small intestine and then stop. The next contraction begins a little bit farther down than the first, forces chyme a bit farther through the small intestine, then stops. These complexes move slowly down the small intestine, forcing chyme on the way, taking around 90 to 120 minutes to finally reach the end of the ileum. At this point, the process is repeated, starting in the duodenum. |
SciQ | SciQ-7262 | human-physiology, digestion, stomach
The stomach accomplishes much of its function by mechanically breaking down the swallowed food particles and mixing them with acid and enzymes into a sort of slurry. To do this, there are three major layers of muscle surround the stomach - from the outside, the longitudinal layer, the circular layer, and the oblique layer. The stomach also has two holes in it - the gastroesophageal opening, coming from the esophagus with the swallowed food/saliva mix, and the pylorus, where the food/acid/enzyme slurry exits into the duodenum, which is the beginning of the small intestine.
Due to the three layers of (rather strong) muscle, the stomach doesn't have a lot of expansion capability once it is filled completely to capacity. Fortunately, this almost never occurs (despite how we may feel after a large meal) because material is always leaving the stomach on its way to enzymatic digestion in the intestines. Additionally, once the stomach is filled to a certain extent, hormones such as leptin are secreted that give you the feeling of being sated, or full, triggering the brain to make you stop eating.
Of course, as we can see with the current epidemic of obesity around the world, the stomach can change its size over time. However, this is a rather slow process (weeks to months to years) of adapting to continuously consuming large meals.
But what would happen if you completely ignored these internal warnings, or were being force-fed, or whatever? Instead of rupturing (the biological equivalent of "exploding"), food would most likely be expelled either into the small intestine or back into the esophagus and back up the way it came down, i.e. causing vomiting.
The following is multiple choice question (with options) to answer.
What does the stomach produce to help digest food? | [
"acetic acid",
"hydrochloric acid",
"lactic acid",
"amino acid"
] | B | Neural Responses to Food In reaction to the smell, sight, or thought of food, like that shown in Figure 34.20, the first response is that of salivation. The salivary glands secrete more saliva in response to stimulation by the autonomic nervous system triggered by food in preparation for digestion. Simultaneously, the stomach begins to produce hydrochloric acid to digest the food. Recall that the peristaltic movements of the esophagus and other organs of the digestive tract are under the control of the brain. The brain prepares these muscles for movement as well. When the stomach is full, the part of the brain that detects satiety signals fullness. There are three overlapping phases of gastric control—the cephalic phase, the gastric phase, and the intestinal phase—each requires many enzymes and is under neural control as well. |
SciQ | SciQ-7263 | 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 plants have vascular tissue but do not have seeds? | [
"starchy vascular plants",
"seedless vascular plants",
"ofen vascular plants",
"rocky vascular plants"
] | B | Seedless vascular plants have vascular tissue but do not have seeds. |
SciQ | SciQ-7264 | cell-biology, cell, eggs, reproductive-biology, chickens
Title: Why are hard boiled eggs so homogeneous? A eukaryotic animal cell is a complicated piece of biological machinery. Some major structures inside of the cell (see the image below) include: the nucleus, mitochondria, Golgi vesicles, and various tubular structures. Why then is the single-celled, unfertilized chicken egg so homogeneous when it is cooked (or before)? The only major structure I can recognize is the cell nucleus.
*Image Credit: "Animal cell structure en" by LadyofHats (Mariana Ruiz) - Own work using Adobe Illustrator. Image renamed from Image:Animal cell structure.svg. Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Animal_cell_structure_en.svg#mediaviewer/File:Animal_cell_structure_en.svg Disclaimer: This is my understanding of the egg anatomy as a general biologist. There is most certainly better references and sources out there to explain this (please add better references if you know of any).
If I understand you correctly, your question is why we do not see cell organelles in a cracked or boiled egg. If so, your question seems to stem from a misunderstanding of what the egg white and egg yolk represents. A chicken egg is not simply an enlarged cell, and the egg yolk is not the cell nucleus.
When an oocyte matures in the chicken ovary, it stores yolk inside the cell and therefore enlarges. The yolk is therefore part of the oocyte cytoplasm. However, as it enlarges, the yolk is separated from the germinal disc, which holds all the other cell organelles (including the nucleus). The germinal disc is seen as a small white area on the egg yolk. Eventually, when the oocyte has accumulated enought yolk, it disattaches from the ovary (ovulation) and goes into the hens oviduct. This process is happening continuously, and oocytes of different stages of maturation are present on the ovary, which can be seen in this image:
The following is multiple choice question (with options) to answer.
After ovulation occurs, the moving “fingers” of what nearby structure sweep the egg into its tube? | [
"androgenen tube",
"nadiad tube",
"vertebral tube",
"fallopian tube"
] | D | After ovulation occurs, the moving “fingers” of the nearby fallopian tube sweep the egg into the tube. Fertilization may occur if sperm reach the egg while it is passing through the fallopian tube. If this happens, the egg finally completes meiosis. This results in two daughter cells that differ in size. The smaller cell is called a polar body. It soon breaks down and disappears. The larger cell is the fertilized egg, which will develop into a new human being. |
SciQ | SciQ-7265 | human-biology, genetics, human-genetics, cytogenetics
Title: How can a chromosome translocation in somatic cells lead to disease? Looking at this picture...
(source: nih.gov)
...I get the impression that the part of chromosome is attached to other chromosome, but it is not mutated. When we assume that all genes in the translocated part are intact and can still make mRNA, my question is:
How can a chromosome translocation in somatic cells lead to abnormality or disease? In the Down syndrom typically, the translocation does not induce (usually; see later) any disease. We call someone carrying the translocation a "balanced carrier". The problem arises after, at the moment of segregation.
When balanced carriers reproduce
Consider someone who has a translocation as you showed. You showed only one chromosome of each types (1N), below are the 2 chromosomes (2N). On the below image, the person with the translocation is assumed to be mating with someone who does not have the translocation.
The balance carrier is usually healthy. As a consequence of this translocation a kid has probability 1/4 to be "normal", 1/4 to have the translocation (and therefore to eventually have offspring with trisomy/monosomy) and a probability 1/2 to have trisomy/monosomy.
Balanced carrier
Citing from wikipedia:
Most balanced translocation carriers are healthy and do not have any symptoms. But about 6% of them have a range of symptoms that may include autism, intellectual disability, or congenital anomalies. A gene disrupted or disregulated at the breakpoint of the translocation carrier is likely the cause of these symptoms.
Indeed, even a balanced carrier can be affected by the translocation. Gene regulation network is often quite complex and separating a gene from its regulatory region can eventually have important impact. It is also possible that the break point occurred in the middle of a gene (or a regulatory sequence).
I think that one cannot say much more about why a balanced carrier can be sick in a general form. We'll need to go case by case and ask specifically what are the genes and regulatory processes involved in the disease. However, it is easy to conceptualize that moving genes around can affect the genetic network and the expression of genes.
The following is multiple choice question (with options) to answer.
Alterations that change chromosome structure are known as? | [
"deformities",
"mutations",
"lesions",
"traits"
] | B | Chromosomal alterations are mutations that change chromosome structure. |
SciQ | SciQ-7266 | cell-biology, cell-culture
Cell Membrane Changes:
Cell membrane to become less fluid,
potentially affecting its permeability and functionality.
Ice Formation:
Extreme cold can cause ice crystals to form
within and around the cells.
But I really want to see these up close under a microscope.
The temperatures don't have to be extreme. Just like mildly cold ice water vs. a warm shower. When the cold water hits a cell do you see it like bounce off? When the warm water hits a cell do you see it enter the cell? You can't see these changes easily under a microscope. It is a challenge to add heat or cold to cells on a microscope in a manner that you might see, unless you have the right equipment.
You might see protein denaturation - it's like an egg cooking, but because the cells are so small, it happens very fast and you aren't left with a residue, the cells detach before this happens or just disintegrate. For this to happen you need to be heating above about 55 - 65 C (131 - 149 F) for observable denaturation - this is about the same temp as egg white denatures (IIRC 61 C/141 F), but some proteins denature much earlier. Part of the reason it is so difficult to see is the range of temperatures it happens over, so the process is spread out.
Membrane fluidity is not something you will see at all unless you are making specific measurements of it - the cells just don't move enough for you to notice the difference between warm and cold. Water doesn't "bounce off" or enter cells because of membrane fluidity - it enters through protein channels called aquaporins - you can't see these either, far far far too small for light microscopy.
Adding water to the cells (note - cells don't like water in general, mammalian cells need isoosmotic conditions with some salt to keep them happy or they undergo osmotic stress and pop, which you might see, but it isn't dramatic at all). As they are already in a liquid - Have you ever added hot water to cold - how much difference do you see? How would you know when the cold/hot water reached the cells?
The following is multiple choice question (with options) to answer.
Membranes will become increasingly what as temperatures rise? | [
"fluid",
"toxic",
"metallic",
"acidic"
] | A | |
SciQ | SciQ-7267 | biochemistry
Title: Is hydrolysis of polypeptides and polysaccharides "anabolic" or "catabolic" When a polysaccharide or polypeptide is hydrolyzed into mono-saccharides or amino acids, the building blocks can be oxidized to release energy. The oxidation is considered to be catabolic since it reduces the building blocks to simple compounds: carbon dioxide, water, ammonia, and releases energy.
Is the process of hydrolysis that breaks up polypeptides and polysaccharides a net endothermic or exothermic process?
Do the free amino acids and monosaccharides have more or less stored energy than the polypeptide or polysaccharide that they were broken down from?
Is it proper to call the isolated process of "hydrolysis" of proteins and polysaccharides "catabolic"?
Are protein synthesis, glycogen synthesis, (and triglyceride formation), by dehydration synthesis processes that require energy or release energy. I think that they release energy which is semantically interesting since protein and glycogen synthesis are the main examples of anabolism in the body but may actually release energy which is a key component of the definition of catabolism. Even if the energy released from protein synthesis is not generating ATP directly, wouldn't the heat produced conserve ATP in the long run.
1) Is the process of hydrolysis that breaks up polypeptides and polysaccharides a net endothermic or exothermic process?
Under physiological conditions, it is a process that goes forward, i.e. the Gibbs energy is negative. As a consequence, it can happen outside of cells in the absence of ATP. When we eat, the hydrolysis of polysaccharides starts in our mouths, while the hydrolysis of proteins occurs under harsher (acidic) conditions in the stomach and continues in the intestine (slightly basic conditions).
For warmblooded animals like us, exothermic or endothermic is less important, but you could look it up.
2) Do the free amino acids and monosaccharides have more or less stored energy than the polypeptide or polysaccharide that they were broken down from?
The following is multiple choice question (with options) to answer.
Catabolism and anabolism are the two types of what? | [
"heart rate",
"calcium",
"metabolism",
"cells"
] | C | 20.8 End-of-Chapter Material Chapter Summary To ensure that you understand the material in this chapter, you should review the meanings of the bold terms in the following summary and ask yourself how they relate to the topics in the chapter. Metabolism is the general term for all chemical reactions in living organisms. The two types of metabolism are catabolism—those reactions in which complex molecules (carbohydrates, lipids, and proteins) are broken down to simpler ones with the concomitant release of energy—and anabolism—those reactions that consume energy to build complex molecules. Metabolism is studied by looking at individual metabolic pathways, which are a series of biochemical reactions in which a given reactant is converted to a desired end product. The oxidation of fuel molecules (primarily carbohydrates and lipids), a process called respiration, is the source of energy used by cells. Catabolic reactions release energy from food molecules and use some of that energy for the synthesis of adenosine triphosphate (ATP); anabolic reactions use the energy in ATP to create new compounds. Catabolism can be divided into three stages. In stage I, carbohydrates, lipids, and proteins are broken down into their individual monomer units—simple sugars, fatty acids, and amino acids, respectively. In stage II, these monomer units are broken down by specific metabolic pathways to form a common end product acetyl-coenzyme A (CoA). In stage III, acetyl-CoA is completely oxidized to form carbon dioxide and water, and ATP is produced. Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-7268 | genetics
Title: Arguments against incest Incest is forbidden in most countries because if there is a genetic disease in the family the child of a incestuous relationship will be at least holder of the gene of that disease. But lets say the members of a family dont have a genetic disease and are not holders of any gene related to a genetic disease then theoretically would a child of a incestuous relationship not suffer from diseases by birth? Incest doesn't necessarily mean that the partners are having unprotected sexual intercourse. It simply means sexual intercourse between closely related member of a family. In case of protected sexual intercourse, it doesn't matter whether or not the family has history of some genetic disorder.
But let's say they are practicing unprotected sexual intercourse. In that case, it does depend on the genetic history of the family. If either or both of the parthers has gene that result in a disorder, then thier offspring who gets that gene expressed in his/her body will suffer from that genetic disorder. And if it is not expressed, they become a carrier for that gene.
Now, coming to the case you mentioned, Yes, if neither of the partner have gene that causes certain genetic disorder, then the offspring will not suffer from the said gentic disorder.
But it only works if there's a no history of incest wihtin that family. In case they do have history of incest within thier family, they are likely to suffer from inbreeding depression. Inbreeding depression 'exposes' deleterious recessive genes by making them homozygous. This causes drop in fitness of the offspring and reduced fertility. Increased homozygosity is what causes issue, which increases chances of a harmful recessive gene getting expressed.
So it's not a big worry, if they don't have any such gene that cause obvious harm by resulting in a certain genetic disorder. But continuous incest in family may result in problems later on.
Anyway, it is possible to be able to determine compatibility of two people by checking thier genetic information [we may become even more advance in near future]. We can selectively edit a gene to make it so that it won't be present in the offspring. Gene editing at advance level will get really popular.
The following is multiple choice question (with options) to answer.
What types of incest behaviors are controlled by genes? | [
"instinctive behaviors like flying and mating",
"physical behaviors like flying and mating",
"byproduct behaviors like flying and mating",
"psychological behaviors like flying and mating"
] | A | Insects are capable of a surprising range of behaviors. Most of their behaviors, such as flying and mating, are instinctive. These are behaviors that don’t need to be learned. They are largely controlled by genes. However, some insect behaviors are learned. For example, ants and bees can learn where food is located and keep going back for more. |
SciQ | SciQ-7269 | the same respect, non-A, then you could make no statements whatsoever. You could not say "this is a cat" or "this conclusion is correct" or even "I am hungry." Why not? Because a cat could be a non-cat (a dog, a bus or a musical symphony); a feeling of hunger could be a sound, a sunrise or a moment in history; and a conclusion would continuously vary in content and in outcome: nothing would be set, nothing would certain, everything would be an ever changing, primordial mixture of colors, sounds and sensations. Because we start with the axiom A is not non-A, we can start with simple observations and form an unbroken chain to the abstract heights where proof, certainty and reason are possible. Without this simple starting point, we would never get there. Anyone who tries to deny the axiom A is not non-A has to use it in order to attempt to prove it is not true, which is another well-known fallacy. • Well a possible objection from intuitionists is that you're making the fallacy of false dichotomy. You claim that every meaningful statement is either true or false but not both. Intuitionists claim is that some meaningful statements are neither true nor false. If you prove "this is a cat" by intuitionistically acceptable means, whatever that means, then intuitionists would accept that statement as true and not false. So that statement would have a fixed truth value, and is is not justifiable for you to claim that without classical truth values every statement would be indeterminate. Feb 25, 2016 at 8:01 • However, your last sentence is still valid in a certain sense, namely that an intuitionist cannot prove intuitionistically that classical logic is false. Feb 25, 2016 at 8:02 It's a heck of a lot more logical than trying to go through infinitely many possibilities. For example, let's say statement $$A$$ is that $$\sqrt{2}$$ is irrational. This means that there is no combination of integers $$p$$ and $$q$$ such that $$\frac{p}{q} = \sqrt{2}.$$ Obviously $$q \neq 0$$. We can assume for convenience that $$p$$ and $$q$$ are both positive. We can actually
The following is multiple choice question (with options) to answer.
What term describes a specific statement that is thought to be never violated by the entire natural universe? | [
"hypothesis",
"scientific law",
"theory",
"evidence"
] | B | A scientific law is a specific statement that is thought to be never violated by the entire natural universe. Everyday laws are arbitrary limits that society puts on its members. |
SciQ | SciQ-7270 | molecular-biology, molecular-genetics, development, sex
Quote from a Review (Yao 2005):
We have just begun to glimpse into the mechanisms underlying ovarian development. Convincing evidence challenges us to reconsider the existing paradigm that describes ovarian development as a default system. The default concept was first proposed in the early 1950s when Jost performed the groundbreaking experiments to demonstrate mechanisms of sex differentiation of reproductive tracts (Jost, 1947, 1953, 1970). The term “default” was not originally intended to describe the developmental status of the ovary. Instead, it is referred to the female reproductive tract or the Mullerian duct based on the fact that the female reproductive tract forms in both XX and XY individuals in the absence of gonads. Indeed, now it has become evident that early ovarian development is an active process involving intrinsic cell fate decisions and complex crosstalks between germ cells and somatic cells. Most intriguingly, the appearance of testicular structures in XX individuals where Sry and its downstream components are absent further raises the improbable question: Could the testicular development be default after all?
The following is multiple choice question (with options) to answer.
When do female reproductive organs mature? | [
"at birth",
"at puberty",
"at menopause",
"periomenopause"
] | B | Female reproductive organs form before birth. However, they do not mature until puberty. |
SciQ | SciQ-7271 | particle-physics, dimensional-analysis, elementary-particles
Title: Minimal size of physical entities I know that per current knowledge there are layers of size of physical entities going from elementary particles to molecules (and from molecules to molecular structures such as bricks or organism cells and further into a tools, buildings, machines and organism bodies).
I understand that the notion between human scientists is that the "size" or "scale" of elementary particles (whatever these will be) is finite;
that is: Elementary particles are the smallest physical entities in this universe and there can't be anything smaller than them in this universe.
Is there a theory according to which infinity for how small physical entities can be, is real?
I am not talking about a theory theorizing even more and smaller elementary particles than accepted, but rather a theory that its theoreticians are "irreverent" to suggest that there is no such thing as "elementary" particle by the sense that one could always go down in the "scale" of size.
One could be further irreverent to derive from such theory that because time passes faster in micro than in macro, entire universes could exist and might appear to an observing organism as a "particle" with a lifespan of way less than a millisecond.
Also, of course the opposite question (Can there be maximal size of physical entities?) is dependent on if the cosmos is finite or infinite, but the current question doesn't seem to me such.
Is there a theory according to which infinity for how small physical entities can be, is real?
You have to define what the definition of "small" is . If you means size, the standard model of particle physics has elementary particles as point particles, no size at all, so they fulfill already the "smallnes".
If you mean if their invariant mass can be very small, already the photon the gluon and maybe the graviton have zero mass in the mainstream models.
am not talking about a theory theorizing even more elementary particles than accepted, but rather a theory that its theoreticians are "irreverent" to suggest that there is no such thing as "elementary" particle by the sense that one could always go down in the "scale" of size.
The following is multiple choice question (with options) to answer.
What are the extremely small particles that comprise all matter? | [
"electrons",
"ions",
"atoms",
"protons"
] | C | All matter is composed of extremely small particles called atoms. |
SciQ | SciQ-7272 | combustion, temperature, fuel
Of course a lot of other factors are involved but this crude picture gives at least some useful insight. This was discovered experimentally in the early days of engine design as the designers observed that different extracts from oil had different combustion properties in engines and refined the way oil was distilled to give them the behaviours they wanted in their engines.
The following is multiple choice question (with options) to answer.
What are the two basic types of combustion engines? | [
"external and internal combustion engines",
"diesel and internal combustion",
"gas and steam",
"spark and steam"
] | A | A combustion engine is a complex machine that burns fuel to produce thermal energy and then uses the energy to do work. Two basic types of combustion engines are external and internal combustion engines. |
SciQ | SciQ-7273 | 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.
Plasmodesmata passes through what part of plants? | [
"cell ridges",
"nucleus",
"cell walls",
"cytoplasm"
] | C | |
SciQ | SciQ-7274 | particle-physics, elements
Title: Is it possible to create a new element that doesn't exist in the universe? When I say something new I do not refer to something already made like H,O etc and when I mean something new I do not refer to a transformation like tritium to helium and gold.
If so how ?(I mean is there a specific way to do that ?) Yes, so far, 20 synthetic elements have been created, with atomic numbers 99 (Einsteinium) to 118 (Ununoctium). All these elements are unstable, with half-lives ranging from a year to a few milliseconds.
You can find a list on wikipedia. These elements are produced in specialized nuclear reactors, by bombarding heavy elements like Uranium and Plutonium with neutrons or other elements.
The following is multiple choice question (with options) to answer.
What element has an atomic number of 6? | [
"oxygen",
"hydrogen",
"silicon",
"carbon"
] | D | numbers have the same value on both sides, the mass number of the daughter isotope must be 12, and its atomic number must be 6. The element having an atomic number of 6 is carbon. Thus the complete nuclear equation is as follows:. |
SciQ | SciQ-7275 | sleep
Sleep and sleep-like activity has not been as well studied in inertebrates. As noted in this thread, there is evidence for sleep in at least some insects. Cephalopods like octopuses show signs of sleep (Mather 2008). Caenorhabditis elegans, a nematode worm and model biological system, shows sleep-like states tht are similar to mammals and fruit flies (Raizen et al. 2008). The most basal organism that shows evidence of sleep-like patterns is a jellyfish called Chironex fleckeri (Kavanau 2006). Cnidarians like jellyfishes are the basal (most "simple") group of organisms with an organized nervous system. Interestingly, C. fleckeri process a lot of visual information obtained through their 24 eyes. Twelve of the eyes are simple, light-receiving structures but 8 of the eyes are camera-like, meaning they have a lens. Kavanau (2006) argued that sleep (up to 15 hours) in this jellyfish allows time for its simple nervous system to process the visual information obtained while it is awake. The presence of sleep-like activity in jellyfish and nematode worms suggest that sleep is an evolutionarily ancient phenomenon.
This Wikipedia page on sleep in non-humans overviews evidence for sleep in vertebrates and invertebrates. It's not clear whether androids sleep or what they dream about if they do sleep.$^1$
Do single-celled organisms sleep?
This is (to me) a tricky question. Sleep is associated with specific types of neural activity in the brain or nervous system. In addition, sleep-like neural activity has been found in diversity of organisms with some type of nervous system, and seems evolutionarily old. I therefore think that any organism that has some form of organized neural center (brain, brain-like organ or centralized nervous system) has the potential to show some type of sleep-like patterns.
The following is multiple choice question (with options) to answer.
What common sea creature can be both awake and asleep at the same time? | [
"Whales",
"sharks",
"dolphins",
"reefs"
] | C | |
SciQ | SciQ-7276 | evolution, biochemistry, mitochondria
Title: Is there any advantage of having mitochondria for aerobic respiration? If we consider the pathway of breakdown of glucose which includes glycolysis, the citric acid cycle and the electron transport chain, all these processes takes place in some prokaryotes and eukaryotes. In prokaryotes all these processes take place in cytoplasm while in eukaryotes the last two processes take place in mitochondria.
So is there any advantage of performing the last two processes in the mitochondria? Does it yield more energy? If there is no advantage, what is the point of having a mitochondria (at least for this process)? From the evolutionary point of view, the eukaryotes acquired these metabolisms (except glycolysis) from their prokaryotic endosymbionts. Not all prokaryotes have the ETC. The free living ancestor of mitohondria is supposed to be the alpha-proteobacterium.
Now, glycolysis is a common pathway in lot of lifeforms perhaps because of abundance of glucose. TCA cycle is coupled with ETC at certain steps which makes it essentially a part of aerobic metabolism.
The reason for having a dedicated organelle for respiration
ATP synthesis is a membrane process. Imagine a large prokaryotic cell- as big as an animal cell. Such a cell cannot take care of its energetic demands which primarily consists of protein synthesis with the given area of membrane i.e it needs much more ATP-synthases than it can have to cope up with the energy demands of maintaining such a huge cell (this index is approximated based on surface to volume ratio). Therefore it is wise to harbor multiple efficient organelles i.e. mitochondria which themselves have just a small essential genome and proteome to maintain.
For a better understanding, please read this article. I just loved it.
There is also a book by the same author about mitochondria called Power, Sex, Suicide.
The following is multiple choice question (with options) to answer.
What is the second stage of cellular respiration? | [
"marr cycle",
"krebs cycle",
"duocycle",
"beatnik cycle"
] | B | The pyruvate molecules from glycolysis next enter the matrix of a mitochondrion. That's where the second stage of cellular respiration takes place. This stage is called the Krebs cycle . During this stage, two more molecules of ATP are produced. Other energy-storing molecules are also produced (to be used to make more ATP in stage 3). The Krebs cycle requires oxygen. Anything that needs oxygen is described as aerobic . The oxygen combines with the carbon from the pyruvate molecules. This forms carbon dioxide, a waste product. |
SciQ | SciQ-7277 | electric-circuits, electrical-resistance, electrical-engineering, batteries
Title: Voltage of a battery in a circuit with an infinite resistance I have a dilemma that I would like to share with you concerning batteries (without neglecting internal resistance), emf and resistance of a circuit.
To better visualize my question you may need to check these pictures:
-First, I'm trying to grasp the concept of why and how the voltage drop at the terminals of a battery depends on the resistance of the circuit.
-Second, knowing that $$\epsilon= V_b + V_c$$ (battery and circuit, respectively), we know that $$\epsilon=I(R+r)$$
Considering the extreme cases where $R=0$ and $R=∞$,
what I expected was that at $R = ∞$, the voltage would be 0, because there would be infinite resistance and zero current, and since $V=RI$, it would be $V= ∞ \times 0=0$ which makes absolutely no sense to me. Plus, an ideal voltmeter has an infinite resistance but it does not give a voltage reading of zero when its terminals are placed on the battery terminals.
What am I doing wrong, and how do the charges on the poles of the battery act in each of these cases?
I'm sorry I could not be clearer in how to propose the question but I hope that it is enough. I'm still learning so do not rely on any of my assumptions. At R→∞ voltage won't be 0 but little
less than EMF off cell, since a series
circuit with voltmeter and battery is
complete.
Yes, voltage across resistor reaches
0.Voltmeter reading is not EMF
because it draw some current which
pass through internal r and gets some
potential across it.
An Ideal voltmeter cannot tell you
voltage across resistance in practical.
The following is multiple choice question (with options) to answer.
As a battery is depleted what happens to its internal resistance? | [
"stagnates",
"increases",
"changes",
"reduces"
] | B | The internal resistance r can behave in complex ways. As noted, r increases as a battery is depleted. But internal resistance may also depend on the magnitude and direction of the current through a voltage source, its temperature, and even its history. The internal resistance of rechargeable nickel-cadmium cells, for example, depends on how many times and how deeply they have been depleted. |
SciQ | SciQ-7278 | botany, plant-anatomy
Title: Is it possible to grow any kind of plant soilless (hydroponics)? Hydroponics is a subset of hydroculture and is a method of growing plants using mineral nutrient solutions, in water, without soil. [wikipedia]
My question is if is it possible to grow any kind of plant soilless (hydroponics)? Yes, There are a few i know of, a quick "air plant" google search will get you quiet a lot.
wiki 1
wiki 2
Edit: I just glanced through the hydroponics article, and now I wonder if my answer actual answers your question.
The following is multiple choice question (with options) to answer.
What is a condition where plants are grown in mineral solutions without soil called? | [
"hydroponics",
"climate zone",
"biosphere",
"hydrozone"
] | A | |
SciQ | SciQ-7279 | human-biology, evolution, speciation, species, human-evolution
Is this definition incorrect?
Are the publications using "species" colloquially, as opposed to scientifically?
Is "species" still a poorly defined concept? (see Ring Species)
Thanks! Short answer
The concept of species is poorly defined and is often misleading. The concepts of lineage and clade / monophyletic group are much more helpful. IMO, the only usefulness of this poorly defined concept that is the "species" is to have a common vocabulary for naming lineages.
Note that Homo neanderthalis is sometimes (although it is rare) called H. sapiens neanderthalis though highlighting that some would consider neanderthals and modern humans as being part of the same species.
Long answer
Are neanderthals and modern humans really considered different species?
Often, yes they are considered as different species, neanderthals being called Homo neanderthalis and modern humans are being called Homo sapiens. However, some authors prefer to call neanderthals Homo sapiens neanderthalis and modern humans Homo sapiens sapiens, putting both lineages in the same species (but different subspecies).
How common were interbreeding between H. sapiens and H. neanderthalis
Please, have a look at @iayork's answer.
The rest of the post is here to highlight that whether you consider H. sapiens and H. neanderthalis to be the same species or not is mainly a matter of personal preference given that the concept of species is mainly arbitrary.
Short history of the concept of species
To my knowledge, the concept of species has first been used in the antiquity. At this time, most people viewed species as fixed entities, unable to change through time and without within-population variance (see Aristotle and Plato's thoughts). For some reason, we stuck to this concept even though it sometimes appears to not be very useful.
Charles Darwin already understood that as he says in On the Origin of Species (see here)
The following is multiple choice question (with options) to answer.
What is the scientific name for the human species? | [
"primate",
"Neanderthal",
"homo erectus",
"homo sapiens"
] | D | The human species evolved during the Cenozoic Era. The scientific name of the human species is Homo sapiens. |
SciQ | SciQ-7280 | cell-biology, meiosis, mitosis
Title: Is the cell cycle applicable to meiosis as well, or just mitosis? All the diagrams I can find, show the cell cycle as having G1 phase (growth 1), S phase (DNA replication), G2 (growth 2) before the Mitotic phase (mitosis + cytokinesis).
Is there an equivalent "cell cycle" for meiosis, since the chromosomes in parent cell in meiosis also having "double" the genetic material prior to cell division (presumably from DNA replication too)?
Is it simply the same cell cycle as mitosis but with a Meiotic phase instead of Mitotic?
If so, would appreciate if anyone had a diagram :) Thanks! The cell cycle is only associated with mitosis. The cell cycle is the normal process of cell division with which cells can indefinitely increase their number by cyclically repeating the process. When a cell goes through the cycle, the result is two cells that are genetically identical.
Meiosis is a special type of cell division (which can occur only in eukaryotes) that produces cells that are not genetically identical to the initiating cell. The number of chromosomes in each of the resulting cells is half the number that were in the initial cell. (These haploid cells can later participate in fertilization, producing a cell with the original number of chromosomes.) Many of the steps of meiosis are similar to the steps involved in mitosis, but overall the process is more complex. Since meiosis reduces the number of chromosomes, it cannot be repeated and so does not take part in a cell division cycle.
The following is multiple choice question (with options) to answer.
Snippet 3: the diploid cells resulting from karyogamy are short-lived and undergo meiosis, producing what? | [
"stunted spores",
"binary spores",
"haploid spores",
"hyperactive spores"
] | C | |
SciQ | SciQ-7281 | in the comments section. At what speed does the second train B travel if the first train travels at 120 km/h. You can approach this as if you were solving for an unknown in math class or you can use the speed triangle. Time, Speed and Distance: Key Learnings. ) Since the distances are the same, I set the distance expressions equal to get: Unit of speed will be calculated based on unit of distance and time. Distance, Rate and Time content standard reference: grade 6 algebra and functions 2. aspxCollins Aerospace ARINCDirect maintains a multitude of data on airports and airways around the world. My other lessons on Travel and Distance problems in this site are - (Since the speed through the steel is faster, then that travel-time must be shorter. Initial speed of the car = 50km/hr Due to engine problem, speed is reduced to 10km for every 2 hours(i. 5th Grade Numbers Page 5th Grade Math Problems As with the speed method of calculation, the denominator must fit into 60 minutes. In National 4 Maths use the distance, speed and time equation to calculate distance, speed and time by using corresponding units. Distance divided by rate was equal to time. Pete is driving down 7th street. Speed, Distance, Time Worksheet. This Speed Problems Worksheet is suitable for 4th - 6th Grade. If the speed of the jeep is 5km/hr, then it takes 3 hrs to cover the same For distance word problems, it is important to remember the formula for speed: Definition: Speed = Distance/Time. An executive drove from home at an average speed of 30 mph to an airport where a helicopter was waiting. Again, if you look at the formula triangle, you can see that you get distance by multiplying speed by time. Next time you are out walking, imagine you are still and it is the world that moves under your feet. Q) Mr. Distance is directly proportional to Velocity when time is constant. The problem gives the distance in feet and the speed in miles per hour. The detailed explanation will help us to understand how to solve the word problems on speed distance time. Average Speed = Total distance ÷ Total time = 110 ÷ 5/6 = 110 × 6/5 = 132 km/h. 6T + 4T = 20 km. The result will be the average speed per unit of time, usually an hour. We will practice different Distance, Speed and
The following is multiple choice question (with options) to answer.
Average speed is equal to distance divided by what? | [
"time",
"height",
"weight",
"magnitude"
] | A | Average speed is distance divided by time. |
SciQ | SciQ-7282 | physical-chemistry, phase
Title: How does the process of nucleation work for boiling liquids? I have a somewhat clear picture how (on the molecular level) a gas turns into a liquids as it cools. When a gas has a certain temperature, its molecules on average have a high enough kinetic energy so that electromagnetic interactions cannot hold the molecules together and they are essentially free. When the gas cools, the kinetic energies are smaller and thus electromagnetic interactions between molecules start to pull the molecules together and the process of turning into a liquid begins. As more molecules lose kinetic energy, initially small numbers of molecules start to cluster up, forming "lumps" that continue growing as more molecules gather up into these clusters. I believe this process is called "nucleation".
I found this video that helps visualize the effect:
https://www.youtube.com/watch?v=wFT6G4CIL1o
But how does the reverse take place? Let's say I'm boiling water. I have a textbook that specifically states:
During nucleation, small droplets of liquid form in gases or gas bubbles form in water as it starts to boil.
The following is multiple choice question (with options) to answer.
When a supercooled liquid boils, the temperature drops as the liquid is converted to what? | [
"atoms",
"solid",
"vapor",
"carbon"
] | C | A superheated liquid exists temporarily as liquid with a temperature above the normal boiling point of the liquid. When a supercooled liquid boils, the temperature drops as the liquid is converted to vapor. Conversely, a supercooled liquid exists temporarily as a liquid with a temperature lower than the normal melting point of the solid. As shown below, when a supercooled liquid crystallizes, the temperature increases as the liquid is converted to a solid. |
SciQ | SciQ-7283 | cell-biology, meiosis, mitosis
Title: Is the cell cycle applicable to meiosis as well, or just mitosis? All the diagrams I can find, show the cell cycle as having G1 phase (growth 1), S phase (DNA replication), G2 (growth 2) before the Mitotic phase (mitosis + cytokinesis).
Is there an equivalent "cell cycle" for meiosis, since the chromosomes in parent cell in meiosis also having "double" the genetic material prior to cell division (presumably from DNA replication too)?
Is it simply the same cell cycle as mitosis but with a Meiotic phase instead of Mitotic?
If so, would appreciate if anyone had a diagram :) Thanks! The cell cycle is only associated with mitosis. The cell cycle is the normal process of cell division with which cells can indefinitely increase their number by cyclically repeating the process. When a cell goes through the cycle, the result is two cells that are genetically identical.
Meiosis is a special type of cell division (which can occur only in eukaryotes) that produces cells that are not genetically identical to the initiating cell. The number of chromosomes in each of the resulting cells is half the number that were in the initial cell. (These haploid cells can later participate in fertilization, producing a cell with the original number of chromosomes.) Many of the steps of meiosis are similar to the steps involved in mitosis, but overall the process is more complex. Since meiosis reduces the number of chromosomes, it cannot be repeated and so does not take part in a cell division cycle.
The following is multiple choice question (with options) to answer.
What process produces four haploid daughter cells, each genetically unique? | [
"mitosis",
"electrolysis",
"meiosis",
"budding"
] | C | Mitosis vs. Meiosis Comparison. Mitosis produces two diploid daughter cells, genetically identical to the parent cell. Meiosis produces four haploid daughter cells, each genetically unique. See How Cells Divide: Mitosis vs. Meiosis at http://www. pbs. org/wgbh/nova/miracle/divide. html for an animation comparing the two processes. |
SciQ | SciQ-7284 | Extraneous roots don't arise only from root equations, though. Consider also:
$$\frac{x^2}x = 0$$
You might choose to multiply both sides by x, and then solve $x^2 = 0$, but the solution $x = 0$ is extraneous since it is excluded from the domain of the equation. Again, there is no soultion in the reals.
But sometimes there are. Consider:
$$\frac{x^2 + x - 6}{x - 2} = 0$$ $$x^2 + x - 6 = 0$$ $$(x + 3)(x - 2) = 0$$ $$x = -3, x = 2$$
But this time, $x = 2$ is extraneous because it is excluded from the domain, but $x = -3$ is a valid root.
So, long story short, going back and checking your work is important not just because you're fallible, but also because it's the easiest way to identify a phony solution that math decided to troll you with.
The following is multiple choice question (with options) to answer.
What is root that does not arise from a usual place? | [
"momentous",
"adventitious",
"monomers",
"hypochlorous"
] | B | the radicle is also growing and producing the primary root. As it grows downward to form the tap root, lateral roots branch off to all sides, producing the typical dicot tap root system. In monocot seeds (Figure 32.21), the testa and tegmen of the seed coat are fused. As the seed germinates, the primary root emerges, protected by the root-tip covering: the coleorhiza. Next, the primary shoot emerges, protected by the coleoptile: the covering of the shoot tip. Upon exposure to light (i. when the plumule has exited the soil and the protective coleoptile is no longer needed), elongation of the coleoptile ceases and the leaves expand and unfold. At the other end of the embryonic axis, the primary root soon dies, while other, adventitious roots (roots that do not arise from the usual place – i. the root) emerge from the base of the stem. This gives the monocot a fibrous root system. |
SciQ | SciQ-7285 | periodic-trends, periodic-table
Title: How long the block starting with element 121 will be? I remember from my chemistry classes that (after the initial irregularities) a new block of elements starts every two periods. After the initial s-block and p-block following it shortly, we have d-block starting at period IV, and f-block starting at period VI.
Now that Element 118 has been discovered, we're about to open period VIII and we're two elements short of a new block.
What block will it be? How many groups, what name etc? As you noted, this is a very appropriate question in light of the IUPAC announcement that we have just finished filling Period 7!
The names of the subshells s, p, d, and f are named after the old spectroscopic terms sharp, principal, diffuse, and fundamental. We ran out of fancy names after that, so the subsequent subshells are named in alphabetical order - g, h, and so on - which means that after the 8s block is filled, we would theoretically have a 5g block.
The orbitals in the g subshell would be labelled with the quantum number $l = 4$, so $m_l$ would take integer values between $-4$ and $4$ (inclusive) giving a total of nine g-orbitals. Each g-orbital could hold two electrons with opposite spins, so the g-block would have $18$ electrons.
However, it is worth noting that the electronic configurations may or may not obey the aufbau principle fully. Whether the 5g orbitals will actually be filled or not will certainly not be easy to determine, considering how short the half-lives of those elements are likely to be.
Wikipedia has an article which talks about it.
The following is multiple choice question (with options) to answer.
In which period of the periodic table is nickel found? | [
"Third Period",
"fourth period",
"Second Period",
"First Period"
] | B | The period to which a given element belongs can easily be determined from its electron configuration. For example, consider the element nickel (Ni). Its electron configuration is [Ar]3 d 8 4 s 2 . The highest occupied principal energy level is the fourth, indicated by the 4 in the 4 s 2 portion of the configuration. Therefore, nickel can be found in the fourth period of the periodic table. |
SciQ | SciQ-7286 | 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.
What serves as the control center of the nervous system? | [
"heart",
"bone",
"spine",
"brain"
] | D | The brain serves as the control center of the nervous system and the body as a whole. It lets us understand what we see, hear, or sense in other ways. It allows us to learn, think, remember, and use language. It controls all the organs and muscles in our body. |
SciQ | SciQ-7287 | pressure, buoyancy
Title: Is there a formula to determine if a ballon on the of deep water rises up? Imagine a balloon (again) that finds itself on the bottom of a mass deep water. The balloon is filled with air. The deep mass of water finds itself on a heavy (w.r.t. Earth) planet.
Initial, the balloon stays put (on the bottom)
After it's not stayed put anymore (it's let loose), what will happen and why?
It's clear that pressure and temperature (or other pairs of state variables) have to do with it. Maybe the water could freeze.
Is there a mathematical formula that can answer this question?
I searched and thought about the solution, but couldn't find it. But after reading the first answer it's as clear as water. The air inside the balloon is lighter than the surrounding water (if the air inside the balloon is not frozen by the high pressure, in which case I'm not sure if the ice density scales with pressure). The first answer made me realize that, so apparently, I had thought about it too little. Due to the immense pressure, the balloon will shrink in size. Once let loose, the balloon will start accelerating by quite a bit (somewhat both 2 and 3) and will eventually attain terminal velocity at a point. Then onwards, the balloon will rise at the same pace.
The following is multiple choice question (with options) to answer.
What is the name for the term that describes deep ocean water rising the surface? | [
"up-rising",
"upwelling",
"leaking",
"percolating"
] | B | Sometimes deep ocean water rises to the surface. This is called upwelling . Figure below shows why it happens. Strong winds blow surface water away from shore. This allows deeper water to flow to the surface and take its place. |
SciQ | SciQ-7288 | special-relativity
Title: How does the comparison of rates depend on mutual speed? If I'm moving with a considerable fraction of speed of light, the time and any process in my system will be going slower. If B is an outstanding person that is watching me passing by, he will see everything in my system in slow motion. This means he observes less ticks per seconds; thus the ticks are slower or the interval between the ticks is bigger. From my perspective everything is normal and time is not running slower.
Is it okay to talk about the speed of time in this context? Is it okay to say: "The shorter the interval between two ticks the faster the speed of time."?
If I'm moving with a considerable fraction of speed of light, the time and any process in my system will be going slower.
That's an improper, careless, lazy description ("slower" -- in comparison to what??).
If B is an outstanding person that is watching me passing by, he will see everything in my system in slow motion.
The following is multiple choice question (with options) to answer.
What is the measure for how fast or slow something moves? | [
"kinetic energy",
"momentum",
"speed",
"inertia"
] | C | Speed is an important aspect of motion. It is a measure of how fast or slow something moves. It depends on how far something travels and how long it takes to travel that far. Speed can be calculated using this general formula:. |
SciQ | SciQ-7289 | evolution, species
Title: Reasons why living fossils exist?
A living fossil is a living species (or clade) that
appears to be similar to another species otherwise known only from fossils,
typically with no close living relatives.
A living fossil is considered as a successful organism, which has made its way through many major extinction events. Also, the morphology of living fossils resemble some species of organisms which we know only through their fossil remains.
What is the reason for a particular type of species to become a living fossil; is the engineering of this particular species extraordinary, in that it can survive any selection process encountered thus far?
Is there not enough selection pressure exerted on this species in order to force it to change morphologically?
Have these organisms modified themselves, so that currently their morphology seems to be similar to a fossil organism? One part of your question betrays a serious error:
Is there not enough selection pressure exerted on this species in order to force it to change morphologically?
Actually the reverse is true; constancy of form can only be maintained in the presence of continuous selective pressure. It's just that this is stabilising selection that acts to maintain the existing form rather than push the organism to new morphologies. In fact, most selection acts in this manner. This shouldn't surprise you: organisms are typically well adapted to their environments so changes are more likely to reduce fitness than increase fitness.
It's also worth noting that although living fossils show little morphological change they can continue to show change at the molecular level at rates as high as, or higher than, other organisms - e.g. (May et al 2007; Cao et al 2013).
The following is multiple choice question (with options) to answer.
What is the term for the decayed remains of living organisms? | [
"waste",
"intermediate material",
"humus",
"necrosis"
] | C | Humus is the decayed remains of living organisms. Humus makes soil fertile. |
SciQ | SciQ-7290 | material-science
Title: Does metal under low tension ever actually bend? Let's assume something like a pair of tweezers, since that's strangely what led to this mental exercise.
Does the metal ever actually permanently transform its shape? Stainless steel is fairly malleable, but in this case even with tweezers held closed, is there ever a point where removing this constriction would result in no change in shape (i.e they stay closed permanently until bent back)? Is there a mathematical way to define how long this would take? Would it simply stay in tension forever unless more force was added to reshape the metal? I would guess you're thinking about the phenomenon called creep.
Your piece of metal is made up from crystals in which each atom has a well defined position with respect to the atoms around it, and it takes a lot of energy to make an atom jump completely out of its position. When you elastically deform the metal you displace atoms very slightly, but when you release the metal the atoms return to their equilibrium positions and the metal returns to its original shape. Permanent deformation happens when you apply so much force that it makes some of the atoms jump completely out of their original locations and into new positions.
However even under small deformations it is possible for atoms to move causing the deformation to become permanent. Metals generally contain defects in their crystal structure called dislocations and the atoms near a dislocation are generally more mobile than atoms in the rest of the metal. Under even small applied forces movement of atoms at a dislocation can cause the dislocation to move and the metal to permanently deform.
Alternatively, at any temperature above absolute zero the atoms in a metal have some thermal energy so they are vibrating about their equilibrium positions. As you increase the temperature the atoms vibrate more and this makes it easier for them to move. The obvious extreme example of this is melting, where the atoms vibrate so much it breaks down the regular crystal lattice and becomes a liquid. However even below the melting point increased temperature can allow atoms to move and this can cause a small deformation to become permanent.
To what extent creep happens, and how fast, depends on the type of metal and how the metal has been treated. Obviously your tweezers are designed to be flexible and will have been made from a metal that does not creep readily.
The following is multiple choice question (with options) to answer.
What happens when materials return to their original shape? | [
"reverberation",
"second life",
"restoration principle",
"elastic rebound"
] | D | Elastic rebound occurs when materials return to their original shape. |
SciQ | SciQ-7291 | genetics
Title: How does chromosome cross-over occur? I have heard that during meiosis, homologous chromosomes from each parent "cross-over", which enables the off-spring to inherit some alleles from the mother and some alleles from the father. The picture below illustrates this "cross-over", but of course this must occur at multiple sites, rather than just the one shown in the picture.
Now my question is what causes the chromosomes to align perfectly during cross-over so that the loci of a particular gene will substitute for the corresponding loci on the homologous chromosome, as opposed to being substituted with a completely random locus? Does each gene have a unique non coding sequence before it specifying what gene it is to enable this process to occur? Quite simply, because chromosome pairing is sequence specific. Holliday Junctions, which are the functional structures of a cross-over, occur through a process called "strand invasion," during which a region of one chromosome physically base-pairs with that of another. Thus one locus cannot pair with a random locus, as there is generally insufficient sequence complimentarity between two random regions to form a functional Holliday Junction. One interesting consequence of this mechanism is gene duplication and deletion in repetitious regions of the chromosome. For example, genes with large repeated regions, such as the gene responsible for Huntington's disease, can expand and contract during homologous recombination due to strand invasion occurring at non-equivalent, but still homologous, sites. Wikipedia does a nice job going over homologous recombination. I also recommend looking over the relevant sections in Molecular Biology of the Cell, available on the PubMed Bookshelf.
The following is multiple choice question (with options) to answer.
Dna segments cross over to form what kind of chromosome? | [
"mutated",
"resistant",
"recombinant",
"autosome"
] | C | Located at intervals along the synaptonemal complex are large protein assemblies called recombination nodules. These assemblies mark the points of later chiasmata and mediate the multistep process of crossover—or genetic recombination—between the non-sister chromatids. Near the recombination nodule on each chromatid, the double-stranded DNA is cleaved, the cut ends are modified, and a new connection is made between the non-sister chromatids. As prophase I progresses, the synaptonemal complex begins to break down and the chromosomes begin to condense. When the synaptonemal complex is gone, the homologous chromosomes remain attached to each other at the centromere and at chiasmata. The chiasmata remain until anaphase I. The number of chiasmata varies according to the species and the length of the chromosome. There must be at least one chiasma per chromosome for proper separation of homologous chromosomes during meiosis I, but there may be as many as 25. Following crossover, the synaptonemal complex breaks down and the cohesin connection between homologous pairs is also removed. At the end of prophase I, the pairs are held together only at the chiasmata (Figure 11.3) and are called tetrads because the four sister chromatids of each pair of homologous chromosomes are now visible. The crossover events are the first source of genetic variation in the nuclei produced by meiosis. A single crossover event between homologous non-sister chromatids leads to a reciprocal exchange of equivalent DNA between a maternal chromosome and a paternal chromosome. Now, when that sister chromatid is moved into a gamete cell it will carry some DNA from one parent of the individual and some DNA from the other parent. The sister recombinant chromatid has a combination of maternal and paternal genes that did not exist before the crossover. Multiple crossovers in an arm of the chromosome have the same effect, exchanging segments of DNA to create recombinant chromosomes. |
SciQ | SciQ-7292 | electric-current, semiconductor-physics
Title: Do molten semiconductors conduct electricity better than solid semiconductors? I read that electrical conductivity goes up as semiconductors rise in temperature as opposed to metals that lose electrical conductivity as temperature rises. Would semiconductors continue to conduct better as they move into thier liquid state? Both silicon and germanium are four-fold coordinated diamond cubic solids as semiconductors. Upon melting the become 8- to 12-fold coordinated metallic liquids, with a conductivity at least 30x that of the semiconductor at the melt point. The coordination number increases with temperature above the melt. The classic reference for the conductivities is V. M. Glaznov et al., "Liquid Semiconductors", Plenum, New York (1969).
This large change in resistivity upon melting was used to good effect in transient conductivity measurements to get at the interface velocity response function for pulsed laser melted silicon and germanium. See, for example, Measurement of the Velocity of the Crystal-Liquid Interface in Pulsed Laser Annealing of Si, G. J. Galvin et al., Phys Rev Lett 48 33-36 (1982).
I make no claims for other semiconductors. Note that compounds like GaAs tend to lose stoichiometry before actually melting, so one would have to be careful about the conditions in any experiment you look at.
The following is multiple choice question (with options) to answer.
Typically hard, high-melting solids that conduct heat and electricity well, the transition elements have many properties in common with other what? | [
"oils",
"organics",
"deposits",
"metals"
] | D | The transition elements have many properties in common with other metals. They are almost all hard, high-melting solids that conduct heat and electricity well. They readily form alloys and lose electrons to form stable cations. In addition, transition metals form a wide variety of stable coordination compounds, in which the central metal atom or ion acts as a Lewis acid and accepts one or more pairs of electrons. Many different molecules and ions can donate lone pairs to the metal center, serving as Lewis bases. In this chapter, we shall focus primarily on the chemical behavior of the elements of the first transition series. |
SciQ | SciQ-7293 | cell-biology, apoptosis, autophagy
Apoptosis: A Review of Programmed Cell Death
Apoptosis vs. Necrosis
Cell death by necrosis: towards a molecular definition
Review Necrosis: a specific form of programmed cell death?
The following is multiple choice question (with options) to answer.
Programmed cell death, which goes by what term, is important for removing damaged or unnecessary cells? | [
"synthesis",
"mutations",
"mytosis",
"apoptosis"
] | D | 9.3 Response to the Signal The initiation of a signaling pathway is a response to external stimuli. This response can take many different forms, including protein synthesis, a change in the cell’s metabolism, cell growth, or even cell death. Many pathways influence the cell by initiating gene expression, and the methods utilized are quite numerous. Some pathways activate enzymes that interact with DNA transcription factors. Others modify proteins and induce them to change their location in the cell. Depending on the status of the organism, cells can respond by storing energy as glycogen or fat, or making it available in the form of glucose. A signal transduction pathway allows muscle cells to respond to immediate requirements for energy in the form of glucose. Cell growth is almost always stimulated by external signals called growth factors. Uncontrolled cell growth leads to cancer, and mutations in the genes encoding protein components of signaling pathways are often found in tumor cells. Programmed cell death, or apoptosis, is important for removing damaged or unnecessary cells. The use of cellular signaling to organize the dismantling of a cell ensures that harmful molecules from the cytoplasm are not released into the spaces between cells, as they are in uncontrolled death, necrosis. Apoptosis also ensures the efficient recycling of the components of the dead cell. Termination of the cellular signaling cascade is very important so that the response to a signal is appropriate in both timing and intensity. Degradation of signaling molecules and dephosphorylation of phosphorylated intermediates of the pathway by phosphatases are two ways to terminate signals within the cell. |
SciQ | SciQ-7294 | geochemistry, chemistry-in-fiction, minerals
They look like extremely poor sources of metals like aluminum, lithium, iron, sodium, calcium, magnesium and potassium.
Now micas. Micas are described by the formula
$\ce{X_2Y_{4–6}Z_8O_{20}(OH,F)_4}$
in which
X is K, Na, or Ca or less commonly Ba, Rb, or Cs;
Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc.;
Z is chiefly Si or Al, but also may include Fe3+ or Ti.
Of interest in this formula are Rb and Cs, no matter how rare, because these are rare by definition. So, adding to the same elements as the above described amphiboles, micas have the advantage of also containing barium, rubidium (!), caesium (!!), manganese, chromium, Titanium and Lithium.
So my question is, what would be a lightly realistic approach to obtain usable compounds from granite? I'm sure real techniques do not exist, but what about science-fictional approaches? Chemists probably have unachievable dreams of tapping this or that potential source for obtaining huge amounts of a substance (until recently, one of those fancy dreams was a way to obtain drinkable water from sea water). I would love to hear any input from this (almost always) lovely community.
The following is multiple choice question (with options) to answer.
What elements do mafic minerals typically include? | [
"sodium and magnesium",
"xerophyte and magnesium",
"iodine and magnesium",
"iron and magnesium"
] | D | First, notice where carbon is fixed by the enzyme Rubisco. In C-3, C-4, and CAM plants, CO 2 enters the cycle by joining with 5-carbon ribulose bisphosphate to form a 6-carbon intermediate, which splits (so quickly that it isn’t even shown) into two 3-carbon 3-phosphoglycerate molecules. Now look for the points at which ATP and NADPH (made in the light reactions) add chemical energy (“Reduction” in the diagram) to the 3-carbon molecules. The resulting glyceraldehyde-3-phosphate “half-sugars” can enter several different metabolic pathways. One recreates the original 5-carbon precursor, completing the cycle. A second combines two of the 3-carbon molecules to form glucose, the universal fuel for life. The cycle begins and ends with the same 5-carbon RuBP molecule, but the process combines carbon and energy to build carbohydrates – food for life. |
SciQ | SciQ-7295 | meteorology, climate-change, gas, pollution
Title: Regarding various types of atmospheric pollution Does all the car pollution (from about 150 million cars at least in the U.S. and a lot more in all of North America and the rest of the world) all the smoke-stack pollution of various factories and all the Airline pollution running day after day have a deleterious and damaging effect on the general atmosphere and, over time, the climate?
Given all the observed pollution that China has caused itself and some of the resulting weird weather events there this certainly seems to be evidence of the damaging effects of car and factory pollution. Has anyone calculated how much exhaust from cars is produced in one day on average in a 'moderate' sized city?
Of course it seems with all the increased oil production in the U.S. and elsewhere we, human beings are going to keep are love-affair with gas-powered cars for the next 200 or 300 years. That is if we don't use up all the oil and gas in the ground before then. As a USA resident, the EPA is the best place to start when wondering about the emissions inventory of atmospheric pollutants or pollutant precursors that affect the National Ambient Air Quality Standards (e.g. Particulate Matter, Carbon Monoxide, Sulfur Dioxide, Lead, Nitrogen Oxides, Volatile Organic Compounds). The EPA compiles a comprehensive emissions inventory of all criteria pollutants at the county level which is available in the National Emissions Inventory (compiled once every 3 years). You can see the summary of your county at http://www.epa.gov/air/emissions/where.htm. As for the effects of atmospheric pollution, it is important to consider the lifetime of said pollutants in the atmosphere in order to put their environmental impacts into perspective. For instance, the air pollutants covered by the National Ambient Air Quality Standards have immediate health effects when high concentrations are breathed in regularly. Both animals and plants are adversely affected by these irritating and sometimes toxic chemicals, but these pollutants are also reactive and do not last long in the atmosphere unless they are constantly being replenished (e.g. daily traffic). Air quality also impacts critical nitrogen loads on ecosystems and possible production of acid rain.
The following is multiple choice question (with options) to answer.
During what time period did poor air quality become a problem? | [
"coal industry boom",
"second world war",
"industrial revolution",
"Chernobyl disaster"
] | C | Poor air quality started to become a serious problem after the Industrial Revolution. The machines in factories burned coal. This released a lot of pollutants into the air. After 1900, motor vehicles became common. Cars and trucks burn gasoline, which adds greatly to air pollution. |
SciQ | SciQ-7296 | evolution, dna, natural-selection
It seems plausible to me that we (advanced life) could have a biological mechanism to "write" needed alterations into either our own DNA or our reproductive DNA over time, triggering the very specific evolutionary developments necessary to our survival without relying on random mutation.
My question:
Is this possible? Does any similar mechanism exist that we know of? If not, how can so many specific (advanced) evolutionary leaps be otherwise explained? This entire answer will be long, so read the short part first, then read the rest if you (or anyone else) is curious. Citations are included in the long section. I can include additional citations in the short section if needed.
Long Story Short
Your question touches on some common misconceptions about how the evolutionary process. Organisms don't "want" to evolve traits. Traits evolve through the biological processes of random mutation and natural selection.
Organisms do not "want" to evolve traits. (Well, OK, I'd love to evolve an extra pair of hands but that is not possible.) Natural selection works by modifying existing traits. Your turtle can stare all she wants at food out of reach but she will not evolve a longer neck. Instead, natural variation exists among neck lengths of the turtles because of variation of the genes that determine features related to overall boxy size. Those individuals with longer necks may be able to get a bit more food, live a little longer, and reproduce a little more. They will pass along their genes to their offspring, so perhaps more of their offspring will also have longer necks. Over many generations, the turtles may have somewhat longer necks.
A common misconception is that the traits of organisms are precisely adapted for a specific need. They are not, for a few reasons. First, natural selection occurs relative to the current environment. Adaptations that work well in one environment may not be so useful in another environment. Environments are rarely stable over evolutionary time so traits are subject to constant change.
Next, as mentioned above, natural selection can only work on what traits are present. While an extra set of arms would be handy, I am a tetrapod. My four appendages, along with the appendages of all other tetrapods, trace back to our common ancestor. The appendages of all tetrapods are modifications of that ancestral trait.
The following is multiple choice question (with options) to answer.
All living organisms must have what ability, in order to make more organisms like themselves? | [
"cloning",
"reproduction",
"absorption",
"variation"
] | B | All living organisms must have the ability to reproduce. Living things make more organisms like themselves. Whether the organism is a rabbit, or a tree, or a bacterium, life will create more life. If a species cannot create the next generation, the species will go extinct. Reproduction is the process of making the next generation and may be a sexual or an asexual process. Sexual reproduction involves two parents and the fusion of gametes , haploid sex cells from each parent. Sexual reproduction produces offspring that are genetically unique and increases genetic variation within a species. Asexual reproduction involves only one parent. It occurs without a fusion of gametes and produces offspring that are all genetically identical to the parent. |
SciQ | SciQ-7297 | thermodynamics, everyday-life, water, ice, freezing
The effects of heating the water:
removing dissolved gases: higher temperature favors endothermic reactions (Le Chatelier's principle). For the gases present in water, dissolution (at room temperature) is an exothermic process, so their solubility decreases when the water is heated. The solubility of gases doesn't reach zero at boiling point, nor does it necessarily decrease over the whole temperature range. For nitrogen in water, the enthalpy of dissolution becomes positive around 75°, and its solubility increases above that temperature.
At 100°C, solubility of air as a whole is $0.93 * 10^{-5}$, about half the solubility at 10°C, $1.82 * 10^{-5}$.
removing dissolved minerals: Heating the water promotes the conversion of soluble Ca and Mg bicarbonates to insoluble carbonates ($2 {HCO_3}^-$ → $CO_3^{2-} + H_2O + CO_2$) which will come out of solution (as limescale). The sulphates (sometimes referred to as "permanent hardness"), and the sodium or potassium (bi)carbonates stay in solution.
The effect of boiling:
Solubility of gas in liquid not only depends on temperature, it is directly proportional to the partial pressure of the gas. When boiling, the gas phase in contact with the water is no longer the air, but the water vapor (in the bubbles and close to the surface). In those bubbles the partial pressure of the gases will be close to zero, so gas molecules will still leave the liquid phase (and the increased surface area and the movement of the water speeds up the process), but hardly any will return. Given sufficient time, the water vapor will remove most of the gas. Boiling is basically the equivalent of degassing by purging: removing a gas (oxygen usually) from a solvent by bubbling an inert gas through it.
How do gases make ice "milky/cloudy"?
The following is multiple choice question (with options) to answer.
If a solute is a gas, increasing the temperature will do what? | [
"have no effect",
"increase its solubility",
"decrease its solubility",
"change to liquid"
] | C | If a solute is a gas, increasing the temperature decreases its solubility. For example, less carbon dioxide can dissolve in warm ocean water than in cold ocean water. |
SciQ | SciQ-7298 | evolution
Not that I can think of or find easily. While there are detriments associated with being born prematurely, and some evidence that women waiting until they're late 30's and men until they're 60 or older can negatively affect their gametes and consequently the development of any children born from them - it's been such a short time since the introduction of hormonal contraception and modern medicine that we may not see results tangible results for hundreds of years. Although condoms have been around for several hundred years, and there's been no associations with condom use that I can think of.
In the short term, what it has done is affect the ethnic diversity of countries. For the first time ever, Hispanic births have outnumbered Caucasian births in 2012 in the United States. Other countries, mostly European countries, are seeing declines in birth rates - which means their populations will decline with age or be compensated for by immigration. Higher birth rates, however, are associated with lower income brackets or very religious communities - both of which are associated with ethnic Minorities, at least in the United States. So while minority populations have more kids, they do so on fewer resources which may negatively affect their children in the long-term, whereas higher-earning segments of the population might have fewer children later in their lives, but can provide a much more stable environment and opportunities to continue that success.
One thing that hormone-centered birth control has done, however, is eliminate rape as a viable form of passing on one's genes. As gruesome as it might be to consider, pregnancies as a result of rape can produce "fit" offspring. It is a legitimate reproductive strategy in nature, and is in humans... unless the woman is using contraception. In the long-term this will probably show some interesting results (nominally an enhanced "Female Choice" effect - which is already evident in human evolution), but nothing right now.
The following is multiple choice question (with options) to answer.
The fetus becoming relatively large and mature before birth increases the chances of what? | [
"disease",
"survival",
"intelligence",
"mutations"
] | B | The placenta permits a long period of fetal growth. As a result, the fetus can become relatively large and mature before birth. This increases its chances of survival. On the other hand, supporting a growing fetus may be difficult for the mother. She has to eat more while pregnant and may become less mobile as the fetus grows larger. Giving birth to a large infant is also risky. |
SciQ | SciQ-7299 | physiology
So, now the question is shifted: why do kisspeptin neurons show up only at puberty? We don't know for sure, but it looks like increased levels of E2 could be important for this.
Again, we get into a self-sustaining cycle. Growth of the body generates an increase in E2 production (possibly due to increased volume of the gonads?), which, when over a certain level permits the development of kisspeptin neurons, which will then stimulate the GnRH neurons, resulting in increased LH and E2. We then have more E2 and this makes kisspeptin neuron grow even more etc etc.
The following is multiple choice question (with options) to answer.
What item starts puberty in girls? | [
"the uterus",
"the ovary",
"the hypothalamus",
"the thyroid"
] | C | Puberty in girls starts when the hypothalamus “tells” the pituitary gland to secrete hormones that target the ovaries. Two pituitary hormones are involved: luteinizing hormone (LH) and follicle-stimulating hormone (FSH) . These hormones stimulate the ovary to produce estrogen . Estrogen, in turn, promotes growth and other physical changes of puberty. It stimulates growth and development of the internal reproductive organs, breasts, and pubic hair (see Figure below ). You can watch an animation of these and other changes that girls experience during puberty at this link: http://www. bbc. co. uk/science/humanbody/body/interactives/lifecycle/teenagers/ . |
SciQ | SciQ-7300 | digestive-system
Title: Energetics and Products of Pepsin/HCl Protein Digestion What are the energetics of protein digestion during which the enzyme pepsin is "activated" (whatever that means) by HCl? I've looked and been unable to find anything like a chemical equation that includes an energy term.
Of course, pepsin, being an enzyme, is not used up in that sought-for equation. Is HCl used up? If so, what are the products? How and in what form is the chlorine removed, assuming the HCl is consumed in the equation? This is well-explained on the Wikipedia page for pepsin. You are misinterpreting the use of the word activated. The protein is secreted by chief cells in the gastric glands in the form of pepsinogen, an inactive pro- form which has an extra ~40 amino acids at its N-terminus (the propeptide). The propeptide binds at the catalytic site of the enzyme and keeps it inactive. At low pH (this is where the HCl comes in - HCl secreted by parietal cells of the gastric glands acidifies the stomach) the protein is able to cleave off its own propeptide, making it fully active.
The following is multiple choice question (with options) to answer.
Protein digestion begins in the stomach as pepsinogen in gastric juice is converted to pepsin, the enzyme that hydrolyzes this? | [
"ionic bonds",
"peptide bonds",
"disulfide bridges",
"hydrogen bonds"
] | B | The digestion of carbohydrates begins in the mouth as α-amylase breaks glycosidic linkages in carbohydrate molecules. Essentially no carbohydrate digestion occurs in the stomach, and food particles pass through to the small intestine, where α-amylase and intestinal enzymes convert complex carbohydrate molecules (starches) to monosaccharides. The monosaccharides then pass through the lining of the small intestine and into the bloodstream for transport to all body cells. Protein digestion begins in the stomach as pepsinogen in gastric juice is converted to pepsin, the enzyme that hydrolyzes peptide bonds. The partially digested protein then passes to the small intestine, where the remainder of protein digestion takes place through the action of several enzymes. The resulting amino acids cross the intestinal wall into the blood and are carried to the liver. Lipid digestion begins in the small intestine. Bile salts emulsify the lipid molecules, and then lipases hydrolyze them to fatty acids and monoglycerides. The hydrolysis products pass through the intestine and are repackaged for transport in the bloodstream. In cells that are operating aerobically, acetyl-CoA produced in stage II of catabolism is oxidized to carbon dioxide. The citric acid cycle describes this oxidation, which takes place with the formation of the coenzymes reduced nicotinamide adenine dinucleotide (NADH) and reduced flavin adenine dinucleotide (FADH2). The sequence of reactions needed to oxidize these coenzymes and transfer the resulting electrons to oxygen is called the electron transport chain, or the respiratory chain. The compounds responsible for this series of oxidation-reduction reactions include proteins known ascytochromes, Fe·S proteins, and other molecules that ultimately result in the reduction of molecular oxygen to water. Every time a compound with two carbon atoms is oxidized in the citric acid cycle, a respiratory chain compound accepts the electrons lost in the oxidation (and so is reduced) and then passes them on to the next metabolite in the chain. The energy released by the electron transport chain is used to transport hydrogen (H+) ions from the mitochondrial matrix to the intermembrane space. The flow of H+ back through ATP synthase leads to the synthesis and release of ATP from adenosine diphosphate (ADP) and inorganic phosphate ions (Pi) in a process known Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-7301 | biochemistry
Title: Why are omega-3 fatty acids so easily oxidized when they're incorporated in cellular membranes? Apparently, this has led to results with clinical significance, as we can see at http://extremelongevity.net/2011/10/03/daily-fish-oil-consumption-may-reduce-lifespan/...
The researchers fed a special genetic variety of mice diets that
either included 5% daily fish oil + 5% safflower oil or instead 10%
daily safflower oil. The mice used were SAMP8 mutants that were bred
to have accelerated aging and shortened lifespans. These mice are
often used in longevity experiments because their average lifespans
are only typically one year. They were fed these diets from 12 weeks
of age on. The researchers hypothesized since fish oil is so easily
oxidized it may lead to greater oxidative stress within cells and thus
actually accelerate aging, a process believed in part due to
accumulative damage from oxidative stress. Safflower oil is an omega-6
fatty acid and is not readily oxidized – it could have beneficial
effects without causing oxidative stress.
Let's not debate the clinical significance here - but I do wonder - why are omega-3 fatty acids so easily oxidized as compared to omega-6 fatty acids? I think the explanation for this description of fish oils as "easily oxidised" can be found in the Introduction to the actual paper (Nutrition 27 (2011) 334–337) that is cited in the article linked to in the question.
The following is multiple choice question (with options) to answer.
What lipid, added to certain foods to keep them fresher longer, increases the risk of heart disease? | [
"cholesterol",
"fatty acids",
"Omega-3 fatty acids",
"trans fat"
] | D | Another type of lipid is called trans fat . Trans fats are manufactured and added to certain foods to keep them fresher for longer. Foods that contain trans fats include cakes, cookies, fried foods, and margarine. Eating foods that contain trans fats increases the risk of heart disease. |
SciQ | SciQ-7302 | evolution, natural-selection, theoretical-biology
Title: Probability of Extinction under Genetic Drift Here is the Wright-Fisher model of genetic drift:
$$\frac{(2N)!}{k!(2N-k)!}p^kq^{2N-k} \Leftrightarrow \binom{2N}{k}p^kq^{2N-k}$$
where $\binom{2N}{k}$ is the binomial coefficient.
This formula gives the probability of obtaining $k$ copies of an allele at generation $t+1$ given that there are $p$ copies of this allele at generation $t$. $N$ is the population size and $2N$ is the number of copies of each gene (this model applies to diploid population only).
From this formula, how can we calculate the probability of extinction of an allele in say 120 generations starting at a given frequency, let's say 0.2?
and
How can we calculate the probability of extinction rather than fixation of an allele present at frequency $p$ if we wait an infinite amount of time? update
The answer is here!
The following is multiple choice question (with options) to answer.
What occurs in a population when its allele frequencies change over time? | [
"evolution",
"extinction",
"variation",
"generation"
] | A | Evolution occurs in a population when its allele frequencies change over time. For example, the frequency of the A allele might change from 0.7 to 0.8. If that happens, evolution has occurred. What causes allele frequencies to change? The answer is forces of evolution. |
SciQ | SciQ-7303 | evolution, zoology
Title: Why are hens so different from other birds? Hens lay many eggs during their lifetime (at least, I don't know of one which can lay more eggs) and they can't fly. Compared to other domestic animals it seems to me they are the least capable of defending themselves or escape if it comes to be left alone in open wild. What is their evolutionary story? Domestic organisms are bred to serve specific purposes for humans. Sheep are bred to produce wool; Cows are bred to provide meat and milk for human consumption; dogs are bred for service and companionship. Since domestic animal do need to survive in the wild in order to reproduce (ignoring feral animals, which is an interesting topic by itself), most of the other aspects of that animal relevant to its survival tend to be minimized.
So one could just as easily point out that there is no other animal that produces as much wool as a sheep, and yet producing copious amounts of wool isn't particularly useful to the animal itself (i.e. other than the fact that humans will tend to select good wool producers for breeding). So sheep are not particularly good at surviving in the wild, and yet they are incredibly successful as a species and are widely distributed, thanks to humans.
In short, domestic hens evolved to produce many eggs in their lifetime because over the past millennia since humans have started keeping them as livestock, humans tended to preferentially breed those individuals which produced more eggs and to eat those individuals which did not. Chickens tended to be kept in pens and guarded by humans or other animals, so the ability to defend themselves or flee from danger was not important to their survival, and in fact, those that did attack their handlers or escape were probably less likely to be bred.
This process is known as selective breeding or artificial selection.
The following is multiple choice question (with options) to answer.
What do some animals use for shelter? | [
"nonliving materials",
"living materials",
"invisible materials",
"indestructible materials"
] | A | |
SciQ | SciQ-7304 | kinematics, measurements, error-analysis, data-analysis
$s$: the measured distance
$t$: the measured time
and the accompanied uncertainties $\sigma_t$ and $\sigma_s$. In addition, the above formula is only valid if we consider random changes and not systematic errors (which is often called bias). Hope this helps.
The following is multiple choice question (with options) to answer.
In statistics a boundary on the precision and accuracy is known as what? | [
"median",
"frequency",
"error",
"instance"
] | C | An error is a boundary on the precision and accuracy of the result of a measurement. Some errors are caused by unpredictable changes in the measuring devices (such as balances, rulers, or calipers), but other errors can be caused by reading a measuring device incorrectly or by using broken or malfunctioning equipment. Such errors can have an impact on the reliability of the experiment’s results; they affect the accuracy of measurements. For example, you use a balance to obtain the mass of a 100 gram block. Three measurements that you get are: 93.1 g, 92.0 g, and 91.8 g. The measurements are precise, as they are close together, but they are not accurate. |
SciQ | SciQ-7305 | evolution, zoology, anatomy, species
Title: Examples of animals with 12-28 legs? Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list:
snakes have 0
Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs)
Most mammals, reptiles, amphibians have 4 legs
Echinoderms (e.g., sea stars) typically have 5 legs.
Insects typically have 6 legs
Octopi and arachnids have 8 legs
decapods (e.g., crabs) have 10 legs
....But I can't really think of many examples of animals containing more legs until you reach 30+ legs in centipedes and millipedes. Some millipedes even have as many as 750 legs! The lone example I am aware of, the sunflower sea star, typically has 16-24 (though up to 40) limbs.
So my question is: what are some examples of animals with 12-28 legs? As a couple of counterexamples, species in the classes Symphyla (Pseudocentipedes) and Pauropoda within Myriapoda have 8-11 and 12 leg pairs respectively, so between 16 to 24 legs (sometimes with one or two leg pair stronlgy reduced in size).
(species in Symphyla, from wikipedia)
Another common and species-rich group with 14 walking legs (7 leg pairs) is Isopoda.
(Isopod, picture from wikipedia)
You also need to define 'legs' for the discussion to be meaningful. As you say, decapods have 10 legs on their thoracic segments (thoracic appendages), but they can also have appendages on their abdomens (Pleopods/swimming legs), which will place many decapods in the 10-20 leg range.
(Decapod abdominal appendages/legs in yellow, from wikipedia)
So overall, in Arthropoda, having 12-28 legs doesn't seem all that uncommon. There are probably other Arthropod groups besides those mentioned here that also have leg counts in this range.
However, for a general account, the most likely answer (if there is indeed a relative lack of 12-28 legged animals) is probably evolutionary contingencies and strongly conservative body plans within organism groups.
The following is multiple choice question (with options) to answer.
How many limbs do all mammals have? | [
"four",
"three",
"it varies",
"two"
] | A | Mammals are endothermic vertebrates with four limbs. Examples of mammals include bats, whales, mice, and humans. Clearly, mammals are a very diverse group. Nonetheless, they share several traits that set them apart from other vertebrates. |
SciQ | SciQ-7306 | parasitology
Title: Tapeworms and their effect on humans I've read that some people in some countries actually use tapeworms as a form of losing weight. What are the dangers to these people? I haven't really found much on this topic (besides popular sites) but I can summarize it here:
There are quite some tapeworms (or cestoda), I found numbers of up to 3500 species. They attach to the intestinal wall of the humans and then start to take up predigested food through their skin. With that, they reduce food from their host and start to grow, some get as long as 15 meters!
Some of the worms seem to be relatively harmless (besides stealing food), but this is more true for the first world. In poor countries, where there is not enough food, tapeworms can cause severe malnutrition.
Some tapeworms can migrate into the blood stream and from there into other tissues or organs like muscles, eye and brain. There they can cause cysts which can lead to organ failure and death.
For more information see this CDC webpage and this article: "Biochemistry and physiology of tapeworms.". This popular article is probably also interesting.
The following is multiple choice question (with options) to answer.
More common in developing countries, parasitic diseases caused by roundworms often result from poor practice of what? | [
"agriculture",
"personal hygiene",
"preventative medicine",
"education"
] | B | Diseases caused by roundworms are more common in developing countries. Many parasitic diseases caused by roundworms result from poor personal hygiene. Contributing factors may include. |
SciQ | SciQ-7307 | microbiology, bacteriology, microscopy, morphology
Title: Why are my bacterial smears disappearing? I'm trying to inspect simple stained bacterial smears. But my smear suddenly disappears after a successful inspection with the oil immersion lenses.
The background can become too red (the color of the stain) and the oil residue coming from the oil immersion objective when it's wiped, is red colored.
Red background
Usual background
Also when I try to wipe the oil from the slide, the smear is removed, even with a gentle wipe.
I'm suspecting three possible causes, which may include dependent causes:
The immersion oil I use makes the smear easy to wipe:
I don't have a dropper that releases just a small drop, but I have used another oil with the same type of dropper that releases more than the needed quantity and it didn't wipe my smear.
The back-and-forth movement that eliminates air bubbles: I hear the spring sound, is this correct?
Smear fixation may not be adequate: could it be possible that the smear can be fixed in an incomplete way so that it resists being wiped from the staining procedure, but not from further manipulation?
My specifications
Immersion oil: Non-drying, non-hardening Cedarwood oil
Stain: Carbol fuchsin (20%)
The following is multiple choice question (with options) to answer.
What type of bacteria stains red? | [
"gram - such bacteria",
"gram-negative bacteria",
"calcium - negative bacteria",
"kilogram-negative bacteria"
] | B | Bacteria that stain red are called gram-negative bacteria. They have a thin cell wall with an outer membrane. |
SciQ | SciQ-7308 | crystal-structure
Title: Why shape of diamond is like diamond? I know that in diamond carbon atoms occur in 3d geometry but i want to ask that why it is in shape of diamond not like some other 3d geometrical shape like cube or cuboid? Diamond has the shape of diamond for precisely the same reason why any other crystal has the shape it has. Some crystal faces have lower surface energy than others, so the crystal grows in these directions, as if it wanted to develop these faces and avoid developing others.
This, BTW, is not determined by crystal family alone. Think of pyrite: it also has cubic unit cell, but it mostly develops the face (001) (see Miller indices) and hence makes those nice cubic crystals. On the contrary, diamond prefers the face (111), which together with its symmetry equivalents produces an octahedron. And that's why natural diamonds are typically found in this shape (not counting scratches and fractures).
Because of its low energy, the (111) face is also the hardest face of a diamond, to the point that jewelers deliberately avoid it when cutting brilliants, for it can't be polished quite as good as any other arbitrary plane.
So it goes.
The following is multiple choice question (with options) to answer.
The shapes of minerals form as they are broken along what planes? | [
"cleavage planes",
"sedimentary planes",
"calcium planes",
"parallel planes"
] | A | Minerals can form various shapes. Polygons are pictured below ( Figure below ). The shapes form as the minerals are broken along their cleavage planes. Cleavage planes determine how the crystals can be cut to make smooth surfaces. People who cut gemstones follow cleavage planes. Diamonds and emeralds can be cut to make beautiful gemstones. |
SciQ | SciQ-7309 | notation
I’m going to answer that as one.
This notation uses irreducible representations to define orbitals. The bit between the initial number and the superscript can be any of the symbols that appear in Little Bobby Tables (courtesy of Orthocresol). They each represent a type of orbital with a certain symmetry.
Orbitals of the same irreducible representation (i.e. the same centre) are numbered from lowest to highest energy — so in principle the sky is the limit. Practically, however, you will be hard-pressed finding three-digit examples.
The exponent can at maximum be $2n$, where $n$ is the number in the first column of the respective character table (the E column). This number corresponds to a certain symmetry’s degeneracy (i.e. so many orbitals of the same energy) and each orbital can be populated by two electrons.
The following is multiple choice question (with options) to answer.
An atomic symbol is used to represent what? | [
"electron shell",
"mole",
"element",
"weight"
] | C | Elements are represented by an atomic symbol. |
SciQ | SciQ-7310 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
Mammals can feed at various levels of food chains, as herbivores, insectivores, carnivores and what else? | [
"vegetarians",
"omnivores",
"nematodes",
"blood eaters"
] | B | Mammals have important roles in the food webs of practically every ecosystem. Mammals are important members of food chains and food webs, as grazers and predators. Mammals can feed at various levels of food chains, as herbivores, insectivores, carnivores and omnivores. |
SciQ | SciQ-7311 | fluid-dynamics, turbulence
Title: Does the wind gust over the ocean? It is easy to observe that on a windy day, the wind does not blow for several hours at constant speed, then gradually subside. Instead, on a time scale of seconds or tens of seconds, there are stronger gusts of wind followed by lulls.
Presumably this is an effect of turbulence. If so, is this turbulence due to the complicated geometry around me - buildings, trees, hills, etc.? If we removed these features and had wind blowing over a flat ocean surface or a flat plain for hundreds of miles, would we still observe the wind to blow in the same sorts of gusts, or should I expect a more steady flow? I believe you're exactly right: it's the complexity of hills, buildings, trees, asphalt, water, etc that make surface winds complicated. As you go higher in the atmosphere, these surface effects disappear and the winds become much more steady. You can see this in the winds aloft forecasts issued by the FAA for use in aviation:
http://aviationweather.gov/adds/winds/
In the upper left there is a drop-down box allowing you to select altitudes from the surface (SFC) to 48,000 feet (FL480). As you go up in altitude, the relatively chaotic surface winds blend into a much smoother (and faster!) flow.
I assume the effect is similar at sea, given the simpler boundary conditions.
(I admit this does not directly address your question of, "how variable are the winds at sea"? I too am curious to hear an authoritive answer.)
The following is multiple choice question (with options) to answer.
What are winds that blow over a limited area called? | [
"local winds",
"trade winds",
"Planetary Winds",
"Periodic Winds"
] | A | Local winds are winds that blow over a limited area. Local winds blow between small low and high pressure systems. They are influenced by local geography. Nearness to an ocean, lake, or mountain range can affect local winds. Some examples are found below. Local winds can affect the weather and climate of a region. |
SciQ | SciQ-7312 | neuroanatomy, anatomy
Title: Lateral corticospinal tract and termination I'm studying the motor pathways of the brain and I'm a bit confused about how the lateral corticospinal tract descends.
From Neuroanatomy: Text and Atlas by Martin, J. H., 4th edition, right before Figure 10-4:
Some of these [terminating] axons descend ipsilaterally; many descend
contra-laterally and re-cross midline within the gray matter in lamina 10.
The function of these ipsilateral axons is not well understood.
I understand that the axons cross over at the Pyramidal decussation, but this paragraph is really confusing me. What descent is being referenced here? Is it descending in the spinal chord? Alternatively, is the paragraph implying that some axons don't decussate in the pyramidal decussation? The answer ends up being on the next page when discussing the ventral corticospinal tract.
Many ventral corticospinal tract axons have branches that decussate in
the spinal cord, similar to the re-crossed lateral coticospinal tract
axons described earlier.
In other words, some axons of the lateral corticospinal tract ignore the pyramidal decussation, join the anterior corticospinal tract (which then synapses bilaterally later at the spinal commissure).
The following is multiple choice question (with options) to answer.
Descending fibers from the cerebrum have branches that connect to neurons in the pons. those neurons project into the cerebellum, providing a copy of motor commands sent to this? | [
"neurotransmitters",
"cerebral cortex",
"umbilical cord",
"spinal cord"
] | D | Descending fibers from the cerebrum have branches that connect to neurons in the pons. Those neurons project into the cerebellum, providing a copy of motor commands sent to the spinal cord. Sensory information from the periphery, which enters through spinal or cranial nerves, is copied to a nucleus in the medulla known as the inferior olive. Fibers from this nucleus enter the cerebellum and are compared with the descending commands from the cerebrum. If the primary motor cortex of the frontal lobe sends a command down to the spinal cord to initiate walking, a copy of that instruction is sent to the cerebellum. Sensory feedback from the muscles and joints, proprioceptive information about the movements of walking, and sensations of balance are sent to the cerebellum through the inferior olive and the cerebellum compares them. If walking is not coordinated, perhaps because the ground is uneven or a strong wind is blowing, then the cerebellum sends out a. |
SciQ | SciQ-7313 | # Number of elements vs cardinality vs size
I have been wondered the definition of cardinality and number of elements. One mathematician told me that one can't said that the cardinality or size of the set $\{1\}$ is one, it should be said that the number of elements in the set is one. I guess that his opinion is that there is no term size in mathematics. Is these true? On the other hand, if we have an infinite set like $\mathbb Z$, can we say that the number of elements of $\mathbb Z$ is infinite or is the term "number of elements" used only in finite sets?
-
I have no idea what the mathematician was thinking. The cardinality of $\{1\}$ is indeed $1$. Of course it’s also true that $1$ is the number of elements in the set. I would probably not use the expression number of elements when the set is infinite, but I’d not complain if someone said ‘$\Bbb R$ has $2^\omega$ elements’ instead of ‘the cardinality of $\Bbb R$ is $2^\omega$’. – Brian M. Scott Jun 15 '12 at 10:51
For finite sets there is absolutely no problem; a set has cardinality or size $n$ if it is in bijection with $\{ 1, 2, ... n \}$, and it has cardinality or size $0$ if it is empty. (The empty set is unique!) It is silly to prevent yourself from being able to say this. – Qiaochu Yuan Jun 15 '12 at 12:39
Converting my comment to an answer:
I have no idea what the mathematician was thinking: the cardinality of the set $\{1\}$ is indeed $1$, and that’s a perfectly normal way to express the fact. Of course it’s also true that $1$ is the number of elements in the set.
I would probably not myself use the expression number of elements when speaking of an infinite set, but ‘$\Bbb R$ has $2^\omega$ elements’ is a perfectly fine synonym of ‘the cardinality of $\Bbb R$ is $2^ω$’.
The following is multiple choice question (with options) to answer.
An element is defined by the number of ____ it contains? | [
"particles",
"neutrons",
"protons",
"electrons"
] | C | An element is defined by the number of protons it contains. All atoms of a given element contain the same number of protons. The number of neutrons in an element may vary. Atoms of an element with different numbers of neutrons are called isotopes . |
SciQ | SciQ-7314 | 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 term is used to describe the distance traveled divided by the time it took to travel that distance? | [
"motion",
"movement",
"speed",
"velocity"
] | C | Speed is the distance traveled divided by the time it took to travel that distance. Velocity is the instantaneous speed and direction. Average velocity is the displacement divided by the time. |
SciQ | SciQ-7315 | geochemistry, paleoclimatology, clathrates
Title: Release mechanism for methane clathrate at the PETM The Paleocene-Eocene Thermal Maximum (PETM) is a well-studied warming event near the Paleocene-Eocene boundary.
It is characterized by its extreme warming rate: from onset to recovery the event lasted ca. 100 kyrs, and the global temperature is thought to have increased by ~6 °C in barely 20 kyrs.
This event is of particular interest not only for its $\delta^{18}\rm O$ but also a sharp negative excursion in the $\delta^{13}\rm C$, implying a strong input of $^{13}\rm C$-depleted carbon into the system.
Simplified and redrawn after Zachos et al. 2001
One frequently invoked hypothesis to explain this input is the leakage of methane from clathrates trapped in seafloor sediments.
Being a paleontologist and not a geochemist, I struggle to understand the actual chemical mechanism involved.
I was thus wondering if someone could explain the mechanisms allowing the destabilization of methane clathrates at the same time on a global scale.
If it's just linked to a temperature threshold, how come it wasn't reach prior to that (warmer temperature were reached during the Cretaceous)? There seems to be some uncertainty as to the cause and mechanism for the PETM. In the Science Daily article Methane may be answer to 56-million-year question: Ocean could have contained enough methane to cause drastic climate change (2011) reporting research from Rice University, they claim that the seafloor was already warmer, thus according to their models:
if the oceans were warmer, they would contain less dissolved oxygen and the kinetics for methane formation would have been faster.
With less oxygen to consume organic matter on the way down, more sank to the ocean floor, Gu said, and there, with seafloor temperatures higher than they are today, microbes that turn organic matter into methane work faster.
Thus, they claim, the amount methane in the form of clathrates would have been approximately the same amount as today, but in a thinner stability zone. They are not clear about what caused the destabilisation, but made the analogy of a charging-discharging capacitor (shown below, from the same source):
The following is multiple choice question (with options) to answer.
Which gas is released by the group of archaea known as methanogens? | [
"methane",
"butane",
"propane",
"sulfur"
] | A | Archaea that produce methane are called methanogens. |
SciQ | SciQ-7316 | evolution, genetics, dna, molecular-evolution, genetic-code
Why are there more redundancy on the third position than on the second (which has more redundancy than the first position) in the codon? To fully comprehend the concept of wobble base-pairing we need to consider the nucleotide sequences of the anti-codons in the tRNAs that have to "read" the genetic code when the mRNA is being translated on the ribosome. The nucleotide in the anti-codon's wobble position is, for example, often inosine. Under the rules for wobble base-pairing an Inosine can potentially base-pair with three other nucleotides.
In real terms that means a cell can use less than 63 unique tRNA genes to decode mRNAs carrying messages made of the 63 different "words" (codons).
In an active cell the Ribosome's A-site, where the charged tRNA binds, is occupied by the incorrect tRNA most of the time (based on the law of mass action where any charged tRNA can randomly diffuse into the binding site). With tRNAs that can recognize multiple codons (which is what the wobble hypothesis gets us), any given protein can be translated faster (assuming that correct charged tRNAs are limiting for the polypeptide polymerization reaction).
So those are the practical ramifications of the table that you presented, but the explanation, as for most why based questions about biological evolution, is a retrofit. Natural selection can only work with the materials at hand, and so we can infer that during the period when this genetic code was finalized that the organisms who used it were more successful than the others. And the current code is based on whatever the previous one looked like. "Descent by modification" is the original description.
[whoops, sorry about the pedantic voice on the "how selection works" bit, I just looked at your profile and realized you can likely teach me on this subject]
The following is multiple choice question (with options) to answer.
Of the four main wobble base pairs, guanine is paired with what? | [
"cytosine",
"adenine",
"thymine",
"uracil"
] | D | A wobble base pair is a non-Watson Crick base pairing between two nucleotides in RNA molecules. The four main wobble base pairs are guanine-uracil, inocine-uracil, inosine-adenine, and inosine-cytosine. Wobble base pairs are fundamental in RNA secondary structure and are critical for the proper translation of the genetic code. Inosine is a nucleoside that is formed from the hydrolytic deamination of adenine. Structurally, it resembles guanine, but lacks the 2-amino group. This lack of the 2-amino group allows inosine to form base pairs with uracil, cytosine and adenine, making it a particularly wobbly base. |
SciQ | SciQ-7317 | bond
Title: Types of bonds in a molecule For example in dinitrogen pentoxide, $\ce{N2O5}$, covalent as well as coordinate bonds (type of covalent bonds) are present, but it appears that it contains only covalent bond.
What is a proper method to find out which type of bonds are present in a molecule? Electrovalent bonds are easiest to identify. If a compound is made up of a metal and non-metal/non-metallic radical (like carbonate), then, 99.99% times, it contains electovalent bond. If a compound is made up of 2 or more non-metals/non-metallic radicals, then it contains covalent bond. Coordinate covalent bonds appear mostly with compounds containing Hydrogen element. To identify the coordinate covalent bonds, you can draw the branched structural formula of the compound and see if the shared pair of electrons are coming from the same molecule.
The following is multiple choice question (with options) to answer.
The atoms of a compound are held together by what type of bonds? | [
"radiation",
"covalent",
"chemical",
"mineral"
] | C | The atoms of a compound are held together by chemical bonds. Chemical bonds form when atoms share electrons. There are different types of chemical bonds, and they vary in how strongly they hold together the atoms of a compound. Two of the strongest types of bonds are covalent and ionic bonds. Covalent bonds form between atoms that have little if any difference in electronegativity, and result when atoms share electrons. Electronegativity is the power of an atom to attract electrons toward itself. Ionic bonds , in contrast, form between atoms that are significantly different in electronegativity. An ion is an atom that has gained or lost at least one electron. Ionic bonds form between ions of opposite charges. |
SciQ | SciQ-7318 | biophysics, theoretical-biology, ecosystem
Systems ecology, especially with regard to energy and nutrient flow.
This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem Ecology: Understanding Element Cycles by Ågren & Bosatta (Ågren was originally a physicist)
Physical limitations to growth and transport
This can include for instance mechanical contraints on plant growth (see e.g. the book Plant Physics by Nicklas & Spatz), water transport in trees (see e.g. this BioSE question) or the biomechanics of movement (see e.g. Hudson et al (2012) on the speed and movement of cheetahs or Wikipedia: Biomechanics).
Allometric relationships between organisms, e.g. with regard to metabolism
To explain these types of relationships knowledge in physics is useful. See e.g. Kleiber's law for more.
MAXENT as a general approach to ecological patterns or to model species distributions
This is basically a tool lifted from physics that can be applied to ecological problems. There are many papers to look at, but Harte & Newman (2014) (Harte is another previous physicist) and Elith et al (2010) are two good starting points.
Dynamical modelling of populations and communities
This field use many of the same tools for analysis as physics, e.g. systems of differential equations. One of the pioneers in this field (among many) were Robert May (also started with a PhD in physics), and his classical book Theoretical Ecology: Principles and Applications is still a good starting point.
Energy harnessing and conversion by organisms
This can refer both to how organsims convert prey to energy (e.g. conversion efficiencies) and the physics of photosynthesis (which is an interesting intersection between physics and molecular biology). See Jang et al (2004) and O'Reilly & Olaya-Castro (2013) for examples of the how quantum mechanics can inform us about photosynthesis.
Hopefully this will give you a sense of some different ways that knowledge in physics can be useful for biology.
The following is multiple choice question (with options) to answer.
Unlike energy, what happens to matter in ecosystems? | [
"it is destroyed",
"it does not exist",
"it is recycled",
"it is filtered"
] | C | Living things need nonliving matter as well as energy. What do you think matter is used for? It's used to build bodies. It's also needed to carry out the processes of life. Any nonliving matter that living things need is called a nutrient . Carbon and nitrogen are examples of nutrients. Unlike energy, matter is recycled in ecosystems. In the figure below, you can see how ( Figure below ). |
SciQ | SciQ-7319 | nomenclature
Title: When to use -ate and -ite for naming oxyanions? I'm now learning about nomenclature. In particular, oxyanions.
Basically, when you have an anion that is a combination of a non-metal with oxygen.
According to my book:
It ends with -ate for the most common oxyanions of the element. It
ends with -ite for the oxyanions that have the same charge but with
one less atom of oxygen.
Example:
$\ce{NO_3^- \implies}$ Nitrate
$\ce{NO_2^- \implies}$ Nitrite
The following is multiple choice question (with options) to answer.
The anion is the methanoate ion, which is commonly called the what? | [
"glutathione ion",
"formate ion",
"isomer",
"metabolized ion"
] | B | The anion is the methanoate ion, which is commonly called the formate ion. One reaction to consider is that of a carboxylic acid and an alcohol. When combined under the proper conditions, a water molecule will be removed, and the remaining pieces will combine to form a new functional group—the ester functional group:. |
SciQ | SciQ-7320 | 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.
Drinking too much water too fast can lead to what potentially fatal condition, which causes dangerous changes to salt levels? | [
"osmosis",
"water intoxication",
"drowning",
"inebriation"
] | B | available; if arsenic is an essential trace mineral in human diets, it is probably required on the order of 50 ppb or less. A toxic dose of arsenic corresponds to about 7,000 ppb and higher, which is over 140 times the trace amount that may be required by the body. Thus, arsenic is not poisonous in and of itself. Rather, it is the amount that is dangerous: the dose makes the poison. Similarly, as much as water is needed to keep us alive, too much of it is also risky to our health. Drinking too much water too fast can lead to a condition called water intoxication, which may be fatal. The danger in water intoxication is not that water itself becomes toxic. It is that the ingestion of too much water too fast dilutes sodium ions, potassium ions, and other salts in the bloodstream to concentrations that are not high enough to support brain, muscle, and heart functions. Military personnel, endurance athletes, and even desert hikers are susceptible to water intoxication if they drink water but do not replenish the salts lost in sweat. As this example shows, even the right substances in the wrong amounts can be dangerous!. |
SciQ | SciQ-7321 | energy, visible-light, photons, atomic-physics, absorption
Why is it that the electron loses energy when it jumps to the next energy level
Let's take the common usage of the word jump as upwards. So in this above case, the electron gains energy. It loses energy when it falls back down to a lower level.
I have to admit that I don't like using words like jump and fall, because they are based on the Bohr model of the atom, which is not correct in almost every aspect.
So let me give you two pictures, one of the old model, which your question is based on, and one of the more modern picture.
The Bohr model (of 100 years ago)
The Orbital Distribution Density model
The electron will tend to lose energy if it can, by emitting a photon of the correct wavelength, that enables it to transition to a lower energy level, but if that lower level is already occupied to the maximum amount, then the electron is forced to stay at a higher level.
The difference between the pictures is the the Bohr model assumes a particle structure, whereas we now think in terms of the probability of finding an electron in a certain region, so we cannot be as definite as in the earlier model. Also, when the transition from one level to another occurs, it is not a smooth transfer like a car changing lanes, it is for a time a more chaotic operation, with the electron (or rather its' likelyhood of being found) bouncing around the place until it settles into a lower orbit.
In the first example the electrons moving with current gives energy to the electron in the atom. So the electron in the atom absorbs the moving electron? If so how is this possible because they are both negative?
There is no question of an electron absorbing another electron. Instead, by means of photon emission, momentum can be transferred between electrons, bearing in mind the conservation laws regarding energy and momentum.
An example of this is a Feynman Diagram:
Where the wavy line represents energy and momentum being transferred by means of a photon.
The following is multiple choice question (with options) to answer.
When electrons move from one atom to another, they become what? | [
"ions",
"neons",
"atoms",
"particles"
] | A | All compounds form when atoms of different elements share or transfer electrons. In water, the atoms share electrons. In some other compounds, called ionic compounds , atoms transfer electrons. The electrons actually move from one atom to another. When atoms transfer electrons in this way, they become charged particles called ions. The ions are held together by ionic bonds. |
SciQ | SciQ-7322 | states-of-matter, matter
Title: What distinguishes the difference states of matter from solid to BEC and perhaps fermionic condensate? Is it something to do with the behavior of electrons? How many states are there either discovered or predicted? 無
'States of matter' is a question of taxonomy, not of reality, and moreover, it's a result of the conditions surrounding the matter, not its internal properties. Certain combinations of properties give us a hint towards calling something 'solid' or 'liquid', but in truth there are no lines, just a continuous spectrum, and under certain conditions, matter transitions seamlessly through all sorts of states, both mundane and exotic:
Behold: Jupiter
A perfect example of this is Jupiter. Composed primarily of hydrogen, this gas giant consists (conjecturally) of a core of high-temperature hydrogen ice, floating in liquid hydrogen, enveloped in hydrogen gas, moving through interplanetary medium composed of hydrogen plasma.
Except not really: Under these conditions, the classical notions of states of matter break down entirely: Between these states of matter there are no interfaces, just a gradual, continuous transition.
In other words: The distinctive line to separate one state from another you are after doesn't really exist.
The following is multiple choice question (with options) to answer.
Another way to classify matter is to describe it as a solid, a liquid, or a gas, which was done in the examples of solutions. these three descriptions, each implying that the matter has certain physical properties, represent the three of these? | [
"types of atoms",
"phases of matter",
"phases of mass",
"forms of substances"
] | B | Another way to classify matter is to describe it as a solid, a liquid, or a gas, which was done in the examples of solutions. These three descriptions, each implying that the matter has certain physical properties, represent the three phases of matter. A solid has a definite shape and a definite volume. Liquids ordinarily have a definite volume but not a definite shape; they take the shape of their containers. Gases have neither a definite shape nor a definite volume, and they expand to fill their containers. We encounter matter in each phase every day; in fact, we regularly encounter water in all three phases: ice (solid), water (liquid), and steam (gas). We know from our experience with water that substances can change from one phase to another if the conditions are right. Typically, varying the temperature of a substance (and, less commonly, the pressure exerted on it) can cause a phase change, a physical process in which a substance goes from one phase to another (Figure 1.4 "Boiling Water"). Phase changes have particular names depending on what phases are involved, as summarized in Table 1.1 "Phase Changes". Table 1.1 Phase Changes. |
SciQ | SciQ-7323 | toxicity
Cigarette smoke is a complex and dynamic aerosol consisting of at least 5,600 chemicals and toxicants found across two phases, the particulate (tar) and vapour phase.
(I would like to add the gas phase...) so when the product of the combustion of the tobacco are in this physical state you have to look at a different method of administration in this case vapour inhalation, Dust and Mist Inhalation and gas inhalation these are the most potentially dangerous method of administration. It seems that after about 40 minutes the liquid and solid part of the aerosol deposit (of course this depends on the condition, T, wind etc. etc.) so is probable that after this period of time the toxicity of tobacco combustion products decrease considerably. However this is not true for all the combustion products. For example: carbon monoxide is recognize tobacco combustion product and it is a gas so it wont deposit after this time and it will be "removed by reactions with OH radicals (85%), by soils (10%), and by diffusion into the stratosphere" very slowly.
Benzene is a good example of how the toxicity depends on the method of administration. LC50 inhalation value of benzene is 10000 ppm TFLo Dermal is 0.92 mL/kg so it is a big difference if you wait that the areosol deposit or if you inhale it.
If you are interested in rate of decomposition of benzene it seems that biodegradation of benzene can reach 0.95% at day according to Chiang.
Regarding 1-3 butadiene according to William A. McClenny and Donald Whitaker:
i.e., a 10-6 lifetime risk level for cancer due to inhalation exposure
of 0.03 $g/m^{3}$ (12.4 pptv at 20 °C and 1 atm pressure).1 This compound
is very reactive in the ambient atmosphere with a short
atmosphericlifetime, estimated to be 2–3 hr.
The half-life of acrolein is 14.4 hr.
You can also find a very complete EPA report EPA/600/P-98/001F
October 2002.
However determine the half-life of all the compounds is a very complex task because is related to how the ecosystem respond to these compounds so to the actual capability to decompose them through different mechanism is strictly related with thousands of factors.
The following is multiple choice question (with options) to answer.
What is the health-threatening smoke exhaled by a cigarette smoker or released from tobacco products? | [
"secondhand smoke",
"contamination smoke",
"primary smoke",
"secondary smoke"
] | A | Secondhand smoke , which comes from breathing the smoke release from tobacco products. Secondhand smoke is also the smoke exhaled by a cigarette smoker. This smoke is extremely dangerous to human health. |
SciQ | SciQ-7324 | waves, pressure, acoustics, density
Title: Why does sound not move through a wall? I'm learning a bit about sound and was wondering:
If the speed of sound is determined by the amount of matter the source is surrounded with, why doesn't it go through a wall?
Example:
Speed of sound in air is 343 m/s but in water, it moves at 1500 m/s because of the increase of matter surrounding it. And since iron has more tightly packed matter, it moves even faster because it's moving the matter to move the vibrations.
If this is true, why doesn't the sound go through walls? Is it because it loses its "strength" for the amount it travels? Sound doesn't go through walls? Please tell my neighbor.
In electromagnetism, a medium has a property called an "impedance" which is related to the index of refraction and the speed of waves in the medium. At an interface between two media, the relative impedances determine how much of an incoming wave is transmitted or reflected, so that the entire power of the incoming wave goes somewhere. At an "impedance-matched" interface the reflection coefficient goes to zero. In signal cables and waveguides for electromagnetic waves this leads to people adding "terminating resistors" in various places, so that an incoming signal doesn't get reflected back from a cable junction. Conversely, at a junction with an impedance mis-match, the reflection coefficient is generally nonzero and not all of the power is transmitted.
You can do the same sort of analysis for sound waves moving from one medium to another. The reflection and transmission coefficients can depend on the frequency of the wave, as well, which is why my neighbor complains when I have my music turned up too loud: they can hear the low-frequency bass sounds just fine through the wall, but the high-frequency components (that they'd need to follow the lyrics) don't reach them.
The following is multiple choice question (with options) to answer.
Why do waves travel faster through solids? | [
"particles range together",
"particles pipe together",
"particles closer together",
"particles fuse together"
] | C | The speed of most waves depends on the medium, or the matter through which the waves are traveling. Generally, waves travel fastest through solids and slowest through gases. That’s because particles are closest together in solids and farthest apart in gases. When particles are farther apart, it takes longer for the energy of the disturbance to pass from particle to particle through the medium. At the following URL, you can watch an animation showing what happens when a wave passes from one medium to another. |
SciQ | SciQ-7325 | earthquakes, soil-science, bedrock
Title: Question regarding underground man-made facilities Why is it that underground facilities (or underground military bases) are almost always built into hollowed out mountains? Examples of (publicly known ones anyway) are Cheyenne Mountain Complex and Mount Weather government/ military facilities. Is having a highland/mountain a prerequisite for construction of military/government facilities? Is is not possible to construct facilities beneath lower ground, plains, dessert or under cities, besides subway stations and tunnels? Say if we wanted to build NORAD bunker somewhere deep beneath San Jose population centers, is this possible discounting the fault lines and permits for now? This question is not about earth science. If anything, it has more to do with engineering.
Strategic or critical defense or government infrastructure needs to be protected against explosive attacks, particularly nuclear attacks. A mountain offers a sizeable protective cap/roof to an underground installation. Similar levels of protection can be provided in flat ground, but the underground installation would need to be significantly deeper.
Critical parts of the installation would not be established within the mountain above the level of the ground surrounding the mountain; it would be established below.
Additionally, many mountains are composed on igneous rock: rock that solidified from a molten mass. Such rock, such as basalt or dolerite (diabase), is typically stronger than sedimentary rock and can thus offer better blast protection than sedimentary rock.
Also, if the installation is established igneous rock, the same strength parameters can also mean reduced geotechnical and subsequent ground support measures would be required for the underground voids that if they were established in sedimentary rock.
Cheyanne Mountain is composed of granite, and igneous rock that solidified while still underground. The NORAD installation within Cheyanne Mountain "was designed to ride out a nuclear attack". Having been completed in 1966, when tunnel boring machines were not a consideration, it was established using drill and blast methods and consumed 500 tons of explosives.
The following is multiple choice question (with options) to answer.
What is the point on the ground that is located directly above where underground rocks fracture (or the "focus" point)? | [
"fault line",
"epicenter",
"seismic point",
"danger zone"
] | B | The focus is where the rocks rupture. The epicenter is the point on the ground directly above the focus. |
SciQ | SciQ-7326 | electrons, charge, quasiparticles, leptons
Title: How do electrons get a charge? Electrons belong to a group of elementary particles called leptons. There are charged and neutral leptons. And electron is the charged one. But how come it got charged?
The negative or positive charges were assigned by convention. But it is a fact that electrons are charged. My question is why electrons? and not neutrons?
Also while reading http://en.wikipedia.org/wiki/Electron, I saw that "Independent electrons moving in vacuum are termed free electrons. Electrons in metals also behave as if they were free. In reality the particles that are commonly termed electrons in metals and other solids are quasi electrons, quasiparticles, which have the same electrical charge, spin and magnetic moment as real electrons but may have a different mass ( or Effective mass - extra mass that a particle seems to have while interacting with some force )."
What does this mean? Your question touches the question of ontology in particle physics. Historically we are used to be thinking of particles as tiny independent entities that behave according to some laws of motion. This stems from the atomistic theory of matter, which was developed some two thousand years ago from the starting point of what would happen if we could split matter in ever smaller parts. The old Greeks came to the conclusion that there had to be a limit to that splitting, hence the atom hypothesis was born.
This was just a philosophical idea, of course, until around the beginning of the 19th century we learned to do chemistry so well that it became obvious that the smallest chunks that matter can be split into seemed to be the atoms of the periodic table. A hundred years later we realized that atoms can be split even further into nuclei and electrons. What didn't change was this idea that each chunk had its own independent existence.
This idea ran into a deep crisis during the early 20th century when we discovered the first effects of quantum mechanics. It turns out that atoms and nuclei and electrons do not, at all, behave like really small pieces of ordinary matter. Instead, they are behaving radically different, so different, indeed, that the human imagination has a hard time keeping up with their dynamic properties.
The following is multiple choice question (with options) to answer.
When atoms gain or lose electrons, they can form electrically charged particles called what? | [
"toxins",
"crystals",
"ions",
"eons"
] | C | In ordinary chemical reactions, the nucleus of each atom (and thus the identity of the element) remains unchanged. Electrons, however, can be added to atoms by transfer from other atoms, lost by transfer to other atoms, or shared with other atoms. The transfer and sharing of electrons among atoms govern the chemistry of the elements. During the formation of some compounds, atoms gain or lose electrons, and form electrically charged particles called ions (Figure 2.28). |
SciQ | SciQ-7327 | organic-chemistry, mixtures
Title: Would Oxygen Gas and Ozone be a pure substance together? If I have oxygen gas and ozone ($\ce{O2 + O3}$) together would it be considered a pure substance or a mixture?
And would pure substances always have the same molecular structure? Ozone is highly reactive and unstable, while dioxygen is stable. There do not combine to form a compound. So, clearly it is a mixture.
To answer the second part of the question, "And would pure substances always have the same molecular structure?", first a Wikipedia definition on substances, to quote:
A chemical substance is a form of matter having constant chemical composition and characteristic properties.[1][2]...
Chemical substances can be simple substances[4], chemical compounds, or alloys. Chemical elements may or may not be included in the definition, depending on expert viewpoint.[4]
Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water...
However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical.
And further:
A chemical substance may well be defined as "any material with a definite chemical composition" in an introductory general chemistry textbook.[5] According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. But, there are exceptions to this definition; a pure substance can also be defined as a form of matter that has both definite composition and distinct properties.[6] The chemical substance index published by CAS also includes several alloys of uncertain composition.[7] Non-stoichiometric compounds are a special case (in inorganic chemistry) that violates the law of constant composition, and for them, it is sometimes difficult to draw the line between a mixture and a compound, as in the case of palladium hydride. Broader definitions of chemicals or chemical substances can be found, for example: "the term 'chemical substance' means any organic or inorganic substance of a particular molecular identity, including – (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature".[8]
The following is multiple choice question (with options) to answer.
What do you call a pure substance that cannot be broken down into different types of substances? | [
"compound",
"sample",
"molecule",
"element"
] | D | An element is a pure substance that cannot be broken down into different types of substances. There are almost 120 known elements ( Figure below ), each with its own personality. The chemical and physical properties of one element differ from any other. Elements are arranged according to their properties in the Periodic Table . |
SciQ | SciQ-7328 | evolution, natural-selection, population-dynamics, adaptation
Title: Genetic Diversity and Adaptation I am somewhat new to evolutionary biology, having studied it on my free time as a computer science student. There is one particular thing that has always bothered me for which I have not seen a good treatment, relating to adaptations to the environment with respect to genetic diversity. If it is possible for a population to adapt to rapid environmental changes, and they don't have an adaptation for dealing with change directly (such as a complex brain), it seems to me that every generation must have present within them almost every possible environmental adaptation that the population is capable of expressing (including many irrelevant ones and a few relevant to the particular environmental challenge). Otherwise, it may take too many generations to deal with a change, which may be disastrous for the population.
So my question would be: how does an evolutionary biologist explain the mechanics behind the ability for a population to adapt quickly? Are most environmental changes slow or gradual enough that the population has a few generations to happen upon the mutations that will allow it to survive, and have generally been successful in this regard for 3.5 billion years? Or, are a large majority of possible adaptations present in almost every generation, and just serve no purpose or advantage for most of the population if the provided "benefit" is unneeded (i.e., are effectively neutral)? Or something in between? It is a good question. The question is hard to answer though because
The answer is not completely resolved
There are many influential parameters hidden behind this question.
Your question, as I understand it, can be formulated as
Do natural populations have enough genetic variance to directly respond to an environmental change or do they have to wait for this variance to be created through mutations?
To address this question, I will have to assume you have some intermediate level of knowledge in evolutionary biology.
How do we call these two alternatives?
Adaptation can occur through selection on:
Standing genetic variance
De novo mutations
How can we tell them apart?
This section is mainly inspired from Barrett and Schluter (2008).
Adaptation from standing genetic variance and from de novo mutations tend to yield different genetic signature.
In comparison to de novo mutations, adaptation from standing genetic variation is likely to lead to
Faster evolution
Because there the respond to the new environmental is immediate, there is no need to wait for more mutations.
Because the fitness variance associated with the trait under selection is very low even when the first mutation occurs.
Fixation of more alleles of small effects.
The following is multiple choice question (with options) to answer.
Natural selection can only take place if there is variation, or differences, among individuals in a population. importantly, these differences must have some genetic basis; otherwise, the selection will not lead to change in this? | [
"spontaneous mutation",
"mass extinction",
"fertilization",
"next generation"
] | D | Processes and Patterns of Evolution Natural selection can only take place if there is variation, or differences, among individuals in a population. Importantly, these differences must have some genetic basis; otherwise, the selection will not lead to change in the next generation. This is critical because variation among individuals can be caused by non-genetic reasons such as an individual being taller because of better nutrition rather than different genes. Genetic diversity in a population comes from two main mechanisms: mutation and sexual reproduction. Mutation, a change in DNA, is the ultimate source of new alleles, or new genetic variation in any population. The genetic changes caused by mutation can have one of three outcomes on the phenotype. A mutation affects the phenotype of the organism in a way that gives it reduced fitness—lower likelihood of survival or fewer offspring. A mutation may produce a phenotype with a beneficial effect on fitness. And, many mutations will also have no effect on the fitness of the phenotype; these are called neutral mutations. Mutations may also have a whole range of effect sizes on the fitness of the organism that expresses them in their phenotype, from a small effect to a great effect. Sexual reproduction also leads to genetic diversity: when two parents reproduce, unique combinations of alleles assemble to produce the unique genotypes and thus phenotypes in each of the offspring. A heritable trait that helps the survival and reproduction of an organism in its present environment is called an adaptation. Scientists describe groups of organisms becoming adapted to their environment when a change in the range of genetic variation occurs over time that increases or maintains the “fit” of the population to its environment. The webbed feet of platypuses are an adaptation for swimming. The snow leopards’ thick fur is an adaptation for living in the cold. The cheetahs’ fast speed is an adaptation for catching prey. |
SciQ | SciQ-7329 | particle-physics, experimental-physics, accelerator-physics
The basic premise of these experiments seems to be that we observe the collision byproducts of energetic particles, where "energetic" presumably refers to kinetic energy, since we used an "accelerator" to energize them. To create interesting collision byproducts, the kinetic energy in the collision (measured in eV) must be at least as large as the mass of the particle (also measured in eV) we wish to create. Thus, we can observe particles of higher mass with a higher powered accelerator.
The second part of my question is this: are particle accelerators the only way of pushing the boundaries of experimental particle physics? Is it conceivable that there is a way to produce these interesting byproducts in an experimental setting without using high-energy collisions? If not, is it conceivable that there is a way to energize particles other than by accelerating them around a track? If not, is it impossible by definition or for some physical reason? If either of these alternatives are conceivable, then assuming they're not practical replacements for large accelerators today, is it possible that they will be in the future? Is it likely?
In a sentence, my question is this: is the future of experimental particle physics now just a matter of building larger and larger particle accelerators? There are many competing limits on the maximum energy an accelerator like the LHC (i.e. a synchrotron, a type of circular accelerator) can reach. The main two are energy loss due to bremsstrahlung (also called synchrotron radiation in this context, but that's a much less fun name to say) and the bending power of the magnets.
The bending power of the magnets isn't that interesting. There's a maximum magnetic field that we can acquire with current technology, and the strength of it fundamentally limits how small the circle can be. Larger magnetic fields means the particles curve more and let you build a collider at higher energy with the same size. Unfortunately, superconducting magnets are limited in field: a given material has a maximum achievable field strength. You can't just make a larger one to get a larger field - you need to develop a whole new material to make them from.
Bremsstrahlung
The following is multiple choice question (with options) to answer.
The large hadron collider is the biggest type of what invention, which boosts particles to high energies? | [
"mass spectrometer",
"nuclear reactor",
"particle accelerator",
"electron microscope"
] | C | Chemistry in Everyday Life CERN Particle Accelerator Located near Geneva, the CERN (“Conseil Européen pour la Recherche Nucléaire,” or European Council for Nuclear Research) Laboratory is the world’s premier center for the investigations of the fundamental particles that make up matter. It contains the 27-kilometer (17 mile) long, circular Large Hadron Collider (LHC), the largest particle accelerator in the world (Figure 21.13). In the LHC, particles are boosted to high energies and are then made to collide with each other or with stationary targets at nearly the speed of light. Superconducting electromagnets are used to produce a strong magnetic field that guides the particles around the ring. Specialized, purpose-built detectors observe and record the results of these collisions, which are then analyzed by CERN scientists using powerful computers. |
SciQ | SciQ-7330 | star, galaxy, history, definition, stellar-structure
Title: Metallicity of Celestial Objects: Why "Metal = Non-metal"? Metallicity of objects refers to the amount of chemical elements present in it other than Hydrogen and Helium.
Note: The other elements may or may not be actual metals in the true sense of their defintion.
The following is multiple choice question (with options) to answer.
Metals, metalloids, and nonmetals are the different classes of what? | [
"structures",
"elements",
"compounds",
"ions"
] | B | The classes of elements are metals, metalloids, and nonmetals. They are color-coded in the table. Blue stands for metals, orange for metalloids, and green for nonmetals. You can read about each of these three classes of elements later in the chapter, in the lesson "Classes of Elements. ". |
SciQ | SciQ-7331 | genetics, cell-biology, chromosome, meiosis, mitosis
https://www.khanacademy.org/science/biology/cellular-molecular-biology/meiosis/a/phases-of-meiosis
So, during metaphase I, homologue pairs—not individual
chromosomes—line up at the metaphase plate for separation.
The following is multiple choice question (with options) to answer.
What holds homologs together as the spindle forms for the first meiotic division? | [
"magnetism",
"pollenation",
"chiasmata",
"spirogyra"
] | C | |
SciQ | SciQ-7332 | periodic-table, history-of-chemistry
Title: Why lanthanides and actinides are shown separate from standard Periodic Table layout? In the standard Periodic Table layout , all the elements up to 56 are in order i.e are in the same layout table. However, lanthanides and actinides are always shown separately from the layout like in this layout:
What is the reason behind this structure?
Is this standard layout or can I represent it like this too? The Periodic Table arranges elements in blocks as each type of orbital fills with electrons - $s,p,d,f,g,h$. Alkali metals and alkaline earths are $s$-block filling (but could be one $s$-block slot). $p$-block six electrons to fill are trelides, tetralides, pnticides, chalcogenides, halides, inert gases (but could be one $p$-block slot). Transition metal $d$-block is ten elements (but could be one $d$-block slot). Filling the $f$-block are 14 elements, lanthanoids and actinoids. That gets sloppy to print and the elements are (or at least were) overall obscure. They get condensed.
Representing the Periodic Table has become an an art form. The plain vanilla variety is terse and useful.
http://en.wikipedia.org/wiki/Alternative_periodic_tables
The following is multiple choice question (with options) to answer.
In the periodic table, elements are arranged from left to right according to what property? | [
"metallic mass",
"major mass",
"atomic mass",
"real mass"
] | C | You can see how Mendeleev organized the elements in Figure below . From left to right across each row, elements are arranged by increasing atomic mass. Mendeleev discovered that if he placed eight elements in each row and then continued on to the next row, the columns of the table would contain elements with similar properties. He called the columns groups . They are sometimes called families, because elements within a group are similar but not identical to one another, like people in a family. |
SciQ | SciQ-7333 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
What is made of gases that are essential for photosynthesis and other life activities? | [
"air",
"stratosphere",
"ocean",
"atmosphere"
] | D | The atmosphere is made of gases that are essential for photosynthesis and other life activities. |
SciQ | SciQ-7334 | rivers, geomorphology
Title: Is initial stream formation in a drainage basin random? It's known that stream orders are highly regular:
Horton showed that stream order is related to number of streams, channel length, and drainage area by simple geometric relationships; that is, stream order plots against these variables as straight lines on semilogarithmic paper.
[...] Among many samples of basins in the United States the bifurcation ratio tends closely to equal 3.5. There are variations, of course. In the examples of basins cited by Horton (1945, p. 290) values of the bifurcation ratio range from 2 to 4.
Fluvial Geomorphology, p.137
The stream bifurcation ratio is so regular in any given drainage basin that it's actually remarkable to look at a graph - as in these Indian continent sub-basins.
The process Fluvial Geomorphology describes for the evolution of these basins involves the random weathering of locally-level surfaces by rain, melt, or less commonly other liquid weathering. Small rivulets form via random depressions in the surface of the earth, which then merge into larger streams of higher order. But this got me thinking...
If the emergence of initial rivulets is a random process, shouldn't that random process be biased towards wherever the drainage basin happens to be the most erodible? I'd only expect this kind of macro-level structure to necessarily emerge if the earth were homogeneous in the drainage basin, but in practice this doesn't seem to need to be required in order for a drainage basin following a regular bifurcation ratio to emerge.
My questions are related:
The following is multiple choice question (with options) to answer.
When a stream flows from a hard to soft rock area, what is often formed? | [
"a lake",
"a waterfall",
"a river",
"a riverbank"
] | B | Mountain streams may erode waterfalls. As shown in Figure below , a waterfall forms where a stream flows from an area of harder to softer rock. The water erodes the softer rock faster than the harder rock. This causes the stream bed to drop down, like a step, creating a waterfall. As erosion continues, the waterfall gradually moves upstream. |
SciQ | SciQ-7335 | design, project-management
The one key I would make sure you have is a way of classifying your different designs by their key parameters. I don't know much about your field, but I'd assume there are certain design parameters that each project has to meet (physical size, capacity, type of plant, etc.). Make sure these are easily visible somewhere, so that when starting a new project, you can identify old projects that are similar in various regards. If you have these discarded ideas stored in those folders, you'll be able to analyze their utility to your current project.
However, I also want to warn in general about going too deep into this. Again, I work in a different industry, where projects are much shorter, and as such, there are many more of them, but some products have been in existence in some form for decades, and there are 15-20 revisions of them. Maintaining a revision history for actual design changes that were implemented is very important. Knowing what the customer was given in the past, when changes were made, and why they were made is key to not repeating past mistakes and correctly servicing old designs. But when you catalog designs that never were fully realized, you're adding non-essential data on top of essential data, and there's only so much you can sort through before things start to get lost. It sounds like you're looking for a replacement for solid communication and good experience. When these projects change hands, the engineers involved have to communicate all the relevant information. I understand wanting to make sure you know what has been considered, but I'd advise you to temper that desire so as not to flood your records with unnecessary data.
The following is multiple choice question (with options) to answer.
What term means taking used items and materials and turning them into something new? | [
"collecting",
"recycling",
"feeding",
"reproducing"
] | B | recycling: Takes used items and materials and turns it into something new. For example, 98% of car batteries are recycled today. In the processing plant, the plastic materials are separated from the lead, so the plastic can then be used for many applications. |
SciQ | SciQ-7336 | evolution, species, molecular-evolution, species-distribution, macroevolution
Lalage leucopygialis, L. nigra, and L. sueurii: Species of triller birds that coexist on Sulawesi Island.
The existence of ring species like this can, as biologist Ernst Mayr puts it, illustrate "how new species can arise through 'circular overlap', without interruption of gene flow through intervening populations…" and offers proof of speciation through a method other than allopatric speciation: speciation that happens when two populations of the same species become isolated from each other due to geographic changes.
The following is multiple choice question (with options) to answer.
What lets different species of anole lizards live in the same area without competing? | [
"cooperation",
"specialization",
"concentration",
"variation"
] | B | Specialization in Anole Lizards. Specialization lets different species of anole lizards live in the same area without competing. |
SciQ | SciQ-7337 | electromagnetism, optics, waves, visible-light, reflection
The closest I have gotten to obtaining the first equation is by making use of the continuity of the tangential component at the first interface. So we have the following:
$$ \hat{\textbf{z}} \times (\textbf{E}_1 - \textbf{E}) = 0$$
where $\textbf{E} = \textbf{e}_{inc} + \textbf{e}_{ref}$ and $\textbf{E}$ is the field inside the anisotropic material. Then we can solve for the $x$ and $y$ component of $\textbf{E}$ at $z = 0$ to obtain
$$ \textbf{e}_{x} = (-a_s \sin \psi - r_s \sin \psi - a_p \cos \theta_{inc} \cos \psi + r_p \cos \theta_{inc} \cos \psi) \exp[i k_0 n_1 ( x \cos \psi + y \sin \psi)]$$
$$ \textbf{e}_{y} = (a_s \cos \psi + r_s \cos \psi - a_p \cos \theta_{inc} \sin \psi + r_p \cos \theta_{inc} \sin \psi) \exp[i k_0 n_1 ( x \cos \psi + y \sin \psi)]$$
But now there is all this junk at the beginning. Not to mention these contain $k_0 n_1$ while the former has $q$ and this doesn't address the $\textbf{e}_{x}$ component.
The following is multiple choice question (with options) to answer.
What are made in the first step of the scientific method? | [
"observations",
"hypothesis",
"conclusions",
"patterns"
] | A | Scientific investigations generally follow a process called the scientific method. Steps of the scientific method include making observations, asking a question, forming a hypothesis, testing the hypothesis, drawing a conclusion, and communicating the results. |
SciQ | SciQ-7338 | evolution, biochemistry, plant-physiology, plant-anatomy, life
Title: Plants without bacteria? is it theoretically possible? I know from school, that all live on the Earth need bacteria as low-level "machines" that break down/extract/convert/produce chemical elements and combinations, other high-level organisms needed. But it is a natural way.
But is it possible to have a world with plants (without mammals or microorganisms and without bacteria) that could exist in the long term. Saying the atmosphere of these world has already enough nitrogen, oxygen and CO2, and of course there is water.
What could break this artificially created world with such conditions (say the world created not from low-level living structures)?
Could bacteria emerge in the world? This is the sort of question that should be considered from more than one perspective. Since this is speculation, take it as a given that there is a lot of 'what if' here.
I doubt most animals and plants can do entirely without bacteria - as you say most of the essential nutrients come from bacteria, who fix nitrogen. If only plants were left on earth, eventually the plants would use up all the nitrogen and they would have to find a way to fix more.
Can bacteria emerge from just a world of plants? I don't think viruses arise spontaneously, but since genomes often have viruses embedded in them, over the course of a billion years or so, its possible since bacteria and viruses continue to be impressed upon our genomes. Would it happen in time? Most would be skeptical whether that timing could work out.
In practice it would be hard to create a world like this. I would be interested to see whether you could sterilize the microorganisms off of seeds without killing the plant for instance. If you're asking about a small sterile environment with only plants, you could do it by adding the nutrients the plants need and giving them sunlight. Such self sustaining systems have been made with cyanobacteria and i'd be surprised if plants could not be included. But these are closed systems and judged by limited amounts of time, so whether this is an answer to your question is not clear. Here it looks like some water plants and fish have been done. If there was a plant that created CO₂ at an adequate rate its possible.
The following is multiple choice question (with options) to answer.
What type of organisms do not need blood? | [
"cold-blooded",
"marine",
"vertebrate",
"single-celled"
] | D | Single-celled organisms do not need blood. They obtain nutrients directly from and excrete wastes directly into their environment. The human organism cannot do that. Our large, complex bodies need blood to deliver nutrients to and remove wastes from our trillions of cells. The heart pumps blood throughout the body in a network of blood vessels. Together, these three components—blood, heart, and vessels—makes up the cardiovascular system. This chapter focuses on the medium of transport: blood. |
SciQ | SciQ-7339 | botany, classification
Title: Is ivy (genus Hedera) a shrub or an herb? It seems like the difference between a bush (shurb) and an herb is that a bush has a woody stem.
What does that make ivy (genus Hedera)? I know that ivy can get a pretty hard stem, does that count as woody? Is there something between a bush and an herb? Woody plants are usually either trees, shrubs, or lianas. Ivies are lianas, they can have 40 years of woody growth rings and bark. The categories are flexible. It's an arbitrary division for convenience, it isn't that clear cut. Bamboos for example, are a woody grass.
https://weedwise.conservationdistrict.org/weeds/english-ivy#foobox-1/7/Untitled-4-copy.jpg
Does that count as a woody plant? yes it's a woody liana.
The following is multiple choice question (with options) to answer.
What type of plants are the mosses, the hornwarts, and the liverworts considered to be? | [
"xerophyte",
"spirogyra",
"Vascular",
"nonvascular"
] | D | Nonvascular plants include the mosses, the hornworts, and the liverworts. |
SciQ | SciQ-7340 | acoustics
Title: How does mass of a sound barrier affect the amplitude of sound waves penetrating the room? I am trying to learn what role mass of sound insulation plays in reducing amplitude of sound waves entering a room from the outside.
In a thought experiment, a person has persuaded an elephant to lean against the party wall with a noisy neighbour. Is it fair to reason that any sound wave entering the room through the party wall will make an attempt to 'move molecules of the elephant' during sound transmission, thus reducing the amplitude of incoming sound?
I suspect that sound waves will attempt to travel down a route that is 'easiest to vibrate', avoiding the elephant.
Would the elephant play any role at all in reducing the apmplitude of incoming sound waves?
EDIT: there are no air gaps in our imaginary room. I don't have the maths to argue this [I'm a sound engineer not a physicist], so let me try to cover it in broad strokes.
Sound isn't all one frequency. To humans it's frequencies from approximately 20Hz to 20kHz [less as you get older]. Higher frequencies tend not to bother humans as we just can't hear them at all. Lower frequencies turn from 'sound' into perceptible 'vibration' - we can feel it even if we can't actually hear it.
Let's consider this like playing back music on a good hifi.
At the top we have cymbals & hi-hats; the bright, fizzy noises.
Below that, the majority of the sounds; guitars, strings, brass, vocals etc.
Then right at the bottom, bass, bass drum [& other lower sounding drums].
The next thing to consider is that higher frequencies take far less energy to generate, but are considerably easier to block. At frequencies from maybe 4kHz & up, you can block them with your fingers in your ears or earplugs, or a wall, or a bit of foam or rockwool.
If you're ever in the market for 'sound absorbing' materials to block sound transmission, always be wary of claims. "Blocks >60dB" ..at what frequencies? 20Hz? Not a chance, mate.
OK, so lower frequencies take much more energy to generate, but as they're carrying more energy, they also take a lot more effort to block.
The following is multiple choice question (with options) to answer.
Wearing what will reduce the amplitude of sound waves entering the ears? | [
"hardhat",
"megaphone",
"hearing protectors",
"goggles"
] | C | Hearing loss due to loud sounds can be prevented by wearing hearing protectors. They reduce the amplitude of sound waves entering the ears. |
SciQ | SciQ-7341 | lagrangian-formalism, variational-principle, boundary-conditions
So, how do you prove that there is only one trajectory that the system can travel from point $q_0$ to point $q_1$ during a fixed time interval $T = t_1 - t_0 > 0$.
I don't understand how to tackle these type of problems. Do I need to solve the equations of motion and show that given the boundary conditions, there is only one solution? Or should I somehow use the action functional? In general you can't, because it isn't true. Consider the simple pendulum with boundary conditions $\phi(0)=0$ and $\phi(T)=0$ for some $T$. There are clearly an infinity of trajectories which obey the equations of motion and obey these fixed boundary conditions, including the trivial solution $\phi(t)=\phi'(t)=0$, because the pendulum could go around the loop any integer number of times.
If you carefully follow the derivation of the Euler-Lagrange equations, the statement is that if there exists an extremal trajectory $\phi$ with fixed boundary conditions which extremizes the action $S[\phi]$, then
$$\delta S[\phi] = 0 \iff \frac{d}{dt}\left(\frac{\partial L}{\partial \dot \phi}\right) = \frac{\partial L}{\partial \phi}$$
This does not guarantee the existence of such a trajectory, and if it does exist, it is not guaranteed to be unique. The pendulum problem has the latter feature; for an example of the former, consider the Lagrangian $L(x,\dot x) = \frac{1}{2}\dot x^2 + \frac{1}{2}x^2$ and boundary conditions $x(0)=0$, $x(2\pi)=1$.
The following is multiple choice question (with options) to answer.
What type of motion only occurs when there is one force applied at the beginning of the trajectory after which there is no interference apart from gravity? | [
"velocity",
"propellant",
"projectile",
"thrust"
] | C | projectile motion: A form of motion where a particle (called a projectile) is thrown obliquely near the earth's surface, & it moves along a curved path under the action of gravity. The path followed by a projectile motion is called its trajectory. Projectile motion only occurs when there is one force applied at the beginning of the trajectory after which there is no interference apart from gravity. |
SciQ | SciQ-7342 | newtonian-mechanics, energy-conservation
Title: Conservation of energy when an object comes to rest Can someone explain conservation of energy to me? Here is what I don't understand: if one particle is moving towards another (say one has a mass much larger than the other, so it is like the Earth and a small object moving towards the Earth), then the particle will be getting faster as it moves closer to the other (kinetic energy increases) and potential energy will decrease. So far so good. But what about when it reaches the particle? Potential energy will be at its minimum here, presumably zero although I've heard that it could be defined to be another value, but speed will also be zero so kinetic energy will be zero. So according to conservation of energy it seems that kinetic energy should be at the maximum value when one particle reaches the other and potential energy should be at its minimum, but what really happens is that they are both at their minimum, although kinetic energy is at its maximum 'just before' it reaches the particle. This seems to me to violate conservation of energy.
Also, at any distance from the more massive particle, one could hold the small particle in place so that it has potential energy but no kinetic energy. So it seems the relationship between potential energy and kinetic energy only holds when particles are allowed to move freely, and conservation of energy is not true in general? Conservation of energy is always true.
In the first case, the two particles start with some potential energy $U$ far apart and then start moving one against each other. As they get closer and closer, potential energy is transformed into kinetic energy $K$ so that at any time conservation of energy holds
$$U(t)+K(t)=U(t')+K(t')$$ where $t$ and $t'$ are any two times. One instant before colliding, the potential energy is at its minimum and the kinetic energy at its maximum (in the case of an attractive force like gravity).
Now, the two particles collide! Unfortunately, collisions are violent events where things get tricky. But this does not mean that conservation of energy is violated! Three main possibilities are there and depends mostly on the size and material properties of the particles and on the strength of the collision:
The following is multiple choice question (with options) to answer.
What type of energy is produced when two objects move together? | [
"mechanical energy",
"physical energy",
"potential energy",
"molecular energy"
] | A | |
SciQ | SciQ-7343 | 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.
Which form of matter assumes the shape of its container? | [
"gas",
"crystals",
"liquids",
"solids"
] | A | Gases assume the shape of their container. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.