source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-144 | ions, crystal-structure, ionic-compounds, solid-state-chemistry
Title: How does NaCl maintain its crystalline structure? My understanding is that $\mathrm{NaCl}$ is an ionic compound, in which $\mathrm{Cl}$ becomes (effectively) $\mathrm{Cl^-}$ and $\mathrm{Na}$ becomes $\mathrm{Na^+}$. So I understand why I would get a "sea" of particles that would stick together.
But why does the above mean that it will have a face centered cubic structure with the ions held in place so rigidly? Crystals have inspired a great many chemists because they are fascinating for a good reason. Not only are they aesthetically pleasing, but they serve as an excellent subject to tour a variety of theoretical subjects important for understanding high-level chemistry.
Crystalline materials are made up of periodic structures. We’re only going to primarily focus on binary compounds where there is not a high degree of covalency. There are several ways to think about this problem, but let’s start with the melting of a crystal.
We say that at some definite temperature a highly ordered crystal will melt into a liquid. Those of us familiar with the language of equilibrium thermodynamics might recognize that the change in free energy for this phase change can be written, at constant temperature, as,
$$ G_\text{liquid} - G_\text{crystal} = H_\text{liquid} - H_\text{crystal} - T ( S_\text{liquid} - S_\text{crystal} ) $$
$$ \Delta G = \Delta H - T \Delta S $$
If we suppose that this process is spontaneous then we would say that the change in Gibbs’ free energy is negative, i.e. $\Delta G < 0$. This is true if and only if,
$$\Delta H < T \Delta S$$
The following is multiple choice question (with options) to answer.
Compounds like sodium chloride form structures called what? | [
"microorganisms",
"crystals",
"ions",
"hydrocarbons"
] | B | Compounds like sodium chloride form structures called crystals. A crystal is a rigid framework of many ions locked together in a repeating pattern. Ions are electrically charged forms of atoms. You can see a crystal of sodium chloride in the Figure below . It is made up of many sodium and chloride ions. |
SciQ | SciQ-145 | organic-chemistry, nomenclature, carbonyl-compounds, cyclohexane
From there, I imagine you can figure out the rest: the cyclohexane as a valid chain is also the longest chain, you start numbering from the functional group, etc. Hope that helped explain the teacher's answer!
The following is multiple choice question (with options) to answer.
What are made of long chains consisting almost solely of carbon and hydrogen? | [
"nucleic acids",
"lipids",
"enzymes",
"proteins"
] | B | Lipids are made of long chains consisting almost solely of carbon and hydrogen. These long chains are called fatty acids. Fatty acids may be saturated or unsaturated. Figure below shows an example of each type of fatty acid. |
SciQ | SciQ-146 | measurements, error-analysis
Different ways of expressing error in a measurement.
Different measures of errors include:
Absolute Error
Percent Error
Relative Error
(source)
same as in 7, 8.
Different ways of expressing Uncertainty in measurement
Absolute uncertainty
Fractional uncertainty
Percent uncertainty
(source). Same as in 9, 10. Now, I don't know which of the above classifications and different ways of expressing is correct.
Are all of the above classifications and different ways of expressing is correct or only some of those are correct? How uncertainties and errors are expressed and classified depends on context and convention. Your listing is correct and more than sufficient for student physics measurements, but there are multiple classification schemes that you might eventually encounter.
Expression
It is best to express uncertainty and error in the way that is most immediately convenient and useful, but with sufficient information to allow conversion into other forms. For example, the current absolute uncertainty on the Gravitational Constant G is $0.00015\times10^{-11}\,\mathrm{N\,m^2/kg^2}$. As long as I know that the current measured value is $6.67430\times10^{-11}\,\mathrm{N\,m^2/kg^2}$, I can also express the relative uncertainty as a fraction ($2.2\times10^{-5}$), a percentage ($0.0022\%$), or in parts-per-million ($22$ ppm).
Expressions of error are always comparisons between two measurements or measurement and theory, and such differences are often expressed in terms of the uncertainty $\sigma$. For example, the "Hubble Tension" is well known disagreement in the values of the Hubble Constant, where the value determined from the local Cosmic distance ladder disagrees by $4-6\,\sigma$ from the value determined from the Cosmic Microwave Background.
Classification
There are multiple ways to classify uncertainty. You likely only need to know about statistical/systematic for now, but it may be worth being aware of the existence of a few other schemes, especially Type A/B.
Statistical/Systematic
Classifies uncertainties by how they scale with how much data is collected:
The following is multiple choice question (with options) to answer.
When a series of measurements is precise but not what, the error is usually systematic? | [
"accurate",
"length",
"color",
"velocity"
] | A | 0 .033 g 1 .117 g × 100 = 3 .0% When a series of measurements is precise but not accurate, the error is usually systematic. Systematic errors can be caused by faulty instrumentation or faulty technique. The difference between accuracy and precision is demonstrated in Skill Builder ES7. |
SciQ | SciQ-147 | cell-biology, dna, molecular-genetics
Title: During the process of correcting mutations via gene therapy, is the defective gene removed? Just recently started learning about gene therapy, many websites explain that the corrected DNA can be added to the genome using a vector and all that. I just don't understand what happens to the other sequence of nitrogenous bases that codes for the incorrect protein.
Thanks in advance for any answers :) To be specific: I am talking about adult, somatic gene therapy here, and germline gene therapy experiments is still a landmine when considering ethical reasons.
The defective gene codes for a defective protein, that usually plays a part in pathways. Since the protein is also defective, that pathway is also rendered defective because of this protein, and usually when pathways go defective, bad things happen.
There are three target approaches to gene therapy:
Gene silencing by Antisense Oligonucleotide Therapy
Genome Surgery by ZFN, Crispr/Cas9 etc..
Gene Replacement by viral vectors
The only method that corrects the defective gene here is the genome surgery method. By using Zinc Finger Nucleases, or Crispr/Cas9s, TALENS or other methods like that, the defective protein is corrected at the genome level, which automatically corrects the mRNA and protein, and everything works as it should.
Other methods like Antisense, just prevent the incorrect protein from forming. This is really useful if the defective protein is itself toxic to the body, and a replacement protein can be achieved by masking the defective region to produce a truncated but functional protein.
Gene replacement usually puts in a healthy copy of the gene in, that functions along with the defective copy, and this solves majority of the problems as the affected pathway is no longer rendered inactive, as the healthy protein takes over the defective pathway. The defective protein is still produced, but doesnt do anything (or rather, is rendered moot as the healthy protein takes over) and gets removed during regular maintenance of the cell.
The following is multiple choice question (with options) to answer.
Inserting copies of normal genes into a patient with defective genes is known as? | [
"chromosome treatment",
"gene therapy",
"cloning",
"pattern therapy"
] | B | treat genetic disorders. For example, copies of a normal gene might be inserted into a patient with a defective gene. This is called gene therapy . Ideally, it can cure a genetic disorder. |
SciQ | SciQ-148 | botany, plant-physiology, reproduction, plant-anatomy, life-history
In dimorphic cleistogamy CL and CH flower differ in the time or place
of production, with CL flowers produced in conditions (underground,
low light levels, early in the season) that are potentially
unfavorable for outcrossing.
In induced cleistogamy potentially CH flowers that experience conditions such as drought or low temperatures fail to open and self-pollinate, becoming, in effect, CL flowers.
You should check out the Culley and Klooster (available online if you make a jstor login) – they discuss complete cleistogamy which addresses your last question. They report several completely CL species in their Table 1, and give references.
More generally, many different plant groups maintain balances of self-pollination and outcrossing (i.e. "real sex"), through an even more diverse set of mechanisms.
Even more generally, many plants and some animals maintain balances of sexual reproduction and clonal reproduction, through an even more diverse set of mechanisms. For instance, vegetative reproduction (e.g., strawberry runners) is very common in many plant groups; facultative and obligate parthenogenesis in animals also occurs.
Culley, Theresa M. and Matthew R. Klooster (2007). The Cleistogamous Breeding System: A Review of Its Frequency, Evolution, and Ecology in Angiosperms. Botanical Review. Vol. 73, No. 1, pp. 1-30
The following is multiple choice question (with options) to answer.
What type of reproduction usually occur during times of environmental stress? | [
"sexual reproduction",
"asexual reproduction",
"hysterical reproduction",
"internal reproduction"
] | A | |
SciQ | SciQ-149 | thermodynamics, energy, terminology
You are absolutely correct. Heat is not a form of energy. It is a mechanism by which energy is transferred from one substance, object, etc., to another due solely to temperature difference.
When I was learning about thermodynamics I found a particular description that, at least for me, help differentiate between the energy of something and the transfer of energy (by work or heat) from one thing to another. In this case the transfer of energy by heat. I'd like to share it with you in case it might be helpful. For simplicity, the description is for heat conduction.
Consider two solid objects, one having a higher temperature than the other. Which means the molecules of the higher temperature object 1 have a higher average translational kinetic energy than the molecules of the lower temperature object 2.
The objects are placed in contact with each other. At the interface between the objects the molecules of the higher temperature object collide with the molecules of the lower temperature object. On average, this results in the transfer of kinetic energy from the molecules of the higher temperature object to molecules of the lower temperature object causing the temperature of the higher temperature object to decrease, and the temperature of the lower temperature object to increase.
This transfer of kinetic energy from the molecules of the higher temperature object to the molecules of the lower temperature object is what we mean by heat. But the increase in the average kinetic energy of the molecules of the lower temperature object and decrease in the average kinetic energy of the molecules of the higher temperature object is what we mean by a change in the internal (kinetic) energy of the two objects. Thus the difference between the transfer of energy and the energy itself.
Hope this helps.
The following is multiple choice question (with options) to answer.
All forms of energy can be interconverted. three things can change the energy of an object: the transfer of heat, work performed on or by an object, or some combination of what? | [
"temperature and work",
"cold and energy",
"humidity and work",
"heat and work"
] | D | All forms of energy can be interconverted. Three things can change the energy of an object: the transfer of heat, work performed on or by an object, or some combination of heat and work. |
SciQ | SciQ-150 | literature-request
For as long as I can remember (okay, since 2002) the standard source of this type has been the Web of Science. It covers all sciences (and engineering, social science) so you have to restrict your search with sensible combinations of keywords, categories, and journal names, but it's the closest thing to a neutral database that we have.
I don't find Google Scholar to be a good substitute. It doesn't have a very good signal to noise, you'll often get multiple hits to entries of the same article in different databases, but direct links to the actual journal article can appear quite low down on the list. I know this has been a problem for EGU/Copernicus journal articles, which appear much lower down than social network (e.g., ResearchGate) links.
The problem with both of those tools though is the sheer volume of articles. So much is published these days that it's simply not possible for anyone to exhaust the search. My lab often recruits post-docs into Earth science positions from other disciplines (e.g., maths, physics) and knowing where to start or finish with the literature can be intimidating for them. What they need is for some experienced researchers in the field to filter the literature for them, which is why I normally recommend reading recent review articles as a way of gauging the knowledge boundaries.
There are journals dedicated to review articles, e.g.,
Earth Science Reviews
Review of Geophysics
Nature Reviews Earth & Environment
Encyclopedia of Geosciences
and doubtlessly there are more than I've forgotten. Some publishers also curate collections of important articles from across their journals, e.g.,
Nature Collections
AGU Grand Challenges
Read the references you find in those and maybe go one level deeper and then you'll have done your due diligence. I still stumble across seams of papers I've missed in fields that I've worked in for years and it's never been a problem; no one expects you to be exhaustive in your search.
The following is multiple choice question (with options) to answer.
What science includes many fields of science related to our home planet? | [
"meteorology",
"zoology",
"biology",
"earth science"
] | D | Earth science includes many fields of science related to our home planet. |
SciQ | SciQ-151 | equilibrium
Title: metallic mercury is shaken with a solution of mercury(II) nitrate
Hi there, I am reviewing equilibrium.
About this question, I wonder if the chemical equation is wrong.
Because the description says 'a solution of mercury(I) nitrate is formed'.
However, in the equation, the product is Hg2 2+?
I thought the product should be Hg1+.
Here is my answer, but my answer seems to be wrong. Your expression would be correct if the mercury(I) ions were individual, separate atoms like most metals. But they are actually paired up, forming $\ce{Hg_2^{2+}}$ with a covalent bond between the metal atoms. Thus, properly,
$\ce{Hg(l) + Hg^{2+} <=> Hg2^{2+}}$
with $K_c$ then equalling $\ce{[Hg2^{2+}]/[Hg^{2+}]}$ as given in the textbook.
This behavior of forming diatomic metal(I) ions is actually known with several elements in Group 2 and Group 12 (or if you are using an older text, Group 2A and Group 2B), but mercury is the one that most commonly has metal(I) ions and not always metal(II). So your textbook (presumably) identifies specifically mercury as forming $\ce{Hg2^{2+}}$.
The following is multiple choice question (with options) to answer.
What are alloys that are mostly composed of mercury known as? | [
"fillings",
"halogens",
"compounds",
"amalgams"
] | D | Alloys that are mostly composed of mercury are known as amalgams . Amalgams often have special properties that stem from the fact that mercury exists as a liquid at room temperature. As a result, metal amalgams are used for a variety of purposes, including dentistry and the extraction of other pure metals such as gold. |
SciQ | SciQ-152 | visible-light, material-science, reflection, metals
The other materials (plastic, glass, apples) have one thing in common: they have a relatively low absorptivity (while for metals the wave only enters a few nanometers, the other materials range from transparent to waves entering at least several micrometers; the absorption caused by pigments in the material is typically much weaker than the one in metals). This means that the reflection is caused by the change of the real part of the index of refraction. As most materials are only slightly dispersive in the optical range, this means that all frequencies are reflected more or less equally, therefore the reflection is not tinted.
The following is multiple choice question (with options) to answer.
What are made from highly reflective metal that is applied to a curved or flat piece of glass? | [
"prisms",
"kaleidoscopes",
"lenses",
"mirrors"
] | D | Mirrors are made from highly reflective metal that is applied to a curved or flat piece of glass. Converging mirrors can be used to focus light – headlights, telescopes, satellite TV receivers, and solar cookers all rely on this principle. |
SciQ | SciQ-153 | supernova, gamma-ray-bursts, wolf-rayet
Title: Should we fear Wolf-Rayet WR-104? I've read on Quora about Wolf-Rayet binary star WR-104, which is thought to be a precursor to a supernova explosion with two accompannying gamma ray bursts. It looks as if the rays will travel in our direction, but it is also said the ray is of by 30 degrees. Not sure what to think, so I thought to ask here. Will it have a real effect on Earth? The comments are pretty disturbing.
Should we fear Wolf-Rayet WR-104?
Not really.
What you should fear more is getting hit by a bolt of lightning from a storm that is 477 miles (768 kilometers) away. This actually happened fairly recently. Should you worry about this? No, you shouldn't. The odds are so small that this is not something to worry about, just as WR-104 is not something you should worry about.
There are plenty of things that are much more worthy of worrying about in the short term and the intermediate term. Could my city get hit by an asteroid or comet? Yep, it can. We saw that somewhat recently in Chelyabinsk in Russia. An even more significant event happened a bit over one hundred years ago in Tunguska, also in Russia. And then there's the a dinosaur-killer that happened 66 or so million years ago. Even that extremely rare event is much more likely than WR-104 hitting Earth with a GRB.
Could worldwide economic collapse, environmental collapse, political collapse, or social collapse occur in the semi-near future? Many experts claim that these are getting close to being inevitable. Those are something worthy of worrying about. A GRB from WR-104 is not worthy of worrying about.
The following is multiple choice question (with options) to answer.
What do ranchers fear will happen if wolves return? | [
"livestock predation",
"loss of environment",
"vegetation predation",
"human predation"
] | A | |
SciQ | SciQ-154 | waves, wavelength, superposition
Title: How many 'wavelengths of length' can a wave have? Since a wavelength, $\lambda$, is the length of a entire cycle
How many $\lambda$ (complete cycles) can a composed wave have? I mean, for $n \lambda$, how big can $n$ be? And what does it mean, physically?
I'm not necessarily talking about an electromagnetic wave, it can be an 'electron wave' since particles can be interpreted as waves. The mathematical wave you are showing , has no limit of length it can go from minus infinity to plus infinity,
When a mathematical wave function is used to fit specific physical behavior, as waves of water and sound, it will depend on the particular boundary conditions of the case under study,and more than one function will be needed.
For the case of the laser, which has a fixed wavelength within error, the length it can travel will depend on the energy available before the wave turns into the photons that compose it, because all laser beams have a divergence with distance . Photons are not a wave, so that will be the end of the laser beam.
The following is multiple choice question (with options) to answer.
How many types of surface waves are there? | [
"two",
"six",
"three",
"over a hundred"
] | A | Surface waves travel along the ground outward from an earthquake’s epicenter. Surface waves are the slowest of all seismic waves. They travel at 2.5 km (1.5 miles) per second. There are two types of surface waves. Love waves move side-to-side, much like a snake. Rayleigh waves produce a rolling motion as they move up and backward ( Figure above ). Surface waves cause objects to fall and rise. They also cause objects to sway back and forth. These motions cause damage to rigid structures during an earthquake. |
SciQ | SciQ-155 | biophysics, cell-membrane
Title: Why doesn't the cell membrane just...break apart? Forgive me if this is a silly question. I can't understand the basics. Why doesn't the cell membrane just break apart? What's keeping the layers in the phospholipid bilayer together? I know that the membrane is embedded with proteins and lipids, but I still can't wrap my head around the "why". Are the hydrophobic interactions in the middle "stronger" than the hydrophilic interactions on the outside? What's keeping the individual phosphate heads together instead of, say, one of them just drifting away due to a nearby water molecule? The membrane bilayer is held together by hydrophobic forces. This is an entropy driven process. When a greasy or hydrophobic molecule is suspended in water, the water molecules form an organized "cage" around the hydrophobic molecule. When two hydrophobic molecules come into contact, they force the water between them out. This increases the entropy because the freed waters don't need to be organized into the cage. Lipid bilayers have many many many hydrophobic lipids that squeeze out a lot of water and greatly increase entropy. The polar phosphates allow the water to interact with the surface of the membrane, without a polar head group the lipids would form a spherical blob instead of a membrane.
Read this section on wikipedia for more.
The following is multiple choice question (with options) to answer.
What is the rigid layer that is found outside the cell membrane and surrounds the cell? | [
"cell shield",
"cell wall",
"cell root",
"cell barrier"
] | B | A cell wall is a rigid layer that is found outside the cell membrane and surrounds the cell. The cell wall contains not only cellulose and protein, but other polysaccharides as well. In fact, two other classes of polysaccharides, hemicelluloses and pectic polysaccharides, can comprise 30% of the dry mass of the cell wall. The cell wall provides structural support and protection. Pores in the cell wall allow water and nutrients to move into and out of the cell. The cell wall also prevents the plant cell from bursting when water enters the cell. |
SciQ | SciQ-156 | blood-circulation
Title: Why don't we bleed interstitial fluid? Interstitial fluid is the fluid between cells in tissues - forming the medium between cells and capillaries. From what I gather, the typical human has 5L of blood and 11L of interstitial fluid. This raises an interesting question. If I get cut, why do I not bleed interstitial fluid?
When humans are cut, generally their capillaries open and blood comes out. But this should also allow the interstitial fluid to come out - so why don't we see it? For fluid to flow from a wound there needs to be a significant pressure gradient between where it is now and the outside of the body. Your skin generally does not have a strong compressive effect, which is why a deep cut exposing fat will not lead to the fatty tissue being expulsed from the body any more than the interstitial fluid is.
Blood, however, flows. For it to circulate there needs to be a pressure gradient between where it is now and where it is going. Since veins (including the vena cava, which channels blood back into the heart) do not have vascular walls strong enough to create a suction effect (i.e. lower pressure than the surrounding tissue), you can conclude that the pressure of blood vessels is always higher than that of surrounding tissues, and thus higher than the pressure outside of your body. This is why all blood vessels, including veins, will bleed, whereas less pressurized systems such as interstitial fluid will not.
The following is multiple choice question (with options) to answer.
Surface tension of alveolar fluid, which is mostly water, creates an inward pull of the tissue of what organ? | [
"lung",
"brain",
"spleen",
"heart"
] | A | Intrapleural pressure is the pressure of the air within the pleural cavity, between the visceral and parietal pleurae. Similar to intra-alveolar pressure, intrapleural pressure also changes during the different phases of breathing. However, due to certain characteristics of the lungs, the intrapleural pressure is always lower than, or negative to, the intra-alveolar pressure (and therefore also to atmospheric pressure). Although it fluctuates during inspiration and expiration, intrapleural pressure remains approximately –4 mm Hg throughout the breathing cycle. Competing forces within the thorax cause the formation of the negative intrapleural pressure. One of these forces relates to the elasticity of the lungs themselves—elastic tissue pulls the lungs inward, away from the thoracic wall. Surface tension of alveolar fluid, which is mostly water, also creates an inward pull of the lung tissue. This inward tension from the lungs is countered by opposing forces from the pleural fluid and thoracic wall. Surface tension within the pleural cavity pulls the lungs outward. Too much or too little pleural fluid would hinder the creation of the negative intrapleural pressure; therefore, the level must be closely monitored by the mesothelial cells and drained by the lymphatic system. Since the parietal pleura is attached to the thoracic wall, the natural elasticity of the chest wall opposes the inward pull of the lungs. Ultimately, the outward pull is slightly greater than the inward pull, creating the –4 mm Hg intrapleural pressure relative to the intraalveolar pressure. Transpulmonary pressure is the difference between the intrapleural and intra-alveolar pressures, and it determines the size of the lungs. A higher transpulmonary pressure corresponds to a larger lung. |
SciQ | SciQ-157 | neuroscience, cancer
Title: Can neurons become cancerous? I've been reading about brain cancer lately, and something I've noticed is that the tumors seem to start in all tissues, except neural tissue. Am I missing something, or is there an explanation? Short answer
Neuronal tumors are rare, but they do exist. These cancers develop from neuroblast cells, a population of undifferentiated, dividing precursor cells that will eventually fully differentiate into functional neuronal cells.
Background
Most neuronal cell types have lost their ability to divide, because of their progressed state of differentiation. There are but a few regions in the brains that generate new nerve cells in adulthood, for example in the hippocampus where neuro-regeneration is believed to be involved in memory formation. Because of the rarity of cell division of neuronal cells in adulthood, neural cancers are rare.
The point where neuronal cells actively divide is during development. These cells are basically still stem cells. A prime example here are retinoblastomas. These are tumors in the photosensitive part of the eye, namely the retina. During early development stem cells actively divide to lay down a layered structure in the back of the eye eventually forming the rods and cones and other visual cells. If this division process goes out of control, tumors can develop. Retinoblasomas can now be diagnosed in utero (Paquette et al., 2012).
Tumors with a neuronal origin developing post natally are rare, but do exist. Neuroblastoma being a prime example. This is a rare cancer (prevalence of 1:100,000) most commonly found in children younger than age 5. It affects the sympathetic nervous system, which regulates involuntary bodily functions such as heart rate, blood pressure, breathing, and digestion. Neuroblastoma typically begins in the nerve tissues of the adrenal glands but may also begin in the nerves that are located anywhere along the spinal cord, including the neck, chest, or abdomen. The cancer can metastasize (spread) to other organs.
The following is multiple choice question (with options) to answer.
What type of tumor mostly does not cause serious problems and can be completely removed by surgery? | [
"persistent",
"toxic",
"benign",
"malignant"
] | C | |
SciQ | SciQ-158 | organs, lifespan
Title: Organs lifespan out of the body What organ can be conserved outside of the body for the longest time and still function when reimplanted? Depends what you consider an organ. Typically though it's the cells which require the most metabolic activity which have the shortest life span. The kidney is the most of the major internal organs with up to 36 hours with liver coming second at up to 16 hours.
The following is multiple choice question (with options) to answer.
What supports and protects the soft organs of the body? | [
"skull",
"Muscle",
"Skin",
"skeleton"
] | D | Protection. The skeleton supports and protects the soft organs of the body. For example, the skull surrounds the brain to protect it from injury. The bones of the rib cage help protect the heart and lungs. |
SciQ | SciQ-159 | thermodynamics, energy, earth, thermal-radiation
@Benjohn has given you the correct answer. Here is my take.
The ultimate heat provider of the earth ( except a small percentage of heat from the magma at the center of the earth) is the sun. It pours down at the surface about 1.2 kilowatts of energy per meter square ( which btw is directly used by solar panels). The same energy falls on the surface of the moon whose surface burns up during its daytime and freezes by black body radiation at night.
The earth is fortunate to have a gas atmosphere which mitigates the extremes of the possible temperatures that the ground would reach otherwise. An example of mitigation is what happens at the sea floor. Most of the energy is picked up by the water and the floor is kept at a steady temperature with small changes day and night in the first meters from the surface, depending on the season, radiating away with the black body radiation, but the body of water has such large heat capacity that variations are small.
The gas atmosphere is a more temperamental "blanket", its heat capacity depends on several gases , called green house gases from the bad impression that agricultural green houses work that way ( they do not, they work by inhibiting heat exchange by convection but that is another story, on which there is no controversy).
The main green house gas is water , H2O. It is worth contemplating this figure :
Solar irradiance spectrum above atmosphere and at surface. Extreme UV and X-rays are produced (at left of wavelength range shown) but comprise very small amounts of the Sun's total output power.
We see that H2O has the most absorption spectrum for infrared wavelengths, (which are the wavelengths of heat )and then comes CO2. Green house gases absorb both incoming and reflected from the surface of the earth infrared, and as most of the reflected wavelengths are in the infrared they act as a slowing down of the black body radiation that would finally leave the earth. As a blanket keeps a person warmer green house gases by playing ball with infrared radiation ( the wavelengths where heat is really transferred) keep the surface of the earth into a reasonable temperature for life, lucky us.
The following is multiple choice question (with options) to answer.
What celestial body is the earth’s main source of energy? | [
"rivers",
"ocean",
"moon",
"sun"
] | D | The Sun is Earth’s main source of energy. The Sun gives us both light and heat. The Sun changes hydrogen into helium through nuclear fusion. This releases huge amounts of energy. The energy travels to Earth mostly as visible light. The energy is carried through the empty space by radiation . We can use sunlight as an energy resource, called solar energy. |
SciQ | SciQ-160 | species-identification, botany
Title: Can you identify this (possibly waterstoring) plant? My son brought home a sapling, and after 4 years in a pot it is now about 30 cm or a foot high (from the "ground" to the top of the "stem"). It doesn't need a lot of water and can go weeks without being watered, in fact it seems to me as if it is storing water in the thicker upper part of its stem. When I water it "too much", new leaves start to grow. There are tiny "blossoms" along the stem, and every now and then small, dark brown, spherical seeds about 2 mm in diameter pop out from the "blossom" and are thrown across the room as far as a meter (about a yard) or two.
What plant is this?
I believe that it is not native to my European home but some kind of decorative plant imported and sold through a florist or imported privately, but I'm not sure. It is an Euphorbia leuconeura (Madagascar Jewel), which is native to Madagaskar. The leaves and the thick (waterstoring) stem with a narrow base is very typical.
The plant is cool in the sense that it easily produces seeds (also as potted) which it can shoot away from the plant. I've had it myself and you can sometimes hear seeds hitting the window or floor. Even if it is easy to grow and to reproduce it is actually considered threatened in its native habitat (IUCN Red-listed as Vulnerable) due to habitat loss
The flowers are very small and found directly on the stem, see below:
(picture from Wikipedia)
The following is multiple choice question (with options) to answer.
What do you call the horizontal stems of a strawberry plant that run over the ground surface? | [
"climbing vines",
"sprouts",
"stolons",
"root volunteers"
] | C | Strawberry plants have horizontal stems called stolons that run over the ground surface. If they take root, they form new plants. |
SciQ | SciQ-161 | mars, obliquity
I don't like to use the word fact in a situation like this. What that variation is, is a mathematical model based on well understood but pretty complicated n-body gravitational perturbations between planets, so, it's likely accurate. Whether it's a fact is perhaps a matter of semantics, but I don't like to use the word fact in this situation.
That said, it's very likely true that Mars undergoes both significant axial tilt changes and eccentricity changes over thousands or tens of thousand year cycles, and if variations like that happened on Earth, they would cause havoc to our climate.
Everything else being equal, that kind of variation should generate considerable glacial movement on Mars' poles, but everything isn't equal between Mars and Earth.
Ice ages on Earth require large land masses on or near one or both poles, where ice can build. Glaciers can't form in open deep ocean water, they require land, where the summers are cold enough that ice can build up, which, over thousands of years of buildup, becomes a glacier.
Mars lacks the water to expand it's glaciers. Nearly all Martian water is either underground or already frozen on it's North pole, so there's no water to add. Literally about 99.99999% of Mars' surface water is already part of one of it's two glaciers on it's North & South poles.
Unlike Earth - where there's always some water in the atmosphere and there's always the possibility of snowfall, so Earth's glaciers can always grow bigger if the seasonal temperature allows it. Mars has no ice to add to it's glaciers.
That limits Mars' glacial expansion to CO2, and that does happen to a degree. Mars glaciers do add CO2 during the winter and return it during the summer, but that's seasonal and Mars has only so much CO2, so it's glaciers could only expand as far as it's atmosphere would allow.
Mars' atmosphere is about 2.5 x 10^16 kg. Mars' surface area is about 1.4 x 10^14th square meters, which means it's entire atmosphere works out to about 180 kg per square meter, which would be about 7 inches high if frozen into dry ice. 7 inches means that Mars can't form glaciers like Earth can, no matter what it's axial tilt or eccentricity variation. It lacks the material.
The following is multiple choice question (with options) to answer.
Glaciers are incredibly powerful agents of what? | [
"climate change",
"extinction",
"erosion",
"insulation"
] | C | Glaciers are incredibly powerful agents of erosion. |
SciQ | SciQ-162 | pressure, collision, fluid-statics
Title: Is Atmospheric Pressure due to weight of air or the collisions of the Molecules This question is in response to @brightmagnus answer whose link is
Pressure in Fluids,in particular horizontal pressure
The question :
Is the atmospheric pressure due to the weight of air or collisions of the molecules?
The following is multiple choice question (with options) to answer.
What type of pressure is the pressure exerted by gas particles in earth’s atmosphere as those particles collide with objects? | [
"atmospheric pressure",
"adjacent pressure",
"vertical pressure",
"adjacent pressure"
] | A | Atmospheric pressure is the pressure exerted by gas particles in Earth’s atmosphere as those particles collide with objects. A barometer is an instrument used to measure atmospheric pressure. A traditional mercury barometer consists of an evacuated tube immersed in a container of mercury. Air molecules push down on the surface of the mercury. Because the inside of the tube is a vacuum, the mercury rises inside the tube. The height to which the mercury rises is dependent on the external air pressure. |
SciQ | SciQ-163 | biophysics, cell-membrane
Title: Why doesn't the cell membrane just...break apart? Forgive me if this is a silly question. I can't understand the basics. Why doesn't the cell membrane just break apart? What's keeping the layers in the phospholipid bilayer together? I know that the membrane is embedded with proteins and lipids, but I still can't wrap my head around the "why". Are the hydrophobic interactions in the middle "stronger" than the hydrophilic interactions on the outside? What's keeping the individual phosphate heads together instead of, say, one of them just drifting away due to a nearby water molecule? The membrane bilayer is held together by hydrophobic forces. This is an entropy driven process. When a greasy or hydrophobic molecule is suspended in water, the water molecules form an organized "cage" around the hydrophobic molecule. When two hydrophobic molecules come into contact, they force the water between them out. This increases the entropy because the freed waters don't need to be organized into the cage. Lipid bilayers have many many many hydrophobic lipids that squeeze out a lot of water and greatly increase entropy. The polar phosphates allow the water to interact with the surface of the membrane, without a polar head group the lipids would form a spherical blob instead of a membrane.
Read this section on wikipedia for more.
The following is multiple choice question (with options) to answer.
What helps the plasma membrane keep its shape? | [
"molecules of cholesterol",
"molecules of oxygen",
"cytoplasm",
"molecules of carbohydrates"
] | A | The plasma membrane also contains other molecules, primarily other lipids and proteins. The green molecules in Figure above , for example, are the lipid cholesterol. Molecules of cholesterol help the plasma membrane keep its shape. Many of the proteins in the plasma membrane assist other substances in crossing the membrane. |
SciQ | SciQ-164 | human-biology, reproduction, human-genetics
Title: Very frequent multiple births in humans 18th century Feodor Vassilyev is said to have had children by two wives, each of whom only ever had twins, triplets or quadruplets. His first wife has 16 sets of twins, 7 of triplets and 4 of quads; his second had 6 sets of twins and 2 of triplets. Is there any known plausible biological explanation for this, or do we have to dismiss it as a fabrication?
I could understand a woman's body being unusually susceptible to multiple births. I can't find information on whether these women tended to have monozygotic or polyzygotic offspring, but neither option seems unviable to me. However, since it's unlikely two of Feodor's sexual partners would share such a trait, one would think to attribute it to him. Presumably there would have to be a mechanism by which paternal DNA can trigger embryo fissions, in which case I imagine the offspring would be polyzygotic. Risk factors for dizygotic twinning are related to multiple follicular development, and include maternal family history, ethnicity, geography, maternal parity, maternal age, and, of course, use of assisted reproductive technology. There may be a genetic component to monozygotic twinning as well, but that rate is fairly consistent across populations. Other risk factors, such as diet and supplementation, have been proposed, but the data are less robust. There are some interesting studies demonstrating geographic clusters of twinning, but these tend to be demographic clusters that are associated with other risk factors.
Though a higher risk of twinning can be transmitted from a father to his daughters, the father's family history of twinning is not a significant risk factor (for his own children to be twins). To clarify -- if a man has a family history of multiple births, his children are no more likely to be twins than the general population, but his daughers are more likely to give birth to twins. This study is one example of the studies that have shown a significant independent association between maternal family history and twinning, with no significant independent association with paternal family history.
The following is multiple choice question (with options) to answer.
What type of reproduction only involves one parent? | [
"primitive",
"organic",
"asexual",
"binary"
] | C | Asexual reproduction involves just one parent. It produces offspring that are genetically identical to the parent. Methods of asexual reproduction include binary fission, fragmentation, and budding. |
SciQ | SciQ-165 | 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 is defined as a repeating series of events that include growth, dna synthesis, and cell division? | [
"cell cycle",
"photosynthesis",
"meiosis",
"puberty"
] | A | Cell division is just one of several stages that a cell goes through during its lifetime. The cell cycle is a repeating series of events that include growth, DNA synthesis, and cell division. The cell cycle in prokaryotes is quite simple: the cell grows, its DNA replicates, and the cell divides. In eukaryotes, the cell cycle is more complicated. |
SciQ | SciQ-166 | inorganic-chemistry
Title: Why do metals tend to lose electrons, as opposed to maintaining electric neutrality? Metals tend to lose electrons to obtain the stable noble gas configuration of 8 valence electrons.
Why do they want to obtain this configuration, and how does the strength of their "desire" to obtain this configuration compare with the "desire" to maintain neutral charge. If the answer depends on the chemical, I'm happy for you to provide some examples.
Thanks. Firstly, atoms "want" to achieve the noble gas configuration of 8 valence electrons because it is the most stable form. All that means is that it doesn't tend to react under normal conditions that we experience on Earth, therefore it will stay in that configuration for quite a while and are less likely to react. There is a more complex quantum physical answer for that but you'll have to go elsewhere for than.
The main force that keeps electrons in atoms is the electrical attraction between the electrons and the protons in the nucleus and so, if it is more energetically favourable to lose that electron in order to form a bond, then that is what will happen.
Focusing on the Alkali metals as an example, as you move down the group, they get more and more reactive. This is because of two main reasons that are a result of the electrons being further away from the nucleus:
Because they're further away, the attraction between the protons and the outer most electron is less
Secondly, taking Rubidium as an example, it has 37 electrons and 37 protons. From the perspective of the outer-most electron, there are 36 electrons repelling it, and 37 protons attracting it, therefore acting as a net charge of 1. However, if you take into account the first point, the repulsion of the closer electrons is stronger than the attraction of the protons so it could even be less than one
The following is multiple choice question (with options) to answer.
How metalloids behave in chemical interactions with other elements depends mainly on the number of what, in the outer energy level of their atoms? | [
"protons",
"positrons",
"neutrons",
"electrons"
] | D | How metalloids behave in chemical interactions with other elements depends mainly on the number of electrons in the outer energy level of their atoms. Metalloids have from three to six electrons in their outer energy level. Boron, pictured in the Figure below , is the only metalloid with just three electrons in its outer energy level. It tends to act like metals by giving up its electrons in chemical reactions. Metalloids with more than four electrons in their outer energy level (arsenic, antimony, and tellurium) tend to act like nonmetals by gaining electrons in chemical reactions. Those with exactly four electrons in their outer energy level (silicon and germanium) may act like either metals or nonmetals, depending on the other elements in the reaction. |
SciQ | SciQ-167 | zoology, terminology, nomenclature, invertebrates, etymology
Urochorda
Cephalochorda
Craniata
which is more or less the accepted division today, with Urochorda being called Urochordata now.
In this essay, Lankester says:
The evidence of degeneration is admitted as conclusive in the case of the parasitic Crustacea and Cirrhipedes. It is equally incontestable in that very large and varied group of non-parasitic organisms, the Tunicata (Urochordate Vertebrata).2
(in the above 'Vertebrata' is what we call 'Chordata'). He adds this footnote:
2The whole argument as to the Tunicates of course rests on the view- supported by many arguments, that the larval urochord, which many of
them possess, is not a larval organ acquired by larval adaptation, but is hereditary and transmitted from adult ancestors.
The term 'urochord' seems to be established and used without comment there, and probably is taken as simple neo-Latin for 'tail chord', although that may be somewhat loose, perhaps meaning the notochord is present but does not extend into the head. A 1913 Webster's Dictionary defines urochord as:
(Zool.) The central axis or cord in the tail of larval ascidians and of certain adult tunicates.
In 1882, Lankester futher discussed the anatomy of the tunicates in the context of the division of the chordata in a paper called "The Vertebration of the Tail of Appendiculariæ". This paper includes an illustration of a larval tunicate with the "notochord (urochord)" indicated.
The following is multiple choice question (with options) to answer.
What distinguishing characteristic of annelid anatomy shows specialization and adaptation? | [
"compression",
"beautiful",
"segmentation",
"asymmetry"
] | C | Annelids are divided into many repeating segments. The earthworm in Figure below is an annelid. You can clearly see its many segments. Segmentation of annelids is highly adaptive. Each segment has its own nerve and muscle tissues. This allows the animal to move very efficiently. Some segments can also be specialized to carry out particular functions. They may have special structures on them. For example, they might have tentacles for sensing or feeding, “paddles” for swimming, or suckers for clinging to surfaces. |
SciQ | SciQ-168 | immunology, reproduction, development
Title: How do Sertoli cells protect sperms? I was reading Developmental biology by Gilbert and stumbled upon a fact that Sertoli cells provide protection to the developing sperms with no futher explanation.
I googled it and found a few books mentioning that it protects sperms from cell mediated immunity and antisperm antibodies. Yet I found a website called fertilitypedia that said:
Sertoli cells do not only control the process of spermatogenesis, but they are also responsible for creating so called immunologically privileged area in the testicles. It means, that Sertoli cell manage to keep blood separated from seminiferous tubules through the connection between them, called tight junction. Tight junction keeps bloodborne substances from reaching germ cells, so all stages of germ cells are protected from the body immunity. Tight junction also keeps surface antigens found on developing germ cells from eluding into the bloodstream so no autoimmune reaction could happen. Since Sertoli cells form the block between the blood and lumen of seminiferous epithelium, they are also in control of the entry and exit of nutrients, hormones and other chemicals into the tubules of the testis.
I'm unable to verify this explanation from the cited sources as none contain the mentioned information.
So my question, how does it actually protect the sperms? The Wikipedia pages on Blood-testis barrier and Sertoli cells have some information relevant to your question, with some academic references included.
You could also search for reviews on Sertoli cells on Google Scholar - several of the first returned results seem relevant, if you are able to access them.
The following is multiple choice question (with options) to answer.
The spermatids are transported from the testes to where? | [
"epididymis",
"abdominis",
"Duodenum",
"vas"
] | A | The spermatids are transported from the testes to the epididymis. Involuntary muscular contraction moves the spermatids along. |
SciQ | SciQ-169 | hydrology, water, rainfall, groundwater
Title: How much time does water takes to reach to the ground? I want to understand the phenomena where water droplets after precipitation reaches to the ground.
How much time does it take to become ground water or in other words how much time is taken by water to recharge the ground after rain.
I am assuming the water droplets falls in the plain having no concrete human constructions. It depends upon the hydraulic conductivity, the degree of saturation, and the depth to water table. Generally, water seeping down in the unsaturated zone moves very slowly. Assuming a typical depth to water table of 10 to 20 metres, the seepage time could be a matter of minutes in the case of coarse boulders, to months or even years if there is a lot of clay in fine sediment. Under saturated conditions, the water might move a lot faster. Other factors include the configuration of the wetting front, the unsaturated storage, temperature, and the hydraulic gradient. So basically, there is no simple answer - it's all a matter of the local hydrogeology.
There is no substitute for local measurement - water levels in an observation bore, in the case of water table conditions, or tensiometry in the case of the unsaturated zone.
The following is multiple choice question (with options) to answer.
How does water from roots reach the leaves? | [
"water-phobic cells",
"water - raising cells",
"water-conducting cells",
"water - combining cells"
] | C | |
SciQ | SciQ-170 | energy, condensed-matter, surface-tension, soft-matter
Title: Interface between two phases minima of the energy and interface between a minimum and a "vacuum" Cahn and Hilliard define the energy of an interface:
the difference per unit area of interface between the actual free
energy of the system and that which it would have if the properties of
the phases were continuous throughout
The following is multiple choice question (with options) to answer.
As a polycrystalline material solidifies, grains with irregular shapes form. the interfaces between grains constitute grain what? | [
"boundaries",
"patterns",
"obstacles",
"waves"
] | A | Grain boundaries. As a polycrystalline material solidifies, grains with irregular shapes form. The interfaces between grains constitute grain boundaries. (Squares represent unit cells within grains. |
SciQ | SciQ-171 | electromagnetism
Title: Is it conductors in magnetic fields or repulsion of poles that provides torque in BLDC motor? So I'm confused by the two different descriptions floating around as to how DC motors generate torque and by extension BLDC: On one hand there is the conductors in magnetic field explanation usually including the term 'Motor Effect' and referencing the Lorentz force then on the other hand you have coils acting as electromagnets and providing poles that push and pull against the corresponding field poles.
Is it one or the other or both or neither? Does it depend on the specific motor geometry? They are different ways to explain the same effect. The explanation using the repulsion/attraction of magnetic poles is a simplification of the more detailed description in terms of all charges in the coil mutually interacting via EM fields.
On the fundamental level of EM theory, there are no magnetic poles, only electric charges, but in some cases (solenoid) the resulting magnetic and electric field acting on other coils or permanent magnets looks like that of a rotating permanent magnet. Then it is possible to mentally replace, for the purpose of calculating mechanical force, the actual system by a fictive system made of permanent magnets and instead of interaction of a magnet and wires, which is complicated to explain in full, consider interaction of permanent magnets, for which there is a simple model - the Coulomb interaction of magnetic poles.
The following is multiple choice question (with options) to answer.
Motors are the most common application of magnetic force on current-carrying wires. motors have loops of wire in this? | [
"capacitors",
"electrical circuit",
"magnetic field",
"spark plugs"
] | C | 22.8 Torque on a Current Loop: Motors and Meters Motors are the most common application of magnetic force on current-carrying wires. Motors have loops of wire in a magnetic field. When current is passed through the loops, the magnetic field exerts torque on the loops, which rotates a shaft. Electrical energy is converted to mechanical work in the process. (See Figure 22.34. |
SciQ | SciQ-172 | organic-chemistry, acid-base, everyday-chemistry, photochemistry
Title: Chemical compounds responsible for the colors in flowers? I know that anthocyanins are a class of compounds responsible for the purple colors found in flower petals.
Anthocyanins (also anthocyans; from Greek: ἀνθός (anthos) = flower + κυανός (kyanos) = blue) are water-soluble vacuolar pigments that may appear red, purple, or blue depending on the pH. (same reference as above)
The anthocyanins, when extracted from flower petals with water, can be used as acid/base indicators, producing red colors in acid and blue in neutral solutions (in basic solutions they turn green, yellow, and then become colorless). When I've done the extractions, some red petals produce a red color in acid and maintain the red color at higher pH than purple flowers (see plate below), but some red flowers produce colors that seem to follow the normal progression.
Row 2 from the top was a purple flower, row 3 a red flower and row 4 also a red flower. (pH values start at 2 on the left and increase by 1 pH unit as you move right by adding the water extracts to buffer samples in the wells.)
So, are there other classes of compounds responsible for the red and yellow colors found in flowers? Can the red colors that give a "normal" anthocyanin pH response arise from pigments held in an acidic environment in the plant? (That may be a biology question, but I'm interested in the chemistry side of where the color comes from.)
are there other classes of compounds responsible for the red and yellow colors found in flowers?
Interest in colors, specifically dyes, was a real motivator for serious chemical work. Some of the early efforts were aiming to mimic Tyrian purple, also known as Royal Purple, because in antiquity it was worth its weight in gold.
Two classes of molecules come to mind other than anthocyanins in phytochemistry, such as the closely related flavones (its root means yellow) and the distinct carotenes (its root means carrot, but also responsible for flamingo color).
Can the red colors that give a "normal" anthocyanin pH response arise from pigments held in an acidic environment in the plant?
The following is multiple choice question (with options) to answer.
What makes and stores pigments that give petals and fruit their orange and yellow colors? | [
"sporozoans",
"pores",
"protozoa",
"chromoplasts"
] | D | Chromoplasts make and store pigments that give petals and fruit their orange and yellow colors. |
SciQ | SciQ-173 | fluid-dynamics, pressure, acoustics, water
Consequently, the thermodynamic activities ($a_i\equiv e^{\mu_i/RT}$) of component $i$ in the dissolved and gaseous states are also equal.
(For that matter, the activities of the liquid and its vapor above are equal as well. Furthermore, the activity of pure condensed matter is simply 1; put another way, we take this state as the reference state. This lets us relate the equilibrium vapor pressure to the enthalpy of vaporization, which shows up in the chemical potential $\mu$. In this way, all materials can be modeled as having a vapor-pressure temperature dependence of $e^{-1/T}$.)
Finally, the activity of a gas can often be approximated by its partial pressure (as mediated by the fugacity), and the activity of a solute can often be approximated by its concentration (as mediated by the activity coefficient). From all these assumptions and idealizations, we obtain Henry's Law. But more generally, the broader framework (starting from entropy maximization and proceeding through the relevant thermodynamic potential, e.g., the Gibbs free energy) advantageously would let one derive a more general law that also incorporates, say, gas nonideality, or gravity, or solute interaction, or surface area, or an applied electric or magnetic field, etc.
The following is multiple choice question (with options) to answer.
What term is used to describe when a liquid is the temperature at which its equilibrium vapor pressure is equal to the pressure exerted on the liquid by its gaseous surroundings? | [
"freezing point",
"boiling point",
"evaporating point",
"burning point"
] | B | Boiling Points When the vapor pressure increases enough to equal the external atmospheric pressure, the liquid reaches its boiling point. The boiling point of a liquid is the temperature at which its equilibrium vapor pressure is equal to the pressure exerted on the liquid by its gaseous surroundings. For liquids in open containers, this pressure is that due to the earth’s atmosphere. The normal boiling point of a liquid is defined as its boiling point when surrounding pressure is equal to 1 atm (101.3 kPa). Figure 10.24 shows the variation in vapor pressure with temperature for several different. |
SciQ | SciQ-174 | electromagnetic-radiation, photons, radiation, photon-emission
Title: Why do electrons come to ground state even after giving absorbing energy? Imagine you have a hydrogen placed under sunlight, now if we look at 1st shell of hydrogen, it has energy of $-13.6$ev now for 2nd shell we have energy of $-3.4$ev.
1st shell -> $-13.6$ev
2st shell -> $-3.4$ev
3rd shell -> $-1.5$ev
4th shell -> $-0.85$ev
The the continous power from sun is more than enough to send knock electrons out of hydrogen atom, even if we assume the power from sun is not "ample" enough at once, for eg: electron in 1st shell need $+10.2$ev so it can jump into 2nd shell, say sun gives $+5.2$ev at $t = 1s$ so this energy will increase kinetic energy of electron, at $t = 2s$ sun gives $+5.2$ev so electron now jumps into 2nd shell and remaining energy will be used to increase kinetic energy of electron. This process can go on until electron is completely removed from atom?
Why doesn't something like this happen? There are also other processes that return the electron into the lower energy states: most notably spontanous emission (when electron lowers its energy and emits a photon), but also various kinds of other interactions, such as collisions with other hydrogen atoms. The drive towards lower energy then wins - this is what thermodynamics and statistical physics teach us.
The following is multiple choice question (with options) to answer.
When electrons return to a lower energy level, they emit the excess energy in the form of what? | [
"energy",
"weight",
"light",
"electricity"
] | C | When electrons return to a lower energy level, they emit energy in the form of light. |
SciQ | SciQ-175 | optics, visible-light, everyday-life, diffraction
Addendum 2: Before the comments below were cleaned out, there was some discussion there about the usefulness of this phenomenon as a quick self-diagnostic test for myopia (nearsightedness).
While I Am Not An Opthalmologist, it does appear that, if you experience this effect with your naked eye, while trying to keep the background in focus, then you may have some degree of myopia or some other visual defect, and may want to get an eye exam.
(Of course, even if you don't, getting one every few years or so isn't a bad idea, anyway. Mild myopia, up to the point where it becomes severe enough to substantially interfere with your daily life, can be surprisingly hard to self-diagnose otherwise, since it typically appears slowly and, with nothing to compare your vision to, you just get used to distant objects looking a bit blurry. After all, to some extent that's true for everyone; only the distance varies.)
In fact, with my mild (about −1 dpt) myopia, I can personally confirm that, without my glasses, I can easily see both the bending effect and the sharpening of background features when I move my finger in front of my eye. I can even see a hint of astigmatism (which I know I have; my glasses have some cylindrical correction to fix it) in the fact that, in some orientations, I can see the background features bending not just away from my finger, but also slightly sideways. With my glasses on, these effects almost but not quite disappear, suggesting that my current prescription may be just a little bit off.
The following is multiple choice question (with options) to answer.
What is another term for nearsightedness? | [
"glaucoma",
"myopia",
"anemia",
"hypoxia"
] | B | Nearsightedness, or myopia, is the condition in which nearby objects are seen clearly, but distant objects are blurry. It occurs when the eyeball is longer than normal. This causes images to be focused in front of the retina. Myopia can be corrected with concave lenses. The lenses focus images farther back in the eye, so they are on the retina instead of in front of it. |
SciQ | SciQ-176 | nuclear-physics, protons
Atoms are attracted to atoms through electromagnetism covalent bonds, ionic bondings and electromagnetic residual forces,. The nuclear force is too short range to affect the atoms: size of nucleus order of 10^-15 cm, size of atom order 10^-10 ; and the electron shells do not allow closer contact.
The following is multiple choice question (with options) to answer.
What are the areas located at fixed distances from the nucleus of the atom? | [
"orbit points",
"energy levels",
"molar levels",
"atomic regions"
] | B | Basic to Bohr’s model is the idea of energy levels. Energy levels are areas located at fixed distances from the nucleus of the atom. They are the only places where electrons can be found. Energy levels are a little like rungs on a ladder. You can stand on one rung or another but not between the rungs. The same goes for electrons. They can occupy one energy level or another but not the space between energy levels. |
SciQ | SciQ-177 | quantum-mechanics, harmonic-oscillator, fermions
Thank you. In general, any states of any energy can be filled - it just depends on the initial conditions. We often consider situations where the lowest-energy states are filled because of statistical mechanics - this is the state of thermal equilibrium at zero temperature, which is often a realistic approximation. But if the system isn't at thermal equilibrium at zero temperature, then other states are possible.
The following is multiple choice question (with options) to answer.
In which state of matter do particles take the shape of their container, but cannot expand to fill it? | [
"chemical",
"gas",
"mixture",
"liquid"
] | D | A liquid is a state of matter in which particles can slip past one another and take the shape of their container. However, the particles cannot pull apart and spread out to take the volume of their container. |
SciQ | SciQ-178 | climate-change, geography, rivers, rainfall, agriculture
Today Climate change and its consequences are some of the biggest challenges facing Humanity, with water scarcity being the big factor in Sub-Sahara Africa.
By Ultimately raising the Rainfall in the entire Southern Africa, through the managed and controlled filling and utilization of the Natural 30 000 - 60 000 square km of evaporation pans more regularly, will this not lower the extreme temperatures (day and night temperatures due to water absorbing much of the daytime heat and releasing it during the night) and drought patterns Southern Africa has experienced, and by all predictions are bound to worsen and could become more extreme?
In effect, creating a second Okavango Delta, but considerably bigger - large parts of Chobe.
A study of such a magnitude will need large amounts of research in multidisciplinary sciences, from Archaeology to Agriculture to Economics, and a much broader field of expertise - the biggest being Politics!
Could such a mammoth project not be but one small answer to a much bigger Climate Change challenge facing the Earth? (and ultimately send a bit of rain to my little piece of land in the Waterberg in the long dry winter months when we receive those dry West Winds - and fires become a serious hazard - simply by adding a bit of moisture from the vast pans Botswana are so blessed with!)
My mind has been going in circles as to the feasibility of such a mammoth, yet so cheap and easily implementable idea?
Any ideas? We agree that additional evaporation enhances energy transport from the surface to the atmosphere and intensifies the hydrological cycle and cloud formation, and that some of the most serious climate change issues such as:
The following is multiple choice question (with options) to answer.
Runoff is likely to cause more what if the land is bare? | [
"erosion",
"abrasion",
"sediment",
"weathering"
] | A | Runoff is likely to cause more erosion if the land is bare. Plants help hold the soil in place. The runoff water in Figure below is brown because it eroded soil from a bare, sloping field. Can you find evidence of erosion by runoff where you live? What should you look for?. |
SciQ | SciQ-179 | bond, ions, ionic-compounds
Title: Why is the overall charge of an ionic compound zero?
My textbook simply says:
Since an ionic compound consists of equal number of positive and negative ions, the overall charge of an ionic compound is zero.
But why is the number of positive and negative ions equal?
Can’t an ionic compound can have an unequal number of negative and positive ions? Why or why not? Sodium needs to lose 1 Electron to attain stable electronic configuration and chlorine needs to gain 1 electron to stable electronic configuration.
In a big picture, the electron was transferred from sodium to chlorine in the same neutral crystal. No electron was supplied to the crystal from outside, it was already in the same system before and after the formation of NaCl.
If the system before formation of NaCl was neutral then it will be neutral even after the formation of NaCl crystal. That may be the reason.
The following is multiple choice question (with options) to answer.
Cations have what type of charge? | [
"constant",
"positive",
"negative",
"neutral"
] | B | Cations have positive charges, and anions have negative charges. |
SciQ | SciQ-180 | neuroscience, neuroanatomy
Likewise, the spinal chord is structured into sensory and motor regions. In summary, the spinal chord consists of: 1) cell bodies (motor, sensory, inter; grey in the picture), 2) ascending axons (blue), 3) descending axons (red). Similar to nerves, axons going up or down the spinal chord are bundled into "tracts". Sensory axons are never bundled with motor axons, making it possible to create a map of the spinal chord in cross-section.
The tracts' names might be a bit confusing at first, but on second look are actually pretty self-explanatory. They usually contain where the axons come from and where they are going in order to synapse with other neurons. E.g. the spinocerebellar tract is formed of axons coming from the spine and going to the cerebellum. Given that the cerebellum is near the brain and the spine is further down, this is obviously an ascending tract - and ascending tracts are always sensory (because sensory information never needs to be carried downwards due to the brain being at the top).
Where it gets blurry
The sensory/motor separation isn't always as clear as I've described above. In fact, nerves (bundles of axons anywhere in the body outside of the CNS) will usually contain both sensory and motor pipelines. In particular, the cranial nerves (12 of the most important nerves) all include sensory and motor components for the respective part of the body that they manage. E.g. the facial nerve contains both the sensory connections for parts of the tongue and the motor connections that control facial muscles.
Another more complex example is pain sensation, where interneurons in the spinal chord can feed back onto sensory neurons and inhibit their signals, or axons can inhibit those packed in the same nerve bundle simply due to electrical effects.
The following is multiple choice question (with options) to answer.
What organ is subdivided into ascending, descending, transverse and sigmoid parts? | [
"colon",
"lungs",
"heart",
"uterus"
] | A | Colon The cecum blends seamlessly with the colon. Upon entering the colon, the food residue first travels up the ascending colon on the right side of the abdomen. At the inferior surface of the liver, the colon bends to form the right colic flexure (hepatic flexure) and becomes the transverse colon. The region defined as hindgut begins with the last third of the transverse colon and continues on. Food residue passing through the transverse colon travels across to the left side of the abdomen, where the colon angles sharply immediately inferior to the spleen, at the left colic flexure (splenic flexure). From there, food residue passes through the descending colon, which runs down the left side of the posterior abdominal wall. After entering the pelvis inferiorly, it becomes the s-shaped sigmoid colon, which extends medially to the midline (Figure 23.21). The ascending and descending colon, and the rectum (discussed next) are located in the retroperitoneum. The transverse and sigmoid colon are tethered to the posterior abdominal wall by the mesocolon. |
SciQ | SciQ-181 | nitrogen
Step three is when plants and the animals that live of the plants die and breaks down into ammonia and other waste products (this is where many explanations of the nitrogen cycle usually starts). The waste products gets converted into ammonia by bacteria and the ammonia gets converted to nitrite and the entire cycle starts all over again.
Legumes have a symbiotic relationship with some bacteria that can fixate nitrogen (N2) https://aces.nmsu.edu/pubs/_a/A129/
sources:
https://science.howstuffworks.com/life/biology-fields/nitrogen-cycle.htm
https://www.britannica.com/science/denitrifying-bacteria
The rest is from my memory.
The following is multiple choice question (with options) to answer.
Ammonia, urea, and uric acid are examples of what kind of waste? | [
"oxygenous",
"nitrogenous",
"carbonous",
"sulphurous"
] | B | |
SciQ | SciQ-182 | dna, dna-sequencing, genomes, human-genome, mouse
I hope this is understandable, if you need any clarification on terms, please ask :)
The following is multiple choice question (with options) to answer.
What are variants of genes called? | [
"mutations",
"allergens",
"alleles",
"antigens"
] | C | Recall that our DNA is wound into chromosomes . Each of our chromosomes contains a long chain of DNA that encodes hundreds, if not thousands, of genes. Each of these genes can have slightly different versions from individual to individual. These variants of genes are called alleles . Each parent only donates one allele for each gene to an offspring. |
SciQ | SciQ-183 | evolution, mycology
Title: Why are some fungi poisonous? There are many poisonous fungi in nature. For example Amanita Phalloides.
What reasons could a fungus need poison for? Some species, like venomous snakes, use poison to kill other species as prey. But what about fungi? I can't think of any purpose for poison in fungi. If poison has no real function in fungi shouldn't evolution get rid of it? The same reason some plants are poisonous: to stop animals from eating them.
The visible part of the fungus is called, rather misleadingly, the fruiting body. It exists to produce and spread spores and thus produce the next fungal generation. Getting eaten, rather obviously, inhibits its ability to do this. Being poisonous discourages animals from eating the fruiting body and thus permits it to complete its life cycle.
The following is multiple choice question (with options) to answer.
Mushrooms are an example of what type of organism, which includes beneficial and toxic specimens? | [
"spores",
"bacteria",
"seeds",
"fungi"
] | D | Some of the best known types of fungi are mushrooms, which can be edible or poisonous ( Figure below ). Many species are grown commercially, but others are harvested from the wild. When you order a pizza with mushrooms or add them to your salad, you are most likely eating Agaricus bisporus , known as white or button mushrooms, the most commonly eaten species. Other mushroom species are gathered from the wild for people to eat or for commercial sale. Many mushroom species are poisonous to humans. Some mushrooms will simply give you a stomachache, while others may kill you. Some mushrooms you can eat when they are cooked but are poisonous when raw. So if you find mushrooms in the wild, don't eat them until you are certain they are safe!. |
SciQ | SciQ-184 | evolution, bioinformatics, sequence-analysis, methods, systems-biology
Title: Is there a system biology approach to compare pathways or famillies of proteins from an evolutionary point of view for the same organism? I would be interested to know if there is a method/analysis or a set of methods to compare two groups of pathways or families of proteins.
I would specifically be interested by a system biology approach which takes all the components of the pathway or family of proteins. I would like to know if there is a method which can not only compare the similarity, homology, divergence and convergence of a family of proteins (like ribosomal proteins) between species but also between groups in the same organism.
For example I would like to compare the molecular components of vesicular trafficking pathways to the molecular components of non-vesicular pathway in the same organism saccharomyces cerevisiae (yeast).
I would greatly appreciate your suggestions. I am not sure that I completely understand, it would be a little easier if you described the problem you are trying to solve or what the motivation is.
However, I think that some of what you want to do can be accomplished by inferring gene/protein trees for each gene/protein of interest across different species (including paralogs, maybe?). This will allow you to see discordance or correlation of evolutionary rates of different genes/proteins across species.
THis kind of analysis is built into HyPhy, though I have never used it. There are also somewhat less involved methods for measuring distances between trees.
You might also be interested in protein co-evolution methods, depending on the question at hand.
Your mentioning systems biology methods suggests that you have something rather different in mind, as none of these things I suggest are really systems biology IMO, but I'm not sure what it would be. Possibly you are interested in integrating e.g. protein-protein interaction or metabolic network information as well, but that would probably involve something more homebrewed that might integrate some of these things.
Hope that helps.
The following is multiple choice question (with options) to answer.
Comparing what sequences provides clues to evolution and development? | [
"organisms",
"genome",
"DNA",
"genes"
] | B | 21.6 Comparing genome sequences provides clues to evolution and development. |
SciQ | SciQ-185 | thermodynamics, energy, statistical-mechanics
When Feynman says "The random motions of the atoms of a body furnish a measure of heat energy" what he is really referring to is a measure of the internal microscopic kinetic energy. That's because, in thermodynamics, the term "heat" strictly refers to the transfer of energy due solely to temperature difference. A body does not "contain" heat.
Hope this helps.
The following is multiple choice question (with options) to answer.
What is a measure of the average amount of energy of motion, or kinetic energy, a system contains called? | [
"variation",
"temperature",
"size",
"precipitation"
] | B | There are other units in chemistry that are important, and we will cover others in the course of the entire book. One of the fundamental quantities in science is temperature. Temperature is a measure of the average amount of energy of motion, or kinetic energy, a system contains. Temperatures are expressed using scales that use units called degrees, and there are several temperature scales in use. In the United States, the commonly used temperature scale is the Fahrenheit scale (symbolized by °F and spoken as “degrees Fahrenheit”). On this scale, the freezing point of liquid water (the temperature at which liquid water turns to solid ice) is 32°F, and the boiling point of water (the temperature at which liquid water turns to steam) is 212°F. Science also uses other scales to express temperature. The Celsius scale (symbolized by °C and spoken as “degrees Celsius”) is a temperature scale where 0°C is the freezing point of water and 100°C is the boiling point of water; the scale is divided into 100 divisions between these two landmarks and extended higher and lower. By comparing the Fahrenheit and Celsius scales, a conversion between the two scales can be determined: °C=(°F–32) × 59° Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-186 | nuclear-technology
Title: Smallest possible controlled chain reaction-based nuclear fission reactor? I think, it could be a reactor utilizing californium-242 (or, at least, weapon-grade U-235) cooled and moderated by heavy water.
Essentially, it were similar to an atomic bomb, but - of course - it would be optimized for stay around the equilibrial state.
The result were probably a very strong neutron source.
I think, it could be used for various things, mainly in the space applications.
Does any cost/size estimations about this ever created? The RM-1 Russian submarine reactor had a core of less than one cubic metre. It had about 100kg fuel load, which was 90% enriched (i.e. 90kg) Uranium 235. This was liquid-metal cooled [specifically a "eutectic lead-bismuth alloy (44.5 wt% lead, 55.5 wt% bismuth)" - source as below, p40], so didn't need a moderator.
Submarine 901 had in its right-board reactor just 30.6 kg of Uranium 235; this was at 20% enrichment, so a total fuel load of 153 kg.
These were controllable chain-reaction based reactors.
Source:
NKS-138 Russian Nuclear Power Plants for Marine Applications
Ole Reistad, Norwegian Radiation Protection Authority, Norway
Povl L. Ølgaard, Risø National Laboratory, Denmark
Published by Nordic Nuclear Safety Research, April 2006
ISBN: 87-7893-200-9
http://www.nks.org/scripts/getdocument.php?file=111010111120029
The following is multiple choice question (with options) to answer.
What is the minimum mass capable of supporting sustained fission called? | [
"particular mass",
"concentrated mass",
"baseline mass",
"critical mass"
] | D | U92235 + n01® B56141a + K3692r + 3n01 This hypothesis was confirmed by detecting the krypton-92 fission product. As discussed in Section 20.2 "Nuclear Reactions", the nucleus usually divides asymmetrically rather than into two equal parts, and the fission of a given nuclide does not give the same products every time. In a typical nuclear fission reaction, more than one neutron is released by each dividing nucleus. When these neutrons collide with and induce fission in other neighboring nuclei, a self-sustaining series of nuclear fission reactions known as anuclear chain reaction can result (Figure 20.16 "The Curve of Nuclear Binding Energy"). For example, the fission of 235U releases two to three neutrons per fission event. If absorbed by other 235U nuclei, those neutrons induce additional fission events, and the rate of the fission reaction increases geometrically. Each series of events is called a generation. Experimentally, it is found that some minimum mass of a fissile isotope is required to sustain a nuclear chain reaction; if the mass is too low, too many neutrons are able to escape without being captured and inducing a fission reaction. The minimum mass capable of supporting sustained fission is called the critical mass. This amount depends on the purity of the material and the shape of the mass, which corresponds to the amount of surface area available from which neutrons can escape, and on the identity of the isotope. If the mass of the fissile isotope is greater than the critical mass, then under the right conditions, the resulting supercritical mass can release energy explosively. The enormous energy released from nuclear chain reactions is responsible for the massive destruction caused by the detonation of nuclear weapons such as fission bombs, but it also forms the basis of the nuclear power industry. Nuclear fusion, in which two light nuclei combine to produce a heavier, more stable nucleus, is the opposite of nuclear fission. As in the nuclear transmutation reactions discussed in Section 20.2 "Nuclear. |
SciQ | SciQ-187 | organic-chemistry, aromatic-compounds, molecular-structure
Title: How does the molecule consisting of two bridged aromatic rings look in 3D? I can't understand how the following compound with bridged benzene rings looks like: This is a cyclophane, namely 4,8-dibromo[2.2]paracyclophane.
Lonsdale et al. [1] first structurally characterized [2.2]paracyclophane in 1960:
The molecule consists of two facing benzene rings linked in para-positions by two $\ce{(CH2)2}$ bridges.
As a result of steric hindrance, the benzene rings are each bent into a boat-shape, but even so, their maximum distance apart in the molecule is only 3.09 Å, whereas the normal van der Waals distance is upwards of 3.4 Å.
[…]
The angle of bending of the benzene ring (14°) does not change
with temperature, but the aliphatic $\ce{CH2-CH2}$ bond appears to be unusually long at room temperatures* and has decreased by 0.07 Å at 93 °K. Moreover, although the distance between the two benzene rings does not change, there is a decrease of 0.03 Å in the overall length of the molecule from 291 to 93 °K.
[…]
Figure 4. Diagram showing projection of molecules at $0, 0, 0;$ $1/2, 1/2, 1/2$ and $0, 0, 1$ on to $(100).$
* The $\ce{CH2-CH2}$ bond length is 1.63 Å, which is above average 1.54 Å expected for the aliphatic $\ce{C-C}$ bond.
See CCDC entry DXYLEN for more details and an interactive 3D image.
Several related polysubstituted [2.2]paracyclophanes have been reported:
The following is multiple choice question (with options) to answer.
Many hydrocarbons are cyclic and adopt specific three-dimensional structures that influence their physical and what properties? | [
"radiation",
"chemical",
"electrical",
"liquid"
] | B | Many hydrocarbons are cyclic and adopt specific three-dimensional structures that influence their physical and chemical properties. |
SciQ | SciQ-188 | 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.
The secondary wall contains _________ , a secondary cell component in plant cells that have completed cell growth/expansion. | [
"lignin",
"glucogen",
"cellulose",
"cytoplasm"
] | A | Microtubules guide the formation of the plant cell wall. Cellulose is laid down by enzymes to form the primary cell wall. Some plants also have a secondary cell wall. The secondary wall contains a lignin, a secondary cell component in plant cells that have completed cell growth/expansion. |
SciQ | SciQ-189 | 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 does the cell cycle do? | [
"only divide cells",
"only reproduce cells",
"divide and reproduce cells",
"create new cells"
] | C | The cell cycle is a repeating series of events, characterizing the life of a eukaryotic cell. |
SciQ | SciQ-190 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
Inside the nasal area of the skull, the nasal cavity is divided into halves by the what? | [
"nasal septum",
"cell wall",
"cerebral cortex",
"cytoplasm"
] | A | Inside the nasal area of the skull, the nasal cavity is divided into halves by the nasal septum. The upper portion of the nasal septum is formed by the perpendicular plate of the ethmoid bone and the lower portion is the vomer bone. Each side of the nasal cavity is triangular in shape, with a broad inferior space that narrows superiorly. When looking into the nasal cavity from the front of the skull, two bony plates are seen projecting from each lateral wall. The larger of these is the inferior nasal concha, an independent bone of the skull. Located just above the inferior concha is the middle nasal concha, which is part of the ethmoid bone. A third bony plate, also part of the ethmoid bone, is the superior nasal concha. It is much smaller and out of sight, above the middle concha. The superior nasal concha is located just lateral to the perpendicular plate, in the upper nasal cavity. |
SciQ | SciQ-191 | bacteriology
Title: Extract bacteria from compost? I'm working on a project where I need to find certain cellulolytic bacteria. I was looking at this list : http://webcache.googleusercontent.com/search?q=cache:CrtQ9T6K7m8J:www.wzw.tum.de/mbiotec/cellmo.htm+&cd=1&hl=nl&ct=clnk&gl=be
How could I selectively separate one of the bacteria types that I had in mind from that list?
So how would I have to extract the bacteria from the compost? A first (and obvious) approach is the use of cellulose agar in order to isolate all the celluloltic bacteria in the sample. Be careful, however, since the nutrient requirements of some of those microbes may be higher and then they won't grow with only cellulose (they may need some other compounds, like a nitrogen source). Be careful with fungi, too.
If you have the proper equipment, it would be ideal to extract DNA and analyze the environmental rRNA 18s sequences. With this, you should be able to know if your bacteria is present in your sample. If so, proceed with the previous steps.
Once you had a set of suspected colonies, you must proceed with more specific culture media (wich would depend of the exact bacteria you're looking for. For example, if you're looking for Clostridium, you should try to grow your sample in an anaerobic jar and test the ability to reduce sulphur). With this approach, you may reach a point where you can't differenciate similar species. At this point, mollecular characterization is the best option, with the use of rRNA 18s again. Note that the mollecular approach, while relative expensive, can be performed in every step, so you can combine cultures and DNA analyses at will.
Lastly, if you're looking for an specific bacteria, it would be useful to know wich one is, so the community can give you more accurate responses.
The following is multiple choice question (with options) to answer.
Bacteria can be chemotrophs, which obtain what by breaking down chemical compounds in their environment? | [
"waste",
"energy",
"food",
"chemials"
] | B | Bacteria can also be chemotrophs. Chemosynthetic bacteria, or chemotrophs , obtain energy by breaking down chemical compounds in their environment. An example of one of these chemicals broken down by bacteria is nitrogen-containing ammonia. These bacteria are important because they help cycle nitrogen through the environment for other living things to use. Nitrogen cannot be made by living organisms, so it must be continually recycled. Organisms need nitrogen to make organic compounds, such as DNA. |
SciQ | SciQ-192 | ecology
Title: Do invasive species cause long-term damage to ecosystems they invade? Growing up in the U.S., I was warned at various times of the dire consequences of a variety of introduced pests (usually insects).
Japanese beetles, gypsy moths, and most recently the brown marmorated stink bug are all introduced pests that, at various times, were described as serious threats to our ecology.
These threats aren't confined to arthropods, either. The giant African land snail is causing a stir in Florida (indeed, Florida seems to suffer from an excessive variety of introduced species.
"Lack of native predators" is frequently cited as the primary reason many invasive species are considered such a risk to the ecology.
I understand that these introduced species can place tremendous pressure on native species that fill similar ecological niches, and may even push these species out of the region due to competition for food and habitat. However, do the overall ecologies that these species are introduced to adjust over long periods of time?
The numbers of Japanese beetles and gypsy moths don't seem anywhere as high as when I was a child. Has the ecosystem adjusted, or has the overpopulation self-corrected as the species ran low on food through over-consumption? Or are the populations still just as problematic now as they were 30 years ago, and I just am not seeing the bigger picture?
What is the long-term impact that we've seen from invasive, introduced species? Is there a significant difference on the long-term impact between introduced flora, arthropods, or mammals? The answer really depends on how you think of invasive. One extreme answer is to say that all things are relative, and that the concepts of local and invasive are all relative. This matters to a certain extent because ecologists draw a fuzzy line between invasive and naturalized. You could start with some basic species that we all think of as either good, local, or neutral. Take the earthworm. Most people think of it as a common native species, but the earthworm is actually an invasive species that has radically changed much of North America that came over with the Europeans. Similarly, brown trout are also invasive, coming to the US in the 1800's.
The following is multiple choice question (with options) to answer.
Habitat loss, introduced species, overharvesting, and global change are major threats to what? | [
"the earth's gravity",
"transportation",
"the sun",
"biodiversity"
] | D | |
SciQ | SciQ-193 | hematology, cardiology, blood-circulation, red-blood-cell, veins
Veins are not like impermeable rubber tubes, they are 'living' structures requiring, like all cells, Oxygen and glucose to survive. Smaller veins get the O2 from diffusion, while the larger veins need help from vasa vasorum, small blood bessels that bring blood to the walls of the veins.
The innermost cells lining veins are epithelial cells. They also line valves.
In the picture you posted, blood is not circulating well behind valves. The cause of hypoxia is that epithelial cells are continually removing O2 from the blood.
When enough O2 is removed to cause hypoxia, the endothelial cells may become damaged by the lack of O2, causing inflammation and (possibly) potentiating clot formation.
Activation of endothelial cells by hypoxia or possibly inflammatory stimuli would lead to surface expression of adhesion receptors that facilitate the binding of circulating leukocytes and microvesicles. Subsequent activation of the leukocytes induces expression of the potent procoagulant protein tissue factor that triggers thrombosis.
Mackman N. (2012). New insights into the mechanisms of venous thrombosis. The Journal of clinical investigation, 122(7), 2331–2336. doi:10.1172/JCI60229
The following is multiple choice question (with options) to answer.
What "plumbing" structures inside the veins maintain a unidirectional flow of blood despite the low blood pressure? | [
"pumps",
"valves",
"funnels",
"tubes"
] | B | |
SciQ | SciQ-194 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
What do we call the cartilaginous structure that surrounds the notochrod? | [
"clavicle",
"osteocytes",
"arcualia",
"membrane"
] | C | distinctly differ from the adult form, spending 3 to 15 years as suspension feeders. Once they attain sexual maturity, the adults reproduce and die within days. Lampreys possess a notochord as adults; however, this notochord is surrounded by a cartilaginous structure called an arcualia, which may resemble an evolutionarily early form of the vertebral column. |
SciQ | SciQ-195 | botany, mathematical-models, statistics, biostatistics, migration
Title: Biostatistics: Pollen dispersal directionality What Information am I looking for?
Think about a tree that is sending pollen all over the place. Because of wind, most pollen grain will go toward one direction. Imagine, we split the 2D area around the tree where pollen grains fall into two half disks of equal size. We chose the disks so that the number of pollen grains falling into one half-disk is minimized and the quantity of pollen falling in the other half-disk is maximized.
The information I need is what proportion of pollen grain falls into each disk? Is it $\frac{0.5}{0.5}$ (in which case the wind would have no effect) or is it something like $\frac{0.8}{0.2}$?
Where to get the information from?
I was reading this paper about pollen dispersal directionality and was trying to extract the info I need.
On pages 4 and 5 they explain their analysis under the section statistical procedure. More specifically, in the first paragraph of the 5th page, they seem to describe the meaning of the parameters that are trying to estimate. One of them is the so-called directionality parameter $\delta$. I don't understand how to interpret this parameter $\delta$. This parameter is part of a logistic regression I think (although the authors do not characterize it as such) of "mating success" $y$ against variables $d$ ("distance") and $h$ ("height") and an angular variable $a = \cos(\alpha_0 - \alpha)$. ($\alpha_0$ is the "presumed prevailing direction of effective pollen dispersal," which apparently is not estimated from these data.) The corresponding parameters of the model are $\beta$, $\gamma$, and $\delta$, respectively, hence
$$\phi_j = \Pr(y_j = 1) = \frac{\exp\left(\beta d_j + \gamma h_j + \delta a_j\right)}{\sum_{k=1}^r \exp\left(\beta d_k + \gamma h_k + \delta a_k\right)}$$
The following is multiple choice question (with options) to answer.
What is the process of the transfer of pollen from an anther to a stigma in angiosperms called? | [
"evolution",
"pollination",
"wind",
"grabation"
] | B | |
SciQ | SciQ-196 | human-biology, biochemistry, hematology, red-blood-cell, human-physiology
Title: Besides hemoglobin, what proteins are present in red blood cells? I knew that mature red blood cells (RBCs) lacked nuclei, but I wasn't aware until just now that they also lacked ribosomes and mitochondria. Most cells in the human body all contain a common laundry list of housekeeping proteins and RNAs (including mitochondrial proteins and ribosomal RNAs), but I guess RBCs lack a number of them. Do they still have all of the other organelles? Obviously hemoglobin (and to a lesser extent carbonic anhydrase) makes up a large portion of the dry weight of RBCs, but are other proteins still present? If so, what are their relative abundances?
For example, do red blood cells have any of the normal metabolic (i.e. ATP producing) proteins? Obviously they don't have any of the TCA cycle proteins, but do they still have the glycolysis ones? Reticulocyte stage is when the ribosomes are still present and after that no new protein synthesis occurs. However RBCs have a lot of proteins and major proteins other than haemoglobin are cytoskeletal proteins and ion channels/pumps (In fact, cytoskeletal proteins are more abundant than haemoglobin). It is the Na+-K+-ATPase that consumes most ATP. As you correctly identified the RBCs produce ATP via glycolysis and glycolytic enzymes are also present. Note that deficiency of pyruvate kinase leads to haemolytic anaemia.
For a detail on the proteins present in human RBSs, see this paper. They have studied the RBC proteome by ion-trap MS. The top 5 proteins (from Table-1) are:
No. Protein description Molecular mass (Da) Gi Number Sequence No. of identified
coverage(%) peptides
1 Spectrin α chain, erythrocyte 279,916.5 1174412 48.0 77*
2 Spectrin β chain, erythrocyte 246,468.1 17476989 48.0 76*
3 Ankyrin 1, splice form 2 206,067.9 105337 45.0 55
The following is multiple choice question (with options) to answer.
Despite its small size, an erythrocyte contains about 250 million molecules of what? | [
"calcium",
"plasma",
"hemoglobin",
"potassium"
] | C | |
SciQ | SciQ-197 | thermodynamics, statistical-mechanics, differentiation, mathematics
$$
(\text{# components})-(\text{# phases}) + 2 = 2
$$
This is the number of independent variables we need to describe the intensive properties of the mixture. In principle we can choose any two among $\{p, T, V, U, S \cdots\}$. Pressure and temperature is a very convenient pair because we can easily measure them and control them experimentally. However, any other set can be used. The equation you wrote,
$$
dU =
\left(\frac{\partial U}{\partial S}\bigg)_VdS
+
\right(\frac{\partial U}{\partial V}\bigg)_SdV
$$
is correct and is equivalent to
$$
dU = T dS - p dV
$$
Mixtures
The number of independent variables is always determined by Gibbs's rule. In a two-component one-phase system we have three independent variables. We normally choose the first two to come from $p, T, V, U, S \cdots$ and the third one is the mol fraction of one of the two components. Again, this is the number of variables we need to describe the intensive properties of the mixture. We may also write equations for the extensive properties of mixture but I will not go there unless there is a question about it.
The following is multiple choice question (with options) to answer.
How many variables are used to describe the condition of a gas? | [
"one",
"five",
"four",
"three"
] | C | Recall from the kinetic-molecular theory that gas particles move randomly and in straight lines until they elastically collide with either other gas particles or with one of the walls of the container. It is these collisions with the walls of the container that defines the pressure of the gas. Four variables are used to describe the condition of a gas. They are pressure , volume , temperature , and the amount of the gas as measured by the number moles . We will examine separately how the volume, temperature, and amount of gas each affect the pressure of an enclosed gas sample. |
SciQ | SciQ-198 | dark-matter
So it's actually a theory to explain a phenomenon.
Dark energy, on the other hand, is an experimental phenomenon. We don't have a good theory to explain it. But it's a phenomenon responsible for many different problems. There's quite a lot of evidence that says, "Something odd is going on."
What I mean by all this is that there's a heck of a lot of evidence for them. Our theories of them were created to explain evidence, and not vice versa (evidence gathered to support or refute a theory).
I advise, once again, that you look at the Wikipedia articles on both concepts to start learning more (especially the sections on evidence). Physics and Astronomy have plenty of good information. arXiv has many pre-prints that may be helpful. And there are lots of books, magazines, and (reputable) web sites that can give you even more detailed information.
The following is multiple choice question (with options) to answer.
What is a suggested explanation for a phenomenon or a suggested explanation for a relationship between many phenomena called? | [
"hypothesis",
"query",
"system",
"process"
] | A | In order to explain the observed phenomenon, scientists develop a number of possible explanations, or hypotheses. A hypothesis is a suggested explanation for a phenomenon or a suggested explanation for a relationship between many phenomena. Hypotheses are always based on evidence that can be tested by observation or experimentation. Scientific investigations are required to test hypotheses. Scientists mostly base hypotheses on prior observations or on extensions of existing scientific explanations. |
SciQ | SciQ-199 | 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.
Land plants are classified into two major groups according to the absence or presence of what tissue? | [
"disease",
"root",
"bacterial",
"vascular"
] | D | The Major Divisions of Land Plants Land plants are classified into two major groups according to the absence or presence of vascular tissue, as detailed in Figure 14.8. Plants that lack vascular tissue formed of specialized cells for the transport of water and nutrients are referred to as nonvascular plants. The bryophytes, liverworts, mosses, and hornworts are seedless and nonvascular, and likely appeared early in land plant evolution. Vascular plants developed a network of cells that conduct water and solutes through the plant body. The first vascular plants appeared in the late Ordovician (461–444 million years ago) and were probably similar to lycophytes, which include club mosses (not to be confused with the mosses) and the pterophytes (ferns, horsetails, and whisk ferns). Lycophytes and pterophytes are referred to as seedless vascular plants. They do not produce seeds, which are embryos with their stored food reserves protected by a hard casing. The seed plants form the largest group of all existing plants and, hence, dominate the landscape. Seed plants include gymnosperms, most notably conifers, which produce “naked. |
SciQ | SciQ-200 | human-biology, physiology
Title: Why should or shouldn't we allow the human body to take its natural course? For example, when you are sick but don't feel thirsty, this could be due to baroreceptor reflex that is attempting to readjust salt and water balancing.
Why shouldn't a patient be left thirsty and let the body to adjust until he or she feels thirsty again? I am assuming that your question is: "why can a human intervention improve health?". Let me know if I misunderstood your question.
Why can a human intervention improve health?
Let's first avoid going into the details of your example. It is quite obvious that human intervention can often improve health in a way that your body alone cannot. To me, an intuitive way to classify the reasons why human intervention are important to improve health into two categories.
The body does not always react in an adaptive manner.
Example: Anaphylaxis is a serious and sudden allergic reaction that may cause death. An allergic reaction is what is happening when your immune system recognize a chemical as a infectious element while it is not. The reaction of the body is not adaptive and taking medication such as an anti-histaminic can force the body to stop this "stupid" reaction.
Note: There are reasons why the body cannot be always perfect but it is a bit long to make an overview here. There is stochasticity in the developmental processes, there is genetic variation for example due to always occurring deleterious mutations, there is also an arms race between parasites and host. This arm race leads parasites to take advantage of normal host physiological pathways. There are tons of other reasons that relate to the stochasticity and to the physic and physiological constraints of evolutionary processes.
The body sometimes cannot (physical constraint) produce the action that is required to be performed to improve health.
Example: If you have an important wound, then a human-made compression can by far improve your chance of the survival. The body is not able by itself to simulate this external compression to prevent blood to exit the body through the wound.
The following is multiple choice question (with options) to answer.
What type of treatment is necessary for anaphylaxis? | [
"allergy shot",
"intensive care",
"emergency",
"outpatient"
] | C | In some people, a food allergy can trigger a severe allergic reaction called anaphylaxis. Emergency treatment is critical for anaphylaxis. Untreated, anaphylaxis can cause a coma or death. Anaphylaxis is vary rare. The vast majority of people will never have an anaphylactic reaction. The life-threatening symptoms of anaphylaxis include:. |
SciQ | SciQ-201 | acid-base, ionic-compounds, erratum
Title: Are all ionic compounds salts? According to Wikipedia:
A salt is an ionic compound that can be formed by the neutralization
reaction of an acid and a base.
Are all ionic compounds salts? Are all salts ionic compounds? Interestingly, IUPAC states that a "salt" is "a chemical compound consisting of an assembly of cations and anions". Under this definition, all ionic compounds are salts, and all salts are ionic compounds.
Therefore, something like sodium hydroxide ($\ce{Na+OH-}$, definitely an ionic compound) could actually be correctly called a salt. This clashes with the commonly taught high-school level definition of a salt ("the product of an acid-base reaction"), unless you consider very general definitions of acids and bases such as the Usanovich definition, whereby sodium metal $\ce{Na^0}$ is an electron donor (and therefore a base) and water is an electron acceptor (and therefore an acid).
That said, the high-school definition is too simplistic. It is common for compounds to be an acid, a base and a salt all at the same time; consider for example sodium bicarbonate ($\ce{Na+HCO3-}$). It is made of cations and anions, and therefore is definitely a salt. Furthermore, it can act as both a Brønsted–Lowry acid ($\ce{NaHCO3 + OH- -> H2O + Na+ + CO3^2-}$) and as a Brønsted–Lowry base ($\ce{NaHCO3 + H+ -> Na+ + H2CO3}$). Another amusing example is hydrazinium sulfate, a salt, acid and base, where both the cation and anion are also both acids and bases!
The following is multiple choice question (with options) to answer.
What substances, which are distinct from acids and bases, form when ions form ionic bonds? | [
"oils",
"vitamins",
"salts",
"water molecules"
] | C | Salts Recall that salts are formed when ions form ionic bonds. In these reactions, one atom gives up one or more electrons, and thus becomes positively charged, whereas the other accepts one or more electrons and becomes negatively charged. You can now define a salt as a substance that, when dissolved in water, dissociates into ions other than H+ or OH–. This fact is important in distinguishing salts from acids and bases, discussed next. A typical salt, NaCl, dissociates completely in water (Figure 2.15). The positive and negative regions on the water molecule (the hydrogen and oxygen ends respectively) attract the negative chloride and positive sodium ions, pulling them away from each other. Again, whereas nonpolar and polar covalently bonded compounds break apart into molecules in solution, salts dissociate into ions. These ions are electrolytes; they are capable of conducting an electrical current in solution. This property is critical to the function of ions in transmitting nerve impulses and prompting muscle contraction. |
SciQ | SciQ-202 | nomenclature, history-of-chemistry, amino-acids
One can only hypothesise what they meant by "associations that might be helpful in remembering the code" in the case of N/Q/D/E. My best guess is:
D and E were possibly chosen for aspartic and glutamic acids because they were the only consecutive pair of letters left, emphasising their chemical similarity. Aspartic acid is shorter than glutamic acid by one methylene group (CH2), so it gets the earlier letter D.
Glutamine sounds like Q-tamine. If you don't think it sounds similar, repeat it 50 times until you do.
AsparagiNe was assigned N.
Reference
IUPAC-IUB Joint Commission on Biochemical Nomenclature. Nomenclature and Symbolism for Amino Acids and Peptides: Recommendations 1983. FEBS J. 1984, 138 (1), 9–37. DOI: 10.1111/j.1432-1033.1984.tb07877.x. A HTML version (perhaps more user-friendly) can be found at this address.
The following is multiple choice question (with options) to answer.
What is the name for biochemical compounds that consist of one or more chains of small molecules called amino acids? | [
"proteins",
"lipids",
"protons",
"hormones"
] | A | Proteins are biochemical compounds that consist of one or more chains of small molecules called amino acids. Amino acids are the monomers of proteins. There are only about 20 different amino acids. The sequence of amino acids in chains and the number of chains in a protein determine the protein’s shape. Shapes may be very complex. You can learn more about the shapes of proteins at this link:. |
SciQ | SciQ-203 | acid-base, ph
Title: When an acid is added to water, why does the hydroxide ion concentration decrease? At equilibrium in pure water, we have
$$\ce{[H_3O+][OH-]} = 10^{-14}$$
Since $\ce{H3O+}$ and $\ce{OH-}$ ions are produced in pairs, we may conclude
$$\ce{[H_3O+]}=\ce{[OH-]} = 10^{-7}$$
So far so good. But shouldn't things change when we introduce a new substance into water ? I mean why does the first equation above hold no matter what ?
Also when I introduce $\ce{H2SO4}$ into the water, it doesn't just give a $\ce{H+}$ ion, it also gives $\ce{HSO4-}$ ion. Shouldn't these new negative ions change the behavior of water? Why does my textbook never talk about these new negative ions? Help appreciated. Thanks! Your question title is a bit misleading, but i try to answer all the small questions in you question text.
The equation $[\ce{H3O^+}][\ce{OH^-}]$ holds true, if other parameters (like T) are constant. Keep in mind, the power of hydroxide decreases, whereas the power oxonium increases. Being equal in the equation and considering how logs are being computed,bthey will add up to 14 every time.
Regarding the introduced $\ce{HSO4^-}$, they don't contribute to pH by definition. On the other hand, they alter the behaviour of the water, by increasing its conductivity.
Your textbooks don't talk about the other negative ions in acidic or alkaline solutions, because they don't directly contribute to the values of pH or pOH by definition. In cases of polyacids like sulfuric acid, ions like $\ce{HSO4^-}$ are accounted for by using a different formula to calculate the actual pH value, but the "not-hydrogen" part is largely irrelevant in the behaviour of the solution itself.
The following is multiple choice question (with options) to answer.
What are the ionic compounds that produce negative hydroxide ions when dissolved in water? | [
"isotopes",
"acids",
"bases",
"enzymes"
] | C | Bases are ionic compounds that produce negative hydroxide ions (OH - ) when dissolved in water. An ionic compound contains positive metal ions and negative nonmetal ions held together by ionic bonds. (Ions are atoms that have become charged particles because they have either lost or gained electrons. ) An example of a base is sodium hydroxide (NaOH). When it dissolves in water, it produces negative hydroxide ions and positive sodium ions (Na + ). This can be represented by the equation:. |
SciQ | SciQ-204 | atoms, terminology
Title: What is a neutral atom? I was told that an atom's atomic number is defined as follows:
The number of electrons or protons present in a neutral atom is called atomic number. It is represented by Z.
What does neutral mean here? Why isn't it just "..present in an atom..."? Electrons and protons are charged particles. The electrons have negative charge, while protons have positive charge. A neutral atom is an atom where the charges of the electrons and the protons balance. Luckily, one electron has the same charge (with opposite sign) as a proton.
Example: Carbon has 6 protons. The neutral Carbon atom has 6 electrons. The atomic number is 6 since there are 6 protons.
The following is multiple choice question (with options) to answer.
The atomic number of tungsten is 74. therefore, in a neutral atom of tungsten, there are 74 electrons. the atomic number of argon is 18. therefore, in a neutral atom of argon, there are how many electrons? | [
"36",
"74",
"18",
"9"
] | C | The atomic number of tungsten is 74. Therefore, in a neutral atom of tungsten, there are 74 electrons. The atomic number of argon is 18. Therefore, in a neutral atom of argon, there are 18 electrons. |
SciQ | SciQ-205 | electrochemistry
Title: What's the name of this electrolysis device? I've seen it in a couple of videos, it's used to electrolyze water in 2 different containers at the same time to make a comparison and thus is very handy.
What is it called (besides just a hydrolizer)? It's a precipitator, also known as TDS indicator.
The following is multiple choice question (with options) to answer.
What is the apparatus used for carrying out an electrolysis reaction? | [
"an electrolytic cell",
"an aqueous cell",
"Golgi apparatus",
"catalyst"
] | A | An electrolytic cell is the apparatus used for carrying out an electrolysis reaction. In an electrolytic cell, electric current is applied to provide a source of electrons for driving the reaction in a nonspontaneous direction. In a voltaic cell, the reaction goes in a direction that releases electrons spontaneously. In an electrolytic cell, the input of electrons from an external source forces the reaction to go in the opposite direction. |
SciQ | SciQ-206 | optics, astronomy, reflection, metals, telescopes
I used a good lens, which is why the effect is so small, but this shows the principle behind it.
Exhibit D
This is a microwave door - it is opaque to microwaves, but as you can see, lets visible light through. (See Faraday Cage)
Exhibit E
WiFi. It can pass through walls and doors.
It should be clear now that light doesn't exactly behave like what our brain calls "light"
Finally
I hope this helps. As you can see - WAAAY to long for a comment.
The following is multiple choice question (with options) to answer.
What two ways may light be transmitted? | [
"magnified or scattered",
"absorption and refraction",
"refracted or scattered",
"reflected or refracted"
] | C | Transmitted light may be refracted or scattered. When does each process occur?. |
SciQ | SciQ-207 | physiology, homework
Title: Order of events in hibernation
Arrange this in sequence :
i. Heat loss exceeds heat production.
ii.As body temperature falls, heat loss decreases.
iii.Body temperature equals environmental temperature.
iv.Metabolic activities fall to the basal level.
I am confused between i,iii,ii,iv and iv,i,ii,iii. I think the order i,ii,iii should be correct, since the fall in temperature occurs after the heat loss exceeds production and will continue only till the temperature equals the ambient temperature. iv is the reason for i. Hence iv,i,ii,iii sounds pretty convincing to me.
With i,iii,ii,iv , the main problem is that there can not be any appreciable fall in temperature ii after the temperature equals the environmental temperature iii. And iv seems more probably to be the reason for i rather than the reverse
The following is multiple choice question (with options) to answer.
Triggered by changes in the environment, migration and hibernation occur as cycles on what temporal basis? | [
"seasonally",
"bi-annually",
"monthly",
"annual"
] | D | Examples of behaviors with annual cycles include migration and hibernation. Both are innate behaviors. They are triggered by changes in the environment, such as the days growing shorter in the fall. |
SciQ | SciQ-208 | 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.
What pair of tubes that extends toward the ovaries features a fringelike structure that sweeps eggs inside? | [
"ovarian tubes",
"golgi apparatus",
"vas deferens",
"fallopian tubes"
] | D | Extending from the upper corners of the uterus are the two fallopian tubes. Each tube reaches (but is not attached to) one of the ovaries. The ovary end of the tube has a fringelike structure that moves in waves. The motion sweeps eggs from the ovary into the tube. |
SciQ | SciQ-209 | classical-mechanics, home-experiment, equilibrium
You can possibly liken your pile of stones like this where a very, very small push will not disturb them but a small push will?
A good example of balance is the bird on the end of a finger which is in stable equilibrium.
The following is multiple choice question (with options) to answer.
In most animals, what sense is related to balance or equilibrium? | [
"hearing",
"tasting",
"feeling",
"vision"
] | A | |
SciQ | SciQ-210 | python, python-3.x, console, shell
you will then
print(NEWS)
The master directory
"/media/GENERAL/Projects/files"
Why this directory? Why can't the user change this? He/she may want to change the location where the files are saved.
You are still sleeping
I said this, others said this, but I will repeat it:
sleeping does not make the terminal feel retro, it is seriously annoying!
Dealing with files with with
Repetita iuvant // repeating helps
with is a nicer way of dealing with files, even the official docs recommend
it.
The commands dictionary
Please go back to my previous answer and re-read this part: it is very important.
The following is multiple choice question (with options) to answer.
Terminal pods are located at the end of what? | [
"spines",
"stems",
"leaves",
"fruits"
] | B | Mendel investigated seven different characteristics in pea plants. In this chart, cotyledons refer to the tiny leaves inside seeds. Axial pods are located along the stems. Terminal pods are located at the ends of the stems. |
SciQ | SciQ-211 | development
Title: How detachment/separation works in biology? It might be a strange question, but I'm interested in the mechanics of separation/detachment during asexual reproduction, for example when an organism reproduces by budding (I don't mean cellular budding like baker's yeast). When the newly formed body is fully matured it detaches itself from the parent / original body.
It might not be caused by a specific tissue, as animals with not so differentiated bodies are (also) capable of such, but I could easily be wrong. Is this (the detachment) triggered by changes in the cell membrane? I can't really think of other explanations. Reproductive budding and what you call 'cellular budding' are really highly related processes. Budding as a form of reproduction essentially partitions protein aggregates and damaged cellular components into the host or mother and builds fresh or 'young' cells on the opposite side of a partition. To begin understanding this look at Saccharomyces cerevisiae (budding yeast) which forms protein rings (from the septin proteins) at the membrane, around the bud neck which separates the mother and daughter cells Hartwell 1971. This ring acts a partition that in part, withholds protein aggregates and certain proteins from diffusing from the mother to the daughter. This protein ring is an example of how cells limit diffusion of proteins and cellular components to the daughter cell. Another good example that comes to mind is Linder 2007, though it is done in E Coli, not budding yeast, where mother cells maintain protein aggregates and age, while the daughter cells are given fresh components and are therefore more fresh and 'young'.
Now like you mention, imagine this process in a multicellular organism to be fundamentally the same. At some point the multicellular organism will start an outgrowth of cells, while restricting what materials are given to the daughter cells to maintain their youth. And eventually a new organism will have been created. Some of the details will be different, but the fundamental process is is quite similar. In that you start with an old cell that creates a new cell from scratch, but rather than splitting all cellular components equally between mother and daughter, the daughter cells is made in peak condition while the mother cell retains much of the cell 'junk' like protein aggregates.
Hopefully that starts to answer your question.
The following is multiple choice question (with options) to answer.
What forms when the spores from two parents fuse during sexual reproduction? | [
"spirogyra",
"monospore",
"xerophyte",
"zygospore"
] | D | Sexual reproduction occurs when spores from two parents fuse and form a zygospore. |
SciQ | SciQ-212 | galaxy
Title: How many galaxies have been discovered? I know Andromeda is our nearest galaxy. But how many known galaxies have been discovered and what are they? First, the nearest galaxy to ours is not Andromeda, according to the NASA based page "The Nearest Galaxies", it was until recently considered to be the Canis Major Dwarf Galaxy at approximately 42,000 light years away. However, recently, there is suggestion that the closer Omega Centauri Globular Cluster may be a disrupted dwarf galaxy (Another source).
Now, in answer to your other query of how many galaxies there are - there is a global project called Galaxy Zoo which is attempting to catalogue and classify all observed galaxies, so far, according to the Galaxy Zoo for astronomers page, thus far they have
the entire Sloan Digital Sky Survey spectroscopic sample and all existing Hubble Space Telescope surveys (around 1.5 million galaxies in total).
Pictured: The Hubble Ultra-Deep Field which contains over 10,000 objects, the majority of which are galaxies. The image is only a bit over 3 arcminutes across--a tiny sliver of the sky.
The following is multiple choice question (with options) to answer.
What is the name of the galaxy we live in? | [
"milky way",
"Centaurus A",
"Andromeda",
"Bode's Galaxy"
] | A | Like other spiral galaxies, our galaxy has a disk, a central bulge, and spiral arms. The disk is about 100,000 light-years across and 3,000 light-years thick. Most of the Galaxy’s gas, dust, young stars, and open clusters are in the disk. |
SciQ | SciQ-213 | genetics, botany, food, ethnobiology, seeds
Title: How are oranges in the US or anywhere made seedless? How are oranges in the US or anywhere made seedless? Please explain the broad principles and not the technicalities. Oranges and other fruits are generally not actively made seedless. Rather, seeds may fail to develop due to either lack of fertilization (pollination) or a natural tendency. The natural production of unfertilized and thus seedless fruit is called Parthenocarpy.
To quote the Scientific American article (3) mentioned by Oreotrephes:
Fruit development normally begins when one or more egg cells in the
ovular compartment of the flower are fertilized by sperm nuclei from
pollen. In some plants, however, fruit develops without fertilization,
a phenomenon known as parthenocarpy. Parthenocarpic fruit has
advantages over seeded fruit: longer shelf life and greater consumer
appeal.
The most frequent reasons for lack of seed development are pollination
failure, or nonfunctional eggs or sperm. In many plants,
self-incompatibility genes limit successful fertilization to
cross-pollination between genetically different male and female
parents. This property is exploited by citrus farmers who grow
seedless fruits, such as navel oranges and clementines. Because these
cultivars are self-incompatible, they fail to set seed when they are
planted in orchards of identical plants (clones). These plants have a
high frequency of parthenocarpy, however, so they still produce fruit.
Parthenocarpic varieties may arise from a lack of pollinators. From the Wikipedia page on Parthenocarpy:
Plants moved from one area of the world to another may not always be
accompanied by their pollinating partner and the lack of pollinators
has spurred human cultivation of parthenocarpic varieties. Some
parthenocarpic varieties have been developed as genetically modified
organisms.
To preserve the seedless trait, parthenocarpic trees can be propagated by grafting. It is possible that more kinds of seedless fruits will be engineered in the future (3):
Plant biologists have learned that if the plant hormone auxin is
produced early in ovule development, parthenocarpic fruit can grow on
plants that do not usually exhibit this property. Thus, genetic
engineering will most likely give consumers parthenocarpic fruit in
many other species in the near future.
The following is multiple choice question (with options) to answer.
What are the most common seedless vascular plants? | [
"trees",
"weeds",
"ferns",
"grasses"
] | C | Ferns are the most common seedless vascular plants ( Figure below ). They usually have large divided leaves called fronds. In most ferns, fronds develop from a curled-up formation called a fiddlehead ( Figure below ). The fiddlehead looks like the curled decoration on the end of a stringed instrument, such as a fiddle. Leaves unroll as the fiddleheads grow and expand. Ferns grow in a variety of habitats, ranging in size from tiny aquatic species to giant tropical plants. |
SciQ | SciQ-214 | evolution, psychology, sociobiology
Title: Female preference for males who are already in a relationship A common saying is that women are generally more attracted towards men who are already in a relationship, and this phenomena does seem to have its own place in popular culture that is not matched by a corresponding male preference for women who are already in a relationship.
From an intuitive viewpoint I think it would make sense from the woman's viewpoint in an system of information economics where the fact that a male is engaged in a successful relationship with another female, or several other females, might provide extra and positive information about the evolutionary value of the male.
But how about the possibility for a male to use the same trick?
Is there any empirical evidence for this behaviour at all either in humans or in other species, or is this just a cultural artefact in some human societies? If there is empirical support, is there a consensus on the plausible evolutionary pathways involved here? This is a widely researched topic in the overlap between social sciences and evolutionary biology. Evolution has become very influential in understanding human interaction and preferences.
This chapter from "The Adapted Mind : Evolutionary Psychology and the Generation of Culture" will give you an idea of how all this plays out in the big picture - its a fairly comprehensive review of many factors considered in human mate choice. The study may be psychological, but the logic is derived from biology these days. (stackexchange won't let me link to google books - you can search for the title and look at chapter 6).
Evolutionary tendencies will favor more successful offspring. But for people it includes not only the genetic qualities of the mate (appearance, height, disease resistance, health) but also social qualities (how reliable or willing a mate is to support offspring).
First off you can see that there are many many factors which women take into consideration in their preferences. Its commonly said they are more complex than men, but that's another question. You have to take a range of factors holistically including the social environment.
I can't find this particular issue addressed in the literature, but I think that it might be attractive to women in some social settings. If there is a lot competition for 'quality' mates or resources for instance - if you have very few secure males or pessimistic females might create pressure which would cause females to prefer males which were successful.
The following is multiple choice question (with options) to answer.
In a monogamous pairing, a male individual is generally paired with what other type of individual in a sexual relationship? | [
"drone",
"male",
"worker",
"female"
] | D | Visit this website (http://openstaxcollege. org/l/sex_selection) for informative videos on sexual selection. In monogamous systems, one male and one female are paired for at least one breeding season. In some animals, such as the gray wolf, these associations can last much longer, even a lifetime. Several explanations have been proposed for this type of. |
SciQ | SciQ-215 | mass, measurements
Title: How precise can current technologies measure the mass of an object? Masses of various objects are listed on this wikipedia page: Orders of magnitude (mass). For example, mass of an HIV-1 virus is on the order of 1 femtogram.
Are these data actually measured (which I really doubt), or calculated?
What is the most precise measurement technique we have to measure the mass of an object? The most precise measurement of the mass of an electron was reported by Sturm et al in Nature 506, 467–470 (27 February 2014), quoting a relative precision of $3\times 10^{-11}$, meaning they determined the mass to better than $3\times 10^{-41}~\rm{kg}$.
If that is not the best, at least it gives you an upper bound...
Note that if you could weigh such a small mass directly with scales on earth, the force would be equivalent to the gravitational pull of a mosquito (mass 2.5 mg) on a grain of sand (0.7 mg) at a distance of about 6 million kilometers - about 17 times the distance to the moon...
Astonishing.
Acknowledgement: CuriousOne's comment got me thinking about the measurement of the mass of the electron, and led me to the above analysis.
The following is multiple choice question (with options) to answer.
What is a mass spectrometer used to measure? | [
"partial atomic masses",
"relative atomic masses",
"optical atomic masses",
"subatomic masses"
] | B | Although the masses of the electron, the proton, and the neutron are known to a high degree of precision (Table 1.3 "Properties of Subatomic Particles*"), the mass of any given atom is not simply the sum of the masses of its electrons, protons, and neutrons. For example, the ratio of the masses of 1H (hydrogen) and 2H (deuterium) is actually 0.500384, rather than 0.49979 as predicted from the numbers of neutrons and protons present. Although the difference in mass is small, it is extremely important because it is the source of the huge amounts of energy released in nuclear reactions (Chapter 20 "Nuclear Chemistry"). Because atoms are much too small to measure individually and do not have a charge, there is no convenient way to accurately measure absolute atomic masses. Scientists can measure relative atomic masses very accurately, however, using an instrument called a mass spectrometer. The technique is conceptually similar to the one Thomson used to determine the mass-to-charge ratio of the electron. First, electrons are removed from or added to atoms or molecules, thus producing charged particles called ions. When an electric field is applied, the ions are accelerated into a separate chamber where they are deflected from their initial trajectory by a magnetic field, like the electrons in Thomson’s experiment. The extent of the deflection depends on the mass-to-charge ratio of the ion. By measuring the relative deflection of ions that have the same charge, scientists can determine their relative masses (Figure 1.25 "Determining Relative Atomic Masses Using a Mass Spectrometer"). Thus it is not possible to calculate absolute atomic masses accurately by simply adding together the masses of the electrons, the protons, and the neutrons, and absolute atomic masses cannot be measured, but relative masses can be measured very accurately. It is actually rather common in chemistry to encounter a quantity whose magnitude can be measured only relative to some other quantity, rather than absolutely. We will encounter many other examples later in this text. In such cases,. |
SciQ | SciQ-216 | genetics
Additional response added as requested:
I see what you are getting at - why do children seem like such individual and unique things sometimes?
In sexual reproduction, the offspring are the product of the shuffling of the parent's genomes through meiosis, where the pairs of chromosomes we have are combined to make a single chromosome that will be half of the children genome.
This process can result in completely novel combinations of genes while conveying many likenesses from the parent. I would guesstimate that this is the major cause of the uniqueness of offspring/children.
Also in mammals there are some cell lines which splice families of genes which will cause offspring to be potentially quite different from either parent. Immune genes for instance are created from scratch from a bunch of genes that the parents give. Making each offspring unique but also the product of the parent's genetic repertoire. This can be significant as it affects health and also to some extent attraction - studies have shown that people who smell attractive to us are immunologically distinct from us.
@David mentions epigenetic variation, which is a more recent significant development. During our life, the germline (sperm/egg) DNA may be chemically labelled depending upon environmental conditions we experience. A famous example is experiencing famine conditions, which caused the children to be born on the small side amongst other effects. More recent studies have shown that this is a widespread mechanism to control cells in our body during our lifetime as well as communicate to our offspring how life is. It is expected that this labeling does not affect us forever - the epigenetic labels change over the course of a generation quite often (we believe).
The following is multiple choice question (with options) to answer.
What combines sets of genes from two different parents leading to genetically diverse offspring? | [
"cellular reproduction",
"sexual reproduction",
"subject reproduction",
"sexual destruction"
] | B | |
SciQ | SciQ-217 | glaciology, antarctic, sea-ice
Fan et al. (2014) (3) describe an earlier idea that the increase in greenhouse gases and ozone depletion may cause an increase in the increased westerly winds, there is considerable uncertainty in the interaction between these factors (4).
Models from Holland et al. (2014) (4) suggest a link between Antarctic-wide ice thickness and area trends contributing to overall sea ice trends.
Related to the models above, several papers suggest that the mechanism is related to increases in meltwater fluxes from the Antarctic continent itself (2)(3). The meltwater flux is modelled to have increased during the southern summer, depositing greater amounts of cool freshwater into the surface layers of the surrounding Southern Ocean, resulting in cooler SSTs in the southern summer, potentially causing the increase in summer sea ice extent trend.
However, most critically, Holland et al. (2014) (4) note that the freshwater 'extraction' by sea ice is a small percentage of the actual fresh meltwater flux. Instead they model that instead of freshwater flux, the driver is based on trends of Antarctic ice thickness and area.
This means that the increase in sea ice is not a 'counter balance' for the ice melted from the continental ice sheets, but rather, according to the models, the increasing sea ice extent appears to be a symptom of the continental ice sheet melting.
References
(1) Simmonds 2015 Comparing and contrasting the behaviour of Arctic and Antarctic
sea ice over the 35 year period 1979–2013 Annals of Glaciology
(2) Bitanja et al. 2015 The effect of increased fresh water from Antarctic ice shelves on
future trends in Antarctic sea ice Annals of Glaciology
(3) Fan et al. 2014 Recent Antarctic sea ice trends in the context
of Southern Ocean surface climate
variations since 1950 Geophysical Research Letters
(4) Holland et al. 2014 Modeled Trends in Antarctic Sea Ice Thickness, Journal of Climate (Full text here)
The following is multiple choice question (with options) to answer.
Global warming will raise ocean levels due to melt water from glaciers and the greater volume of what? | [
"rainforests",
"rain",
"warmer water",
"greenhouse gases"
] | C | Range shifts are already being observed: for example, some European bird species ranges have moved 91 km northward. The same study suggested that the optimal shift based on warming trends was double that distance, suggesting that the populations are not moving quickly enough. Range shifts have also been observed in plants, butterflies, other insects, freshwater fishes, reptiles, and mammals. Climate gradients will also move up mountains, eventually crowding species higher in altitude and eliminating the habitat for those species adapted to the highest elevations. Some climates will completely disappear. The rate of warming appears to be accelerated in the arctic, which is recognized as a serious threat to polar bear populations that require sea ice to hunt seals during the winter months: seals are the only source of protein available to polar bears. A trend to decreasing sea ice coverage has occurred since observations began in the mid-twentieth century. The rate of decline observed in recent years is far greater than previously predicted by climate models. Finally, global warming will raise ocean levels due to melt water from glaciers and the greater volume of warmer water. Shorelines will be inundated, reducing island size, which will have an effect on some species, and a number of islands will disappear entirely. Additionally, the gradual melting and subsequent refreezing of the poles, glaciers, and higher elevation. |
SciQ | SciQ-218 | galaxy, gravity, star-systems
Title: Why are stars still distant from one another? Why are stars so far from each other? Shouldn't gravity pull them closer over time? And if the effects of gravity are negligible is there an explanation why stars have to be so distant from one another?
The closest star is Alpha Centauri (I think) and it is 4.4 light years away. The initial star formation regions were regions that have a high enough mass density to form a star. The density of the early universe was not constant at different locations. Some regions had high enough density to form a star, and some didn't.
When a star forms it draws in matter from a large distance away. This forms an accretion disk and leaves a temporary relatively empty space around the star at a large distance away. There is no way a star can form in this low mass region. Once you get further away from this region the matter density may return to a level where a star can form. But this region is far from a star.
Yes, gravity from a particular star is pulling at other stars but there are many stars pulling on the particular star of interest. So the net force on the star may be very small.
The following is multiple choice question (with options) to answer.
What are groups of young stars loosely held together by gravity called? | [
"closed clusters",
"galaxies",
"constellations",
"open clusters"
] | D | Open clusters are groups of young stars loosely held together by gravity. |
SciQ | SciQ-219 | evolution, speciation
Lastly, I consider whether primary and secondary sympatric speciation represent a mechanistic dichotomy, I suggest that primary and secondary contact can leave a similar genomic signature, when speciation is driven by tightly clustered or large effect loci. Arguably, the advent of affordable population genomic studies should place less focus on whether study systems result from primary or secondary contact and instead focus on the mechanistic aspects of the genomic architecture and making progress in identifying the conditions and processes under which natural and sexual selection can drive speciation, without extrinsic barriers to gene flow. TLDR
Sympatric speciation and allopatric speciation with later migration into the same habitat were historically diffucult to distinguish without looking at palaeo-biological data. The paper argues that while palaeo-genetics has made this easier, it is still difficult to distinguish pure sympatric speciation (which it calls primary) and sympatric speciation with a geneflow from an geographically separated (allopatrically speciated?) subpopulation (which it terms "secondary sympatric speciation" or "speciation with secondary gene flow", "...with secondary contact" etc.).
Speciation
Speciation is the divergence of one species (with one gene pool) into two different species (with different gene pools). It is obvious that this will happen if subpolulations are geographically separated and continue to adapt to their local conditions (allopatric speciation).
However, Mayr suggested (back in the 1940s) that there is another type of speciation that happens while the speciating populations share a habitat, and, consequently, while gene flow between these subpopulations is maintained until the speciation process is complete. This requires strong selection pressure towards two different ecological niches each with their associated adaptations.
Empirical examples have been discussed and called into question again. One cool and frequently discussed example is that of the apple maggot in North America that has developed from the hawthorn maggot after the introduction of apples in North America.
Debate
The following is multiple choice question (with options) to answer.
What does a pollinator pick up from its body and carry directly to another plant of the same species? | [
"seed",
"pathogen",
"pollen",
"spore"
] | C | Wind-blown pollen might land anywhere and be wasted. Another adaptation solved this problem. Plants evolved traits that attract specific animal pollinators. Like the bee in Figure below , a pollinator picks up pollen on its body and carries it directly to another plant of the same species. This greatly increases the chance that fertilization will occur. |
SciQ | SciQ-220 | acid-base, water, ions, ph
Title: Hydrogen peroxide from water Is it possible that $\ce{2 OH-}$ from water could react to form $\ce{H2O2}$?
I mean most autoionization forms $\ce{H3O+}$ and $\ce{OH-}$.
However I think it is possible that $\ce{H-}$ and $\ce{OH+}$ forms, though the amount formed of these 2 is small. This is from water acting as an acid and H+ acting as a base. The only "hydroxyl"-type species whose recombination has been observed to yield hydrogen peroxide are hydroxyl radicals.
$$\ce{HO^. + ^.OH -> H2O2}$$
In order to generate these hydroxyl radicals from water, a lot of energy has to be provided, typically by radiolysis (short wave uv, $\gamma$, electron beam).
The conceivable steps yielding $\ce{HO^.}$ are either
$$\ce{H2O -> H^. + ^.OH}$$
or
$$\ce{H2O -> H2O^{+.} + e-}$$
$$\ce{H2O^{+.} -> H+ + ^.OH}$$
The following is multiple choice question (with options) to answer.
What is formed when an oxygen atom picks up a pair of hydrogen ions from a solution? | [
"ammonia",
"turpentine",
"liquid",
"water"
] | D | |
SciQ | SciQ-221 | thermodynamics, steam
The steam pressure is roughly identical against the turbine and the pump; the pressure of the boiler section.
What makes the steam power the turbine instead of backing up and forcing the pump to turn backwards? - well, this one is simple, power delivered to the pump. But then how comes the turbine produces more power than the pump takes? The pump, after all, must overcome the same pressure that propels the turbine and deliver the same amount of water that is being ejected as steam. I'm missing some significant element of the device. What is it? Pressure is force/area, if the area offered by the pump impeller is smaller than the area against wich the steam must force its way out of the boiler, and both the turbine and the pump are linked, then, the same pressure will result in a smaller force on the pump than on the turbine.
Example :
Lets suppose that the pump is a piston pump, and on the steam side there is a piston engine (for simplicity). In a certain part of the cycle, both the pump piston and the engine piston valves are open towards the boiler (the pump is feeding water to the boiler and the engine is taking steam from the boiler).
The "face" of the pump piston has, lets say, a surface area of 10cm², while the steam engine piston has a surface area of 100cm². Lets suppose the pressure on the boiler is 200kPascal. This means that the pump piston will need to force its way against 200000N/M² * 0.001M² = 200N of force. While this pressure on the steam engine produces 200000N/M² * 0.1M² = 20kN. It's clear that in a direct linkage between the pump and the engine, the steam engine will produce much more force than the pump needs to feed water inside the boiler against the pressure gradient.
The following is multiple choice question (with options) to answer.
What does the driving of turbines by the heating of water to steam accomplish? | [
"generation of electricity",
"depletion of electricity",
"diffusion of electricity",
"absorption of electricity"
] | A | Nuclear reactors heat water to steam to drive a turbine for generation of electricity. |
SciQ | SciQ-222 | electromagnetism, energy, electric-circuits, integration
Title: Electromagnetic converters, differentials and integrals In the context of electromagnetic converters, a converter can be modeled by a system that receives electrical energy and outputs mechanical energy. At some point in my textbook, the authors present the following differential that represents a small change in the co-magnetic energy of the system:
$$ \mathrm dW_\mathrm{cmag} = \sum_{k=1}^n \phi_k di_k$$
where $\phi_k = \phi_k(i_1,i_2,...,i_n)$ the total flux generated by the currents $i_1,...,i_n$ in the $k$th winding/coil that is part of the system. $W_\mathrm{cmag}$ represents a co-magnetic energy of the system (state function). $\mathrm dW_\mathrm{cmag}$ is then simply a small change in the system's co-magnetic energy. They then do something that I'm not sure I understand, that is how they integrate $dW_\mathrm{cmag}$ in order to get $W_\mathrm{cmag}$:
$$W_\mathrm{cmag} = \int_{0,0,\ldots,0}^{i_1,i_2,\ldots,i_n} \sum_{k=1}^n \phi_k \mathrm di_k$$
The following is multiple choice question (with options) to answer.
What is a device that changes kinetic energy to electrical energy through electromagnetic induction? | [
"a windmill",
"an electric generator",
"a battery",
"a diesel engine"
] | B | An electric generator is a device that changes kinetic energy to electrical energy through electromagnetic induction. A simple diagram of an electric generator is shown in Figure below . In a generator, some form of energy is applied to turn a shaft. This causes a coil of wire to rotate between opposite poles of a magnet. Because the coil is rotating in a magnetic field, electric current is generated in the wire. If the diagram in Figure below looks familiar to you, that’s because a generator is an electric motor in reverse. Look back at the electric motor in Figure above . If you were to mechanically turn the shaft of the motor (instead of using electromagnetism to turn it), the motor would generate electricity just like an electric generator. You can learn how to make a very simple electric generator by watching the video at the URL below. Making your own generator will help you understand how a generator works. |
SciQ | SciQ-223 | isotope
On top of the previous 254, another 34 isotopes have half-lives which have actually been measured in laboratory, but are still large enough (>50 million years) so that a small fraction of the isotope could conceivably have survived since the creation of the Earth 4.6 billion years ago, and may be of interest in geological timescales. There are also isotopes with smaller half-lives, but which are continuously replenished by the decay of heavier atoms or by the action of cosmic rays, so they can still be found on Earth today. In all, about 339 different isotopes can be found naturally on our planet.
However, as many as 3100-3300 different isotopes of the first 118 elements are claimed to have been detected in laboratories, most of them with very small half-lives (seconds or less). Nobody knows for sure how many elements and how many isotopes can exist, though the number is finite.
The following is multiple choice question (with options) to answer.
How many naturally occurring elements are known on earth? | [
"90",
"87",
"60",
"85"
] | A | An element, as defined in Chapter 1 "Chemistry, Matter, and Measurement", is a substance that cannot be broken down into simpler chemical substances. There are about 90 naturally occurring elements known on Earth. Using technology, scientists have been able to create nearly 30 additional elements that do not occur in nature. Today, chemistry recognizes 118 elements—some of which were created an atom at a time. Figure 2.1 "Samples of Elements" shows some of the chemical elements. |
SciQ | SciQ-224 | biochemistry, cell-biology, neurotransmitter, membrane-transport, synapses
Title: Exocytosis of synaptic vesicles I'm reading the following paper:
http://jcs.biologists.org/content/123/6/819
The part I am really confused about is when they say:
Exocytosis appears to use two alternative pathways: clathrin-mediated endocytosis (CME), which is well established by numerous lines of evidence, and the more controversial ‘kiss-and-run’ pathway, which involves direct retrieval of a vesicle at the site of fusion
My question is .. How can exocytosis (contents inside of cell are transported to outside of cell) use clathrin mediated endocytosis?
I thought endocytosis is the opposite of exocytosis, so why do synaptic vesicles use clathrin mediated endocytosis as a method of exocytosis? That sentence is located in a paragraph titled "Stages 5-7: Endocytosis and recycling": it's talking about recycling exocytosed membrane which is necessary for making vesicles for further exocytosis.
The sentences before the part you quoted are:
Synapses possess highly efficient mechanisms for retrieving SVs from the plasma membrane of the presynaptic terminal after exocytosis. Fast regeneration of functional SVs is a prerequisite for synapses to function during prolonged activity.
I think the passage is just somewhat confusingly worded, in that "exocytosis" is used as the subject of the sentence which is strange in this context. You could rewrite that sentence:
There appear to be two alternative pathways to recycle membrane for exocytosis: clathrin-mediated...
The following is multiple choice question (with options) to answer.
What are the two types of vesicle transport called? | [
"dielectric and exocytosis",
"eptocytosis and exocytosis",
"endocytosis and exocytosis",
"epithelium and exocytosis"
] | C | |
SciQ | SciQ-225 | evolution, species, speciation
Title: Are there any half-evolved animals alive today? I know that there are animals that are "simpler" than other animals but are there any that are half-evolved? Are there any animals with half-evolved functions, like arms, legs, etc?
This was part of the original question, but it was incorrect.
Saying that every species on the planet is "transitional" is an unacceptable answer because it only works on the assumption that macro-evolution is true.
Saying that all the transitional animals just died off also doesn't seem quite right. If all the previous transitional animals just went extinct, then wouldn't we just have a few specialized species alive today? This wouldn't allow for the diversity we see today.
I know that there are animals that are "simpler" than other animals but are there any that are half-evolved? Why aren't there living half ape and half humans?
Oh come on. You know if Australopithecines or Homo habilis still existed you would be asking "Why aren't there living half Homo habilis and half humans"? And when the other Great Apes go extinct you'll be wondering why there are no transitional forms between humans and monkeys. The answer to that question is, humans are apes; chimpanzees and we are pretty much as close as two species can be; we could have closer forms that survived but we could also have a much bigger gap between us and our closest relatives than we currently do. In other words, any ape is a valid example of something "half-human half-ape". It's like asking for a vehicle that's half-car, half-volvo.
Are there animals that are just starting to evolve arms and legs?
You mean, modifying fins into limbs in a general movement from water-living to land-living, like the first tetrapods are thought to have done? I like mudskippers.
Saying that every species on the planet is "transitional" because there are no ultimate or final species is an unacceptable answer because it only works on the assumption that macro-evolution is true.
The following is multiple choice question (with options) to answer.
What do you call a species that has died out in the past? | [
"remnant",
"endangered",
"inhabit",
"extinct"
] | D | Life is complex, and there are millions of species alive today. Many millions more lived in the past and then went extinct. Organisms include microscopic, single-celled organisms. They also include complex, multicellular animals such as you. Clearly, life science is a huge science. That’s why a life scientist usually specializes in just one field within life science. Dr. Smith, for example, specializes in ecology. You can see the focus of ecology and several other life science fields in Table below . Click on the links provided if you want to learn about careers in these fields. |
SciQ | SciQ-226 | botany
Title: What are embryophytes? And how are they characterized? What does it mean when it's said that plants are embryophytes?
What are the specific characteristics that help determine that? The name derives from their innovative characteristic of nurturing the young embryo sporophyte during the early stages of its multicellular development within the tissues of the parent gametophyte.
source
https://www.revolvy.com/main/index.php?s=Embryophytes&item_type=topic
Similar definitions are in the New World Encyclopedia and Merriam Webster Dictionary.
The following is multiple choice question (with options) to answer.
Where does the embryo develop in a plant? | [
"inside the female plant after fertilization",
"inside the stem after fertilization",
"outside the female plant after fertilization",
"inside the male plant after fertilization"
] | A | In plants, the embryo develops inside of the female plant after fertilization. Algae do not keep the embryo inside of themselves but release it into water. This was the first feature to evolve that separated plants from green algae. This is also the only adaptation shared by all plants. |
SciQ | SciQ-227 | measurements, error-analysis
Title: How to define Uncertainty (instrument error analysis)? Is it correct to define uncertainty as "The distinction between the measurements with different instruments"?
Thanks :D Uncertainty in the context of instrument error analysis usually describes the random component of measurements of the same workpiece done by the same instrument.
Let's consider as an example the task to measure the length of a piece to a "high" degree of accuracy. The measured value contains many different types of errors. Some errors are attributed to the workpiece itself (e.g. if the two faces are not plan parallel, ...) and some are due to the measurement device itself. The uncertainty of the instrument only considers the second type.
E.g., if we use a laser interferometer to measure the distance of the workpiece, we will have fluctuations of the laser power, the wavelength, the temperature of the air above the workpiece (affecting the refractive index), ... All these different errors contribute to the measured value. However, since we are unable/unwilling to control each and every contribution, we obtain different measurement values if we keep remeasuring the same workpiece several times. This type of uncertainty should be called precision. Although the instrument contains other components of uncertainty as well, most people mean precision if they use uncertainty in this context.
The following is multiple choice question (with options) to answer.
What is the method of setting or correcting a measuring device by matching it to known measurement standards called? | [
"parallax",
"distortion",
"calibration",
"precision"
] | C | When using measuring devices, we often use a technique called calibration to increase the accuracy of our measurements. Calibration is a method of setting or correcting a measuring device by matching it to known measurement standards. To better understand calibration, we will look at the example of calibrating a thermometer. All thermometers are slightly different in their temperature readings. One way to calibrate a thermometer is by using the freezing point and boiling point of water ( Figure below ). If we know that water freezes at 0°C and boils at 100°C, we can calibrate our thermometer by measuring the temperature of ice water and of boiling water. We place the thermometer in ice water and wait for the thermometer liquid to reach a stable height, then place a mark at this height which represents 0°C. Then we place the thermometer in boiling water, and after waiting for the thermometer liquid to reach a stable height, we place a mark at this height which represents 100°C. We can then place 100 equally spaced divisions between our 0 and 100°C marks to each represent 1°C. Our thermometer has now been calibrated using the known values for the freezing point and boiling point of water, and can be used to measure temperatures of objects between 0 and 100°C. |
SciQ | SciQ-228 | density, air, buoyancy
Title: Feeling of coldness in heights We know that due to buoyancy the cold air sinks and warm air floats above it due to it being less dense than cold air. Then why do we feel cold as we go to greater heights/hill stations and feel hot when we are in the normal surface of earth? This is because the air pressure changes significantly with height, and compression or expansion of a gas causes it to warm or cool. In a convective atmosphere, temperature differences cause air to rise in some places and descend in others. When it rises, it expands, and that causes it to cool. When air descends, it is compressed, and that causes it to warm.
(The compressive warming/cooling of gases is also why a bicycle tyre air pump gets hot when you use it, and how a refrigerator works.)
This warming and cooling effect stabilises the atmosphere against heat rising. If the rate of temperature change with height is less than a particular value called the adiabatic lapse rate (ALR), then the atmosphere is stable and warm air won't rise. ('Adiabatic' means that we assume there is no heat gained or lost from an air packet by radiation or conduction.) If the gradient exceeds the adiabatic lapse rate, then convection suddenly starts up again, the heat rises and reduces the gradient back down until, usually in a matter of minutes to a few hours, it once again equals the adiabatic lapse rate.
The adiabatic lapse rate in dry air is about $9.8$ K/km, so for every $1$ km you rise, the temperature drops $1$ K (= $1^\circ$C). However, in the presence of water vapour, there is an additional heating and cooling effect from the condensation or evaporation of water droplets (latent heat of condensation). This reduces the lapse rate down to around $6.5$ K/km, called the moist adiabatic lapse rate (MALR). This is the value the International Standard Atmosphere assumes for aviation purposes, and is generally a pretty accurate approximation, but there are variations from it depending on humidity and weather conditions. (In particular, at night or in the polar winters you can get temperature inversions when surface heating stops and cold air pools near the surface.)
The following is multiple choice question (with options) to answer.
What property of warm air causes it to rise above cold air? | [
"lower density",
"higher temperature",
"greater pressure",
"greater density"
] | A | The warm-air vent is placed near the floor of the room. Warm air is less dense than cold air so it rises. If the warm-air vent were placed near the ceiling instead, how would this affect the transfer of thermal energy throughout the room?. |
SciQ | SciQ-229 | zoology, physiology, brain, ethology, behaviour
Robins, A., Lippolis, G., Bisazza, A., Vallortigara, G. & Rogers, L. J. (1998). Lateralized agonistic responses and hindlimb use in toads. Animal Behaviour, 56, 875–881.
Rogers, L. J. & Andrew, R. J. (Eds) (2002). Comparative Vertebrate Lateralization. Cambridge: Cambridge University Press.
Roth, E. D. (2003). ‘Handedness’ in snakes? Lateralization of coiling behaviour in a cottonmouth, Agkistrodon piscivorus leucostoma, population. Animal behaviour, 66(2), 337-341.
Shine, R., Olsson, M. M., LeMaster, M. P., Moore, I. T., & Mason, R. T. (2000). Are snakes right-handed? Asymmetry in hemipenis size and usage in gartersnakes (Thamnophis sirtalis). Behavioral Ecology, 11(4), 411-415.
Sovrano, V. A., Rainoldi, C., Bisazza, A. & Vallortigara, G. (1999). Roots of brain specializations: preferential left-eye use during mirror-image inspection in six species of teleost fish. Behavioural Brain Research, 106, 175–180.
Sovrano, V. A., Bisazza, A. & Vallortigara, G. (2001). Lateralization of response to social stimuli in fishes: a comparison between different methods and species. Physiology & Behavior, 74, 237– 244.
Vallortigara, G., Rogers, L. J., Bisazza, A., Lippolis, G. & Robins, A. (1998). Complementary right and left hemifield use for predatory and agonistic behaviour in toads. NeuroReport, 9, 3341–3344.
Vallortigara, G., Rogers, L. J. & Bisazza, A. (1999). Possible evolutionary origins of cognitive brain lateralization. Brain Research Reviews, 30, 164–175.
The following is multiple choice question (with options) to answer.
Which branch of biology studies animal behavior? | [
"ethology",
"microbiology",
"anthropology",
"embryology"
] | A | The branch of biology that studies animal behavior is called ethology. Ethologists usually study how animals behave in their natural environment. They try to determine the cause of behaviors, how behaviors develop, and how and why behaviors evolve. |
SciQ | SciQ-230 | • Thanks to everyone!! First, I had messed up my vars as Henderson, SteveKass and others pointed, and second, I was ignoring the minute - hour relaationship. Solved. Lots of thanks. – Vladislav Vordank Jan 10 '18 at 15:25
• Xander, I wonder if you would consider actually including the units in your equations? I consider writing units to be such an important best practice (and, in particular, one that would have made one of the errors obvious) that I'd like to see it represented among the answers. But I don't think I could improve on your explanation, which is why I didn't just write my own answer. – David Z Jan 11 '18 at 0:38
• @DavidZ Indeed, and I probably would have done that in the first place if the "obvious" sign error hadn't made me complacent. I've edited the answer to include units in the setup. – Xander Henderson Jan 11 '18 at 6:29
• Thanks! (Your edit looked a little strange at first and I took a while to realize it's because I would omit units after the variables, e.g. let $v_1$ represent a speed, not just a number, and then write things like $v_1 = v_2 + 12\ \mathrm{km/hr.}$, but I suppose that's just a matter of preference.) – David Z Jan 11 '18 at 7:08
The question states that "One train covers this distance in 40 mins less than the other". Although it does not tell you which train, it is quite obvious that the faster train (i.e. train 2) takes 40 mins less.
So instead, it should be $96/(v2)=(96/v1)−40$.
• Also, you've mixed up hours and minutes. It should be 2/3 not 40. – Michael Behrend Jan 10 '18 at 14:46
• Thanks to everyone!! First, I had messed up my vars as Henderson, SteveKass and others pointed, and second, I was ignoring the minute - hour relaationship. Solved. Lots of thanks. – Vladislav Vordank Jan 10 '18 at 15:25
The following is multiple choice question (with options) to answer.
What unit of measure is equal to the amount of work a horse can do in 1 minute? | [
"joule",
"torque",
"watt",
"horsepower"
] | D | Power may be measured in a unit called the horsepower. One horsepower is the amount of work a horse can do in 1 minute, which equals 745 watts of power. |
SciQ | SciQ-231 | zoology, organs, vestigial
Title: Is the appendix a vestigial structure in all vertebrates? In humans the Appendix is a vestigial organ. Does it serve no apparent purpose in all the vertebrates that have one? Smith et al. (2009) provide a survey of the morphology of the cecal appendix. One current hypothesis is that the appendix provides "safe harbor" for symbiotic gut bacteria. Among mammals, there is a vast array of cecal appendices:
In summary:
A comparative anatomical approach reveals three apparent morphotypes
of the cecal appendix, as well as appendix-like structures in some
species that lack a true cecal appendix. Cladistic analyses indicate
that the appendix has evolved independently at least twice (at least
once in diprotodont marsupials and at least once in Euarchontoglires),
shows a highly significant (P < 0.0001) phylogenetic signal in its
distribution, and has been maintained in mammalian evolution for 80
million years or longer.
The following is multiple choice question (with options) to answer.
What organism is characterized by an incomplete digestive system and a single, tentacled opening? | [
"sponges",
"annelids",
"prokaryotes",
"cnidarians"
] | D | Cnidarians have an incomplete digestive system with a single opening. The opening is surrounded by tentacles, which are covered with nematocyst cells and used to capture prey. Digestion takes place in the digestive cavity. Nutrients are absorbed and gases are exchanged through the cells lining this cavity. Fluid in the cavity supports and stiffens the cnidarian body. |
SciQ | SciQ-232 | electrostatics, charge, potential-energy, voltage
Title: If voltage represents an energy difference between two points, why don't electronic appliances all use the same amount of energy? As I understand it, voltage is an energy difference between two points.
$$V_f - V_i = - \int \mathbf{E} \cdot d\mathbf{s}$$
But consider a toaster and a refrigerator each using their own 120V outlets. They don't use the same amount of energy right? Why?
MY THOUGHTS SO FAR:
I understand the electric potential difference causes charges to flow through the wires. During this process, the energy can be used in a variety of ways. For instance to power a motor or to heat up coils. But by the time the charge has traveled from one point to the other, hasn't it use the same amount of energy by definition of the voltage difference? Also I know
$$V=IR$$
$$I(t) = \frac {dq}{dt}$$
So I recognize that, depending on the resistance, two circuits with the same voltage could have very different currents. but current is not a measure of energy, correct? Voltage is about the amount of work required to move a charge from one area to another.
So why wouldn't a toaster and a refrigerator both use the same amount of energy to function? The voltage $V$ across a device represents the energy difference per unit charge between the input and output. The amount of energy that a device consumes in a given period of time is the voltage drop $V$, times the amount of charge that has crossed the device. The energy used per unit time (the power) is the current $I$ (charge per unit time) passing through,
$$P= VI.$$
The following is multiple choice question (with options) to answer.
What term is not the same as energy, but means the energy per unit charge? | [
"frequency",
"mass",
"speed",
"voltage"
] | D | The second equation is equivalent to the first. Voltage is not the same as energy. Voltage is the energy per unit charge. Thus a motorcycle battery and a car battery can both have the same voltage (more precisely, the same potential difference between battery terminals), yet one stores much more energy than the other since ΔPE = qΔV . The car battery can move more charge than the motorcycle battery, although both are 12 V batteries. |
SciQ | SciQ-233 | species-identification, mycology
Title: ID of a purple fungus in Virginia Could someone tell me a bit more about this fungus found growing in a nearly straight line in the lawn in a wooded area of Virginia, USA? It seems rather fragile, maybe a bit "dry" This is not a moss, but a fungus of the family Clavariaceae. Most likely this is Clavaria zollingeri, commonly known as violet coral, but there are a few resembling species. Microscopy might be needed to be entirely sure.
The species is saprotrophic, so it grows on the woody debris in your picture.
The following is multiple choice question (with options) to answer.
What specific part of the african violet is used to propagate other plants? | [
"leaves",
"roots",
"spores",
"petals"
] | A | |
SciQ | SciQ-234 | cellular-respiration, glucose, fermentation
The so-called cycle of Cori & Cori
In my opinion it is best to approach glycolysis as I have done above, without reference to the tissue or organism, so as to understand the essential features of the process.
In the specific case of mammals, some tissues perform glycolysis anaerobically, e.g. the red blood cell (which lacks mitochondria) or rapidly excercising muscle (where the blood supply and number of mitochondria are not sufficient to generate ATP for muscle contraction. The liver, in contrast, has a plentiful supply of oxygen and hence NAD+, and so can reoxidize lactate to pyruvate if the former is transported in the blood from the anaerobic tissue to the liver, salvaging the carbon skeleton.
Under conditions of low blood sugar (e.g. starvation) it is important that the pyruvate be reconverted into glucose in the liver by gluconeogenesis, rather than be converted to other products, and the glucose is released into the blood. In this case one goes full circle, this process is generally referred to as the Cori Cycle. I always avoided this term myself in teaching students as I found it caused confusion with cycles such as the tricarboxylic acid cycle and the urea cycle, where all the chemical interconversions take place in the same tissue.
Footnote: Glycolysis under aerobic conditions
Under aerobic conditions (e.g. in the liver after a carbohydrate meal) the purpose of glycolysis is not primarily to generate energy but to utilize the glucose, storing it as fat (after glycogen capacity is reached) or using it to synthesize intermediates. There are different fates for the pyruvate (acetyl-CoA is shown), but lactate is not one of them as the NADH can be reoxidized far more efficiently in the mitochondria, with molecular oxygen being the ultimate oxidizing agent.
Text References
Berg et al. Section. 16.1 (5th ed.) covers glycolysis in great detail under aerobic conditions. The lactic dehydrogenase reaction is given little emphasis, but can be found in section 16.1.9.
The following is multiple choice question (with options) to answer.
What are fibers that depend on aerobic respiration called? | [
"hydrogen fibers",
"fragile fibers",
"oxidative fibers",
"evaporative fibers"
] | C | |
SciQ | SciQ-235 | electromagnetic-radiation, earth, gamma-rays
Title: EM waves with frequency much higher than gamma rays penetrate a planet like Earth? I have just started to study the electromagnetic waves as a personal interest. I wonder if there exist a much higher frequency of electromagnetic wave than Gamma Ray's which can even penetrate Earth. With our current measuring apparatus, is it possible to measure such high frequency waves if they penetrate everything?
Like passing through the earth without any significant energy loss? For an electro-magnetic wave, the ability to penetrate matter goes as $1/{\sqrt{f}}$.
So as you increase the frequency, the penetration gets worse. By the time you get to gamma-rays, the energy is so high that the "rays" (at this point you're better thinking of them as particles - photons) interact with the matter and cause an electromagnetic shower of sub-atomic particles (read up on pair-production and ionisation).
If you want the wave to remain coherent after traversing a large body, you want a very low frequency. Radio waves in the few Hertz range have been used to communicate with submarine deep underwater. The data-rate is very low.
The following is multiple choice question (with options) to answer.
Which form of electromagnetic waves have more energy: low frequency wave or high frequency waves? | [
"low frequency waves",
"neither",
"high frequency waves",
"the same"
] | C | The energy of electromagnetic waves depends on their frequency. Low-frequency waves have little energy and are normally harmless. High-frequency waves have a lot of energy and are potentially very harmful. |
SciQ | SciQ-236 | virus, life, philosophy-of-science
Title: Is there any definition of life which makes viruses undeterminable? There are many different definitions of life (RNA, something that comes through evolution) but not one I have seen which could not determine wheter viruses are living things (even though there are many definitions both for YES and NO). Are there any such definitions (I'm looking for cases where it's really fundamental debate, not only struggling for the correct dictionary definition)?
Thank you. Your last sentence is the key: defining life really is just finding a dictionary definition that we can agree upon. Biology is something that defies discrete definitions at times: "What is it to be alive?" "What is a species?" maybe even "What is the wild type allele of a gene?"
I would recommend not looking at viruses as a challenge to determine if they are alive or not so much as an excellent opportunity to discuss what we think are important characteristics of life.
Life can alternately be described as:
"Comprised of self-replicating cells" (a paraphrase of the "Cell Theory of Life"
or
As things that embody at least most of the following characteristics:
1. Self-Replicating
2. Metabolizing
3. Growing
4. Showing signs of adaptation
5. Being organized
6. Respond to their environment
7. Being comprised of cells
I like to think that we should focus on extraterrestrial forms when we define life. i.e. what would we want to see in an extraterrestrial in order to call it 'life'? While some are troubled by calling viruses alive here on earth, the same people might be willing to say that we have found extraterrestrial life on another planet if it was similar (granted, it's hard to imagine this kind of life existing without a host...)
as an aside: You might also ask whether this question is fit for this stack as it can not be supported by literature references (at least none that would actually support a conclusion). So should this be posted as 'Biology' or 'Philosophy'?
The following is multiple choice question (with options) to answer.
Something that has all of the characteristics of life is considered to be what? | [
"organism",
"ecosystem",
"alive",
"molecule"
] | C | There is not just one distinguishing feature that separates a living thing from a non-living thing. A cat moves but so does a car. A tree grows bigger, but so does a cloud. A cell has structure, but so does a crystal. Biologists define life by listing characteristics that living things share. Something that has all of the characteristics of life is considered to be alive. The duck decoy in Figure below may look like a duck, act like a duck in that it floats about, but it is not alive. The decoy cannot reproduce, respond to its environment, or breathe. |
SciQ | SciQ-237 | c
Title: Match blood types in C I have written a solution to the blood-type matching problem, as described at https://projectlovelace.net/problems/blood-types/. The problem is to determine whether a given recipient (in this case, argv[1]) will find a match for a blood transfusion in an array of available donors (argv + 2).
Input blood type: B+
Input list of available blood types: A- B+ AB+ O+ B+ B-
Output: match
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <err.h>
typedef struct {
enum { O, A, B, AB } abo;
enum { P, M } rh;
} Blood;
const int abo[4][4] = {
{ O, O, O, O }, // O
{ O, A, O, A }, // A // *
{ O, B, O, B }, // B // *
{ O, A, B, AB }, // AB
};
const int rh[2][2] = {
{ P, M }, // P
{ M, M }, // M // *
};
Blood
parse(char *s){
char rh0 = s[strlen(s)-1];
char *abo0 = strdup(s);
abo0[strlen(s)-1] = '\0';
Blood b = {
!strncmp(abo0, "O", 1) ? O
: !strncmp(abo0, "A", 1) ? A
: !strncmp(abo0, "B", 1) ? B
: !strncmp(abo0, "AB", 2) ? AB
: -1,
rh0 == '+' ? P
: rh0 == '-' ? M
: -1,
};
return b;
}
The following is multiple choice question (with options) to answer.
What do the letters in our blood types represent? | [
"genomes",
"proteins",
"iron levels",
"alleles"
] | D | Another exception to Mendel's laws is a phenomenon called codominance . For example, our blood type shows codominance. Do you know what your blood type is? Are you A? O? AB? Those letters actually represent alleles. Unlike other traits, your blood type has three alleles, instead of two!. |
SciQ | SciQ-238 | photosynthesis
Title: Photosystem I and the ETC In the light reactions of photosynthesis, Photosystem I receives electrons from the ETC after Photosystem II sends them to the ETC. Then, when Photosystem I receives light, the electron becomes excited and passes the electron back to the ETC. This leads me to my question: In the following question, are both $B$ and $E$ correct?
Which of the following are directly associated with photosystem I?
$A)$ harvesting of light energy by ATP
$B)$ receiving electrons from the thylakoid membrane electron transport chain
$C)$ generation of molecular oxygen
$D)$ extraction of hydrogen electrons from the splitting of water
$E)$ passing electrons to the thylakoid membrane electron transport chain It appears the author of the question is trying to use "thylakoid electron transport chain" in an overly specific way. The chain from which PS I receives electrons has far more components and is different from the shorter chain to which PS I passes its electrons. But according to my copy of Biology, Campbell & Reece 7th edition, both are called "electron transport chains" and both reside in, or on, the thylakoid membrane. Perhaps the "directly" in the question refers to the fact that PS I's electron is first captured by a "primary receptor" before being passed to ferredixon, the first member of the chain to which PS I passes electrons. But, again according to Campbell, this primary acceptor is considered part of the photosystem.
I used to teach this stuff. I'd toss out the question.
The following is multiple choice question (with options) to answer.
The two stages of photosynthesis are the light reactions and what? | [
"digestive cycle",
"reproductive cycle",
"respiratory cycle",
"calvin cycle"
] | D | The two stages of photosynthesis are the light reactions and the Calvin cycle. Do you see how the two stages are related?. |
SciQ | SciQ-239 | food, nutrition, energy-metabolism
Title: What are the bare minimum nutrients required to survive as a human? I am trying to determine the bare minimum nutritional requirements to survive as a human, ignoring energy (caloric) requirements. Another way to ask this question is: What elements can humans not live without? I am not inquiring solely about what nutrients are needed, but also their approximate amounts.
Imagine pills that a person can take that covers all their base nutritional needs and that after taking this pill the person can eat whatever they want to meet their caloric requirements. Hypothetically, this pill could have some amount (how much?) fat, carbohydrates, protein, fiber, minerals, and vitamins, and the person could subsequently eat any other food to meet their caloric requirements knowing their nutritional needs would already be otherwise met. Lets ignore the possibility of the person suffering from health issues due to eating too much of any specific food to meet their caloric requirements (e.g., taking the magic pills and then eating only butter).
A person in this situation could think "Ok I've got most of my bases covered, now I just need to ingest another 1000 calories of (almost) anything I want).
What nutrients are absolutely necessary for humans to survive indefinitely, and how much of these nutrients are required?
I am hoping for a complete list with approximate amounts (e.g., 20g fat, 20g carbohydrates, 1mg Vitamin X, .05mg Vitamin Y, 10mg mineral X). Essential nutrients include (NutrientsReview):
Water
9 amino acids: histidine, isoleucine, leucine, lysine, methionine,
phenylalanine, tryptophan, threonine, valine
2 fatty acids (alpha linolenic and linoleic acid)
Vitamins: A, B1, B2, B3, B5, B6, folic acid, biotin, B12, C,
D, E and K (and choline, which is considered a vitamin-like substance)
Minerals: calcium, chromium, chloride, copper, iodine, iron,
manganese, molybdenum, phosphorus, potassium, selenium, sodium, zinc
The following is multiple choice question (with options) to answer.
What do living things need to survive? | [
"nutrients",
"molecules",
"heat",
"oxygen"
] | A | There are three main ocean zones based on distance from shore. They are the intertidal zone , neritic zone , and oceanic zone . Distance from shore influences how many nutrients are in the water. Why? Most nutrients are washed into ocean water from land. Therefore, water closer to shore tends to have more nutrients. Living things need nutrients. So distance from shore also influences how many organisms live in the water. |
SciQ | SciQ-240 | interstellar-medium, density
These transitions produce optical forbidden lines which are quenched at different characteristic densities. Measuring a line strength ratio is important because the ratio will be independent of the abundance of OIII. The ratio will depend on electron density, providing the electron density is $>10^{5}\ cm^{-3}$, and temperature (at lower densities, the ratio is just temperature dependent).
To get the density in this case requires more information - usually supplied by a similar line ratio for something like NII, which has a similar set of forbidden lines, but with differing density and temperature dependence.
A more straightforward route is to use the line ratio for forbidden lines of OII or SII where there are a closely spaced pair of energy levels, both undergoing forbidden transitions to the same lower level. In this case the ratios are density sensitive, but not temperature sensitive, again over a range of densities where one or other of the transitions is in the process of being quenched (e.g. for OII 372.6/372.8nm, $10^2 <n_e < 10^{6}\ cm^{-3}$.)
The following is multiple choice question (with options) to answer.
The denser regions of the electron cloud are called what? | [
"lattices",
"isotopes",
"cores",
"orbitals"
] | D | Some regions of the electron cloud are denser than others. The denser regions are areas where electrons are most likely to be. These regions are called orbitals . Each orbital has a maximum of just two electrons. Different energy levels in the cloud have different numbers of orbitals. Therefore, different energy levels have different maximum numbers of electrons. Table below lists the number of orbitals and electrons for the first four energy levels. Energy levels farther from the nucleus have more orbitals. Therefore, these levels can hold more electrons. |
SciQ | SciQ-241 | newtonian-mechanics, energy, work
Title: Types of energy and work I am learning about energy and work, and am a beginner to this topic. Energy is defined as the ability to do work. In some cases, the ability to do work directly follows the type of energy. For instance, heat energy can be used to do work through isothermal expansion of gas, for instance.
Is there a relationship/concept between how easy it is to get a type of energy to do work? Some types of energy might make them more suitable to do work, whereas others might involve a more indirect/contrived route. Energy defined as the ability to do work; this does not mean that only work is done, it means that work can be done.
Here is an expanded definition that should help.
The energy of a system is a property of the system that is increased (decreased) by the following mechanisms:
work done on (or done by) the system from its surroundings
heat added to (or removed from) the system from its surroundings
mass transfer into (or from) the system to its surroundings.
"How easy it is to get a type of energy to do work" depends how the system interacts with the surrounding.
For example, if a system comprised of a gas has a higher pressure than its surroundings and can move a boundary (say a piston), the system can lose energy by doing work on the surroundings as the gas expands. Or if the gas is in a closed container (fixed volume) and has a higher temperature than its surroundings, the gas can lose energy by transferring heat to the surroundings. A liquid can have a decrease in its energy, with a decrease in its temperature, by evaporation (mass transfer from the liquid).
The details of energy transfer is addressed by the laws of thermodynamics (e.g., the first and second laws).
The following is multiple choice question (with options) to answer.
In studying energy, what term do scientists use to refer to the matter and its environment involved in energy transfers? | [
"world",
"molecule",
"system",
"ecosystem"
] | C | 6.3 The Laws of Thermodynamics In studying energy, scientists use the term “system” to refer to the matter and its environment involved in energy transfers. Everything outside of the system is called the surroundings. Single cells are biological systems. Systems can be thought of as having a certain amount of order. It takes energy to make a system more ordered. The more ordered a system is, the lower its entropy. Entropy is a measure of the disorder of a system. As a system becomes more disordered, the lower its energy and the higher its entropy become. A series of laws, called the laws of thermodynamics, describe the properties and processes of energy transfer. The first law states that the total amount of energy in the universe is constant. This means that energy can’t be created or destroyed, only transferred or transformed. The second law of thermodynamics states that every energy transfer involves some loss of energy in an unusable form, such as heat energy, resulting in a more disordered system. In other words, no energy transfer is completely efficient and tends toward disorder. |
SciQ | SciQ-242 | physical-chemistry, thermodynamics
Title: Temperature change in isobaric processes with and without change in number of molecules Hello I was thinking about two thermodynamics problems and I wanted to get some insights into how to solve them.
The first problem was: Suppose we have one mole of ideal gas under constant external pressure (1 atm) conditions, and let it conduct a reaction (for example a photoinduced isomerization) where there is no net change in number of molecules. This reaction for example has an enthalpy change which is not known. We can measure the total heat Q evolved due to the reaction (like in a constant pressure calorimeter).
So because there is no change of molecules this can be treated as a formal isobaric change (can it?). As enthalpy change is equal to heat Q in isobaric processes, we can say that the measured heat when reaction goes to completion is equal to the reaction enthalpy change, and therefore we can calculate the temperature change.
My doubt is: Is the work the system performs on its surroundings included in ΔH?
How can we determine the temperature change then if we have an reaction of the type:
Also at constant external pressure? Here, the particle number changes. When you measure the heat evolved in an isobaric calorimeter, it is assumed that the process takes place nearly isothermally (for the reaction mixture) and the heat involved is equal to the standard change in enthalpy $\Delta H^0$. Whether the total number of moles changes or not, $\Delta H^0$ includes the work done on the surroundings.
The following is multiple choice question (with options) to answer.
To measure what changes that occur in chemical reactions, chemists usually use a related thermodynamic quantity, calledenthalpy? | [
"ion exchange",
"entropy",
"energy",
"evaporation"
] | C | (a) Initially, the system (a copper penny and concentrated nitric acid) is at atmospheric pressure. (b) When the penny is added to the nitric acid, the volume of NO2 gas that is formed causes the piston to move upward to maintain the system at atmospheric pressure. In doing so, the system is performing work on its surroundings. The symbol E in represents the internal energy of a system, which is the sum of the kinetic energy and potential energy of all its components. It is the change in internal energy that produces heat plus work. To measure the energy changes that occur in chemical reactions, chemists usually use a related thermodynamic quantity calledenthalpy (H) (from the Greek enthalpein, meaning “to warm”). The enthalpy of a system is defined as the sum of its internal energy E plus the product of its pressure Pand volume V:. |
SciQ | SciQ-243 | thermodynamics, statistical-mechanics, entropy, non-equilibrium
To reiterate: if you take option 3 and try to infer laws of physics based on the start and end states of an inconsistently isolated system, you can violate whatever you want.
The system is a box with a ball rolling around in it. I allow magic transport of stuff across the boundary (I take the ball out of the box) and then I look at the box again. The ball is gone! The Second Law, gone! The First Law, gone! Newton's laws of motion, gone! Quantum mechanics, gone!
The following is multiple choice question (with options) to answer.
A system in what state cannot spontaneously change, and therefore can do no work? | [
"equilibrium",
"equality",
"balance",
"stability"
] | A |
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