source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-1644 | sensation, olfaction
http://www.comeaddestrareuncane.com/blog/tag/cani-molecolari/
In the dog, the surface of the olfactory mucosa varies between 70 and 150 cm2 - in this tissue the number of olfactory receptors varies from 250 to 280 million - In 1962, Becker et al. showed that dogs are able to recognize substances in dilutions from 1/100 to 1/10.000.000.
- http://milano.corriere.it/milano/notizie/cronaca/12_febbraio_19/cani-olfatto-parere-esperto-1903358352720.shtml
Have you noticed how a dog sniffs the urine of a female "tasting it"? It is the same action that makes the viper when it follows the track of the mouse: it evertes the tongue and carries on it the odorous particles in the buccal cavity, and this organ has a function in the middle between the olfactory and gustatory ones. "Pointing dogs" is as pointing "the wild" taste the smell.
"Eat the scent", in the jargon, because savored, not only in terms of smell, the smell of the wild. The Jacobson's organ is then a second organ capable of perceiving odors, the first we've said is represented ciliated epithelium of the mucous membrane of the nose.
But there is a third organ called the "Rodolfo-Masera" which also serves to sense the emanations chemical (not yet known which), that way you could explain a specialization of these organs to perceive certain groups of biochemicals than others.
- http://www.laciotola.net/Cani/la-funzione-olfattiva-del-cane.html
The following is multiple choice question (with options) to answer.
Instead of using their nose, reptiles can use what organ to smell scents? | [
"tongue",
"eye",
"bladder",
"liver"
] | A | Reptiles have a circulatory system with a heart that pumps blood. Reptiles also have a centralized nervous system with a brain. Their brain is relatively small, but the parts of the brain that control the senses and learning are larger than in amphibians. Reptiles have good senses of sight and smell. They use their tongue to smell scents. That’s what the blue-tongued lizard in Figure below is doing. Some reptiles also have a heat-sensing organ that helps them locate the warm bodies of prey animals such as birds and small mammals. |
SciQ | SciQ-1645 | 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.
How does the diaphragm look like when it is at rest? | [
"dome-shaped",
"dam - shaped",
"inverted",
"flat"
] | A | The Diaphragm The change in volume of the thoracic cavity during breathing is due to the alternate contraction and relaxation of the diaphragm (Figure 11.17). It separates the thoracic and abdominal cavities, and is dome-shaped at rest. The superior surface of the diaphragm is convex, creating the elevated floor of the thoracic cavity. The inferior surface is concave, creating the curved roof of the abdominal cavity. |
SciQ | SciQ-1646 | quantum-gravity, physical-constants
Title: What is the smallest existing thing in theory and law? What is the smallest existing thing in theory and law?
"What is the smallest existing thing in theory and law?"
The Merriam Webster Dictionary defines a "thing" as:
: an object or entity not precisely designated or capable of being
designated
a: an inanimate object distinguished from a living being
b: a separate and distinct individual quality, fact, idea, or usually
entity
c: the concrete entity as distinguished from
...
A Photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles). Mass: 0 < 1×10−18 eV/c^2.
The photon has zero rest mass and always moves at the speed of light within a vacuum. Since the Photon is a Point Particle and has a size of zero you might say it's not a thing, nothing; that leaves us with:
The smallest real thing is the Neutrino. Mass: ≤ 0.120 eV/c^2.
The smallest theoretical thing is the Planck Particle. Radius: 5.72947×10−35 m, Mass: 3.85763×10−8 kg.
The following is multiple choice question (with options) to answer.
What is the smallest unit of matter that still maintains it's properties of being an element? | [
"a cell",
"an atom",
"a proton",
"an electron"
] | B | |
SciQ | SciQ-1647 | evolution
Title: Which of this 2 affirmations is more close to the explanation of evolution? I am almost secure that this affirmation aren't exactly true but I want to know which of these statements is more near to a description of how evolution works:
The evolution has an exactly target and always progress to it, each generation the childs are more close to make complete a certain task, that is beacuse evolution is like "directional".
For example: The task is be 10cm taller. Each generation the race become 1mm taller up to complete the task.
The evoultion is random but the specie (or natual selection) try to reach a target, each generation has random traits but only benefical traits tends to "survive" and get offpring.
For example: In order to survive the task is be 10cm taller. Some childs are half cm taller and other childs are half cm smaller, the last ones die naturally and only the taller ones survive enough to get offspring. The second is marginally better because it mentions randomness and emphasizes differential survivorship, but the parts about "trying to reach a target" and specifying a particular "task" are misleading at best. I would rewrite the statement as follows (I have edited for grammar, spelling and style as well, but emphasize more substantive deviations with strikeout for omitted parts and boldface for added parts). The substantive edits change the meaning of the statement significantly: most evolutionary biologists would be very uncomfortable with the second statement as written above (setting aside any grammatical issues).
Evolution is has a random component but the species (or natural selection) tries to reach a target, may result in directional change: each generation has some random variation in traits but only individuals with beneficial traits tends to are more likely to survive and produce offspring. For example, In order to survive the task is be 10cm taller. taller individuals survive better than smaller ones. Some offspring are a half cm taller and other children are a half cm smaller; the latter die naturally and only the taller ones survive long enough to produce offspring.
I would probably say "offspring" rather than "children" in a technical context.
Note also that this emphasizes evolution by natural selection; broadly speaking, there are many non-adaptive processes (vicariance, drift ...) that also lead to evolution (change in gene frequencies between generations).
The following is multiple choice question (with options) to answer.
Evolution occurs by what process whereby better-adapted members pass along their traits, according to darwin? | [
"natural change",
"spontaneous variation",
"natural selection",
"organic selection"
] | C | Evolution is a change in the characteristics of living things over time. As described by Darwin, evolution occurs by a process called natural selection . In natural selection, some members of a species, being better adapted or suited to their environment, produce more offspring than others, so they pass "advantageous traits" to their offspring. Over many generations, this can lead to major changes in the characteristics of the species. Evolution explains how living things are changing today and how modern living things have descended from ancient life forms that no longer exist on Earth. As living things evolve, they generally become better suited for their environment. This is because they evolve adaptations. An adaptation is a trait that helps an organism survive and reproduce in a given environment. |
SciQ | SciQ-1648 | botany, plant-physiology, plant-anatomy
Title: Sporophyte and gametophyte
My textbook says that in both groups of seedless plants (vascular plants, non-vascular plants) the gametophyte is a free-living plant, independent of the sporophyte.
I don't understand this statement and am now wondering if the sporophyte and gametophyte are stages in a plant's lifecycle, or are they individual parts of the plant, or are the sporophyte and the gametophyte different plants altogether? Secondly, does this differ depending on the organism?
Different plants or different structures that make up the same organism? The sporophtye is the diploid stage in the life cycle. In comparison, with humans, you and I would be sporophytes.
The Gametophyte is the haploid stage in the life cycle. In comparison, with humans, spermatozoids and ovules are gametophytes.
The following is multiple choice question (with options) to answer.
In flowering plants, male gametophytes are in grains of what? | [
"viruses",
"nitrogen",
"bacteria",
"pollen"
] | D | |
SciQ | SciQ-1649 | biochemistry, molecular-biology, cell-biology, cell-membrane
Once you have a firm grasp on that, consider that in order for a hydrophobic molecule to reach a plasma membrane, it must already be solvated by water. The transfer of a hydrophobe from one hydrophillic environment (water) to another (head groups of the phospholipids in the plasma membrane) should be energetically negligible. The limiting step for passive diffusion across a membrane is transfer from the hydrophillic environment of the phospholipid head groups to the hydrophobic environment of their tails. In fact, the rate of diffusion across a plasma membrane increases with hydrophobicity.
The following is multiple choice question (with options) to answer.
How many different ways can molecules pass through a phospholipid membrane? | [
"four",
"three",
"six",
"five"
] | B | There are three main ways that molecules can pass through a phospholipid membrane. The first way requires no energy input by the cell and is called passive transport. The second way requires that the cell uses energy to pull in or pump out certain molecules and ions and is called active transport. The third way is through vesicle transport, in which large molecules are moved across the membrane in bubble-like sacks that are made from pieces of the membrane. |
SciQ | SciQ-1650 | meteorology, snow, radar
Also note that winter precipitation adds an extra complication because the particles are lighter in weight and can thus be blown about more by vertical and horizontal winds. Raindrops (and hail) are quite likely to fall unless extreme updrafts exist because they are heavy. But drizzle, snow, and sleet may be blown around quite a bit. Without a time-intensive dual-Doppler analysis, you cannot know the wind motion in the storm thoroughly, and therefore will have varying results at times.
And finally, the big wrench is unfortunate inherent to how radars work. They measure the percentage of their sent energy that is reflected back to them. That's great because that's directly connected to the diameter of the item falling (to the 6th power). But unfortunately the grand problem is that in a storm, there is a huge variety of drop/flake sizes mixed together at once... such that we can't extract which combination of particle sizes created it (and thus can't calculate volume to actually know the rain/snow amount that falls). It could be like 6 medium size flakes causing the 10 dBZ echo... or 2 large flakes and 10 small flakes... and each combination is a different volume/snow total. (to see the nitty-gritty math details on this, read more here.) So we can never know for sure the exact rain/snow falling using just radar. The good news is we've at least done lots of experiments and come up with some fairly useful best-practice formulas for using the Z-R ratio in different scenarios. Good, but not perfect.
The following is multiple choice question (with options) to answer.
Snow and rain are forms of what weather? | [
"cold fronts",
"precipitation",
"evaporation",
"sediment"
] | B | |
SciQ | SciQ-1651 | energy, electricity, heat
Title: Electricity directly from heating a material I am looking for some more information about how to obtain electricity from heat directly. This e.g. involves the Seebeck effect, as I have found it is called, where a material produces a voltage across when heated in one end and having the other end slightly cooler. This should be the princip in measuring instruments etc., since just a small voltage is created.
This Wikipedia link explains what the phenomenon is about. But it is not well explained in an understandable language (for me at least). And it doesn't dive deep enough into the reason.
Are there someone who can in a down-to-earth way explain how and why a voltage can be measured between the ends of a bar of a certain material, when it is heated in one end? My question regards what happens on the atomic scale - can heat push electrons or what?
Thanks. The electrons in a metal are whizzing around due to thermal energy. Lattice vibrations excite the electrons, the electrons travel some distance then scatter off the lattice again and transfer energy back to the lattice. Just like a gas, the electrons have some average mean free path, and this depends on the temperature. You would think the mean free path would increase with temperature, because the lattice transfers more energy to the electrons, but the rate of scattering off the lattice also increases with temperature. How the mean free path behaves with temperature depends on the trade-off between these two effects, and the varation with temperature can be positive or negative.
Anyhow, if you heat one end of a metal rod and cool the other then the mean free path will be different at the two ends, and the electrons at the end with the higher mean free path will tend to diffuse into the end with the lower mean free path. The result is a net charge movement, and this creates the potential difference.
The following is multiple choice question (with options) to answer.
There is a positive correlation between the ability to conduct thermal energy and what other energy, as exemplified by metals? | [
"gravitational",
"elastic",
"nuclear",
"electricity"
] | D | Your feet feel cold as you walk barefoot across the living room carpet in your cold house and then step onto the kitchen tile floor. This result is intriguing, since the carpet and tile floor are both at the same temperature. The different sensation you feel is explained by the different rates of heat transfer: the heat loss during the same time interval is greater for skin in contact with the tiles than with the carpet, so the temperature drop is greater on the tiles. Some materials conduct thermal energy faster than others. In general, good conductors of electricity (metals like copper, aluminum, gold, and silver) are also good heat conductors, whereas insulators of electricity (wood, plastic, and rubber) are poor. |
SciQ | SciQ-1652 | fluid-dynamics, waves, geophysics
Title: What is the dominant cause for ocean waves at a beach? What is the dominant cause for ocean waves at a beach? Are they the result of wind/pressure difference? If so, the waves do seem to exist in similar intensity even during relative quiet times of the day.
Is there a simple mathematical model that we can quickly explain the intensity/frequency of waves with? Does the strength of the waves (say the variance and mean of the amplitude of waves) relate to a simple physical quantity (temperature, off shore wind, pressure difference)? Yes, primarily wind. It's called the Kelvin-Helmholtz instability. Strong winds in an area will excite a range of wavelengths, the longer wavelengths will go faster according to the deep water dispersion relation ( speed proportional to square root of wavelength). So if you see a train of waves with decreasing wavelength over time, you could in principle infer a common point of origin (this is a common textbook or qualifying exam type problem).
The following is multiple choice question (with options) to answer.
Most ocean waves are caused by what? | [
"wind",
"animals",
"radiation",
"gravity"
] | A | A: Most ocean waves are caused by wind blowing across the water. Moving air molecules transfer some of their energy to molecules of ocean water. The energy travels across the surface of the water in waves. The stronger the winds are blowing, the larger the waves are and the more energy they have. |
SciQ | SciQ-1653 | terminology, meteorology
I've tried to illustrate the relationships with insolation and temperature here:
There are some other ways too:
Ecological. Scientists who study the behaviour of organisms (hibernation, blooming, etc.) adapt to the local climate, sometimes using 6 seasons in temperature zones, or only 2 in polar and tropical ones.
Agricultural. This would centre around the growing season and therefore, in North America and Europe at least, around frost.
Cultural. What people think of as 'summer', and what they do outdoors (say), generally seems to line up with local weather patterns. In my own experience, there's no need for these seasons to even be 3 month long; When I lived in Calgary, summer was July and August (hiking), and winter was December to March (skiing). Here's another example of a 6-season system, and a 3-season system, from the Aboriginal people of Australia, all based on weather.
Why do systems with later season starting dates prevail today? Perhaps because at mid-latitudes, the seasonal lag means that the start of seasonal weather is weeks later than the start of the 'insolation' period. In a system with no heat capacity, there would be no lag. In systems with high heat capacity, like the marine environment, the lag may be several months (Ibid.). Here's what the lag looks like in three mid-latitude cities:
The exact same effect happens on a diurnal (daily) basis too — the warmest part of the day is often not midday (or 1 pm in summer). As with the seasons, there are lots of other factors too, but the principle is the same.
These aren't mutually exclusive ways of looking at it — there's clearly lots of overlap here. Cultural notions of season are surely rooted in astronomy, weather, and agriculture.
The following is multiple choice question (with options) to answer.
What kind of climates are found at or near the equator? | [
"dry grasslands",
"tropical climates",
"arctic climates",
"tundra"
] | B | Tropical climates are found at or near the Equator. Because warm air rises at the Equator, there is a lot of rain. |
SciQ | SciQ-1654 | elements, isotope
In these materials, deviations from "natural abundance" are sometimes
measured in factors of 100
Terrestial
When our solar system was forming, elements and isotopes were not uniformly distributed - close to uniform, but not exactly uniform. This is due to processes like diffusion in which a mass-dependent fractionation occurs. A heavier isotope won't travel as far as a lighter isotope in a given amount of time, so the resulting distribution of the two isotopes will not be exactly equal. While these mass-dependent processes account for most of the isotopic variation in our solar system, mass-independent processes can play a smaller role. It is also suggested that catastrophic events in nearby stars may have also influenced local elemental and isotopic homogeneity. These "original" inhomogeneities will be further altered by a continuation of the mass-dependent (diffusion, bond-breaking and making, etc.) and -independent processes. Natural radioactive decay processes can also lead to changes in local isotope ratios. For example, $\ce{^238U}$ ultimately decays to $\ce{^206Pb}$, so it wouldn't be surprising to find an altered lead isotope ratio (e.g. enriched in $\ce{^206Pb}$) around large uranium deposits.
This paper presents a study of the natural isotopic variation found on earth. Here is a table from the paper that gives an idea of the range in variation. As expected it is much smaller than the extraterrestial variation, but certainly not insignificant. For boron and copper, the isotopic variation is on the order of parts per hundred, but more typically isotopic variation is on the order of parts per thousand.
The following is multiple choice question (with options) to answer.
The uranium series is a chain constituting one what, which encompass naturally occurring isotopes of the heaviest elements? | [
"radioactive decay family",
"gland decay family",
"fuel decay family",
"nuclear decay family"
] | A | Radioactive Decay Series The naturally occurring radioactive isotopes of the heaviest elements fall into chains of successive disintegrations, or decays, and all the species in one chain constitute a radioactive family, or radioactive decay series. Three of these series include most of the naturally radioactive elements of the periodic table. They are the uranium series, the actinide series, and the thorium series. The neptunium series is a fourth series, which is no longer significant on the earth because of the short half-lives of the species involved. Each series is characterized by a parent (first member) that has a long half-life and a series of daughter nuclides that ultimately lead to a stable end-product—that is, a nuclide on the band of stability (Figure 21.9). In all three series, the end-product is a stable isotope of lead. The neptunium series, previously thought to terminate with bismuth-209, terminates with thallium-205. |
SciQ | SciQ-1655 | thermodynamics, electromagnetic-radiation
Suppose your 100W light source emits all its energy as wavelengths longer than 4$\mu$m where the absorptance is virtually 100%. That means the glass is absorbing the whole 100W and heating up at some corresponding rate.
Between about 200nm and 2000nm the absorption is only about 10%, so if if you tweak your light bulb to emit all its energy as wavelengths in this range it would only absorb 10W. So it would still heat up but at only one tenth the speed of of the other bulb.
So you could still solve the puzzle, but you might need a sensitive thermometer. To make the puzzle impossible to solve you would need a glass that absorbs no radiation at all, and as far as I know no such glass exists.
The following is multiple choice question (with options) to answer.
Producing light without a high temperature is called? | [
"plasma",
"fluorescence",
"luminescence",
"effervescence"
] | C | Producing light without a high temperature is called luminescence. Types of luminescence include fluorescence, electroluminescence, and bioluminescence. |
SciQ | SciQ-1656 | botany, plant-physiology, ecology, virology, host-pathogen-interaction
Note about symbiosis - comes in reaction to @Gerhard's comment
Different authors use the word symbiosis differently. From wikipedia:
The definition of symbiosis is controversial among scientists. Some believe symbiosis should only refer to persistent mutualisms, while others believe it should apply to any type of persistent biological interaction (i.e. mutualistic, commensalistic, or parasitic).4 After 130+ years of debate,5 current biology and ecology textbooks now use the latter "de Bary" definition or an even broader definition (i.e. symbiosis = all species interactions), with the restrictive definition no longer used (i.e. symbiosis = mutualism)
The following is multiple choice question (with options) to answer.
Mutualism is a symbiotic relationship that has what effect on both species involved? | [
"destructive",
"beneficial",
"disadvantageous",
"harmful"
] | B | Mutualism is a symbiotic relationship in which both species benefit. |
SciQ | SciQ-1657 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
What do you call chemical reactions that take place inside living things? | [
"contaminated reactions",
"autonomous reactions",
"biochemical reactions",
"physical reactions"
] | C | Chemical reactions that take place inside living things are called biochemical reactions . Living things depend on biochemical reactions for more than just energy. Every function and structure of a living organism depends on thousands of biochemical reactions taking place in each cell. |
SciQ | SciQ-1658 | cell-biology, hematology, red-blood-cell
Title: Why are red blood cells considered to be cells? Wikipedia states that a cell is
the basic structural, functional and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently.
It then goes on to state that
All cells (except red blood cells which lack a cell nucleus and most organelles to accommodate maximum space for hemoglobin) possess DNA.
Then why are red blood cells still considered cells, while they can't replicate? Is the definition on Wikipedia just a bad definition? Or are red blood cells wrongly considered cells, but remain so for historical reasons? Or are they considered cells for some other reason, such as this answer which states that red blood cells do contain a nucleus at some point? A very good question, and it is most likely because of the last option. It had a nucleus for part of its life. After the RBC jettisons its nucleus, it still remains very metabolically active for approximately 3 months. It maintains its cell membrane integrity, it metabolizes glucose, it interacts constantly with its environment, numerous cellular functions and structure remain intact... It is extremely specialized for a primary purpose, and no longer requires the nucleus to provide more proteins. It has limited capacity to heal from injury, so it has a limited life span.
Speculation: I wonder if it might lose the nucleus early on so that when it is destroyed in the spleen at the end of its life as RBCs are, the spleen macrophages are not overwhelmed with additional processing of nucleic acids? Macrophage type cells are already working hard in there to clear infectious agents and some immune cells from the blood.
The following is multiple choice question (with options) to answer.
What types of blood cells are required for aerobic respiration? | [
"white blood cells",
"red blood cells",
"grey blood cells",
"large blood cells"
] | B | |
SciQ | SciQ-1659 | thermodynamics, phase-transition, symmetry-breaking, phase-diagram
Title: How to differentiate solid, liquid and gas on the basis of symmetry breaking? I want to ask this question how to solid, liquid and gaseous state arises due to the concept of symmetry breaking? I will differentiate solids from liquids and gases first (which are similar to each other from the symmetry viewpoint) and denote the latter two as fluids.
While going from the fluid to the solid phase there is a first order phase transition. This breaks the translational symmetry in Poincare group to a periodic translational symmetry. In addition rotational symmetry is also broken to rotation by specific angles. You can think of the density and internal energy as the order parameters for this phase transition. Also for solids the n-point correlation functions should be constrained by this broken translational symmetry.
Liquid and gas phases both respect the translational and rotational symmetries which are broken in solids. Their n-point correlators are constrained by similar symmetry principles (though the correlators are different). However they can be distinguished by their density, bulk modulus among other order parameters. For a range of pressure and temperature their phase transition is first order in nature, which becomes second order at the critical pressure and temperature (See the critical point here).
Second order phase transitions can be understood using Landau theory. This nicely models the phase transition as a symmetry breaking problem. Calculation of critical exponents using behaviour of order parameter, response and the response functions allow us to classify all such liquid-gas transitions into different universality classes.
The following is multiple choice question (with options) to answer.
The phase transition of a substance changing from a liquid state to a gaseous state is an example of what? | [
"entropoy",
"catostrophy",
"spirogyra",
"trichina"
] | A | There are many examples in the chemical world of changes in entropy. Phase transitions are one obvious example. When a substance makes a transition from the liquid state to the gaseous state, the particles have many more possible arrangements, because they are no longer confined to a specified volume in which they are close to each other; gas particles can move freely throughout their container. Vaporization represents an increase in entropy. In the opposite direction, a liquid loses entropy when it freezes to a solid. Because solids have very ordered structures, there are fewer possible arrangements of particles that would result in the properties associated with a solid. |
SciQ | SciQ-1660 | homework-and-exercises, kinematics, projectile, displacement
Title: Displacement related question So you have two tracks of different inclines meeting at a point. Two stones are released from this point each one along the direction of one incline, from rest.
Which stone reaches the ground faster? The one on the steeper incline? I don't understand why. By the kinematic equations of motion displacement in the y direction is equal to -gt^2 for both the motions, and since they are released from the same height, they should reach at the same time. I feel like i'm missing something very important... You are forgetting the fact that here normal reaction acting from the track changes the direction of motion the object and only a smaller component of acceleration due to gravity is acting along the direction of motion ($\leq g$).
The following is multiple choice question (with options) to answer.
What is the fracture called when rocks on both sides move? | [
"a crevice",
"a shear",
"a fault",
"a stress fracture"
] | C | If the rocks on one or both sides of a fracture move, the fracture is called a fault ( Figure below ). Faults can occur alone or in clusters. A cluster of faults creates a fault zone . Earthquakes happen when rocks break and move suddenly. The energy released causes an earthquake. |
SciQ | SciQ-1661 | neuroscience, cardiology, action-potential
Title: Do nerve cells cause action potential in cardiac muscle? I think the answer is no, but I am not 100% sure.
If it was yes, then the dendrite of the nerve cell should each time receive a stimulus causing Na+ channels to open, when the contraction happen.
Also, then it would mean that outside events could alter the function of hearth, which would be dangerous.
The heart has a special excitatory system and a contractile system - Sinoatrial node and Pacemaker cells, which control the action potentials in different portions of the heart.
So heart and primarily myocardium i.e. cardiac muscle can depolarise without any external influence with a slow, positive increase in voltage across the cell's membrane.
Do nerve cells cause action potential in cardiac muscle? The vagus nerve controls heart rate. This is the best example of a direct nerve action potential impacting cardiac muscle, although one could argue the adrenaline system to be an indirect mechanism.
The vagus nerve is part of the parasympathetic system, it acts to decrease heart rate. Resting heart rate is maintained by permanent vagal stimulation/tone by the release of acetylcholine.
The following is multiple choice question (with options) to answer.
In heart muscle, what released by neurons activates a signal transduction pathway? | [
"dopamine",
"glutamate",
"glucose",
"acetylcholine"
] | D | |
SciQ | SciQ-1662 | evolution, botany, development, fruit, seeds
What is the point of fruit if not to be eaten? It’s my understanding that organisms will adapt to survive and thrive. I understand that being eaten can spread seeds, but this just seems like too much of a risky tactic to rely on.
Following on from part one: If being eaten is the best way to spread seed, why do some plants avoid this (such as by being poisonous or thorny)? Seeds are spread by many mechanisms
Wind dispersal: When air currents used to spread seeds. Often these plants have evolved features to facilitate wind catching, for example dandelions. Aka, anemochory.
Propulsion & bursting: When seeds are propelled from the plant in an such as in these videos. This is called Ballochory.
Water: Similarly to wind dispersal plants can spread seeds by water movement/currents, aka Hydrochory. This is used by many algae and water living plants.
Sticky Seeds: There are many ways a seed can attach to the outside of an animal - by using hooks, barbs, sticky excretions, hairs. Seeds then get carried by an animal and fall off later. This is epizoochory.
Fruiting: Plants can use seed-bearing fruit to encourage animals to eat the seeds. They will then be spread when the waste is excreted after digestion. This is a process of endozoochory.
More than one way to spread a seed
The following is multiple choice question (with options) to answer.
What do some plants produce that protects dormant seeds and aids in their dispersal? | [
"leaves",
"fruit",
"stems",
"roots"
] | B | |
SciQ | SciQ-1663 | 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.
In a generator, work done to turn the coil is converted to what type of energy? | [
"voltage",
"power",
"electric",
"solar"
] | C | Figure 23.5 Rotation of a coil in a magnetic field produces an emf. This is the basic construction of a generator, where work done to turn the coil is converted to electric energy. Note the generator is very similar in construction to a motor. |
SciQ | SciQ-1664 | star, night-sky
Title: What is this rapidly twinkling red, blue, and white star I saw? Last night, I was on my balcony at 1AM (PST) and I looked up and saw two stars near the horizon (I'd guess ~30 degrees above the horizon), and they were "twinkling" about twice as fast as other stars higher in the sky, and I could clearly see them changing from red to white to blue repeatedly. Other stars in the sky only appeared white to me, and didn't seem to "twinkle" as rapidly as these two stars did. The red and blue make me think of red-shift and blue-shift, but I don't know how I would see both from the same object.
What was I seeing?
I don't know if it helps, but I am in the Los Angeles area, and I was looking in a roughly north direction. almost exactly to the east, according to google maps.
Edit: I tried taking a picture, but light pollution from the nearby street lights wouldn't permit me taking a decent picture. However, I noticed a group of three stars close together in nearly a perfect almost vertical line, and managed to find that in Stellarium. I think I found the two stars I am seeing: Procyon and Sirius
Is there anything about either of these stars that would make them show as red/blue? It's most probably Sirius. At this time of year (at 1 am local time) it's low in the sky in the East, so there is a lot of atmosphere in the way, and as Sirius is a bright bluish star, it will show all the colours described as it twinkles.
The following is multiple choice question (with options) to answer.
What do you call a pattern of stars in the night sky? | [
"constellation",
"planets",
"Solar Systems",
"cluster"
] | A | This is a constellation, a pattern of stars in the night sky. This constellation is called Orion. The features you can see best are his belt and sword. You can see Orion's belt in the sky from many locations. These stars are very bright. For many constellations, the stars are not near each other. They just happen to appear near each other in our sky. |
SciQ | SciQ-1665 | biochemistry, molecules, polymers, chemical-biology
A monomer is the simplest building block of a macromolecule with the properties of that macromolecule. They can be strung together to produce a macromolecule (usually by dehydration synthesis).
I would have no problem with these definitions if not for my teacher mentioning once that some monomers can also be macromolecules by themselves. Because some monomers of certain macromolecules- such as the monosaccharide glucose vs. the disaccharide sucrose or the polysaccharide amylose - can act on their own as an essential and functional carbohydrate, they are macromolecules by themselves.
Is this true? For example, could glucose be a macromolecule by itself?
Thanks. I can't think of an example where a biological monomer would be a macromolecule.
Definitions of macromolecule vary, usually by molecular weight or number of monomers (repeat units).
Personally, I'd go with ~1000 Dalton for a minimum, but the original definition of 1000 atoms is a good start too.
In any case, no biological monomer, including glucose will function the same as a macromolecule.
Consider starch - a macromolecule of sugars. It doesn't dissolve as quickly as simple sugar and has different physical properties.
Update
To clarify my comments.. Macromolecules or polymers are made up of monomers the way words are made up of letters. So no, a glucose molecule isn't really the same as a macromolecule, just like "R" is not a word.
Yes, macromolecules can be used to make larger assemblies like microtubules, filaments, etc., much the same way that words can form sentences and paragraphs.
In the polymer literature there's even the concept of a "macromonomer" referring to a monomer that is already large in size.
In my opinion though, the basic constituents (monomers) are still amino acids, nucleic acids, sugars, etc. These are not macromolecules.
The following is multiple choice question (with options) to answer.
An antigen is a macromolecule that reacts with components of what? | [
"pulmonary system",
"circulatory system",
"digestion system",
"immune system"
] | D | Figure 42.10 An antigen is a macromolecule that reacts with components of the immune system. A given antigen may contain several motifs that are recognized by immune cells. Each motif is an epitope. In this figure, the entire structure is an antigen, and the orange, salmon and green components projecting from it represent potential epitopes. |
SciQ | SciQ-1666 | thermodynamics, entropy
Title: What is at 298 K at standard entropy?
The standard entropy of a substance is the entropy of $1$ mol at $298$K and $1$ bar pressure.
What exactly is at $298$K? The system or the surrounding?
Let's take vapour as an example where $ \ \ce{H2O(g)} \ \ \ \ S^{\Phi}_{298}\approx188.8 \ JK^{-1}mol^{-1}$. Is the $298$K referring to the temperature of the gaseous $\ce{H2O}$? I'm confused. 298K refers to the temperature of the substance and its surroundings. 298K is about 25 degrees Celsius. In other words, the statement can be simplified as:
The standard entropy of a substance is the entropy of 1 mol at room temperature and pressure.
The following is multiple choice question (with options) to answer.
The measure of a substances entropy at 25 degrees celsius is known as it's? | [
"specific entropy",
"standard entropy",
"limited entropy",
"new entropy"
] | B | As the temperature of a perfect crystal increases, its particles start to vibrate slightly around their optimal positions, thus increasing the entropy of the system. The dependence of entropy on temperature varies by substance, so the only temperature at which all crystals have the same entropy is absolute zero. The standard entropy of a substance is a measure of its entropy at 25°C and 1 atm of pressure. Like standard enthalpy of formation values, standard entropies are tabulated for a wide range of substances. However, unlike enthalpy of formation values, all standard entropy values are positive, because the absolute zero for entropy is the most ordered possible state. Additionally, this means that pure elements in their standard states do not have a standard entropy of zero. |
SciQ | SciQ-1667 | human-physiology, digestion, stomach
The stomach accomplishes much of its function by mechanically breaking down the swallowed food particles and mixing them with acid and enzymes into a sort of slurry. To do this, there are three major layers of muscle surround the stomach - from the outside, the longitudinal layer, the circular layer, and the oblique layer. The stomach also has two holes in it - the gastroesophageal opening, coming from the esophagus with the swallowed food/saliva mix, and the pylorus, where the food/acid/enzyme slurry exits into the duodenum, which is the beginning of the small intestine.
Due to the three layers of (rather strong) muscle, the stomach doesn't have a lot of expansion capability once it is filled completely to capacity. Fortunately, this almost never occurs (despite how we may feel after a large meal) because material is always leaving the stomach on its way to enzymatic digestion in the intestines. Additionally, once the stomach is filled to a certain extent, hormones such as leptin are secreted that give you the feeling of being sated, or full, triggering the brain to make you stop eating.
Of course, as we can see with the current epidemic of obesity around the world, the stomach can change its size over time. However, this is a rather slow process (weeks to months to years) of adapting to continuously consuming large meals.
But what would happen if you completely ignored these internal warnings, or were being force-fed, or whatever? Instead of rupturing (the biological equivalent of "exploding"), food would most likely be expelled either into the small intestine or back into the esophagus and back up the way it came down, i.e. causing vomiting.
The following is multiple choice question (with options) to answer.
Gastric emptying is regulated by both the stomach and what other digestive structure? | [
"small intestine",
"duodenum",
"esophagus",
"appendix"
] | B | greater amount of chyme at one time would overwhelm the capacity of the small intestine to handle it. The rest of the chyme is pushed back into the body of the stomach, where it continues mixing. This process is repeated when the next mixing waves force more chyme into the duodenum. Gastric emptying is regulated by both the stomach and the duodenum. The presence of chyme in the duodenum activates receptors that inhibit gastric secretion. This prevents additional chyme from being released by the stomach before the duodenum is ready to process it. |
SciQ | SciQ-1668 | 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 the type of cell division where the number of chromosomes is reduced in half? | [
"interphase",
"mitosis",
"cloning",
"meiosis"
] | D | The process that produces haploid gametes is meiosis. Meiosis is a type of cell division in which the number of chromosomes is reduced by half. It occurs only in certain special cells of the organisms. During meiosis, homologous chromosomes separate, and haploid cells form that have only one chromosome from each pair. Two cell divisions occur during meiosis, and a total of four haploid cells are produced. The two cell divisions are called meiosis I and meiosis II. The overall process of meiosis is summarized in Figure below . You can watch an animation of meiosis at this link: http://www. youtube. com/watch?v=D1_-mQS_FZ0 . |
SciQ | SciQ-1669 | human-biology, cancer, medicine
Title: Why are only few cigarette smokers prone to cancer? It's tacit that only a few populace of smokers get cancer. What spares the others from it or what specifically cause cancer in those populace? See this Washington Post Article Cigarette smokers are most certainly prone to cancer. See Cecil Medicine, Chapter 183, on the epidemiology of cancer, exposure to tobacco is the most important environmental risk factor for cancer development, at least in the US:
Exposure to tobacco is the single largest cause of cancer in the United States... All forms of tobacco can cause cancer. Cigarette smoking causes cancer of the lip, oral cavity, nasal cavity, paranasal sinuses, pharynx (nasal, oral, and hypopharnyx), larynx, lung, esophagus (squamous cell and adenocarcinoma), stomach, colorectum, pancreas, liver, kidney (adenocarcinoma and renal pelvis), urinary bladder, uterine cervix, and myeloid leukemia.
Cancer may be identified or the cause of death in fewer smokers than might be expected, though, because smoking is an even greater risk factor for cardiovascular disease, and death due to cardiovascular disease.
Cancer is an unlikely phenomenon in an individual cell, but becomes more likely at the organism level, and even more likely over time. Though tobacco may be the most important environmental risk factor for cancer, age is actually a stronger predictor of cancer (see again, Cecil Chapter 183. Autopsy studies give us a quite remarkable example, this one shows incidental prostate cancer in nearly 60% of men over 80 who died from other causes. That figure is not out of the ordinary. Live long enough and you are likely to develop cancer.
Death due to heart disease may account for the lower than expected rates of cancer diagnoses and deaths in smokers. Nothing prevents cancer as well as dying from something else. And as discussed in the blog in the Washington Post you linked to, up to 2/3 of smokers die from smoking related causes
The following is multiple choice question (with options) to answer.
What is the most common cause of lung cancer? | [
"tobacco smoke exposure",
"restaurant smoke exposure",
"coal smoke exposure",
"tree smoke exposure"
] | A | The new cells gradually move up through the epidermis toward the surface of the body. As they move, they produce the tough, fibrous protein called keratin. |
SciQ | SciQ-1670 | species-identification, mycology
Title: What is these mushrooms in my indoor pot? I am living in Japan and in summer, it's very hot and humid even inside my room.
Today, I've found two mushrooms in the pot of a plant.
What is this species? It's very surprising than within one day they grew like this. They do look a lot like a common mushroom called "shaggy mane" mushroom (Coprinus comatus). This may not be a correct identification though, so do not eat them. They are widespread around the world, but usually grow outside.
Yes it is amazing how rapidly the fruiting body of many fungi can grow. I am providing an interesting Wikipedia link with more information. You can also search to find other images using Google images online.
https://en.wikipedia.org/wiki/Coprinus_comatus
The following is multiple choice question (with options) to answer.
Some consumers such as the mushroom get their energy from what? | [
"inorganic matter",
"dead organic matter",
"solar energy",
"minerals"
] | B | Some consumers such as the mushroom in Figure above get their energy from dead organic matter. For example, they might consume dead leaves on a forest floor. |
SciQ | SciQ-1671 | # 2.2 Histograms, frequency polygons, and time series graphs (Page 2/15)
Page 2 / 15
The smallest data value is 60. Since the data with the most decimal places has one decimal (for instance, 61.5), we want our starting point to have two decimal places. Since the numbers 0.5, 0.05, 0.005, etc. are convenient numbers, use 0.05 and subtract it from 60, the smallest value, for the convenient starting point.
60 – 0.05 = 59.95 which is more precise than, say, 61.5 by one decimal place. The starting point is, then, 59.95.
The largest value is 74, so 74 + 0.05 = 74.05 is the ending value.
Next, calculate the width of each bar or class interval. To calculate this width, subtract the starting point from the ending value and divide by the number of bars (you must choose the number of bars you desire). Suppose you choose eight bars.
$\frac{74.05-59.95}{8}=1.76$
## Note
We will round up to two and make each bar or class interval two units wide. Rounding up to two is one way to prevent a value from falling on a boundary. Rounding to the next number is often necessary even if it goes against the standard rules of rounding. For this example, using 1.76 as the width would also work. A guideline that is followed by some for the width of a bar or class interval is to take the square root of the number of data values and then round to the nearest whole number, if necessary. For example, if there are 150 values of data, take the square root of 150 and round to 12 bars or intervals.
The boundaries are:
• 59.95
• 59.95 + 2 = 61.95
• 61.95 + 2 = 63.95
• 63.95 + 2 = 65.95
• 65.95 + 2 = 67.95
• 67.95 + 2 = 69.95
• 69.95 + 2 = 71.95
• 71.95 + 2 = 73.95
• 73.95 + 2 = 75.95
The following is multiple choice question (with options) to answer.
What does the second number in a blood pressure reading measure? | [
"external pressure",
"optimal pressure",
"epithelial pressure",
"diastolic pressure"
] | D | Blood pressure is read as two numbers. The first number is the systolic pressure. The systolic pressure is the pressure on the blood vessels when the heart beats. This is the time when there is the highest pressure in the arteries. The diastolic pressure, which is the second number, is when your blood pressure is lowest, when the heart is resting between beats. |
SciQ | SciQ-1672 | plate-tectonics, crust, mantle, cavern
Title: How likely are caverns inside the mantle? Almost everyone wrongly assumes that the Earth's mantle is liquid, but it isn't (only the outer core is). Is it possible then that there are hollow spaces within the mantle, similar to caves in the crust? What could they look like and up to how much of the mantle could be hollow? What might be inside mantle caverns? Would they be filled with gas or rather vacuum? It is extremely unlikely that any hollow volumes exist in the mantle.
The mantle is a convecting solid which can deform over long timescales. Let's assume that such a cavern did somehow form. Whatever it is filled it, would be of lower density than the surrounding rock. It would slowly rise upwards through the solid-yet-deformable mantle until it reaches a place where the rocks are brittle, not ductile. That place is the crust. And as you know, the crust is full of caverns and there is no problem with that.
The following is multiple choice question (with options) to answer.
The rock of the mantle is mostly what? | [
"metamorphic",
"crystalline",
"peridotite",
"silicon"
] | C | The rock of the mantle is mostly peridotite. Peridotite is formed of crystals of olivine (green) and pyroxene (black). |
SciQ | SciQ-1673 | species-identification, invertebrates
Title: Identification of odd jellyfish-like creature in the Mediterranean My parents encountered this unknown creature on a beach in Karpathos, Greece.
None of the locals have seen it before, it may be a species that has moved further north due to ocean warming.
Any ideas what it is? It seems to be a "Hula skirt siphonophore" - Physophora hydrostatica
Physophora hydrostatica, also known as hula skirt siphonophore, is a
species of siphonophores in the family Physophoridae.1
https://en.wikipedia.org/wiki/Physophora_hydrostatica
The following is multiple choice question (with options) to answer.
Ocean ridges formed by marine invertebrates living in warm shallow waters within the photic zone of the ocean are called what? | [
"trenches",
"break water",
"coral reefs",
"lagoon"
] | C | In which of the following regions would you expect to find photosynthetic organisms? a. The aphotic zone, the neritic zone, the oceanic zone, and the benthic realm. The photic zone, the intertidal zone, the neritic zone, and the oceanic zone. The photic zone, the abyssal zone, the neritic zone, and the oceanic zone. The pelagic realm, the aphotic zone, the neritic zone, and the oceanic zone. Coral Reefs Coral reefs are ocean ridges formed by marine invertebrates living in warm shallow waters within the photic zone of the ocean. They are found within 30˚ north and south of the equator. The Great Barrier Reef is a well-known reef system located several miles off the northeastern coast of Australia. Other coral reefs are fringing islands, which are directly adjacent to land, or atolls, which are circular reefs surrounding a former island that is now underwater. The coral-forming colonies of organisms (members of phylum Cnidaria) secrete a calcium carbonate skeleton. These calcium-rich skeletons slowly accumulate, thus forming the underwater reef (Figure 20.29). Corals found in shallower waters (at a depth of approximately 60 m or about 200 ft) have a mutualistic relationship with photosynthetic unicellular protists. The relationship provides corals with the majority of the nutrition and the energy they require. The waters in which these corals live are nutritionally poor and, without this mutualism, it would not be possible for large corals to grow because there are few planktonic organisms for them to feed on. Some corals living in deeper and colder water do not have a mutualistic relationship with protists; these corals must obtain their energy exclusively by feeding on plankton using stinging cells on their tentacles. |
SciQ | SciQ-1674 | inorganic-chemistry
Title: What causes triboluminescence and what process occurs to produce light? I have observed this effect by rubbing together two pieces of quartz in a dark room but am unable to explain this effect. Would it be something to do with the way quartz is bonded as a covalent network? I'm only a first year chemical engineering student, and we haven't really covered this topic in our course yet, but I will try and answer your question to the best of my knowledge.
(I am sure people more qualified me would provide better responses.)
When we apply certain stresses to a material such as a crystal, we separate charges (which is why it usually is asymmetric... the presence of anistropy allows charge separation.) These charges then can cause electric discharge, which ionizes the surrounding air and releases a flash of light.
There exist symmetric crystals which display this phenomenon as well... and it is suggested that (probably) impurities exist within such crystals which break the symmetry.
Anyway, this is my understanding of the phenomenon, and I don't claim is perfect in any way, but hopefully is helpful to you.
The following is multiple choice question (with options) to answer.
What compound is formed when there are sparking electrical equipment? | [
"water",
"smog",
"ozone",
"carbon"
] | C | The sharp odor associated with sparking electrical equipment is due, in part, to ozone. |
SciQ | SciQ-1675 | nuclear-physics, physical-chemistry, mass-energy, binding-energy
Nuclear reactions are kind of in the middle between the two extremes of chemical reactions and elementary particle reactions. In an atomic nucleus, the binding energy contributes anywhere from 0.1% up to about 1% of the total energy of the nucleus. This is a lot less than with the color force in the proton, but it's still enough that it needs to be counted as a contribution to the mass of the nucleus. So that's why we say that mass is converted to energy in nuclear reactions: the "mass" that is being converted is really just binding energy, but there's enough of this energy that when you look at the nucleus as a particle, you need to factor in the binding energy to get the right mass. That's not the case with chemical reactions; we can just ignore the binding energy when calculating masses, so we say that chemical reactions do not convert mass to energy.
The following is multiple choice question (with options) to answer.
What is the number of protons in the nucleus? | [
"metallic number",
"element",
"atomic mass",
"atomic number"
] | D | At least by our current understanding, a given atom can be defined by its atomic number and its mass number. The atomic number is the number of protons in the nucleus. All atoms with a given atomic number are the same element, because the chemical properties of an atom are primarily determined by the number of positive charges in its nucleus (and therefore the number of negatively charged electrons needed to make it neutral). The mass number of an atom is equal to the number of protons plus the number of neutrons. Since these particles both have a mass of approximately 1 amu and electrons are much smaller, the mass number is approximately equal to the mass of the atom in units of amu. |
SciQ | SciQ-1676 | species-identification, entomology
Title: Unknown larvae in grey cocoon Location: Germany
While cleaning the windows today, I realized some dirt falling off the top of the window frame. By looking further, it seemed to be some kind of cocoon. (The first picture is very bad, I'm sorry)
Those cocoons were about 2-3cm long. There was a total of 6 cocoons.
Two were damaged by falling down.
The last picture shows the inner part of the second picture I think. The larvae(?) was about 0.8cm to 1cm long.
Not sure if it matters, but the window is an attic window, located at the third floor.
Do you have any idea, what kind of larvae it is? This is a neophyte that has been recorded in Europe since 1979:
Sceliphron curvatum, in German also known as orientalische Mörtelwespe. Unusually large considering what else is buzzing around, but mostly harmless.
The nests, or rather individual larvae cells, are made of mud and while there are about thirty species in the genus, only Sceliphron curvatum is found in Germany - there‘s no other wasp or other insect in Germany that builds similar nest cells, especially the size is a good indicator. Your description of nest location in a window frame is typical, curtain folds or (vertical) nooks in furniture, e.g. shelves are also welcome. Our specimen picked a hiding spot behind a few books a few years ago.
Because of their size, there are usually some articles about them in the low-news summer media lull, describing baffled citizens and their “discovery”. A few less sensational descriptions, photos and further information can be found here (sorry, in German).
Nice find!
The following is multiple choice question (with options) to answer.
What organism is at the top of the energy pyramid? | [
"carnivore",
"insects",
"primate",
"herbivore"
] | A | Each step of the food chain in the energy pyramid is called a trophic level . Plants or other photosynthetic organisms ( autotrophs ) are found on the first trophic level, at the bottom of the pyramid. The next level will be the herbivores, and then the carnivores that eat the herbivores. The energy pyramid ( Figure below ) shows four levels of a food chain, from producers to carnivores. Because of the high rate of energy loss in food chains, there are usually only 4 or 5 trophic levels in the food chain or energy pyramid. There just is not enough energy to support any additional trophic levels. Heterotrophs are found in all levels of an energy pyramid other than the first level. |
SciQ | SciQ-1677 | human-biology, physiology, cardiology, anatomy
Title: Can humans live without their right atrium? The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated blood from the superior and inferior venae cavae, the coronary sinus, and the anterior and smallest cardiac veins, and pumps it into the right ventricle through the tricuspid valve.
Can humans survive without right atrium? In this condition blood would fill the right ventricle directly, comparable to some animals like frogs, toads, snakes and lizards. What advantages does the normal human heart have to this anatomy ? If we had this anatomy, where would the best place for pacemakers be, like the sinus node? This is an interesting theoretical question, but several things would need to be clarified:
Does removing the R atrium relocate the SA node to the R ventricle or remove it completely from the picture?
Does the remaining R ventricle have a tricuspid valve?
Technically, the R atrium is the home of the sino-atrial node, which provides natural pacing of the human heart between 60-80 beats/min. Without this natural pacing, our hearts would rely on back-up pacer systems such as atrioventricular node, His-Purkinje systems or the intrinsic but ectopic pacing of individual atrial or ventricular cells.
The following is multiple choice question (with options) to answer.
What structure of the heart receives oxygen-poor blood from the body, then pumps the blood into the right ventricle? | [
"left ventricle",
"left atrium",
"right atrium",
"right ventricle"
] | C | One path of blood in the heart is through the right atrium and right ventricle. The right atrium receives oxygen-poor blood from the body. It pumps the blood into the right ventricle. Then the right ventricle pumps the blood out of the heart to the lungs. This path through the heart is part of the pulmonary circulation. |
SciQ | SciQ-1678 | cell-biology, molecular-biology
Title: Intracellular lipid transport I know that lipids are carried around the body in the blood either as micelles or by lipid-binding proteins which allow them to be solved.
Lipids can't always be integrated in a membrane though, the phospholipids used in membranes have to be synthesised somewhere from a precursor which will also by hydrophobic.
Consequently, at some point there will have to be transport of lipids within the cell where the lipids will need to be in solution. How is this facilitated? Like in the blood, intracellular lipid trafficking is facilitated by vesicular transport and lipid carriers like fatty acid binding proteins. In addition, intracellular membranes are densely packed and they can exchange lipids by collision and transient hemifusion. If you have access to Cell, a good review is from Prinz W. 2010 Lipid Trafficking sans vesicles, Where, Why, How?
The following is multiple choice question (with options) to answer.
Which organelle is often compared to a post office, moving proteins and lipids to where they need to go? | [
"the golgi apparatus",
"the cytoplasm",
"the nucleus",
"the cell wall"
] | A | The Golgi apparatus is a large organelle that sends proteins and lipids where they need to go. It’s like a post office. It receives molecules from the endoplasmic reticulum. It packages and labels the molecules. Then it sends them where they are needed. Some molecules are sent to different parts of the cell. Others are sent to the cell membrane for transport out of the cell. Small bits of membrane pinch off the Golgi apparatus to enclose and transport the proteins and lipids. You can see a Golgi apparatus at work in this animation:. |
SciQ | SciQ-1679 | Is it 10% from each dimension or from the volume? Hard to figure out from the problem.
Why? The problems says "The dimension of each container is decreased by 10 percent". That tells you precisely which is intended
If from the each dimension then:
V 1= 50x 60x 120 = 360000 cm3 = 360 litres
V2=45 x 54 x 108 = 262440 cm3 = 262.4 liltres
V 3 = 40.5 x 48.6 x 97.2 = 191.3litres
V4 = 36.45 x 43.74 x 87.48 =139.4 litres
V5 = 32.81 x 39.37 x 78.74 = 101.7 litres
V6 = 29.61 x 35.47 x 70.94 =74.5 litres
I need some feedback.
4. Hello, terminator!
A hardware supplier has designed a series of six plastic containers with lids
. . where each container (after the first) can be placed into the next larger one.
The containers are rectangular boxes.
. . The dimensions of the largest one are 120 cm by 60 cm by 50 cm.
The dimensions of each container are decreased by 10 percent
. . with respect to the next larger one.
(a) Determine the volume of each container.
(b) Determine the volume of all the containers.
Write your answers in litres (one litre = 1000 cubic cm).
The original box has dimensions $L,\,W,\,H$
. . Its volume is: . $L\!\cdot\!W\!\cdot\!H\text{ cm}^3$
The next box has dimensions: $0.9L,\,0.9W,\,0.9H$
. . Its volume is: . $(0.9L)(0.9W)(0.9H) \:=\:0.729(LWH)$
That is, each box is 0.729 of the volime of the next larger box.
The first box has volume: . $120\cdot60\cdot50 \:=\:360,\!000\text{ cm}^3$
. . That is: . $V_1 \:=\:360\text{ liters.}$
The following is multiple choice question (with options) to answer.
What takes both the shape and the volume of their container? | [
"fluids",
"tissues",
"solids",
"gases"
] | D | Solids have a fixed volume and a fixed shape. Liquids have a fixed volume but take the shape of their container. Gases take both the volume and the shape of their container. |
SciQ | SciQ-1680 | 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 is the lowest level of organization that can perform all activities required for life? | [
"the cell",
"nucleii",
"organs",
"tissues"
] | A | |
SciQ | SciQ-1681 | dna, zoology, radiation, entomology
1.-3. Therefore, the only sensitive part of insects is the intestinal epithelium which gets renewed on a regular basis (similar to that of humans, also a known target of radiation), but...
Insects (and generally the arthropodes) are known to have exoskeleton. This potentially serves as a good "armor" for vulnerable intestine cells, filtering out the most heavy particles (like alpha- and in some respect also the beta-particles).
EDIT: This seems not to be real protection, see the discussion in comments.
Therefore it is not a surprise that insects generally show much higher resistance against radiation.
EDIT:
As it was correctly added in the comments, there are also gamets, that are most sensitive to radiation (because they bear only the half of the normal genetic information and cannot repair mutations). Even though the lesions in gamets do not lead to immediate death, the potential sterility can easily cause the extinction.
However, cockroaches (and insects generally) are known to be r-animals, meaning that they favor the quantity (r) over quality (K) of their off-spring. This strategy is optimal when dealing with radiation-induced changes in gametes: the high number of offsprings compensates for the genetic imperfections in gametes.
[a] -- meaning that is has secreted peptides in their hemolymph that protect them
[b] -- there are phagocytes, somewhat similar to tissue magrophages in humans, but the rest of the cell chains in immune response in vertrebrates, like T- and B-cells, are completely missing. Those are responsible for the mediation and amplification of the immune response in vertebrates and are the cells that are most susceptible to radiation damage.
The following is multiple choice question (with options) to answer.
Where are most of the organs contained in insects? | [
"the abdomen",
"head",
"thorax",
"appendages"
] | A | Like other arthropods, insects have three body segments and many jointed appendages. The abdomen contains most of the internal organs. Six legs are attached to the thorax. There are several appendages on the insect’s head:. |
SciQ | SciQ-1682 | 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.
The appendicular skeleton is made up of all bones of the upper and lower what? | [
"limbs",
"hemispheres",
"digestive tract",
"organs"
] | A | Figure 7.2 Axial and Appendicular Skeleton The axial skeleton supports the head, neck, back, and chest and thus forms the vertical axis of the body. It consists of the skull, vertebral column (including the sacrum and coccyx), and the thoracic cage, formed by the ribs and sternum. The appendicular skeleton is made up of all bones of the upper and lower limbs. |
SciQ | SciQ-1683 | electricity, batteries
A battery's capacity is the amount of electric charge it can deliver
at the rated voltage. The more electrode material contained in the
cell the greater its capacity. A small cell has less capacity than a
larger cell with the same chemistry, although they develop the same
open-circuit voltage.[30] Capacity is measured in units such as
amp-hour (A·h). The rated capacity of a battery is usually expressed
as the product of 20 hours multiplied by the current that a new
battery can consistently supply for 20 hours at 68 °F (20 °C), while
remaining above a specified terminal voltage per cell. For example, a
battery rated at 100 A·h can deliver 5 A over a 20-hour period at room
temperature. The fraction of the stored charge that a battery can
deliver depends on multiple factors, including battery chemistry, the
rate at which the charge is delivered (current), the required terminal
voltage, the storage period, ambient temperature and other
factors.[30]
The higher the discharge rate, the lower the capacity.[31] The
relationship between current, discharge time and capacity for a lead
acid battery is approximated (over a typical range of current values)
by Peukert's law:
${\displaystyle t={\frac {Q_{P}}{I^{k}}}}$
$Q_P$ is the capacity when discharged at a rate of 1 amp.
${\displaystyle I}$ is the current drawn from battery (A).
${\displaystyle t}$ is the amount of time (in hours) that a battery
can sustain.
${\displaystyle k}$ k is a constant around 1.3.
Using this law, you can see that for lower current, the discharge (drain) time is larger. Vice versa, for higher current, the discharge time is smaller.
In other words, $t_1(T_1) < t_2(T_2)$ or for higher temperature the discharge time is longer.
The following is multiple choice question (with options) to answer.
What can be thought of as the capacity a device has for storing charge? | [
"velocity",
"resonance",
"capacitance",
"potential"
] | C | The amount of charge, , held by each plate is given by where again is the voltage difference between the plates and is the capacitance of the plate configuration. Capacitance can be thought of as the capacity a device has for storing charge . In the parallel plate case the capacitance is given by where is the area of the plates, is the distance between the plates, and is the permittivity of free space whose value is . |
SciQ | SciQ-1684 | waves, electromagnetic-radiation
(Image Credit: https://www4.uwsp.edu/physastr/kmenning/Phys202/Lect16.html)
The following is multiple choice question (with options) to answer.
What do electromagnetic receptors detect? | [
"subtle radiation",
"dangerous radiation",
"background radiation",
"electromagnetic radiation"
] | D | |
SciQ | SciQ-1685 | cell-biology, nutrition, blood-circulation, liver
Title: How do nutrients get to the cells they need to get to? I understand the basics of digestion. I know that nutrients get absorbed by the microvilli, enter the bloodstream and travel to the liver but after all that, what is the biological mechanism that guides these nutrients to the proper receiving location? Broadly speaking, nutrients that enter the blood from the gut, and those that are released into the blood by the liver, are available to any cells that require them. So there is no "guiding to the correct location" in the sense that you suggest.
Lipids for example are present in the various lipoproteins and can be acquired from these by all cells. Iron is bound to transferrin, and any cell with transferrin receptors can internalise the transferrin and take the iron. Glucose is available in solution in the plasma, and free fatty acids are bound to serum albumin in the blood. During starvation the liver produces ketones ("ketone bodies") which are taken up by many different tissues/cell types.
The following is multiple choice question (with options) to answer.
Nutrients from food are absorbed by the blood for transport around the body as part of what system? | [
"growth",
"digestive",
"respiratory",
"circulatory"
] | B | In the digestive system, food is digested and its nutrients are absorbed by the blood for transport around the body. The blood is part of the cardiovascular system. |
SciQ | SciQ-1686 | thermodynamics, evaporation, gas, liquid-state
On the water surface, knowing the temperature, we can estimate the vapor pressure and vapor mixture fraction. Then there will be an diffusion process for the water vapor to move out and for the ambient air to move in. Because the water surface doesn't allow the air to further move, a circulation forms. When the water vapor moves out, the water vapor pressure drops, so more liquid water evaporates to fill up the loss of water vapor. The evaporation associates latent heat so water surface area temperature drops (you may see dew on the bowl wall). Then a heat transfer process starts which may initiate water circulation as well.
As this is complex, doing test might be a quick way to get the K value if you assume it is a constant, which is questionable.
The following is multiple choice question (with options) to answer.
What occurs when plants release water vapor through stomata (leaf pores)? | [
"inhalation",
"evaporation",
"transpiration",
"crystallization"
] | C | Transpiration occurs when plants release water vapor through leaf pores called stomata (see Figure below ). The water is a product of photosynthesis. |
SciQ | SciQ-1687 | human-biology, immunology, antibody
Title: Transfer of antibodies in breast milk of humans Why isn't the IgA secreted in breast milk digested due to proteases of the digestive system in the baby?
Wikipedia says:
The secretory component of sIgA protects the immunoglobulin from being
degraded by proteolytic enzymes, thus sIgA can survive in the harsh
gastrointestinal tract environment and provide protection against
microbes that multiply in body secretions.
But what exactly does the secretory component do? What is the secretory component? Is IgA absorbed in the circulation of fetus? I remember reading it somewhere that it is not absorbed, at least in humans. Please answer these questions focusing more on humans. Though, information about other animals will be appreciated as well. It is! Here is an amazing review from 2011 that literally has all the answers. I'm not kidding, all of them. I would marry this review if I could.1 It also includes information on other animals.
The main takeaway is that IgA from milk is not readily absorbed by the infant body. Secreted IgA is mainly to provide a protective coating for the mucosa while the infant is developing its own nascent immune system. IgG passed along from the placenta (your other question) provides the main source of absorbed antibodies. As it says in the review:
Milk sIgA is not taken up by the infant’s intestinal mucosa. In fact, gut closure in humans occurs before birth and little immunoglobulin is absorbed intact in the intestine after birth. However, the presence of sIgA in the intestinal lumen is part of the protective function of the epithelial barrier in the intestine... Secretory IgA is considered to be the primary immunoglobulin responsible for immune protection of mucosal surfaces such as the intestine.
In terms of enzymatic activity, the digestive system will in indeed chomp up the antibodies; that's part of the reason breast feeding should continue as needed. That's okay, because there's plenty to go around:
Much of the immunoglobulin consumed in an immune milk can be expected to be partially or completely digested, however some portion of the immunoglobulin will remain intact or at least partially intact and capable of binding to an antigen.
The following is multiple choice question (with options) to answer.
The stomach mucosa’s epithelial lining consists only of surface mucus cells, which secrete a protective coat of what? | [
"phosphate mucus",
"alkaline mucus",
"acidic mucus",
"bile mucus"
] | B | The stomach mucosa’s epithelial lining consists only of surface mucus cells, which secrete a protective coat of alkaline mucus. A vast number of gastric pits dot the surface of the epithelium, giving it the appearance of a well-used pincushion, and mark the entry to each gastric gland, which secretes a complex digestive fluid referred to as gastric juice. Although the walls of the gastric pits are made up primarily of mucus cells, the gastric glands are made up of different types of cells. The glands of the cardia and pylorus are composed primarily of mucus-secreting cells. Cells that make up the pyloric antrum secrete mucus and a number of hormones, including the majority of the stimulatory hormone, gastrin. The much larger glands of the fundus and body of the stomach, the site of most chemical digestion, produce most of the gastric secretions. These glands are made up of a variety of secretory cells. These include parietal cells, chief cells, mucous neck cells, and enteroendocrine cells. Parietal cells—Located primarily in the middle region of the gastric glands are parietal cells, which are among the most highly differentiated of the body’s epithelial cells. These relatively large cells produce both hydrochloric acid (HCl) and intrinsic factor. HCl is responsible for the high acidity (pH 1.5 to 3.5) of the stomach contents and is needed to activate the protein-digesting enzyme, pepsin. The acidity also kills much of the bacteria you ingest with food and helps to denature proteins, making them more available for enzymatic digestion. Intrinsic factor is a glycoprotein necessary for the absorption of vitamin B12 in the small intestine. Chief cells—Located primarily in the basal regions of gastric glands are chief cells, which secrete pepsinogen, the inactive proenzyme form of pepsin. HCl is necessary for the conversion of pepsinogen to pepsin. Mucous neck cells—Gastric glands in the upper part of the stomach contain mucous neck cells that secrete thin, acidic mucus that is much different from the mucus secreted by the goblet cells of the surface epithelium. The role of this mucus is not currently known. Enteroendocrine cells—Finally, enteroendocrine cells found in the gastric glands secrete various hormones into the interstitial fluid of the lamina propria. These include gastrin, which is released mainly by enteroendocrine G cells. Table 23.6 describes the digestive functions of important hormones secreted by the stomach. |
SciQ | SciQ-1688 | nutrition, hematology, metabolism
Title: How does a glucose molecule enter the cell from blood vessel? The transporters in the plasma membrane of the cells promote the entry of glucose molecules from the extracellular matrix to the cytosol of the cell. Could someone explain how does the nutrient molecule enter the extracellular space from the blood vessel?
For instance, in the context of the pancreas, the walls of the blood vessel is fenestrated. The literature also provides evidence for the presence of connexon in the endothelium of the capillaries.
My doubt is, the nutrient molecule that diffuses from the blood vessel reaches the cytosol of the cell through
Diffusing through connexon ?(or)
Does it reach the interstitial matrix(the fluid surrounding the cells) and then uptaken by the transporters present in the plasma membrane of the cell? I think I understand your question, Natasha. In short, your own answer #2 is correct.
There are 3 spaces, and 2 pathways for glucose to pass from one to the next:
intracapillary plasma
extracellular fluid
the cytosol.
Ways glucose gets into the cell:
(2->3) To get from the ECF to the cytosol , glucose always needs a transport protein. These are the GLUTs. In two cases, the small intestine and kidney, these are part of a secondary active transport system based on the Na/K-ATPase. In the pancreas, it's GLUT2.
(1->2) To get from the capillary plasma to the ECF requires filtration, the process of applying hydrostatic pressure to the plasma and literally squeezing it like a sponge. The boundary of the "blood sponge" is the basement membrane. The membrane holds in the proteins, and lets anything dissolved in the watery serum (like glucose) through.
The Filtration Constant Kf is proportional to the percentage of the BM that is exposed in a given capillary, which varies by the type and other factors like histamine release.
The following is multiple choice question (with options) to answer.
A substance too big to be pumped across the cell membrane may enter or leave the cell by what method? | [
"vesicle infusion",
"absorption",
"vesicle transport",
"passive transpiration"
] | C | Some substances are too big to be pumped across the cell membrane. They may enter or leave the cell by vesicle transport . This takes energy, so it's another form of active transport. You can see how vesicle transport occurs in Figure below . |
SciQ | SciQ-1689 | elements, radioactivity
Title: Why radioactive elements emit alpha beta and gamma rays I am confused about this that why radioactive elements emits alpha beta and gamma rays WHILE other elements can't do so. The stability of nuclei is really a sophisticated topic in theoretical quantum mechanics. But there is a simple way to think about what is happening that doesn't get too intense with the quantum mechanical theory.
Nuclei are made from two particles: protons and neutrons. But protons are positively charged and repel each other. The electromagnetic force is very strong and therefore this force is very large. So the first mystery is why all nuclei don't just fly apart.
The reason they don't is that there are two very short-range but very strong forces that bind the nucleus together: the strong and weak nuclear forces. Without getting into mind-bending topics in theoretical physics we can understand something about their net effect like this.
The interaction of the electromagnetic force and the two nuclear forces has some structure (it's quantum stuff, just accept it). Some combinations of protons and neutrons are more stable than others. Each combination has an energy level and some combinations have lower energy than others. Nuclei with even numbers of protons and neutrons are more stable than odd-odd combinations and nuclei with wildly unbalanced neutron to proton ratios are less stable. Neutrons act a little like a glue, helping protons stick together (this is an oversimplification as too many neutrons is also a source of instability: this is a consequence of a complicated interplay of several forces). But bigger nuclei are less stable and need a higher ratio of neutrons. And some large nuclei are just too large for the forces to keep them together so beyond a certain point all nuclei are unstable.
Some nuclei can be transformed into a more stable (lower energy) nucleus by various forms of radioactive decay. Nuclei with too many neutrons can emit a beta particle (this decay mode converts a neutron into a proton); elements with too many protons can emit a positron (converting a proton into a neutron). Bigger nuclei can become more stable by kicking out an alpha particle (which makes the nucleus significantly smaller, moving it towards the stable zone). Gamma radiation is associated with some of these modes: the high energy photons "mop up" the excess energy (I'm simplifying a lot).
The following is multiple choice question (with options) to answer.
What is the process in which unstable nuclei become stable by emitting particles and energy and changing to different elements called? | [
"nuclear decay",
"radioactive decrease",
"initial decay",
"radioactive decay"
] | D | Radioactive decay is the process in which unstable nuclei become stable by emitting particles and energy and changing to different elements. There are three types of radioactive decay: alpha, beta, and gamma decay. Each differs in what is emitted, how far it can travel, and what it can penetrate. |
SciQ | SciQ-1690 | sensation, olfaction
http://www.comeaddestrareuncane.com/blog/tag/cani-molecolari/
In the dog, the surface of the olfactory mucosa varies between 70 and 150 cm2 - in this tissue the number of olfactory receptors varies from 250 to 280 million - In 1962, Becker et al. showed that dogs are able to recognize substances in dilutions from 1/100 to 1/10.000.000.
- http://milano.corriere.it/milano/notizie/cronaca/12_febbraio_19/cani-olfatto-parere-esperto-1903358352720.shtml
Have you noticed how a dog sniffs the urine of a female "tasting it"? It is the same action that makes the viper when it follows the track of the mouse: it evertes the tongue and carries on it the odorous particles in the buccal cavity, and this organ has a function in the middle between the olfactory and gustatory ones. "Pointing dogs" is as pointing "the wild" taste the smell.
"Eat the scent", in the jargon, because savored, not only in terms of smell, the smell of the wild. The Jacobson's organ is then a second organ capable of perceiving odors, the first we've said is represented ciliated epithelium of the mucous membrane of the nose.
But there is a third organ called the "Rodolfo-Masera" which also serves to sense the emanations chemical (not yet known which), that way you could explain a specialization of these organs to perceive certain groups of biochemicals than others.
- http://www.laciotola.net/Cani/la-funzione-olfattiva-del-cane.html
The following is multiple choice question (with options) to answer.
Most taste buds on the tongue are associated with nipple-shaped projections called what? | [
"antennae",
"papillae",
"mucosa",
"cilia"
] | B | |
SciQ | SciQ-1691 | condensed-matter, solid-state-physics, semiconductor-physics
Title: Is there a energy lower to -13.6 eV in a given atom/element? The Hydrogen atom fundamental energy is -13.6 eV.
Is there an atom that has an energy level lower to -13.6 eV ?
if no, then why, in semiconductor physics, the integral on energy start at $-\infty$ instead of $-13.6\ eV$ ? Yes. Neglecting effects of other electrons, the ground-state energy scales like $Z^2$. So probably all other elements have more negative ground-state energies than hydrogen does.
I recommend reviewing either the Bohr or Schrodinger models for a hydrogen-like atom that has a nucleus that has $Z$ protons.
The following is multiple choice question (with options) to answer.
What is the lowest energy state of the atom called? | [
"active state",
"base state",
"ground state",
"work state"
] | C | The electrons in an atom tend to be arranged in such a way that the energy of the atom is as low as possible. The ground state of an atom is the lowest energy state of the atom. When those atoms are given energy, the electrons absorb the energy and move to a higher energy level. These energy levels of the electrons in atoms are quantized, meaning again that the electron must move from one energy level to another in discrete steps rather than continuously. An excited state of an atom is a state where its potential energy is higher than the ground state. An atom in the excited state is not stable. When it returns back to the ground state, it releases the energy that it had previously gained in the form of electromagnetic radiation. |
SciQ | SciQ-1692 | immunology, cancer, immunosuppression
Title: Normal cells and the immune system Normal or healthy cells have a natural ability to avoid being attacked by the immune system.
So if a cancer cell has all inherited 'strategies' for avoiding the immune system (that are from their earlier pre-cancerous states) does this make them hard to detect or be affected by the immune system. The development of cancer has various reasons. For example in more than 50% of tumors, p53 is mutated. p53 among other things regulates mitosis and forces the cell to arrest in a specific growth state if other systems detected a mutation in the DNA.
But in your special case we have to look at major histocompatibility complexes (MHCs) and NLRC5. There are two types of MHC, namely MHC class I and class II. MHC II presents mostly bacterial peptides to CD4+ T cells causing a immune response. However, MHC I presents viral peptides and peptides from your own body. These peptides are detected by CD8+ T cells which are cytotoxic T cells initializing apoptosis. Without these own peptides natural killer (NK) cells are activated because of a missing-self signal causing apoptosis, too.
The following is multiple choice question (with options) to answer.
What kind of diseases involve the immune system accidentally attacking healthy body cells? | [
"contagious diseases",
"autoimmune",
"metabolic",
"inflammation"
] | B | Autoimmune diseases occur when the immune system fails to recognize the body’s own molecules as “self,” or belonging to the person. Instead, it attacks body cells as though they were dangerous pathogens. Some relatively common autoimmune diseases are listed in Table below . These diseases cannot be cured, although they can be treated to relieve symptoms and prevent some of the long-term damage they cause. |
SciQ | SciQ-1693 | bacteriology
Title: How quickly is antibiotic resistance lost? I would imagine the bacterial genome is highly conserved and limited in its space, but maybe I am wrong.
If you were to take a strain of antibiotic resistant bacteria and kept them isolated, but fed well and so forth, how long would it take for them to lose their resistance? A year? A decade? 100 years? 1000 years? At some point it seems like that trait would disappear, but I have no feeling for how long. Please support your answer with a relevant citation.
EDIT:
My purpose is simple: I am thinking about a strategy for dealing with antibiotic resistance. If we were to ban them across the entire world (could be impossible) how long would we need to wait before they would be usable again. If it was a matter of years, then we could almost do a rotation of existing antibiotics (if we had enough) because I would rather not live in post-antiobitic world. Antibiotic resistances in bacteria is commonly encoded by extrachromosomal DNA, the plasmids. These are circular pieces of DNA, which are much smaller than the hosts genome and which replicate independently from it. See the image from the Wikipedia:
These plasmids can be transfered between different bacterial cells, which then also get resistant. Plasmids are divided between daughter cells, when the parent cell divides. One of the few exceptions seems to be Mycobacterium tuberculosis, which does not seem to carry plasmids but also develops resistances. It has been hypothesized that they contain extrachromosomal single-stranded DNA ("Does Mycobacterium tuberculosis have plasmids?")
Regarding your question: Plasmids which carry antibiotic resistances will only disappear, when the antibiotic is not seen for a while, since the cells, which don't carry it, have a growth advantage over cells who are still carriers (since they save the energy of forming the plasmid). However, these resistance plasmids are nothing new, evolutionary speaking. They appeared as a countermeasure against fungal toxins.
In the lab, bacterial strains loose plasmids within a few days, when not kept under selection pressure according to my experience. There are a few paper who looked into it:
The following is multiple choice question (with options) to answer.
Bacteria may divide several what an hour? | [
"hosts",
"times",
"cells",
"days"
] | B | Asexual reproduction can be very rapid. This is an advantage for many organisms. It allows these organisms to crowd out other organisms that reproduce more slowly. Bacteria, for example, may divide several times per hour. Under ideal conditions, 100 bacteria can divide to produce millions of bacterial cells in just a few hours. However, most bacteria do not live under ideal conditions. If they did, the entire surface of the planet would soon be covered with them. Instead, their reproduction is kept in check by limited resources, predators, and their own wastes. This is true of most other organisms as well. |
SciQ | SciQ-1694 | pressure, ideal-gas
Title: Relationship between the partial pressure $p_J = x_J p$ and the perfect gas law $pV = nRT$ I am currently studying Atkins' Physical Chemistry, 11th edition, by Peter Atkins, Julio de Paula, and James Keeler. Chapter 1A.2 Equations of state says the following:
When dealing with gaseous mixtures, it is often necessary to know the contribution that each component makes to the total pressure of the sample. The partial pressure, $p_J$, of a gas $J$ in a mixture (any gas, not just a perfect gas), is defined
$$p_J = x_J p \tag{1A.6}$$
where $x_J$ is the mole fraction of the component $J$, the amount of $J$ expressed as a fraction of the total amount of molecules, $n$, in the sample:
$$x_J = \dfrac{n_J}{n} \ \ \ n = n_A + n_B + \dots \tag{1A.7}$$
When no $J$ molecules are present, $x_J = 0$; when only $J$ molecules are present, $x_J = 1$. It follows from the definition of $x_J$ that, whatever the composition of the mixture, $x_A + x_B + \dots = 1$ and therefore that the sum of the partial pressures is equal to the total pressure:
$$p_A + p_B + \dots = (x_A + x_B + \dots)p = p \tag{1A.8}$$
This relation is true for both real and perfect gases.
When all the gases are perfect, the partial pressure as defined in eqn 1A.6 is also the pressure that each gas would exert if it occupied the same container alone at the same temperature.
It is this last part that I am unsure about:
When all the gases are perfect, the partial pressure as defined in eqn 1A.6 is also the pressure that each gas would exert if it occupied the same container alone at the same temperature.
The following is multiple choice question (with options) to answer.
The partial pressure of each gas in a mixture is proportional to its what? | [
"mole fraction",
"mesh fraction",
"lactic fraction",
"chemical fraction"
] | A | The partial pressure of each gas in a mixture is proportional to its mole fraction. KEY EQUATIONS Mole fraction. |
SciQ | SciQ-1695 | thermodynamics, experimental-chemistry, coordination-compounds
Decomposition of $\ce{3 H2O}$ and $\ce{2 CO(NH2)2}$:
$\ce{[Cr(CO(NH2)2)6]Cl3 $\cdot$ 3 H2O -> [Cr(CO(NH2)2)4]Cl3 + 3 H2O \uparrow + 2 CO(NH2)2 \uparrow}$
Decomposition of $\ce{2 CO(NH2)2}$ and $\ce{2 HCl}$:
$\ce{[Cr(CO(NH2)2)4]Cl3 -> CrH6C2N4ClO2 + 2 CO(NH2)2 \uparrow + 2 HCl \uparrow}$
Decomposition of $\ce{2 CO2}$, $\ce{N2}$, $\ce{3 H2}$ and $\ce{1/2 Cl2}$ and oxidation of $\ce{Cr}$ to form $\ce{CrN2}$:
$\ce{CrH6C2N4ClO2 -> CrN2 + 2 CO2 \uparrow + N2 \uparrow + 3 H2 \uparrow + 1/2 Cl2 \uparrow}$
Given the temperature range and pressure (probably standard pressure), the formation of $\ce{CrO2}$ is unlikely.
The following is multiple choice question (with options) to answer.
The combination decomposition or rearrangement of elements and compounds to form new substances is known as? | [
"carbon changes",
"chemical changes",
"mineral changes",
"ionic changes"
] | B | As the rust forms on the surface of the iron, it flakes off to expose more iron, which will continue to rust. Rust is clearly a substance that is different from iron. Rusting is an example of a chemical change. Some chemical changes are not as obvious but are still hugely important. For example, photosynthesis and cellular respiration are chemical changes that we could not live without. Chemical changes involve the combination, decomposition, or rearrangement of elements and compounds to form new substances. |
SciQ | SciQ-1696 | human-biology, digestive-system, circadian-rhythms
Title: Is there a circadian component to hunger? I'm wondering what produces the feeling of hunger in humans. Checking Wikipedia revealed that leptin and ghrelin are two hormones involved. I've also read that the digestive system produces its own melatonin.
Because melatonin is related to circadian rhythm and the biological clock,Is melatonin involved in feeling hungry? Is there a circadian pattern to the levels of leptin and ghrelin in humans? Yes, absolutely. A major focus of understanding obesity, diabetes and other metabolic disorders are targeted to understanding the circadian (and other cyclical nature) systems in neurobiology and endocrinology. I can speak within the study of diabetes, there is an observed diabetic "dawn effect" in which there is an early morning (dawn) spike in blood glucose. The exact mechanism for this spike in blood glucose is not fully known, but the general circadian nature is intriguing and would suggest a dominant hormonal cause.
Some other review articles may be found here. An overall review of homeostatic balance as it relates to the central nervous system and apetite regulation. The second review more closely focuses on the biochemistry and endocrinology of central and peripheral regulation on food intake and physical activity.
Berthoud HR, Morrison C. The brain, appetite, and obesity. Annu Rev Psychol. 2008;59:55-92.
Lenard NR, Berthoud HR. Central and peripheral regulation of food intake and physical activity: pathways and genes. Obesity (Silver Spring). 2008 Dec;16 Suppl 3:S11-22.
The following is multiple choice question (with options) to answer.
When is melatonin secreted? | [
"in the morning",
"in the afternoon",
"all day",
"at night"
] | D | |
SciQ | SciQ-1697 | 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.
In which phase do the chromosomes duplicate? | [
"prophase",
"mitosis",
"metaphase",
"interphase"
] | D | |
SciQ | SciQ-1698 | human-anatomy
In the wrist, you can have palmar flexion, dorsiflexion (extension), ulnar flexion (abduction) and radial flexion (adduction) (Teachmeanatomy).
In the ankle, you can have plantar flexion, dorsiflexion (extension), inversion (inward rotation, adduction) and eversion (outward rotation, abduction). (ScienceDirect).
In the shoulder and hip, raising a limb to the same side as the limb is, is abduction (lateral extension) and raising it to the opposite side is adduction.
Moving the thumb toward the palm (in the same plane as palm) is flexion (adduction) and moving it away from it is extension (abduction).
You can read about flexion and extension and other movements here: Types of Body Movements (BCcampus)
The following is multiple choice question (with options) to answer.
Which muscle is a band-like muscle that extends from the anterior superior iliac spine to the medial side? | [
"sartorius",
"soleus",
"tibialis anterior",
"vastus medialis"
] | A | The muscles of the anterior compartment of the thigh flex the thigh and extend the leg. This compartment contains the quadriceps femoris group, which actually comprises four muscles that extend and stabilize the knee. The rectus femoris is on the anterior aspect of the thigh, the vastus lateralis is on the lateral aspect of the thigh, the vastus medialis is on the medial aspect of the thigh, and the vastus intermedius is between the vastus lateralis and vastus medialis and deep to the rectus femoris. The tendon common to all four is the quadriceps tendon (patellar tendon), which inserts into the patella and continues below it as the patellar ligament. The patellar ligament attaches to the tibial tuberosity. In addition to the quadriceps femoris, the sartorius is a band-like muscle that extends from the anterior superior iliac spine to the medial side. |
SciQ | SciQ-1699 | zoology, circulatory-system, heart-output, amphibians
I would add to this my notes from when I was a biochem student (but studied Zoology), mentioning the arterial cone and a spiral valve. This is better described in Britannica:
The conus arteriosus is muscular and contains a spiral valve. Again, as in lungfishes, this has an important role in directing blood into the correct arterial arches. In the frog, Rana, venous blood is driven into the right atrium of the heart by contraction of the sinus venosus, and it flows into the left atrium from the lungs. A wave of contraction then spreads over the whole atrium and drives blood into the ventricle, where blood from the two sources tends to remain separate. Separation is maintained in the spiral valve, and the result is similar to the situation in lungfishes. Blood from the body, entering the right atrium, tends to pass to the lungs and skin for oxygenation; that from the lungs, entering the left atrium, tends to go to the head. Some mixing does occur, and this blood tends to be directed by the spiral valve into the arterial arch leading to the body.
The following is multiple choice question (with options) to answer.
Filter feeders, such as sponges, pump water into their body through what structures? | [
"fibers",
"pores",
"valves",
"lungs"
] | B | Sponges are filter feeders. They pump water into their body through their pores. The water flows through a large central cavity called the spongocoel (see Figure above ). As the water flows by, specialized collar cells filter out food particles such as bacteria. Collar cells have tiny hairs that trap the particles. They also have a flagellum that whips the water and keeps it moving. Once the food is trapped, the collar cells digest it (see Figure below ). Cells called amebocytes also help digest the food. They distribute the nutrients to the rest of the body as well. Finally, the water flows back out of the body through an opening called the osculum. As water flows through the sponge, oxygen diffuses from the water to the sponge’s cells. The cells also expel wastes into the water for removal through the osculum. |
SciQ | SciQ-1700 | 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 are ionic solutes? | [
"solvent",
"salts",
"carbohydrates",
"electrolytes"
] | D | Each substance can be classified as an ionic solute or a nonionic solute. Ionic solutes are electrolytes, and nonionic solutes are nonelectrolytes. Potassium chloride is an ionic compound; therefore, when it dissolves, its ions separate, making it an electrolyte. Fructose is a sugar similar to glucose. (In fact, it has the same molecular formula as glucose. ) Because it is a molecular compound, we expect it to be a nonelectrolyte. Isopropyl alcohol is an organic molecule containing the alcohol functional group. The bonding in the compound is all covalent, so when isopropyl alcohol dissolves, it separates into individual molecules but not ions. Thus, it is a nonelectrolyte. Magnesium hydroxide is an ionic compound, so when it dissolves it dissociates. Thus, magnesium hydroxide is an electrolyte. |
SciQ | SciQ-1701 | organic-chemistry, acid-base
The difference is most clear for water. Water molecules solvated by water itself have a $\mathrm{p}K_\mathrm{a}$ of 15.7 in ambient conditions, but if the unusual stabilization from hydrogen bonding were removed, they would have a $\mathrm{p}K_\mathrm{a}$ of around 28. In other words, $\ce{H2O}$ is a weaker acid by some 10 orders of magnitude in non-protic solvents compared to water, and correspondingly, its conjugate base $\ce{OH^{-}}$ is a stronger base by the same factor. This means hydroxide ions can effect quantitative deprotonation of even rather weak acids, including the hydrocarbons cyclopentadiene, indene and fluorene, in solvents such as 1,2-dimethoxyethane.
Unfortunately, compounds containing hydroxide ions have somewhat limited use as superbases in non-protic solvents because the solubility of common hydroxide bases such as $\ce{NaOH}$ or $\ce{KOH}$ is rather small. Other hydroxides such as quaternary ammonium hydroxides have appreciable solubility in non-protic solvents, but they are always found in the form of hydrates. Attempts to prepare anhydrous $\ce{R_4N^+OH^{-}}$ inevitably result in decomposition, because the crystallized water solvates the hydroxide ion and tames its reactivity; once the water is removed, the bare hydroxide ion immediately attacks the quaternary ammonium cation creating an alcohol and a tertiary amine.
As mentioned previously, other compounds containing hydroxyls also show changes in $\mathrm{p}K_\mathrm{a}$ comparing water and non-protic solvents, though the difference tends to be smaller. For ethanol, the difference is at most about 4 units of $\mathrm{p}K$.
The following is multiple choice question (with options) to answer.
As with other organic compounds that form hydrogen bonds, water solubility of amines is reflected in the length of what? | [
"carbon chains",
"complex carbohydrates",
"hydrocarbon bonds",
"nuclei chains"
] | A | Amines are capable of hydrogen bonding though their boiling points are generally a bit lower than the corresponding alcohol. Methylamine and ethylamine are gases at room temperature, while larger amines are liquids. As with other organic compounds that form hydrogen bonds, water solubility is reflected in the length of the carbon chains. Smaller amines are soluble, while larger ones are less soluble. |
SciQ | SciQ-1702 | pregnancy, children
Title: What happens to the umblical cord inside the mother? After giving birth to a child, the umblical cord is cut (and stored if they want). The end connected to the child's navel will fell off eventually but what happens to the end inside the mother?
Will it be removed right after birth by doctors or what happens? Labor is typically divided into 3 stages:
Stage 1: From the onset of contractions (true labor pains) to full dilatation of the cervix (which is about 10 cm) - this takes about 12 to 18 hours
Stage 2: From full dilatation of cervix to expulsion of fetus - This takes about ~ 30 minutes
Stage 3. From expulsion of fetus to expulsion of placenta - this takes about ~ 15 minutes. During the third stage, the umblical cord which is attached to placenta is expelled along with the placenta. This would be the answer to your question.
Source:Hympath.com
The following is multiple choice question (with options) to answer.
What is the tubular passageway through which the embryo or fetus leaves the mother’s body during birth? | [
"penis",
"cervix",
"uterus",
"vagina"
] | D | The vagina is a tubular passageway through which the embryo or fetus leaves the mother’s body during birth. The vagina is also where the male deposits sperm during mating. |
SciQ | SciQ-1703 | meteorology, climate-change, temperature, seasons
Title: How is this global temperature chart compiled? In this BBC News article, there is a chart labelled "Hottest day on record globally - Daily average air temperature, 1940-2023". It shows temperatures that are higher in summer and lower in winter for the northern hemisphere, which leads me to wonder what exactly this chart is showing. If it were a global average, would the temperature in summer (or winter) not be offset by the fact that the other side of the globe has its winter (or summer) at the same time?
So what is the method used in this chart? Is it just for the northern hemisphere? Is it the temperature over the land mass but not over the sea? Is the data for the southern hemisphere offset by half a year? Or is the world actually hotter in July because there's more land mass in the nothern hemisphere? As stated in your linked article, the graph shows the global average temperature based on ERA5 reanalysis data.
Typically for graphs like this you integrate the surface temperature over the whole domain (surface of earth) and normalise the result with Earth's surface area.
A short explanation for the seasonal cycle is that the northern hemisphere has more land surface area (less water surface area) compared to the southern hemisphere. Water surfaces heat much slower than land surfaces, which introduces a phase lag with respect to the solar heating. Very simplified think about it like this: High solar radiation in the southern hemisphere leads to high temperatures a few weeks/months later, while in the northern hemisphere high temperatures coincide with high radiation levels. This leads to the sinusoidal pattern you observed in the graph.
In the introduction of this article you can find many nice references if you are interested in some more details. Apparently, this has been textbook knowledge since at least 1903.
The following is multiple choice question (with options) to answer.
What has the average global temperature done since the 1900s? | [
"risen",
"decreased",
"changed randomly",
"stayed constant"
] | A | Average global temperature has risen since 1900. |
SciQ | SciQ-1704 | measurements, error-analysis, statistics, data-analysis, metrology
Flat Surfaces:
Similarly, you can produce flat surfaces by lapping two surfaces against each other and if you do it properly (it actually requires three surfaces and is known as the 3-plate method), the high points wear away first leaving two surfaces which must be symmetrical, aka flat. In this way, flat-surfaces have a self-referencing method of manufacture. This is supremely important because, as far as I know, they are the only things that do.
I started talking about squares first since the symmetry is easier to describe for them, but it is the flatness of surface plates and their self-referencing manufacture that allow you to begin making the physical tools to actually apply the concept of symmetries to make the other measurements. You need straight edges to make squares and you can't make (or at least, check) straight edges without flat surface plates, nor can you check if something is round...
"Roundness":
After you've produced your surface plate, straight edges,and squares using the methods above, then you can check how round something is by rolling it along a surface plate and using a gauge block or indicator to check how much the height varies as it rolls.
The following is multiple choice question (with options) to answer.
An solid object with an irregular shape can be measured via what method? | [
"displacement",
"variation",
"vibration",
"radiation"
] | A | The volume of an irregularly shaped solid can be measured by the displacement method. You can read below how this method works. For a video on the displacement method, go to this URL: http://www. youtube. com/watch?v=e0geXKxeTn4 . |
SciQ | SciQ-1705 | physical-chemistry, acid-base, equilibrium
*There is perhaps some subtlety here. As an example, consider the salt $\ce{MX}$, which dissociates weakly into $\ce{M+}$ and $\ce{X-}$. The intuition behind the greater degree of dissociation is that (1) upon dilution, the equilibrium constant for dissociation doesn't change, whereas (2) the concentration of each species decreases. Because dissociation produces more ions than was originally present, this always leads to $Q < K$, and more dissociation will occur.
If we add a salt $\ce{MY}$, then, we are introducing two effects: (1) decreased concentration of $\ce{X-}$ and (2) increased concentration of $\ce{M+}$. Because these effects pull the equilibrium in opposite directions, we can't conclusively determine what exactly will happen. Going back to your example, if we add a slightly stronger base, then we get exactly these two contrasting effects, and the change in the degree of dissociation is indeterminate. In contrast, if we add a much stronger base, then certainly (2) dominates and the degree of dissociation is reduced.
The following is multiple choice question (with options) to answer.
Deterioration of limestone occurs more rapidly as the concentration of what increases? | [
"ocean pollutants",
"water pollutants",
"air pollutants",
"ground pollutants"
] | C | Figure 12.7 Statues made from carbonate compounds such as limestone and marble typically weather slowly over time due to the actions of water, and thermal expansion and contraction. However, pollutants like sulfur dioxide can accelerate weathering. As the concentration of air pollutants increases, deterioration of limestone occurs more rapidly. (credit: James P Fisher III). |
SciQ | SciQ-1706 | reactivity
Title: Why is there no Activity Series for general non-metals? In school, for determining whether single displacement reactions occur, we use an activity series. There is one for metals, and one for halogens. Why is there none for non-metals in general? Are halogens the only ones that will participate in single displacement reactions? I think, periodic trends is the key word. For the halogens, they are homologue elements from a single group. Therefore, they display very similar overall reactivity and typically either fluorine or iodine is best at something, either because a large size and low electronegativity is good for a process or because of the opposite.
I don’t know which metals are included in your series. But I think that if they are from the first two groups and maybe including aluminium, then the reactivities are still similiar enough to compare along the lines of general trends.
However, once you start going to different non-metals — or worse, to metalliods — things become a lot less predictable. You can no longer draw a line down (or up) a group because you have different groups involved. And you can not draw a line along a period because there will be multiple periods. Quick and dirty methods are bound to fail soon.
The following is multiple choice question (with options) to answer.
In which order does the reactivity of halogen group decline? | [
"top to bottom",
"bottom to top",
"right to left",
"left to right"
] | A | The halogens are among the most reactive of all elements, although reactivity declines from the top to the bottom of the halogen group. Because all halogens have seven valence electrons, they are “eager” to gain one more electron. Doing so gives them a full outer energy level, which is the most stable arrangement of electrons. Halogens often combine with alkali metals in group 1 of the periodic table. Alkali metals have just one valence electron, which they are equally “eager” to donate. Reactions involving halogens, especially halogens near the top of the group, may be explosive. You can see some examples in the video at the URL below. ( Warning: Don’t try any of these reactions at home!). |
SciQ | SciQ-1707 | biochemistry, photosynthesis
Title: When is Water Produced During Photosynthesis? The formula for photosynthesis is: $$6CO_2+12H_2O \rightarrow C_6H_{12}O_6+6O_2+6H_2O$$
I can count the carbons, the waters on the reactant side, the oxygens, and the glucose, but I cannot seem to locate where in either light or dark reaction 6 water molecules were produced again. Where and when were they produced? Some of the water that's split is regenerated when the hydroxyl radicals (reactive oxygen species) are converted to hydrogen peroxide, water, etc. by superoxide dismutases and antioxidative mechanisms in the chloroplast (peroxisomes/catalases, etc. take care of this). There's also some evidence that the presence of mannitol, ascorbate and glutathione protect against ROS produced in chloroplasts as well. So you input water, and in an effort to avoid oxidative damage, you do get some water generated. However, the balanced equation doesn't reflect this because it's not an actual product of photosynthesis.
About ROS and protective elements
Extra Reading on ROS in photosynthetic systems
I think that's a very obscure fact, and despite the reality of things, it's actually difficult to query the literature. Good question.
The following is multiple choice question (with options) to answer.
Photosynthesis converts carbon dioxide and water into what? | [
"glucose",
"carbon",
"glutamate",
"insulin"
] | A | In food chemistry, the substances known as antioxidants are reducing agents. Ascorbic acid (vitamin C; C6H8O6) is thought to retard potentially damaging oxidation of living cells. In the process, it is oxidized to dehydroascorbic acid (C6H6O6). In the stomach, ascorbic acid reduces the nitrite ion (NO2−) to nitric oxide (NO): C6H8O6 + 2H+ + 2NO2− → C6H6O6 + 2H2O + 2NO If this reaction did not occur, nitrite ions from foods would oxidize the iron in hemoglobin, destroying its ability to carry oxygen. Tocopherol (vitamin E) is also an antioxidant. In the body, vitamin E is thought to act by scavenging harmful by-products of metabolism, such as the highly reactive molecular fragments called free radicals. In foods, vitamin E acts to prevent fats from being oxidized and thus becoming rancid. Vitamin C is also a good antioxidant. Finally, and of greatest importance, green plants carry out the redox reaction that makes possible almost all life on Earth. They do this through a process calledphotosynthesis, in which carbon dioxide and water are converted to glucose (C6H12O6). The synthesis of glucose requires a variety of proteins called enzymes and a green pigment called chlorophyll that converts sunlight into chemical energy (Figure 5.7 "Life on Earth"). The overall change that occurs is as follows:. |
SciQ | SciQ-1708 | human-biology, hair
In most people this receptor functions as intended, and melanocytes in the skin produce varying degrees of brown-black eumelanin (the extent of which depending on one's ethnic background) while pheomelanin is switched on in the few key areas listed above. When both copies of the MC1R gene inherited from each of your parents are disfunctional, this switching mechanism no longer works and your melanocytes will produce primarily pheomelanin ubiquitously across your body. This is what we know as 'redheads'.
What isn't immediately obvious is that red-haired individuals are not unique in just the aspect of their hair. Their whole body presents with a deficiency in eumelanin and as such they also carry a pale/rosy complexion as well as an inability to tan and a propensity to sunburn easily. This is a consequences of the fact that eumelanin is our primary defense against UV radiation.
While melanocytes in the skin and eyes are responsible for the production of melanin, the melanin in one's hair gets there as a result of a handoff between melanocytes and the keratin producing keratinocytes. Melanin within melanocytes is produced and stored within organelles known as melanosomes and, through a complex formed by the 3 genes MYO5A, RAB27A, and MLPH, the transfer of these melanosomes through the tendrils of the melanocytes to the keratinocytes is facilitated. Defects in any of these 3 genes can result in a condition known as Griscelli syndrome (types 1, 2, and 3, respectively) where the transfer of melanin from melanocytes to keratinocytes is impaired.
The following is multiple choice question (with options) to answer.
Which genetic disorder results in the inability of melanocytes to produce melanin? | [
"hyperthyroidism",
"albinism",
"anemia",
"cancers"
] | B | Integumentary System The first thing a clinician sees is the skin, and so the examination of the skin should be part of any thorough physical examination. Most skin disorders are relatively benign, but a few, including melanomas, can be fatal if untreated. A couple of the more noticeable disorders, albinism and vitiligo, affect the appearance of the skin and its accessory organs. Although neither is fatal, it would be hard to claim that they are benign, at least to the individuals so afflicted. Albinism is a genetic disorder that affects (completely or partially) the coloring of skin, hair, and eyes. The defect is primarily due to the inability of melanocytes to produce melanin. Individuals with albinism tend to appear white or very pale due to the lack of melanin in their skin and hair. Recall that melanin helps protect the skin from the harmful effects of UV radiation. Individuals with albinism tend to need more protection from UV radiation, as they are more prone to sunburns and skin cancer. They also tend to be more sensitive to light and have vision problems due to the lack of pigmentation on the retinal wall. Treatment of this disorder usually involves addressing the symptoms, such as limiting UV light exposure to the skin and eyes. In vitiligo, the melanocytes in certain areas lose their ability to produce melanin, possibly due to an autoimmune reaction. This leads to a loss of color in patches (Figure 5.10). Neither albinism nor vitiligo directly affects the lifespan of an individual. |
SciQ | SciQ-1709 | pathology
Title: Are all diseases caused by organisms (microorganisms)? Are there other causes? Or is it correct to say that all diseases are in fact caused by organisms (microorganisms)? It is not correct to say that all diseases are caused by foreign organisms. Counterexamples are:
Cancer is caused by random genetic mutations in the cells of our body. The mutations can be caused by many factors such as ionizing radiation, smoking, chemical toxins etc.
Diseases such as stroke or heart attack are caused by blood clots blocking the blood flow to essential organs.
Autoimmune diseases are caused by the immune system falsely recognizing cells of the body as foreign and attacking that tissue leading to a wide variety of symptoms.
Alzheimer's disease is caused by chronic neurodegeneration, meaning that the cells in the brain die. The causes are not quite understood but as Alzheimer's usually appears late in life it is likely related to ageing. Also, it is known that some genetic defects can lead to early-onset Alzheimers.
Prion proteins can cause diseases such as Creutzfeldt–Jakob disease also known as mad-cow disease.
Hereditary diseases such as early-onset Alzheimers or ALS are cause by gene defects inherited from the parents.
Toxins can cause chronic diseases such as lead poisoning.
The list probably goes on...
Please note that the first two on the list are the most common cause of death in developed countries.
The following is multiple choice question (with options) to answer.
Most diseases caused by bacteria can be cured by which medicines? | [
"antibiotics",
"hydroxides",
"inhibitors",
"antioxidants"
] | A | Living things that cause human diseases include bacteria, fungi, and protozoa. Most infectious diseases caused by these organisms can be cured with medicines. For example, medicines called antibiotics can cure most diseases caused by bacteria. Bacteria are one-celled organisms without a nucleus. Although most bacteria are harmless, some cause diseases. |
SciQ | SciQ-1710 | oceanography, sea-level, tides
Title: Why do high tides vary month to month? I've noticed that some ‘highest‘ high tides in one month are bigger than the highest high-tide of previous months. Why is this so? The dynamics of the tides are quite complex. The main idea is that gravity from the Moon and the Sun affect water (and everything else) on Earth. The issue is that there are several motions that alter the distance between the 3 systems and those motions cause interactions between the different frequencies involved. The Equilibrium Theory of Tides separates the different effects into a set of constituents by conducting a harmonic analysis. The relevant periods are:
the lunar day (period of lunar rotation), 24.84 mean solar hours.
the sidereal month (period of lunar declination), 27.32 mean solar days.
the tropical year (period of solar declination), 365.24 mean solar days.
the period of the lunar perigee, 8.85 years (1 year = 365.2421988 days).
the period of the lunar node, 18.61 years.
the period of the solar perihelion, 20940 years.
The explanation of each constituent can be rather complex (some examples in this other answer). The different amplitudes in a day and the spring-neap cycle are related to the combination of the main lunar and solar effects.
The differences in high/low tide from month to month are related to the next two main frequencies of oscillation. Mainly, the variations in Earth-Sun distance associated occurring in a period of tropical year. The lunar distance also contributes to these differences, but its cycle is much longer (~9 years). Also, the spring-neap cycle (with a frequency of half a lunar month ~13.5 days) will occur at different times of the month and can lead to differences in tidal amplitude if you compare the tides measured the same day of consecutive months.
(Source www.niwa.co.nz)
The following is multiple choice question (with options) to answer.
What season do the largest waves for surfers typically come? | [
"autumn",
"winter",
"spring",
"summer"
] | B | Jaws Beach in Maui, Hawaii has legendary waves. The largest waves come when winds are very strong, usually in the winter. The rocks and reef offshore magnify the size of the incoming wave energy. Cowabunga!. |
SciQ | SciQ-1711 | neuroscience
Title: Nervous system : Nerve signals If the electrical signals from all the various organs throughout the body eventually connect to the nerves in the spinal column traveling up to the brain, how does the brain differentiate the different signals. Is the nerve in the spinal column like an electrical conduit with many wires inside? Yes is the simple answer. A nerve will go up to a specific part of the brain which the brain knows corresponds to a certain region of the body. It isn't perfect though e.g. pain in the diaphragm confuses the brain which doesn't recognise that pain must be coming from there so instead tells the body there is shoulder pain, however this is useful in medicine. Another infamous example is pain from heart disease (angina) which causes pain in the jaw and arm. Perhaps even more interestingly, if a nerve is cut and then grows back linking to the wrong nerve it may lead to the completely wrong part of the body being identified when touched. Also if the brain itself is stimulated in these corresponding areas, a person will feel he or she is indeed being touched in a certain part of the body.
The following is multiple choice question (with options) to answer.
The peripheral nervous system has major nerves that travel through every part of the body except which two places? | [
"lungs and spinal cord",
"brain and spinal cord",
"muscles and brain",
"brain and heart"
] | B | All the other nervous tissues in the body are part of the peripheral nervous system. If you look again at Figure above , you can see the major nerves of the peripheral nervous system. They include nerves that run through virtually every part of the body, both inside and out, except for the brain and spinal cord. |
SciQ | SciQ-1712 | acid-base, equilibrium, ph, electronic-configuration
Title: Why is it that weak bases usually contain nitrogen? Why do weak bases usually contain nitrogen? I know there are two electrons on top for a bond of $\ce{H}$ but why is it mostly nitrogen? I know there are other elemental bases too but why do I keep seeing $\ce{N}$'s mostly?
Is there something special about nitrogen in this respect? The short answer is that yes, the fact that many weak bases contain nitrogen does have to do with nitrogen itself. However, it's not really accurate to say that weak bases "usually" contain nitrogen.
For simplicity, I'm limiting my explanation to aqueous solutions, the Brønsted-Lowry definition, and main-group compounds. A base must do one of two things: either remove a proton ($\ce{H+}$) from water or dissociate to produce something else (typically $\ce{OH-}$) that can remove a proton from water. Most compounds that produce $\ce{OH-}$ directly are ionic; even if they don't dissolve much (like alkaline earth hydroxides), these ionic compounds dissociate completely and are therefore strong bases.
A base that removes protons from water must have a free pair of electrons for the proton to bond to. In period 2, boron tends to form compounds that tie up all three of its electrons. Carbon compounds, likewise, tend to have no free electron pairs. Oxygen and fluorine compounds (e.g., water and hydrogen fluoride) have free electron pairs, but because of their high electronegativity these elements keep their electrons to themselves and are unlikely to grab protons from water if they already have a full octet. Nitrogen is the only element in this period that balances two factors: it has a free electron pair in many of its compounds (e.g., ammonia and organic amines) and has a low enough electronegativity that it can share those electrons with a proton to form a cation (e.g., ammonium, $\text{NH}_3$).
The following is multiple choice question (with options) to answer.
Each nitrogenous base has one or two rings that include which atoms? | [
"carbon",
"hydrogen",
"nitrogen",
"oxygen"
] | C | |
SciQ | SciQ-1713 | newtonian-gravity, orbital-motion, planets, solar-system, celestial-mechanics
Title: Will Neptune change Pluto's orbit some day? My seven-year-old son loves astronomy-- so much so that we read space books before bed time. One of our books talks about Pluto's orbit crossing over Neptune's orbit and will be (or is) closer to the Sun than Neptune for a period of years.
I'm assuming the orbits actually never have a collision path, but what will happen when Neptune and Pluto get as close to each other as possible-- will Neptune's gravity do something to Pluto's orbit? The Wikipedia article on Pluto has a good explanation.
Basically, the inclinations of their orbits are such that they never approach each other more closely than about 17 AU (more than 1.5 billion kilometers). In fact, Pluto comes closer to Uranus (11 AU) than it does to Neptune. And since Pluto and Neptune are in a 3:2 gravitational resonance, their orbital relationship should be stable over millions of years.
... will Neptune's gravity do something to Pluto's orbit?
It already has.
The following is multiple choice question (with options) to answer.
Pluto's orbit is so elliptical that sometimes it is inside the orbit of which planet? | [
"neptune",
"Mars",
"titan",
"Earth"
] | A | For decades Pluto was a planet. But even then, scientists knew it was an unusual planet. The other outer planets are all gas giants. Pluto is small, icy and rocky. With a diameter of about 2400 kilometers, it has only about 1/5 the mass of Earth’s Moon. The other planets orbit in a plane. Pluto's orbit is tilted. The shape of the orbit is like a long, narrow ellipse. Pluto's orbit is so elliptical that sometimes it is inside the orbit of Neptune. |
SciQ | SciQ-1714 | organic-chemistry, inorganic-chemistry, physical-chemistry
Title: What are the main axis of research in Chemistry? I would like to know what are the main problems currently studied in Chemistry.
For some reason, it seems that there is far less vulgarisation in chemistry than the other fields, and it's hard to find an overview of the field accessible to a layman (compared to math or physics for instance).
I only found this wikipedia page, but I have no idea how relevant it is. Even though I voted to close this question as not constructive, these are among the most important unsolved problems in chemistry:
The following is multiple choice question (with options) to answer.
More than half the compounds produced by the chemical industry are what? | [
"artificial polymers",
"gas polymers",
"synthetic polymers",
"replacement polymers"
] | C | fibers, films, plastics, semisolid resins, and rubbers are also polymers. More than half the compounds produced by the chemical industry are synthetic polymers. Some common addition polymers are listed in http://catalog. flatworldknowledge. com/bookhub/reader/2547 - gob-ch13_s05_t01. Note that all the monomers have carbon-to-carbon double bonds. Many polymers are mundane (e. , plastic bags, food wrap, toys, and tableware), but there are also polymers that conduct electricity, have amazing adhesive properties, or are stronger than steel but much lighter in weight. Table 13.2 Some Addition Polymers. |
SciQ | SciQ-1715 | energy, particle-physics, electrons, atomic-physics
Title: Can only two electrons be in ground state? Are the energy levels the same thing as the energy shells? I can't find a straight answer
So for a model like this one, can there be two electrons in one energy level?
And I don't understand the Pauli principle that two electrons can't be on the same energy level when there are 2 electrons in the first shell of most atoms???
Does this then mean that shells and energy levels aren't the same thing? Wikipedia says it well:
The Pauli exclusion principle is the quantum mechanical principle
which states that two or more identical fermions (particles with
half-integer spin) cannot occupy the same quantum state within a
quantum system simultaneously.
The 'same quantum state' here can be understood as a set of quantum numbers $n$, $l$, $m_l$ and $m_s$ to be the same.
For example, if $2$ electrons are in the $\text{1s}$ orbital, that is $1,0,0$, then they must have a different spin quantum number $m_s$, one with $m_s=+1/2$ and the other with $m_s=-1/2$. Both will have the same energy (ground state in this case).
The following is multiple choice question (with options) to answer.
What is it called when electrons are shared equally? | [
"helices bonds",
"polar bonds",
"metabolized bonds",
"nonpolar bonds"
] | D | In other covalent bonds, electrons are shared equally. These bonds are called nonpolar bonds. Neither atom attracts the shared electrons more strongly. As a result, the atoms remain neutral. Figure below shows an example of nonpolar bonds. |
SciQ | SciQ-1716 | cell-biology
Title: Are ribosomes assembled in rough ER and Golgi body, or in the nucleolus? I mean all the components, such as ribosomal RNA (rRNA) are synthesized in the nucleolus, but is the whole ribosome structure assembled in the nucleolus or is it also done in the rough endoplasmic reticulum and Golgi apparatus? Ribosome assembly starts in the nucleolus (of eukaryotes) and finishes in the cytoplasm. However, in the cytoplasm the Golgi apparatus is certainly not involved, and, as some cells have little rough endoplasmic reticulum, assembly does not require that. Thus, the abstract of a review by Fromont-Racine et al. in Gene (2003) vol 313 pp. 17–42 starts with the statement:
Ribosome synthesis is a highly complex and coordinated process that occurs not only in the nucleolus but also in the nucleoplasm and the cytoplasm of eukaryotic cells.
In the 26 pages of this review there is not a single mention of the words ‘endoplasmic reticulum’ or ‘Golgi’.
A more recent (and freely available) review by Thomson et al. in Journal of Cell Science (2013) vol 126 pp. 4815-4820 is in accord with this. It has a pretty poster insert which presents the assembly as a succession of events, starting in the nucleolus, proceeding to the nucleoplasm, and with some final polishing in the cytoplasm.
The following is multiple choice question (with options) to answer.
Ribosomes are cellular substructures where what are synthesized? | [
"acids",
"proteins",
"Molecule",
"cells"
] | B | Ribosomes are cellular substructures where proteins are synthesized. They contain about 65% rRNA and 35% protein, held together by numerous noncovalent interactions, such as hydrogen bonding, in an overall structure consisting of two globular particles of unequal size. Molecules of tRNA, which bring amino acids (one at a time) to the ribosomes for the construction of proteins, differ from one another in the kinds of amino acid each is specifically designed to carry. A set of three nucleotides, known as a codon, on the mRNA determines which kind of tRNA will add its amino acid to the growing chain. (For more information on sequences, see Section 19.4 "Protein Synthesis and the Genetic Code". ) Each of the 20 amino acids found in proteins has at least one corresponding kind of tRNA, and most amino acids have more than one. The two-dimensional structure of a tRNA molecule has three distinctive loops, reminiscent of a cloverleaf (Figure 19.11 "Transfer RNA"). On one loop is a sequence of three nucleotides that varies for each kind of tRNA. This triplet, called the anticodon, is complementary to and pairs with the codon on the mRNA. At the opposite end of the molecule is the acceptor stem, where the amino acid is attached. Figure 19.11 Transfer RNA Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-1717 | geochemistry, earth-history, co2, carbon-cycle
Source: Wikimedia Commons.
I heard this argument at the University of Zaragoza. However, I am uncertain if both my teacher and I have a comprehensive understanding of this matter. One of my concerns is that CO2 dissolves below the Calcite Compensation Depth. I'm unsure if all sediments dissolve or just the top layers. This uncertainty leaves me pondering whether my argument could be refuted on this basis. I couldn't find any clarifications on Science Direct either.
Could someone elucidate this matter for both my friend (who will read this) and me?
Are the Phanerozoic CO2 levels indeed linked with the Wilson Cycle? If so, why?
Bonus Question:
If humans wouldn't exist, would we run out of CO2? (To me, this seems like an absurd query, especially in the context of that Nobel Prize article, because we'll likely gain control over Earth's geochemistry and climate long before then.) To rephrase: if we exclude human influence, would shell organisms eventually consume all the CO2 by the end of the Phanerozoic era, leading to a mass extinction and the emergence of a distinct form of life? Would this scenario transpire in this cycle or the next? On geological timescales, yes, the Wilson cycle (opening and closing of ocean basins) is bound to have an effect on atmospheric CO2 levels, if only because it will affect rainfall patterns, which in turn will affect chemical weathering of rocks, which is one of the things that removes CO2 from the air on very long timescales.
This obviously doesn't explain the post-industrial rise in atmospheric CO2 though, which has occurred on the scale of a century or so, rather than tens to hundreds of millions of years. So it seems like a grain of truth, but the argument is a non-sequitur.
"In the forthcoming million years, CO2 stored by organisms will be
released."
The following is multiple choice question (with options) to answer.
How long can carbon be stored in sedimentary rock? | [
"around 10,000 years",
"millions of years",
"22 weeks",
"less than 1000 years"
] | B | Carbon cycles quickly between organisms and the atmosphere. Cellular respiration releases carbon into the atmosphere as carbon dioxide. Carbon is also released when organisms decompose. Human actions, such as the burning of fossil fuels, also release carbon into the atmosphere. Natural processes, such as volcanic eruptions, release carbon from magma into the atmosphere. Warm ocean waters also release carbon, whereas cold ocean water dissolves carbon from the atmosphere. Photosynthesis (autotrophs) removes carbon dioxide from the atmosphere and uses it to make organic compounds. Carbon cycles far more slowly through geological processes such as sedimentation. Runoff, rivers and streams dissolve carbon in rocks and carry it to the ocean. Sediments from dead organisms may form fossil fuels or carbon-containing rocks. Carbon may be stored in sedimentary rock for millions of years. |
SciQ | SciQ-1718 | 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 you call an animal in which the embryo, often termed a joey, is born immature and must complete its development outside the mother's body? | [
"placental mammal",
"eukaryotic",
"monotreme",
"marsupial"
] | D | All other mammals give birth to live young and belong to one of two different categories, the marsupials and the placental mammals. A marsupial is an animal in which the embryo, which is often called a joey, is born at an immature stage. Development must be completed outside the mother's body. Most female marsupials have an abdominal pouch or skin fold where there are mammary glands. The pouch is a place for completing the development of the baby. Although blind, without fur, and with only partially formed hind legs, the tiny newborns have well developed forelimbs with claws that enable them to climb their way into their mother's pouch where they drink their mother's milk and continue their development. Marsupials include kangaroos, koalas, and opossums. Other marsupials are the wallaby and the Tasmanian Devil. Most marsupials live in Australia and nearby areas. ( Figure below ). |
SciQ | SciQ-1719 | evolution, biochemistry, life-history
Title: Was iron important for the first life on Earth? Some ions or compounds are thought not to have become involved or important in the metabolism of living organisms until some time after certain mutations took place. For instance, early life is thought to selectively allow calcium ions through its membrane, but eventually also evolved the ability to selectively allow sodium ions, specifically through a mutation that lead to a change in the composition of a channel protein from glutamine to lysine.
Currently, iron is involved in oxidations involving molecular oxygen, such as in cytochromes and clearly holds a key role in modern life, despite that free iron or even ferric compounds are rarely accessible. From my understanding, iron most likely became incorporated into the metabolism of microbes after during/after aerobic organisms had developed, but this does not rule out the possibility that iron was involved earlier on. So, I am wondering if iron was involved in early life, and details on how would be appreciated. Cyanobacteria require iron for photosynthesis and can be found as fossil stromatolites dating back to 3.5 billion years ago. Stromatolites are layered structures made up of cyanobacteria and sediment.
Source: https://en.wikipedia.org/wiki/Stromatolite
Modern stromatolites can be found at Shark Bay in Australia, Chetumal Bay in Belize, and Laguna Bacalar in the Yucatan Peninsula.
Cyanobacteria are also believed to have evolved into the first microbes to produce oxygen by photosynthesis, which was a catalyst for the Great Oxygenation Event which occurred around 2.45 billion years ago.
The following is multiple choice question (with options) to answer.
What is the most important element to life? | [
"nitrogen",
"hydrogen",
"carbon",
"oxygen"
] | C | Carbon is the most important element to life. Without this element, life as we know it would not exist. As you will see, carbon is the central element in compounds necessary for life-organic compounds. These compounds include carbohydrates, lipids, proteins and nucleic acids. |
SciQ | SciQ-1720 | evolution, terminology, history, species, definitions
Title: Was Darwin aware of the difficulties behind the concept of species? Introduction
The concept of species is a very old concept that suffers from not being a natural category. There exists no single definition that would categorize living beings into groups and that would fit our intuitions of what a species should be.
Many of such problems in definitions are revealed in the field of evolutionary biology. For more information about the difficulties behind the definition of the concept of species, have a look at
How could humans have interbred with neanderthals if were a different species?
This post on ring species.
Question
Did Charles Darwin comment on this problem?
If yes, did Charles Darwin comment on the reason why he chose to keep using the term "species" instead of simply "lineage"? The whole point of Darwin's theory was that transition from one species to another is extremely slow and gradual. There are plenty of quotes in "Origin of Species" stating this, and also affirming that there is no clear boundary between species and subspecies, or "races".
Quotes from Origin of Species > Variation under Nature (Chapter 2)
Quote 1
Nevertheless, no certain criterion can possibly be given by which variable forms, local forms, sub species and representative species can be recognised
Quote 2
Several experienced ornithologists consider our British red grouse as only a strongly marked race of a Norwegian species, whereas the greater number rank it as an undoubted species peculiar to Great Britain. A wide distance between the homes of two doubtful forms leads many naturalists to rank them as distinct species; but what distance, it has been well asked, will suffice if that between America and Europe is ample, will that between Europe and the Azores, or Madeira, or the Canaries, or between the several islets of these small archipelagos, be sufficient?
Quote 3
It is here the most definitive quote I managed to find and partially answers to your second question.
From these remarks it will be seen that I look at the term species as one arbitrarily given, for the sake of convenience, to a set of individuals closely resembling each other, and that it does not essentially differ from the term variety, which is given to less distinct and more fluctuating forms. The term variety, again, in comparison with mere individual differences, is also applied arbitrarily, for convenience sake.
The following is multiple choice question (with options) to answer.
The idea of evolution has been around for centuries. in fact, it goes all the way back to the ancient greek philosopher named? | [
"Xerxes",
"aristotle",
"Galileo",
"Pluto"
] | B | The idea of evolution has been around for centuries. In fact, it goes all the way back to the ancient Greek philosopher Aristotle. However, evolution is most often associated with Charles Darwin. Darwin published a book on evolution in 1859 titled On the Origin of Species . In the book, Darwin stated the theory of evolution by natural selection. He also presented a great deal of evidence that evolution occurs. |
SciQ | SciQ-1721 | electricity, electrostatics
Title: Why does hair stand up when standing under power lines? My initial guess would be the immense electric field around the lines, that causes hair to get charged and due to each hair having the same charge they start to repel each other.
So what is exactly happening here? I believe the mechanism is somewhat different: the electric field polarizes, rather than charges, hair, and then acts on the resulting electric dipoles, judging by the formulas in:
"Proceedings of the 2005 IEEE Engineering in Medicine and Biology 27th Annual Conference, Shanghai, China, September 1-4, 2005", p. 4266. "Analysis of Body Hair Movement in ELF Electric Field Exposure", H. O. Shimizu, K. Shimizu. According to the formulas, it is essential that the electric field is not uniform. The authors claim good agreement with experimental results.
The following is multiple choice question (with options) to answer.
When a balloon is rubbed against hair, why do they attract each other? | [
"lean electron charge",
"constantly electron charge",
"opposite electron charge",
"same electron charge"
] | C | Electrons are transferred from hair to a balloon rubbed against the hair. Then the oppositely charged hair and balloon attract each other. |
SciQ | SciQ-1722 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
Living things get energy from food in a process called respiration, which releases what gas back into the atmosphere? | [
"nitrogen",
"oxygen",
"carbon dioxide",
"hydrogen"
] | C | Carbon doesn’t stop there. Living things get energy from food in a process called respiration. This releases carbon dioxide back into the atmosphere. The cycle then repeats. |
SciQ | SciQ-1723 | 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 is the name of the scientific field that deals with the general study of the solid earth? | [
"physics",
"astronomy",
"chemistry",
"geology"
] | D | Geology is the study of the solid Earth. Geologists study how rocks and minerals form. The way mountains rise up is part of geology. The way mountains erode away is another part. Geologists also study fossils and Earth’s history. There are many other branches of geology. There is so much to know about our home planet that most geologists become specialists in one area. For example, a mineralogist studies minerals, as seen in ( Figure below ). |
SciQ | SciQ-1724 | enzymes
Accepted Name: pyruvate kinase
(because that’s what everyone uses and is in all the text books)
Other names: phosphoenolpyruvate kinase; phosphoenol transphosphorylase
pyruvate kinase (phosphorylating); fluorokinase; fluorokinase (phosphorylating); pyruvic kinase; pyruvate phosphotransferase
(note these include naming it for the reverse reaction)
Systematic name ATP:pyruvate 2-O-phosphotransferase
So why is that the systematic name? If you click back from this page to the group EC 2.7.1 to which this belongs, you will find that this group is of ‘Phosphotransferases with an Alcohol Group as Acceptor’, itself a subgroup of phosphotransferases.
So, to summarize, there is a systematic name that have been arrived at after long and careful deliberation and appears in the introductory paragraphs of scientific publications. Thereafter the common name is used, which although sometimes now recognized as a misnomer, seemed most appropriate at the time.
The following is multiple choice question (with options) to answer.
What kind of enzyme is phosphofructokinase? | [
"allosteric",
"intracellular",
"covalent",
"orthosteric"
] | A | |
SciQ | SciQ-1725 | volcanology, igneous
If lunar maria seem that large from Earth, it's only because the Moon is small!
But to know if lunar maria or LIPs would have looked like "glowing lava oceans shinning in the night", we need to look at emplacement rates rather than just areas and volumes. From the same chapter, one can calculate LIP emplacement rates of ~3-13 km3 per year. It may seem quite low (for comparison, ocean ridges quietly produce ~20 km3 per year), but it is an average output rate over a few million years. As noted on largeigneousprovinces.org, their might be pulses of magmatic activity, with peaks in production rate. This is exactly what's been inferred for lunar maria by Wilson and Head (2017): even if the average output rate has been calculated at a very low 0.01 km3 per year, they found that some flows could have been emplaced with rates up to 106 m3s-1!
As to whether this would have been visible from space: define "from space"! From low Earth orbit like the ISS? From the Moon itself? :)
The following is multiple choice question (with options) to answer.
Covering about 16 percent of the moon's surface, maria are dark, solid, flat areas consisting of what substance? | [
"lava",
"ash",
"debris",
"dust"
] | A | When you look at the Moon from Earth, you notice dark and light areas. The maria are dark, solid, flat areas of lava. Maria covers around 16% of the Moon’s surface, mostly on the near side. The maria formed about 3.0 to 3.5 billion years ago, when the Moon was continually bombarded by meteorites ( Figure below ). Large meteorites broke through the Moon’s newly formed surface. This caused magma to flow out and fill the craters. Scientists estimate volcanic activity on the Moon ended about 1.2 billion years ago. |
SciQ | SciQ-1726 | evolution
An Immune Basis for Malaria Protection by the Sickle Cell Trait
Sickle Cell Anaemia and Malaria
If you look further, you will find a number of different examples, where evolution is present after humans went through a genetic bottleneck (meaning the number of humans was drastically reduced).
The following is multiple choice question (with options) to answer.
Sickle cell disease is caused by production of an abnormal type of what? | [
"fat globule",
"leukocyte",
"thrombocyte",
"hemoglobin"
] | D | down into three major groups: those caused by blood loss, those caused by faulty or decreased RBC production, and those caused by excessive destruction of RBCs. Clinicians often use two groupings in diagnosis: The kinetic approach focuses on evaluating the production, destruction, and removal of RBCs, whereas the morphological approach examines the RBCs themselves, paying particular emphasis to their size. A common test is the mean corpuscle volume (MCV), which measures size. Normal-sized cells are referred to as normocytic, smaller-than-normal cells are referred to as microcytic, and larger-than-normal cells are referred to as macrocytic. Reticulocyte counts are also important and may reveal inadequate production of RBCs. The effects of the various anemias are widespread, because reduced numbers of RBCs or hemoglobin will result in lower levels of oxygen being delivered to body tissues. Since oxygen is required for tissue functioning, anemia produces fatigue, lethargy, and an increased risk for infection. An oxygen deficit in the brain impairs the ability to think clearly, and may prompt headaches and irritability. Lack of oxygen leaves the patient short of breath, even as the heart and lungs work harder in response to the deficit. Blood loss anemias are fairly straightforward. In addition to bleeding from wounds or other lesions, these forms of anemia may be due to ulcers, hemorrhoids, inflammation of the stomach (gastritis), and some cancers of the gastrointestinal tract. The excessive use of aspirin or other nonsteroidal anti-inflammatory drugs such as ibuprofen can trigger ulceration and gastritis. Excessive menstruation and loss of blood during childbirth are also potential causes. Anemias caused by faulty or decreased RBC production include sickle cell anemia, iron deficiency anemia, vitamin deficiency anemia, and diseases of the bone marrow and stem cells. • A characteristic change in the shape of erythrocytes is seen in sickle cell disease (also referred to as sickle cell anemia). A genetic disorder, it is caused by production of an abnormal type of hemoglobin, called hemoglobin S, which delivers less oxygen to tissues and causes erythrocytes to assume a sickle (or crescent) shape, especially at low oxygen concentrations (Figure 18.9). These abnormally shaped cells can then become lodged in narrow capillaries because they are unable to fold in on themselves to squeeze through, blocking blood flow to tissues and causing a variety of serious problems from painful joints to delayed growth and even blindness and cerebrovascular accidents (strokes). Sickle cell anemia is a genetic condition particularly found in individuals of African descent. |
SciQ | SciQ-1727 | electromagnetism, soft-question, history, maxwell-equations
Title: Maxwell's Equations-Relativity How did Maxwell develop the magnetic field without relativity? Was it purely experimental? I don't see how else he would have developed any understanding for the magnetic field. A long time before Maxwell wrote down a unified theory, Oersted discovered a connection between electricity and magnetism. In the development of electromagnetism, there were many bits and pieces of partial knowledge that were discovered and formulated by many different scientists. The popular ones (after whom we've named partial "laws") that immediately come to mind are Faraday (who came up with the concept of a field), Ampere, Gauss, Coulomb, etc. In fact, Faraday put together electric and magentic fields to make motors and generators. If I recall the history correctly, Maxwell understood the connections and put together all these partial results into a coherent mathematical formulation.
As it happened, it was noticed that this theory was not invariant under Galiean transformations and the challenge was to figure out which of the two concepts to be modified. To make a long story short, there were many proposals and notable the Michelson-Morley experiment, but the one that we now know to be correct was Einstein's theory of Special Relativity.
Some references for the history of E&M
http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-013-electromagnetics-and-applications-spring-2009/lecture-notes/MIT6_013S09_res_maxwell.pdf
http://digitalcommons.sacredheart.edu/cgi/viewcontent.cgi?article=1002&context=wac_prize
The following is multiple choice question (with options) to answer.
Who first proposed that earth is a magnet? | [
"Albert Einstein",
"Isaac Newton",
"william gilbert",
"Marconi"
] | C | The molar mass of any substance is the mass in grams of one mole of representative particles of that substance. The representative particles can be atoms, molecules, or formula units of ionic compounds. This relationship is frequently used in the laboratory. Suppose that for a certain experiment you need 3.00 moles of calcium chloride (CaCl 2 ). Since calcium chloride is a solid, it would be convenient to use a balance to measure the mass that is needed. The molar mass of CaCl 2 is 110.98 g/mol. The conversion factor that can be used is then based on the equality that 1 mol = 110.98 g CaCl 2 . Dimensional analysis will allow you to calculate the mass of CaCl 2 that you should measure. |
SciQ | SciQ-1728 | physical-chemistry, atoms
Title: Why don't electrons simply stick to the nucleus on account of being *oppositely* charged, instead of moving around it? Why don't electrons stick to the nucleus on account of being oppositely charged charged (the nucleus being positively charged)? But contrary to my intuition, electrons seem to follow a whole bunch of wacky paths (orbitals) around the nucleus (as demarcated by orbital wave-functions). Why is this?
Do note:
I'm not asking "What keeps the electron in orbit". All I want to know, is why electrons don't simply find themselves attached to the nucleus, and why do they even bother moving around the nucleus (in orbitals) at all? My textbooks, unfortunately, make no reference to this issue...they wholeheartedly adopt the "current" QM model of the (hydrogen) atom. Richard Feynman alludes to this exact problem in the first volume of the Feynman Lectures on Physics. I'll present his argument here (based on the Uncertainty Principle), albeit, in my own words ;)
The German physicist [since he dealt with atomic chemistry/physics...by all means, go ahead and call him a "chemist" ;) ], Werner Karl Heisenberg came up with what we now know as "The Heisenberg Uncertainty Principle"... a revolutionary idea that points to an "inherent fuzziness", that exists within quantum systems (which is a fancy word that refers to any region of space that is sufficiently "small" enough to introduce wave-particle duality), and becomes apparent when we try to "measure" the various parameters that constitute them.
Basically, what (one version of) the Uncertainty Principle states is that:
The product of the uncertainty in measurement of velocity and the uncertainty in measurement of the position of a particle can never be less than a certain constant; i.e- ħ/2
Rephrasing this
If we were to know a particle's position to a very high precision (i.e- small uncertainty in measurement of position) then the corresponding uncertainty in the measurement of the particle's velocity (or momentum, if you know its mass) increases greatly. The same holds true vice versa.
In other words,
You cannot know both a particle's position and momentum in a quantum system to a great precision simultaneously.
The following is multiple choice question (with options) to answer.
Which atomic model shows that the distances of electrons from the nucleus is not a fixed value? | [
"the electron model",
"the distance model",
"the equivocation model",
"the quantum model"
] | D | In the Bohr model, the atom is viewed as a densely packed nucleus comprised of neutrons and protons that is surrounded by electrons at fixed distances, which correspond to specific energy levels. However, the quantum model showed that the distances between electrons and the nucleus are not really fixed. Due to their wave-like nature, we cannot pinpoint the exact location of an electron that is in motion, but we can determine the probability that a given electron will be in a particular region in three-dimensional space. Schrӧdinger’s equations are used to determine the position of a specific electron with respect to a nearby nucleus. The region in space in which an electron is most likely to be found is referred to as an orbital . |
SciQ | SciQ-1729 | materials, metallurgy, metals, material-science, corrosion
Title: Why does corrosion take place at certain stressed regions? Why does certain parts of metal show more corrosion at the place where there is high dislocation density in comparison to the place where the dislocation density is less? I do sincerely feel that this is particularly because of the fact that the activity is less in that particular localized region where the corrosion is taking place. I think the situation is similar where grain boundaries act as stressed region but what has this to do with the activity. A detailed answer to the above situation will most certainly be welcome. In the real world ,I don't believe I have seen CORROSION at STRESSED areas. Corrosion may be accelerated at STRAINED areas; the strains introduce energy to the microstructure which may promote corrosion. Cracking is another story - which you did not ask about . Hydrogen cracking of high strength steels is likely the most common case . It can often occur with no apparent corrosion ; In particular cathodic protection which prevents corrosion ,can introduce hydrogen which causes cracking.
The following is multiple choice question (with options) to answer.
What is it called when breaks in bone occur that is usually caused by excessive stress on the bone? | [
"faults",
"fractures",
"fragments",
"ruptures"
] | B | Fractures are breaks in bone, usually caused by excessive stress on bone. Fractures heal when osteoblasts form new bone. The animation at this link shows how this happens: http://www. youtube. com/watch?v=qVougiCEgH8 . Soon after a fracture, the body begins to repair the break. The area becomes swollen and sore. Within a few days, bone cells travel to the break site and begin to rebuild the bone. It takes about two to three months before compact and spongy bone form at the break site. Sometimes the body needs extra help in repairing a broken bone. In such a case, a surgeon will piece a broken bone together with metal pins. Moving the broken pieces together will help keep the bone from moving and give the body a chance to repair the break. |
SciQ | SciQ-1730 | bond, atoms, molecules, valence-bond-theory
So the short answer to your first question is: "Molecular orbitals hold atoms together in covalent bonds, and those are a result of electrostatic interactions and the quantum nature of electrons."
Yes, ionic compounds are large collections of ions, and you can't really define "molecules" for them - instead we talk about "formula units" which are the lowest possible whole-number ratio of elements that represent the compound. Groups of covalently bonded atoms are also held together by electrostatic interactions, but since the covalent bonds are so much stronger, a molecular compound can exist "on its own" as a single molecule. Collectively, the forces that hold collections of molecules together are called van der Waals forces if they don't involve ions. In any atom or molecule, there is never a completely uniform charge density on the surface. For some molecules, this is extreme (water is a good example) and we say it is very polar, or that it has a large dipole moment. This is just another way of saying that one part has a negative charge and the other has a positive charge. In water it looks like this (from wikipedia):
In this picture, red means "more electrons" and blue means "less electrons." Water can form hydrogen bonds, which are very strong electrostatic interactions. Some atoms and molecules have an almost uniform charge density on the surface. We call these "non-polar" molecules - noble gases are good examples. However, even noble gases have what is called an induced dipole due to statistically correlated fluctuations in electron density when the atoms are near each other. As a result, even noble gases can be cooled to the point where they become liquid - the very, very weak electrostatic interactions will hold them together at low temperature, when they are not moving very fast. These forces are called London Dispersion Forces - after the guy who first described them. London dispersion forces are important, because they are found in all molecules - polar or not. In fact, this is what makes most plastics solid. Polyethylene, for example, is made of very long chains of essentially non-polar molecules (from wikipedia):
The following is multiple choice question (with options) to answer.
What crystals consist of molecules at the lattice points of the crystal, held together by relatively weak intermolecular forces? | [
"salt crystals",
"healing crystals",
"molecular crystals",
"quartz crystals"
] | C | 4. Molecular crystals -- Molecular crystals typically consist of molecules at the lattice points of the crystal, held together by relatively weak intermolecular forces (see Figure below ). The intermolecular forces may be dispersion forces in the case of nonpolar crystals, or dipole-dipole forces in the case of polar crystals. Some molecular crystals, such as ice, have molecules held together by hydrogen bonds. When one of the noble gases is cooled and solidified, the lattice points are individual atoms rather than molecules. In all cases, the intermolecular forces holding the particles together are far weaker than either ionic or covalent bonds. As a result, the melting and boiling points of molecular crystals are much lower. Lacking ions or free electrons, molecular crystals are poor electrical conductors. |
SciQ | SciQ-1731 | geophysics, plate-tectonics
Title: Equatorial bulge and tectonic plates It is well known that the Earth is not a sphere, but rather it bulges at the equator. Also it is well known that the Earth's crust is composed of 7 or 8 (depending on definition) major tectonic plates, which are able to move on top of the asthenosphere, the upper layer of the Earth's mantle.
Due to the equatorial bulge, it would seem as though plates near the equator should not be able to drift away from the equator, and plates away from the equator should not be able to drift near the equator, since they will not be of the right shape to fit over these portions of the Earth. So how are the plates able to drift to and from the equator when the surface of the Earth is shaped differently there? The plates are not as rigid as you think. You seem to be imagining the situation as something like this: I boil an egg and take the shell off in pieces, but I can't take a piece of shell from the end and make it lay flat on the side of the egg. However, rock is not that rigid on scales of thousands of kilometres and millions of years (I don't think there exists any material which would be that rigid). Also, Earth's equatorial bulge is tiny relative to its diameter -- less than 50km. Tectonic plates move very slowly, and there is plenty of time for them to deform as they move.
The following is multiple choice question (with options) to answer.
What causes continents to drift closer to the poles or the equator? | [
"plate movements",
"time",
"plate tectonics",
"earthquakes"
] | A | Plate movements cause continents to drift closer to the poles or the equator. Ocean currents also shift when continents drift. All these changes can affect Earth’s temperature. |
SciQ | SciQ-1732 | neurophysiology
Title: Why myelin sheat does not cover the whole axon? Is there an optimal lenght for myelin sheats to be effective and lead potential across the nerve cell? This has always bugged me. The nodes of Ranvier (the gaps between myelin sheath segments) speed up the action potential because the electric current can jump from node to node (or gap to gap). If the myelin covered the entire axon, the signal wouldn't have the gaps to speed up the signal. As for optimal length, the gap is 1μm long, but can be longer, on the order of millimeters depending on the type of cell. The length of the myelin doesn't matter so much as the length of the nodes of Ranvier because they are where the Na+/K+ channels are found so the ion exchange can occur. This is how an action potetial can occur, so the myelin not covering the entire axon is crucial for the ability of neurons to propagate a signal.
The following is multiple choice question (with options) to answer.
What is the major selective advantage of myelination? | [
"space efficiency",
"storage capacity",
"potentiation",
"heat regulation"
] | A | |
SciQ | SciQ-1733 | neuroscience, neuroanatomy, neurology
Title: Is it possible to temporarily paralyze someone through the use of electric signals or focused ultrasound? I've been reading about how it is possible to send signals to the brain using focused ultrasound or electrical impulses. It is possible to make someone see a certain shape or color by stimulating different areas of the brain. I was wondering whether or not it would be possible to temporarily shut off a person's motor functions by for example, sending signals to the cerebellum or perhaps intercepting them before they can travel down the spinal chord. With in-depth study and research, it would be possible on 1 person. However, it's unlikely that this type of technology could ever be weaponized.
Nerves and neural networks are particularly known for having unique calibrations per individual. Even if you can decipher every neural communication protocol on a test subject, the signal protocol would be at least slightly different on others, even for crude movement control.
Mind control would be several orders of magnitude harder - each person's brain is different.
Most neurons communicate through neurotransmitters rather than electricity, completely ignoring your control scheme.
Even if none of these barriers existed, people could always block them using "tinfoil hats".
The following is multiple choice question (with options) to answer.
What debated therapy offers a potential method for replacing neurons lost to injury or disease? | [
"cell duplication",
"stem cell therapy",
"cell production therapy",
"stem cell reduction"
] | B | |
SciQ | SciQ-1734 | classical-mechanics
Title: Help me find flaws on my simple machines invention I have a work to make an invention on simple machines. First of all I am sorry if my English is not very good or clear. As we all know, simple machines are used to simplify things in life and use less work (mechanical advantage). My concept is using a pulley to pull things up, but I want to use like a machine that needs to be stepped (lever type 3) to move the pulley. But I feel like there is a flaw to my invention, and feel very frustated. This is my concept visualization:
P.S: Sorry for the language usage (Image is semi-English and semi-Indonesian language)
Thank you for the help. The idea of simple machines is usually "sacrifice length to gain force". Or the opposite, but more rarely. You have incorporated a level and pulleys in your design. Let's analyze those.
The lever
The first problem is that you have made a lever that, if you step on it, the weight will go down. But, it would already go down by gravity, this is not useful. You probably want to counteract gravity and make it go up, so something like this:
The other problem is the general idea of using a level with your foot. The thing is, you can't move your foot much. This means do not really have length to sacrifice to gain force. So, to use a lever with your foot, you have to either:
Use it to lift something very light with a single motion of the foot. It's hard to find a use for this, though. Also, it means that the edge of the lever would be really long a take much space.
Use it to lift a heavy weight, but your foot won't have enough room. To gain multiple times one floor's height, you'd probably want to jump from some roof:
Now that we got the lever "solved", let's discuss the pulley (which is much easier for you to do without being unrealistic).
Note that just having a pulley somewhere doesn't provide you an advantage. You have to use something like a snatch block:
This will indeed allow you to use a long rope to raise the weight with less effort:
The following is multiple choice question (with options) to answer.
How many types of simple machines are there? | [
"three types",
"ten types",
"six types",
"two types"
] | C | There are six types of simple machines. Machines that consist of two or more simple machines are called compound machines. |
SciQ | SciQ-1735 | evolution, botany, development, fruit, seeds
What is the point of fruit if not to be eaten? It’s my understanding that organisms will adapt to survive and thrive. I understand that being eaten can spread seeds, but this just seems like too much of a risky tactic to rely on.
Following on from part one: If being eaten is the best way to spread seed, why do some plants avoid this (such as by being poisonous or thorny)? Seeds are spread by many mechanisms
Wind dispersal: When air currents used to spread seeds. Often these plants have evolved features to facilitate wind catching, for example dandelions. Aka, anemochory.
Propulsion & bursting: When seeds are propelled from the plant in an such as in these videos. This is called Ballochory.
Water: Similarly to wind dispersal plants can spread seeds by water movement/currents, aka Hydrochory. This is used by many algae and water living plants.
Sticky Seeds: There are many ways a seed can attach to the outside of an animal - by using hooks, barbs, sticky excretions, hairs. Seeds then get carried by an animal and fall off later. This is epizoochory.
Fruiting: Plants can use seed-bearing fruit to encourage animals to eat the seeds. They will then be spread when the waste is excreted after digestion. This is a process of endozoochory.
More than one way to spread a seed
The following is multiple choice question (with options) to answer.
After dispersal of a seed, what next step may occur if environmental conditions are favorable? | [
"germination",
"bloom",
"degradation",
"infection"
] | A | |
SciQ | SciQ-1736 | quantum-gravity, physical-constants
Title: What is the smallest existing thing in theory and law? What is the smallest existing thing in theory and law?
"What is the smallest existing thing in theory and law?"
The Merriam Webster Dictionary defines a "thing" as:
: an object or entity not precisely designated or capable of being
designated
a: an inanimate object distinguished from a living being
b: a separate and distinct individual quality, fact, idea, or usually
entity
c: the concrete entity as distinguished from
...
A Photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles). Mass: 0 < 1×10−18 eV/c^2.
The photon has zero rest mass and always moves at the speed of light within a vacuum. Since the Photon is a Point Particle and has a size of zero you might say it's not a thing, nothing; that leaves us with:
The smallest real thing is the Neutrino. Mass: ≤ 0.120 eV/c^2.
The smallest theoretical thing is the Planck Particle. Radius: 5.72947×10−35 m, Mass: 3.85763×10−8 kg.
The following is multiple choice question (with options) to answer.
What is the term for the smallest particle of an element that still has the properties of that element? | [
"neutron",
"atom",
"nucleus",
"electron"
] | B | An element is a pure substance. It cannot be broken down into other types of substances. Each element is made up of just one type of atom. An atom is the smallest particle of an element that still has the properties of that element. |
SciQ | SciQ-1737 | entomology, parasitology, parasitism
The male (microgametocytes) and female (macrogametocytes) gametocytes are ingested by a female Anopheles mosquito during a blood meal (8) - only female mosquitoes (of pretty much any species) drink blood. The parasites' multiplication in the mosquito is known as the sporogonic cycle (stage C). While in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes (9). The zygotes in turn become motile and elongated (ookinetes) (10) which invade the midgut wall of the mosquito where they develop into oocysts (11). The oocysts grow, rupture, and release sporozoites (12), which make their way to the mosquito's salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle (1).
Sources
The following is multiple choice question (with options) to answer.
What are insect parasites transmitted sexually? | [
"deer ticks",
"pubic lice",
"pinworms",
"chlamydia"
] | B | Pubic lice , like the one in Figure below , are insect parasites that are transmitted sexually. They suck the blood of their host and irritate the skin in the pubic area. |
SciQ | SciQ-1738 | mechanical-engineering, electric-vehicles, regenerative-braking
Title: Does an electric vehicle going downhill recover energy? I have to model the behavior of an electric car. For this, I use these equations and I can observe by "playing" with parameters that, when going downhill at constant speed, the car has a negative consumption (i.e. recovers energy). I was wondering if this is realistic? It depends on how steep the hill is. On a slight hill, the energy added by gravity is still not enough to overcome rolling friction and air resistance, so the car still needs power to maintain speed. On a steeper hill, the two may balance out, so no power is used, and no power is generated. On a hill that's steep enough to require braking to control the speed, the car recovers energy. It's called regenerative braking. If the car is going too fast, applying the brakes turns the motor into a generator and charges the battery.
The following is multiple choice question (with options) to answer.
What type of energy is used when a roller coaster runs downhill? | [
"vibrational energy",
"kinetic energy",
"proportional energy",
"residual energy"
] | B | For some, the exciting part of a roller coaster is speeding down; for others it is the anticipation of climbing up. While the coaster is being towed up, it is having work done on it. The work done towing it to the top of the hill becomes potential energy stored in the coaster and that potential energy is converted to kinetic energy as the coaster runs down from the top of the hill to the bottom. |
SciQ | SciQ-1739 | biochemistry
Alright so this is the oxidation of one mole of glucose equation (Without the ATPs) but till now I don't exactly know the correct answer for this question, but to not create any confusion this question is related to the Aerobic respiration (Glycolysis, Krebs Cycle and Electron transport chain).
Here's how I approached this question:
(a) is obviously not correct because the products of glycloysis are 2 pyruvate molecules and 2 ATP molecules so I checked off this choice.
(b) However seems correct because the products of 2 Krebs cycle is 4 CO2 and there is already 2CO2 when the pyruvate acid formed the 2 acetyl CoA molecules so in total that's 6CO2, but still what about the 6 Water molecules?
(c) is a very debating choice because when there is a "Complete occurrence of oxidative phosphorylation process" so that means 2 Krebs cycles had already occurred and formed the 6CO2, and during the oxidative phosphorylation process Water molecules are formed. and ATPs too? I don't exactly know about the ATPs, but aren't they supposed to be in the equation's products in order for this choice to be correct?
(d) This choice indicates to Krebs cycle but the water molecules only are formed during oxidative phosphorylation only.
So basically all the choices seems very debating and confusing and if I were to choose then I'll go with (C) because it's the only choice that makes sense for the water molecules (and the question asks for water), but I want someone to please answer this question with a brief explanation to why he chose this answer,
Thanks :) This reaction only means complete oxidation of glucose to 6 molecules of carbon dioxide and 6 molecules of water.
Reaction presented in question is very generalized, but the presence of six water molecules only means complete cellular respiration. Check out the actual biochemical pathways which take place to oxidize one glucose molecule.
And other options do not represent the complete cellular respiration, so there will not be formation of six water molecules, only option C means complete oxidation of glucose.
The following is multiple choice question (with options) to answer.
In what process is atp created by glycolysis, without oxygen? | [
"oxidation",
"sedimentation",
"condensation",
"fermentation"
] | D | Two different pathways accomplish the regeneration of NAD + with rather famous products: lactic acid (C 3 H 6 O 3 ) and ethyl alcohol (C 2 H 6 O) ( Figure above ). Making ATP in the absence of oxygen by glycolysis alone is known as fermentation . Therefore, these two pathways are called lactic acid fermentation and alcoholic fermentation . If you lack interest in organisms, such as yeast and bacteria, which have “stuck with” the anaerobic tradition, the products of these chemical reactions may still intrigue you. Fermentation makes bread, yogurt, beer, wine, and some new biofuels. In addition, some of your body’s cells are facultative anaerobes, retaining one of these ancient pathways for short-term, emergency use. |
SciQ | SciQ-1740 | civil-engineering
Other things that can be done is to place hay bales, or rocks, on the soil slope and on the slope above the deposited soil. These can help to reduce the speed of surface water running down the slope.
If hay bales are used they should be placed in a staggered, off-set pattern, so that long drainage channels, which would lead to the formation of erosion gullies, are not created by the bales.
Moonscaping of the upper natural slope, above the deposited soil slope would also help in preserving the deposited soil slope.
The following is multiple choice question (with options) to answer.
What helps deposit the material in caves as stalactites, stalagmites, and columns | [
"gas",
"precipitation",
"wastewater",
"groundwater"
] | D | Groundwater deposits the material in caves as stalactites, stalagmites, and columns. |
SciQ | SciQ-1741 | bacteriology, infection
Are there any studies that show the population of V. vulnificus over a time period covering the BP Horizon spill (this happened in April 2010, and oil products are still washing up on beaches in small amounts)
Is it possible that it could be metabolizing oil or other chemicals related to the spill? I found these article, which show exponential increase in population of Vibrio in BP oil spill region (published in 2011 supported in 2013).$^{1,2}$
There is evidence that Vibrio representatives can metabolize oil-derived compounds $^{3,4}$. There is a sizable amount, more than 31%, where found in the Deepwater Horizon Spill.$^5$. Though the reason is still to be proved $in\ vitro$, but studies shows they can persist in the presence of oil.$^6$
Source:
[1]:
High Numbers of Vibrio vulnificus in Tar Balls Collected from Oiled Areas of the North-Central Gulf of Mexico Following the 2010 BP Deepwater Horizon Oil Spill
[2]:
Associations and dynamics of Vibrionaceae in the environment, from the genus to the population level
[3]: West 1984, Numerical taxonomy of phenanthrene-degrading bacteria isolated from the Chesapeake Bay.
[4]: Moxley K., Schmidt S. (2010). Preliminary characterization of an estuarine, benzoate-utilizing Vibrio sp. isolated from Durban Harbour, South Africa. Curr. Res. Technol. Educ. Top. Appl. Microbiol. Microb. Biotechnol. 1249–1254
[5]: Hamdan L. J., Fulmer P. A. (2011). Effects of COREXIT® EC9500A on bacteria from a beach oiled by the Deepwater Horizon spill. Aquat. Microb. Ecol. 63, 101 10.3354/ame01482
[6]: In situ and in vitro impacts of the Deepwater Horizon oil spill on Vibrio parahaemolyticus.
The following is multiple choice question (with options) to answer.
A recent deadly explosion in the gulf of mexico exemplified what source of ocean pollution? | [
"fracking disaster",
"algal bloom",
"greenhouse gases",
"oil spill"
] | D | Oil spills are another source of ocean pollution. To get at oil buried beneath the seafloor, oil rigs are built in the oceans. These rigs pump oil from beneath the ocean floor. Huge ocean tankers carry oil around the world. If something goes wrong with a rig on a tanker, millions of barrels of oil may end up in the water. The oil may coat and kill ocean animals. Some of the oil will wash ashore. This oil may destroy coastal wetlands and ruin beaches. Figure below shows an oil spill on a beach. The oil washed ashore after a deadly oil rig explosion in the Gulf of Mexico in 2010. |
SciQ | SciQ-1742 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
Plants supply, ultimately, most of the food eaten by terrestrial animals, along with what gas? | [
"carbon dioxide",
"oxygen",
"nitrogen",
"hydrogen"
] | B | |
SciQ | SciQ-1743 | physical-chemistry, kinetics
Title: If a reactant appears on both sides of an elementary equation, can it be cancelled? Me and a friend were debating the following. For the elementary reaction
$$\ce{A + B -> A + C}$$
my friend says that it is unimolecular because $\ce{A}$ does not "participate" in the reaction. So, he says that the rate law is
$$\text{rate} = k[\ce{B}].$$
But, I think that that since it is an elementary reaction step, you cannot cancel $\ce{A}$ from both sides. I think that it is a bimolecular reaction with
$$\text{rate} = k[\ce{A}][\ce{B}].$$
Who is correct? If the elementary step is indeed written
$$\ce{A + B -> A + C}$$
and assuming that you haven't just written in $\ce{A}$ for fun, i.e. $\ce{A}$ is actually a participant in the step, then yes, this would be considered bimolecular. This sort of step, featuring the same chemical species on both sides of the reaction, does pop up in (for example) the Lindemann mechanism.
With regard to kinetics, however, it is worth noting that steps of this kind can sometimes indicate a reaction that is catalytic with respect to $\ce{A}$. If that is the case, then the concentration of $\ce{A}$ is essentially constant and you would obtain pseudo-first-order kinetics.
The following is multiple choice question (with options) to answer.
Chemical reactions are typically written to imply that they proceed in one direction - if they can occur in either direction, they are considered what? | [
"reversible",
"singular",
"observable",
"reactive"
] | A | A chemical reaction is usually written in a way that suggests it proceeds in one direction, the direction in which we read, but all chemical reactions are reversible, and both the forward and reverse reaction occur to one degree or another depending on conditions. In a chemical equilibrium, the forward and reverse reactions occur at equal rates, and the concentrations of products and reactants remain constant. If we run a reaction in a closed system so that the products cannot escape, we often find the reaction does not give a 100% yield of products. Instead, some reactants remain after the concentrations stop changing. At this point, when there is no further change in concentrations of reactants and products, we say the reaction is at equilibrium. A mixture of reactants and products is found at equilibrium. For example, when we place a sample of dinitrogen tetroxide (N2O4, a colorless gas) in a glass tube, it forms nitrogen dioxide (NO2, a brown gas) by the reaction N 2 O 4(g) ⇌ 2NO 2(g) The color becomes darker as N2O4 is converted to NO2. When the system reaches equilibrium, both N2O4 and NO2 are present (Figure 13.2). |
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