source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-3744 | newtonian-mechanics, forces, free-body-diagram
Title: How can I actually push heavier objects? I've been thinking about Newton's third law lately because I couldn't understand a few things and I think I actually answered my own question. Could someone confirm if my reasoning is right or show me my mistakes?
So the question is: If force and reaction force are always the same, and less mass means greater acceleration, how can I actually push heavier objects? Then I got my idea of an answer that I will try to show with a picture:
I exert $F_{\text{action}}$ force on a Box (much heavier than me) and an equal $F_{\text{reaction}}$ is exerted on me in the opposite direction, but $F_{\text{action}}$ is caused by the $F_{\text{muscle}}$ force which is exerted on me and has the same direction as $F_{\text{action}}$
The box changes position but I don't change position myself because $F_{\text{muscle}}$ still acts and prevents it.
Step 1 is repeated and that way I can push much heavier objects.
(I am sorry that box looks little different in every step. It was hand-drawn - the box in steps 2 and 3 is meant to be in the same position)
The following is multiple choice question (with options) to answer.
What do we call something that pushes or pulls on an object? | [
"friction",
"reaction",
"force",
"annoyance"
] | C | 4.1 Development of Force Concept Dynamics is the study of the forces that cause objects and systems to move. To understand this, we need a working definition of force. Our intuitive definition of force—that is, a push or a pull—is a good place to start. We know that a push or pull has both magnitude and direction (therefore, it is a vector quantity) and can vary considerably in each regard. For example, a cannon exerts a strong force on a cannonball that is launched into the air. In contrast, Earth exerts only a tiny downward pull on a flea. Our everyday experiences also give us a good idea of how multiple forces add. If two people push in different directions on a third person, as illustrated in Figure 4.3, we might expect the total force to be in the direction shown. Since force is a vector, it adds just like other vectors, as illustrated in Figure 4.3(a) for two ice skaters. Forces, like other vectors, are represented by arrows and can be added using the familiar head-to-tail method or by trigonometric methods. These ideas were developed in Two-Dimensional Kinematics. |
SciQ | SciQ-3745 | kinematics, vectors, calculus
Title: Direction of velocity vector in two dimensions I'm having some problems understanding the velocity vector in two dimensions.
Any given trajectory it's expressed by a curve.
Here we have two metrics to calculate how much the point has traveled:
Displacement: a vector that only takes into account the initial position and the final position.
Distance: a scalar that tells us about the amount of space the point has traveled.
In one dimension the velocity can be expressed simply as $v = \frac{dx}{dt}$ because we're moving along one axis and the two are the same.
However, in two or more dimensions we have a problem with the definition of velocity because, since it's a scalar we have no clue about its direction.
The displacement vector is like this:
if we define velocity as $\vec{v} = \frac{\Delta\vec{r}}{dt}$ we make an error but taking the limit we get that error close to $0$.
My books explains how essentially $d\vec{r} = ds\ \hat{u_T}$, where $\hat{u_T}$ is a versor tangent to the trajectory.
This makes sense because if the displacement is infinitesimal then it must be tangent to the trajectory so it's like if we move an infinitesimal step along the tangent direction.
Here confusion kicks in, because it also says that now the velocity vector can be expressed as $\vec{v} = \frac{ds}{dt}\hat{u_T}$ so it means that the velocity vector can be expressed as a vector tangent to the trajectory that has the magnitude of the instantaneous velocity.
I don't get why this is the case, if we consider pointwise the vector $d\vec{r}$
The following is multiple choice question (with options) to answer.
Velocity is a vector that has both direction and what? | [
"latitude",
"magnitude",
"radiation",
"variable"
] | B | Because acceleration is velocity in m/s divided by time in s, the SI units for acceleration are m/s 2 , meters per second squared or meters per second per second, which literally means by how many meters per second the velocity changes every second. Recall that velocity is a vector—it has both magnitude and direction. This means that a change in velocity can be a change in magnitude (or speed), but it can also be a change in direction. For example, if a car turns a corner at constant speed, it is accelerating because its direction is changing. The quicker you turn, the greater the acceleration. So there is an acceleration when velocity changes either in magnitude (an increase or decrease in speed) or in direction, or both. Acceleration as a Vector Acceleration is a vector in the same direction as the change in velocity, Δv . Since velocity is a vector, it can change either in magnitude or in direction. Acceleration is therefore a change in either speed or direction, or both. Keep in mind that although acceleration is in the direction of the change in velocity, it is not always in the direction of motion. When an object slows down, its acceleration is opposite to the direction of its motion. This is known as deceleration. |
SciQ | SciQ-3746 | species-identification, microbiology, microscopy
Title: Identification of protozoa under microscope I observed maybe Protozoa from standing FRESH water and from slowly flowing FRESH water. I am complete dilettante. Can you tell what these creatures are?
https://www.youtube.com/watch?v=6D5ck3zNJzA&t=474s
Thank you.
Added picture for to be more specific At first glance, the organisms may hold the appearance of protozoans like ciliates. However, I am of the belief that these 'totally tubular' micro organisms are in fact diatoms.
The diatoms are a diverse range of eucaryotic microalgae which comprise a large percentage of the phytoplankton group. (Diatomaceous earth is the residual remains of their calcareous walls)
They are likely diatoms because of their apparent hard membrane, and slight brown-green pigment, typical of heterokont diatoms.
I would be unable to specify the organism to family level. However, you may wish to complete your investigation by looking under the order 'Pennales'.
For general information regarding the Diatoms, you may visit https://en.wikipedia.org/wiki/Diatom
Morphology and description available from: https://books.google.co.uk/books?id=xhLJvNa3hw0C&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
Good luck
The following is multiple choice question (with options) to answer.
What are the two classifications for organisms living in water? | [
"arctan and plankton",
"arctan and nekton",
"nekton and plankton",
"scharwenka and plankton"
] | C | Nekton are living things that swim through the water. They may live at any depth, in the photic or aphotic zone. Most nekton are fish, although some are mammals. Fish have fins and streamlined bodies to help them swim. Fish also have gills to take oxygen from the water. Figure below shows examples of nekton. |
SciQ | SciQ-3747 | geology, volcanology, mineralogy, minerals
Title: Where can obsidian be found? Where is obsidian found?
Is it typically found on the surface or underground?
If underground, how far under (meters or feet would be perfect)?
Also, is it found everywhere on Earth, or just in areas where volcanic activity is (or was recently) high? Obsidian is formed when a rhyolitic (or felsic) lava flows cool rapidly. This must mean that it's mostly available on the surface (and I think if you go near volcanos you can find pieces of Obsidian on the ground) because molten rock cools much faster above ground than it does below, allowing the melt to cool with small crystals (as opposed to intrusive rocks which have larger crystals). This means that Obsidian is an extrusive igneous rock.
I am betting that Obsidian is very common around most active volcanos around the world!
The following is multiple choice question (with options) to answer.
Where are hotspot volcanoes commonly found? | [
"the ocean",
"rivers",
"lakes",
"streams"
] | A | Hotspot volcanoes are better able to penetrate oceanic crust than continental crust. We see many more hotspot volcanoes in the oceans. |
SciQ | SciQ-3748 | human-biology, human-anatomy, terminology, anatomy, etymology
Title: Why is the opposite of plantar flexion called "dorsiflexion"? Why is the action of flexing the foot so that the toes move anteriorly/superiorly (i.e. in the direction opposite that which they move during plantar flexion) described as "dorsiflexion?" In the same vein, why is the top surface of the foot called the "dorsal surface?"
If anything, the action opposite to plantar flexion moves the foot in the ventral direction, doesn't it? And surely if you've ever seen a human in the anatomical position, you can see that there's nothing dorsal about the top surface of the foot - it's superior, perhaps, but by no means dorsal. Anatomical terms must be able to fit a wide variety of organisms, from insects to fish, dogs, horses, chimpanzees to humans. That's why the terms are sometimes confusing to people who are thinking only of bipedal humans.
In anatomy, the dorsum is the upper side of animals that typically run fly, swim or crawl in a horizontal position. In vertebrates the dorsum contains the backbone. In such an animal the "ground side" is the ventrum.
Due to varied orientation on quadrupedal mammals (where the term is more appropriately used) the "back"-side of the hand, the "top"-side of the foot and the upper surface of the tongue are referred to by the term dorsum.
Does this picture help? Note the dorsal surfaces of the body, muzzle, feet.
In anatomy, the sole of the foot is called the plantar surface. The top of the foot is called the dorsum of the foot. (Imagine us walking on all fours like apes.) Therefore when you extend your foot, it's called plantar flexion; when you flex your foot upwards towards your head, it's called dorsiflexion.
Similarly, the arteries feeding the bottom of your foot form the plantar arch. Those feeding the top are the dorsal artery (or the dorsalis pedis).
Because anatomy must describe other animals than ourselves with other orientations, it must be consistent. In a quadruped, the dorsum of the tongue and the feet do actually point to it's "back" surface. See the picture below:
The following is multiple choice question (with options) to answer.
The muscles of the anterior compartment of the lower leg are generally responsible for dorsiflexion, and the muscles of the posterior compartment of the lower leg are generally responsible for this? | [
"posterior flexion",
"walking flexion",
"plantar flexion",
"ganglion flexion"
] | C | Figure 11.32 Muscles of the Lower Leg The muscles of the anterior compartment of the lower leg are generally responsible for dorsiflexion, and the muscles of the posterior compartment of the lower leg are generally responsible for plantar flexion. The lateral and medial muscles in both compartments invert, evert, and rotate the foot. |
SciQ | SciQ-3749 | kinetics, catalysis, surface-chemistry
Title: Does someone know a unique testable questions surrounding 1 of the 5 variables that affect the rate of a chemical reaction? I am a year 11 student studying high school chemistry and we are currently studying catalysts.
I am working on an assessment and need to come up with a unique but testable hypothesis surrounding one of the 5 variables of chemical reaction rate.
The 5 variables that affect the rate of a chemical reaction that my teacher have given to the class are as follows:
The concentration of each reactant (pressure of gases)
The temperature
The surface area of reacting solids
The nature of catalytic material
The quantity of catalytic material
The following is multiple choice question (with options) to answer.
The presence of what, which acts as a trigger, affects the rate of chemical reaction? | [
"friction",
"light",
"catalyst",
"heat"
] | C | rates The rates at which reactants are consumed and products are formed during chemical reactions vary greatly. We can identify five factors that affect the rates of chemical reactions: the chemical nature of the reacting substances, the state of subdivision (one large lump versus many small particles) of the reactants, the temperature of the reactants, the concentration of the reactants, and the presence of a catalyst. |
SciQ | SciQ-3750 | quantum-mechanics, nuclear-physics, atomic-physics, atoms
Title: Could I turn into a nuclear bomb? Just out of curiousity, could the nuclei of our atoms split via quantum tunnelling, thereby leading to nuclear reactions and ultimately turning us into atomic bombs? I know that this is near-impossible, but wondering if it was technically possible. The thing is, we're made of mostly stable matter of low atomic number. In a nuclear bomb, unstable nuclei split, releasing a number of energetic neutrons which strike other unstable nuclei, and the reactions chain uncontrollably. Splitting a small nucleus actually costs energy, so even if a carbon atom in your body did split, it would only split into smaller, still low-energy atoms, which would interact normally with other atoms in your body. A couple extra lithium or helium atoms isn't going to do anything drastic.
The following is multiple choice question (with options) to answer.
What do you call the splitting of the nucleus of an atom into two smaller nuclei? | [
"critical fission",
"nuclear fusion",
"cell division",
"nuclear fission"
] | D | Nuclear fission is the splitting of the nucleus of an atom into two smaller nuclei. This type of reaction releases a great deal of energy from a very small amount of matter. For example, nuclear fission of a tiny pellet of uranium-235, like the one pictured in Figure below , can release as much energy as burning 1,000 kilograms of coal!. |
SciQ | SciQ-3751 | fundamental-astronomy, coordinate, software, declination
In your case, longitude and latitude will actually be right ascension and declination respectively. They are basically stellar coordinates for the celestial sphere as opposed to ground coordinates for the geode.
There are many, many other map projections possible, but equi-rectangular is the simplest.
However, your question is a little vague because you mentioned a "virtual 3D world", yet also asked how much you need to flatten it. If you already have a 3D model of a sphere in your computer graphics, you don't have to flatten it at all. You just draw the 3D model (sphere) with a texture on it. If you want to represent it as a map, then of course you have to flatten it, and equi-rectangular projection is the simplest way.
The following is multiple choice question (with options) to answer.
What method is used to map the earth on flat paper? | [
"projections",
"surveying",
"calculations",
"forecasts"
] | A | Earth is a round, three-dimensional ball. In a small area, Earth looks flat, so it is not hard to make accurate maps of a small place. When mapmakers want to map the round Earth on flat paper, they use projections. What happens if you try to flatten out the skin of a peeled orange? Or if you try to gift wrap a soccer ball? To flatten out, the orange peel must rip, and its shape must become distorted. To wrap a round object with flat paper requires lots of extra cuts and folds. A projection is a way to represent Earth’s curved surface on flat paper ( Figure below ). |
SciQ | SciQ-3752 | microbiology, cancer, toxicology
Title: Molds associated with Aflatoxin? I've been reading how some molds may be carcinogenic. In particular, molds associated with the fungus metabolite, Aflatoxin.
Are the types of mold that produce this toxin, present in buildings/showers/domestic environments, or do they only grow on food-stuffs? Strictly speaking the common bread mould Rhizopus sp. does not produce aflatoxin.
The fungus Aspergillus flavus which belongs to the class Ascomycetes secretes aflatoxin. It attacks cereal grains , legumes, tree nuts. The fungi are green in colour and 'mould' like in appearance.
The fungus attacks the food stuffs and storage grains. So under favourable conditions it may grow in your store room if it finds food for its growth. Also Aspergillus can grow at temperatures as high as 48°C and even at low temperatures like 5-8°C.
Edit: On being asked for sources I include some which strongly support my claim
1. For suitable conditions of growth of the fungi visit https://en.m.wikipedia.org/wiki/Aspergillus_flavus and read under the Environment heading.
2. Visit https://bioweb.uwlax.edu/bio203/s2013/ernst_ale2/habitat.htm and read from " Aspergillus flavus is omnipresent " upto " Aspergillus may also grow on or inside walls in homes, especially if the house is damp or has been damaged by flooding. "
3.https://www.moldbacteria.com/mold-types.html this site provides a list of different fungi found in our homes. Here you can find Aspergillus flavus to grow in flower pot soil. Moreover other species of Aspergillus are found in kitchens and bathrooms.
The following is multiple choice question (with options) to answer.
Water molds mostly live in water or moist? | [
"biomes",
"soil",
"plants",
"cells"
] | B | Define physical change, and give examples of physical change. |
SciQ | SciQ-3753 | human-biology, brain, vision, optics
It's important to note that this study found that no listeners interpreted the stimulus properly. We know this because the researchers only used 400Hz & 800Hz frequencies and controlled exactly which ear was receiving it. People either heard something that was not there or something contradictory to what was being played. This shows we can measure what actually happened in the illusions since we created it and are able to quantify it.
This can similarly be done with your image.
1) A human created that image thus we can create a similar image and know exactly if we created a moving image or not, then compare to what people interpret to see if illusions occur.
2) You can track any pixel on that image using software to see if it moves and compare to what subjects interpret.
There are also other interesting studies such as the optical illusion of a baseball being in motion. [3] This is particularly useful as this can be described with physics which can tell us what is actually going on versus what we are thinking is going on.
Another interesting study is that autism may change the way the brain interprets optical illusions. [4] Leading more to the idea that our brains are flat out wrong about what is happening because even though the information has not changed it has been interpreted differently. Sometimes resulting it people being less susceptible to an illusion.
The answer to "How does everyone know?" is that people can know because we can use tested methods of interpreting data correctly and observe the difference between that and what our brains alone interpret. Our brains are evolved for specific types of environments and sensory illusions are things that are often too unfamiliar to our brains to deal with properly.
The following is multiple choice question (with options) to answer.
What is the act of noting or detecting phenomenon through the senses | [
"overstimulation",
"sensory overload",
"an observation",
"invention"
] | C | Scientists first make observations that raise questions. An observation is the act of noting or detecting phenomenon through the senses. For example, noting that a room is dark is an observation made through sight. |
SciQ | SciQ-3754 | the two rectangles = … Level 5 - Real life composite area questions from photographs. Math Practice Online > free > lessons > Texas > 8th grade > Perimeter and Area of Composite Figures. Match. Solving Practice Area of Composite Figures. The 2 green points in the diagram are the … Edit. Question 4 : Find the area of the figure shown below. Area of Composite Figures DRAFT. Today Courses Practice Algebra Geometry Number Theory Calculus Probability ... and the area of the figure is 15, what is the perimeter of the figure? Circumference. Geometry Parallelogram Worksheet Answers Unique 6 2 Parallelograms Fun maths practice! Area of Composite Figures DRAFT. Share practice link. Filesize: 428 KB; Language: English; Published: December 14, 2015; Viewed: 2,190 times; Multi-Part Lesson 9-3 Composite Figures - Glencoe. A = 3 + 44 + 4.5. 9th - 12th grade . More Composite Figures on Brilliant, the largest community of math and science problem solvers. Therefore, we'll focus on applying what we have learned about various simple geometric figures to analyze composite figures. Area of composite shapes (practice) | Khan Academy Practice finding the areas of complex shapes that are composed of smaller shapes. This presentation reviews what is required to determine the area of composite figures and presents sample problems Terms in this set (20) Area. Emily_LebronC106. 00:30:09 – Finding area of composite figures (Examples #13-15) 00:40:27 – Using ratios and proportions find the area or side length of a polygon (Examples #16-17) 00:49:51 – Using ratios and proportions find the area or length of a diagonal of a rhombus (Examples #18-19) Practice Problems with Step-by-Step Solutions Separate the figure into smaller, familiar figures: a two triangles and a rectangle. Click here to find out how you can support the site. LESSON 27: Surface Area of Composite Shapes With HolesLESSON 28: Surface Area AssessmentLESSON 29: 3-D Models from 2-D Views LESSON 30: Exploring Volume and Surface Area with Unifix CubesLESSON 31: Explore Volume of Rectangular PrismsLESSON 32: Find the … So, the area of the given composite figure is 51.5 square feet. Area of Composite Figures Practice:I have used this with my 6th grade students, but it would also be
The following is multiple choice question (with options) to answer.
What two measurements are multiplied to find the area of a rectangle? | [
"length and depth",
"volume and mass",
"depth and width",
"length and width"
] | D | Assume you are finding the area of a rectangle with a length of 6.8 m and a width of 6.9 m. When you multiply the length by the width on your calculator, the answer you get is 46.92 m 2 . Is this the correct answer? No; the correct answer is 46.9 m 2 . The correct answer must be rounded down so there is just one digit to the right of the decimal point. That’s because the answer cannot have more digits to the right of the decimal point than any of the original measurements. Using extra digits implies a greater degree of precision than actually exists. The correct number of digits is called the number of significant figures . To learn more about significant figures and rounding, you can watch the videos at the URLs below. |
SciQ | SciQ-3755 | dna, dna-sequencing, genomes, human-genome, mouse
I hope this is understandable, if you need any clarification on terms, please ask :)
The following is multiple choice question (with options) to answer.
What is the term for biologically meaningful dna sequences? | [
"babies",
"genes",
"atoms",
"eggs"
] | B | disease is sex-linked and effects mainly males (who are XY, compared to XX females).273 In the unaffected population, the FMR-1 gene contains between 6 to 50 copies of a CGG repeat. Individuals with between 6 to 50 repeats are phenotypically normal. Those with 50 to 200 repeats carry what is known as a pre-mutation; these individuals rarely display symptoms but can transmit the disease to their children. Those with more than 200 repeats typically display symptoms and often have what appears to be a broken X chromosome – from which the disease derives its name. The pathogenic sequence in Fragile X is downstream of the FMR1 gene's coding region. When this region expands, it inhibits the gene's activity. 274 Other DNA Defects: Defects in DNA repair can lead to severe diseases and often a susceptibility to cancer. A OMIM search for DNA repair returns 654 entries! For example, defects in mismatch repair lead to a susceptibility to colon cancer, while defects in translation-coupled DNA repair are associated with Cockayne syndrome. People with Cockayne's syndrome are sensitive to light, short and appear to age prematurely.275 Summary: Our introduction to genes has necessarily been quite foundational. There are lots of variations and associated complexities that occur within the biological world. The key ideas are that genes represent biologically meaningful DNA sequences. To be meaningful, the sequence must play a role within the organism, typically by encoding a gene product (which we will consider next) and/or the information needed to insure its correct “expression”, that is, where and when the information in the gene is used. A practical problem is that most studies of genes are carried out using organisms grown in the lab or in otherwise artificial or unnatural conditions. It might be possible for an organism to exist with an amorphic mutation in a gene in the lab, whereas organisms that carry that allele may well be at a significant reproductive disadvantage in the real world. Moreover, a particular set of alleles, a particular genotype, might have a reproductive advantage in one environment (one ecological/ behavioral niche) but not another. Measuring these effects can be difficult. All of which should serve as a warning to consider skeptically pronouncements that a gene, or more accurately a specific allele of a gene, is responsible for a certain trait, particularly if the trait is complex, ill-defined, and likely to be significantly influenced by genomic context (the rest of the genotype) and environmental factors. Questions to answer & to ponder: • What happens in cells with defects in DNA repair systems when they attempt to divide? • I thought RNA primers were used to make DNA! So why is there no uracil in a DNA molecule? • A base is lost, how is this loss recognized by repair systems? • How could a DNA duplication lead to the production of a totally new gene (rather than just two copies of a pre-existing gene)? • How does a mutation generate a new allele? And what exactly is the difference between a gene and an allele? 273. |
SciQ | SciQ-3756 | history, autoimmune, diabetes-mellitus
Title: When was it determined that Type 1 Diabetes is an autoimmune disease? I just found out today that type 1 diabetes is an autoimmune disease. When was this discovered? This question has two answers: The difference was first described in 1936 by Harold Percival Himsworth, which described it in this article.
At this time it was established that there are two forms of Diabetes, one sensitive to insuline while the other is not.
The terms Diabetes type 1 and 2 where established somewhere between 1974 and 1976, for details see the review "The discovery of type 1 Diabetes".
The following is multiple choice question (with options) to answer.
Which common type of diabetes is also known as noninsulin-dependent or adult-onset diabetes? | [
"type 2",
"gestational diabetes",
"type 1",
"juvenile diabetes"
] | A | inner aspect of the atlas, where it is held in place by a ligament. Rotation at this joint allows you to turn your head from side to side. A second pivot joint is found at the proximal radioulnar joint. Here, the head of the radius is largely encircled by a ligament that holds it in place as it articulates with the radial notch of the ulna. Rotation of the radius allows for forearm movements. |
SciQ | SciQ-3757 | human-biology, digestive-system, immune-system, microbiome
The next level of defense comes from the cells of the innate immune system (14). In innate immunity, specialized cells monitor the area they are in for Pathogen-Associated Molecular Patterns (PAMPs). PAMPs can be sugars that make up the cell walls of the microbe or proteins that get expressed on the surface of the organism, such as Flagellin, a protein only found in the flagella of certain pathogen. The innate immune cells have pattern recognition receptors (PRR) that have a general specificity for recognizing and responding to the PAMPs. Our cells even have PRRs for DNA and Double Stranded RNA's, however those are usually found in vesicles on the inside of the cell. These interactions are very general, however once PRRs bind to the PAMP, they are able to signal into the cytoplasm, which can lead to the production of proteins, among other possible responses.
Here you can think of PRRs like a motion detector in a security system; the dog, or your two year old, or an intruder are going to set off the alarm just the same. It is not specific. The motion sensor "knows" that something that it is supposed to recognize, i.e. a moving object larger than a mouse passed by and it triggered the response, but it cannot tell you which moving object triggered it, only that it was triggered.
The innate immune cells are also able to respond by "eating" the pathogen in a process called phagocytosis. Here, they break up the bacteria, yeast, or the remnants of other dead host cells or large pathogens, things like worms, and put the broken up pieces on protein molecules on their surface.
When innate immune cells do this, they are presenting molecules to specialized immune cells (adaptive immune cells (14)), B-Cells and T-Cells, that are highly specific as to what they will react to. These cells can also cause a lot of damage to the host, so they are tightly regulated. Think of the interactions as keys and locks. A protein from a bacteria should turn a few of these cells on, but a protein from the host should not fit the lock.
The following is multiple choice question (with options) to answer.
Recognition of pathogens is a function of what type of response? | [
"hormones",
"inhalation",
"digestion",
"immune"
] | D | Recognition of Pathogens Cells of the innate immune response, the phagocytic cells, and the cytotoxic NK cells recognize patterns of pathogenspecific molecules, such as bacterial cell wall components or bacterial flagellar proteins, using pattern recognition receptors. A pattern recognition receptor (PRR) is a membrane-bound receptor that recognizes characteristic features of a pathogen and molecules released by stressed or damaged cells. These receptors, which are thought to have evolved prior to the adaptive immune response, are present on the cell surface whether they are needed or not. Their variety, however, is limited by two factors. First, the fact that each receptor type must be encoded by a specific gene requires the cell to allocate most or all of its DNA to make receptors able to recognize all pathogens. Secondly, the variety of receptors is limited by the finite surface area of the cell membrane. Thus, the innate immune system must “get by” using only a limited number of receptors that are active against as wide a variety of pathogens as possible. This strategy is in stark contrast to the approach used by the adaptive immune system, which uses large numbers of different receptors, each highly specific to a particular pathogen. Should the cells of the innate immune system come into contact with a species of pathogen they recognize, the cell will bind to the pathogen and initiate phagocytosis (or cellular apoptosis in the case of an intracellular pathogen) in an effort to destroy the offending microbe. Receptors vary somewhat according to cell type, but they usually include receptors for bacterial components and for complement, discussed below. |
SciQ | SciQ-3758 | 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.
Typically done to find food or mates, what do you call the regular movement of individuals or populations each year during certain seasons? | [
"industrialization",
"emmigration",
"migration",
"erosion"
] | C | Migration is another type of movement that changes population size. Migration is the regular movement of individuals or populations each year during certain seasons. The purpose of migration usually is to find food, mates, or other resources. For example, many northern hemisphere birds migrate thousands of miles south each fall. They go to areas where the weather is warmer and more resources are available (see Figure below ). Then they return north in the spring to nest. Some animals, such as elk, migrate vertically. They go up the sides of mountains in spring as snow melts. They go back down the mountain sides in fall as snow returns. |
SciQ | SciQ-3759 | vaccination
Title: Are there any papers arguing against vaccination in French? Disclaimer: This question is NOT about challenging the safety or efficacy of vaccines. It is only asking for tips on providing credible references that may show harmful effects of vaccination, if any.
In my French class, we were asked to debate an issue in current events. My topic is vaccines in children or adults.
The challenging part is that I was assigned to argue against vaccination, and I have to back up my arguments with credible sources (not blogs) that are in French. Hopefully some of you could point me towards some links to articles or research papers in French.
Please avoid discussion on safety and efficacy of vaccines, including local and global policies on their use. I just need help with this topic for my French class I wish you good luck, as 99.99% of the anecdotal claims out there that conclude vaccination is bad are based on unfounded rumors.
Note that much of the negative public opinion is based on a fraudulent (and retracted) paper by Wakefield in The Lancet (1998). Unfortunately for you, however, it is in English.
My French is a bit rusty, but if you go to Google Scholar and type in a search term like vaccination results in autism (les résultats de la vaccination dans l'autisme) or Wakefield vaccination autisme something might pop up in French that advocates against vaccination.
The following is multiple choice question (with options) to answer.
What is the vaccine to prevent infection of hpv? | [
"gardasil",
"cervical",
"herpes",
"HIV"
] | A | Infections with the human papillomavirus (HPV) are very common. HPV may cause genital warts , which are small, rough growths on the genitals. It may also cause cancer of the cervix in females. A simple test, called a Pap test , can detect cervical cancer . If the cancer is detected early, it usually can be cured with surgery. There is also a vaccine , GARDASIL, to prevent infection with HPV. The vaccine is recommended for females aged 11 to 26 years. |
SciQ | SciQ-3760 | geology, volcanology, mineralogy, minerals
Title: Where can obsidian be found? Where is obsidian found?
Is it typically found on the surface or underground?
If underground, how far under (meters or feet would be perfect)?
Also, is it found everywhere on Earth, or just in areas where volcanic activity is (or was recently) high? Obsidian is formed when a rhyolitic (or felsic) lava flows cool rapidly. This must mean that it's mostly available on the surface (and I think if you go near volcanos you can find pieces of Obsidian on the ground) because molten rock cools much faster above ground than it does below, allowing the melt to cool with small crystals (as opposed to intrusive rocks which have larger crystals). This means that Obsidian is an extrusive igneous rock.
I am betting that Obsidian is very common around most active volcanos around the world!
The following is multiple choice question (with options) to answer.
Mineral crystals that form when magma cools are usually _______ than crystals that form when lava cools. | [
"larger",
"older",
"smaller",
"denser"
] | A | Mineral crystals that form when magma cools are usually larger than crystals that form when lava cools. |
SciQ | SciQ-3761 | energy, fuel, environmental-chemistry
Title: Effect of coal and natural gas burning on particulate matter pollution I sometimes hear people talking about how we should replace coal burning plants with natural gas ones, to alleviate the case of particulate matter pollution. What exactly is the difference between coal fuel and natural gas that makes the latter seem "cleaner"?
At the same energy outcome, natural gas produces less carbon dioxide than coal. In a way, natural gas is half way between coal and hydrogen.
Coal produces smelly smoke, solid particles, sulfur dioxide and minor or trace heavy metal pollutants.
It is less known to common people, but power plants burning coal are more significant source of radioactive pollution than nuclear plants. This pollution is very diluted, but rather significant in absolute amount. Coal ash, used in past as a filler for some construction materials, has lead in some cases to significantly increased content of radium-226 in building walls. This radium is a product of long term decay of natural uranium. It further decays while producing radioactive gaseous radon-222, which is dangerous in long term inhalation because of lung cancer. As it stays in lungs as polonium-218 and its decay products.
See e.g. Uranium produced from coal ash
... the uranium concentration in the ash pile is about 150-180 parts per million, about 1/4th of the concentration often thought of as commercially viable for ISL[In Situ Leaching] mining. However, coal ash piles have some physical characteristics that might help overcome that disadvantage since they may be easier to drill and it might be easier to protect the local groundwater from contamination. ...
See Radon in building materials by Czech government agency for radiation protection.
The following is multiple choice question (with options) to answer.
What element makes up the majority of coal? | [
"carbon",
"lead",
"silicon",
"iron"
] | A | Coal is a black or brownish-black rock that burns easily ( Figure below ). Most coal is sedimentary rock. The hardest type of coal, anthracite, is a metamorphic rock. That is because it is exposed to higher temperature and pressure as it forms. Coal is mostly carbon, but some other elements can be found in coal, including sulfur. |
SciQ | SciQ-3762 | body diagram of the situation. You can use the Inclined Plane – Simple Machine Gizmo™ to see how inclined planes can help to lift objects. An inclined plane of angle θ = 20. The inclined plane is one of the six classical simple machines defined by Renaissance scientists. A cylinder of mass m = 250 g and length l = 10 cm is placed on an inclined plane of a rake angle α = 30 °. Materials: spring scale, object: block of wood or similar object, flat board, string, masking tape, protractor. QUESTIONS: 1. A very important application in mechanics is the inclined plane. First draw a free body diagram of the block. Floating displays using a DCRA have the space efficiency problem of having a system thickness equal to the height of the floating image and the problem of a ghost image interrupting the visibility of the floating display. It allows one to use less force to move an object. A ramp is the most basic example of an inclined plane. The lecture begins with the application of Newton’s three laws, with the warning that they are not valid for objects that move at speeds comparable to the speed of light or objects that are incredibly small and of the atomic scale. 0-kilogram object accelerating at 10. In today's lab, you will be investigating how different angles of an inclined plane affect the easiness to pull up an object. Acceleration = m/s 2 compared to 9. A force of magnitude $$T=\text{312} \text{N}$$ up an incline is required to keep a body at rest on a frictionless inclined plane which makes an angle of $$\text{35}$$ $$\text{°}$$ with the horizontal. Compute The Component Of The Gravitational Force Acting Down The Inclined Plane. A body resting on a plane inclined at at an angle α to the horizontal plane is in a state of equilibrium when the gravitational force tending to slide the body down the inclined plane is balanced by an equal and opposite frictional force acting up the inclined plane. angle of inclination: The angle that the inclined surface makes with the horizontal ground. Get an answer for 'Work on an incline plane. Simple machines are tools that make your work easier. ) and Inclined Planes Overview. Most things would rapidly slide across a floor that was slanted almost vertically steep. Then, measure the distance from that point to the bottom of the plane. Lifting a load vertically straight up takes
The following is multiple choice question (with options) to answer.
What do you call a simple machine consisting of a sloping surface that connects lower and higher elevations? | [
"wedge",
"jack",
"inclined plane",
"lever"
] | C | An inclined plane is a simple machine consisting of a sloping surface that connects lower and higher elevations. The ideal mechanical advantage of an inclined plane is always greater than 1. |
SciQ | SciQ-3763 | organic-chemistry, reaction-mechanism
Title: How to synthesise N,N,3‐trimethylbutanamide from 1‐chloro‐2‐methylpropane?
Suggest a synthetic route to amide C from the alkyl chloride B (reaction mechanisms are not required). Standard reagents and solvents may also be used.
The following is multiple choice question (with options) to answer.
What can be combined with an amine to form an amide? | [
"carboxylic acid",
"carbon dioxide",
"ketones",
"acetic acid"
] | A | An amide can be formed by combining a carboxylic acid and an amine. Only primary and secondary amines can be used to form amides, since they have a hydrogen that can be replaced with the carbonyl carbon; tertiary amines will not form amides. The amide shown in the Figure above was formed from a carboxylic acid and a primary amine. |
SciQ | SciQ-3764 | taxonomy, history
Title: How many species did Carl Linnaeus classify? How many species did Carl Linnaeus (senior) classify? More than 13,000.
Plants: >9,000 names.
In Systema Naturae 10th edition, commonly taken as the starting point of modern taxonomy, Linnaeus is reported to have published around 6,000 plant names (I haven't counted, but Müller-Wille gives 5,900 and Stearn says "almost 6,000". The Wikipedia figure of 7,700 may come from a different edition of Systema Naturae).
However, that's just SN10. Luckily, a wonderful source has compiled the names from all of Linnaeus's work:
The Linnaean Plant Name Typification Project of the Natural History Museum says that Linnaeus published more than 9,000 valid plant names in his life (names that are still valid under current nomenclatural conventions), and they have many of them in a searchable database with references to where Linnaeus published them.
Animals: >4,200 names.
For SN10, different authors give 4,236 or 4,378 animal names. Stearn says "nearly 4,400", so perhaps he too was unsure. The total number Linnaues described in his life is probably higher, as he did write separate zoological publications like Fauna Svevica, but I couldn't find a source like the project bringing together all of his animal names.
Müller-Wille S. 2006. Linnaeus' herbarium cabinet: a piece of furniture and its function. Endeavour 30: 60–64.
Stearn WT. 1959. The Background of Linnaeus's Contributions to the Nomenclature and Methods of Systematic Biology.)
The following is multiple choice question (with options) to answer.
There are about 50,000 vertebrate species, and they are placed in how many different classes? | [
"four",
"three",
"ten",
"nine"
] | D | There are about 50,000 vertebrate species, and they are placed in nine different classes. Five of the classes are fish. The other classes are amphibians, reptiles, birds, and mammals. Table below lists some of the distinguishing traits of each class. |
SciQ | SciQ-3765 | 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.
In which kind of species do open circulatory systems serve additional functions? | [
"some seedlings",
"some invertebrates",
"some earthworms",
"some apes"
] | B | |
SciQ | SciQ-3766 | fluid-dynamics, pressure, acoustics, water
Consequently, the thermodynamic activities ($a_i\equiv e^{\mu_i/RT}$) of component $i$ in the dissolved and gaseous states are also equal.
(For that matter, the activities of the liquid and its vapor above are equal as well. Furthermore, the activity of pure condensed matter is simply 1; put another way, we take this state as the reference state. This lets us relate the equilibrium vapor pressure to the enthalpy of vaporization, which shows up in the chemical potential $\mu$. In this way, all materials can be modeled as having a vapor-pressure temperature dependence of $e^{-1/T}$.)
Finally, the activity of a gas can often be approximated by its partial pressure (as mediated by the fugacity), and the activity of a solute can often be approximated by its concentration (as mediated by the activity coefficient). From all these assumptions and idealizations, we obtain Henry's Law. But more generally, the broader framework (starting from entropy maximization and proceeding through the relevant thermodynamic potential, e.g., the Gibbs free energy) advantageously would let one derive a more general law that also incorporates, say, gas nonideality, or gravity, or solute interaction, or surface area, or an applied electric or magnetic field, etc.
The following is multiple choice question (with options) to answer.
Boyle’s law applies to matter which is in what state? | [
"plasma",
"liquids",
"gas",
"solids"
] | C | A piston having a certain pressure and volume (left piston) will have half the volume when its pressure is twice as much (right piston). One can also plot P versus V for a given amount of gas at a certain temperature; such a plot will look like the graph on the right. Boyle’s law is an example of a second type of mathematical problem we see in chemistry—one based on a mathematical formula. Tactics for working with mathematical formulas are different from tactics for working with conversion factors. First, most of the questions you will have to answer using formulas are word-type questions, so the first step is to identify what quantities are known and assign them to variables. Second, in most formulas, some mathematical rearrangements (i. , algebra) must be performed to solve for an unknown variable. The rule is that to find the value of the unknown variable, you must mathematically isolate the unknown variable by itself and in the numerator of one side of the equation. Finally, units must be consistent. For example, in Boyle’s law there are two pressure variables; they must have the same unit. There are also two volume variables; they also must have the same unit. In most cases, it won’t matter what the unit is, but the unit must be the same on both sides of the equation. |
SciQ | SciQ-3767 | hydrology, mountains, rivers
Title: Why do rivers have 'wells' in mountains? Why/how can rivers have sources in places high above the sea level? The presence of water underground has nothing to do with sea level in mountainous country.
When rain fails on a mountain, or snow falls on a mountain and the snow eventually melts, the water from the rain or snow melt mostly travels downhill via rivers to the sea.
In getting to a river some of the water will fall on the ground. In places where the ground is covered by soil, water can travel through the soil via the pore spaces between the grains of soil. Similarly if porous rock, such as sandstone lies beneath the soil water can travel through the pores in the rock.
If a layer of impervious rock lies under the porous rock or soil, the water cannot move downwards, due to gravity, any further. This can lead to water accumulating in the soil or porous rock and saturating the soil or rock. In such situations an aquifer can form. The top of the saturated zone in an aquifer is called a water table.
The ground beneath a river is saturated and the surface of the river shows the water table exposed to atmosphere. Thus in mountainous regions the ground beneath rivers will be saturated and capable of supporting a well developed from the bank of a river.
The following is multiple choice question (with options) to answer.
What do we call heated groundwater that erupts from the ground under pressure? | [
"springs or geysers",
"aquifers",
"volcanic eruptions",
"spas"
] | A | |
SciQ | SciQ-3768 | human-biology, senses
Olfaction (smell, as carried out by neurons in the nasal epithelium; e.g. smell of vanilla, and smell of bad food)
Gustation (taste, as carried out by neurons on the tongue; e.g. salt, sugar)
Antigen chemosensing (chemical sensing, as carried out by, for instance, immune antigen receptors on B cells)
Hormonal signaling chemosensing (chemical sensing of hormones such as insulin, as carried out for instance by myocytes)
Starch sensing? (amylase in saliva can be used as a test for digestable starch)
Visual system, at the retina?
Visible light (sensing electromagnetic radiation on the order of a few hundred nanometers in wavelength)
Internal methanol sensing (the visual system as a sensor for methanol, which disproportionately affects myelin surrounding the optic nerve)
Pressure sensing (see phosphenes)
The vestibular system
Gravity sensing
Balance
Coordination
Motion sensor
Head position sensor
Spatial orientation
Skin
thermosensation (touching a hot kettle!)
Nociception (pain sensing)
allergen sensing
sensor for gamma rays, X-rays and UV light (indicated by radiation burns, development of skin cancer, sunburns, etc.)
Bones and muscles?
Kinesthetic and bodily proprioception
Brain/mind/mental/social senses?
mental pain
boredom
mental or spiritual distress
sense of self and other, including friendship, power, place in social hierarchy, reputation, companionship
motivation and love (oxytocin, dopamine, etc. in limbic systems and other neural correlates)
I'm sure some would agree, and some would disagree about the specific cases I provide. Thus the definition of senses, or sensing, seems to be opinion-based or at the very least very sensitive to an agreed-upon operational definition, for which there is none.
The following is multiple choice question (with options) to answer.
Sensory organs that respond to particular sensory stimuli contain cells called what? | [
"whole receptors",
"stimulus receptor",
"artificial receptors",
"sensory receptors"
] | D | Sensory organs such as the eyes contain cells called sensory receptors that respond to particular sensory stimuli. |
SciQ | SciQ-3769 | thermodynamics, energy, electricity, efficient-energy-use
Title: Cutting down on power by bypassing mechanical to electrical conversions: Why not? The only answer to this I can think of is energy portability issues.
Another modern-world insanity is converting mechanical energy to electrical, only to turn it back into mechanical. The example I like to use is a refrigerator's reciprocating compressor.
If we directly attach a steam turbine's axle to the crankshaft of the compressor, we will not need to suffer losses in heat in our conversion of mechanical to electrical (at the power plant) then back to mechanical energy (in our appliance). Long ago, a primitive factory used one big engine or turbine or water wheel to rotate a set of overhead shafts, from which leather belts were suspended at intervals to power small pieces of machinery scattered throughout the factory. This arrangement was inflexible in that when the single big engine stopped, so did the entire factory, and when electricity came into common use, this overhead shafting arrangement fell quickly out of favor.
The power losses in long-distance electrical power transmission are more than made up for by the ease with which it is performed and the flexibility it affords. This makes "local power generation" as you describe it impractical because a hundred small steam turbines are much more wasteful of heat energy than one large turbine.
The only practical exception is integrated co-generation in which a small engine running on, for example, natural gas powers a generator while also spinning the shaft of a heat pump. The waste heat from the engine's cooling system makes residential hot water, the waste heat from its exhaust goes through a heat exchanger to provide hot air for space heating, the heat pump furnishes air conditioning (or pulls heat from outside the dwelling) and the electricity from the generator powers up your small appliances in the home while also charging a set of batteries.
Overall thermodynamic efficiency of such a device can exceed 95%, and examples of this technology are just now coming onto the market.
The following is multiple choice question (with options) to answer.
How can we reduce use of energy resources? | [
"modification",
"conservation",
"liberation",
"restoration"
] | B | We can reduce our use of energy resources and the pollution they cause by conserving energy. Conservation means saving resources by using them more efficiently or not using them at all. Figure below shows several ways that people can conserve energy in their daily lives. You can find more energy-saving tips at the URL below. What do you do to save energy? What else could you do?. |
SciQ | SciQ-3770 | geology, earth-history, paleontology, stratigraphy, mass-extinction
Why did this idea develop only in the 1980s? It was known since the 19th century that extinctions had occurred. Even the stratigraphic time is divided into units constrained by different fauna found in the fossil records. What was it that made the change from a "gradualist" perspective of things to the "catastrophic" point of view? The idea of mass extinction is not that recent actually: Cuvier (1798), Buckland (1823) and d'Orbigny (1851) for instance were already talking about global catastrophes in earth history, linked to extinctions. But during the same period, Brocchi (1814) and Lyell (1832) proposed that extinctions of species occurred individually and were a gradual process (either only linked to an intrinsic taxa longevity for Brocchi, or variations in the environment for Lyell). Darwin, following Lyell, also thought that extinctions were gradual and not catastrophic. He also noted the fact that hiatuses in the fossil record or artificial concentration in some strata could show apparent extinction event.
The issue with mass extinction is that to demonstrate their existence you need to be able to demonstrate extinction synchronicity and quantify the amount of species going extinct (to show that it is more than just background noise).
Demonstrating the synchronicity of one mass extinction is what Alvarez et al. 1980 managed to do thanks to the Iridium layer at the K/Pg boundary. More generally, the possibility of correlating extinctions precisely is something that evolved in par with the evolution of stratigraphic tools, and the 1970-1980s is the period during which high-resolution stratigraphic methods arose (chronostratigraphy, magnetostratigraphy, stable isotope stratigraphy for instance).
Quantifying mass extinction is what Jack Sepkoski did with his compendium of marine invertebrates (see Sepkoski 1978, 1979; Raup & Sepkoski 1982, etc.). Today, the PbDb (PaleoBiology DataBase) is the project which focusses on that specific issue (see for instance Alroy et al. 2001). It still remains today the main hurdle in studying mass extinctions.
Alroy, J. et al., 2001. Effects of sampling standardization on estimates of Phanerozoic marine diversification. PNAS, 98(11): 6261-6266.
The following is multiple choice question (with options) to answer.
About 50% of all animal species died off between the mesozoic and which other era? | [
"cretaceous",
"jurassic",
"precambrian",
"cenozoic"
] | D | The most famous mass extinction was 65 million years ago. Between the Mesozoic Era and the Cenozoic Era, about 50% of all animal species died off. This mass extinction is when the dinosaurs became extinct. Most scientists think that the extinction was caused by a giant meteorite that struck Earth. The impact heated the atmosphere until it became as hot as a kitchen oven. Animals roasted. Dust flew into the atmosphere and blocked sunlight for a year or more. This caused a deep freeze and ended photosynthesis. Sulfur from the impact mixed with water in the atmosphere. The result was acid rain. The rain dissolved the shells of the tiny marine plankton that form the base of the food chain. With little food being produced, animals starved. |
SciQ | SciQ-3771 | entomology, ethology, parasitology, ant, parasitism
Title: The emergence of Phengaris butterflies from ant nests The butterflies of the Phengaris genus (also known as Maculinea) are known to be brood parasitic. During the fourth instar, the caterpillars leave their food plant and mimic ant larvae, causing the ants to take them back to their nest as if they were ant larvae that had escaped.
While in the nest, the caterpillars mimic ant larvae by means both of surface chemicals and acoustic mimickry (including, I understand it, mimicking sounds made by queens!) After pupating, the pupa continues to engage in acoustic mimickry, although I can't find any reference to whether it does (or even could!) engage in continued chemical mimickry.
But I can't find anything in the literature regarding the adult butterfly's emergence from the pupa and exit from the ant nest. A non-academic book and some web pages claim that the alcon blue (Phengaris alcon) and mountain alcon blue (Phengaris rebeli) adults are no longer engaged in any form of mimickry at this point, and may be attacked by the ants. These accounts differ as to how likely an attack is, how much danger the butterfly is in, and the level of protection afforded by the butterfly scales.
The webpages I mention belong to a University of Copenhagen researcher (Dr. David Nash) who has published work in this field. This suggests that the claim is probably correct.
That said, none of the peer-reviewed publications coauthored by him appear to mention it, and each of the two webpages creates a different impression as to the level of danger involved:
"If an ant tries to bite the butterfly it will only get a mouthful of scales." states one, suggesting that there is little the ants can do to harm or hinder the butterfly. But the other states "The adult has to get out of the ant nest quickly to prevent the ants killing it."
The book is written by someone else. It cites three papers, which do discuss the larvae/pupae and ants. But none of these have any information regarding this specific topic.
The following is multiple choice question (with options) to answer.
Transforming from a caterpillar to a butterfly requires a lot of what? | [
"Water",
"fuel",
"energy",
"food"
] | C | This caterpillar is busily munching its way through leaf after leaf. In fact, caterpillars do little more than eat, day and night. Like all living things, they need food to provide their cells with energy. The caterpillar will soon go through an amazing transformation to become a beautiful butterfly. These changes require a lot of energy. |
SciQ | SciQ-3772 | reproduction
Excerpts from the references that lead to the short answer above:
In the developing female fetus, oogonia become primary oocytes that begin the first division of meiosis. However, this division is not completed and the primary oocytes remain “frozen” in the prophase stage of the first meiotic division.
At birth, oogonia are no longer present. Each primary oocyte is surrounded by a single layer of squamous epithelial cells called follicular cells. The primary oocyte together with its follicular cells is called a primordial follicle. There are about two million primordial follicles with their primary oocytes in the ovaries at birth suspended in the first division of meiosis.
As the female grows, primary oocytes begin to die and disappear with their follicular cells. This process continues until puberty when there are only about 400,000 primordial follicles left in the ovaries. The primary oocytes continue the process of oogenesis after puberty begins.[Source]
The total number of primary oocytes at birth is estimated to vary from 700,000 to2 million. During childhood most oocytes become atretic; only approximately400,000 are present by the beginning of puberty, and fewer than 500 will be ovulated.[Source]
Primary oocytes reach their maximum development at ~20[6] weeks of gestational age, when approximately seven million primary oocytes have been created; however, at birth, this number has already been reduced to approximately 1-2 million.Recently, however, two publications have challenged the belief that a finite number of oocytes are set around the time of birth.[Source]
In the human embryo, the thousand or so oogonia divide rapidly from the second to the seventh month of gestation to form roughly 7 million germ cells.[Source]
REFERENCES:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0008772
The following is multiple choice question (with options) to answer.
What two cycles make up the female reproductive cycle? | [
"cervical and menstrual",
"ovarian and menstrual",
"digestive and menstrual",
"ovarian and cesarean"
] | B | Female Hormones The control of reproduction in females is more complex. The female reproductive cycle is divided into the ovarian cycle and the menstrual cycle. The ovarian cycle governs the preparation of endocrine tissues and release of eggs, while the menstrual cycle governs the preparation and maintenance of the uterine lining (Figure 18.17). These cycles are coordinated over a 22–32 day cycle, with an average length of 28 days. As with the male, the GnRH from the hypothalamus causes the release of the hormones FSH and LH from the anterior pituitary. In addition, estrogen and progesterone are released from the developing follicles. As with testosterone in males, estrogen is responsible for the secondary sexual characteristics of females. These include breast development, flaring of the hips, and a shorter period for bone growth. The Ovarian Cycle and the Menstrual Cycle The ovarian and menstrual cycles are regulated by hormones of the hypothalamus, pituitary, and ovaries (Figure 18.17). The ebb and flow of the hormones causes the ovarian and menstrual cycles to advance. The ovarian and menstrual cycles occur concurrently. The first half of the ovarian cycle is the follicular phase. Slowly rising levels of FSH cause the growth of follicles on the surface of the ovary. This process prepares the egg for ovulation. As the follicles grow, they begin releasing estrogen. The first few days of this cycle coincide with menstruation or the sloughing off of the functional layer of the endometrium in the uterus. After about five days, estrogen levels rise and the menstrual cycle enters the proliferative phase. The endometrium begins to regrow, replacing the blood vessels and glands that deteriorated during the end of the last cycle. |
SciQ | SciQ-3773 | biochemistry, botany, plant-physiology, photosynthesis, agriculture
The above image is an example of a "potato battery" made without the potato. Identical setup and the energy obtained is identical given everything else the same.
Potato power- er, metal power?
This experiment is supposed to demonstrate the concept of an electrochemical cell. Electrochemical cells obtain their energy from the reduction-oxidation reactions that happen between two metals with different reduction potentials. When two metals - such as copper and zinc - are placed in a medium that permits the exchange of electrons and ions, an electrical gradient is produced as electrons move from one metal to the other and ions move the other direction. This gradient can then be captured and used to do work such as powering a lightbulb or an AI.
In the potato powered example, the power comes from zinc and copper. If you want a more powerful battery, use more zinc and more copper- not a bigger potato. If that is not good enough, try replacing the zinc with something like lithium- this is what we've done with modern, rechargeable batteries.
In truth, the potato battery would be better described as a normal battery that just happens to be inserted into a potato. You'll make a better battery if you use copper pennies and aluminum foil in vinegar.
I do not mean to shoot down your idea, and I am glad you are looking into renewable energy sources- but you may be better served by a class on electricity and batteries than by asking questions on biology.SE!
EDIT: I would assume that the electrical potential of this kind would also kill the plant, given that you're essentially electrocuting it. However, I was unable to find any information on the resistance of potato plants to electrocution.
The following is multiple choice question (with options) to answer.
Uranium is an example of a non-renewable resource used to produce what type of power? | [
"water",
"wind",
"electrical",
"nuclear"
] | D | Some resources can’t be renewed. At least, they can’t be renewed fast enough to keep up with use. Fossil fuels are an example. It takes millions of years for them to form. We are using them up much more quickly. Elements that are used to produce nuclear power are also non-renewable resources. Uranium, for example, which is rare. Sooner or later, it will run out. |
SciQ | SciQ-3774 | pathology
Title: Why are some bodily fluids more of an infection risk than others? Whilst on a recent refresher course it was highlighted that when considering risk of exposure to infection from bodily fluids we should be aware of two distinct risk levels:
High Risk:
Blood
Semen
Vaginal Secretions
Diarrhea
Low Risk:
Saliva
Vomit
Urine
CSF (Cerebrospinal fluid)
Why is it that some bodily fluids are a greater infection risk than others? Is it related to the fluids themselves or the species of pathogen that are located within them? This is just about where the pathogens can be found that are dangerous to people.
Vomit is highly acidic and less accommodating to microbe growth. Similarly saliva has many immune components in it as well as digestive enzymes that keep most microorganisms down.
Urine and CSF are actually quite sterile as they come from environments that are highly filtered - the kidney is an osmotic processor that essentially is a molecular filter and does not allow cells to pass, the spine is highly insulated from the blood and other direct exposure to microorganisms.
Compare that with the 'dangerous' list and you have organs that are open to human pathogens. Venerial disease like HPV is so common that what - about 1 in 5 people under a certain age carry it. That is a pretty high expectation of a biohazard. most infections and viruses are blood bourne - influenza, cold, as well as any bacterial infections.
Feces is always a dangerous thing to handle as the digestive tract is rich in nutrients and essentially directly open to external bacteria and fungi. (and its not acidified like the stomach). Also parasites like tape worms and other multicelled animals! yum!
Diarrhea is often caused by an infection of some sort, so its just more likely a hazard, but feces is always a place where you might find a pathogen.
This is not to say that the 'safe' list is totally safe. Its just less likely to bear disease causing agents.
The following is multiple choice question (with options) to answer.
One of the early signs of cell disease is this "leaking" of what into the body cells? | [
"sodium ions",
"potassium ions",
"proteins",
"glucose"
] | A | Potassium Concentration Glial cells, especially astrocytes, are responsible for maintaining the chemical environment of the CNS tissue. The concentrations of ions in the extracellular fluid are the basis for how the membrane potential is established and changes in electrochemical signaling. If the balance of ions is upset, drastic outcomes are possible. Normally the concentration of K+ is higher inside the neuron than outside. After the repolarizing phase of the action potential, K+ leakage channels and the Na+/K+ pump ensure that the ions return to their original locations. Following a stroke or other ischemic event, extracellular K+ levels are elevated. The astrocytes in the area are equipped to clear excess K+ to aid the pump. But when the level is far out of balance, the effects can be irreversible. Astrocytes can become reactive in cases such as these, which impairs their ability to maintain the local chemical environment. The glial cells enlarge and their processes swell. They lose their K+ buffering ability and the function of the pump is affected, or even reversed. One of the early signs of cell disease is this "leaking" of sodium ions into the body cells. This sodium/potassium imbalance negatively affects the internal chemistry of cells, preventing them from functioning normally. |
SciQ | SciQ-3775 | thermodynamics, forces, torque, power
Today, many engines on the road use double overhead cam valve systems, which can squeeze almost 7000RPM out of that engine.
Smaller pistons support faster operation of the engine, so a parallel trend has been to smaller-displacement engines, which when coupled with dual overhead cam valves can pull almost 70HP out of 1 liter displacement turning at 9000RPM, as on my Suzuki GS1000GL motorcycle.
The following is multiple choice question (with options) to answer.
What does the moving piston in an engine turn? | [
"hammer",
"brake",
"crankshaft",
"muffler"
] | C | |
SciQ | SciQ-3776 | inorganic-chemistry, solubility, analytical-chemistry
Title: Solubility and wetting of substances in water We have seen that, when we pour salt in water then it gets dissolved, that means it is soluble in water. But when we pour sand into water then it doesn't dissolve in water, that means it is insoluble, but still sand gets wet. But there are certain substances which doesn't get wet by water for example, sulfur particles don't get wet by water but wet in oil, as I was studying about froth floatation method.
My question is that:
What is the difference between solubility and wetting in water ?
What is the reason that the sulfur particle doesn't get wet by water? Polar/hydrophilic soluble substances get dissolved, like table salt or sugar.
Polar/hydrophilic insoluble substances get wet, as they attract water, like sand, or limestone.
Nonpolar/hydrophobic insoluble substances do not get wet, as they repulse water, like wax, teflon or silanized glass.
The following is multiple choice question (with options) to answer.
What type of chloride is a non-volatile material, but does not dissolve in water? | [
"lead chloride",
"pink chloride",
"silver chloride",
"yellow chloride"
] | C | Silver chloride is a non-volatile material, but does not dissolve in water. What effect will it have on the vapor pressure of water?. |
SciQ | SciQ-3777 | homework-and-exercises, thermodynamics, thermal-radiation, thermoelectricity
Title: The thermal expansion of material The question is that: they drill a hole in the middle of a metal. Then when this metal is heated, will the hole become larger or smaller? The hole will get bigger, by experiment, but I think that when material expands, the hole must get smaller. What's wrong with this?
In general, can anyone please tell me how material expands exactly? When the metal is heated, all inter-atomic distances increase by the same factor. This drawing may help understand why the hole also increases in size. Here, I increased all distances by a factor a two.
Replace the atoms with galaxies, and you have a model of the expanding Universe, which may help understand why an observer in any galaxy will see herself as the center of the Universe, with all other galaxies flying away from her.
If the hole should shrink, it would mean that some distances should increase more than other. This doesn't happen:
The following is multiple choice question (with options) to answer.
In general, objects expand in all directions as temperature does what? | [
"increases",
"stays the same",
"decreases",
"cycles"
] | A | Figure 13.11 In general, objects expand in all directions as temperature increases. In these drawings, the original boundaries of the objects are shown with solid lines, and the expanded boundaries with dashed lines. (a) Area increases because both length and width increase. The area of a circular plug also increases. (b) If the plug is removed, the hole it leaves becomes larger with increasing temperature, just as if the expanding plug were still in place. (c) Volume also increases, because all three dimensions increase. |
SciQ | SciQ-3778 | 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.
Paddles and hammers are examples of simple machines that increase the distance over which force is applied, while reducing what? | [
"momentum",
"strength",
"gravity",
"intensity"
] | B | Examples of machines that increase the distance over which force is applied are paddles and hammers. Figure below explains how these machines work. In each case, the machine increases the distance over which the force is applied, but it reduces the strength of the applied force. |
SciQ | SciQ-3779 | pressure, collision, fluid-statics
Title: Is Atmospheric Pressure due to weight of air or the collisions of the Molecules This question is in response to @brightmagnus answer whose link is
Pressure in Fluids,in particular horizontal pressure
The question :
Is the atmospheric pressure due to the weight of air or collisions of the molecules?
The following is multiple choice question (with options) to answer.
What two things collide to cause gas pressure? | [
"gas particles and a wave",
"gas particles and an object",
"light particles and an object",
"gas particles and an electron"
] | B | Gas pressure is the result of collisions between gas particles and an object. |
SciQ | SciQ-3780 | cell-biology, microbiology
Title: Are there any organisms that are made of more than one (~5-12) cell? Prokaryotes and eukaryotes are unicellular, made of one cell. Great. Eukaryotes are unicellular or multicellular. But the typical examples of multicellular eukaryotes we have are made of, often, trillions of cells, like us humans. Ants must still be made of many millions of cells. Are there known eukaryotes with very few cells that make them up? Like, 5, or something? Or maybe a dozen cells making up the whole organism in its fully developed state? There's Trichoplax adhaerens, a Placozoa, made of a few thousand cells. Then there is Dicyema japonicum, a simple mesozoan, made up of 9 to 41 cells. Arguably, the simplest multicellular organism is the algae Tetrabaena socialis, whose body consists of 4 cells. Then, there's the parasitic Myxozoa which have 7 cells.
The following is multiple choice question (with options) to answer.
Every human cell has the same what, and each cell has thousands of them? | [
"chromosomes",
"ribosomes",
"genes",
"DNA"
] | C | There are about 22,000 genes in every human cell. Does every human cell have the same genes? Yes. Does every human cell make the same proteins? No. In a multicellular organism, such as us, cells have specific functions because they have different proteins. They have different proteins because different genes are expressed in different cell types (which is known as gene expression ). |
SciQ | SciQ-3781 | evolution, zoology, taxonomy, phylogenetics
The apomorphy that defines the tetrapods is "paired limbs". You have Amphibia to the left and Amniota to the right, whose apomorphy is " egg with extraembrionic membranes". Inside them, you have Reptilia, whose apomorphies are "skull with upper and lower fenestra and beta-keratin in epidermis". Turtles came from an ancestor with these characteristics. So, turtles belong to the monophyletic group of "Reptiles".
Post scriptum: You wrote that "turtles (specifically sea turtles) live on both land and water, very much like amphibians". Just a curiosity: the reason why sea turtles leave the water (sea) from time to time shows exactly that they are not amphibians! Amphibians, being non-amniotes, have eggs that survive under water (actually, with few exceptions, they need to be under water). Turtles, on the other hand, are amniotes, and the amniotic egg cannot be laid under water. That's why the turtles have to leave the water to lay eggs: because, contrary to the amphibians, they cannot lay eggs under water.
The following is multiple choice question (with options) to answer.
What are a class of tetrapod vertebrates that produce amniotic eggs called? | [
"mammals",
"amphibians",
"insects",
"reptiles"
] | D | Reptiles are a class of tetrapod vertebrates that produce amniotic eggs. They include crocodiles, alligators, lizards, snakes, and turtles. The reptile class is one of the largest classes of vertebrates. It consists of all amniotes except birds and mammals. |
SciQ | SciQ-3782 | evolution, zoology, taxonomy, phylogenetics
The apomorphy that defines the tetrapods is "paired limbs". You have Amphibia to the left and Amniota to the right, whose apomorphy is " egg with extraembrionic membranes". Inside them, you have Reptilia, whose apomorphies are "skull with upper and lower fenestra and beta-keratin in epidermis". Turtles came from an ancestor with these characteristics. So, turtles belong to the monophyletic group of "Reptiles".
Post scriptum: You wrote that "turtles (specifically sea turtles) live on both land and water, very much like amphibians". Just a curiosity: the reason why sea turtles leave the water (sea) from time to time shows exactly that they are not amphibians! Amphibians, being non-amniotes, have eggs that survive under water (actually, with few exceptions, they need to be under water). Turtles, on the other hand, are amniotes, and the amniotic egg cannot be laid under water. That's why the turtles have to leave the water to lay eggs: because, contrary to the amphibians, they cannot lay eggs under water.
The following is multiple choice question (with options) to answer.
What characteristic of reptile eggs allows them to be laid on land instead of in water? | [
"they trap gas",
"they are circular",
"they are amniotic",
"they are dry"
] | C | Reptile eggs are amniotic, so they can be laid on land instead of in water. |
SciQ | SciQ-3783 | ecology
Title: Statement about Tropical Rainforests I made a statement about tropical rainforests, and I want to know if it's somewhat true or not:
The soil in tropical rainforests is not exceptionally fertile, because it contains few minerals. The reason that a tropical rainforest has a huge amount of vegetation is because of the quick mineralisation. If a dead leaf falls onto the ground, it immediately gets turned into minerals, which the plants immediately use for sustaining theirselves There are many websites which describe this phenomenon. They all seem to confirm the basic premise of the question: in tropical rain forests most of the minerals are held in the biomass and rapid decomposition contributes to the recycling of these nutrients for new growth. One example is here.
Tropical rainforests are noted for the rapid nutrient cycling that occurs on the ground. In the tropics, leaves fall and decompose rapidly. The roots of the trees are on the surface of the soil, and form a thick mat which absorbs the nutrients before they reach the soil (or before the rain can carry them away). The presence of roots on the surface is a common phenomenon in all mature forests; trees that come along later in succession win out in competition for nutrients by placing their roots over top of the competitors, and this pattern is seen in the temperate rainforest as well. What does not occur in the temperate rainforest, however, is a rapid cycling of nutrients. Because of the cold conditions and the acidity released by decomposing coniferous needles on the forest floor, decomposition is much slower. More of the nutrients are found in the soil here than would be the case in a tropical forest, although like the tropical forest most of the nutrients are held in the plants and animals themselves.
I looked for actual evidence of these differences in rates of decomposition and I found this:
Salinas, N. et al. (2011) The sensitivity of tropical leaf litter decomposition to temperature: results from a large-scale leaf translocation experiment along an elevation gradient in Peruvian forests. New Phytologist 189: 967-977
The following is multiple choice question (with options) to answer.
What part of the rainforest commonly has ferns and other ground plants? | [
"forest floor",
"emergent layer",
"understory",
"canopy layer"
] | C | Ferns are common in the understory of the tropical rainforest. |
SciQ | SciQ-3784 | 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.
The primary function of insulin is to facilitate the uptake of what into body cells? | [
"glucose",
"chloride",
"sucralose",
"water"
] | A | Insulin The primary function of insulin is to facilitate the uptake of glucose into body cells. Red blood cells, as well as cells of the brain, liver, kidneys, and the lining of the small intestine, do not have insulin receptors on their cell membranes and do not require insulin for glucose uptake. Although all other body cells do require insulin if they are to take glucose from the bloodstream, skeletal muscle cells and adipose cells are the primary targets of insulin. The presence of food in the intestine triggers the release of gastrointestinal tract hormones such as glucose-dependent insulinotropic peptide (previously known as gastric inhibitory peptide). This is in turn the initial trigger for insulin production and secretion by the beta cells of the pancreas. Once nutrient absorption occurs, the resulting surge in blood glucose levels further stimulates insulin secretion. Precisely how insulin facilitates glucose uptake is not entirely clear. However, insulin appears to activate a tyrosine kinase receptor, triggering the phosphorylation of many substrates within the cell. These multiple biochemical reactions converge to support the movement of intracellular vesicles containing facilitative glucose transporters to the cell membrane. In the absence of insulin, these transport proteins are normally recycled slowly between the cell membrane and cell interior. Insulin triggers the rapid movement of a pool of glucose transporter vesicles to the cell membrane, where they fuse and expose the glucose transporters to the extracellular fluid. The transporters then move glucose by facilitated diffusion into the cell interior. |
SciQ | SciQ-3785 | molecular-biology, chromosome, meiosis, mitosis
Which flags are used by the enzymes in the process of making the
centromere to tell them that it is the right spot
There are some centromere associated repeats in the DNA which mark the site for centromere assembly. There is no particular consensus sequence of this repeat. However, this study says that in certain cases stable chromosomes are formed in the absence of centromeric repeats.
are the sister chromatids physically intertwined around each other for
the purpose of joining, or are they simply adjacent?
They are joined by proteins called cohesins. Cohesins looks like rings which form around the sister chromatids. During anaphase, the anaphase promoting complex (APC) activates an enzyme called separase, which in turn degrades cohesin.
what in the centromeres do the spindle fibres attach to, and how do
the tips of the growing fibres notice it to head it its general
direction?
Centromeres serve as a site for the assembly of kinetochore. Kinetochore is a multi-protein complex which forms contact with the spindle fibres (specifically, K-fibres. Refer this previous post). An essential component of kinetochore is the motor protein dynein which makes the kitetochore to crawl along the spindle fibres, towards the pole. The wikipedia article on kinetochore is quite descriptive and you can refer that for details.
The following is multiple choice question (with options) to answer.
Spindle fibers form between the centrioles during prophase i of what process? | [
"photosynthesis",
"hydrolysis",
"mitosis",
"meiosis"
] | D | Prophase I: Chromosomes form, and the nuclear membrane breaks down. Centrioles move to opposite poles of the cell. Spindle fibers form between the centrioles. Here’s what’s special about meiosis : Homologous chromosomes pair up! You can see this in Figure below . |
SciQ | SciQ-3786 | particle-physics, experimental-physics, standard-model, quarks, protons
Title: In which experiment did protons seem to consist of infinite amount of quarks? In this video Richard Feynman is telling that in some experiment it seems that the proton should consist of infinite amount of quarks.
What is this case he's mentioning? Is it solved now? Thanks for finding this amazing historical video.
He's talking about the deep inelastic scattering electron proton experiment at SLAC. This showed evidence that high energy electrons scattered off pointlike charged particles within the proton, which Feynman named 'partons'. It took some time to establish that these partons are the same as quarks, which had been postulated to make sense of the patterns of mesons and baryons. We now understand that they are the same, but that the proton consists of three 'valence' quarks (up up down) plus a 'sea' of quarks and antiquarks which the electrons will scatter off (as well as gluons). So in a sense there are three quarks in a proton and in a sense there are an infinite number.
The SLAC measurements were confirmed by later experiments, particularly the HERA electron proton ring at DESY, with much more detail. In particular the early evidence for 'scaling': that scattering depended only on $x$, the fraction of the proton momentum embodied in the stuck Parton, and not on $Q^2$, the mass of the exchanged virtual photon, turned out to be wrong. The experiment just happened to look at a region where it was approximately true, and maybe that misled us for a while. But apart from that the results hold, and we now understand that the contradiction that was puzzling Feynman in the video is not a contradiction after all.
The following is multiple choice question (with options) to answer.
How many quarks are in each proton and neutron? | [
"three",
"five",
"ten",
"four"
] | A | Remember the quarks from the first page of this chapter? Quarks are even tinier particles of matter that make up protons and neutrons. There are three quarks in each proton and three quarks in each neutron. The charges of quarks are balanced exactly right to give a positive charge to a proton and a neutral charge to a neutron. It might seem strange that quarks are never found alone but only as components of other particles. This is because the quarks are held together by very strange particles called gluons. |
SciQ | SciQ-3787 | magnetic-fields, astrophysics, sun
Title: How and why do sunspots occur? I am studying sunspot behavior, and the causes for the occurrence sunspots occur. I've come across the phrase 'local magnetic fields of the Sun'. I have no idea what that means.
Can someone please explain to me how/why sunspots form? The sun is a giant turbulent ball of plasma. It has a certain amount of angular momentum that gives rise to currents, and magnetic fields. As the large planets (Jupiter and Uranus) orbit the Sun, they cause the Sun to wobble about the barycenter. This disturbs the magnetic fields and creates local "vortices" that cause magnetic field lines to move in and out of the sun's surface:
Image and inspiration for this answer from this link which I recommend for further reading.
Because plasmas are "confined" by magnetic field lines, the temperature of the surface of the sun as observed from Earth is changed by the presence of these magnetic fields and the associated coronal flares that follow these lines. An explanation for how that creates a sun spot is given by this image (found on this page) :
image source
The following is multiple choice question (with options) to answer.
What is the year cycle that sunspots occur? | [
"22",
"12",
"11",
"15"
] | C | The most noticeable magnetic activity of the Sun is the appearance of sunspots. Sunspots are cooler, darker areas on the Sun’s surface ( Figure below ). Sunspots occur in an 11-year cycle. The number of sunspots begins at a minimum. The number gradually increases to the maximum. Then the number returns to a minimum again. |
SciQ | SciQ-3788 | 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.
When an unstable nucleus emits radiation and is transformed into the nucleus of other elements this is called? | [
"naturally decay",
"fusion decay",
"radioactive decay",
"explosive decay"
] | C | To balance a nuclear reaction. The two general kinds of nuclear reactions are nuclear decay reactions and nuclear transmutation reactions. In a nuclear decay reaction, also called radioactive decay, an unstable nucleus emits radiation and is transformed into the nucleus of one or more other elements. The resulting daughter nuclei have a lower mass and are lower in energy (more stable) than the parent nucleus that decayed. In contrast, in anuclear transmutation reaction, a nucleus reacts with a subatomic particle or another nucleus to form a product nucleus that is more massive than the. |
SciQ | SciQ-3789 | food, biotechnology
Title: How to increase the shelf life of yogurt without refrigeration? When we make yogurt at home and do not refrigerate it, it will become sour because of conversion of lactose into lactic acid by Lactobacillus bacteria, but this does not happen in case of Nestle's yogurt or any other brand until it remains air tight.
I wonder though bacteria is still present in it and continue to convert lactose into lactic acid then why does not packed yogurt becomes sour? How these companies increase the shelf life of yogurt..? This article gives an excellent review on yogurt manufacturing, but to summarize:
-Raw milk goes through centrifugation to remove somatic cells and other solid impurities.
-Thermalization is conducted at "60–69 °C for 20–30 s, aiming at the killing of many vegetative microorganisms and the partial inactivation of some enzymes."
After this point, the milk may be inoculated with lactic acid bacteria or other microfloras.
-Then, standardization occurs which for milk refers to the standardization of fat and solid-non-fat content (SNF). This in short affects the fermentation process ("an increase of SNF increases the duration of the fermentation process").
-The next step is homogenization, which prevents milk fat from rising to the top of the liquid. This has an effect on the stability of the emulsion.
-I think this step is where "sterility" comes into play, "heat treatment of milk reduces the number of pathogenic microorganisms to safe limits for the consumer’s health. Various heat treatments can be applied, which are classified based on the duration and the temperature. The most common are known as thermalization, low and high pasteurization, sterilization and UHT (Ultra Heat Treatment)." The review goes into more detail about each type and what they eliminate or don't eliminate (spores, vegetative bacteria, etc.).
The following is multiple choice question (with options) to answer.
What is manufactured and added to foods to preserve freshness? | [
"carbohydrates",
"vitamin c",
"protein",
"trans fat"
] | D | A type of lipid called trans fat is found in many processed foods. Trans fat is rare in nature but is manufactured and added to foods to preserve freshness. Eating foods that contain trans fat increases the risk of heart disease. Trans fat may be found in such foods as cookies, doughnuts, crackers, fried foods, ground beef, and margarine. |
SciQ | SciQ-3790 | vacuum, space
Title: What is in space? I was recently on a chat server having a random discussion about science stuff and someone I was talking to then made the comment that "space is not a complete vacuum and it's full of plasma / matter".
That got me thinking ... ok so I don't expect that the bulk of space is totally empty but if I took a "cube volume of the space outside the ISS" (or further out for scientific accuracy) ... do we know what would be observed inside that cube in terms of "real particles" from the standard model?
I'm thinking that there would be some amount of photons (light) and possibly some other stuff, by the other guys claim of "plasma being everywhere" raised some weirdness in my head I couldn't resolve.
He followed that up with "we live in an electric universe".
Does anyone have a professional / academic viewpoint on this (i'm no physics grad though so go easy on me)?
EDIT:
I've had time to go deeper in to this concept with the person I was talking to earlier and he cited NASA as a source and linked me to this ...
https://science.nasa.gov/science-news/science-at-nasa/1999/ast07sep99_1
This article clearly states ...
"99.9 percent of the Universe is made up of plasma," says Dr. Dennis Gallagher, a plasma physicist at NASA's Marshall Space Flight Center. "Very little material in space is made of rock like the Earth."
... surely this is a contextual statement but what is the context and does this literally mean as is worded or is there something else here? 1) To begin with, space or the interstellar medium if that is what you are refering to, accounts for all the matter that is not in stars, neither in planets or asteroids, and there is actually a lot of matter in there.
The following is multiple choice question (with options) to answer.
Scientists think that stars and galaxies make up only a small part of the matter in the universe. what is the rest of the matter called? | [
"cold matter",
"light matter",
"dark matter",
"typical matter"
] | C | We see many objects out in space that emit light. This matter is contained in stars, and the stars are contained in galaxies. Scientists think that stars and galaxies make up only a small part of the matter in the universe. The rest of the matter is called dark matter . |
SciQ | SciQ-3791 | zoology, microbiology, pathology
Title: Prevention of disease spreading in animal kingdom It's my first question on here, so I'm not sure If my question fits the theme. Please refer me to the appropriate one, If I have made a mistake.
So a question that I wanted to ask has to do with whether or not animals potentially try to avoid spreading diseases. So I was thinking... In an event that a really deadly disease emerges in a population, it would be really dangerous for animals that live in social groups, of any size really, not to have any instinctual behaviours that try and prevent the disease to spread. Animals that live in big heads, like wildebeests would just probably leave the diseased individuals behind, apes and monkey could potentially cast out individuals from the group, etc. Ants have separate sections in their tunnels that serve as graveyards, I presume for this exact purpose.
A lot of parasitic organisms have adaptations that specifically target animals with social behaviour, so why wouldn't animals adapt against that?
Something that also came to my mind is that this could possibly evolve not as a social behaviour of a group, but sometimes that individuals in a group would do, for example self isolation. However, I do not find this likely, I possibly requires higher cognitive understanding of disease spread.
Am I way of base here? If not, could you please provide some interesting examples you are familiar with.
The following is multiple choice question (with options) to answer.
Why are noninfectious diseases not contagious? | [
"non-pathogen caused",
"they are inherited",
"they are contagious",
"they are viral"
] | A | Noninfectious diseases are not contagious because they are not caused by pathogens. Instead, they are caused by such factors as lifestyle choices, environmental toxins, or mutations. |
SciQ | SciQ-3792 | bacteriology, ph, gut-bacteria
Any one of these is enough to have a bactericidal or bacteriostatic effect! This is also why cells that do live in slightly alkaline or acidic environments have to specialize, and they have narrow windows of pH that they can survive under, because they have to compensate so much to counteract the protonation or lack-thereof in their environments.
The following is multiple choice question (with options) to answer.
Organisms that "love" acids are known as what? | [
"acidophobes",
"acidophiles",
"acid heads",
"acidic"
] | B | Acidophiles are organisms that "love" acids. They live in very acidic environments, such as acid mine drainage. They are also found near vents of volcanoes. The most acidophilic archaeans can thrive at negative pH values. No other organisms can survive in such acidic conditions. |
SciQ | SciQ-3793 | molecular-biology, pcr, ligation
Title: modify PCR steps to include a ligation Imagine a multiplex PCR in which after the extension step, the dsDNA is nicked and requires a ligation reaction to repair the nick before the next denaturation step. So the steps would be:
Denature
Anneal
Extend
Ligate
steps 1-4 X 30
There are thermostable DNA ligase enzymes available (best activity at 65C), which don't get heat-inactivated by the high temp at the denaturation step.
It seems like this should work, but I can't find any info on anyone trying this. Any ideas? In case this helps anyone, I found a technique called Gap Ligase Chain Reaction which includes both a thermostable ligase and a DNA polymerase enzyme in the same reaction:
Ligase Chain Reaction (LCR) --Overview and Applications (Wiedmann et al.) PCR Methods and Applications
Amplification of Chlamydia trachomatis DNA by Ligase Chain Reaction
Preliminary Evaluation of the Ligase Chain Reaction for Specific Detection of Neisseria gonorrhoeae
Detection of point mutations with a modified ligase chain reaction (Gap-LCR)
The following is multiple choice question (with options) to answer.
Which enzyme is used in step three of the polymerase chain reaction because of it's ability to withstand high temperatures? | [
"backronym polymerase",
"minocycline polymerase",
"taq polymerase",
"carbon polumerase"
] | C | When appropriate, a symbol may be written above or below the arrow to indicate some special circumstance. The symbol "Δ" is often used to indicate that the reaction is to be heated. |
SciQ | SciQ-3794 | geography, mantle, crust, mining, cavern
6.Record absolute depth under sea level a person has reached "on foot".
If you consider Vescoso to have been "on foot", he wins again. If not, and you consider miners going to their jobs as being "on foot", then it would be the Canadian miners (2.65 km below see level). If you are strict against both, my first thougth is then maybe port workers (note a submariner won't win in this case neither), or maybe a spelunker, but user Semidiurnal Simon clarifies it on comments. I was wrong (I said I made the estimations quickly) as: "For the strictest "on foot", it won't be port workers, it'll be somebody in a below-sea-level basin (e.g. by the Dead Sea), or possibly a low-altitude mine that has a drift (slanted corridor) entry and so doesn't require an elevator."
7.Record absolute depth under surface by drilling.
Sending machines from the surface (by borehole) rather than humans, the Kola Superdeep Borehole is the deepest (12km).
8.Record closest drill to Earth's Center.
The Ocean Drilling Program could have this record, but I cannot determine where. Average seabed deep rounds -4.000 m. and the Arctic Ocean is not a deep ocean in comparison with the Pacific and Atlantic. So the Kola Borehole may well have this record too.
The following is multiple choice question (with options) to answer.
What do scientists use to study the deep without going to the seafloor? | [
"remotely operated vehicles",
"drill rigs",
"ultrasound machines",
"telescopes"
] | A | Sending humans to the seafloor is expensive and dangerous. Having to return humans safely to the surface limits what a mission can do. Remotely operated vehicles , or ROVs, allow scientists to study the deep without going to the seafloor. These small vehicles carry cameras and scientific instruments. ROVs were used to study inside the Titanic . This would have been far too dangerous for a manned sub to enter. Scientists control ROVs electronically with sophisticated operating systems. |
SciQ | SciQ-3795 | orbit, earth, climate
Title: Why don't we have 2 Summers and 2 Winters? Due to Earth's elliptical orbit, its distance from Sun varies by almost 5 million Kilometers (147 million Kilometers at closest point & 152 million Kilometers at farthest point, i.e. almost 3% of the average distance).
As evident from the fact that that Venus has hotter environment than Mars due to their respective distances from the sun.
Why then Earth does not observe two winters (at farthest points) and two summers (at closest points)?
Additional Note:
I know that Earth's seasonal climate change is caused by its 23 degrees tilt that causes the sunlight density variations for the hemispheres.
But to me this 5 million Km distance seems more relevant than the 23 degrees tilt. There are a few incorrect assumptions in your post, so it is difficult to answer as asked. But I can address the misconceptions.
1. The seasons are not caused by our distance from the sun
The seasons are caused by the 23.5° tilt in Earth's axis. When the Northern Hemisphere is tilted towards the sun (summer), the Southern Hemisphere is simultaneously tilted away from the sun (winter). So the seasonal temperature difference has little to do with the Earth's position in its elliptical orbit. Without this tilt, there would be no seasons and the temperature day to day across the globe would be relatively uniform.
2. Even the GLOBAL temperature is NOT consistent with our change in distance
As a matter of fact, the average temperature of the Earth globally is hottest when it is the furthest from the sun — hotter by about 2.3°C (ref). That's because there is a lot more landmass in the Northern Hemisphere facing the sun (when Earth is farthest away in its orbit). So even though there is less intensity of sunlight, the land is able to be heated up much faster than the vast oceans which have to be heated at perihelion.
This distance-temperature inconsistency isn't unique to the Earth. Look at the average temperature of the other inner planets as we move away from the sun:
Mercury (167°C)
Venus (460°C) ← farther, but hotter than Mercury?
Earth (14.0°C)
Mars (-60°C)
The following is multiple choice question (with options) to answer.
The hemisphere that is tilted away from the sun is cooler because it receives less what? | [
"direct rays",
"direct electrons",
"pollution",
"x-rays"
] | A | The hemisphere that is tilted away from the Sun is cooler because it receives less direct rays. As Earth orbits the Sun, the Northern Hemisphere goes from winter to spring, then summer and fall. The Southern Hemisphere does the opposite from summer to fall to winter to spring. When it is winter in the Northern hemisphere, it is summer in the Southern hemisphere, and vice versa. |
SciQ | SciQ-3796 | waves, harmonic-oscillator, oscillators, string, harmonics
Title: Simple harmonic motion versus oscillations I want to see whether certain oscillations in my daily life, such as the oscillation of violin strings when plucked, are simple harmonic motion or not. Can we identify whether an oscillation is simple harmonic motion or just an oscillation by observing it?
I don't truly understand the difference between the two - mathematically, we know that acceleration should be proportional to negative displacement for simple harmonic motion. Am I right when I say that an oscillation, such as violin strings oscillating when plucked, cannot be identified to be either a regular oscillation or simple harmonic motion until its motion is precisely tracked and analysed? The pure simple harmonic motion is in real life very very rare. There are some cases which are really close (e.g. for engineering purposes). That might be:
Small-amplitude oscillation of a mass on a spring (small enough for spring nonlinearities not to be pronounced) or other kinds of these simple or moreless model oscillators.
Tuning fork. Strictly speaking it has more oscillatory modes but it is hard to effectively excite more than the one.
Speaker membrane when playing a pure sine tone (that's easy to be generated).
For the last but not least case, there is a practical possibility to excite just a harmonic oscillation of the damped system with just pure harmonic driving force. That is what it's done e.g. when the room acoustics is examined using sine sweep tones.
The following is multiple choice question (with options) to answer.
Like the strings of cello, anything that vibrates produces waves of what? | [
"sound",
"energy",
"light",
"heating"
] | B | A: Like the strings of cello, anything that vibrates produces waves of energy that travel through matter. For example, when you throw a pebble into a pond, waves of energy travel from the pebble through the water in all directions. Like an incandescent light bulb, anything that glows consists of matter that produces light energy. For example, fireflies use chemicals to produce light energy. Like a moving tennis racket, anything that moves has energy because it is moving, including your eyes as they read this sentence. |
SciQ | SciQ-3797 | titration
Title: Strong Acid/Strong Base Titration Bromothymol Blue is an indicator that turns yellow in acid, blue in base.
If I were to titrate NaOH with HCl, what color should I look for at the equivalence point? Should I titrate until the solution turns from blue to yellow or will there be an intermediate colour of green?
I know the salt produced (NaCl) has a pH of 7. http://antoine.frostburg.edu/chem/senese/101/acidbase/indicators.shtml
This is a link to a webpage that talks all about pH indicators and the different pH ranges if you're looking for more info.
When it comes to your question, the color should go from yellow to green because in your breaker is where you add the indicator fluid and HCl acid and you titrate that with the NaOH base. If you titrate further than your green color you have now made your solution more basic.
The following is multiple choice question (with options) to answer.
The point in the titration at which an indicator changes color is called what? | [
"tipping point",
"chromatic point",
"end point",
"zeta point"
] | C | Acid–Base Titrations Because most common acids and bases are not intensely colored, a small amount of an acid– base indicator is usually added to detect the equivalence point in an acid–base titration. The point in the titration at which an indicator changes color is called theendpoint. The procedure is illustrated in Example 21. |
SciQ | SciQ-3798 | botany, plant-physiology, plant-anatomy
It made me wonder if we are simulating the sun in a dark room for growing the plants with the help of red, blue, and a little bit of far-red light, what will happen to the plants if we keep the ideal conditions for which the plants carry out photosynthesis whole day? Does it affect its yield or the plants die out quick?
I am an engineering student working on indoor farming, my knowledge of botany is the same as a high school student. So if I am wrong please tell me. Ideal conditions for photosynthesis
You mention ideal conditions to carry out photosynthesis, I would just like to point out that this includes carbondioxide levels, temperature, and nutrients as well as light.
Flowering
As anongoodnurse mentions performance might be measured by blooming which, in most flowering plants, has a day-light related component. However, for general growth increasing daylight over the 'natural' day length can often increase yield.
Daylight Cycles
The important point to note is that plants do 'ramp up' at dawn getting ready to start photosynthesizing (for some plants with temporal photosynthesis mechanisms (see CAM photosynthesis) this can be even more important). The reason plants do this is because plants can suffer from 'photobleaching' which can be considered similar to sunburn in humans, if they are not ready for sunlight. Getting 'ready' can involve lots of things including opening stomata (pores) to let CO2 in, changing which metabolic pathways are active, and moving about chloroplasts inside cells. Plants 'figure out' how and when to ramp up based on circadian rhythms which work well on 24 hour clocks and slight changes over time. Thus 12 hrs to 16 hrs can be a big change, particularly if the change happens by lights coming on earlier. Additionally, the 24 hour 'clock' means that plants will do better with 18hr light then 6hrs dark cycles than 36hrs light 6 hrs dark, because the total cycle length should be about 24hrs.
Photosynthesis Side Effects
The following is multiple choice question (with options) to answer.
On a hot, dry day, plants close their stomata to conserve what? | [
"air",
"water",
"sunlight",
"cold"
] | B | ART CONNECTION QUESTIONS 1. Figure 5.7 On a hot, dry day, plants close their stomata to conserve water. What impact will this have on photosynthesis?. |
SciQ | SciQ-3799 | human-biology, digestive-system, immune-system, microbiome
All of these immune cells also respond to diffused chemical signals called cytokines. These molecules are secreted by some cells and are received by receptors on the host cells. Sometimes the secretion is by another immune cell, sometimes it is from a non-immune system host cell, and sometimes these molecules can be secreted by the bacteria, fungi, or worms themselves.
Depending on the chemical signals that are secreted, and how the cells are interacting at the time of the message, and which cells are receiving the message, will determine the response to the message. It is contextual. Think of the phrase "You're killing me." If someone says it, while laughing, to a good friend who is telling jokes, it means one thing. If it is screamed as someone is being choked by an attacker, it means something very different.
To summarize, the immune cells are surveilling the environment and trying to pick up what is friend and what is foe and they try to respond accordingly.
Over time and coevolution, our microbiomes have developed ways of communicating with our immune system to let it know that these microbes do not mean any harm. They are able to "train" the immune cells using chemical signaling to temper the immune systems response to them (15), and this is how they are able to coexist within our body and with an immune system that is constantly on seek an destroy missions. Also because of the mucus, our microbiome usually isn't in direct contact with our cells, so it is a different kind of interaction than if an infecting pathogen were to breech the barriers and gain access to sterile areas where no bacteria or fungi should be found, and as a result, the immune system reacts differently.
The following is multiple choice question (with options) to answer.
What do you call the system of glands that release chemical messenger molecules into the bloodstream? | [
"nervous system",
"homeostasis system",
"limbic system",
"endocrine system"
] | D | The nervous system isn’t the only message-relaying system of the human body. The endocrine system also carries messages. The endocrine system is a system of glands that release chemical messenger molecules into the bloodstream. The messenger molecules are hormones. Hormones act slowly compared with the rapid transmission of electrical messages by the nervous system. They must travel through the bloodstream to the cells they affect, and this takes time. On the other hand, because endocrine hormones are released into the bloodstream, they travel throughout the body. As a result, endocrine hormones can affect many cells and have body-wide effects. |
SciQ | SciQ-3800 | equilibrium
Title: Why is equilibrium achieved at different stages of a reaction? In other words, I want to know why some reactions attain equilibrium early in the reaction while some reactions obtain equilibrium at the end of the reaction.
Why is this the case? If you define early or end of reaction by the how much the concentration of reactants change from initial reaction to once equilibrium is reached, it is because the equilibrium constant itself is essentially a ratio of the forward and reverse rate constants (can be approximated by the Arrhenius equation posted by t.c.). A high ratio means "more" products (at least a higher concentration) are present at equilibrium than reactants (so in a sense near the "end of the reaction"), since the forward rate is much higher than the reverse, a lower concentration of reactants compared to products is needed to maintain equilibrium. A low ratio means the opposite.
The following is multiple choice question (with options) to answer.
Reactant concentrations are highest at which part of a reaction? | [
"concurrent",
"ending",
"middle",
"beginning"
] | D | Reactant concentrations are highest at the beginning of a reaction. The plot of [C] versus tis a curve with a slope that becomes steadily less positive. |
SciQ | SciQ-3801 | thermodynamics, energy, temperature, work, volume
In particular, since a phase change happens we have a huge absorption of heat energy that doesn't result in a temperature increase because that energy instead is used for the phase transition (typically called latent heat).
Also, as the solution shows, we have to take into account the work energy that is spent for this phase change to be able to happen. Meaning, for the gas to form it must expand and "push away" the surrounding air. It must do work on the surroundings. Some energy is thus spent on doing that, and this energy delivered to the surroundings and thus removed from the internal energy.
All in all, these two energy contributions (one positive, one negative) play a role in the final internal energy that is stored in the substance. And none of them change the amount of thermal energy so we see no temperature change.
* With this I am referring to the thermal energy change within the substance that absorbs the energy. If you instead use the formula to calculate the thermal energy change within another substance which is supplying the energy, then you have calculated the amount of heat energy that is transferred from the supplier to the absorber - but we can't know from that whether the absorber converts this absorbed into an equivalent thermal energy change or to other types of non-thermal energies.
The following is multiple choice question (with options) to answer.
What happens to the temperature of a system during phase change? | [
"decreases",
"increases",
"fluctuates rapidly",
"remains constant"
] | D | This plot of temperature shows what happens to a 75 g sample of ice initially at 1 atm and −23°C as heat is added at a constant rate: A–B: heating solid ice; B–C: melting ice; C–D: heating liquid water; D– E: vaporizing water; E–F: heating steam. Thus the temperature of a system does not change during a phase change. In this example, as long as even a tiny amount of ice is present, the temperature of the system remains at 0°C during the melting process, and as long as even a small amount of liquid water is present, the temperature of the system remains at 100°C during the boiling process. The rate at which heat is added does not affect the temperature of the ice/water or water/steam mixture because the added heat is being used exclusively to overcome the attractive forces that hold the more condensed phase together. Many cooks think that food will cook faster if the heat is turned up higher so that the water boils more rapidly. Instead, the pot of water will boil to dryness sooner, but the temperature of the water does not depend on how vigorously it boils. |
SciQ | SciQ-3802 | meteorology, climate-change, gas, pollution
Title: Regarding various types of atmospheric pollution Does all the car pollution (from about 150 million cars at least in the U.S. and a lot more in all of North America and the rest of the world) all the smoke-stack pollution of various factories and all the Airline pollution running day after day have a deleterious and damaging effect on the general atmosphere and, over time, the climate?
Given all the observed pollution that China has caused itself and some of the resulting weird weather events there this certainly seems to be evidence of the damaging effects of car and factory pollution. Has anyone calculated how much exhaust from cars is produced in one day on average in a 'moderate' sized city?
Of course it seems with all the increased oil production in the U.S. and elsewhere we, human beings are going to keep are love-affair with gas-powered cars for the next 200 or 300 years. That is if we don't use up all the oil and gas in the ground before then. As a USA resident, the EPA is the best place to start when wondering about the emissions inventory of atmospheric pollutants or pollutant precursors that affect the National Ambient Air Quality Standards (e.g. Particulate Matter, Carbon Monoxide, Sulfur Dioxide, Lead, Nitrogen Oxides, Volatile Organic Compounds). The EPA compiles a comprehensive emissions inventory of all criteria pollutants at the county level which is available in the National Emissions Inventory (compiled once every 3 years). You can see the summary of your county at http://www.epa.gov/air/emissions/where.htm. As for the effects of atmospheric pollution, it is important to consider the lifetime of said pollutants in the atmosphere in order to put their environmental impacts into perspective. For instance, the air pollutants covered by the National Ambient Air Quality Standards have immediate health effects when high concentrations are breathed in regularly. Both animals and plants are adversely affected by these irritating and sometimes toxic chemicals, but these pollutants are also reactive and do not last long in the atmosphere unless they are constantly being replenished (e.g. daily traffic). Air quality also impacts critical nitrogen loads on ecosystems and possible production of acid rain.
The following is multiple choice question (with options) to answer.
What is the major cause of outdoor air pollution? | [
"electric lines",
"burning fossil fuels",
"manufacturing industry",
"agricultural equipment"
] | B | The major cause of outdoor air pollution is the burning of fossil fuels. Fossil fuels are burned in power plants, factories, motor vehicles, and home heating systems. Ranching and using chemicals such as fertilizers also cause outdoor air pollution. Erosion of soil in farm fields, mining activities, and construction sites adds dust particles to the air as well. Some specific outdoor air pollutants are described in Table below . |
SciQ | SciQ-3803 | water, experimental-chemistry, heat
Title: How can 30 ml of water be heated in less than 10 seconds? How is it possible to heat a tiny amount (30 ml)[1] of water to a high enough temperature to make a coffee, in less than 10 seconds and possibly instantly?
Most heaters that I know of heat water in no less than 90 seconds (induction heater) or 3 minutes which is way too much for my purposes, and a microwave oven takes me one minute and a half to heat.
[1] A single coffee is between 20 - 30 ml and my coffee machine makes 30 ml for each cup. Well, let's do some math:
Assuming 30 mL of water is 30 g, and we want to heat our water from 20 °C to 90 °C, the energy required is:
$$\begin{align}E&=C_Pm\Delta K \\
&=\left(4.18 \mathrm{\frac{ J}{gK}}\right)(30\mathrm{\ g})(70\mathrm{\ K})\\
&=8.778\mathrm{\ kJ}\end{align}$$
So how much power do we need to do this in a given time? "Instant" doesn't really mean anything, so let's go with 10 seconds:
$$\begin{align}P&=\frac{E}{t}\\
&=\frac{8778\mathrm{\ J}}{10\mathrm{\ s}}\\
&=877.8 \mathrm{\ W}\end{align}$$
This is not an enormous amount of power, but the trick is that it all has to go into heating the water. A good microwave outputs a fair bit more power than this, but it generally doesn't all get absorbed by such a such a small amount of water in only 10 seconds. Your best bet is probably an electric heating element directly inserted into the liquid, though I don't know if you can get a ~1000 W one small enough to sit in that much water.
As Jon Custer notes, it's not necessary to produce all the heat at once. If you heat some kind of thermal reservoir and flow the liquid past/through it, it reduces the demands on your heat source.
The following is multiple choice question (with options) to answer.
Why does a metal spoon heat up quickly when placed in a hot drink? | [
"low specific heat",
"insulation",
"convection",
"high specific heat"
] | A | The Table below compares the specific heat of four different substances. Metals such as iron have low specific heat. It doesn’t take much energy to raise their temperature. That’s why a metal spoon heats up quickly when placed in a cup of hot coffee. Sand also has a relatively low specific heat. Water, on the other hand, has a very high specific heat. It takes a lot more energy to increase the temperature of water than sand. This explains why the sand on a beach gets hot while the water stays cool. Differences in the specific heat of water and land even affect climate. To learn how, watch the video at this URL: http://www. youtube. com/watch?v=dkBStF2Rnu4. |
SciQ | SciQ-3804 | development
Title: How detachment/separation works in biology? It might be a strange question, but I'm interested in the mechanics of separation/detachment during asexual reproduction, for example when an organism reproduces by budding (I don't mean cellular budding like baker's yeast). When the newly formed body is fully matured it detaches itself from the parent / original body.
It might not be caused by a specific tissue, as animals with not so differentiated bodies are (also) capable of such, but I could easily be wrong. Is this (the detachment) triggered by changes in the cell membrane? I can't really think of other explanations. Reproductive budding and what you call 'cellular budding' are really highly related processes. Budding as a form of reproduction essentially partitions protein aggregates and damaged cellular components into the host or mother and builds fresh or 'young' cells on the opposite side of a partition. To begin understanding this look at Saccharomyces cerevisiae (budding yeast) which forms protein rings (from the septin proteins) at the membrane, around the bud neck which separates the mother and daughter cells Hartwell 1971. This ring acts a partition that in part, withholds protein aggregates and certain proteins from diffusing from the mother to the daughter. This protein ring is an example of how cells limit diffusion of proteins and cellular components to the daughter cell. Another good example that comes to mind is Linder 2007, though it is done in E Coli, not budding yeast, where mother cells maintain protein aggregates and age, while the daughter cells are given fresh components and are therefore more fresh and 'young'.
Now like you mention, imagine this process in a multicellular organism to be fundamentally the same. At some point the multicellular organism will start an outgrowth of cells, while restricting what materials are given to the daughter cells to maintain their youth. And eventually a new organism will have been created. Some of the details will be different, but the fundamental process is is quite similar. In that you start with an old cell that creates a new cell from scratch, but rather than splitting all cellular components equally between mother and daughter, the daughter cells is made in peak condition while the mother cell retains much of the cell 'junk' like protein aggregates.
Hopefully that starts to answer your question.
The following is multiple choice question (with options) to answer.
What does the megaspore mother cell produce after meiosis division? | [
"two haploid megaspores",
"two diploid megapores",
"four diploid megaspores",
"four haploid megaspores"
] | D | Watch this video (http://openstaxcollege. org/l/pollen_release) to see a cedar releasing its pollen in the wind. Female Gametophyte The female cone also has a central axis on which bracts known as megasporophylls (Figure 32.10) are present. In the female cone, megaspore mother cells are present in the megasporangium. The megaspore mother cell divides by meiosis to produce four haploid megaspores. One of the megaspores divides to form the multicellular female gametophyte, while the others divide to form the rest of the structure. The female gametophyte is contained within a structure called the archegonium. |
SciQ | SciQ-3805 | neuroscience, neurophysiology
Title: Questions concerning synaptic input and dendritic processing In the article How Spike Generation Mechanisms Determine the Neuronal
Response to Fluctuating Inputs, I read (p.11629)
I have four questions concerning some formulations:
What is "the membrane time constant" if this depends on the membrane resistance and capacitance which varies over the membrane? Maybe "local membrane time constant"? Or "mean membrane time constant"?
What do the authors probably mean with "instantaneous postsynaptic currents"? Occurring at the same time all over the dendritic tree?
What do they probably mean with "exponentially decaying synaptic currents"? The decaying of the PSPs while travelling down the dendritic tree?
What's the relation between "synaptic decay time constant" and "membrane time constant"?
The following is multiple choice question (with options) to answer.
Synaptic connections can change over time depending on what? | [
"activity level",
"diet",
"age",
"weight"
] | A | |
SciQ | SciQ-3806 | species-identification
Title: What species is this worm? I was at the park lying on the grass and its the third time I have seen them, I used to think they were parasites when I was like 7. It is the very small brown worm on the green leaf. It moves by squiggling. It comes in different colors but same size.
http://postimg.org/image/ea3x2nw95/
http://postimg.org/image/zfawh9pr1/ For me it looks like an inchworms which are the larvae of geometer moth or Geometridae.
By your picture it is almost impossible to see of which type it is.
I took picture of one in Switzerland (but likely not the same as yours).
Full resolution here: https://flic.kr/p/utFsiU
The following is multiple choice question (with options) to answer.
What is the body of a roundworm covered with? | [
"thin epidermis",
"thick scales",
"slime",
"tough cuticle"
] | D | Roundworms have a pseudocoelom and hydrostatic skeleton. Their body is covered with tough cuticle. |
SciQ | SciQ-3807 | biochemistry, molecular-biology, cell-biology, cell-membrane
Title: Why should phospholipid non-polar tails be "protected" in the membrane bilayer?
lipids are arranged within the membrane with polar head towards the outer side and non polar tails towards inner side, this ensures that the non polar tail is protected from aqueous environment.
My question is why should we protect non polar part ,will it destroy in contact with polar part?
What should be the correct reason for bilayer arrangement?
What should be the correct reason for bilayer arrangement?
I'll answer your second question first, but there is an almost identical question on this site already: Why do cells have a bilayer?
There is water on the extracellular and intracellular side of the membrane. What's actually happening at a molecular dynamics level is the self-association of the hydrophobic lipid tail groups driven entropically by water. In other words the polar (hydrophilic) head-groups "prefer" interacting with the water (called the interfacial region) and the the hydrophobic tail groups "prefer" not interacting with the water. With those two preferences in play, the lipid bilayer formation we know and love emerges.
why should we protect non-polar part, will it destroy in contact with
polar part?
To directly address the first part of the question: no, nothing would be destroyed. The word "protect" isn't appropriate (it's a bit too anthropomorphic for my taste!). Here is a video showing the bilayer spontaneously assemble in a molecular dynamics simulation. Read the more thorough 2003 journal article for an idea of early MD simulations of the bilayer formation. As you can see nothing "bad" happens when the water collides with the lipid tails and the lipids aren't destroyed.
Interesting read: MEMBRANE LIPIDS OF THE PAST AND PRESENT. Good animations and explanations of different membrane formations.
For an academic perspective, I'd recommend a couple of reviews: Cournia et al., 2015 and Gerit et al., 2008.
The following is multiple choice question (with options) to answer.
The end of the phospholipid molecule that is polar and attracts water is called what? | [
"hydrophobic",
"magnetic",
"hydrophilic",
"cytosolic"
] | C | Figure below shows how phospholipid molecules are arranged in a cell membrane. One end (the head) of each phospholipid molecule is polar and attracts water. This end is called hydrophilic ("water loving"). The other end (the tail) is nonpolar and repels water. This end is called hydrophobic ("water hating"). The nonpolar tails are on the inside of the membrane. The polar heads are on the outside of the membrane. These differences in polarity allow some molecules to pass through the membrane while keeping others out. You can see how this works in the video at the URL below. |
SciQ | SciQ-3808 | solutions
Title: Can the total amount of solution be found as a ratio between molar mass of a component and total mass of solution? I wonder whether the following relation is true:
$$n_\mathrm{solvent} + n_\mathrm{solute} = \frac{M}{m_\mathrm{solvent} + m_\mathrm{solute}},$$
where $M$ is the molar mass of the component, $n$ is the amount of substance and $m$ is the mass.
It was derived assuming $n = m/M,$ $n = n_\mathrm{solvent} + n_\mathrm{solute}$ and $m = m_\mathrm{solvent} + m_\mathrm{solute}.$
I don't think this is true, but I wanted to be sure before doing anything weird on a test. To sum up the comments, only the following relation for the total amount of solution $n_\mathrm{tot}$ is universally true:
$$n_\mathrm{tot} = n_\mathrm{solvent} + n_\mathrm{solute} = \frac{m_\mathrm{solvent}}{M_\mathrm{solvent}} + \frac{m_\mathrm{solute}}{M_\mathrm{solute}}\tag{1}$$
The best you can do is to assume that $n_\mathrm{tot}\approx n_\mathrm{solvent}$ for the diluted solutions of small molecules. Also, if the molar masses are similar $(M_\mathrm{solvent}\approx M_\mathrm{solute}\approx \bar{M}),$ the expression can be lead to a common denominator:
$$n_\mathrm{tot} \approx \frac{m_\mathrm{solvent} + m_\mathrm{solute}}{\bar{M}}\tag{2}$$
The following is multiple choice question (with options) to answer.
What is known as the universal solvent? | [
"vinegar",
"water",
"air",
"oil"
] | B | The ability of a solute to dissolve in a particular solvent is called solubility . Many chemical substances are soluble in water. In fact, so many substances are soluble in water that water is called the universal solvent. Water is a strongly polar solvent, and polar solvents are better at dissolving polar solutes. Many organic compounds and other important biochemicals are polar, so they dissolve well in water. On the other hand, strongly polar solvents like water cannot dissolve strongly nonpolar solutes like oil. Did you ever try to mix oil and water? Even after being well shaken, the two substances quickly separate into distinct layers. |
SciQ | SciQ-3809 | 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.
Any organism that causes disease is called what? | [
"a parasite",
"a microbe",
"a virus",
"a pathogen"
] | D | You have ten times as many bacterial cells as human cells in your body. Luckily for you, most of these bacteria are harmless. However, some of them can cause disease. Any organism that causes disease is called a pathogen . Diseases caused by bacterial pathogens include food poisoning, strep throat, and Lyme disease. |
SciQ | SciQ-3810 | electromagnetism, electricity, energy-conservation, perpetual-motion
Title: Auto spinning turbine generator This might be dumb question but I'm so curious to know if this actually works or is impossible. I was researching how you could generate electricity from magnets and copper wire and also have read how the hydroelectric generators work and it seems like they share the same concept. So if we are able to generate electricity by moving the turbine with water then why not have a some sort of motor which will make the turbine spin by getting power from the generator. I mean first there needs to be some sort of initial mechanical source to make the turbine spin then once the turbine starts moving and the generator gives power, the other motor gets power and it will take over the spinning of the turbine. So that way it will auto spin itself and basically means free energy. Can someone explain why this is not possible? As with virtually all perpetual motion machines, the reason becomes obvious once you consider the thermodynamic efficiency of the components involved. No turbine is 100% efficient, and also no motor is 100% efficient. This means that out of the initial energy you put in to make the turbine spin, only a certain percentage will be converted to electricity, with the rest being converted to heat. Then, out of that electricity, only a certain percentage is converted to mechanical energy to drive the turbine again. Then we go round again, losing some of that energy to heat until pretty soon the whole thing stops turning.
Of course, it would work just fine if you had an engine or a turbine that was more than 100% efficient, putting out more energy than you have to put in to drive it. But then, that's exactly the reason why we know that efficiencies over 100% are impossible: we observed that perpetual machines seem to be impossible, and from that Carnot derived his thermodynamic limits. The resulting theory has stood the test of time since the 19th century.
The following is multiple choice question (with options) to answer.
Electric generators change kinetic energy to what type of energy? | [
"thermal",
"light",
"electrical",
"intrinsic"
] | C | Sources of voltage include electric generators and cells. Electric generators change kinetic energy to electrical energy. Chemical cells change chemical energy to electrical energy, and solar cells change solar energy to electrical energy. |
SciQ | SciQ-3811 | species-identification, botany, ecology
Title: Algae or Lichen identification. Coastal BC, Canada I have tried all books and internet resources I know of, but I still have no idea what this might be — a lichen or something else.
At first glimpse, I thought it was something man-made and unnatural, but then I looked closer and saw how it appears to be attached and growing. It grows on exposed rocks well above the high tide. The photo is taken in late March, on northern Vancouver Island. It's loosely attached to the rock.
It was somewhat abundant around the general area (within of a few km), but I haven't seen it elsewhere - although I'm not from BC so there might be a lot of this around.
The water droplet in the lower right corner give a rough sense of scale.
Edit:
Adding another photo in which I just noticed a streak of white, which I included in original resolution. I want to propose you expand your search to a broader taxonomic scope. Specifically, I think you might be looking at a species of "red" green algae (family: Trentepohliaceae).
From Nelson et al. (2011):
All Trentepohliaceae have filamentous growth forms and often contain large amounts of carotenoid pigments (ß-carotene and hematochrome), causing the algae to appear yellow orange in color (Thompson and Wujek 1997, Lo´pez-Bautista et al. 2002).
The Trentepohliaceae contains five genera: (Trentepohlia, Printzina, Phycopeltis, Cephaleuros and Stomatochroon) and 70+ species worldwide.
For example, the following algae (picture from England) looks fairly similar to your specimen:
Trentepohlia aurea
Source: David Fenwick
If your specimen is a species in this family of algae, it is most likely in the Trentepohlia genus (or possibly Printzina genus).
Trentepohlia is a genus of filamentous chlorophyte green algae in the family Trentepohliaceae.
Typically orange or yellow in color.
Live on tree trunks and wet rocks or symbiotically in lichens.
Here's a picture of a free-living Trentepohlia species from coastal Oregon, USA:
Source: Richard C. Hoyer (2015)
The following is multiple choice question (with options) to answer.
Brown algae are important commodities for what? | [
"parasites",
"humans",
"reptiles",
"fish"
] | B | |
SciQ | SciQ-3812 | neuroscience, cell-membrane, action-potential
I totally get the main takeaway, that Vm results from the net accumulation of ion gradients, rather than the immediate consequences of the ion pumps. But I'm unclear on the phrase large cells -- whose surface-to-volume is so large that ion gradients run down slowly.
Presumably a cell with a large surface-to-volume ratio, like a long thin neuron, would have many ion channels which leak constitutively. So I'd expect the net ion conductance to be high, and gradients would run down quickly. But that contradicts the book's run down slowly point, so I'm confused.
Does passive diffusion play a role here? A long, thin cell would have slow passive ion diffusion, so is that why Vm would run down slowly?
Am I overthinking this?
What is the authors' point here? In a typical neuron at rest, potassium is high inside the cell and low outside, with the opposite true for sodium. The membrane is mostly permeable to potassium. Let's ignore the other ions.
The resting potential in this situation will be something like -70 mV. Rest means that the net current flow is zero; however, there is still current: potassium is flowing out of the cell and sodium is flowing in. Therefore, if we turn off the sodium-potassium pump, over time, the concentration gradients will slowly equalize.
The authors are making an assumption that the current is roughly a function of membrane surface area: more membrane = more current. However, the "reservoir" of concentration imbalance is a function of volume: a bigger cell has more total potassium ions than a smaller cell.
Therefore, in a large cell, if the membrane potential is mostly driven by the concentration gradient, and it takes a long time for the concentration inside to equalize with the outside because the current is small relative to the volume, the membrane potential will only change slowly if you use a toxin to stop the sodium-potassium pump.
I don't think the authors are really intending to say anything special about large cells versus small ones, they are just setting up some assumptions under which their argument about the resting potential is going to be most evident. This is a bit like in a physics textbook where you read something like "assume a uniform spherical baseball."
The following is multiple choice question (with options) to answer.
What does the large central vacuole do? | [
"use water",
"create glucose",
"heat water",
"store water"
] | D | First, plant cells have a large central vacuole that holds a mixture of water, nutrients, and wastes. A plant cell's vacuole can make up 90% of the cell’s volume. The large central vacuole essentially stores water. In animal cells, vacuoles are much smaller. |
SciQ | SciQ-3813 | solutions
Title: Can the total amount of solution be found as a ratio between molar mass of a component and total mass of solution? I wonder whether the following relation is true:
$$n_\mathrm{solvent} + n_\mathrm{solute} = \frac{M}{m_\mathrm{solvent} + m_\mathrm{solute}},$$
where $M$ is the molar mass of the component, $n$ is the amount of substance and $m$ is the mass.
It was derived assuming $n = m/M,$ $n = n_\mathrm{solvent} + n_\mathrm{solute}$ and $m = m_\mathrm{solvent} + m_\mathrm{solute}.$
I don't think this is true, but I wanted to be sure before doing anything weird on a test. To sum up the comments, only the following relation for the total amount of solution $n_\mathrm{tot}$ is universally true:
$$n_\mathrm{tot} = n_\mathrm{solvent} + n_\mathrm{solute} = \frac{m_\mathrm{solvent}}{M_\mathrm{solvent}} + \frac{m_\mathrm{solute}}{M_\mathrm{solute}}\tag{1}$$
The best you can do is to assume that $n_\mathrm{tot}\approx n_\mathrm{solvent}$ for the diluted solutions of small molecules. Also, if the molar masses are similar $(M_\mathrm{solvent}\approx M_\mathrm{solute}\approx \bar{M}),$ the expression can be lead to a common denominator:
$$n_\mathrm{tot} \approx \frac{m_\mathrm{solvent} + m_\mathrm{solute}}{\bar{M}}\tag{2}$$
The following is multiple choice question (with options) to answer.
What is the ratio of solutes in a solution to a volume of solvent in a solution known as? | [
"equilibrium",
"molality",
"molarity",
"osmolality"
] | D | Regulation of Water Intake Osmolality is the ratio of solutes in a solution to a volume of solvent in a solution. Plasma osmolality is thus the ratio of solutes to water in blood plasma. A person’s plasma osmolality value reflects his or her state of hydration. A healthy body maintains plasma osmolality within a narrow range, by employing several mechanisms that regulate both water intake and output. Drinking water is considered voluntary. So how is water intake regulated by the body? Consider someone who is experiencing dehydration, a net loss of water that results in insufficient water in blood and other tissues. The water that leaves the body, as exhaled air, sweat, or urine, is ultimately extracted from blood plasma. As the blood becomes more concentrated, the thirst response—a sequence of physiological processes—is triggered (Figure 26.10). Osmoreceptors are sensory receptors in the thirst center in the hypothalamus that monitor the concentration of solutes (osmolality) of the blood. If blood osmolality increases above its ideal value, the hypothalamus transmits signals that result in a conscious awareness of thirst. The person should (and normally does) respond by drinking water. The hypothalamus of a dehydrated person also releases antidiuretic hormone (ADH) through the posterior pituitary gland. ADH signals the kidneys to recover water from urine, effectively diluting the blood plasma. To conserve water, the hypothalamus of a dehydrated person also sends signals via the sympathetic nervous system to the salivary glands in the mouth. The signals result in a decrease in watery, serous output (and an increase in stickier, thicker mucus output). These changes in secretions result in a “dry mouth” and the sensation of thirst. |
SciQ | SciQ-3814 | mineralogy, mining
Because monazite. Monazite is a rare earth element phosphate, with the formula CePO4 (where Ce stands not only for cerium, but all of the are earth elements and yttrium as well). It is one of the main ore minerals for the rare earths. It's a very common mineral in granites and similar rocks, and it's very resistant to erosion.
Therefore, it commonly accumulates in placer deposits, together with other resistant minerals such as quartz, magnetite, zircon, rutile, etc. Essentially, nature breaks down the rocks and concentrates those minerals in mineral sands (sometimes known as black sands). These sands are not unique to India, and many examples can be found across the world. Essentially you find them where ever you have sandy beaches developed in areas of granite mountains (in the case of monazite).
Why thorium? Because monazite shares the same crystal structure with a mineral called cheralite: CaTh(PO4)2, and the two components (monazite and cheralite) can exist in the same mineral via solid solution. Some monazites can contain 20 and 30% thorium! Granite-derived monazite is particularly rich in Th, unlike carbonatite-derived monazite which usually has little Th. The Th is usually an unwanted by-product, with monazite mined primarily for the rare earths. But, if you're looking for the Th - this is something that you actually want.
The following is multiple choice question (with options) to answer.
What type of rock contains concentrations of valuable minerals? | [
"metamorphic",
"igneous",
"ores",
"sedimentary"
] | C | A mineral deposit that contains enough minerals to be mined for profit is called an ore . Ores are rocks that contain concentrations of valuable minerals. The bauxite shown in the Figure below is a rock that contains minerals that are used to make aluminum. |
SciQ | SciQ-3815 | neuroscience, neurophysiology, neuroanatomy, neurology
Conceptually, rather than thinking about extra parts, all of your same questions apply just as much to what is "normal". There is no evidence that brain development has any assumption built in that there will be 4 limbs or 5 digits on a hand, rather, connections are made with the nervous system as the limbs and digits develop, and these connections carry information between the CNS and sensory neurons and motor neurons, and the brain develops in response to those connections.
The following is multiple choice question (with options) to answer.
How many digits do primates have on each extremity? | [
"ten",
"five",
"four",
"three"
] | B | Primates have five digits (fingers or toes) on each extremity. Unlike the hooves of horses or the paddles of whales, the digits of primates are relatively unspecialized. Therefore, they can be used to do a variety of tasks, including grasping branches and holding tools. |
SciQ | SciQ-3816 | genetics, dna, dna-sequencing, human-genetics
Title: Do eukaryote cells contain DNA that isn't part of a chromosome or located in the mitochondria? I specify eukaryote in the title, but I'm also interested if this question isn't applicable to eukaryote cells in general but is to humans. I was reading "RNA-seq: An assessment of technical reproducibility and comparison with gene expression arrays" (John Marioni 2008).
In the results it states
"By these criteria, 40% of reads mapped uniquely to a genomic location, and of these, 65% mapped to autosomal or sex chromosomes (the remainder mapped almost exclusively to mitochondrial DNA)."
I couldn't help but notice the "almost exclusively to mitochondrial DNA". Almost exclusively? Can DNA be found in places other than chromosones or mitochondria? Perhaps I'm interpreting the sentence wrong. Any pointers would be appreciated
Thanks In plants, chloroplasts and other plastids contain DNA, but I suppose you are more interested in humans. Quoting from wikipedia,
In many cells cytoplasmic DNA is also found, which is different from
nuclear DNA, both in methylation levels (cytoplasmic has less), and in
sequence. EccDNA or extrachromosomal circular DNA is present in all
eukaryotic cells, derived from genomic DNA and consists of repetitive
sequences of DNA found in both coding and non-coding regions of
chromosomes. EccDNA can vary in size from less than 2000 more than
20,000 base pairs. In animals, eccDNA molecules have been shown to
contain repetitive sequences that are seen in satellite DNA, 5S
ribosomal DNA and telomere DNA. The function of eccDNA has not been widely studied, but it has been proposed that the production of elements of eccDNA from genomic DNA sequences adds to the plasticity of the eukaryotic genome and can influence genome stability, cell aging and the evolution of chromosomes
The following is multiple choice question (with options) to answer.
Dna is normally found within what region of a cell? | [
"genome sequence",
"mitochondria",
"nucleus",
"Golgi apparatus"
] | C | the nucleus. The nucleus contains one or more nucleoli, which serve as sites for ribosome synthesis. The nucleus houses the genetic material of the cell: DNA. DNA is normally found as a loosely contained structure called chromatin within the nucleus, where it is wound up and associated with a variety of histone proteins. When a cell is about to divide, the chromatin coils tightly and condenses to form chromosomes. There is a pool of cells constantly dividing within your body. The result is billions of new cells being created each day. Before any cell is ready to divide, it must replicate its DNA so that each new daughter cell will receive an exact copy of the organism’s genome. A variety of enzymes are enlisted during DNA replication. These enzymes unwind the DNA molecule, separate the two strands, and assist with the building of complementary strands along each parent strand. The original DNA strands serve as templates from which the nucleotide sequence of the new strands are determined and synthesized. When replication is completed, two identical DNA molecules exist. Each one contains one original strand and one newly synthesized complementary strand. |
SciQ | SciQ-3817 | 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.
Water and carbon dioxide molecules are reactants in what plant process? | [
"photosynthesis",
"glycolysis",
"breathing",
"digestion"
] | A | Water and carbon dioxide molecules are reactants in the process of photosynthesis. Does this mean they are “food” for plants, algae, and blue-green bacteria? Use the definition of “food” to answer this question. |
SciQ | SciQ-3818 | cell-biology, dna, molecular-genetics
Title: During the process of correcting mutations via gene therapy, is the defective gene removed? Just recently started learning about gene therapy, many websites explain that the corrected DNA can be added to the genome using a vector and all that. I just don't understand what happens to the other sequence of nitrogenous bases that codes for the incorrect protein.
Thanks in advance for any answers :) To be specific: I am talking about adult, somatic gene therapy here, and germline gene therapy experiments is still a landmine when considering ethical reasons.
The defective gene codes for a defective protein, that usually plays a part in pathways. Since the protein is also defective, that pathway is also rendered defective because of this protein, and usually when pathways go defective, bad things happen.
There are three target approaches to gene therapy:
Gene silencing by Antisense Oligonucleotide Therapy
Genome Surgery by ZFN, Crispr/Cas9 etc..
Gene Replacement by viral vectors
The only method that corrects the defective gene here is the genome surgery method. By using Zinc Finger Nucleases, or Crispr/Cas9s, TALENS or other methods like that, the defective protein is corrected at the genome level, which automatically corrects the mRNA and protein, and everything works as it should.
Other methods like Antisense, just prevent the incorrect protein from forming. This is really useful if the defective protein is itself toxic to the body, and a replacement protein can be achieved by masking the defective region to produce a truncated but functional protein.
Gene replacement usually puts in a healthy copy of the gene in, that functions along with the defective copy, and this solves majority of the problems as the affected pathway is no longer rendered inactive, as the healthy protein takes over the defective pathway. The defective protein is still produced, but doesnt do anything (or rather, is rendered moot as the healthy protein takes over) and gets removed during regular maintenance of the cell.
The following is multiple choice question (with options) to answer.
Gene therapy is a type of what kind of engineering? | [
"genetic engineering",
"chemical engineering",
"mechanical engineering",
"electrical engineering"
] | A | Biotechnology in Medicine and Agriculture It is easy to see how biotechnology can be used for medicinal purposes. Knowledge of the genetic makeup of our species, the genetic basis of heritable diseases, and the invention of technology to manipulate and fix mutant genes provides methods to treat the disease. Biotechnology in agriculture can enhance resistance to disease, pest, and environmental stress, and improve both crop yield and quality. Genetic Diagnosis and Gene Therapy The process of testing for suspected genetic defects before administering treatment is called genetic diagnosis by genetic testing. Depending on the inheritance patterns of a disease-causing gene, family members are advised to undergo genetic testing. For example, women diagnosed with breast cancer are usually advised to have a biopsy so that the medical team can determine the genetic basis of cancer development. Treatment plans are based on the findings of genetic tests that determine the type of cancer. If the cancer is caused by inherited gene mutations, other female relatives are also advised to undergo genetic testing and periodic screening for breast cancer. Genetic testing is also offered for fetuses (or embryos with in vitro fertilization) to determine the presence or absence of disease-causing genes in families with specific debilitating diseases. Gene therapy is a genetic engineering technique used to cure disease. In its simplest form, it involves the introduction of a good gene at a random location in the genome to aid the cure of a disease that is caused by a mutated gene. The good gene is usually introduced into diseased cells as part of a vector transmitted by a virus that can infect the host cell and deliver the foreign DNA (Figure 17.9). More advanced forms of gene therapy try to correct the mutation at the original site in the genome, such as is the case with treatment of severe combined immunodeficiency (SCID). |
SciQ | SciQ-3819 | isotope
Title: Is it possible to find the ratio of isotopes only given the mean mass number?
Three isotopes of an element have mass numbers $(M)$, $(M+1)$ and $(M+2)$. If the mean mass number is $(M+0.5)$, then the ratio of the amounts of the three isotopes is?
Let amount of $(M)$, $(M+1)$, and $(M+2)$ be $x$, $y$ and $z$ respectively.
$$\frac{(M)x + (M + 1)y + (M + 2)z}{x + y + z} = (M + 0.5)$$
After further simplification, I got $x-y=3z$.
I don't know how to proceed further. Can someone give me a hint, or reassure me that this question can't be solved with the given data?
The answer is given as $x:y:z=4:1:1$. You have two equations and 3 unknowns, so you can't solve it with just that. Say a, b, c are the fractions (as a decimal) of each isotope...
$$ a(x) + b(x+1) + c(x+2) = (x+\frac{1}{2}) $$
$$a + b + c = 1 $$
The 4:1:1 solution works. Another that works is 3:0:1. Another is 7:4:1. There are infinitely many solutions.
The following is multiple choice question (with options) to answer.
What is mass number? | [
"to total number of electrons and neutrons in a nucleus",
"the total number of protons and chondrichthyes in a nucleus",
"the total number of protons and neutrons in a nucleus",
"to total number of protons and electrons in a nucleus"
] | C | All oxygen atoms have eight protons, and most have eight neutrons as well. What is the mass number of an oxygen isotope that has nine neutrons? What is the name of this isotope?. |
SciQ | SciQ-3820 | hydrology, mountains, rivers
Title: Why do rivers have 'wells' in mountains? Why/how can rivers have sources in places high above the sea level? The presence of water underground has nothing to do with sea level in mountainous country.
When rain fails on a mountain, or snow falls on a mountain and the snow eventually melts, the water from the rain or snow melt mostly travels downhill via rivers to the sea.
In getting to a river some of the water will fall on the ground. In places where the ground is covered by soil, water can travel through the soil via the pore spaces between the grains of soil. Similarly if porous rock, such as sandstone lies beneath the soil water can travel through the pores in the rock.
If a layer of impervious rock lies under the porous rock or soil, the water cannot move downwards, due to gravity, any further. This can lead to water accumulating in the soil or porous rock and saturating the soil or rock. In such situations an aquifer can form. The top of the saturated zone in an aquifer is called a water table.
The ground beneath a river is saturated and the surface of the river shows the water table exposed to atmosphere. Thus in mountainous regions the ground beneath rivers will be saturated and capable of supporting a well developed from the bank of a river.
The following is multiple choice question (with options) to answer.
What rises through solid rocks where conditions are right? | [
"magma",
"water",
"crystals",
"nitrogen"
] | A | Lithospheric plates do a lot of moving on Earth's surface. Slabs of lithosphere smash into each other. They move sideways past each other along faults. Where conditions are right, magma rises through solid rock. It's no wonder that rocks experience stress! Rocks respond differently to different types of stress and under different conditions. |
SciQ | SciQ-3821 | mechanical-engineering, valves, liquid, connections
Title: Is there a male and female valve that is closed until connected together? I'm trying to make a quick release male and female connector similar to the one shown here.
One connector is attached to the bottom of a container filled with liquid. When it is not connected it is closed and none of the liquid can flow out of it. However when it is in contact with another connector it then opens and allows the liquid to flow out of it. Any ideas where these kind of connectors can be found or made? There are many, many different commercially-available designs of fluid connectors that shut off automatically when disconnected and open up when connected. They are available in plastic and metal, permanent and disposable, in all sorts of sizes. Try a search on "make-and-break fluid connectors".
The following is multiple choice question (with options) to answer.
What is the connecting piece of a sperm packed with? | [
"Gelatin",
"glucose",
"mitochondria",
"protein"
] | C | The connecting piece of the sperm is packed with mitochondria. Mitochondria are organelles in cells that produce energy. Sperm use the energy to move. |
SciQ | SciQ-3822 | biophysics, theoretical-biology, ecosystem
Systems ecology, especially with regard to energy and nutrient flow.
This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem Ecology: Understanding Element Cycles by Ågren & Bosatta (Ågren was originally a physicist)
Physical limitations to growth and transport
This can include for instance mechanical contraints on plant growth (see e.g. the book Plant Physics by Nicklas & Spatz), water transport in trees (see e.g. this BioSE question) or the biomechanics of movement (see e.g. Hudson et al (2012) on the speed and movement of cheetahs or Wikipedia: Biomechanics).
Allometric relationships between organisms, e.g. with regard to metabolism
To explain these types of relationships knowledge in physics is useful. See e.g. Kleiber's law for more.
MAXENT as a general approach to ecological patterns or to model species distributions
This is basically a tool lifted from physics that can be applied to ecological problems. There are many papers to look at, but Harte & Newman (2014) (Harte is another previous physicist) and Elith et al (2010) are two good starting points.
Dynamical modelling of populations and communities
This field use many of the same tools for analysis as physics, e.g. systems of differential equations. One of the pioneers in this field (among many) were Robert May (also started with a PhD in physics), and his classical book Theoretical Ecology: Principles and Applications is still a good starting point.
Energy harnessing and conversion by organisms
This can refer both to how organsims convert prey to energy (e.g. conversion efficiencies) and the physics of photosynthesis (which is an interesting intersection between physics and molecular biology). See Jang et al (2004) and O'Reilly & Olaya-Castro (2013) for examples of the how quantum mechanics can inform us about photosynthesis.
Hopefully this will give you a sense of some different ways that knowledge in physics can be useful for biology.
The following is multiple choice question (with options) to answer.
What is a diagram that shows a single way that energy flows throughout an ecosystem? | [
"fuel chain",
"food chain",
"dependent chain",
"water cycle"
] | B | A food chain is a simple diagram that shows one way energy flows through an ecosystem. Pictured below is an example of a food chain ( Figure below ). Producers form the base of all food chains. The consumers that eat producers are called primary consumers. The consumers that eat primary consumers are secondary consumers. This chain can continue to multiple levels. |
SciQ | SciQ-3823 | visible-light
The color we call 'red' is the color with the longest wavelength.
Prisms and water droplets are not the only things that affect the propagation direction of light. As light travels through the atmosphere it has a small probability of being scattered. The short wavelengths (the colors we perceive as shades of blue) are more prone to being scattered.
In the evening and in the morning the Sun is close to the horizon and the light has to travel through a lot of atmosphere to get to us. In general the composition of the light from the Sun is such that we will perceive that as white light. But with the atmosphere scattering the blue end of the spectrum, we often see the Sun having a red color when the Sun is close to the horizon.
The Sun gives us warmth, so naturally all us humans will associate the color we call 'Red' with warmth. Conversely, we will all associate absence of any hint of red (the blue colors) as comparatively cold.
We perceive Yellow as a particularly bright color, because we perceive incoming light as yellow when it has such a composition that it triggers two of our three light-sensitive molecules in about equal measure. Put differently: we perceive a mix of different colors of light as Yellow when it has the Red portion and The green portion of the spectrum in it, but little blue portion.
To get from light entering the eye to the perception of color by the visual cortex is a long way; it involves stages of processing information. It is remarkable that we experience different colors so vividly different, given that the perception of color is very much a constructed perception.
I suppose that our brain makes the different colors so vividly different by having specific strong associations. For instance, it seems to me that we will naturally associate the spectrum of greens that we perceive with the things around us that are predominantly green. It seems to me that these associations, not all of them conscious associations, allow us to feel a lot of distinction between the colors we perceive.
Your question, 'why are the colors ordered that way'.
The following is multiple choice question (with options) to answer.
Different colors of light differ in terms of which important attribute? | [
"frequencies",
"prisms",
"lenses",
"wavelengths"
] | D | Nobody really has such colorful eyes! The colors were added digitally after the photo was taken. They represent all the different colors of light. Light is a form of energy that travels in waves. Light of different colors has different wavelengths. |
SciQ | SciQ-3824 | electrostatics, accelerator-physics, particle-accelerators
Before going too far, I'd like to touch on a few factors that might not be well understood. First, an ion accelerator is not normally run like the lab-display generators, which just charge up a sphere and leak current somewhere/somehow. Instead, one wants a steady voltage on the terminal and that is only achieved through matching the current going both to the terminal and away from the terminal. At steady state (constant voltage) the two are the same. So, in the absence of an actual ion beam, the charging systems sends X amount of current up, (X-C) goes down the accelerator tube through precision resistors to set a steady voltage gradient, and C goes out as corona current, an intentional flow of charge from the terminal to the corona points. The corona current is used as the fast feedback loop on the voltage (much faster than throwing more/less charge on the belt/chain and waiting for it to be mechanically transported to the terminal). Once you add an ion beam in, you need to add more current going up to the terminal while keeping the column and corona currents the same (to keep the same potential on terminal). Should the beam current be too large a proportion of the charging current, the machine can become unstable to variation in the ion source. If you run the terminal at lower voltage, the current required is smaller (V = IR down the column). So, you might get more beam current possible at lower terminal voltages.
Second, there are two types of Van de Graaff type accelerators to consider, the single-ended systems and tandem accelerators. In a single ended machine, the ion source is housed in the terminal, making positive ions which are then accelerated down to ground. The tandem accelerator puts the terminal in the middle of the tank, and accelerates negative ions to the terminal, strips electrons in the terminal, and accelerates all the various positive charge states back to ground. So, two things with a tandem - you have two accelerating columns, so twice the column current, only one corona, and even more possible variation in beam current if the source blinks (since an ion traversing the machine goes both up and down). I will add that a positive ion source makes a lot more current than a negative ion source - it is just the nature of the beast. So, max current will be possible out of a single ended machine.
The following is multiple choice question (with options) to answer.
Ion drives have low thrust but high what? | [
"efficiency",
"acceleration",
"tolerance",
"power"
] | A | Ion drives have low thrust but high efficiency. They have already been used on several space missions, including NASA’s Deep Space 1spacecraft and Japan’sHayabusa asteroid sampling probe. Source: Photo courtesy of NASA,http://commons. wikimedia. org/wiki/File:Ion_Engine_Test_Firing_-_GPN2000-000482. |
SciQ | SciQ-3825 | energy, waves
Title: Calculating Energy of a Wave So my physics examinations are coming up and I was going through my notes on waves, but I realized that there were some discrepancies.
In my notes, the energy of a wave is directly proportional to the square of the amplitude, ie. $E \propto A^2$
However, I recalled that, in one of my physics lessons, our physics teacher told us that the energy of a wave can be calculated using $E=hf$, where $h$ is the Planck constant and $f$ the frequency.
Hence I was rather confused and tried searching google for answers but couldn't find any suitable ones. To the best extent of that research, what I found out was (apparently) (for visible light), the frequency of the wave could be used to calculate the energy of the wave, while the amplitude was used to determine the intensity of the wave.
So I was wondering, firstly, whether the above statement was correct, and secondly, in the event it is correct, whether it would be applicable to all kinds of waves, (ie. Sound waves, water waves, other EM waves, etc.), and thirdly, back to the original question, how do we calculate the energy of a wave?
Thanks. :) Both the equations you cite are correct.
The energy carried by a wave is indeed proportional to the amplitude squared. for what it's worth, you don't even need a propagating wave, any harmonic oscillator (e.g. a pendulum) will follow that rule. The validity of this rule remains unaffected even in quantum mechanics (actually, since in QM everything can be described by a wave function, it is even more fundamental there).
The second formula expresses the energy of a single photon. A photon is the smallest quantity of radiation that can exist at that frequency. This is completely unrelated to the total energy of the wave! For instance even a small light bulb will emit something like $10^{20}$ photons each second. Each carries an energy of $hf$. Together they sum up to the total power of the beam.
The following is multiple choice question (with options) to answer.
For most waves, energy is proportional to what, a term that describes the height of the wave? | [
"wave threshold",
"wave frequency",
"wave amplitude",
"wave volume"
] | C | Light also behaves like a package of energy. It turns out that for light, the energy of the “package” of energy is proportional to its frequency. (For most waves, energy is proportional to wave amplitude, or the height of the wave. ) The mathematical equation that relates the energy (E) of light to its frequency is. |
SciQ | SciQ-3826 | pathophysiology, kidney
Title: To diagnose osteomyelitis of vertebral column in chronic kidney failure Assume you suspect amyloidosis because of the history of the patient: problem with vertebral column and "purulent" (serous, fibrous, or hemorrhagic) inflammation when patient very young.
Now, the patient has a chronic renal failure.
Is there any other method to diagnose the fracture of some bone than röntgen?
Assume you do not know where the fracture is exactly. Osteomyelitis can be diagnosed with the following imaging techniques [1]:
first of all: radiography to view the anatomy of the bone
the sonography can be used to diagnose fluid collections, periosteal involvement. It is also the most useful procedure for kidney assessment [2].
CT is also useful to detect early osseous erosion, but is less sensitive when it comes to bone infection
MRI is the most sensitive and specific for osteomyelitis
Nuclear imaging can be used to identify multifocal osseous involvement.
References:
Carlos Pineda et al., Radiographic Imaging in Osteomyelitis: The Role of Plain Radiography, Computed Tomography, Ultrasonography, Magnetic Resonance Imaging, and Scintigraphy
American College of Radiology, Renal failure
The following is multiple choice question (with options) to answer.
What are the primary causes of bone fractures? | [
"overuse",
"step impact or bending",
"sideways impact or bending",
"spiral impact or bending"
] | C | Each ionic compound has its own unique name that comes from the names of the ions. |
SciQ | SciQ-3827 | electrostatics, solid-state-physics
The trick? The "head" of this thing is polar, but it's covalently bonded to these tails which are these nonpolar hydrocarbon chains. In water, all of the hydrocarbon chains want to get away from the water, so these things naturally twist around to form surfaces where the polar "heads" point outwards and the nonpolar "tails" point inwards. We say that they "self-assemble" into a bilayer, literally the water would rather be around other water so much that it accidentally kicks these things together until the phosphate groups are on the outside--these, it doesn't kick so hard. You really have to imagine the microscopic world as a constant storm of particles bashing up against each other to understand this self-assembly process!
Then the cell will often embed all sorts of other junk inside these cool boundaries by giving that junk a fatty center with polar outsides, so that it wants to "stick" inside the layer. This might include a channel to let water in or out, or how the injector needles that malicious bacteria can use to infect your cells are embedded within their walls -- or any number of other things like that! Cells often have "hairs" sticking out that help hold water molecules nearby or sometimes help them crawl around their environments.
So when your skin is touching the table, it's actually a layer of dead skin cells and hairs and such, with lots of room for air gaps, touching the table. Even if your cells themselves touched, they probably have a lot of stuff around them which keeps their actual phospholipids from touching the cell. And even if those touch the table and some of them get left behind, the rest of the ones on the nearest cell will spontaneously want, in any wet condition (and your body is one big wet condition!) to "fix" that wall.
It's just added layers of complexity atop these basic ideas that "molecules stay together more than they stick to other molecules, and some molecules attract these other molecules with a different strength than they stick to those other molecules." If you can master those basic physics ideas, then the rest is biology.
The following is multiple choice question (with options) to answer.
Water is polar and has electrically charged ends, so it is attracted to the oppositely charged end of a phospholipid molecule, which is described by what term meaning "water-loving"? | [
"cytosolic",
"hydrophilic",
"hydrophobic",
"aqueous"
] | B | One end of each phospholipid molecule is polar, so it has a partial electric charge. Water is also polar and has electrically charged ends, so it is attracted to the oppositely charged end of a phospholipid molecule. This end of the phospholipid molecule is described as hydrophilic, which means “water loving. ”. |
SciQ | SciQ-3828 | equilibrium, aqueous-solution, hydrolysis
$\ce {Mg^2+ + 2H2O <=> Mg(OH)2 + 2H+}$
(We usually call this as hydrolyzation of salt.)
And because $\ce {Mg^2+}$ is a weak base, you may expect that there will be not a lot $\ce {Mg(OH)2}$ and it's still soluable. Also there will be not a lot $\ce {H+}$ so the solution is just a bit more acidic then water.
The following is multiple choice question (with options) to answer.
What is produced when a base is dissolved in water? | [
"hydroxide ions",
"synthesis ions",
"alkaline ions",
"ingredient ions"
] | A | Acids are ionic compounds that produce positively charged hydrogen ions (H + ) when dissolved in water. Acids taste sour and react with metals. Bases are ionic compounds that produce negatively charged hydroxide ions (OH - ) when dissolved in water. Bases taste bitter and do not react with metals. Examples of acids are vinegar and battery acid. The acid in vinegar is weak enough to safely eat on a salad. The acid in a car battery is strong enough to eat through skin. Examples of bases include those in antacid tablets and drain cleaner. Bases in antacid tablets are weak enough to take for an upset stomach. Bases in drain cleaner are strong enough to cause serious burns. |
SciQ | SciQ-3829 | cellular-respiration
Title: Do cold blooded animals generate any heat? In explaining energy and work to an 8 year-old I said that all conversion of energy generates heat as a by-product. For example, cars generate heat in their engines and running generates heat in our bodies. Then the 8 year-old said, except for cold-blooded animals.
So my question is, do cold-blooded animals generate any heat in their conversion of stored energy (food, fat, etc) into motion? If they generate heat, why are they cold-blooded? They do generate heat. They just do not SPEND energy specifically on heating their bodies by raising their metabolisms. This is a form of energy conservation. The metabolic rate they need to live is not nearly enough to heat their bodies.
An example of spending energy to heat the body is seen in humans shivering. Here muscle is activated not for its usual purpose, but to function as a furnace. "Warm-blooded" and "cold-blooded" is somewhat a misnomer. The correct way to think of it is...
Endotherm or ectotherm. Does the heat primarily come from within (endo) or from the surroundings (ecto). Endothermic animals include mammals. Most of their body heat is generated by their own metabolisms. Ectothermic animals include reptiles and insects. They absorb most of their body heat from the surroundings. This is not the same as saying they let their body temperature fluctuate with their surroundings, some avoid this by moving around to accomodate themselves.
Homeotherm or poikilotherm. Homeotherms want to maintain homeostasis for their body temperatures. They don't want it to change. Poikilotherms do not exhibit this behaviour, instead their body temperatures vary greatly with the environment.
We can have endotherm poikilotherms, such as squirrels, who let their body temperature drop while hibernating. Endotherm homeotherms, such as humans, where temperature is constant by means of complex thermoregulation. Ectotherm homeotherms, such as snakes (moving into shadow or into the sun to regulate temperature), and ectotherm poikilotherms, such as maggots.
The following is multiple choice question (with options) to answer.
What do mammals conserve heat with? | [
"hair or fur",
"fur or muscle",
"tendons or hair",
"skin or bones"
] | A | Mammals conserve heat with their hair or fur. It works like the layer of insulation in the walls of a house. It traps warm air next to the skin so it can’t escape into the environment. Like the squirrel in Figure below , most mammals can make their hair or fur stand up from the skin. This makes it a better insulator. Mammals also have a layer of insulating fat beneath their skin. Other vertebrates lack this layer of fat. |
SciQ | SciQ-3830 | genetics, mutations
Title: Are there any mutagens that can undo the mutations they cause? I was reading a section from my textbook about tautomeric shifts, and it seems to suggest that there are some mutagens that can be directly responsible for the phenomenon. The section is mainly describing spontaneous mutations as opposed to induced mutations, and examples of mutagens are mentioned. However, the author explicitly states that the sort of changes made to DNA due to spontaneous mutations also occur at a higher rate during induced mutagenesis.
If a tautomeric shift can occur due to mutagenic activity, is it possible for the mutagen to undo and "correct" the mutation by reversing the shift? If so, what kind of chemicals or physical mutagens (e.g. radiation) would be involved? It is possible but extremely unlikely.
When a base undergoes tautomeric shift the DNA does not contain a mutation yet, just an unmatched pair. The mutation will only becomes inscribed into the DNA permanently after the DNA is replicated or wrongly repaired.
In order to reverse the mutation you would need to provoke a chemical change to that specific base using the same or another mutagen and as most of them are unspecific the likelihood of obtaining both the correct mutation to reverse the effect AND at that specific location is extremely low. Just for the location itself (i.e. that base pair), in human you have ~0.000000033% chances (1/3 billions) to mutate that base. This is assuming equal probabilities across the genome and a single modification event which is of course not true but shouldn't modify much the conclusion. I am not even speaking about provoking the chemical modification that will reverse it which will even further reduce that probability.
Such induced or natural mutations will actually only rarely appear in the genome permanently as the cell has multiple DNA repair mechanisms (see this wiki). So in this case the modified base does not need to be reverse as the cell will make sure to repair it directly but using mechanisms not based on mutagenesis.
The following is multiple choice question (with options) to answer.
What is a mutation that changes all or much of a particular chromosome? | [
"chromosomal mutation",
"muscular mutation",
"biochemical mutation",
"kinetic mutation"
] | A | A mutation that changes all or a large part of a chromosome is called a chromosomal mutation. This type of mutation tends to be very serious. Sometimes chromosomes are missing or extra copies are present. An example is the mutation that causes Down syndrome. In this case, there is an extra copy of one of the chromosomes. |
SciQ | SciQ-3831 | electromagnetism, energy, definition
Title: Dependence of current in electronvolts Definition: 1 eV is when an electron passes through a potential difference of 1 V and gains/loses energy.
Where is this potential difference? Is it between two plates in a apparatus setup?
Is this potential difference and applied voltage to the experimental setup/circuit, are they two different things?
If the device used to create a potential difference of 1 V used a power of 1 watt and 1 ampere current, then can we define 1 eV as being the energy gained by electron when it passes through a electric field using 1 watt power using 1 ampere current?
I am not sure if my third question makes sense. If you could help me with corrections or clarification, that would be great. Your definition is not accurate. One electron-volt is an energy unit equivalent to the amount of energy gained (or lost) by one electron accelerated across a potential difference of 1 V. What you have stated is simply a result of the acceleration, not the definition of the electron-volt. Plus, we should be even more general and instead of using the electron, we should use a particle with a charge of 1 electronic unit, e.
The acceleration of an actual electron doesn't have to happen. Nor does there actually have to be a potential difference. Those are merely concrete items which are used to define an equivalent amount of energy. The mass energy of an electron is approximately 511,000 electron volts, but there doesn't have to be any potential of 511,000 volts for the electron to exist.
The following is multiple choice question (with options) to answer.
Defined as a difference in electric potential energy, a source of what is required in order to produce an electrical current? | [
"magnetism",
"momentum",
"wattage",
"voltage"
] | D | Current requires a source of voltage, which is a difference in electric potential energy. Sources of voltage include chemical cells and solar cells. |
SciQ | SciQ-3832 | organic-chemistry, bond
Title: Bond length comparison between two carbon atoms Why is the bond length of double and triple bonds between two carbon atoms shorter than the single bond length between two carbon atoms? In the case of a carbon-carbon single bond, 2 electrons are shared in the bond connecting the two carbon atoms. With a carbon-carbon double bond, 4 electrons are shared between the two carbon atoms and 6 electrons are shared in a triple bond. Having additional electrons between the two atoms 1) improves the bonding overlap (makes the bond stronger) between the two carbon atoms and 2) better screens the two carbon nuclei form each other.
Both of these factors, better bonding overlap and better nuclear screening, will allow the two carbon atoms to approach closer together. Consequently, the more electrons (or the more bonds) between two carbon atoms, the shorter the distance between them.
The following is multiple choice question (with options) to answer.
What hydrocarbons contain only single bonds between carbon atoms? | [
"caloric hydrocarbons",
"simple carbohydrates",
"saturated hydrocarbons",
"unsaturated hydrocarbons"
] | C | Saturated hydrocarbons are hydrocarbons that contain only single bonds between carbon atoms. As a result, each carbon atom is bonded to as many hydrogen atoms as possible. |
SciQ | SciQ-3833 | neuroscience, cell-membrane, action-potential
I totally get the main takeaway, that Vm results from the net accumulation of ion gradients, rather than the immediate consequences of the ion pumps. But I'm unclear on the phrase large cells -- whose surface-to-volume is so large that ion gradients run down slowly.
Presumably a cell with a large surface-to-volume ratio, like a long thin neuron, would have many ion channels which leak constitutively. So I'd expect the net ion conductance to be high, and gradients would run down quickly. But that contradicts the book's run down slowly point, so I'm confused.
Does passive diffusion play a role here? A long, thin cell would have slow passive ion diffusion, so is that why Vm would run down slowly?
Am I overthinking this?
What is the authors' point here? In a typical neuron at rest, potassium is high inside the cell and low outside, with the opposite true for sodium. The membrane is mostly permeable to potassium. Let's ignore the other ions.
The resting potential in this situation will be something like -70 mV. Rest means that the net current flow is zero; however, there is still current: potassium is flowing out of the cell and sodium is flowing in. Therefore, if we turn off the sodium-potassium pump, over time, the concentration gradients will slowly equalize.
The authors are making an assumption that the current is roughly a function of membrane surface area: more membrane = more current. However, the "reservoir" of concentration imbalance is a function of volume: a bigger cell has more total potassium ions than a smaller cell.
Therefore, in a large cell, if the membrane potential is mostly driven by the concentration gradient, and it takes a long time for the concentration inside to equalize with the outside because the current is small relative to the volume, the membrane potential will only change slowly if you use a toxin to stop the sodium-potassium pump.
I don't think the authors are really intending to say anything special about large cells versus small ones, they are just setting up some assumptions under which their argument about the resting potential is going to be most evident. This is a bit like in a physics textbook where you read something like "assume a uniform spherical baseball."
The following is multiple choice question (with options) to answer.
What is a decrease in the magnitude of the membrane potential? | [
"digestion",
"ionization",
"inflammation",
"depolarization"
] | D | |
SciQ | SciQ-3834 | POLLUTION - A contaminated lake is treated with a bactericide
POLLUTION - A contaminated lake is treated with a bactericide. The rate of increase in harmful bacteria t days after the treatment is given by Where N (t) is the number of bacteria per milliliter of water. Find the minimum value of dN/dt. If the initial count was 5,000 bacteria per milliliter, find N (t). Find the bacteria count after 10 days. Use your calculator to minimize the given function. The minimum value is – 1000. b. Integrate dN/dt ’ to find N. Let u = 1 + t 2 then du = 2t dt and the integral becomes CONTINUED
Find C. The initial count was 5000 when t = 0.
c. Find N (10). 10 days after treatment the bacteria count will be 385 bacteria per milliliter of water.
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The following is multiple choice question (with options) to answer.
Water pollution occurs when chemicals, sewage, trash, or heat enter what? | [
"renewable resources",
"water resources",
"natural resources",
"air resources"
] | B | Water pollution occurs when chemicals, sewage, trash, or heat enter water resources. Water pollution is threatening the limited supply of clean, fresh water that human beings and other living things depend on. |
SciQ | SciQ-3835 | nuclear-physics, radioactivity, differential-equations
Title: Can the decay rate of nuclear decay be proportional to the second/third exponent of number of nuclei? A equation we all come across in high-school physics:
$$\frac{-dN}{dt}= kN$$ where N is number nuclei left
Is this always true for spontaneous nuclear decays? In chemistry, we find second, third order reactions. Similarly, has anyone found spontaneous decay where the decay rate is proportional not to the first exponent of remaining nuclei, rather to second or third exponent? The nuclear forces responsible for radioactive decay are short ranged and so isolated from other forces (such as the much weaker E$M forces) that this results in the exponential decay law. I believe there have been experiments that demonstrate that these decays can be slightly affected by exposure to very strong E&M fields, but this is a special circumstance that normally does not occur. I would have to Google to find references to those experiments. I believe the experiments were conducted on nuclear isomers.
Edit: The experiments that I was remembering took place between 1998 and 2007, but a Google search reveals that those experiments have now been discredited. You may read about this episode here. The search terms that I used were: nuclear, isomer, decay, stimulated. If you follow the links resulting from this search, you may find the original sources.
The following is multiple choice question (with options) to answer.
Radioisotopes may vary greatly in their rate of decay, decaying faster if their nuclei are more what? | [
"mature",
"immature",
"stable",
"unstable"
] | D | Different radioisotopes may vary greatly in their rate of decay. The more unstable their nuclei are, the faster they decay. |
SciQ | SciQ-3836 | volcanology, paleontology, volcanic-hazard, archaeology, pyroclastic-flows
Title: Are Pompeii and Herculaneum unique? Has anyone ever found or gone looking for similar locations, i.e. volcanic eruption sites in which unfortunate victims – human and non-human – have been entombed in the volcanic ash, with the possibility of revealing their forms by producing casts from the voids? Such sites, if they exist, could reveal exciting new knowledge about ancient peoples and animals. Probably the best known is more recent, the 1902 eruption of Mt. Pelée on Martinique, where 30,000 people were killed by pyroclastic flows. I don't know the extent of burial - it appears that the city may have been destroyed more by the ash cloud than the dense part of the flow.
The following is multiple choice question (with options) to answer.
Where can composite volcanoes most frequently be found? | [
"astatine boundaries",
"convergent boundaries",
"transform boundaries",
"divergent boundaries"
] | B | Composite volcanoes are common at convergent boundaries. Shield volcanoes are produced at divergent plate boundaries and intraplate. |
SciQ | SciQ-3837 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
The digestive, excretory, and reproductive systems of amphibians share a body cavity called what? | [
"stoma",
"urethra",
"cloaca",
"anus"
] | C | All amphibians have digestive, excretory, and reproductive systems. All three systems share a body cavity called the cloaca. Wastes enter the cloaca from the digestive and excretory systems, and gametes enter the cloaca from the reproductive system. An opening in the cloaca allows the wastes and gametes to leave the body. |
SciQ | SciQ-3838 | 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.
Vertebrates are a subphylum of what phylum? | [
"hydrozoa",
"chordata",
"arthropoda",
"porifera"
] | B | Vertebrates are a subphylum of the phylum Chordata. Like all chordates, vertebrates have a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. What other characteristics do vertebrates have? What traits set them apart from invertebrate chordates?. |
SciQ | SciQ-3839 | ecliptic, inclination
We think that over millions of years, the tiny off-center forces from that difference slowly wobbled Mercury's orbit, pushing it into a higher inclination and altering its rotation and orbital eccentricity until it reached a stable resonance that it has maintained since then. In short, Mercury is so close to the sun that its orbit has to be a little weird to stay stable.
The following is multiple choice question (with options) to answer.
What is the latin name for mercury? | [
"trichina",
"hydrargyrum",
"spirogyra",
"stibium"
] | B | In this image, you see small pools of elemental mercury. The Latin name for mercury is hydrargyrum, a compound word meaning “water-silver” (hydr- = water, -argyros = silver), since it is liquid like water but shiny like silver. Mercury is the only pure metal that exists as a liquid at room temperature. |
SciQ | SciQ-3840 | neuroscience, neuroanatomy
Title: Are cortical columns restricted to somatosensory cortical sections? From this previous question, it seems like evidence for the minicolumn organisation of the neocortex seems to be primarily based off observations around the sensory parts of the cortex, such as the primary visual cortex and the barrel cortex. Have column-like organisation been observed in non-sensory regions of the neocortex? Cortical columns (also called minicolumns) are not limited to the somatosensory cortex. As shown in this paper (which discusses how the miniucolumns change in response to aging), it is also present in the associative cortex.
However, it should be noted that "minicolumn" in this paper is defined as neurons that are close together and form a minimum spanning tree, as shown below.
Connectivity doesn't seem to be analysed, probably because connectivity information is really painful to collect, but I'm not sure given I'm an amateur when it comes to neuroscience.
The following is multiple choice question (with options) to answer.
The brain is said to contain gray matter, while what related structure contains white matter separated into columns? | [
"brain stem",
"amygdala",
"spinal cord",
"orbital lobe"
] | C | White Columns Just as the gray matter is separated into horns, the white matter of the spinal cord is separated into columns. Ascending tracts of nervous system fibers in these columns carry sensory information up to the brain, whereas descending tracts carry motor commands from the brain. Looking at the spinal cord longitudinally, the columns extend along its length as continuous bands of white matter. Between the two posterior horns of gray matter are the posterior columns. Between the two anterior horns, and bounded by the axons of motor neurons emerging from that gray matter area, are the anterior columns. The white matter on either side of the spinal cord, between the posterior horn and the axons of the anterior horn neurons, are the lateral columns. The posterior columns are composed of axons of ascending tracts. The anterior and lateral columns are composed of many different groups of axons of both ascending and descending tracts—the latter carrying motor commands down from the brain to the spinal cord to control output to the periphery. |
SciQ | SciQ-3841 | behaviour, language, genetic-code
Title: How does DNA encode high level features like animal behaviour and language? We know there are complex features which animals supposed to develop based on their genes as opposed to learning from the environment and the collective, also sometimes being very specific to certain species:
Concepts how to build homes
Animal languages including social insect interactions responsible for information transmission (or do they have to learn them through an acquisition process, let's exclude languages of ape tribes where "term" creation has been demonstrated?)
Valid answer: if already known, one or to examples to corresponding research.
Constraint: we are not talking about genes responsible for some sort of tendencies in behaviour but situations where there seems to be a more or less complex "blue print". I suppose we are yet very far from understanding these things. Relation of genotype to phenotype is teh subject of much contemporary research, but it is mainly limited to simple phenotypic features, explainable by action of a few genes, such as the colors of zebra fish mutants: see, e.g., this paper and the related publications by Nüsseln-Vollhardt group. Perhaps closer to your question is circadian rythms, which also have genetic determinants.
The complex behaviors are likely a result of the complex interactions of many genes, which are a very interesting, but also a very difficult problem to solve.
The following is multiple choice question (with options) to answer.
What type of behavior occurs naturally in all animals of a given species? | [
"observational",
"innate",
"learned",
"reflex"
] | B | An innate behavior is any behavior that occurs naturally in all animals of a given species. An innate behavior is also called an instinct . The first time an animal performs an innate behavior, the animal does it well. The animal does not have to practice the behavior in order to get it right or become better at it. Innate behaviors are also predictable. All members of a species perform an innate behavior in the same way. From the examples described above, you can probably tell that innate behaviors usually involve important actions, like eating and caring for the young. |
SciQ | SciQ-3842 | nuclear-physics, atomic-physics, stability, elements
Now, according to Coulomb's law, if the electron orbits about the nucleus the centripetal motion can be described by $$\frac{Ze^2}{4\pi\epsilon_or}=m_ev^2, $$ where $Z$ denotes the number of protons in the nucleus (the atomic number), and $e$ the elementary charge. Solving for $Z$ and substituting in $r$ from above yields $$Z=\frac{4\pi\epsilon_o \hslash v}{e^2}. $$ But what is $v$? Well, the maximum velocity an electron could ever have is the speed of light, and we wish to find the atomic number associated with an orbiting electron traveling at this speed, so we set $v=c$ and obtain our final result of $$Z=\frac{4\pi\epsilon_o\hslash c}{e^2}\approx 137.521,$$ which implies that for $Z>137$, the electrons at a position of $n=1$ in the Bohr model would have a velocity $>c$; and thus the highest atomic number achievable on the periodic table is 137.
Again, I just want to make sure this is a correct method for deriving element-137 before presenting. Perhaps one could explain how relativity plays a role here. I know Feynman used the Dirac equation to get this result...so could anyone (subsequently of course) expatiate on this in a simplistic manner? Thanks! No, electrons cannot impose any upper limit on the maximum $Z$ of atoms.
The whole research of heavy elements is the research of the nuclei, not the electrons that orbit them. Nuclear physics is about protons, neutrons (or quarks, gluons) and forces in between them and the typical speeds of the constituents are always rather close to the speed of light. Some nuclei classified by $(A,Z)$ are stable, some are short-lived, some are long-lived, some don't exist, and there are islands of stability etc.
For an arbitrarily charged nucleus, however, it's always possible to place an arbitrarily high number of electrons to the orbits.
The following is multiple choice question (with options) to answer.
What orbits an atoms' nucleus? | [
"neutrally charged ions",
"isotopes",
"positively charged protons",
"negatively charged electrons"
] | D | An atom has negatively-charged electrons in orbit around its nucleus. |
SciQ | SciQ-3843 | experimental-chemistry, water, hydrogen
Help. What is 3? How many deuterium atoms (symbol D for deuterium) are present in $\pu {3.00 x 10^{-6} g}$ of water?
Answer:
$$\pu{3.00 x 10^{-6} g} \;\ \ce{H2O} \times \frac{\pu{1 mol} \;\ce{H2O}}{\pu{18.015 g} \;\ce{H2O}}\times \frac{\pu{2 mol} \;\text{H}}{\pu{1 mol} \;\ce{H2O}}\times 0.000156 \times \frac{N_\mathrm A \;\text{D atoms}}{\pu{1 mol} \;\text{D atoms}} = \pu{3.12 x 10^{13} D atoms}$$
where $N_\mathrm A = \pu{6.0221415 x 10^{23}}$ is Avogadro's number and the deuterium fractional isotopic abundance (from the wiki article on "Deuterium") is 1 deuterium atom per 6420 atomic number 1 species, i.e., 1/6420 = 0.000156 = 0.0156%. The units can be mol D per mol H.
Alternate solution: The probability that a water molecule is HOD, rather than HOH, is 2/6420, i.e., 1/3210 = 0.000312 = 0.0312%. This is simply due to ordinary (unsubstituted) water having two hydrogens per molecule, i.e., it is HOH, so it has two independent chances to have H replaced by D. So, on average, there is one HOD molecule out of every 3210 water molecules. Likewise, every 3210 moles of water contains, on average, 1 mole of HOD molecules.
The following is multiple choice question (with options) to answer.
What are the three forms of water as found in nature? | [
"solid, liquid, gas",
"ice, vapor, sleet",
"solid , mixture , gas",
"balanced , liquid , gas"
] | A |
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