source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-5244 | molecules, atoms, intermolecular-forces, vsepr-theory
Title: Why do single, double and triple bonds repel each other equal amounts? I'm here to share with you something that totally confuses me, as I can't see the logic behind it, and my teacher doesn't know either.
Let's take a set of bonds that's trigonal pyramidal, with a lone pair of electrons and three bonds. The angle between the bonds is 107 degrees.
Now, the part where I get confused is if, say, we have one double and two single bonds (I know this makes the atom have 10 electrons, but just ignore that. It's not the point).
Now, in my brain, it would be logical that the double bonds, containing four electrons, would repel more than a single bond, containing just two. However, according to what I've been taught, it doesn't. What is that? The way you have learnt to predict molecular geometries is called the VSEPR theory. As all theories, it makes assumptions and has a certain number of limitations. The issue you are asking about is one such limitation.
When predicting the geometry of molecules with VSEPR, one should treat multiple bonds as a single entity. However, the geometry obtained is just a first approximation, or “idealized” geometry. In fact, multiple bonds induce distortions from this ideal geometry, pretty much like lone pairs do (I assume you know that already. If not, well, check the above-linked Wikipedia page for “lone pair”.) Citing from this online course:
Multiple bonds contain a higher electronic-charge density than do single bonds, so multiple bonds also represent larger electron domains ("fatter balloons"). Consider the structure of phosgene, Cl2CO, which is shown below.
From the Lewis structure of phosgene, we might expect a trigonal planar geometry with 120°-bond angles. However, the double bond seems to act much like a nonbonding pair of electrons, reducing the ClCCl bond angle from 120° to 111°. In general, electron domains for multiple bonds exert a greater repulsive force on adjacent electron domains than do single bonds.
So: yes, lone pairs and multiple bonds give rise to deviations from the ideal VSEPR geometries. It's nice that you figured it out on your own!
The following is multiple choice question (with options) to answer.
The domain geometry for a molecule with four electron pairs is called what? | [
"tetrahedral",
"bent",
"trigonal planar",
"linear"
] | A | As for methane and ammonia, the domain geometry for a molecule with four electron pairs is tetrahedral. In the water molecule, two of the electron pairs are lone pairs rather than bonding pairs. The molecular geometry of the water molecule is bent. The H-O-H bond angle is 104.5°, which is smaller than the bond angle in NH 3 (see Figure below ). |
SciQ | SciQ-5245 | cell-biology, terminology
Title: What is the difference between cytosol and cytoplasm? I've generally seen cytosol defined as the solution inside cells minus the organelles, cytoskeleton, etc and cytoplasm as the cytosol plus the organelles, cytoskeleton, etc. This naturally leads to the impression that cytosol is the cytoplasm minus all the solids. The problem here is that there are all sorts of other large molecules in the cells which could be thought of as solid. Are they also part of the cytosol or are they suspended in it? (I.e. are they part of the cytosol or are they non-cytosol components of the cytoplasm?)
Basically, I'm asking if the precise definition of cytosol is just anything in the cell that's not behind an endomembrane (save the exoskeleton) or if the dividing line is something else.
Subquestion: things can get even more terminologically confused because the cytosol is sometimes called the matrix. What the heck is the preferred terminology with this stuff? IMO, the definitive answer to this question is given in a paper by J. S Clegg. He traced the origin of the term cytosol to a book chapter by H. A. Lardy, and confirmed by email that Lardy had indeed coined the term. Their definition of cytosol is as follows:
... that portion of the cell which is found in the supernatant fraction after centrifuging the homogenate at 105 000 x g for 1 hour.
The following is multiple choice question (with options) to answer.
What is the gel-like material between the cell membrane and the nucleus called? | [
"cytoplasm",
"vacuole",
"ribosome",
"mucus"
] | A | Cytoplasm is one component of cells that is common to all cells. Cytoplasm is the gel-like material between the cell membrane and the nucleus. The cytoplasm plays an important role in a cell, serving as a "jelly" in which organelles are suspended and held together by the cell membrane. Though prokaryotic cells do not have organelles (though they do have ribosomes), they still have cytoplasm. It is within the cytoplasm that most cellular activities occur, including the many metabolic pathways that occur within organelles, such as photosynthesis and aerobic respiration. |
SciQ | SciQ-5246 | human-biology, physiology, cardiology, anatomy
Title: Can humans live without their right atrium? The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated blood from the superior and inferior venae cavae, the coronary sinus, and the anterior and smallest cardiac veins, and pumps it into the right ventricle through the tricuspid valve.
Can humans survive without right atrium? In this condition blood would fill the right ventricle directly, comparable to some animals like frogs, toads, snakes and lizards. What advantages does the normal human heart have to this anatomy ? If we had this anatomy, where would the best place for pacemakers be, like the sinus node? This is an interesting theoretical question, but several things would need to be clarified:
Does removing the R atrium relocate the SA node to the R ventricle or remove it completely from the picture?
Does the remaining R ventricle have a tricuspid valve?
Technically, the R atrium is the home of the sino-atrial node, which provides natural pacing of the human heart between 60-80 beats/min. Without this natural pacing, our hearts would rely on back-up pacer systems such as atrioventricular node, His-Purkinje systems or the intrinsic but ectopic pacing of individual atrial or ventricular cells.
The following is multiple choice question (with options) to answer.
Like mammals and birds, and unlike other reptiles, crocodiles have how many chambers in their heart? | [
"six",
"two",
"four",
"one"
] | C | Like mammals and birds, and unlike other reptiles, crocodiles have a four-chambered heart. But, unlike mammals, blood with and without oxygen can be mixed. |
SciQ | SciQ-5247 | waves, acoustics, diffraction, wave-particle-duality
Title: Diffraction of Sound Waves We know that Sound waves are Longitudinal waves. It mean that there is pressure difference created when medium particles move. But while diffraction of sound waves "How will the medium particles move". Will they get any sideward push. So that sound diffract sidewards.
Is the reason for this question is same for light diffraction... If photon theory worked out then it might be same. What if wave nature worked out in light diffraction?
When wave length increases then diffraction effects will be more. How are they related? It's ultimately the same reason why light refracts, Huygens's Principle.
You're thinking of the sound as "a wave", in this particular case you're looking at it where its roughly linear. So then, why does this linear thing suddenly move sideways when it goes through a hole?
Think about it differently; according to Huygens a wave front is the mathematical addition of an infinity of spherical waves. You see a linear wave, but that's because you're macroscopic. At the microscopic level that's not what's happening, at that level its moving in all directions all the time.
So wait, if the microscopic "things" are moving spherically, then why did you have a linear wavefront to start with? Because over an extended front, every bit of the wave that's going, say, right, has another bit somewhere else going left. When you sum it all up, all the "sideways bits" sum to zero, and the only leftover terms are the ones from the original disturbance, moving outward.
So what happens at the slit? Well consider the spot right on the left edge of the opening... the left side of it is moving left and the right side is moving right (its spherical). Now before it got to the slit there was another spot to it's left that was doing the same thing. So the left moving bit of spot A was being cancelled out by the right moving bit of spot B. Ahhh, but B just hit the wall, literally. So no no one is stopping the left-moving side of A.
Presto, at our macroscopic level, it looks like it started moving left. But that's not "really" what happened.
The following is multiple choice question (with options) to answer.
What is the phenomenon in which light and sound waves become circular at the point source of a barrier? | [
"diffraction",
"sonic wave",
"refraction",
"reflection"
] | A | When a series of straight waves strike an impenetrable barrier, the waves stop at the barrier. However, the last particle of the medium at the back corner of the barrier will create circular waves from that point, called the point source. This can be seen in the image below. This phenomenon is called diffraction , and it occurs in liquid, sound, and light waves. While the waves become circular waves at the point source, they continue as straight waves where the barrier does not interfere with the waves. |
SciQ | SciQ-5248 | human-biology, endocrinology, organs
Title: Is there a blood panel lab test that measures all the hormone-producing glands? I understand that there are gland-specific hormone tests, such as:
Secretin: for the pancreas; and
Prolactin/ACTH: for the pituitary; and
PTH: for the payathyroid, etc.
However, are there any "composite" blood panels that test the "entire gamut/spectrum" of organs/glands, similar to what composite metabolic panels do for your cell counts? There are no composite tests that measure all the clinically important hormone producing glands. There are too many hormones produced by too many hormone producing cells/tissues in the body to test for all of them all at once (i.e. in a panel).
For illustrative purposes only... if you go to wikipedia they have a list of all hormones in the human body which is definitely far from complete! But it gives you an indication of just "how many" hormones there are and why testing for all of them is impossible in a panel.
Even with regard only to pancreatic hormones, there are several hormones produced (e.g. insulin, glucagon, somatostatin) that aren't necessarily a marker of the glands overall function (because they are not necessarily involved in the same function). Each of these hormones has different functions even though they are produced by the same gland.
Regardless, from a medical perspective you would never have a reason to test for all of them anyway. If you tested enough of them you'd find at least one of them that would - by chance - be abnormal.
Additionally, if you asked a handful of scientists to name fifty hormones there would be a lot of different hormones on each of their lists. The definition of hormone is vague, and we are learning more about new hormones every day. In the last decade we have learned that bile acids - chemicals predominately produced by the liver that are involved in dietary fat absorption - also act as hormones. There aren't clinical reasons to study all of these molecules just yet, but this demonstrates that it would be impossible to measure all of them all at the same time in one particular "panel".
The following is multiple choice question (with options) to answer.
What is the name of the relatively large gland in the neck that secretes thyroxin? | [
"thyroid",
"Pancreas",
"Thyroid",
"Pituitary"
] | A | The thyroid gland is a relatively large gland in the neck. Hormones secreted by the thyroid gland include thyroxin. Thyroxin increases the rate of metabolism in cells throughout the body. |
SciQ | SciQ-5249 | cell-signaling, chemical-communication
Title: How many molecules are generally required for cell signallng processes for given cases? I know its really a broad topic but I am interested in just few cases:
Quorum sensing
neurotransmitters for the communication of images/ general information
hormones/pheromones
I actually want to know that does a single or hundreds of molecules are needed to communicate information from one cell to another.
I searched but approx number of molecules, I can't find anywhere. A cell can interact with other cells in zillions of ways. You can send information from one cell to other cells via neurotransmitters, hormones, pheromones, electric signals, magnetic resonance ,leukotrines etc.
In general a single type of molecule is enough to send such information. Like you require only Acetylcholine(Ach) as neurotransmitter to transmit various nerve impulses.
But, even for a single type, you require thousands of molecules. Like 1 molecule of Ach can do almost nothing and would immediately be broken by Acetylcholinesterase. You require 1000s of such molecules.
You can modify the communicating information via different types of transmitters. You can use GABA or glycine to supress any information exchange or use dopamine to enhance it. But again you will need many molecules of GABA or Glycine.
For visual pathway, you can use no. of types of transmitters like glutamate, glycine, gaba, dopamine, acetylcholine, substance P etc.
Neurotransmitters for visual pathway.
Hormones are transmitters that are required in small quantities. But, again you require certain concentration. There is normal blood concentration of various hormones like 80 pg/ml for calcitonin.
Quorum sensing use transmitters like AHLs. Again a certain threshold value is required for them to act.
Again, to produce these transmitters you have to go through a rigorous process of transcription, translation and post-translational modifications.
So, for cell to communicate a rigorous process is used.
The following is multiple choice question (with options) to answer.
Amplification that occurs in which cells often requires signal transduction pathways involving second messengers? | [
"catayst cells",
"optic nerves",
"sensory receptor",
"axons"
] | C | |
SciQ | SciQ-5250 | infection, amphibians
Title: What is this toad suffering from? Myiasis or chytridiomycosis? I found this toad on Aug. 29th at this location: position on osm
I think it is a bufo bufo, approx. 10 cm long. The nostrils seemed to be completely filled with a grey matter and from the activity of the floor of the mouth it apparently tried to breathe againgst this obstruction. It probably had enough oxygen via its skin though.
I tried to remove the obstruction using a blade of grass but this seemed to produce some pain as the toad closed its eyes on contact, so I stopped. The skin looked fairly normal and the toad was able to walk away after a while.
I can think of two causes for this condition.
Batrachochytrium dendrobatidis infestation
Lucilia bufonivora larvae
I could not see properly, if there were any larvae or unhatched eggs inside the nostrils, but as the rest of the skin seemed unharmed I assume the latter.
Is my assumption valid or is there even a third possibility? It is a female Bufo Bufo and you are right, there are toad fly (Lucilia bufonivora) larvae/eggs inside her nostrills. These flies lay their eggs inside toads' nostrills (specifically on Bufo Bufos) and the larvae start eating them. Sadly this disease ends up by the death of toad. They slowly eat nostrills, then mouth, eyes, and all the head.
Here's a photo of a male bufo bufo, without a head. Someone found it walking around at this situation. https://i.stack.imgur.com/I6twl.jpg
The following is multiple choice question (with options) to answer.
As adults, amphibians are completely _______, meaning they feed on other animals. | [
"carnivorous",
"herbivorous",
"omnivorous",
"monogamous"
] | A | Amphibians are an important food source for animals such as birds, snakes, raccoons, and fish. Amphibians are also important predators. As larvae, they feed mainly on small aquatic animals such as water insects. They may also feed on algae. As adults, amphibians are completely carnivorous . They may catch and eat worms, snails, and insects, as the frog in Figure below is doing. Unlike other amphibians, caecilians are burrowers . They use their head to dig in the soil, and they feed on earthworms and other annelids. Caecilians can be found in moist soil near rivers and streams in tropical regions. |
SciQ | SciQ-5251 | earth-history, planetary-science, geochemistry, geochronology, planetary-formation
This means that the Earth has been here at least ~4.4 billion years ago, because you need the Earth to have a moon. The Earth didn't just pop into existence, but it formed over a period of time, in which small planetesimals collided with each other and accreted to form a larger body.
The question now is, what is the age of the planetesimals? We can't know for sure because they are all integrated into Earth, but we can look at asteroids and see their age. We do that by dating the meteorites that fall on the Earth, which in some cases are blasted off asteroids by (even more) collisions and impacts.
When you look inside a specific type of meteorites called chondrites, you can see objects that are called CAIs (calcium-aluminum inclusions). These things are solids condensed from vapourised gas that existed in the solar nebula before any planets and planetesimals formed. These are basically the first solid to form in the solar system, and they define the birth of the solar system. We know that they formed 4568(3,4) or 4569.5(5) million years ago.
Planetary bodies (which for this discussion will be considered as km-sized chucks or rock with the ability to melt and differentiate to mantle and crust, and accrete to form proper planets) began forming around 4566.2 to 4567 million years ago(5,6,7). We know that because we can date meteorites that we know originated in asteroids. This is just 2 million years after the formation of the first solid droplets in the solar system. Now, while 2 million may seem like a long time for your daily commute, it is not too long for planetary processes (considering Earth is 4.5-4.4 billion years old).
The following is multiple choice question (with options) to answer.
Approximately how many billion years ago did our solar system begin? | [
"five billion",
"four billion",
"nine billion",
"three billion"
] | A | Our solar system began about 5 billion years ago. The Sun, planets, and other solar system objects all formed at about the same time. The leading hypothesis for how they formed is called the nebular hypothesis . |
SciQ | SciQ-5252 | botany, virus
Title: What virus transforms full grown plants? I read an article by a gardener describing how a virus had transmitted a negative trait to his plants. It rather shocked me, because I hadn't realized that a virus could transform an adult plant. I was aware of dipping arabadopsis flowers in agrobacterium tumefaciens, but the concept of non-reproductive structures being transformed seems fascinating. What kind of virus is capable of that? These are just a couple of short examples, but Witch's broom structures in trees can sometimes be caused by viruses - see Wikipedia: Witch's broom (fungi is maybe the most common cause though). In rose species you also have the similar Rose rosette disease (also called witches’-broom of rose), which is caused by a virus. The same webpage from Missouri Botanical Garden also includes a list of other plant viruses that you might find interesting.
Plant viruses that infect non-reproductive structures are common though - a overview can be found here: The American Phytopathological Society: Introduction to Plant Viruses, the Invisible Foe. More indepth information can be found in Plant Pathology (Agrios, 2012) (see ch. 12: "Plant diseases caused by viruses").
The following is multiple choice question (with options) to answer.
A type of what organism causes ergot, a disease that impacts crops directly and has more devastating effects on animals? | [
"virus",
"bacteria",
"fungus",
"insects"
] | C | Plant Parasites and Pathogens The production of enough good-quality crops is essential to our existence. Plant diseases have ruined crops, bringing widespread famine. Most plant pathogens are fungi that cause tissue decay and eventual death of the host (Figure 13.25). In addition to destroying plant tissue directly, some plant pathogens spoil crops by producing potent toxins. Fungi are also responsible for food spoilage and the rotting of stored crops. For example, the fungus Claviceps purpurea causes ergot, a disease of cereal crops (especially of rye). Although the fungus reduces the yield of cereals, the effects of the ergot’s alkaloid toxins on humans and animals are of much greater significance: In animals, the disease is referred to as ergotism. The most common signs and symptoms are convulsions, hallucination, gangrene, and loss of milk in cattle. The active ingredient of ergot is lysergic acid, which is a precursor of the drug LSD. Smuts, rusts, and powdery or downy mildew are other examples of common fungal pathogens that affect crops. |
SciQ | SciQ-5253 | 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.
Plant-like protists are commonly called what? | [
"sponge",
"fungus",
"seaweed",
"algae"
] | D | Plant-like protists are commonly called algae (alga, singular) . Some algae consist of single cells. They are called diatoms. Other algae are multicellular. An example is seaweed. Seaweed called kelp can grow as large as trees. You can see both a diatom and kelp in Figure below . Algae are probably ancestors of plants. |
SciQ | SciQ-5254 | human-biology, plant-physiology, stem-cells
Title: Is that true that plant stem cells can be used in humans? I was reading an article (which seems very fake to me) on sensitive topics, but there was one astonishing statement:
Stem cells are obtained from certain plants that grow all over the world. Once the stem cells have been obtained, the doctor will inject them on the target organ...
I want to ask specialists if this particular statement can be true. If yes, does it imply nucleus replacement in stem cells, or anything like that?
Sorry guys, for the stupid question. https://stemcells.nih.gov/info/basics/6.htm
...
Viruses are currently used to introduce the reprogramming factors into adult cells, and this process must be carefully controlled and tested before the technique can lead to useful treatment for humans. In animal studies, the virus used to introduce the stem cell factors sometimes causes cancers. Researchers are currently investigating non-viral delivery strategies. In any case, this breakthrough discovery has created a powerful new way to "de-differentiate" cells whose developmental fates had been previously assumed to be determined. In addition, tissues derived from iPSCs will be a nearly identical match to the cell donor and thus probably avoid rejection by the immune system. The iPSC strategy creates pluripotent stem cells that, together with studies of other types of pluripotent stem cells, will help researchers learn how to reprogram cells to repair damaged tissues in the human body.
So as that all points out, no, the genetics of it will cause a plant stem cell to be genetically not a match, where it might do something for a little while, but upon that cells first interactions, it will stimulate the immune system to get rid of it, rather than incorporate it.
Anymore, I want to know about how Bone Morphinogenic Proteins (BMP-4 or above) can be injected into an organ, and if that will help stem cells for reviving an organ at all.
The following is multiple choice question (with options) to answer.
Which cell gives rise to all cells of the human body? | [
"signaler stem cell",
"schwann stem cell",
"omnipoten stem cell",
"totipotent stem cell"
] | D | ability to diversify at each step. The totipotent stem cell is the zygote, or fertilized egg. The totipotent (toti- = “all”) stem cell gives rise to all cells of the human body. The next level is the pluripotent stem cell, which gives rise to multiple types of cells of the body and some of the supporting fetal membranes. Beneath this level, the mesenchymal cell is a stem cell that develops only into types of connective tissue, including fibrous connective tissue, bone, cartilage, and blood, but not epithelium, muscle, and nervous tissue. One step lower on the hierarchy of stem cells is the hemopoietic stem cell, or hemocytoblast. All of the formed elements of blood originate from this specific type of cell. Hemopoiesis begins when the hemopoietic stem cell is exposed to appropriate chemical stimuli collectively called hemopoietic growth factors, which prompt it to divide and differentiate. One daughter cell remains a hemopoietic stem cell, allowing hemopoiesis to continue. The other daughter cell becomes either of two types of more specialized stem cells (Figure 18.4): • Lymphoid stem cells give rise to a class of leukocytes known as lymphocytes, which include the various T cells, B cells, and natural killer (NK) cells, all of which function in immunity. However, hemopoiesis of lymphocytes progresses somewhat differently from the process for the other formed elements. In brief, lymphoid stem cells quickly migrate from the bone marrow to lymphatic tissues, including the lymph nodes, spleen, and thymus, where their production and differentiation continues. B cells are so named since they mature in the bone marrow, while T cells mature in the thymus. • Myeloid stem cells give rise to all the other formed elements, including the erythrocytes; megakaryocytes that produce platelets; and a myeloblast lineage that gives rise to monocytes and three forms of granular leukocytes: neutrophils, eosinophils, and basophils. |
SciQ | SciQ-5255 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
What term describes the long tube that connects the mouth to the anus? | [
"esophagus tract",
"metabolism tract",
"gastrointestinal tract",
"lungs tract"
] | C | The organs in Figure below make up the gastrointestinal (GI) tract. This is essentially a long tube that connects the mouth to the anus. Food enters the mouth and then passes through the rest of the GI tract. Food waste leaves the body through the anus. In adults, the GI tract is more than 9 meters (30 feet) long!. |
SciQ | SciQ-5256 | mixtures, gas-phase-chemistry
Now as it happens, for ideal gases, which the atmosphere is close to being, you can mentally subdivide the volume into tiny little equal-sized cubes, one for each atom or molecule in the mixture, and on average there would be one atom/molecule of $X$ in each fourth cube if $X$ is 25% by volume of the mixture. (I emphasize "on average" because of course since the gas atoms or molecules are continuously moving around randomly, they will bunch up and spread out momentarily all the time, so at any given instant there may be zero or many more than one $X$ atom/molecule per tiny cube.) Real mixtures in the liquid state often have at least some nonideality, e.g. even in a dilute solution of $\ce{NaCl}$ in water, you will find "structure" in the solution, with the $\ce{Na+}$ cations and $\ce{Cl-}$ anions surrounded by a fairly fixed arrangement of $\ce{H2O}$ molecules, almost like a tiny piece of clathrate, so a mental arrangement of tiny boxes is an even less accurate atomic-scale description of the solution.
In short, the percent by volume description of a mixture is only a way to characterize the amount of material that goes into it, it is not intended as any kind of implication of what the mixture looks like at the atomic scale.
As for why NASA reports the composition of the atmosphere by percent by volume: probably because it's closest to the actual experiments done to measure it. You would typically measure the composition of a gas mixture by physically separating it (e.g. by lowering the temperature until each gas liquefied) and then measuring the volume of each component. You certainly could from those measurements easily calculate a percent by moles, but – why? You introduce a calculational step between the measurement and what you report, and scientists tend to prefer getting original data, right what comes from the instrument, if possible, as a way of avoiding even the smallest risk of some error introduced in calculation.
The following is multiple choice question (with options) to answer.
In some ways, a collection of gas molecules represents the simplest form of what? | [
"energy",
"life",
"protein",
"matter"
] | D | In some ways, a collection of gas molecules represents the simplest form of matter. Because the individual molecules are so far apart, they have only fleeting interactions with one another. In contrast, molecules that have clustered together to form a liquid or solid are constantly exerting forces on each other. In fact, it is only because of these attractive forces that molecular solids and liquids exist at all. In this lesson, we will look at some of the ways in which molecules and ions attract one another to form solids and liquids. |
SciQ | SciQ-5257 | cell-biology, neuroscience, histology
Although the paper mainly talks of the sorting of axonal and somatodendritic vesicles as seen in the picture, they also seem to apply for the RER which actually are the basis for Nissl's granules.
This structure excludes not only somatodendritic vesicles but also larger organelles, such as the Golgi complex and the rough ER, in effect constituting the cytoplasmic boundary for the somatodendritic and axonal domains..... The exclusion of the rough ER and Golgi complex, in addition to somatodendritic vesicles, at the PAEZ suggests that a common restriction mechanism may operate for all of these organelles.
Well, as you might have understood by now, it's not a matter of the size of the axon/ dendrite since same sized vesicles are being diverted in either direction and as previously mentioned, even mitochondria enter the axon.
The following is multiple choice question (with options) to answer.
Are vesicles larger or smaller than vacuoles? | [
"larger",
"narrower",
"smaller",
"wider"
] | C | Vesicles are much smaller than vacuoles and have a variety of functions. Some vesicles pinch off from the membranes of the endoplasmic reticulum and Golgi apparatus. These vesicles store and transport proteins and lipids. Other vesicles are used as chambers for biochemical reactions. |
SciQ | SciQ-5258 | human-anatomy
Title: Difference between Appendix and the Cecum? What's the difference between an appendix and a cecum, and what are their functions? In herbivores the Cecum is an area that stores plant matter and helps digest it via symbiotic bacteria. Carnivores have smaller Cecums because meat is easier to digest than plant matter. In humans the Cecum is also an anatomical landmark that delineates the change from small intestine (a digesting organ) to the large intestine (mostly a capacity/storage organ).
The Appendix is a small, previously thought "superfluous" fleshy worm-shaped organ at the junction between the small and large intestines. Recent research posits that the appendix is sort of a harbor for a person's gut flora that can re-populate the intestines should the existing bacteria die or get removed (diarrhea being the most common cause). It can also become infected, inflamed, and require surgery to remove (Appendicitis).
The following is multiple choice question (with options) to answer.
The duodenum is the first and the shortest part of what, and is where most chemical digestion takes place? | [
"rectum",
"small intestine",
"large intestine",
"stomach"
] | B | The duodenum is the first part of the small intestine. It is also the shortest part. This is where most chemical digestion takes place. Many enzymes and other substances involved in digestion are secreted into the duodenum. |
SciQ | SciQ-5259 | 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.
Which system consists of all the bones of the body? | [
"digestive system",
"nervous system",
"circulatory system",
"skeletal system"
] | D | The skeletal system consists of all the bones of the body. How important are your bones?. |
SciQ | SciQ-5260 | programming-challenge, rust
return horizontal * depth;
}
fn main() {
let inputs = read_inputs().expect("Input read correctly");
let answer = part1(&inputs);
println!("Answer: {}", answer)
}
Conclusion
Idiomatic, terse and fast Rust is often functional. Get to know functional style.
know your crates
The following is multiple choice question (with options) to answer.
What is rusting an example of? | [
"chemical change",
"Decomposition",
"contamination change",
"radiation change"
] | A | Comets carry materials in from the outer solar system. Comets may have brought water into the early Earth. Other substances could also have come from comets. |
SciQ | SciQ-5261 | molecules, atoms, mole
Title: Why is O2 enough to form a mole of Oxygen? I understand that this is the most basic knowledge of moles, however I'm still unsure - according to easy research, $\ce{O2}$ forms a mole of Oxygen. As a mole is $6.022*10^{23}$, exactly what on the periodic table can we use to find out that it's 2 Oxygen in one mole? Wouldn't it be $6.022*10^{23}$, instead of 2? $\rm O_2$ is the most common form of oxygen---the periodic table won't really tell you that.
Avogadro's number tells you how many particles there are in a mole.
There are $6.022\times 10^{23}$ O atoms in a mole of O atoms.
There are $6.022\times 10^{23}$ $\rm O_2$ molecules in a mole of $\rm O_2$.
Since you have 2 oxygen atoms in one $\rm O_2$ molecule, there are
$2\times 6.022\times 10^{23}$ O atoms in a mole of $\rm O_2$.
Do you see the difference?
The following is multiple choice question (with options) to answer.
What molecule consists of two atoms of hydrogen and one atom of oxygen? | [
"hydrogen peroxide",
"carbon monoxide",
"water",
"air"
] | C | Water is an example of a common chemical compound. As you can see in the Figure below , each water molecule consists of two atoms of hydrogen and one atom of oxygen. Water always has this 2:1 ratio of hydrogen to oxygen. Like water, all compounds consist of a fixed ratio of elements. It doesn’t matter how much or how little of a compound there is. It always has the same composition. |
SciQ | SciQ-5262 | bond, ionization-energy
The Polish chemist Kazimierz Fajans simplified this in his set of Fajans’ rules:
A compound will be covalent, if:
there is a high positive charge;
the anion is large; and/or
the cation is small.
A compound will be ionic, if:
there is a low positive charge;
the anion is small; and/or
the cation is large.
Note that in ambiguous cases such as $\ce{AlF3}$, (small cation, high positive charge but small anion) the rules fail to predict a mainly ionic compound, but correctly make us assume a rather high covalent character of said ionic bonds.
[1] Even beryllium forms rather covalent compounds most of the time. Due to the electronegativity difference of $2.5$ on the Pauling scale, we may just be able to consider solid $\ce{BeF2}$ as an ionic compound. All of these are borderline cases in one way or the other, though.
The following is multiple choice question (with options) to answer.
All compounds, whether ionic or covalent, must be what? | [
"metallic neutral",
"organic neutral",
"abnormal neutral",
"electrically neutral"
] | D | When chemists synthesize a new compound, they may not yet know its molecular or structural formula. In such cases, they usually begin by determining itsempirical formula, the relative numbers of atoms of the elements in a compound, reduced to the smallest whole numbers. Because the empirical formula is based on experimental measurements of the numbers of atoms in a sample of the compound, it shows only the ratios of the numbers of the elements present. The difference betweenempirical and molecular formulas can be illustrated with butane, a covalent compound used as the fuel in disposable lighters. The molecular formula for butane is C4H10. The ratio of carbon atoms to hydrogen atoms in butane is 4:10, which can be reduced to 2:5. The empirical formula for butane is therefore C2H5. The formula unit is the absolutegrouping of atoms or ions represented by the empirical formula of a compound, either ionic or covalent. Butane, for example, has the empirical formula C2H5, but it contains two C2H5 formula units, giving a molecular formula of C4H10. Because ionic compounds do not contain discrete molecules, empirical formulas are used to indicate their compositions. All compounds, whether ionic or covalent, must be electrically neutral. Consequently, the positive and negative charges in a formula unit must exactly cancel each other. If the cation and the anion have charges of equal. |
SciQ | SciQ-5263 | medicine
Kiekeboe 21: the Piri-Piri Pills, Page 17, strip 30. Author: Merho. Publisher: J.Hoste NV (currently part of Standaard Uitgeverij). Picture taken by Nate Kerkhofs on 16 september 2014.
It is in Dutch, but the names of the illenesses are clearly readable (since they're Latin anyway).
The doctor asks "what are you here for, madame? a cold, reumathism, headache?" right before this. The woman answers "no, doctor, I'm struggling with ... and also ... not to mention ... and a really annoying .... The doctor then replies "but madame, where did you get all those illnesses?" the woman replies "in my medical encyclopaedia!". Erythema multiforme (minor) can and does occur in a lot of people; while it is usually self-limited, it can recur, especially when the trigger is an unsuspected food.[1] How common is it? It is very common.
Necrobiosis Lipoidica is not uncommon in diabetics, less common but still found in non-diabetics. It can occur at any age, including the eighth decade. It also shows a sex predilection, being 3 times more common in women than in men.[2] How common is it? It is not rare.
Phlegmasia Alba and Cerulea Dolens[3] is serious and associated with deep vein thrombosis, which is an acute event. It is not uncommon, but it's not chronic. (More than 600,000 cases of venous thromboembolism are estimated to occur each year in the United States, all of which can lead to Phlegmasia Alba and Cerulea Dolens. How common is it? Luckily, not very. If the author is referring to garden-variety thrombophlebitis, though, that's a chronic problem, and not uncommon in the elderly. Thrombophlebitis is chronic and common enough.
I'm not going to address Metropathia Haemorrhagica, because, as you have noted, it's found in menstruating women.
The following is multiple choice question (with options) to answer.
Which is the most common sti (sexually transmitted infection) in the united states? | [
"AIDS",
"syphilis",
"giardia",
"chlamydia"
] | D | Chlamydia is the most common STI in the United States. As shown in the graph in Figure below , females are much more likely than males to develop chlamydia. Like most STIs, rates of chlamydia are highest in teens and young adults. |
SciQ | SciQ-5264 | physical-chemistry, reaction-mechanism, everyday-chemistry, experimental-chemistry
Title: Need reactants for a rocket I am doing a project in chemistry at the moment to build a rocket out of materials that can be easily bought and that react strongly to create thrust.
I was wondering if anyone knew a good chemical formula for my rocket fuel? I know lots of good fuels and reactants used in amateur rocketry however commercial fuels have been banned from the project.
Any help would be appreciated. Put some potassium nitrate $\ce{KNO3}$ plus powdered charcoal and sulfur in a mortar. Wet it carefully and grind the whole until you get a black homogeneous paste. Let it dry overnight in the mortar. The obtained black gun powder may be detached from the mortar with a wooden spoon. It is a safe rocket fuel. The proportions of the powders are defined by stoichiometry. They must allow the chemical reaction : $$\ce{2 KNO3 + 3 C + S -> K2S + 3 CO2 + N2}$$
I have done it many times with my students. It's a good exercice of stoichiometry. Never had an accident ! And remember : Never ! Never grind dry powders ! Grind as wet powders as possible ! In case of doubt add more water ! Pastes are even a better choice for grinding purposes !
The following is multiple choice question (with options) to answer.
What do all chemical reactions need to get started? | [
"expression energy",
"potential energy",
"activation energy",
"kinetic energy"
] | C | All chemical reactions, even exothermic reactions, need activation energy to get started. Activation energy is needed to bring reactants together so they can react. |
SciQ | SciQ-5265 | muscles, lungs, human-physiology
Title: Why is there smooth muscle in our bronchioles? Having muscle tissue in our bronchioles that can constrict seems like a poor choice for tissue. Why would our airway want to ever close up? Wouldn't it be more beneficial for our bronchioles to just remain open? There are at least two things to consider.
First, ability to limit airflow is a defense mechanism for animal. Imagine getting into area of some sort of toxic evaporation, e.g. CO2 cloud near volcano , then it makes sense to decrease delivery of toxin via lungs to minimum. As I understand, that is what an allergic asthma attack. (Sorry for not providing good enough source of that)
Secondly, you are incorrect in assuming that normal state is "dilated". Dilation of branchioles is sympathetic ("fight-and-fly") response of the nervous system to something like danger, that requires short-term boost in energy production. That is, by default, your airflow is limited. Probably, to limit amount of energy you effectively burn via oxygenation. But most importantly, you leave yourself a reserve in terms of oxygen supply for critical moments.
Some more information you might find here.
The following is multiple choice question (with options) to answer.
What organ does asthma periodically cause to narrow? | [
"lungs",
"liver",
"ovaries",
"intestines"
] | A | Asthma is a disease in which the air passages of the lungs periodically become too narrow, often with excessive mucus production. This causes difficulty breathing, coughing, and chest tightness. An asthma attack may be triggered by allergens, strenuous exercise, stress, or other factors. |
SciQ | SciQ-5266 | electrochemistry, metal
Title: Corrosion of a galvanic couple made with silver and gold If a bangle is made out of gold and silver, connected with each-other would there be corrosion happening?
If so, can it be explained using the galvanic series?
Also do those metals undergo oxidation under normal conditions? As you state, though silver is not very reactive, silver jewelry would corrode more rapidly when in contact with gold and a bit of sweat as electrolyte. Though the difference in electronegativity of pure gold and pure silver is 0.15V, and is considered acceptably corrosion resistant, commercial jewelry contains copper and other metals in the alloys. There is clearly evident corrosion in photos of copper/silver jewelry. According to the Victoria and Albert Museum staff, "All metals, with the exception of 24 carat gold, suffer the effects of corrosion."
However, in a bangle, physical abrasion is likely to cause more damage and loss of material than galvanic corrosion. Wear the jewelry and enjoy it, but it will not last forever.
The following is multiple choice question (with options) to answer.
Silver, gold, and copper all conduct what very well? | [
"microwaves",
"light",
"sound",
"electricity"
] | D | The electrical conductivity of a substance is a property that depends only on the type of substance. Silver, gold, and copper are excellent conductors of electricity, while glass and plastic are poor conductors. A larger or smaller piece of glass will not change this property. An intensive property is a property of matter that depends only on the type of matter in a sample and not on the amount. Other intensive properties include color, temperature, density, and solubility. |
SciQ | SciQ-5267 | sequence-alignment, phylogenetics, genome, phylogeny
Title: What is the most appropriate way to find the most recent common ancestor between two distantly related species I want to specifically find the common ancestor between a lobster and a humans. I suspect it was an aquatic worm of some description. But I want to know about the nervous system of this common ancestor. Because I've now posted several comments, I'll just roll them all up.
For background on the approaches used to identify most recent common ancestors and a high-level look at how animal taxonomy has been inferred, I suggest Lynch 1999.
I think that there are 2 interpretations of this question. If you are interested in just looking up a single MRCA of well-defined clades, such as lobster and human, here are some approaches:
Easy way:
Look at a tree diagram, e.g. this:
Find the tips that correspond to your species of interest (arthropods for lobster, chordata for humans).
Find where they join together in the diagram (the branch labeled "true coelom").
You have your answer, the MRCA is the group of organisms with a true coelom, coelomates.
A more involved way using a database
Go to this website.
Find the group of species 1 (arthropods, protostomes, etc. for lobster, chordata, deuterostomes etc. for human)
navigate around until you see the group containing the two groups (in this case listed as "bilateria"). In this case you are looking for the bilaterian common ancestor.
another database
Go to this website.
Point and click your way to a view where you see your 2 clades of interest (arthropods, chordates in this case). See figure.
Find where they join (in this case, it is less certain about the existence of a coelomate common ancestor, so it just says "bilaterians").
The following is multiple choice question (with options) to answer.
Pakicetus and rodhocetus are considered to be ancestors of modern what? | [
"primates",
"hominins",
"rodents",
"whales"
] | D | Pakicetus and Rodhocetus are considered to be ancestors of modern whales. Scientists still argue about how aquatic Pakicetus was, but Rodhocetus is considered to be a largely aquatic animal. Where is the nostril located on Pakicetus ?. |
SciQ | SciQ-5268 | thermodynamics, entropy
Title: Why does entropy increase when the difference in temperatures is decreased? From the Wikipedia article about Entropy (Source view via The Internet Archive):
In irreversible heat transfer, heat energy is irreversibly transferred from the higher temperature system to the lower temperature system, and the combined entropy of the systems increases.
If entropy were a measure of disorder, or randomness, or the amount of information needed to describe the microstates of a system, then it seems that when the difference in temperatures is high, entropy should be high. A temperature gradient in the systems is a form of ‘disorder’ hence should be a sign of higher entropy.
So why does entropy increase after the heat transfer, as the combined system approaches a uniform temperature? It seems to me like a state with less randomness or disorder. Temperature is a tricky concept, because a "uniform" temperature does not mean the system has a lot of order. Uniform temperature merely means the statistical distribution of particle velocities is homogenous.
Before the systems are combined, you know a fair amount about the system. For instance, you know particles on the "cold" side are going to stay on the cold side, and particles on the "warm" side are going to stay on the warm side. Informally, this means you know something about every particle in the system. Once you combine the systems, you no longer know where the particles are going to be, so there is more disorder to the system.
The following is multiple choice question (with options) to answer.
Chemical and physical changes in a system may be accompanied by an increase or a decrease in the disorder of the system, corresponding to an increase or decrease in what? | [
"entropy",
"enthalpy",
"volume",
"vibration"
] | A | Chemical and physical changes in a system may be accompanied by either an increase or a decrease in the disorder of the system, corresponding to an increase in entropy (ΔS> 0) or a decrease in entropy (ΔS < 0), respectively. As with any other state function, the change in entropy is defined as the difference between the entropies of the final and initial states: ΔS = Sf − Si. When a gas expands into a vacuum, its entropy increases because the increased volume allows for greater atomic or molecular disorder. The greater the number of atoms or molecules in the gas, the greater the disorder. The magnitude of the entropy of a system depends on the number of microscopic states, or microstates, associated with it (in this case, the number of atoms or molecules); that is, the greater the number of microstates, the greater the entropy. We can illustrate the concepts of microstates and entropy using a deck of playing cards, as shown in Figure 18.7 "Illustrating Low- and High-Entropy States with a Deck of Playing Cards". In any new deck, the 52 cards are arranged by four suits, with each suit arranged in descending order. If the cards are shuffled, however, there are approximately 1068 different ways they might be arranged, which corresponds to 1068different microscopic states. The entropy of an ordered new deck of cards is therefore low, whereas the entropy of a randomly shuffled deck is high. Card games assign a higher value to a hand that has a low degree of disorder. In games such as five-card poker, only 4 of the 2,598,960 different possible hands, or microstates, contain the highly ordered and valued arrangement of cards called a royal flush, almost 1.1 million hands contain one pair, and more than 1.3 million hands are completely disordered and therefore have no value. Because the last two arrangements are far more probable than the first, the value of a poker hand is inversely proportional to its entropy. We can see how to calculate these kinds of probabilities for a chemical system by considering the possible arrangements of a sample of four gas molecules in a two-bulb container (Figure 18.8 "The Possible Microstates for a Sample of Four Gas Molecules in Two Bulbs of Equal Volume"). There are five possible arrangements: all four molecules in the left bulb (I); three molecules in the left bulb and one in the right bulb (II); two molecules in each bulb (III); one molecule in the left bulb and three molecules in the right bulb (IV); and four molecules in the right bulb (V). If we assign a different color to each molecule to keep track of it for this discussion (remember, however, that in reality the molecules are indistinguishable from one another), we can see that there are 16 different ways the four molecules can be distributed in the bulbs, each corresponding to a particular microstate. As shown in Figure 18.8 "The Possible Microstates. |
SciQ | SciQ-5269 | organic-chemistry, physical-chemistry, biochemistry, alcohols
Title: Storage of Urine Not all may be favorable to this project, but I will explain what I am trying to do. I work at home, and instead of walking a moderate distance to the bathroom and loosing my focus, I've been, at times, peeing in a 3 Quart Poland Springs water bottle. If you take offense at this, please do not continue reading except to be helpful in the scientific goal. I know this subject won't suit many types of people, so just ignore it if that is your case.
I noticed first of all that urine is not at all as sterile as people say that it is. The rate of growth of bacteria is relatively slow, but as a precaution, I found the need to use additional measures to prevent the growth of bacteria. I settled on the following method: I have two bottles and I add to each bottle about enough salt as can be soluble in the urine and sometimes maybe a little more. The one bottle then fills up throughout the day and is emptied, washed, and refilled with salt. The salt helps to kill the bacteria which would be lingering in the empty bottle. The next day, the bottle stays empty and the other is used.
I would add that I discovered that the bacteria (without the salt) does not usually grow unless the bottle is left with urine for two days. After this, however, that same bottle (without the salt) would retain the bacteria and immediately grow, if used again.
This system works relatively well, so long as it is done every day. It will even withstand 2 days with only moderate growth. (If I should leave it by mistake for longer it can get ugly). Nevertheless, I am still looking to improve upon this. One reason is that, if I drink less water or relieve myself normally, the bottle does not fill in one day. I am looking for someone with knowledge of chemistry to help me find a substance that can be added to this solution which fits a number of common sense criteria. I will also add a list of the substances that I have tried or already considered.
Necessary qualities
The following is multiple choice question (with options) to answer.
What is the only way to completely avoid stis? | [
"contraceptive use",
"avoid sexual contact",
"oral sex",
"cover your mouth"
] | B | The only completely effective way to prevent infection with STIs is to avoid sexual contact and other risky behaviors. Using condoms can lower the risk of becoming infected with STIs during some types of sexual activity. However, condoms are not foolproof. Pathogens may be present on areas of the body not covered by condoms. Condoms can also break or be used incorrectly. |
SciQ | SciQ-5270 | physical-chemistry, electrochemistry, aqueous-solution, solutions
Title: What is the interaction between dissolved ions of opposite valence in a solution at rest? NaCl is dissolved in water. Ions sodium and chloride are sufficiently free from each other so that they may occupy different regions of the solution after an active transport process through a membrane, or a mere electric field is in place.
They still act upon each other, and a membrane voltage is set by oppositely charged ions lining its interior and exterior surfaces.
So my question is this: how free are those ions in a uniform solution at equilibrium? Aren't they actually forming pairs of watered ions, although weakly bound? Can they form even bigger clusters, be them of short lifetime?
Note: I originally asked this on Physics SE but after several weeks I have received no answer nor any other kind of reaction, so I am trying Chemistry SE now. The answer is: it depends. Dissolution of a salt implies that the entropy gained exceeds the cost of breaking lattice interactions (the solution enthalpy, assuming it is positive). Electrostatic interactions compete with kT (thermal jostling). Under physiological conditions, long range interactions are strongly screened by intervening solvent molecules and other ions. At best ions are subject to an effective potential due to distant ions, in particular between segregated charges as in the cases you present (e.g. on opposite sides of a membrane).
However, ionic solutions are generally regarded as "non-ideal". This means that interactions between the ions and with the solvent cannot be dismissed. At high salt concentration ion pairing will be encouraged. Above the solubility limit salt precipitation will occur, preceded by formation of clusters (seeds). If an ion has multiple charges, then electrostatic interactions will be stronger and pairing will be encouraged. Some metal ions form permanent ligand complexes that can attenuate the overall charge or distribute it over the complex, and the ligands can form a "cage" about the central ion, altering the interaction potential with solvent and other ions. The effect of temperature is complex. The entropic cost of association increases with T, but the dielectric constant of the solvent tends to decrease also.
If you are interested in reading on ion-pairing in NaCl solutions you may want to start with Ref. 1. It explains that association is negligible in dilute solutions:
The following is multiple choice question (with options) to answer.
What is an ion that is in common to both salts in a solution? | [
"regular ion",
"strong ion",
"common ion",
"native ion"
] | C | This situation describes the common ion effect. A common ion is an ion that is in common to both salts in a solution. In the above example, the common ion is Ca 2+ . The common ion effect is a decrease in the solubility of an ionic compound as a result of the addition of a common ion. Adding calcium ion to the saturated solution of calcium sulfate causes additional CaSO 4 to precipitate from the solution, lowering its solubility. The addition of a solution containing sulfate ion, such as potassium sulfate, would result in the same common ion effect. |
SciQ | SciQ-5271 | evolution, biochemistry, life-history
Title: Was iron important for the first life on Earth? Some ions or compounds are thought not to have become involved or important in the metabolism of living organisms until some time after certain mutations took place. For instance, early life is thought to selectively allow calcium ions through its membrane, but eventually also evolved the ability to selectively allow sodium ions, specifically through a mutation that lead to a change in the composition of a channel protein from glutamine to lysine.
Currently, iron is involved in oxidations involving molecular oxygen, such as in cytochromes and clearly holds a key role in modern life, despite that free iron or even ferric compounds are rarely accessible. From my understanding, iron most likely became incorporated into the metabolism of microbes after during/after aerobic organisms had developed, but this does not rule out the possibility that iron was involved earlier on. So, I am wondering if iron was involved in early life, and details on how would be appreciated. Cyanobacteria require iron for photosynthesis and can be found as fossil stromatolites dating back to 3.5 billion years ago. Stromatolites are layered structures made up of cyanobacteria and sediment.
Source: https://en.wikipedia.org/wiki/Stromatolite
Modern stromatolites can be found at Shark Bay in Australia, Chetumal Bay in Belize, and Laguna Bacalar in the Yucatan Peninsula.
Cyanobacteria are also believed to have evolved into the first microbes to produce oxygen by photosynthesis, which was a catalyst for the Great Oxygenation Event which occurred around 2.45 billion years ago.
The following is multiple choice question (with options) to answer.
Prokaryotes and the nitrogen cycle nitrogen is a very important element for life because it is part of proteins and this? | [
"nerve cells",
"nucleic acids",
"nuclear forces",
"molecules"
] | B | Prokaryotes and the Nitrogen Cycle Nitrogen is a very important element for life because it is part of proteins and nucleic acids. It is a macronutrient, and in nature, it is recycled from organic compounds to ammonia, ammonium ions, nitrate, nitrite, and nitrogen gas by myriad processes, many of which are carried out only by prokaryotes. As illustrated in Figure 22.19, prokaryotes are key to the nitrogen cycle. The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen from the air, but this nitrogen is not usable by plants, which are primary producers. Gaseous nitrogen is transformed, or “fixed” into more readily available forms such as ammonia through the process of nitrogen fixation. Ammonia can be used by plants or converted to other forms. Another source of ammonia is ammonification, the process by which ammonia is released during the decomposition of nitrogen-containing organic compounds. Ammonia released to the atmosphere, however, represents only 15 percent of the total nitrogen released; the rest is as N2 and N2O. Ammonia is catabolized anaerobically by some prokaryotes, yielding N2 as the final product. Nitrification is the conversion of ammonium to nitrite and nitrate. Nitrification in soils is carried out by bacteria belonging to the genera Nitrosomas, Nitrobacter, and Nitrospira. The bacteria performs the reverse process, the reduction of nitrate from the soils to gaseous compounds such as N2O, NO, and N2, a process called denitrification. |
SciQ | SciQ-5272 | physical-chemistry, kinetic-theory-of-gases, statistical-mechanics
Title: Derivation of mean kinetic energy I read from a book that average kinetic energy is equal to $3kT/2$ where $k$ is Boltzmann's constant and $T$ is the kelvin temperature. I don't know how the formula was derived. Any help to gain insights into the derivation of this formula would be helpful. A simple validation
The result you quoted is the average translational kinetic energy for an ideal gas.
First, let's sketch out a rough derivation for the average kinetic energy of a particles of an ideal gas using nothing more than high school physics.
The gas molecules just undergo translations, and don't rotate/vibrate. Also, they don't interact with each other.
Imagine a rectangular box which contains an ideal gas; the gas molecules have a speed $v_x$ in the $x$-direction. Since the box has a uniform cross-section of area $A$, a volume element spanned by a gas molecule in the box is $V'= |v_x\Delta t|A$. On average half the molecules move to the right, and half the molecules move to the left, since there is no preferred direction of motion. Thus, the number of molecules colliding with the container walls is
no. of molecules $= \frac{1}{2}.\frac{nN_a}{V}.|v_x\Delta t|A$
The momentum transferred per molecule is $2mv_x$, so the total momentum transferred is $ \Delta P = \frac{1}{2}.\frac{nN_a}{V}.|v_x\Delta t| 2mv_x$
Since force is rate of change of momentum, $F = \lim_{\Delta t \to 0} \frac{\Delta P}{\Delta t} = \frac{nMAv_x^2}{V}$
Pressure is force per unit area, so the average pressure is $P = \frac{nM \langle v_x^2\rangle}{V}$
The following is multiple choice question (with options) to answer.
What property is a measure of the average kinetic energy of molecules? | [
"velocity",
"mass",
"temperature",
"density"
] | C | Temperature is a measure of the average kinetic energy of molecules. Consider a mixture of hydrogen and oxygen gas at a certain temperature. Use the formula for kinetic energy to explain why the hydrogen molecules move faster than the oxygen molecules. Then explain why there’s no hydrogen in the earth’s atmosphere, and why the moon has no atmosphere at all. |
SciQ | SciQ-5273 | measurements, non-linear-systems, noise
Title: How to express the "size" of measurement noise in a dynamical system I have a discrete [non-linear] dynamical system $x_{n+1} = f(x_{n})$. There is measurement error, so my observables are a time series $\left\{ \hat{x}_{n}\right\} _{n=1}^{N}$ where $\hat{x}_{n}=x_{n}+\eta_{n}$ and $\eta_{n}\sim\mathcal{N}\left(0,\sigma^2\right)$ i.i.d.
It seems to me that $\sigma$ is not enough to convey the "size" of the noise, which should be somehow expressed in comparison to the size of the dynamics. Is there a canonical way of doing this? Perhaps as a fraction of the dynamics' size, but what would that be? The range of the time series? Its standard deviation? What if it were multiple separate time series originating from the same dynamical system (perhaps with different parameters) and which are subjected to the same type of measurement noise? should it be measured as a fraction of the size of phase space? Any such "size" parameter trying to compare the noise to the dynamics of the system would have to be intrinsically tied to the behavior of f(x) and what you seek to convey with it.
As an extreme example, consider a dynamic system with a discontinuity. As the system gets very close to that discontinuity, it becomes critically important to know whether the system appears to have fallen off the edge because it actually did, or if that's just a measurement error.
On the other hand, if I have a non-linear system which I am trying to make as linear as possible, concepts like Total Harmonic Distortion become very applicable.
If I'm trying to achieve a goal state, I could measure how much this noise affects my final state. For example, if my goal is to land on the moon, I can propagate these errors forward and see how large of a "landing patch" I end up with (or whether I will land at all!)
The following is multiple choice question (with options) to answer.
A measure of the disorder of a system is called its what? | [
"function",
"entropy",
"lose",
"spectral"
] | B | Summary A measure of the disorder of a system is its entropy (S), a state function whose value increases with an increase in the number of available microstates. Areversible process is one for which all intermediate states between extremes are equilibrium states; it can change direction at any time. In contrast, anirreversible process occurs in one direction only. The change in entropy of the system or the surroundings is the quantity of heat transferred divided by the temperature. The second law of thermodynamics states that in a reversible process, the entropy of the universe is constant, whereas in an irreversible process, such as the transfer of heat from a hot object to a cold object, the entropy of the universe increases. |
SciQ | SciQ-5274 | -plane. The horizontal distance the projectile travels is called the range. The projectile covers the same horizontal distance reaching its maximum height as it does falling from its maximum height back to the ground. Sqrt((x * x) + (y * y)); This is the equation of a parabola which is symmetric about the y-axis. 80665 m/s²). 95m (the intial horizontal displacement is 0), the angle of release is 35 degrees and the range of the projectile (or the horizontal displacement at impact) is 90. However, this takes advantage of the fact that horizontally, acceleration is Characteristics of a Projectile's Trajectory · Horizontal and Vertical Components The above equations work well for motion in one-dimension, but a projectile is A projectile is an object that is given an initial velocity, and is acted on by gravity. Note: Use g = 9. However, the distance it travels vertically (on the Y-axis) is given as y = vtsinΦ – (½)gt². The time for projectile motion is completely determined by the vertical motion. Trajectory of projectile motion when u is intial speed inclined Ф angle with horizontal the equation of projectile is : y = xTanФ - gx²/ 2u²Cos²Ф and the given equation is : y = √3x - gx²/2 on comparing both the equations ,we get TanФ = √3 so, Ф = 60° HENCE, the angle of projectile is 60° and 2u²Cos²Ф = 2 so u²Cos²Ф = 1 u²cos²60° = 1 Horizontal distance traveled Horizontal range = OR = s x (t = t f) g u g u u θ θ θ sin2 cos 2 sin 2 = = (8) Half horizontal range = OA = g u 2 2sin2θ (9) By using different angle of projectile θ, we can change the horizontal distance OR. Objects such as a basketball are released into the air at an angle and as such have vertical and horizontal velocity. Equation 9 thus becomes: Equation 10: Now we can use Equations 8 and 10 to plot the motion of a projectile in the (x,y) plane. Air Resistance. Projectile motion is considered here with the following approximations: 1. x = distance travelled by the object in horizontal direction in time t y = distance travelled by the object in vertical direction in time t Now the velocity
The following is multiple choice question (with options) to answer.
What influence does the horizontal motion of a projectile have on free fall? | [
"vertical",
"decrease acceleration",
"increase acceleration",
"none"
] | D | The horizontal motion of a projectile does not influence its free fall. |
SciQ | SciQ-5275 | evolution, speculative
Title: Why Didn't Evolution Cause the Human Body to become Streamlined? If streamlining makes movement/locomotion quicker and easier, why didn't the apes evolve into life-forms that had streamlined bodies (much like fish)?
If streamlining makes movement/locomotion quicker and easier, why didn't the apes evolve into life-forms that had streamlined bodies (much like fish)?
As with everything in Evolutionary Biology, you must ask yourself: Gain vs. Cost?
In your specific case, the Gain is very little. Air isn't nearly as dense as water, so a streamlined form won't show a major benefit unless the organism is traveling very, very quickly. This is why you see it in birds; raptors can travel over 100mph while diving, and at those speeds small changes in drag can mean the difference between dinner and starving. Smaller birds often make very quick turnabouts and changes in direction mid-flight where, again, small changes in efficiency can mean the difference between life and death. The cost was is worth it.
For apes and monkeys, moving very quickly isn't a case of living or dying. That's what we evolved opposable thumbs and prehensile feet(/tails) for. You don't need to run fast when you can climb a tree and simply get away from any predators on the ground. After we came down from the trees permanently, our larger brains allowed us to use tools to fend off predators - which, again, is much simpler than evolving an aerodynamic form that won't make a difference until you're running at the speed of a car.
So, in lieu of becoming a land-shark, we have hands that can use keyboards and minds that can invent the keyboard. Unfortunately, while the gains are many, the costs do include both a very long period of time where humans are helpless without parents, and an absolutely terrible form of locomotion with our upright stance on forward-pointing knees. Though you won't catch Cheetahs digging sewers anytime soon.
The following is multiple choice question (with options) to answer.
Larger animals expend more of what to achieve locomotion? | [
"energy",
"neurons",
"time",
"distance"
] | A | |
SciQ | SciQ-5276 | orbitals
Title: Difference between subshell and sub-subshell? I consider the s p d f orbitals as a subshell, but I have heard about the term sub-subshell. what is the difference between these two? As you pointed out the the s, p, d, and f denoted subshells of atoms.
The term sub-subshells is very uncommon. I did find a couple of uses.
Materials Science
By G. K. Narula, K. S. Narula, V. K. Gupta
pdf file about Modern Atomic Mechanical Theory, page 24
What the authors are noting is that the 2p subshell will have three orbitals which can support two electrons each. Each of these three orbitals is being referred to as a sub-subshell.
As I said it seems a very uncommon term, and I'd suggest you avoid using it.
The following is multiple choice question (with options) to answer.
Subshells are subdivisions of what groupings of electrons that can be found surrounding atoms? | [
"orbitals",
"isotopes",
"analogous",
"globals"
] | A | Carbon (atomic number 6) has six electrons. Four of them fill the 1s and 2s orbitals. The remaining two electrons occupy the 2p subshell. We now have a choice of filling one of the 2p orbitals and pairing the electrons or of leaving the electrons unpaired in two different, but degenerate, p orbitals. The orbitals are filled as described by Hund’s rule: the lowest-energy configuration for an atom with electrons within a set of degenerate orbitals is that having the maximum number of unpaired electrons. Thus, the two electrons in the carbon 2p orbitals have identical n, l, and ms quantum numbers and differ in their ml quantum number (in accord with the Pauli exclusion principle). The electron configuration and orbital diagram for carbon are:. |
SciQ | SciQ-5277 | 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.
The number of moles of solute in 1 kg of solvent is defined as what? | [
"kilocalorie",
"pollenation",
"singularity",
"molarity"
] | D | An alternative way to define the concentration of a solution is molality, abbreviated m. Molality is defined as the number of moles of solute in 1 kg of solvent. How is this different from molarity? Would you expect a 1 M solution of sucrose to be more or less concentrated than a 1 m solution of sucrose? Explain your answer. What are the advantages of using solutions for quantitative calculations?. |
SciQ | SciQ-5278 | homework, plant-physiology, plant-anatomy
and 'Vascular Plants = Winning! - Crash Course Biology #37'
https://youtu.be/h9oDTMXM7M8?t=373
[5] Osmosis (water compensating solutes) "In Da Club - Membranes & Transport: Crash Course Biology #5"
https://youtu.be/dPKvHrD1eS4?list=PL3EED4C1D684D3ADF&t=148
Ian (and dad <= all errors and approximations are his :) ).
The following is multiple choice question (with options) to answer.
What is the name for the pores in leaves that allow a plant to retain water or exchange gases? | [
"chloroplasts",
"neurons",
"rhizomes",
"stomata"
] | D | To allow the plant to retain water and exchange gases, small pores (holes) in the leaves called stomata also evolved ( Figure below ). The stomata can open and close depending on weather conditions. When it's hot and dry, the stomata close to keep water inside of the plant. When the weather cools down, the stomata can open again to let carbon dioxide in and oxygen out. |
SciQ | SciQ-5279 | rotation
Title: Cycles that are longer than the year, but less than 1000 years Wondering what primary astronomical cycles there are that are greater than a year (which is a cycle around the sun), but less than 1000 years-ish (on that scale). There is the cycle of the moon phases too, and the cycle of the earth making a full rotation (a day). But I wonder if there are any cycles at a bigger-than-a-year scale, but not too big. I guess there's also the cycle of a stars life (but that is kind of a big scale, on the order of billions of years), but I am more wondering in terms of rotation what sort of cycles there are. I guess there is another one, Axial Precession, but that is a bit large such as on the order of tens of thousands of years. Maybe there are some cycles of the planets in which they are visible from earth, or of their moons, or of comets, or of nearby stars or that kind of thing.
If there were ones around each of these points that would be nice: 2, 5, 10, 20, 50, 100, 500, or 1000 years sort of thing.
Basically I am looking for "interesting" or "popular" cycles rather than just picking any of them (since every planet and moon has an orbital period). I am looking for ones that (a) we can observe most easily either directly without a telescope, or with a simple telescope/binoculars, and/or (b) have significance of some kind historically perhaps. If there is one that is historically significant or historically popular (say something Newton or Kepler talked about for example) but is difficult to see, that would be okay too.
The following is multiple choice question (with options) to answer.
What is part of a cycle that holds an element or water for a long period of time called? | [
"a reservoir",
"a holding tank",
"a ditch",
"homeostasis"
] | A | Part of a cycle that holds an element or water for a long period of time is called a reservoir . The ocean is a reservoir for water. The deep ocean may hold water for thousands of years. |
SciQ | SciQ-5280 | 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.
What theory states that all organisms are made up of one or more cells? | [
"the molecular anatomy theory",
"the micro theory",
"the cell theory",
"the atomic theory"
] | C | According to the cell theory, all organisms are made up of one or more cells. Cells are the sites where all life processes take place. Cells come only from pre-existing cells. New cells forms when existing cells divide. |
SciQ | SciQ-5281 | genetics, homework, meiosis
This random alignment at the equator makes it so that during anaphase, random proportions of maternal and paternal chromosomes get assorted into each of the resulting daughter cells. Some cells could get more maternal chromosomes and the other would get more paternal chromosomes, and vice versa. On the other hand, they could get similar amounts. Independent assortment increases genetic variation by allowing daughter cells to each randomly receive a different proportion of paternal and maternal chromosomes.
In conclusion, crossing over and independent assortment (sometimes called random assortment) are different independent processes that both lead to an increase in genetic diversity.
References
Reece, Jane A., Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, and Robert B. Jackson. “Meiosis and Sexual Life Cycles." Campbell Biology. 10th ed. Glenview: Pearson, 2014. 252-266. Print.
https://www.quia.com/files/quia/users/dschnepp/Meiosis/Metaphase-I
The following is multiple choice question (with options) to answer.
What does rearrangements of chromosomes contribute to the emergence of? | [
"clones",
"extinction",
"fewer species",
"new species"
] | D | |
SciQ | SciQ-5282 | astrophysics, fusion
Title: Will Helium any time in the future make up the most part of the Univers? as Stars are using Nuclear Fusion to produce energy, will there theoretically be a time in the future of the universe where helium will take over hydrogens first place as the most common element in the universe? It is actually probable that this will happen. It's not easy to work out when in the universes' history this will happen, but some scientists (by looking at the ratio of hydrogen/helium in the universe after 13.7 billion years of universal evolution) estimate that helium, by the fusion of hydrogen, will become more abundant than hydrogen in about 1,000 to 1,000,000 times the current age of the universe (in about 10,000,000,000,000 to 10,000,000,000,000,000 years).
Then following similar periods of time, the next most abundant element will be carbon by the fusion of helium, and then similarly oxygen (maybe) by the fusion of carbon and helium and so on.
The following is multiple choice question (with options) to answer.
In the universe as a whole, what is the most common element? | [
"oxygen",
"carbon",
"helium",
"hydrogen"
] | D | Abundance The elements vary widely in abundance. In the universe as a whole, the most common element is hydrogen (about 90% of atoms), followed by helium (most of the remaining 10%). All other elements are present in relatively minuscule amounts, as far as we can detect. On the planet Earth, however, the situation is rather different. Oxygen makes up 46.1% of the mass of Earth’s crust (the relatively thin layer of rock forming Earth’s surface), mostly in combination with other elements, while silicon makes up 28.5%. Hydrogen, the most abundant element in the universe, makes up only 0.14% of Earth’s crust. Table 2.1 "Elemental Composition of Earth" lists the relative abundances of elements on Earth as a whole and in Earth’s crust. Table 2.2 "Elemental Composition of a Human Body" lists the relative abundances of elements in the human body. If you compare Table 2.1 "Elemental Composition of Earth" and Table 2.2 "Elemental Composition of a Human Body", you will find disparities between the percentage of each element in the human body and on Earth. Oxygen has the highest percentage in both Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-5283 | organic-chemistry, mixtures
Title: Would Oxygen Gas and Ozone be a pure substance together? If I have oxygen gas and ozone ($\ce{O2 + O3}$) together would it be considered a pure substance or a mixture?
And would pure substances always have the same molecular structure? Ozone is highly reactive and unstable, while dioxygen is stable. There do not combine to form a compound. So, clearly it is a mixture.
To answer the second part of the question, "And would pure substances always have the same molecular structure?", first a Wikipedia definition on substances, to quote:
A chemical substance is a form of matter having constant chemical composition and characteristic properties.[1][2]...
Chemical substances can be simple substances[4], chemical compounds, or alloys. Chemical elements may or may not be included in the definition, depending on expert viewpoint.[4]
Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water...
However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical.
And further:
A chemical substance may well be defined as "any material with a definite chemical composition" in an introductory general chemistry textbook.[5] According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. But, there are exceptions to this definition; a pure substance can also be defined as a form of matter that has both definite composition and distinct properties.[6] The chemical substance index published by CAS also includes several alloys of uncertain composition.[7] Non-stoichiometric compounds are a special case (in inorganic chemistry) that violates the law of constant composition, and for them, it is sometimes difficult to draw the line between a mixture and a compound, as in the case of palladium hydride. Broader definitions of chemicals or chemical substances can be found, for example: "the term 'chemical substance' means any organic or inorganic substance of a particular molecular identity, including – (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature".[8]
The following is multiple choice question (with options) to answer.
What are substances that cannot be broken down into simpler substances with different properties called? | [
"atoms",
"compounds",
"molecules",
"elements"
] | D | Elements are substances that cannot be broken down into simpler substances with different properties. |
SciQ | SciQ-5284 | solubility, gas-laws, pressure, ideal-gas
Title: Dissolution of CO2 in water The following question has troubled me for a while.
For gases that are slightly soluble in water, there is a proportional relationship between the partial
pressure, $P$, and the mole fraction, $x$, of the gas molecules dissolved in water (Henry's law):
$\ce{P = k_H*x}$
A container ($V$ = $570$ $mL$) is filled with water ($V_l$ = $500$ $mL$) and pressurized with $CO_2$ gas ($P_0$ = $50$ $atm$), before it is allowed to stand at $10^\circ$C until the vapor–liquid equilibrium is established.
Calculate the pressure of $CO_2$ $[atm]$ in the container and the amount of $CO_2$ $[mol]$ dissolved in the water. The Henry coefficient of $CO_2$ for water at $10^\circ$C is $k_H$ = $0.104 × 10^4$ $atm$, and we will consider that the reaction of $CO_2$ in water can be ignored.
I did the following calculations but I am unsure with the outcome.
$\ce{n_{total}\approx n(H_2O) = \frac{\rho V}{M(H_2O)} = 27.753 mol}$
$\ce{x = \frac{P_0}{k_H} = 0.048077}$
$\ce{n(CO_2)_{dissolved} = x*n_{total} \approx 1.3343 mol}$
$\ce{P_1 = \frac{nRT}{V} = \frac {1.3343*0.0831451*1.01325*283}{0.570} = 55.8 atm}$
Shouldn't the final pressure be smaller than the initial pressure ($50$ $atm$)? Assumptions:
The following is multiple choice question (with options) to answer.
What gas, that is dissolved in solution, is used in carbonated beverages? | [
"hydrogen peroxide",
"carbon dioxide",
"carbon monoxide",
"phosphorus dioxide"
] | B | Carbonated beverages contain carbon dioxide gas that is dissolved in solution. Do you think a carbonated beverage is a mixture or a pure substance? Explain. |
SciQ | SciQ-5285 | biochemistry, pathology, teeth, decay, minerals
Title: How does fluoride prevent tooth decay? Fluoride is a common active ingredient in tooth paste to prevent dental caries. It is also added or removed from the water supply in some communities for the same reason, but in children only.
My understanding is that the fluoride in tooth paste reacts with minerals in saliva then bonds to the tooth enamel. The fluoride in water is ingested and is somehow added to the developing bones and teeth of growing children, to the benefit of making decay resistant teeth.
What is the biochemical pathway of each process? A perfect answer will also discuss fluorosis and when that occurs and why. Your understanding is correct to some extent. Tooth enamel mostly consists of a mineral called hydroxyapatite ($\ce{Ca_{10}(PO4)6(OH)2}$) (Staines et al, 1981). Though this makes enamel the strongest material in the body, it is susceptible to degradation. In acidic environment, hyrdoxyapatite gets dissolved and leads to cavities (Brown, p. 688). The reaction is:
$\ce{Ca_{10}(PO4)6(OH)2_{(s)}~+~8~H+_{(aq)} -> 10~Ca^{2+}_{(aq)}~+~6~HPO4^{2-}_{(aq)}~+~2~H2O_{(l)}}$
To overcome this, fluoride is added in toothpastes. Fluoride ($\ce{F-}$) reacts with hydroxyapatite of enamel to form fluoroapatite via demineralization and remineralization cycle. The 3 main mechanisms through which it happens are (Rošin-Grget et al, 2013):
Iso-ionic exchange of $\ce{F-}$ for $\ce{OH-}$ in apatite:
$\ce{Ca_{10}(PO4)6(OH)2~+~2~F- -> Ca_{10}(PO4)6F2~+~2~OH-}$
The following is multiple choice question (with options) to answer.
Fluoride ion is widely used in water supplies to help prevent what? | [
"bacteria",
"tooth decay",
"chlorine taste",
"rust"
] | B | Fluoride ion is widely used in water supplies to help prevent tooth decay. Chloride is an important component in ion balance in blood. Iodide ion is needed by the thyroid gland to make the hormone thyroxine. |
SciQ | SciQ-5286 | biochemistry, proteins, amino-acids
Title: Arrangement of Amino Acids in the Protein alphabet I am a software engineer with little knowledge of molecular biology. However I am trying to understand some bioinformatics computer code where the protein alphabet appears to be represented as the following string, with each of the twenty amino acid constituents of protein:
ACDEFGHIKLMNPQRSTVWY
The code appears to define a second string in which the first is reordered as:
DEKRHNQSTPGAVILMCFYW
I am not sure of the biological significance of this. Does this reordering represent some specific interaction between these molecules? As suggested by tyersome's comment, the amino acids are grouped by their physiochemical properties. Let's add some commas:
DE,KRH,NQ,ST,PGAVIL,MC,FYW
aspartic acid (D) and glutamic acid (E) are acidic
lysine (K), arginine (R), and histidine (H) are basic
asparagine (N) and glutamine (Q) are amidic
serine (S) and threonine (T) are hydroxylic
proline (P), glycine (G), alanine (A), valine (V), isoleucine (I), and leucine (L) are aliphatic
methionine (M) and cysteine (C) are sulfur-containing
phenylalanine (F), tyrosine (Y), and tryptophan (W) are aromatic
My source is this graphic.
The following is multiple choice question (with options) to answer.
Amino acids are joined together to form a chain at what molecular structure? | [
"chloroplasts",
"DNA",
"chromosomes",
"ribosomes"
] | D | At the ribosome, the amino acids are joined together to form a chain of amino acids. |
SciQ | SciQ-5287 | physical-chemistry, phase-transition, states-of-matter, matter
What phases are available to what material is studied in materials science and there are books of tables on the topic. As you might guess by now, one can get arbitrarily detailed...
By the way, Helium also has more than two phases, as there is also a superfluid phase. All other materials can be made solid at appropriately low temperatures with potentially higher-than average pressure.
Finally, compound materials such as wood usually are not considered to make phase transitions as a whole, since the different materials that wood is made of might behave very differently at different temperatures/pressures.
The following is multiple choice question (with options) to answer.
What is the name of the science that studies matter and the changes material substances undergo? | [
"geology",
"physics",
"biology",
"chemistry"
] | D | Summary Chemistry is the study of matter and the changes material substances undergo. It is essential for understanding much of the natural world and central to many other scientific disciplines, including astronomy, geology, paleontology, biology, and medicine. |
SciQ | SciQ-5288 | thermodynamics, pressure, temperature
Title: Relations between pressure and temperature I have several questions concerning thermodynamics and I order them in 4 points that may be related:
What's the difference between heat and work at the atomic level? Isn't heat simply work between particles colliding with different momentum against each other?
Consider a chamber containing a gas. Does an increase of pressure also increases the temperature of the gas? Is that a result of the mechanical action that puts the piston to move delivering energy to the gas through work?
But if one is able to displace the piston a little bit so that during this process no collision happens there will be no energy delivered, and the temperature doesn't rise. Is that possible?
Excluding water and other special materials, why does a increase of pressure over a solid rises is melting point?
My teacher said that pressure would decrease the molecules motion, so in order to melt the solid we should give more energy through heat. Is this correct? If yes, then see the link referred on the $4^{th}$ point (the document says that pressure rises temperature)
The inner core of the Earth is solid but is also at higher temperatures than the liquid outer core. I did some research and is often stated that pressure is the reason why the inner core is solid. But returning to the $3^{rd}$ point, if the pressure reduces the motion of the particles, how can the inner core have material with higher temperatures (i.e. particles with higher average kinetic energy)?
In this link the article states that pressure over the material inside earth increases the temperature. However if the pressure doesn't reduce the particles motion, then how can particles that jiggle so much be in the solid state? I'll give brief answers to your questions. If you need more detail, you should ask your questions separately.
What's the difference between heat and work at the atomic level? Isn't heat simply work between particles colliding with different momentum against each other?
The following is multiple choice question (with options) to answer.
Which process changes rocks by heat and pressure? | [
"metamorphism",
"Changes",
"weathering",
"sediments"
] | A | Metamorphism changes rocks by heat and pressure. These agents create an entirely new type of rock. Metamorphism changes rocks physically and/or chemically. |
SciQ | SciQ-5289 | molecular-biology, cell-biology, immunology
Title: MHC restricted peptide What is an MHC restricted peptide?
I got this definition from wikipaedia, but cannot exactly extract what the phrase MHC restricted peptide means.
MHC-restricted antigen recognition, or MHC restriction, refers to the fact that a given T cell will recognize a peptide antigen only when it is bound to a host body's own MHC molecule. Normally, as T cells are stimulated only in the presence of self-MHC molecules, antigen is recognized only as peptides bound to self-MHC molecules.
The following is multiple choice question (with options) to answer.
What is defined as an antigen that causes an allergy? | [
"a disinfectant",
"an expectorant",
"a pollutant",
"an allergen"
] | D | An antigen that causes an allergy is called an allergen. |
SciQ | SciQ-5290 | biochemistry
Another important difference with respect to resulting polymers formed from these bonds - polysaccharides, in contrast to proteins and nucleic acids, form branched as well as linear polymers
α-Amylose is a linear polymer of several thousand glucose residues linked by α(1 >4) bonds. Note that although α-amylose is an isomer of cellulose, it has very different structural properties. This is because cellulose’s β-glycosidic linkages cause each successive glucose residue to flip 180° with respect to the preceding residue, so that the polymer assumes an easily packed, fully extended conformation.
Peptide bond
The resulting linkage formed when α-amino acids polymerize, through the elimination of a water molecule is known as a peptide bond (sometimes called an amide bond):
Peptide bond (shown in red)
Glycosidic bonds between monosaccharide units are the basis for the formation of oligosaccharides and polysaccharides.
The glycosidic bond is therefore the carbohydrate analog of the peptide bond in proteins. (The bond in a nucleoside linking its ribose residue to its base is also a glycosidic bond)
The following is multiple choice question (with options) to answer.
What can be linked together to form disaccharides or polysaccharides? | [
"monosaccharides",
"nitrates",
"amino acids",
"carbohydrates"
] | A | Monosaccharides can be linked together to form disaccharides or polysaccharides. |
SciQ | SciQ-5291 | evolution, molecular-biology, molecular-evolution, abiogenesis
The issue isn't actually as clear-cut as it may seem, since there is a very wide unknown space between what we consider the most archaic forms of life, and any entity that could plausibly arise via purely abiotic processes; every theory of abiogenesis does assume that a lot of the features we consider essential to life must have arisen after some kind of replication appeared, meaning those features would have evolved. So there definitely is some evolutionary biology involved in investigating abiogenesis, and maybe if we ever solve abiogenesis it will be folded into the ToE (like I said, the ToE is actually a complex set of theories and observations, not one single thing. So while our understanding of what the theory says and can say currently excludes abiogenesis, our understanding and definition of the theory could evolve). But we haven't, and it currently isn't.
You need to edit your question however, because it is completely unclear from the title or text that you are asking about abiogenesis. Your question sounds like it's about embryonic development or biochemistry. Those are the current instances we have of organisms forming; whatever processes were at work in creating the very first life, well for one thing maybe we wouldn't want to call whatever that was an "organism", but more to the point those processes cannot happen today. The atmosphere is wrong and too full of oxygen, there are organisms everywhere vaccuuming up whatever resources those original biochemical processes might have used, basically there is likely no chemical environment on modern Earth that's anything like the chemical environment life originated in.
To answer your question though, abiogenesis is currently an unsolved question, so no, Science does not have an explanation of how the first organisms formed. But if you want to have an idea of how things could have happened, what the challenges are in figuring things out, and what things Science currently considers likely or impossible, there is a lot of active research in the field and many different hypotheses. The Wikipedia page for Abiogenesis has a fairly comprehensive rundown on this.
This video describes one of them (my favorite and the first I've found actually convincing, I have no expertise whatsoever to base this on but I plug it anyway; if nothing else it gives an appreciation for what kind of things the researchers in this field look at when thinking abiogenesis) :
The following is multiple choice question (with options) to answer.
What were the first living things to evolve on earth? | [
"prokaryotes",
"carbon",
"DNA",
"eukaryotes"
] | A | Prokaryotes were the first living things to evolve on Earth, probably around 3.8 billion years ago. They were the only living things until the first eukaryotic cells evolved about 2 billion years ago. Prokaryotes are still the most numerous organisms on Earth. |
SciQ | SciQ-5292 | evolution, cell-biology
What do you mean by multicellularity?
The evolution of multicellularity can be discussed in the context where sister cells form an organism together or when unrelated cells (among the same species or even cells from different species) come together to form an organism. Also, the multicellularity can be discussed at a different level depending on how we want to define multicellularity. Is a stack of cells reproducing individually, working for their own benefit a multicellular? Do we need a division of labor? Do we need a division between germline (reproductive caste) and soma line (non-reproductive case)?
How many times did multicellularity evolve independently?
Some people consider that there are multicellular bacteria (biofilms) but we will avoid discussions that are based on limit-case definitions. Let's talk about eukaryotes. Most Eukaryotes are unicellular and multicellularity evolved many times independently in eukaryotes. To my knowledge, complex multicellularity however evolved only (only?) 6 times independently in eukaryotes.
The following is multiple choice question (with options) to answer.
All members of a species living together form a what? | [
"group",
"organization",
"family",
"population"
] | D | Recall that the four different sublevels (s, p, d, and f) each consist of a different number of orbitals. The s sublevel has one orbital, the p sublevel has three orbitals, the d sublevel has five orbitals, and the f sublevel has seven orbitals. In the first period, only the 1s sublevel is being filled. Since all orbitals can hold two electrons, the entire first period consists of just two elements. In the second period, the 2s sublevel, with two electrons, and the 2p sublevel, with six electrons, are being filled. Consequently, the second period contains eight elements. The third period is similar to the second, except the 3s and 3p sublevels are being filled. Because the 3d sublevel does not fill until after the 4s sublevel, the fourth period contains 18 elements, due to the 10 additional electrons that can be accommodated by the 3d orbitals. The fifth period is similar to the fourth. After the 6s sublevel fills, the 4f sublevel is populated with up to 14 electrons. This is followed by the 5d and the 6p sublevels. The total number of elements in the sixth period is 32. The seventh period also contains 32 elements, most of which are too unstable to be found in nature. All 32 have been detected or synthesized, although for some of the later elements in this period, only a handful of atoms have ever been made. |
SciQ | SciQ-5293 | ecology, biogeography
Edit in response to comments
Comment about biome scale
The reason behind the scale comment is that typically we observe succession for a given habitat. Part of this stems from the origin of the succession ideas, where Frederic Clements posited that climate was the major driving factor of successional trajectories (Clements 1916). This would actually fit well with the biome view of succession, however in order for this model to explain all the variation we see in the world (eg. why a tree grows in location X but not location Y 4 metres away), you devolve into splitting the world into infinitesimally small micro-climates. Henry Gleason proposed a more individualistic model, which suggested that climate was just one influence, and that each plant species responds to a myriad of different environmental cues (Gleason 1927). The sum of these responses results in the community at a given location. This seems to fit better with our current understanding of succession but is not without problems. In a Gleasonian model, any variation can be expected to result in a different community. Since it would be strange for the pampas region to be homogeneous over 1.2 million km2, there are likely distinct communities within the biome, each developing as a result of factors like soil moisture, soil chemistry, climate, wind exposure, and herbivore use. One can still talk about succession at a biome scale, but at that scale we would be thinking about what factors lead the pampas region to become a grassland, rather than what factors lead grass X, tree Y and forb Z to coexist next to each other.
Factors maintaining grassland type ecosystems are fairly uniform globally. You need some sort of event that will kill woody vegetation but not kill grasses and forbs. Fire and grazing are natural examples (Briggs et al. 2002), but mowing would also maintain grassland (Fidelis et al. 2012). Earthquakes are unlikely to maintain grassland as trees and shrubs are likely to survive earthquakes.
Comment about global pampas
The following is multiple choice question (with options) to answer.
What type of disturbance do even dominant plants depend on in many biomes? | [
"seismic force",
"radiation",
"mass extinction",
"periodic"
] | D | |
SciQ | SciQ-5294 | zoology, entomology
Title: How do insects know what is edible? What is the current scientific consensus on how insects innately know what is food and not food? If they are introduced to new food sources do they experiment with eating the new food? Could you teach a preying mantis to eat beef? Insect feeding behaviour is generally triggered by one or more conditions which may include colour, shape, chemical traces or temperature.
Insects generally locate food based on some combination of olfactory, thermal and visual queues (colour and shape). If their minimum criteria are met to specified tolerance, they will attempt to feed on whatever is nearby using their usual feeding method.
When these conditions appear on the 'wrong' target, it attracts insects and triggers feeding attempts. Insects can be triggered to feed on atypical food sources if the relevant aspects of their environment match those of their normal feeding environments. For example, here is a report from a professor of entomology recollecting his observations of being bitten by pea aphids while handling plants, which he assumes is because of the scent on his hands.
We can exploit this in various ways for research. One is for artificial blood-feeding of insects: most systems, like the Hemotek membrane feeding system, warm blood to the body temperature of the host. They do not normally resemble a target host in any other way. Some blood-feeding insects have very specific requirements for temperature (for example they will only feed on blood if it is heated to the body temperature of birds; the same blood heated to mammalian body temperature will be ignored) but we do not need to make the target look or smell like the natural host. Other species may need olfactory cues, which can be provided by researchers rubbing the membranes on their forearms before placing them on the feeding system, or by breathing on cages as you add the food.
A second way we exploit this is for insect traps. Although not all traps work this way, some work by mimicking the host and attracting insects that are looking for a meal. This can be via olfactory/chemical mimicry (for example carbon dioxide baited traps - try Googling "CO2-baited traps") or visual. Different degrees of visual 'deception' may be needed; for instance to attract tsetse flies, colour is important but shape is not:
The following is multiple choice question (with options) to answer.
What type of behaviors are triggered by pheromones in moths? | [
"illuminating",
"courtship",
"exhibit",
"peculiar"
] | B | |
SciQ | SciQ-5295 | biochemistry, plant-physiology, plant-anatomy
Title: Why do plants store energy as carbohydrates and not as fats? In my introductory biology class, we are learning about biomolecules. The textbook says fats are a more efficient energy store than carbohydrates.
So my question is - why would plants store their energy as carbohydrates and not as fats, if fats are a more efficient energy store? There are quite some reasons for why plants prefer carbohydrates for energy storage rather than fats. I will reach some of them one at a time.
The following is multiple choice question (with options) to answer.
What do organisms use to store energy? | [
"lipids",
"proteins",
"metabolytes",
"tissues"
] | A | A lipid is an organic compound such as fat or oil. Organisms use lipids to store energy, but lipids have other important roles as well. Lipids consist of repeating units called fatty acids. Fatty acids are organic compounds that have the general formula CH 3 (CH 2 ) n COOH, where n usually ranges from 2 to 28 and is always an even number. There are two types of fatty acids: saturated fatty acids and unsaturated fatty acids. |
SciQ | SciQ-5296 | botany, terminology, nomenclature
Regnum Animale: the animals;
Regnum Vegetabile: the plants;
Regnum Lapideum: the minerals (you read it right).
Note that, in this classification, "animals" correspond to what nowadays we call animals and protozoans, and "plants" correspond to what nowadays we call plants, algae, fungi and bacteria.
You have to keep in mind that this book was first published in 1735, well before the evolutionary biology being proposed in the XIX century and established in the XX century. Therefore, it is a book published when fixism was the current paradigm, full of mentions to the scala naturae.
So, the plants (as well as the animals) showed a continuum of species, going to the lower plants (the bacteria) to the higher plants (the flowering ones). It's worth mentioning again that, by that time, bacteria were plants: Phylum Schyzophyta, to be more precise.
Thus, we have "lower plants" and "higher plants", "lower animals" and "higher animals", as well as "lower minerals" and "higher minerals"!
Unfortunately, this terminology is so embedded in the biological sciences that even today, as I mentioned, we struggle to get rid of it.
Just drop "higher plants", whatever it means
As your Wikipedia link says, "higher plants" is a synonym of vascular plants. However, there are a lot of problems here:
First, this is a remnant of the scala naturae and, just because of that, should be avoided. Think of it as a meaningless term, just like "more evolved organism".
Second, there is no clear and indisputable definition of what is a "higher" plant. Some authors used to define the "higher plants" as the Angiosperms only, or the seed plants (Angiosperms + Gymnosperms), or the vascular plants (Angiosperms, Gymnosperms and Pteridophyta).
For instance, in lusophone biology books, it was very common a division in three groups:
lower plants: bacteria and algae;
intermediate plants: bryophytes and pteridophytes;
higher plants: gymnosperms and angiosperms.
The following is multiple choice question (with options) to answer.
The scientific practice of classifying organisms is also known as what? | [
"methodology",
"taxodermy",
"terminology",
"taxonomy"
] | D | 22 Classification of Living Things 22.0.1 Classification of Living Things & Naming With so many flora and fauna on planet Earth, there must be a method to classify each organism to distinguish it from others so it can be correctly identified. Classification does not only apply to biology. For example, supermarkets and grocery stores organise their products by classifying them. Beverages may occupy one aisle, while cleaning supplies may occupy another. In science, the practice of classifying organisms is called taxonomy (Taxis means arrangement and nomos means law). The modern taxonomic system was developed by the Swedish botanist Carolus (Carl) Linneaeus (1707-1788). He used simple physical characteristics of organisms to identify and differentiate between different species. Linneaeus developed a hierarchy of groups for taxonomy. To distinguish different levels of similarity, each classifying group, called taxon (pl. taxa) is subdivided into other groups. To remember the order, it is helpful to use a mnemonic device. The taxa in hierarchical order: • • • • • • • •. |
SciQ | SciQ-5297 | cell-biology, meiosis, mitosis
Title: Is the cell cycle applicable to meiosis as well, or just mitosis? All the diagrams I can find, show the cell cycle as having G1 phase (growth 1), S phase (DNA replication), G2 (growth 2) before the Mitotic phase (mitosis + cytokinesis).
Is there an equivalent "cell cycle" for meiosis, since the chromosomes in parent cell in meiosis also having "double" the genetic material prior to cell division (presumably from DNA replication too)?
Is it simply the same cell cycle as mitosis but with a Meiotic phase instead of Mitotic?
If so, would appreciate if anyone had a diagram :) Thanks! The cell cycle is only associated with mitosis. The cell cycle is the normal process of cell division with which cells can indefinitely increase their number by cyclically repeating the process. When a cell goes through the cycle, the result is two cells that are genetically identical.
Meiosis is a special type of cell division (which can occur only in eukaryotes) that produces cells that are not genetically identical to the initiating cell. The number of chromosomes in each of the resulting cells is half the number that were in the initial cell. (These haploid cells can later participate in fertilization, producing a cell with the original number of chromosomes.) Many of the steps of meiosis are similar to the steps involved in mitosis, but overall the process is more complex. Since meiosis reduces the number of chromosomes, it cannot be repeated and so does not take part in a cell division cycle.
The following is multiple choice question (with options) to answer.
What is the type of cell division that produces gametes? | [
"electrolysis",
"meiosis",
"mitosis",
"budding"
] | B | Meiosis is the type of cell division that produces gametes. |
SciQ | SciQ-5298 | newtonian-mechanics, forces, mass, acceleration
Title: Can we determine the force an object exerts by its mass and acceleration? I understand that the objects acceleration is determined by the force exerted on it, and that the force exerted on it is determined by its acceleration.
But, does an object's (named A) acceleration (and mass) tell us anything about how much force the object will exert on another object (named B)? No, in general it will not. The acceleration and mass tell you only the total (net) force being exerted on object A at that moment. That is equivalent to the total force object A is exerting on all other objects (B, C, etc.) it is interacting with at that moment. However, the mass and acceleration do not tell you anything about the individual forces that object A exerts on, say, just object B.
If you are able to determine that object A is only subject to one force, then you can find that one force because you know it's equal to the total force. But that's the only case in which the mass and acceleration tell you about a specific force.
The following is multiple choice question (with options) to answer.
The force applied to an object is called? | [
"strain",
"torque",
"stress",
"gravity"
] | C | Stress is the force applied to an object. Stresses can be confining, compression, tension, or shear. |
SciQ | SciQ-5299 | metallurgy, nuclear-chemistry, geochemistry
Title: Why are rare earth metals and platinum group metals are often found clustered together in ores Rare earth and platinum group metals are often found clustered together in the earth's crust. Mining for platinum, for instance, also yields Rhodium and Ruthenium belonging to the same group. Likewise, rare earth elements such as Neodymium, Europium and Samarium also cooccur in the same ore, so much so, that they are difficult to chemically separate.
It could be reasoned that it's the result of nucleogenesis where elements are formed consecutively based on their atomic number. While it might explain the first row and the second row of each group, where each metal is only one atomic number apart, it doesn't explain why metals from both rows are found together which are much further apart.
Alternatively, the similar chemistry of each group could explain the clustering. The two groups are the only group with this property. It fails to explain, however, how these metals found each other in a molten soup of heterogeneous elements. There may be some geological factors in the clustering, but it's unclear.
Why are the two groups of elements found clustered together? The factors that generate mineral concentrations are complex and often only partly known
Introduction: geology is complicated
The one thing we can be very certain about is is that the distribution of minerals in the earth's crust has very little to do with the primordial origins of the component elements (that is where they came from in the early solar system and how they were originally generated). Most "heavy" elements are originally formed in the cores of supernovae and not in either the big bang or in normal stars.
The distribution of elements in the earth is mostly unrelated to the cosmic origins of elements because the earth's crust is not static but is frequently churned up by a variety of processes on a geological timescale. If we go back far enough in the history of the planet, everything was molten and this allowed some of the denser components to separate out before the surface cooled enough to be solid. The led to the core being mostly metallic (and consisting of mostly iron and nickel). Higher layers contain less dense minerals containing a lot of silicate minerals. At the top there is a thin layer, the crust, which is where we find useful minerals and it is even more concentrated in silicate minerals and even less dense.
The following is multiple choice question (with options) to answer.
What is the largest mineral group, comprising over 90% of earth's crust? | [
"oxides",
"silicates",
"soils",
"carbonates"
] | B | Silicates are the largest mineral group. About 1,000 silicate minerals are known. Silicate minerals are also extremely common. They make up over 90% of Earth's crust!. |
SciQ | SciQ-5300 | slam
Title: Can standard SLAM techniques be used in maritime environments, where waves and currents move the vessel even with no control input I am trying to implement a functioning SLAM system for an autonomous surface vessel (ASV). I don't have any direct experience with SLAM, and I am therefore researching the topic before I try to implement anything.
I am trying to figure out, if a maritime environment will make this job much harder than if our vessel was in a more static environment.
From my readings, I am getting the impression that you need to have a fair estimate of your location over time, given your inputs. Usually SLAM techniques are described for robots that don't move, if you don't tell it to, and this puts a strong constraint on the possible error between estimated location and actual location.
For ASV's the position moves constantly, depending on waves and currents, both in xyz and in pitch, yaw and roll directions. Will this be a problem for standard SLAM techniques? If I have an IMU, can I potentially correct for these disturbances?
For reference, the ASV I'm working with has a GPS and an IMU, and a lidar and cameras for landmark detection. One of the central elements of SLAM is the map itself, build from sensor readings. There is a wide range of sensors which can be used, but they all have in common a capability of building a map (2D or 3D). In the case of an ASV, in a generic maritime environment, I doubt that there are features in the surrounding environment which can be picked up by a lidar/cameras and used to create a map. As the map element is unlikely, I would say that SLAM does not make sense.
I am not familiar with sonar and the resolution/performance of sonars. It might be possible to use the ocean floor as a map and then SLAM would make sense (similar to upward facing cameras for robots in environments with ceilings.
Also, if you are near a coastline, which can be detected by sensors, than again, slam does make sense.
The following is multiple choice question (with options) to answer.
Sound navigation and ranging is an acronym for what, which is used to locate underwater objects such as submarines? | [
"sonar",
"GPS",
"radar",
"sound transmission"
] | A | Sonar stands for sound navigation and ranging. It is used to locate underwater objects such as submarines. |
SciQ | SciQ-5301 | $$\int_0^{\pi/4} dt \, \cos{x t^2} \, \tan^2{t} = \operatorname{Re} \int_0^{\pi/4} dt \, e^{i x t^2} \, \tan^2{t}$$
Our contour $C$ is just a line segment over the real axis. What would be the steepest descent contour $C'$? It is that over which $\operatorname{Im}{\rho(z)}$ is constant. Letting $z=u+i v$, this would mean that we want a contour over which $i z^2 = -2 u v+i (u^2-v^2)$ is constant.
At $z=0$, $\operatorname{Im}{(i z^2)}=0$, so we can use a contour defined by $u=v$. ($u=-v$ defines a steepest ascent contour, which does not deliver an integral useful for Laplace's method.) Thus, the contour $C_1$ coming from $z=0$ is $z=e^{i \pi/4} t$.
We will discuss a contour $C_3$ coming from the other endpoint at $z=\pi/4$ in a minute. We deform the original integral into a closed contour $\gamma=C_1+C_2-C_3-C$ as follows:
The contour $C_2$ is the top piece and vanishes as we go farther along the contours $C_1$ and $C_3$. Thus, by Cauchy's theorem we have
$$\int_0^{\pi/4} dt \, e^{i x t^2} \tan^2{t} = \int_{C_1} dz \, e^{i x z^2} \tan^2{z} - \int_{C_3} dz \, e^{i x z^2} \tan^2{z}$$
Now,
The following is multiple choice question (with options) to answer.
What is the term for the difference in elevation between two contour lines? | [
"mapping interval",
"height",
"contour interval",
"design interval"
] | C | Contour lines are lines of equal elevation. Contour intervals are the difference in elevation between two contour lines. |
SciQ | SciQ-5302 | biochemistry, cell-biology, cell-membrane, cellular-respiration, membrane-transport
Title: Membrane Permeability to Pyruvate Pyruvate seems to pass easily through the outer membrane of the mitochondrion but has difficulty entering the inner membrane (and gets in by H+ symport). I have two questions: (1) what property of pyruvate disallows it from passing through the inner membrane? Is it its charge? and (2) what structural differences are there between the outer and inner membranes of the mitochondrion that create their disparate permeabilities to pyruvate? Pyruvate is negatively charged and quite polar, which makes it unfavourable to diffuse directly through any membrane. The outer mitochondrial membrane contains porins, which allow small molecules, like pyruvate, to passively diffuse through. Specifically, pyruvate uses voltage dependent anion channels. The inner mitochondrial membrane lacks such channels and depends on active transport by the long anticipated but only recently discovered mitochondrial pyruvate carrier (Herzig et al. and Bricker et al., 2012).
The following is multiple choice question (with options) to answer.
The same reaction regenerates pyruvate, which is transported to which cells? | [
"outermost",
"mesophyll",
"skin",
"symbionts"
] | B | |
SciQ | SciQ-5303 | organic-chemistry, acid-base, hydrogen-bond
Title: Which dicarboxylic acid has the most acidic hydrogen?
Which of the following acids (maleic, fumaric, succinic, or malonic) has the most acidic hydrogen?
The following is multiple choice question (with options) to answer.
What large carboxylic acid with three ionizable hydrogen atoms gives some fruits a sour or tart flavor? | [
"beryllium acid",
"citric acid",
"hydrochloric acid",
"ammonia acid"
] | B | Citric acid is a large carboxylic acid with three ionizable hydrogen atoms. It is found in citrus fruits and gives them their sour or tart flavor. |
SciQ | SciQ-5304 | botany, plant-physiology, climate-change
Title: How would a warm winter affect maple sap production? The past winter (2011-2012) was warmer than usual.
Trees are normally tapped in late February when the daily maximum temperature goes above freezing. However, assuming that there have been relatively few days with a maximum temperature below freezing, how would this affect the timing and quantity of sap flow? This article has a clear explanation (backed up by good links) of the effects of climate change on maple sap production, including the following:
Maple trees produce the best sap on cool days preceded by freezing nights – the cold weather causes the sap in the tree to freeze, creating a low-pressure vacuum that draws more sap up from the roots. When temperatures rise the next day, the sap melts and oozes through the tree, making for easy collection. When temperatures stay abnormally warm, as they have been lately, this process does not occur.
Additionally, the warm weather causes the trees to begin to bud. The hormones that trigger budding also decrease the sap’s sugar content and spoil its taste. This means that it takes much larger quantities of sap to boil down to a gallon of syrup.
The following is multiple choice question (with options) to answer.
How does sap get to the tops of tall trees? | [
"through negative pressure",
"through suction power",
"through pressure from below",
"via Coriolis forces"
] | A | How does sap get to the tops of tall trees? (Recall that a column of water can only rise to a height of 10 m when there is a vacuum at the top—see Example 11.5. ) The question has not been completely resolved, but it appears that it is pulled up like a chain held together by cohesive forces. As each molecule of sap enters a leaf and evaporates (a process called transpiration), the entire chain is pulled up a notch. So a negative pressure created by water evaporation must be present to pull the sap up through the xylem vessels. In most situations, fluids can push but can exert only negligible pull, because the cohesive forces seem to be too small to hold the molecules tightly together. But in this case, the cohesive force of water molecules provides a very strong pull. Figure 11.36 shows one device for studying negative pressure. Some experiments have demonstrated that negative pressures sufficient to pull sap to the tops of the tallest trees can be achieved. |
SciQ | SciQ-5305 | plant-anatomy
Title: Are bryophyte sporangia multicellular? My research on the matter can be summarized in a sentence: "It [sporangium] can be composed of a single cell or can be multicellular" (Source: https://en.wikipedia.org/wiki/Sporangium). Yet there shouldn't be a reply placed between "They are" and "They aren't" test options, speaking of "Are bryophyte sporangia multicellular?". A link to the source where I could ascertain whether the bryophyte sporangia is multicellular (if I could ascertain) is highly appreciated. In Embryophyta (land plants), including bryophytes, the sporangium is usually a multicellular structure.
Perhaps you meant to ask about the number of spore mother cells (SMCs) in each sporangium? That varies across groups. In bryophytes, each sporangium has many SMCs, and accordingly produces a large number of spores. (Contrast this with angiosperms, where a megasporangium [called an ovule] has only one megaspore mother cell.)
References and further reading:
https://courses.lumenlearning.com/boundless-biology/chapter/bryophytes/
https://www.britannica.com/science/plant-development
Image attribution:
By LadyofHats. (Public domain;
https://commons.wikimedia.org/wiki/File:Hornwort_structures.jpg)
The following is multiple choice question (with options) to answer.
Each megasporangium has a single functional one of what? | [
"antispore",
"megaspore",
"spicule",
"cocklebur"
] | B | |
SciQ | SciQ-5306 | 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.
Somatosensation refers to what of the five senses? | [
"balance",
"touch",
"thought",
"sight"
] | B | 36.2 | Somatosensation By the end of this section, you will be able to: • Describe four important mechanoreceptors in human skin • Describe the topographical distribution of somatosensory receptors between glabrous and hairy skin • Explain why the perception of pain is subjective Somatosensation is a mixed sensory category and includes all sensation received from the skin and mucous membranes, as well from as the limbs and joints. Somatosensation is also known as tactile sense, or more familiarly, as the sense of touch. Somatosensation occurs all over the exterior of the body and at some interior locations as well. A variety of receptor types—embedded in the skin, mucous membranes, muscles, joints, internal organs, and cardiovascular system—play a role. Recall that the epidermis is the outermost layer of skin in mammals. It is relatively thin, is composed of keratin-filled cells, and has no blood supply. The epidermis serves as a barrier to water and to invasion by pathogens. Below this, the much thicker dermis contains blood vessels, sweat glands, hair follicles, lymph vessels, and lipid-secreting sebaceous glands (Figure 36.4). Below the epidermis and dermis is the subcutaneous tissue, or hypodermis, the fatty layer that contains blood vessels, connective tissue, and the axons of sensory neurons. The hypodermis, which holds about 50 percent of the body’s fat, attaches the dermis to the bone and muscle, and supplies nerves and blood vessels to the dermis. |
SciQ | SciQ-5307 | human-biology, biochemistry, molecular-biology, cell-membrane, pulmonology
Title: How does lipoid pneumonia lead to acute respiratory distress syndrome (ARDS)? How does lipoid pneumonia lead to acute respiratory distress syndrome (ARDS)?
The vaping illnesses that have been happening on the news in the United States are being caused by the federal prohibition on marijuana. Smugglers will legally go to recreational marijuana dispensaries in legal states and purchase cartridges that contain about a gram of "wax". Proper cartridges will use polyethylene glycol, polypropylene glycol, or vegetable glycerin to suspend the THC for vaporizing, but the smugglers have been known to open up the tank and remove some of the wax and refill the remaining volume with Vitamin E Oil. These tampered cartridges are then sold on the black market to recreational and medical consumers in illegal states.
The CDC Report: "Outbreak of Lung Injury Associated with the Use of E-Cigarette, or Vaping, Products"
Edit: So, I was on some conspiracy shtuff when I wrote this post because I was worried about impurities in my vapes killing me. I don't want to take this down because I want my cognitive distortion to remain visible as a reminder of how we can succumb to biased reasoning. Also, the answer I marked correct contextualized the fragmented information of which I was aware and attempted to give me an improved framework for understanding the terms I was using incorrectly as a layman. There are several ways to get ARDS (sepsis, pneumonia, trauma, pancreatitis, etc). Pathophysiologically, they all converge at alveolar insult. So however it happens, there's alveolar insult, cytokine release that recruits neutrophils, and the activated neutrophils release toxic mediators that destroy the alveolar membranes. So for your question specifically, the mineral oil in the vape cartridges (theoretically) is instigating an inflammatory reaction that destroys alveolar membranes.
The following is multiple choice question (with options) to answer.
Respiratory distress syndrome results from insufficient production of what? | [
"pulmonary surfactant",
"alveoli",
"carbon dioxide",
"lung tissue"
] | A | Respiratory System: Respiratory Distress Syndrome Respiratory distress syndrome (RDS) primarily occurs in infants born prematurely. Up to 50 percent of infants born between 26 and 28 weeks and fewer than 30 percent of infants born between 30 and 31 weeks develop RDS. RDS results from insufficient production of pulmonary surfactant, thereby preventing the lungs from properly inflating at birth. A small amount of pulmonary surfactant is produced beginning at around 20 weeks; however, this is not sufficient for inflation of the lungs. As a result, dyspnea occurs and gas exchange cannot be performed properly. Blood oxygen levels are low, whereas blood carbon dioxide levels and pH are high. The primary cause of RDS is premature birth, which may be due to a variety of known or unknown causes. Other risk factors include gestational diabetes, cesarean delivery, second-born twins, and family history of RDS. The presence of RDS can lead to other serious disorders, such as septicemia (infection of the blood) or pulmonary hemorrhage. Therefore, it is important that RDS is immediately recognized and treated to prevent death and reduce the risk of developing other disorders. Medical advances have resulted in an improved ability to treat RDS and support the infant until proper lung development can occur. At the time of delivery, treatment may include resuscitation and intubation if the infant does not breathe on his or her own. These infants would need to be placed on a ventilator to mechanically assist with the breathing process. If spontaneous breathing occurs, application of nasal continuous positive airway pressure (CPAP) may be required. In addition, pulmonary surfactant is typically administered. Death due to RDS has been reduced by 50 percent due to the introduction of pulmonary surfactant therapy. Other therapies may include corticosteroids, supplemental oxygen, and assisted ventilation. Supportive therapies, such as temperature regulation, nutritional support, and antibiotics, may be administered to the premature infant as well. |
SciQ | SciQ-5308 | electrochemistry, redox
Title: How many electrons are transferred in this redox reaction? I have the following reaction:
$$\ce{CH_4 (g) + 2O_2 (g) \rightarrow CO_2 (g) + 2H_2 O(l)}$$
How do I determine how many electrons are transferred in this reaction? More specifically, I need to know the value of $v_e$ which I am supposed to plug into the Nernst equation, which my textbook explains as the coefficient of the number of electrons transferred in each half-reaction. How does one go about splitting this into two half-reactions? The carbon atom must have an oxidation state (O.S.) of -4 on the left hand side since each hydrogen bonded to it must have an O.S. of +1. On the right hand side, the carbon atom has an O.S. of +4 since each oxygen bonded to it has an O.S. of -2. The carbon's oxidation state increased by 8. This is a hint that 8 electrons were transferred. To verify, examine the oxygen atoms. On the left, we only have free oxygen, therefore the O.S. is 0. On the right, we have 4 total oxygen atoms, each with an O.S. of -2. Thus our net change in oxidation state is 0 - 8 = -8. We can almost conclude that all these electrons were transferred from carbon, but we must check the oxidation states of the hydrogen atoms. On both sides, each H atom has an O.S. of +1, so there is no net O.S. change. Thus we can confirm that 8 electrons were indeed transferred in this reaction.
The following is multiple choice question (with options) to answer.
Redox reactions can always be recognized by a change in what number of two of the atoms in the reaction? | [
"fermentation",
"precipitation",
"oxygen",
"oxidation"
] | D | Again, the transfer of an H + ion leaves the oxidation numbers unaffected. In summary, redox reactions can always be recognized by a change in oxidation number of two of the atoms in the reaction. Any reaction in which no oxidation numbers change is not a redox reaction. |
SciQ | SciQ-5309 | human-anatomy
Title: Difference between Appendix and the Cecum? What's the difference between an appendix and a cecum, and what are their functions? In herbivores the Cecum is an area that stores plant matter and helps digest it via symbiotic bacteria. Carnivores have smaller Cecums because meat is easier to digest than plant matter. In humans the Cecum is also an anatomical landmark that delineates the change from small intestine (a digesting organ) to the large intestine (mostly a capacity/storage organ).
The Appendix is a small, previously thought "superfluous" fleshy worm-shaped organ at the junction between the small and large intestines. Recent research posits that the appendix is sort of a harbor for a person's gut flora that can re-populate the intestines should the existing bacteria die or get removed (diarrhea being the most common cause). It can also become infected, inflamed, and require surgery to remove (Appendicitis).
The following is multiple choice question (with options) to answer.
In humans, the anus is attached to what kind of intestine? | [
"small",
"internal",
"huge",
"large"
] | D | Anal Canal Finally, food residue reaches the last part of the large intestine, the anal canal, which is located in the perineum, completely outside of the abdominopelvic cavity. This 3.8–5 cm (1.5–2 in) long structure opens to the exterior of the body at the anus. The anal canal includes two sphincters. The internal anal sphincter is made of smooth muscle, and its contractions are involuntary. The external anal sphincter is made of skeletal muscle, which is under voluntary control. Except when defecating, both usually remain closed. |
SciQ | SciQ-5310 | sexual-reproduction
So when it's not maintained -- when there's no selection pressure on two populations -- inevitably there will be genetic drift that will randomly disrupt this fine-tuned system. If a population of, say, voles is isolated on an island, they will continue to have pressure to be able to interbreed with other voles on the island, but if they can't interbreed with those on the mainland there won't be any consequences, and so over long enough time they'll drift and lose that ability -- just as many apes, not suffering any consequences from not synthesizing vitamin C, gradually lost that ability from random drift.
There's another side to it. Two populations in the same location may be positively selected to not be able to interbreed. Think about two groups of finches, one with small fine beaks that eat tiny seeds deep inside pine cones, and one with heavy beaks that crush and eat thick-shelled nuts. They each do fine, but they can interbreed and produce offspring that have intermediate beaks -- too thick to reach the fine seeds that one parent eats, but too delicate to crush the nuts that the other parent eats. Those intermediate offspring will die off, and both parents will have wasted their resources raising them. Both parents would be better off not breeding with each other, but only breeding with their own kind to produce specialized and efficient offspring. There is now selection pressure on the birds to recognize their own kind (perhaps through songs or mating displays) and ultimately to be inter-sterile, so they never waste resources on the un-fit offspring. There's a gradation of separation over time, in which the different populations become more and more distinct. Eventually, at some arbitrary point, humans start calling them "species", but that's just us, not biology.
"Species" is an important concept, but it's not special in evolution; speciation is just one aspect of natural selection, there's nothing magical about it.
The following is multiple choice question (with options) to answer.
What does interspecific competition between species often lead to? | [
"extinction",
"evolution",
"symbiosis",
"immigration"
] | A | Interspecific competition often leads to extinction . The species that is less well adapted may get fewer of the resources that both species need. As a result, members of that species are less likely to survive, and the species may go extinct. |
SciQ | SciQ-5311 | atoms, nuclear, radioactivity
Also, the answer depends on exactly what you mean by "power". Assuming you're comparing kinetic energies, Wikipedia says gamma rays from nuclear decay rarely have energy above 10 MeV, and another source says electrons from beta decay usually have energies up to 4 MeV. The energies are all of the same order of magnitude, which makes sense because all the particles are coming from the same source (an unstable nucleus). Theoretically gamma rays can have a slightly higher kinetic energy than other decay particles because photons have zero rest mass, therefore all the decay energy is converted into kinetic energy, whilst for electrons 511 keV is "wasted" on creating the rest mass (and even higher "wastes" for heavier particles such as protons/neutrons/alpha particles etc). I think one can also consider that some energy is used up in "climbing out" of the electrical potential and residual strong nuclear potential wells of the nucleus, neither of which applies to gamma ray photons (though positively charged species would in fact gain energy, being electrically accelerated away from the nucleus by repulsion, but this contribution is probably smaller than the nuclear force one). However, different types of nucleus have different allowed decay paths, and depending on complicated details the most energetic beta particles or proton/neutron emissions might have a slightly higher energy than the most energetic nuclear decay gamma ray.
As a final note, it is also possible to create even more energetic photons than any that could be produced via nuclear decay by putting electrons in a sufficiently powerful particle accelerator. Any charged particle under acceleration/deceleration loses some energy in the form of electromagnetic radiation. For ultrarelativistic charged particles, the photons emitted can be of extremely high energy. These are a type of x-ray termed "hard x-rays" (more energetic than so called "soft x-rays").
Edit: Correction regarding energy lost in rest masses of particles from decay. Energy is used up in the creation of electrons, but protons/neutrons/clusters already exist inside the nucleus, and so are not created. These particles could never be produced directly as a single one would have upwards of 930 MeV, far above typical nuclear decay energies.
The following is multiple choice question (with options) to answer.
Radioactive decay can give off energy and what else? | [
"atoms",
"ions",
"light",
"particles"
] | D | Radioactive elements and isotopes have unstable nuclei. To become more stable, the nuclei undergo radioactive decay. In radioactive decay, the nuclei give off, or emit, radiation in the form of energy and often particles as well. There are several types of radioactive decay, including alpha, beta, and gamma decay. Energy is emitted in all three types of decay, but only alpha and beta decay also emit particles. |
SciQ | SciQ-5312 | visible-light, reflection
Title: Why are reflected objects blurry? While this may seems like a strange question, I'll try to explain it the best I can. Like 75% of Americans, I wear glasses and contacts to correct my worsening vision. I'm not far sighted so objects in the distance appear blurry. I took my glasses off to look at my iPad. After doing so I noticed in the reflection of the glass, my lamp. The lamp is in the distance and looks blurry to me. But on my iPad's glass it was blurry unlike the rest of the objects on screen, including the glass which I could see clearly because I'm near-sighted. It is strange to me why the reflection was blurry even though it was close up. How can this be? This is simply the law of reflexion: if you trace a ray diagram for objects reflecting in your iPad screen, you are looking at light from a virtual image that is as far beyond your screen as the real source of light is from the iPad screen. So if the lamp is, say, 3 metres behind your shoulder, when you look at the iPad screen the reflected light is exactly like that from a lamp 3 metres beyond you iPad screen ahead of you. Put simply, you are looking at light diverging from a distant source, not from the iPad screen, so it will look blurry to you if a lamp that is really 3 metres beyond your iPad screen is blurry.
The following is multiple choice question (with options) to answer.
What is the condition in which distant objects are seen clearly, but nearby objects appear blurry? | [
"farsightedness, or hyperopia",
"gleam , or hyperopia",
"synthesise , or hyperopia",
"nearsightedness or hyperopia"
] | A | Farsightedness, or hyperopia, is the condition in which distant objects are seen clearly, but nearby objects appear blurry. It occurs when the eyeball is shorter than normal (see Figure below ). This causes images to be focused in a spot that would fall behind the retina (if light could pass through the retina). Hyperopia can be corrected with convex lenses. The lenses focus images farther forward in the eye, so they fall on the retina instead of behind it. |
SciQ | SciQ-5313 | evolution
Title: Homologous structures under Lamarck I've read that Lamarck's theory doesn't explain homologous structures.
But, what about the following hypothetical under Lamarck's theories:
A population develops an adaptation to its environment
Part of the adapted population moves away
The adaptation is passed onto the population's offspring
All offspring of the original population have the adaptation, regardless of whether or not their ancestors moved away
Isn't this adaptation a homologous structure? I agree with you that I can't see why Lamarck's hypothesis could not explain the presence of homologous structures.
The link you offer also claim that Larmarck's hypothesis would fail to explain "Biogeographical diversity patterns". While this expression is a little vague, I would fail to understand why Lamarck's hypothesis would fail to explain patterns of biogeographical diversity.
The phrasing of your scenarios (absence of the term allopatric speciation, usage of the term "develops" instead of "evolves" of just "adapts") suggests that you may take advantage of an intro course to evolutionary biology such as the short and good course by UC Berkeley called Understanding Evolution
The following is multiple choice question (with options) to answer.
What novelties can also arise when structures that originally played one role gradually acquire a different one? | [
"mutation",
"interactions",
"evolutionary",
"reproduction"
] | C | |
SciQ | SciQ-5314 | geology, rocks, sedimentology, geomorphology, terminology
Title: What do you call boulders of non sedimentary rock that were lithified into sandstone? I'm convinced there is a word for this. I was in the Hoodoos at Writing on Stone this weekend and kept noticing what looked like reddish quartzite boulders laying around in the sand, or sometimes sticking partially out of the hoodoos.
When a non-sedimentary rock gets washed out into silt which later lithifies, what's it called? It's kind of like a conglomerate, except there's only a couple of really big rocks, which eventually fall out out the rock because all the sandstone around them eroded away. The technical term for a sedimentary rock that has a lithified fine-grained sediment with larger pieces of rocks suspended in it upon lithification is a conglomerate. The fine-grained interstitial part is called the matrix, and the large pieces suspended in it are called clasts. Clasts can range from gravel- to boulder-size. These are technical terms used by sedimentologists.
It is tempting to refer to these fragments as xenoliths but as that word has a very specific meaning in igneous petrology, it is best to avoid it to remove any confusion.
The following is multiple choice question (with options) to answer.
What is a gap in rock layers called? | [
"an unconformity",
"an anomaly",
"a mutation",
"a crevice"
] | A | An unconformity is a gap in rock layers. They occur where older rock layers eroded away completely before new rock layers were deposited. |
SciQ | SciQ-5315 | bacteriology
Title: Extract bacteria from compost? I'm working on a project where I need to find certain cellulolytic bacteria. I was looking at this list : http://webcache.googleusercontent.com/search?q=cache:CrtQ9T6K7m8J:www.wzw.tum.de/mbiotec/cellmo.htm+&cd=1&hl=nl&ct=clnk&gl=be
How could I selectively separate one of the bacteria types that I had in mind from that list?
So how would I have to extract the bacteria from the compost? A first (and obvious) approach is the use of cellulose agar in order to isolate all the celluloltic bacteria in the sample. Be careful, however, since the nutrient requirements of some of those microbes may be higher and then they won't grow with only cellulose (they may need some other compounds, like a nitrogen source). Be careful with fungi, too.
If you have the proper equipment, it would be ideal to extract DNA and analyze the environmental rRNA 18s sequences. With this, you should be able to know if your bacteria is present in your sample. If so, proceed with the previous steps.
Once you had a set of suspected colonies, you must proceed with more specific culture media (wich would depend of the exact bacteria you're looking for. For example, if you're looking for Clostridium, you should try to grow your sample in an anaerobic jar and test the ability to reduce sulphur). With this approach, you may reach a point where you can't differenciate similar species. At this point, mollecular characterization is the best option, with the use of rRNA 18s again. Note that the mollecular approach, while relative expensive, can be performed in every step, so you can combine cultures and DNA analyses at will.
Lastly, if you're looking for an specific bacteria, it would be useful to know wich one is, so the community can give you more accurate responses.
The following is multiple choice question (with options) to answer.
Bacteria are often used to make cheese from what? | [
"meat",
"milk",
"egg",
"water"
] | B | Bacteria are often used to make cheese from milk. But making foods is not the only beneficial role of bacteria. For example, they also play an essential role in your gut!. |
SciQ | SciQ-5316 | bond, metal
But, I do not understand why the metal atoms turn into ions and delocalize the electrons, why don't the metal atoms stay as atoms? When electricity flows, the electrons are considered "free" only because there are more electrons than there should be, and because the transition metals, such as iron, copper, lead, zinc, aluminum, gold etc. are willing to transiently accept and give up electrons from the d-orbitals of their valence shell.
Transition metals are defined in part by their stability in a wide range of "oxidation states"; that is, in several combinations of having too many or too few electrons compared to protons. This is thought to be because of the d orbital in their valence shells. Compared to the s and p orbitals at a particular energy level, electrons in the d shell are in a relatively high energy state, and by that token they have a relatively "loose" connection with their parent atom; it doesn't take much additional energy for these electrons to be ejected from one atom and go zooming through the material, usually to be captured by another atom in the material (though it is possible for the electron to leave the wire entirely). This impetus can be caused by many things, from mechanical impact to chemical reactions to electromagnetic radiation (aka light, though not all of it visible); antennas work to capture radio frequencies, because the light at those frequencies induces an electric current in the wire of the antenna. Now, in the absence of a continuous force keeping the electron in this higher energy state, the electron (and the metal atoms) will naturally settle into a state of equilibrium. Electricity is generated when just such a force is acting on the metal, giving energy to the electrons in the d orbital and forcing them to move in a certain direction.
This impetus can come from many sources, as discussed, be it the movement of a magnet within a coil of wire, or a chemical redox reaction in a battery creating a relative imbalance of electrons at each of two electrodes. The end result is that the electrons, given additional energy from this voltage source, are ejected from their "parent" atom and are captured by another. The "holes" left behind by these electrons are filled by other electrons coming in behind them from further back in the circuit. Thus, the energy provided by the voltage source is carried along the wire by the transfer of electrons.
The following is multiple choice question (with options) to answer.
Why are atoms of metals good conductors of electricity? | [
"break into smaller parts",
"hold on to electrons",
"give up electrons",
"conserve heat"
] | C | Electricity is a flow of electrons. Atoms of metals tend to give up electrons, explaining why they are good conductors of electricity. The tendency to give up electrons also explains many of the other properties of metals. |
SciQ | SciQ-5317 | units, si-units, metrology
Title: How units were defined? I was wondering how we humans can be sure that one meter is one meter and that one second is one second. Nowadays, except for the Kilogram, all other units are well defined using highly accurate techniques (frequency of atoms vibrations or stuff like that). But at the end all units are kind of related to each other and the definition of each unit is based on a combination of other units. There must be some viable sources that have constant measurable values that we used to define the basic units. What is those sources?
To explain more let's start with the meter. From wikipedia, the definition is: The metre is the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second. So here it is clear that the definition of a meter relies on the accuracy of how we define a second.
Now let's look at the second:
the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.
How is this period calculated? The sensor has probably some equations that imply transformations using other units like Kg etc...
Where does this loop stops?
EDIT:
I think I was a little bit mistaken. Not all units are directly related and there is 3 totally independent units which are : Time (second), Temperature (kelvin) and Mass (kilogram). Time and Temperature are well defined but Kilogram is still unclear. Every existing unit can be transformed into a combination of those three. It means that all units based on Kilogram are not absolute. In short, up until now, the $kg$ was arbitrary, but now people are trying to define it based on universal constants
There is a ongoing process to try and link all the units to universal constants.
This has been done already for the second (using Cesium) and the meter (using the speed of light in a vacuum)
However, the kilogram is a little less straightforward. An interesting read is SI units revision proposal.
It proposes to link the kg to the Plank constant $h$, but also to link Kelvin $K$ to the Stefan-Boltzman constant $k$ and more of these constructions.
The following is multiple choice question (with options) to answer.
What is the basic unit of an organism called? | [
"electron",
"particle",
"singularity",
"cell"
] | D | While cells are the basic units of an organism, groups of cells can perform a job together. These cells are called specialized because they have a special job. Specialized cells can be organized into tissues . For example, your liver cells are organized into liver tissue. Your liver tissue is further organized into an organ, your liver. Organs are formed from two or more specialized tissues working together to perform a job. All organs, from your heart to your liver, are made up of an organized group of tissues. |
SciQ | SciQ-5318 | human-biology, endocrinology, circadian-rhythms
Title: Which human body hormonal systems exhibit 24 hour diurnal cyclical activity? I'm researching the possible connection between the dream content and the activity of various organ or hormonal systems within the human body. I'm looking for information on biological cycles within the human body that occur on a 24 hour cycle and may influence the sleep cycle, dream content or the overall state of awareness.
So far I was able to find:
Adrenaline, cortisol, testesterone - circadian endogenous cycle.
leptin, glucose, insuline - peak with awakening, decline with bedtime
What else within the human body is functioning on a predictable 24 hour cycle?
Thank you for any information! The real answer is probably more than you want, but its easy to do better than the list above.
I took a look through GEO for human circadian expression data and surprisingly I only found 2.
Looking at GSE2703 - the rhesus circadian expression experiment, they have shown 355 genes that are rhythmically expressed. This is not a great experiment because they only looked over a single 24 hour period. Its only the adrenal gland. Nonetheless they found 355 genes which seemed to be circadian. the table is supplemental data to the article, listed below.
I see a fibroblast growth factor receptor, some hydrocarbon nuclear receptor components, sterol regulatory factors, bone morphogenic protein 2, glutamate receptor, thrombonspondin receptor, ryanodine receptor 3 (what is that?) , lysophosphatidic acid G-protein-coupled receptor 2, purinergic receptor P2Y, G-protein coupled. You might find more if you know what you are looking for.
The other circadian study was on human muscle, which will no doubt give different answers. I imagine circadian behavior is highly tissue dependent.
Reference: Lemos DR, Downs JL, Urbanski HF. Twenty-four-hour rhythmic gene expression in the rhesus macaque adrenal gland. Mol Endocrinol 2006 May;20(5):1164-76
The following is multiple choice question (with options) to answer.
All the blood in the human body is filtered about 60 times a day by what? | [
"kidneys",
"lungs",
"heart",
"liver"
] | A | blood containing the metabolic wastes from cells. All the blood in the human body is filtered about 60 times a day by the kidneys. The nephrons remove wastes, concentrate them, and form urine that is collected in the bladder. Internally, the kidney has three regions—an outer cortex, a medulla in the middle, and the renal pelvis, which is the expanded end of the ureter. The renal cortex contains the nephrons—the functional unit of the kidney. The renal pelvis collects the urine and leads to the ureter on the outside of the kidney. The ureters are urine-bearing tubes that exit the kidney and empty into the urinary bladder. |
SciQ | SciQ-5319 | orbitals
Title: Why do higher orbitals have more energy? I have seen in textbooks and videos that an electron must absorb energy (become excited) to enter a farther-away orbital.
The amount of energy that must be gained is equal to the difference in energy between the orbitals. When the electron relaxes and returns to its ground state, it emits that energy.
However, I am not sure I understand why "higher" orbitals are of greater energy, for a couple of reasons.
When I think of the potential energy of the electron, as given by $U = \frac{kQq}{r}$, it seems that $U \propto \frac{1}{r}$, which would indicate less energy as distance increases.
I also know that the electron is attracted to the nucleus due to opposing charge. By this logic, an electron closer to the nucleus would be more stable (have a lower energy state) than an electron farther from the nucleus (which would thus have a higher energy state). This line of thinking is somewhat similar to how a ball that's still high in the air is in a higher energy state than a ball that's closer to the ground.
So #1 is inconsistent with what we are taught about electrons and orbitals, while #2 would support it.
I am attempting to clarify the misunderstanding I must have somewhere (possibly not making a proper analogy) - and better understand why higher orbitals are of greater energy. potential energy is negative between infinity to nucleus
It varies with .Thus, U∝(−1)1/r so it means the father you go from nucleus the value become less negative that is higher in energy than equilibrium energy.
The following is multiple choice question (with options) to answer.
What happens to the energy levels of electrons as they are closer to the nucleus? | [
"they divide",
"they are lower",
"they balance",
"they are higher"
] | B | Electrons at lower energy levels, which are closer to the nucleus, have less energy. At the lowest energy level, which has the least energy, there is just one orbital, so this energy level has a maximum of two electrons. |
SciQ | SciQ-5320 | human-anatomy, human-physiology, blood-circulation, physiology
Title: Common site for atherosclerosis My book( textbook of anatomy abdomen and lower limb 2nd edition - by vishram Singh pg.no:286) says:
Acute arterial occlusion: It is mostly caused by embolism or thrombosis. It usually occurs in the femoral artery where it gives off the profunda femoris artery.
The following is multiple choice question (with options) to answer.
What is the term for the blockage of an artery by the buildup of fatty plaques? | [
"cancers",
"atherosclerosis",
"clumps",
"fibrosis"
] | B | make up the middle layer and the bulk of the heart wall. The outer layer of cells is called the epicardium, of which the second layer is a membranous layered structure called the pericardium that surrounds and protects the heart; it allows enough room for vigorous pumping but also keeps the heart in place to reduce friction between the heart and other structures. The heart has its own blood vessels that supply the heart muscle with blood. The coronary arteries branch from the aorta and surround the outer surface of the heart like a crown. They diverge into capillaries where the heart muscle is supplied with oxygen before converging again into the coronary veins to take the deoxygenated blood back to the right atrium where the blood will be re-oxygenated through the pulmonary circuit. The heart muscle will die without a steady supply of blood. Atherosclerosis is the blockage of an artery by the buildup of fatty plaques. Because of the size (narrow) of the coronary arteries and their function in serving the heart itself, atherosclerosis can be deadly in these arteries. The slowdown of blood flow and subsequent oxygen deprivation that results from atherosclerosis causes severe pain, known as angina, and complete blockage of the arteries will cause myocardial infarction: the death of cardiac muscle tissue, commonly known as a heart attack. |
SciQ | SciQ-5321 | mammals, sex-chromosome, gender
Title: What processes regulate the sex of offspring? It is known that some species are more likely to born male than female (and some maybe vice versa). I understand that it is due to evolutionary perspective (average number of adult males is close to that of females), I want to know about how it is regulated.
What I thought is that spermatozoa are made by half as Y and half as X chromosome. Then mitosis and meiosis and the probability that one of them will die is equal for both types. So, somewhere I feel lost.
Also, can it be regulated by female body or not? According to this paper claiming that hormone levels in women affect the likelyhood to born son. Possibly it is just because they choose males that are more likely to have more Y spermatozoa than X, but if it is some chemical mechanism to regulate that I'd like to know.
I'm not asking only about humans, mechanisms can be similar in almost all mammals. I'm not asking about other species: I know some are regulated by temperature, etc. This question is only about mammals.
What processes regulate the sex of offspring?
The processes rulating the sex of offspring may occur in both males and females and be direct or indirect.
What I thought is that spermatozoa are made by half as Y and half as X chromosome. Then mitosis and meiosis and the probability that one of them will die is equal for both types. So, somewhere I feel lost.
This may not be entirely true. The phenomenon called "Meiotic drive" may change the ratio from 1:1. Meiotic Drive occurs through selfish genes. See "Selfish-gene theory" for more info.
Also, can it be regulated by female body or not?
if it is some chemical mechanism to regulate that I'd like to know.
Possibly, there is such in mammals. There is a bunch of mechanisms called "Cryptic female choice". Some of them are chemical. Although, the article is about birds, it can be the case similar mechanism is present in mammals.
Given that higher androgen level exposure in mothers affect make their offspring more male-typical in playing behavior we might consider that in general makes offsrpings more masculine. This would be a good reason for female organisms with higher androgen levels to favor sperm with Y chromosome present.
The following is multiple choice question (with options) to answer.
In what type of reproduction do parents of different sexes mate to produce offspring? | [
"dual reproduction",
"sexual reproduction",
"subject reproduction",
"parallel reproduction"
] | B | Many organisms reproduce sexually. In sexual reproduction, parents of different sexes mate to produce offspring. The offspring have some combination of the traits of the two parents. Ducks are examples of sexually reproducing organisms. Other organisms reproduce asexually. In asexual reproduction, a single parent can produce offspring alone. For example, a bacterial cell reproduces by dividing into two daughter cells. The daughter cells are identical to each other and to the parent cell. |
SciQ | SciQ-5322 | h. Evaluate C.
i. Compute Q(7), the amount of glucose produced during the day.
Exercise 10.3.5 “Based on studies using isolated animal pancreas preparations
maintained in vitro, it has been determined that insulin is secreted in a biphasic manner in response to a marked increase in blood glucose. There is an initial burst of insulin secretion that may last 5-15 minutes, a result of secretion of preformed insulin secretory granules. This is followed by more gradual and sustained insulin secretion that results largely from biosynthesis of new insulin molecules. ” (Rhoades and Tanner, P 710)
a. A student eats a candy bar at 10:20 am. Draw a graph representative of the rate of insulin secretion between 10:00 and 11:00 am.
b. Draw a graph representative of the amount of serum insulin between 10:00 and 11:00. Assume that insulin is degraded throughout 10 to 11 am at a rate equal to insulin production before the candy is eaten, and that serum insulin at 10:00 was Iq.
CHAPTER 10. THE FUNDAMENTAL THEOREM OF CALCULUS
468
c. Write an expression for the amount of serum insulin, I(t), for t between 10:00 and 11:00 am.
Exercise 10.3.6 Equal quantities of gaseous hydrogen and iodine are mixed resulting in the reaction
which runs until I 2 is exhausted [H 2 is also exhausted). The rate at which I 2 disappears is ^°’^ 2 gm/sec. How much I 2 was initially introduced into the mixture?
a. Sketch the graph of the reaction rate, r(t) = jp^yi-
b. Approximately how much I 2 combined with H 2 during the first second?
c. Approximately how much I 2 combined with H 2 during the second second?
d. Let Q(x) be the amount of I 2 that combines with H 2 during time 0 to 2; seconds. Write an integral that is Q(x).
e. What is Q\x)l
f. Compute W'{x) for W(x) = =^.
g. Show that there is a number, C, for which Q(x) = W(x) + C.
h. Show that C = 0.2 so that Q(x) = 0.2 – g.
The following is multiple choice question (with options) to answer.
Insulin and glucagon help keep blood glucose levels in the normal range because of what type of effects? | [
"ABNORMALISTIC",
"sympathetic",
"opportunistic",
"antagonistic"
] | D | |
SciQ | SciQ-5323 | volcanology, paleontology, volcanic-hazard, archaeology, pyroclastic-flows
Title: Are Pompeii and Herculaneum unique? Has anyone ever found or gone looking for similar locations, i.e. volcanic eruption sites in which unfortunate victims – human and non-human – have been entombed in the volcanic ash, with the possibility of revealing their forms by producing casts from the voids? Such sites, if they exist, could reveal exciting new knowledge about ancient peoples and animals. Probably the best known is more recent, the 1902 eruption of Mt. Pelée on Martinique, where 30,000 people were killed by pyroclastic flows. I don't know the extent of burial - it appears that the city may have been destroyed more by the ash cloud than the dense part of the flow.
The following is multiple choice question (with options) to answer.
What phenomenon has severe consequences on both natural and man-made objects, including killing trees and degrading marble statues? | [
"carbon rain",
"oxygen rain",
"natural rain",
"acid rain"
] | D | Acid rain has severe consequences on both natural and man-made objects. Acid rain degrades marble statues like the one on the left (A). The trees in the forest on the right (B) have been killed by acid rain. |
SciQ | SciQ-5324 | thermodynamics, metal, boiling-point, metallurgy, alloy
Title: How do foundries prevent zinc from boiling away when alloyed with Aluminum? How do foundries prevent lower boiling point metals such as zinc from boiling away when alloyed in a furnace with higher boiling point metals such as aluminum? When alloys are made by mixing molten metals (actually an alloy only need contain one metal and at least one other compound, metal or not) the metals only need to be heated to their melting point, not all the way to their boiling point. In the example you've given, the melting point of aluminum is $\pu{660^oC}$, which is $\pu{247^oC}$ below the boiling point of zinc, so the volatilization of zinc is negligible under these conditions.
However, the issue you bring up does present problems in other cases. For example this article states the following:
One difficulty in making alloys is that metals have different melting points. Thus copper melts at $\pu{1,083^oC}$, while zinc melts at $\pu{419^oC}$ and boils at $\pu{907^oC}$. So, in making brass, if we just put pieces of copper and zinc in a crucible and heated them above $\pu{1,083^oC}$, both the metals would certainly melt. But at that high temperature the liquid zinc would also boil away and the vapour would oxidize in the air. The method adopted in this case is to heat first the metal having the higher melting point, namely the copper. When this is molten, the solid zinc is added and is quickly dissolved in the liquid copper before very much zinc has boiled away. Even so, in the making of brass, allowance has to be made for unavoidable zinc loss which amounts to about one part in twenty of the zinc. Consequently, in weighing out the metals previous to alloying, an extra quantity of zinc has to be added.
The following is multiple choice question (with options) to answer.
What alloy is made from copper and zinc? | [
"brass",
"iron",
"manganate",
"stele"
] | A | Brass saxophone: Brass is an alloy of copper and zinc. It is softer than bronze and easier to shape. It's also very shiny. Notice the curved pieces in this shiny brass saxophone. Brass is used for shaping many other curved objects, such as doorknobs and plumbing fixtures. Stainless steel sink: Stainless steel is a type of steel that contains nickel and chromium in addition to carbon and iron. It is shiny, strong, and resistant to rusting. This makes it useful for sinks, eating utensils, and other objects that are exposed to water. "Gold" bracelet: Pure gold is relatively soft, so it is rarely used for jewelry. Most "gold" jewelry is actually made of an alloy of gold, copper and silver. Bronze statue: Bronze was the first alloy ever made. The earliest bronze dates back many thousands of years. Bronze is a mixture of copper and tin. Both copper and tin are relatively soft metals, but mixed together in bronze they are much harder. Bronze has been used for statues, coins, and other objects. |
SciQ | SciQ-5325 | human-biology, human-anatomy
Title: Difference between the spinal cord and vertebrae column What is the difference between the spinal cord and the vertebrae column, they both run through from the head to the abdomen. Does any one have any idea. The vertebral column is a bony, segmented structure that supports the torso/head and thorax. The spinal cord is a bundle of nerves that runs inside the structure of the vertebral column. So - they run together, but are completely separate.
The following is multiple choice question (with options) to answer.
The accumulation of what cells begin the development of the vertebral column and thoracic cage? | [
"False cells",
"semiosis cells",
"mesenchyme cells",
"hindbrain cells"
] | C | Development of the Vertebral Column and Thoracic cage Development of the vertebrae begins with the accumulation of mesenchyme cells from each sclerotome around the notochord. These cells differentiate into a hyaline cartilage model for each vertebra, which then grow and eventually ossify into bone through the process of endochondral ossification. As the developing vertebrae grow, the notochord largely disappears. However, small areas of notochord tissue persist between the adjacent vertebrae and this contributes to the formation of each intervertebral disc. The ribs and sternum also develop from mesenchyme. The ribs initially develop as part of the cartilage model for each vertebra, but in the thorax region, the rib portion separates from the vertebra by the eighth week. The cartilage model of the rib then ossifies, except for the anterior portion, which remains as the costal cartilage. The sternum initially forms as paired hyaline cartilage models on either side of the anterior midline, beginning during the fifth week of development. The cartilage models of the ribs become attached to the lateral sides of the developing sternum. Eventually, the two halves of the cartilaginous sternum fuse together along the midline and then ossify into bone. The manubrium and body of the sternum are converted into bone first, with the xiphoid process remaining as cartilage until late in life. |
SciQ | SciQ-5326 | ecology, biogeography
Edit in response to comments
Comment about biome scale
The reason behind the scale comment is that typically we observe succession for a given habitat. Part of this stems from the origin of the succession ideas, where Frederic Clements posited that climate was the major driving factor of successional trajectories (Clements 1916). This would actually fit well with the biome view of succession, however in order for this model to explain all the variation we see in the world (eg. why a tree grows in location X but not location Y 4 metres away), you devolve into splitting the world into infinitesimally small micro-climates. Henry Gleason proposed a more individualistic model, which suggested that climate was just one influence, and that each plant species responds to a myriad of different environmental cues (Gleason 1927). The sum of these responses results in the community at a given location. This seems to fit better with our current understanding of succession but is not without problems. In a Gleasonian model, any variation can be expected to result in a different community. Since it would be strange for the pampas region to be homogeneous over 1.2 million km2, there are likely distinct communities within the biome, each developing as a result of factors like soil moisture, soil chemistry, climate, wind exposure, and herbivore use. One can still talk about succession at a biome scale, but at that scale we would be thinking about what factors lead the pampas region to become a grassland, rather than what factors lead grass X, tree Y and forb Z to coexist next to each other.
Factors maintaining grassland type ecosystems are fairly uniform globally. You need some sort of event that will kill woody vegetation but not kill grasses and forbs. Fire and grazing are natural examples (Briggs et al. 2002), but mowing would also maintain grassland (Fidelis et al. 2012). Earthquakes are unlikely to maintain grassland as trees and shrubs are likely to survive earthquakes.
Comment about global pampas
The following is multiple choice question (with options) to answer.
What are terrestrial biomes determined by? | [
"time and temperature",
"moisture and elevation",
"pressure and temperature",
"temperature and moisture"
] | D | Terrestrial biomes are determined mainly by temperature and moisture. Plants are the primary producers. Examples of terrestrial biomes include tropical rainforests, temperate grasslands, and tundra. |
SciQ | SciQ-5327 | 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 protects reptiles from injury and loss of water? | [
"pores",
"tail",
"hairs",
"scales"
] | D | Molecules move from an area of high concentration to an area of lower concentration until an equilibrium is met. The molecules continue to cross the membrane at equilibrium, but at equal rates in both directions. |
SciQ | SciQ-5328 | zoology, entomology
Title: How do insects know what is edible? What is the current scientific consensus on how insects innately know what is food and not food? If they are introduced to new food sources do they experiment with eating the new food? Could you teach a preying mantis to eat beef? Insect feeding behaviour is generally triggered by one or more conditions which may include colour, shape, chemical traces or temperature.
Insects generally locate food based on some combination of olfactory, thermal and visual queues (colour and shape). If their minimum criteria are met to specified tolerance, they will attempt to feed on whatever is nearby using their usual feeding method.
When these conditions appear on the 'wrong' target, it attracts insects and triggers feeding attempts. Insects can be triggered to feed on atypical food sources if the relevant aspects of their environment match those of their normal feeding environments. For example, here is a report from a professor of entomology recollecting his observations of being bitten by pea aphids while handling plants, which he assumes is because of the scent on his hands.
We can exploit this in various ways for research. One is for artificial blood-feeding of insects: most systems, like the Hemotek membrane feeding system, warm blood to the body temperature of the host. They do not normally resemble a target host in any other way. Some blood-feeding insects have very specific requirements for temperature (for example they will only feed on blood if it is heated to the body temperature of birds; the same blood heated to mammalian body temperature will be ignored) but we do not need to make the target look or smell like the natural host. Other species may need olfactory cues, which can be provided by researchers rubbing the membranes on their forearms before placing them on the feeding system, or by breathing on cages as you add the food.
A second way we exploit this is for insect traps. Although not all traps work this way, some work by mimicking the host and attracting insects that are looking for a meal. This can be via olfactory/chemical mimicry (for example carbon dioxide baited traps - try Googling "CO2-baited traps") or visual. Different degrees of visual 'deception' may be needed; for instance to attract tsetse flies, colour is important but shape is not:
The following is multiple choice question (with options) to answer.
What are the different feeding positions in a food chain or web called? | [
"trophic levels",
"neural levels",
"convoluted levels",
"Primary Level"
] | A | The different feeding positions in a food chain or web are called trophic levels. Generally, there are no more than four trophic levels because energy and biomass decrease from lower to higher levels. |
SciQ | SciQ-5329 | ros, rostopic, ros-indigo, joint-state
I know this is documented somewhere more officially - I'll try to get a link.
As gvdhoorn mentioned, I made a mistake here, either the gripper joints are there, or the other joints are there.
This is expected behavior. See this Wiki for the reference.
The following is multiple choice question (with options) to answer.
What is the joint where the pelvic girdle and leg come together? | [
"hip joint",
"hip socket",
"meniscus",
"femur joint"
] | A | 11.6 Appendicular Muscles of the Pelvic Girdle and Lower Limbs The pelvic girdle attaches the legs to the axial skeleton. The hip joint is where the pelvic girdle and the leg come together. The hip is joined to the pelvic girdle by many muscles. In the gluteal region, the psoas major and iliacus form the iliopsoas. The large and strong gluteus maximus, gluteus medius, and gluteus minimus extend and abduct the femur. Along with the gluteus maximus, the tensor fascia lata muscle forms the iliotibial tract. The lateral rotators of the femur at the hip are the piriformis, obturator internus, obturator externus, superior gemellus, inferior gemellus, and quadratus femoris. On the medial part of the thigh, the adductor longus, adductor brevis, and adductor magnus adduct the thigh and medially rotate it. The pectineus muscle adducts and flexes the femur at the hip. The thigh muscles that move the femur, tibia, and fibula are divided into medial, anterior, and posterior compartments. The medial compartment includes the adductors, pectineus, and the gracilis. The anterior compartment comprises the quadriceps femoris, quadriceps tendon, patellar ligament, and the sartorius. The quadriceps femoris is made of four muscles: the rectus femoris, the vastus lateralis, the vastus medius, and the vastus intermedius, which together extend the knee. The posterior compartment of the thigh includes the hamstrings: the biceps femoris, semitendinosus, and the semimembranosus, which all flex the knee. The muscles of the leg that move the foot and toes are divided into anterior, lateral, superficial- and deep-posterior compartments. The anterior compartment includes the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the fibularis (peroneus) tertius. The lateral compartment houses the fibularis (peroneus) longus and the fibularis (peroneus) brevis. The superficial posterior compartment has the gastrocnemius, soleus, and plantaris; and the deep posterior compartment has the popliteus, tibialis posterior, flexor digitorum longus, and flexor hallucis longus. |
SciQ | SciQ-5330 | evolution, zoology, anatomy, species
Title: Examples of animals with 12-28 legs? Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list:
snakes have 0
Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs)
Most mammals, reptiles, amphibians have 4 legs
Echinoderms (e.g., sea stars) typically have 5 legs.
Insects typically have 6 legs
Octopi and arachnids have 8 legs
decapods (e.g., crabs) have 10 legs
....But I can't really think of many examples of animals containing more legs until you reach 30+ legs in centipedes and millipedes. Some millipedes even have as many as 750 legs! The lone example I am aware of, the sunflower sea star, typically has 16-24 (though up to 40) limbs.
So my question is: what are some examples of animals with 12-28 legs? As a couple of counterexamples, species in the classes Symphyla (Pseudocentipedes) and Pauropoda within Myriapoda have 8-11 and 12 leg pairs respectively, so between 16 to 24 legs (sometimes with one or two leg pair stronlgy reduced in size).
(species in Symphyla, from wikipedia)
Another common and species-rich group with 14 walking legs (7 leg pairs) is Isopoda.
(Isopod, picture from wikipedia)
You also need to define 'legs' for the discussion to be meaningful. As you say, decapods have 10 legs on their thoracic segments (thoracic appendages), but they can also have appendages on their abdomens (Pleopods/swimming legs), which will place many decapods in the 10-20 leg range.
(Decapod abdominal appendages/legs in yellow, from wikipedia)
So overall, in Arthropoda, having 12-28 legs doesn't seem all that uncommon. There are probably other Arthropod groups besides those mentioned here that also have leg counts in this range.
However, for a general account, the most likely answer (if there is indeed a relative lack of 12-28 legged animals) is probably evolutionary contingencies and strongly conservative body plans within organism groups.
The following is multiple choice question (with options) to answer.
Snails, scallops, and squids are examples of invertebrates called what? | [
"mollusks",
"clams",
"orthopods",
"gastropods"
] | A | Mollusks are invertebrates such as snails, scallops, and squids. |
SciQ | SciQ-5331 | inorganic-chemistry, redox, combustion
As M. Farooq pointed out a combustion reaction happens quickly, producing heat, and usually light and fire. For example, lets look at combustion reaction of an alkene (a hydrocarbon). If it is a complete combustion, the fire have a blue flame:
$$\ce{C_nH_{2n} + $\frac{3n}{2}$ O2 -> nCO2 + n H2O}$$
If it is a partial combustion, it can have a multiple $\ce{C}$ compounds as products, and have a yellow flame due to presence of elemental $\ce{C}$:
$$\ce{C_nH_{2n} + x O2 -> m C + p CO + $(n-m-p)$CO2 + n H2O}$$
where $x = \frac{2(n-p-m) +p}{2} = \frac{2n-2p-2m +p}{2} = \frac{2n-p-2m)}{2}$. In your reaction would not produce fire and it didn't use either oxygen or other oxidants ($\ce{CuO}$ is not that type of oxidant). It is true that the reaction is a redox reaction.
The following is multiple choice question (with options) to answer.
Synthesis, decomposition, replacement, and combustion are all types of what reaction? | [
"chemical",
"natural",
"mineral",
"toxic"
] | A | Types of chemical reactions include synthesis, decomposition, replacement, and combustion reactions. |
SciQ | SciQ-5332 | energy-conservation, electrical-resistance, potential-energy, capacitance, dissipation
Title: Is the overall energy conserved in this situation? Imagine a fully charged capacitor.
This will create an electric field, and if a fixed charged particle is nearby, it will possess some amount of electric potential energy.
But what happens to the potential energy if one discharges the capacitor?
The potential energy must be converted into other forms of energy, but I can't understand how. If totally discharged the energy will have been dissipated as heat in cicuit resistance. If partially discharged, part of the energy is dissipated as heat, part stored somewhere else in the circuit, and part retained by the capacitor. In all cases the total energy is conserved.
All circuits have resistance (except supercooled conductors) so when a capacitor discharges at least part of its potential energy is dissipated as resistance heating. If the circuit consists only of resistance, all the energy will be dissipated as heat.
But if there’s other energy storage devices in the circuit some of the discharge energy can be stored in those devices. For example if there are other capacitors in the discharging circuit some of the discharge energy can be stored as electrical potential energy in those other capacitors. If there are rechargeable batteries in the circuit, part of the discharged energy may be stored as chemical potential energy in the batteries. The same would apply to any other electrical energy storage devices.
The above neglects a small amount of electromagnetic energy that may be radiated away from the circuit.
Hope this helps.
The following is multiple choice question (with options) to answer.
What are the devices placed in electric circuits where charge can build up, which store energy when charged and release it when they discharge? | [
"capacitors",
"antennas",
"generators",
"resistors"
] | A | When current flows through wires and resistors in a circuit as a result of a difference in electric potential, charge does not build up significantly anywhere on its path. Capacitors are devices placed in electric circuits where charge can build up. The amount of charge a capacitor can store before it “fills up” depends on its shape and how much electric potential is applied. The ratio of charge stored in a capacitor to the voltage applied is called its capacitance , measured in Farads . The larger the electric potential in volts, the stronger the electric field that is used to “cram” the charge into the device. Any capacitor will fill up with enough charge. Capacitors store energy when charged, and release it when they discharge. |
SciQ | SciQ-5333 | zoology, ecology
Giraffes' this is an energy saving feature. Giraffes don't need to use muscles to hold their neck. They just use when flexing their necks down, when drinking water etc.
According to Wikipedia, for an alternative hypothesis Ouranosaurus have a hump. (Other hypothesis is display sail or termoregulation sail of course. Also spinosaurus have this kind of alternative hypotesis but this hypothesis not accepted much as sail. and spinosaurus' spine different from bisons. Bison spines concentrating at shoulder but spinosaurs' not at the shoulder. You can find spinosaurus info from this page.)
The following is multiple choice question (with options) to answer.
What is the hinged structure attached to the cranium that allows an animal to grasp and tear its food? | [
"neck",
"jaw",
"tooth",
"throat"
] | B | Gnathostomes: Jawed Fishes Gnathostomes or “jaw-mouths” are vertebrates that possess jaws. One of the most significant developments in early vertebrate evolution was the development of the jaw, which is a hinged structure attached to the cranium that allows an animal to grasp and tear its food. The evolution of jaws allowed early gnathostomes to exploit food resources that were unavailable to jawless fishes. Early gnathostomes also possessed two sets of paired fins, allowing the fishes to maneuver accurately. Pectoral fins are typically located on the anterior body, and pelvic fins on the posterior. Evolution of the jaw and paired fins permitted gnathostomes to expand from the sedentary suspension feeding of jawless fishes to become mobile predators. The ability of gnathostomes to exploit new nutrient sources likely is one reason that they replaced most jawless fishes during the Devonian period. Two early groups of gnathostomes were the acanthodians and placoderms (Figure 29.10), which arose in the late Silurian period and are now extinct. Most modern fishes are gnathostomes that belong to the clades Chondrichthyes and Osteichthyes. |
SciQ | SciQ-5334 | physical-chemistry, terminology, units, filtering
Title: What is a Herzberg? Whatman lists the flow rates for their filters in a unit called a 'Herzberg':
What is this?
I've been searching around and I did find information about Herzberg flow rate testers, for example this old paper on filtration flow rate measurement and this summary of filtration terminology, but I can't seem to find two sources that agree with eachother.
The clearest looking description I found was that second link above, which states:
Whatman quantifies liquid flow rate for its range of filters by using a Herzberg flow rate tester. Prefiltered deaerated water is applied to the test filter (effective area $\pu{10 cm2}$) at a constant hydrostatic head ($\pu{10 cm}$). The rate of the flow is measured in seconds per $\pu{100 mL}$. Flow rate can also be measured by the modified ASTM method which uses a quadrant folded filter held in a wire loop. It is not considered to be as reliable or consistent as the Herzberg test.
The following is multiple choice question (with options) to answer.
The svedberg unit is a measure of the rate of what, which is tested in a centrifuge? | [
"secretion",
"precipitation",
"temperature",
"sedimentation"
] | D | The two ribosomal subunits are named base on their sedmentation rate in a centrifuge. The unit of measurement is the Svedberg unit , a measure of the rate of sedimentation, not the size. This accounts for why fragment names do not add up (70S is made of 50S and 30S). |
SciQ | SciQ-5335 | cell-biology
Title: Structure of Cell Are cells spheres or ovals/circles bound by phospholipidbilayer?
If they are spherical how are we able to see the nucleus through the phospholipid bilayer under a microscope? Not exactly. That is a stereotype of cells. Muscle cells are not round nor oval, but rather elongated rods. If you were to look up epithelia cells, you can quickly see that cells are grouped based on their physical characteristics; simple (round/oval & single layer), columnar, and cuboidal to name a few. Cells come in many shapes and sizes. As Hans stated, stains are vital in viewing cellular components. There is a diverse amount of stains used - which all carry a purpose and benefit in a specific application.
The following is multiple choice question (with options) to answer.
Muscles and skin are examples of what, consisting of specialized cells? | [
"ligaments",
"tissues",
"molecules",
"layers"
] | B | |
SciQ | SciQ-5336 | cell-biology, development
Title: What determines the fate of a cell with respect to differentiation? I have been reading about Townes and Holtfreter's work in 1955, in which cells are dissociated from a blastocyst in an alkaline solution then mixed together and spontaneously reaggregates based on type, so epidermal cells around the outside and neural plate cells in the middle.
I understand enough about cell adhesion to understand why the cells will seem to attract cells of their own type, but would like to know how they can initially detect what to become and where they are needed in a specialised form, without something acting like a brain telling them what to become and where to go.
If the selection from the available types is random, as I suspect, what happens to blastocysts with too much epidermal tissue or vice versa? I'm struggling to imagine how organisms like this can develop without something taking the lead and actively coordinating what goes where. Cell differentiation, cell fate and cell mapping is an interplay of accessible evolutionary strategies/programmes and responses to dynamic environmental cues such as specialized hormones (e.g. morphogens) and physical parameters and constraints. That is putting it very broadly. It is a complex issue, if L. Wolpert's PLOS assays are any indication. I compiled a few links to get you started.
Specifically, reappraising the topic of your cited classical experiment are R.Moore et al:
The classical cell sorting experiments undertaken by Townes and
Holtfreter described the intrinsic propensity of dissociated embryonic
cells to self-organize and reconcile into their original embryonic
germ layers with characteristic histotypic positioning. Steinberg
presented the differential adhesion hypothesis to explain these
patterning phenomena.....
The following is multiple choice question (with options) to answer.
When do cells acquire different identities in an ordered spatial arrangement? | [
"during morphogenesis",
"before morphogenesis",
"larval stage",
"during mitosis"
] | A | |
SciQ | SciQ-5337 | evolution, zoology, anatomy
Title: Are the transverse septum in sharks and the diaphragm in mammals homologous structures? Are the transverse septum in sharks and the diaphragm in mammals homologous structures?
I have searched on Google Scholar and Web of Science, but haven't found substantial evidence to prove or falsify the claim. A beginning of answer here below, I hope. Please first consider that many structures are involved in the question here, the diaphragm (UBERON:0001103), the diaphragmaticus muscle (UBERON:0036071) and the septum transversum (UBERON:0004161). At Bgee (bgee.org) we aim annotating relations of similarity between anatomical structures, please have a look at our GitHub
https://github.com/BgeeDB/anatomical-similarity-annotations
We already annotated 'diaphragm' as a mammalian structure, not homologous in Amniota (please see https://raw.githubusercontent.com/BgeeDB/anatomical-similarity-annotations/master/release/similarity.tsv). In our next release, you will see the annotation for the 'diaphragmaticus muscle' which is an analog organ in Crocodylians (and Turtles) but not homologous to the mammalian diaphragm either. See here for more details about this new Uberon class:
https://github.com/obophenotype/uberon/issues/1229.
Based on the comments here above, I would say that currently we can argue that there is no evidence for a homologous relationship between the 'septum transversum' in sharks and the mammalian diaphragm. Please note that UBERON:0004161 septum transversum describes the (mammalian) embryonic structure that will give rise to the central tendon of the diaphragm, while here you are talking about a adult structure closer to a 'diaphragmaticus muscle'-like septum, as far as I understand.
But anyway thank you for your interesting question that points out a very exciting and rapidly evolving evo-devo field, as this recent paper also suggests
The following is multiple choice question (with options) to answer.
What structures sweep laterally, hugging the pelvic walls, then turn medially and pierce the bladder wall obliquely? | [
"tubules",
"catheters",
"ureters",
"fallopian tube"
] | C | Ureters The kidneys and ureters are completely retroperitoneal, and the bladder has a peritoneal covering only over the dome. As urine is formed, it drains into the calyces of the kidney, which merge to form the funnel-shaped renal pelvis in the hilum of each kidney. The hilum narrows to become the ureter of each kidney. As urine passes through the ureter, it does not passively drain into the bladder but rather is propelled by waves of peristalsis. As the ureters enter the pelvis, they sweep laterally, hugging the pelvic walls. As they approach the bladder, they turn medially and pierce the bladder wall obliquely. This is important because it creates an one-way valve (a physiological sphincter rather than an anatomical sphincter) that allows urine into the bladder but prevents reflux of urine from the bladder back into the ureter. Children born lacking this oblique course of the ureter through the bladder wall are susceptible to “vesicoureteral reflux,” which dramatically increases their risk of serious UTI. Pregnancy also increases the likelihood of reflux and UTI. The ureters are approximately 30 cm long. The inner mucosa is lined with transitional epithelium (Figure 25.6) and scattered goblet cells that secrete protective mucus. The muscular layer of the ureter consists of longitudinal and circular smooth muscles that create the peristaltic contractions to move the urine into the bladder without the aid of gravity. Finally, a loose adventitial layer composed of collagen and fat anchors the ureters between the parietal peritoneum and the posterior abdominal wall. |
SciQ | SciQ-5338 | geophysics, plate-tectonics, earth-history, continent
Title: Why Do Supercontinents Form? It would seem, on the face of it, improbable that the continental land-masses would accumulate into a single composite, yet it has happened numerous times, and is expected to again in the future.
There must likely then be some aspect of plate tectonics which favors these arrangements.
Can anyone provide an explanation?
EDIT: This is not, as I see it, a duplicate of the 'What are the causes of the supercontinent cycle?' question. This question goes to what process drives the formation of any & all supercontinent formations, which I assert should be improbable, made more improbable by their recurrence, not so much the cycle itself. The other question did not address this more fundamental aspect, or in any case receive a pertinent account of its resolution. If anyone wants to engage on this, or doesn't see the distinction, please do so in the comments or a chat. I think the mechanisms that you're looking for are subduction, paired with the "stickiness" of continental crust.
The subduction of oceanic crust under continental crust inevitably creates a net movement of crustal material toward a continental plate. Any oceanic plate that is carrying continental material will therefore always drag that continent toward the continental plate that it is subducting underneath, always resulting in eventual collision.
If an oceanic plate has subduction occurring on both sides, the ocean will inevitably narrow until it closes, thereby causing the continental plates on either side to collide.
In every case, subduction inevitably pulls continents together.
Furthermore, once continental plates collide, they have a tendency to stick together for long periods of time, increasing the likelihood that all continental material will eventually accumulate there.
The following is multiple choice question (with options) to answer.
What was the last supercontinent on earth? | [
"pangaea",
"eurasia",
"rodinia",
"laurasia"
] | A | There are times in Earth history when all of the continents come together to form a supercontinent . Supercontinents come together and then break apart. Pangaea was the last supercontinent on Earth, but it was not the first. The supercontinent before Pangaea is called Rodinia. Rodinia contained about 75% of the continental landmass that is present today. The supercontinent came together about 1.1 billion years ago. Rodinia was not the first supercontinent either. Scientists think that three supercontinents came before Rodina, making five so far in Earth history. |
SciQ | SciQ-5339 | evolution, natural-selection, mutations, sexual-reproduction
The testis seems to be the Oven in which genetic variation is baked. The rapid turnover of spermatogenesis, whereby each primary spermatocyte finally results in 4 sperms (Compared to One Ovum resulting from each primary Oogonia), that's beside the very large number of sperms produced daily, that continues for years and year. While with the Oogenesis everything really finishes at the foetal life, the remaining is just maturation steps, nothing is new as far as change of genetic material inside the Oocytes is concerned, this is the state throughout most of the female's life.
When I look at the seminiferous tubules, and see all those layers of spermatocytes leading to sperms, I tend to think that there is even some small scale natural selection, that bad mutated germline cells would die off, and only the ones with good genomes would survive all the stages of spermatogensis, and possibly the ones with beneficial mutation might have an advantage in survival in that milieu and even might have better chances of fertilizing the ovum?
Not only that, the testis seems to be more exposed to stressors inside the body and even to direct external environmental stressors, while the Ovaries lying deep inside, seem to be more protected. The Oocyte actually "selects" one sperm, so it's rule is selective rather than productive of change.
All of that makes one think that it is the male germline cells that could mediate high mutation rate in response to stressors, or even without stressors by virtue of the very high production rate of germline cells for very long periods of time. It seems that this is the real source of beneficial mutations that would ultimately drive evolution.
The following is multiple choice question (with options) to answer.
When conditions deteriorate, hydras can reproduce sexually, forming resistant zygotes that remain dormant until when? | [
"conditions improve",
"Hydras choose",
"Spring",
"Temperature rise"
] | A | |
SciQ | SciQ-5340 | waves, conservation-laws, acoustics
Therefore B will be moving, and A will be stationary.
multi dimensional space
In 2d/3d space, most collisions involves vectors that won't transfer 100% of energy from A to B... This is because the only energy that is transferred is the energy that is pointed at B. All energy that is perpendicular to B is not transferred. So in non 1d space, when A collides with B. All of A's KE directed to B is transferred to B, and all of B's energy that is directed A is transferred A. Any energy perpendicular to A/B remains with A/B and is not transferred.
The following is multiple choice question (with options) to answer.
Because collisions are ______, energy can be transferred between molecules during them. | [
"conductive",
"preservative",
"elastic",
"inelastic"
] | C | Energy can be transferred between molecules during collisions. Collisions are completely elastic. |
SciQ | SciQ-5341 | at that point). Label the identification points above. torque about the center from the force of tension. "Rolling resistance " which slows the wheel is a completely different force. At the bottom of the incline, the speed of the hoop's center-of-mass is v. Cylinder, sphere, hoop) Pure rolling motion (rolling without slipping) Rolling motion along a flat surface (inclined, horizontal or even vertical). The motion of a disk that is spun on a smooth flat surface slowly damps out due to friction. Energy is still conserved, but the initial potential energy is now converted into two types of kinetic energy. Consider two cylinders that start down identical inclines from rest except that one is frictionless. For analyzing rolling motion in this chapter, refer to Figure 10. In this section, we compare two situations: (1) rolling and slipping, and (2) rolling without slipping. 4 – A vertical force but a horizontal motion A spool of mass M has a string wrapped around its. these aspects should be properly darified. If the pulley makes four revolutions without the rope slipping, what length of. 26A is Without slipping, the disk has two variables, X and β, but only one degree of freedom. Physics Flash Animations. In other words, at any particular instant of time, the part of the disc in contact with the surface is at rest with respect to the surface. Salukvadze optimal solution and ranked Pareto optimal solutions. To define such a motion we have to relate the translation of the object to its rotation. Each can starting from rest means each starts with the same gravitational potential energy , which is converted entirely to , provided each rolls without slipping. It is known that this motion can be considered as a rotation about an. rolls without slipping on a horizontal terrain in such a way that it touches the terrain on the surface line parallel to the y-axis. • The red curve shows the path (called a cycloid) swept out by a point on the rim of the wheel ω swept out by a point on the rim of the wheel. Rolling Motion + = Rolling without slipping Pure translation Pure rotation about CM Subscribe to view the full document. 4 m/s rolls up a hill without slipping. • Describing rotational motion • Rolling without slipping • Torque Lecture 24: Rotational Motion. Iclicker #1. Consider a thin axisymmetric disk with mass and radius that rolls without slipping over a stationary and rough
The following is multiple choice question (with options) to answer.
What is the tendency of an object to remain at rest or remain in motion called? | [
"impetus",
"magnetism",
"inertia",
"flow"
] | C | 4.2 Newton’s First Law of Motion: Inertia • Newton’s first law of motion states that a body at rest remains at rest, or, if in motion, remains in motion at a constant velocity unless acted on by a net external force. This is also known as the law of inertia. • Inertia is the tendency of an object to remain at rest or remain in motion. Inertia is related to an object’s mass. • Mass is the quantity of matter in a substance. |
SciQ | SciQ-5342 | neuroscience, neuroanatomy
Title: Why is the anterior pituitary not considered part of the diencephalon? According to the wikipedia page on the diencephalon, the posterior pituitary gland is considered part of the diencephalon, but the anterior is not. Is there a reason that these two lobes of the same gland are considered different enough not to be part of the same brain region? Worth going to the wikipedia page on the pituitary:
In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary, which is an extension of the hypothalamus.
The anterior pituitary arises from an invagination of the oral ectoderm (Rathke's pouch). This contrasts with the posterior pituitary, which originates from neuroectoderm.
The posterior lobe develops as an extension of the hypothalamus, from the floor of the third ventricle.
In other words, the different parts of the pituitary are, developmentally, entirely separate. The posterior lobe is actually part of the hypothalamus. The anterior lobe is not even part of the brain.
Lumping them together with one label happened because the anatomists who originally named the thing didn't know much about it, which is not surprising because anatomical names are quite old and understanding of the functions of any parts of the brain is quite new. Old names stick.
The following is multiple choice question (with options) to answer.
The pituitary gland is called the “master gland” of what system? | [
"nervous",
"digestive",
"hormonal",
"endocrine"
] | D | The pea-sized pituitary gland is just below the hypothalamus and attached directly to it. The pituitary receives hormones from the hypothalamus. It also secretes its own hormones. Most pituitary hormones control other endocrine glands. That’s why the pituitary gland is called the “master gland” of the endocrine system. Table below lists several pituitary hormones and what they do. |
SciQ | SciQ-5343 | dna, sequence-analysis, nucleic-acids
Some of the nucleotides force the DNA polymer molecule to take on different shapes, or to be stiffer or more flexible, because of their underlying chemical shape.
A polyacrylamide gel is basically a big tangle of polyacrylamide molecules and bonds. So think of DNA moving through it like trying to drag a rope through a forest. A very long rope will tangle more than a short one and will take more effort/time to pull through the trees. However, a rope of the same length that has a different structure (maybe it has lots of knots tied in it, or it is stiff rather than flexible) may also be harder to pull through the forest, even though it's not any longer.
The following is multiple choice question (with options) to answer.
What links together to form long polymeric chains? | [
"nucleotides",
"peptides",
"genes",
"lipids"
] | A | (a) When pyrimidine or purine and a sugar react to form a glycosidic bond, a nucleoside is produced. Adding a phosphoric acid group to the sugar of a nucleoside produces a nucleotide. (b) Nucleotides link together to form long polymeric chains. A DNA molecule consists of two such chains held together by hydrogen bonding between the purine and pyrimidine components on different chains. Mutations in the DNA of an organism may lead to the synthesis of defective proteins. Phenylketonuria (PKU), for example, is a condition caused by a defective enzyme. Left. |
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