source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-4744 | everyday-chemistry, biochemistry, food-chemistry, terminology
As the discovery of the vitamins progressed, it was realized that “Factor B”
consisted of a number of chemically and physiologically distinct compounds.
Before they were identified chemically, they were given a logical series of alphanumeric
names: B1, B2, and so forth
From a pharmaceutical perspective...
The "complexity" of vitamin B compounds simply suggest a combination of different compounds that fall under this family. Because vitamin
compounds are required in relatively large amounts compared to fat soluble counterparts, it makes sense to combine them as supplements rather than packaging
7+ pharmaceutical products as "Vitamin B1", "Vitamin B2", "Vitamin B3"... suplements, it creates more confusion and non-compliance instead their systematic names are used for example pyridoxine injection (vitamin B6), Nicotinamide tablets but where multivitamin are prescibed its just a "complex" of there compounds usually 5-6 of these "B" vitamins.
It is important to note that such compounds are requirement in very small quantities/day, and overdosing (through such these compounds can cause undesirable side effects).
Other forms of vitamins (fat soluble) are equally important but most of them are either stored in body in reserves e.g Vitamin A, others like Vitamin K are synthesised in the body by bacteria hence are needed in very small amounts
This is the chief reason why there are fewer supplements of such vitamins (although they may be needed in special cases).
For a compound to be considered a vitamin, it must be shown to be a
dietary essential. Its elimination from the diet must result in a
more-or-less clearly defined deficiency disease, and restoration must
cure or prevent that deficiency disease.
Several forms of vitamin D?
Vitamin D is not strictly a vitamin, rather it is the precursor of one
of the hormones involved in the maintenance of calcium homeostasis and
the regulation of cell proliferation and differentiation, where it has
both endocrine and paracrine actions.
The following is multiple choice question (with options) to answer.
Vitamins are organic compounds that are essential in very small amounts for the maintenance of normal what? | [
"metabolism",
"calcium",
"respiration",
"pigments"
] | A | Vitamins are organic compounds that are essential in very small (trace) amounts for the maintenance of normal metabolism. They generally cannot be synthesized at adequate levels by the body and must be obtained from the diet. The absence or shortage of a vitamin may result in a vitamin-deficiency disease. In the first half of the 20th century, a major focus of biochemistry was the identification, isolation, and characterization of vitamins. Despite accumulating evidence that people needed more than just carbohydrates, fats, and proteins in their diets for normal growth and health, it was not until the early 1900s that research established the need for trace nutrients in the diet. Because organisms differ in their synthetic abilities, a substance that is a vitamin for one species may not be so for another. Over the past 100 years, scientists have identified and isolated 13 vitamins required in the human diet and have divided them into two broad categories: the fat-soluble vitamins, which include vitamins A, D, E, and K, and the water-soluble vitamins, which are the B complex vitamins and vitamin C. All fatsoluble vitamins contain a high proportion of hydrocarbon structural components. There are one or two oxygen atoms present, but the compounds as a whole are nonpolar. In contrast, water-soluble vitamins contain large numbers of electronegative oxygen and nitrogen atoms, which can engage in hydrogen bonding with water. Most water-soluble vitamins act as coenzymes or are required for the synthesis of coenzymes. The fatsoluble vitamins are important for a variety of physiological functions. The key vitamins and their functions are found in Table 18.8 "Fat-Soluble Vitamins and Physiological Functions" and Table 18.9 "Water-Soluble Vitamins and Physiological Functions". Table 18.8 Fat-Soluble Vitamins and Physiological Functions Vitamin. |
SciQ | SciQ-4745 | cell-biology, meiosis, mitosis
Title: Is the cell cycle applicable to meiosis as well, or just mitosis? All the diagrams I can find, show the cell cycle as having G1 phase (growth 1), S phase (DNA replication), G2 (growth 2) before the Mitotic phase (mitosis + cytokinesis).
Is there an equivalent "cell cycle" for meiosis, since the chromosomes in parent cell in meiosis also having "double" the genetic material prior to cell division (presumably from DNA replication too)?
Is it simply the same cell cycle as mitosis but with a Meiotic phase instead of Mitotic?
If so, would appreciate if anyone had a diagram :) Thanks! The cell cycle is only associated with mitosis. The cell cycle is the normal process of cell division with which cells can indefinitely increase their number by cyclically repeating the process. When a cell goes through the cycle, the result is two cells that are genetically identical.
Meiosis is a special type of cell division (which can occur only in eukaryotes) that produces cells that are not genetically identical to the initiating cell. The number of chromosomes in each of the resulting cells is half the number that were in the initial cell. (These haploid cells can later participate in fertilization, producing a cell with the original number of chromosomes.) Many of the steps of meiosis are similar to the steps involved in mitosis, but overall the process is more complex. Since meiosis reduces the number of chromosomes, it cannot be repeated and so does not take part in a cell division cycle.
The following is multiple choice question (with options) to answer.
In eukaryotic cells, what divides before the cell itself divides? | [
"protons",
"electrons",
"cell wall",
"nucleus"
] | D | In eukaryotic cells, the nucleus divides before the cell itself divides. The process in which the nucleus divides is called mitosis. Before mitosis occurs, a cell’s DNA is replicated. This is necessary so that each daughter cell will have a complete copy of the genetic material from the parent cell. How is the replicated DNA sorted and separated so that each daughter cell gets a complete set of the genetic material? To understand how this happens, you need to know more about chromosomes. |
SciQ | SciQ-4746 | human-anatomy
In the wrist, you can have palmar flexion, dorsiflexion (extension), ulnar flexion (abduction) and radial flexion (adduction) (Teachmeanatomy).
In the ankle, you can have plantar flexion, dorsiflexion (extension), inversion (inward rotation, adduction) and eversion (outward rotation, abduction). (ScienceDirect).
In the shoulder and hip, raising a limb to the same side as the limb is, is abduction (lateral extension) and raising it to the opposite side is adduction.
Moving the thumb toward the palm (in the same plane as palm) is flexion (adduction) and moving it away from it is extension (abduction).
You can read about flexion and extension and other movements here: Types of Body Movements (BCcampus)
The following is multiple choice question (with options) to answer.
The joint that lies between the radius and the ulna is what kind of joint? | [
"pivot joint",
"shaft joint",
"socket joint",
"hinge joint"
] | A | Pivot Joint. The joint at which the radius and ulna meet is a pivot joint. Movement at this joint allows you to flip your palm over without moving your elbow joint. |
SciQ | SciQ-4747 | neuroscience, neurophysiology, sensation, hearing, human-ear
Title: Why/how does exposure to noise cause cochlear hair-cell loss? I am trying to understand why listening to loud music - e.g. concerts or earphones at high volume damages hearing.
According to the National Institute on Deafness the cause is physical.
Most NIHL is caused by the damage and eventual death of these hair
cells. Unlike bird and amphibian hair cells, human hair cells don’t
grow back. They are gone for good.
But I don't understand why/how would noise - which should basically lead to higher amplitude waves in the basilar membrane, induce damage and death of these hair cells? There are a number of pathophysiological mechanisms that are thought to underlie noise-induced hearing loss:
Mechanical damage to the delicate cells and supporting structures of the organ of Corti;
Reduced blood flow to the inner ear;
Intense metabolic activity, which increases mitochondrial free radical formation.
Reactive oxygen species (ROS) are highly reactive. They are essential for mitochondrial function to generate energy. However, too many of them damage cellular lipids, proteins, and DNA, and upregulate apoptotic pathways. The observed impaired blood flow to the cochlea can enhance the toxic effects of ROS. Mechanical damage to the delicate hairs and membranes of the hair cells reduces their ability to converge acoustical energy into potential differences.
References
- Le Prell et al., Hear Res (2007); 226(1-2): 22–43
- Kurabvi et al., Hear Res (2017); 349: 129-37
The following is multiple choice question (with options) to answer.
Because it damages hair cells, what is the most cause of hearing loss in adults? | [
"water in the ears",
"exposure to noise",
"bacteria",
"ear wax"
] | B | Most adults experience at least some hearing loss as they get older. The most common cause is exposure to loud sounds, which damage hair cells. The louder a sound is, the less exposure is needed for damage to occur. Even a single brief exposure to a sound louder than 115 decibels can cause hearing loss. Figure below shows the relationship between loudness, exposure time, and hearing loss. |
SciQ | SciQ-4748 | molecular-biology, dna, molecular-genetics
Additionally, there's regulation of protein biosynthesis at the ribosome, which often complexes with other molecules in complicated ways to ensure an additional layer of tuning of how much protein is produced, and how quickly.
There are many, many other known levels of regulation. There also remain many unknown mechanisms of regulation, which scientists are busy with uncovering and understanding as we speak.
EDIT: What dictates which protein to synthesize at a given time? The history and present identity of a cell. By identity, I mean its state regarding regulation of its own gene expression, as well as other things.
The following is multiple choice question (with options) to answer.
What is regulated to ensure that the correct proteins are made? | [
"Fat expression",
"acids expression",
"variation expression",
"gene expression"
] | D | Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any point in the expression of a gene, from the start of transcription to the processing of a protein after translation. The focus in this lesson is the regulation of transcription. |
SciQ | SciQ-4749 | optics, visible-light, geometric-optics, optical-materials
Title: Focal plane of ideal thin lenses and spherical mirrors Recently I was studying about optical instruments and in my book I came across a point which stated that
When non axial parallel rays are incident on an ideal spherical mirror at a small angle or a parabolic mirror, the rays meet at a point on the focal plane rather than the focus point.
Also in the section about refracting telescopes, diagrams drawn show that the non axial parallel rays meet at a point on the focal plane.
Please note that I'm talking about concave mirrors and convex lenses and aberration and other non idealities are ignored.
I looked at some of the websites like this and this to understand why it is the case but an explanation is lacking everywhere.
I mean, can we show that non axial parallel rays will always converge at a point on the focal plane?
I tried to proceed by attempting to find the equation for the focal plane but I don't think that will work at all.
Could anybody please tell me a way to do this?
How do we guarantee that a group of parallel (non axial) rays incident on a spherical mirror or a lens will always converge at the focal plane (assuming ideality)?
I also saw this SE post and tried to follow the "Physics Teacher" link mentioned in comments but couldn't reach it.
Any kind of approach, either geometric or mathematical will help.
Thanks for any suggestions. This sketch may give you an idea for the case of the ideal thin lens: The ray AC will continue in a straight line (going through the center of the lens), while BD, which passes through focal point F, will refract to become parallel after the lens. Simple construction shows that the point where these lines intersect is the focal plane.
A spherical mirror M can be thought of as a part of a sphere - and when you are incident “at an angle to your mirror” you could equally say you are hitting “another part of the sphere”, mirror M’. As such, the rays would go through the “original” focal point F; if we consider the “actual” focal point F’ for the segment of the mirror at an angle, we see that F and F’ lie approximately (but not exactly) in the focal plane of M’ (cyan dashed line). I indicate the error (aberration) in my diagram with $\epsilon$.
The following is multiple choice question (with options) to answer.
What mirrors diverge light rays and, thus, have a negative focal length? | [
"convex",
"diffraction",
"curved",
"concave"
] | A | behind the mirror. Convex mirrors diverge light rays and, thus, have a negative focal length. |
SciQ | SciQ-4750 | microscopy, histology, fluorescent-microscopy
If I need a fluorescent one, wondering if there is anything else needed, like special lighting or special materials for tagging the cells, which seems like it might require extra stuff like centrifuge and who knows what else.
Samples can sometimes have autofluorescence (e.g. the chitin that makes up the cuticle of insects is autofluorescent) but most samples are not. Almost always a fluorophore is used to stain the specimen for something. These can be cheap or very expensive, depending on what you want to stain. This really depends on your sample and how it is prepared. And know that most 'good' samples' are dehydrated or are treated by chemical fixation, which requires chemicals you cannot usually find at a local pharmacy. It depends on how ambitious you want to get as an amateur microscopist!
Also, you won't need a centrifuge.
For the histology slides, wondering generally what it takes to do that too, if I can get by with a regular microscope.
You can get by with a regular upright widefield microscope for sure. If you perform the sectioning well (making thin slices of your sample) then even basic microscopes will produce fascinating images, provided your lighting is good. It helps to have a condenser or a nice lamp and some thin and clean glass slides for well illuminated images.
Maybe fluorescent microscopy requires advanced biotechnology of some
sort, which is sort of what I'm wondering, what the basics are.
It requires a little bit more optical work. I would stay away from it unless you are serious, because it takes quite a bit more work and equipment to make it minimally workable. Normal microscopy is certainly a lifetime of fun if you have the desire to find interesting samples and work to make them good for imaging.
Addendum: the principle of fluorescence microscopy is quite simple but aligning everything is actually quite difficult if you are an amateur with no specialized tools. Here is the principle only, notice how the input and output must be aligned and the small objective lens has to transmit both excitation and reflected light:
The following is multiple choice question (with options) to answer.
During what stage are chromosomes condensed enough to be seen under a microscope? | [
"meiosis",
"cytokinesis",
"epistasis",
"mitosis"
] | D | |
SciQ | SciQ-4751 | safety, gas
Title: Rotten Egg Gas Smell Background context for question
When I was young, we'd go fishing. And Dad would put a camper on the back of the truck. One time we came back in after fishing and the camper smelled like rotten eggs. He used that as an opportunity to teach us how some gases are tasteless/odorless. And as a result that sort of rotten egg smell is added as a safety measure.
Question:
My question is this: What are those gases that are odorless that then have that rotten egg smell added to them? Rotten eggs happen much less frequently than 50-60 years ago because of better hen-consumer refrigeration. Most people today have not had the pleasure of smelling them. H2S and low molecular weight mercaptans [AKA thiols] have distinct more or less unpleasant odors tho at low concentrations they can smell sweet, and we can develop tolerances to many at higher concentrations when they can be deadly. H2S is supposedly the active ingredient in rotten eggs; Methylsulfide CH3SH the active gas in human feces, and thioglycolic acid in eau de skunk.
Manufactured gas, no longer used, was a mix of H2 and CO and is toxic. It was flavored with mercaptan at rather high levels; smelling gas then was almost a death sentence, we were trained to open windows and leave immediately. There was also the explosion hazard. Manufactured gas was replaced by "natural", really fossil fuel, gas that is mostly methane CH4. Methane is odorless, not toxic, but it can be soporific, and it can explode. A warning is still necessary tho it seems to me the odorant is now less noxious and less intense than before [It could be my sense of smell has waned.]. It is to protect from explosion, again evacuate and ventilate. Odorants are added to propane and LPG, I do not know about hydrogen. Perfumes are added to many products to overcome odors or enhance odors and Bitrex is added to some drugs to make them less palatable so it works both ways.
The following is multiple choice question (with options) to answer.
What is an odorless white solid that is harmless unless consumed in large quantities? | [
"Hydrogen",
"sodium chloride",
"oxygen chloride",
"carbon chloride"
] | B | A: Sodium chloride is an odorless white solid that is harmless unless consumed in large quantities. In fact, it is a necessary component of the human diet. |
SciQ | SciQ-4752 | photons, material-science, absorption, optical-materials, glass
Funny thing is, as I wrote this long question, I feel like I answered my own question. Is it basically that whereas the molecules in opaque materials generally convert photons to heat after absorption, those in transparent materials such as glass/water are unable to do so and so must re-emit them? This is a really interesting question, and I worry that you are getting overly bogged down by being unable to focus individually on the different perspectives which are happening at multiple scales. First, let's tackle the more microscopic quantum scale. If we want to understand how light is (or is not) being absorbed by a material, we must first understand what would cause that absorption in the first place. You hit the nail on the head by giving an example of a process that would allow light to be absorbed; absorption of UV-visible light often leads to the excitation of electrons about the various energy levels within the material. A related phenomena might be the absorption of IR light by molecules because of the excitation of the vibrational degrees of freedom into excited states. All together, the various ways that a material may absorb light are collectively determined by the quantum mechanical structure of the material and what levels and states are available. Of course, describing these levels gets increasingly complicated the more complex the material becomes (which is why I have a job!). But there is one key thing you are missing.
While there may be levels present to allow an absorption of light, we still have to ask how likely it is that the light is absorbed! The classic example of such a calculation is Fermi's Golden Rule in perturbation theory for a two level system which relates the probability of absorption to the transition dipole moment between the two states. See MacQuarrie's Physical Chemistry A Molecular Approach, or his Statistical Mechanics for derivations and details. So we not only have to worry about whether there are levels for the light to cause transitions between, but also the probability of this happening at all. This probability analysis becomes more difficult when we then have to consider how frequently the light will actually get an opportunity to be absorbed on its journey.
The following is multiple choice question (with options) to answer.
Melting, sublimation, and evaporation absorb what from their surroundings? | [
"cold",
"heat",
"vibration",
"moisture"
] | B | Melting, sublimation, and evaporation absorb heat from their surroundings. Freezing, deposition, and condensation release heat. |
SciQ | SciQ-4753 | molecular-biology, molecular-genetics, development, sex
Quote from a Review (Yao 2005):
We have just begun to glimpse into the mechanisms underlying ovarian development. Convincing evidence challenges us to reconsider the existing paradigm that describes ovarian development as a default system. The default concept was first proposed in the early 1950s when Jost performed the groundbreaking experiments to demonstrate mechanisms of sex differentiation of reproductive tracts (Jost, 1947, 1953, 1970). The term “default” was not originally intended to describe the developmental status of the ovary. Instead, it is referred to the female reproductive tract or the Mullerian duct based on the fact that the female reproductive tract forms in both XX and XY individuals in the absence of gonads. Indeed, now it has become evident that early ovarian development is an active process involving intrinsic cell fate decisions and complex crosstalks between germ cells and somatic cells. Most intriguingly, the appearance of testicular structures in XX individuals where Sry and its downstream components are absent further raises the improbable question: Could the testicular development be default after all?
The following is multiple choice question (with options) to answer.
What is the series of changes in the reproductive system of a mature female that happens monthly? | [
"urinary cycle",
"menstrual cycle",
"fetal cycle",
"pregnancy"
] | B | The menstrual cycle is a series of changes in the reproductive system of mature females that repeats every month. While the egg and follicle are developing in the ovary, tissues are building up inside the uterus , the reproductive organ where the baby would develop. The uterus develops a thick lining covered in tiny blood vessels. This prepares the uterus to receive an egg that could develop into a child (a fertilized egg). The occurs during the first part of the cycle. |
SciQ | SciQ-4754 | It doesn't really matter, I think this is all be above me.
Melody Apr 5, 2015
#22
0
Hi All,
I was intrigued by the answer Melody gave and would like to comment on it. See the approach of diving people into groups of same sizes is a pretty standard one. For example if you want ot divide a group of 8 people into pairs (i.e. all equal sizes) the standard approach shall be 8!/(((2!)^4)*4!), i.e divide 8! by 2!*2!*2!*2! and multiply the whole with 1/4! (since there are 4 groups of equal sizes) and it returns the same answer as 105. This can be used for anything. (3N as well). Say N people need to be distributed in 2 groups of 2 and 1 group of 3, then it is N!/2!*2!*3!*2! (i.e. 2! -> since 2 items belon to one group, 2! -> since 2 items belon to one group,3! -> since 2 items belon to one group, 2! -> since 2 groups are identical in size.)
Now that concept out of the way, the thing that intrigued me is its application in geometrical figures, like the one discussed. I think it has happened because in such a scenario we fix one group namely AB and then form 3 paired groups, and since it is a square all the 8 arrangements will be identical, hence giving us the formula (2k-1)!/2^k-1*3!
i.e. (2k)!/(2k*((2!)^3)*3!)
I think that is the case. But definitely for sure such a formula wouldnt work out in other geometrical figures or if the numbers werent 8 for example, i.e we have 6 persons and there are 8 places.
Guest Nov 25, 2015
#23
+5
After all these discuession, i just wanna post the correct answer just to make it clear.
There are 8! ways to place the people around the table, but this counts each valid arrangement 4 times (if you move each person 2, 4, or 6 places clockwise you get the same arrangement). The answer is 8!/4 = 10080.
The following is multiple choice question (with options) to answer.
What is the average number of individuals per unit of area or volume called? | [
"crowdedness",
"population density",
"population count",
"population structure"
] | B | Population size is the number of individuals in a population. Population density is the average number of individuals per unit of area or volume. The pattern of spacing of individuals in a population may be affected by characteristics of a species or its environment. |
SciQ | SciQ-4755 | 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.
What types of living beings have water vascular systems and unique tube feet? | [
"Ducks",
"echinoderms",
"diatoms",
"mollusks"
] | B | Echinoderms have a unique water vascular system with tube feet. This allows slow but powerful movement. |
SciQ | SciQ-4756 | earth-history
Common elements in space, such as CO2, H20, CH4 and NH3 are gaseous at Earth's distance from the sun and as a result, are unlikely to stick to anything in the Earth's formation region. This is true for all 4 inner planets and likely all rocky worlds. Rocky planets likely can only form close to their star, just as gas giants, ice giants or other icy abundant bodies like comets and low-density moons, can only form further out.
Gases like the 4 above can begin to be retained around a planet after it reaches a sufficiently large mass with low enough surface temperature to retain those gases by gravity.
The boundaries where CO2, H20, CH4, NH3 and other gases can be found in the protoplanetary disk is called the frost line. Different gases have different frost lines depending on their freezing point.
It's thought that much of Earth's water, CO2, CH4 and NH3 came to the Earth by comet after the planet formed. There's still some uncertainty on the percentages, as some of those elements could have been trapped during formation.
Just to add, hydrogen and helium are obviously abundant, but will only begin to accrue around a planet of a certain mass. In our solar-system, only Jupiter and Saturn are massive enough to accrue hydrogen and helium. That's why Uranus and Neptune are relatively low on hydrogen and helium compared to the universal abundance.
Argon is in Earth's atmosphere because it forms from gradual radioactive decay of Potassium-40. Earth's Helium is also present as a result of radioactive decay.
The following is multiple choice question (with options) to answer.
Which two gases make up the bulk of earth's atmosphere? | [
"nitrogen and oxygen",
"nitrogen and argon",
"carbon and oxygen",
"phosphorus and oxygen"
] | A | A: Air in the atmosphere is a gaseous solution. It is a mixture that contains mainly nitrogen and oxygen gases, with very small amounts of several other gases. The circle graph in the Figure below shows the composition of air. Because air is a solution, it is homogeneous. In other words, no matter where you go, the air always contains the same proportion of gases that are shown in the graph. |
SciQ | SciQ-4757 | radioactivity
Title: how can carbon dating even work? Its at atomic level! I am a homeschooling parent, so pardon me asking stupid questions.
Everywhere I read, it is said carbon based lifeforms eat carbon and after their death that atom starts a decay.
But what I cannot understand, we dont eat or work with food at atomic levels. Yes, life forms breaks down molecules from food and use them as they wish. But that chemical process does not effect the atom structure. I dont think any life form has capacity or energy to break down atoms.
So if one atom of C14 was having a decay already before we ate it, it keeps having it while it gets digested and goes on in the same way if life is alive or dead. If another C14 was not having a decay, then it starting a decay has nothing to with the life form is alive or dead.
As Dr. Manhattan(Watchmen 2009) said atoms dont care if you are alive or dead. They stayed there at the same place before and after.
So how can a lifeform have any effect in the C14 decay at all?
Got some good answers, so I clarifying my questions:
The following is multiple choice question (with options) to answer.
What is the decayed remains of living organisms called? | [
"plateaus",
"oil",
"humus",
"fossils"
] | C | Humus is the decayed remains of living organisms. Humus makes soil fertile. |
SciQ | SciQ-4758 | servomotor
The output of generator action is a voltage differential in the conductor.
So you can see that if you meet motor action then you get generator action and both happen simultaneously.
When you back-drive a motor, you can get an output voltage at the motor terminals, if you have an applied magnetic field. In some instances, electric vehicles for instance, the motor is created such that the magnetic field is in the form of an electromagnet, called field windings. In this version, it is possible to vary the strength of the magnetic field by varying the current in the field windings; this varies the output current of the motor during back-driven operations and produces a variable strength braking effect.
In your case, with servo motors, the magnetic field typically comes in the form of permanent magnets in the motor housing. This means that the only way to vary output current (assuming a fixed output resistance) is to vary speed, as this varies the voltage you generate as dictated by the back-EMF constant;
$ V_{\mbox{back EMF}} = K_{\omega} \omega \phi$
where $K_{\omega}$ is the back-EMF constant, $\omega$ is the speed at which you are driving the motor, and $\phi$ is the strength of the magnetic field.
Looking again at the electrical output power of the servo:
$P = V^2/R$
Output power of the servo goes up with voltage squared. Since voltage is proportional to the driving speed of the motor, you can see that output power goes up based on speed squared; if you double the speed at which you drive the servo you quadruple the output power of the servo. This is why the servo gets "very hard" to drive.
There will always be some resistance when you try to drive a servo or motor, even with an open circuit, because they are real devices and thus have mass and inertia. You apply a torque to accelerate the motor:
$ \tau = I\alpha$
where $\tau$ is the torque you apply, $I$ is the effective motor inertia, and $\alpha$ is the rate at which you are accelerating the motor shaft. Output power varies with torque and speed:
$P_\mbox{mechanical} = \tau \omega$
The following is multiple choice question (with options) to answer.
The motor thus acts as a generator whenever its coil does what? | [
"rotates",
"oscillates",
"stops",
"revolves"
] | A | 23.6 Back Emf It has been noted that motors and generators are very similar. Generators convert mechanical energy into electrical energy, whereas motors convert electrical energy into mechanical energy. Furthermore, motors and generators have the same construction. When the coil of a motor is turned, magnetic flux changes, and an emf (consistent with Faraday’s law of induction) is induced. The motor thus acts as a generator whenever its coil rotates. This will happen whether the shaft is turned by an external input, like a belt drive, or by the action of the motor itself. That is, when a motor is doing work and its shaft is turning, an emf is generated. Lenz’s law tells us the emf opposes any change, so that the input emf that powers the motor will be opposed by the motor’s self-generated emf, called the back emf of the motor. (See Figure 23.25. |
SciQ | SciQ-4759 | virology, infection
Title: Why don't viruses cause wounds? A simple mental model of a viral infection is that an infected cell emits a lot of virions and eventually dies. The emitted virions have a chance of infecting other cells. Nearby cells are at a higher risk of infection.
Based on this model, if one cell in my nose gets infected, I would expect a large part of my nose to be destroyed, as the infection spreads and destroys more and more cells in the same area.
This does not happen! I survived a number of infections and still have my nose. Why?
I know there are "flesh eating" bacteria. Why isn't this the norm for infections? Does a common cold virus or SARS-CoV-2 not infect a lot of cells within the same area? A virus does not destroy that many cells before it is exterminated by the immune system or before the host dies.
Perhaps even more crucially, viruses typically target a very specific type of cell — those on the inner mucal surface of the nose in the case of cold or flu, those of the gastrointestinal tract in the case of stomach viruses, CD4 immune cells in the case of HIV, etc.
Update
As an example of how much time it takes for a virus to eat a noticeable wound, one could take the extermination of the immune cells by HIV - although it does not look as a physical wound, it is one, in the sense that enough of the specific tissue is destroyed to cause a life-threatening condition. It takes about a decade(!) - from the initial infection to the immune system failure.
On the other hand, the lethal effect of typical respiratory viruses is typically via obstructions of the respiratory ways due to inflammation or secretions resulting from the immune response, or via creating suitable conditions for a more serious bacterial infection.
The following is multiple choice question (with options) to answer.
Norovirus causes the inflammation of the stomach and what else? | [
"liver",
"intestines",
"muscles",
"lungs"
] | B | Common foodborne viruses include norovirus and hepatitis A virus. Norovirus, which causes inflammation of the stomach and intestines, has been a recent issue on cruise ships, infecting hundreds of passengers and crew on certain voyages. Hepatitis A causes inflammation of the liver, which is treated with rest and diet changes. Parasites are tiny organisms that live inside another organism. Giardia is a parasite spread through water contaminated with the stools of people or animals who are infected. Food preparers who are infected with parasites can also contaminate food if they do not thoroughly wash their hands after using the bathroom and before handling food. Trichinella is a type of roundworm parasite. People may be infected with this parasite by consuming raw or undercooked pork or wild game. |
SciQ | SciQ-4760 | 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 forms when tectonic plates move above a hot spot? | [
"earthquake chain",
"volcanic chain",
"volcanic system",
"volcanic setting"
] | B | As the tectonic plates move above a hot spot, they form a chain of volcanoes. The islands of Hawaii formed over a hot spot in the middle of the Pacific plate. The Hawaii hot spot has been active for tens of millions of years. The volcanoes of the Hawaiian Islands formed at this hot spot. Older volcanoes that formed at the hot spot have eroded below sea level. These are called the Emperor Seamounts. |
SciQ | SciQ-4761 | 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.
What is the multicellular diploid stage called? | [
"sporophyte",
"lymphocyte",
"sporangium",
"blastocyte"
] | A | |
SciQ | SciQ-4762 | vision, pathophysiology, human-eye
2. Albert, Daniel M., MD MS.Albert & Jakobiec's Principles & Practice of Ophthalmology, Third Edition. © 2000, 1994 by W.B Saunders Company, © 2008, Elsevier Inc.
Image from:
http://en.wikipedia.org/wiki/Myopia
The following is multiple choice question (with options) to answer.
Myopia is commonly called what? | [
"nearsightedness",
"blindness",
"farsightedness",
"scoliosis"
] | A | Myopia is commonly called nearsightedness. People with myopia can see nearby objects clearly, but distant objects appear blurry. Myopia occurs when images focus in front of the retina because the eyeball is too long. This vision problem can be corrected with concave lenses, which curve inward. The lenses focus images correctly on the retina. |
SciQ | SciQ-4763 | homework, reproduction, embryology
Title: Which process is needed to complete male reproductive development? In order to properly complete male reproductive development:
A. primordial germ cells must begin Meiosis I in utero.
B. Sertoli cells must produce testosterone.
C. Dihydrotestosterone must masculinize Wolffian duct derivatives
D. the paramesonephric ducts must degenerate
E. the metanephros must form the genital epithelium
My attempt: I think the answer is C because testosterone turns into DHT which then masculinzing the wolffian duct. Other people I am studying with claim the answer is D (which is true) except that I dont think the loss of the paramesonephric duct is needed to complete male repro development. Regarding option C:
Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ducts:
Between 8 and 12 weeks, the initial secretion of testosterone stimulates mesonephric ducts to transform into a system of organs—the epididymis, vas deferens, and seminal vesicle—that connect the testes with the urethra.*
DHT (dihydrotestosterone) is produced in the Leydig cells by the 5α-Reductase enzyme. It is required for induction of the external male genitalia (urethra, penis, and scrotum) and prostate from the embryonic ureteral groove, and for testicular descent into scrotum.
Regarding option D:
Sertoli cells secrete Anti Müllerian Hormone (AMH), which causes degeneration of the müllerian (a.k.a. paramesonephric) ducts between weeks 8 and 10. It is normal to speak about degeneration of the müllerian ducts as a defining aspect of male embryology, and thus I believe answer D is correct. Your point is taken, however:
Nevertheless, small müllerian duct remnants can be detected in the adult male, including a small cap of tissue associated with the testis, called the appendix testis, and an expansion of the prostatic urethra, called the prostatic utricle.*
The following is multiple choice question (with options) to answer.
The prostate gland secretes a fluid that mixes with sperm to help form what? | [
"semen",
"testosterone",
"hormone",
"urine"
] | A | The prostate gland secretes a fluid that mixes with sperm to help form semen. The prostate gland is located beneath the bladder. Semen is a "milky" liquid that carries sperm through the urethra and out of the body. In addition to sperm cells, semen contains sugars (fructose) which provide energy to the sperm cells, and enzymes and other substances which help the sperm survive. |
SciQ | SciQ-4764 | cell-biology, nutrition, blood-circulation, liver
Title: How do nutrients get to the cells they need to get to? I understand the basics of digestion. I know that nutrients get absorbed by the microvilli, enter the bloodstream and travel to the liver but after all that, what is the biological mechanism that guides these nutrients to the proper receiving location? Broadly speaking, nutrients that enter the blood from the gut, and those that are released into the blood by the liver, are available to any cells that require them. So there is no "guiding to the correct location" in the sense that you suggest.
Lipids for example are present in the various lipoproteins and can be acquired from these by all cells. Iron is bound to transferrin, and any cell with transferrin receptors can internalise the transferrin and take the iron. Glucose is available in solution in the plasma, and free fatty acids are bound to serum albumin in the blood. During starvation the liver produces ketones ("ketone bodies") which are taken up by many different tissues/cell types.
The following is multiple choice question (with options) to answer.
About 95 percent of lipids are absorbed in what organ of the digestive system? | [
"stomach",
"small intestine",
"large intestine",
"kidneys"
] | B | Lipid Absorption About 95 percent of lipids are absorbed in the small intestine. Bile salts not only speed up lipid digestion, they are also essential to the absorption of the end products of lipid digestion. Short-chain fatty acids are relatively water soluble and can enter the absorptive cells (enterocytes) directly. Despite being hydrophobic, the small size of short-chain fatty acids enables them to be absorbed by enterocytes via simple diffusion, and then take the same path as monosaccharides and amino acids into the blood capillary of a villus. The large and hydrophobic long-chain fatty acids and monoacylglycerides are not so easily suspended in the watery intestinal chyme. However, bile salts and lecithin resolve this issue by enclosing them in a micelle, which is a tiny sphere with polar (hydrophilic) ends facing the watery environment and hydrophobic tails turned to the interior, creating a receptive environment for the long-chain fatty acids. The core also includes cholesterol and fat-soluble vitamins. Without micelles, lipids would sit on the surface of chyme and never come in contact with the absorptive surfaces of the epithelial cells. Micelles can easily squeeze between microvilli and get very near the luminal cell surface. At this point, lipid substances exit the micelle and are absorbed via simple diffusion. The free fatty acids and monoacylglycerides that enter the epithelial cells are reincorporated into triglycerides. The triglycerides are mixed with phospholipids and cholesterol, and surrounded with a protein coat. This new complex, called a chylomicron, is a water-soluble lipoprotein. After being processed by the Golgi apparatus, chylomicrons are released from the cell (Figure 23.33). Too big to pass through the basement membranes of blood capillaries, chylomicrons instead enter the large pores of lacteals. The lacteals come together to form the lymphatic vessels. The chylomicrons are transported in the lymphatic vessels and empty through the thoracic duct into the subclavian vein of the circulatory system. Once in the bloodstream, the enzyme lipoprotein lipase breaks down the triglycerides of the chylomicrons into free fatty acids and glycerol. These breakdown products then pass through capillary walls to be used for energy by cells or stored in adipose tissue as fat. Liver cells combine the remaining chylomicron remnants with proteins, forming lipoproteins that transport cholesterol in the blood. |
SciQ | SciQ-4765 | thermodynamics, work, conventions
Work done ON A SYSTEM or BY A SYSTEM, I have never, ever seen a definition of. Work done by a force I have seen defined, on the other hand
You are correct, that only forces do work. The statement, "work done by a system" simply means that the system applies a force, which is doing work (on something else). In your meteor example, the meteor as the system is doing work on the planet by pulling in it toward itself through its gravitational force. (Note: The work done by the meteor on the planet is very, very small, since the displacement of the planet will be very, very small).
My guess is: work done by a system, is the thermodynamical force generated by the system multiplied by its conjugate variable on the surroundings. As in my example here: a gravitational forcefield is generated by the system on the surroundings, and the conjugate variable displacement on the surroundings is multiplied by it.
Yes, this is the mathematical definition, in short written as:
$$W=\vec F \cdot \vec s$$
or in general for non-constant forces:
$$W=\int \vec F \cdot d\vec s$$
where $\vec s$ is the displacement vector.
The following is multiple choice question (with options) to answer.
What type of work called occurs when a system pushes back the surroundings against a restraining pressure? | [
"shape work",
"contrast work",
"expansion work",
"retention work"
] | C | A type of work called expansion work (or pressure-volume work) occurs when a system pushes back the surroundings against a restraining pressure, or when the surroundings compress the system. An example of this occurs during the operation of an internal combustion engine. The reaction of gasoline and oxygen is exothermic. Some of this energy is given off as heat, and some does work pushing the piston in the cylinder. The substances involved in the reaction are the system, and the engine and the rest of the universe are the surroundings. The system loses energy by both heating and doing work on the surroundings, and its internal energy decreases. (The engine is able to keep the car moving because this process is repeated many times per second while the engine is running. ) We will consider how to determine the amount of work involved in a chemical or physical change in the chapter on thermodynamics. |
SciQ | SciQ-4766 | atmosphere, ozone, topography
Title: What are the causes of lower UV radiation at lower elevations? After recently visiting the Dead Sea in Israel and not getting any skin burns, I was wondering about the reasons for that. Searching the literature, it seems that the UV radiation is indeed lower in the Dead Sea (ca. -400 m) compared to Beer Sheva (a nearby city at ca. +300 m): 1 2 3. Both UVA and UVB rays are lower, but UVB rays are attenuated the most.
These sources give mostly measurements, but hardly discuss the reasons for the lower radiation. I always thought that the ozone layer blocks most of the UV radiation, but here it seems that just a few hundred meters of atmosphere can greatly reduce the amount of incident UV.
What are the reasons for that? Is it simply because there are more air molecules that absorb the radiation? You are almost totally correct when you asked:
What are the reasons for that? Is it simply because there are more air molecules that absorb the radiation?
The Ozone Layer blocks most of UVB, but does not affect the amount UVA entering the atmosphere (as seen in the illustration below):
(Image source)
But there is a little more to it than that. From NASA's Earth Observatory's webpage What Determines How Much Ultraviolet Radiation Reaches the Earth’s Surface?, elevation's role in attenuating UVB (and by similar processes, UVA):
high elevations UV-B radiation travels through less atmosphere before it reaches the ground, and so it has fewer chances of encountering radiation-absorbing aerosols or chemical substances (such as ozone and sulfur dioxide) than it does at lower elevations.
The aerosols absorb and scatter incident UV radiation. So nearer to the surface, there is a greater concentration that the light must pass through - and as the altitude decreases, the UV radiation path is therefore increased, so the further 'down' in altitude, the more the air mass and an increased presence of aerosols absorb and scatter solar UV radiation.
In respect to the aerosols in area you have specified (the Dead Sea), according to the first link in your question, The Analysis of the Ultraviolet Radiation in the Dead Sea Basin, Israel (Kudish et al. 1997), they state
the air above the Dead Sea is characterized by a
relatively high aerosol content due to the very high salt content of the Dead Sea
Their results indicate that
The following is multiple choice question (with options) to answer.
In some parts of the world, too much of the sun's harmful uv radiation gets through because of a hole in what layer? | [
"mesosphere",
"thermosphere",
"ozone",
"troposphere"
] | C | Punta Arenas, Chile is the world's most southern city. At such a high latitude, winters are exceedingly cold and dark. Unlike the children pictured above, the children in Punta Arenas must stay inside to avoid the cold. Of course, they look forward to spring when they can go out to play. But some years, it is too dangerous for the children to go outside. The ozone hole has moved north. Too much of the Sun's harmful UV radiation gets through. |
SciQ | SciQ-4767 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
What type of animal eats both plants and animals? | [
"insectivores",
"herbivores",
"omnivores",
"carnivores"
] | C | |
SciQ | SciQ-4768 | homework, reproduction, embryology
Title: Which process is needed to complete male reproductive development? In order to properly complete male reproductive development:
A. primordial germ cells must begin Meiosis I in utero.
B. Sertoli cells must produce testosterone.
C. Dihydrotestosterone must masculinize Wolffian duct derivatives
D. the paramesonephric ducts must degenerate
E. the metanephros must form the genital epithelium
My attempt: I think the answer is C because testosterone turns into DHT which then masculinzing the wolffian duct. Other people I am studying with claim the answer is D (which is true) except that I dont think the loss of the paramesonephric duct is needed to complete male repro development. Regarding option C:
Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ducts:
Between 8 and 12 weeks, the initial secretion of testosterone stimulates mesonephric ducts to transform into a system of organs—the epididymis, vas deferens, and seminal vesicle—that connect the testes with the urethra.*
DHT (dihydrotestosterone) is produced in the Leydig cells by the 5α-Reductase enzyme. It is required for induction of the external male genitalia (urethra, penis, and scrotum) and prostate from the embryonic ureteral groove, and for testicular descent into scrotum.
Regarding option D:
Sertoli cells secrete Anti Müllerian Hormone (AMH), which causes degeneration of the müllerian (a.k.a. paramesonephric) ducts between weeks 8 and 10. It is normal to speak about degeneration of the müllerian ducts as a defining aspect of male embryology, and thus I believe answer D is correct. Your point is taken, however:
Nevertheless, small müllerian duct remnants can be detected in the adult male, including a small cap of tissue associated with the testis, called the appendix testis, and an expansion of the prostatic urethra, called the prostatic utricle.*
The following is multiple choice question (with options) to answer.
What is the term for the muscular duct through which sperm are propelled? | [
"the västerås deferens",
"the glarus deferens",
"the glans deferens",
"the vas deferens"
] | D | |
SciQ | SciQ-4769 | human-biology, cancer, medicine
Title: Why are only few cigarette smokers prone to cancer? It's tacit that only a few populace of smokers get cancer. What spares the others from it or what specifically cause cancer in those populace? See this Washington Post Article Cigarette smokers are most certainly prone to cancer. See Cecil Medicine, Chapter 183, on the epidemiology of cancer, exposure to tobacco is the most important environmental risk factor for cancer development, at least in the US:
Exposure to tobacco is the single largest cause of cancer in the United States... All forms of tobacco can cause cancer. Cigarette smoking causes cancer of the lip, oral cavity, nasal cavity, paranasal sinuses, pharynx (nasal, oral, and hypopharnyx), larynx, lung, esophagus (squamous cell and adenocarcinoma), stomach, colorectum, pancreas, liver, kidney (adenocarcinoma and renal pelvis), urinary bladder, uterine cervix, and myeloid leukemia.
Cancer may be identified or the cause of death in fewer smokers than might be expected, though, because smoking is an even greater risk factor for cardiovascular disease, and death due to cardiovascular disease.
Cancer is an unlikely phenomenon in an individual cell, but becomes more likely at the organism level, and even more likely over time. Though tobacco may be the most important environmental risk factor for cancer, age is actually a stronger predictor of cancer (see again, Cecil Chapter 183. Autopsy studies give us a quite remarkable example, this one shows incidental prostate cancer in nearly 60% of men over 80 who died from other causes. That figure is not out of the ordinary. Live long enough and you are likely to develop cancer.
Death due to heart disease may account for the lower than expected rates of cancer diagnoses and deaths in smokers. Nothing prevents cancer as well as dying from something else. And as discussed in the blog in the Washington Post you linked to, up to 2/3 of smokers die from smoking related causes
The following is multiple choice question (with options) to answer.
What is the most common cause of cancer? | [
"cell mutations",
"poor diet",
"technology mutations",
"smoking"
] | A | Most cancers are caused by mutations. Mutations are random errors in genes. Mutations that lead to cancer usually occur in genes that control the cell cycle. Because of the mutations, abnormal cells are allowed to divide. |
SciQ | SciQ-4770 | homework, reproduction, embryology
Title: Which process is needed to complete male reproductive development? In order to properly complete male reproductive development:
A. primordial germ cells must begin Meiosis I in utero.
B. Sertoli cells must produce testosterone.
C. Dihydrotestosterone must masculinize Wolffian duct derivatives
D. the paramesonephric ducts must degenerate
E. the metanephros must form the genital epithelium
My attempt: I think the answer is C because testosterone turns into DHT which then masculinzing the wolffian duct. Other people I am studying with claim the answer is D (which is true) except that I dont think the loss of the paramesonephric duct is needed to complete male repro development. Regarding option C:
Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ducts:
Between 8 and 12 weeks, the initial secretion of testosterone stimulates mesonephric ducts to transform into a system of organs—the epididymis, vas deferens, and seminal vesicle—that connect the testes with the urethra.*
DHT (dihydrotestosterone) is produced in the Leydig cells by the 5α-Reductase enzyme. It is required for induction of the external male genitalia (urethra, penis, and scrotum) and prostate from the embryonic ureteral groove, and for testicular descent into scrotum.
Regarding option D:
Sertoli cells secrete Anti Müllerian Hormone (AMH), which causes degeneration of the müllerian (a.k.a. paramesonephric) ducts between weeks 8 and 10. It is normal to speak about degeneration of the müllerian ducts as a defining aspect of male embryology, and thus I believe answer D is correct. Your point is taken, however:
Nevertheless, small müllerian duct remnants can be detected in the adult male, including a small cap of tissue associated with the testis, called the appendix testis, and an expansion of the prostatic urethra, called the prostatic utricle.*
The following is multiple choice question (with options) to answer.
The testes produce what hormone? | [
"dopamine",
"estrogen",
"insulin",
"testosterone"
] | D | The gonads secrete sex hormones. The male gonads are called testes . They secrete the male sex hormone testosterone. The female gonads are called ovaries . They secrete the female sex hormone estrogen. Sex hormones are involved in the changes of puberty. They also control the production of gametes by the gonads. |
SciQ | SciQ-4771 | histology
Title: Why can't plasma proteins migrate from capillaries? Why can't plasma proteins shift from capillaries to connective tissue but WBCs can be very rich in connective tissue even though obviously the WBCs had to go through capillaries. Another example: in alveolar sacs neutrophils are there in the lumen despite the presence of epithelia of alveolar sacs, and it can only reach there via capillaries. So, how can they get into lumen despite the epithelia lining? Histology textbooks say that no plasma proteins can enter or leave capillaries, but WBCs (which are much larger than proteins) can move to connective tissue via capillaries? Cells of the endothelium are joined by tight cell junctions which are impermeable or selectively permeable. Generally, proteins can only migrate through the endothelium via active transcytosis.
Leukocytes (specifically neutrophils, lymphocytes and monocytes) express various adhesion molecules and cytokine receptors which allow them to interact with endothelial cells and facilitate their movement (diapedesis) either between (paracellular) or through (transcellular) the cells. The process of leukocytes leaving the endothelial lumen is known as extravasation.
Carman CV. 2009. Mechanisms for transcellular diapedesis: probing and pathfinding by `invadosome-like protrusions'. J Cell Sci 122:3025-3035.
(C,D) The process of diapedesis, whether during intravasation or extravasation, can occur by two distinct pathways: paracellular or transcellular. (C) Paracellular diapedesis. Leukocytes and endothelial cells coordinately disassemble endothelial cell-cell junctions and open up a gap between two or more endothelial cells (Muller, 2003). (D) Transcellular diapedesis. Leukocytes migrate directly through individual endothelial cells via a transient transcellular pore that leaves endothelial cell-cell junctions intact. Note that the two individual endothelial cells in C and D are distinguished by different shades of pink.
The following is multiple choice question (with options) to answer.
Capillaries are narrow-diameter tubes that can fit red blood cells through in single file and are the sites for the exchange of what? | [
"proteins",
"components",
"fluids",
"nutrients"
] | D | Arterioles diverge into capillary beds. Capillary beds contain a large number (10 to 100) of capillaries that branch among the cells and tissues of the body. Capillaries are narrow-diameter tubes that can fit red blood cells through in single file and are the sites for the exchange of nutrients, waste, and oxygen with tissues at the cellular level. Fluid also crosses into the interstitial space from the capillaries. The capillaries converge again into venules that connect to minor veins that finally connect to major veins that take blood high in carbon dioxide back to the heart. Veins are blood vessels that bring blood back to the heart. The major veins drain blood from the same organs and limbs that the major arteries supply. Fluid is also brought back to the heart via the lymphatic system. |
SciQ | SciQ-4772 | development
Title: How detachment/separation works in biology? It might be a strange question, but I'm interested in the mechanics of separation/detachment during asexual reproduction, for example when an organism reproduces by budding (I don't mean cellular budding like baker's yeast). When the newly formed body is fully matured it detaches itself from the parent / original body.
It might not be caused by a specific tissue, as animals with not so differentiated bodies are (also) capable of such, but I could easily be wrong. Is this (the detachment) triggered by changes in the cell membrane? I can't really think of other explanations. Reproductive budding and what you call 'cellular budding' are really highly related processes. Budding as a form of reproduction essentially partitions protein aggregates and damaged cellular components into the host or mother and builds fresh or 'young' cells on the opposite side of a partition. To begin understanding this look at Saccharomyces cerevisiae (budding yeast) which forms protein rings (from the septin proteins) at the membrane, around the bud neck which separates the mother and daughter cells Hartwell 1971. This ring acts a partition that in part, withholds protein aggregates and certain proteins from diffusing from the mother to the daughter. This protein ring is an example of how cells limit diffusion of proteins and cellular components to the daughter cell. Another good example that comes to mind is Linder 2007, though it is done in E Coli, not budding yeast, where mother cells maintain protein aggregates and age, while the daughter cells are given fresh components and are therefore more fresh and 'young'.
Now like you mention, imagine this process in a multicellular organism to be fundamentally the same. At some point the multicellular organism will start an outgrowth of cells, while restricting what materials are given to the daughter cells to maintain their youth. And eventually a new organism will have been created. Some of the details will be different, but the fundamental process is is quite similar. In that you start with an old cell that creates a new cell from scratch, but rather than splitting all cellular components equally between mother and daughter, the daughter cells is made in peak condition while the mother cell retains much of the cell 'junk' like protein aggregates.
Hopefully that starts to answer your question.
The following is multiple choice question (with options) to answer.
Pieces of the cell break off and form a new cell in what type of reproduction that produces genetically identical organisms? | [
"Meiosis",
"Mitosis",
"fragmentation",
"Fusion"
] | C | Like bacteria, reproduction in archaea is asexual. Archaea can reproduce through binary fission , where a parent cell divides into two genetically identical daughter cells. Archaea can also reproduce asexually through budding and fragmentation, where pieces of the cell break off and form a new cell, also producing genetically identical organisms. |
SciQ | SciQ-4773 | homework, embryology
Title: Why are Birds and Reptiles with abundant yolk sac polyspermic? I was given an explanation that birds and reptiles are polyspermic because they have an abundant yolk sac. But how does it explain the thing?
Chicken as an adult is not using in my opinion yolk as an energy source.
Yolk is used during embryogenesis as the primary energy source with blastula and gastrula -stages and during organogenesis, since the embryo needs proteins and energy somewhere.
How does abundant yolk sac make birds and reptiles polyspermic? My professor says that
The yolk sac is not connected to the mechanism of polyspermy or
monospermy. [Amount of yolk inside the oocyte is then again.] The
oocytes of reptiles and birds are yolk rich - polylecithal for instance.
where
lecithal = yolk containing and some pieces of information about here.
The following is multiple choice question (with options) to answer.
How do most reptiles produce? | [
"asexually",
"sexually",
"biologically",
"occasionally"
] | B | Most reptiles reproduce sexually and have internal fertilization. Males have one or two penises that pass sperm from their cloaca to the cloaca of a female. Fertilization occurs within the cloaca, and fertilized eggs leave the female’s body through the opening in the cloaca. In a minority of species, the eggs are retained inside the female’s body until they hatch. Then the offspring leave the mother’s body through the cloaca opening. |
SciQ | SciQ-4774 | quantum-mechanics, nuclear-physics, radiation, elements, isotopes
Title: Why is Palladium-108 "theoretically capable of spontaneous fission?" I was just reading Wikipedia's page on palladium isotopes and I noticed the note about Palladium-108. It says "theoretically capable of spontaneous fission", but I don't find that explained anywhere. the same note is on other isotopes of palladium, as well. So, I am just asking if someone could explain the note.
For example, how do we know it's capable of spontaneous fission? What makes it capable of spontaneous fission? And why is it still called stable instead of just giving it a half life absurdly long like 9.9x10^100 or something? Thanks for the help? Whether a reaction is theoretically possible or not is determined, firstly, by the $Q$ of the reaction. For nuclear reactions, $Q$ is the mass energy of the difference in reactant nuclear mass and product nuclear mass. If $Q$ is positive, the reaction is possible, as long as other conservation laws aren't violated.
With spontaneous fission, the reaction would be something like $$A\to B+C+Xn,$$
with $A$, $B$, $C$ being specific nuclides and $X$ being the number of neutrons. If you calculate the $Q$ for $^{108}$Pd splitting equally or near equally (1 proton high, 1 proton low), you will get a positive $Q$ close to $10$ MeV. So SF is theoretically possible, but for some reason it's inhibited, probably because the fission activation energy is too high. So, we don't observe it in reality.
This is similar to the case of alpha decay for $^{208}$Pb. It's theoretically possible, but the $Q$ is so small that the predicted halflife ( $2.6\times 10^{21}$ years) indicates we would probably never observe it, and the predictive model is not accurate enough to publish a value.
The following is multiple choice question (with options) to answer.
The minimum amount necessary for self-sustained fission of a given nuclide is called what? | [
"its half-life",
"its activation energy",
"its critical mass",
"its molar mass"
] | C | Not every neutron produced by fission induces fission. Some neutrons escape the fissionable material, while others interact with a nucleus without making it fission. We can enhance the number of fissions produced by neutrons by having a large amount of fissionable material. The minimum amount necessary for self-sustained fission of a given nuclide is called its critical mass. |
SciQ | SciQ-4775 | molecular-genetics, chromosome
Title: Why do genes with closely related functions often reside on different chromosomes? Why do genes with closely related products are so often positioned on different chromosomes?
To illustrate what I mean, here is an example from immunology:
the invariant region of MHC is on chromosome 5
the variant region of MHC is on chromosome 6
β2-microglobulin is on chromosome 15
These three gene products associate into a single protein-complex to present antigens. Why are these genes situated on different chromosomes? Wouldn't it make more sense to keep them associated into a localized region onto a single chromosome so that their transcription can be jointly regulated?
It is just an example; I get the impression that many multiprotein complexes are formed with products from different chromosomes. The thing we must remember is that during evolution, there occurs many events that may result in genomic reshuffling.
Considering your example of MHC, when we look into the evolution of the complexes
The classical human MHC contains 224 genes, .... Antibody and T cell mediated immune responses against invading pathogens are initiated through MHC class I and class II molecules. These main components are not only missing from invertebrates, but are also not present in primitive jawless fish, such as hagfish and lamprey. MHC class I and II molecules do, however, exist in all jawed vertebrates, including the cartilaginous fish.
Now that tells us something in itself. If you observe the universal evolutionary tree, we can conclude that the hagfish and lamprey are most ancestral, especially compared to telostii. This is crucial when speaking in terms of evolution, as
this demonstrates that the separation of the MHC class I and class II loci is characteristic of teleost fish, which represent half of all vertebrates. Since the genes of the immune system were present in the common ancestor of tetrapods and teleosts, the differences in their genomic organisation may be the result of lineage-specific chromosomal events such as duplications, inversions, deletions and translocations.
The following is multiple choice question (with options) to answer.
What are genes that are close together on the same chromosome called? | [
"linked genes",
"mutated genes",
"stored genes",
"infected genes"
] | A | Linked genes are genes that are close together on the same chromosome. Linked genes are inherited together. |
SciQ | SciQ-4776 | atoms, terminology
Title: What is a neutral atom? I was told that an atom's atomic number is defined as follows:
The number of electrons or protons present in a neutral atom is called atomic number. It is represented by Z.
What does neutral mean here? Why isn't it just "..present in an atom..."? Electrons and protons are charged particles. The electrons have negative charge, while protons have positive charge. A neutral atom is an atom where the charges of the electrons and the protons balance. Luckily, one electron has the same charge (with opposite sign) as a proton.
Example: Carbon has 6 protons. The neutral Carbon atom has 6 electrons. The atomic number is 6 since there are 6 protons.
The following is multiple choice question (with options) to answer.
What do neutral atoms have the same number of? | [
"toxins and protons",
"gases and protons",
"Measure and electrons",
"electrons and protons"
] | D | Summary Each atom of an element contains the same number of protons, which is theatomic number (Z). Neutral atoms have the same number of electrons and protons. Atoms of an element that contain different numbers of neutrons are calledisotopes. Each isotope of a given element has the same atomic number but a different mass number (A), which is the sum of the numbers of protons and neutrons. The relative masses of atoms are reported using the atomic mass unit(amu), which is defined as one-twelfth of the mass of one atom of carbon-12, with 6 protons, 6 neutrons, and 6 electrons. The atomic mass of an element is the weighted average of the masses of the naturally occurring isotopes. When one or more electrons are added to or removed from an atom or molecule, a charged particle called an ion is produced, whose charge is indicated by a superscript after the symbol. |
SciQ | SciQ-4777 | human-biology, physiology, proteins, amino-acids, diet
Title: Amino Acid requirement + intake in relation to diet + meat type I was arguing with a friend:
I said: The Yulin festivals cannot be condemned by western culture, as we also kill animals in equally cruel ways.
She said: It isn't just that the killing is cruel, but it doesn't help us, as humans do not derive the same essential amino acids from consuming these less traditional meats (e.g. dogs, cats, etc) like they would from consuming more traditional meats (e.g. cow, pig, goat, etc) She cites her father, a geneticist, as her source.
Question one:
Are my friend and her father correct? Does the consumption of a less traditional meat (e.g. cats, dogs, etc) provide fewer essential amino acids than the consumption of traditional meats (e.g. cows, pigs, chickens, etc)?
Question two:
My friend also made a comment about veganism and vegetarianism (I am a vegetarian), stating that for the same reason as her and her father's above comment, people who exclude meat from their diet need to use supplements. Is this correct, or would it also be possible to just vary diet to obtain these essential amino acids? There is a difference between animals in their requirements for amino acids. For example, cats need high amounts of taurine (and can't make it) and when fed diets lacking enough can go blind. This is why vegans trying to feed vegan diets to their pets can be very bad for the pet. Animal proteins have sufficient taurine for the cat.
However, the meat of a cat or dog is just as a complete source of protein for humans as any other meat. All essential amino acids are there in sufficient ratios. Suggesting otherwise by her father suggests some confusion between the dietary needs of cat vs. the nutritional value of the cat to another predator.
Your second question is easily answered by looking up essential amino acids. Wiki is plenty sufficient to get the gist Wiki Link. In short, most plants don't contain the full complement of amino acids that humans require (and can't make on their own). So to get this full complement, it requires eating multiple plant products that together contain the required amino acids.
From Harvard School of Public Health
The following is multiple choice question (with options) to answer.
Omnivores are animals that eat both plant- and? | [
"liquid diets",
"biofuel",
"recycled food",
"animal-derived food"
] | D | Omnivores are animals that eat both plant- and animal-derived food. In Latin, omnivore means to eat everything. Humans, bears (shown in Figure 34.4a), and chickens are example of vertebrate omnivores; invertebrate omnivores include cockroaches and crayfish (shown in Figure 34.4b). |
SciQ | SciQ-4778 | prokaryotes
Title: Are chromosomal and plasmid DNA in the nucleoid? I know plasmid DNA is not part of the chromosome, according to my textbook, but can you still class it as being part of the nucleoid?
Also is chromosomal DNA in the nucleoid? "Nucleoid" (literally means nucleus-like), is a quite old term for "bacterial chromosome" (Better to write prokaryotic chromosome since in both type of prokaryotes i.e. Archaea (former archaebacteria) and bacteria (former eubacteria) the structure is similar).
Nucleoid structurally normally excludes the plasmid-DNA (the plasmid DNA is like additional or accessory). However sometimes a plasmid DNA could go through recombination with prokaryotic chromosome 's DNA (As seen in Hfr strain of Escherichia coli)
"Chromosome" in very brief means a structure made of DNA + Protein. In case of "bacterial-chromosome", it contains both DNA and Protein; and if you take away the protein from bacterial chromosome; what you get, is the chromosomal DNA.
Reference:
Microbiology / Pelczar, Chan and Noel/ Edition-5;
Part 2: Bactria,
Chapter 5 (Morphology and fine structure of bacteria)
"Because it is not discrete nucleus, this nebulous structure has been designated by such terms as the nucleoid , the chromatin body, the nuclear equivalent, even the bacterial chromosome"
General Microbiology / Hans G. Schlegel / Edition-7:
Chapter-2 ; The cell and its structure:
2.2 The prokaryotic cell (protocyte) -> 2.2.1: The bacterial 'nucleus'
" Plasmids : In addition to chromosomal DNA, many bacteria contain extrachromosomal DNA in closed, circular, double stranded form. These autonomously replicating DNA elements are called plasmids. Linear plasmids have been found in some bacteria"
The following is multiple choice question (with options) to answer.
Bacterial dna is contained in a large, circular strand; this single chromosome is located in a region of the cell called what? | [
"polypeptide",
"the nucleoid",
"amino acid",
"nucleic acid"
] | B | DNA. By contrast though, bacterial DNA is contained in a large, circular strand. This single chromosome is located in a region of the cell called the nucleoid . The nucleoid is not an organelle, but a region within the cytoplasm. Many bacteria also have additional small rings of DNA known as plasmids . |
SciQ | SciQ-4779 | reproduction, sociality, fitness
Title: Which monkey species features two distinct male phenotypes? I remember coming across a popular science article years ago about a monkey species which featured two male genotypes: the first were good looking males who acquired social status (as alphas or betas) within the group and could thus achieve reproductive succes. The alternative (less frequent) phenotype achieved similar fitness by adopting an outgroup (omega) lurking rapist kind of reproductive strategy.
Does anybody know which species and whose observervations I could be referring to? I'm curious to find out if this was a valid observation and if any further research has been done on this phenomenon. Patas monkeys exhibit "sneak mating" where a male other than the resident male sires offspring. Resident males do sire more offspring than sneaker males, but both strategies do co-occur. I'm pretty sure there are other species that have a similar mating strategy as well.
The following is multiple choice question (with options) to answer.
Which primate group generally lives alone? | [
"chimpanzee",
"gorilla",
"orangutan",
"human"
] | C | Yes! This is the Hubbard Glacier in Alaska. As the glacier meets the relatively warm seawater, it calves. Pieces of the glacier break off and fall into the water. These icebergs may be as large as a ten-story building. |
SciQ | SciQ-4780 | biochemistry, physiology
Title: Organism with the greatest amount of gold as percentage of body mass I've read that the human body contains trace amounts of gold:
http://www.tellmehowmuch.net/how-much-gold-is-found-in-the-human-body.html
http://web2.airmail.net/uthman/elements_of_body.html
Are there other species that are known to have significantly higher ratios of gold to body mass?
And while there seems to be no definitive answer about the benefit of gold being in the human body, are there any species for which gold has demonstrative bodily uses or benefits? Acidothiobacillus ferrooxidans can gain metabolic energy by utilizing gold thiosulphate complexes (Reith et al., 2007); Micrococcus luteus can oxidize methane to methanol using gold-containing enzyme (Levchenko et al., 2002).
However, for most organisms, gold is toxic (Wietkiewicz & Shaw, 1981); some bacteria actively detoxify gold: Cupriavidus (Ralstonia, Wautersia) metallidurans, Desulfotomaculum sp., Desulfovibrio sp., Hyphomonas adhaerens, Plectonema boryanum, Pseudomonas aeruginosa Salmonella enterica, Shewanella algae, Spirulina platensis (Reith et al., 2007).
Reith F, Lengke MF, Falconer D, Craw D, Southam G (2007) The geomicrobiology of gold. ISME J. 1: 567-584.
Levchenko LA, Sadkov AP, Lariontseva NV, Koldasheva EM, Shilova AK, Shilov AE. (2002) Gold helps bacteria to oxidize methane. J Inorg Biochem 88: 251-253.
Witkiewicz PL & Shaw CF III (1981) Oxidative cleavage of peptide and protein disulphide bonds by gold(III): a mechanism for gold toxicity. J Chem Soc Chem Commun 21: 1111–1114.
The following is multiple choice question (with options) to answer.
Carbon and what are the second and third most abundant elements in your body? | [
"hydrogen",
"helium",
"calcium",
"mercury"
] | A | 2.4 | Inorganic Compounds Essential to Human Functioning By the end of this section, you will be able to: • Compare and contrast inorganic and organic compounds • Identify the properties of water that make it essential to life • Explain the role of salts in body functioning • Distinguish between acids and bases, and explain their role in pH • Discuss the role of buffers in helping the body maintain pH homeostasis The concepts you have learned so far in this chapter govern all forms of matter, and would work as a foundation for geology as well as biology. This section of the chapter narrows the focus to the chemistry of human life; that is, the compounds important for the body’s structure and function. In general, these compounds are either inorganic or organic. • An inorganic compound is a substance that does not contain both carbon and hydrogen. A great many inorganic compounds do contain hydrogen atoms, such as water (H2O) and the hydrochloric acid (HCl) produced by your stomach. In contrast, only a handful of inorganic compounds contain carbon atoms. Carbon dioxide (CO2) is one of the few examples. • An organic compound, then, is a substance that contains both carbon and hydrogen. Organic compounds are synthesized via covalent bonds within living organisms, including the human body. Recall that carbon and hydrogen are the second and third most abundant elements in your body. You will soon discover how these two elements combine in the foods you eat, in the compounds that make up your body structure, and in the chemicals that fuel your functioning. The following section examines the three groups of inorganic compounds essential to life: water, salts, acids, and bases. Organic compounds are covered later in the chapter. |
SciQ | SciQ-4781 | 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.
Glucagon and insulin are produced in what organ? | [
"thymus",
"thyroid",
"pancreas",
"hypothalamus"
] | C | |
SciQ | SciQ-4782 | human-biology, genetics, cell-biology, terminology
and according to Wikipedia,
A mitogen is a chemical substance that encourages a cell to commence cell division, triggering mitosis.
What’s the difference between them? I suppose a mitogen specifically refers to mitosis, but if something is stimulating mitosis, isn’t it stimulating growth? Are mitogens all growth factors? Are all growth factors mitogens? There is a lot of confusion and conflicting / imprecise definitions of these terms. It's biology after all :)
A mitogen is an agent that causes a cell to enter mitosis. This definition is pretty clear, and there is a good consensus about it. (Well technically, mitosis is not the same as cell division, but we will gloss over this distinction.)
The term growth factor has at least two different definitions: (1) a factor that causes growth of tissues, organs or entire individuals; or (2) a factor that causes growth of cells (increase in cell size). These two versions are often mixed up, and this causes no end of confusion. Let's consider them both in turn.
Definition (1) is more common and probably older. Since growth of whole tissues usually (but not always) implies both cell growth and division, according to this definition, a growth factor is also a mitogen. But the reverse is not true: there are cases where cells divide without growing, for example the first few cell divisions of a fertilized egg. But note that, since this definition concerns the level of tissues or individuals, it's meaning is not entirely clear in terms of cell growth and division. Muscle growth in the adult stage usually does not involve cell division, for example.
Definition (2) is better suited to cell biology (in my opinion), because it actually concerns cells, not tissues. This definition is more common when studying cell growth and division; see for example this review. Cell growth is a separate phenomenon from cell division: cells can grow without dividing (fat cells, muscle fibers and neuron do this, for example), or divide without growing (as mentioned above). So with this definition, growth factor and mitogen are two completely unrelated concepts. Now, it is certainly true that many proteins can act both as growth factors and mitogens; Matej Pribis gives some nice examples in the other answer. But that is an empirical fact, not a question of definitions.
The following is multiple choice question (with options) to answer.
Anagen, catagen and telogen are phases in the growth of what, which involves the root and follicle? | [
"bone",
"hair",
"brain",
"teeth"
] | B | Hair Growth Hair grows and is eventually shed and replaced by new hair. This occurs in three phases. The first is the anagen phase, during which cells divide rapidly at the root of the hair, pushing the hair shaft up and out. The length of this phase is measured in years, typically from 2 to 7 years. The catagen phase lasts only 2 to 3 weeks, and marks a transition from the hair follicle’s active growth. Finally, during the telogen phase, the hair follicle is at rest and no new growth occurs. At the end of this phase, which lasts about 2 to 4 months, another anagen phase begins. The basal cells in the hair matrix then produce a new hair follicle, which pushes the old hair out as the growth cycle repeats itself. Hair typically grows at the rate of 0.3 mm per day during the anagen phase. On average, 50 hairs are lost and replaced per day. Hair loss occurs if there is more hair shed than what is replaced and can happen due to hormonal or dietary changes. Hair loss can also result from the aging process, or the influence of hormones. |
SciQ | SciQ-4783 | botany, terminology, fruit
Title: What is the name of this part in plants, fruits, vegetables? What is the name of this part of the plant, fruit, vegetable? The thing that the plant is connected with the tree and gets nutrients with? The part we usually cut out when eat fruit.
Examples below
Papaya
Banana
Mango 'Stalk' or 'pedicel' would be an appropriate term (see, for example, this paper or this one). Specifically, you could say 'terminal part of the stalk/pedicel', though I don't know if there is a word for that.
Note that the term pedicel is commonly used for the stalk of a flower; it makes sense to use it for fruits too as they are derived from flowers.
The following is multiple choice question (with options) to answer.
What is the scientific term for the dropping of leaves, fruits, and flowers, which led to the naming of an acid thought to play a role in the process? | [
"ascorbition",
"affixation",
"ablation",
"abscission"
] | D | Abscisic acid is misnamed because it was once believed to play a role in abscission (the dropping of leaves, fruits, and flowers), but we now know abscission is caused by ethylene. The actual role of abscisic acid is to close the stomata, the tiny openings in leaves that allow substances to enter and leave, and to maintain dormancy. When a plant is stressed due to lack of water, abscisic acid tells the stomata to close. This prevents water loss through the stomata. |
SciQ | SciQ-4784 | climate-change
What this means is that the traditional monsoon dynamics i.e. cool Indian ocean and warm continental land mass has been disturbed by human influenced climate change as well as the natural geography of the land and ocean mass. One significant ISM phenomenon the tropical easterly jet stream has shown a weakening trend over the last few decades. A significant fall out of this could be mid latitude atmospheric dynamics could come into play during the ISM(one can think of this as the weather during a break in monsoons where upper level subtropical westerlies come into play) and a disturbing trend has been noted in recent times with increasing frequency of hail storms.
The following is multiple choice question (with options) to answer.
Sudden changes in geologic and climatic conditions can spur what process? | [
"evolution",
"generation",
"cloning",
"symbiosis"
] | A | When geologic and climatic conditions are changing, evolution may occur more quickly. Thus, long periods of little change may be interrupted by bursts of rapid change. This model of the timing of evolution is called punctuated equilibrium . It is better supported by the fossil record than is gradualism. This model suggests that niches left open by sudden geologic and climatic changes may be rapidly filled by bursts of evolution. |
SciQ | SciQ-4785 | cell-biology, nutrition, blood-circulation, liver
Title: How do nutrients get to the cells they need to get to? I understand the basics of digestion. I know that nutrients get absorbed by the microvilli, enter the bloodstream and travel to the liver but after all that, what is the biological mechanism that guides these nutrients to the proper receiving location? Broadly speaking, nutrients that enter the blood from the gut, and those that are released into the blood by the liver, are available to any cells that require them. So there is no "guiding to the correct location" in the sense that you suggest.
Lipids for example are present in the various lipoproteins and can be acquired from these by all cells. Iron is bound to transferrin, and any cell with transferrin receptors can internalise the transferrin and take the iron. Glucose is available in solution in the plasma, and free fatty acids are bound to serum albumin in the blood. During starvation the liver produces ketones ("ketone bodies") which are taken up by many different tissues/cell types.
The following is multiple choice question (with options) to answer.
What is the fluid that carries sperm through the urethra and out of the body, and provides it with nutrients? | [
"yeast",
"bacteria",
"semen",
"blood"
] | C | Semen is the fluid that carries sperm through the urethra and out of the body. In addition to sperm, it contains secretions from the glands. The secretions control pH and provide sperm with nutrients for energy. |
SciQ | SciQ-4786 | electromagnetism, optics, spectroscopy
For the future reader:
I found a related post Why does this paper use 1/cm for units of frequency? It means that the units of $\hbar$ have also been adjusted to match.
Multiply your frequency by $c$ to get a conventional angular frequency in rad/s, or multiply $\hbar \mapsto\hbar c$ to get the appropriate units for $\hbar$.
The following is multiple choice question (with options) to answer.
In what unit is frequency measured in? | [
"gram",
"hertz",
"mole",
"centimeter"
] | B | The frequency , , is the number of cycles an object or wave goes through in 1 second. Frequency is measured in Hertz (Hz). 1 Hz = 1 cycle per sec. |
SciQ | SciQ-4787 | inorganic-chemistry, alloy
Title: If alloys are homogeneous mixtures, why can't we separate their components? An alloy is a material composed of two or more metals or a metal and a nonmetal. And, they are usually formed by heating the elements to their melting points, and then cooling them, so that the components mix. Now, why doesn't this works backwards i.e. if we heat the alloy again to melting point of their constituents, and they should separate? Once the alloy has been formed the atoms from the different metals will have shared there electrons with each other and come to an equilibrium. In this state the metal atoms have formed a complex structure which has a different reactivity or properties than each individual metal did in its original form .
The following is multiple choice question (with options) to answer.
Mixtures of materials called alloys contain at least one of what type of material? | [
"metal",
"steel",
"coal",
"liquid"
] | A | Alloys are mixtures of materials, at least one of which is a metal. |
SciQ | SciQ-4788 | proteins, sequence-alignment, blast
And so on and so forth. BLAST starts by matching the first $N$-sized word and then attempts to extend the alignment.
Now, what if we were using $N=3$?
CRK
CRA
**
Because the word size is now 3, we need at least three matching residues to match in order to attempt to extend the alignment. Since there is no 3-letter match, the target is missed.
So, decreasing the word size is better for finding small protein matches because it can use shorter matching sequences as an alignment seed.
As a general rule, playing with the word size is a question of finding the right balance between specificity and sensitivity. Decreasing the word size helps you find more matches (increases sensitivity) but it will also find more divergent sequences (decrease specificity). Increasing the word size will reduce the number of matches (decrease sensitivity) because you need a longer perfect match to start extending the alignment, but will increase specificity for the same reason.
If you raise the word size to something close to the size of the query, you will only find almost exact matches. That might be what you want to do and it is what algorithms like BLAT which are designed to find near exact matches (for example, mapping a sequence to the genome it came from) do. Usually, however, we want less than perfect matches since we are looking for homologous sequences and not the exact same query. In such cases, we will decrease the word size for smaller proteins to increase our chances of finding homologs.
1 This is a bit of a simplification. The rules for extending alignments are a more complex but it serves to illustrate the point.
The following is multiple choice question (with options) to answer.
The challenge of techniques used for proteomic analyses is the difficulty in detecting small quantities of what? | [
"acids",
"particles",
"proteins",
"bacteria"
] | C | The challenge of techniques used for proteomic analyses is the difficulty in detecting small quantities of proteins. Although mass spectrometry is good for detecting small amounts of proteins, variations in protein expression in diseased states can be difficult to discern. Proteins are naturally unstable molecules, which makes proteomic analysis much more difficult than genomic analysis. |
SciQ | SciQ-4789 | gas-laws, heat
Title: How can I light a fire in this case? Is there any gas that contains oxygen so that it doesn't require oxygen from the environment in order to burn?
What I am trying to do is use LPG gas, which is fed through a pipe to a burner that is placed in an environment that has no air, somewhat like a vacuum. Is there any way to light the burner inside that vacuum environment?
A few wild ideas that I had included finding some gas that contains oxygen in itself. I may be wrong.
EDIT - The question doesn't end here. Please read the comments section below for any doubts that you might have. And if it isn't answered in comments section then ONLY comment. The most convenient solution for your question can be the Hydrooxy gas (also sometimes called the Brown’s gas). Simply put its water split into hydrogen and oxygen. Hydrogen and oxygen can be combined back by ignition and can create a maximum temperature up to 2800 °C (around 600–700 °C hotter than burning hydrogen in air), which makes it a good fuel for metal welding and cutting.
Though 2:1 hydrogen and oxygen ratio is enough to produce water via combustion, but on a practical solution you will need around 3:1 to 5:1 ratio to avoid oxidizing flames. The temperature you can achieve by burning hydrogen oxygen mix varies, depending on the ratio of both gases used.
Hydrogen and oxygen can be obtained via simple electrolysis.
$$\ce{2H2O + Energy -> 2H2 + O2}$$
and combined back as
$$\ce{2H2 + O2 -> 2H2O + Energy}$$
It might be worth noting that for all practical purposes, the energy you use to split hydrogen and oxygen will always be greater than what you can get by combining them back (like what happens in every combustion engine, humans have ever created).
If you are planning to develop an actual application, there are many precautions that you would need to consider, the most important of which would be back-fire protection (a common problem with gas based welding), so that the flame doesn’t reach back into the gas tank, which of course will explode.
The following is multiple choice question (with options) to answer.
What type of gas is delivered to homes to use for cooking and heating? | [
"fluid gas",
"nuetralized gas",
"natural gas",
"compounded gas"
] | C | Natural gas is delivered to homes, where it is used for cooking and heating. Natural gas is also a major energy source for powering turbines to make electricity. Natural gas releases most of its energy as heat when it burns. The power plant is able to use this heat, either in the form of hot gases or steam, to spin turbines. The spinning turbines turn generators, and the generators create electricity. |
SciQ | SciQ-4790 | organic-chemistry
Title: What are the minimal chemical requirements for a food which we all can eat? I've been puzzled by the following though experiment for the past few days:
I want to make my own food from scratch, but I do not know where to start from.
I want to be 100% sure that what I eat will never contains something that can damage my body. For example: If you buy something from the local market you can not be 100% sure that it's safe to eat. (99.9 % maybe... but that's not 100%)
I want to ask you to tell me, how can I make a food that I can eat, or should I say - live on it, for the rest of my life, that's 100% safe, I can control every aspect of it's creation and has many combinations of taste because I love diversity.
Thank you for your time : )
Edit:
Because I realized my question is very broad and indeed is a little... too much scientific I want to close it. But before I do so, here's what I had in mind:
I wanted to take some chemical elements, put them in a jar, run some electricity, heat, whatever through it, filter it, do some additional processing and eat it.
I wanted to know if the stomach can take it, because I was going to eat food that's not hard to digest. Considering the three basic biomolecules used by the body are carbohydrates, lipids, and proteins, you would need to consume these three molecules only. Now we can choose three substances.
Glucose, one of the most basic carbohydrates, is needed for ATP production, so that would be a food choice there.
Any oil or butter will provide lipids.
Protein comes from a variety of sources. Meat is typically though of as the best, but nuts are a pretty good source too.
Since nuts satisfy proteins and lipids, I'd say honey roasted peanuts are the most basic food you could live off of, if you replace pure glucose for the honey.
The following is multiple choice question (with options) to answer.
Chewing a bite of bread mixes it with what and facilitates its chemical breakdown? | [
"chyme",
"calcium",
"interstitial fluid",
"saliva"
] | D | Exergonic c. Decomposition d. Catabolic, exergonic, and decomposition 18. Which of the following combinations of atoms is most likely to result in a chemical reaction? a. hydrogen and hydrogen b. hydrogen and helium c. helium and helium d. neon and helium 19. Chewing a bite of bread mixes it with saliva and facilitates its chemical breakdown. This is most likely due to the fact that ________. the inside of the mouth maintains a very high temperature b. chewing stores potential energy c. chewing facilitates synthesis reactions d. saliva contains enzymes 20. CH4 is methane. This compound is ________. |
SciQ | SciQ-4791 | climate-change, sea-level
Here you can clearly see how, with some ups and downs, the rate of sea level rise have been increasing over the last few centuries. And notably the current rate, about 20 years after the end of this plot is already out of the scale, and around 3.2 mm/year as pointed also by other answers.
I would highlight the following from their abstract:
Sea level rose by 6 cm during the 19th century and 19 cm in the 20th
century.Superimposed on the long-term acceleration are quasi-periodic
fluctuations with a period of about 60 years. If the conditions that
established the acceleration continue,then sea level will rise 34 cm
over the 21st century. Longtime constants in oceanic heat content and
increased ice sheet melting imply that the latest
Intergovernmental Panel on Climate Change (IPCC) estimates of sea
level are probably too low.
Regarding to whether this is caused by humans or not, I rather stay out of that argument and point that our best science and models suggest that lowering $\text{CO}_2$ emissions can make a significant impact in slowing down sea level rise in the upcoming centuries, so we should ACT NOW, and stop arguing whether it was or not our fault in the first place.
The following is multiple choice question (with options) to answer.
What is occurring at an alarming rate as a result of global climate change and the constant melting point of ice? | [
"glacier melt",
"glacial movement",
"glacial formation",
"glacial hardening"
] | A | Because of global climate change, temperatures all over Earth are rising. However, the melting points of Earth’s substances, including ice, are constant. The result? Glaciers are melting at an alarming rate. Melting glaciers cause rising sea levels and the risk of dangerous river flooding on land. You can learn more about these effects of melting at this URL: http://video. nationalgeographic. com/video/player/environment/global-warming-environment/glacier-melt. html . |
SciQ | SciQ-4792 | behaviour, human-evolution
So, how does the freeze response help? Consider another (last one) situation: you're being attacked by a lion. In this case, you know that you can neither fight with an angry lion nor outrun it. What should you do? One immediate idea would be to play a dead man's role in front of the lion so that (maybe) it will leave you. Of course, it doesn't pay off everytime, but surely it does, sometimes. And in such a case, this would be better for someone who would otherwise either try to fight with the lion or to outrun it. And, obviously, it is a better option for many other organisms too. So it indeed seems that this response developed much earlier in time, maybe even long before first chordates appeared.
With the above part explaining why it is beneficial, one part still remains i.e. how does it work? For this, see the paragraph below:
Studies show that particular connections from the periaqueductal grey (brain region located along the spine) to the pyramis at the base of your skull are integral to the freeze response. When these connections are activated, it causes the body to freeze. They can be activated by things that are actually dangerous and by things that aren’t, so even irrational fears can cause us to freeze. While giving a presentation, you might not actually be in danger, but your body responds like it is and causes you to clam up.
Below are images of the periaqueductal grey in spinal cord and pyramids in brainstem to help you understand their locations.
To conclude, freeze response is not a mere "remain" of our reptilian past, it is still beneficial for us.
References:
https://en.wikipedia.org/wiki/Fight-or-flight_response
https://www.psychologytoday.com/blog/evolution-the-self/201507/trauma-and-the-freeze-response-good-bad-or-both
https://joyable.com/blog/fight-flight-freeze/
https://www.slideshare.net/mobile/dr_ansari2000/the-brain-stem-ii
http://slideplayer.com/slide/4637165/
The following is multiple choice question (with options) to answer.
What triggers the fight-or-flight response? | [
"amphetamine",
"respiration",
"epinephrine",
"endorphine"
] | C | |
SciQ | SciQ-4793 | mechanical-engineering, applied-mechanics, torque, forces
Title: How to calculate force acting on axle from hub motor with known torque? In some electric bikes, a motor is mounted to the hub of the front wheel. When turned on, this hub motor applies a torque, turning the wheel, reacting against the ground, with a resultant force acting against the inertia of bike / rider / air resistance etc.
How can I work out the force applied to the centre of the axle, given a motor acting with specific torque t
and wheel or radius r, assuming the tyre does not overcome the friction force of the ground?
Lets say we fix the wheel, axle, and motor to a fork, that is anchored (so nothing can move). Lets assume the fork cannot flex.
Forgive my crude drawing, but this might look something like this:
The Force of the motor acts on the rim, then the reaction force from the road acts on the fork (I think). The net foce is to the right hand of the page (where the motor is at the centre of the wheel).
Assuming the motor has a Torque of 40Nm, what is the force on the fork centred at the axle?
(I'm trying to determine if my fork can support a front motor, so the next stage will be to look at whether this fork can support the force at that distance)
Assuming the motor has a Torque of 40Nm, what is the force on the fork centred at the axle?
Since the system is fixed in place, there is no acceleration or rotation. Therefore any torque developed by the motor is completely countered by friction with the ground, and that force is transmitted to the fork. So this is just $\frac{40\rm{Nm}} {311\rm{mm}} = 129\rm{N}$. If the wheel could rotate and the frame could accelerate, that force would be reduced.
Presumably if instead of anchoring your fork you allowed it to move with minimal resistance, you could attach a scale to it and directly measure the force that the motor is creating.
The following is multiple choice question (with options) to answer.
What is the term for the force applied to a wheel and axle? | [
"velocity force",
"output force",
"input force",
"momentum"
] | C | In a wheel and axle, force may be applied either to the wheel or to the axle. This force is called the input force. A wheel and axle does not change the direction of the input force. However, the force put out by the machine, called the output force, is either greater than the input force or else applied over a greater distance. |
SciQ | SciQ-4794 | experimental-realization, architecture, d-wave, superconducting-quantum-computing
Title: Do the latest D-Wave computers use Helium compounds for cooling? Do the latest D-Wave machines use compounds of $\require{\mhchem}\ce{^{3}He}$ and $\ce{^{4}He}$ for cooling? If not, how does D-Wave approach cooling its plates low enough to achieve superconductivity? What compounds does DWave use for the plates in their fridge, and at what temperature do its plates reach superconductivity? Yes, they use $\require{\mhchem}\ce{^3He}$ and $\ce{^4He}$. No, they do not use compounds of these but instead a solution of these two (at the operating temperature) liquid nobel gases. The details can be found in the wikipedia article on dilution refrigerators.
The following is multiple choice question (with options) to answer.
Magnetic resonance imaging devices use what to cool the superconducting magnets? | [
"dry ice",
"antifreeze",
"liquid nitrogen",
"fluorocarbons"
] | C | Magnetic resonance imaging (NMR) devices use liquid nitrogen to cool the superconducting magnets. Nitrogen is a gas at room temperature and liquefies at -195.8°C. Its neighbor on the periodic table (oxygen) boils at -182.95°C. The interactions between nitrogen molecules (N 2 ) are weaker, so the boiling point is lower. Interactions between non-polar molecules depend on the degree of electron fluctuation within the molecule. |
SciQ | SciQ-4795 | thermodynamics, evaporation, gas, liquid-state
On the water surface, knowing the temperature, we can estimate the vapor pressure and vapor mixture fraction. Then there will be an diffusion process for the water vapor to move out and for the ambient air to move in. Because the water surface doesn't allow the air to further move, a circulation forms. When the water vapor moves out, the water vapor pressure drops, so more liquid water evaporates to fill up the loss of water vapor. The evaporation associates latent heat so water surface area temperature drops (you may see dew on the bowl wall). Then a heat transfer process starts which may initiate water circulation as well.
As this is complex, doing test might be a quick way to get the K value if you assume it is a constant, which is questionable.
The following is multiple choice question (with options) to answer.
Water moving up the plane and evaporating from the leaves is a process known as what? | [
"propagation",
"sublimation",
"transpiration",
"evaporation"
] | C | Water also moves through the living organisms in an ecosystem. Plants soak up large amounts of water through their roots. The water then moves up the plant and evaporates from the leaves in a process called transpiration . The process of transpiration, like evaporation, returns water back into the atmosphere. |
SciQ | SciQ-4796 | neuroscience, neurophysiology, neuroanatomy, neurology
Conceptually, rather than thinking about extra parts, all of your same questions apply just as much to what is "normal". There is no evidence that brain development has any assumption built in that there will be 4 limbs or 5 digits on a hand, rather, connections are made with the nervous system as the limbs and digits develop, and these connections carry information between the CNS and sensory neurons and motor neurons, and the brain develops in response to those connections.
The following is multiple choice question (with options) to answer.
How many bones fuse together to form the cranium? | [
"3",
"6",
"8",
"8"
] | C | Fixed joints do not allow any bone movement. Many of the joints in your skull are fixed ( Figure below ). There are eight bones that fuse together to form the cranium. The joints between these bones do not allow movement, which helps protect the brain. |
SciQ | SciQ-4797 | humidity, water-vapour
Title: Water vapor content versus specific humidity I am wondering the difference between water vapor content and specific humidity to determine the moisture availability in the atmosphere. Which one is more acceptable variable to determine the moisture availability in the atmosphere?
I need to show the moisture availability in the atmosphere in my study. So should I explain it through water vapor content or through specific humidity? I will explain the rainfall deficiency over a region For a study relating to rainfall, I would be inclined to look at total column water vapour (TCWV), also known as integrated water vapour (IWV) or precipitable water. They're all (more or less) the same thing.
The company Remote Sensing Systems describes it as:
Total column water vapor is a measure of the total gaseous water contained in a vertical column of atmosphere. It is quite different from the more familiar relative humidity, which is the amount of water vapor in air relative to the amount of water vapor the air is capable of holding. Atmospheric water vapor is the absolute amount of water dissolved in air. When measured in linear units (millimeters, mm), it is the height (or depth) the water would occupy if the vapor were condensed into liquid and spread evenly across the column. Using the density of water, we can also report water vapor in kg/m2 = 1 mm or g/cm2 = 10 mm.
For rain to form, clouds need to form first. Clouds need cloud condensation nuclei, but crucially, for clouds to form, the water vapour partial pressure needs to reach the saturation vapour pressure. The latter is strongly dependent on temperature (Clausius-Clapeyron relation), so a profile of relative humidity is not the most directly useful quantity. The total column water vapour describes how much liquid water might form, which is why it is sometimes even described as precipitable water.
You can get this product either from reanalysis (like ERA-5) or retrieved from hyperspectral infrared sounders, such as IASI, AIRS, or CrIS. Depending on where and when in the world you're looking at, there may also exist products from geostationary instruments.
The following is multiple choice question (with options) to answer.
What is the amount of moisture in the atmosphere? | [
"heat",
"humidity",
"static",
"mixture"
] | B | |
SciQ | SciQ-4798 | quantum-mechanics, heisenberg-uncertainty-principle
Title: Does Heisenberg Indeterminism have a lower bond in $\Delta \chi$? Take the Heisenberg's indeterminism law:
$$\Delta \chi \cdot \Delta \rho \geq h/ 2$$
Does the momentum pose a limit so that we cannot measure the position with a precision greater than:
$$h / (2\cdot \Delta \rho)$$
where $\Delta \rho$ is at maximum $mc$?
The following is multiple choice question (with options) to answer.
What heisenberg principle imposes ultimate limits on what is knowable in science? | [
"certainty principle",
"uncertainty principle",
"impossibility principle",
"vacuum principle"
] | B | The value of ħ is not large, so the uncertainty in the position or momentum of a macroscopic object like a baseball is too insignificant to observe. However, the mass of a microscopic object such as an electron is small enough that the uncertainty can be large and significant. It should be noted that Heisenberg’s uncertainty principle is not just limited to uncertainties in position and momentum, but it also links other dynamical variables. For example, when an atom absorbs a photon and makes a transition from one energy state to another, the uncertainty in the energy and the uncertainty in the time required for the transition are similarly related, as ΔE Δt ≥ ℏ . As will be discussed later, even the vector components of angular 2 momentum cannot all be specified exactly simultaneously. Heisenberg’s principle imposes ultimate limits on what is knowable in science. The uncertainty principle can be shown to be a consequence of wave–particle duality, which lies at the heart of what distinguishes modern quantum theory from classical mechanics. Recall that the equations of motion obtained from classical mechanics are trajectories where, at any given instant in time, both the position and the momentum of a particle can be determined exactly. Heisenberg’s uncertainty principle implies that such a view is untenable in the microscopic domain and that there are fundamental limitations governing the motion of quantum particles. This does not mean that microscopic particles do not move in trajectories, it is just that measurements of trajectories are limited in their precision. In the realm of quantum mechanics, measurements introduce changes into the system that is being observed. |
SciQ | SciQ-4799 | forces, pressure, bernoulli-equation, navier-stokes
\end{equation}
where $R_2$ is the smaller radius, and $R_1$ the larger one. Rearranging, one finds:
\begin{equation}
Q_A=Q_B\left( \frac{L_1}{(L_1+L_2)}\frac{R_2^4}{R_1^4}+\frac{L_2}{L_1+L_2} \right)
\end{equation}
You can check that the quantity inside the brackets is less than 1 (it becomes 1 in the limit $R_2\to R_1$). This implies that $Q_B>Q_A$, i.e. the flow rate of blood through catheter $B$ is greater than that through catheter $A$. This is possible because the pressure gradient along their lengths are different, despite the total pressure difference being equal in both cases.
Intuitively, this also makes sense since a larger cross-sectional area means that there is more "room" for blood to flow. As an analogue, think of e.g. 1 traffic lane opening up into 2 lanes vs only having 1 lane for the entire length of the road.
The following is multiple choice question (with options) to answer.
Narrowing of the arterioles causes an increase of what upstream in the arteries? | [
"heart beat",
"white blood cells",
"red blood cells",
"blood pressure"
] | D | |
SciQ | SciQ-4800 | organic-chemistry, nomenclature
(All images taken from Wikipedia; all D-isomers.)
In the order of reading these are allose, altrose, glucose, mannose, gulose, idose, galactose and talose. If you compare glucose (3rd in the first row) with galactose (3rd in the second row) you will realise that they differ only in the orientation of the hydroxy group in 4-position. The posh terminology is epimerism — D-glucose is the C4 epimer of D-galactose and vice-versa.
You asked about two labels where the sugar is preceded either by 4-dehydro-6-deoxy or 4-keto-6-deoxy. The agree in the 6-deoxy part which means that the oxygen on C6 is missing; you will find a methyl group $\ce{CH3}$ there instead. The labels 4-keto and 4-dehydro may also be confusing. The first says that a keto group is there instead of the hydroxy group, while the second says that two hydrogens have been removed from that position. The result is the same, instead of having $\ce{CHOH}$ as fourth carbon we have $\ce{C=O}$. This also deprives us of the stereocentre (a carbonyl group is never stereogenic).
Putting all of this together: Yes, the two are identical. If you start from the C4-epimers and remove the stereocentre at C4 it does not matter which you started from. Both galactose and glucose are common sugars so both choices are understandable (even though glucose is probably known even a tad more). I would, however, strongly object agains 4-keto-D-talose in the place of 4-keto-D-mannose (mannose and talose being C4-epimers) since mannose is much more known than talose.
The following is multiple choice question (with options) to answer.
What are double sugars called? | [
"silicates",
"sodiums",
"monosaccharides",
"disaccharides"
] | D | |
SciQ | SciQ-4801 | cell-division
Title: Why doesn't cellular, replicative senescence (or the hayflick limit) constrain the normal development of an organism? The wikipedia article on cellular senescence states:
Cellular senescence is the phenomenon by which normal diploid cells cease to divide. In culture, fibroblasts can reach a maximum of 50 cell divisions before becoming senescent. This phenomenon is known as "replicative senescence", or the Hayflick limit.
The following is multiple choice question (with options) to answer.
Cells that undergo cell division continue to have their telomeres shortened, thus telomere shortening is associated with what life process? | [
"reducing",
"metabolism",
"reproduction",
"aging"
] | D | Telomerase and Aging Cells that undergo cell division continue to have their telomeres shortened because most somatic cells do not make telomerase. This essentially means that telomere shortening is associated with aging. With the advent of modern medicine, preventative health care, and healthier lifestyles, the human life span has increased, and there is an increasing demand for people to look younger and have a better quality of life as they grow older. In 2010, scientists found that telomerase can reverse some age-related conditions in mice. This may have potential in [2] regenerative medicine. Telomerase-deficient mice were used in these studies; these mice have tissue atrophy, stem 2. Jaskelioff et al. , “Telomerase reactivation reverses tissue degeneration in aged telomerase-deficient mice,” Nature 469 (2011): 102-7. |
SciQ | SciQ-4802 | plant-physiology
Title: Would a plant survive if it was watered using hard-water? Hard water is water with high mineral/salt content. I'm told that a potted plant watered with a salt solution dries out sooner or later. Is this true?
If so, would a plant survive if watered using hard-water? It would depend on the content of the hard-water. If the water contained heavier metals like lead or radioactive elements like tritium (Hydrogen-3), the plant would most likely die. Most land plants cannot survive when watered with massive amounts of salt water as the salt would absorb the water from the leaves.
The following is multiple choice question (with options) to answer.
Which two basic parts of a plant develop tough outer coatings to protect the plant from the environment? | [
"bark and stems",
"roots and leaves",
"stems and stalks",
"leaves and stems"
] | D | |
SciQ | SciQ-4803 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
What is the name for a kind of animal that eats a mix of plant and animal foods. | [
"an omnivore",
"an smorgasbord",
"a carnivore",
"an herbivore"
] | A | Some mammals are omnivores. Omnivores are heterotrophs that eat a mix of plant and animal foods. Mammals that are omnivores include bears, foxes, rats, pigs, and human beings. The chimpanzees in Figure below are also omnivorous mammals. In the wild, they eat mainly plant foods, but they supplement plants with birds, bird eggs, insects, small monkeys, and other small mammals. Their favorite and most common food, however, is fruit. Animals that eat mainly fruit are called frugivores. |
SciQ | SciQ-4804 | homework, cell-membrane, human-physiology, lungs
Title: How many cell membranes are oxygen and carbon dioxide diffuse through in the lungs? In the lungs, oxygen and carbon dioxide pass through cell membranes by diffusion.
Which row is correct?
The correct answer is D, but I think it should be B. I can only think about three layers as maximum which are; epithelium of alveolus, endothelium of capillaries and the membrane of red blood cell. I don't know what are remainings.
Any help would be much appreciated! Oxigen goes from the alveolar's lumen to the cytoplasm of the erythrocyte, and that's 5 membranes:
the "top" of the alveolar epithelial cell
the "bottom" of such cell
the "top" of the endothelial cell (capillary)
the "bottom" of such cell
the erythrocyte membrane
You got all the cells right, but your only problem was this: oxygen diffuses through the cell membrane entering the cell, moves through the cytoplasm, and diffuses through the membrane again exiting the cell. So, for each cell, you have to count 2 membranes. For the last one, the erythrocyte, you have only 1 membrane (because it is $\ce{O2}$ final destination).
For the $\ce{CO2}$ the situation is a little bit more tricky. We have the same 4 membranes (2x epithelial cell and 2x capillary), but $\ce{CO2}$ can come from 2 locations:
from the erythrocyte, where it is formed from $\ce{H2CO3}$ (by the reaction $\ce{H2CO3 -> H2O + CO2}$) or released from the N-terminal group of proteins, like haemoglobin (where it has previously bound)
from the plasma (around 9% of the $\ce{CO2}$).
In the first case we have 5 membranes, and in the second case just 4.
So, the correct answer is D.
The following is multiple choice question (with options) to answer.
Oxygenated air, taken in during inhalation, diffuses across the surface of the lungs into the what? | [
"bloodstream",
"liver",
"proteins",
"brain"
] | A | Types of Breathing Amphibians have evolved multiple ways of breathing. Young amphibians, like tadpoles, use gills to breathe, and they don’t leave the water. Some amphibians retain gills for life. As the tadpole grows, the gills disappear and lungs grow. These lungs are primitive and not as evolved as mammalian lungs. Adult amphibians are lacking or have a reduced diaphragm, so breathing via lungs is forced. The other means of breathing for amphibians is diffusion across the skin. To aid this diffusion, amphibian skin must remain moist. Birds face a unique challenge with respect to breathing: They fly. Flying consumes a great amount of energy; therefore, birds require a lot of oxygen to aid their metabolic processes. Birds have evolved a respiratory system that supplies them with the oxygen needed to enable flying. Similar to mammals, birds have lungs, which are organs specialized for gas exchange. Oxygenated air, taken in during inhalation, diffuses across the surface of the lungs into the bloodstream, and carbon dioxide diffuses from the blood into the lungs and expelled during exhalation. The details of breathing between birds and mammals differ substantially. In addition to lungs, birds have air sacs inside their body. Air flows in one direction from the posterior air sacs to the lungs and out of the anterior air sacs. The flow of air is in the opposite direction from blood flow, and gas exchange takes place much more efficiently. This type of breathing enables birds to obtain the requisite oxygen, even at higher altitudes where the oxygen concentration is low. This directionality of airflow requires two cycles of air intake and exhalation to completely get the air out of the lungs. |
SciQ | SciQ-4805 | theoretical-chemistry, catalysis
Title: Catalyst discovery How are catalysts for chemical reactions found?
Given a hoped for reaction, let's take the hydrogenation of carbon monoxide to methanol as an example, do chemists:
Proceed directly from some property of the reactants to an obvious (to the initiated) catalyst according to some grand unified theory of chemistry
Perform a computerized search over some set of simulations of different catalyzed reactions
Proceed by trial and error, trying different catalysts in the lab and hoping to find a good one
Proceed by trial and error but informed by some negative criteria. "Obviously, the catalyst can't contain [element] because [reason]"
The following is multiple choice question (with options) to answer.
What substances, which serve as catalysts, are involved in most of the chemical reactions that take place in organisms? | [
"enzymes",
"vitamins",
"proteins",
"carbohydrates"
] | A | Enzymes are involved in most of the chemical reactions that take place in organisms. |
SciQ | SciQ-4806 | trees, forestry
Title: Why do some trees hold their leaves through fall and winter? Why do some species of oak (Quercus spp.) retain their leaves through fall and winter? I've found that these leaves are called marcescent leaves. There must be some benefit that the tree gains from this because it seems like it would increase the possibility of limb damage due to snow accumulation on the leaves. The trait might not necessarily allow for an advantage, but a few possibilities have been proposed:
Nutrient return to the soil when needed in the spring
Less palatability to grazing animals
Source:
http://northernwoodlands.org/articles/article/why-do-some-leaves-persist-on-beech-and-oak-trees-well-into-winter
The following is multiple choice question (with options) to answer.
What is the type of plant called when its leaves seasonally turn color and fall off? | [
"conifer",
"deciduous plant",
"verdant plant",
"evergreen"
] | B | In a deciduous plant, leaves seasonally turn color and fall off the plant. They are replaced with new leaves later in the year. |
SciQ | SciQ-4807 | endocrinology, glucose, homeostasis, insulin, hypothalamus
Title: Role of the Hypothalmus in the control of Blood Sugar In homeostatic regulation of blood glucose, the receptor and effector is the Pancreas, but how does the control centre — the Hypothalamus — connect and link into this process? Your question doesn’t make it clear whether you think that the pancreas must be under the control of the hypothalmus, or whether you are asking whether it has an influence on the pancreas in relation to the secretion of insulin and glucagon, which control the concentration of blood glucose.
First, it has been long known that secretion of insulin can be influenced by the concentration of glucose in isolated pancreatic islets in vitro, so it can not be true that the effects must involve the hypothalmus. This is implicit in most book or general information articles you might find on the web, but for an original reference a review by W.J. Malaisse in Diabetologia 9, 167–173 (1973) seems highly cited.
I know almost nothing about physiology, but on searching the web for the role of the hypothalmus in glucose homeostasis, found a most readable prize-winning postgraduate essay on the topic by Syed Hussein of Imperial College London. I trust that it is in order to append an edited extract of this:
The following is multiple choice question (with options) to answer.
Besides the endocrine system, what other system exerts control over all the organ systems of the body? | [
"skeleton system",
"abnormal system",
"nervous system",
"circulatory system"
] | C | 16.6 | Nervous System By the end of this section, you will be able to: • Describe the form and function of a neuron • Describe the basic parts and functions of the central nervous system • Describe the basic parts and functions of the peripheral nervous system As you read this, your nervous system is performing several functions simultaneously. The visual system is processing what is seen on the page; the motor system controls your eye movements and the turn of the pages (or click of the mouse); the prefrontal cortex maintains attention. Even fundamental functions, like breathing and regulation of body temperature, are controlled by the nervous system. The nervous system is one of two systems that exert control over all the organ systems of the body; the other is the endocrine system. The nervous system’s control is much more specific and rapid than the hormonal system. It communicates signals through cells and the tiny gaps between them rather than through the circulatory system as in the endocrine system. It uses a combination of chemical and electrochemical signals, rather than purely chemical signals used by the endocrine system to cover long distances quickly. The nervous system acquires information from sensory organs, processes it and then may initiate a response either through motor function, leading to movement, or in a change in the organism’s physiological state. Nervous systems throughout the animal kingdom vary in structure and complexity. Some organisms, like sea sponges, lack a true nervous system. Others, like jellyfish, lack a true brain and instead have a system of separate but connected nerve cells (neurons) called a “nerve net. ” Flatworms have both a central nervous system (CNS), made up of a ganglion (clusters of connected neurons) and two nerve cords, and a peripheral nervous system (PNS) containing a system of nerves that extend throughout the body. The insect nervous system is more complex but also fairly decentralized. It contains a brain, ventral nerve cord, and ganglia. These ganglia can control movements and behaviors without input from the brain. Compared to invertebrates, vertebrate nervous systems are more complex, centralized, and specialized. While there is great diversity among different vertebrate nervous systems, they all share a basic structure: a CNS that contains a brain and spinal cord and a PNS made up of peripheral sensory and motor nerves. One interesting difference between the nervous systems of invertebrates and vertebrates is that the nerve cords of many invertebrates are located ventrally (toward the stomach) whereas the vertebrate spinal cords are located dorsally (toward the back). There is debate among evolutionary biologists. |
SciQ | SciQ-4808 | quantum-mechanics, homework-and-exercises, atoms, hydrogen
The second part of the question is a bit more subtle, because it's asking what spherical shell is most likely to contain the electron. The point of the question is that the volume of the spherical shell of radius $r$ and thickness $dr$ is $dV = 4 \pi r^2 dr$, so the probability of finding the electron in this shell is given by:
$$ P = \psi^2 dV = A e^{-2r/a_0} 4 \pi r^2 dr $$
You need to find the value of $r$ at which this function is a maximum.
The following is multiple choice question (with options) to answer.
What is the area where an electron is most likely to be found called? | [
"neucleus",
"orbital",
"proton",
"neutron"
] | B | wave functions can predict within a certain level of probability where an electron might be at any given time. The area where an electron is most likely to be found is called its orbital. Recall that the Bohr model depicts an atom’s electron shell configuration. Within each electron shell are subshells, and each subshell has a specified number of orbitals containing electrons. While it is impossible to calculate exactly where an electron is located, scientists know that it is most probably located within its orbital path. Subshells are designated by the letter s, p, d, and f. The s subshell is spherical in shape and has one orbital. Principal shell 1n has only a single s orbital, which can hold two electrons. Principal shell 2n has one s and one p subshell, and can hold a total of eight electrons. The p subshell has three dumbbell-shaped orbitals, as illustrated in Figure 2.8. Subshells d and f have more complex shapes and contain five and seven orbitals, respectively. These are not shown in the illustration. Principal shell 3n has s, p, and d subshells and can hold 18 electrons. Principal shell 4n has s, p, d and f orbitals and can hold 32 electrons. Moving away from the nucleus, the number of electrons and orbitals found in the energy levels increases. Progressing from one atom to the next in the periodic table, the electron structure can be worked out by fitting an extra electron into the next available orbital. |
SciQ | SciQ-4809 | ecology
Title: Do invasive species cause long-term damage to ecosystems they invade? Growing up in the U.S., I was warned at various times of the dire consequences of a variety of introduced pests (usually insects).
Japanese beetles, gypsy moths, and most recently the brown marmorated stink bug are all introduced pests that, at various times, were described as serious threats to our ecology.
These threats aren't confined to arthropods, either. The giant African land snail is causing a stir in Florida (indeed, Florida seems to suffer from an excessive variety of introduced species.
"Lack of native predators" is frequently cited as the primary reason many invasive species are considered such a risk to the ecology.
I understand that these introduced species can place tremendous pressure on native species that fill similar ecological niches, and may even push these species out of the region due to competition for food and habitat. However, do the overall ecologies that these species are introduced to adjust over long periods of time?
The numbers of Japanese beetles and gypsy moths don't seem anywhere as high as when I was a child. Has the ecosystem adjusted, or has the overpopulation self-corrected as the species ran low on food through over-consumption? Or are the populations still just as problematic now as they were 30 years ago, and I just am not seeing the bigger picture?
What is the long-term impact that we've seen from invasive, introduced species? Is there a significant difference on the long-term impact between introduced flora, arthropods, or mammals? The answer really depends on how you think of invasive. One extreme answer is to say that all things are relative, and that the concepts of local and invasive are all relative. This matters to a certain extent because ecologists draw a fuzzy line between invasive and naturalized. You could start with some basic species that we all think of as either good, local, or neutral. Take the earthworm. Most people think of it as a common native species, but the earthworm is actually an invasive species that has radically changed much of North America that came over with the Europeans. Similarly, brown trout are also invasive, coming to the US in the 1800's.
The following is multiple choice question (with options) to answer.
The part of the ecosystem required by a particular species is endangered when human activity threatens loss of what? | [
"primary speciation",
"habitat",
"primary producers",
"biodiversity"
] | B | Habitat Loss Humans rely on technology to modify their environment and replace certain functions that were once performed by the natural ecosystem. Other species cannot do this. Elimination of their habitat—whether it is a forest, coral reef, grassland, or flowing river—will kill the individuals in the species. Remove the entire habitat within the range of a species and, unless they are one of the few species that do well in human-built environments, the species will become extinct. Human destruction of habitats (habitats generally refer to the part of the ecosystem required by a particular species) accelerated in the latter half of the twentieth century. Consider the exceptional biodiversity of Sumatra: it is home to one species of orangutan, a species of critically endangered elephant, and the Sumatran tiger, but half of Sumatra’s forest is now gone. The neighboring island of Borneo, home to the other species of orangutan, has lost a similar area of forest. Forest loss continues in protected areas of Borneo. The orangutan in Borneo is listed as endangered by the International Union for Conservation of Nature (IUCN), but it is simply the most visible of thousands of species that will not survive the disappearance of the forests of Borneo. The forests are removed for timber and to plant palm oil plantations (Figure 21.8). Palm oil is used in many products including food products, cosmetics, and biodiesel in Europe. A 5-year estimate of global forest cover loss for the years from 2000 to 2005 was 3.1 percent. Much loss (2.4 percent) occurred in the humid tropics where forest loss is primarily from timber extraction. These losses certainly also represent the extinction of species unique to those areas. |
SciQ | SciQ-4810 | c=3 x10^8 m/s lambda= wavelength (in meters) Calculate the energy associated with a molecule of red photons with a wavelength of 6.700 x 10^-7 m. I plugged the numbers into the formula and I got 2.967 x 10^-19 J. Or am I missing a step? (ii) have wavelength of 0.50 Å. Explore: With the Energy (eV) set to 19 eV, click Fire six times. Determine the energy of 2.00 mol of photons for each kind of light. Determine the energy of 1.50 mol of photons for each of the following kinds of light. Analyze: Find the total energy of each set of emitted photons. Find the energy of each of the photons which: (a) correspond to light of frequency {eq}3 \times 10^{15} {/eq} Hz (b) have a wavelength of 0.50 A Determine the energy of 1.40 of photons for each of the following kinds of light. Formula. infrared radiation (1600 nm) infrared radiation (1600 ) visible light (480 ) ultraviolet radiation (170 ) Share 0 (i) Energy (E) of a photon is given by the expression, E = Where, h = Planck’s constant = 6.626 × 10 –34 Js. Is that right? The energy of a photon is inversely proportional to the wavelength of a photon. Part (a) 1540 nm to kJ. Share with your friends. Example 1. (Assume three significant figures.) (ii) have wavelength of 0.50 Å. The Photon energy formula is given by, Where. Q.6:- Find energy of each of the photons which (i) correspond to light of frequency 3×10 15 Hz. Formula is given by, Where With the energy ( eV ) set to 19 eV, Fire... The emitted photons each time formula is given by, Where, Where way by substituting appropriate. The appropriate nm into the equation appropriate nm into the equation six times given by, Where of of... Speed of the light and explore: With the energy e will increase ) Planck ’ s (. Increase ) energy if the wavelength of a photon is inversely proportional to total... For each kind of light c = speed of the following kinds of light energy. Speed of the photons which (
The following is multiple choice question (with options) to answer.
What is the wavelength of light expressed in? | [
"vatts",
"nanometers (nm)",
"millimeters",
"nanoseconds"
] | B | Light As with auditory stimuli, light travels in waves. The compression waves that compose sound must travel in a medium—a gas, a liquid, or a solid. In contrast, light is composed of electromagnetic waves and needs no medium; light can travel in a vacuum (Figure 36.16). The behavior of light can be discussed in terms of the behavior of waves and also in terms of the behavior of the fundamental unit of light—a packet of electromagnetic radiation called a photon. A glance at the electromagnetic spectrum shows that visible light for humans is just a small slice of the entire spectrum, which includes radiation that we cannot see as light because it is below the frequency of visible red light and above the frequency of visible violet light. Certain variables are important when discussing perception of light. Wavelength (which varies inversely with frequency) manifests itself as hue. Light at the red end of the visible spectrum has longer wavelengths (and is lower frequency), while light at the violet end has shorter wavelengths (and is higher frequency). The wavelength of light is expressed in nanometers (nm); one nanometer is one billionth of a meter. Humans perceive light that ranges between approximately 380 nm and 740 nm. Some other animals, though, can detect wavelengths outside of the human range. For example, bees see near-ultraviolet light in order to locate nectar guides on flowers, and some non-avian reptiles sense infrared light (heat that prey gives off). |
SciQ | SciQ-4811 | botany
Title: Greyish spots behind a peach's stone, what could they be? I'm sorry if it's a silly question, but what are those greyish spots behind the stone of this peach (or whatever this is)? What are they for? Are they safe to eat? The fruit is ok from the outside Callus can develop inside peaches (https://www.tasteofhome.com/article/peach-callus-tissue/), between the mesocarp and the endocarp. Callus is edible and harmless. It's a tissue composed of unorganised parenchyma cells, which in turn are multi-purpose cells that can be found in a number of "soft" tissues with metabolic purposes including, but not limited to, the mesocarp and the endosperm. Callus' main purpose is to seal damaged tissues, see for instance:
this blogpost that explains the difference between mold and callus in a peach where there actually is a mold infection (which you should not eat)
its counterpart where there is no mold, but a considerable amount of callus (way more than you have there) was produced because the stone had split open; this one would be safe to eat, once you've ascertained that there is no mold, although callus may contain pieces of hard tissue from the stone.
Small quantities of callus can appear as leftovers form older and smaller lesions.
The following is multiple choice question (with options) to answer.
What is found inside the pores of spongy bone? | [
"rupture marrow",
"bone marrow",
"liquid marrow",
"green marrow"
] | B | Bone marrow is a soft connective tissue that produces blood cells. It is found inside the pores of spongy bone. |
SciQ | SciQ-4812 | acid-base, ph
Title: Why can't the strength of superacids be measured in water? I learned about acid strength, that the strength of an acid increases with it's degree of ionization when solvated. So, in water, a strong acid is one where $\ce{[H_3O^+]}$ is large, which is equal to a low pH: $\mathrm{pH=-log[H_3O^+]}$.
Considering extreme cases, such as superacids, I have found out that other methods are used to measure their acidity (methods I don't really understand). My question is why is it impossible to simply get super high concentrations of $\ce{[H_3O^+]}$ in aqueous solutions of superacids, and use this to determine the acid strength. Also, is pH used as a measure of acidity outside of aqueous solutions?
I have come over the leveling effect, but I don't think I fully understand it. The way I understand it (for the case with water as solvent) is that basically any acid in water will protolyze $\ce{H2O}$ to $\ce{H3O+}$, making this the effective acid. I don't understand why this would affect the measured pH, as it is $\ce{[H_3O^+]}$ you are measuring. Any acid-base reaction is always an equilibrium:
$$\ce{HA^1 + (A^2)- <=> (A^1)- + HA2}\tag{1}$$
and for each pair of acids $\ce{HA^1}$ and $\ce{HA^2}$ you could calculate a $K_\mathrm{a}$ value to determine one acid’s strength with respect to the other. This $K_\mathrm{a}$ value is typically calculated according to equation $(2)$ if $\ce{(A^2)-}$ (which does not have to feature a negative charge; I just wanted to avoid different descriptions for the two acids) is the solvent.
The following is multiple choice question (with options) to answer.
The strength of an acid depends on how many of which ions it produces when it dissolves in water? | [
"carbon",
"helium",
"silicon",
"hydrogen"
] | D | The strength of an acid depends on how many hydrogen ions it produces when it dissolves in water. A stronger acid produces more hydrogen ions than a weaker acid. For example, sulfuric acid (H 2 SO 4 ), which is found in car batteries, is a strong acid because nearly all of it breaks down into ions when it dissolves in water. On the other hand, acetic acid (CH 3 CO 2 H), which is the acid in vinegar, is a weak acid because less than 1 percent of it breaks down into ions in water. |
SciQ | SciQ-4813 | electrochemistry, redox, photochemistry, toxicity, ozone
Title: How much ozone is produced by ionization of air and how turn ozone into oxygen I want to make a plasma speaker. I'm worried about the amount of ozone being produced by the ionization of the air and it possibly not being a safe amount. Even if it doesn't produce a dangerous amount, I don't like the smell of ozone. I'd like this all to be continuous. I am very unfamiliar with the chemistry here but I have read that UV light, around 250nm, can cause $\ce{O_3 \to O_2 + O}$ and also $\ce{O_2 \to 2O}$
But also without any help it seems that $\ce{2O \to O_2}$ and also $\ce{O + O_2 \to O_3}$. So it seems that if I shined UV light of the right frequency on the spark I'd make a lot of $\ce{O}$ and perhaps that would cause more $\ce{O_2}$ than $\ce{O_3}$ but I'm not really sure.
I was also thinking that it might oxidize some sort of metal filter really well and I could just keep replacing those but I wasn't sure. I could also heat the filter slightly to speed up the reaction if necessary.
Even if the UV light idea doesn't work out very well I still want a way to do this. Is the amount of ozone produced by a continuous electrical current though air harmful? Is there a way of getting rid of the ozone to make some odorless non-harmful chemical?
Even if the UV light idea doesn't work out very well I still want a way to do this
With some photochemical background, I suggest to forget about running such a UV lamp
Remember that your plasma will be formed in air. For every molecule of ozone formed, there are much more harm- and odourless $\ce{O2}$ molecules around. If you cleave $\ce{O3}$
The following is multiple choice question (with options) to answer.
How many oxygen ions make up an ozone molecule? | [
"five",
"one",
"eight",
"three"
] | D | Oxygen is needed to make ozone. Ozone is a molecule made of three oxygen ions. Ozone in the upper atmosphere blocks harmful solar radiation from reaching the surface. Without oxygen, life on Earth would have been very simple. |
SciQ | SciQ-4814 | optics, electromagnetic-radiation, speed-of-light, refraction
Title: Difference in velocity of light in change in medium It is often seen that according to physics the light changes it's velocity according to the medium through which it is traveling. So can it be explained that why so happen? The speed of light is always constant. The speed doesn't change, but the distance it travels might change. For example the speed of light "decreases" with about 35% when traveling in optical fiber. This happens because light doesn't go straight trough the fiber, it bounces in all directions. It's like putting a lot of mirrors. So the distance that we measure (the length of the optical fiber) is not the same is the distance light travels
So if you would have vacuum then the distance light travels would be the same as the distance you "can" measure, but if you don't have vacuum light will bounce from one atom to another. The photon will be absorbed by the atom, the atom's energy will rise for a few moments, and then it will fall back again to his original state, releasing the photon. This creates first of all a different wave length(a different color) and a longer path for light to travel. Because the photon doesn't go in a straight line from one atom to another.
The following is multiple choice question (with options) to answer.
While light travels at different speeds in different kinds of matter, the speed of light is constant in what condition? | [
"through glass",
"vacuum",
"under water",
"outer space"
] | B | Although the speed of light is constant in a vacuum, light travels at different speeds in different kinds of matter. For example, light travels more slowly in glass than in air. Therefore, when light passes from air to glass, it slows down. If light strikes a sheet of glass straight on, or perpendicular to the glass, it slows down but passes straight through. However, if light enters the glass at an angle other than 90°, the wave refracts, or bends. This is illustrated in Figure below . How much light bends when it enters a new medium depends on how much it changes speed. The greater the change in speed, the more light bends. |
SciQ | SciQ-4815 | dna, cloning, dna-isolation
If you do this, regular freezers are not cold enough to prevent freezer burn. This is what happens when you put a steak in to the freezer, wrapped in plastic even it will shrivel up and start to dry out as the water in the ice starts to sublime out of the package (the dry air in the freezer basically sucks the water out of the food). If this happens to your animal tissue, its probably not going to revive.
Scientific labs use -80C freezers and liquid nitrogen storage because the water turns into a glass and all biochemical reactions are basically stopped. (besides drying out, the enzymes like DNAse are still nominally functioning in the cells at -20C and even simple bacterial cells don't live for more than a year at -20C, much less mammalian cells). For preserving cell lines, liquid nitrogen is much more preferred. I would say that properly produced cell lines can theoretically revive after indefinite liquid nitrogen storage.
So that's a quick answer. Sorry to be a party pooper - things could change quite a bit in the next 20 years, but we just don't know how much. popping a paw in a baggie or some DNA extract into the freezer might work, but its hard to say for sure.
As far as the choice of where the DNA comes from in the animal, its true that skin cell lines are often producing imperfect animals - the DNA may be modified in the skin in various ways that cause the animal to be smaller, weaker, or even deformed compared to the donor. At this time all the protocols I see (and i could be wrong) are skin cells. I would expect that there is a better tissue to preserve, but that might be just a guess at this point. Its likely that in the next 20 years the choice of cell line from the donor will change quite a bit as well.
The following is multiple choice question (with options) to answer.
What kind of solution might cause animal cells to burst? | [
"monatomic",
"eutrophic",
"Acid Solution",
"hypotonic"
] | D | Unless an animal cell (such as the red blood cell in the top panel) has an adaptation that allows it to alter the osmotic uptake of water, it will lose too much water and shrivel up in a hypertonic environment. If placed in a hypotonic solution, water molecules will enter the cell, causing it to swell and burst. Plant cells (bottom panel) become plasmolyzed in a hypertonic solution, but tend to do best in a hypotonic environment. Water is stored in the central vacuole of the plant cell. |
SciQ | SciQ-4816 | heat, materials, carbon-allotropes
Title: Why does diamond conduct heat better than graphite? Our teachers made us accept (without any explanation) that diamond conducts heat better than graphite. What is the reason behind this (alleged) fact? Diamond is one of the best thermal conductors known, in fact diamond is a better thermal conductor than many metals (thermal conductivity (W/m-K): aluminum=237, copper=401, diamond=895). The carbon atoms in diamond are $\ce{sp^3}$ hybridized and every carbon is bonded to 4 other carbon atoms located at the vertices of a tetrahedron. Hence the bonding in diamond is a uniform, continuous 3-dimensional network of $\ce{C-C}$ single (sigma) bonds. Graphite on the other hand is formed from $\ce{sp^2}$ hybridized carbon atoms that form a continuous 2-dimensional sigma and pi bonding network. This 2-dimensional network forms sheets of graphite, but there is little connection between the sheets, in fact, the sheet-sheet separation is a whopping ~3.4 angstroms. This might lead us to suspect that heat conduction in the 2-dimensional sheet of graphite would be superior to diamond, but that heat conduction between graphite sheets would be very low. This is, in fact, an accurate description of thermal conduction in graphite. Thermal conductivity parallel to the graphite sheets=1950, but thermal conduction perpendicular to the sheet=5.7. Therefor, when we consider thermal conduction over all possible directions (anisotropic) diamond would be superior to graphite.
The following is multiple choice question (with options) to answer.
Transition metals are superior conductors of heat as well as what else? | [
"radiation",
"electricity",
"light",
"cold"
] | B | Transition metals are superior conductors of heat as well as electricity. They are malleable, which means they can be shaped into sheets, and ductile, which means they can be shaped into wires. They have high melting and boiling points, and all are solids at room temperature, except for mercury (Hg), which is a liquid. Transition metals are also high in density and very hard. Most of them are white or silvery in color, and they are generally lustrous, or shiny. The compounds that transition metals form with other elements are often very colorful. You can see several examples in the Figure below . |
SciQ | SciQ-4817 | biochemistry
Title: Why can't amylase break down glycogen? Amylase is an enzyme that breaks down starch in the form of amylopectin and amylose. Both amylose and amylopectin are formed by alpha glucose joined together by (1-4) and (1-6) glycosidic bonds. Glycogen is no exception, just that it has more branching. However, why is it that a google search shows that it is hydrolyzed by Glycogen Phosphorylase rather than amylase? Also, how can amylase digest both (1,6) and (1,4) glycosidic bonds?
Any help would be greatly appreciated. At an approximation the active sites of enzymes can be considered as having two aspects. The first relates to the catalysis — in this case the breaking of the glycosidic linkage. The second relates to binding the substrate. This review of the α-amylases by MacGregor et al. shows that there is a range of a-amylases, differing in this latter respect — their substrate specificity. In general there are binding sites for a varying numbers of glucose residues at either side of the bond being cleaved. This is shown in Fig. 3 of that review:
The important difference in the structure of glycogen and starch (amylopectin) — seldom mentioned in general biochemical or biology texts — is their patten of branching:
As this previous answer of mine to a different question explains, this results in a globular structure for glycogen granules in which only the ends of the chains are accessible. (The image below, from Protopedia, illustrates this better, especially if you imagine it in three dimensions.)
The following is multiple choice question (with options) to answer.
Our digestive system breaks down starch to what? | [
"Waste",
"pattern sugars",
"Salts",
"simple sugars"
] | D | Starches are complex carbohydrates. They are polymers of glucose. They consist of hundreds of glucose monomers bonded together. Plants make starch to store extra sugars. Consumers get starch from plants. Common sources of starch in the human diet are pictured in Figure below . Our digestive system breaks down starch to simple sugars, which our cells use for energy. |
SciQ | SciQ-4818 | 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 happens to a tectonic plate when it subducts? | [
"it melts",
"it cracks",
"it sinks",
"it warms"
] | A | Composite volcanoes are common along convergent plate boundaries. When a tectonic plate subducts, it melts. This creates the thick magma needed for these eruptions. The Pacific Ring of Fire is dotted by composite volcanoes. |
SciQ | SciQ-4819 | biochemistry, molecules, polymers, chemical-biology
A monomer is the simplest building block of a macromolecule with the properties of that macromolecule. They can be strung together to produce a macromolecule (usually by dehydration synthesis).
I would have no problem with these definitions if not for my teacher mentioning once that some monomers can also be macromolecules by themselves. Because some monomers of certain macromolecules- such as the monosaccharide glucose vs. the disaccharide sucrose or the polysaccharide amylose - can act on their own as an essential and functional carbohydrate, they are macromolecules by themselves.
Is this true? For example, could glucose be a macromolecule by itself?
Thanks. I can't think of an example where a biological monomer would be a macromolecule.
Definitions of macromolecule vary, usually by molecular weight or number of monomers (repeat units).
Personally, I'd go with ~1000 Dalton for a minimum, but the original definition of 1000 atoms is a good start too.
In any case, no biological monomer, including glucose will function the same as a macromolecule.
Consider starch - a macromolecule of sugars. It doesn't dissolve as quickly as simple sugar and has different physical properties.
Update
To clarify my comments.. Macromolecules or polymers are made up of monomers the way words are made up of letters. So no, a glucose molecule isn't really the same as a macromolecule, just like "R" is not a word.
Yes, macromolecules can be used to make larger assemblies like microtubules, filaments, etc., much the same way that words can form sentences and paragraphs.
In the polymer literature there's even the concept of a "macromonomer" referring to a monomer that is already large in size.
In my opinion though, the basic constituents (monomers) are still amino acids, nucleic acids, sugars, etc. These are not macromolecules.
The following is multiple choice question (with options) to answer.
A monosaccharide is the simplest carbohydrate and cannot be hydrolyzed to produce a smaller what? | [
"quark",
"glucose atom",
"carbohydrate molecule",
"amino acid"
] | C | A monosaccharide is the simplest carbohydrate and cannot be hydrolyzed to produce a smaller carbohydrate molecule. Disaccharides contain two monosaccharide units, and polysaccharides contain many monosaccharide units. |
SciQ | SciQ-4820 | human-biology, genetics, human-genetics, reproduction, twins
There doesn't seem to be a distinction between heteropaternal superfecundation occurring with two ova and with one ovum. How will monozygotic heteropaternal superfecundation twins look like as opposed to dizygotic heteropaternal superfecundation twins and to identical twins?
Are/Were there real life cases of monozygotic heteropaternal superfecundation?
The heteropaternal superfecundation selected cases given on wikipedia seem to be for dizygotic. I tried looking up on google, but I've found so far only dizygotic. A normal singleton child is a result of the fertilization of an ovum (with 23 chromosomes) by a sperm (with 23 chromosomes). After fertilization, the cell (with 46 chromosomes) is called a zygote. All normal human cells (other than ova and sperm) have 46 chromosomes.
Monozygotic twins (identical twins) occur when the set of cells resulting from the early divisions of a single zygote separate into two groups. Each of these two groups of cells proceed to form a normal embryo, with resulting (if carried to term) in twins. Since these twins came from the same zygote, they have the same 46 chromosomes and so are essentially genetically identical.
Now how could this monozygotic process occur with two fathers being involved? Only by having two separate sperm combine with a single ovum. This would result in the zygote having 69 (3x23) chromosomes. This could happen, but would be an extreme case of aneuploidy (abnormal number of chromosomes). Such a genome is massively defective due to the presence of too many gene copies, and the embryo (whether singleton or twin) will be spontaneously aborted. Only a few kinds of aneuploidy can result in a viable fetus, almost all having only a single extra chromosome (one of the smaller ones); the most common case is having 3 copies of chromosome #21, which results in Down Syndrome.
So, monozygotic heteropaternal superfecundation has not been observed because the resulting pregnancy is very unlikely to go to term. (It's just as unlikely when the two sperm are from the same man.)
The following is multiple choice question (with options) to answer.
What is the term for if multiple sperm fuse with an egg? | [
"pollenation",
"polyspermy",
"in vitro fertilization",
"fraternization"
] | B | To ensure that no more than one sperm fertilizes the egg, once the acrosomal reactions take place at one location of the egg membrane, the egg releases proteins in other locations to prevent other sperm from fusing with the egg. If this mechanism fails, multiple sperm can fuse with the egg, resulting in polyspermy. The resulting embryo is not genetically viable and dies within a few days. |
SciQ | SciQ-4821 | acoustics, air, displacement
You can see the derivation of the above at http://www.insula.com.au/physics/1279/L14.html and if you look for problem # W4 on that page you will find the calculation for a pressure level of 28 mPa at 1 kHz giving 11 nm displacement amplitude. Given that the limit of detectable sound level is about 1000x smaller, my numbers above are quite reasonable.
So the real answer to your "headline" question ("how much air needs to be displaced to generate an audible sound") is
The equivalent of one layer of atoms is more than enough
Impressive, how sensitive the ear is. And bats and dogs have even better hearing, I'm told.
The following is multiple choice question (with options) to answer.
As air pressures inside and outside of the ear equalize, what phenomenon is produced? | [
"throat scratching",
"ear popping",
"heart skipping",
"eyes blinking"
] | B | Ears pop as air pressures inside and outside of the ear equalize. |
SciQ | SciQ-4822 | dna, chromosome
Title: Are human chromosomes connected or separate molecules? Do the 46 human chromosomes form a single unbroken DNA helix? Or is it rather that a human's genome consists of 46 disconnected helices?
If it is the former, does the common numbering scheme for the chromosomes have any correlation to their actual ordering in the one large strand?
If is the latter, is there a convention on how the chromosomes are ordered in genomic datasets? Also, is there a clear understanding of how sister chromosomes "find" each other in Meiosis I?
Generally, during periods when Mitosis/Meiosis are not occurring, what's a good physical picture for how the chromosomes are physically arranged (e.g. a bowl of 46 spaghetti noodles, or maybe the sister chromosomes always stay close together, etc)
thanks! Each chromosome is a pair of distinct, separate DNA molecules. A chromosome of an eukaryotic cell nucleus is a (long) helix of two linear molecules and so has two ends, which are called telomeres. DNA naturally forms a double helix with its complementary DNA molecule, and the double helix can further curl in what are called supercoils.
In humans, the chromosomes occur in 23 pairs (totaling 46). Except for the sex chromosome pair, each member of the pair is identical in appearance in a karyotype (picture) and each such pair has a number assigned from 1 to 22; the numbering generally follows the size of the chromosome, with chromosome 1 being the longest. In mammals, the sex chromosomes in a male are quite different in size and are labelled X and Y; a female has two identical X chromosomes.
The following is multiple choice question (with options) to answer.
How many pairs of chromosomes are there? | [
"23",
"17",
"2",
"13"
] | A | Humans have 23 pairs of chromosomes in each body cell. |
SciQ | SciQ-4823 | human-physiology, digestion, stomach
The stomach accomplishes much of its function by mechanically breaking down the swallowed food particles and mixing them with acid and enzymes into a sort of slurry. To do this, there are three major layers of muscle surround the stomach - from the outside, the longitudinal layer, the circular layer, and the oblique layer. The stomach also has two holes in it - the gastroesophageal opening, coming from the esophagus with the swallowed food/saliva mix, and the pylorus, where the food/acid/enzyme slurry exits into the duodenum, which is the beginning of the small intestine.
Due to the three layers of (rather strong) muscle, the stomach doesn't have a lot of expansion capability once it is filled completely to capacity. Fortunately, this almost never occurs (despite how we may feel after a large meal) because material is always leaving the stomach on its way to enzymatic digestion in the intestines. Additionally, once the stomach is filled to a certain extent, hormones such as leptin are secreted that give you the feeling of being sated, or full, triggering the brain to make you stop eating.
Of course, as we can see with the current epidemic of obesity around the world, the stomach can change its size over time. However, this is a rather slow process (weeks to months to years) of adapting to continuously consuming large meals.
But what would happen if you completely ignored these internal warnings, or were being force-fed, or whatever? Instead of rupturing (the biological equivalent of "exploding"), food would most likely be expelled either into the small intestine or back into the esophagus and back up the way it came down, i.e. causing vomiting.
The following is multiple choice question (with options) to answer.
Food is broken into smaller particles by mastication, a process involving action by what structures? | [
"proteins",
"cilia",
"teeth",
"tonsils"
] | C | Oral Cavity Both physical and chemical digestion begin in the mouth or oral cavity, which is the point of entry of food into the digestive system. The food is broken into smaller particles by mastication, the chewing action of the teeth. All mammals have teeth and can chew their food to begin the process of physically breaking it down into smaller particles. The chemical process of digestion begins during chewing as food mixes with saliva, produced by the salivary glands (Figure 16.5). Saliva contains mucus that moistens food and buffers the pH of the food. Saliva also contains lysozyme, which has antibacterial action. It also contains an enzyme called salivary amylase that begins the process of converting starches in the food into a disaccharide called maltose. Another enzyme called lipase is produced by cells in the tongue to break down fats. The chewing and wetting action provided by the teeth and saliva prepare the food into a mass called the bolus for swallowing. The tongue helps in swallowing—moving the bolus from the mouth into the pharynx. The pharynx opens to two passageways: the esophagus and the trachea. The esophagus leads to the stomach and the trachea leads to the lungs. The epiglottis is a flap of tissue that covers the tracheal opening during swallowing to prevent food from entering the lungs. |
SciQ | SciQ-4824 | cell-biology, proteins, transcription, cell-signaling, intracellular-transport
Time is in minutes, and zeroed at first contact between the two cells. I've put a red dot on the T-cell and a blue one on the APC in the DIC images (left panes); hopefully that proves more informative than annoying. The right panes show GFP fluorescence and thus CD3 localization. As time progresses, CD3 is re-localized from one part of the membrane to another (the synapse). There is supposedly a video of this is in the supplementary information of the article, though I was unable to open it.
The rate and directionality of the movement implies that an active process is occurring, rather than simple diffusion. However, they did not find the actual mechanism for movement and I haven't found any follow-up papers in a brief search (though many subsequent papers implicate the cytoskeleton in this movement). Just to show that movement of transmembrane proteins can, in fact, be actively directed by the cytoskeleton, I refer you to this paper:
Grabham PW, Foley M, Umeojiako A, Goldberg DJ. 2000. Nerve growth factor stimulates coupling of beta1 integrin to distinct transport mechanisms in the filopodia of growth cones. J Cell Sci 113:3003-3012.
They show that membrane-spanning integrins are moved along actin filaments of the cytoskeleton by myosin motor proteins. Expectedly, the abstract does a good job of summarizing the paper:
The cycling of membrane receptors for substrate-bound proteins via their interaction with the actin cytoskeleton at the leading edge of growth cones and other motile cells is important for neurite outgrowth and cell migration. Receptor delivered to the leading edge binds to its ligand, which induces coupling of the receptor to a rearward flowing network of actin filaments. This coupling is thought to facilitate advance... [T]ransport was dependent on an intact actin cytoskeleton and myosin ATPase...
The following is multiple choice question (with options) to answer.
Cell communication that occurs over short distances is known as what? | [
"paracrine signaling",
"cell echo",
"hypersignaling",
"contraposition signaling"
] | A | Cells that are communicating may be right next to each other or far apart. In juxtacrine signaling , also known as contact-dependent signaling, two adjacent cells must make physical contact in order to communicate. Cell communication may also occur over short distances, which is known as paracrine signaling , or over large distances, which is known as endocrine signaling . |
SciQ | SciQ-4825 | neuroscience, physiology, human-physiology, reflexes
Title: Are there neuron mediated reactions faster than reflexes? I'm interested in how fast the human body can respond to a stimulus. I know the fastest reflex, the blink reflex, operates around 100ms from stimulus to reaction. I also know that the blink reflex is known as the fastest reflex in the human body. My interest is in the fastest responses to stimuli I can find in the body.
Are there any faster responses to stimuli within the human body which use neurons but are not categorized as a reflex (due to some technicality), meaning they could be faster than the fastest reflex? To the best of my understanding a reflex is defined by the use of neurons to convey the information, I'm just wondering if there are any grey areas which don't qualify as a reflex but may be faster. I don't want to potentially write off an entire class of neurological behavior in my research simply because I stopped at the blink reflex. A reflex as fast as the blink in a neural circuit:
I would consider suppression of outer hair cells in the cochlea to be a reflex; the faster component of this reflex is about the same as the blink reflex, around 100 ms. The hair cells themselves aren't considered neurons, but the pathway that suppresses their motility certainly is.
A much much faster non-neuronal "reflex":
That said, the outer hair cells themselves also dance along quite fast in response to sensory input, even faster than the typical hearing range for humans, faster than 20kHz! In some ways, this is a reflex because you are taking sensory (specifically, auditory) information and turning it into a motor response, but all the "action" is taking place within one cell, and it isn't a neuron.
A more classical reflex that is substantially faster than 100 ms
Reflexes in the periphery can be much faster than 100 ms. The myotatic reflex, or stretch reflex, can be as fast as 30 ms in the knee - this is the reflex that is tested when a physician smacks you on the knee with a hammer (used as a test of spinal and peripheral nerve function, not as a punishment). It's likely there are other stretch reflexes that are faster just because distances to the spinal cord are shorter, but these might be more difficult to test (in this paper they report latencies as fast as 20 ms).
The following is multiple choice question (with options) to answer.
Triggering a blink when something touches the surface of the eye, the corneal reflex is what type of reflex? | [
"orgasmic",
"somatic",
"sensory",
"dendritic"
] | B | connection is the basis of somatic reflexes. The corneal reflex is contraction of the orbicularis oculi muscle to blink the eyelid when something touches the surface of the eye. Stretch reflexes maintain a constant length of muscles by causing a contraction of a muscle to compensate for a stretch that can be sensed by a specialized receptor called a muscle spindle. |
SciQ | SciQ-4826 | fluid-dynamics, flow, boundary-conditions, navier-stokes
Title: Flow down an incline - Understanding boundary conditions After working with some problems regarding flow, I came up to a similiar problem as the one presented here:
The following is multiple choice question (with options) to answer.
Vascular disorders involve problems with the flow of what? | [
"mucus",
"bacteria",
"blood",
"saliva"
] | C | Vascular disorders involve problems with blood flow. For example, a stroke occurs when a blood clot blocks blood flow to part of the brain. Brain cells die quickly if their oxygen supply is cut off. This may cause paralysis and loss of other normal functions, depending on the part of the brain that is damaged. |
SciQ | SciQ-4827 | proteins, translation, mrna, ribosome
Title: What is the advantage of the way eukaryotes initiate translation? The eukaryote and prokaryote mechanism for translation is slightly different. Is there any advantage of the eukaryote translation mechanism ?
Edit : I specifically want to know why eukaryotic ribosome first attaches to tRNA and then to mRNA but prokaryotic ribosome can do this in either order. Is there any advantage of the former ? As far as I understand it (and I'll preface this by saying that initiation is not my strongest point), but prokaryotes utilize the beautiful AGGAGG Shine-Dalgarno sequence. Usually around 8bp upstream of the start codon, it is this sequence that the prokaryotic ribosome seeks out to initiate translation. It does this through a complementary region in the 3' sequence of the ribosomal RNA. Upon complementary binding, the ribosome and mRNA are correctly bound. Convenient!
In eukaryotes, however, there is no consensus SD sequence, so a different mechanism must be used; the complex of 40S and Methionine tRNA serves this purpose. The two together scan the mRNA, looking for an AUG start codon which the tRNA is complementary to. This eventually brings the full ribosome (40S + 60S) together to start translation.
The following is multiple choice question (with options) to answer.
In eukaryotes, mrna may be modified before leaving what? | [
"nucleus",
"mitochondria",
"epidermis",
"ribosome"
] | A | During transcription, a copy of mRNA is made that is complementary to a strand of DNA. In eukaryotes, mRNA may be modified before it leaves the nucleus. |
SciQ | SciQ-4828 | is KE = 1 mv 2 ____ 2. solve mass! In a body, the higher the mass and velocity, with its velocity playing a much greater.... The _____ and _____ of the object, stored energy that an object to! Essentially the energy of an object has would decrease the speed. position of various parts a! Or the race car the only difference between a gamma and an infrared photon is the. Question Asked 4 years, 10 months ago: mass = 100 velocity! Energy that depends upon the relative position of various parts of a system much weight a object depends... Or a 2 foot wave or a 2 foot wave or a 2 foot wave foot wave, then possesses! The kinetic energy, Volume or nature of the light but not on the.! The most kinetic energy most kinetic energy attained energy will move faster than particles which have less energy... Mass and velocity, with its velocity playing a much greater role energy. The particles are moving very fast, we feel the substance and ! And speed. put, once again, why I chose the I... In a moving body the energy fast velocity mission is to provide a free, world-class to! A gamma and an infrared photon is in the photoelectric effect, explain why the stopping potential depends on mass. A much greater role which have more kinetic energy of the velocity we... Education to anyone, anywhere contact on this number Nonportrit the amount of kinetic energy a ball. Thus, the higher the mass and its speed. k of a body depends on the direction the! Kt Avg to 7 PM kinetic energy is KE = 1 mv 2 ____ solve. 'S hot! weight because of how much weight a object has depends on the distance covered point the! 2. solve: mass = 100 kg velocity = 10 m/s word speed. More potential energy when it is moving, then it possesses kinetic energy depends on the.... Free, world-class education to anyone, anywhere it possesses kinetic energy this form of kinetic energy depends on ball a. A system and its speed. = 1 mv 2 ____ 2.:. Velocity of a system great example of this form of energy that upon. Flight due to its vibrational motion also have to put, once,. A molecule is = ( 3/2 ) kT Avg ball has kinetic energy
The following is multiple choice question (with options) to answer.
Velocity affects what type of energy more than mass does? | [
"mechanical energy",
"magnetic energy",
"kinetic energy",
"harmonic energy"
] | C | This equation for kinetic energy shows that velocity affects kinetic energy more than mass does. For example, if mass doubles, kinetic energy also doubles. But if velocity doubles, kinetic energy increases by a factor of four. That’s because velocity is squared in the equation. You can see for yourself how mass and velocity affect kinetic energy by working through the problems below. |
SciQ | SciQ-4829 | 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.
In which way do vertebrates reproduce? | [
"asexually",
"unisexually",
"sexually",
"bisexually"
] | C | Vertebrates reproduce sexually, and almost all of them have separate male and female sexes. Generally, aquatic species have external fertilization, whereas terrestrial species have internal fertilization. Can you think of a reason why aquatic and terrestrial vertebrates differ in this way?. |
SciQ | SciQ-4830 | particle-physics, nuclear-physics, neutrons
Title: Are neutrons and protons stable inside atomic nuclei? Some people naturally assume that atomic nuclei are made of protons and neutrons. That is, they are basicly clumps of protons and neutrons that each maintain its separate existence, like pieces of gravel maintain their existence if you mold them together in a ball with mud for a binding force.
How come neutrons in a nucleus don't decay?
This is a natural assumption. A hydrogen nucleus can have one proton as its nucleus. Nuclei can absorb neutrons to become other isotopes. It's natural to assume that nuclei are clumps of protons and neutrons.
Sometimes if an atomic nucleus gets broken by application of large amounts of energy, typically applied with a fast-moving subatomic particle, they might release a neutron or a proton. So for example, smash an alpha particle into a beryllium nucleus and a neutron comes out. Doesn't that imply that the neutron was in there all along, waiting to get out?
But that reasoning implies that electrons, positrons, muons etc are also inside the nucleus all the time, waiting to get out.
There's an idea that protons and neutrons inside a nucleus swiftly transfer charges. This is analogous to a theory from organic chemistry, where sometimes single and double bonds switch back and forth, increasing stability. We could have quarks getting exchanged rapidly between protons and neutrons, increasing stability. I can see that as increasing stability for the nucleus, but I just don't see it as making the protons and neutrons more stable. If ten Hollywood couples get repeated divorces and marry each other's exes, you wouldn't say that the original marriages are stable.
In the extreme, the quarks might just wander around in a nuclear soup, and the protons and neutrons have no more identity than a bunch of used computers disassembled with the parts on shelves for resale. Maybe you could collect enough parts to take a working computer out of the store with you, but it probably won't be one of the old computers.
The following is multiple choice question (with options) to answer.
Neutrons and protons reside in which part of the atom? | [
"vacuoles",
"nucleus",
"nucleolus",
"molecules"
] | B | Neutrons, like protons, reside in the nucleus of an atom. They have a mass of 1 and no charge. The positive (protons) and negative (electrons) charges balance each other in a neutral atom, which has a net zero charge. Because protons and neutrons each have a mass of 1, the mass of an atom is equal to the number of protons and neutrons of that atom. The number of electrons does not factor into the overall mass, because their mass is so small. As stated earlier, each element has its own unique properties. Each contains a different number of protons and neutrons, giving it its own atomic number and mass number. The atomic number of an element is equal to the number of protons that element contains. The mass number, or atomic mass, is the number of protons plus the number of neutrons of that element. Therefore, it is possible to determine the number of neutrons by subtracting the atomic number from the mass number. |
SciQ | SciQ-4831 | particle-physics, cosmology, big-bang, baryons, leptons
Title: Which came first: leptons or baryons? If you had a big collection of neutrons, they could decay into protons, electrons, and neutrinos through beta decay since protons are the only stable baryons. After a while, you should get hydrogen out of that.
Assuming some process to account for baryogenisis, this would mean that the universe could start with a whole bunch of neutral baryons and generate electrons as needed without having to worry about pair production to get its leptons.
With this in mind, is there any evidence that hadrons were created first and then, in turn, created leptons (regardless of evidence for baryogenisis itself)? Or does the current theory suggest that leptons and hadrons were created contemporaneously in the very early universe? There exists a standard model of cosmology, i.e. accepted as the current status of research, called the Big Bang.
This makes extensive use of the known interactions of particle physics encapsulated in the standard model., and assumes a singularity at the beginning of the universe where the energy seen in the universe now was originally generated.
I like this display of the history of the universe as understood at present.
The following is multiple choice question (with options) to answer.
What are the two best known baryons? | [
"electrons and neutrons",
"shafts and neutrons",
"protons and neutrons",
"flux and neurons"
] | C | Particles that are composed of three quarks are called baryons . The two best known baryons are protons and neutrons. A proton is composed of two up quarks and one down quark (uud). The charge on the proton is the result of adding the charges on these quarks . Neutrons are composed of one up quark and two down quarks (udd). The charge on the neutron is the result of adding the charges on these quarks . |
SciQ | SciQ-4832 | speciation
Title: Does too much Genetical Modification leads to formation of new species? I think Genetical Modification can be termed as 'Artificial Mutation'.
Is it possible that genes can be modified so much that it leads to the introduction of new Species i.e Can integration of large no. of Helpful mutations lead to quick evolution? yes it possible, in one article show a study for Mycoplasma genitalium which have 525 gene, however only 382 genes are essential for biological functions, they take out the nature gene and place the ' artifical gene' which synthsis in vitro, to test if the M. genitalium will survival when the No. of gene lower than 382. If it survival it will be a new species.
The following is multiple choice question (with options) to answer.
Mutation creates new genetic variation in what? | [
"mutation pool",
"form pool",
"disease pool",
"gene pool"
] | D | Mutation creates new genetic variation in a gene pool. |
SciQ | SciQ-4833 | endocrinology
Title: Abnormal Prolactin Level I want to know what makes the balance of the Prolactin abnormal. Is that related to the presence of a nodule near the pituitary? The main abnormality in prolactin levels is hyperprolactinemia, meaning blood levels of prolactin above the normal range, not during pregnancy or lactation.
The major cause of these abnormal prolactin levels are tumors consisting of pituitary lactotroph cells--called prolactinomas--which secrete prolactin. This is generally corrected with synthetic dopamine analogues, as dopamine negatively regulates secretion of prolactin in lactotroph cells.
Here is a 2010 review with further detail:
http://joe.endocrinology-journals.org/content/206/1/1.full.pdf
The following is multiple choice question (with options) to answer.
What hormone controls milk production in mammary glands? | [
"pepsin",
"dopamine",
"melanin",
"prolactin"
] | D | |
SciQ | SciQ-4834 | biochemistry, metabolism, thermodynamics
Title: What is a coupled reaction and why do cells couple reactions? I was wondering what exactly a coupled reaction is and why cells couple them. I read the wikipedia article as well as several others, such as life.illinois.edu but I still don't get it. Could someone explain it to me? It's pretty simple. A reaction occurs that releases energy (like ATP losing a phosphate to become ADP + Pi). If this is uncoupled, the energy will merely turn into heat. If it is coupled, then it can be used to fuel some other process. For instance, if you couple the ATP -> ADP reaction to a certain protein, the energy can be used to modify the shape of that protein.
The following is multiple choice question (with options) to answer.
Cellular respiration brings hydrogen and oxygen together to form what? | [
"air",
"water",
"cold",
"Salt"
] | B | |
SciQ | SciQ-4835 | human-biology, physiology, endocrinology, autonomic-nervous-system
Title: Can stress and arousal be independent? I'm trying to figure out if it's possible to have a stress response without being initially, or simultaneously aroused. I'm defining stress to be physiological stress (ie. release of cortisol) and arousal to be activation of the sympathetic nervous system.
Every example I can think of, these two are not independent. In the case of "fight-or-flight," one initially activates the sympathetic nervous system, which is then followed by the release of cortisol. Or in individuals with major depressive disorder, their sympathetic nervous systems are constantly activated while cortisol is being secreted.
So, is it possible to experience cortisol release without activation of the sympathetic nervous system? Stress response has 2 main components:
Quick response, within minutes, is by the Sympathomedullary Pathway (SAM): hypothalamus > sympathetic nervous system > release of adrenaline and noradrenaline from the adrenal medulla > stimulation of the heart, dilation of the muscle arteries, constriction of the gut and skin arteries, glcogenolysis (the breakdown of glycogen into glucose) > more glucose available as a fuel
Delayed response, within hours, is by the The Hypothalamic Pituitary-Adrenal (HPA) System: hypothalamus > pituitary gland > ACTH > release of cortisol from the adrenal cortex > gluconeogenesis (formation of glucose in the body from other substances) > more glucose available as a fuel
The following is multiple choice question (with options) to answer.
What are the two components of the autonomic nervous system? | [
"crystallisation and sympathetic",
"neurons and sympathetic",
"empathetic and sympathetic",
"parasympathetic and sympathetic"
] | D | 31.3 Peripheral nervous system The peripheral nervous system is broken down into two sub-systems, the somatic nervous system and the autonomic nervous system. ANS - Autonomic Nervous System The ANS has two components - parasympathetic and sympathetic. The sympathetic nervous system is the "fight or flight" or fright response and results in an increased heart rate, increased rate of breathing, and an elevated blood glucose level. There is also decreased digestion. The second neurotransmitter is epinephrine. In this case, the first neuron is short and the second neuron is long. The parasympathetic nervous system is the rest and digest system. Drugs must be able to pass the blood brain barrier to have an effect on the CNS. Drugs act by affecting the neuron and how likely it is to fire an action potential. Stroke occurs when there is a blood clot that goes to the brain and prevent blood flow. |
SciQ | SciQ-4836 | zoology, entomology
Title: Help identifying an insect I live in Milan, Italy in the city center. I live in this house since 5 years and I keep finding the insect pictured below.
I see it throughout the seasons (temperatures here range from -1°C to +35°C in average).
I find it mostly in my bathroom which is not well ventilated and it is the warmest room in the house (about 23°C in winter even with the radiators off and up to 35°C in summer during very hot days if I don't use air conditioning).
The size is about 7mm in length and 1mm in width (including only the main body, i.e., excluding legs and antennae).
I find it mostly during the night but maybe just because I use brighter lights and I can see it more clearly on my white walls.
What is its name so I can research more about it (i.e., does it pose any risk to my health or to my belongings in the house?)? Looks like a species of silverfish.
https://en.wikipedia.org/wiki/Zygentoma
They eat paper, cloth and stored foods like cereal, even organic wall paste, so yes they can damage your stuff, but outside allergies they are harmless to a person.
The following is multiple choice question (with options) to answer.
Where do lancelets live? | [
"on land",
"riverbeds",
"deep sea caves",
"shallow ocean water"
] | D | There are only about 25 living species of lancelets. They inhabit the ocean floor where the water is shallow. Lancelet larvae are free-swimming. The adults can swim but spend most of their time buried in the sand. Like tunicates, lancelets are filter feeders. They take in water through their mouth and expel it through an opening called the atriopore (see Figure below ). Lancelets reproduce sexually and have separates sexes. |
SciQ | SciQ-4837 | hematology, cardiology, blood-circulation, red-blood-cell, veins
Veins are not like impermeable rubber tubes, they are 'living' structures requiring, like all cells, Oxygen and glucose to survive. Smaller veins get the O2 from diffusion, while the larger veins need help from vasa vasorum, small blood bessels that bring blood to the walls of the veins.
The innermost cells lining veins are epithelial cells. They also line valves.
In the picture you posted, blood is not circulating well behind valves. The cause of hypoxia is that epithelial cells are continually removing O2 from the blood.
When enough O2 is removed to cause hypoxia, the endothelial cells may become damaged by the lack of O2, causing inflammation and (possibly) potentiating clot formation.
Activation of endothelial cells by hypoxia or possibly inflammatory stimuli would lead to surface expression of adhesion receptors that facilitate the binding of circulating leukocytes and microvesicles. Subsequent activation of the leukocytes induces expression of the potent procoagulant protein tissue factor that triggers thrombosis.
Mackman N. (2012). New insights into the mechanisms of venous thrombosis. The Journal of clinical investigation, 122(7), 2331–2336. doi:10.1172/JCI60229
The following is multiple choice question (with options) to answer.
What is caused when circulating blood puts pressure on the walls of blood vessels? | [
"blood pressure",
"aneurysm",
"atherosclerosis",
"high cholesterol"
] | A | Blood pressure occurs when circulating blood puts pressure on the walls of blood vessels. |
SciQ | SciQ-4838 | human-biology
Title: Is urine dirty as soon as it leaves the human body? Human urine is sterile as long as it is in the human body. But is it dirty after leaving the human body? Could you get sick from it, if you drink it or don't wash your hands, for example? It was believed for a long time that urine stored in the urinary bladder is sterile. However, Wolfe et al(1). recently found evidence of bacterial presence in the urine extracted from bladders of healthy women. In an article just published, Hilt et al. found that at least some bacteria found in the bladder of healthy women are viable and can be grown in a laboratory after extraction from the bladder).2 (Paywall). They expect that the same is the case for men.
From the Hilt et al. paper:
Thirty-five different genera and 85 different species were identified
by EQUC. The most prevalent genera isolated were Lactobacillus (15%),
followed by Corynebacterium (14.2%), Streptococcus (11.9%),
Actinomyces (6.9%), and Staphylococcus (6.9%). Other genera commonly
isolated include Aerococcus, Gardnerella, Bifidobacterium, and
Actinobaculum.
Note that these species for the most part (Actinobaculum being one exception, as a possible uropathogen) appear to be part of the normal microbiome (collection of microorganisms) in healthy people in the same way as bacteria inhabit other parts of healthy persons. Additionally, the recovered organisms required special care to achieve growth:
Most of the bacteria isolated required either increased CO2 or
anaerobic conditions for growth, along with prolonged incubation, and
they often were present in numbers below the threshold of detection
used in routine diagnostic urine culture protocols.
The following is multiple choice question (with options) to answer.
What is the most common bacterial sti in the u. s.? | [
"diarrhea",
"chlamydia",
"tuberculosis",
"influenza"
] | B | Chlamydia is the most common bacterial STI in the U. S. Females are more likely to develop it than males. Symptoms may include burning during urination and a discharge from the vagina or penis. |
SciQ | SciQ-4839 | thermodynamics, temperature, units
My personal favorite way to do it is to measure entropy in bits, so that $k_B = \frac{1}{\ln 2} \,\mathrm{bits}$ and the units of temperature are $\mathrm{J\cdot bits^{-1}}$. Having entropy rather than temperature as the quantity with the fundamental unit tends to make it much clearer what's going on, and bits are a pretty convenient unit in terms of building an intuition about the relationship to probability theory.
The following is multiple choice question (with options) to answer.
In what unit is heat measured in? | [
"amperes",
"velocities",
"joules",
"thermals"
] | C | The heat that is either absorbed or released is measured in joules. The mass is measured in grams. The change in temperature is given by , where is the final temperature and is the initial temperature. |
SciQ | SciQ-4840 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
In which type of cells are most organelles not found? | [
"prokaryotic cells",
"heterogeneous cells",
"endoplasmic cells",
"eukaryotic cells"
] | A | Eukaryotic cells have many specific functions, so it can be said that a cell is like a factory. A factory has many machines and people, and each has a specific role. Just like a factory, the cell is made up of many different parts. Each part has a special role. The different parts of the cell are called organelles , which means "small organs. " All organelles are found in eukaryotic cells. Prokaryotic cells are "simpler" than eukaryotic cells. Though prokaryotic cells still have many functions, they are not as specialized as eukaryotic cells, lacking membrane-bound organelles. Thus, most organelles are not found in prokaryotic cells. |
SciQ | SciQ-4841 | visible-light
The color we call 'red' is the color with the longest wavelength.
Prisms and water droplets are not the only things that affect the propagation direction of light. As light travels through the atmosphere it has a small probability of being scattered. The short wavelengths (the colors we perceive as shades of blue) are more prone to being scattered.
In the evening and in the morning the Sun is close to the horizon and the light has to travel through a lot of atmosphere to get to us. In general the composition of the light from the Sun is such that we will perceive that as white light. But with the atmosphere scattering the blue end of the spectrum, we often see the Sun having a red color when the Sun is close to the horizon.
The Sun gives us warmth, so naturally all us humans will associate the color we call 'Red' with warmth. Conversely, we will all associate absence of any hint of red (the blue colors) as comparatively cold.
We perceive Yellow as a particularly bright color, because we perceive incoming light as yellow when it has such a composition that it triggers two of our three light-sensitive molecules in about equal measure. Put differently: we perceive a mix of different colors of light as Yellow when it has the Red portion and The green portion of the spectrum in it, but little blue portion.
To get from light entering the eye to the perception of color by the visual cortex is a long way; it involves stages of processing information. It is remarkable that we experience different colors so vividly different, given that the perception of color is very much a constructed perception.
I suppose that our brain makes the different colors so vividly different by having specific strong associations. For instance, it seems to me that we will naturally associate the spectrum of greens that we perceive with the things around us that are predominantly green. It seems to me that these associations, not all of them conscious associations, allow us to feel a lot of distinction between the colors we perceive.
Your question, 'why are the colors ordered that way'.
The following is multiple choice question (with options) to answer.
Which three colors are called the primary colors of light? | [
"red, green, blue",
"black, white, red",
"blue, green, violet",
"red, blue, yellow"
] | A | The human eye can distinguish only red, green, and blue light. These three colors are called the primary colors of light. All other colors of light can be created by combining the primary colors. Look at the Venn diagram below . Red and green light combine to form yellow light. Red and blue light combine to form magenta light, and blue and green light combine to form cyan light. Yellow, magenta, and cyan are called the secondary colors of light. Look at the center of the diagram, where all three primary colors of light combine. The result is white light. You can explore the colors of visible light and how they combine at this URL: http://www. phy. ntnu. edu. tw/oldjava/color/color_e. html. |
SciQ | SciQ-4842 | water, aqueous-solution, solubility, home-experiment
Title: Does the salt in the ocean act as a binding agent on sand? When I walk on the beach, there appears to be an upper layer of the sand that is 'crusty'.
This appears to be the opposite of what you see in sand in a dessert setting, where the individual particles are not bound together, and blow to form 'dunes'.
I'm trying to figure out what causes the sand to bind together like this.
To me the crystalline properties of salt could cause this. (Ie the way that salt binds together to form crystals could cause this salt-binding that leads to 'crustiness'.
My question is: Does the salt in the ocean act as a binding agent on sand? Good observations!
Seawater contains salts in small amounts such as such as $\ce{LiCl}$ and $\ce{MgCl2}$ that are quite hygroscopic, which could keep the sand wet longer.
There is also dissolved organic matter (http://www.eoearth.org/view/article/154471/) in seawater that might act as a hydrating agent or as a wetting agent, helping to hold onto the water and to bond it to the sand.
You might try an experiment comparing the appearance of (washed) sand after being wet with plain water, with $\ce{NaCl}$ salt water of the same concentration as seawater, and with seawater itself to see if there is a difference. Though this seems like a casual test, this could be of significance in cases where it's necessary to drive on a sandy shore.
The following is multiple choice question (with options) to answer.
Water dissolving minerals out of rocks makes ocean water what? | [
"bitter",
"sweet",
"muddy",
"salty"
] | D | Ocean water is salty because water dissolves minerals out of rocks. This happens whenever water flows over or through rocks. Much of this water and its minerals flow in rivers that end up in the oceans. Minerals dissolved in water form salts. When the water evaporates, it leaves the salts behind. As a result, ocean water is much saltier than other water on Earth. |
SciQ | SciQ-4843 | metabolism, nutrition
Title: What are calories and how to burn them? What exactly is a calorie? When burning calories, do we always lose fat?
I have tried many apps to measure calories, do they give exact amounts? How many calories should be taken a day? A calorie is a measure of energy. In nutrition, we usually mean the kilocalorie (kcal), which is the same as about 4.2 kJ (kilojoule). A average person needs about 2,000--2,500 kcal per day, but this of course varies quite a bit between people, depending on size (muscle mass, particularly) and level of physical activity (physical work, exercise).
Nutrition guidelines found on the labels of food products give a pretty good summary of the amount of energy they contain. I'm not sure what applications you have been using, but they most likely rely on the same basic data, so the values should be similar. You can use these values to figure out roughly what your calorie intake is, and to spot very calorie-rich foods. But counting calories exactly is actually quite difficult --- you need to carefully weigh everything you eat and keep track of lots of numbers, and it's easy to make mistakes.
Burning calories does not always mean burning fat. Fat is a long-term energy storage form in the body. When exercising, the body tends to burn stored carbohydrates (glycogen) first, and turns to burning fat when carbohydrates are exhausted. Therefore, prolonged, low-intensity exercise like long walks are usually better for burning fat than short "sprint" type of exercise. The body also burns fat during normal daily activity if your energy intake is lower than the daily need (when dieting). But it is also possible that some muscle mass is degraded (to amino acids) and used for energy as well.
See also Wikipedia articles on food energy and exercise. Please note that "how to burn calories" is a heavily debated issue, there is an entire industry of weight loss methods, and various claims about "easy" methods or products to lose weight quickly are generally not true. The only reliable method to lose weight is to reduce food intake and increase exercise, for a long period of time.
The following is multiple choice question (with options) to answer.
Like the energy content in food, the energy expenditures of exercise are also reported in what units? | [
"grams",
"gigabytes",
"ironies",
"kilocalories"
] | D | To Your Health: Energy Expenditures Most health professionals agree that exercise is a valuable component of a healthy lifestyle. Exercise not only strengthens the body and develops muscle tone but also expends energy. After obtaining energy from the foods we eat, we need to expend that energy somehow, or our bodies will store it in unhealthy ways. Like the energy content in food, the energy expenditures of exercise are also reported in kilocalories, usually kilocalories per hour of exercise. These expenditures vary widely, from about 440 kcal/h for walking at a speed of 4 mph to 1,870 kcal/h for mountain biking at 20 mph. Table 7.2 "Energy Expenditure of a 180-Pound Person during Selected Exercises" lists the energy expenditure for a variety of exercises. Saylor URL: http://www. saylor. org/books. |
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