source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-4444 | podcasts that examine what mathematics can say about the nature of the reality we live in. The reason mathematics is the natural language of science, is that the universe is underpinned by the same order. Read Later . Topics Biology Earth Science math WIRED is where tomorrow is realized. FrannyFam5 Fridley, Minnesota. Get Free Mathematics In Nature Textbook and unlimited access to our library by created an account. Bees, masters of geometry, use hexagons to build their honeycombs. Paradoxically, the abundance of tight interactions among living species usually leads to disasters in ecological models. Chenavard, it will float. The shell of this deep-sea creature is a classic example of maths in nature, as it consists of the Fibonacci sequence. In this excerpt from his new book, Our Mathematical Universe, M.I.T. In the next article we’ll bring e and ln together, and the sweet aroma of math will fill the air. Mathematicians use this one a lot. Sure my 3 year old can count to 10, but does he really grasp the concept of WHAT the number 10 is? The spiral happens naturally because each new cell is … Exhibit. Learn more. The probabilistic nature of the "laws of nature" manifests itself in the case of machines also, and can be verified, at least in the case of nuclear reactors, if one runs them at very low power. Some people like to say that everything was already there in the nature, and people only found a way to invent the system to explain the processes and everything else that is happening in nature. Der aufmerksame Beobachter unter den Lesern dieses Textes wird sie an vielen Stellen seines Alltages wiederentdecken können. It’s what I like to call a win win! So do lots of other plants and animals. This is … These patterns recur in different contexts and can sometimes be modelled mathematically.Natural patterns include symmetries, trees, spirals, meanders, waves, foams, tessellations, cracks and stripes. Do you see a pattern in the way the seeds are arranged? Plus, get practice tests, quizzes, and personalized coaching to help you succeed. Look at this picture of a pinecone. A good comparison to math and science is language. Fast Download speed and ads Free! The page will
The following is multiple choice question (with options) to answer.
Science is a process of knowing about the natural universe through what two actions? | [
"thinking and guessing",
"changes and experimentation",
"guessing and observing",
"observation and experimentation"
] | D | Science is a process of knowing about the natural universe through observation and experiment. |
SciQ | SciQ-4445 | electromagnetism, electricity, energy-conservation, perpetual-motion
Title: Auto spinning turbine generator This might be dumb question but I'm so curious to know if this actually works or is impossible. I was researching how you could generate electricity from magnets and copper wire and also have read how the hydroelectric generators work and it seems like they share the same concept. So if we are able to generate electricity by moving the turbine with water then why not have a some sort of motor which will make the turbine spin by getting power from the generator. I mean first there needs to be some sort of initial mechanical source to make the turbine spin then once the turbine starts moving and the generator gives power, the other motor gets power and it will take over the spinning of the turbine. So that way it will auto spin itself and basically means free energy. Can someone explain why this is not possible? As with virtually all perpetual motion machines, the reason becomes obvious once you consider the thermodynamic efficiency of the components involved. No turbine is 100% efficient, and also no motor is 100% efficient. This means that out of the initial energy you put in to make the turbine spin, only a certain percentage will be converted to electricity, with the rest being converted to heat. Then, out of that electricity, only a certain percentage is converted to mechanical energy to drive the turbine again. Then we go round again, losing some of that energy to heat until pretty soon the whole thing stops turning.
Of course, it would work just fine if you had an engine or a turbine that was more than 100% efficient, putting out more energy than you have to put in to drive it. But then, that's exactly the reason why we know that efficiencies over 100% are impossible: we observed that perpetual machines seem to be impossible, and from that Carnot derived his thermodynamic limits. The resulting theory has stood the test of time since the 19th century.
The following is multiple choice question (with options) to answer.
Through a process called electromagnetic induction, generators change what energy form of a spinning turbine to electrical energy? | [
"kinetic",
"seismic",
"electric",
"potential"
] | A | Generators change the kinetic energy of a spinning turbine to electrical energy in a process called electromagnetic induction. You can read about generators and how they work in the chapter "Electromagnetism. ". |
SciQ | SciQ-4446 | fossils, drilling
Title: What would people drilling through Mount Everest find? I am interested in knowing what kind of fossils we would find if we were to drill horizontally through the mountain and what we would find if we were to drill vertically. Would we find anything interesting other than the fossils? Looks like some basic hints are necessary (as a complement to @AndyM's answer):
stratigraphy usually goes from younger to older when going down.
there'll be little chance to find any macrofossils in rocks that formed before sufficiently complex life was around.
there'll be little chance to find fossils in rocks that underwent metamorphism, that is have been in pressure/temperature regimes that aren't conducive for their preservation, even if they initially were present in the pre existing rocks.
'trace fossils' are not small remains of fossils but fossilized traces ('footprints'). Very rare thing.
it may be possible to find fossils in overlaying, younger sediments that formed during or after the uplift or were trapped or transported in depressions, but that's not the point of the question I think.
So, below the uppermost formations around the summit you'll likely find nothing of interest in the sense of the question when drilling down.
Will provide sources on specificically focussed request, but this isn't top notch geoscience.
The following is multiple choice question (with options) to answer.
Footprints, burrows, and waste are considered what type of fossils? | [
"morphology fossils",
"crater fossils",
"movement fossils",
"trace fossils"
] | D | Preserved traces can include footprints, burrows, or even wastes. Examples of these types of fossils, called trace fossils are picture below ( Figure below and Figure below ). |
SciQ | SciQ-4447 | 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 process of allows multicellular organisms to grow and repair themselves? | [
"DNA division",
"proteins division",
"atom split",
"cell division"
] | D | The process of cell division is how multicellular organisms grow and repair themselves. It is also how many organisms produce offspring. For many single-celled organisms, asexual reproduction is a similar process. The parent cell simply divides to form two daughter cells that are identical to the parent. Asexual reproduction produces offspring that are genetically identical to the parent, whereas sexual reproduction produces a similar, but genetically unique offspring. In sexual reproduction, meiosis produces haploid gametes that fuse during fertilization to produce a diploid zygote ( Figure below ). In other words, a child inherits half of the genetic material from each parent. Look at the family in Figure below . The children resemble their parents, but they are not identical to them. Instead, each has a unique combination of characteristics inherited from both parents. The children, of course, result from sexual reproduction. |
SciQ | SciQ-4448 | pressure
Title: Microscopic idea of sudden extreme pressure difference I'm having some issues understanding what's happening microscopic when there's sudden changes in the pressure.
The microscopic idea, is that particles randomly bounces around each other. It's even possible with entropy to state all the air can go to one side of the room, and leave a vacuum on the other side but off course very improbable.
But if particles just randomly just bounces around, why are you being sucked out of a space station, if the doors are suddenly opened into the vacuum? Why can the molecules around you feel the doors has been opened another place, if they just randomly bounces around? They are still just "randomly" bouncing around. The problem is that you've now changed the constraints for which they can randomly bounce.
Before, the odds that they could randomly bounce outside the ship are extremely limited. For the most part, bouncing is constrained to other particles and the walls of the ship itself. As soon as you introduce an easier pathway out of the ship, some of the gas will begin randomly bouncing out that hole. What's especially important is that once they start to move away, it's extremely unlikely that much of the air escaping will bounce back into the ship. Instead, they are free to start permeating space where they have very low chances of collisions that would send them back. This creates a net flow rate out of the hole compared to the essentially evenly distributed bouncing around when it is enclosed by walls and pressurized gases.
If you're facing the hole, collisions with gasses behind you are likely to send the air essentially backwards, hitting the air behind it, which cascades until it hits the wall and essentially pushes back on you. In front of you, when you push against the air, it collides with more air, which cascades; but there is no wall to push back against it, so the air just starts flowing out the hole.
The following is multiple choice question (with options) to answer.
What is the process of a confined gas escaping through a tiny hole in its container called? | [
"dissipation",
"dilution",
"effluent",
"effusion"
] | D | Another related process is effusion. Effusion is the process of a confined gas escaping through a tiny hole in its container. Effusion can be observed by the fact that a helium-filled balloon will stop floating and sink to the floor after a day or so. This is because the helium gas effuses through tiny pores in the balloon. Both diffusion and effusion are related to the speed at which various gas molecules move. Gases that have a lower molar mass effuse and diffuse at a faster rate than gases that have a higher molar mass. While they are similar processes, there is a key difference between diffusion and effusion. Diffusion describes the process of a gas spreading out at a constant pressure, such as throughout a room. Effusion, on the other hand, describes the process of a gas spreading out from a high pressure surroundings to lower pressure surroundings. |
SciQ | SciQ-4449 | biophysics, theoretical-biology, ecosystem
Systems ecology, especially with regard to energy and nutrient flow.
This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem Ecology: Understanding Element Cycles by Ågren & Bosatta (Ågren was originally a physicist)
Physical limitations to growth and transport
This can include for instance mechanical contraints on plant growth (see e.g. the book Plant Physics by Nicklas & Spatz), water transport in trees (see e.g. this BioSE question) or the biomechanics of movement (see e.g. Hudson et al (2012) on the speed and movement of cheetahs or Wikipedia: Biomechanics).
Allometric relationships between organisms, e.g. with regard to metabolism
To explain these types of relationships knowledge in physics is useful. See e.g. Kleiber's law for more.
MAXENT as a general approach to ecological patterns or to model species distributions
This is basically a tool lifted from physics that can be applied to ecological problems. There are many papers to look at, but Harte & Newman (2014) (Harte is another previous physicist) and Elith et al (2010) are two good starting points.
Dynamical modelling of populations and communities
This field use many of the same tools for analysis as physics, e.g. systems of differential equations. One of the pioneers in this field (among many) were Robert May (also started with a PhD in physics), and his classical book Theoretical Ecology: Principles and Applications is still a good starting point.
Energy harnessing and conversion by organisms
This can refer both to how organsims convert prey to energy (e.g. conversion efficiencies) and the physics of photosynthesis (which is an interesting intersection between physics and molecular biology). See Jang et al (2004) and O'Reilly & Olaya-Castro (2013) for examples of the how quantum mechanics can inform us about photosynthesis.
Hopefully this will give you a sense of some different ways that knowledge in physics can be useful for biology.
The following is multiple choice question (with options) to answer.
What is a relationship between living things that depend on the same resources? | [
"parasitic",
"symbiotic",
"contention",
"competition"
] | D | Competition is a relationship between living things that depend on the same resources. The resources may be food, water, or anything else they both need. Competition occurs whenever they both try to get the same resources in the same place and at the same time. The two organisms are likely to come into conflict, and the organism with better adaptations may win out over the other organism. |
SciQ | SciQ-4450 | human-anatomy
Title: What is the ratio of head to waist and waist to floor of the human anatomy? I'm trying to find the ratio of upper body to lower body. That is, the ratio of the length of the waist to the head over the length of the waist to the floor.
It's been harder to track down a readable outline of the ratios of the human body than I expected. The study of those measures is called anthropometry. Typing anthropometry on google image returned this
This is definitely not a peer-review source and might eventually be a good approximation only for white males (or whoever they considered to take these measurements on) but if we believe this image, then the ratio head-to-waist over waist-to-floor is $\frac{0.52}{0.485} = 1.072$.
The following is multiple choice question (with options) to answer.
What is the measure of an individual’s weight-to-height ratio called? | [
"body matter index (bmi)",
"density index (di)",
"body mass index (bmi)",
"body density index (bdi)"
] | C | Metabolism and Obesity Obesity in the United States is epidemic. The rate of obesity has been steadily rising since the 1980s. In the 1990s, most states reported that less than 10 percent of their populations was obese, and the state with the highest rate reported that only 15 percent of their population was considered obese. By 2010, the U. Centers for Disease Control and Prevention reported that nearly 36 percent of adults over 20 years old were obese and an additional 33 percent were overweight, leaving only about 30 percent of the population at a healthy weight. These studies find the highest levels of obesity are concentrated in the southern states. They also find the level of childhood obesity is rising. Obesity is defined by the body mass index (BMI), which is a measure of an individual’s weight-to-height ratio. The normal, or healthy, BMI range is between 18 and 24.9 kg/m2. Overweight is defined as a BMI of 25 to 29.9 kg/m2, and obesity is considered to be a BMI greater than 30 kg/m2. Obesity can arise from a number of factors, including overeating, poor diet, sedentary lifestyle, limited sleep, genetic factors, and even diseases or drugs. Severe obesity (morbid obesity) or long-term obesity can result in serious medical conditions, including coronary heart disease; type 2 diabetes; endometrial, breast, or colon cancer; hypertension (high blood pressure); dyslipidemia (high cholesterol or elevated triglycerides); stroke; liver disease; gall bladder disease; sleep apnea or respiratory diseases; osteoarthritis; and infertility. Research has shown that losing weight can help reduce or reverse the complications associated with these conditions. |
SciQ | SciQ-4451 | newtonian-mechanics, forces, water, collision, estimation
The reason why the deceleration times are different between concrete and water is related to the fact that concrete is a solid and water is a liquid. The molecules in concrete are locked into a rigid configuration. Concrete molecules don't move around freely - when you push on concrete, the concrete doesn't move, it pushes back to resist even large forces. Molecules in water, on the other hand, freely flow past one another - when you push on water, it accelerates out of the way. When confronted with a large force, a material can either resist it (like concrete), or yield to it (like water). Imagine being on ice skates - you can push off a rigid wall to accelerate yourself backwards, but if you push off another person on skates, you won't move as quickly, since the thing you're pushing off of yielded to the force of the push.
The following is multiple choice question (with options) to answer.
When you are walking on a sidewalk, what occurs between your shoes and the concrete each time you put down your foot? | [
"grip",
"static friction",
"progress",
"movement"
] | B | Static friction acts on objects when they are resting on a surface. For example, if you are walking on a sidewalk, there is static friction between your shoes and the concrete each time you put down your foot (see Figure below ). Without this static friction, your feet would slip out from under you, making it difficult to walk. Static friction also allows you to sit in a chair without sliding to the floor. Can you think of other examples of static friction?. |
SciQ | SciQ-4452 | result as fluid ounces, 1/4 th a. Or 56 cubic feet per second ( ft³/s - per second ( ft³/s per. ( ft³/s - per second ( ft³/s - per second ( ft³/s - per second ( ft³/s - second! Gallon, or 2 pints 0.033420139 cubic feet ( rounded to 8 digits ) Display as! The conversion walls and stem walls need different calculations feet, its volume 8... To area times height, simply multiply square feet times the height in feet by its square measurement!
The following is multiple choice question (with options) to answer.
According to the english system measurement, how much is equal to 2 pints, 1 quart, and ¼ of a gallon? | [
"1 cup",
"4 cups",
"2 cups",
"3 cups"
] | B | Many quantities can be expressed in several different ways. The English system measurement of 4 cups is also equal to 2 pints, 1 quart, and ¼ of a gallon. |
SciQ | SciQ-4453 | agriculture
The primary cereals for making bread are wheat and rye, while barley and oats may be mixed in. Historically significant portions of the rural population of Europe were sustained by cereal-based food in the form of gruel and porridge rather than by bread, especially prior to the introduction of the potato. Barley can be consumed in the form of pearl barley and groats and oats in the form of oatmeal. Especially in cool and humid climates not very suitable for cultivating wheat and rye, oats were once commonly cultivated and consumed. When Samuel Johnson wrote his dictionary, he famously defined oats as: "A grain which in England is generally given to horses, but in Scotland supports the people." A major historical and modern use of barley has been as malted barley, the main ingredient in beer brewing.
In the case of Finland it is interesting to note how late the transition from slash-and-burn agriculture to the use of permanent fields occurred. According to Teija Alenius, Environmental change and anthropogenic impact on lake sediments during the Holocene in the Finnish − Karelian inland area, Ph.D. thesis, University of Helsinki, 2007 (online)
The following is multiple choice question (with options) to answer.
Many important crops, such as corn, are planted and harvested as what? | [
"cuttings",
"trees",
"seeds",
"berries"
] | C | Many important crops, such as corn, are planted and harvested as seeds. These seeds are important sources of food. For example, corn is ground into feed for chickens and cows. And corn syrup is used to sweeten beverages and candy. But most importantly, seeds are the starting point for a new plant. |
SciQ | SciQ-4454 | electromagnetism, electricity, energy-conservation, perpetual-motion
Title: Auto spinning turbine generator This might be dumb question but I'm so curious to know if this actually works or is impossible. I was researching how you could generate electricity from magnets and copper wire and also have read how the hydroelectric generators work and it seems like they share the same concept. So if we are able to generate electricity by moving the turbine with water then why not have a some sort of motor which will make the turbine spin by getting power from the generator. I mean first there needs to be some sort of initial mechanical source to make the turbine spin then once the turbine starts moving and the generator gives power, the other motor gets power and it will take over the spinning of the turbine. So that way it will auto spin itself and basically means free energy. Can someone explain why this is not possible? As with virtually all perpetual motion machines, the reason becomes obvious once you consider the thermodynamic efficiency of the components involved. No turbine is 100% efficient, and also no motor is 100% efficient. This means that out of the initial energy you put in to make the turbine spin, only a certain percentage will be converted to electricity, with the rest being converted to heat. Then, out of that electricity, only a certain percentage is converted to mechanical energy to drive the turbine again. Then we go round again, losing some of that energy to heat until pretty soon the whole thing stops turning.
Of course, it would work just fine if you had an engine or a turbine that was more than 100% efficient, putting out more energy than you have to put in to drive it. But then, that's exactly the reason why we know that efficiencies over 100% are impossible: we observed that perpetual machines seem to be impossible, and from that Carnot derived his thermodynamic limits. The resulting theory has stood the test of time since the 19th century.
The following is multiple choice question (with options) to answer.
The turbine of a windmill spins and creates what? | [
"electricity",
"grains",
"lightning",
"pollution"
] | A | Wind power uses moving air as a source of energy. Some types of wind power have been around for a long time. People have used windmills to grind grain and pump water for hundreds of years. Sailing ships have depended on wind for millennia. Wind is now used to generate electricity. Moving air can make a turbine spin, just like moving water can. Moving air has kinetic energy. When wind hits the blades of the turbine, the kinetic energy makes the blades move. The turbine spins and creates electricity. |
SciQ | SciQ-4455 | human-biology, plant-physiology, stem-cells
Title: Is that true that plant stem cells can be used in humans? I was reading an article (which seems very fake to me) on sensitive topics, but there was one astonishing statement:
Stem cells are obtained from certain plants that grow all over the world. Once the stem cells have been obtained, the doctor will inject them on the target organ...
I want to ask specialists if this particular statement can be true. If yes, does it imply nucleus replacement in stem cells, or anything like that?
Sorry guys, for the stupid question. https://stemcells.nih.gov/info/basics/6.htm
...
Viruses are currently used to introduce the reprogramming factors into adult cells, and this process must be carefully controlled and tested before the technique can lead to useful treatment for humans. In animal studies, the virus used to introduce the stem cell factors sometimes causes cancers. Researchers are currently investigating non-viral delivery strategies. In any case, this breakthrough discovery has created a powerful new way to "de-differentiate" cells whose developmental fates had been previously assumed to be determined. In addition, tissues derived from iPSCs will be a nearly identical match to the cell donor and thus probably avoid rejection by the immune system. The iPSC strategy creates pluripotent stem cells that, together with studies of other types of pluripotent stem cells, will help researchers learn how to reprogram cells to repair damaged tissues in the human body.
So as that all points out, no, the genetics of it will cause a plant stem cell to be genetically not a match, where it might do something for a little while, but upon that cells first interactions, it will stimulate the immune system to get rid of it, rather than incorporate it.
Anymore, I want to know about how Bone Morphinogenic Proteins (BMP-4 or above) can be injected into an organ, and if that will help stem cells for reviving an organ at all.
The following is multiple choice question (with options) to answer.
Found in cord blood and other sources, what kind of cells hold the promise of renewing and repairing body tissues? | [
"red blood cells",
"white blood cells",
"stem cells",
"neurons"
] | C | Stem Cell Research Stem cell research aims to find ways to use stem cells to regenerate and repair cellular damage. Over time, most adult cells undergo the wear and tear of aging and lose their ability to divide and repair themselves. Stem cells do not display a particular morphology or function. Adult stem cells, which exist as a small subset of cells in most tissues, keep dividing and can differentiate into a number of specialized cells generally formed by that tissue. These cells enable the body to renew and repair body tissues. The mechanisms that induce a non-differentiated cell to become a specialized cell are poorly understood. In a laboratory setting, it is possible to induce stem cells to differentiate into specialized cells by changing the physical and chemical conditions of growth. Several sources of stem cells are used experimentally and are classified according to their origin and potential for differentiation. Human embryonic stem cells (hESCs) are extracted from embryos and are pluripotent. The adult stem cells that are present in many organs and differentiated tissues, such as bone marrow and skin, are multipotent, being limited in differentiation to the types of cells found in those tissues. The stem cells isolated from umbilical cord blood are also multipotent, as are cells from deciduous teeth (baby teeth). Researchers have recently developed induced pluripotent stem cells (iPSCs) from mouse and human adult stem cells. These cells are genetically reprogrammed multipotent adult cells that function like embryonic stem cells; they are capable of generating cells characteristic of all three germ layers. Because of their capacity to divide and differentiate into specialized cells, stem cells offer a potential treatment for diseases such as diabetes and heart disease (Figure 3.36). Cell-based therapy refers to treatment in which stem cells induced to differentiate in a growth dish are injected into a patient to repair damaged or destroyed cells or tissues. Many obstacles must be overcome for the application of cell-based therapy. Although embryonic stem cells have a nearly unlimited range of differentiation potential, they are seen as foreign by the patient’s immune system and may trigger rejection. Also, the destruction of embryos to isolate embryonic stem cells raises considerable ethical and legal questions. |
SciQ | SciQ-4456 | forces, torque, buoyancy
(The translation is from me and it's old French that I sometimes struggle to get in shape!)
Third section, Chapter I: From the point around which the vessel oscillates, which is called roll, and the part that gravity has in these oscillations. (p 369 ....)
"The problem is solved, it is no longer possible to doubt that it is around its center of gravity that the ship makes its oscillation."
...
"It must be remarked that we neglect here the resistance which the water makes to the swaying of the ship; just as the resistance of the air to the movement of pendulums is usually neglected. This resistance is as null, compared to the other forces we consider, because no matter how large the oscillations of the ship, it has, because of the figure, that little water to move and that it does not shocked her with rather little speed. It is still assumed that the alternative inclinations are not large enough, so that the metacentre changes substantially in height relative to the center of gravity. "
In 1762, he problem is clearly stated!
Hope it can help !
The following is multiple choice question (with options) to answer.
Which law explains why a ship weighing thousands of metric tons floats on water? | [
"archimedes' law",
"hofstadter ' law",
"water pressure law",
"ganymede ' law"
] | A | Do you see the man sitting on top of this tanker truck? He gives you a sense of how big the truck is. What’s behind the truck? Is it a huge apartment complex? It’s just as massive as a very large building, but it’s not even resting on land. It’s a giant cruise ship, and it’s floating on water. The ship weighs about 100,000 metric tons. How can such a tremendous weight float on water? Why doesn’t it sink to the bottom of the ocean instead? Archimedes’ law explains why. |
SciQ | SciQ-4457 | evolution, mammals
Title: Why haven't land animals evolved beyond urination? It occurred to me (while urinating) that this would seem to be selected against because water is a scarce resource. Why are we constantly losing water we don't need to through urination? What is it about the chemistry of urine and the waste products eliminated that make urination necessary as opposed to eliminating them through defecation and recovering the water on the way out? It is probably true that toilets and other resting-ish area are always a great place to think about biology, I agree $\ddot \smile$.
Why do we urinate?
In short, urine contains the waste from our blood while defecation is just the stuff that we haven't digested. Kidneys are the organs responsible for draining wastes (mostly nitrogen-containing, or nitrogenous, wastes) from our blood.
Trade-off: energy cost vs. water loss
You're correct that the loss of water through urination is a considerable cost for an organism (especially those living in dry environments). But the amount of water used to excrete nitrogenous wastes is negatively correlated with the energy it costs to perform this excretion. In other words, there is a trade-off between water and energy loss during nitrogen excretion. Also, the question of toxicity is important.
Three ways to excrete nitrogenous wastes
Animals basically have three choices to excrete nitrogenous wastes:
Uric acid (excreted by uricotelic organisms)
Solid (crystal) with low water solubility
Low toxicity
Little water is needed
Lots of energy is needed
Ammonia (excreted by aminotelic organisms)
Highly soluble in water
High toxicity
Lots of water is needed to dilute it because of the toxicity
Not much energy is needed
Urea (excreted by ureotelic organisms)
Solid but highly soluble in water
"medium" amount of water is needed
"medium" toxicity
"medium" amount of energy is needed
The following is multiple choice question (with options) to answer.
The urinary system can be considered a smaller part of what other body system? | [
"excretory",
"sensory",
"circulatory",
"extraneous"
] | A | Sometimes, the urinary system ( Figure below ) is called the excretory system. But the urinary system is only one part of the excretory system. Recall that the excretory system is also made up of the skin, lungs, and large intestine, as well as the kidneys. The urinary system is the organ system that makes, stores, and gets rid of urine. |
SciQ | SciQ-4458 | food, nutrition, energy-metabolism
Title: What are the bare minimum nutrients required to survive as a human? I am trying to determine the bare minimum nutritional requirements to survive as a human, ignoring energy (caloric) requirements. Another way to ask this question is: What elements can humans not live without? I am not inquiring solely about what nutrients are needed, but also their approximate amounts.
Imagine pills that a person can take that covers all their base nutritional needs and that after taking this pill the person can eat whatever they want to meet their caloric requirements. Hypothetically, this pill could have some amount (how much?) fat, carbohydrates, protein, fiber, minerals, and vitamins, and the person could subsequently eat any other food to meet their caloric requirements knowing their nutritional needs would already be otherwise met. Lets ignore the possibility of the person suffering from health issues due to eating too much of any specific food to meet their caloric requirements (e.g., taking the magic pills and then eating only butter).
A person in this situation could think "Ok I've got most of my bases covered, now I just need to ingest another 1000 calories of (almost) anything I want).
What nutrients are absolutely necessary for humans to survive indefinitely, and how much of these nutrients are required?
I am hoping for a complete list with approximate amounts (e.g., 20g fat, 20g carbohydrates, 1mg Vitamin X, .05mg Vitamin Y, 10mg mineral X). Essential nutrients include (NutrientsReview):
Water
9 amino acids: histidine, isoleucine, leucine, lysine, methionine,
phenylalanine, tryptophan, threonine, valine
2 fatty acids (alpha linolenic and linoleic acid)
Vitamins: A, B1, B2, B3, B5, B6, folic acid, biotin, B12, C,
D, E and K (and choline, which is considered a vitamin-like substance)
Minerals: calcium, chromium, chloride, copper, iodine, iron,
manganese, molybdenum, phosphorus, potassium, selenium, sodium, zinc
The following is multiple choice question (with options) to answer.
Essential minerals that the body needs in tiny quantities are called what? | [
"byproduct minerals",
"draw minerals",
"flux minerals",
"trace minerals"
] | D | Food and Drink App: Vitamins and Minerals Vitamins are nutrients that our bodies need in small amounts but cannot synthesize; therefore, they must be obtained from the diet. The word vitamin comes from “vital amine” because it was once thought that all these compounds had an amine group (NH2) in it. This is not actually true, but the name stuck anyway. All vitamins are covalently bonded molecules. Most of them are commonly named with a letter, although all of them also have formal chemical names. Thus vitamin A is also called retinol, vitamin C is called ascorbic acid, and vitamin E is called tocopherol. There is no single vitamin B; there is a group of substances called the B complex vitamins that are all water soluble and participate in cell metabolism. If a diet is lacking in a vitamin, diseases such as scurvy or rickets develop. Luckily, all vitamins are available as supplements, so any dietary deficiency in a vitamin can be easily corrected. A mineral is any chemical element other than carbon, hydrogen, oxygen, or nitrogen that is needed by the body. Minerals that the body needs in quantity include sodium, potassium, magnesium, calcium, phosphorus, sulfur, and chlorine. Essential minerals that the body needs in tiny quantities (so-called trace elements) include manganese, iron, cobalt, nickel, copper, zinc, molybdenum, selenium, and iodine. Minerals are also obtained from the diet. Interestingly,. |
SciQ | SciQ-4459 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
The process by which leaves collect sunlight and make food is called this? | [
"budding",
"photosynthesis",
"pollination",
"glycolysis"
] | B | The primary function of leaves is to collect sunlight and make food by photosynthesis. |
SciQ | SciQ-4460 | genetics, biochemistry, proteins, rna
Title: Where do amino acids get attached to tRNA and where is it synthesized? Some very basic parts of transcription/translation seem to be left out in various literature. I can't find the answer to this anywhere:
How exactly is tRNA synthesized? I realize that mRNA is synthesized through transcription and I know a lot about that. However tRNA is supposedly synthesized the same way but every time you read about transcription they just talk about how the mRNA then gets this and that...?
Where do the amino acids get attached? Is it in the nucleus or outside the nucleus?
Thanks. A pre-tRNA is transcribed from tRNA genes in DNA by RNA polymerase III. Processing occurs in the nucleus, where a 5' sequence is cleaved by RNase P, the 3's CCA motif is added, and ~10% of the nucleotides are substituted. The tRNA are transported out via the pore complexes. Aminoacyl-tRNA synthetase enzymes attach amino acids in the cytoplasm in a 2-step reaction that requires ATP. You'll find there's a unique splicing mechanism in tRNA that additionally splices out an anticodon intron which is abesnt in mature tRNA's:
The wikipedia article notes RNA Pol III generally recognizes internal control elements rather than upstream control elements as in a normal gene.
Source: Qiagen
Source: Molecular Cell Biology. 4th edition.
Addendum: I said in my post that tRNA is charged in the cytoplasm, this is somewhat true. In mammalian cells, we also see that tRNA are charged in the nucleus as well, and it might aid in the export of some of these charged tRNAs. (Source)
The following is multiple choice question (with options) to answer.
What are the three types of rna involved in protein synthesis? | [
"messenger, transfer, and ribosomal",
"organic , transfer , and ribosomal",
"messenger, organic and transfer",
"messenger, transfer, and organic"
] | A | There are three types of RNA involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribisomal RNA (rRNA). All three of these nucleic acids work together to produce a protein. The mRNA takes the genetic instructions from the nucleus to the cytoplasm, where the ribosomes are located. Ribosomes are the organelles where the proteins are made. The ribosomes themselves are made out of rRNA and other proteins. The mRNA binds to the ribosome, bringing the genetic instructions to order the amino acids to the site of protein synthesis. Finally, the tRNA brings the correct amino acid to the ribosome ( Figure below and Figure below ). In mRNA, the four nucleotides (A, C, G, and U) are arranged into codons of three bases each. Each codon encodes for a specific amino acid, except for the stop codons , which terminate protein synthesis. tRNA, which has a specific “3-leaf clover structure,” contains a three base region called the anticodon , which can base pair to the corresponding three-base codon region on mRNA. More will be discussed on these processes in the Protein Synthesis: The Genetic Code (Advanced) and Protein Synthesis: Translation (Advanced) concepts. |
SciQ | SciQ-4461 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
What is the term for chordates with a vertebral column and endoskeleton of cartilage and bone? | [
"am",
"insect",
"mammel",
"vertebrate"
] | D | Vertebrates are chordates with a vertebral column and endoskeleton of cartilage and bone. Vertebrates also have several organ systems. |
SciQ | SciQ-4462 | optics, models, vision
The radius of the eye is $ER$ and the radius of the hole is $AR$, and with the length $DA$ these form a right angled triangle. Pythagoras' theorem tells us:
$$ DA^2 + AR^2 = ER^2 $$
so:
$$ DA = \sqrt{ER^2 - AR^2} $$
which is what your first line of code calculates. So $DA$ is the distance from the centre of the eye to the centre of the hole. The angle $AC$ is then given by:
$$ \tan AC = \frac{AR}{DA} $$
so:
$$ AC = \arctan \left( \frac{AR}{DA} \right) $$
which is what the second line of code calculates. If you now put a cornea over the hole to make the eye spherical again:
Then the length of the arc $AD$ is simply:
$$ AD = EC \frac{AC}{2\pi} $$
which is what your third line calculates, although there's something a bit odd here as if $AD$ stands for Aperture Diameter then there is a factor of two missing.
The following is multiple choice question (with options) to answer.
What does a keratometer measure in the cornea? | [
"curve",
"Lenght",
"diameter",
"Width"
] | A | 25.7 Image Formation by Mirrors 53. What is the focal length of a makeup mirror that has a power of 1.50 D? 54. Some telephoto cameras use a mirror rather than a lens. What radius of curvature mirror is needed to replace a 800 mm focal length telephoto lens? 55. (a) Calculate the focal length of the mirror formed by the shiny back of a spoon that has a 3.00 cm radius of curvature. (b) What is its power in diopters? 56. Find the magnification of the heater element in Example 25.9. Note that its large magnitude helps spread out the reflected energy. What is the focal length of a makeup mirror that produces a magnification of 1.50 when a person’s face is 12.0 cm away? Explicitly show how you follow the steps in the Problem-Solving Strategy for Mirrors. A shopper standing 3.00 m from a convex security mirror sees his image with a magnification of 0.250. (a) Where is his image? (b) What is the focal length of the mirror? (c) What is its radius of curvature? Explicitly show how you follow the steps in the Problem-Solving Strategy for Mirrors. An object 1.50 cm high is held 3.00 cm from a person’s cornea, and its reflected image is measured to be 0.167 cm high. (a) What is the magnification? (b) Where is the image? (c) Find the radius of curvature of the convex mirror formed by the cornea. (Note that this technique is used by optometrists to measure the curvature of the cornea for contact lens fitting. The instrument used is called a keratometer, or curve measurer. ) 60. Ray tracing for a flat mirror shows that the image is located a distance behind the mirror equal to the distance of the object from the mirror. This is stated d i = –d o , since this is a negative image distance (it is a virtual image). (a) What is the focal length of a flat mirror? (b) What is its power?. |
SciQ | SciQ-4463 | genetics, cell-biology, embryology, meiosis, gamete
Title: Fertilization of the human egg- where does our centrosome come from? Is there a centrosome in a human egg cell? Is the reason why the egg cell remains paused before meiosis 2 because there isn't a centrosome, and it only divides when the sperm fertilizes it thus it can have a centrosome? If this is so, then how did oogenesis happen? ? To answer the first part of your question. The sperm actually introduces two centrosomes. The centrosome then nucleates the new microtubule assembly to form the sperm aster — a step essential for successful fertilization. You can visit these sites Simerly, et al as well as Paweltz, et al
The following is multiple choice question (with options) to answer.
What is it called when an egg develops into an individual without being fertilized? | [
"abiogenesis",
"symbiosis",
"parthenogenesis",
"metamorphosis"
] | C | Parthenogenesis Parthenogenesis is a form of asexual reproduction in which an egg develops into an individual without being fertilized. The resulting offspring can be either haploid or diploid, depending on the process in the species. Parthenogenesis occurs in invertebrates such as water fleas, rotifers, aphids, stick insects, and ants, wasps, and bees. Ants, bees, and wasps use parthenogenesis to produce haploid males (drones). The diploid females (workers and queens) are the result of a fertilized egg. Some vertebrate animals—such as certain reptiles, amphibians, and fish—also reproduce through parthenogenesis. Parthenogenesis has been observed in species in which the sexes were separated in terrestrial or marine zoos. Two female Komodo dragons, a hammerhead shark, and a blacktop shark have produced parthenogenic young when the females have been isolated from males. It is possible that the asexual reproduction observed occurred in response to unusual circumstances and would normally not occur. |
SciQ | SciQ-4464 | human-biology, brain, endocrinology, behaviour
Title: Is there a hormone combination that makes humans grumpy? Imagine a typical situation that is likely to give rise to a bad temper within an individual: a person is awoken very early in the morning by a sound of a lawn being mowed next door.
Unlike expected awakening by an alarm clock, such unexpected awakening by a lawn mower is likely to leave the person in a bad temper, feeling grumpy or sulky.
I'm interested if there's a specific hormone or process that makes a person experience the feeling of grumpiness? Is it related to adrenaline and fight or flight instinct?
In other words, can experience of grumpiness be induced under laboratory conditions by using some combination of hormones/drugs? This is a hard question to respond to.
Many things might make someone grumpy. There are also individual temperaments, making grumpy hard to quantify - a Grumpy to one person might barely be a blip on another individual's scale. Hormones like cortisol reflect stress, and can make people in general irritable, but I doubt any one combination of hormones would always cause grumpiness.
But I thought I'd venture an answer since I did see this paper today: "Low glucose relates to greater aggression in married couples" doi: 10.1073/pnas.1400619111
Being hungry will do this for lots of people, so maybe a bit of an answer for you. There are lots of different kinds of signals that mediate hunger though, so still a tough call.
Update: here's an additional article that specifically talks about parts of the brain involved in aggression and grumpiness as response to a drop in glucose.
The following is multiple choice question (with options) to answer.
Many adolescents experience frequent mood swings. name one of the causes for this. | [
"maturing nervous system",
"surging hormones",
"psychological changes",
"growing hormones"
] | B | Adolescents may have mood swings because of surging hormones. |
SciQ | SciQ-4465 | neuroscience
Title: Nervous system : Nerve signals If the electrical signals from all the various organs throughout the body eventually connect to the nerves in the spinal column traveling up to the brain, how does the brain differentiate the different signals. Is the nerve in the spinal column like an electrical conduit with many wires inside? Yes is the simple answer. A nerve will go up to a specific part of the brain which the brain knows corresponds to a certain region of the body. It isn't perfect though e.g. pain in the diaphragm confuses the brain which doesn't recognise that pain must be coming from there so instead tells the body there is shoulder pain, however this is useful in medicine. Another infamous example is pain from heart disease (angina) which causes pain in the jaw and arm. Perhaps even more interestingly, if a nerve is cut and then grows back linking to the wrong nerve it may lead to the completely wrong part of the body being identified when touched. Also if the brain itself is stimulated in these corresponding areas, a person will feel he or she is indeed being touched in a certain part of the body.
The following is multiple choice question (with options) to answer.
Through what does the nerve impulses travel to the brain? | [
"trochlear nerve",
"abducent nerve",
"optic nerve",
"oculomotor nerve"
] | C | When light hits rods and cones, it causes chemical changes. The chemical changes start nerve impulses. The nerve impulses travel to the brain through the optic nerve . |
SciQ | SciQ-4466 | electromagnetism, electrostatics, potential-energy
Aside: there is a unit of energy which derives from the relationship between charge, potential and energy described above. It's called electronvolt: 1eV is the amount of electrostatic potential energy that a particle with electric charge equal to the charge of electron gains as it moves across electric potential difference of 1V.
*The curious properties of static electric field alluded to above are formalized using mathematical notion of conservative vector field (of which electric field produced by a group of static charges is an example).
The following is multiple choice question (with options) to answer.
The difference in electric potential energy which allows for an electric charge to move from one position to another is measured by what si unit? | [
"ohm",
"meter",
"joule",
"volt"
] | D | In general, for an electric charge to move from one position to another, there must be a difference in electric potential energy between the two positions. The difference in electric potential energy is called potential difference, or voltage . Voltage is measured in an SI unit called the volt (V). For example, the terminals of the car battery in Figure below have a potential difference of 12 volts. This difference in voltage results in a spontaneous flow of charges, or electric current. |
SciQ | SciQ-4467 | inorganic-chemistry, reaction-mechanism, ions
Weiss, A. W. Theoretical Electron Affinities for Some of the Alkali and
Alkaline-Earth Elements. Phys. Rev., 1968, 166 (1), 70-74
Tehan, F. J.; Barnett, B. L.; Dye, J. L. Alkali anions. Preparation and Crystal Structure of a Compound which contains the Cryptated Sodium Cation and the Sodium Anion. J. Am. Chem. Soc., 1974, 96 (23), 7203–7208
Dye, J. L. Compounds of Alkali Metal Anions. Angew. Chem., 1979, 18 (8), 587-598
Dye, J. L.; Ceraso, J. M.; Lok, M. T.; Barnett, B. L.; Tehan, F. J. A Crystalline Salt of the Sodium Anion (Na-). J. Am. Chem. Soc., 1974, 96 (2), 608-609
The following is multiple choice question (with options) to answer.
The properties of the alkali metals are similar to each other as expected for elements in the same what? | [
"class",
"family",
"farm",
"branch"
] | B | The properties of the alkali metals are similar to each other as expected for elements in the same family. The alkali metals have the largest atomic radii and the lowest first ionization energy in their periods. This combination makes it very easy to remove the single electron in the outermost (valence) shell of each. The easy loss of this valence electron means that these metals readily form stable cations with a charge of 1+. Their reactivity increases with increasing atomic number due to the ease of losing the lone valence electron (decreasing ionization energy). Since oxidation is so easy, the reverse, reduction, is difficult, which explains why it is hard to isolate the elements. The solid alkali metals are very soft; lithium, shown in Figure 18.3, has the lowest density of any metal (0.5 g/cm3). The alkali metals all react vigorously with water to form hydrogen gas and a basic solution of the metal hydroxide. This means they are easier to oxidize than is hydrogen. As an example, the reaction of lithium with water is: 2Li(s) + 2H 2 O(l) ⟶ 2LiOH(aq) + H 2(g). |
SciQ | SciQ-4468 | neuroscience
Title: Nervous system : Nerve signals If the electrical signals from all the various organs throughout the body eventually connect to the nerves in the spinal column traveling up to the brain, how does the brain differentiate the different signals. Is the nerve in the spinal column like an electrical conduit with many wires inside? Yes is the simple answer. A nerve will go up to a specific part of the brain which the brain knows corresponds to a certain region of the body. It isn't perfect though e.g. pain in the diaphragm confuses the brain which doesn't recognise that pain must be coming from there so instead tells the body there is shoulder pain, however this is useful in medicine. Another infamous example is pain from heart disease (angina) which causes pain in the jaw and arm. Perhaps even more interestingly, if a nerve is cut and then grows back linking to the wrong nerve it may lead to the completely wrong part of the body being identified when touched. Also if the brain itself is stimulated in these corresponding areas, a person will feel he or she is indeed being touched in a certain part of the body.
The following is multiple choice question (with options) to answer.
Which division of the peripheral nervous system carries messages from sense organs and internal organs to the central nervous system? | [
"vascular division",
"sensory division",
"neural division",
"extrasensory division"
] | B | All other nervous tissue in the body makes up the peripheral nervous system, which has two major divisions. The sensory division carries messages from sense organs and internal organs to the central nervous system. The motor division carries messages from the central nervous system to muscles, internal organs, and glands throughout the body. The motor division is further divided into parts that control involuntary or voluntary responses. |
SciQ | SciQ-4469 | organic-chemistry, bond, halides, hydrocarbons
Thus, we can confidently suggest that the $\ce{C-H}$ bond lengths of given compounds are in following order:
ethane > 1,2-dibromoethane >ethene > 1,2-dibromoethene
The following is multiple choice question (with options) to answer.
An ether is an organic compound in which two hydrocarbon groups are bonded to the same atom of what? | [
"nitrogen",
"sulfur",
"hydrogen",
"oxygen"
] | D | An ether is an organic compound in which two hydrocarbon groups are bonded to the same atom of oxygen. An ether is represented by the general formula R−O−R’. The R’ in the formula means that the hydrocarbon group can be the same as R or it can be different. The steps for naming ethers are listed below. |
SciQ | SciQ-4470 | botany, anatomy, plant-anatomy
Title: Plant anatomy, what are these stem like filaments growing under the flower The picture below shows what I am talking about. Each flower has one and I am just wondering what they are? Looking at this, it looks like a spur. A quite overbreed one, though.
The following is multiple choice question (with options) to answer.
Featuring a stalk-like filament that ends in an anther, what is the male reproductive organ in a flower? | [
"angiosperms",
"petals",
"cones",
"stamen"
] | D | The male reproductive organ in a flower is the stamen . It has a stalk-like filament that ends in an anther. The anther is where pollen forms. |
SciQ | SciQ-4471 | control, robotic-arm, force
To go with the example from the lecture slides:
Imagine standing in front of a wall blindfolded (slide 10 in reference [1]). You know that a flat wall is in front of you, but not where exactly. So in order to get into contact, you cautiously / softly move your arm forwards until you make contact.
Perpendicular to the wall you can move rigidly without excessive force (neglecting friction).
This system can be extended by using various state-dependent matrices depending on where in your task space you are and how certain you are that there might be contacts.
Also, to quote the main points from the introduction of [1]:
Impedance Control
The following is multiple choice question (with options) to answer.
What controls the movements of hands and arms? | [
"somatic nervous system",
"autonomic nervous system",
"functional nervous system",
"voluntary nervous system"
] | A | Scott Schram. The somatic nervous system controls the movements of hands and arms . CC BY 2.0. |
SciQ | SciQ-4472 | general-relativity, electromagnetic-radiation, spacetime, refraction, aether
Title: Bending light due to gravity My question is can you consider the fabric of spacetime to be a medium? And if so, can one explain the bending light due to gravity, that warps spacetime, as analogous to light changing between the medium of air and glass in Snell's law.
Let me clarify further:
Imagine a cartesian coordinate system with a mass located at the origin with mass $M$.
a beam of light is shot parallel to the plane $x=1$.
at the point <1,0,0> gravity is warping the space time medium between the the beam of light and the mass much more than the the space time on the opposite side of the plane x=1. Therefore the discrepancies in the density(this maybe the wrong terminology do not murder me on this) of the medium on both sides light is propagating through has created an effect that is exactly the same as the the case we experience on earth and teach in class room when light is shot a block of glass and refracts.
So to summarize, can the bending of light due to gravity simply be thought of as refraction. First we need to clarify:
According to GR, it is spacetime itself that bends, due to stress-energy (not mass).
Even particles with no rest mass, like a photon, have energy, so they bend spacetime.
When there is a large mass, like the sun, it bends spacetime around it, so when light passes next to it, light's path will be bent, because it goes through a bent spacetime.
We do not know what it is exactly or how it bends, GR only talks about the extent to what spacetime bends.
The photon passing next to the sun will bend spacetime too, and the sun will bend it too, so they both have gravitational effects on each other.
It is not like with the case of glass.
When spacetime is bent because of the sun's gravity, and light passes next to it, it is not going in any medium, it is going in vacuum.
In the case of glass, whenever light interacts with an atom, three things can happen:
elastic scattering, the photon keeps its energy, but changes angle.
inelastic scattering, the photon gives part of its energy to the atom, and changes angle.
absorption, the photon gives all its energy to the atom.
The following is multiple choice question (with options) to answer.
Refraction happens when light bends from doing what in a new medium? | [
"changing trajectory",
"changing brightness",
"changing color",
"changing speed"
] | D | Facts are true. Data, gathered correctly, is factual. Facts and data are not subject to opinion or bias. |
SciQ | SciQ-4473 | botany, plant-physiology, plant-anatomy
Title: Caudex vs Xylopodium difference I live in Brazil and many plants from the brazilian grasslands/prairies exhibit an structure called, by the brazilian literature, "xylopodium" (or "xilopódio" in portuguese) - which are tickened, underground, lignified structures (root or stem) to store water and nutrients. I couldn't really find any work outside Brazil that mentions this kind of strucutre, and as far as I know, the structure known as "caudex" fits the very same definition. That being said, are these two terms synonyms? The New York Botanic Garden gives the definition of xylopodium as:
An underground, woody, storage organ derived from stems or roots and common in cerrado vegetation.
And the definition of caudex as:
A short, vertical, usually woody and persistent stem at or just below the surface of the ground.
I think the main difference here is the focus on the xylopodium as a storage organ, as well as the fact that it is fully underground and can be derived from either the stem or root. A caudex doesn't necessarily primarily provide storage, and as a modified stem, is at or above the surface.
*There is also a definition of xylopodium meaning the type of fruit found in Anacardium (cashews).
The following is multiple choice question (with options) to answer.
What is the basic structure that holds plants upright, allowing plants to get the sunlight and air they need? | [
"twig",
"root",
"stamen",
"stem"
] | D | Stems are organs that hold plants upright. They allow plants to get the sunlight and air they need. Stems also bear leaves, flowers, cones, and smaller stems. These structures grow at points called nodes. The stem between nodes is called an internode. (See Figure below . ). |
SciQ | SciQ-4474 | electromagnetic-radiation, visible-light, aether
Title: If sound travels through matter what medium does light travel through? So sound is a wave and is basically just vibrations, an atom vibrates causing another next to it vibrate and so on until it finally reaches our ears to become sound.
If that's normally how waves behaves, what about light? I understand it's also a particle but something must have caused its starting point to influence its next point in space thereby allowing it to travel through space. what is the cause and effect relationship that allows light to propagate through space? I ruled out matter because most visible light is blocked by matter. The process of light propagation is described by the Maxwell equations.
$$ \nabla\cdot{\bf D} = \rho $$
$$ \nabla\cdot{\bf B} = 0 $$
$$ \nabla\times{\bf E} = - {{\partial{\bf B}}\over{\partial t}} $$
$$ \nabla\times{\bf H} = {\bf J} + {{\partial{\bf D}}\over{\partial t}} $$
These equations say (in simple terms) that: change in the electric field is causing a change in magnetic field, while change in magnetic field is causing a change in the electric field.
The original source of electromagnetic waves is some oscillating charge (for instance an electron) which has an electric field around it. This field is changing (because the charge is oscillating). Therefore (according to the fourth equation) a magnetic field $H$ is formed. But the creation of magnetic field is in fact a change in magnetic field. This leads (according to the third equation) to creation of new electric field $E$. But this change in $E$ leads to $H$, which leads to $E$, etc.
The following is multiple choice question (with options) to answer.
The waves on the strings of musical instruments are transverse—so are electromagnetic waves, such as visible light. sound waves in air and water are this? | [
"longitudinal",
"horizontal",
"hydroelectric",
"symmetrical"
] | A | Waves may be transverse, longitudinal, or a combination of the two. (Water waves are actually a combination of transverse and longitudinal. The simplified water wave illustrated in Figure 16.30 shows no longitudinal motion of the bird. ) The waves on the strings of musical instruments are transverse—so are electromagnetic waves, such as visible light. Sound waves in air and water are longitudinal. Their disturbances are periodic variations in pressure that are transmitted in fluids. Fluids do not have appreciable shear strength, and thus the sound waves in them must be longitudinal or compressional. Sound in solids can be both longitudinal and transverse. |
SciQ | SciQ-4475 | evolution, zoology, anatomy
Title: Are the transverse septum in sharks and the diaphragm in mammals homologous structures? Are the transverse septum in sharks and the diaphragm in mammals homologous structures?
I have searched on Google Scholar and Web of Science, but haven't found substantial evidence to prove or falsify the claim. A beginning of answer here below, I hope. Please first consider that many structures are involved in the question here, the diaphragm (UBERON:0001103), the diaphragmaticus muscle (UBERON:0036071) and the septum transversum (UBERON:0004161). At Bgee (bgee.org) we aim annotating relations of similarity between anatomical structures, please have a look at our GitHub
https://github.com/BgeeDB/anatomical-similarity-annotations
We already annotated 'diaphragm' as a mammalian structure, not homologous in Amniota (please see https://raw.githubusercontent.com/BgeeDB/anatomical-similarity-annotations/master/release/similarity.tsv). In our next release, you will see the annotation for the 'diaphragmaticus muscle' which is an analog organ in Crocodylians (and Turtles) but not homologous to the mammalian diaphragm either. See here for more details about this new Uberon class:
https://github.com/obophenotype/uberon/issues/1229.
Based on the comments here above, I would say that currently we can argue that there is no evidence for a homologous relationship between the 'septum transversum' in sharks and the mammalian diaphragm. Please note that UBERON:0004161 septum transversum describes the (mammalian) embryonic structure that will give rise to the central tendon of the diaphragm, while here you are talking about a adult structure closer to a 'diaphragmaticus muscle'-like septum, as far as I understand.
But anyway thank you for your interesting question that points out a very exciting and rapidly evolving evo-devo field, as this recent paper also suggests
The following is multiple choice question (with options) to answer.
What is the name of the elongated bony structure that anchors the anterior thoracic cage? | [
"tibia",
"collar bone",
"pelvis",
"sternum"
] | D | Sternum The sternum is the elongated bony structure that anchors the anterior thoracic cage. It consists of three parts: the manubrium, body, and xiphoid process. The manubrium is the wider, superior portion of the sternum. The top of the manubrium has a shallow, U-shaped border called the jugular (suprasternal) notch. This can be easily felt at the anterior base of the neck, between the medial ends of the clavicles. The clavicular notch is the shallow depression located on either side at the superior-lateral margins of the manubrium. This is the site of the sternoclavicular joint, between the sternum and clavicle. The first ribs also attach to the manubrium. The elongated, central portion of the sternum is the body. The manubrium and body join together at the sternal angle, so called because the junction between these two components is not flat, but forms a slight bend. The second rib attaches to the sternum at the sternal angle. Since the first rib is hidden behind the clavicle, the second rib is the highest rib that can be identified by palpation. Thus, the sternal angle and second rib are important landmarks for the identification and counting of the lower ribs. Ribs 3–7 attach to the sternal body. The inferior tip of the sternum is the xiphoid process. This small structure is cartilaginous early in life, but gradually becomes ossified starting during middle age. |
SciQ | SciQ-4476 | taxonomy, history
Title: How many species did Carl Linnaeus classify? How many species did Carl Linnaeus (senior) classify? More than 13,000.
Plants: >9,000 names.
In Systema Naturae 10th edition, commonly taken as the starting point of modern taxonomy, Linnaeus is reported to have published around 6,000 plant names (I haven't counted, but Müller-Wille gives 5,900 and Stearn says "almost 6,000". The Wikipedia figure of 7,700 may come from a different edition of Systema Naturae).
However, that's just SN10. Luckily, a wonderful source has compiled the names from all of Linnaeus's work:
The Linnaean Plant Name Typification Project of the Natural History Museum says that Linnaeus published more than 9,000 valid plant names in his life (names that are still valid under current nomenclatural conventions), and they have many of them in a searchable database with references to where Linnaeus published them.
Animals: >4,200 names.
For SN10, different authors give 4,236 or 4,378 animal names. Stearn says "nearly 4,400", so perhaps he too was unsure. The total number Linnaues described in his life is probably higher, as he did write separate zoological publications like Fauna Svevica, but I couldn't find a source like the project bringing together all of his animal names.
Müller-Wille S. 2006. Linnaeus' herbarium cabinet: a piece of furniture and its function. Endeavour 30: 60–64.
Stearn WT. 1959. The Background of Linnaeus's Contributions to the Nomenclature and Methods of Systematic Biology.)
The following is multiple choice question (with options) to answer.
What is the most numerous species on the planet? | [
"viruses",
"humans",
"bacteria",
"trees"
] | C | Practically all surfaces. Bacteria can live and grow in practically any environment. It is this ability that has made bacteria the most numerous species on the planet. |
SciQ | SciQ-4477 | geodesy
Title: Is there a name for the great circle where latitude and longitude are equal? Is there a name for the great circle where latitude and longitude are equal? I have attempted a google search but only the equator and the prime meridian are defined in the sources I can find. ( It is of relevance in developing a map application which keeps track of latitude and longitude ). The curve where latitude and longitude are equal is not a great circle. But as joe khool writes in his excellent answer, it's called the curve of Viviani! It's easy to see that the curve is not a great circle, because, using naïve spherical coordinates (in radians) $(\phi,\lambda)$ with $\lambda$ being longitude and $\phi$ being latitude (zero at equator), this curve passes through $(0,0)$, and also through $(\pi/2,\pi/2)$ which is the north pole ($(\pi/2,\lambda)$ is the north pole for any $\lambda$), But it also passes through, say, $(1,1)$ which is not on the great circle the between previous two points.
In fact the curve you get looks like this:
Note. I plotted this by defining Cartesian coordinates in the obvious way:
$$
\begin{align}
x &= R\cos\phi\cos\lambda\\
y &= R\cos\phi\sin\lambda\\
z &= R\sin\phi
\end{align}$$
and then plotting $(x,y,z)$ for $\phi = \lambda$ and $\lambda\in[-\pi/2,\pi/2]$.
An earlier version of this answer plotted $(x,y,z)$ for $\phi = \lambda$ and $\lambda\in[-\pi,\pi]$. This means that $\phi$ takes values which are not in $[-\pi/2,\pi/2]$ of course. I had assumed that these points would end up around the back of the planet: that you'd get a kind of 'S' which wraps around the planet, but in fact it ends up around the front of it again:
This surprised me!
The following is multiple choice question (with options) to answer.
What are the earth's two poles called? | [
"north and south",
"east and west",
"southwest and south",
"west and south"
] | A | A magnet is an object that attracts certain materials such as iron. You’re probably familiar with common bar magnets, like the one shown in the Figure below . Like all magnets, this bar magnet has north and south magnetic poles . The red end of the magnet is the north pole and the blue end is the south pole. The poles are regions where the magnet is strongest. The poles are called north and south because they always line up with Earth’s north-south axis if the magnet is allowed to move freely. (Earth’s axis is the imaginary line around which the planet rotates. ). |
SciQ | SciQ-4478 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
Chloroplasts and chromoplasts are examples of which membrane bound organelle containing their own dna? | [
"bacteria",
"plastids",
"chromosomes",
"polymers"
] | B | Plastids are membrane-bound organelles with their own DNA. Examples are chloroplasts and chromoplasts. Chloroplasts contain the green pigment chlorophyll and carry out photosynthesis. Chromoplasts make and store other pigments. They give flower petals their bright colors. |
SciQ | SciQ-4479 | evolution, taxonomy, ornithology
Title: Birds and Dinosaurs This came up in an argument with some friends. I know that birds are direct descendants of dinosaurs, shown pretty clearly through the fossil record. However, is it proper to say that birds are dinosaurs, or is there an actual distinction? I bet you'll be interested about the concept monophyly. Any human-made group of species (or taxon) like birds dinosaurs, primate, bacteria, angiosperm, reptiles, … are either monophyletic, polyphyletic or paraphyletic. This picture explain the concept When the taxon is monophyletic it is called a clade.
Monophyletic taxon are those groups of species that can be considered to be objective in the sense that it represents a group of species where each species in the taxon is more related (in terms of time to common ancestor, not according to their genetic similarity) to any other species within the same taxon than to any other species outside this taxon. This is obviously not the case for paraphyletic or polyphyletic taxon.
Typically, we do not consider a parrot or a deer to be reptiles. Therefore, the ususal understanding of "reptiles" makes this taxon paraphyletic. Now, one should not confound the common understanding (what is a reptile in our everyday life) with the strict definition of the taxon Reptilia, which is a monophyletic taxon (or a clade in other words). Probably the best source for exploring the tree of life is tolweb.org. Here, you will find the clade Reptilia (who include birds, snakes, turtles and lizards). Note: Mammals are within the Reptiliomorpha, not the Reptilia.
It is exactly the same issue with the dinosaurs. When we talk about dinosaurs in our everyday life we do not mean birds. But there is a clade called Dinosauria, which include both dinosaurs and birds.
In short, I would say that a bird is a Dinosauria (monophyletic taxon) but is not a dinosaur (paraphyletic taxon). But this little play on word is not a scientific issue but an issue of english usage.
You will also find in this post an introduction to phylogeny
The following is multiple choice question (with options) to answer.
Birds are the most numerous type of what vertebrates? | [
"arachnipod",
"ornithopod",
"tetrapod",
"amphipod"
] | C | Birds evolved from a reptile ancestor but they are very different from reptiles today. Birds are also the most numerous tetrapod vertebrates. |
SciQ | SciQ-4480 | evolution, virology
Title: How did viruses come to be? My question is out of curiosity and got me thinking. How did viruses with the head, tail and tail fibres actually evolve? These viruses look more like machines than biological entities. Are there any theories to how these viruses evolved? I found a book chapter for you here
Quick summary:
3 hypotheses to Origin of viruses
From pre-cellular world (virus first hypothesis)
From reductive evolution of parasites (reduction hypothesis)
From fragments of cellular genetic material (escape hypothesis)
Drawbacks:
virus require cells (to infect) so how can they come first
virus do not look like known reduced parasites from Bacteria/Eukarya/Archaea
unlikely that genetic fragments form complex viral structures for viral function
Because of these drawbacks, the problem of virus origin was for a
long time considered untractable and not worth serious consideration
The rest of the chapter looks more in-depth into the 3 hypotheses
The following is multiple choice question (with options) to answer.
Viruses were assumed to exist before they were first seen with an electron microscope in which decade? | [
"1930 ' s",
"1940's",
"1890's",
"1960's"
] | A | Viruses were assumed to exist before they were first seen with an electron microscope in the 1930s. Multiple hypotheses for viral origins have been proposed. |
SciQ | SciQ-4481 | electric-circuits, electricity, electrical-resistance
Charge conservation is always true.
Current conservation is true during steady state (which in usual electronics is always reached).
The following is multiple choice question (with options) to answer.
Matter is always conserved in what type of reaction? | [
"toxic reaction",
"Quick reaction",
"chemical reaction",
"developed reaction"
] | C | In a chemical reaction, the quantity of each element does not change; there is the same amount of each element in the products as there was in the reactants. This is because matter is always conserved. The conservation of matter is reflected in a reaction’s chemical equation. The same number of atoms of each element appears on each side of the arrow. For example, in the chemical equation above, there are four hydrogen atoms on each side of the arrow. Can you find all four of them on each side of this equation?. |
SciQ | SciQ-4482 | botany, reproduction
Hileman, L.C. and P. Cubas. 2009. An expanded evolutionary role for flower symmetry genes. Journal of Biology 8: 90.
Rohwer, J.G., et al. 2014. A phylogenetic analysis of the Cryptocarya group (Lauraceae), and relationships of Dahlgrenodendron, Sinopora, Triadodaphne, and Yasunia. Phytotaxa 158: 111-132.
The following is multiple choice question (with options) to answer.
Most flowers carry both stamens and carpels; however, a few species are capable of what and are nicknamed "perfect" flowers? | [
"sexual reproduction",
"germination",
"self-pollination",
"cloning"
] | C | Most flowers carry both stamens and carpels; however, a few species self-pollinate. These are known as “perfect” flowers because they contain both types of sex organs (Figure 14.25. Biochemical and anatomical barriers to self-pollination promote cross-pollination. Self-pollination is a severe form of inbreeding, and can increase the number of genetic defects in offspring. A plant may have perfect flowers, and thus have both genders in each flower; or, it may have imperfect flowers of both kinds on one plant (Figure 14.28). In each case, such species are called monoecious plants, meaning “one house. ” Some botanists refer to plants with perfect flowers simply as hermaphroditic. Some plants are dioecious, meaning “two houses,” and have male and female flowers (“imperfect flowers”) on different plants. In these species, cross-pollination occurs all the time. |
SciQ | SciQ-4483 | 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.
The entry of food into the esophagus marks the beginning of the esophageal phase of deglutition and the initiation of this? | [
"relaxation",
"peristalsis",
"propagation",
"digestion"
] | B | The Esophageal Phase The entry of food into the esophagus marks the beginning of the esophageal phase of deglutition and the initiation of peristalsis. As in the previous phase, the complex neuromuscular actions are controlled by the medulla oblongata. Peristalsis propels the bolus through the esophagus and toward the stomach. The circular muscle layer of the muscularis contracts, pinching the esophageal wall and forcing the bolus forward. At the same time, the longitudinal muscle layer of the muscularis also contracts, shortening this area and pushing out its walls to receive the bolus. In this way, a series of contractions keeps moving food toward the stomach. When the bolus nears the stomach, distention of the esophagus initiates a short reflex relaxation of the lower esophageal sphincter that allows the bolus to pass into the stomach. During the esophageal phase, esophageal glands secrete mucus that lubricates the bolus and minimizes friction. |
SciQ | SciQ-4484 | species-identification
Title: What is the name of this plant (see pic)? This plant was found growing in Colombia. That looks like a member of genus Lupinus, flowering plants native to North and South America:
I couldn't find a good resource for species of Lupinus in Columbia so I can't help you with the species, unfortunately.
The following is multiple choice question (with options) to answer.
Where are the seeds in gymnosperms found? | [
"in cones",
"in folds",
"in leaves",
"in roots"
] | A | Gymnosperms have seeds, but they do not produce fruit. Instead, the seeds of gymnosperms are usually found in cones. |
SciQ | SciQ-4485 | climate-change, geothermal-heat, crust, thermodynamics, fossil-fuel
Title: Do fossil fuels insulate the crust from the Earth's interior? I was doing a project for my English class, and I came upon the article Energy conservation in the earth's crust and climate change. I can't view the full text of the article, but the abstract piqued my interest:
Do long hydrocarbons in the earth actually have a significant effect in insulating the surface? Also, has the lack of these hydrocarbons resulted in any significant warming of the Earth thus far? Quoting from John Russell's response to this article, "This is arrant nonsense!"
Russell concludes with
How did this paper get through the peer-review and editorial review processes? What technical standards were applied to determine the apparent merit of its contents so as to justify its inclusion in a reputable journal?
Just because something is published in a scientific journal does not mean it is fact. Publication is where science starts rather than ends. Sometimes, pure garbage manages to slip through peer review and get published, even in reputable journals. This is one of those times. Moreover, the publisher of the underlying journal, Taylor & Francis, has had issues with shoddy peer review.
The Earth's energy imbalance is 0.6±0.17 W/m2. The Earth's internal energy budget, the amount of energy that escapes from the interior of the Earth, is 0.087 W/m2, about half the uncertainty in the Earth's energy imbalance. (That largish uncertainty is because the imbalance is a difficult quantity to measure.) Even if all of that 0.087 W/m2 is due to humans removing the Earth's insulating layer of hydrocarbons (it isn't), it does not come close to accounting for the 0.6±0.17 W/m2 imbalance. The numbers don't add up.
Or as John Russell put it in his response to the referenced article, "This is arrant nonsense!"
The following is multiple choice question (with options) to answer.
Oil is found in the porous rock layer and trapped by the what? | [
"\\",
"mantle",
"crystalline layer",
"impermeable layer"
] | D | Oil (red) is found in the porous rock layer (yellow) and trapped by the impermeable layer (brown). The folded structure has allowed the oil to pool so a well can be drilled into the reservoir. |
SciQ | SciQ-4486 | inorganic-chemistry, electronic-configuration, periodic-trends
As we can see, a rather complex dependence is observed. However, it is clear, that the increase in ionic radius from the d8 to the d10 state is not a random fluctuation, it is observed for all three rows. To understand the nature of this dependence it is critical to understand that the values are for an octahedral ligand field (the values would be difference for tetrahedral and other coordinations). In such a field d-orbitals become unequal — three of them are lower in energy while two are higher. In high-spin complexes the difference is not enough to overcome electron pairing energy, while in low-spin ones it is. As result, for low-spin complexes we see a clear minimum at d6, corresponding to the three lower d-orbitals being fully filled, while for high-spin complexes we see changes in the trend for the 4th (first on higher orbital) 6th (all orbitals half-filled) and 9th (first paired on higher orbital) electrons. Now, let's check out the orbitals mentioned (thanks to chemwiki)
The following is multiple choice question (with options) to answer.
The number of valence electrons determines variation of what property in nonmetals? | [
"permeability",
"reactivity",
"density",
"turbidity"
] | B | Reactivity is how likely an element is to react chemically with other elements. Some nonmetals are extremely reactive, whereas others are completely nonreactive. What explains this variation in nonmetals? The answer is their number of valence electrons. These are the electrons in the outer energy level of an atom that are involved in interactions with other atoms. Let’s look at two examples of nonmetals, fluorine and neon. Simple atomic models of these two elements are shown in the Figure below . |
SciQ | SciQ-4487 | special-relativity, nuclear-physics, mass-energy, fusion, binding-energy
This energy (which is 0.42 Mev) is usually the kinetic energy associated with the products of the reaction (and sometimes in other reactions even with radiation).
I really appreciate an answer, because many books are not absolutely clear about this point. I would tweak your description a few different ways.
First, it’s fine that you start off with zero kinetic energy. The reaction is exothermic, so it’s technically allowed at zero temperature. The rate of the reaction rapidly approaches zero as the temperature falls, so spontaneous fusion is not a thing in neutral hydrogen molecules, but for the sake of argument it’s fine.
I would split the formation of deuterium into two steps:
The strong interaction forms the remarkably unstable nucleus $\rm^2He$, with two protons and zero neutrons.
Instead of immediately disintegrating via the strong interaction, the $^2\rm He$ has some minuscule chance of decaying via the weak interaction to deuterium.
The energy of the “virtual” helium state is not well-defined. But you are quite correct that the total (mass-)energy of the final state is reduced because of an attracting interaction between the nucleons. The comparison with gravitational potential energy is good.
The energy released in the reaction is shared among all three of other particles in the final state. In the center-of-momentum reference frame, the three particles will have roughly equal momenta, depending on the angles they make with each other. If you know that the kinetic energy is $T=pc-mc^2$ for massive particles (which becomes $T≈p^2/2m$ for non-relativistic particles), you should convince yourself that most of the energy leaves the system with the least-massive particles.
The following is multiple choice question (with options) to answer.
Hydrogen and helium are specifically involved as reactants in what nuclear reaction that is useful for making energy? | [
"radioactive fusion",
"nuclear fission",
"nuclear fusion",
"destructive fusion"
] | C | The use of nuclear fusion for energy has several pros. Unlike nuclear fission, which involves dangerous radioactive elements, nuclear fusion involves just hydrogen and helium. These elements are harmless. Hydrogen is also very plentiful. There is a huge amount of hydrogen in ocean water. The hydrogen in just a gallon of water could produce as much energy by nuclear fusion as burning 1,140 liters (300 gallons) of gasoline! The hydrogen in the oceans would generate enough energy to supply all the world’s people for a very long time. |
SciQ | SciQ-4488 | atmosphere, ocean, hydrology, climate-change
Comment: I strongly endorse the use of wind and hydropower as sources of energy over the further use of fossil fuels. However, I still think it is important to do research into the actual renewability of presumed-renewable energy sources, as we don't want to end up with another fossil fuel-type situation, in which we become aware of dependency on these energy sources and their malignant environmental side-effects long after widespread enthusiastic adoption. Electricity from waves, from hydro (both run-of-river and storage) and from wind, are all indirect forms of solar power. Electricity from tides is different, and we can deal with that in a separate question. Global tidal electricity generation is not yet at the scale of gigawatts, so it's tiny for now.
Winds come about from the sun heating different parts of the planet at different rates, due to insolation angles, varying cloud cover, varying surface reflectivity, and varying specific heat of surface materials. Temperature differentials create wind currents.
Waves come about from wind, so they're a twice-indirect form of solar power.
Sunlight on water speeds up evaporation, lifting the water vapour into clouds, giving them lots of gravitational potential. That rain then falls, sometimes onto high land, from where it can be gathered into storage reservoirs that are tapped for electricity, or where it flows into rivers that are then harnessed in run-of-river hydro.
How much power is there? Well, the insolation from the sun is, at the outer boundary of the Earth's atmosphere, at an intensity of about 1400 Watts per square metre. The Earth's albedo is roughly about 30% - i.e. on average about 400 Watts are reflected back into space, giving an average irradiation into the Earth of about 1000 Watts per square metre. Picture the Earth's surface as seen from the Sun: wherever the Earth is in its orbit on its own axis, and around the Sun, the Sun sees a disc that has the Earth's diameter, so the surface area exposed to the Sun is just $\pi$ times the square of Earth's radius, which is about 6 300 kilometres.
So the incoming solar radiation is $1000 \times 6,300,000^2 \times \pi \approx 125 \times 10^{15} \rm \ W$
The following is multiple choice question (with options) to answer.
What is the most widely used form of renewable energy in the world? | [
"hydropower",
"wind",
"fossil fuel",
"solar"
] | A | Moving water has energy ( Figure above ). That energy is used to make electricity. Hydroelectric power , or hydropower, harnesses the energy of water moving down a stream. Hydropower is the most widely used form of renewable energy in the world. This abundant energy source provides almost one fifth of the world’s electricity. The energy of waves and tides can also be used to produce water power. At this time, wave and tidal power are rare. |
SciQ | SciQ-4489 | newtonian-mechanics, classical-mechanics, angular-velocity, rotational-kinematics
$$
The rotational energy of the system is the sum of rotational energies of the particles:
$$
E_\text{rot} = \sum_i \frac{\;\; L_i^2}{2J_i}
$$
There are two translational energies:
The following is multiple choice question (with options) to answer.
What energy is the energy of motion? | [
"potential",
"thermal",
"optimal",
"kinetic"
] | D | Kinetic energy is the energy of motion. Any object that is moving possesses kinetic energy. Baseball involves a great deal of kinetic energy. The pitcher throws a ball, imparting kinetic energy to the ball. When the batter swings, the motion of swinging creates kinetic energy in the bat. The collision of the bat with the ball changes the direction and speed of the ball, with the idea of kinetic energy being involved again. |
SciQ | SciQ-4490 | waves, atmospheric-science, turbulence
The clouds form if the rising air reaches the lifted condensation level before the updrafts are stopped by an inversion or stable layer. The air is (relatively) clear above the downdrafts. If the convection rolls were perfectly circular, the cloud row spacing would be twice the height of the inversion/stable layer.
Mathematically, there are many wavelength solutions to convection, but the wavelength that dominates is the fastest growing one. In the Boussinesq approximation, which is reasonably valid here, this turns out to have a wavelength of $2\sqrt{2}\sim 3$ times the height of the convecting layer, i.e. slightly flattened. (See, for example, Eq. 21 of Kuettner (1971) "Cloud bands in the earth's atmosphere: Observations and Theory".)
For typical cumulus cloud heights of $\sim 2$ km, we expect typical spacings of about $6$ km.
Wave, lee, or mountain clouds are lines of clouds downwind of an obstacle (such as a mountain range). The lines are parallel to the wind direction. These are buoyancy waves where wind pushes denser air over an obstacle (e.g. a mountain range) and it ends up above less dense air on the other side. This dense air starts to fall but it overshoots into even higher density air at lower altitude, which forces it back up, and the air ends up bouncing up and down until the oscillations die out. If the vertical temperature profile of the air then is known, it is possible to estimate the vertical buoyancy angular frequency
$$N=\sqrt{\frac{g}{\theta}\frac{d\theta}{dz}}$$
The following is multiple choice question (with options) to answer.
Where do stratus clouds occur in the troposphere? | [
"mid-region",
"low",
"mid to high region",
"high"
] | B | Stratus clouds occur low in the troposphere. They form in layers that spread horizontally and may cover the entire sky like a thick blanket. Stratus clouds that produce precipitation are called nimbostratus. The prefix nimbo- means “rain. ”. |
SciQ | SciQ-4491 | galaxy, space-time, expansion, planetary-ring, galaxy-center
Title: Can expansion of space cause the motion of galaxies, does expansion of space do effect motion of our sun around center and earth around Sun? I'm just wondering that expansion is anyway related to in effecting motion of a star under the galaxies ? Planets are currently revolving around sun in helix motion, if galaxies has motion as well reason to expansion of space then it is possible that, that can effect anyway on that planetary motion around stars ? No. The solar system is a gravitationally bound system so it is unaffected by the large scale expansion of the universe - see this Wikipedia article for further explanation. Similarly, galaxies like the Milky Way, and even groups of galaxies such as the Local Group, which includes the Milky Way and Andromeda, are gravitationally bound systems and are also unaffected.
The following is multiple choice question (with options) to answer.
What kind of movement do planets in the solar system make around the sun? | [
"spinning orbits",
"optical orbits",
"elliptical orbits",
"round orbits"
] | C | Flickr:Image Editor. Planets in the solar system make elliptical orbits around the Sun . CC BY 2.0. |
SciQ | SciQ-4492 | biochemistry, metabolism
The second system, glycolysis, simply refers to the breakdown of carbohydrates (e.g. glucose) to resynthesize ATP from the energy stored in those carbohydrates. Your muscles contain a buffer of glycogen, approx. 300~ gr for the average Joe (give or take). The glycogen can be broken down to glucose-6-phosphate, which can then enter glycolysis. The glucose-6-phosphate is broken down to 2 pyruvate and yields 3 ATP netto (2 when derived from glucose, rather than glycogen, due to a first enzymatic step which requires 1 ATP). The enzymatic steps of glycolysis are controlled by ATP, AMP, ADP and other factors, factually integrating the energy status of the muscle (primarly through allosteric regulation of enzymes, especially phosphofructokinase).
The third system, the oxidative system, refers to the breakdown of carbohydrates and fatty acids, requiring oxygen to 'burn' them (citric acid cycle). The yield of this is much higher than for glycolysis, but the process is way slower.
In essence, all are regulated by the concentration of substrates and products, as well as through allosteric regulation (binding of a molecule at a different site, inhibiting or activating the enzyme, often by intermediates of the pathways themselves). Additionally, there is some long-term regulation through gene expression (e.g. up- or down-regulating expression of genes involved in these pathways), mostly by hormones.
Edit:
Well, I guess this is described in any basic biochemistry book (I'm very fund of the book 'Fundamentals of Biochemistry: Life at the Molecular Level'). If you want to see a description of these energy systems in a more exercise related context (since you were aiming at myocytes) I suggest reading Strength and Condition: Biological Principles and Practical Applications from Marco Cardinale et al., and the NSCA book Essentials of Strength and Conditioning.
The following is multiple choice question (with options) to answer.
Which process breaks down glucose to extract energy for cell metabolism? | [
"photosynthesis",
"glycolysis",
"mitosis",
"meiosis"
] | B | Glycolysis You have read that nearly all of the energy used by living things comes to them in the bonds of the sugar, glucose. Glycolysis is the first step in the breakdown of glucose to extract energy for cell metabolism. Many living organisms carry out glycolysis as part of their metabolism. Glycolysis takes place in the cytoplasm of most prokaryotic and all eukaryotic cells. Glycolysis begins with the six-carbon, ring-shaped structure of a single glucose molecule and ends with two molecules of a three-carbon sugar called pyruvate. Glycolysis consists of two distinct phases. In the first part of the glycolysis pathway, energy is used to make adjustments so that the six-carbon sugar molecule can be split evenly into two three-carbon pyruvate molecules. In the second part of glycolysis, ATP and nicotinamide-adenine dinucleotide (NADH) are produced (Figure 4.13). If the cell cannot catabolize the pyruvate molecules further, it will harvest only two ATP molecules from one molecule of glucose. For example, mature mammalian red blood cells are only capable of glycolysis, which is their sole source of ATP. If glycolysis is interrupted, these cells would eventually die. |
SciQ | SciQ-4493 | molecules, molecular-dynamics
Title: Why do two molecules of an element attract each other? I was thinking about molecular attraction and a question suddenly struck in my mind which is 'Why do two molecule of an element attract each other?'
The answer is easy when we discuss about compound materials. The molecules of a compound have dipoles that can attract each other. But what happens about elements? The molecules of an element don't have dipoles.
After so many attempts, I thought there are only two particles in those molecules that can attract each other — Neucleus and Electron. But also there works repulsive forces between the electrons and between the neucleus of two molecules. It seems like the repulsion is stronger attraction.
So how the attraction force get stronger than the repulsion force so that two molecules of an element attract each other? There are only seven elements which naturally form stable molecules, namely hydrogen, oxygen, nitrogen, fluorine, chlorine, bromine and iodine. At room temperature only iodine is a solid. When they do liquify or solidify, they do so as a result of Van Der Waals forces, which are electromagnetic in nature, acting at short range between the individual molecules. See https://en.wikipedia.org/wiki/Van_der_Waals_force
The following is multiple choice question (with options) to answer.
What does fluorine attract better than any other element? | [
"electron shells",
"shared electrons",
"ionic bonds",
"magnets"
] | B | Valence electrons of both atoms are always involved when those two atoms come together to form a chemical bond. Chemical bonds are the basis for how elements combine with one another to form compounds. When these chemical bonds form, atoms of some elements have a greater ability to attract the valence electrons involved in the bond than other elements. Electronegativity is a measure of the ability of an atom to attract shared electrons when the atom is part of a compound. Electronegativity differs from electron affinity because electron affinity is a measure of the actual energy released when an atom gains an electron. In contrast, electronegativity is a relative scale, so it is not measured in units of energy. All elements are compared to one another, and the most electronegative element, fluorine, is assigned an electronegativity value of 3.98. Fluorine attracts shared electrons better than any other element. Figure below shows the electronegativity values of most elements. |
SciQ | SciQ-4494 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
What term is used to describe the muscular canal (approximately 10 cm long) that serves as the entrance to the reproductive tract? | [
"uterus",
"cervix",
"urethra",
"vagina"
] | D | Vagina The vagina, shown at the bottom of Figure 27.9 and Figure 27.9, is a muscular canal (approximately 10 cm long) that serves as the entrance to the reproductive tract. It also serves as the exit from the uterus during menses and childbirth. The outer walls of the anterior and posterior vagina are formed into longitudinal columns, or ridges, and the superior portion of the vagina—called the fornix—meets the protruding uterine cervix. The walls of the vagina are lined with an outer, fibrous adventitia; a middle layer of smooth muscle; and an inner mucous membrane with transverse folds called rugae. Together, the middle and inner layers allow the expansion of the vagina to accommodate intercourse and childbirth. The thin, perforated hymen can partially surround the opening to the vaginal orifice. The hymen can be ruptured with strenuous physical exercise, penile–vaginal intercourse, and childbirth. The Bartholin’s glands and the lesser vestibular glands (located near the clitoris) secrete mucus, which keeps the vestibular area moist. The vagina is home to a normal population of microorganisms that help to protect against infection by pathogenic bacteria, yeast, or other organisms that can enter the vagina. In a healthy woman, the most predominant type of vaginal bacteria is from the genus Lactobacillus. This family of beneficial bacterial flora secretes lactic acid, and thus protects the vagina by maintaining an acidic pH (below 4.5). Potential pathogens are less likely to survive in these acidic conditions. Lactic acid, in combination with other vaginal secretions, makes the vagina a self-cleansing organ. However, douching—or washing out the vagina with fluid—can disrupt the normal balance of healthy microorganisms, and actually increase a woman’s risk for infections and irritation. Indeed, the American College of Obstetricians and Gynecologists recommend that women do not douche, and that they allow the vagina to maintain its normal healthy population of protective microbial flora. |
SciQ | SciQ-4495 | electricity, visible-light, waves
Title: Electromagnetic Waves We all know that light is an electro magnetic wave. but is electricity a EM wave? If it is then why light does not requires a medium to travel and why on the other side electricity needs a conductor ( I mean a medium) to travel. WHY? Or HOW? Electricity, understood as movement of electrical charges, can generate an EM-Wave, if the geometric conditions of the circuit and frequency conditions in the current flow are given.
As for the means to travel, it is interesting to refer to "skin effect." As the frequency of the current passing through a conductor is increased, the flow of electric charge moves to the outer surface of the conductor.
When the wavelength of the frequency associated with the movement of electric charges, it becomes comparable to the conductor length, the phenomenon of "radiation" is produced.
Ultimately, the movement of electric charge is normally performed in a conductive medium. If the specified conditions are met, this movement can generate an electromagnetic wave, which can propagate even in a vacuum.
So, electricity is not an electromagnetic wave, but can generate a disturbance in the associated electromagnetic field that has the ability to spread like a wave.
Something interesting to note is that an electromagnetic wave can generate electricity (photoelectric effect).
The following is multiple choice question (with options) to answer.
What type of energy travels through space as electrical and magnetic waves? | [
"solar energy",
"mechanical energy",
"sound energy",
"electromagnetic energy"
] | D | 4. Electromagnetic energy is energy that travels through space as electrical and magnetic waves. The light flooding the stage in the Figure above is one type of electromagnetic energy. Other types include radio waves, microwaves, X rays, and gamma rays. |
SciQ | SciQ-4496 | particle-physics
Title: What is the "shape" of atomic/subatomic particles? I apologize in advance for my ignorance if this is a question with an obvious answer... I am not experienced in this field. But are such particles in the universe points with a charge, or are they very small spheres with a charge? Or does it not even matter in the end? This isn't homework, it's just curiosity. In the current model used to describe elementary particles, the Standard Model, the particles (leptons, quarks and gauge bosons) are point-like particles. Experimentally no substructure has been observed for either of those particles (e.g. the upper limit for the electron radius is something like $10^{-22}$m). Some particles that were thought to be elementary (but later turned out to be bound states of quarks), like the proton and the neutron, or all baryons and mesons for that matter, actually do have a substructure that can be and has been measured (or at least the charge distribution).
The following is multiple choice question (with options) to answer.
What are subatomic particles of the nucleus called? | [
"nucleons",
"cores",
"baryons",
"isotopes"
] | A | Summary Subatomic particles of the nucleus (protons and neutrons) are called nucleons. Anuclide is an atom with a particular number of protons and neutrons. An unstable nucleus that decays spontaneously is radioactive, and its emissions are collectively called radioactivity. Isotopes that emit radiation are calledradioisotopes. Each nucleon is attracted to other nucleons by the strong nuclear force. Stable nuclei generally have even numbers of both protons and neutrons and a neutron-to-proton ratio of at least 1. Nuclei that contain magic numbers of protons and neutrons are often especially stable. Superheavy elements, with atomic numbers near 126, may even be stable enough to exist in nature. |
SciQ | SciQ-4497 | physiology, cardiology, blood-circulation
Title: What is the quality rate of intrinsic autoregulation in the heart? Autoregulation is the maintenance of constant blood flow to an organ in spite of fluctuations in Blood pressure.
It involves the relaxation of myocardium and contraction.
It is local.
I know that autoregulation is best done in the brain, well in kidneys and badly in skeletal muscle.
I am interested how it is in the heart.
I think it should be at least good.
Brain can be thought more important.
However, I am not sure.
How good is the autoregulation of the blood flow in the heart? My conjecture: Intrinsic regulation is done in the heart the second best, after the brain.
This idea is based on the fact that the brain controls heart's some autonomic functions.
It is an open research question how the autonomic nervous system affects the intrinsic functions of the heart - and the reverse is true too.
To answer this question, we need to understand the autonomic regulation of the heart better i.e. the inner-physiology of the heart's electrical activity.
The following is multiple choice question (with options) to answer.
What blood pressure reading measures the pressure in the vessels between heartbeats? | [
"diastolic",
"systolic",
"metabolic",
"plasma"
] | A | 40.4 | Blood Flow and Blood Pressure Regulation By the end of this section, you will be able to: • Describe the system of blood flow through the body • Describe how blood pressure is regulated Blood pressure (BP) is the pressure exerted by blood on the walls of a blood vessel that helps to push blood through the body. Systolic blood pressure measures the amount of pressure that blood exerts on vessels while the heart is beating. The optimal systolic blood pressure is 120 mmHg. Diastolic blood pressure measures the pressure in the vessels between heartbeats. The optimal diastolic blood pressure is 80 mmHg. Many factors can affect blood pressure, such as hormones, stress, exercise, eating, sitting, and standing. Blood flow through the body is regulated by the size of blood vessels, by the action of smooth muscle, by one-way valves, and by the fluid pressure of the blood itself. |
SciQ | SciQ-4498 | bond, atoms, molecules, valence-bond-theory
So the short answer to your first question is: "Molecular orbitals hold atoms together in covalent bonds, and those are a result of electrostatic interactions and the quantum nature of electrons."
Yes, ionic compounds are large collections of ions, and you can't really define "molecules" for them - instead we talk about "formula units" which are the lowest possible whole-number ratio of elements that represent the compound. Groups of covalently bonded atoms are also held together by electrostatic interactions, but since the covalent bonds are so much stronger, a molecular compound can exist "on its own" as a single molecule. Collectively, the forces that hold collections of molecules together are called van der Waals forces if they don't involve ions. In any atom or molecule, there is never a completely uniform charge density on the surface. For some molecules, this is extreme (water is a good example) and we say it is very polar, or that it has a large dipole moment. This is just another way of saying that one part has a negative charge and the other has a positive charge. In water it looks like this (from wikipedia):
In this picture, red means "more electrons" and blue means "less electrons." Water can form hydrogen bonds, which are very strong electrostatic interactions. Some atoms and molecules have an almost uniform charge density on the surface. We call these "non-polar" molecules - noble gases are good examples. However, even noble gases have what is called an induced dipole due to statistically correlated fluctuations in electron density when the atoms are near each other. As a result, even noble gases can be cooled to the point where they become liquid - the very, very weak electrostatic interactions will hold them together at low temperature, when they are not moving very fast. These forces are called London Dispersion Forces - after the guy who first described them. London dispersion forces are important, because they are found in all molecules - polar or not. In fact, this is what makes most plastics solid. Polyethylene, for example, is made of very long chains of essentially non-polar molecules (from wikipedia):
The following is multiple choice question (with options) to answer.
What holds ionic and covalent compounds together? | [
"gravity",
"electrostatic attractions",
"magnetic force",
"water"
] | B | Ionic and covalent compounds are held together by electrostatic attractions between oppositely charged particles. Describe the differences in the nature of the attractions in ionic and covalent compounds. Which class of compounds contains pairs of electrons shared between bonded atoms?. |
SciQ | SciQ-4499 | acid-base
Title: Reactions of acidified substances Case study: acidified potassium manganate(VII)
Does "acidified" suggest that the substance contains $\ce{H+}$ions?
If so, will acidified $\ce{KMnO4}$ react with a base, such as ammonia? Permanganates, like KMnO4 are powerful oxidizers, but their redox potential and thus reactions are pH dependent. Lowering the pH by adding an acid increases the oxidizing power of permanganates.
Acidified KMnO4 most likely means a solution of KMnO4, with some sulfuric acid added. Since the solution is acidic it will react with bases like ammonia, but that is not the intended reaction of such a solution. It is used to oxidize a wide range of organic and inorganic chemicals, for example toluene to benzoic acid.
The following is multiple choice question (with options) to answer.
Amines are bases; they react with acids to form what? | [
"oils",
"ions",
"proteins",
"salts"
] | D | Amines are bases; they react with acids to form salts. |
SciQ | SciQ-4500 | forces, water, surface-tension
Now, if we suddenly boost up this adhesion a billion times stronger (limit: imagination) from what is the real and cohesion stays same, then it's gonna suck. Literally. Everything the water or any liquid comes to contact with, it will immediately start to evenly spread out, clothing every nooks and cranny on that surface of that object. It'd be much like when we spill water on the floor. But now it'd be happening EVERYWHERE, on the sides and on the roofs. The rivers, lakes and oceans start allowing a layer of water to swallow everything up, and a carpet of water will cover the world. Trees and plants burst as there is an immense rush of water inside them. The large droplets of water we adored will never form, a droplet release in the air will torn into tiny minuscule droplets, that we can't see. Maybe into water vapor. And Life? I wonder... ;)
Hope that helped. Went a little overboard. :D
The following is multiple choice question (with options) to answer.
If water from a spring can't flow downwards, it can spread out to form one of 2 things. what are they? | [
"lake or ocean",
"ocean or river",
"pond or lake",
"ocean or sea"
] | C | Water flowing out of the ground at a spring may flow downhill and enter a stream. That’s what happens to the water that flows out of Big Spring in Missouri. If the water from a spring can’t flow downhill, it may spread out to form a pond or lake instead. Lake George in New York State, which is pictured in Figure below , is a spring-fed lake. The lake basin was carved by a glacier. |
SciQ | SciQ-4501 | thermodynamics
Title: Can diffusion,osmosis be explained by second law of thermodynamics? Second law of thermodynamics states:
Energy tends to disperse from localized to more spread out form, if not hindered from doing so.
So, can the two processes diffusion,osmosis be explained by the law? Please help.
[Note: I am not an advocate of entropy as disorder. Entropy as energy dispersal is more intuitive!] There is an intuitive explanation. First, remember that
the second law of thermodynamics is an expression of the universal principle of dissipation of kinetic and potential energy observable in nature. The second law is an observation of the fact that over time, differences in temperature, pressure, and chemical potential tend to even out in a physical system that is isolated from the outside world. Entropy is a measure of how much this process has progressed. The entropy of an isolated system that is not in equilibrium tends to increase over time, approaching a maximum value at equilibrium.
In classical thermodynamics, the second law is a basic postulate applicable to any system involving heat energy transfer; in statistical thermodynamics, the second law is a consequence of the assumed randomness of molecular chaos.
In the case of osmosis, you have intead of temperature, a new variable called chemical potential, but it works in a very similar way. Energy will flow towards equilibrium in a way to make the chemical potential at the two sides of a membrane equal. If you have more salt on one side of a membrane that on the other, and the membrane allows water to cross, but not salt, then the water will flow to diminish the density of the salt on the side of larger concentration. The flow will stop when both chemical potentials are the same.
Update: what is chemical potential asked by OP
The following is multiple choice question (with options) to answer.
Energy is lost as heat between each trophic level due to the second law of what? | [
"chemistry",
"particles",
"thermodynamics",
"reactions"
] | C | One major factor that limits the length of food chains is energy. Energy is lost as heat between each trophic level due to the second law of thermodynamics. Thus, after a limited number of trophic energy transfers, the amount of energy remaining in the food chain may not be great enough to support viable populations at yet a higher trophic level. The loss of energy between trophic levels is illustrated by the pioneering studies of Howard T. Odum in the Silver Springs, Florida, ecosystem in the 1940s (Figure 46.5). The primary producers generated 20,819 kcal/m2/yr (kilocalories per square meter per year), the primary consumers generated 3368 kcal/m2/yr, the secondary consumers generated 383 kcal/m2/yr, and the tertiary consumers only generated 21 kcal/m2/yr. Thus, there is little energy remaining for another level of consumers in this ecosystem. |
SciQ | SciQ-4502 | electrons, atomic-physics, rydberg-states
Title: Why does a Rydberg atom increases the excitation energy threshold of its neighboring atoms? The hydrogen atom has one electron with specific energy levels allowed,
If the electron is at the lowest energy level -13.59, then it takes a photon with energy of more than 10.19 but less than 12.08 to send this electron definitely to the next allowed energy level of -3.40, is this right? Excess energy from the precisely allowed level will be radiated away as photon.
If the hydrogen atom's single electron is excited to very high energies, for example n=100, it is called a "Rydberg atom".
The very high energy electron results in a much "larger" radius of the hydrogen atom.
Suppose E is the energy necessary to send the electron from n=100 to n=102 level.
Then, if we place two such atoms near enough,
The following is multiple choice question (with options) to answer.
What are electrons in the outer energy level of an atom called? | [
"positive electrons",
"shell electrons",
"outer electrons",
"valence electrons"
] | D | The electrons in the outer energy level of an atom are called valence electrons . It is valence electrons that are potentially involved in chemical reactions. The number of valence electrons determines an element’s reactivity, or how likely the element is to react with other elements. The number of valence electrons also determines whether the element can conduct electric current. That’s because electric current is the flow of electrons. Table below shows how these properties vary in elements from each class. |
SciQ | SciQ-4503 | nomenclature, ionic-compounds, history-of-chemistry
Title: How did Halogens become known as Halogens? They are not the only elements that form salts! Having never given it a though before, I recently discovered (in a different context) that the prefix halo- actually means 'salt' or 'sea' and the suffix -gen means 'to form' or 'to generate'. So the Halogens are the elements that 'form salts'. But there are salts that do not have halogens in them, like $\ce{Na2S}$ or $\ce{(NH4)2SO4}$. Was it known at the time that other salts existed, and what other names for this group might have been considered?
On a side note, why aren't Group I metals called halogens? Doesn't it take two to tango (I mean, to form salts?) This seems like a bit of a rhetorical question, so this isn't a terribly formal or authoritative answer, but anyhow - a lot of chemical nomenclature is like lava flow. It solidified and people just worked around it.
The halogens are so named because they have a rich chemistry of ionic compounds (fluorine through iodine, anyhow). However, both the halogens and the group I metals can form a wide range of things that aren't salts. The noble gases can form compounds with elements of low birth. The rare earth elements aren't particularly rare. Oxygen ('acid-former') is not a necessary component of acids. Technetium ('artificial' + ium) is produced in nature in significant quantities.
In addition, a lot of chemistry defies our human efforts to succintly categorise things, so at some point chemists have tried their best to find pragmatic general descriptors that unite groups of elements or molecules on the basis of the properties or constitution. The divide between organic and inorganic chemistry and the resulting exceptions and edge cases in classification (such as mellitic anhydride) is a good example of this. The map is not the territory.
The following is multiple choice question (with options) to answer.
Halogens tend to form salts with what type of element? | [
"man-made",
"nonmetals",
"metals",
"metalloids"
] | C | Halogens have filled valence electron configurations. Halogens tend to form salts with metals. As the free elements, halogens are monatomic. Halogens have appreciable nonmetallic character. Halogens tend to have an oxidation state of −1. Halogens are good reductants. |
SciQ | SciQ-4504 | electric-circuits, voltage
Title: Unsatisfactory explanation for the EMF measurement of a battery Experimentally, I have seen how hooking up a battery to a simple circuit just with a high-resistance voltmeter raises the voltage reading (allegedly to a level equal to the EMF of the battery).
However, I find the explanation for why the reading rises, much less to an EMF, very unconvincing. We were told that the internal resistance and the necessary potential drop is ignored, because there is no current in the said circuit, hence why the voltmeter measures an EMF. How can this make sense? There clearly must be some current, albeit very little, flowing, for the high-resistance voltmeter to even have a reading, and that little current will still experience resistive forces from the internal resistance of the cell - so the EMF should not be attainable. Or is there a mechanism by which, when there is very little current, resistors are ignored, hence no work has to be done to traverse them?
Clearly I am wrong, as experimentally I saw the voltage rise in that super simple cell. My point of view suggests that there shouldn't be a difference between the reading in said circuit and the potential difference in a circuit consisting of 3 resistors (the voltmeter in this case measures the drop between these 3 resistors, note there is no other significant source of resistance other than the internal resistance). Really, in my theoretical understanding they should produce an equal reading, but they don't.
So, to be honest, not only do I believe that the reading we saw shouldn't have been the EMF, but not even any different from the reading in a normal circuit, as described (the latter belief clearly conflicts with reality).
I an eager to know what I am thinking wrongly about. Please ask if I can help clarify anything!
Thank you very much :)! You're quite correct that there will be some current flowing, so there must be a voltage drop due to the internal resistance of the battery. The EMF measured by any voltmeter will always be less than the true EMF.
If the internal resistance of the battery is $R_b$ and the resistance of your voltmeter is $R_m$ then the voltage you measure will be:
$$ V = \frac{R_m}{R_m + R_b} E $$
The following is multiple choice question (with options) to answer.
The voltage is measured using a voltmeter, which measures which difference across two points? | [
"Distance",
"potential difference",
"actual difference",
"average difference"
] | B | A uniform electric field makes it easier to measure the difference in electric potential energy. This energy, also called the electric potential difference is commonly referred to as the voltage , based on the unit, volt (V). To measure the voltage across some distance, it is necessary to pick a position to be the relative zero, because voltage is the change in potential difference. Any point in a system can be given the value of zero volts, but it is typically the point of a point charge or one plate in a uniform electric field as shown above. The voltage is measured using a voltmeter, which measures the electric potential difference across two points. |
SciQ | SciQ-4505 | fluid-statics
Title: In static fluid, pressure at same heights are equal. Is this applicable to the oceans? Generally we consider the reference as horizontal line. But if we consider a vertical water column in the ocean. Then, if we want to consider the reference it should be a circular not a horizontal line, so that we get equal pressures at equal heights. This is generally true but only to a first approximation. There are tides which mean that the shape of the surface of the ocean is actually something complicated. The Earth is rotating which means that nothing is spherical. There are also atmospheric pressure effects and wind which can make significant differences to the surface of the oceans. There are differences in temperature which make things yet more complicated. Finally as a result of most of the previous effects there are large currents which make things yet more complicated.
So it's true to a simple-minded physicist's approximation (if I wanted to know what kind of diving suit I'd need to go $1\,\mathrm{km}$ down it would be a good enough approximation I think) but in real life things are hugely complicated.
The following is multiple choice question (with options) to answer.
What is the vertical extent of ocean water called? | [
"oceanic pillar",
"water column",
"ocean column",
"water row"
] | B | Scientists refer to the vertical extent of ocean water as the water column . Two main zones based on depth of water are the photic zone and aphotic zone. The photic zone is the top 200 meters of water. The aphotic zone is water deeper than 200 meters. The deeper you go, the darker the water gets. That’s because sunlight cannot penetrate very far under water. Sunlight is needed for photosynthesis. So the depth of water determines whether photosynthesis is possible. There is enough sunlight for photosynthesis only in the photic zone. |
SciQ | SciQ-4506 | ocean, ocean-currents, tides
Direct disruption of seabed habitats by physical interference, e.g. from moorings
Disruption of ecological niches: Some organisms have evolved to survive in areas where others cannot - e.g. high current speed environments. Changes in seabed conditions, e.g. from greater or lesser current speeds, may cause them to be out-competed by other species that can then settle there.
Similarly, changes to sediment distribution represent changes to seabed habitats.
Alteration of flow patterns could have implications for species with a dispersive juvenile stage (e.g. larvae that rely on currents to spread) or those that rely on current flow for nutrient or waste transport.
The following is multiple choice question (with options) to answer.
Echinoderms are found in many different ocean environments, but most are found where? | [
"in waterfalls",
"in beaches",
"in tidepools",
"in reefs"
] | D | Echinoderms are found in many different ocean environments, but most are found in reefs. |
SciQ | SciQ-4507 | plate-tectonics, mountains, tectonics
Title: What is the impact of divergent tectonic plates on old mountain ranges? I found this question, which is similar to what I'm wondering, but my question is slightly different:
What happens if a new divergent boundary forms in a way that bisects a mountain range, especially one formed by converging plates -- and is that even possible?
Purely for the sake of example, if a divergent rift somehow formed on the North American plate, dividing the Appalachians [ETA: apparently I circled a valley, please pretend I'm not a geography-illiterate dork and that it's actually some old mountains.]:
What would happen to the circled area? Anything? Would the mountain range be recognizable after an ocean formed between them? Considering the timescale involved, perhaps an older range would be unrecognizably eroded? I've tried to find examples in the real world, but my Google-fu fails me.
Somewhere I picked up the idea that the Appalachian and Welsh coal seams were once connected or formed together (I think it may have been from an offhand comment in a movie about Welsh miners, so a] maybe I understood wrong and b] who knows how accurate it was), so I initially wondered if that might be an example of what I'm curious about. Unfortunately, some light research seems to indicate that's not the case (if I'm understanding this and this correctly, the connection ends at "both formed, at least partially, during the Carboniferous.)
I'm most interested in what the effects (if any) would be on older mountain ranges such as the Urals or Appalachians, but if anyone knows what kind of effects it might have on younger, taller ranges, I'd love to hear about it.
If anyone has sources I could look into for a deeper understanding, I'd love to have those as well! My lack of knowledge is distressing me to no end. The example of the East African Rift was given in a different answer.
Splitting of mountain ranges in two becomes even more apparent as you go up north from there.
The Red Sea between Egypt and Saudi Arabia is a young new spreading ocean, that cuts through Precambrian mountains.
The following is multiple choice question (with options) to answer.
A convergent plate boundary is created when two plates do what? | [
"move perpendicular to each other",
"come toward each other",
"stay stationary",
"move away from each other"
] | B | When two plates come toward each other, they create a convergent plate boundary. |
SciQ | SciQ-4508 | volcanology
Title: Does the size of Earth increase due to volcanism? In a volcanic eruption, magma rushes to the 'outside' of the Earth. Does this mean the size of Earth also increases? If not, how is the volume left after the magma rushed out refilled? This is actually a more complicated question than it seems on the surface (no pun intended). The short answer is that the volume vacated by the magma is eventually refilled by the very tectonic processes that filled it in the first place. Crust is subducted, molten, and then rises to fill magma chambers. The process goes on and on. In some cases the plate that was being subducted eventually disappears (this will happen to the Juan de Fuca plate in a few million years), and the volcanoes associated with become extinct, not dormant but extinct. But generally speaking, volcanism is an ongoing process; the Earth is constantly recycling crustal material
The following is multiple choice question (with options) to answer.
When volcanoes erupt, what from the mantle is released as carbon dioxide into the air? | [
"vapor",
"carbon",
"lava",
"hydrogen"
] | B | Carbon from decaying organisms enters the ground. Some carbon is stored in the soil. Some carbon may be stored underground for millions of years. This will form fossil fuels. When volcanoes erupt, carbon from the mantle is released as carbon dioxide into the air. Producers take in the carbon dioxide to make food. Then the cycle repeats. |
SciQ | SciQ-4509 | botany, plant-physiology, plant-anatomy
Title: Sporophyte and gametophyte
My textbook says that in both groups of seedless plants (vascular plants, non-vascular plants) the gametophyte is a free-living plant, independent of the sporophyte.
I don't understand this statement and am now wondering if the sporophyte and gametophyte are stages in a plant's lifecycle, or are they individual parts of the plant, or are the sporophyte and the gametophyte different plants altogether? Secondly, does this differ depending on the organism?
Different plants or different structures that make up the same organism? The sporophtye is the diploid stage in the life cycle. In comparison, with humans, you and I would be sporophytes.
The Gametophyte is the haploid stage in the life cycle. In comparison, with humans, spermatozoids and ovules are gametophytes.
The following is multiple choice question (with options) to answer.
Sepals, petals, pistils, and stamens are contained in all what, which are actually modified leaves or sporophylls organized around a central stalk? | [
"stems",
"roots",
"chlorophyll",
"flowers"
] | D | Flowers Flowers are modified leaves or sporophylls organized around a central stalk. Although they vary greatly in appearance, all flowers contain the same structures: sepals, petals, pistils, and stamens. A whorl of sepals (the calyx) is located at the base of the peduncle, or stem, and encloses the floral bud before it opens. Sepals are usually photosynthetic organs, although there are some exceptions. For example, the corolla in lilies and tulips consists of three sepals and three petals that look virtually identical—this led botanists to coin the word tepal. Petals (collectively the corolla) are located inside the whorl of sepals and usually display vivid colors to attract pollinators. Flowers pollinated by wind are usually small and dull. The sexual organs are located at the center of the flower. As illustrated in Figure 14.25, the stigma, style, and ovary constitute the female organ, the carpel or pistil, which is also referred to as the gynoecium. A gynoecium may contain one or more carpels within a single flower. The megaspores and the female gametophytes are produced and protected by the thick tissues of the carpel. A long, thin structure called a style leads from the sticky stigma, where pollen is deposited, to the ovary enclosed in the carpel. The ovary houses one or more ovules that will each develop into a seed upon fertilization. The male reproductive organs, the androecium or stamens, surround the central carpel. Stamens are composed of a thin stalk called a filament and a sac-like structure, the anther, in which microspores are produced by meiosis and develop into pollen grains. The filament supports the anther. |
SciQ | SciQ-4510 | biochemistry, cell-biology, proteins
Title: Why is protein turnover necessary or important for cells to function? Cells constantly create new proteins in order to maintain their normal function, this is called protein turnover.
Why is that? Do the old molecules wear out as time passes, so that they need a replacement? Biology is an intricate orchestration of chemical reactions and their products. Generally, this fete is accomplished by enzymatic facilitation of certain reactions that would otherwise occur too slowly.
However, "unwanted" reactions occur spontaneously all the time, too. One important mechanism for these reactions is the presence of free radicals causing oxidative stress: reactive molecules are present in cells as a consequence of the energy necessary for metabolism, and these can react with proteins and other cellular components and change their structure. Modified proteins may fold incorrectly and lose their function (or gain harmful function). There is very little that can be done to prevent these reactions from occurring except to clean up afterwards.
Half-lives vary by protein, but for most proteins are measured in the scale of hours (Chen et al, 2016) to a couple days (Boisvert et al, 2012). By constantly degrading and replacing proteins, cells ensure that their proteins are functional and fresh. You might consider this as analogous to performing regular maintenance on a machine like an automobile, using replacement parts as the originals become worn.
Both protein degradation (e.g., via the ubiquitin-proteasome system) and synthesis are highly regulated.
Boisvert, F. M., Ahmad, Y., Gierliński, M., Charrière, F., Lamont, D., Scott, M., ... & Lamond, A. I. (2012). A quantitative spatial proteomics analysis of proteome turnover in human cells. Molecular & Cellular Proteomics, 11(3).
Chen, W., Smeekens, J. M., & Wu, R. (2016). Systematic study of the dynamics and half-lives of newly synthesized proteins in human cells. Chemical science, 7(2), 1393-1400.
The following is multiple choice question (with options) to answer.
What do cells do in order to replace damaged or worn out cells? | [
"divide",
"replicate",
"die",
"fold"
] | A | Cells also divide in order to replace damaged or worn-out cells. |
SciQ | SciQ-4511 | agriculture
Title: What does "permanent field" mean in agriculture? I am reading a book that in a paragraph talks about the agricultural methods used in prehistoric Finland.
The further north and east, the more extensive the amount of
burn-beat cultivation, which was a far from primitive form of
agriculture. The yield was many times higher (twenty- to thirty-fold)
than on permanent fields (five- to ten-fold), and there were multiple
varieties of the technique
A history of Finland by Henrik Meinander.
One of them is burn-beating. Like I understand, in burn-beating people cut down the trees in the forests and burn the topsoil. This way they can use that soil for 3 to 6 years for cultivation.
The other method is permanent field. I have searched the internet and the result I got was "permanent crops", like here. In which case people planted trees once in a field and harvested them multiple times.
But in another research about prehistoric Finland it was saying:
The site of Orijärvi shows that permanent field cultivation, with
hulled barley as the main crop was conducted from approximately cal AD 600 onwards.
The following is multiple choice question (with options) to answer.
What kind of agriculture destroyed about 10% of madagascar's native plants? | [
"fertilizer use",
"crop rotation",
"hybridization",
"slash-and-burn"
] | D | Another example of species loss due to habitat destruction happened on Madagascar’s central highland plateau. From 1970 to 2000, slash-and-burn agriculture destroyed about 10% of the country’s total native plants. The area turned into a wasteland. Soil from erosion entered the waterways. Much of the river ecosystems of several large rivers were also destroyed. Several fish species are almost extinct. Also, some coral reef formations in the Indian Ocean are completely lost. |
SciQ | SciQ-4512 | botany, color
Hypothesis 1
It should be remembered that chlorophyll is far from being the only pigment found in leaves. For example, carotenoids - which give yellow and reddish colors - are present in plant leaves. There are many carotenoids (according to Wikipedia there are over 1100 known, but that number will continue to grow). The biological roles of these carotenoids are also varied. In the course of the question, we may be interested, for example, in the photoprotective role of carotenoids. They are involved in the deactivation of reactive oxygen species (ROS). ROS can be formed during photosynthesis and can potentially be harmful to cells. Therefore, in conditions of excess solar radiation, plants can increase concentrations of carotenoids to prevent oxidative stress. It has already been pointed out to you in the comments that younger leaves look yellow - this is a common occurrence. The leaf is a very expensive organ, in the sense that the plant invests a lot of plastic substances in its development. So it makes sense that young, growing leaves get extra protection. That is, a young leaf that has not yet formed all the necessary structures (thick enough cuticle, efficient conductive system, etc.) is less efficient in terms of photosynthesis and therefore more susceptible to negative processes of photodamage. Increased concentrations of carotenoids, among other things, can reduce such risks. If you add to this the small thickness, it is understandable why young leaves often look more yellow.
Hypothesis 2
I have already said that leaves are expensive organs. They have a high protein content, which is very valuable to the plant. If a leaf is damaged or aged, there is a threat of irreversible loss of protein, which would be a great waste. Therefore, in such cases, plants trigger complex processes of removing valuable substances from the leaves. In particular, chlorophyll begins to break down, and the decomposition products are transported to the more durable parts of the plant. This is the reason why leaves change color in the fall, before defoliation. When the concentration of chlorophyll decreases, other pigments, such as carotenoids, increasingly affect leaf color. That's why damaged and old leaves often turn yellowish.
Although, I doubt that in the case of your plant, this process is often the cause for yellow leaves.
Hypothesis 3
The following is multiple choice question (with options) to answer.
Chloroplasts are the little green particles in plants made up of what colorful pigment? | [
"chlorophyll",
"melanin",
"verdigris",
"carbonate"
] | A | |
SciQ | SciQ-4513 | organs, lifespan
Title: Organs lifespan out of the body What organ can be conserved outside of the body for the longest time and still function when reimplanted? Depends what you consider an organ. Typically though it's the cells which require the most metabolic activity which have the shortest life span. The kidney is the most of the major internal organs with up to 36 hours with liver coming second at up to 16 hours.
The following is multiple choice question (with options) to answer.
What is the largest organ of the human body? | [
"your skin",
"your blood",
"your brain",
"your lungs"
] | A | You couldn’t survive without your skin. It has many important functions. In several ways, it helps maintain homeostasis. The main function of the skin is controlling what enters and leaves the body. It prevents the loss of too much water from the body. It also prevents bacteria and other microorganisms from entering the body. Melanin in the epidermis absorbs ultraviolet light. This prevents the light from reaching and damaging the dermis. |
SciQ | SciQ-4514 | electromagnetism, electrostatics, electricity
Title: Why is the charge of an electron taken to be the negative of the charge of a proton and vice versa? Let us assume that all we know till now is that two types of charges exist. One of them is possessed by an elementary particle called an electron and the other by another elementary particle called a proton. We also know that the effect of a proton on another proton is the same as that of an electron on another electron in terms of the force of repulsion and an electron and proton also have a similar effect on each other other than the fact that they attract each other, and not repel.
Now, let us say that the charge of an electron is $1 \text{ e}$. Why do we take the charge of a proton as $-1 \text{ e}$ only based on the information that they have similar but opposite effects? Now, if we define the charge of a proton as $-1 \text{ e}$, the net charge of a body with $n_1$ electrons and $n_2$ protons becomes $n_1e+n_2(-e) = (n_1-n_2)e$. How do we know that the results obtained from these mathematical operations will be what the actual effects will be?
I don't know if I was able to express my question properly. I'm finding it hard to express what I have in mind. Please let me know if it is not clear, I will try my best to improve it.
Thanks! I think your question is a little unclear, so let me know if I've misunderstood what you were asking.
If your question is about how we know that the electron and the proton have the same magnitude but opposite signs, it's simple (at least in theory): create a Hydrogen atom. It has one proton and one electron, and it's neutral overall, meaning it has a net charge of zero. Since charges simply add up, the proton and the electron must have opposite charges.
On the other hand, if your question is about why one of them is "called" negative and the other positive, I refer you to E.M. Purcell's excellent text. From Chapter 1.1 (Electric Charge):
The following is multiple choice question (with options) to answer.
What kind of charge does a proton have? | [
"ionic",
"constant",
"negative",
"positive"
] | D | Electric charge is a physical property of particles or objects that causes them to attract or repel each other without touching. All electric charge is based on the protons and electrons in atoms. A proton has a positive electric charge, and an electron has a negative electric charge (see Figure below ). |
SciQ | SciQ-4515 | geomorphology
Title: What causes these mound-like ground formations? Whilst riding on Mam Tor in Castleton, England I came across this scene (not my photo) and I would like to know what causes the formations which I have ringed in red. They look like piles of earth have been deposited a long time ago, but clearly that can't be the case, so what causes them?
Another image of these mounds They're landslide deposits; Mam Tor gets its name, which translates as "mother hill", from the regular landslides that come off the higher slopes and form hillocks further down into the valley.
The following is multiple choice question (with options) to answer.
What are boggy regions with thick layers of peat called? | [
"meadows",
"wetlands",
"peatlands",
"tropics"
] | C | |
SciQ | SciQ-4516 | tissue
Title: What are the main differences between lab-grown tissues and natural tissues from living animals? What are the main differences between lab-grown tissues and natural tissues from living animals?
Using a biologist's classic "structure (anatomy) and function (physiology)" idea, I thought about the followings:
Structure:
It might be difficult to recreate the composition of different tissues / cells in living things precisely with artificial methods. This may lead to bad results when the tissue is used for tests of medicines and cosmetics.
Function:
Cells might not function and produce as expected (or is harder to make them function) in artificial compositions, as cells need strictly regulated environments to function correctly.
The following is multiple choice question (with options) to answer.
What type of compounds make up the cells and tissues of living things? | [
"biochemical",
"proximal",
"hormonal",
"microbial"
] | A | Biochemical compounds make up the cells and tissues of living things. They are also involved in all life processes. Given their diversity of functions, it’s not surprising that there are millions of different biochemical compounds. Even so, all biochemical compounds can be grouped into just four main classes: carbohydrates, proteins, lipids, and nucleic acids. The classes are summarized in Table below . |
SciQ | SciQ-4517 | relativity
Title: Photons inside a box One of my friends told me that the definition of mass is the amount of matter. I told him that mass is not the amount of matter, because when we heat an object, the mass of the object increases.
I gave an example: Photons moving around inside a closed massless box having walls of perfectly reflecting mirrors gives mass to the box, because the definition of mass is
$\sqrt{E^2-p^2}$ .
Inside the box, when we consider the photons as a whole they don't have momentum, thus mass becomes $m=E$ when $c=1$.
But I'm really confused what happens when the box starts moving, because in that case the momentum as a whole of the photons is not zero? What will be the mass of the box then? Don't worry too much about the word "matter": the modern view afforded by GTR, quantum field theory and much more means that the word "matter" has become very vague. If you look up the "matter" Wikipedia page, this seems to agree that the word "matter" is very vague now indeed, so as a useful concept in physics, the word seems clearly to have passed its use-by date. I actually got to the age of 45 before one day I realised ashamedly that I couldn't define the word "matter" anymore, a situation I thought was disgraceful for a physicist, but a quick sweep of the web shows that there was good reason for my plight.
The following is multiple choice question (with options) to answer.
Anything that has mass and takes up space is considered what? | [
"light",
"energy",
"power",
"matter"
] | D | Matter is anything that has mass and takes up space. Matter is everywhere. The air we breathe, the water we drink, the food we eat, and the ground we walk on are all comprised of matter. Matter can take on a variety of different forms which all have a variety of different properties. In this chapter, we will introduce the characteristics of matter and study how these characteristics vary in different types of matter. |
SciQ | SciQ-4518 | star, planet, telescope, light, space
Title: How do I know what I'll be able to see? So I live in a suburb in Victoria, Australia. Less than an hour away from the city and I guess there is a bit of light pollution because from my backyard I can probably only see about 15 - 20 stars (probably less), I'm wondering what these stars are, and what I'll see when I get this telescope:
https://www.opticscentral.com.au/saxon-707az2-refractor-telescope.html?___SID=U#.WXQNMtN940r
This is going to sound stupid but how do I know when there are planets in the sky that I can see? I don't think I've ever actually seen a planet other than the moon.
Thank you. Firstly, if you're planet spotting, don't worry too much about light pollution. The planets are some of the brightest objects in the sky and some (especially Jupiter) can easily be observed even with a full Moon - the full Moon (along with the Sun!) is the biggest contributor to light pollution!
Take a look at the list of brightest stars ( https://en.wikipedia.org/wiki/List_of_brightest_stars ), which also contains estimates for the brightness of the Sun, Moon and major planets. There aren't typically any stars brighter from Earth than Venus, Jupiter, Mars and Mercury and precious few brighter than Saturn. I'm going to suggest you probably have seen many of the planets - but just didn't recognise them.
+1 for Stellarium ( http://www.stellarium.org/en_GB/ ). It's free, intuitive and very visual to use. You can put in your local viewing location and it gives you a view for any time of the night, future or past. At the time of writing (23 July 2017), Saturn and Jupiter should be looking good for the Southern Hemisphere. This rotates throughout the year, and Stellarium will help with this.
Do a web search for "the sky at night in the southern hemisphere" and you'll find a number of examples of websites with highlights to look for when you get out.
Couple of final suggestions:
The following is multiple choice question (with options) to answer.
What will you see if you look at a star through a prism? | [
"kaleidoscope",
"spots",
"rainbow",
"spectrum"
] | D | If you look at a star through a prism, you will see a spectrum . The spectrum is the range of colors seen in a rainbow. The spectrum has specific dark bands where elements in the star have absorbed light of certain energies. An astronomer can use these lines to determine which elements are in a distant star. In fact, the element helium was first discovered in our Sun, not on Earth. This was done by analyzing the absorption lines in the spectrum of the sun. |
SciQ | SciQ-4519 | 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.
Where is most digestion completed? | [
"the esophagus",
"the cavity",
"the stomach",
"the duodenum"
] | D | |
SciQ | SciQ-4520 | volcanology, paleontology, volcanic-hazard, archaeology, pyroclastic-flows
Title: Are Pompeii and Herculaneum unique? Has anyone ever found or gone looking for similar locations, i.e. volcanic eruption sites in which unfortunate victims – human and non-human – have been entombed in the volcanic ash, with the possibility of revealing their forms by producing casts from the voids? Such sites, if they exist, could reveal exciting new knowledge about ancient peoples and animals. Probably the best known is more recent, the 1902 eruption of Mt. Pelée on Martinique, where 30,000 people were killed by pyroclastic flows. I don't know the extent of burial - it appears that the city may have been destroyed more by the ash cloud than the dense part of the flow.
The following is multiple choice question (with options) to answer.
Explosive eruptions associated with what can be tens of thousands of times as powerful as an atomic bomb? | [
"volcanoes",
"earthquakes",
"hurricanes",
"forest fires"
] | A | An explosive eruption produces huge clouds of volcanic ash. Chunks of the volcano fly high into the atmosphere. Explosive eruptions can be tens of thousands of times as powerful as an atomic bomb ( Figure below ). Hot magma beneath the surface mixes with water. This forms gases. The gas pressure grows until it must be released. The volcano erupts in an enormous explosion. |
SciQ | SciQ-4521 | 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 gland secretes its products directly into the urethra through several small ducts | [
"thyroid",
"pituitary",
"prostate",
"adrenal"
] | C | |
SciQ | SciQ-4522 | organic-chemistry
$\ce{CH3-X + X-CH2-CH3 + Na ->[][-2NaX] CH3-CH2-CH3}$
Sure, you've produced an alkane with an odd number of carbon atoms, but at the same time you have a mixture of alkanes (this is not really a selective reaction), that you will have a hard time separating.
The following is multiple choice question (with options) to answer.
The complete combustion of alkanes to carbon dioxide is an extremely __________ reaction. | [
"hydrolic",
"exothermic",
"reactive",
"geothermal"
] | B | Each step in the process is either a gain of oxygen or a loss of hydrogen. Each step also releases energy, which explains why the complete combustion of alkanes to carbon dioxide is an extremely exothermic reaction. |
SciQ | SciQ-4523 | computability, turing-machines, physics
Title: Can normal physics laws be simulated in Digital physics? Physics is defined as the study of an object {matter or energy} with its interaction with other objects:
Physics is the study of matter, energy, and the interaction between them.
On the other hand, Digital physics is based on computations and information.
Digital physics is a collection of theoretical perspectives based on the premise that the universe is, at heart, describable by information, and is therefore computable.
The following is multiple choice question (with options) to answer.
What is the study of structure, properties, and interactions of matter? | [
"biology",
"chemistry",
"petrology",
"geology"
] | B | Chemistry is the study of the structure, properties, and interactions of matter. Important concepts in chemistry include physical changes, such as water freezing, and chemical reactions, such as fireworks exploding. Chemistry concepts can answer all the questions on the left page of the notebook in Figure below . Do you know the answers?. |
SciQ | SciQ-4524 | human-biology, human-anatomy, human-genetics
Title: Are males taller than females in humans? Is there any scientific evidence that in humans males are taller than females? And if so, what is the reason that they are taller (please include genes or hormones that accounts for human growth and how they are affected in males and females)? Are males taller than females?
Best data I could find come from the Statistical Abstract of the United States (1999) > Section 3. Here is a table reporting the percentage of the male and female population which height is lower than a given threshold
Note that this data collection was done among students in US universities and is therefore not representative of the whole world or even the whole country.
Does height follow a bimodal distribution?
A difference in height between males and females is often used as a classical example in introductory statistic class to exemplify a bimodal distribution as seen in this picture
and on these (a priori fake) data
However, Schilling et al. 2002 argued that while the difference in mean height between the sexes is real, this difference is too small relative to the variance in height within each sex to be clearly depicted on a graph.
Note that I found this non-peer-reviewed paper which shows real data that display a truly bimodal distribution of height.
Genetics of height
The question why are they taller? is very broad. I will just focus to give you some hints about the genetics of height in humans. First, you want to make sure you understand the concept of heritability.
Evoy and Vissher 2009 report a heritability coefficient of 0.8. This estimate is impressively high - only a few phenotypic traits have such high heritability. They also review articles discussing that 50 loci are correlated with variation in height (actually, today, more than 500 loci are known to contribute to height, see the link in AlexDeLarge's comment to this answer). However, these loci are not sufficient to explain the whole heritability observed (common missing heritability issue). Yang et al. 2010 provide evidence that the remaining heritability is due to incomplete linkage
disequilibrium between causal variants and loci of weak effects. In short, height is a highly polygenic trait.
Related post
You should have a look at Is there a genetic reason explaining the difference of the height of male and female? for more information.
The following is multiple choice question (with options) to answer.
Because several genes, each with more than one allele, contribute to determining height in humans, height is considered what kind of trait? | [
"epigenetic",
"maladaptive",
"adaptive",
"polygenic"
] | D | An example of a human polygenic trait is adult height. Several genes, each with more than one allele, contribute to this trait, so there are many possible adult heights. For example, one adult’s height might be 1.655 m (5.430 feet), and another adult’s height might be 1.656 m (5.433 feet) tall. Adult height ranges from less than 5 feet to more than 6 feet, but the majority of people fall near the middle of the range, as shown in Figure below . |
SciQ | SciQ-4525 | mycology
Title: How do fairy rings propagate? It was somewhat new to me that mushrooms usually aren't individual organisms, but are merely the visible bodies of a bunch of fungi living in the soil. I know that mushrooms emit spores to reproduce, but what has been bizarre to me is how fairy rings form. Why do the fruiting bodies arrange themselves in a more or less circular shape, as opposed to the random scattering one would expect from wind-borne spores? When a fungal spore germinates in a suitable location, the growing mycelium will spread underground in all directions. In the ideal situation, the result is that the mycelium will become circular. Over time, the center of the mycelium will die out whereas the newly formed mycelium (underground) will develop the familiar mushrooms above ground and this will result in a fairy ring.
The following is multiple choice question (with options) to answer.
A basidium is the fruiting body of a mushroomproducing fungus, and it forms four what? | [
"basidiocarps",
"schizonts",
"tunnels",
"fossiliferous"
] | A | Figure 24.16 Which of the following statements is true? a. A basidium is the fruiting body of a mushroomproducing fungus, and it forms four basidiocarps. The result of the plasmogamy step is four basidiospores. Karyogamy results directly in the formation of mycelia. A basidiocarp is the fruiting body of a mushroom-producing fungus. Figure 24.20 If symbiotic fungi are absent from the soil, what impact do you think this would have on plant growth?. |
SciQ | SciQ-4526 | taxonomy, phylogenetics
Title: Usage of the taxonomic classification "Pinnipedia" According to ITIS the classification Pinnipedia is invalid, and it is proposed to rather use Caniformia. The later group however includes a range of terrestrial animals as opposed to the pinnipeds (the seals), which only include marine mammals.
Is the term Pinnipedia nevertheless still accepted and used in scientific media? Is there any debate whether to use one and not the other? The Comments section of that page has the explanation:
Wilson & Reeder (eds., 1993) note that "the pinnipeds (otariids,
odobenids, and phocids) are included within the suborder Caniformia;
placing them in a separate Order would make the Carnivora
paraphyletic." This arrangement continues to be followed in Wilson &
Reeder (eds., 2005)
If both Carnivora (Bowdich, 1821) and Pinnipedia (Illiger, 1811) are orders in the traditional Linnean taxonomic sense, then one cannot be nested within the other. If this were to happen, then Carnivora would be paraphyletic because it would exclude some of its members. The same argument is made when discussion birds as dinosaurs (you can't talk about Dinosauria that doesn't include Aves).
The problem arises when phylogenetic systematics (clade names) meets traditional Linnean systematics (orders, suborders, etc.). Phylogenetic systematics does not distinguish these higher taxonomic groups. Clades are just nested groups of monophyletic taxa.
So then to answer your last question, Pinnipedia does appear to be in common usage (Google Scholar reports several hundred citations in the past few years). The key is to distinguish Pinnipedia as a traditional Linnean order (not valid) and Pinnipedia as a monophyletic clade that includes seals, walrus, and sea lions (perfectly fine). Seals, walrus, and sea lions are all more closely related to each other than to other Carnivora, so they are monophyletic, and the name for that grouping is Pinnipedia.
Here's the Tree of Life page that has all the clade names.
The following is multiple choice question (with options) to answer.
Traditional classification of mammals are based on similarities in what two things? | [
"structure & function",
"density & function",
"solution & function",
"Density and Structure"
] | A | |
SciQ | SciQ-4527 | thermodynamics
$$\Delta G_{\text{total}} = \pu{1 mol }\int_0^1 \left[ \Delta_r G^\circ\text{(dissolution)} + R T \ln(x) dx \right] $$
Taking constants and constant factors out of the integral, we get:
$$\Delta G_{\text{total}} = \pu{1 mol } \Delta_r G^\circ\text{(dissolution)} + \pu{1 mol } R T \int_0^1 \ln(x) dx$$
The value of the integral is negative one, so overall we have:
$$\Delta G_{\text{total}} = \pu{1 mol } (\Delta_r G^\circ\text{(dissolution)} - R T) $$
3. Running the reaction at a constant concentration of 1 M
Here, we will use a process that keeps the glucose concentration constant. We place a semi-permeable membrane into the pure water, separating it into two compartments. At the beginning, one compartment (the one in contact with the solid glucose) has a volume of zero. As glucose dissolves, we move the membrane, increasing the volume of the compartment so that the glucose concentration remains at 1 mol/L. We keep doing that over the course of the dissolution reaction until the volume of solution is one liter at the end (and the volume of pure water is zero).
Because all species are at standard state at all time, we can use the standard Gibbs energy of reaction without a term correcting for concentration. This is one component of the total change in Gibbs energy. The other one is work against the osmotic pressure difference between pure water and 1 M glucose:
$$ w = \Pi \times V = \Delta c R T \times V = \pu{1 mol } R T$$
This work represents the difference between dissolving 1 mol glucose into pure water and dissolving 1 mol glucose into a 1 M glucose solution, so we have to add (or subtract?) it to get the Gibbs energy of our original process.
Which calculation is correct, and where are the problems with the other ones?
The following is multiple choice question (with options) to answer.
The rest of the energy stored in glucose is lost as what? | [
"volume",
"mass",
"heat",
"humidity"
] | C | |
SciQ | SciQ-4528 | physiology, respiration
Title: Why does a worm's skin need to be wet for oxygen to diffuse across it? Pages I've read about worms' respiratory systems says that the skin needs to be wet (covered in mucus) or oxygen won't diffuse across the skin. Why? If there is more oxygen outside the worm's skin than inside, what prevents it from diffusing across the skin, even if the skin is dried out? The quick answer: When the skin dries, the lipids in the cell membranes of the skin tissue undergo a phase transition which makes the membranes less permeable for oxygen.
Explanation: The lipids of the cell membrane can exist in different phase states. In the liquid disordered phase the lipids are relatively flexible and mobile, making this phase more oxygen permeable compared to the liquid ordered phase, in which the lipids are more rigidly packed.
The phase transition temperature of lipids increases upon dehydration (another reference), meaning that at the same ambient temperature, a dry lipid membrane is in the liquid ordered state and a wet lipid membrane is in the liquid disordered state.
Therefore, a dry cell membrane is less oxygen permeable than a wet one.
The following is multiple choice question (with options) to answer.
Water that is lost through the skin through evaporation from the skin surface without overt sweating and from air expelled from the lungs is known as what? | [
"dehydration",
"insensible water loss",
"logical water loss",
"osmotic process"
] | B | 26.2 | Water Balance By the end of this section, you will be able to: • Explain how water levels in the body influence the thirst cycle • Identify the main route by which water leaves the body • Describe the role of ADH and its effect on body water levels • Define dehydration and identify common causes of dehydration On a typical day, the average adult will take in about 2500 mL (almost 3 quarts) of aqueous fluids. Although most of the intake comes through the digestive tract, about 230 mL (8 ounces) per day is generated metabolically, in the last steps of aerobic respiration. Additionally, each day about the same volume (2500 mL) of water leaves the body by different routes; most of this lost water is removed as urine. The kidneys also can adjust blood volume though mechanisms that draw water out of the filtrate and urine. The kidneys can regulate water levels in the body; they conserve water if you are dehydrated, and they can make urine more dilute to expel excess water if necessary. Water is lost through the skin through evaporation from the skin surface without overt sweating and from air expelled from the lungs. This type of water loss is called insensible water loss because a person is usually unaware of it. |
SciQ | SciQ-4529 | human-biology, neuroscience, zoology, physiology, history
If it is a mutation or set of mutations as the current thinking implies, there is a good chance that it is a combination of strong selection and accident. Its true that cooperation is often enjoys a strong selective advantage, but it doesn't make you smart or hospitable. When we talk in biology we don't say altruism, we say cooperation. If such cooperation happened only because of selection, we would see such behavior in other primates. So if we see this, I would lay odds to look for a rather complicated story...
Another interesting person to read is anthropologist Terrence Deacon, who is trying to understanding the terms with which we define intelligence. About ten years ago there were actually experiments that showed that chimpanzee some strong candidate intelligence genes related to cognition could be put into people (who needed gene therapy because they had lost cognitive function) and restore that function. Apologies, this is anecdotal - i saw him give a great talk, but he's moved on a bit and can't find the references.
This is important I think because the fundamental definitions of human intelligence have failed over the years, from the old chestnut of using tools, to a recognition of mortality, to awareness, animals have surprised us, particularly primates. I wonder whether we will be able to confirm these vital factors until we get a monkey asking for the keys to the car so that they can go get some pizza.
The following is multiple choice question (with options) to answer.
What are the only innate behaviors in humans? | [
"learned behaviors",
"reflex behaviors",
"inherited traits",
"insight behaviors"
] | B | Innate behaviors occur in all animals. However, the more intelligent a species is, the fewer innate behaviors it generally has. The human species is the most intelligent animal species, and it has very few innate behaviors. The only innate behaviors in humans are reflex behaviors. A reflex behavior is a simple response that always occurs when a certain stimulus is present. |
SciQ | SciQ-4530 | development
Title: How detachment/separation works in biology? It might be a strange question, but I'm interested in the mechanics of separation/detachment during asexual reproduction, for example when an organism reproduces by budding (I don't mean cellular budding like baker's yeast). When the newly formed body is fully matured it detaches itself from the parent / original body.
It might not be caused by a specific tissue, as animals with not so differentiated bodies are (also) capable of such, but I could easily be wrong. Is this (the detachment) triggered by changes in the cell membrane? I can't really think of other explanations. Reproductive budding and what you call 'cellular budding' are really highly related processes. Budding as a form of reproduction essentially partitions protein aggregates and damaged cellular components into the host or mother and builds fresh or 'young' cells on the opposite side of a partition. To begin understanding this look at Saccharomyces cerevisiae (budding yeast) which forms protein rings (from the septin proteins) at the membrane, around the bud neck which separates the mother and daughter cells Hartwell 1971. This ring acts a partition that in part, withholds protein aggregates and certain proteins from diffusing from the mother to the daughter. This protein ring is an example of how cells limit diffusion of proteins and cellular components to the daughter cell. Another good example that comes to mind is Linder 2007, though it is done in E Coli, not budding yeast, where mother cells maintain protein aggregates and age, while the daughter cells are given fresh components and are therefore more fresh and 'young'.
Now like you mention, imagine this process in a multicellular organism to be fundamentally the same. At some point the multicellular organism will start an outgrowth of cells, while restricting what materials are given to the daughter cells to maintain their youth. And eventually a new organism will have been created. Some of the details will be different, but the fundamental process is is quite similar. In that you start with an old cell that creates a new cell from scratch, but rather than splitting all cellular components equally between mother and daughter, the daughter cells is made in peak condition while the mother cell retains much of the cell 'junk' like protein aggregates.
Hopefully that starts to answer your question.
The following is multiple choice question (with options) to answer.
What occurs when a parent organism breaks into fragments, or pieces, and each fragment develops into a new organism? | [
"absorption",
"sollution",
"erosion",
"fragmentation"
] | D | Fragmentation occurs when a parent organism breaks into fragments, or pieces, and each fragment develops into a new organism. Starfish, like the one in Figure below , reproduce this way. A new starfish can develop from a single ray, or arm. Starfish, however, are also capable of sexual reproduction. |
SciQ | SciQ-4531 | reproduction
Excerpts from the references that lead to the short answer above:
In the developing female fetus, oogonia become primary oocytes that begin the first division of meiosis. However, this division is not completed and the primary oocytes remain “frozen” in the prophase stage of the first meiotic division.
At birth, oogonia are no longer present. Each primary oocyte is surrounded by a single layer of squamous epithelial cells called follicular cells. The primary oocyte together with its follicular cells is called a primordial follicle. There are about two million primordial follicles with their primary oocytes in the ovaries at birth suspended in the first division of meiosis.
As the female grows, primary oocytes begin to die and disappear with their follicular cells. This process continues until puberty when there are only about 400,000 primordial follicles left in the ovaries. The primary oocytes continue the process of oogenesis after puberty begins.[Source]
The total number of primary oocytes at birth is estimated to vary from 700,000 to2 million. During childhood most oocytes become atretic; only approximately400,000 are present by the beginning of puberty, and fewer than 500 will be ovulated.[Source]
Primary oocytes reach their maximum development at ~20[6] weeks of gestational age, when approximately seven million primary oocytes have been created; however, at birth, this number has already been reduced to approximately 1-2 million.Recently, however, two publications have challenged the belief that a finite number of oocytes are set around the time of birth.[Source]
In the human embryo, the thousand or so oogonia divide rapidly from the second to the seventh month of gestation to form roughly 7 million germ cells.[Source]
REFERENCES:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0008772
The following is multiple choice question (with options) to answer.
What does the triploid cell develop into during fertilization? | [
"membrane",
"zygote",
"endosperm",
"tubers"
] | C | Double Fertilization After pollen is deposited on the stigma, it must germinate and grow through the style to reach the ovule. The microspores, or the pollen, contain two cells: the pollen tube cell and the generative cell. The pollen tube cell grows into a pollen tube through which the generative cell travels. The germination of the pollen tube requires water, oxygen, and certain chemical signals. As it travels through the style to reach the embryo sac, the pollen tube’s growth is supported by the tissues of the style. In the meantime, if the generative cell has not already split into two cells, it now divides to form two sperm cells. The pollen tube is guided by the chemicals secreted by the synergids present in the embryo sac, and it enters the ovule sac through the micropyle. Of the two sperm cells, one sperm fertilizes the egg cell, forming a diploid zygote; the other sperm fuses with the two polar nuclei, forming a triploid cell that develops into the endosperm. Together, these two fertilization. |
SciQ | SciQ-4532 | mathematics, theory-of-everything, laws-of-physics
Title: What is fundamentally physically impossible? Mathematical logic defines quite clearly what is true or false in math, and also that some theorems are impossible to prove. This resulted in some clear definitions of axioms set like Peano, ZF or ZFC, which are proved (or strongly believed) to be consistent, i.e do not allow to demonstrate both a theorem and its negation.
In physics, the distinction between axioms, postulates, principles and laws isn't clear at all. Some laws are linked to others, however not by simple derivation. For example the first law of thermodynamics is related to conservation of energy, which in turn is equivalent to the invariance by time translation by by Noether's theorem, which means (to me) it depends on the (perfect) cosmological principle.
We consider as "impossible" anything that violates any of those laws or principles, but are some violations "more impossible" than others because some laws are "stronger"?
For example thermodynamics or energy conservation are definitely unquestionable at our scale, but since they're connected to the cosmological principle at large scale (which can be criticized), are we sure they're "absolutely true"?
Are we sure the principles of physics are consistent, or might we end up with contradictions between, say, Einstein's principles and quantum mechanics?
And do we have something approaching Gödel's theorem in physics to assert that some things that we observe (dark matter?) are impossible to describe with our current laws, but that we need some more?
Well, I realize my question is actually several. Please answer with just a link or book reference if you think I should just read more. This is a question of philosophy of science.
Some philosophers have held that generic principles, such as conservation laws, are more conventional than really true (neither true or false e.g. Wittgenstein viewed the principle of causality and perhaps all scientific laws as a 'fishnet' for apprehending reality. Something that does not follow the principle of causality, he assumed, is not thinkable which does not entail that this principle belongs to the world itself) Poincaré also held conventionalist thesis.
The following is multiple choice question (with options) to answer.
The law of conservation of matter, which says that matter cannot be created or this? | [
"destroyed",
"stopped",
"damaged",
"abandoned"
] | A | the law of conservation of matter, which says that matter cannot be created or destroyed. This means we must have the same number of protons and neutrons on both sides of the nuclear equation. If our uranium nucleus loses 2 protons, there are 90 protons remaining, identifying the element as thorium. Moreover, if we lose four nuclear particles of the original 235, there are 231 remaining. Thus we use subtraction to identify the isotope of the Th atom—in this case,. |
SciQ | SciQ-4533 | electromagnetism, electrostatics, electricity
Title: Why is the charge of an electron taken to be the negative of the charge of a proton and vice versa? Let us assume that all we know till now is that two types of charges exist. One of them is possessed by an elementary particle called an electron and the other by another elementary particle called a proton. We also know that the effect of a proton on another proton is the same as that of an electron on another electron in terms of the force of repulsion and an electron and proton also have a similar effect on each other other than the fact that they attract each other, and not repel.
Now, let us say that the charge of an electron is $1 \text{ e}$. Why do we take the charge of a proton as $-1 \text{ e}$ only based on the information that they have similar but opposite effects? Now, if we define the charge of a proton as $-1 \text{ e}$, the net charge of a body with $n_1$ electrons and $n_2$ protons becomes $n_1e+n_2(-e) = (n_1-n_2)e$. How do we know that the results obtained from these mathematical operations will be what the actual effects will be?
I don't know if I was able to express my question properly. I'm finding it hard to express what I have in mind. Please let me know if it is not clear, I will try my best to improve it.
Thanks! I think your question is a little unclear, so let me know if I've misunderstood what you were asking.
If your question is about how we know that the electron and the proton have the same magnitude but opposite signs, it's simple (at least in theory): create a Hydrogen atom. It has one proton and one electron, and it's neutral overall, meaning it has a net charge of zero. Since charges simply add up, the proton and the electron must have opposite charges.
On the other hand, if your question is about why one of them is "called" negative and the other positive, I refer you to E.M. Purcell's excellent text. From Chapter 1.1 (Electric Charge):
The following is multiple choice question (with options) to answer.
Which particle of an atom has a positive electric charge? | [
"proton",
"nutron",
"electron",
"nucleus"
] | A | A proton is a particle in the nucleus of an atom that has a positive electric charge. All protons are identical. It is the number of protons that gives atoms of different elements their unique properties. Atoms of each type of element have a characteristic number of protons. For example, each atom of carbon has six protons, as you can see in Figure below . No two elements have atoms with the same number of protons. |
SciQ | SciQ-4534 | kinetics, temperature
So if you have a system which can undergo first-order and second order reactions (for example, a molecule which has ) and choose your reactant such such that the first order reaction has a more favorable enthalpy and a less favorable entropy than the second order reaction (or vice versa), there will be a temperature where the thermodynamically favored product will go from that of the first-order reaction to that of the second order reaction. Whether this would be enough to manifest itself as an appreciable difference in product depends on the particular numbers.
While we're on the discussion, there is another technique related to controlling product outcome, that exploits the balance between the two factors already discussed. That's using thermodynamic versus kinetic reaction control. In this setup, you have one reaction which provides a more stable product, but due to things like steric hindrance the reaction rate is lower. The other product forms faster, but the product is less stable. If you set up reaction conditions such as short reaction times at high temperature where the speed of the reaction is the dominant factor, the faster-made "kinetically controlled" product dominates. However, if you use conditions such as long reaction times at low temperatures, where the stability of the products is the dominant factor, the more stable "thermodynamicly controlled" product dominates.
The following is multiple choice question (with options) to answer.
How is a reaction described when the given conditions favor formation of products? | [
"instantaneous",
"planned",
"spontaneous",
"fluctuations"
] | C | Chemists want to be able to predict the outcome of reactions. They would like it to be possible to predict what will happen when reactants are added together under a given set of conditions. The conditions of a reaction might include things like temperature, pressure, and concentrations of various reaction components. If the given conditions favor the formation of products, the reaction is said to be spontaneous . |
SciQ | SciQ-4535 | electrostatics, electric-fields, potential, dipole, multipole-expansion
Title: Why does the electric field in a dipole cancel out at distances much larger than the separation of the two charges forming a dipole ($r \gg 2a$)? The electric field of the electric dipole is not zero. Since the charge $q$ and $–q$ are separated by some distance, the electric fields due to them, when added, do not exactly cancel out.
However, why do the fields due to $q$ and $–q$ cancel out at distances much larger than the separation of the two charges forming a dipole ($r \gg 2a$)? The total electric field is a sum of two fields: $${\bf{E}}({\bf{r}}_1)+{\bf{E}}({\bf{r}}_2)\propto q\left(\frac{1}{r_1^2}-\frac{1}{r_2^2}\right)=q\frac{\left(r_2^2-r_1^2\right)}{r_1^2r_2^2}\approx q\frac{a}{r^3},\;\;$$
Note : $${r_1\approx r_2}$$
$$({r_2^2-r_1^2})=({r_2+r_1})(r_2-r_1)=2r $$
At large distances the denominator is much larger than the numerator; that is why the total field is much less than that from one charge $\propto 1/r^2$ by the factor $a/r\ll 1$.
The following is multiple choice question (with options) to answer.
What does an electric field surround? | [
"a charged particle",
"negative particle",
"charged ions",
"neutral particles"
] | A | An electric field is a space surrounding a charged particle where the particle exerts electric force. |
SciQ | SciQ-4536 | food, nutrition, energy-metabolism
Title: What are the bare minimum nutrients required to survive as a human? I am trying to determine the bare minimum nutritional requirements to survive as a human, ignoring energy (caloric) requirements. Another way to ask this question is: What elements can humans not live without? I am not inquiring solely about what nutrients are needed, but also their approximate amounts.
Imagine pills that a person can take that covers all their base nutritional needs and that after taking this pill the person can eat whatever they want to meet their caloric requirements. Hypothetically, this pill could have some amount (how much?) fat, carbohydrates, protein, fiber, minerals, and vitamins, and the person could subsequently eat any other food to meet their caloric requirements knowing their nutritional needs would already be otherwise met. Lets ignore the possibility of the person suffering from health issues due to eating too much of any specific food to meet their caloric requirements (e.g., taking the magic pills and then eating only butter).
A person in this situation could think "Ok I've got most of my bases covered, now I just need to ingest another 1000 calories of (almost) anything I want).
What nutrients are absolutely necessary for humans to survive indefinitely, and how much of these nutrients are required?
I am hoping for a complete list with approximate amounts (e.g., 20g fat, 20g carbohydrates, 1mg Vitamin X, .05mg Vitamin Y, 10mg mineral X). Essential nutrients include (NutrientsReview):
Water
9 amino acids: histidine, isoleucine, leucine, lysine, methionine,
phenylalanine, tryptophan, threonine, valine
2 fatty acids (alpha linolenic and linoleic acid)
Vitamins: A, B1, B2, B3, B5, B6, folic acid, biotin, B12, C,
D, E and K (and choline, which is considered a vitamin-like substance)
Minerals: calcium, chromium, chloride, copper, iodine, iron,
manganese, molybdenum, phosphorus, potassium, selenium, sodium, zinc
The following is multiple choice question (with options) to answer.
Lack of what mineral causes rickets? | [
"potassium",
"zinc",
"calcium",
"magnesium"
] | C | Rickets is softening of the bones in children that occurs because bones do not have enough calcium. Rickets can lead to fractures and bowing of the leg bones, which is illustrated in the Figure below . |
SciQ | SciQ-4537 | newtonian-mechanics, energy, work, definition
Note that I wrote "the amount of a body's kinetic energy" rather than just "a body's kinetic energy". To say that the work done on the body (even with my amendments above) is the kinetic energy that it acquires doesn't give you much of an idea as to what kinetic energy IS. Your (2) gives you a better idea.
The following is multiple choice question (with options) to answer.
What do we call the energy of motion? | [
"binary energy",
"kinetic energy",
"electromagnetic energy",
"harmonic energy"
] | B | The energy of motion is called kinetic energy. |
SciQ | SciQ-4538 | quantum-mechanics, electromagnetism, electromagnetic-radiation
Thus one can imagine such a scenario, but can never actually do it except over some finite area. You can actually see such calm areas if you have a nice water table with two sources of waves operating in synch; you can also sometimes see it in nature.
The following is multiple choice question (with options) to answer.
Earthquakes and visible light are examples of what? | [
"geological phenomena",
"currents",
"winds",
"waves"
] | D | Introduction to Oscillatory Motion and Waves What do an ocean buoy, a child in a swing, the cone inside a speaker, a guitar, atoms in a crystal, the motion of chest cavities, and the beating of hearts all have in common? They all oscillate—-that is, they move back and forth between two points. Many systems oscillate, and they have certain characteristics in common. All oscillations involve force and energy. You push a child in a swing to get the motion started. The energy of atoms vibrating in a crystal can be increased with heat. You put energy into a guitar string when you pluck it. Some oscillations create waves. A guitar creates sound waves. You can make water waves in a swimming pool by slapping the water with your hand. You can no doubt think of other types of waves. Some, such as water waves, are visible. Some, such as sound waves, are not. But every wave is a disturbance that moves from its source and carries energy. Other examples of waves include earthquakes and visible light. Even subatomic particles, such as electrons, can behave like waves. By studying oscillatory motion and waves, we shall find that a small number of underlying principles describe all of them and that wave phenomena are more common than you have ever imagined. We begin by studying the type of force that underlies the simplest oscillations and waves. We will then expand our exploration of oscillatory motion and waves to include concepts such as simple harmonic motion, uniform circular motion, and damped harmonic motion. Finally, we will explore what happens when two or more waves share the same space, in the phenomena known as superposition and interference. |
SciQ | SciQ-4539 | human-biology, breathing
Our lungs work off of pressure. Specifically our lungs inflate by using "negative pressure" (a word I've always hated). The pressure is not actually negative it is simply lower than the surroundings. Since there is less air in your lungs the air from the atmosphere rushes in because the pressure is higher outside your lungs. This is Boyle's Law (not the pressure outside being higher, but what happens when your lungs expand). Where an increase in Volume means a decrease in Pressure (if all else remains unchanged). In fact plants pull water up using negative pressure.
However to push out the air from our lungs we supply pressure using our muscles that overcomes the outside pressure and forces the air out.
The reason you feel your breathing change is because when that train passes by you correctly observed the strong gust of wind. This gust of wind has some force behind it that normally is not in the air you are breathing from the atmosphere. It has more force which increases the air's velocity. This actually decreases the pressure, but there's no need to get into that here (Bernoulli's).
The reason it feels like your body is "fighting to breath" is because the air is traveling in a direction with some force that you need to overcome by opening up your lungs just enough to "suck" the air in with negative pressure. This is more than the pressure you usually need to produce in order to breath in air that is "still".
What is funny to think about is we don't really have a muscle that "pulls" air in, even though it feels like you are actively doing that. The air actually rushes in on its own. All you do is expand your rib cage, which your lungs are attached to (look up on how, it's actually pretty cool), thereby making inhalation occur.
Now an interesting question for you to ask yourself is why is cold air harder to breathe?
The following is multiple choice question (with options) to answer.
There is always a slightly negative pressure within what cavity, helping keep the airways of the lungs open? | [
"thoracic",
"cervical",
"anal",
"spinal"
] | A | There is always a slightly negative pressure within the thoracic cavity, which aids in keeping the airways of the lungs open. During inhalation, volume increases as a result of contraction of the diaphragm, and pressure decreases (according to Boyle’s Law). This decrease of pressure in the thoracic cavity relative to the environment makes the cavity less than the atmosphere (Figure 39.16a). Because of this drop in pressure, air rushes into the respiratory passages. To increase the volume of the lungs, the chest wall expands. This results from the contraction of the intercostal muscles, the muscles that are connected to the rib cage. Lung volume expands because the diaphragm contracts and the intercostals muscles contract, thus expanding the thoracic cavity. This increase in the volume of the thoracic cavity lowers pressure compared to the atmosphere, so air rushes into the lungs, thus increasing its volume. The resulting increase in volume is largely attributed to an increase in alveolar space, because the bronchioles and bronchi are stiff structures that do not change in size. |
SciQ | SciQ-4540 | homework-and-exercises, fluid-dynamics
Title: Hydrostatics: Log floating in water near a dam So I am studying for a final and can't seem to solve this. There is a log floating in water and I need to find its weight. The question I have is what parts of the volume of the log count when summing the forces in the Y axis.
What i have now for AREA alone is $r^2 - .25\pi r^2$ pushes down
and $.5\pi r^2 + r^2$ pushes up. however this does not take into account the air above the log in the upper right quadrant. is the force pushing up taking into account the half circle below the water and also the $2r^2$ above the horizontal of the log?
The actual question for this image says:
A log is stuck against a dam as shown in the diagram. given the radius of the log of 1.4 m and the length of the log into the page, 10 m find the weight of the log in kN. There are two possibilities.
Water is not leaking up between the log and the dam and flowing over the dam. In this case, the pressure on the bottom of the log depends only on the depth, and the amount of force needed to balance the water is the same as the weight of a log with the density of water, with an extra corner added; i.e., the red area in the crude picture below. This would be the weight of water in a volume $L(\frac{3}{4} \!\pi R^2 + R^2)$, where $L$ is the length of the log and $R$ is the radius of the log. (I expect this was not the way that your teacher intended you to solve the problem. Also note that this log is denser than water, which means that it is very difficult to see how it could have reached this position.)
Water is leaking, and flowing up between the log and the dam. In this case, you have a very complicated problem in hydrodynamics which you cannot solve without more information.
,
The following is multiple choice question (with options) to answer.
What property allows cut logs to float on water? | [
"precipitation",
"polarity",
"density",
"heat"
] | C | After trees are cut, logging companies often move these materials down a river to a sawmill where they can be shaped into building materials or other products. The logs float on the water because they are less dense than the water they are in. Knowledge of density is important in the characterization and separation of materials. Information about density allows us to make predictions about the behavior of matter. |
SciQ | SciQ-4541 | condensed-matter
Title: Bravais lattice with sublattices : why multiple bands? I have a very naive question : given a tight-binding model (with nearest-neighbor hoping) on a lattice defined by a Bravais lattice with a number of sublattices (for instance the honeycomb lattice is a triangular lattice with two sublattices), why is there a band associated with each sublattice ? For instance when a lattice is defined by a Bravais lattice with a 2 sublattice basis, the tight-binding model will have 2 bands.. But why is that ? There must be something very simple that I am not getting here... is it just because that to define a band structure, you need some translation invariance ? Think of a tight binding model without hopping. This situation would even be accurate for a bulk where the distance between atoms is very large. What do we have in this situation when we look at the energys of the atoms?
For simplicity lets only look at the s-orbitals and 2 sublattices A and B (= 2 Atoms in the unit cell) - you would find 2 different discrete energies:
The energy of a s-orbital of the type A and the energy of a s-orbital of the type B. You only have to look into the unit cell to get that. And since the unit cell has 2 atoms in it there are two energys. If you would include p-orbitals, you would add 3 p-energies of the A type and 3 of the B type and so on...
Now "turn on" the hopping (doesn't matter how much neighbors you include). The interaction between the atoms now forms the bands, which means that the energies we have talked about previousely smear to the bands. So the actual number of bands equals the number of discrete energys you would have without interaction.
Another way to look at it would be the Hamiltonmatrix, of which the eigenenvalues are the energies we look for:
The following is multiple choice question (with options) to answer.
Different interatomic distances produce different lattice what? | [
"weights",
"surfaces",
"energies",
"qualities"
] | C | in which C is a constant that depends on the type of crystal structure; Z+ and Z– are the charges on the ions; and Ro is the interionic distance (the sum of the radii of the positive and negative ions). Thus, the lattice energy of an ionic crystal increases rapidly as the charges of the ions increase and the sizes of the ions decrease. When all other parameters are kept constant, doubling the charge of both the cation and anion quadruples the lattice energy. For example, the lattice energy of LiF (Z+ and Z– = 1) is 1023 kJ/mol, whereas that of MgO (Z+ and Z– = 2) is 3900 kJ/ mol (Ro is nearly the same—about 200 pm for both compounds). Different interatomic distances produce different lattice energies. For example, we can compare the lattice energy of MgF2 (2957 kJ/mol) to that of MgI2 (2327 kJ/mol) to observe the effect on lattice energy of the smaller ionic size of F– as compared to I–. |
SciQ | SciQ-4542 | blood-circulation, kidney
Title: Why does glomerulus don't allow white blood cells to leave? The glomerulus in nephrons are just a ball of capillaries, so why can't it allow the white blood cells to squeeze though the epithelial cells into Bowman's capsule just like the formation of tissue fluid in other capillaries by filtration? Red blood cells, White blood cells, platelets and proteins with large molecular weight cannot pass through the podocyte and fenestrations in glomerular capillary, but small molecules like water, salts and sugars are filtered out as part of urine.
As these cells and proteins are large to cross through this filter, they remain in the capillary and create osmotic pressure within the capillary. Bowman’s space has osmotic pressure approximately zero. So, only hydrostatic pressure works in this state and help in movement of fluid across the capillary wall.
Via: https://opentextbc.ca/anatomyandphysiology/chapter/25-5-physiology-of-urine-formation/
The following is multiple choice question (with options) to answer.
What organs filter blood and form urine? | [
"the appendix",
"the spleen",
"the kidneys",
"the liver"
] | C | The kidneys filter blood and form urine. They are part of the urinary system, which also includes the ureters, bladder, and urethra. |
SciQ | SciQ-4543 | geophysics, earthquakes, plate-tectonics, geography
Title: Why is the Ring of Fire there? The Ring of Fire goes through the places that have the most earthquakes. Why is the Ring of Fire there, not somewhere else?
Any help would be appreciated! This question is very similar to: Why does the "Ring of Fire" pretty much define "Pacific Rim"
The high levels of volcanoes and earthquakes are primarily due to subduction. So why is the Pacific surrounded by subduction zones?
Think back to Pangaea. This was a supercontinent that formed in the late Palaeozoic. Virtually all of the Earth's land masses were concentrated in one large supercontinent. When this broke up, the new continents moved away from each other. Fast forward 200Ma or so, and you find that the continents have moved so far apart that they are now converging on a point on the other side of the planet - the continents are moving towards each other! Hence the remains of the super ocean (which was actually multiple ocean plates - today's Pacific & Nazca plates, plus the Farrallon plate (RIP),etc ) is shrinking as the continental plates move towards it. This destruction of the ocean plate(s) occurs at subduction zones.
This is a big picture generalisation. Not all of the Pacific's boundaries are marked with subduction zones (e.g. North America has two large strike slip systems + a new spreading ridge). Also, not all of the continents are converging on each other. Africa is doing a pirouette, India is moving northwards, etc.
The following is multiple choice question (with options) to answer.
A chain of what structures form as an oceanic plate moves over a hotspot? | [
"ridges",
"earthquakes",
"outcrops",
"volcanoes"
] | D | A chain of volcanoes form as an oceanic plate moves over a hotspot. This is how it happens. A volcano forms over the hotspot. Since the plate is moving, the volcano moves off of the hotspot. When the hotspot erupts again, a new volcano forms over it. This volcano is next to the first. Over time, there is a line of volcanoes. The youngest is directly above the hotspot. The oldest is the farthest away ( Figure below ). |
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