source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-7044 | gene-expression, ebola, gene
Title: Why we do not use RNAi to control ebola? As you know using RNAi we are able to prevent gene expression. so why we do not use it to stop viral genes expression? Delivering siRNA in vivo is a difficult prospect, but has been overcome in research environments and several commercial in vivo solutions are on the market see examples from Life Technologies here.
The bigger problems come from potential off-target effects. siRNA tend to be double stranded and both the 'guide' and 'passenger' strand can occasionally target multiple sequences that you did not intend. Additionally, siRNA tend to activate the body's immune system in ways that would inhibit therapy or cause excess inflammation and cell death. See the detailed review here.
In short, it is a good idea, and the current research in the field is working to overcome technical challenges, but we are not there yet.
The following is multiple choice question (with options) to answer.
What is used as a vector for gene insertion in ex vivo gene therapy? | [
"bacteria",
"typhus",
"virus",
"penicillin"
] | C | In ex vivo gene therapy, done outside the body, cells are removed from the patient and the proper gene is inserted using a virus as a vector. The modified cells are placed back into the patient. |
SciQ | SciQ-7045 | human-biology, immunology
Title: Why doesn't our immune system react to infused antibodies produced in a horse? Calmette tried injecting horses with snake venom and then taking out the serum which has produced antibodies against the venom and injecting in the snake-bitten human.
Shouldn't our immune system recognize this exogenous protein and try to eliminate it as it's a non-self protein? Our immune system does react to horse antibodies, but as with any adaptive immune response it takes some time for the response to develop. In the weeks before our immune response fully responds to the horse antibodies, the infused antibodies can have their effect.
If you then have a second infusion of horse antibodies, the immune response would not only prevent them from having their beneficial effect, but it might case serious adverse effects. This serum sickness (Wikipedia link) has been known for over a century; here is a paper from 1918 discussing it as a well-known issue:
The injection of horse serum either in small or in large amounts in human beings is always followed sooner or later by the development of hypersensitiveness of the skin to subsequent injections of horse serum. For the development of this reaction serum disease is not essential.
--THE RELATION OF CIRCULATING ANTIBODIES TO SERUM DISEASE. J. Exp. Med. Published March 1, 1918
Although there aren't many modern situations in which horse (or other non-human species) serum is injected into humans, when it is (as with anti-venom, which is generally produced in non-human animals) serum sickness is still a concern.
Serum sickness is a delayed immune reaction resulting from the injection of foreign protein or serum. Antivenom is known to cause serum sickness but the incidence and characteristics are poorly defined. ... The primary outcome was the proportion with serum sickness, pre-defined as three or more of: fever, erythematous rash/urticaria, myalgia/arthralgia, headache, malaise, nausea/vomiting 5–20 days post-antivenom.
--Incidence of serum sickness after the administration of Australian snake antivenom (ASP-22). Clinical Toxicology. Published 2016
The following is multiple choice question (with options) to answer.
In artificial passive immunization, which items from an immune animal are injected into a nonimmune animal? | [
"allergies",
"antibodies",
"platelets",
"parasites"
] | B | |
SciQ | SciQ-7046 | redox, combustion, carbohydrates
Title: Why do gummy bears explode when added to hot potassium chlorate? This link shows that a gummy bear explodes when in contact with heated potassium chlorate, $\ce{KClO3}$. But what in a gummy bear creates this reaction?
Also, do other foods (fruit, icing sugar...) react as violently with potassium chlorate? Potassium chlorate is a source of oxygen. After heating, it decomposes to $\ce{O2}$ and $\ce{KCl}$:
$$\ce{4 KClO3 → KCl + 3 KClO4}$$
$$\ce{KClO4 → KCl + 2O2}$$
The gummy bear is mainly composed of sugar and other carbohydrates. Those carbohydrates will react with oxygen, combustion occurs. For example, glucose will react in this manner:
$$\ce{6O2 + C6H12O6 -> 6CO2 + 6H2O}$$
If there is any material present which does not burn, such as $\ce{H2O}$, the temperature will not rise as high. For gummy bears the reaction works spectacularly because they are mainly carbohydrates (>70%).
An apple, for example, has only ~13% carbohydrates – unless you dry it, of course. On the other hand, this video on YouTube is an example of how sugar itself reacts violently with potassium chlorate.
The following is multiple choice question (with options) to answer.
What kind of solids are gummi bears or taffy? | [
"amorphous solids",
"phenomena solids",
"imperative solids",
"candy solids"
] | A | Some types of candy, such as gummi bears or taffy, are amorphous solids. Table salt has a crystalline geometry. |
SciQ | SciQ-7047 | species-identification
Title: Identification of a lifeform There's a video I found on Facebook and I'm unable to figure out what the creature featured happens to be.
Adding images that have been taken from the video itself, apologies in advance since they're not high qualify images.
Can anybody shed any light on what it is?
The video was shot near Ratan Babu Ghat which is situated along the bank of Hooghly river, Kolkata, West Bengal, India. Here to be precise. This is a polyclad flatworm.
Here is a video of notoplana vitrea moving similarly to the one in the video that you linked:
https://www.asturnatura.com/especie/notoplana-vitrea.html
Here is a gallery of polyclad flatworms observed in India:
https://inaturalist.ca/observations?place_id=6681&subview=grid&taxon_id=52318
A number of the images in this gallery look similar to the one in your video, but very few of them are identified beyond this order taxon of polyclad flatworm.
The following is multiple choice question (with options) to answer.
In the freshwater flatworms, protonephridia serve chiefly in what? | [
"excretion",
"enculturation",
"thermoregulation",
"osmoregulation"
] | D | |
SciQ | SciQ-7048 | physiology, herpetology, poison, amphibians
+
0.002 mg/L will fatally damage the sensitive skin on tadpoles, frogs, salamanders and other amphibians.
another source:
Free chlorine (Cl2) is a greenish gas that is well known for its
highly toxic properties as can be attested to by the thousands of
soldiers that died and were severely injured from chlorine exposure
during World War I. In water, chlorine is the most toxic substance
that we will discuss. Ironically for the amphibian keeper, it is this
toxic nature of chlorine and its ability to denature proteins, which
makes its encounter inevitable. Chlorine is generally used as an
antibacterial agent in municipal water supplies and may be present in
concentrations of over 9 mg/1 in some tap water (measured in Houston,
Texas as an example, although levels were generally lower). The
concentration of chlorine in municipal water supplies can vary greatly
from day to day, or even hour to hour, depending on conditions at the
water treatment facilities. Concentrations as low as 0.0034 mg/1 have
been noted to reduce reproduction in fathead minnows with 72 hour
LC100 (lethal concentration for 100% kill) at 0.15 mg/1 (Arthur and
Eaton,1971). LC50 (96 hour) for the shiners (Notemigonus chrysoleucas)
was as low as 0.19 mg/1 (Esvelt et al., 1971). The concentrations
found in municipal water supplies are many times greater than the
minimum lethal concentrations for many aquatic life forms.
Thus, the well being of the frog in the water of the swimming pool depends on the time the frog spends in the water. Eventually, with extended exposure the chlorine concentration will exceed the one compatible will life and the frog will die. This time is multifactorial variable, thus cannot be assessed easily - the weight and the skin surface area and skin permeability will affect the frog survival in a great degree.
The following is multiple choice question (with options) to answer.
What is contained in the skin of brightly colored poison dart frogs? | [
"poison",
"acid",
"spores",
"toxins"
] | D | Adrian Pingstone (Wikimedia: Arpingstone). Brightly colored poison dart frogs have toxins in their skin . Public Domain. |
SciQ | SciQ-7049 | prokaryotes
Title: Are chromosomal and plasmid DNA in the nucleoid? I know plasmid DNA is not part of the chromosome, according to my textbook, but can you still class it as being part of the nucleoid?
Also is chromosomal DNA in the nucleoid? "Nucleoid" (literally means nucleus-like), is a quite old term for "bacterial chromosome" (Better to write prokaryotic chromosome since in both type of prokaryotes i.e. Archaea (former archaebacteria) and bacteria (former eubacteria) the structure is similar).
Nucleoid structurally normally excludes the plasmid-DNA (the plasmid DNA is like additional or accessory). However sometimes a plasmid DNA could go through recombination with prokaryotic chromosome 's DNA (As seen in Hfr strain of Escherichia coli)
"Chromosome" in very brief means a structure made of DNA + Protein. In case of "bacterial-chromosome", it contains both DNA and Protein; and if you take away the protein from bacterial chromosome; what you get, is the chromosomal DNA.
Reference:
Microbiology / Pelczar, Chan and Noel/ Edition-5;
Part 2: Bactria,
Chapter 5 (Morphology and fine structure of bacteria)
"Because it is not discrete nucleus, this nebulous structure has been designated by such terms as the nucleoid , the chromatin body, the nuclear equivalent, even the bacterial chromosome"
General Microbiology / Hans G. Schlegel / Edition-7:
Chapter-2 ; The cell and its structure:
2.2 The prokaryotic cell (protocyte) -> 2.2.1: The bacterial 'nucleus'
" Plasmids : In addition to chromosomal DNA, many bacteria contain extrachromosomal DNA in closed, circular, double stranded form. These autonomously replicating DNA elements are called plasmids. Linear plasmids have been found in some bacteria"
The following is multiple choice question (with options) to answer.
What is the exchange of plasmids by prokaryotes called? | [
"genetic transfer",
"biochemical transfer",
"transcription",
"artificial transfer"
] | A | For natural selection to take place, organisms must vary in their traits. Asexual reproduction results in offspring that are all the same. They are also identical to the parent cell. So how can prokaryotes increase genetic variation? They can exchange plasmids. This is called genetic transfer . It may happen by direct contact between cells. Or a "bridge" may form between cells. Genetic transfer mixes the genes of different cells. It creates new combinations of alleles. |
SciQ | SciQ-7050 | geology, rocks, sedimentology, geomorphology, terminology
Title: What do you call boulders of non sedimentary rock that were lithified into sandstone? I'm convinced there is a word for this. I was in the Hoodoos at Writing on Stone this weekend and kept noticing what looked like reddish quartzite boulders laying around in the sand, or sometimes sticking partially out of the hoodoos.
When a non-sedimentary rock gets washed out into silt which later lithifies, what's it called? It's kind of like a conglomerate, except there's only a couple of really big rocks, which eventually fall out out the rock because all the sandstone around them eroded away. The technical term for a sedimentary rock that has a lithified fine-grained sediment with larger pieces of rocks suspended in it upon lithification is a conglomerate. The fine-grained interstitial part is called the matrix, and the large pieces suspended in it are called clasts. Clasts can range from gravel- to boulder-size. These are technical terms used by sedimentologists.
It is tempting to refer to these fragments as xenoliths but as that word has a very specific meaning in igneous petrology, it is best to avoid it to remove any confusion.
The following is multiple choice question (with options) to answer.
What do we call the study of rock layers? | [
"geology",
"mineralogy",
"stratigraphy",
"sedimentary"
] | C | The study of rock layers is called stratigraphy. Laws of stratigraphy help scientists determine the relative ages of rocks. The main law is the law of superposition. This law states that deeper rock layers are older than layers closer to the surface. |
SciQ | SciQ-7051 | cell-biology
Title: Are there human cells, apart from red blood cells and platelets, without a nucleus? I know that blood platelets and erythrocytes do not have a nucleus. Are there more cells in the human body without a nucleus, such as pancreas, cartilage, or lung cells? Short answer
As far as I know, red blood cells and blood platelets are the only human cells in our body without a nucleus.
Background
Erythrocytes and thrombocytes are the only human cells without a nucleus, as far as I know. However, if you count the gut as being part of the human body (in essence it is a continuation of the skin and as such it can be considered to be on our outside), then we are loaded with cells lacking a nucleus, namely all the bacteria that live in our intestines such as E. coli. Bacteria, being prokaryotes, lack a nucleus. In fact, there are ten times more bacteria than human cells in our gut (Wenner, 2007).
Reference
Wenner, Sci Am 2007
The following is multiple choice question (with options) to answer.
What are single-celled organisms that lack a nucleus called? | [
"eukaryotes",
"prokaryotes",
"protists",
"fungi"
] | B | Prokaryotes are single-celled organisms that lack a nucleus. They are placed in two domains: the Bacteria Domain and the Archaea Domain. They were the first organisms to evolve. It's not certain how they are related to each other or to eukaryotes. |
SciQ | SciQ-7052 | time, astronomy
Title: How to measure the age of light? We measure distances in universe by the units of light year/s or parsec. Which means distance traveled by light in one year equals one light year. Thus the lights we receive from the distant stars or galaxies are coming from many light years away.
So how do we know the age of the light so that we determine the distance it has traveled to reach earth? We actually measure the distance, and infer the age of the light from the distance. There are many answers on the site discussing how cosmological distances are measured.
The following is multiple choice question (with options) to answer.
The distance that light can travel in a year is known as what? | [
"solar year",
"beam year",
"earth year",
"light year"
] | D | Most of the stars pictured in this view of the night sky are hundreds of light years from Earth. A light year is the distance that light can travel in a year, or about 6 trillion (6,000,000,000,000) miles. As this example shows, quantities in science may be very large. Many other quantities in science are very small. Both very large and very small numbers have many zeroes, so they are hard to read and write without making mistakes. That’s where scientific notation comes in. |
SciQ | SciQ-7053 | paleontology
Title: How to start studying dinosaurs and pre-historic mammals/sea creatures I'm kind new to this hole thing of dinosaurs that I'm really interested in, are there any good books/websites/webpages to study the biology of pre-historic creatures? Dinosaurs, mammals, fishes, anything that is not alive anymore. Also, any good books about the history of how these species evolved and the history behind them would be appreciated. Here's what it takes to really study this: you need to go through the whole bachelor program for geoscientists, that includes fundamental geodynamics like plate tectonics, magmatism, volcanism, volcanic and metamorphic rocks and generally the cycles that make up earth's internal dynamics.
Then there is the huge field of external factors, like sediment geology (that's really complicated stuff), weathering and transport and how soils come to being, diagenesis and the structures sediments can form and their classifications. Role of the ocean (that's where it starts, before all) and the atmosphere, of course.
When through that, usually 4 semesters or so, you can start to specialize. For paleontolgy you need knowledge of earth history, of course, it's subdivision, and the conditions at certain times as far as they are known. Once that's done, then comes real paleontology: Animals (invertebrates and vertebrates), plants, and their development, biological evolution (that's frequently underrated, I find), taphonomy, ... For a sturdy base count another 2-4 semesters.
You may see that even a bunch of websites, maybe all of them together, cannot replace actual study. I am not aware of any site that even gives a reasonable overview of the field. Geoscience, and thus paleontology, touch many fields of natural science.
That said, when asked "How to learn about animal paleontology ?" I allways mention Micheal Benton, Vertebrate Paleontology. It needs a basic understanding of geoscience, evolution and skeleton anatomy. Functional morphology, phylogeny and an overview over sediment geology and earth history also won't harm, but you could give it a try. Some things are explained in between.
The following is multiple choice question (with options) to answer.
Scientists who find and study fossils are called what? | [
"paleontologists",
"geologists",
"anthropologist",
"biologists"
] | A | Fossils are a window into the past. They provide clear evidence that evolution has occurred. Scientists who find and study fossils are called paleontologists . How do they use fossils to understand the past? Consider the example of the horse, shown in Figure below . The fossil record shows how the horse evolved. |
SciQ | SciQ-7054 | human-biology, circadian-rhythms, digestive-system
Title: What influences the timing of human bowel movements in the morning? I'm trying to understand if the timing of human bowel movements in the morning is associated with the circadian rhythm, and can thus be used to make predictions about the circadian rhythm.
What influences the timing of bowel movements? Is it the timing of meals, caffeine intake or is it a biologically programmed time?
Thank you! The bowel movements are influenced by a lot of factors. For example, when you eat a meal it induces a movement in your large intestines, to defecate and clear up space for new food.
Also, there is MMC, migrating motor complex, which is responsible for the bowel movements when you are fasting. It causes a flushing effect, which prevents bacteria to overproduce in intestines.
So, the daily bowel movements are mainly influenced by the timing and content of the food that you eat. But as I said there are many other factors. The gastrointestinal system has a very complex nervous system. Even psychological factors can effect the bowel movements greatly, for example extreme physical pain may induce the symphatetic system and cause constipation.
Also caffeine may affect it, like many drugs do.
The following is multiple choice question (with options) to answer.
What is it called when feces move along the colon too slowly? | [
"respiratory",
"diarrhea",
"constipation",
"relaxation"
] | C | |
SciQ | SciQ-7055 | thermodynamics, atoms, phase-transition
But let's look at how the states change. In a solid, you have a bunch of atoms that can be thought of as masses connected by springs. As heat is added to the system, the atoms begin to vibrate in the lattice of springs. As more heat is added, they vibrate enough to break the springs. This is when the solid begins to melt and turn to a liquid.
Now you have a liquid where the atoms are all moving around but they aren't free to move wherever they want. More heat is added to the system and the atoms begin to translate faster and faster. Eventually they translate fast enough to overcome the forces that are holding them together in a liquid. Now they fly free and are a gas.
So ultimately, heat is energy that makes atoms and molecules move in some way. They may translate, rotate, vibrate, or the electrons may begin moving around depending on how much heat is there and what configuration the molecule has.
The following is multiple choice question (with options) to answer.
What is the process in which a solid changes directly to a gas called? | [
"solidification",
"vaporization",
"condensation",
"sublimation"
] | D | The process in which a solid changes directly to a gas is called sublimation . It occurs when the particles of a solid absorb enough energy to completely overcome the force of attraction between them. Dry ice (solid carbon dioxide, CO 2 ) is an example of a solid that undergoes sublimation. Figure below shows a chunk of dry ice changing directly to carbon dioxide gas. Sometimes snow undergoes sublimation as well. This is most likely to occur on sunny winter days when the air is very dry. What gas does snow become?. |
SciQ | SciQ-7056 | geothermal-heat
Title: What Keeps the Earth Cooking? If radioactive decay supplies only about half the Earth’s heat, what are the remaining sources of heat?
If radioactive decay supplies only about half the Earth’s heat, what are the remaining sources of heat?
Mostly it is residual heat energy from when the Earth was very young. The biggest source came from the kinetic energy of all the bodies, big and small, that collided to form the Earth being converted to heat. The differentiation of the Earth added even more heat energy to the Earth.
In addition to radioactive decay, the on-going freezing of the outer core material onto to the inner core adds a bit more heat to the system, but neither one compensates for heat transported through the mantle and crust and then out into space. Note that this heating from below is but a tiny portion of the overall energy budget for the Earth's surface.
Even the Earth's surface was very hot shortly after the formation and differentiation of the Earth. While the surface cooled quickly (geologically speaking), the interior has not. The key reason is that 2,890 km of rock makes for a fairly thick blanket.
The following is multiple choice question (with options) to answer.
What part of the atmosphere is the heat source? | [
"magnetosphere",
"ionosphere",
"stratosphere",
"troposphere"
] | C | Temperature decreases in the mesosphere with altitude. This is because the heat source is the stratosphere. |
SciQ | SciQ-7057 | evolution, natural-selection, population-dynamics, adaptation
Title: Genetic Diversity and Adaptation I am somewhat new to evolutionary biology, having studied it on my free time as a computer science student. There is one particular thing that has always bothered me for which I have not seen a good treatment, relating to adaptations to the environment with respect to genetic diversity. If it is possible for a population to adapt to rapid environmental changes, and they don't have an adaptation for dealing with change directly (such as a complex brain), it seems to me that every generation must have present within them almost every possible environmental adaptation that the population is capable of expressing (including many irrelevant ones and a few relevant to the particular environmental challenge). Otherwise, it may take too many generations to deal with a change, which may be disastrous for the population.
So my question would be: how does an evolutionary biologist explain the mechanics behind the ability for a population to adapt quickly? Are most environmental changes slow or gradual enough that the population has a few generations to happen upon the mutations that will allow it to survive, and have generally been successful in this regard for 3.5 billion years? Or, are a large majority of possible adaptations present in almost every generation, and just serve no purpose or advantage for most of the population if the provided "benefit" is unneeded (i.e., are effectively neutral)? Or something in between? It is a good question. The question is hard to answer though because
The answer is not completely resolved
There are many influential parameters hidden behind this question.
Your question, as I understand it, can be formulated as
Do natural populations have enough genetic variance to directly respond to an environmental change or do they have to wait for this variance to be created through mutations?
To address this question, I will have to assume you have some intermediate level of knowledge in evolutionary biology.
How do we call these two alternatives?
Adaptation can occur through selection on:
Standing genetic variance
De novo mutations
How can we tell them apart?
This section is mainly inspired from Barrett and Schluter (2008).
Adaptation from standing genetic variance and from de novo mutations tend to yield different genetic signature.
In comparison to de novo mutations, adaptation from standing genetic variation is likely to lead to
Faster evolution
Because there the respond to the new environmental is immediate, there is no need to wait for more mutations.
Because the fitness variance associated with the trait under selection is very low even when the first mutation occurs.
Fixation of more alleles of small effects.
The following is multiple choice question (with options) to answer.
Some mutations lead to new versions of proteins that help organisms adapt to changes in their environment and are essential for evolution to occur. what are these mutations known as? | [
"beneficial mutations",
"superficial mutations",
"provisional mutations",
"evolutionary mutations"
] | A | Some mutations have a positive effect on the organism in which they occur. They are called beneficial mutations. They lead to new versions of proteins that help organisms adapt to changes in their environment. Beneficial mutations are essential for evolution to occur. They increase an organism’s changes of surviving or reproducing, so they are likely to become more common over time. There are several well-known examples of beneficial mutations. Here are just two:. |
SciQ | SciQ-7058 | thermodynamics, material-science, phase-transition, states-of-matter
Title: Why does matter exist in 3 states (liquids, solid, gas)? Why does matter on the earth exist in three states? Why cannot all matter exist in only one state (i.e. solid/liquid/gas)? The premise is wrong. Not all materials exist in exactly three different states; this is just the simplest schema and is applicable for some simple molecular or ionic substances.
Let's picture what happens to a substance if you start at low temperature, and add ever more heat.
Solid
At very low temperatures, there is virtually no thermal motion that prevents the molecules sticking together. And they stick together because of various forces (the simplest: opposite-charged ions attract each other electrostatically). If you picture this with something like lots of small magnets, it's evident enough that you get a solid phase, i.e. a rigid structure where nothing moves.
Actually though:
Helium won't freeze at any temperature: its ground state in the low-temperature limit at atmospheric pressure is a superfluid. The reason is that microscopically, matter does not behave like discrete magnets or something, but according to quantum mechanics.
There is generally not just one solid state. In the magnet analogy, you can build completely different structures from the same components. Likewise, what we just call “ice” is actually just one possible crystal structure for solid water, more precisely called Ice Ih. There are quite a lot of other solid phases.
Liquid
Now, if you increase temperature, that's like thoroughly vibrating your magnet sculpture. Because these bonds aren't infinitely strong, some of them will release every once in a while, allowing the whole to deform without actually falling apart. This is something like a liquid state.
Actually though:
The following is multiple choice question (with options) to answer.
What is the only substance on earth that is stable in all three states? | [
"carbon",
"mercury",
"water",
"air"
] | C | Water is the only substance on Earth that is stable in all three states. |
SciQ | SciQ-7059 | 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.
What is the process whereby excess water and waste is removed from the body? | [
"diffusion",
"excretion",
"filtration",
"exhalation"
] | B | Excretion is any process in which excess water or wastes are removed from the body. Excretion is the job of the excretory system. Besides the kidneys, other organs of excretion include the large intestine, liver, skin and lungs. |
SciQ | SciQ-7060 | cell-biology, proteins, transcription, cell-signaling, intracellular-transport
Time is in minutes, and zeroed at first contact between the two cells. I've put a red dot on the T-cell and a blue one on the APC in the DIC images (left panes); hopefully that proves more informative than annoying. The right panes show GFP fluorescence and thus CD3 localization. As time progresses, CD3 is re-localized from one part of the membrane to another (the synapse). There is supposedly a video of this is in the supplementary information of the article, though I was unable to open it.
The rate and directionality of the movement implies that an active process is occurring, rather than simple diffusion. However, they did not find the actual mechanism for movement and I haven't found any follow-up papers in a brief search (though many subsequent papers implicate the cytoskeleton in this movement). Just to show that movement of transmembrane proteins can, in fact, be actively directed by the cytoskeleton, I refer you to this paper:
Grabham PW, Foley M, Umeojiako A, Goldberg DJ. 2000. Nerve growth factor stimulates coupling of beta1 integrin to distinct transport mechanisms in the filopodia of growth cones. J Cell Sci 113:3003-3012.
They show that membrane-spanning integrins are moved along actin filaments of the cytoskeleton by myosin motor proteins. Expectedly, the abstract does a good job of summarizing the paper:
The cycling of membrane receptors for substrate-bound proteins via their interaction with the actin cytoskeleton at the leading edge of growth cones and other motile cells is important for neurite outgrowth and cell migration. Receptor delivered to the leading edge binds to its ligand, which induces coupling of the receptor to a rearward flowing network of actin filaments. This coupling is thought to facilitate advance... [T]ransport was dependent on an intact actin cytoskeleton and myosin ATPase...
The following is multiple choice question (with options) to answer.
What cellular structure moves molecules between locations inside the cell? | [
"capillaries",
"transport vessels",
"transport vesicles",
"dna vesicles"
] | C | Transport vesicles are able to move molecules between locations inside the cell. For example, transport vesicles move proteins from the rough endoplasmic reticulum to the Golgi apparatus. |
SciQ | SciQ-7061 | organic-chemistry, reaction-mechanism, redox
Aldehydes are very easily oxidized to carboxylic acids, and thus the aldehydes formed in the cleavage reaction do not survive. They are rapidly transformed into carboxylic acid groups, by a complex reaction whose mechanism you need not worry about.
Now, if the alkene had not had any hydrogens attached, the product in that case would have been a ketone
rather than an aldehyde. Ketones are not easily oxidized further, and the reaction would have stopped at that
stage.
If one of the alkene carbons had a hydrogen substituent, while the other did not, then we would get both acid
and ketone groups in our product, as shown below.
The following is multiple choice question (with options) to answer.
Alcohols can be oxidized to aldehydes or _______. | [
"carbohydrates",
"sugars",
"sugars",
"ketones"
] | D | Alcohols can be oxidized to aldehydes or ketones. |
SciQ | SciQ-7062 | meteor, meteorite, meteoroid, estimate
Title: How long between the moment a meteor is first visible and the moment a meteorite hits the ground? A meteor is usually only visible for a couple seconds at most, but I would guess that it usually stops being visible high above the ground.
Meteors often don't make it to the ground as they completely burn up before. But among those that do reach the ground, how long does it take for a meteoroid to go through the Earth's atmosphere and hit the ground? How many seconds between the moment it is first visible and the moment it hits the ground? I'm a researcher at Curtin University working on the Desert Fireball Network. The DFN is the largest fireball observation network in the world, and our primary goal is to recover meteorites with orbital information attached.
The traditional rule of thumb for meteorite-dropping events is a final luminous height below 35 km and a final luminous velocity below 10 km s-1
So when I refer to the luminous part of the trajectory, I am referring to the portion in which ablation is occurring and optical light is emitted. As you said, this portion typically lasts a few seconds depending on the initial size, strength, speed, and slope of the meteoroid. After this, if the object still has mass left, the speed continuously decreases. We call this portion of the trajectory the "dark-flight" (as opposed to the "bright-flight" which is the luminous part) because we can longer observe the meteoroid.
During the dark flight, the rock goes from <10 km s-1 to tens to a few hundred m s-1 when it finally impacts the ground as a meteorite. This part of the trajectory can be greatly affected by wind as seen below from the dark flight modeling done for the recovered Dingle Dell meteorite:
So, in total, from first becoming a meteor to impacting the surface, you should expect about tens of seconds to minutes to pass. Of course, this is dependent on things I have mentioned like mass, speed, and slope notably.
The following is multiple choice question (with options) to answer.
What causes a meteoroid to vaporize after it enters the atmosphere? | [
"spontaneous combustion",
"gravitational pull",
"atmospheric pressure",
"friction with atmosphere"
] | D | A meteoroid is dragged toward Earth by gravity and enters the atmosphere. Friction with the atmosphere heats the object quickly, so it starts to vaporize. As it flies through the atmosphere, it leaves a trail of glowing gases. The object is now a meteor. Most meteors vaporize in the atmosphere. They never reach Earth’s surface. Large meteoroids may not burn up entirely in the atmosphere. A small core may remain and hit Earth’s surface. This is called a meteorite . |
SciQ | SciQ-7063 | experimental-physics, nuclear-physics, radioactivity, statistics, half-life
$$t_{\rm average} = \frac{6.45\times 10^9\times 365.2422\times 86400}{2.53\times 10^{24}}{\rm seconds} = 8.05\times 10^{-8} {\rm seconds}. $$
So one gets about 12.4 million decays during one second. (Thanks for the factor of 1000 fix.) These decays may be observed on an individual basis. Just to be sure, $T$ was always a lifetime in the text above. The half-life is simply $\ln(2) T$, about 69 percent of the lifetime, because of some simple maths (switching from the base $e$ to the base $2$ and vice versa).
If we observe $\Delta N$ decays, the typical relative statistical error of the number of decays is proportional to $1/(\Delta N)^{1/2}$. So if you want the accuracy "1 part in 1 thousand", you need to observe at least 1 million decays, and so on.
The following is multiple choice question (with options) to answer.
How is the radioactive decay measured? | [
"alpha emission",
"quarter-life",
"carbon dating",
"half-life"
] | D | The rate of radioactive decay varies from one radioisotope to another. The rate is measured by the half-life. This is the length of time it takes for half of a given amount of a radioisotope to decay. |
SciQ | SciQ-7064 | molecular-biology, molecular-genetics, development, sex
Quote from a Review (Yao 2005):
We have just begun to glimpse into the mechanisms underlying ovarian development. Convincing evidence challenges us to reconsider the existing paradigm that describes ovarian development as a default system. The default concept was first proposed in the early 1950s when Jost performed the groundbreaking experiments to demonstrate mechanisms of sex differentiation of reproductive tracts (Jost, 1947, 1953, 1970). The term “default” was not originally intended to describe the developmental status of the ovary. Instead, it is referred to the female reproductive tract or the Mullerian duct based on the fact that the female reproductive tract forms in both XX and XY individuals in the absence of gonads. Indeed, now it has become evident that early ovarian development is an active process involving intrinsic cell fate decisions and complex crosstalks between germ cells and somatic cells. Most intriguingly, the appearance of testicular structures in XX individuals where Sry and its downstream components are absent further raises the improbable question: Could the testicular development be default after all?
The following is multiple choice question (with options) to answer.
What term means a reproductive cell, like the human egg in females? | [
"embryo",
"gamete",
"zygote",
"sperm"
] | B | This represents a human egg, which is the gamete, or reproductive cell, in females. Notice that is does not have a distinct shape, like a sperm cell has. The egg is a round cell with a haploid nucleus in the center. The egg contains most of the cytoplasm and organelles present in the first cell of a new organism. |
SciQ | SciQ-7065 | hematology, cardiology, blood-circulation, red-blood-cell, veins
Veins are not like impermeable rubber tubes, they are 'living' structures requiring, like all cells, Oxygen and glucose to survive. Smaller veins get the O2 from diffusion, while the larger veins need help from vasa vasorum, small blood bessels that bring blood to the walls of the veins.
The innermost cells lining veins are epithelial cells. They also line valves.
In the picture you posted, blood is not circulating well behind valves. The cause of hypoxia is that epithelial cells are continually removing O2 from the blood.
When enough O2 is removed to cause hypoxia, the endothelial cells may become damaged by the lack of O2, causing inflammation and (possibly) potentiating clot formation.
Activation of endothelial cells by hypoxia or possibly inflammatory stimuli would lead to surface expression of adhesion receptors that facilitate the binding of circulating leukocytes and microvesicles. Subsequent activation of the leukocytes induces expression of the potent procoagulant protein tissue factor that triggers thrombosis.
Mackman N. (2012). New insights into the mechanisms of venous thrombosis. The Journal of clinical investigation, 122(7), 2331–2336. doi:10.1172/JCI60229
The following is multiple choice question (with options) to answer.
Veins are blood vessels that carry blood toward what? | [
"extremities",
"brain",
"heart",
"lung"
] | C | Veins are blood vessels that carry blood toward the heart. This blood is no longer under much pressure, so many veins have valves that prevent backflow of blood. Veins generally carry deoxygenated blood. The largest vein is the inferior vena cava, which carries blood from the lower body to the heart. |
SciQ | SciQ-7066 | quantum-mechanics, electrons, quantum-spin
Title: Spin of electrons Do electrons possess spin quantum number only in a central potential or can they have spin in other cases also?
Specifically, can two electrons be distinguished based on their spin if they are in a box with infinite potential at the boundaries? Electrons always have spin quantum number $s=\frac{1}{2}$, and all electrons are indistinguishable, and since they are fermions, an $N$ electron wave function must be antisymmetric under interchange of any two electrons.
Regarding 2 electrons in a box, the eigenstates of total spin are the singlet and triplet states. The singlet state ($S=0, S_z=0)$ is antisymmetric:
$$ |0,0\rangle=\frac{1}{\sqrt 2}[\uparrow_1\downarrow_2 - \downarrow_2\uparrow_1] $$
The antisymmetric part arises from the fact that swapping particle subscripts $(1, 2)\rightarrow(2,1)$ flips the sign of the spin wave function.
Moreover, the statement that the electrons have opposite spin is somewhat of a classical view--their is one spin up electron and it is 50% particle 1 and 50% particle 2, likewise for the one spin down electron.
Note that that statement also applies to the $S_z=0$ triplet state:
$$ |1,0\rangle=\frac{1}{\sqrt 2}[\uparrow_1\downarrow_2 + \downarrow_2\uparrow_1] $$
which differs by a sign (so it is symmetric under particle interchange).
Regarding a particle in a box, the eigenstates are:
$$ \psi_n(x) \propto \sin{\frac{n\pi}{L}(x+\frac L 2)}$$
Note that $\psi_n(x)$ is even (odd) for odd (even) $n$.
The two particle spatial wave functions are:
The following is multiple choice question (with options) to answer.
The spin quantum number describes the spin for a given what? | [
"element",
"proton",
"electron",
"ion"
] | C | The spin quantum number describes the spin for a given electron. An electron can have one of two associated spins, spin, or spin. An electron cannot have zero spin. We also represent spin with arrows or . A single orbital can hold a maximum of two electrons and each must have opposite spin. |
SciQ | SciQ-7067 | geology, fossil-fuel, petroleum
For some transport applications, the energy density is still a winning attribute of hydrocarbons: most notably, powered flight for freight and travel.
We already have two routes to non-fossil hydrocarbons: biological sources, and direct chemical synthesis. Each involves capturing atmospheric CO2, and combining with water, to generate a blend of hydrocarbons.
Now, we already have means of creating hydrocarbons suitable for flight (e.g. Jet-A and Jet-A1 fuels). And there are already demonstration plants that have closed-loop generation of synthetic hydrocarbons, for use in electricity-grid-balancing, by using surplus electricity to synthesise methane, which is then burnt in gas turbines when required. Similarly, Tony Marmont's team have been synthesising petrol (gasoline) from air, water, and electricity.
However, none of those things mean that hydrocarbons necessarily have much of a future, beyond plastics production. Because hydrocarbon-powered aviation has a lot of environmental problems beyond just CO2 emissions, in particular it makes other contributions to exacerbating global warming. And there are lots of options for energy storage within the electricity supply chain.
The following is multiple choice question (with options) to answer.
What fuels provide most of the energy used worldwide? | [
"hydroelectric",
"fossil",
"solar",
"renewable"
] | B | Fossil fuels provide most of the energy used worldwide. Richer nations use far more energy resources, especially fossil fuels, than poorer nations do. There are several ways that people can conserve energy in their daily lives. |
SciQ | SciQ-7068 | angular-momentum, rotational-kinematics, rotation, rocket-science, angular-velocity
Euler angles are almost never actually used for equations of motion or interpolation. They're terrible at it because they behave borderline non-physical. For instance, if you try to rotate smoothly from one orientation to another just by linearly interpolating the yaw pitch and roll channels, you find the object takes a rather exotic looking path to get to its final orientation. They're convenient for a quick way to describe an orientation in a physically meaningful way, but they act squirely when you start to vary them over time.
If you want to have things like a rate of change of orientation, use a orientation format which supports that better. Direction Cosine Matrixes and Quaternions have far superior properties. From my experience, quaternions are by far the most popular way to handle rotations, although it takes a while to wrap your head around them. Both of them have straightforward ways of dealing with the conservation of angular momentum.
If you want a sense of how wonky euler angles can be, look at gimbal lock. This is a quirky situation where two of the axes generate the same rotation. It happens when the second rotation rotates the third rotation into the same axis as the first rotation. This is a major issue with gimbals because, when it occurs, you end up with one rotational dimension that you simply cannot observe. This means that once gimbal lock occurs, you no longer know what your orientation is.
We nearly failed to go to the moon because of this. Apollo 11 had a standard 3 ring gyro, so was susceptible to gimbal lock. To combat this, they had a clever little "kicker" device which would rotate one of the axes at a critical moment to sidestep this horrid alignment from occuring. As it so happened, the code to handle this had a bug, and caused the subsystem to cease operating. They flew onward knowing the risk that a gimbal lock would cause them to lose track of their attitude. (Contingency plans included re-acquiring alignment by observing stars, which would be slow and error prone, but would get astronauts home safely).
The following is multiple choice question (with options) to answer.
What instruments used in guidance systems to indicate directions in space must have an angular momentum that does not change in direction? | [
"actuators",
"gyroscopes",
"magnets",
"elevators"
] | B | Gyroscopes used in guidance systems to indicate directions in space must have an angular momentum that does not change in direction. Yet they are often subjected to large forces and accelerations. How can the direction of their angular momentum be constant when they are accelerated?. |
SciQ | SciQ-7069 | geography, mantle, crust, mining, cavern
6.Record absolute depth under sea level a person has reached "on foot".
If you consider Vescoso to have been "on foot", he wins again. If not, and you consider miners going to their jobs as being "on foot", then it would be the Canadian miners (2.65 km below see level). If you are strict against both, my first thougth is then maybe port workers (note a submariner won't win in this case neither), or maybe a spelunker, but user Semidiurnal Simon clarifies it on comments. I was wrong (I said I made the estimations quickly) as: "For the strictest "on foot", it won't be port workers, it'll be somebody in a below-sea-level basin (e.g. by the Dead Sea), or possibly a low-altitude mine that has a drift (slanted corridor) entry and so doesn't require an elevator."
7.Record absolute depth under surface by drilling.
Sending machines from the surface (by borehole) rather than humans, the Kola Superdeep Borehole is the deepest (12km).
8.Record closest drill to Earth's Center.
The Ocean Drilling Program could have this record, but I cannot determine where. Average seabed deep rounds -4.000 m. and the Arctic Ocean is not a deep ocean in comparison with the Pacific and Atlantic. So the Kola Borehole may well have this record too.
The following is multiple choice question (with options) to answer.
What are the deepest places on earth? | [
"deep sea diversions",
"deep sea trenches",
"deep sea resonances",
"deep sea caves"
] | B | Deep sea trenches are found near chains of active volcanoes. These volcanoes can be at the edges of continents or in the oceans. Trenches are the deepest places on Earth. The deepest trench is the Mariana Trench in the southwestern Pacific Ocean. This trench plunges about 11 kilometers (35,840 feet) beneath sea level. The ocean floor does have lots of flat areas. These abyssal plains are like the scientists had predicted. |
SciQ | SciQ-7070 | cell-biology, meiosis, mitosis
Title: Is the cell cycle applicable to meiosis as well, or just mitosis? All the diagrams I can find, show the cell cycle as having G1 phase (growth 1), S phase (DNA replication), G2 (growth 2) before the Mitotic phase (mitosis + cytokinesis).
Is there an equivalent "cell cycle" for meiosis, since the chromosomes in parent cell in meiosis also having "double" the genetic material prior to cell division (presumably from DNA replication too)?
Is it simply the same cell cycle as mitosis but with a Meiotic phase instead of Mitotic?
If so, would appreciate if anyone had a diagram :) Thanks! The cell cycle is only associated with mitosis. The cell cycle is the normal process of cell division with which cells can indefinitely increase their number by cyclically repeating the process. When a cell goes through the cycle, the result is two cells that are genetically identical.
Meiosis is a special type of cell division (which can occur only in eukaryotes) that produces cells that are not genetically identical to the initiating cell. The number of chromosomes in each of the resulting cells is half the number that were in the initial cell. (These haploid cells can later participate in fertilization, producing a cell with the original number of chromosomes.) Many of the steps of meiosis are similar to the steps involved in mitosis, but overall the process is more complex. Since meiosis reduces the number of chromosomes, it cannot be repeated and so does not take part in a cell division cycle.
The following is multiple choice question (with options) to answer.
While the chromosome is replicating, the cell does what? | [
"shrinks",
"diffuses",
"elongates",
"propagates"
] | C | |
SciQ | SciQ-7071 | evolution, zoology, literature
Title: Which Darwin book (and today edition) is illustrated by his own drawings? I am interested in buying Charles Darwin books and mostly drawings (nowadays editions, I am not a collector). Please, can you advise in which book and which edition I can find the most of his drawings? I found some books as On the Origin of Species ad the Geology of The Voyage of The Beagle but I am not sure if there are his drawings too. I am a student so I couldn't spend too much money on it, but I was interested in his texts and drawings, supporting each other in one book/journal/publication. Thank you ! I believe that there is only one drawing in the first edition of On the Origin of Species, and it is Darwin's. Any good edition such as the fascimile edition with an introduction by Ernst Mayr, will include this drawing. I'm not sure about other editions of the Origin or other books of Darwin's. However, maybe you don't need to buy anything. Darwin Online is a wonderful collection that includes many (all?) of Darwin's writings over the years, including images of many of them; the drawings are no doubt included.
It's possible that the History of Science and Mathematics StackExchange site would be a better place for this question.
The following is multiple choice question (with options) to answer.
On the origin of species is a book by darwin that spells out what theory? | [
"theory of reproduction",
"theory of the computation",
"theory of evolution",
"theory of the universe"
] | C | Wallace’s paper on evolution confirmed Darwin’s ideas. It also pushed him to publish his book, On the Origin of Species. The book clearly spells out his theory. It also provides evidence and logic to support it. |
SciQ | SciQ-7072 | immunology
Title: Is Plasmablast a precursor of Plasma cell? I read it in Roitt's Essential Immunology.
Plasmablasts are precursor cells of short- and long-lived plasma cells and
are generally described as a proliferating fraction of
antibody-secreting cells, often found in the bloodstream
emigrating to organs such as the bone marrow.
I coudn't find any authentic source repeating the same.
Is it true? Is this book authentic enough to follow? Antigen activated B-cells enter the germinal centre dark zone to form centroblasts which undergo somatic hypermutation. These then form centrocytes in the light zone. The various possibilities/routes the centrocyte can take are shown in the following figure. If the centrocyte undergoes a class switch recombination, it becomes a plasmablast.
A plasmablast is defined as
Plasmablast
The B-cell lineage precursor of non-dividing plasma cells, which has the capacity to divide and that has migratory potential.
Once it matures as a plasma cell, it is out in the blood secreting soluble immunoglobulins or antibodies.
Another important definition to mentioned here would be of antibody secreting cells.
Antibody-secreting cells
A term that denotes both proliferating plasmablasts and non-proliferating plasma cells. The term is used when both cell types might be present
So, yes, they indeed are a precursor of plasma cells.
Also, it is necessary to clarify here that although both plasma cells and plasmablasts are antibody secreting cells, plasma cells lack membrane bound antibodies while plasmablasts retain them.
Finally, this is just the germinal centre response that is shown over here. Plasma cells and plasmablasts can also form in an extrafollicular response in extrafollicular sites in the spleen or in the medullary cords of the liver. That's another story altogether!
For a more detailed explanation, have a look at my other answer.
Image and reference: http://www.nature.com/nri/journal/v8/n1/full/nri2217.html
The following is multiple choice question (with options) to answer.
After an adaptive defense is produced against a pathogen, typically plasma cells first secrete immunoglobin, which constitutes about ten percent of all what? | [
"parasites",
"antibodies",
"allergies",
"hormones"
] | B | After an adaptive defense is produced against a pathogen, typically plasma cells first secrete IgM into the blood. BCRs on naïve B cells are of the IgM class and occasionally IgD class. IgM molecules make up approximately ten percent of all antibodies. Prior to antibody secretion, plasma cells assemble IgM molecules into pentamers (five individual antibodies) linked by a joining (J) chain, as shown in Figure 42.23. The pentamer arrangement means that these macromolecules can bind ten identical antigens. However, IgM molecules released early in the adaptive immune response do not bind to antigens as stably as IgGs, which are one of the possible types of antibodies secreted in large quantities upon re-exposure to the same pathogen. Figure 42.23 summarizes the properties of immunoglobulins and illustrates their basic structures. |
SciQ | SciQ-7073 | energy, solar-cells
Title: what limitations stop a person from installing solar panels on his/her house? Solar energy is a great form of energy. sourced from the sun, it can save a great deal of electricity bill cost. My question is why doesn't everyone uses it and install panels on their roof.
Of course, sun rays is the most significant factor of all but what other limitations are there to it? Cost of panels, less availability, not efficient, less generation of electricity are few I could think of. But, I'm not sure about any of them.
Since limitations can be many in number and can belong to different nodes of stack exchange network. The question was little related to energy, so I decided to ask it here. If this is not the right platform then do tell. The reason that not everyone has solar panels is that they are not economical.
Simply put, investing X dollars in bonds will usually generate a greater financial return than putting the same X dollars into solar panels. This is because the price of a solar panel is larger than the value of the electricity it will produce during its lifetime.
However, in very sunny climates - and when the government will help pay for the panels - they can be made economical from the point of view of a consumer. Usually, though, governments will subsidize solar panels only to the point where they are almost, but not quite, a good return on investment.
To the extent that solar panels are actually economically efficient utility companies do employ them - and in a much more cost-efficient way than having individual homeowners install and maintain small-scale systems.
The following is multiple choice question (with options) to answer.
Solar and wind are still expensive compared to what? | [
"coal fuels",
"fossil fuels",
"electricity",
"batteries"
] | B | Solar and wind are still expensive relative to fossil fuels. The technology needs to advance so that the price falls. |
SciQ | SciQ-7074 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
The pollen tube discharges two sperm into the female gametophyte after what occurs? | [
"evolution",
"pollination",
"hibernation",
"excrement"
] | B | |
SciQ | SciQ-7075 | physical-chemistry
Title: Which is hardest: iron, brass or bone? I was hopping around random wikipedia articles when I came across the article for the Behemoth. In the description for the beast it says:
His bones are as strong pieces of brass; his bones are like bars of
iron
So it got me thinking, which of these three substances is hardest: iron, brass or bone?
(I had a quick look at the Mohs scale, which lists iron as 4, but could not find anything for brass or bone.) These two sources both put bone at a hardness of 5:
http://www.chacha.com/question/how-hard-is-bone-according-to-moh's-hardness-scale
https://answers.yahoo.com/question/index?qid=20110310200841AABwtMj
Whether they are trustworthy is questionable though, so take it as you will.
This source put brass at 3 and iron at 4.5:
http://www.jewelrynotes.com/the-mohs-scale-of-hardness-for-metals-why-it-is-important/
and this image puts brass at 4 and iron at 4-5 (Similar to 4.5):
http://patentimages.storage.googleapis.com/WO2001048807A1/imgf000009_0001.png
While these different sources seem to have conflicting data, I think it would be safe to assume that Brass is the softest of these three materials, Iron comes second, and Bone is the hardest.
Edit: In the description of that monster, the adjective used is 'strong'. You may want to consider how much force each of these materials can withstand instead of how hard they each are :)
The following is multiple choice question (with options) to answer.
Steel, bronze, and brass are good examples of what? | [
"salts",
"elements",
"metalloids",
"alloys"
] | D | Examples of alloys include steel, bronze, and brass. |
SciQ | SciQ-7076 | taxonomy
Title: Why are sponges sometimes not considered multicellular? I read somewhere (I can't find where) that there is no scientific consensus whether sponges should be considered multicellular organisms.
It seems I don't understand where is the line between unicellular and multicellular life.
I am not able to find a more elaborate explanation of that doubt. What are the reasons for it? Sponges are generally considered as colonial organisms because there is little cell specialization and little separation of function/role. All cells do pretty much the same thing; it looks more like a pile of individual cells than an actual multicellular organism. In reality it is a little bit in between.
In any case, what one wants to call multicellular or unicellular is a matter of definition and preferences. You cannot find the line between unicellular and multicellular because there is no such line that would not be very arbitrary and filled with special cases.
You can study a little more the physiology of sponges and then decide for yourself if it looks sufficiently like a multicellular organism or more like a colony of cells (a colonial organism).
The following is multiple choice question (with options) to answer.
Most hydrozoa have both polyp and what forms in their life cycle? | [
"polypoid",
"globular",
"medusa",
"hydra"
] | C | Hydrozoa includes nearly 3,500 species, most of which are marine. Most species in this class have both polyp and medusa forms in their life cycle. Many hydrozoans form colonies composed of branches of specialized polyps that share a gastrovascular cavity. Colonies may also be free-floating and contain both medusa and polyp individuals in the colony, as in the Portuguese Man O’War (Physalia) or By-the-Wind Sailor (Velella). Other species are solitary polyps or solitary medusae. The characteristic shared by all of these species is that their gonads are derived from epidermal tissue, whereas in all other cnidarians, they are derived from gastrodermal tissue (Figure 15.14ab). “The Hydrozoa Directory,” Peter Schuchert, Muséum Genève, last updated November 2012, http://www. ville-ge. ch/mhng/hydrozoa/hydrozoadirectory. |
SciQ | SciQ-7077 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
Mammalian lungs are located in what cavity, where they are surrounded and protected by the rib cage, intercostal muscles, and chest wall? | [
"dorsal",
"ventral",
"thoracic",
"abdominopelvic"
] | C | 39.3 | Breathing By the end of this section, you will be able to: • Describe how the structures of the lungs and thoracic cavity control the mechanics of breathing • Explain the importance of compliance and resistance in the lungs • Discuss problems that may arise due to a V/Q mismatch Mammalian lungs are located in the thoracic cavity where they are surrounded and protected by the rib cage, intercostal muscles, and bound by the chest wall. The bottom of the lungs is contained by the diaphragm, a skeletal muscle that facilitates breathing. Breathing requires the coordination of the lungs, the chest wall, and most importantly, the diaphragm. |
SciQ | SciQ-7078 | parasitology
Title: Tapeworms and their effect on humans I've read that some people in some countries actually use tapeworms as a form of losing weight. What are the dangers to these people? I haven't really found much on this topic (besides popular sites) but I can summarize it here:
There are quite some tapeworms (or cestoda), I found numbers of up to 3500 species. They attach to the intestinal wall of the humans and then start to take up predigested food through their skin. With that, they reduce food from their host and start to grow, some get as long as 15 meters!
Some of the worms seem to be relatively harmless (besides stealing food), but this is more true for the first world. In poor countries, where there is not enough food, tapeworms can cause severe malnutrition.
Some tapeworms can migrate into the blood stream and from there into other tissues or organs like muscles, eye and brain. There they can cause cysts which can lead to organ failure and death.
For more information see this CDC webpage and this article: "Biochemistry and physiology of tapeworms.". This popular article is probably also interesting.
The following is multiple choice question (with options) to answer.
Segmented worms have a digestive,nervous and what type of system? | [
"vascular",
"pulmonary",
"lymphatic",
"circulatory"
] | D | Segmented worms have a digestive system, nervous system, and circulatory system. |
SciQ | SciQ-7079 | chemical-potential, osmosis
Our models and theories require the introduction of a parameter that
explicitly represents structure in liquids, which until now has had no
place in the thermodynamic description of solutions. This lack is
surprising, when one remembers that experimental results from the
broad range of fields of colloid, clay and biological sciences have
clearly established the marked effect of solutes on the structural
properties of water, globally called ‘hydration phenomena’.
The introduction of such a parameter can help explain the direction in
which energy flows during osmosis, which has been so puzzling to those
of us interested in mechanism since the time of Pfeffer, more than a
century ago. Further, elementary work cycles show, that changes in
this parameter correspond to changes in the energy associated with
solvent structure which can be used to produce useful work. The
ability of osmotic systems to do work is familiar to all of us
(indeed, a nuisance to many!), and is the basis of cytomechanics,
i.e., the physical processes observed in the living cell. The fact
that it still has no satisfactory explanation is clearly an urgent
problem for us all.
In his article "Quantum Worlds", James Watson reviews osmotic theory of Watterson:
The following is multiple choice question (with options) to answer.
In what route do water and solutes move along the continuum of cytosol? | [
"hydrophobic",
"hydrophylic",
"nonvascular",
"symplastic"
] | D | |
SciQ | SciQ-7080 | electrons, orbitals
Similarly, $\ce{LiH}$ has unlimited number of atomic or molecular orbitals ( depending on the quantum model ), as they are features of quantum models, not real objects. And again, only highest "valence" occupied and few lowest unoccupied ones are worthy to consider. (For $\ce{LiH}$, s and p for atomic ones, $\sigma, \pi $ for molecular ones. )
The following is multiple choice question (with options) to answer.
Atomic orbitals are populated with what subatomic particles? | [
"protons",
"neurons",
"electrons",
"atoms"
] | C | A completely bonding molecular orbital contains no nodes (regions of zero electron probability) perpendicular to the internuclear axis, whereas a completelyantibonding molecular orbital contains at least one node perpendicular to the internuclear axis. A sigma (σ) orbital (bonding) or a sigma star (σ*) orbital(antibonding) is symmetrical about the internuclear axis. Hence all cross-sections perpendicular to that axis are circular. Both a pi (π) orbital (bonding) and a pi star (π*) orbital (antibonding) possess a nodal plane that contains the nuclei, with electron density localized on both sides of the plane. The energies of the molecular orbitals versus those of the parent atomic orbitals can be shown schematically in an energy-level diagram. The electron configuration of a molecule is shown by placing the correct number of electrons in the appropriate energy-level diagram, starting with the lowest-energy orbital and obeying the Pauli principle; that is, placing only two electrons with opposite spin in each orbital. From the completed energy-level diagram, we can calculate thebond order, defined as one-half the net number of bonding electrons. In bond orders, electrons in antibonding molecular orbitals cancel electrons in bonding molecular orbitals, while electrons in nonbonding orbitals have no effect and are not counted. Bond orders of 1, 2, and 3 correspond to single, double, and triple bonds, respectively. Molecules with predicted bond orders of 0 are generally less stable than the isolated atoms and do not normally exist. Molecular orbital energy-level diagrams for diatomic molecules can be created if the electron configuration of the parent atoms is known, following a few simple rules. Most important, the number of molecular orbitals in a molecule is the same as the number of atomic orbitals that interact. The difference between bonding and antibonding molecular orbital combinations is proportional to the overlap of the parent orbitals and decreases as the energy difference between the parent atomic orbitals increases. With such an approach, the electronic structures of virtually all commonly encountered homonuclear diatomic molecules, molecules with two identical atoms, can be understood. The molecular orbital approach correctly predicts that the O2 molecule has two unpaired electrons and hence is attracted into a magnetic field. In contrast, most substances have only paired electrons. A similar procedure can be applied to molecules with two dissimilar atoms, calledheteronuclear diatomic molecules, using a molecular orbital energy-level diagram that is skewed or tilted toward the more electronegative element. |
SciQ | SciQ-7081 | electrostatics, charge
Title: Why identical spheres gain identical charges? My textbook quotes
Because the spheres are identical, connecting them means that they end up with identical charges.
One sphere is neutral and another has charge $+Q$ initially. After connecting them with very thin conducting wire they both acquire same amount of charge $+Q/2$.
Can anyone explain the mechanism of charge transfer please? And also why above quoted implication is true? The important thing to realize is that the spheres must have equal charge density on their surfaces (and it will be concentrated on their surfaces, assuming that they are conductors - your book probably discusses this point). The reason is that if one sphere acquired more positive charge density than the other, it would have higher electrostatic potential (if you haven't gotten to this idea yet, it basically means that it would be energetically favorable for negative charges to migrate towards the sphere and positive charges to migrate away from it). In other words, any charge density imbalance between the two spheres will cause a migration of electrons in a way that cancels the imbalance - so when the two bodies reach equilibrium, their charge densities will be identical as desired.
Now, because the spheres are identical, they also have equal surface area - and equal charge density distributed across equal surface area will ultimately mean equal total charge as desired. If one sphere was bigger than the other, the charge would be distributed proportional to their two surface areas.
The following is multiple choice question (with options) to answer.
Which law refers to the electron charge remaining the same during transfer? | [
"law of conservation of charge",
"law of conservation of speculation",
"law of construct of charge",
"law of change"
] | A | Three ways electrons can be transferred are conduction, friction, and polarization. In each case, the total charge remains the same. This is the law of conservation of charge. |
SciQ | SciQ-7082 | homework-and-exercises, kinematics, reference-frames, velocity
Title: Perceiving travel speeds from different view points Scenario:
Two vehicles pass each other on a highway moving at 100km's an hour; from a stationary position beside the road you witness these cars pass each-other directly in front of you: from your perspective these cars are moving at 100km's an hour.
My Question: If you were inside either one of the 2 cars, looking straight out the window to where the other car would cross, would you perceive the vehicle to be moving at 200km's an hour as it passed you- due to both cars moving at 100km's in opposite directions?
I'm unsure if thats right or not- whenever I personally travel by car and bare-witness to another vehicle pass my window in the opposite direction at the same speed, it seems to always be moving much faster than it really is, assuming it was only because of the speed I was going when passing it.
Is this correct? Rough impressions can be misleading. The other car really is moving 200 km/h from your point of view.
One thing to keep in mind is that you tend to perceive motion more readily when it is closer to you. This is at least partly due to the fact that you really only can see angular speed across your field of view (like degrees per second). To convert this into an actual speed, you need a sense of distance to the object in question, which you only have for nearby things where for example parallax kicks in.
As a result, if you are moving at 200 km/h, a stopped car right next to you will appear to be moving very fast, whereas the distant scenery off to the side won't, even though both are moving relative to you at the same speed.
The following is multiple choice question (with options) to answer.
Hotspots can be used to tell the speed and direction that what object is moving? | [
"electrons",
"crystals",
"glaciers",
"plates"
] | D | Hotspots can be used to tell the speed and direction that a plate is moving. |
SciQ | SciQ-7083 | fluid-statics
Title: Is this watering with gravity concept possible with physics?
I was thinking of putting together a auto watering scheme for my plants. Main objective is to just have one place to fill water, and it will disperse to several cups equally. I might have the physics wrong but i remember some force which creates suction with gravity and keeps the containers equally filled. I tried to draw the idea, and i'm wondering if anyone have any feedback on if this is possible?
The idea here is that the gravity will bring the water from the top container which stands taller, and then fills the small containers with water. The sketch is of a high reservoir, with multiple level-controlled smaller tanks.
So, it implies that the (lower level) tanks are equipped with a valve that
shuts off the water when a target level is reached: it's just like the
shutoff mechanism in the tank of a toilet. There's a float, which operates
the valve. It doesnt equalize gallons per day, though, just level-in-a-tank.
So, you can definitely find items at a hardware store to build such a system.
If, on the other hand, you want to partition a water source to multiple
destinations based on delivered water volume being equal, the usual
approach is to use a timed valve to a pressurized manifold, and use
matched emitters (i.e. drip irrigation controlled-flow drip fittings).
The physical principle of these emitters is the Bernoulli effect, they
are fabricated so that too-fast water flow in the valve pulls the
aperture shut (this sounds hard, but it isn't). Over a range
of water pressure, the drip rate stays nearly constant. They usually
require pump pressure (or water-utility pressure) though, would clog
if you just used a few feet of gravity-driven flow.
The following is multiple choice question (with options) to answer.
Does overhead irrigation or drip irrigation use less water? | [
"drip irrigation",
"constant flow",
"mist irrigation",
"stream irrigation"
] | A | Irrigation is the single biggest use of water. Overhead irrigation wastes a lot of water. Drip irrigation wastes a lot less. Figure below shows a drip irrigation system. Water pipes run over the surface of the ground. Tiny holes in the pipes are placed close to each plant. Water slowly drips out of the holes and soaks into the soil around the plants. Very little of the water evaporates or runs off the ground. |
SciQ | SciQ-7084 | pathology
Title: Are all diseases caused by organisms (microorganisms)? Are there other causes? Or is it correct to say that all diseases are in fact caused by organisms (microorganisms)? It is not correct to say that all diseases are caused by foreign organisms. Counterexamples are:
Cancer is caused by random genetic mutations in the cells of our body. The mutations can be caused by many factors such as ionizing radiation, smoking, chemical toxins etc.
Diseases such as stroke or heart attack are caused by blood clots blocking the blood flow to essential organs.
Autoimmune diseases are caused by the immune system falsely recognizing cells of the body as foreign and attacking that tissue leading to a wide variety of symptoms.
Alzheimer's disease is caused by chronic neurodegeneration, meaning that the cells in the brain die. The causes are not quite understood but as Alzheimer's usually appears late in life it is likely related to ageing. Also, it is known that some genetic defects can lead to early-onset Alzheimers.
Prion proteins can cause diseases such as Creutzfeldt–Jakob disease also known as mad-cow disease.
Hereditary diseases such as early-onset Alzheimers or ALS are cause by gene defects inherited from the parents.
Toxins can cause chronic diseases such as lead poisoning.
The list probably goes on...
Please note that the first two on the list are the most common cause of death in developed countries.
The following is multiple choice question (with options) to answer.
Stis are diseases caused by what that spread through sexual contact? | [
"parasites",
"pathogens",
"amoeba",
"ecosystems"
] | B | STIs are diseases caused by pathogens that spread through sexual contact. Abstinence from sexual activity and other risk behaviors is the only completely effective way to prevent the spread of STIs. |
SciQ | SciQ-7085 | 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.
The heart is a muscular organ that pumps blood through which system? | [
"nervous",
"circulatory",
"pulmonary",
"endocrine"
] | B | Mollusks have a circulatory system with one or two hearts that pump blood. The heart is a muscular organ that pumps blood through the circulatory system when its muscles contract. The circulatory system may be open or closed, depending on the species. |
SciQ | SciQ-7086 | evolution, brain, development
Title: Why does it take so long for the human brain to develop from an evolutionary point of view?
I have read that it takes about 25 years for the brain to be fully developed.
Coincidentally, humans from the Neolithic and Bronze Age had a very short life expectancy, in fact most of their life their brain wasn't fully developed.
My question is:
from an evolutionary point of view, is there a reason why humans spend so much of their life not being fully developed even long after being sexually fully developed? We can say that brain and our nerve system is the first system in embryo that starts to develop and as you said this system is continuing to develop until after birth.
So here is a question that why our brain don't develop completely before the birth ? Evolution has gone so far as to limit the development of the brain in the human embryonic phase and to allow it to continue into the postnatal phase. This helps the infant to be born and ease the birth both for mother and the new born because if the brain had fully grown, the size of the head would have made problem in birth. Now, after birth, the brain continues to grow and develop majorly between ages 2-3 and becomes more mature after that . The ability of the brain to grow over the years gives us the ability to adapt to different environments , learnings and new issues and other capabilities That happens with the subsequent creation and pruning of dendritic spines.
The following is multiple choice question (with options) to answer.
Being dependent on adults for a long maturation period allows young primates ample time for what? | [
"attachment",
"learning",
"socialization",
"sleeping"
] | B | Primates have slower rates of development than other mammals their size. They reach maturity later and have longer lifespans. Being dependent on adults for a long maturation period gives young primates plenty of time to learn from their elders. |
SciQ | SciQ-7087 | biochemistry, botany
Title: Ripening bananas artificially: What is the biological theory behind? I am a resident of the tropical island of Sri Lanka, and we have a strange traditional method to ripen our banana harvest quickly.
What we do is this: We dig a pit in earth that is enough to put the whole banana cluster in. Then, after safely laying the bananas in the pit, we cover up the pit with a sheet such that only a small hole from a side remains: visualize a small 3-4 inch door to the pit.
After that, we light a fire with semi-dry leaves just outside the pit's door. (Semi-dry leaves are used to get as much smoke as possible. Dry leaves do not give that much smoke, because they completely oxidize quickly). And the smoke is sent through the door by blowing it with the aid of a bamboo.
This sends a good amount of smoke and warms the inside of the pit considerably. And by experience I can tell you that this makes the bananas to ripen really quickly. I have done a controlled experiment where half of the cluster was not put into the pit. Bananas in the pit ripen overnight and the control sample took days to ripen.
Can anybody explain what are the bio-mechanisms that are working here? Ripening of bananas (and other fruits) is induced by acetylene and ethylene (Ethyne and Ethene) (see reference 1), which acts as a hormone and induces the ripening process. The incomplete combustion of the leaves produces ethylene, additionally the warmth of the process will help the enzymes as well. There is even a paper about this technique (although it is unfortunately not accessible), see reference 2 for more information. Smoking Chambers are routinely used in this process, see reference 3 and 4.
References:
Role of Ethylene in Fruit Ripening
Effects of smoking on some physiological changes in bananas.
Fruit Ripening
Technology for ripening fruits as important as marketing them
The following is multiple choice question (with options) to answer.
What process can be triggered by a burst of ethylene production in the fruit? | [
"pickling",
"hardening",
"ripening",
"drying"
] | C | |
SciQ | SciQ-7088 | terminology, human-physiology, organs
Title: Medical term for "holding urine for a long time" Sometimes I get/feel pain in my stomach because of holding urine for long time. Is there any medical terminology describing: "holding urine for a long time", or pain associated with this activity? A swollen organ may be described as distended if the swelling is symptomatic of a medical disfunction.
The purpose of most bladders is to collect and retain a fluid; if that fluid needs to be discharged periodically, and is not able to do so, then there is usually pain as a result of the distension.
Inability to urinate is known as ischuria or urinary retention, and could be the result of obstruction to the urethra, could be a failure of the bladder to fully contract during urination, or could many other possible causes.
The following is multiple choice question (with options) to answer.
What is a sac-like organ that stores urine? | [
"the urinary liver",
"the colon",
"the small intestine",
"the urinary bladder"
] | D | From the kidneys, urine enters the ureters. These are two muscular tubes that carry urine to the urinary bladder. Contractions of the muscles of the ureters move the urine along by peristalsis. The urinary bladder is a sac-like organ that stores urine. When the bladder is about half full, a sphincter relaxes to let urine flow out of the bladder and into the urethra. The urethra is a muscular tube that carries urine out of the body through another sphincter. The process of urine leaving the body is called urination. The second sphincter and the process of urination are normally under conscious control. |
SciQ | SciQ-7089 | neuroscience, neurophysiology, sensation, hearing
Fig. 1. Frequency tuning along the basilar membrane. source: Purves et al., 2001
References
- Purves et al. (eds.) Neuroscience 2nd ed. Sunderland (MA): Sinauer Associates (2001)
- Snow & Wyckam, Ballenger's Otorhinolaryngology: Head and Neck Surgery, John Jacob Ballenger (2009)
The following is multiple choice question (with options) to answer.
When the pressure waves from the scala move the basilar membrane, the tectorial membrane slides across the what? | [
"cytoplasm",
"keratin",
"stereocilia",
"dendrites"
] | C | The organs of Corti contain hair cells, which are named for the hair-like stereocilia extending from the cell’s apical surfaces (Figure 14.8). The stereocilia are an array of microvilli-like structures arranged from tallest to shortest. Protein fibers tether adjacent hairs together within each array, such that the array will bend in response to movements of the basilar membrane. The stereocilia extend up from the hair cells to the overlying tectorial membrane, which is attached medially to the organ of Corti. When the pressure waves from the scala move the basilar membrane, the tectorial membrane slides across the stereocilia. This bends the stereocilia either toward or away from the tallest member of each array. When the stereocilia bend toward the tallest member of their array, tension in the protein tethers opens ion channels in the hair cell membrane. This will depolarize the hair cell membrane, triggering nerve impulses that travel down the afferent nerve fibers attached to the hair cells. When the stereocilia bend toward the shortest member of their array, the tension on the tethers slackens and the ion channels close. When no sound is present, and the stereocilia are standing straight, a small amount of tension still exists on the tethers, keeping the membrane potential of the hair cell slightly depolarized. |
SciQ | SciQ-7090 | ocean, waves, ocean-currents, tides
(i) Wave generation by wind—the effective wind is that relative to the surface current, and the wave age (cp/U*) and effective surface roughness may be important, e.g., Janssen (1989). Here cp is the wave phase speed and U* is the friction velocity of the wind. The effective fetch also changes in the presence of a current.
(ii) Wave propagation—the effects of depth refraction are easy to spot, turning the mean wave direction towards shore-normal. Current refraction has a more subtle effect, dependent on the spatial variation of currents, whether decreasing or increasing towards the coast. Generally shoaling depths will increase the tidal amplitude towards the coast until friction reverses this trend. The waves will tend to turn towards the direction of the current axis.
(iii) Doppler shift—the effect of a steady current on intrinsic (relative) wave frequency. Waves of the same apparent (absolute) period will have a longer intrinsic period in a favourable (following) current and a shorter intrinsic period in an opposing current.
(iv) Steepening of waves on an opposing current (related to (iii)), due to shorter wavelength and increased wave height from wave action conservation.
(v) Modulation of absolute frequency by unsteady currents and modulation of intrinsic frequency by propagation over spatial gradients of current. If the current is steady the absolute frequency should be constant, if the current is homogeneous the intrinsic frequency should be constant. If both intrinsic and absolute period show a tidal modulation, the currents must be effectively inhomogeneous and unsteady.
(vi) Wave–current bottom stress. Various empirical theories for wave–current interaction in the bottom boundary layer suggest that the friction coefficient experienced by waves in a current regime will be larger than in no current. This also applies to the effective current friction factor in the presence of waves.
(vii) Effect of vertical current shear on wave breaking. Wind-driven surge currents would be relevant to this, the tidal currents have no surface shear.
The following is multiple choice question (with options) to answer.
What are surface currents generally caused by? | [
"minor wind belts",
"major humidity belts",
"major steam belts",
"major wind belts"
] | D | Like air in the atmosphere, ocean water moves in currents. A current is a stream of moving water that flows through the ocean. Surface currents are caused mainly by winds but not daily winds. Surface currents are caused by the major wind belts. These winds blow in the same direction all the time. So they can keep water moving in the same direction. |
SciQ | SciQ-7091 | nutrition, hematology, metabolism
Title: How does a glucose molecule enter the cell from blood vessel? The transporters in the plasma membrane of the cells promote the entry of glucose molecules from the extracellular matrix to the cytosol of the cell. Could someone explain how does the nutrient molecule enter the extracellular space from the blood vessel?
For instance, in the context of the pancreas, the walls of the blood vessel is fenestrated. The literature also provides evidence for the presence of connexon in the endothelium of the capillaries.
My doubt is, the nutrient molecule that diffuses from the blood vessel reaches the cytosol of the cell through
Diffusing through connexon ?(or)
Does it reach the interstitial matrix(the fluid surrounding the cells) and then uptaken by the transporters present in the plasma membrane of the cell? I think I understand your question, Natasha. In short, your own answer #2 is correct.
There are 3 spaces, and 2 pathways for glucose to pass from one to the next:
intracapillary plasma
extracellular fluid
the cytosol.
Ways glucose gets into the cell:
(2->3) To get from the ECF to the cytosol , glucose always needs a transport protein. These are the GLUTs. In two cases, the small intestine and kidney, these are part of a secondary active transport system based on the Na/K-ATPase. In the pancreas, it's GLUT2.
(1->2) To get from the capillary plasma to the ECF requires filtration, the process of applying hydrostatic pressure to the plasma and literally squeezing it like a sponge. The boundary of the "blood sponge" is the basement membrane. The membrane holds in the proteins, and lets anything dissolved in the watery serum (like glucose) through.
The Filtration Constant Kf is proportional to the percentage of the BM that is exposed in a given capillary, which varies by the type and other factors like histamine release.
The following is multiple choice question (with options) to answer.
What helps cells take up glucose from the blood? | [
"hemoglobin",
"insulin",
"estrogen",
"oxygen"
] | B | Insulin was the first human protein to be produced in this way. Insulin helps cells take up glucose from the blood. People with type 1 diabetes have a mutation in the gene that normally codes for insulin. Without insulin, their blood glucose rises to harmfully high levels. At present, the only treatment for type 1 diabetes is the injection of insulin from outside sources. Until recently, there was no known way to make insulin outside the human body. The problem was solved by gene cloning. The human insulin gene was cloned and used to transform bacterial cells, which could then produce large quantities of human insulin. |
SciQ | SciQ-7092 | newtonian-mechanics, energy, kinematics, speed
Potential energy on the Earth's surface is linear in height
Objects falling on the Earth's surface have constant acceleration
The following is multiple choice question (with options) to answer.
What is the term for potential energy due to the position of an object above earth? | [
"gravitational pull energy",
"gravitational potential energy",
"gravitational recovery energy",
"gravitational indication energy"
] | B | Potential energy due to the position of an object above Earth is called gravitational potential energy. Like the leaves on trees, anything that is raised up above Earth’s surface has the potential to fall because of gravity. You can see examples of people with gravitational potential energy in Figure below . |
SciQ | SciQ-7093 | 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 type of engineers influence community structure through their effects on the physical environment? | [
"electrical engineers",
"mechanical engineers",
"ecosystem engineers",
"civil engineers"
] | C | |
SciQ | SciQ-7094 | atoms, terminology
Title: What is a neutral atom? I was told that an atom's atomic number is defined as follows:
The number of electrons or protons present in a neutral atom is called atomic number. It is represented by Z.
What does neutral mean here? Why isn't it just "..present in an atom..."? Electrons and protons are charged particles. The electrons have negative charge, while protons have positive charge. A neutral atom is an atom where the charges of the electrons and the protons balance. Luckily, one electron has the same charge (with opposite sign) as a proton.
Example: Carbon has 6 protons. The neutral Carbon atom has 6 electrons. The atomic number is 6 since there are 6 protons.
The following is multiple choice question (with options) to answer.
The atomic number defines the identity of what? | [
"element",
"neutralized molecule",
"atomic reaction",
"periodic table"
] | A | The atomic number defines the identity of an element. |
SciQ | SciQ-7095 | elements, radioactivity
Title: Why radioactive elements emit alpha beta and gamma rays I am confused about this that why radioactive elements emits alpha beta and gamma rays WHILE other elements can't do so. The stability of nuclei is really a sophisticated topic in theoretical quantum mechanics. But there is a simple way to think about what is happening that doesn't get too intense with the quantum mechanical theory.
Nuclei are made from two particles: protons and neutrons. But protons are positively charged and repel each other. The electromagnetic force is very strong and therefore this force is very large. So the first mystery is why all nuclei don't just fly apart.
The reason they don't is that there are two very short-range but very strong forces that bind the nucleus together: the strong and weak nuclear forces. Without getting into mind-bending topics in theoretical physics we can understand something about their net effect like this.
The interaction of the electromagnetic force and the two nuclear forces has some structure (it's quantum stuff, just accept it). Some combinations of protons and neutrons are more stable than others. Each combination has an energy level and some combinations have lower energy than others. Nuclei with even numbers of protons and neutrons are more stable than odd-odd combinations and nuclei with wildly unbalanced neutron to proton ratios are less stable. Neutrons act a little like a glue, helping protons stick together (this is an oversimplification as too many neutrons is also a source of instability: this is a consequence of a complicated interplay of several forces). But bigger nuclei are less stable and need a higher ratio of neutrons. And some large nuclei are just too large for the forces to keep them together so beyond a certain point all nuclei are unstable.
Some nuclei can be transformed into a more stable (lower energy) nucleus by various forms of radioactive decay. Nuclei with too many neutrons can emit a beta particle (this decay mode converts a neutron into a proton); elements with too many protons can emit a positron (converting a proton into a neutron). Bigger nuclei can become more stable by kicking out an alpha particle (which makes the nucleus significantly smaller, moving it towards the stable zone). Gamma radiation is associated with some of these modes: the high energy photons "mop up" the excess energy (I'm simplifying a lot).
The following is multiple choice question (with options) to answer.
The nuclei of radioisotopes are unstable, so they constantly decay and emit what? | [
"radiation",
"acid",
"chemicals",
"moisture"
] | A | The nuclei of radioisotopes are unstable, so they constantly decay and emit radiation. |
SciQ | SciQ-7096 | reproduction, asexual-reproduction
Title: can self-fertilization in flowers be called asexual reproduction? Suppose a flower having both male and female reproductive parts is self-fertilized then can this be called asexual reproduction...?I'm quite confused cause in this case the fusion of male and female gametes do take place but again the gametes are from the same parent....please help. According to this article from Berkeley, asexual reproduction is:
Any reproductive process that does not involve meiosis or syngamy
Using this definition of asexual reproduction and knowing self-fertilization involves meiosis and syngamy, it is not asexual.
The following is multiple choice question (with options) to answer.
Parthenogenesis is the most common form of what in animals that at other times reproduce sexually? | [
"cell division",
"sexual dimorphism",
"asexual reproduction",
"budding"
] | C | |
SciQ | SciQ-7097 | geology, paleontology, dating, history-of-science
Title: Did geologists determine the age of rocks and fossils before the advent of modern scientific dating methods? Did geologists determine the age of rocks and fossils before the advent of modern scientific dating methods such as radiometric, electron spin resonance and thermoluminescence?
If they did, does anyone know how they went about it? The approach adopted by Charles Lyell (and other writers in a similar timeframe), in his book 'Principles of Geology' which was first published in the 1830s was to look at processes in the modern landscape where the rate of change could be determined by observation or from historical evidence, and assuming that similar processes operated at similar rates in the geological past. So, for instance, if you measure the amount of sediment transported by a river today, and you measure the volume of sediment in that river's delta, you can estimate how long that delta took to form. If you see a similar delta in the geological record, you can assume it took a similar time to form. Lyell's estimates of the age of the earth were low, but as the concept of plate tectonics, with it's progressive recycling of rocks through subduction wasn't recognised, it was remarkably prescient.
The following is multiple choice question (with options) to answer.
What kind of fossils are excellent markers for correlating the ages of sedimentary rocks? | [
"foram",
"agonum",
"vertiscom",
"euglena"
] | A | |
SciQ | SciQ-7098 | cell-biology, neuroscience, physiology, neurotransmitter, cell-signaling
Title: Is every neurotransmitter receptor an ion channel? This is a rudimentary question--perhaps the answer is well known to biologists, but is every neurotransmitter receptor also an ion channel?
For example, NMDAR is a glutamate receptor and cation channel and GABA_A receptors are gated ion channels. Is this true generally? If not, is there a classification of neurotransmitter receptors according to abstract function (e.g. all gated ion channels would form one class, then perhaps there are others)?
Thank you in advance! I am a mathematician just getting interested in some biology problems and trying to organize the basic knowledge in this area. I appreciate any insights here!
is every neurotransmitter receptor also an ion channel?
No.
There are two general types of receptors for neurotransmitters, ligand gated ion channels and receptors that activate second messenger systems, for example, G protein coupled receptors. They are sometimes referred to as ionotropic and metabotropic receptors. This figure from Principles of Neural Science, Ch. 10 illustrates the difference nicely:
The following is multiple choice question (with options) to answer.
Gated ion channels have a central role in what system's function? | [
"generous",
"endocrine",
"skeletal",
"nervous"
] | D | |
SciQ | SciQ-7099 | astrophysics, stars, fusion
Now, if we regard our star as spherically symmetric and dynamically stable, we can kick out the velocity terms and time derivatives in Euler's equation. Supposing gravity is the only external body force, we end up at the equation of hydrostatic equilibrium:
$$\frac{dP}{dr}=-\frac{Gm\rho}{r^2}=-\rho g$$
Remember, this follows from the conservation of momentum. To conserve energy, like mass, we say that the contribution to the total luminosity at $r$ is the mass of the shell times the specific energy generation rate $\epsilon$, so we write
$$\frac{dL}{dr}=4\pi r^2\rho\epsilon$$
To keep it simple, I've neglected to specify where $\epsilon$ will come from. It generally includes the energy generated by nuclear reactions rates, less the losses due to neutrinos streaming out in some reactions, plus—in some phases—the energy released by contraction. (It can be shown that when a star contracts it heats up but loses energy overall. See the Virial Theorem.) The energy generation depends on the density, temperature and chemical composition of the material. It isn't something we know from first principles. Instead, we use tables of data taken either from detailed calculations or laboratory experiments.
We now have to describe how energy is transported inside the star. The equations are a bit of a mouthful, so I won't write them here, but basically energy can either be transported by radiation or convection, depending on the temperature structure. In either case, you get an equation of the form $dT/dr=$(some right-hand side, see the notes). In the case of radiation, the transport coefficient depends on the opacity of the stellar material, denoted $\kappa$, which itself depends again on the density, temperature and chemical composition. (Strictly speaking, opacity depends on frequency, but we use a specific average opacity: the Rosseland mean opacity.) Like the energy generation rate, this isn't known from first principles: we use tabulated lab data.
The following is multiple choice question (with options) to answer.
Energy that the sun and other stars release into space is called what? | [
"static energy",
"mechanical energy",
"kinetic energy",
"electromagnetic energy"
] | D | Energy that the sun and other stars release into space is called electromagnetic energy . This form of energy travels through space as electrical and magnetic waves. Electromagnetic energy is commonly called light. It includes visible light, as well as radio waves, microwaves, and X rays ( Figure below ). |
SciQ | SciQ-7100 | inorganic-chemistry, redox, concentration, oxidation-state, mercury
Title: Why does mercury(II) nitrate form only when using concentrated nitric acid? In the reaction between mercury and nitric acid, mercury(II) nitrate only forms when concentrated nitric acid is heated up and added to it, if the acid is dilute, mercury(I) nitrate forms.
I understand heat must be added to make the nitric acid properly oxidise with the mercury, but how does the concentration affect the reaction? Is it due to extra water content in dilute nitric acid? How does that affect it? Why does mercury in dilute HNO3 give mercurous nitrate while hot concentrated HNO3 produces mercuric nitrate?
“Mercury dissolves in oxidizing acids, producing either Hg${^{2+}}$ or Hg$_2$$^{2+}$, depending on which reagent (mercury or e.g., nitric acid) is in excess.” Ref 1
Wikipedia says
“Mercuric nitrate can be reacted with elemental mercury to form mercurous nitrate…(and)…If the solution is boiled or exposed to light, mercury(I) nitrate undergoes a disproportionation reaction yielding elemental mercury and mercury(II) nitrate:” Ref 2
So, dilute acid is simply acid that is insufficient to oxidize all the mercury to mercuric; excess mercury reduces mercuric to mercurous nitrate by disproportionation. The equilibrium seems labile enough. In my simplified imagination, a mercuric ion just picks up a mercury atom and brings mercury nuclei even closer together than in the metal. The $\ce{Hg-Hg}$ bond length in mercurous nitrate is 254 pm (Ref 3) and 253 pm in mercurous chloride vs 300 pm in the metal. Ref 4
Figure 1. Structure of mercurous nitrate
The following is multiple choice question (with options) to answer.
Hydrogen gas is generated by the reaction of nitric acid and what else? | [
"elemental iron",
"martian iron",
"carbon",
"gaseous iron"
] | A | E XA MP L E 1 7 Hydrogen gas is generated by the reaction of nitric acid and elemental iron. The gas is collected in an inverted 2.00 L container immersed in a pool of water at 22°C. At the end of the collection, the partial pressure inside the container is 733 torr. How many moles of H2 gas were generated?. |
SciQ | SciQ-7101 | oceanography, stratigraphy, paleogeography
Title: Was the Caribbean Sea a closed sea during the last glaciation? Taking a look at Google Earth the straits between the Caribbean Sea and the Atlantic Ocean are not very deep.
The sealevel during the last glaciation was 120 meters lower than the present level.
Was the Caribbean Sea a closed or semi-closed sea during the last glaciation or the straits were deep enough to make it a connected sea? Thanks to @Eartworm I learned today I was totally incorrect: the straits are more than 2000 meters deep.
Tool to see bathymetry, navionics.com
The following is multiple choice question (with options) to answer.
What is the top 200 meters of water in the ocean called? | [
"photic zone",
"over zone",
"thymic zone",
"organelle zone"
] | A | ocean zone in the top 200 meters of water that receives enough sunlight for photosynthesis. |
SciQ | SciQ-7102 | inorganic-chemistry
Title: Zinc evaporation/toxicity at room temperature I have a (slightly embarrassing) question regarding zinc powder.
I have recently broken an old mercury thermometer, and read that I can handle the mercury with powdered zinc - so I've sprinkled some on my floor. Too much probably. It turned out that unfortunately the powder is then quite hard to get out of the particular material of my floor (wood). I got out as much as possible, but I think there's still some left. So now I'm wondering if there is some danger if having all that zinc laying around.
Thanks anybody for the answer :) Zinc will amalgamate with mercury, but whether that reduces the vapor pressure of mercury very much is debatable. At best, the increased volume of zinc amalgam and the ability to amalgamate with fine droplets of mercury would make it easier to clean up the mercury as amalgam.
It might be better to spread some sulfur dust (flowers of sulfur) over the area. The sulfur should react with the mercury and tie it up as sulfide, with very low vapor pressure. Sulfur powder (and possibly the HgS) might also be easier to clean up than zinc dust, because sulfur is more like ordinary dust than a dense metal dust.
BTW, I love mercury thermometers. And I hate it when I break them!
The following is multiple choice question (with options) to answer.
Zinc is what kind of metal.? | [
"passive stagnant metal",
"active move metal",
"active transition metal",
"active flow metal"
] | C | Figure 18.7 Zinc is an active transition metal. It dissolves in hydrochloric acid, forming a solution of colorless Zn 2+ ions, Cl– ions, and hydrogen gas. |
SciQ | SciQ-7103 | human-biology, cell-biology
Title: Body's decomposition Does a human body decompose in a completely sterile environment ? If yes, what decomposes it ? And how fast ? What happens in vacuum ? Can it remain exactly the same ?
Thanks
Does a human body decompose in a completely sterile environment ?
No it wont. Unstable molecules like ATP will quickly degrade spontaneously. The stable ones like many proteins and lipids wont degrade spontaneously. Enzymes are essential to degrade them and are to be supplied extraneously.
What happens in vacuum ?
Body will dry up :P
The following is multiple choice question (with options) to answer.
What do decomposers release when they break down dead organisms? | [
"carbon dioxide",
"methane",
"acids",
"nutrients"
] | D | Decomposers release nutrients when they break down dead organisms. |
SciQ | SciQ-7104 | waves, interference, wavelength, superposition
The wavelength is the distance of a "cycle". Take the horizontal length between any two crests, or any two troughs, and what you get is called the wavelength. In physics, this is notated with the $\lambda$ symbol (the Greek letter Lambda). In the plot above, the wavelength has a value of $\pi$.
The amplitude is the height from the centre line to either the crest or the trough.
Destructive interference happens when the squared amplitude of the sum of the waves is lower than the sum of the squared amplitudes of the waves.
Therefore, the interference between two waves is the "most destructive" when the phase difference is an odd number of half-wavelengths, as shown in the plot above with the "$\pi/2$", "$3\pi/2$", "$5\pi/2$" points on the horizontal axis.
The following is multiple choice question (with options) to answer.
Wavelengths are described by a unit of what? | [
"weight",
"direction",
"speed",
"distance"
] | D | Wavelengths are described by a unit of distance, typically meters. |
SciQ | SciQ-7105 | human-biology, reproduction, reproductive-biology
Also condom is not a modern mechanism it was used in ancient times, but the usage was to protect oneself from sexually transmitted diseases, but an unknown chemical used which is a spermicide and this resulted in contraception.
Records of condom use dates back to 3000 B.C. where King Minos of Crete, son of Zeus and Europa, utilized the bladders of goats to protect himself during intercourse.
In the 1500s, a syphilis epidemic spread across Europe. It was at this time that Gabriel Fallopius,created a linen
condom as a means to protect from the continuing spread of disease . This proved especially effective when soaked in an unknown chemical solution acting as a spermicide.
Reference
The medieval contraception methods includes,
Condoms
Female Barrier Methods
Herbs and Rituals
Intrauterine devices
Male methods
The Pill
These methods are widely described in this article.
The following is multiple choice question (with options) to answer.
Chlamydia, gonorrhea, and syphilis are examples of which type of sti? | [
"bacterial",
"non-contagious",
"incurable",
"viral"
] | A | Bacterial STIs include chlamydia, gonorrhea, and syphilis. |
SciQ | SciQ-7106 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
Which process acts as a natural complement for cellular respiration? | [
"atherosclerosis",
"glycolysis",
"absorption",
"photosynthesis"
] | D | Photosynthesis and cellular respiration are connected through an important relationship. This relationship enables life to survive as we know it. The products of one process are the reactants of the other. Notice that the equation for cellular respiration is the direct opposite of photosynthesis :. |
SciQ | SciQ-7107 | entomology, reptile
Title: Had there been a non-flying pterosaur? Since there are non-flying birds and secondary non-flying insects, it is reasonable to assume there were also non-flying pterosaurs. Well, according to this source there are no flightless bats, so it isn't an absolute that all flying clades have flightless members:
https://pterosaurheresies.wordpress.com/2011/07/21/meet-the-first-flightless-pterosaur-sos-2428/
Everyone knows about the various flightless birds: the penguin, the dodo, the ostrich… the list goes on. There are no flightless bats. And no one has ever discovered a flightless pterosaur… until now.
But the short answer to your question is: no confirmed flightless pterosaur fossil seems to have been discovered so far.
The longer answer is: from what I can tell no pterosaur has been found that was clearly flightless, but pterosaur flight isn't well-understood in the first place so there is debate as to how and whether some specimens could have flown. It seems to be the consensus so far that they did fly however (based on the lack of mention of flightlessness on the Wikipedia page, and the last paper I link to in this answer is fairly convincing).
As far as not finding flightless specimen, the above link claims to have found one but the source is not reputable and I found no confirmation of it elsewhere (Wikipedia confirms, and I'm usually all about Wikipedia but here the page has all the hallmarks of having been written by the same person who wrote the blog). The same author argues a large pterosaur is flightless here, but their arguments are quite poor compared to others made in the field and they seem again to be the only ones making them.
Here is a post from Tetrapod Zoology in 2008 imagining what a flightless pterosaur might be like, and also claiming none have been found:
The following is multiple choice question (with options) to answer.
What are the only invertebrates that can fly? | [
"birds",
"insects",
"amphibians",
"mammels"
] | B | The main reason that insects have been so successful is their ability to fly. Insects are the only invertebrates that can fly and the first animals to evolve flight. Flight has important advantages. It’s a guaranteed means of escape from nonflying predators. It also aids in the search for food and mates. |
SciQ | SciQ-7108 | physiology, hematology
Title: What is the function of clot retraction? I am thinking how clot retraction and fibrinolysis work together.
I think that clot retraction is a process that gets clot towards fibrinolysis process.
Fibrinolysis process then lyses the clot.
However, I am not sure if it is so simple.
Some seems to be discussing about how to differentiate start of fibrinolysis from clot retraction morphologically.
So they probably seem to be at this stage similar processes visually, but not functionally.
What is the function of clot retraction? The platelets in the clot contain contractile proteins. They bring the edges of the wound together, which also reduces the chance of further bleeding. The contraction process also supports the wound healing process as it brings the ends of the wound together.
For more information see this article: "Mechanics and contraction dynamics of single platelets and implications for clot stiffening"
The following is multiple choice question (with options) to answer.
What is the term for the cell fragments involved in blood clotting, which stick to tears in blood vessels and to each other? | [
"cells",
"platelets",
"droplets",
"molecules"
] | B | Platelets are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur. |
SciQ | SciQ-7109 | star, observational-astronomy, amateur-observing, asteroids
Title: Do objects that are invisible to the naked eye occlude much of the stars to Earth based observers? I was looking at a star recently and some other object that appeared to be stationary in relation to the star was occluding the light to only one of my eyes. This is why it caught my attention.
I was able to move my head around this shadow and see the star but there was a definite tiny area where the star was clearly hidden. The object hiding the star also appeared to be a similar size to the tiny point of light of the star. Is this common to observe?
For the last few days I have been asking myself how many objects could be hidden like this (though most with shadows that engulf the earth); How thick are asteroid belts etc, that are between our eyes and the rest of the stars.
Is most of it hidden? From your description, an object that blocks out light from a star in only one location cannot be an astronomical object.
Occultations by asteroids are fairly common. You can see a list at http://www.asteroidoccultation.com/. When a star is being occluded by an asteroid there will be a fairly narrow strip from which the star will be hidden. But it is still about 50km wide. The star appears to rapidly fade, and it remains hidden for at most a few seconds, then reappears. Your description of "only hidden to one of my eyes" doesn't fit an asteroid occultation.
The object hiding the star must, therefore, have been local, and not moving. It would be speculation to suggest what it could be.
There are may objects that are hidden in visible light, not by asteroids, but by interstellar dust clouds. We can see them by using other wavelengths.
The following is multiple choice question (with options) to answer.
What celestial body is often discovered because it causes a star to move or to dim? | [
"exoplanet",
"satellite",
"asteroid",
"comet"
] | A | We have been able to take pictures of only a few exoplanets. Most are discovered because of some tell-tale signs. One sign is a very slight motion of a star that must be caused by the pull of a planet. Another sign is the partial dimming of a star’s light as the planet passes in front of it. |
SciQ | SciQ-7110 | optics, reflection, geometric-optics
Well, your eyes are lenses, and they form images on your retina. So while there is no image being formed at the location of your eye, the light can be focused to then form an image on your retina.
So, when we talk about real images being formed, we are not talking about the image one would see if their eyes were in that location. We are just talking about a place where light rays from an object converge after interacting with the mirror / lens. If you want to describe what you see through your eyes, you have to add in the additional lenses that make up your eyes.
The following is multiple choice question (with options) to answer.
What shape is the lens of the eye? | [
"spherical",
"convex",
"concave",
"angular"
] | B | The lens of the eye is a convex lens. It fine-tunes the focus so an image forms on the retina at the back of the eye. Tiny muscles control the shape of the lens to focus images of close or distant objects. |
SciQ | SciQ-7111 | gene-expression
Title: How does a gene "know" what to change to? Excuse my ignorance but I've always been curious about this...
For example, a frog is red, but it starts living in a green forest. Over time the frog becomes green to camouflage. But a gene can't see and I'm sure there's no mechanism for color info to be transmitted to individual genes from the brain. So how does a gene know to pick green over, say, blue? Using your example, the gene doesn't know anything. Mutations cause some of the offspring of the red frog to turn green, some to turn blue, some to turn fluorescent yellow, and some stay red. Birds can't see the green ones as well as the others, so more green frogs survive and make more green frogs. The red frogs, the fluorescent yellow ones, the blue ones, mostly get eaten. After a few generations, almost all the frogs are green -- not because the gene knew anything, not because the mutations went in any direction, but because all the other changes were counterproductive and got eaten.
The gene doesn't know anything. It's just a bunch of chemicals that randomly react with cosmic rays, chance, whatever. Most of the changes are irrelevant or actively bad, and the frog that's carrying those particular chemicals doesn't survive. But sometimes the change benefits the frog carrying the particular chemicals and then the frog sends those chemicals down to its progeny.
Obviously this is hugely over-simplified. A short and simple intro to the basics of evolution is Understanding Evolution, by UC Berkeley.
The following is multiple choice question (with options) to answer.
What is the change frogs and butterflies go through? | [
"transformation",
"metamorphosis",
"parthenogenesis",
"hiatus"
] | B | |
SciQ | SciQ-7112 | molecules, adhesion
Title: What is the difference between intermolecular (cohesive, adhesive) and van der Waals force? I recently learnt that intermolecular force is the force of attraction between molecules and van der Waals force does the same so is there any difference ? Cohesion refers to the force of attraction between two of the same molecules, whereas adhesion refers to the force of attraction between two foreign molecules.
This is better depicted in the image below.
Van der Waals force simply refers weak electrostatic forces of attraction AND repulsion, caused by electric dipole moments.
The following is multiple choice question (with options) to answer.
What term is used to describe the attractive force between molecules of the same substance? | [
"magnetism",
"strength",
"cohesion",
"attraction"
] | C | |
SciQ | SciQ-7113 | life, extremophiles
Title: How close to Earth's core can organisms live? We don't to know much about organisms living deep below the Earth's crust. Recently a team led by S. Giovanni discovered some microbes 300 m below the ocean floor. The microbes were found to be a completley new and exotic species and apparently they feed off hydrocarbons like methane and benzene. Scientists speculate that life may exist in our Solar System far below the surface of some planets or moons. This raises some questions:
What is the theoretical minimum distance from Earth's core where life can still exist. Please explain how you came up with this number. For example, there are temperature-imposed limits on many biochemical processes.
Is there the potential to discover some truly alien life forms in the Earth's mantle (by this I mean, life which is not carbon based, or life which gets its energy in ways we have not seen before, or non DNA-based life, or something along these lines)?
What is the greatest distance below the Earth's crust that life has been discovered? I believe it is the 300 m I cited above, but I am not 100% sure. There's a lot we don't know about life in deep caves, but we can bound the deepest living organism to at least 3.5 kilometers down, and probably not more than 30 kilometers down.
The worms recovered from deep mining boreholes are not particularly specifically adapted to live that far down: they have similar oxygen/temperature requirements as surface nematodes.
The Tau Tona mine is about 3.5 kilometers deep and about 60˚ C at the bottom. Hydrothermal vent life does just fine up to about 80˚C, and the crust gets warmer at "about" 25˚C per kilometer. It's entirely reasonable to expect life to about 5 kilometers down, but further than that is speculation.
Increasing pressure helps to stabilize biological molecules that would otherwise disintegrate at those temperatures, so it's not impossible there could be life even deeper. It may even be likely, given that the Tau Tona life breathes oxygen.
I am certain no life we might recognize as life exists in the upper mantle.
The following is multiple choice question (with options) to answer.
Where do archea live? | [
"in mammals",
"everywhere",
"in the ocean",
"underground"
] | B | Archaea live everywhere on Earth, including extreme environments. |
SciQ | SciQ-7114 | vacuum, space
Title: What is in space? I was recently on a chat server having a random discussion about science stuff and someone I was talking to then made the comment that "space is not a complete vacuum and it's full of plasma / matter".
That got me thinking ... ok so I don't expect that the bulk of space is totally empty but if I took a "cube volume of the space outside the ISS" (or further out for scientific accuracy) ... do we know what would be observed inside that cube in terms of "real particles" from the standard model?
I'm thinking that there would be some amount of photons (light) and possibly some other stuff, by the other guys claim of "plasma being everywhere" raised some weirdness in my head I couldn't resolve.
He followed that up with "we live in an electric universe".
Does anyone have a professional / academic viewpoint on this (i'm no physics grad though so go easy on me)?
EDIT:
I've had time to go deeper in to this concept with the person I was talking to earlier and he cited NASA as a source and linked me to this ...
https://science.nasa.gov/science-news/science-at-nasa/1999/ast07sep99_1
This article clearly states ...
"99.9 percent of the Universe is made up of plasma," says Dr. Dennis Gallagher, a plasma physicist at NASA's Marshall Space Flight Center. "Very little material in space is made of rock like the Earth."
... surely this is a contextual statement but what is the context and does this literally mean as is worded or is there something else here? 1) To begin with, space or the interstellar medium if that is what you are refering to, accounts for all the matter that is not in stars, neither in planets or asteroids, and there is actually a lot of matter in there.
The following is multiple choice question (with options) to answer.
What is the 'stuff' that all things are made of? | [
"minerals",
"metal",
"matter",
"plasma"
] | C | Living things are made of matter. In fact, matter is the “stuff” of which all things are made. Anything that occupies space and has mass is known as matter. Matter, in turn, consists of chemical substances. A chemical substance is a material that has a definite chemical composition. It is also homogeneous, so the same chemical composition is found uniformly throughout the substance. A chemical substance may be an element or a chemical compound. |
SciQ | SciQ-7115 | evolution
Title: How to define "evolution"? The standard answer found in intro course to evolutionary biology to the question:
what is evolution?
is:
It is a change in allele frequency over time!
I believe a complete definition should encompass the following concepts:
mutations
copy number variation (CNV)
codon usage
chromosome numbers
phenotypic change (whether heritable or not)
Complex phenotypic trait such as plasticity and developmental noise
maybe some other things...
My questions are:
Would it be worth it to talk about phenotype in a definition of evolution?
What are the alternative definitions that have been proposed?
What is your definition?
Note: I would rather talk about genetic evolution, but if you think it is worth making one definition for genetic and cultural (and some other stuff maybe) evolution, you're free to suggest it! What is evolution?
In a non-biological sense, evolution means change:
"a process of [...] change"
Biological evolution (seeing as this is Biology stack exchange) then needs to be tweaked to give a biologically specific context. Many textbooks etc. give definitions of evolution and here are a few good ones from across the history of evolutionary biology:
Charles Darwin:
"Descent with modification".
Mark Ridley1:
"Evolution means change, change in the form and behaviour of organisms between generations. ... When members of a population breed and produce the next generation we can imagine a lineage of populations, made up of a series of populations through time. Each population is ancestral to the descendant population in the next generation: a lineage is an ancestor-descendent series of populations. Evolution is then change between generations within a population lineage."
Brian and Deborah Charlesworth2:
"Evolution means cumulative change over time in the characteristics of a population of living organisms. ... All evolutionary changes require initially rare genetic variants to spread among the members of a population, rising to high frequency..."
All of these have a common theme. Biological information is moving through time, descending with a degree of directionality (e.g. parent $\rightarrow$ offspring), and the information is modified with time.
Personally I would define evolution as:
The following is multiple choice question (with options) to answer.
What is the change of characteristics of living things over time? | [
"evolution",
"spontaneous mutation",
"adaptation",
"generation"
] | A | Evolution is a change in the characteristics of living things over time. Evolution occurs by a process called natural selection. In natural selection , some living things produce more offspring than others, so they pass more genes to the next generation than others do. Over many generations, this can lead to major changes in the characteristics of living things. Evolution explains how living things are changing today and how modern living things have descended from ancient life forms that no longer exist on Earth. |
SciQ | SciQ-7116 | electromagnetism, energy, electric-current, charge
Title: Charge and Current in an electrical circuit This is a question about the differences between charge and current.
First, why is current a more fundamental, or 'base' unit than the charge? It seems like a charge particle) would be more fundamental than 'charge per second', so why isn't the Coulomb used instead?
What is the SI unit for 'the total amount of charge' that has been pushed through a circuit? In my head it would be number of electrons that have went from the positive potential different to zero (similar to a ball dropping to the ground for a certain height).
Is there some sort of relationship between the total amount of charge that has went through a circuit and the potential energy released by the battery? I assume they would be the same.
This is a question about the differences between charge and current.
Actually, it is several questions :)
First, why is current a more fundamental, or 'base' unit than the charge? It seems like a charge particle) would be more fundamental than 'charge per second', so why isn't the Coulomb used instead?
Historically current could be measured more accurately than charge. So it made practical sense to choose current as the base unit despite the theoretical preference for charge as the base unit. SI is intended to be practical above all, so practical concerns won out over theoretical concerns.
What is the SI unit for 'the total amount of charge' that has been pushed through a circuit? In my head it would be number of electrons that have went from the positive potential different to zero (similar to a ball dropping to the ground for a certain height).
The coulomb.
Is there some sort of relationship between the total amount of charge that has went through a circuit and the potential energy released by the battery? I assume they would be the same.
They are not the same but closely related: $E=VQ$ where $E$ is the energy $V$ is the voltage of the battery and $Q$ is the charge
The following is multiple choice question (with options) to answer.
What is the si unit for electric current? | [
"joule",
"planck",
"ampere",
"ohm"
] | C | Electric current is a continuous flow of electric charges (electrons). Current is measured as the amount of charge that flows past a given point in a certain amount of time. The SI unit for electric current is the ampere (A), or amp. Electric current may flow in just one direction (direct current), or it may keep reversing direction (alternating current). You can watch an animation of electric current at this URL: http://www. schoolphysics. co. uk/animations/Electric_current/index. html. |
SciQ | SciQ-7117 | redox, oxidation-state
Title: Terminology of redox reactions: which species are the oxidizing and reducing agents? I've got a question regarding 'notation' for redox reactions. Suppose you are asked to identify the oxidizing and reducing agents for a simple reaction like this one:
$$\ce{Cl2(aq)}+\ce{2KI(aq)} \longrightarrow \ce{2KCl(aq)}+\ce{I2(aq)}$$
Now are you supposed to say $\ce{Cl}$ is the oxidizing agent or $\ce{Cl2}$? Also, is $\ce{KI}$ the reducing agent or $\ce{I}$ or $\ce{I^-}$?
By the way, if you were instead asked to identify which species got oxidized, would you again say that $\ce{KI}$ is oxidized or $\ce{I}$ or $\ce{I^-}$? Ignoring spectator ions,
$\ce{Cl2 +2 I- ->2Cl- +I2}$
So, $\ce{Cl2}$ is the oxidant and $\ce{I-}$ is the reductant.
The following is multiple choice question (with options) to answer.
What abbreviated form refers to oxidation-reduction reactions, which are part of respiration and photosynthesis? | [
"morph reactions",
"reflex reactions",
"oxid reactions",
"redox reactions"
] | D | In stoichiometry, quantities of reactants and/or products can be related to each other using the balanced chemical equation. The coefficients in a balanced chemical reaction are used to devise the proper ratios that relate the number of molecules of one substance to the number of molecules of another substance. Chemical reactions can be classified by type. Combination reactions (also called composition reactions) make a substance from other substances. Decomposition reactions break one substance down into multiple substances. Combustion reactions combine molecular oxygen with the atoms of another reactant. Oxidation reactions are reactions in which an atom loses an electron. Reduction reactions are reactions in which an atom gains an electron. These two processes always occur together, so they are collectively referred to as oxidationreduction (or redox) reactions. The species being oxidized it called the reducing agent, while the species being reduced is the oxidizing agent. Alternate definitions of oxidation and reduction focus on the gain or loss of oxygen atoms, or the loss or gain of hydrogen atoms. Redox reactions are easily balanced if the overall reaction is first separated into half reactions, which are individually balanced. Oxidation-reduction reactions are common in organic and biological chemistry. Respiration, the process by which we inhale and metabolize oxygen, is a series of redox reactions. In the absence of oxygen, redox reactions still occur in a process called anaerobic metabolism. Antioxidants such as ascorbic acid also play a part in the human diet, acting as reducing agents in various biochemical reactions. Photosynthesis, the process by which plants convert water and carbon dioxide to glucose, is also based on redox reactions. |
SciQ | SciQ-7118 | genetics, molecular-biology, cell-biology, cancer, mutations
Title: Question about proto-oncogenes and oncogenes? My textbook says:
Growth-promoting genes are called proto-oncogenes. Some can be changed into oncogenes by a point mutation that alters the ability of the proto-oncogene to be switched off. They remain permanently switched on. Oncogenes promote unregulated cell division. Such cell division leads to a tumour.
Does this mean that the change from proto-oncogene to oncogene is not a mutation in the exon, but rather in the intron?
I hope I used these terms correctly. Thank you for any help :) I am going to add to @MattDMo 's answer a bit.
Proto-oncogenes Function, Developmental Program, and Regulation
Proto-oncogenes are normally functioning genes that are more often than not in the pathways that lead to mitosis and cellular replication. They have important roles in the development, growth, and maintenance of the organism. Proto-oncogene is an accurate description of the genes, but I unfortunately think that sometimes people think that the genes themselves are bad and that isn't the case.
Growth and development in multicellular organisms are highly regulated processes with many checks and balances. Certain cells need to grow in certain places at certain times, and then they need to go into and remain in interphase. If they don't, or they do things at the incorrect times, the multicellular organism will not develop properly or will develop conditions such as cancer.
It is often these points of regulation that become dysregulated when a proto-oncogene becomes oncogenic. If there are regions of allostery that are affected by a mutation in the coding sequence (exon) and a control molecule that represses the activity of the enzyme through conformation change can no longer bind, then that enzyme can remain active, always turned on.
You can also have a situation where you have transcriptional regulators of proto-oncogenes that can be effected making the gene product oncogenic. If there is a mutation in an enhancer (intronic) of the gene that affects the binding kinetics of enhancers leading to a great increase in transcription, this concentrational difference can lead to uncontrolled grown and tumor formation.
The following is multiple choice question (with options) to answer.
In a cell cycle, what kind of regulator molecules allow advancement to the next stage? | [
"strong",
"similar",
"negative",
"positive"
] | D | 10.3 Control of the Cell Cycle Each step of the cell cycle is monitored by internal controls called checkpoints. There are three major checkpoints in the cell cycle: one near the end of G1, a second at the G2/M transition, and the third during metaphase. Positive regulator molecules allow the cell cycle to advance to the next stage. Negative regulator molecules monitor cellular conditions and can halt the cycle until specific requirements are met. |
SciQ | SciQ-7119 | javascript, object-oriented, unit-conversion
All units are converted to a base unit type (kelvin and meters per second)
Usage as follows
Units.kmph = 100;
const mph = Units.mph;
Units.celsius = 38;
const f = Units.fahrenheit;
The following is multiple choice question (with options) to answer.
What are kpa, atm, and mmhg measurement units for? | [
"temperature",
"weight",
"velocity",
"pressure"
] | D | The value of , the ideal gas constant, depends on the units chosen for pressure, temperature, and volume in the ideal gas equation. It is necessary to use Kelvin for the temperature and it is conventional to use the SI unit of liters for the volume. However, pressure is commonly measured in one of three units: kPa, atm, or mmHg. Therefore, can have three different values. |
SciQ | SciQ-7120 | cell-biology, cell, eggs, reproductive-biology, chickens
Title: Why are hard boiled eggs so homogeneous? A eukaryotic animal cell is a complicated piece of biological machinery. Some major structures inside of the cell (see the image below) include: the nucleus, mitochondria, Golgi vesicles, and various tubular structures. Why then is the single-celled, unfertilized chicken egg so homogeneous when it is cooked (or before)? The only major structure I can recognize is the cell nucleus.
*Image Credit: "Animal cell structure en" by LadyofHats (Mariana Ruiz) - Own work using Adobe Illustrator. Image renamed from Image:Animal cell structure.svg. Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Animal_cell_structure_en.svg#mediaviewer/File:Animal_cell_structure_en.svg Disclaimer: This is my understanding of the egg anatomy as a general biologist. There is most certainly better references and sources out there to explain this (please add better references if you know of any).
If I understand you correctly, your question is why we do not see cell organelles in a cracked or boiled egg. If so, your question seems to stem from a misunderstanding of what the egg white and egg yolk represents. A chicken egg is not simply an enlarged cell, and the egg yolk is not the cell nucleus.
When an oocyte matures in the chicken ovary, it stores yolk inside the cell and therefore enlarges. The yolk is therefore part of the oocyte cytoplasm. However, as it enlarges, the yolk is separated from the germinal disc, which holds all the other cell organelles (including the nucleus). The germinal disc is seen as a small white area on the egg yolk. Eventually, when the oocyte has accumulated enought yolk, it disattaches from the ovary (ovulation) and goes into the hens oviduct. This process is happening continuously, and oocytes of different stages of maturation are present on the ovary, which can be seen in this image:
The following is multiple choice question (with options) to answer.
Each month, starting in puberty, one egg matures and is released from where? | [
"pollen",
"testes",
"uterus",
"ovary"
] | D | Each month, starting in puberty, one egg matures and is released from the ovary. |
SciQ | SciQ-7121 | neuroscience, neuroanatomy
Likewise, the spinal chord is structured into sensory and motor regions. In summary, the spinal chord consists of: 1) cell bodies (motor, sensory, inter; grey in the picture), 2) ascending axons (blue), 3) descending axons (red). Similar to nerves, axons going up or down the spinal chord are bundled into "tracts". Sensory axons are never bundled with motor axons, making it possible to create a map of the spinal chord in cross-section.
The tracts' names might be a bit confusing at first, but on second look are actually pretty self-explanatory. They usually contain where the axons come from and where they are going in order to synapse with other neurons. E.g. the spinocerebellar tract is formed of axons coming from the spine and going to the cerebellum. Given that the cerebellum is near the brain and the spine is further down, this is obviously an ascending tract - and ascending tracts are always sensory (because sensory information never needs to be carried downwards due to the brain being at the top).
Where it gets blurry
The sensory/motor separation isn't always as clear as I've described above. In fact, nerves (bundles of axons anywhere in the body outside of the CNS) will usually contain both sensory and motor pipelines. In particular, the cranial nerves (12 of the most important nerves) all include sensory and motor components for the respective part of the body that they manage. E.g. the facial nerve contains both the sensory connections for parts of the tongue and the motor connections that control facial muscles.
Another more complex example is pain sensation, where interneurons in the spinal chord can feed back onto sensory neurons and inhibit their signals, or axons can inhibit those packed in the same nerve bundle simply due to electrical effects.
The following is multiple choice question (with options) to answer.
Synostoses unite the sacral vertebrae that fuse together to form the what? | [
"permanent sacrum",
"young sacrum",
"adult sacrum",
"lower sacrum"
] | C | synostoses and fusing the bony components together into the single hip bone of the adult. Similarly, synostoses unite the sacral vertebrae that fuse together to form the adult sacrum. |
SciQ | SciQ-7122 | food, decomposition
Title: Worm compost cannot have cooked food I live in the Netherlands and it is getting fashionable to compost with worms. After investigating a few websites I noticed that most websites suggested that I cannot feed the worms leftovers from citrus fruits. This seems logical. I then started noticing that people advise against feeding the worms cooked food.
I'm no biologist but I cannot imagine a reason why cooked food is bad for the worms. Could anybody explain why this might be in layman’s terms? There are a few reasons for not feeding cooked foods to worms (Eisenia spp.) in a smaller household size worm farm. It's not because the food is cooked but what it often contains.
The earthworm used in vermiculture is usually Eisenia fetida (red wigglers) though other Eisenia species are sometimes used. All Eisenia are epigeic species meaning they live in the junction of decomposing organic matter (such as leaf litter, aging manure, rotted fallen trees) and their natural food is decaying plant matter and bacteria that are also digesting the organic matter. They don't make use of small dead animals (meat and fat).
In large scale commercial vermiculture operations, leftover and past-due-date foods from restaurants, institutions, nursing homes and schools are used along with plant matter and carboard and paper. I'm not sure how they balance cooked foods but possibly much less is used than plant matter.
The fact food is cooked isn't the problem but what's in it and/or what happens to it when added to the bin. If you have leftover vegetables and fruit that's been cooked with no added salt, it's perfectly acceptable. A certain amount of sweetened cooked fruit is also fine as the worms will eat that too. But ready-made foods usually have preservatives, salt, fats and spices added. Either worms won't eat it, leading to odour caused by mouldy rotten food, or it can make them unthrifty and even killing off your worms if it's fed them repeatedly.
The following is multiple choice question (with options) to answer.
What eliminates food wastes that remain after digestion takes place? | [
"large intestine",
"liver",
"small intestine",
"gall bladder"
] | A | The large intestine eliminates food wastes that remain after digestion takes place. |
SciQ | SciQ-7123 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
What is the membrane that surrounds a fetus called? | [
"cell membrane",
"umbilical sac",
"amniotic sac",
"umbilicus"
] | C | The amniotic sac is a membrane that surrounds the fetus. It is filled with water and dissolved substances, known as amniotic fluid. Imagine placing a small plastic toy inside a balloon and then filling the balloon with water. The toy would be cushioned and protected by the water. It would also be able to move freely inside the balloon. The amniotic sac and its fluid are like a water-filled balloon. They cushion and protect the fetus. They also let the fetus move freely inside the uterus. |
SciQ | SciQ-7124 | terminology, meteorology
I've tried to illustrate the relationships with insolation and temperature here:
There are some other ways too:
Ecological. Scientists who study the behaviour of organisms (hibernation, blooming, etc.) adapt to the local climate, sometimes using 6 seasons in temperature zones, or only 2 in polar and tropical ones.
Agricultural. This would centre around the growing season and therefore, in North America and Europe at least, around frost.
Cultural. What people think of as 'summer', and what they do outdoors (say), generally seems to line up with local weather patterns. In my own experience, there's no need for these seasons to even be 3 month long; When I lived in Calgary, summer was July and August (hiking), and winter was December to March (skiing). Here's another example of a 6-season system, and a 3-season system, from the Aboriginal people of Australia, all based on weather.
Why do systems with later season starting dates prevail today? Perhaps because at mid-latitudes, the seasonal lag means that the start of seasonal weather is weeks later than the start of the 'insolation' period. In a system with no heat capacity, there would be no lag. In systems with high heat capacity, like the marine environment, the lag may be several months (Ibid.). Here's what the lag looks like in three mid-latitude cities:
The exact same effect happens on a diurnal (daily) basis too — the warmest part of the day is often not midday (or 1 pm in summer). As with the seasons, there are lots of other factors too, but the principle is the same.
These aren't mutually exclusive ways of looking at it — there's clearly lots of overlap here. Cultural notions of season are surely rooted in astronomy, weather, and agriculture.
The following is multiple choice question (with options) to answer.
What is the long-term average of weather in a particular spot called? | [
"climate",
"weather",
"migration",
"temperature"
] | A | Almost anything can happen with the weather. Climate, however, is more predictable. Climate is the long-term average of weather in a particular spot. Good climate is why we choose to vacation in Hawaii in February (usually on the leeward side). Of course, the weather is not guaranteed to be good! A location’s climate considers the same characteristics as its weather. These are its air temperature, humidity, wind speed and direction, and the type, quantity, and frequency of precipitation. For climate, these things are averaged over time. |
SciQ | SciQ-7125 | earth-history
Common elements in space, such as CO2, H20, CH4 and NH3 are gaseous at Earth's distance from the sun and as a result, are unlikely to stick to anything in the Earth's formation region. This is true for all 4 inner planets and likely all rocky worlds. Rocky planets likely can only form close to their star, just as gas giants, ice giants or other icy abundant bodies like comets and low-density moons, can only form further out.
Gases like the 4 above can begin to be retained around a planet after it reaches a sufficiently large mass with low enough surface temperature to retain those gases by gravity.
The boundaries where CO2, H20, CH4, NH3 and other gases can be found in the protoplanetary disk is called the frost line. Different gases have different frost lines depending on their freezing point.
It's thought that much of Earth's water, CO2, CH4 and NH3 came to the Earth by comet after the planet formed. There's still some uncertainty on the percentages, as some of those elements could have been trapped during formation.
Just to add, hydrogen and helium are obviously abundant, but will only begin to accrue around a planet of a certain mass. In our solar-system, only Jupiter and Saturn are massive enough to accrue hydrogen and helium. That's why Uranus and Neptune are relatively low on hydrogen and helium compared to the universal abundance.
Argon is in Earth's atmosphere because it forms from gradual radioactive decay of Potassium-40. Earth's Helium is also present as a result of radioactive decay.
The following is multiple choice question (with options) to answer.
What are the three most common elements in the air we breathe? | [
"nitrogen, oxygen and argon",
"nitrogen, argon, hydrogen",
"argon, oxygen, hydrogen",
"oxygen, nitrogen, H20"
] | A | Most nonmetals are poor conductors of heat. In fact, they are such poor conductors of heat that they are often used for insulation. For example, the down filling in this sleeping bag is full of air, which consists primarily of the nonmetal gases oxygen and nitrogen. These gases prevent body heat from escaping to the cold outside air. |
SciQ | SciQ-7126 | atmosphere, temperature, humidity, atmospheric-optics
Source As described here, condensation of cloud particles (i.e., contrail formation) will occur if the mixing between hot and moist exhaust from an aircraft engine and ambient environmental air results in the mixed air exceeding the ice saturation vapor pressure as its temperature changes. A conceptual diagram of this mixing process is shown here, for exhaust (parcel A) and environmental air (parcel B) with generic temperatures and saturation vapor pressures is shown here:
However, this would require knowledge of these specific temperatures and corresponding saturation vapor pressures. More practically, contrail prediction often just assumes that the air at altitudes where jets typically cruise (commonly, though not always, above 8 km/26,000 ft and at air temperatures below -40°C) is near or above supersaturation with respect to ice. This assumption is used operationally, for example, in NASA's publicly-available persistent contrail forecast. Note that the first source indicates that low wind speeds are also useful in identifying likely regions of persistent contrails.
Several sources of data may be useful in constructing similar analyses or forecasts and comparing to what might be expected on an average day, based on the local climatology. Observational data from radiosondes (i.e., weather balloons with instruments measuring temperature, moisture, and winds) is available globally in near-real time. This provides actual measurements of weather conditions through the relevant altitudes for contrail formation, and is particularly useful if measurements are needed relatively close to a radiosonde launch site.
For broader coverage in both space and time, the US National Oceanic and Atmospheric Administration provides archives of past weather analyses and operational forecast model output that can be requested by the general public. These datasets contain gridded model output with common parameters at various levels through the atmosphere on a national to global scale. While these datasets do not strictly consist of observed measurements, they are useful for analyses extending beyond the relatively limited set of observations available in most circumstances. Output from various operational forecast models is available for near-current or future conditions, whereas the reanalysis datasets provide similar information obtained from model analyses of past weather.
The following is multiple choice question (with options) to answer.
Cirrus, stratus, and cumulus are the main types of what? | [
"weather",
"storms",
"climate",
"clouds"
] | D | Clouds are classified on the basis of where and how they form. Three main types of clouds are cirrus, stratus, and cumulus. Figure below shows these and other types of clouds. |
SciQ | SciQ-7127 | circulatory-system, lymphatic-system, veins
Title: How does most of lymph get back into the blood stream? (I don't mean the lymphatic system) I once read that it was because of osmotic pressure that it returns to the blood stream, by entering the venules. But why? If lymph originated as plasma how come that the solute concentration is higher in the venule? Doesn't plasma contain solutes such as salts, nutrients, oxygen, etc. ? Technically 'lymph' is used to refer to the fluid found within the lymphatic system. If it's not in the lymphatic system, it is not lymph fluid. Thus, your question is really asking about interstitial fluid or the plasma that was filtered out of blood capillaries.
The answer to your question is based on the Starling equation. Normally fluid leaves a capillary due to a net pressure that favors the interstitium. This net pressure is based on the hydrostatic pressure within the capillary being greater than the interstitial pressure of the surrounding tissues, and the oncotic pressure of the capillary (that draws fluid in) being weaker than the hydrostatic pressure of the capillary (that pushes fluid out). At the venule end of this system, the capillary oncotic pressure is stronger than the capillary hydrostatic pressure, drawing fluid back into the circulatory system.
Remember that albumin is the most important component which establishes the oncotic pressure within a vessel, and that this protein is normally NOT released out of a vessel during filtration. Thus, it passes from the capillary into its corresponding venule directly.
The following is multiple choice question (with options) to answer.
Lymphatic capillaries are interlaced with the arterioles and venules of which system? | [
"skeletal systems",
"cardiovascular system",
"atmospheric system",
"circulatory system"
] | B | Figure 21.3 Lymphatic Capillaries Lymphatic capillaries are interlaced with the arterioles and venules of the cardiovascular system. Collagen fibers anchor a lymphatic capillary in the tissue (inset). Interstitial fluid slips through spaces between the overlapping endothelial cells that compose the lymphatic capillary. |
SciQ | SciQ-7128 | cell-signaling, chemical-communication
Title: How many molecules are generally required for cell signallng processes for given cases? I know its really a broad topic but I am interested in just few cases:
Quorum sensing
neurotransmitters for the communication of images/ general information
hormones/pheromones
I actually want to know that does a single or hundreds of molecules are needed to communicate information from one cell to another.
I searched but approx number of molecules, I can't find anywhere. A cell can interact with other cells in zillions of ways. You can send information from one cell to other cells via neurotransmitters, hormones, pheromones, electric signals, magnetic resonance ,leukotrines etc.
In general a single type of molecule is enough to send such information. Like you require only Acetylcholine(Ach) as neurotransmitter to transmit various nerve impulses.
But, even for a single type, you require thousands of molecules. Like 1 molecule of Ach can do almost nothing and would immediately be broken by Acetylcholinesterase. You require 1000s of such molecules.
You can modify the communicating information via different types of transmitters. You can use GABA or glycine to supress any information exchange or use dopamine to enhance it. But again you will need many molecules of GABA or Glycine.
For visual pathway, you can use no. of types of transmitters like glutamate, glycine, gaba, dopamine, acetylcholine, substance P etc.
Neurotransmitters for visual pathway.
Hormones are transmitters that are required in small quantities. But, again you require certain concentration. There is normal blood concentration of various hormones like 80 pg/ml for calcitonin.
Quorum sensing use transmitters like AHLs. Again a certain threshold value is required for them to act.
Again, to produce these transmitters you have to go through a rigorous process of transcription, translation and post-translational modifications.
So, for cell to communicate a rigorous process is used.
The following is multiple choice question (with options) to answer.
What is required for communication? | [
"weight and reception of signals",
"transmission and weight of signals",
"transmission and reception of signals",
"lack and reception of signals"
] | C | |
SciQ | SciQ-7129 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
When gametes unite during fertilization, the resulting zygote inherits two of what for each gene, one from each parent? | [
"chromosomes",
"molecules",
"genomes",
"alleles"
] | D | When gametes unite during fertilization, the resulting zygote inherits two alleles for each gene. One allele comes from each parent. The alleles an individual inherits make up the individual’s genotype . The two alleles may be the same or different. As shown in Table below , an organism with two alleles of the same type ( BB or bb ) is called a homozygote . An organism with two different alleles ( Bb ) is called a heterozygote . This results in three possible genotypes. |
SciQ | SciQ-7130 | human-biology, digestive-system, immune-system, microbiome
The next level of defense comes from the cells of the innate immune system (14). In innate immunity, specialized cells monitor the area they are in for Pathogen-Associated Molecular Patterns (PAMPs). PAMPs can be sugars that make up the cell walls of the microbe or proteins that get expressed on the surface of the organism, such as Flagellin, a protein only found in the flagella of certain pathogen. The innate immune cells have pattern recognition receptors (PRR) that have a general specificity for recognizing and responding to the PAMPs. Our cells even have PRRs for DNA and Double Stranded RNA's, however those are usually found in vesicles on the inside of the cell. These interactions are very general, however once PRRs bind to the PAMP, they are able to signal into the cytoplasm, which can lead to the production of proteins, among other possible responses.
Here you can think of PRRs like a motion detector in a security system; the dog, or your two year old, or an intruder are going to set off the alarm just the same. It is not specific. The motion sensor "knows" that something that it is supposed to recognize, i.e. a moving object larger than a mouse passed by and it triggered the response, but it cannot tell you which moving object triggered it, only that it was triggered.
The innate immune cells are also able to respond by "eating" the pathogen in a process called phagocytosis. Here, they break up the bacteria, yeast, or the remnants of other dead host cells or large pathogens, things like worms, and put the broken up pieces on protein molecules on their surface.
When innate immune cells do this, they are presenting molecules to specialized immune cells (adaptive immune cells (14)), B-Cells and T-Cells, that are highly specific as to what they will react to. These cells can also cause a lot of damage to the host, so they are tightly regulated. Think of the interactions as keys and locks. A protein from a bacteria should turn a few of these cells on, but a protein from the host should not fit the lock.
The following is multiple choice question (with options) to answer.
What provides an early, rapid, and nonspecific defense against invading pathogens? | [
"bacteria",
"toxins",
"neutrophils",
"microorganisms"
] | C | Figure 42.1 In this compound light micrograph purple-stained neutrophil (upper left) and eosinophil (lower right) are white blood cells that float among red blood cells in this blood smear. Neutrophils provide an early, rapid, and nonspecific defense against invading pathogens. Eosinophils play a variety of roles in the immune response. Red blood cells are about 7–8 µm in diameter, and a neutrophil is about 10–12µm. (credit: modification of work by Dr. David Csaba). |
SciQ | SciQ-7131 | brain, terminology, neuroanatomy, etymology
anterior to or involving the anterior part of a frontal structure
Anterior meaning
situated before or toward the front
Indeed Siddiqui et al (2008) mention:
The anterior part of the frontal lobe referred in the literature as ‘pre’-frontal lobe has been simultaneously referred to as ‘frontal granular cortex’ and ‘frontal association cortex.’ The anterior most portion of the frontal lobe is occupied by the PFC...
Reference
- Siddiqui et al., Indian J Psychiatry (2008); 50(3): 202–8
Fig. 1. The frontal lobe includes the prefrontal cortex (PFC). source: Socratic
The following is multiple choice question (with options) to answer.
In a mammal the front part of the brain is called the what? | [
"cerebellum",
"cerebrum",
"thallus",
"brain stem"
] | B | Of all vertebrates, mammals have the biggest and most complex brain for their body size (see Figure below ). The front part of the brain, called the cerebrum , is especially large in mammals. This part of the brain controls functions such as memory and learning. |
SciQ | SciQ-7132 | 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 term is used to describe joints in which the bones are connected by cartilage? | [
"spinal joins",
"blob joints",
"capillaries joints",
"cartilaginous joints"
] | D | Cartilaginous Joints Cartilaginous joints are joints in which the bones are connected by cartilage. There are two types of cartilaginous joints: synchondroses and symphyses. In a synchondrosis, the bones are joined by hyaline cartilage. Synchondroses are found in the epiphyseal plates of growing bones in children. In symphyses, hyaline cartilage covers the end of the bone but the connection between bones occurs through fibrocartilage. Symphyses are found at the joints between vertebrae. Either type of cartilaginous joint allows for very little movement. Synovial Joints Synovial joints are the only joints that have a space between the adjoining bones (Figure 38.25). This space is referred to as the synovial (or joint) cavity and is filled with synovial fluid. Synovial fluid lubricates the joint, reducing friction between the bones and allowing for greater movement. The ends of the bones are covered with articular cartilage, a hyaline cartilage,. |
SciQ | SciQ-7133 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
What type of tissue is made up of cells that have the unique ability to contract? | [
"connective tissue",
"nervous tissue",
"muscle tissue",
"epithelial tissue"
] | C | Muscle tissue is made up of cells that have the unique ability to contract, or become shorter. Muscles attached to bones enable the body to move. |
SciQ | SciQ-7134 | evolution, speculative
Title: Why Didn't Evolution Cause the Human Body to become Streamlined? If streamlining makes movement/locomotion quicker and easier, why didn't the apes evolve into life-forms that had streamlined bodies (much like fish)?
If streamlining makes movement/locomotion quicker and easier, why didn't the apes evolve into life-forms that had streamlined bodies (much like fish)?
As with everything in Evolutionary Biology, you must ask yourself: Gain vs. Cost?
In your specific case, the Gain is very little. Air isn't nearly as dense as water, so a streamlined form won't show a major benefit unless the organism is traveling very, very quickly. This is why you see it in birds; raptors can travel over 100mph while diving, and at those speeds small changes in drag can mean the difference between dinner and starving. Smaller birds often make very quick turnabouts and changes in direction mid-flight where, again, small changes in efficiency can mean the difference between life and death. The cost was is worth it.
For apes and monkeys, moving very quickly isn't a case of living or dying. That's what we evolved opposable thumbs and prehensile feet(/tails) for. You don't need to run fast when you can climb a tree and simply get away from any predators on the ground. After we came down from the trees permanently, our larger brains allowed us to use tools to fend off predators - which, again, is much simpler than evolving an aerodynamic form that won't make a difference until you're running at the speed of a car.
So, in lieu of becoming a land-shark, we have hands that can use keyboards and minds that can invent the keyboard. Unfortunately, while the gains are many, the costs do include both a very long period of time where humans are helpless without parents, and an absolutely terrible form of locomotion with our upright stance on forward-pointing knees. Though you won't catch Cheetahs digging sewers anytime soon.
The following is multiple choice question (with options) to answer.
Recent fossil evidence has shown that the evolutionary divergence of what group from other land animals was characterized by streamlining and simplifying the digestive system, which allowed a high metabolic rate? | [
"fish",
"birds",
"marsupials",
"rats"
] | B | Avian Adaptations Birds have a highly efficient, simplified digestive system. Recent fossil evidence has shown that the evolutionary divergence of birds from other land animals was characterized by streamlining and simplifying the digestive system. Unlike many other animals, birds do not have teeth to chew their food. In place of lips, they have sharp pointy beaks. The horny beak, lack of jaws, and the smaller tongue of the birds can be traced back to their dinosaur ancestors. The emergence of these changes seems to coincide with the inclusion of seeds in the bird diet. Seed-eating birds have beaks that are shaped for grabbing seeds and the two-compartment stomach allows for delegation of tasks. Since birds need to remain light in order to fly, their metabolic rates are very high, which means they digest their food very quickly and need to eat often. Contrast this with the ruminants, where the digestion of plant matter takes a very long time. Ruminants Ruminants are mainly herbivores like cows, sheep, and goats, whose entire diet consists of eating large amounts of roughage or fiber. They have evolved digestive systems that help them digest vast amounts of cellulose. An interesting feature of the ruminants’ mouth is that they do not have upper incisor teeth. They use their lower teeth, tongue and lips to tear and chew their food. From the mouth, the food travels to the esophagus and on to the stomach. |
SciQ | SciQ-7135 | 2. If we know that at least one will give birth to a boy (suppose we have accurate ultra-sound results), what is the probability all three will have a boy?
In general, the probability of an outcome $$A$$, given some event $$B$$, is $$P(A \mid B) = \frac{P(A)}{P(B)}.$$ This is, basically, the Law of Total Probability. Take $$A$$ to be the event "three boys are born" and $$B$$ to be the event "at least one boy is born". The probability of at least one boy was computed in the first part of the question: $$P(B) \approx 0.8634$$. Following the same kind of argument as in the first part (i.e. multiply the probabilities along the path from the root node to the leaf labeled "3 boys"), $$P(A) = P(\text{three boys}) = (0.485)^3 \approx 0.1141.$$
Then \begin{align} P(\text{three boys} \mid \text{at least one boy}) &= \frac{P(\text{three boys})}{P(\text{at least one boy})} \\ &\approx \frac{0.1141}{0.8634} \\ &\approx 0.1322. \end{align} In other words, if you know that one of the babies is a boy, then the probability that all three are boys is about 13.2%.
The following is multiple choice question (with options) to answer.
Probability can be used to predict the chance of gametes and offspring having certain what? | [
"atoms",
"molecules",
"alleles",
"particles"
] | C | Probability can be used to predict the chance of gametes and offspring having certain alleles. |
SciQ | SciQ-7136 | physical-chemistry, equilibrium, kinetics, stoichiometry
I might try to give you some intuition to back up that, for a given (elementary) reaction $\ce{A ->[k] B}$, the reaction rate $r$ can be written as
$$r = \frac{d P_\ce{B}}{dt} = -\frac{d P_\ce{A}}{dt} \propto P_\ce{A}\text{.}$$
(Observe that the second equality above is true due to $P_\ce{A} + P_\ce{B} = \text{constant}$.)
First, for an ideal gas, $P_\ce{A} = \frac{n_\ce{A}}{V} RT$.
This means that $P_\ce{A} \propto n$ for fixed temperature and volume.
Let's say the reaction happens as a random process.
That is to say that, for every time interval $\Delta t$, we have a probability per unit time $p$ of having a single molecule $\ce{A}$ turning into $\ce{B}$.
If we wait longer, proportionally more molecules will turn.
We'll thus have, for initially $n_\ce{A}$ molecules of $\ce{A}$, after $\Delta t$ seconds,
$$\Delta n_\ce{B} = p n_\ce{A} \Delta t\text{.}$$
This means that, in the time interval $\Delta t$, the population of $\ce{B}$ goes from 0 to $\Delta n_\ce{B}$ (assuming no $\ce{B}$ initially).
From the stoichiometry of the reaction, $\Delta n_\ce{B} = -\Delta n_\ce{A}$ (i.e., there's conservation of moles).
Thus,
$$\frac{\Delta n_\ce{B}}{\Delta t} = -\frac{\Delta n_\ce{A}}{\Delta t} = p n_\ce{A}\text{.}$$
The following is multiple choice question (with options) to answer.
What happens to the reaction rate over the course of a reaction? | [
"slows down",
"speeds up",
"stays the same",
"reverses"
] | A | At the beginning of the reaction, only the reactants A and B are present. Recall that over the course of a reaction, the reaction rate slows down. This is because the rate depends on the concentrations of one or more reactants. As the reactants are used up, their concentrations drop, thus decreasing the reaction rate. |
SciQ | SciQ-7137 | homework-and-exercises, energy-conservation
Title: Finding Speed with the Energy Principle - Nuclear Fission The question goes along the lines:
Uranium-$236$ fissions when it absorbs a slow-moving neutron. The two fission fragments can be almost any two nuclei whose charges $Q_1$ and $Q_2$ add up to $92e$ ($e$ is the charge of a proton, $1.6 \times 10^{-19}C$), and whose nucleons add up to $236$ protons and neutrons. One of the possible fission modes involves nearly equal fragments of the two palladium nuclei with $Q_1 = Q_2 = 46e$. The rest masses of the two palladium nuclei add up to less than the rest of the mass of the original nucleus. Make the assumption that there are no free neutrons, jus the palladium nuclei. The rest mass of the U-$236$ is 235.996 u (unified atomic mass units), and the rest mass of each $Pd-118$ nucleus is 117.894 u, where $1$ $u = 1.7 \times 10^{-27} kg$.
(a) Calculate the final speed $v$, when the Pd nuclei have moved far apart (due to the mutual electric repulsion). Is this speed small enough that $\frac{p^2}{2m}$ is an adequate ($p$ is momentum) approximation for the kinetic energy of one of the palladium nuclei? (make the non relativistic assumption first, then compare $v$ is indeed small enough to $c$)
(b) Using energy considerations, calculate the distance between centers of the palladium nuclei just after fission, when they are starting from rest.
The following is multiple choice question (with options) to answer.
The first reported nuclear fission occurred in 1939 when three german scientists bombarded uranium-235 atoms with slow-moving what? | [
"electrons",
"isotopes",
"neutrons",
"protons"
] | C | Nuclear Fission Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger binding energies per nucleon—that is, mass numbers and binding energies per nucleon that are closer to the “peak” of the binding energy graph near 56 (see Figure 21.3). Sometimes neutrons are also produced. This decomposition is called fission, the breaking of a large nucleus into smaller pieces. The breaking is rather random with the formation of a large number of different products. Fission usually does not occur naturally, but is induced by bombardment with neutrons. The first reported nuclear fission occurred in 1939 when three German scientists, Lise Meitner, Otto Hahn, and Fritz Strassman, bombarded uranium-235 atoms with slow-moving neutrons that split the U-238 nuclei into smaller fragments that consisted of several neutrons and elements near the middle of the periodic table. Since then, fission has been observed in many other isotopes, including most actinide isotopes that have an odd number of neutrons. A typical nuclear fission reaction is shown in Figure 21.14. |
SciQ | SciQ-7138 | human-biology, human-anatomy, terminology, anatomy, etymology
Title: Why is the opposite of plantar flexion called "dorsiflexion"? Why is the action of flexing the foot so that the toes move anteriorly/superiorly (i.e. in the direction opposite that which they move during plantar flexion) described as "dorsiflexion?" In the same vein, why is the top surface of the foot called the "dorsal surface?"
If anything, the action opposite to plantar flexion moves the foot in the ventral direction, doesn't it? And surely if you've ever seen a human in the anatomical position, you can see that there's nothing dorsal about the top surface of the foot - it's superior, perhaps, but by no means dorsal. Anatomical terms must be able to fit a wide variety of organisms, from insects to fish, dogs, horses, chimpanzees to humans. That's why the terms are sometimes confusing to people who are thinking only of bipedal humans.
In anatomy, the dorsum is the upper side of animals that typically run fly, swim or crawl in a horizontal position. In vertebrates the dorsum contains the backbone. In such an animal the "ground side" is the ventrum.
Due to varied orientation on quadrupedal mammals (where the term is more appropriately used) the "back"-side of the hand, the "top"-side of the foot and the upper surface of the tongue are referred to by the term dorsum.
Does this picture help? Note the dorsal surfaces of the body, muzzle, feet.
In anatomy, the sole of the foot is called the plantar surface. The top of the foot is called the dorsum of the foot. (Imagine us walking on all fours like apes.) Therefore when you extend your foot, it's called plantar flexion; when you flex your foot upwards towards your head, it's called dorsiflexion.
Similarly, the arteries feeding the bottom of your foot form the plantar arch. Those feeding the top are the dorsal artery (or the dorsalis pedis).
Because anatomy must describe other animals than ourselves with other orientations, it must be consistent. In a quadruped, the dorsum of the tongue and the feet do actually point to it's "back" surface. See the picture below:
The following is multiple choice question (with options) to answer.
What are temporary feet that protists have called? | [
"pedicules",
"transient pseudopodia",
"spontaneous pseudopodia",
"temporary flagella"
] | B | Other protists have what are called transient pseudopodia , which are like temporary feet. The cell surface extends out to form feet-like structures that propel the cell forward. An example of a protist with pseudopodia is the amoeba. |
SciQ | SciQ-7139 | dna, human-genetics, dna-sequencing, genomics
Title: Is it possible to deduce facts about a person's parents just by studying his/her genome? As an example, suppose Anne had abusive parents. Is it theoretically possible to deduce this from her genome even if she didn't inherit this quality (of being an abusive parent)? It might seem pernickety but you often can't deduce from a genome; you can only infer from it. For many characteristics about a person, there are only rough, probabilistic associations between genotype and phenotype. Not one-to-one relationships.
You can take an educated guess that someone with a certain genotype could be a social person of European ethnicity with a low risk of psychosis, which might suggest things about their parents. But there are likely many genes that influence those characteristics and still more non-genetic factors. So you couldn't be certain.
For a factor like whether the persons parents had abusive personalities, I think the genetic differences would be so subtle (if existent) and there would be so many other factors (such as the habits and choices of the parents) that you would be very unlikely to be able to draw any conclusive associations. Articles and studies about linking human genetics with a person's characteristics are listed below. If any of the genes in question are linked with those characteristics then the parents of someone with the gene could possibly have those genes and characteristics too.
Personality types including belligerence, charisma, cynicism, housekeeping, lack of personality, obsessive-compulsive behaviour and gullibility.
Psychosis and Schizophrenia risks.
Ethnicity and European ethnicity, which in turn correlate with geographical location, language and certain phenotypes.
Height.
If anyone would like to suggest additions to that list, I'll happily add them.
The following is multiple choice question (with options) to answer.
Predicting the possible genotypes and phenotypes from a genetic cross is often aided by a what? | [
"punnett square",
"dinobot square",
"balusters square",
"axle square"
] | A | Though the above fruit may not result, it would be nice to scientifically predict what would result. Predicting the possible genotypes and phenotypes from a genetic cross is often aided by a Punnett square. |
SciQ | SciQ-7140 | genetics, evolution, population-genetics, population-biology, allele
Title: Relationship between genetic diversity within and between species Here is a quote from Wagner (2008)
A second line of evidence [against neutralism] comes from the relationship between the mean number of polymorphic differences between alleles within a species, $\pi$, and the number of fixed differences between genes in two species, $d$. For neutral mutations, a positive association between $\pi$ and $d$ should exist, because the neutral theory predicts that both quantities are linearly proportional to the rate at which neutral mutations arise. Recent genome-scale data shows instead that this association is in fact negative.
What do "the mean number of polymorphic differences between alleles within a species" and "the number of fixed differences between genes in two species" have to do with each other? Why should there be any relationship at all? And by "two species", are they talking about Eastern Yellowback Whooping Finches versus Western Yellowback Whooping Finches, or any arbitrary two species, like E. Coli versus Muskrats?
I found this related question, but it doesn't say anything about different species. Metrics of interest
The two metrics you are interested in are
$\pi$ - the mean number of differences between two randomly sampled (with replacement) alleles in a population
$d$ - the mean number of differences between two randomly sampled (with replacement) alleles coming from two different species
Consider two sequences
ATCGTCAAT
ATAGTTAAT
There are 2 pairwise differences between these two sequences (positions 3 and 6).
The whole point here is to understand that two individuals in the same population coalesce at a given time in the past just like two individuals coming from two different species. The number of pairwise differences is just equal to the rate at which mutations accumulate multiplied by the coalescence time. Let me develop this idea with a few equations below.
Neutral Expectations
Let's do the math! We will do two important assumptions below.
Every mutation makes a new allele (it is an infinite allele model)
All mutations are substitutions (no indels, no gene duplication, etc...)
The following is multiple choice question (with options) to answer.
What is a relationship between organisms that strive for the same resources in the same place? | [
"symbiotic",
"competition",
"antagonistic",
"parasitic"
] | B | Competition is a relationship between organisms that strive for the same resources in the same place. The resources might be food, water, or space. There are two different types of competition:. |
SciQ | SciQ-7141 | human-biology, cell-biology
Title: What kinds of cells does human saliva contain? I have heard that our saliva contains cells. What cell types can be found in human saliva? It contains white blood cells (leukocytes) and cells from the inner lining of the mouth (buccal epithelial cells). The DNA obtained from these cells is the basis of DNA profiling based on saliva samples.
Source: Salimetrics
The following is multiple choice question (with options) to answer.
What is a collection of lymphatic tissue that combines with epithelial tissue lining the mucosa throughout the body? | [
"spheroids associated lymphoid tissue ( malt )",
"mucosa associated lymphoid tissue (malt)",
"cottony associated lymphoid tissue ( malt )",
"unassociated lymphoid tissue"
] | B | Mucosal Immune System The innate and adaptive immune responses compose the systemic immune system (affecting the whole body), which is distinct from the mucosal immune system. Mucosa associated lymphoid tissue (MALT) is a crucial component of a functional immune system because mucosal surfaces, such as the nasal passages, are the first tissues onto which inhaled or ingested pathogens are deposited. The mucosal tissue includes the mouth, pharynx, and esophagus, and the gastrointestinal, respiratory, and urogenital tracts. Mucosal immunity is formed by MALT, which functions independently of the systemic immune system, and which has its own innate and adaptive components. MALT is a collection of lymphatic tissue that combines with epithelial tissue lining the mucosa throughout the body. This tissue functions as the immune barrier and response in areas of the body with direct contact to the external environment. The systemic and mucosal immune systems use many of the same cell types. Foreign particles that make their way to MALT are taken up by absorptive epithelial cells and delivered to APCs located directly below the mucosal tissue. APCs of the mucosal immune system are primarily dendritic cells, with B cells and macrophages. |
SciQ | SciQ-7142 | zoology, ecology, species-distribution, migration
Title: How do animals end up in remote areas? I was thinking specifically about random marshy water holes on farmers fields. It seems that you can visit just about any one of these and you will find frogs if you look hard enough.
They usually don't seem to be connected to each other. If it were any other land animal I would figure they walk from one spot to another, but in the case of frogs, I don't imagine their range is very vast. But often these marshy spots can be separated by fairly large distances to a frog.
So this brings me to my question: how do each of these spots end up with frogs in them? I don't imagine a frog is going to go hopping over a hill to get to a marsh on the other side, is it? This question pertains to organism dispersal, which is a very active field of study with relation to it's impact on conservation efforts. Much of what I will say below has been covered in this wiki.
Definition: From the Wiki
Technically, dispersal is defined as any movement that has the
potential to lead to gene flow.
It can be broadly classified into two categories:
Density dependent dispersal
Density independent dispersal
The question of frogs and fishes both refer to Density independent dispersal, while an example of density independent dispersal can be the competition for habitat space between big cats and humans (this is a WWF pdf)
From the wiki:
Density-independent dispersal
Organisms have evolved adaptations for dispersal that take advantage
of various forms of kinetic energy occurring naturally in the
environment. This is referred to as density independent or passive
dispersal and operates on many groups of organisms (some
invertebrates, fish, insects and sessile organisms such as plants)
that depend on animal vectors, wind, gravity or current for dispersal.
Density-dependent dispersal
Density dependent or active dispersal for many animals largely depends
on factors such as local population size, resource competition,
habitat quality, and habitat size.
Currently, some studies suggest the same.
This study in particular studied the movement and habitat occupancy patterns within ephemeral and permanent water bodies in response to flooding. They found that during flooding these frogs moved out to flooded ephemeral water bodies and later on moved back again to the permanent ones.
Other suggested readings for those highly interested in the subject may include this (a phd thesis) and this (a project report)
The following is multiple choice question (with options) to answer.
What is the term for individuals of a species that live in a particular habitat? | [
"biosphere",
"ecosystem",
"family",
"population"
] | D | CHAPTER SUMMARY 45.1 Population Demography Populations are individuals of a species that live in a particular habitat. Ecologists measure characteristics of populations: size, density, dispersion pattern, age structure, and sex ratio. Life tables are useful to calculate life expectancies of individual population members. Survivorship curves show the number of individuals surviving at each age interval plotted versus time. |
SciQ | SciQ-7143 | biochemistry, gas-laws
Title: What is the state of aggregation (gas, liquid) of oxygen in blood? Atmospheric oxygen is in O2 and a gas. Then we inhale the air, our efficient lungs do the magic to filter out the oxygen and push them into the blood stream.
When we say hemo and globin transport the oxygen using the iron ions. In what state oxygen is transported in the blood? as a gas or a liquid or an ion? It is hard for me to conceive of the idea that oxygen would be in gaseous form in the blood. "GAS in blood?" e.g. Arterial Blood Gas Test
Also, how does the lungs convert the gas into something that is compatible to be in blood?
References:
Amount of Oxygen in the Blood Regarding the state of oxygen in blood: It is in solution in the blood plasma (which mostly consists of water), in the form of single molecules. Think of water which you leave exposed to air: carbon dioxide will be captured and dissolved (along with the other gases in air), but these molecules are not gaseous or liquid, but rather "in solution", which is different from the "classical" states.
Back to oxygen: As your reference already states, most of the oxygen in solution will bind to hemoglobin. The actual state of oxygen in that complex has been debated, but it is believed to be reduced by the hemoglobin iron to the superoxide anion, coordinated to Fe$^{3+}$. See Wikipedia on this.
Also, the lungs do not "convert" the atmospheric oxygen to anything, they rather allow, due to their very large surface area, the quick exchange of oxygen/carbon dioxide in solution and in the air.
The following is multiple choice question (with options) to answer.
Which gas moves from the blood in the capillaries into the air? | [
"carbon monoxide",
"nitrogen",
"carbon dioxide",
"oxygen"
] | C | Unlike oxygen, carbon dioxide is more concentrated in the blood in the capillaries surrounding the alveoli than it is in the air inside the alveoli. Therefore, carbon dioxide diffuses in the opposite direction. It moves out of the blood and into the air. |
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