source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-644 | 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.
By breaking down wastes and remains of dead organisms, decomposers perform what function in an ecosystem? | [
"reproduction",
"recycling",
"collecting",
"symbiosis"
] | B | Most prokaryotes get both energy and carbon from other living things. Many of them are decomposers. They break down wastes and remains of dead organisms. In this way, they help to recycle carbon and nitrogen through ecosystems. |
SciQ | SciQ-645 | human-biology, biochemistry, metabolism, food
Absorption in the gut is different for glucose and fructose, as is transport into cells.
Both glucose and fructose are (or can be) metabolised to pyruvate. However fructose is first metabolised to fructose 1-phosphate, and only enters glycolysis at the triose phosphate stage. A consequence of this is that it by-passes any regulation that occurs for the metabolism of glucose after conversion to glucose 6-phosphate. (In addition, glucose 6-phosphate has alternative metabolic possibilities not shown).
Postscript
This provides the framework for considerations of the consequences of dietary intake of sucrose, which are not part of the question and off-topic here, as already mentioned. Despite that, this topic has been addressed in questions in SE Biology, as well as elsewhere on the internet. I try not to offer advice to others (nor to take it from strangers). However my wife, whose advice I am sometimes obliged to take, professes the following:
“All things in moderation, and moderation in all things.”
The following is multiple choice question (with options) to answer.
What are sugars broken down into in your digestive system? | [
"starch",
"insulin",
"glucose",
"nicotine"
] | C | Sugars are small, simple carbohydrates. They are found in foods such as milk and fruit. Sugars in foods such as these are broken down by your digestive system to glucose, the simplest of all sugars. Glucose is taken up by cells for energy. |
SciQ | SciQ-646 | human-biology
Title: Do biological facts determine when a human fetus is considered alive and human? I often hear or read this statement:
"It's not a human, it's a fetus."
In other words, some think a fetus is non-human until a certain point.
And another similar statement:
"The fetus isn't alive until 26 weeks of gestation."
So some think the fetus is not actually "alive" until a certain point.
What does biology have to say about these two statements?
I encounter these statements often in discussions about abortion, but that issue, and other similar philosophical issues, are outside this question. I'm wondering strictly from a scientific/biological standpoint: are these statements true?
Is the fetus in a human mother non-human until a certain point?
Does the fetus not classify as "alive" until a certain point?
The people I encountered truly believed these statements (3 of the 4 in mind also claimed science was on their side), so it's not as if the question has no merit. I assumed that in the realm of science and biology, there must be a convincing and sure answer. Life is generally distinguished from non-life by metabolism and growth. As such, a fetus is alive. The reference to "not...until 26 weeks gestation" that you've heard likely refers to viability.* With the most aggressive medical care, this is the approximate age when a fetus may be able to survive outside the womb.
The term human from a biologic perspective is a species label.** Given that a fetus is genetically indistinguishable (in broad strokes) from a post-natal human, I think it would be hard to argue that it is anything other than human.
Summary: Yes, a human fetus is both alive and human.
*Note that this use of the word viable is standard but deviates somewhat from the etymology of the word.
**I'm ignoring here other ancient species (homo-) which may be considered human but are irrelevant to the question.
The following is multiple choice question (with options) to answer.
Approximately how many weeks does the fetal period last? | [
"27 weeks",
"30 weeks",
"25 weeks",
"10 weeks"
] | B | From the eighth week following fertilization until birth, the developing human being is called a fetus. Birth typically occurs at about 38 weeks after fertilization, so the fetal period generally lasts about 30 weeks. During this time, the organs complete their development. The fetus also grows rapidly in length and weight. Some of the specific changes that occur during the fetal stage are listed in Figure below . |
SciQ | SciQ-647 | human-biology, twins, oogenesis
Title: How does the genetic material differ between dizygotic twins and ordinary siblings? I am going to give a rough presentation on twin studies.
The terms heritability and concordance are included already, but I struggle with understanding the difference of the genetic material of dizygotic twins and ordinary siblings.
While ordinary siblings evolved from different sperm and egg cells, I only know that dizygotic twins form when two different sperm cells fertilize egg cells of the same cycle. However, I'm not sure if these cells are identical products of the same meiosis process.
I appreciate your help and time. Differences in genetic material between dizygotic twins and siblings are likely to be very similar.
Dizygotic twins, or so-called fraternal twins, on the other hand, are no more genetically similar than any other set of siblings. - Utah.edu
Since all oocytes are all synthesized during fetal development, dizygotic twins are no more likely to come from a single mitotic division than siblings are.
Also note that in human females, only one egg comes from the a full mitotic division:
The following is multiple choice question (with options) to answer.
Because dizygotic twins develop from two eggs fertilized by two sperm, they are no more identical than siblings born at what? | [
"other eras",
"other times of day",
"different places",
"different times"
] | D | birth of dizygotic (or fraternal) twins. Because dizygotic twins develop from two eggs fertilized by two sperm, they are no more identical than siblings born at different times. Much less commonly, a zygote can divide into two separate offspring during early development. This results in the birth of monozygotic (or identical) twins. Although the zygote can split as early as the two-cell stage, splitting occurs most commonly during the early blastocyst stage, with roughly 70–100 cells present. These two scenarios are distinct from each other, in that the twin embryos that separated at the two-cell stage will have individual placentas, whereas twin embryos that form from separation at the blastocyst stage will share a placenta and a chorionic cavity. |
SciQ | SciQ-648 | biochemistry, biophysics, cell-membrane, literature
Title: How does membrane potential vary between intraceullar membranes and the cellular membrane? Question
Does each type of membrane have a different membrane potential? I'm especially interested in answers that can cite academic papers that have attempted to measure membrane potentials.
Discussion
I've asked about the composition of membranes before , and although I recieved some information, I didn't get all the information I was after. This isn't a problem with our community but rather with the field at large: the popular thinking is membranes are membranes are membranes (mostly due to the difficulties in studying membrane biophysics experimentally).
This is how wikipedia defines membrane potential:
Membrane potential (also transmembrane potential or membrane voltage)
is the difference in electric potential between the interior and the
exterior of a biological cell. - Wikipedia
This isn't strictly true. Intracellular membranes also have membrane potentials as one can imagine, and there is some unverified information regarding compartmental pH values. This is why I am interested to find out if there have been studies attempting to quantify this across the cell membrane, and across different subcellular membranes. Yes, various intracellular membranes do have potential differences, but as you can imagine they are more difficult to measure experimentally, so in general data on this is scarce.
Summary
Mitochondrial membrane: 150mV-180mV with negativity on the matrix side. Seth et al 2011
Endoplasmic reticulum membrane: 75-95mV with negativity in the ER. Qin et al 2011, Worley et al 1994
Golgi: No notable membrane potential. Schapiro & Grinstein 2000
Lysosomal: 20mV with more negativity on the cytosolic side. Koivusalo et al 2011
The following is multiple choice question (with options) to answer.
What is the plasma membrane mainly composed of? | [
"phospholipids",
"filaments",
"antibodies",
"carbon"
] | A | The plasma membrane is composed mainly of phospholipids, which consist of fatty acids and alcohol. The phospholipids in the plasma membrane are arranged in two layers, called a phospholipid bilayer . As shown in Figure below , each phospholipid molecule has a head and two tails. The head “loves” water (hydrophilic) and the tails “hate” water (hydrophobic). The water-hating tails are on the interior of the membrane, whereas the water-loving heads point outwards, toward either the cytoplasm or the fluid that surrounds the cell. |
SciQ | SciQ-649 | big-bang-theory, expansion
Title: How do we know the universe's expansion is speeding up? Please forgive my ignorance, I am not an astronomer, just an interested layman.
The further away a galaxy is from us, the faster it is moving away from us. But the galaxies we see exist in the distant past because it takes a long time for their light to reach us. The closer galaxies are, the more recent their light is, and the slower they move away from us. Doesn’t this seem to indicate that the expansion of the universe is slowing down, because the more recent light from galaxies, appears to be moving away slower? Does this make sense?
Quote from Wikipedia:
Hubble observed that the distances to faraway galaxies were strongly correlated with their redshifts. This was interpreted to mean that all distant galaxies and clusters are receding away from our vantage point with an apparent velocity proportional to their distance: that is, the farther they are, the faster they move away from us, regardless of direction. As a fellow layman, I'll give this my best shot.
The further away a galaxy is from us, the faster it is moving away
from us. But the galaxies we see exist in the distant past because it
takes a long time for their light to reach us. The closer galaxies
are, the more recent their light is, and the slower they move away
from us.
All true. Think of a single point explosion, at any given time, the object twice as far should be moving twice as fast, cause they both started in the same place at the same time, so twice as fast moves twice s far. There are, complications - with the explosion there's air resistance, with the universe well, I'll get to that.
Doesn’t this seem to indicate that the expansion of the universe is
slowing down, because the more recent light from galaxies, appears to
be moving away slower? Does this make sense?
The following is multiple choice question (with options) to answer.
Astronomers have wondered if the universe is expanding fast enough to escape the pull of what? | [
"kinetic energy",
"Coreolis effect",
"light",
"gravity"
] | D | We know that the Universe is expanding. Astronomers have wondered if it is expanding fast enough to escape the pull of gravity. Would the Universe just expand forever? If it could not escape the pull of gravity, would it someday start to contract? This means it would eventually get squeezed together in a big crunch. This is the opposite of the Big Bang. |
SciQ | SciQ-650 | newtonian-mechanics, energy, newtonian-gravity
Title: Kinetic energy with no velocity When a body is displaced against the gravitational field of force it gains potential energy. When we drop the body it begins to move downward with a certain amount of acceleration, and the potential energy turns into kinetic energy. Kinetic energy is given by the equation:
$$ E_k = \frac{1}{2}mv^2$$
When the body falls off the ground, and it stops moving then its velocity is zero, and therefore the kinetic energy is also zero in this case. In which form of energy does this kinetic energy usually convert into? It is zero, because kinetic energy is the one associated only with an object in motion. It is maximum just before it touches the ground. And once it reaches the ground, most of the energy is perceived as sound, lost as heat and some as stress, which causes deformation of the body. If the body can't sustain the stress on its impact with the ground, it breaks.
The following is multiple choice question (with options) to answer.
When someone falls, the kinetic energy the person has upon reaching the floor is the amount of what energy lost by falling through height? | [
"potential energy",
"nuclear energy",
"thermal energy",
"gravitational energy"
] | A | with a minus sign because the displacement while stopping and the force from floor are in opposite directions (cos θ = cos 180º = − 1) . The floor removes energy from the system, so it does negative work. The kinetic energy the person has upon reaching the floor is the amount of potential energy lost by falling through height. |
SciQ | SciQ-651 | particle-physics, nuclear-physics, neutrons
Title: Are neutrons and protons stable inside atomic nuclei? Some people naturally assume that atomic nuclei are made of protons and neutrons. That is, they are basicly clumps of protons and neutrons that each maintain its separate existence, like pieces of gravel maintain their existence if you mold them together in a ball with mud for a binding force.
How come neutrons in a nucleus don't decay?
This is a natural assumption. A hydrogen nucleus can have one proton as its nucleus. Nuclei can absorb neutrons to become other isotopes. It's natural to assume that nuclei are clumps of protons and neutrons.
Sometimes if an atomic nucleus gets broken by application of large amounts of energy, typically applied with a fast-moving subatomic particle, they might release a neutron or a proton. So for example, smash an alpha particle into a beryllium nucleus and a neutron comes out. Doesn't that imply that the neutron was in there all along, waiting to get out?
But that reasoning implies that electrons, positrons, muons etc are also inside the nucleus all the time, waiting to get out.
There's an idea that protons and neutrons inside a nucleus swiftly transfer charges. This is analogous to a theory from organic chemistry, where sometimes single and double bonds switch back and forth, increasing stability. We could have quarks getting exchanged rapidly between protons and neutrons, increasing stability. I can see that as increasing stability for the nucleus, but I just don't see it as making the protons and neutrons more stable. If ten Hollywood couples get repeated divorces and marry each other's exes, you wouldn't say that the original marriages are stable.
In the extreme, the quarks might just wander around in a nuclear soup, and the protons and neutrons have no more identity than a bunch of used computers disassembled with the parts on shelves for resale. Maybe you could collect enough parts to take a working computer out of the store with you, but it probably won't be one of the old computers.
The following is multiple choice question (with options) to answer.
What are protons and neutrons that make up the nucleus of an atom called? | [
"electron shells",
"pions",
"baryons",
"nucleons"
] | D | and Z, the atomic number, is the number of protons. The protons and neutrons that make up the nucleus of an atom are callednucleons, and an atom with a particular number of protons and neutrons is called anuclide. Nuclides with the same number of protons but different numbers of neutrons are called isotopes. Isotopes can also be represented by an alternative notation that uses the name of the element followed by the mass number, such as carbon-12. The stable isotopes of oxygen, for example, can be represented in any of the following ways:. |
SciQ | SciQ-652 | planet, natural-satellites, nomenclature
Title: Is the satellite of a small star in a binary solar system a moon or a planet? What exaclty distinguishes a moon from a planet?
In a binary solar system that has a large star in the center and a smaller star - among some planets - orbiting that large star, and the smaller star has natural satellites - are these satellites called moons or planets?
Or asked in a different way - if Jupiter would ignite and become a star (which it can't because its mass doesn't suffice, but let's assume it was larger and could ignite), would its moons then be considered planets? A planetary mass object (also callled a planemo) is an astronomical object large enough to be pulled into a roughly spherical shape by its gravity compressing its matter. A planetary mass object must also have less than about 13 times the mass of Jupiter or about 4,131.4 times the mass of Earth.
If a planetary mass object orbits around the Sun in our solar system it is called a planet (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, & Neptune) or a dwarf planet (Ceres, Pluto, Eris, Hamaea, and Makemake, plus of number of candidate objects).
If a planetary mass object orbits around a planet in our solar system it is considered to be a natural satellite or a moon. Smaller objects which orbit around planets are also considered to be moons.
Any object smaller than a planetary mass object that orbits the Sun in our solar system is a small solar system body. They include all comets, asteroids, etc. that orbit the Sun ddirectly instead of orbiting one of the planets, moons, asteroids etc. that orbit the sun.
Any astronomical body with a mass greater than about 75 times the mass of Jupiter, or about 23,835 times the mass of the Earth, is a star are the stellar remnant of a star which has completed its "life cycle".
Any planetary mass object which directly orbits a star which is not the Sun, in another star system, is usually considered to be planet. So far there has been no effort to classify exoplanets (planets orbiting other stars) in other star systems as planets or dwarf planets. If they are large enough to be detected they are considered to be explanets. That might possibly change sometime in the future.
The following is multiple choice question (with options) to answer.
The sun, stars, moon, planets and comets are all type of what objects? | [
"celestrial",
"spacial",
"extraterrestrial",
"universal"
] | A | |
SciQ | SciQ-653 | lab-techniques, mutations, biostatistics, protein-engineering
NNK = 32 combinations, 50 mutants (n=32, k=50): $p_{all}$ < 0.07%
NNK = 32 combinations, 100 mutants (n=32, k=100): $p_{all}$ < 25.5%
NNK = 32 combinations, 200 mutants (n=32, k=200): $p_{all}$ < 94.6%
As you can see there's a sharp transition as the coverage count increases.
Important caveat: the theoretical value may not give you what you want. In the paper I linked above, we used two degenerate primers with 18 N bases to inject 36bp of random material, which means we had $4.7x10^{21}$ possible combinations and should never have seen a repeat --- except that sequencing showed that we did indeed get several repeats out of only a few hundred colonies. Thus, biases in the biology may lead your statistics to be skewed from what the theory suggests.
The following is multiple choice question (with options) to answer.
What is the total number of codons? | [
"51",
"64",
"45",
"68"
] | B | The mRNA is divided into three-base segments called codons. A codon is the segment of nucleotides that codes for an amino acid, or for a start or stop signal. There are 64 codons. |
SciQ | SciQ-654 | waves, harmonics
Title: Standing waves confusion Its just so confusing as to why the antinodes are formed from the constructive interference by superposition of the wave formed by the incident wave and the reflected wave... The phase difference is clearly 180° and not 0°, so shouldn't the reflected wave and incident wave superpose to destructive interference? which would then make it a node.. but not the antinode.. similarly.. with the node.. the phase difference is 0°.. so how come it does not oscillate at that point?.. Honestly, I think how standing waves arise itself is confusing me.. Standing wave animation and see that at a node the phase difference between the two travelling waves is always $180^\circ$ and at an antinode the phase between the two travelling waves is $0^\circ$.
The following is multiple choice question (with options) to answer.
Solution nodes and antinodes are both areas of wave interference, but they differ in the presence of what condition? | [
"radiation",
"speed",
"gravity",
"motion"
] | D | Check Your Understanding Define nodes and antinodes. Solution Nodes are areas of wave interference where there is no motion. Antinodes are areas of wave interference where the motion is at its maximum point. |
SciQ | SciQ-655 | evolution, zoology, anatomy, species
Title: Examples of animals with 12-28 legs? Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list:
snakes have 0
Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs)
Most mammals, reptiles, amphibians have 4 legs
Echinoderms (e.g., sea stars) typically have 5 legs.
Insects typically have 6 legs
Octopi and arachnids have 8 legs
decapods (e.g., crabs) have 10 legs
....But I can't really think of many examples of animals containing more legs until you reach 30+ legs in centipedes and millipedes. Some millipedes even have as many as 750 legs! The lone example I am aware of, the sunflower sea star, typically has 16-24 (though up to 40) limbs.
So my question is: what are some examples of animals with 12-28 legs? As a couple of counterexamples, species in the classes Symphyla (Pseudocentipedes) and Pauropoda within Myriapoda have 8-11 and 12 leg pairs respectively, so between 16 to 24 legs (sometimes with one or two leg pair stronlgy reduced in size).
(species in Symphyla, from wikipedia)
Another common and species-rich group with 14 walking legs (7 leg pairs) is Isopoda.
(Isopod, picture from wikipedia)
You also need to define 'legs' for the discussion to be meaningful. As you say, decapods have 10 legs on their thoracic segments (thoracic appendages), but they can also have appendages on their abdomens (Pleopods/swimming legs), which will place many decapods in the 10-20 leg range.
(Decapod abdominal appendages/legs in yellow, from wikipedia)
So overall, in Arthropoda, having 12-28 legs doesn't seem all that uncommon. There are probably other Arthropod groups besides those mentioned here that also have leg counts in this range.
However, for a general account, the most likely answer (if there is indeed a relative lack of 12-28 legged animals) is probably evolutionary contingencies and strongly conservative body plans within organism groups.
The following is multiple choice question (with options) to answer.
While similar to insects, what eight-legged invertebrates lack antennae or wings? | [
"crustaceans",
"spiders",
"arachnids",
"reptiles"
] | C | Arachnids do not have antennae or wings. |
SciQ | SciQ-656 | dna, dna-sequencing
Except for Red Blood Cells, every somatic cell contains two copies of the autosomal chromosomes and a pair of sex chromosomes, either XX or XY (Assuming an average human being) One set is maternal and one is paternal
Some lymphocytes actually recombine their chromosomes, so their DNA will be functionally different to all of the other somatic cells in the body.
Gametes undergo Meiosis and will be haploid, only containing one copy of each autosomal chromosome and one of the sex chromosomes
Cells accumulate mutations over time. The closest you could probably come to an exact clone of a person is if you harvested one of the cells from the eight-cell stage of development. The other seven are able to go on and produce a viable and healthy person. The harvested cells DNA would be the closest to the DNA that combined in the fertilization of the egg. The next closest would likely be stem cells from cord blood. Then probably neurons, as they tend to divide the least.
As the link you posted said, ATCG can be represented in a two bit code, so for about 6 billion bases, you would need about 1.5GB of storage (You need to capture both sets of chromosomes in order to produce a person).
The following is multiple choice question (with options) to answer.
How many chromosomes do mature gametes contain? | [
"19",
"23",
"17",
"13"
] | B | Spermatogenesis As just noted, spermatogenesis occurs in the seminiferous tubules that form the bulk of each testis (see Figure 27.4). The process begins at puberty, after which time sperm are produced constantly throughout a man’s life. One production cycle, from spermatogonia through formed sperm, takes approximately 64 days. A new cycle starts approximately every 16 days, although this timing is not synchronous across the seminiferous tubules. Sperm counts—the total number of sperm a man produces—slowly decline after age 35, and some studies suggest that smoking can lower sperm counts irrespective of age. The process of spermatogenesis begins with mitosis of the diploid spermatogonia (Figure 27.5). Because these cells are diploid (2n), they each have a complete copy of the father’s genetic material, or 46 chromosomes. However, mature gametes are haploid (1n), containing 23 chromosomes—meaning that daughter cells of spermatogonia must undergo a second cellular division through the process of meiosis. |
SciQ | SciQ-657 | agriculture
Title: What does "permanent field" mean in agriculture? I am reading a book that in a paragraph talks about the agricultural methods used in prehistoric Finland.
The further north and east, the more extensive the amount of
burn-beat cultivation, which was a far from primitive form of
agriculture. The yield was many times higher (twenty- to thirty-fold)
than on permanent fields (five- to ten-fold), and there were multiple
varieties of the technique
A history of Finland by Henrik Meinander.
One of them is burn-beating. Like I understand, in burn-beating people cut down the trees in the forests and burn the topsoil. This way they can use that soil for 3 to 6 years for cultivation.
The other method is permanent field. I have searched the internet and the result I got was "permanent crops", like here. In which case people planted trees once in a field and harvested them multiple times.
But in another research about prehistoric Finland it was saying:
The site of Orijärvi shows that permanent field cultivation, with
hulled barley as the main crop was conducted from approximately cal AD 600 onwards.
The following is multiple choice question (with options) to answer.
What is the term for land that has permanently frozen soil? | [
"snow-field",
"permafrost",
"Arctic",
"ice desert"
] | B | Permafrost is land with permanently frozen soil. |
SciQ | SciQ-658 | redox, reactivity, reaction-control
Title: Oxidation Reactions/Reactivity of Manganese Metal in Air and Water I am planning on doing some reactions that lead to Manganese metal and a neutral solution containing $\ce{Mn^{2+}}$ as by-products, and I wanted to try some things out with the Manganese as well.
Since Manganese has common charges of II and III, will a relatively fine, grainy form of the metal burn (and at what temperature) in air to form a mixed "$\ce{Mn(II, II)}$" oxide, $\ce{Mn3O4}$, the way Iron does as it rusts, or is $\ce{MnO}$ more predominant?
I have the same question about whether or not $\ce{Mn3O4}$ is formed in "thermite-like" reactions such as reacting $\ce{CuO}$ with $\ce{Mn}$.
As for water, I know that Manganese metal is one of the more active metals among the transition metals, so I am also concerned with whether Aluminum can be used to reduce $\ce{Mn^{2+}}$ to the metal in boiling water without the formation of any Manganese Oxide or Hydroxide side products due to the water (especially due to the fact that reducing metals like this precipitates them out as a fine powder).
$\ce{ 2Al + 3Mn^{2+} -> 2Al^{3+} + 3Mn}$ Unlike your claim, manganese is relatively inert despite it being a little more electropositive than its neighbors in the periodic table. It is not particularly reactive to air. The surface of manganese lumps oxidize to a minor extent but when it is finely divided, it becomes pyrophoric and burns in air. It tends to form the oxide $\ce{Mn3O4}$ and the nitride $\ce{Mn3N2}$. Temperature for such reactions are reaches more than 500 °C.
$$\ce{3Mn(s) + 2O2(g) ->[\Delta] Mn3O4(s)}$$
The following is multiple choice question (with options) to answer.
When sparks from a steel grinder react with oxygen, what do they form? | [
"spontaneous combustion",
"steel oxide",
"rust",
"iron oxide"
] | D | The sparks from a steel grinder are molten iron. The iron reacts with oxygen to form iron(III) oxide. |
SciQ | SciQ-659 | experimental-chemistry, safety
Title: What components of safety should be included in a chemistry laboratory experiment conclusion?
The focus of my question here is this: In a laboratory there is a Bunsen burner, a hot plate, hydrochloric acid, and concentrated ammonia. What would you mention about safety precautions?
As students of chemistry and science, we often need to write detailed conclusions about our laboratory experiments. This eventually becomes second-nature, but to have an an idea of which of the safety measures taken to include are often useful to ensure ourselves that we have not left anything out.
I believe that the following are some of the the most important components of any well written conclusion in a lab entry, something that your lab instructor will read and grade you on.
Purpose: Explain the goal and purpose of the experiment in a clear and concise manner.
Findings: Presents a reasonable interpretation of, and logical explanation for all findings pertaining to the problem and stated purpose.
Discussion: Discusses possible sources of error in detail, including their effect on the results and ways of avoiding them in the future.
Referencing experimental findings and explaining the known/expected results we were looking for. Mentioning and discussing reasons for trends, if any.
In particular my instructors last year were often interested in:
Safety: This is often what I always got marked down for. I would explain that hydrochloric acid is a caustic substance and should be treated with care to not get on your tissue by wearing clothing that does not expose skin and closed toe shoes, and to always carry out the experiment with safety goggles securely fastened. It never seems to be enough for them, even if I mention eye flush and chemical shower in case of emergencies. Should I mention to not snort or freebase it? /end sarcasm
The following is multiple choice question (with options) to answer.
What should you learn that allows you to recognize and avoid the dangers of specific hazards when experimenting, such as flames or broken glass? | [
"medical safety symbols",
"first aid safety symbols",
"available safety symbols",
"lab safety symbols"
] | D | Lab safety symbols warn of specific hazards, such as flames or broken glass. Knowing the symbols allows you to recognize and avoid the dangers. |
SciQ | SciQ-660 | thermodynamics, energy, power
Toyota Corolla, 13 gallon tank, 20% efficiency, 103 kWh usable energy
Tesla Roadster, 56 kWh battery capacity
Chevy Volt, 16 kWh battery capacity
If we compare a liquid Nitrogen car to the Chevy Volt it might not be so bad. But why would we do that? That car can still augment its range with gasoline. A part of the argument for electric cars is that you don't have the same energy loss from idling. Would that be true for a liquid Nitrogen car? There is no reason to believe that.
Let's say we assume a reasonable efficiency of half the isothermal process, which is illustrated in Figure 2 of the reference. Let's also say we'll hold 50 kWh of usable energy in the tank (even though this could still cause range problems). We've increased the tank size by a factor of 4 and the weight of the full tank is now around $1000 kg$. This is close to what many cars weigh.
The energy content relative to gasoline, as well as the alternatives, kills the idea. It would seem to require extremely optimistic assumptions to make it a reasonable proposal before we even get into the discussion about infrastructure needed to make it happen. The most fair comparison would be to other cars that also use alternative fuels, but it fails there too. EVs seem to have better viability on the basis of simple energetics. Maybe you're concerned that we'll run out of Lithium. A vehicle powered by compressed natural gas (not even the super-high pressure tanks that many have hope in) would blow it away, and the tank would be more manageable. Plus the fuel would be (dramatically) cheaper. Plus the infrastructure would be there. Plus, the engine is a proven design. We could do better with coal-to-liquids, we could probably do better with biofuels.
The following is multiple choice question (with options) to answer.
Motor vehicles account for almost half of the consumption of what? | [
"greenhouse gases",
"electricity",
"fossil fuel",
"hydrocarbon"
] | C | Motor vehicles account for almost half of fossil fuel use. Most vehicles run on gasoline, which comes from petroleum. |
SciQ | SciQ-661 | human-biology, cell-biology, bacteriology, cell-membrane
Title: Can general soap kill bacteria? I have read that general soap can kill bacteria by opening holes in the bacterial membrane.
http://questions.sci-toys.com/node/90
However, I found some articles as well saying that it cannot.
http://goaskalice.columbia.edu/answered-questions/does-soap-kill-germs
There seems split answers among experts,
so I would like to know which one is correct.
Could anyone advise me?
Thanks. Soap kills nearly all the bacteria it comes into contact with by dissolving the bacterial membrane. Some viruses with protein coats can resist soap, but many viruses have similar membranous coats (like HIV) and are usually disrupted by soap. I'm sure it washes some away too, but to say they don't kill bacteria is misleading. In the end, though, they are gone.
Antibacterial soap with triclosan does not kill bacteria on contact and are no more effective than if they had no triclosan at all. That's actually a good thing since really using an antibiotic would probably accelerate antibiotic resistant bacteria which is a serious - probably catastrophic public health failure. A recent study showed that killing bacteria by soaking with triclosan took 9 hours to start showing an effect.
To achieve full sterility, surgeons bathe their gloves in iodine (see details in the comments below) and their instruments will be sterilized by heating them beyond the boiling point in an autoclave under pressure. That's useful when you are breaching the skin in surgery, but the skin needs some bacteria to be healthy long term and works well to fend off bacterial infections.
Your confusion seems to come from finding a page full of errors. Alice didn't really do her homework.
The following is multiple choice question (with options) to answer.
Bacterial stis can be cured with what? | [
"pesticides",
"antiviral drugs",
"antibiotics",
"antioxidants"
] | C | Most STIs are caused by bacteria or viruses. Bacterial STIs can be cured with antibiotics. Viral STIs cannot be cured. Once you are infected with a viral STI, you are likely to be infected for life. |
SciQ | SciQ-662 | biochemistry, food, diet
Title: Why is coconut oil healthier when it has so much saturated fat? I noticed that coconut oil has ~96% saturated fat, and I was under the assumption that saturated fats = bad for health.
Why is it that coconut oil is healthier to alternatives with much less saturated fat? coconut oil is composed mainly of medium-chain triglycerides, 1)it is smaller than other long-chain triglycerides so that it can be digested easily, 2)the digestion of coconut oil does not involve in the Pancreatic digestive enzyme system, 3) liver prefer use medium-chain triglycerides as the fuel sources 4) medium-chain triglycerides will convert to monoglyceride and medium-chain fatty acid which have strong antibacterial
The following is multiple choice question (with options) to answer.
Fats are also called triacylglycerols or triglycerides because of their what? | [
"chemical structure",
"chemical weight",
"elemental type",
"atomic number"
] | A | During this ester bond formation, three water molecules are released. The three fatty acids in the triacylglycerol may be similar or dissimilar. Fats are also called triacylglycerols or triglycerides because of their chemical structure. Some fatty acids have common names that specify their origin. For example, palmitic acid, a saturated fatty acid, is derived from the palm tree. Arachidic acid is derived from Arachis hypogea, the scientific name for groundnuts or peanuts. Fatty acids may be saturated or unsaturated. In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is said to be saturated. Saturated fatty acids are saturated with hydrogen; in other words, the number of hydrogen atoms attached to the carbon skeleton is maximized. Stearic acid is an example of a saturated fatty acid (Figure 3.14). |
SciQ | SciQ-663 | evolution, zoology, anatomy
Title: Are the transverse septum in sharks and the diaphragm in mammals homologous structures? Are the transverse septum in sharks and the diaphragm in mammals homologous structures?
I have searched on Google Scholar and Web of Science, but haven't found substantial evidence to prove or falsify the claim. A beginning of answer here below, I hope. Please first consider that many structures are involved in the question here, the diaphragm (UBERON:0001103), the diaphragmaticus muscle (UBERON:0036071) and the septum transversum (UBERON:0004161). At Bgee (bgee.org) we aim annotating relations of similarity between anatomical structures, please have a look at our GitHub
https://github.com/BgeeDB/anatomical-similarity-annotations
We already annotated 'diaphragm' as a mammalian structure, not homologous in Amniota (please see https://raw.githubusercontent.com/BgeeDB/anatomical-similarity-annotations/master/release/similarity.tsv). In our next release, you will see the annotation for the 'diaphragmaticus muscle' which is an analog organ in Crocodylians (and Turtles) but not homologous to the mammalian diaphragm either. See here for more details about this new Uberon class:
https://github.com/obophenotype/uberon/issues/1229.
Based on the comments here above, I would say that currently we can argue that there is no evidence for a homologous relationship between the 'septum transversum' in sharks and the mammalian diaphragm. Please note that UBERON:0004161 septum transversum describes the (mammalian) embryonic structure that will give rise to the central tendon of the diaphragm, while here you are talking about a adult structure closer to a 'diaphragmaticus muscle'-like septum, as far as I understand.
But anyway thank you for your interesting question that points out a very exciting and rapidly evolving evo-devo field, as this recent paper also suggests
The following is multiple choice question (with options) to answer.
What mammalian structure allows the exchange of gases, nutrients, and other substances between the fetus and mother? | [
"uterus",
"mitochondria",
"placenta",
"notochord"
] | C | Placenta of a Placental Mammal (Human). The placenta allows the exchange of gases, nutrients, and other substances between the fetus and mother. |
SciQ | SciQ-664 | atmospheric-chemistry
But some researchers have argued it does make a notable contribution in the lower atmosphere, but indirectly. There doesn't appear to be a consensus on how big this effect is (and the Wikipedia reference is old and obsolete). The argument for ozone being a notable contributor is based on the following. Hydrocarbon pollution in the lower atmosphere (often from vehicle emissions) leads to a variety of undesirable reactions some of which lead to the production of ozone (as well as many other irritating components of smog). We really don't want too much smog or ozone in the lower atmosphere because it is bad for health. Some have estimated that it also adds to the warming caused by hydrocarbon emissions (exacerbating the warming potential of methane, for example).
It is hard to judge the estimates of its contribution to warming not least because they rely on models of complex reactions caused indirectly by other pollutants. Also, the big issue with emissions leading to ozone are not its contribution to warming but its contribution to pollution which causes direct harm to people in the short term. In fact regulations around emissions has been striving to reduce those emissions since before we started worrying about global warming. And, many countries have sharply reduced them (this is a major reasons why most western countries insist on catalytic converters in their vehicles). We should reduce ozone pollution by reducing the other emissions that cause it and we have been doing that for decades.
I would argue that ozone is essentially irrelevant to global warming. We should strive to reduce it in the lower atmosphere even if we were not worried by global warming. So even if we can't agree on how big its contribution to warming is (which the literature isn't clear on) we should be reducing it as much as we can for more direct reasons.
And, even if we wanted to report its contribution to warming, the best place to account for it is to add it to the contribution of other emissions (eg methane) rather than to account for it separately as we don't directly emit it from anything.
The following is multiple choice question (with options) to answer.
Fossil fuel consumption is a major contributor to global emissions of what gas? | [
"carbon monoxide",
"methane",
"oxygen",
"carbon dioxide"
] | D | Global carbon dioxide emissions from fossil fuel consumption and cement production. The black line represents all emission types combined. The colored lines show emissions from individual fossil fuels. |
SciQ | SciQ-665 | cell-biology, hematology, red-blood-cell
Title: Why are red blood cells considered to be cells? Wikipedia states that a cell is
the basic structural, functional and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently.
It then goes on to state that
All cells (except red blood cells which lack a cell nucleus and most organelles to accommodate maximum space for hemoglobin) possess DNA.
Then why are red blood cells still considered cells, while they can't replicate? Is the definition on Wikipedia just a bad definition? Or are red blood cells wrongly considered cells, but remain so for historical reasons? Or are they considered cells for some other reason, such as this answer which states that red blood cells do contain a nucleus at some point? A very good question, and it is most likely because of the last option. It had a nucleus for part of its life. After the RBC jettisons its nucleus, it still remains very metabolically active for approximately 3 months. It maintains its cell membrane integrity, it metabolizes glucose, it interacts constantly with its environment, numerous cellular functions and structure remain intact... It is extremely specialized for a primary purpose, and no longer requires the nucleus to provide more proteins. It has limited capacity to heal from injury, so it has a limited life span.
Speculation: I wonder if it might lose the nucleus early on so that when it is destroyed in the spleen at the end of its life as RBCs are, the spleen macrophages are not overwhelmed with additional processing of nucleic acids? Macrophage type cells are already working hard in there to clear infectious agents and some immune cells from the blood.
The following is multiple choice question (with options) to answer.
What is the main function of blood? | [
"to transport",
"digestion",
"excretion of waste",
"respiration"
] | A | The main function of blood is transport. Blood in arteries carries oxygen and nutrients to all the body’s cells. Blood in veins carries carbon dioxide and other wastes away from cells to be excreted. Blood also transports the chemical messengers called hormones to cells throughout the body where they are needed to regulate body functions. Blood has several other functions as well. For example, blood:. |
SciQ | SciQ-666 | systems-biology
Rather I would read this talk as saying that the models we are using for action are not very good yet. What is happening is that synthetic biology (engineering approaches), experimental observation, and intensive modeling (the 'inverse' and 'forward' approaches Brenner mentions) are all happening at once and are informing each other.
Its hard to imagine that data from inverse approaches can't be an important part of any solution to biology. Its also looking likelier that a mathematical model alone of biology will be difficult or impossible to find also. What is currently (IMHO) working is a framework that is both conceptual (and not entirely quantitative) as well as analytical (mathematical) and data driven.
The following is multiple choice question (with options) to answer.
Biotechnology is the use of biological agents for technological advancement. what two areas are the primary applications of this technology used? | [
"medicine and philosophy",
"medicine and architecture",
"medicine and agriculture",
"medicine and psychology"
] | C | Biotechnology is the use of biological agents for technological advancement. Biotechnology was used for breeding livestock and crops long before the scientific basis of these techniques was understood. Since the discovery of the structure of DNA in 1953, the field of biotechnology has grown rapidly through both academic research and private companies. The primary applications of this technology are in medicine (production of vaccines and antibiotics) and agriculture (genetic modification of crops, such as to increase yields). Biotechnology also has many industrial applications, such as fermentation, the treatment of oil spills, and the production of biofuels (Figure 17.2). |
SciQ | SciQ-667 | 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.
Unlike free-living species of flatworms that are predators or scavengers, what forms feed from the tissues of their hosts? | [
"mutualistic",
"aquatic",
"herbiverous",
"parasitic"
] | D | Flatworms The relationships among flatworms, or phylum Platyhelminthes, is being revised and the description here will follow the traditional groupings. Most flatworms are parasitic, including important parasites of humans. Flatworms have three embryonic germ layers that give rise to surfaces covering tissues, internal tissues, and the lining of the digestive system. The epidermal tissue is a single layer of cells or a layer of fused cells covering a layer of circular muscle above a layer of longitudinal muscle. The mesodermal tissues include support cells and secretory cells that secrete mucus and other materials to the surface. The flatworms are acoelomate, so their bodies contain no cavities or spaces between the outer surface and the inner digestive tract. Physiological Processes of Flatworms Free-living species of flatworms are predators or scavengers, whereas parasitic forms feed from the tissues of their hosts. Most flatworms have an incomplete digestive system with an opening, the “mouth,” that is also used to expel digestive. |
SciQ | SciQ-668 | thermodynamics, energy, terminology
You are absolutely correct. Heat is not a form of energy. It is a mechanism by which energy is transferred from one substance, object, etc., to another due solely to temperature difference.
When I was learning about thermodynamics I found a particular description that, at least for me, help differentiate between the energy of something and the transfer of energy (by work or heat) from one thing to another. In this case the transfer of energy by heat. I'd like to share it with you in case it might be helpful. For simplicity, the description is for heat conduction.
Consider two solid objects, one having a higher temperature than the other. Which means the molecules of the higher temperature object 1 have a higher average translational kinetic energy than the molecules of the lower temperature object 2.
The objects are placed in contact with each other. At the interface between the objects the molecules of the higher temperature object collide with the molecules of the lower temperature object. On average, this results in the transfer of kinetic energy from the molecules of the higher temperature object to molecules of the lower temperature object causing the temperature of the higher temperature object to decrease, and the temperature of the lower temperature object to increase.
This transfer of kinetic energy from the molecules of the higher temperature object to the molecules of the lower temperature object is what we mean by heat. But the increase in the average kinetic energy of the molecules of the lower temperature object and decrease in the average kinetic energy of the molecules of the higher temperature object is what we mean by a change in the internal (kinetic) energy of the two objects. Thus the difference between the transfer of energy and the energy itself.
Hope this helps.
The following is multiple choice question (with options) to answer.
When heat flows into an object, its thermal energy increases and so does its what? | [
"matter",
"speed",
"color",
"temperature"
] | D | When heat flows into an object, its thermal energy increases and so does its temperature. |
SciQ | SciQ-669 | general-relativity, visible-light, astronomy, gravitational-lensing
Title: Can something you see through a telescope be behind you? I read somewhere that gravity is able to bend light.
Is there a chance that, if the conditions are right, the light from one star could bend so much through space that when it reaches the telescope we use to look at it, it could actually be behind us?
As an analogy, imagine you have a piece of rope (the light) and every time it goes past an object that has gravity it bends a tiny bit, in the end it has made a 180* turn and is traveling back to the point it started. For the 1st part of your question:-
You need light to see anything.
Firstly I will emphasize on my comment.
If you reach the event horizon of a black hole safely (where light can get into orbit around the black hole), then since the light is in orbit, the light from the back of your head would go around the black hole and come back to reach the front of your eyes enabling you to see the back of your head. But there are subtleties involved and I am just a beginner in general relativity.
Secondly for your question. It does happen. It's called:-
Gravitational Lensing.
A gravitational lens is a distribution of matter (such as a cluster of galaxies) between a distant light source and an observer, that is capable of bending the light from the source as the light travels towards the observer. This effect is known as gravitational lensing, and the amount of bending is one of the predictions of Albert Einstein's general theory of relativity.
In general relativity, light follows the curvature of spacetime, hence when light passes around a massive object, it is bent. This means that the light from an object on the other side will be bent towards an observer's eye, just like an ordinary lens. Since light always moves at a constant speed, lensing changes the direction of the velocity of the light, but not the magnitude.
From Wikipedia:
The following is multiple choice question (with options) to answer.
What are telescopes that use lenses to bend light called? | [
"reflecting telescopes",
"layering telescopes",
"refracting telescopes",
"sliding telescopes"
] | C | Telescopes that use lenses to bend light are called refracting telescopes , or refractors ( Figure below ). The earliest telescopes were all refractors. Many amateur astronomers still use refractors today. Refractors are good for viewing details within our solar system. Craters on the surface of Earth’s Moon or the rings around Saturn are two such details. |
SciQ | SciQ-670 | remote-sensing, forest
Title: How is tree age estimated? I am trying to study about forest biomass and carbon amount of forest.
First of all, I studied some papers, they mentioned that age of forest is related to the biomass. So, How do we measure the age of tree? What are the practical ways used to estimate tree age? Biomass itself isn't a great measure of tree age because the size of a tree is affected by a number of factors. Assuming the same species of tree:
Soil nutrients: more nutrients in general means better growth for most species
Availability of water: scare water means less growth
Availability of light: a tree with more light grows more than one that's constrained
A tree with good soil, lots of water and light will grow more than one without those things, so the same age of tree could be very different sizes and biomasses. The only way to get an exact age of a tree is to get a core sample or cut it down and count the rings, every ring represents a growing year. A tree that grows very little will have narrowly spaced rings, a tree that grows a lot has wider space rings as it's putting more biomass. Note that wood density is also an important measurement for biomass, the denser the wood the more biomass is compacted in the same amount of space. Slower growing trees tend to be more dense, tree twice the size of another may not be twice the mass.
That's for a single tree, but you're asking about forests. It's impractical to core sample a million trees, but you can core sample a fair number of live ones or take samples of fallen ones. Along with measurements of circumference and height you can build a database and estimate the average age of the rest of the trees in the forest from their heights and circumferences. It's also possible to estimate the biomass of the forest from estimating the number of trees in and using an average biomass.
The following is multiple choice question (with options) to answer.
The science of analyzing tree rings is called what? | [
"algorithms",
"dendrochronology",
"conservation",
"estradiol"
] | B | |
SciQ | SciQ-671 | immunology, immune-system, autoimmune
As for why autoimmunity occurs you also understood the basics, however the devil is in the details: wikipedia does have a much longer list of mechanistically different causes. While its often sufficient to explain immune recognition using 'keys' (T cell receptor / B cell receptor = antibody) and their respective 'locks' (peptides bound to MHC / antigens), the exact process of immune cell activation becomes important in autoimmunity, where cells are wrongly activated. This means that there are many possible points at which the 'security system' of the immune cell maturation can (or rather has to) fail to allow autoimmunity.
As for the cross-reactivity of cells: the difference between the binding of B cells (via antibody/B cell receptor to protein surfaces) and T cells (via T cell receptor to peptide sequences) means that in general T cells are much more likely to show cross reactivity - just because the possibility space of a 10-12aa peptide is much smaller than that of a protein surface (even though the probability is still very low).
Additionally - as stated in the comments to your question - both the immune activation pathway and the issue of cross reactivity, while principally understood, are not 'completely solved'. The immune system is insanely complex just by itself and the addition of interactions with both almost all human proteins AND proteins any kind of pathogen, mean that it will take quite a lot of time until researchers can figure out all the weird quirks caused by the 'wrong' combinations.
The following is multiple choice question (with options) to answer.
Which type of arthritis causes the immune system to attack joints? | [
"rheumatoid",
"Gout",
"Osteoarthritis",
"Spondylarthropathies"
] | A | In rheumatoid arthritis, the immune system attacks joints. This causes joint damage and pain. |
SciQ | SciQ-672 | evolution, taxonomy
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves, but do not breed freely with members of another species in the wild.
That last part takes care of the ligers and tiglons. But what if we consider plants? Under the definition I just gave, most grasses (around 11,000 species) would have to be considered as one species. In the wild, most grasses will freely pollinate related species and produce hybrid seed, which germinates. You might then think we could just modify the definition to specify that the offspring must be fertile (i.e. able to reproduce with one another)...
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves, but do not breed freely with members of another species in the wild to produce fertile progeny.
Unfortunately, the situation is still more complicated (we've barely started!). Often wild hybridisation events between plants lead to healthy, fertile offspring. In fact common wheat (Triticum aestivum) is a natural hybrid between three related species of grass. The offspring are able to breed freely with one another.
Perhaps we could account for this by taking into account whether the populations usually interbreed, and whether they form distinct populations...
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of populations or meta-populations of related individuals that resemble one another, are able to breed among themselves, but do tend not to breed freely with members of another species in the wild to produce fertile progeny.
The following is multiple choice question (with options) to answer.
A species is a subdivision of a genus in what classification system? | [
"mammalian",
"crocodilian system",
"linnaean system",
"calcareous system"
] | C | Linnaean Classification System: Classification of the Human Species. This chart shows the taxa of the Linnaean classification system. Each taxon is a subdivision of the taxon below it in the chart. For example, a species is a subdivision of a genus. The classification of humans is given in the chart as an example. |
SciQ | SciQ-673 | newtonian-mechanics, forces, fluid-dynamics, reference-frames, drag
Title: Is drag force in the direction of particle motion or opposite to motion? Suppose water is flowing in horizontal direction (positive $x$-direction) and a particle immersed in that water is also moving in the same direction.
In this case, is the drag force $F_D$ in the direction of particle motion or opposite to it?
I get from wikipedia that drag force is a frictional force and hence is opposite to particle motion, but then what is the force that is making the particle move. Because in one journal paper, I see that drag force $F_D$ is shown as force in the direction of particle motion.
This is a sketch from the paper, you can see that flow velocity and drag force are both in the same direction. Drag force opposes the motion of a body relative to the surrounding fluid. In this case the surrounding fluid moves to the right and relative to that the solids move to the left.
The drag force is opposing the motion to the left, hence it is towards the right. The solids are being swept away by the fluid.
The following is multiple choice question (with options) to answer.
What is the force that pulls particles at the exposed surface of a liquid toward other liquid particles called? | [
"shinking tension",
"conservative tension",
"surface tension",
"transfer tension"
] | C | Two unique properties of liquids are surface tension and viscosity. Surface tension is a force that pulls particles at the exposed surface of a liquid toward other liquid particles. Surface tension explains why water forms droplets, like the water droplet that has formed on the leaky faucet pictured in the Figure below . You can learn more about surface tension at this URL: http://io9. com/5668221/an-experiment-with-soap-water-pepper-and-surface-tension . |
SciQ | SciQ-674 | thermodynamics, energy, energy-conservation, phase-transition, physical-chemistry
Title: Why is Energy change occurring during the reaction at constant temperature and constant volume given by internal energy change? When volume and temperature are kept constant, shouldn't internal energy remain constant (as it's a state function depending on state variables)? When heat is supplied, why does the internal energy increase if state variables are kept constant? For a system likely to be the seat of a chemical reaction, the variables of state are not limited to the temperature and the volume: it is necessary to add the extent of reaction.
The following is multiple choice question (with options) to answer.
What state is achieved when the body's internal environment is kept more-or-less constant? | [
"hypothesis",
"cancerous",
"consciousness",
"homeostasis"
] | D | The organ systems of the body work together to carry out life processes and maintain homeostasis. The body is in homeostasis when its internal environment is kept more-or-less constant. For example, levels of sugar, carbon dioxide, and water in the blood must be kept within narrow ranges. This requires continuous adjustments. For example:. |
SciQ | SciQ-675 | homework-and-exercises, electromagnetism, classical-mechanics, lagrangian-formalism, potential-energy
Title: Charge, velocity-dependent potentials and Lagrangian Given an electric charge $q$ of mass $m$ moving at a velocity ${\bf v}$ in a region containing both electric field ${\bf E}(t,x,y,z)$ and magnetic field ${\bf B}(t,x,y,z)$ (${\bf B}$ and ${\bf E}$ are derivable from a scalar potential $\phi(t, x, y, z) $and a vector potential ${\bf A}(t,x,y,z)$),
knowing that
${\bf E}=- \nabla \phi - \frac{\partial {\bf A}} {\partial t}$
${\bf B}= \nabla \times {\bf A} $
$U=q \phi - q {\bf A} \cdot{\bf v}$ ($U$ is the velocity-dependent potential)
The following is multiple choice question (with options) to answer.
Kinetic and potential are two forms of what? | [
"energy",
"fuel",
"pressure",
"exercise"
] | A | Energy is the ability to do work. When work is done, energy is transferred from one object to another. Energy can exist in different forms, such as electrical and chemical energy. Most forms of energy can also be classified as kinetic or potential energy. |
SciQ | SciQ-676 | human-biology, evolution
Humans are off the charts in the amount of resources we invest in our children - our lives are 1/4 to 1/3 over before we sometimes leave our parents household (in some societies of course they never leave the house, but step into an extended family). This may be one of the reasons we are so successful as a species - we live in practically every place we possibly could and have no danger of competition from any other living thing excepting ourselves.
The grandmother effect is essentially the idea that if women, who are more attached to the offspring in more cases than fathers, continue to live and help support the grandchildren and make them more successful, then this will allow post menopausal women to have a longer lifespan (which they do).
The evolutionary biologist Sara Hrdy, emeritus UC Davis, has written quite a bit about the nuances of the evolution of the role of motherhood - reading some of her articles or books might give you a deeper sense of how profoundly filial love has shaped human beings.
--- more answer this stuff may or may not be worth reading depending on how broadly you want to understand this question...
Its important to say that many of the expansions of human average human lifespan have not been genetic. Its commonly cited that sewer systems, clean water, antibiotics and plentiful food are the three most important factors in human lifespan - and before modern developed world nations, the average lifespan of human beings was somewhere in the 30s. And there are significant lifespan differences in regions where these factors and others (education of women, access to prenatal and early care etc) are available.
Studies continue to be published that examine environmental and lifestyle factors compared to genetics and it seems that environment and lifestyle can make an astounding difference.
But genetics undoubtedly has a role to play here too. There are probably some individual humans and animals which have evolved to live longer. This has been found to be genetically related in some humans by demographics and family lines.
The following is multiple choice question (with options) to answer.
Humans are unique in their ability to alter their environment with the conscious purpose of increasing what, which acts as a limiting factor on populations in general? | [
"carrying capacity",
"niche",
"density dependent limitation",
"containing capacity"
] | A | Overcoming Density-Dependent Regulation Humans are unique in their ability to alter their environment with the conscious purpose of increasing its carrying capacity. This ability is a major factor responsible for human population growth and a way of overcoming density-dependent growth regulation. Much of this ability is related to human intelligence, society, and communication. Humans can construct shelter to protect them from the elements and have developed agriculture and domesticated animals to increase their food supplies. In addition, humans use language to communicate this technology to new generations, allowing them to improve upon previous accomplishments. Other factors in human population growth are migration and public health. Humans originated in Africa, but have since migrated to nearly all inhabitable land on the Earth. Public health, sanitation, and the use of antibiotics and vaccines have decreased the ability of infectious disease to limit human population growth. In the past, diseases such as the bubonic plaque of the fourteenth century killed between 30 and 60 percent of Europe’s population and reduced the overall world population by as many as 100 million people. Today, the threat of infectious disease, while not gone, is certainly less severe. According to the World Health Organization, global death from infectious disease declined from 16.4 million in 1993 to 14.7 million in 1992. To compare to some of the epidemics of the past, the percentage of the world's population killed between 1993 and 2002 decreased from 0.30 percent of the world's population to 0.24 percent. Thus, it appears that the influence of infectious disease on human population growth is becoming less significant. |
SciQ | SciQ-677 | cell-biology
Title: Are There Exceptions to Animal Cells not Having Cell Walls? In the January Issue of SciAm (discussing Haemophilia):
When damage occurs to blood vessels, exposure of the blood to collagen in the cell walls and material released by the cells triggers the activation of clotting factors.
I read the original in print, but it is available online here.
This seems to imply that animal cells (in this example, those of humans) have cell walls. I sometimes see similar implications in other resources. However, in elementary biology, one is taught that animal cells never have cell walls.
Therefore, my question: Are references to animal cell cell walls (such as the above, for human animal cells) simple mistakes--or are they exceptions to a generalization? Humans, as well as the rest of the metazoans (i.e. animals), absolutely do not have cell walls. What humans do have is extracellular matrix (ECM), which is the sort of fibrous, sort of gel-like material in which cells in many of the tissues are embedded. Collagen is a major component of ECM.
From the old copy of Alberts that is hosted on the NCBI website:
Tissues are not made up solely of cells. A substantial part of their volume is extracellular space, which is largely filled by an intricate network of macromolecules constituting the extracellular matrix (Figure 19-33). This matrix is composed of a variety of proteins and polysaccharides that are secreted locally and assembled into an organized meshwork in close association with the surface of the cell that produced them...
Two main classes of extracellular macromolecules make up the matrix: (1) polysaccharide chains of the class called glycosaminoglycans (GAGs), which are usually found covalently linked to protein in the form of proteoglycans, and (2) fibrous proteins, including collagen, elastin, fibronectin, and laminin, which have both structural and adhesive functions.
The following is multiple choice question (with options) to answer.
A desmosome is a cell structure that anchors the ends of what fibers together? | [
"skeletal muscle",
"smooth muscle",
"cardiac muscle",
"controllable muscle"
] | C | 30.5 Applications of Atomic Excitations and De-Excitations 30. Figure 30.39 shows the energy-level diagram for neon. (a) Verify that the energy of the photon emitted when neon goes from its metastable state to the one immediately below is equal to 1.96 eV. (b) Show that the wavelength of this radiation is 633 nm. (c) What wavelength is emitted when the neon makes a direct transition to its ground state? 31. A helium-neon laser is pumped by electric discharge. What wavelength electromagnetic radiation would be needed to pump it? See Figure 30.39 for energy-level information. Ruby lasers have chromium atoms doped in an aluminum oxide crystal. The energy level diagram for chromium in a ruby is shown in Figure 30.64. What wavelength is emitted by a ruby laser?. |
SciQ | SciQ-678 | special-relativity, string-theory, spacetime, differential-geometry, metric-tensor
Title: Area in Minkowskian Spacetime If, in a $d$ dimensional space with Euclidean metric, we parametrize a two-dimensional surface with parameters $\xi^1$ and $\xi^2$ then the area can be written as
$$A = \int ~\mathrm d\xi^1 \mathrm d\xi^2 \sqrt{\left(\dfrac{\mathrm d \vec x}{\mathrm d\xi^1}\right)^2 \left(\dfrac{\mathrm d \vec x}{\mathrm d\xi^2}\right)^2} \sqrt{1-\dfrac{\left(\dfrac{\mathrm d \vec x}{\mathrm d\xi^1} \dot{}{} \dfrac{\mathrm d \vec x}{\mathrm d\xi^2}\right)^2}{\left(\dfrac{\mathrm d \vec x}{\mathrm d\xi^1}\right)^2 \left(\dfrac{\mathrm d \vec x}{\mathrm d\xi^2}\right)^2}}$$
Or,
$$A = \int ~\mathrm d\xi^1~\mathrm d\xi^2 \sqrt{\left(\dfrac{\mathrm d \vec x}{\mathrm d\xi^1}\right)^2 \left(\dfrac{\mathrm d \vec x}{\mathrm d\xi^2}\right)^2 -\left(\dfrac{\mathrm d \vec x}{\mathrm d\xi^1} \dot{}{} \dfrac{\mathrm d \vec x}{d\xi^2}\right)^2}$$
The following is multiple choice question (with options) to answer.
How much space a surface covers is known as what? | [
"Lenght",
"Height",
"area",
"Flatness"
] | C | The area of a surface is how much space it covers. It’s easy to calculate the area of a surface if it has a regular shape, such as the blue rectangle in the sketch below. You simply substitute measurements of the surface into the correct formula. To find the area of a rectangular surface, use this formula:. |
SciQ | SciQ-679 | pressure, gas
Title: water diving and nitrogen gas I have a teacher who dives underwater using supplied air. So he was asking me if I could find him a solution on the internet on how could a diver decreases the amount of nitrogen gas getting inside his body? And how could he get rid of it more quickly? Trimix, Heliox are typically reserved for commercial divers. Assuming your teacher is not a commercial diver, sport diving offers Nitrox systems that increase the amount of oxygen in the gas mix relative to nitrogen. The risk here though is that icreasing oxygen increases the risk of oxygen toxicity at depth, so if your teacher is really interested they should attend a certified Nitrox training course from PADI or the like.
Sport diving also now offers mixed gas closed loop rebreathers that can be programmed to minimize nitrogen content,but this also requires special training because of the oxygen toxicity issue, and decompression schedules.
Lastly if your teacher limits their dive to less than or equal to 20 feet of seawater, no decompression is required according to the latest no decompression dive tables for sport diving.
The following is multiple choice question (with options) to answer.
What do aquatic arthropods use to exchange gases? | [
"diaphragm",
"lungs",
"pores",
"gills"
] | D | Aquatic arthropods use gills to exchange gases. These gills have a large surface area in contact with the water, so they can absorb more oxygen. |
SciQ | SciQ-680 | thermodynamics, electromagnetic-radiation, terminology, infrared-radiation
Title: Why are only infrared rays classified as "heat rays"? I've often heard that Infrared rays are called "heat rays". However, I feel like this term is a misnomer. Don't all the wavelengths of electromagnetic radiation carry energy?
Judging by how gamma rays are highly penetrating and are dangerous when absorbed by tissues, radiations of lower wavelengths should carry more energy, and should be able to increase the internal energy of the object that absorbed it much more than infrared rays can. This seems consistent with the conservation of energy for an isolated system: $$T_{ER} = \Delta E_{int}$$
where $T_{ER}$ stands for transfer of energy by electromagnetic radiation
Then why are UV rays, X-rays and gamma rays not classified as "heat rays".
Don't all the wavelengths of electromagnetic radiation carry energy?
Yes. And that photon energy $E$ is given by
$$E=h\nu$$
Where $h$ = Planck's constant and $\nu$ = frequency.
But not all frequencies interact with matter in the same way.
Judging by how Gamma rays are highly penetrating and are dangerous
when absorbed by tissues
Very little of the energy of Gamma rays is absorbed by tissue, i.e., tissue is basically transparent to Gamma rays. They can even pass through several inches of lead. But as they pass though human tissue they energy that is absorbed can cause ionizations that damage tissue and DNA. For this reason, it is called ionizing radiation.
...radiations of lower wavelengths should carry more energy, and
should be able to increase the internal energy of the object that
absorbed it much more than Infrared rays can.
The following is multiple choice question (with options) to answer.
What kind of rays can travel thousands of meters through air and can penetrate and damage cells deep inside the body? | [
"cosmic rays",
"plasma rays",
"x-rays",
"gamma rays"
] | D | Alpha particles can travel only a few centimeters through air. They can burn the skin but not penetrate it. Beta particles can travel up to a meter through air. They can penetrate and damage skin. Gamma rays can travel thousands of meters through air. They can penetrate and damage cells deep inside the body. |
SciQ | SciQ-681 | 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.
Of the three types of skeleton designs - hydrostatic skeletons, exoskeletons, and endoskeletons - which do humans possess? | [
"hydrostatic skeleton",
"exoskeleton",
"none of the above",
"endoskeleton"
] | D | CHAPTER SUMMARY 38.1 Types of Skeletal Systems The three types of skeleton designs are hydrostatic skeletons, exoskeletons, and endoskeletons. A hydrostatic skeleton is formed by a fluid-filled compartment held under hydrostatic pressure; movement is created by the muscles producing pressure on the fluid. An exoskeleton is a hard external skeleton that protects the outer surface of an organism and enables movement through muscles attached on the inside. An endoskeleton is an internal skeleton composed of hard, mineralized tissue that also enables movement by attachment to muscles. The human skeleton is an endoskeleton that is composed of the axial and appendicular skeleton. The axial skeleton is composed of the bones of the skull, ossicles of the ear, hyoid bone, vertebral column, and ribcage. The skull consists of eight cranial bones and 14 facial bones. Six bones make up the ossicles of the middle ear, while the hyoid bone is located in the neck under the mandible. The vertebral column contains 26 bones, and it surrounds and protects the spinal cord. The thoracic cage consists of the sternum, ribs, thoracic vertebrae, and costal cartilages. The appendicular skeleton is made up of the limbs of the upper and lower limbs. The pectoral girdle is composed of the clavicles and the scapulae. The upper limb contains 30 bones in the arm, the forearm, and the hand. The pelvic girdle attaches the lower limbs to the axial skeleton. The lower limb includes the bones of the thigh, the leg, and the foot. |
SciQ | SciQ-682 | endocrinology, glucose, homeostasis, insulin, hypothalamus
Title: Role of the Hypothalmus in the control of Blood Sugar In homeostatic regulation of blood glucose, the receptor and effector is the Pancreas, but how does the control centre — the Hypothalamus — connect and link into this process? Your question doesn’t make it clear whether you think that the pancreas must be under the control of the hypothalmus, or whether you are asking whether it has an influence on the pancreas in relation to the secretion of insulin and glucagon, which control the concentration of blood glucose.
First, it has been long known that secretion of insulin can be influenced by the concentration of glucose in isolated pancreatic islets in vitro, so it can not be true that the effects must involve the hypothalmus. This is implicit in most book or general information articles you might find on the web, but for an original reference a review by W.J. Malaisse in Diabetologia 9, 167–173 (1973) seems highly cited.
I know almost nothing about physiology, but on searching the web for the role of the hypothalmus in glucose homeostasis, found a most readable prize-winning postgraduate essay on the topic by Syed Hussein of Imperial College London. I trust that it is in order to append an edited extract of this:
The following is multiple choice question (with options) to answer.
What regulates homeostasis and basic survival behaviors? | [
"hippocampus",
"mitosis",
"cell membrane",
"hypothalamus"
] | D | |
SciQ | SciQ-683 | electromagnetism, energy, electric-circuits, integration
Title: Electromagnetic converters, differentials and integrals In the context of electromagnetic converters, a converter can be modeled by a system that receives electrical energy and outputs mechanical energy. At some point in my textbook, the authors present the following differential that represents a small change in the co-magnetic energy of the system:
$$ \mathrm dW_\mathrm{cmag} = \sum_{k=1}^n \phi_k di_k$$
where $\phi_k = \phi_k(i_1,i_2,...,i_n)$ the total flux generated by the currents $i_1,...,i_n$ in the $k$th winding/coil that is part of the system. $W_\mathrm{cmag}$ represents a co-magnetic energy of the system (state function). $\mathrm dW_\mathrm{cmag}$ is then simply a small change in the system's co-magnetic energy. They then do something that I'm not sure I understand, that is how they integrate $dW_\mathrm{cmag}$ in order to get $W_\mathrm{cmag}$:
$$W_\mathrm{cmag} = \int_{0,0,\ldots,0}^{i_1,i_2,\ldots,i_n} \sum_{k=1}^n \phi_k \mathrm di_k$$
The following is multiple choice question (with options) to answer.
What device changes kinetic energy to electrical energy through electromagnetic induction? | [
"real generator",
"Emission generator",
"due generator",
"electric generator"
] | D | An electric generator is a device that changes kinetic energy to electrical energy through electromagnetic induction. Electromagnetic induction is the process of generating electric current with a magnetic field. It occurs when a magnetic field and an electric conductor, such as a coil of wire, move relative to one another. |
SciQ | SciQ-684 | evolution, biochemistry, plant-physiology, plant-anatomy, life
Title: Plants without bacteria? is it theoretically possible? I know from school, that all live on the Earth need bacteria as low-level "machines" that break down/extract/convert/produce chemical elements and combinations, other high-level organisms needed. But it is a natural way.
But is it possible to have a world with plants (without mammals or microorganisms and without bacteria) that could exist in the long term. Saying the atmosphere of these world has already enough nitrogen, oxygen and CO2, and of course there is water.
What could break this artificially created world with such conditions (say the world created not from low-level living structures)?
Could bacteria emerge in the world? This is the sort of question that should be considered from more than one perspective. Since this is speculation, take it as a given that there is a lot of 'what if' here.
I doubt most animals and plants can do entirely without bacteria - as you say most of the essential nutrients come from bacteria, who fix nitrogen. If only plants were left on earth, eventually the plants would use up all the nitrogen and they would have to find a way to fix more.
Can bacteria emerge from just a world of plants? I don't think viruses arise spontaneously, but since genomes often have viruses embedded in them, over the course of a billion years or so, its possible since bacteria and viruses continue to be impressed upon our genomes. Would it happen in time? Most would be skeptical whether that timing could work out.
In practice it would be hard to create a world like this. I would be interested to see whether you could sterilize the microorganisms off of seeds without killing the plant for instance. If you're asking about a small sterile environment with only plants, you could do it by adding the nutrients the plants need and giving them sunlight. Such self sustaining systems have been made with cyanobacteria and i'd be surprised if plants could not be included. But these are closed systems and judged by limited amounts of time, so whether this is an answer to your question is not clear. Here it looks like some water plants and fish have been done. If there was a plant that created CO₂ at an adequate rate its possible.
The following is multiple choice question (with options) to answer.
What are two nonliving things that all living things need for survival? | [
"methane",
"water and air",
"sunlight",
"calcium"
] | B | |
SciQ | SciQ-685 | behaviour, human-evolution
So, how does the freeze response help? Consider another (last one) situation: you're being attacked by a lion. In this case, you know that you can neither fight with an angry lion nor outrun it. What should you do? One immediate idea would be to play a dead man's role in front of the lion so that (maybe) it will leave you. Of course, it doesn't pay off everytime, but surely it does, sometimes. And in such a case, this would be better for someone who would otherwise either try to fight with the lion or to outrun it. And, obviously, it is a better option for many other organisms too. So it indeed seems that this response developed much earlier in time, maybe even long before first chordates appeared.
With the above part explaining why it is beneficial, one part still remains i.e. how does it work? For this, see the paragraph below:
Studies show that particular connections from the periaqueductal grey (brain region located along the spine) to the pyramis at the base of your skull are integral to the freeze response. When these connections are activated, it causes the body to freeze. They can be activated by things that are actually dangerous and by things that aren’t, so even irrational fears can cause us to freeze. While giving a presentation, you might not actually be in danger, but your body responds like it is and causes you to clam up.
Below are images of the periaqueductal grey in spinal cord and pyramids in brainstem to help you understand their locations.
To conclude, freeze response is not a mere "remain" of our reptilian past, it is still beneficial for us.
References:
https://en.wikipedia.org/wiki/Fight-or-flight_response
https://www.psychologytoday.com/blog/evolution-the-self/201507/trauma-and-the-freeze-response-good-bad-or-both
https://joyable.com/blog/fight-flight-freeze/
https://www.slideshare.net/mobile/dr_ansari2000/the-brain-stem-ii
http://slideplayer.com/slide/4637165/
The following is multiple choice question (with options) to answer.
The fight or flight response involves what system? | [
"functional nervous system",
"voluntary nervous system",
"autonomic nervous system",
"cellular nervous system"
] | C | Figure 15.1 Fight or Flight? Though the threats that modern humans face are not large predators, the autonomic nervous system is adapted to this type of stimulus. The modern world presents stimuli that trigger the same response. (credit: Vernon Swanepoel). |
SciQ | SciQ-686 | galaxy
Title: How many galaxies have been discovered? I know Andromeda is our nearest galaxy. But how many known galaxies have been discovered and what are they? First, the nearest galaxy to ours is not Andromeda, according to the NASA based page "The Nearest Galaxies", it was until recently considered to be the Canis Major Dwarf Galaxy at approximately 42,000 light years away. However, recently, there is suggestion that the closer Omega Centauri Globular Cluster may be a disrupted dwarf galaxy (Another source).
Now, in answer to your other query of how many galaxies there are - there is a global project called Galaxy Zoo which is attempting to catalogue and classify all observed galaxies, so far, according to the Galaxy Zoo for astronomers page, thus far they have
the entire Sloan Digital Sky Survey spectroscopic sample and all existing Hubble Space Telescope surveys (around 1.5 million galaxies in total).
Pictured: The Hubble Ultra-Deep Field which contains over 10,000 objects, the majority of which are galaxies. The image is only a bit over 3 arcminutes across--a tiny sliver of the sky.
The following is multiple choice question (with options) to answer.
How many types of galaxies are there? | [
"three",
"two",
"one",
"five"
] | A | Galaxies are divided into three types, according to shape. There are spiral galaxies, elliptical galaxies, and irregular galaxies. Spiral galaxies are a rotating disk of stars and dust. In the center is a dense bulge of material. Several arms spiral out from the center. Spiral galaxies have lots of gas and dust and many young stars. Figure below shows a spiral galaxy from the side. You can see the disk and central bulge. |
SciQ | SciQ-687 | organic-chemistry, biochemistry, color, electromagnetic-radiation
Title: How does UV affect skin colors in dark-skinned people? Skin color is one of the things one would rather not ask anything about! Only in humans, it can vary from very dark brown to pale pink. In darker-skinned people, the color is mainly due to melanin, which is produced by melanocytes.
There are three types of melanin: eumelanin, pheomelanin, and neuromelanin. Eumelanin is the most common; so it must be the reason of the dark skin of the dark-skinned. And that's true, since the two major groups of eumelanin are black and brown species.
The first ray produced by sun that comes to mind when you think about affecting the attributes of skin is UVA, since it penetrates most into the skin (Even though its energy is lesser than UVB). So, when I attach these two together I reach the fact that if UV rays do not cause free radicals they will eventually change the skin's color. (This is what is mostly believed and its effect on natural selection is impossible to hide)
Now, I give up. How does UV do to the skin that makes it darker? This must be very easy, huh? What am I missing? There is a journal article almost exactly about the title question, Mechanisms of Skin Tanning in Different Racial/Ethnic Groups in Response to Ultraviolet Radiation Journal of Investigative Dermatology (2005) 124, 1326–1332.
However, the body of the question assumes that eumelanin changes color. Instead, the article finds that melanin gets closer to the surface of the skin, and the degree to which this effect occurs varies with race/ethnicity.
The following is multiple choice question (with options) to answer.
Skin color is controlled by genes but also influenced by exposure to what? | [
"food",
"sunlight",
"precipitation",
"makeup"
] | B | Genes play an important role in determining an organism's traits. However, for many traits, phenotype is influenced by the environment as well. For example, skin color is controlled by genes but also influenced by exposure to sunlight. You can see the effect of sunlight on skin in Figure below . |
SciQ | SciQ-688 | phase, temperature
Title: Why does the distance between molecules increase when the temperature is raised? I have learnt that when we heat ice-like substances it changes to water and when I asked my teacher she said that the distance between molecules increases.
When I thought about it a bit more a question arose: Why does the distance between the molecule increase as we raise the temperature? The answer "the distance between molecules increase" is incomplete if not plain wrong.
Temperature is an effect of energy present. Basically, it's an effect of little movements and vibrations of molecules and atoms due to their energy.
In an crystal, the energy of the molecules is so low, that they don't vibrate and move enough to break the structure. The more energy you put into the system, the more the molecules move. At one point, the movement is too much to keep the molecules in place, the crystal structure breaks apart, the ice melts.
A liquid (NOT WATER, IT IS A SPECIAL CASE) has lower density than the crystal because the molecules are moving around a lot and "need more space".
The following is multiple choice question (with options) to answer.
Higher temperatures increase the rate of reaction in a lot of chemical reactions because they increase the frequency of what interaction between reactant particles? | [
"electric",
"waves",
"explosions",
"collisions"
] | D | Raising the temperature of a chemical reaction usually results in a higher rate of reaction. When the reactant particles are heated, they move faster and faster. This results in a greater frequency of collisions. A more important effect of the temperature increase is that the collisions occur with a greater force and are thus more likely to surmount the activation energy barrier and go on to form products. Increasing the temperature of a reaction increases the number of effective collisions between reacting particles, so the reaction rate increases. |
SciQ | SciQ-689 | human-anatomy, muscles
Title: Contracting muscles in humans I study biology at school, and unfortunately for me, my program skips the muscles in humans chapter.
I know (and mainly, feel) that the movement in one direction isn't created by the same muscle as the movement in the opposite direction, e.g the Triceps ("front") and Biceps ("back").
I know that the triceps straightens the elbow, while the biceps contracts the elbow.
I also know that, instead of actually moving the arm, I can contract these two muscles (when I show off, for example...) without actually moving the arm. That area becomes hard. Both muscles, as I feel, are contracting. I cannot statically contract only one of them.
My question is whether this action is something "special", or simply both muscles working against each other, resulting in zero movement? The situation you are describing where muscles are situated on opposites sides of a joint and produce opposing movements is called "antagonism." Most joints are set up where one or more muscles on either sides will produce such movements (e.g., flexors vs. extensors). Here's a question about muscles without antagonists.
When you contract all the muscles crossing a joint (i.e., when you are "showing off"), the muscles balance each other. If not, the bones would move and the joint angles would change. So taking the elbow as an example, in the image below, Arnold is contracting the elbow flexors (biceps brachii, brachialis) as well as the elbow extensors (triceps brachii). In order for the bones to remain static, the forces must be equal and opposite.
The following is multiple choice question (with options) to answer.
Knees and elbows are examples of what part of the skeletal system? | [
"cartilage",
"nerves",
"muscles",
"joints"
] | D | As you age, you might start noticing pain in your knees or elbows. These are examples of joints. Joints are the part of the skeletal system that connect your bones. Joint pain is a common problem as people age. |
SciQ | SciQ-690 | quantum-mechanics, fusion
Title: Nuclear fusion in Chadwick’s experiment I got confused when I was researching about “neutron’s discovery in Chadwick’s experiment”. There was a nuclear equation said that when we bombard the alpha particles into beryllium, it will emits neutron particles as shown in this equation
$$\rm {^9Be} + \alpha(^4He) \to {^{12}C} + {^1n}$$
What I am confused about is, isn’t the equation above a nuclear fusion reaction? As far as I know, nuclear fusion reactions require really high energy like on the Sun, but this experiment happens in a laboratory. So I wonder if nuclear fusion reactions can happen in laboratory, why can’t we use it to produce clean energy? It is not difficult to achieve fusion reactions in a laboratory. To this end, one can use, for example, accelerators or fusors. What is extremely difficult is achieving net energy gain.
The following is multiple choice question (with options) to answer.
Einstein’s equation helps scientists understand what happens in nuclear reactions and why they produce so much what? | [
"food",
"energy",
"light",
"hydrogen"
] | B | Einstein’s equation helps scientists understand what happens in nuclear reactions and why they produce so much energy. When the nucleus of a radioisotope undergoes fission or fusion in a nuclear reaction, it loses a tiny amount of mass. What happens to the lost mass? It isn’t really lost at all. It is converted to energy. How much energy? E = mc 2 . The change in mass is tiny, but it results in a great deal of energy. |
SciQ | SciQ-691 | 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.
Ovulation is the release of an egg from the what? | [
"fallopian tubes",
"vagina",
"cervix",
"ovary"
] | D | Ovulation, the release of an egg from the ovary, occurs at about the midpoint of the cycle. This would be around day 14 of a 28 day cycle. The egg is swept into the fallopian tube. If sperm is present, fertilization may occur. As sperm can only survive in the fallopian tube for up to a few days, fertilization can only occur within those few days post-ovulation. |
SciQ | SciQ-692 | cell-division
Title: Are free-nuclear division and endomitosis the same? As far as I understood it, both are cases of karyokinesis, not followed by cytokinesis. No. If you google the terms you'll get a lot of sites with definitions. For example:
Nuclear division
Definition
noun
The process by which a nucleus divides, resulting in the segregation of the genome to opposite poles of a dividing cell.
source: http://www.biology-online.org/dictionary/Nuclear_division
Edit:
or
free nuclear division mitotic division of nuclei without accompanying cytokinesis, i.e. nuclei divide in a common cytoplasm, the cells walls only forming around each later
source: http://ecflora.cavehill.uwi.edu/bio_courses/bl14apl/Gloss.htm
versus
endomitosis
mitosis taking place without dissolution of the nuclear membrane, and not followed by cytoplasmic division, resulting in doubling of the number of chromosomes within the nucleus.
source: http://medical-dictionary.thefreedictionary.com/endomitosis
or a bit more revealing:
Duplicated chromosomes produced by endomitosis exist as discrete units
in a single polyploid nucleus or may be packaged into separate nuclei,
depending on the phase at which mitosis is aborted
source: http://en.wikipedia.org/wiki/Endoreduplication
So as you see by definition nuclear division is part of a bigger process (cell division), and accoriding to the first source karyokinesis is a synonim for nuclear division (karyo = nucleus kinesis = moving, both come form greek language).
Edit:
If you check the definition above, you can see that free-nuclear division is a mitosis without cytokinesis, thus chromosome separation still occurs.
In endomitosis the can end up with a polyploid nucleus, in contrast to the other two aforementioned mechanism where no polyploidy occurs.
The following is multiple choice question (with options) to answer.
The process in which the nucleus divides is called what? | [
"meiosis",
"mitosis",
"epistasis",
"cytokinesis"
] | B | In eukaryotic cells, the nucleus divides before the cell itself divides. The process in which the nucleus divides is called mitosis. Before mitosis occurs, a cell’s DNA is replicated. This is necessary so that each daughter cell will have a complete copy of the genetic material from the parent cell. How is the replicated DNA sorted and separated so that each daughter cell gets a complete set of the genetic material? To understand how this happens, you need to know more chromosomes. |
SciQ | SciQ-693 | aqueous-solution, solubility, solvents, solutions
Title: Does removing solution affect a supersaturated solution Given a mixture of: a saturated solution of a solute in a solvent together with excess of the solute compound as crystalline material.
If one were to change the bulk composition of the mixture by removing some of the solution could this cause dissolution or precipitation of the solid in the remaining mixture, or the concentration of the remaining solution?
Presumably one should expect some crystallisation in the portion of the solution that is removed from the mixture?
If one were to change the bulk composition of the mixture by removing some of the solution [...]
This does not change the composition of the solution above the solid. Since the concentration of the solute remains constant, I do not expect a change.
Presumably one should expect some crystallisation in the portion of the solution that is removed from the mixture?
It still is a saturated solution. Unless you evaporate the solvent (= increase the concentration of the solute) or change the temperature, nothing will change.
The following is multiple choice question (with options) to answer.
What is used to recrystallize excess dissolved solute in a supersaturated solution? | [
"seed crystal",
"starter crystal",
"energy crystal",
"fertilizer crystal"
] | A | Some solutes, such as sodium acetate, do not recrystallize easily. Suppose an exactly saturated solution of sodium acetate is prepared at 50°C. As it cools back to room temperature, no crystals appear in the solution, even though the solubility of sodium acetate is lower at room temperature. A supersaturated solution is a solution that contains more than the maximum amount of solute that is capable of being dissolved at a given temperature. The recrystallization of the excess dissolved solute in a supersaturated solution can be initiated by the addition of a tiny crystal of solute, called a seed crystal. The seed crystal provides a nucleation site on which the excess dissolved crystals can begin to grow. Recrystallization from a supersaturated solution is typically very fast. |
SciQ | SciQ-694 | biochemistry, metabolism, bioenergetics
Title: What is the energy source for adipocytes? Since adipocytes export fatty acids and glycerol and don't use them as an energy source, what is the main source of energy for adipocytes? Adipocytes use glucose as an energy source. They express the insulin-responsive glucose transporter GLUT4 just like muscle cells so that when blood glucose levels rise they are primed to take the glucose up for fatty acid biosynthesis, but they also use glucose as a fuel molecule.
The following is multiple choice question (with options) to answer.
Our bodies use what, primarily in the form of glucose, for our immediate energy needs - although they are not as energy dense or capable of long-term storage as lipids? | [
"proteins",
"electrolytes",
"carbohydrates",
"enzymes"
] | C | Opening Essay On July 11, 2003, the Food and Drug Administration amended its food labeling regulations to require that manufacturers list the amount of trans fatty acids on Nutrition Facts labels of foods and dietary supplements, effective January 1, 2006. This amendment was a response to published studies demonstrating a link between the consumption of trans fatty acids and an increased risk of heart disease. Trans fatty acids are produced in the conversion of liquid oils to solid fats, as in the creation of many commercial margarines and shortenings. They have been shown to increase the levels of low-density lipoproteins (LDLs)—complexes that are often referred to as bad cholesterol—in the blood. In this chapter, you will learn about fatty acids and what is meant by a trans fatty acid, as well as the difference between fats and oils. You will also learn what cholesterol is and why it is an important molecule in the human body. Fats and oils, found in many of the foods we eat, belong to a class of biomolecules known as lipids. Gram for gram, they pack more than twice the caloric content of carbohydrates: the oxidation of fats and oils supplies about 9 kcal of energy for every gram oxidized, whereas the oxidation of carbohydrates supplies only 4 kcal/g. Although the high caloric content of fats may be bad news for the dieter, it says something about the efficiency of nature’s designs. Our bodies use carbohydrates, primarily in the form of glucose, for our immediate energy needs. Our capacity for storing carbohydrates for later use is limited to tucking away a bit of glycogen in the liver or in muscle tissue. We store our reserve energy in lipid form, which requires far less space than the same amount of energy stored in carbohydrate form. Lipids have other biological functions besides energy storage. They are a major component of the membranes of the 10 trillion cells in our bodies. They serve as. |
SciQ | SciQ-695 | biochemistry, entomology
Title: How do ants follow each other? I was observing ants in my house.They all were going in a straight line and also some of the ants were coming back through the the same line.
I took some water and rubbed the line with my finger, then the ants were not able to follow each other. Looks like they were confused.
My assumption is that they may had secreted some chemical .
Am I right ?
If yes, then which chemical is that and how it is secreted? The chemical we are talking about here is called pheromone, trail pheromone to be specific.
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individuals.1
Pheromones are of mainly 9 types (13 exactly, but 4 not so common) which are:
Aggregation pheromones
Alarm pheromones
Epideictic pheromones
Releaser pheromones
Signal pheromones
Primer pheromones
Territorial pheromones
Trail pheromones
Sex pheromones
Nasonov pheromones
Royal pheromones
Calming pheromones
Necromones2
Ants, and many other animals, use trail pheromones to mark their trail as a guide for others in their gang. Other ants, catching the signal of trail pheromone, follow the way it goes and reach their gang leader. Trail pheromones are volatile compounds, so it is not very likely that you would see ants following the exactly same path tomorrow or a week later. All ants release trail pheromones, so as long as ants are going through that path, the trail signal will keep getting stronger and will also tell lost ants "Hey, bro! We are going this way. Don't you want to join us?" See, for example, here3:
The following is multiple choice question (with options) to answer.
What part of the body do ants use to detect chemicals? | [
"fins",
"thorax",
"eyes",
"antennae"
] | D | Some animals communicate with scent. They release chemicals that other animals of their species can smell or detect in some other way. Ants release many different chemicals. Other ants detect the chemicals with their antennae. This explains how ants are able to work together. The different chemicals that ants produce have different meanings. Some of the chemicals signal to all of the ants in a group to come together. Other chemicals warn of danger. Still other chemicals mark trails to food sources. When an ant finds food, it marks the trail back to the nest by leaving behind a chemical on the ground. Other ants follow the chemical trail to the food. |
SciQ | SciQ-696 | forces, water, surface-tension
Now, if we suddenly boost up this adhesion a billion times stronger (limit: imagination) from what is the real and cohesion stays same, then it's gonna suck. Literally. Everything the water or any liquid comes to contact with, it will immediately start to evenly spread out, clothing every nooks and cranny on that surface of that object. It'd be much like when we spill water on the floor. But now it'd be happening EVERYWHERE, on the sides and on the roofs. The rivers, lakes and oceans start allowing a layer of water to swallow everything up, and a carpet of water will cover the world. Trees and plants burst as there is an immense rush of water inside them. The large droplets of water we adored will never form, a droplet release in the air will torn into tiny minuscule droplets, that we can't see. Maybe into water vapor. And Life? I wonder... ;)
Hope that helped. Went a little overboard. :D
The following is multiple choice question (with options) to answer.
Water has the properties of cohesion and what else? | [
"degradation",
"adhesion",
"diffusion",
"absorption"
] | B | Water has the properties of cohesion and adhesion. Define these two properties, and explain why they occur in water. |
SciQ | SciQ-697 | 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.
Fitness and natural selection are parts of what theory that might describe how organisms change over time? | [
"dessication",
"gravity",
"implementation",
"evolution"
] | D | All of these animal behaviors are important. They help the animals get food for energy, make sure their young survive, or ensure that they, themselves, survive. Behaviors that help animals or their young survive, increase the animals’ fitness. Animals with higher fitness have a better chance of passing their genes on to the next generation. If genes control behaviors that increase fitness, the behaviors become more common in the species. This occurs through the process of evolution by natural selection. |
SciQ | SciQ-698 | newtonian-mechanics, forces, reference-frames, acceleration
Title: Given Newton's Third law, why don't we have to include acceleration or energy lost to Earth in calculations? This is probably an elementary question, but I am trying to help my nephew answer a worry. His question is: given Newton's third law, when a ball is thrown up in the air, we would push the earth a little downward. But whatever acceleration imparted and distance traveled during the throw the earth moved, why don't we have to take this into consideration?
I know from experience it is because we assume the earth didn't move. But I want to give him a better reason. I think the following, can someone confirm it is right we can assume it doesn't move because:
There are thousands of things happening at once, therefore all these actions/reactions tend to cancel out.
Earth is too massive to make a difference.
Our force might only compress part of earth, not earth as a whole.
Even if it did move or accelerate when the ball was thrown, when they collide as it comes back to ground, technically each would stop one another.
The following is multiple choice question (with options) to answer.
What three forces are involved in erosion? | [
"radiation, gravity, precipitation",
"water, wind, gravity",
"heat, pressure, gravity",
"water, temperature, altitude"
] | B | |
SciQ | SciQ-699 | thermodynamics, statistical-mechanics, pressure, temperature, entropy
Title: The definition of Spontaneous in thermodynamics? The definition of spontaneous is often briefly glossed over in most of the thermodynamics texts that I own. Peter Atkins in Physical chemistry defines spontaneous as follows
Some things happen naturally, some things don’t. Some aspect
of the world determines the spontaneous direction of change,
the direction of change that does not require work to bring it
about.
Later in the text and in many others you then find that
The entropy of an isolated system increases in the course
of a spontaneous change: $\Delta S_{tot} > 0$
The following is multiple choice question (with options) to answer.
Thermodynamics do not give us any insight into what attribute of spontaneous processes? | [
"rate",
"decrease",
"increase",
"acceleration"
] | A | It should be noted that just because a process is spontaneous does not mean that it occurs quickly. The rusting of iron is a spontaneous process that takes place over a long period of time. The combustion of gasoline in oxygen (also a spontaneous process) is extremely fast when provided with a spark, but gasoline can be stored in air for quite a while without spontaneously combusting. Thermodynamics predicts the direction in which a reaction will eventually proceed, but it does not tell us anything about the rate at which the reaction occurs. The rate of a reaction depends on many factors, including activation energy, temperature, concentration, and the presence or absence of a catalyst. Chemical kinetics focuses on the pathway between reactants and products, while thermodynamics considers only the difference between the initial and final states. |
SciQ | SciQ-700 | 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 is the main source of hydrocarbons? | [
"decomposers",
"photosynthesis",
"greenhouse gases",
"fossil fuels"
] | D | Hydrocarbons are extremely important to modern life. Their most important use is as fuels. Hydrocarbons are also used to manufacture many products including plastics. The main source of hydrocarbons is fossil fuels. |
SciQ | SciQ-701 | cell-biology, development, embryology
Title: What is cytoplasmic localization? I was studying development of chick but didn't understand what is cytoplasmic localization. My book says:
After third cleavage , the rest of the cleavages are irregular and completely delimited cells are formed all over the germinal disc which is termed as blastoderm. This outcome of cleavage called cytoplasmic localization helps seal the developmental fate of each cell's descendants. "Cytoplasmic localization" is a very general term and it means that something is present in the cytoplasm. For instance (hypothetical but there are known examples), you can say protein-X is localized to cytoplasm or the cytoplasmic localization of protein-Y is reduced upon phosphorylation. Similarly, there are terms like "nuclear localization", "ER localization", "mitochondrial localization" etc.
The usage mentioned in your excerpt is actually unclear and misleading. There is no process called cytoplasmic localization. What it actually means is that there are proteins/RNA inside the cytoplasm of the embryo that are asymmetrically distributed. When the cell divides, these molecules are therefore asymmetrically sorted to the daughter cells. Depending on what (and how much of) molecules the daughter cells receive, different cells adopt different phenotypes. Also note that the axis of division also plays a role; if lets say the distribution of a given molecule is asymmetric only about the anteroposterior axis and the division happens along that axis then both daughter cells receive the same amount of molecule and both the cells would be similar (w.r.t that molecule). This won't be the case if the division is along left-right axis. See the figure below.
From: Berika et al., 2014
I am not sure which book you are following but Developmental Biology by Scott F Gilbert is a good book and explains these processes nicely.
The following is multiple choice question (with options) to answer.
What is the process of the blastula forming 3 layers of cells called? | [
"fermentation",
"Mitosis",
"gastrulation",
"internalization"
] | C | Gastrulation The typical blastula is a ball of cells. The next stage in embryonic development is the formation of the body plan. The cells in the blastula rearrange themselves spatially to form three layers of cells. This process is called gastrulation. During gastrulation, the blastula folds upon itself to form the three layers of cells. Each of these layers is called a germ layer and each germ layer differentiates into different organ systems. The three germs layers, shown in Figure 43.26, are the endoderm, the ectoderm, and the mesoderm. The ectoderm gives rise to the nervous system and the epidermis. The mesoderm gives rise to the muscle cells and connective tissue in the body. The endoderm gives rise to columnar cells found in the digestive system and many internal organs. |
SciQ | SciQ-702 | thermodynamics, pressure, atmospheric-science, density, air
Title: Why does air pressure decrease with altitude? I am looking to find the reason: why air pressure decreases with altitude? Has it to do with the fact that gravitational force is less at higher altitude due to the greater distance between the masses? Does earth’s spin cause a centrifugal force? Are the molecules at higher altitude pushing onto the molecules of air at lower altitudes thus increasing their pressure? Is the earths air pressure higher at the poles than at the equator? The air pressure at a given point is the weight of the column of air directly above that point, as explained here. As altitude increases, this column becomes smaller, so it has less weight. Thus, points at higher altitude have lower pressure.
While gravitational force does decrease with altitude, for everyday purposes (staying near the surface of the Earth), the difference is not very large. Likewise, the centrifugal force also does not have significant impact.
The following is multiple choice question (with options) to answer.
How does air pressure change as altitude increases? | [
"It increases",
"goes up and down",
"stays the same",
"it decreases"
] | D | Like density, the pressure of the air decreases with altitude. There is less air pressing down from above the higher up you go. Look at the bottle pictured below ( Figure below ). It was drained by a hiker at the top of a mountain. Then the hiker screwed the cap on the bottle and carried it down to sea level. At the lower altitude, air pressure crushed it. Can you explain why?. |
SciQ | SciQ-703 | electromagnetism, general-relativity, forces, reference-frames, equivalence-principle
Title: Do all forces of nature produce opposite force when they move? I am not sure if I understand it right but as I see it any two moving charge particles must repel each other like they are not moving relative to observer that moving at the same speed as they moving,
according to this
https://www.youtube.com/watch?v=rKFzV8sVDsA
.
but accept the magnetic force and gravity there is also the strong force and the week force would they produce force to the opposite direction as well in case they are moving? Force is rate of change of momentum. As total momentum is conserved and constant, as long as you stay in the same inertial reference frame, the total force is zero. This the basis of Newton's third law.
The following is multiple choice question (with options) to answer.
In harmonic motion there is always what force, which acts in the opposite direction of the velocity? | [
"restorative force",
"magnetic force",
"locomotion force",
"inorganic force"
] | A | In harmonic motion there is always a restorative force , which acts in the opposite direction of the velocity. The restorative force changes during oscillation and depends on the position of the object. In a spring the force is the spring force; in a pendulum it is the component of gravity along the path. In both cases, the force on the oscillating object is directly opposite that of the direction of velocity. |
SciQ | SciQ-704 | species-identification, microbiology, microscopy
Title: Identification of protozoa under microscope I observed maybe Protozoa from standing FRESH water and from slowly flowing FRESH water. I am complete dilettante. Can you tell what these creatures are?
https://www.youtube.com/watch?v=6D5ck3zNJzA&t=474s
Thank you.
Added picture for to be more specific At first glance, the organisms may hold the appearance of protozoans like ciliates. However, I am of the belief that these 'totally tubular' micro organisms are in fact diatoms.
The diatoms are a diverse range of eucaryotic microalgae which comprise a large percentage of the phytoplankton group. (Diatomaceous earth is the residual remains of their calcareous walls)
They are likely diatoms because of their apparent hard membrane, and slight brown-green pigment, typical of heterokont diatoms.
I would be unable to specify the organism to family level. However, you may wish to complete your investigation by looking under the order 'Pennales'.
For general information regarding the Diatoms, you may visit https://en.wikipedia.org/wiki/Diatom
Morphology and description available from: https://books.google.co.uk/books?id=xhLJvNa3hw0C&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
Good luck
The following is multiple choice question (with options) to answer.
Many of the protist species classified into the supergroup excavata are asymmetrical, single-celled organisms with a feeding groove “excavated” from one side. this supergroup includes heterotrophic predators, photosynthetic species, and these? | [
"parasites",
"mammals",
"insects",
"reptiles"
] | A | Excavata Many of the protist species classified into the supergroup Excavata are asymmetrical, single-celled organisms with a feeding groove “excavated” from one side. This supergroup includes heterotrophic predators, photosynthetic species, and parasites. Its subgroups are the diplomonads, parabasalids, and euglenozoans. Diplomonads Among the Excavata are the diplomonads, which include the intestinal parasite, Giardia lamblia (Figure 23.10). Until recently, these protists were believed to lack mitochondria. Mitochondrial remnant organelles, called mitosomes, have since been identified in diplomonads, but these mitosomes are essentially nonfunctional. Diplomonads exist in anaerobic environments and use alternative pathways, such as glycolysis, to generate energy. Each diplomonad cell has two identical nuclei and uses several flagella for locomotion. |
SciQ | SciQ-705 | materials, structural-analysis, applied-mechanics, solid-mechanics, elastic-modulus
Figure 2: A Plot of Potential Energy versus Internuclear Distance for the Interaction between Two Gaseous Hydrogen Atoms. (source: libretexts
The atoms want to settle at the lowest energy point. If you compress/pull them apart then you quickly get a response back, which is the force. The more you pull/push, the higher up you go to the potential well and the higher the force.
Additionally, if you remove the external stimulus (the force you are applying), all that potential energy quickly returns the material to the "resting state".
(That doesn't explain plastic deformation, but its beyond the scope of this question).
Where does the extra energy go
Only a small part of your energy you are expending when you are pushing on the wall is stored as elastic energy.
The rest of the energy that is being burned away, is converted to heat from you body which is trying to maintain the force.
I guess an example that can help you understand that, is if you try to hold a bottle of water on the palm of your hand. You can try it in two ways
like the following image (arm extended)
Figure 3: bottle in hand not supported (source: saltysoulsexperience.com
everything is the same apart from the fact that you can support the back of your hand on a table.
You will be able to sustain position 2. a LOT longer, and the only reason is that the muscles will not need to contract as much in the second case.
excellent resource
An excellent book about this is Prof. Gordon's "The New Science of Strong Materials: Or Why You Don't Fall through the Floor", although it has only a handful of equations if you are interested, and its almost bed time reading (or sometimes a bit more than that).
The following is multiple choice question (with options) to answer.
What is the thick fluid in the space between bones that cushions the joint? | [
"interstitial fluid",
"collagen",
"amniotic fluid",
"synovial fluid"
] | D | Movable joints are also known as synovial joints. This is because the space between the bones is filled with a thick fluid, called synovial fluid, that cushions the joint (see Figure below ). |
SciQ | SciQ-706 | biochemistry, ph, dna-rna
Title: net charge nucleobases at alkaline conditions While doing anion exchange chromatography of a short oligonucleotide, I have noticed that at $\rm pH=12$, the oligo retains longer on the column than the same oligo- at $\rm pH=8$. I thought the reason for this could be the change in the net charge of nucleobases.
Could anyone suggest what is the net charge of RNA nucleobases (adenine, guanine, cytosine, uracil) at $\rm pH=12$ (denaturing conditions)? The conjugate acids of the adenine and guanine have pKa's between 9-10. Guanine also has a nitrogen with a pKa of 12.3, which would be mostly protonated at pH 12. The pKa for the phosphoric acid proton of a nucleotide is significantly lower than 7.
Therefore, in a pH 8 buffer, the basic nitrogens of each adenine and guanine are protonated, while the phosphate is deprotonated. This gives an overall net charge closer to zero than you would see at pH 12.
In a pH 12 buffer, where the pH is above the pKa of both the phosphoric acid protons and the nitrogen conjugate acid protons (except the last one on each guanine), all of these positions would be deprotonated. Therefore, the formal charge on the nitrogens would be zero (again, except the most basic nitrogen on guanine), but the phosphates would still have a charge of -1 each. This would lead to a net charge of significantly higher charge magnitude because there would be very few positive charges to balance out the negative charges.
At pH 12, the net charge should be approximately: $$(n_N +n_u) - (n_c + n_g).$$
Approximate net charge at pH 8: $$n_N - (n_a + n_c + 2n_g).$$
nN= number of nucleotides
nu= number of uracils/thymines
nc= number of cytosines
ng= number of guanosines
na= number of adenosines
The following is multiple choice question (with options) to answer.
What is the name of the portion of a nucleotide lacking phosphate groups? | [
"nuclear shell",
"a nucleoside",
"a nucleobase",
"nucleolus"
] | B | |
SciQ | SciQ-707 | solid-state-physics, fourier-transform, crystals, electronic-band-theory, dispersion
Title: How to interpret band structure of $\rm Si$? I found it very instructive to see how the $E$-$k$ relationship of a free particle can be roughly identified from the extended band structure of a solid: The following is the outcome of the one dimensional Kronig–Penney model.
For three dimensions things get more complicated. Lets have a look on Si:
Taking only the 100-Direction and putting the slices together, I come to this "extended" zone scheme:
The red and blue branches are what I expect from the one-dimensional picture. But, to put an example, where is the yellow branch coming from? It doesn't fit in to the "simple" picture.
I always thought, that that there is a unique k(E) Relationship for each Brillouin-Zone and the red, blue and green branches are from first, second and third Zone, respectively.
Now I see, that my picture cannot be completely true, because the yellow branch doesn't fit into my model in mind. Can the yellow branch assigned to a particular zone or is my idea of a one-to-one relationship Branch<-->Zone not reasonable at all? First, it's not correct to call the shifted first Brillouin zone (as in the extended zones scheme) "second" BZ. The higher-order Brillouin zones are still $\Gamma$-centered, with the shape becoming more complicated as the zone order increases. See e.g. the pictures here.
Next, your 1-dimensional band structure is deceiving you, making you forget that in 2 dimensions the band structure will have additional branches for the added dimension. E.g. for the 1D free-electron dispersion relation
$$E_n(k)=\left(k+\frac{2\pi}a n\right)^2$$
we have the following band diagram:
The following is multiple choice question (with options) to answer.
The band disappears before metaphase but predicts the future plane of what? | [
"cell solution",
"cell division",
"cell matter",
"cell wall"
] | B | |
SciQ | SciQ-708 | biochemistry
Specific Force Deficit in Skeletal Muscles of Old Rats Is Partially
Explained by the Existence of Denervated Muscle Fibers
Association of adiponectin and resistin with adipose tissue
compartments, insulin resistance and dyslipidaemia
Shifts in the Distribution of Mass Densities Is a Signature of
Caloric Restriction in Caenorhabditis elegans
The following is multiple choice question (with options) to answer.
What is a common age-related bone disease in which bone density and strength is decreased? | [
"lupus",
"fibrosis",
"arthritis",
"osteoporosis"
] | D | View this animation (http://openstaxcollege. org/l/ headblow) to see how a blow to the head may produce a contrecoup (counterblow) fracture of the basilar portion of the occipital bone on the base of the skull. Why may a basilar fracture be life threatening? 3. Osteoporosis is a common age-related bone disease in which bone density and strength is decreased. Watch this video (http://openstaxcollege. org/l/osteoporosis) to get a better understanding of how thoracic vertebrae may become weakened and may fractured due to this disease. How may vertebral osteoporosis contribute to kyphosis? 4. Watch this animation (http://openstaxcollege. org/l/ diskslip) to see what it means to “slip” a disk. Watch this second animation (http://openstaxcollege. org/l/ herndisc) to see one possible treatment for a herniated disc,. |
SciQ | SciQ-709 | mutations, genomes
Title: Bacterial division and mutation rate When a bacteria A divides it produces two cells A', A''. Each of them receives a copy of the chromosome/plasmids. Now, DNA replication occurs way before division in a semiconservative manner. That is, each new chromosome has an 'old' strand and a 'new' strand. Since the polymerase is error prone, my belief is that both genomes can potentially have mutations. Now when people refer to the mutation rate/genome/replication, e.g. 3x10-4 , Does this mean that:
The following is multiple choice question (with options) to answer.
Bacteria reproduce through what process? | [
"tertiary fission",
"residual fission",
"binary fusion",
"binary fission"
] | D | Bacteria reproduce through a process called binary fission . During binary fission, the chromosome copies itself, forming two genetically identical copies. Then, the cell enlarges and divides into two new daughter cells. The two daughter cells are identical to the parent cell. Binary fission can happen very rapidly. Some species of bacteria can double their population in less than ten minutes! This process makes it possible for a tremendous bacterial colony to start from a single cell. |
SciQ | SciQ-710 | waves
Title: Is there a specific branch of physics that studies waves? Is there a branch of physics that studies waves and how they propagate through air, wires etc.? Acoustic physic deals with mechanical waves. But as CuriousOne says, many areas of physics uses waves in some way, so it's hard to pinpoint a "wave-only" physics.
The following is multiple choice question (with options) to answer.
What is the branch of science that studies the physical world? | [
"physics",
"social science",
"botany",
"Ecology"
] | A | What is physics ? Physics is the branch of science that studies the physical world, including objects as small as subatomic particles and as large as galaxies. It studies the nature of matter and energy and how they interact. Physicists are inquisitive people who want to know the causes of what they see. How does the moon move? Why does the moon move? Why do the stars shine? Why do your hands get warm when you rub them together? Physicists, like all scientists, hope to find explanations that describe more than one phenomenon and offer a better understanding of how the universe works. |
SciQ | SciQ-711 | human-biology, physiology, endocrinology, vitamins, homeostasis
Title: Counterintuitive action of Vitamin D? Vitamin D acts in a way which to me is counterintuitive. It functionally supplemets Parathormone. It in the intestinal tract steps up calcium absorption by altering nuclear gene expression and also prevents calcium excretion in kidneys. All of this is understandable. But it also, like parathormone, steps up osteoclast action in bone (actually steps up both osteoclast and osteoblast, but the osteoclast action is increased more to result in net bone resorption). This means that Vitamin D increases blood calcium level by increasing bone resorption.
Then how does Vitamin D help in improving bone density, bone strength and prevent rickets or osteoporosis? All of these would require bone deposition rather than resorption. There are two pieces to this question:
a) How does bone resorption (movement of Ca/Phos out of bone into the blood) result in net improvement in bone structure?
Bones are constantly remodeling, primarily in response to mechanical stressors. Although you clearly already realize this, I will make it explicit: osteoblasts are the cells that create new bone; osteoclasts break down (resorb) bone.
Quoting Harrison’s Internal Medicine1:
Radioisotope studies indicate that as much as 18% of the total skeletal calcium is deposited and removed each year. Thus, bone is an active metabolizing tissue.…The cycle of bone resorption and formation is a highly orchestrated process carried out by the basic multicellular unit, which is composed of a group of osteoclasts and osteoblasts
The following is multiple choice question (with options) to answer.
Osteoclasts break down bone to maintain mineral what? | [
"fluctuations",
"density",
"homeostatis",
"polarity"
] | C | Under the direction of osteocytes, osteoblasts continuously build up bone, while osteoclasts continuously break down bone to maintain mineral homeostasis. Bone tissues include compact bone, spongy bone, bone marrow, and periosteum. |
SciQ | SciQ-712 | organic-chemistry, nomenclature, carbonyl-compounds, cyclohexane
From there, I imagine you can figure out the rest: the cyclohexane as a valid chain is also the longest chain, you start numbering from the functional group, etc. Hope that helped explain the teacher's answer!
The following is multiple choice question (with options) to answer.
Which carbohydrates can be classified in terms of chain length? | [
"atomic",
"binary",
"complex",
"simple"
] | D | Simple carbohydrates can be classified in terms of chain length. |
SciQ | SciQ-713 | blood-circulation, blood-pressure, tissue
Title: Blood circulation and blood pressure in different tissues The volume of blood coursing the blood circulation is approximately five litres. A typical vein will stretch about eight times as much as corresponding artery. Because veins have high capacitance, large changes in blood volume have little effect on arterial blood pressure.
If the volume rise or falls, the elastic walls stretch or recoil, changing the volume of blood thus blood pressure in the nervous system.
What else tissues can we consider?
I am interested in blood circulation and blood pressures in different tissues. I'm not sure I understand your question very well-maybe try and rephrase it? As another example, low blood pressure in the kidneys is sensed by the juxtaglomerular apparatus which secretes renin into the circulation. Renin converts angiotensinogen (released by the liver) into angiotensin I. Angiotensin I is then converted into angiotensin II by angiotensin converting enzyme (this is the target of anti-hypertensives called ACE inhibitors) secreted by the lungs. Angiotensin II is a potent vasoconstrictor which directly increases the blood pressure (and hence glomerular filtration rate). Angiotensin II also causes the release of aldosterone which acts on the kidneys to re-absorb salt and water again all facilitating an increase in blood pressure. I hope I've answered your question, if not please edit the question so it very clear.
The following is multiple choice question (with options) to answer.
What is altered by changes in cardiac output by variable contriction of the arterioles? | [
"pulse",
"heart rhythm",
"blood type",
"blood pressure"
] | D | |
SciQ | SciQ-714 | genetics, dna, dna-sequencing, human-genetics
Title: Do eukaryote cells contain DNA that isn't part of a chromosome or located in the mitochondria? I specify eukaryote in the title, but I'm also interested if this question isn't applicable to eukaryote cells in general but is to humans. I was reading "RNA-seq: An assessment of technical reproducibility and comparison with gene expression arrays" (John Marioni 2008).
In the results it states
"By these criteria, 40% of reads mapped uniquely to a genomic location, and of these, 65% mapped to autosomal or sex chromosomes (the remainder mapped almost exclusively to mitochondrial DNA)."
I couldn't help but notice the "almost exclusively to mitochondrial DNA". Almost exclusively? Can DNA be found in places other than chromosones or mitochondria? Perhaps I'm interpreting the sentence wrong. Any pointers would be appreciated
Thanks In plants, chloroplasts and other plastids contain DNA, but I suppose you are more interested in humans. Quoting from wikipedia,
In many cells cytoplasmic DNA is also found, which is different from
nuclear DNA, both in methylation levels (cytoplasmic has less), and in
sequence. EccDNA or extrachromosomal circular DNA is present in all
eukaryotic cells, derived from genomic DNA and consists of repetitive
sequences of DNA found in both coding and non-coding regions of
chromosomes. EccDNA can vary in size from less than 2000 more than
20,000 base pairs. In animals, eccDNA molecules have been shown to
contain repetitive sequences that are seen in satellite DNA, 5S
ribosomal DNA and telomere DNA. The function of eccDNA has not been widely studied, but it has been proposed that the production of elements of eccDNA from genomic DNA sequences adds to the plasticity of the eukaryotic genome and can influence genome stability, cell aging and the evolution of chromosomes
The following is multiple choice question (with options) to answer.
Eukaryotic cells are cells that contain what? | [
"energy",
"a nucleus",
"pathogens",
"inorganic matter"
] | B | Eukaryotic cells are cells that contain a nucleus. |
SciQ | SciQ-715 | dna, terminology
Title: Is a DNA molecule a single strand of polynucleotide or two of them linked together? Our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds. The thing is, until now, I always thought a DNA molecule was composed of two strands, those being polynucleotides, both of them being linked together. I can't find a link which is saying the same as my teacher, even if it seems technically correct to call a double helix a dimer of two DNA molecules.
I was curious to know what was the exact terminology. As you pointed out, though this may be basic biology, seeking clarification when receiving conflicting information is a good thing. Don't feel embarrassed for asking. :)
.. our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds.
Respectfully, your teacher is incorrect. A single, double-stranded DNA molecule is comprised of two helical shaped polynucleotides, and are connected together via hydrogen bonding.
Highlight of each polynucleotide
Highlight of hydrogen bonding
And just for further validation, according to Molecular Biology of the Cell, 4th ed., by Alberts B, Johnson A, Lewis J, et al.:
A DNA molecule consists of two long polynucleotide chains composed of four types of nucleotide subunits. Each of these chains is known as a DNA chain, or a DNA strand. Hydrogen bonds between the base portions of the nucleotides hold the two chains together.
So, it would seem that your teacher is referring to each polynucleotide, a.k.a. DNA strand, as a DNA molecule. Instead, she should use the verbiage: a single DNA molecule is composed of two DNA strands, which are helical-shaped polynucleotides.
The following is multiple choice question (with options) to answer.
What distinctive dna shape forms when the two nucleotide chains wrap around the same axis? | [
"double spiral",
"chain helix",
"double helix",
"single spiral"
] | C | Simple Model of DNA. In this simple model of DNA, each line represents a nucleotide chain. The double helix shape forms when the two chains wrap around the same axis. |
SciQ | SciQ-716 | bond
Title: How can oxygen have three bonds? I was reading an article about a chemical reaction, and I came across the phrase:
The oxygen atom at this point has three bonds and has a net positive charge
How can this happen? Oxygen has 2 missing electrons in the valence shell. Therefore it can only form 2 bonds at the most, if both are sigma bonds.
Does it mean the 3rd bond is not covalent? Can it happen with a hydrogen or an ionic bond? Consider the auto-ionization of water :
$\ce{ 2H_2O->H_3O+ + OH-}$
The first oxygen has three bonds, the second only has one.
You can think of the reaction taking place by a lone pair on the oxygen of one water molecule ripping off the proton only of the hydrogen of another water molecule to form a covalent bond between them using just the lone pair. The electron of the hydrogen is left behind and stays with the oxygen of the other molecule.
If you calculate the formal charges on each oxygen you will see the first one has a positive charge and the second one has a negative. The formal charge is just the valence number of electrons minus the number of bonds minus non-bonding electrons (using the lewis structure) and is a useful book keeping method to think about where the electrons go/are and what are the most stable structures.
Formal Charge Calculation
The following is multiple choice question (with options) to answer.
The oxygen regions of the water molecules have what kind of charge? | [
"positive",
"negative",
"neutral",
"certain"
] | B | |
SciQ | SciQ-717 | history-of-chemistry, salt
I can provide the references he uses if requested.
The problem was introducing a systematic nomenclature for describing substances because there was an ever-increasing number of them being discovered.
The general historical evolution starts with the fields of botany and chemistry at the beginning of the 18th century, where Linnaeus' botanical binomial nomenclature was used by Bergman toward the end of the century. Guyton de Morveau extended and refined Bergman's scheme and collaborated with Lavoisier to establish what we work with today.
In the 16th century, Paracelsus referred to potassium bisulphate (which is more soluble than potassium sulphate) as ${\it sal\ enixum}$ in the alchemical literature. Paracelsus was famous (in part) for putting forth the theory that metals are composed of "Mercury, Sulphur and Salt," arising in alchemy.
Later, in 1664, the French chemist Le Fubure published work in which he differentiated salts of nitre by crystal habit. Duhamel, in 1736, showed that the salts of potassium and sodium were distinguishable by their bases.
In any case, there was a pressing need to formalize a nomenclature. Torbern Bergman (1735-84) is credited with taking on the task of reform in the first orderly manner. He introduced (via publication) his ideas towards a binomial system for naming, which was limited although a good start.
Guyton de Morveau expanded on Bergman's ideas and was able to systematically name 500 salts from 18 acids and 24 bases (earths, alkalis, and metals).
The big arrival was ${\it Méthode\ de\ nomenclature\ chimique}$ in 1787 and was authored by Guyton de Morveau, Lavoisier, Berthollet, and Fourcroy. It is at the point that the system for naming chemicals was in place. From here, the contributions of British, German, and other chemists was incorporated.
By the early 19th century, additions and revisions to the above were made and the systems of naming was largely in place. The evolution of naming things from the earth as 'salts' to naming things in a certain class as 'salts' largely took place during the last quarter of the 18th century.
The following is multiple choice question (with options) to answer.
Humans use many compounds that were first discovered or derived from living organisms as medicines: secondary plant compounds, animal toxins, and antibiotics produced by these? | [
"bacteria and fungi",
"molecules and fungi",
"tumors and fungi",
"bacteria and tumors"
] | A | 47.2 The Importance of Biodiversity to Human Life Humans use many compounds that were first discovered or derived from living organisms as medicines: secondary plant compounds, animal toxins, and antibiotics produced by bacteria and fungi. More medicines are expected to be discovered in nature. Loss of biodiversity will impact the number of pharmaceuticals available to humans. Crop diversity is a requirement for food security, and it is being lost. The loss of wild relatives to crops also threatens breeders’ abilities to create new varieties. Ecosystems provide ecosystem services that support human agriculture: pollination, nutrient cycling, pest control, and soil development and maintenance. Loss of biodiversity threatens these ecosystem services and risks making food production more expensive or impossible. Wild food sources are mainly aquatic, but few are being managed for sustainability. Fisheries’ ability to provide protein to human populations is threatened when extinction occurs. Biodiversity may provide important psychological benefits to humans. Additionally, there are moral arguments for the maintenance of biodiversity. |
SciQ | SciQ-718 | evolution, zoology, anatomy, species
Title: Examples of animals with 12-28 legs? Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list:
snakes have 0
Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs)
Most mammals, reptiles, amphibians have 4 legs
Echinoderms (e.g., sea stars) typically have 5 legs.
Insects typically have 6 legs
Octopi and arachnids have 8 legs
decapods (e.g., crabs) have 10 legs
....But I can't really think of many examples of animals containing more legs until you reach 30+ legs in centipedes and millipedes. Some millipedes even have as many as 750 legs! The lone example I am aware of, the sunflower sea star, typically has 16-24 (though up to 40) limbs.
So my question is: what are some examples of animals with 12-28 legs? As a couple of counterexamples, species in the classes Symphyla (Pseudocentipedes) and Pauropoda within Myriapoda have 8-11 and 12 leg pairs respectively, so between 16 to 24 legs (sometimes with one or two leg pair stronlgy reduced in size).
(species in Symphyla, from wikipedia)
Another common and species-rich group with 14 walking legs (7 leg pairs) is Isopoda.
(Isopod, picture from wikipedia)
You also need to define 'legs' for the discussion to be meaningful. As you say, decapods have 10 legs on their thoracic segments (thoracic appendages), but they can also have appendages on their abdomens (Pleopods/swimming legs), which will place many decapods in the 10-20 leg range.
(Decapod abdominal appendages/legs in yellow, from wikipedia)
So overall, in Arthropoda, having 12-28 legs doesn't seem all that uncommon. There are probably other Arthropod groups besides those mentioned here that also have leg counts in this range.
However, for a general account, the most likely answer (if there is indeed a relative lack of 12-28 legged animals) is probably evolutionary contingencies and strongly conservative body plans within organism groups.
The following is multiple choice question (with options) to answer.
Millipedes and centipedes are the most commonly found examples of what group of arthropods? | [
"subphylum myriapoda",
"Disperse Myriapoda",
"unicellular myriapoda",
"protists myriapoda"
] | A | Subphylum Myriapoda includes arthropods with legs that may vary in number from 10 to 750. This subphylum includes 13,000 species; the most commonly found examples are millipedes and centipedes. All myriapods are terrestrial animals and prefer a humid environment (Figure 15.21). |
SciQ | SciQ-719 | particle-physics
Title: Explanation for self-rupture glass is needed I witnessed a phenomenon that I couldn't conclude its cause. Please bear with me for the length of the recall, for I merely want to include any details that might help us to investigate. I had a cooking glass lid sat on a wooden shelf that is away from the stove and oven and other heating objects. The shelf is nailed on the wall and is situated just above my eye level, and a counter top is also on the same side of the wall where the shelf is installed.
Now here comes the surprise. In a winter afternoon 2011, my room had almost the same temperature as an autumn morning, and while I was cutting my lettuce on that counter top which I pointed out in above passage, a pounding sound, as if a heavy car door slam or a tree trump falling on top of the roof, knocked its introduction from the shelf that was just above my eye level. First, I thought I may had knocked something around me off(which I didn't believe that for there wasn't anything around me to knock off); then I thought it may be my neighbor next door dropping a heavy box; last, I suspected somewhere my roof top collapsed.
But it was my third suspicion directed me to meet that glass lid I mentioned above, and I found it had ruptured completely like glacier creaked BUT still having all broken pieces bounded without any pieces scattering toward random direction! Only the nob of the lid popped out partially. Before this happened, I hadn't used that lid for cooking for years, and I didn't removed it from any heating object nor there was something on top of the lid that day, and I believe what the lid had maybe just an invisible layer of dust.
I was glad my face hadn't been stung by any glass residues, but ponder what really happen to that glass lid and why it ruptured without collapsed. Below, I attached 2 pictures of the scene from that day. If you have any similar experience or know the theory behind it, may you please drop me an explanation to this incidence? Thank you in advance.
The following is multiple choice question (with options) to answer.
Glass breaking is an example of what type of change that doesn't affect the makeup of matter? | [
"physical",
"chemical",
"thermal",
"reversible"
] | A | Physical changes are changes in the physical properties of matter but not in the makeup of matter. An example of a physical change is glass breaking. |
SciQ | SciQ-720 | organic-chemistry, redox, carbonyl-compounds
activated silyl carboxylates
Corriu, R. J. P.; Lanneau G. F.; Perrot M. The one-pot conversion of carboxylic acids to aldehydes via activated silyl carboxylates. Tetrahedron Letters 1987, 28 (34), 3941–3944.
titanium-catalyzed Grignard
Sato, F.; Jinbo, T.; Sato, M. The Reduction of Carboxylic Acids to Aldehydes by Dichlorobis[π-cyclopentadienyl]titanium-Catalyzed Grignard Reactions. Synthesis 1981, 1981 (11), 871
N,N-dimethylchloromethyleniminium chloride and lithium tri-t-butoxyaluminum hydride
Fujisawa, T.; Mori, T.; Tsuge, S.; Sato, T. Direct and chemoselective conversion of carboxylic acids into aldehydes. Tetrahedron Letters 1983, 24 (14), 1543–1546.
$o\text{-}\ce{HSC6H4OH, POCl3, HClO4/LiAlH4/H2O, HgCl2}$
Costa, L.; Degani, I.; Fochi, R.; Tundo, P. Pentaatomie heteroaromatic cations. Note III. A Convenient Synthesis of Aldehydes from Carboxylic Acids via 2-Substituted 1,3-Benzoxathiolium Perchlorates. J. Heterocyclic Chem. 1974, 11, 943–948.
$o\text{-}\ce{(NH2)C6H4, PPA/NaOet/MeI/NaBH4}$ or $\ce{LiAlH4/H3O+}$
Craig, J. C.; Ekwurire, N. N.; Fu, C. C.; Walker, K. A. M. Conversion of Carboxylic Acids into Aldehydes and their C-1 or C-2 Deuteriated Derivatives. Synthesis 1981, 1981 (4), 303–305.
The following is multiple choice question (with options) to answer.
Aldehydes, ketones, carboxylic acids, esters, and ethers all have functional groups containing what element? | [
"methane",
"silicon",
"oxygen",
"carbon"
] | C | Aldehydes, ketones, carboxylic acids, esters, and ethers h ave oxygencontaining functional groups. |
SciQ | SciQ-721 | electrons, metal, electronic-configuration
Title: Can a metal be forced to form an anion theoretically? I know that metals have the capability to lose electrons and form cations, but is it also theoretically possible to supply an electron to a metal so that it forms an anion?
If so, has it ever been done?
I referred this question (Can two metals combine to form a compound?) but could not get a satisfactory solution from that. Absolutely! You will find these mostly in electride systems and off these, mostly in alkali metals.
Here is an example research paper:
"Superakali-Alkalide Interactions and Ion Pairing in Low-Polarity Solvents, J. Am. Chem. Soc., 2021, 143(10), 3934–3943 (https://pubs.acs.org/doi/10.1021/jacs.1c00115)
Remember, metals have a positive charged when ionized because it is energetically more favorable to lose electrons than to gain them, this being of course an oversimplified version of electron orbitals and shells. If you have a situation in which this is reverse or not possible, you will get a negative metal ion
The following is multiple choice question (with options) to answer.
What forms when an atom gains electrons? | [
"cations",
"crystals",
"bonds",
"anions"
] | D | Anions form when an atom gains electrons. Nonmetallic atoms typically gain enough electrons to obtain the same electron configuration as the nearest noble gas. All the elements in Group 17 have seven valence electrons, which are arranged into an outer configuration of n s 2 n p 5 . To achieve a noble gas configuration ( n s 2 n p 6 ), each of these elements needs to gain just one electron, resulting in an anion with a 1− charge. Similarly, Group 16 elements can obtain an n s 2 n p 6 valence configuration by forming ions with a 2− charge, and the Group 15 nonmetals will form ions with a 3− charge. Naming anions is slightly different than naming cations. The end of the element’s name is dropped and replaced with the – ide suffix. For example, when the chlorine atom (Cl) gains one electron, it becomes the chloride ion (Cl - ). This structure has the same electron configuration as the noble gas argon. Similarly, sulfur can gain two electrons to become the sulfide ion (S 2- ), which also has a noble gas configuration. |
SciQ | SciQ-722 | botany, marine-biology, salt
Title: Mangroves and desalination of sea water I am not an expert but I guess that mangroves (or some other plants that thrive in sea water) perform some kind of desalination to extract fresh water from sea water.
Is this true? If yes, What biological mechanisms are used to remove salt from sea water?
I am interested in any research about biological desalination. This paper might be of interest to you: https://advances.sciencemag.org/content/6/8/eaax5253.
The researchers created a synthetic mangrove that actually performs desalination, using the principles of natural mangroves.
The introduction has a good overview of the main ways mangroves desalinate saline water, namely:
Physical blockage by suberin within cells walls
Selective permeability of cell membranes in root
Negative pressure caused by evaporation that acts as hydraulic pressure to cause take-up of water by roots
All these combine to turn the mangrove into a kind of natural RO (reverse osmosis) machine.
The following is multiple choice question (with options) to answer.
There are several types of wetlands including marshes, swamps, bogs, mudflats, and salt marshes. the three shared characteristics among these types—what makes them wetlands—are their hydrology, hydrophytic vegetation, and this? | [
"niya soils",
"stibnite soils",
"hydric soils",
"sandy soils"
] | C | may not be able to use vision as their primary sense to find food. Instead, they are more likely to use taste or chemical cues to find prey. Wetlands Wetlands are environments in which the soil is either permanently or periodically saturated with water. Wetlands are different from lakes because wetlands are shallow bodies of water whereas lakes vary in depth. Emergent vegetation consists of wetland plants that are rooted in the soil but have portions of leaves, stems, and flowers extending above the water’s surface. There are several types of wetlands including marshes, swamps, bogs, mudflats, and salt marshes (Figure 44.25). The three shared characteristics among these types—what makes them wetlands—are their hydrology, hydrophytic vegetation, and hydric soils. |
SciQ | SciQ-723 | nuclear-engineering, gamma-rays, medical-physics
Title: X-ray shielding X-ray shielding, why is lead used to shield us when taking X-ray images?
As far as I remember (but can't find it on wikipedia ... ), the deflection on (high energy) photons increases the more heavier the nuclei are. (Don't remember and don't find if it's really the mass or rather the proton number.)
In either case, there are heavier, more dense materials with higher proton numbers.
The material is not consumed nor altered by exposure to X-rays. So why don't we use gold or depleted uranium (just to name some alternatives)?
(Not sure about tags, if anyone knows better, please feel free to suggest/add some others.)
Edit: as the answers and comments here helped me to clear my mind to change the question, but the new question is sufficiently different, I've asked a follow-up here: Formula for scattering and energy change of photons on (naked) nuclei I pulled out my notes from a shielding class and found that the absorption cross section per atom follows a rule: $$\sigma_a\sim\frac{Z^p}{E^3},$$
where $z$ is the atomic number of the absorber atom, $E$ is the energy of the photon, and $p$ is an energy dependent value between 3 and 5. For most x-rays, $p\simeq 4$.
While the cross-section per atom does indeed get larger for increasing $Z$, the density of the material is important, too. The density peaks at osmium ($Z=76$), then drops off, then climbs again in the actinides, but never reaches densities near osmium and iridium ($Z=77$).
When considering the effectiveness of an shield/absorber, one must consider the combined effects of cross-section per atom and density. The result of this is a quantity known as the linear attenuation coefficient, $\mu$, which is typically quoted in $\mathrm{cm}^{-1}$. This is used to calculated the intensity of radiation after travelling through a thickness, $x$ of a material: $$I(x)=I_0 e^{-\mu x}.$$
The following is multiple choice question (with options) to answer.
What element is typically used to shield things from gamma rays? | [
"aluminum",
"gold",
"silver",
"lead"
] | D | High-density materials are much more effective protection against gamma emissions than low-density ones. Gamma rays are usually blocked effectively by lead shielding. The thickness of the shielding will determine the effectiveness of the protection offered by the lead. |
SciQ | SciQ-724 | botany, homework, terminology, plant-anatomy, tissue
Interfascicular cambium differentiates from parenchyma or collenchyma cells located between the vascular bundles (mainly in stem)
The following is multiple choice question (with options) to answer.
What is the combination of tissues that provides a tough, woody external covering on the stems of trees called? | [
"scale",
"bark",
"epidermis",
"cuticle"
] | B | In trees, some of the epidermal tissue is replaced by bark. Bark is a combination of tissues that provides a tough, woody external covering on the stems of trees. The inner part of bark is alive and growing; the outer part is dead and provides strength, support, and protection. |
SciQ | SciQ-725 | evolution, mutations, antibiotic-resistance
Title: If bacterial resistance randomly occur, then why limit broad-spectrum antibiotic use? If there is importance to study some discipline, then one of the main matters is its applications, so besides the primary goal of knowing the truth of the matter regarding what that discipline is investigating, applicability or usefulness of that study in other fields or in the field itself is a very important matter. I'll direct my attention here to Evolution, and its mechanisms. So accordingly if something that I personally want to come up with is application of that knowledge to the field of my work.
In reality we don't study evolution extensively at college level in medicine, since it doesn't have a direct clinical impact on the diagnosis and treatment of patients in most of the cases. However, one possible area of interaction is "bacterial resistance to antibiotics", since this is related to "mutations", and generally viewed as a mechanism whereby the bacterium adapts to its environment.
Now all of my life in medicine from college through specialty and academic teaching, we've never ceased being reminded about not dispensing antibiotics liberally, and the main concern outlined is "emergence of resistant strains of bacteria" due to this liberal use of antibiotics itself. There are other reasons of course, like side effects and cost, but they are not the main concern most of the times.
During my recent review of Evolution, looking at the introductory courses that were cited to me by many participants here, in particular this page of Evo101 titled "Mutations are Random" I was really shocked to know that even the mutations that resulted in bacterial resistance were not "directed mutations", i.e. it is not the case that the exposure to the antibiotic caused the bacteria to have that mutation in the first place, actually the page mentions Esther and Joshua Lederberg experiments showing that those resistant bacteria were already there before the population was exposed to the antibiotics?
So why have we been always reminded by bacteriologists of limiting our antibiotic usage if emergence of drug resistance is not due to exposure to it?
The following is multiple choice question (with options) to answer.
Because microorganisms can go through several generations in a matter of hours, their gene expression profiles adapt to the new laboratory environment very quickly. in addition, the vast majority of bacterial species resist being cultured in this? | [
"substrate",
"colonies",
"water",
"isolation"
] | D | Microbial Genomics: Metagenomics Traditionally, microbiology has been taught with the view that microorganisms are best studied under pure culture conditions, which involves isolating a single type of cell and culturing it in the laboratory. Because microorganisms can go through several generations in a matter of hours, their gene expression profiles adapt to the new laboratory environment very quickly. In addition, the vast majority of bacterial species resist being cultured in isolation. Most microorganisms do not live as isolated entities, but in microbial communities known as biofilms. For all of these reasons, pure culture is not always the best way to study microorganisms. Metagenomics is the study of the collective genomes of multiple species. |
SciQ | SciQ-726 | immunology, virology, virus, infection, immunity
Title: Why don't we develop immunity against common cold? We all suffer from common cold, and that, frequently. Why have we not developed immunity against it till now? By immunity I mean immunity as a species. Long lasting immunity is obtained by means of the adaptive immune system, and mainly involves the development of antibodies that identify specific parts (epitopes) of the pathogen's proteins. Common cold is typically caused by a type of virus called rhinovirus. Viruses have very high mutation rates, which alter the sequence of the virus proteins, modifying their antigenic properties. This consequently alters the ability of antibodies to recognize a particular antigen.
In other words, we do develop long lasting immunity against the virus that causes us a cold today, but the virus that causes us a cold a few months later is somewhat different, and the adaptive immune system has to start from scratch.
The following is multiple choice question (with options) to answer.
Examples of acute forms of what type of diseases include the common cold and influenza? | [
"attributable diseases",
"viral diseases",
"inherited diseases",
"bacterial diseases"
] | B | As you will learn in the next module, animal viruses are associated with a variety of human diseases. Some of them follow the classic pattern of acute disease, where symptoms get increasingly worse for a short period followed by the elimination of the virus from the body by the immune system and eventual recovery from the infection. Examples of acute viral diseases are the common cold and influenza. Other viruses cause long-term chronic infections, such as the virus causing hepatitis C, whereas others, like herpes simplex virus, only cause intermittent symptoms. Still other viruses, such as human herpesviruses 6 and 7, which in some cases can cause the minor childhood disease roseola, often successfully cause productive infections without causing any symptoms at all in the host, and thus we say these patients have an asymptomatic infection. In hepatitis C infections, the virus grows and reproduces in liver cells, causing low levels of liver damage. The damage is so low that infected individuals are often unaware that they are infected, and many infections are detected only by routine blood work on patients with risk factors such as intravenous drug use. On the other hand, since many of the symptoms of viral diseases are caused by immune responses, a lack of symptoms is an indication of a weak immune response to the virus. This allows for the virus to escape elimination by the immune system and persist in individuals for years, all the while producing low levels of progeny virions in what is known as a chronic viral disease. Chronic infection of the liver by this virus leads to a much greater chance of developing liver cancer, sometimes as much as 30 years after the initial infection. As already discussed, herpes simplex virus can remain in a state of latency in nervous tissue for months, even years. As the virus “hides” in the tissue and makes few if any viral proteins, there is nothing for the immune response to act against, and immunity to the virus slowly declines. Under certain conditions, including various types of physical and psychological stress, the latent herpes simplex virus may be reactivated and undergo a lytic replication cycle in the skin, causing the lesions associated with the disease. Once virions are produced in the skin and viral proteins are synthesized, the immune response is again stimulated and resolves the skin lesions in a few days by destroying viruses in the skin. As a result of this type of replicative cycle, appearances of cold sores and genital herpes outbreaks only occur intermittently, even though the viruses remain in the nervous tissue for life. Latent infections are common with other herpesviruses as well, including the varicellazoster virus that causes chickenpox. After having a chickenpox infection in childhood, the varicella-zoster virus can remain latent for many years and reactivate in adults to cause the painful condition known as “shingles” (Figure 21.11ab). |
SciQ | SciQ-727 | human-biology, biochemistry, hematology, red-blood-cell, human-physiology
Title: Besides hemoglobin, what proteins are present in red blood cells? I knew that mature red blood cells (RBCs) lacked nuclei, but I wasn't aware until just now that they also lacked ribosomes and mitochondria. Most cells in the human body all contain a common laundry list of housekeeping proteins and RNAs (including mitochondrial proteins and ribosomal RNAs), but I guess RBCs lack a number of them. Do they still have all of the other organelles? Obviously hemoglobin (and to a lesser extent carbonic anhydrase) makes up a large portion of the dry weight of RBCs, but are other proteins still present? If so, what are their relative abundances?
For example, do red blood cells have any of the normal metabolic (i.e. ATP producing) proteins? Obviously they don't have any of the TCA cycle proteins, but do they still have the glycolysis ones? Reticulocyte stage is when the ribosomes are still present and after that no new protein synthesis occurs. However RBCs have a lot of proteins and major proteins other than haemoglobin are cytoskeletal proteins and ion channels/pumps (In fact, cytoskeletal proteins are more abundant than haemoglobin). It is the Na+-K+-ATPase that consumes most ATP. As you correctly identified the RBCs produce ATP via glycolysis and glycolytic enzymes are also present. Note that deficiency of pyruvate kinase leads to haemolytic anaemia.
For a detail on the proteins present in human RBSs, see this paper. They have studied the RBC proteome by ion-trap MS. The top 5 proteins (from Table-1) are:
No. Protein description Molecular mass (Da) Gi Number Sequence No. of identified
coverage(%) peptides
1 Spectrin α chain, erythrocyte 279,916.5 1174412 48.0 77*
2 Spectrin β chain, erythrocyte 246,468.1 17476989 48.0 76*
3 Ankyrin 1, splice form 2 206,067.9 105337 45.0 55
The following is multiple choice question (with options) to answer.
What do red blood cells carry? | [
"hydrogen",
"oxygen",
"carbon dioxide",
"nitrogen"
] | B | Blood is a fluid connective tissue that contains a liquid component called plasma. It also contains dissolved substances and blood cells. Red blood cells carry oxygen, white blood cells defend the body, and platelets help blood clot. |
SciQ | SciQ-728 | human-biology, neuroscience, physiology, anatomy
Title: Why does sympathetic activity constrict pulmonary vessels? I don't know understand why sympathetic stimulation constricts pulmonary vessels?
I thought that the sympathetic nervous system activated the body for physical activity. Physical activity would need more oxygen supply. Doesn't constriction of pulmonary vessels reduce the gas exchange? Short answer
The sympathetic nervous system mediates the fight, flight and fright response. It constricts the arteries and arterioles to increase blood pressure, in turn pushing the blood to the muscles and other organs vital for physical activity.
Background
The sympathetic nervous system functions triggers the fight, fright, flight (FFF) response (Fig. 1). It provides the body with a burst of energy so that it can respond to danger (source: Harvard Medical School).
The FFF response is initiated in the hypothalamus by activating the sympathetic nervous system through the adrenal glands. These glands release epinephrine (adrenaline) into the bloodstream. Epi increases heart rate and blood pressure to push blood to the muscles, heart, and other vital organs. The person also starts to breathe more rapidly and the small airways in the lungs open up. This way, the lungs can take in as much oxygen as possible with each breath. Extra oxygen is sent to the brain, increasing alertness (source: Harvard Medical School).
In blood vessels, as you say, sympathetic activation constricts arteries and arterioles (resistance vessels), which increases vascular resistance and decreases distal blood flow. When this occurs throughout the body, the increased vascular resistance causes arterial pressure to increase (Klabunde, 2012). This enhances the distribution of oxygen already present in the blood. I don't think the pulmonary circulation responds differently than that in the rest of the body. The stress response is meant to support the evasion of acute dangers. But indeed, chronic exposure to adrenaline may eventually lead to impaired oxygen exchange in the lungs (Krishnamoorthy et al., 2012).
Fig. 1. Fight, flight, fright response. source: Freelap USA
References
- Klabunde, Cardiovascular Physiology Concepts, 2nd ed. (2012). Lippincott Williams & Wilkins
- Krishnamoorthy et al., Anesthesiology (2012); 117(10): 745-54
The following is multiple choice question (with options) to answer.
The sympathetic division of the vertebrate autonomic nervous system has evolved the fight-or-flight response to counter stress-induced disruptions of this? | [
"blood pressure",
"equilibrium",
"body temperature",
"homeostasis"
] | D | Fight-or-Flight Response Interactions of the endocrine hormones have evolved to ensure the body’s internal environment remains stable. Stressors are stimuli that disrupt homeostasis. The sympathetic division of the vertebrate autonomic nervous system has evolved the fight-or-flight response to counter stress-induced disruptions of homeostasis. In the initial alarm phase, the sympathetic nervous system stimulates an increase in energy levels through increased blood glucose levels. This prepares the body for physical activity that may be required to respond to stress: to either fight for survival or to flee from danger. However, some stresses, such as illness or injury, can last for a long time. Glycogen reserves, which provide energy in the short-term response to stress, are exhausted after several hours and cannot meet long-term energy needs. If glycogen reserves were the only energy source available, neural functioning could not be maintained once the reserves became depleted due to the nervous system’s high requirement for glucose. In this situation, the body has evolved a response to counter long-term stress through the actions of the glucocorticoids, which ensure that long-term energy requirements can be met. The glucocorticoids mobilize lipid and protein reserves, stimulate gluconeogenesis, conserve glucose for use by neural tissue, and stimulate the conservation of salts and water. The mechanisms to maintain homeostasis that are described here are those observed in the human body. However, the fight-or-flight response exists in some form in all vertebrates. The sympathetic nervous system regulates the stress response via the hypothalamus. Stressful stimuli cause the hypothalamus to signal the adrenal medulla (which mediates short-term stress responses) via nerve impulses, and the adrenal cortex, which mediates long-term stress responses, via the hormone adrenocorticotropic hormone (ACTH), which is produced by the anterior pituitary. |
SciQ | SciQ-729 | thermodynamics, statistical-mechanics, electromagnetic-radiation, visible-light, thermal-radiation
Title: Why does a blackbody object emit light if it only absorbs light? I have learned that a blackbody object only absorbs light and thus does not reflect any light. The blackbody object will, however, emit light, and none of this light is due to reflection. Where does this light/energy come from? I assume, given an atom, that the light emitted is due to excitation and decay of electron states. Is this correctly understood, and can there be other methods of emission? The energy comes from whatever is keeping the blackbody in thermal equilibrium at its characteristic temperature even as it radiates energy away.
That can be the energy absorbed from its surroundings, or it can be some internal energy source.
Taking the Sun as an example - a cube of material inside the Sun (but not near the centre) emits an almost perfect blackbdy spectrum at a temperature characteristic of its position within the Sun (cooler as it gets closer to the surface). The energy comes from the radiation that the same cube of material absorbs from its immediate surroundings.
But we could consider a bigger picture and look at the Sun as a whole. It also emits a spectrum that approximates reasonably well to a blackbody. The energy for that radiation does not comes from radiation absorbed by the Sun as a whole, but is supplied by nuclear fusion reactions in its core.
If you are asking what microscopic processes give rise to the blackbody radiation, then there are many examples/duplicates of that question on Physics SE. The most general answer that can be given is that they are the microscopic inverse processes of whatever causes the blackbody to absorb all radiation incident upon it. Thus, as an example, the photosphere of the Sun is opaque across all visible wavelengths because visible photons can photodissociate electrons from H$^{-}$ ions that are present. The inverse process - photons emitted when electrons combine with hydrogen atoms - provides the blackbody continuum radiation.
The following is multiple choice question (with options) to answer.
What light-producing process occurs when a substance absorbs shorter-wavelength ultraviolet light and then gives off the energy as visible light? | [
"candescence",
"fluorescence",
"luminescence",
"resistance"
] | B | A fluorescent light bulb produces visible light by fluorescence. Fluorescence occurs when a substance absorbs shorter-wavelength ultraviolet light and then gives off the energy as visible light. The compact fluorescent light bulb (CFL) in the Figure below contains mercury gas that gives off ultraviolet light when electricity passes through it. The inside of the bulb is coated with a substance called phosphor. Phosphor absorbs the ultraviolet light and then gives off most of the energy as visible light. |
SciQ | SciQ-730 | oceanography, rivers, satellite-oddities
Title: What are these river/canyon-like carvings in the ocean? Browsing around Google Maps, I came across this off the south-west coast of Ireland
It looks very consistent with the shape rivers and their tributaries might make, but it has me puzzled since it's all underwater!
The main, most "river-like" one is in the middle-left of the picture but there are more (which look more like fjords) at the bottom.
What caused this feature? The carvings are submarine canyons, a part of the continental slope leading from the continental shelf to the continental rise and ultimately the Abyssal plains. They are a product of :
erosion through currents and
slumping of the continental shelf
Like other erosive or slumping effects, they can be self-reinforcing, leading to canyon-like structures. The highlighted canyon here is the Gollum Channel system, seen here.
The following is multiple choice question (with options) to answer.
What lies between the continental shelf and the abyssal plain? | [
"equator",
"continental belt",
"successive slope",
"continental slope"
] | D | The continental slope lies between the continental shelf and the abyssal plain. It has a steep slope with a sharp drop to the deep ocean floor. |
SciQ | SciQ-731 | water, electricity
Title: Why is distilled water such a poor conductor of electricity? Water is composed of hydronium ions and hydroxide ions. Since ions do conduct electricity, why is distilled water such a poor conductor of electricity? You are mistaken.
Water is not composed of these ions. There is ongoing autodissociation equilibrium reaction$$\ce{2 H2O <<=> H3O+ + OH- }$$ shifted strongly toward left, with concentration of ions $\pu{1e-7 mol/L}$ at $\pu{25 ^{\circ}C}$ .
Therefore conductivity of water itself is very low.
The following is multiple choice question (with options) to answer.
In the first beaker, distilled water does not conduct a current because water is a what? | [
"pure element",
"solute",
"magnetic compound",
"molecular compound"
] | D | In the first beaker, distilled water does not conduct a current because water is a molecular compound. In the second beaker, solid sodium chloride also does not conduct a current. Despite being ionic and thus composed of charges particles, the solid crystal lattice does not allow the ions to move between the electrodes. Mobile charged particles are required for the circuit to be complete and the light bulb to light up. In the third beaker, the NaCl has been dissolved into the distilled water. Now the crystal lattice has been broken apart and the individual positive and negative ions can move. Cations move to one electrode, while anions move to the other, allowing electricity to flow (see Figure below ). Melting an ionic compound also frees the ions to conduct a current. Ionic compounds conduct an electric current when melted or dissolved in water. |
SciQ | SciQ-732 | geophysics, petroleum
Title: Glossary of oil and gas industry geophysical terms Reviewing market regulatory standards I came across the problem of finding a source that I could cite of concise, worldwide accepted industry geophysical terms.
So far I know Schlumberger Oilfield Glossary, SEG Wiki, SPE PetroWiki that give some information on some terms. In practice I need something like this definition in SEG Wiki for seismic crooked lines. Although in this case I don't think the term is well defined.
I am looking for a worldwide industry accepted glossary that I could rely on and cite. The broader it is the best will be for having less problems in future. Where would be the best place to find such source of information? Any other suggestions will be welcome. Sheriff's Encyclopedic Dictionary is the closest thing to a canonical text, but the Schlumberger glossary is more up to date.
Sheriff is a scientific text, whereas the Schlumberger glossary is a little more generally accessible, but neither is comprehensive. Sheriff is especially poor on recent advances. On the plus side, you can edit it, if you're an SEG member.
After those two, Wikipedia is probably your next best bet.
The following is multiple choice question (with options) to answer.
What is another term for hydraulic fracturing? | [
"fracking",
"erupting",
"permeating",
"drilling"
] | A | Hydraulic fracturing, known as fracking, is a relatively new method for extracting natural gas. Fracking may be linked to groundwater contamination and small earthquakes in non-seismic regions. |
SciQ | SciQ-733 | 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.
In what unit is speed usually measured? | [
"radians",
"calories",
"miles per hour",
"Celcius"
] | C | |
SciQ | SciQ-734 | human-biology, physiology, digestive-system, liver, bile
Both solid lines are subsets of bile acids, measured in the serum of cholecystectomized patients in a classic 1978 study. The shaded areas represent control (not cholecystectomized) patients. These measurements suggest that enterohepatic circulation still follows a pulsatile pattern after cholecystectomy.
The following is multiple choice question (with options) to answer.
Unlike liver bile, 'juice' produced by what organ is clear and composed mostly of water along with some salts, sodium bicarbonate, and digestive enzymes? | [
"pancreas",
"stomach",
"gallbladder",
"spleen"
] | A | Pancreatic Juice The pancreas produces over a liter of pancreatic juice each day. Unlike bile, it is clear and composed mostly of water along with some salts, sodium bicarbonate, and several digestive enzymes. Sodium bicarbonate is responsible for the slight alkalinity of pancreatic juice (pH 7.1 to 8.2), which serves to buffer the acidic gastric juice in chyme, inactivate pepsin from the stomach, and create an optimal environment for the activity of pH-sensitive digestive enzymes in the small intestine. Pancreatic enzymes are active in the digestion of sugars, proteins, and fats. The pancreas produces protein-digesting enzymes in their inactive forms. These enzymes are activated in the duodenum. If produced in an active form, they would digest the pancreas (which is exactly what occurs in the disease, pancreatitis). The intestinal brush border enzyme enteropeptidase stimulates the activation of trypsin from trypsinogen of the pancreas, which in turn changes the pancreatic enzymes procarboxypeptidase and chymotrypsinogen into their active forms, carboxypeptidase and chymotrypsin. The enzymes that digest starch (amylase), fat (lipase), and nucleic acids (nuclease) are secreted in their active forms, since they do not attack the pancreas as do the protein-digesting enzymes. |
SciQ | SciQ-735 | electrostatics, electricity, electric-current, charge, flow
Title: Why does the flow of charge even create electricity? Okay this is a question I’ve asked a lot of places but I always get its the flow of charges and it’s like a property. What I don’t really understand is how is this flow of charges creating electric current.
My guess is that as these charges get closer to the desired potential(to satisfy potential difference) Energy is released which happens continuously and it is the reason for electric current atleast in a conductor.
Can I get some insight into what is happening down at the quantum level. First of all you have to understand that flow of electrical current and dissipation of energy are two completely different concepts.
Electrical current: The flow of electrical charges is called electrical current. This is like a definition and has nothing to do with dissipation. There are systems, where current flows without dissipation. At the elementary level, you get the electrical current $I$, if you count, how many elementary charges $e$ cross a specific cross-sectional area of your "conductor" per second. Mathematically this means:
$$ I := \frac{e\Delta N}{\Delta t},$$
where $I$ is the current, $\Delta t$ is the time interval (e.g. 1 second), $e$ is the elementary charge, and $\Delta N$ is the number of elementary charges that you count within time $\Delta t$.
Usually, conductors are metals, and you may think of the cross sectional area of a copper wire, for example. But you can also imagine other "conductors" that are liquids with ions in them, or even gases with charged atoms in them.
Electrical resistance: Flowing charge carriers dissipate energy, if they scatter with other particles and thereby lose energy. In metals, for example, electrons forming the electrical current will scatter from lattice vibrations (phonons) and thereby dissipate energy. This energy dissipation leads to electrical resistance, usually denoted by $R$.
The following is multiple choice question (with options) to answer.
What term means opposition to the flow of electric charges that occurs when electric current travels through matter? | [
"resistance",
"polarity",
"diffusion",
"antagonism"
] | A | Resistance is opposition to the flow of electric charges that occurs when electric current travels through matter. The SI unit of resistance is the ohm (named for the scientist Georg Ohm, whom you can read about below). Resistance is caused by electrons in a current bumping into electrons and ions in the matter through which the current is flowing. Resistance is similar to the friction that resists the movement of one surface as it slides over another. Resistance reduces the amount of current that can travel through the material because some of the electrical energy is converted to other forms of energy. For example, when electric current flows through the tungsten wire inside an incandescent light bulb, the tungsten resists the flow of electric charge, and some of the electrical energy is converted to light and thermal energy. |
SciQ | SciQ-736 | food-chemistry
popcorn (kernels)
honey (jar of)
sugar (most forms)
alcohol (spirits like vodka, whiskey)
dried beans, dried lentils
I would not be planning to eat any of these stored for 25 years myself. And in general I'd suggest testing the items before trying them after 25 years or more (if you feel you must).
I would not expect cans or glass or plastic bottles of soda to be in good shape after anything like 25 years. The plastic might not survive without degrading. The can and plastic might react with the liquid over that timescale and the glass would survive but I'd be less optimistic about a sugar laced chemical soup like soda or cola not undergoing some changes. Hard to say.
If you want more info on this try this website.
Will it be ok to drink it, if it won't explode?
I would not try it. At best it soda would be flat and possibly not taste the same (chemical changes over that timescale ?) and at worst it could actually be harmful.
Exploding seems very unlikely.
Also, what about Snickers or a hamburger in a ziploc package with air sucked out of it with vacuum cleaner?
Air isn't the issue. There are bacteria that will happily live (and increase in numbers) on what's in the food. Well, it is food, after all. There are bacteria that will survive refrigeration as well. Over the timescale you're talking about I'd say it's all bets are off territory.
So: will Snickers, Hamburger in a ziploc, Bottle (or can) of Cola, all not opened, go crazy in 25 years? In 50 years?
All of those could be dangerous over such a long time period, IMO. At the very least they'd taste bad and at worst they'd kill you if you consumed them.
If so, can they go out of their packages and ruin the contents of the time capsule? If not, will it be safe to consume one of them?
Depends on the packaging. Glass would last indefinitely baring physical force or extreme of hot and cold (which might possibly cause fatigue cracking). The other wrappers would last pretty well (structurally), but 25 years is way past their design intentions. It would be a dice throw.
The following is multiple choice question (with options) to answer.
According to law, what must packaged foods carry? | [
"pricing",
"nutrition facts label",
"country of origin",
"warnings"
] | B | Packaged foods are required by law to carry a nutrition facts label, like the one in Figure below . The labels show the nutrient content and ingredients of foods. Reading labels can help you choose foods that are high in nutrients you need more of (such as proteins) and low in nutrients you need less of (such as fats). |
SciQ | SciQ-737 | neuroscience, neuroanatomy, neurotransmitter
Activity at the axoaxonic synapse partially hypopolarizes the terminal so that, when an action potential comes down the [...] afferent fiber into that terminal, its amplitude is reduced. Because the amount of transmitter substance released by a bouton is proportional to the amplitude of the action potential in it, less transmitter substance is released, resulting in a smaller EPSP and less excitation of the postsynaptic cell [...]
Links:
http://en.wikipedia.org/wiki/Synapse
http://www.getbodysmart.com/ap/nervoussystem/neurophysiology/synapses/introduction/synaptic_contacts/tutorial.html
http://michaeldmann.net/mann13.html
The following is multiple choice question (with options) to answer.
What type of terminal releases neurotransmitters at a synapse? | [
"acetylcholine,",
"chloride",
"axon",
"secretion"
] | C | At a synapse, neurotransmitters are released by the axon terminal. They bind with receptors on the other cell. |
SciQ | SciQ-738 | botany
Title: Do any plants exhibit hormonal changes similar to puberty? Just what the title states.
Are there any plants/trees that exhibit a growth spurt at a definite interval after the shoot appears? In flowering plants (the angiosperms) there are several developmental transitions in the life of the plant. I won't list the plants, because the list includes pretty much all of them (although the magnitude in the change of developmental pace differs widely between taxa and environments).
First there is seed germination, which is controlled hormonally. Absence of germination is usually imposed by abscisic acid, whilst germination is caused at the appropriate time by gibberellic acid and ethylene (among other things; Holdsworth, Bentsink & Soppe, 2008).
Next, in many herbaceous species there is a transition between a spreading growth stage (e.g. rosette growth) and the flowering stage. The 'growth spurt' here is the differentiation and elongation of the flowering stem, and then subsequently the sudden flowering of buds. The transition is also controlled hormonally, by a variety of hormones including auxin (Zhao, 2010), gibberellic acid, ethylene (Schaller, 2012), and the long anticipated, recently confirmed florigen (Choi, 2012). Ethylene and abscisic acid then play important roles in the next developmental transition when seeds and fruits are produced and dehisced.
Small RNAs are also now being revealed to play a large role in controlling the timing of developmental, but they are upstream of the hormonal changes. In particular some key miRNAs are involved in auxin-based regulation of branching, and in embryogenesis (Nodine & Bartel, 2010), and RNA silencing is involved in the switch from rosette growth to flowering growth (reviewed in Poethig, 2009 and Baurle & Dean 2006).
The following is multiple choice question (with options) to answer.
What chemical affects the onset of puberty and duration? | [
"acids",
"hormones",
"enzymes",
"steroids"
] | B | Puberty lasts from about ages 12 to 18 years and is controlled by hormones. |
SciQ | SciQ-739 | botany, plant-physiology, plant-anatomy
Title: Sporophyte and gametophyte
My textbook says that in both groups of seedless plants (vascular plants, non-vascular plants) the gametophyte is a free-living plant, independent of the sporophyte.
I don't understand this statement and am now wondering if the sporophyte and gametophyte are stages in a plant's lifecycle, or are they individual parts of the plant, or are the sporophyte and the gametophyte different plants altogether? Secondly, does this differ depending on the organism?
Different plants or different structures that make up the same organism? The sporophtye is the diploid stage in the life cycle. In comparison, with humans, you and I would be sporophytes.
The Gametophyte is the haploid stage in the life cycle. In comparison, with humans, spermatozoids and ovules are gametophytes.
The following is multiple choice question (with options) to answer.
What are the only plants with a life cycle in which the gametophyte generation is dominant? | [
"nonvascular",
"vascular plants",
"nonpermeable",
"photoreactive"
] | A | Nonvascular plants include mosses, liverworts, and hornworts. They are the only plants with a life cycle in which the gametophyte generation is dominant. Figure below shows the life cycle of moss. The familiar, green, photosynthetic moss plants are gametophytes . The sporophyte generation is very small and dependent on the gametophyte plant. |
SciQ | SciQ-740 | plant-physiology, botany
Title: Do plants produce any heat? Many plants (e.g. roses, palms) can be protected from frost during the winter if shielded with an appropriate coat that can be bought in garden shops. Do plants produce any heat that can be kept inside with these "clothes"? Cellular respiration in plants is slightly different than in other eukaryotes because the electron transport chain contains an additional enzyme called Alternative Oxidase (AOX). AOX takes some electrons out of the pathway prematurely - basically the energy is used to generate heat instead of ATP.
The exact purpose of AOX in plants is still unclear. Plants will make more AOX in response to cold, wounding, and oxidative stress. We know of at least one plant (skunk cabbage) that exploits this pathway to generate enough heat to melt snow. This link gives a pretty good overview.
(AOX is dear to my heart, since my first 3 years working in a laboratory were spent studying this gene <3)
The following is multiple choice question (with options) to answer.
What do angiosperms produce? | [
"flowers and fruit",
"leaves",
"needles",
"scales"
] | A | a phosphate group, which contains phosphorus and oxygen. |
SciQ | SciQ-741 | biochemistry
Title: Bradford Reagent Disposal I am a graduate student volunteering in a professor's lab being tasked with finding out how to dispose of certain hazardous materials. I have encountered a problem with disposing of Bradford's Reagent. I have checked online, but am running into problems due to the methanol component of this compound. Can someone help me with the proper disposal procedure? Thank you in advance. I would strongly suggest to ask someone in your lab about this, they will have a better idea about the different waste disposal methods you have available.
In general you would dispose anything that contains organic solvents like methanol in a waste container for generic solvent waste. You should have something like that somewhere in the lab.
One thing you always have to keep in mind is to never put anything still reactive into your waste container. A popular example would be a strong oxidizing agent, putting that into a solvent waste container is dangerous and could e.g. ignite the waste. This is not an issue in this case, but you should always keep that in mind.
Another aspect is the pH of the waste, in many cases the waste disposal facility will only accept reasonably neutral waste, so you should neutralize your waste before putting it into a container. Neutralizing it inside the container can be much more annoying. This might not be necessary if you have a dedicated acidic waste, you'll have to ask someone in your lab about that. The Bradford reagent is strongly acidic, so you'll have to pay attention to this aspect.
The following is multiple choice question (with options) to answer.
What should you let liquid waste do before placing the container in the trash? | [
"melt",
"generate",
"expand",
"evaporate"
] | D | Always properly dispose of hazardous waste. For example, let liquid waste evaporate before placing the container in the trash. |
SciQ | SciQ-742 | evolution, zoology, adaptation
One answer that came to mind is domestic animals - the horse and dog in prehistory, the cat in ancient Egypt, etc. That seems too obvious on one hand, and on the other hand may not really be an answer, as there seems to be no indication that pre-domestic animals were endangered by humans in any meaningful way. Are there animals that have significantly adapted themselves to surviving as wild animals in human-influenced environments? Note: This is an answer to the last line of your question.
A classical example of animals adapting to the influence of humans on their environment is the adaption of the Peppered Moth.
Here is a brief summary:
The peppered moth was originally a mostly unpigmented animal (<1800). During the industrial revolution in the southern parts of the UK a lot of coal was burned. This led to soot blackening the countryside. Soon afterwards, a fully pigmented variety was first observed. Only a hundred years later, in 1895, this pigmented variety almost completely displaced the unpigmented variety.
It has been shown that the pigmentation is under strong selective pressure as birds hunt these moths. Since birds rely on their visual system to detect their prey, the variety that blends in with its environment (=camouflage) has a selective advantage over the variety that stands out.
As pointed out by Tim in the comments, since the 1970s there has been a rapid reversal with unpigmented animals being more abundant. As far as I understand, it is accepted that this reversal is due to a decrease in human induced air pollution leading to less sooty barks on trees which makes the unpigmented variety harder to prey upon.
Addendum: genetic basis of adaption
In a beautiful recent study, the causal mutation for the pigmented, or melanic, variety was identified: A ~9kb transposon insertion in the first intron of the gene cortex. The authors calculate that this mutation happened in the year 1819, a few years after the industrial revolution was in full swing. The interpretation is that due to sooty tree bark this mutation, causing pigmented moth, was under strong selection.
The following is multiple choice question (with options) to answer.
Mammoths, close genetic relatives of modern elephants, are believed to have gone extinct due to hunting by humans and what factor? | [
"climate change",
"migration change",
"earthquakes",
"volcanic eruptions"
] | A | It's easy to get lost in the discussion of dinosaurs and theories about why they went extinct 65 million years ago. Was it due to a meteor slamming into Earth near the coast of modern-day Mexico, or was it from some long-term weather cycle that is not yet understood? One hypothesis that will never be proposed is that humans had something to do with it. Mammals were small, insignificant creatures of the forest 65 million years ago, and no humans existed. Woolly mammoths, however, began to go extinct about 10,000 years ago, when they shared the Earth with humans who were no different anatomically than humans today (Figure 45.12). Mammoths survived in isolated island populations as recently as 1700 BC. We know a lot about these animals from carcasses found frozen in the ice of Siberia and other regions of the north. Scientists have sequenced at least 50 percent of its genome and believe mammoths are between 98 and 99 percent identical to modern elephants. It is commonly thought that climate change and human hunting led to their extinction. A 2008 study estimated that climate change reduced the mammoth’s range from 3,000,000 square miles 42,000 years [7] ago to 310,000 square miles 6,000 years ago. It is also well documented that humans hunted these animals. A 2012 study showed that no single factor was exclusively responsible for the extinction of these [8] magnificent creatures. In addition to human hunting, climate change, and reduction of habitat, these scientists demonstrated another important factor in the mammoth’s extinction was the migration of humans across the Bering Strait to North America during the last ice age 20,000 years ago. The maintenance of stable populations was and is very complex, with many interacting factors determining the outcome. It is important to remember that humans are also part of nature. Once we contributed to a species’ decline using primitive hunting technology only. |
SciQ | SciQ-743 | organic-chemistry, acid-base, ph
The usual rule that "$\mathrm{pH}$ of 7 is neutral" comes from solutions in water: Water has the property that it can be converted into, and self-converts between ("auto-ioniziation") separate $\mathrm{H}^{+}$ and $\mathrm{OH}^{-}$ ions and its usual molecular form, $\mathrm{H}_2\mathrm{O}$. When one is dealing with pure water with no adulterants present, there is always, due to this process, around $10^{-7}\ \mathrm{\frac{mol}{dm^3}}$ of $\mathrm{H}^{+}$ present (though actually, this depends on temperature, but around room temp, it is around this much). Decimal logarithm of $10^{-7}$ is -7, hence the $\mathrm{pH}$ is 7. When you throw some acid in and it releases its protonic payload, the concentration of $\mathrm{H}^{+}$ rises by that amount, thus the $\mathrm{pH}$ drops.
The following is multiple choice question (with options) to answer.
What is the ph level of neutral, pure water? | [
"five",
"six",
"seven",
"six and a half"
] | C | The ion concentration of neutral, pure water gives water a pH of 7 and sets the standard for defining acids and bases. Acids have a pH lower than 7, and bases have a pH higher than 7. |
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