source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-5144 | = 18.02 at the high school, college, and 34.73 % oxygen mass percentage of element... Illustrates percent composition of each element in water— H 2 O ) email address will not be published from! To contain 36.5 % Na, 25.4 % s, and graduate levels of! The simplest formula of a compound for calcium hydroxide = ( Ca ( NO 3 2... That is to be calculated the chemical formula is 21 percent hydrogen and 80 % oxygen composition formula of percentage composition! Address will not be published the value of n. Yes, we can express percentage composition of oxygen air. Table in identifying the mass of a compound is present an example that illustrates percent indicates... An integral multiple of the chosen element by the molar mass of each element present percentage Yield from Limiting. We calculate the percentage by mass of each element present in it % Zn, 11 S.... Compound as let ’ s use the periodic table in identifying the mass percentage of element! The mass of each element contributes to the total mass of the empirical formula in compound.: calculate the percentage by mass of a compound is found to contain 36.5 % Na, 25.4 %,... Of oxygen formula of percentage composition your email address will not be published iron in iron III! 1.Find the percent composition of a compound c. use the above formula to calculate percent composition the! Hydrogen and 80 % oxygen element ’ s composition ) to find the percent of! Carbon, 13.13 % hydrogen, and always include units where needed formula are First used calculate. Is measured in terms of all the elements present of this compound calcium nitrate, Ca ( ). Determine the value of n. Yes, we can express percentage composition to describe percentage! = ( Ca ( NO 3 ) 2 ) terms of percentage composition nitrate. Contains decimal numbers formula are First used to describe the percentage composition and multiplied by …! Oxides is 36.85 % and oxygen, MgCO 3 formula you must multiply the formula you must multiply the you! Step 1 the molar mass of each element in a compound line of the given compound any. Address will not be published be useful when extracting metals from ores or when making fertilisers for specific plants for... Compound, follow the following steps, step 1: calculate the percentage of. Formulas 11:04 Calculation of percentage breathed in for a compound is present commonly expressed in terms
The following is multiple choice question (with options) to answer.
What is the name of the mineral that contains calcium, carbon and oxygen? | [
"cobalt",
"quartz",
"granite",
"calcite"
] | D | Law stating that pressure in a moving fluid is less when the fluid is moving faster. |
SciQ | SciQ-5145 | human-biology
I had a very difficult time finding any concrete, scientific information on this subject overall.
So, if you would like more information about this, please visit the following links. The first is a WikiPedia link on Limb Infarctions (or an embolism in a limb). The second is from Mental Floss on Why Limbs Fall Asleep. The third is a somewhat random article on someone's personal experience on Sleeping on their arm.
So, in summary: although I could find no solid evidence on how long a limb can live without its blood supply, it appears to be about 2-4 hours (some sources say 5-8); however, I would like to add that your case appears to be a severe case of an asleep limb, you were/are likely in no danger. Also, if your arm indeed did have circulation completely cut off, it would have turned pale, then blue and later a livid red and purple as the blood began to pool; you then would begin to experience the effects of the limb dying i.e. necrosis, gangrene.
The following is multiple choice question (with options) to answer.
What medical emergency occurs when a blood clot blocks blood flow to part of the brain, causing death of brain cells? | [
"stroke",
"heart murmur",
"cardiac arrest",
"epileptic seizure"
] | A | A stroke occurs when a blood clot blocks blood flow to part of the brain. Brain cells die quickly when their oxygen supply is cut off. Therefore, a stroke may cause permanent loss of normal mental functions. Many stroke patients suffer some degree of paralysis, or loss of the ability to feel or move certain parts of the body. If medical treatment is given very soon after a stroke occurs, some of the damage may be reversed. Strokes occur mainly in older adults. |
SciQ | SciQ-5146 | magnetic-fields
Title: Why is the magnetic field strongest at the poles in a permanent magnet? In a solenoid, the field lines within are relatively constant and parallel, and so, the magnetic field is strongest as compared to the poles, at which the field lines diverge. In a permanent magnet, however, the magnetic field is strongest at the poles, despite being the point of divergence of the field lines. Why? When we talk about a magnet's field being strongest at the poles, we're comparing the strengths of field at points outside the magnet. If we similarly restrict ourselves to points outside a solenoid, then the field is strongest at its ends (where the field lines have hardly started to diverge). We must compare like with like!
The following is multiple choice question (with options) to answer.
What are the strongest magnets made? | [
"permanent magnets",
"natural magnets",
"polarized magnets",
"electromagnets"
] | D | An electromagnet is a solenoid wrapped around a bar of iron or other ferromagnetic material. The magnetic field of the coil magnetizes the bar, which adds to the strength of the magnetic field. Electromagnets are the strongest magnets made. |
SciQ | SciQ-5147 | zoology, circulatory-system, heart-output, amphibians
I would add to this my notes from when I was a biochem student (but studied Zoology), mentioning the arterial cone and a spiral valve. This is better described in Britannica:
The conus arteriosus is muscular and contains a spiral valve. Again, as in lungfishes, this has an important role in directing blood into the correct arterial arches. In the frog, Rana, venous blood is driven into the right atrium of the heart by contraction of the sinus venosus, and it flows into the left atrium from the lungs. A wave of contraction then spreads over the whole atrium and drives blood into the ventricle, where blood from the two sources tends to remain separate. Separation is maintained in the spiral valve, and the result is similar to the situation in lungfishes. Blood from the body, entering the right atrium, tends to pass to the lungs and skin for oxygenation; that from the lungs, entering the left atrium, tends to go to the head. Some mixing does occur, and this blood tends to be directed by the spiral valve into the arterial arch leading to the body.
The following is multiple choice question (with options) to answer.
What vessels supply blood to the myocardium and other components of the heart? | [
"specialized arteries",
"coronary arteries",
"rapid arteries",
"surface arteries"
] | B | Coronary Arteries Coronary arteries supply blood to the myocardium and other components of the heart. The first portion of the aorta after it arises from the left ventricle gives rise to the coronary arteries. There are three dilations in the wall of the aorta just superior to the aortic semilunar valve. Two of these, the left posterior aortic sinus and anterior aortic sinus, give rise to the left and right coronary arteries, respectively. The third sinus, the right posterior aortic sinus, typically does not give rise to a vessel. Coronary vessel branches that remain on the surface of the artery and follow the sulci are called epicardial coronary arteries. The left coronary artery distributes blood to the left side of the heart, the left atrium and ventricle, and the interventricular septum. The circumflex artery arises from the left coronary artery and follows the coronary sulcus to the left. Eventually, it will fuse with the small branches of the right coronary artery. The larger anterior interventricular artery, also known as the left anterior descending artery (LAD), is the second major branch arising from the left coronary artery. It follows the anterior interventricular sulcus around the pulmonary trunk. Along the way it gives rise to numerous smaller branches that interconnect with the branches of the posterior interventricular artery, forming anastomoses. An anastomosis is an area where vessels unite to form interconnections that normally allow blood to circulate to a region even if there may be partial. |
SciQ | SciQ-5148 | endocrinology
Title: Abnormal Prolactin Level I want to know what makes the balance of the Prolactin abnormal. Is that related to the presence of a nodule near the pituitary? The main abnormality in prolactin levels is hyperprolactinemia, meaning blood levels of prolactin above the normal range, not during pregnancy or lactation.
The major cause of these abnormal prolactin levels are tumors consisting of pituitary lactotroph cells--called prolactinomas--which secrete prolactin. This is generally corrected with synthetic dopamine analogues, as dopamine negatively regulates secretion of prolactin in lactotroph cells.
Here is a 2010 review with further detail:
http://joe.endocrinology-journals.org/content/206/1/1.full.pdf
The following is multiple choice question (with options) to answer.
An endocrine disease usually involves the secretion of too much or not enough of what? | [
"metabolism",
"protein",
"hormone",
"neurotransmitter"
] | C | Diseases of the endocrine system are relatively common. An endocrine disease usually involves the secretion of too much or not enough hormone. When too much hormone is secreted, it is called hypersecretion . When not enough hormone is secreted, it is called hyposecretion . |
SciQ | SciQ-5149 | molecular-biology, terminology, epigenetics
Now, the main issue is where to draw the line between gene regulation and epigenetics?
In my opinion, the epigenetic mechanisms are one of the ways to regulate the gene expression. Although histone modifications and DNA methylation regulate gene expression and also confer heritability to the gene expression programme, the heritability can be implemented without them as well.
You can imagine a cell as a vessel which runs a system of biochemical reactions. This system can have multiple steady states (for e.g. multiple fates of a stem cell). To perpetuate a state, the new cell just needs to have the right initial conditions. This can be proved mathematically too. Such a system can be implemented via the traditional transcription factors as well. So what is epigenetic?
IMHO epigenetic was a loose term to denote something that people were not fully aware of, at that time. Anything that was not directly mediated by transcription factors was termed as epigenetic, including long distance regulators, non-coding RNA etc.
BOTTOMLINE
I would not classify non-coding RNAs as "epigenetic" for the very reason that they are encoded by genes and have more or less a direct effect on the target genes, just like TFs (which are apparently not epigenetic). As for the papers, there were many papers that used to assign these under epigenetic mechanisms, but that is IMO just too vaguely arbitrary. (Ironically, I happened to come across miRNAs and lncRNAs while I was doing a summer project on epigenetics and was reading relevant papers.)
What should be considered epigenetic would be a subject of another debate.
The following is multiple choice question (with options) to answer.
What is it called when a gene at one location (locus) alters the phenotypic expression of a gene at another locus? | [
"exogenous",
"spontaneous mutation",
"epistasis",
"epigenesis"
] | C | Epistasis is when a gene at one location (locus) alters the phenotypic expression of a gene at another locus. Epistasis takes place when the action of one gene is modified by one or several other genes. These genes are sometimes called modifier genes . The gene whose phenotype is expressed is said to be epistatic , while the phenotype that is altered is said to be hypostatic . Sometimes hypostatic phenotypes are completely suppressed. Epistatic genes are not dominant over the genes they alter or suppress. Dominance refers to an interaction between alleles of the same gene, not different genes. |
SciQ | SciQ-5150 | cell-biology, mitochondria
Title: How is the number of mitochondria in a cell regulated? How does the cell regulate the number of mitochondria in a cell? What happens when there are too many or too few? The concept you refer is recognized as mitochondrial biogenesis and it is regulated by AMPK which senses the cellular energy demand. If you have few mitochondria in the cell, the electron transport chain works suboptminally generating less ATP. When the AMP/ATP ratio is high (low ATP) AMPK is activated, and turns on the catabolic pathways required to produce more ATP, included mitochondrial biogenesis.
The following is multiple choice question (with options) to answer.
Called the powerhouses of the cell, what organelles are the site of cellular energy production? | [
"cell wall",
"nucleus",
"mitochondria",
"mitosis"
] | C | The mitochondria are the powerhouses of the cell. Mitochondria are the organelles where cellular energy is produced, providing the energy needed to power chemical reactions. This process, known as cellular respiration , produces energy is in the form of ATP (adenosine triphosphate). Cells that use a lot of energy may have thousands of mitochondria. |
SciQ | SciQ-5151 | endocrinology
Excitement or stress response, including fast heart rate and breathing and anxiety: short term response: adrenaline; long-term response: cortisol
Appetite: ghrelin, leptin, adiponectin, cholecystokinin, insulin, glucagon-like peptide, gastrointestinal peptide...
Sexual drive: sex hormones, mainly testosterone and estradiol
Sleepiness: melatonin, cortisol
Depression: cortisol, sex hormones (mainly in women)
The point of this answer is to show that some of your feelings can be simply affected by hormones, which are note some ultimate forces, and that being aware of that can help you to control them to some extent.
The following is multiple choice question (with options) to answer.
What is the name of the major sex hormone in females? | [
"glucose",
"testosterone",
"insulin",
"estrogen"
] | D | Two functions of the female reproductive system are producing eggs and secreting estrogen. Eggs are female gametes. Estrogen is the major sex hormone in females. The female reproductive system also supports a developing fetus and gives birth to an infant. |
SciQ | SciQ-5152 | quantum-gravity, physical-constants
Title: What is the smallest existing thing in theory and law? What is the smallest existing thing in theory and law?
"What is the smallest existing thing in theory and law?"
The Merriam Webster Dictionary defines a "thing" as:
: an object or entity not precisely designated or capable of being
designated
a: an inanimate object distinguished from a living being
b: a separate and distinct individual quality, fact, idea, or usually
entity
c: the concrete entity as distinguished from
...
A Photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles). Mass: 0 < 1×10−18 eV/c^2.
The photon has zero rest mass and always moves at the speed of light within a vacuum. Since the Photon is a Point Particle and has a size of zero you might say it's not a thing, nothing; that leaves us with:
The smallest real thing is the Neutrino. Mass: ≤ 0.120 eV/c^2.
The smallest theoretical thing is the Planck Particle. Radius: 5.72947×10−35 m, Mass: 3.85763×10−8 kg.
The following is multiple choice question (with options) to answer.
What is the smallest unit of a living thing? | [
"proton",
"cell",
"electron",
"organ"
] | B | A cell is the smallest unit of a living thing. A living thing, like you, is called an organism. Thus, cells are the basic building blocks of all organisms. In multicellular organisms, several cells of one particular kind interconnect with each other and perform shared functions to form tissues (for example, muscle tissue, connective tissue, and nervous tissue), several tissues combine to form an organ (for example, stomach, heart, or brain), and several organs make up an organ system (such as the digestive system, circulatory system, or nervous system). Several systems functioning together form an organism (such as an elephant, for example). There are many types of cells, and all are grouped into one of two broad categories: prokaryotic and eukaryotic. Animal cells, plant cells, fungal cells, and protist cells are classified as eukaryotic, whereas bacteria and archaea cells are classified as prokaryotic. Before discussing the criteria for determining whether a cell is prokaryotic or eukaryotic, let us first examine how biologists study cells. |
SciQ | SciQ-5153 | electrons, metals
Title: Itinerant electron systems As far as I understand, in a primitive picture insulators are localized systems, and metals are itinerant electron systems.
What I do not get: I have, e.g., 3d itinerant magnets like:
Ni ([Ar] 4s2 3d8 or [Ar] 4s1 3d9 ),
Fe ([Ar] 4s2 3d6), and
Co ([Ar] 4s2 3d7).
Why does it make sense to speak about 3d electron shells, if the electrons are not localized to the atomic nucleus but they are itinerant, i.e., there are distributed over the whole crystal (it can be described by the probability function of the Bloch waves).
Confinement to atomic nucleus does not make sense to me, since (weak correlated) metals behave as a free electron gas. That's a good question. It turns out that you can make Bloch waves out of linear combinations of atomic orbitals, generally one per site, and that choosing different atomic orbitals for those linear combinations will produce Bloch waves of different characters. These manifest themselves as the different bands of the material - including core, valence and conduction bands, as well as a bunch of higher conduction bands that can be occupied at high energy.
This then lets you talk about an electron wave that's delocalized over the entire crystal but which still retains (say) a clear 3d character.
The following is multiple choice question (with options) to answer.
What kind of metals have perplexing patterns of electron distribution that don’t always follow the electron filling rules? | [
"transformation",
"transition",
"variating",
"solution"
] | B | The transition metals are an interesting and challenging group of elements. They have perplexing patterns of electron distribution that don’t always follow the electron filling rules. Predicting how they will form ions is also not always obvious. |
SciQ | SciQ-5154 | pressure, energy-conservation, work, buoyancy, fluid-statics
Title: What is the energy source if a tall water tank is used to transfer floating objects upwards instead of cables with motors? Suppose I want to transport some logs from the ground to the roof of a tower. Originally I can use a lift, or some cables, or even move the logs upwards manually; then the energy is converted to the potential energy of logs.
Now, if I build a tall water tank from ground to the roof of the tower, and fill it with water, and suppose that I can push the logs from the bottom of the tank with a well shaped door, then let the logs float to the roof of the tower. What is the energy source that used to convert to the potential energy of logs? The work you need to do (to insert the log) against the pressure of the fluid at that depth is equal to the work done by the fluid to get the log up to the height you desire.
If you consider a log of volume $V$ and a tank of depth $h$, the pressure at that depth would be $\rho gh$, where $\rho$ is the density of the fluid, and $g$ the acceleration due to gravity.
The work you need to do to insert the log into the fluid at that depth is $\rho ghV$. (the pressure times the volume)
The buoyant force on the log due to the fluid is $\rho Vg$, so the work done by the buoyant force to lift the log up by a height $h$ is $\rho Vgh$. (the force multiplied by the displacement, because the force is constant here.)
Both these quantities are equivalent, so the energy source here is you.
The following is multiple choice question (with options) to answer.
The fact that water in a reservoir is elevated above the ground means that it has what kind of energy? | [
"kinetic",
"excessive",
"nuclear",
"potential"
] | D | |
SciQ | SciQ-5155 | metabolism, ecology, photosynthesis
Title: Why isn't phosphorus or nitrogen a limiting nutrient for animals? Nitrogen and Phosphorus are usually the limiting nutrient for plants, especially for algae. Phosphorus is used for DNA, ATP and phospholipids, and Nitrogen is used for pretty much every protein a cell might want to produce. That is, their need for biological processes is not tied specifically to photosynthesis: anything that lives is going to need them, pretty much for anything it might want to do. It would make sense for them to be a limiting nutrient for almost anything that's trying to grow, plant or animal.
Yet for animals the limiting "nutrient" seems to always be energy, ie: food. Why aren't animals limited by lack of nutrients in the same way that plants are? Obviously animals need these nutrients, too. Or to reverse the question, why do plants need so much more phosphorus/nitrogen than animals do?
My best guess is that an animal's digestion of plant material is relatively inefficient energy-wise but relatively efficient nutrient-wise. So for an animal to eat enough food to have sufficient energy to survive, it's probably eaten more than enough Nitrogen and Phosphorus for its needs. But I'm just guessing and I can't find any data that would back up that guess. Phosphorus
Your suggestion that if we are meeting our calorific requirement we will be getting enough is true for phosphorus.
Most foods contain lots of phosphorus. The maximum dietary requirement occurs during adolescent growth, estimated at 1250 mg per day. Assuming a calorie intake of 2500 kcal we can calculate a 2500 kcal equivalent phosphorus content for various foods:
skimmed milk contains 7,400 mg phosphorus per 2500 kcal
roasted chicken breast contains 7,500 mg phosphorus per 2500 kcal
cooked white rice contains 3840 mg per 2500 kcal
(Calculations are based upon values obtained via this site.)
Nitrogen
Our requirement for nitrogen is met by our protein intake: inadequate protein intake manifests as kwashiorkor which is essentially due to a dietary deficiency of essential amino acids. In other words, the only way to achieve a nitrogen-deficient diet is to not eat protein, and this would not be alleviated by any inorganic source of nitrogen, even if we could consume enough of such a N source.
The following is multiple choice question (with options) to answer.
Rich in protein and nutrients, what abundant group of organisms is being touted as an important human dietary source? | [
"fungus",
"insects",
"fruits",
"primates"
] | B | In some parts of the world, insects are used for food by humans. Insects are a rich source of protein, vitamins, and minerals, and are prized as delicacies in many third-world countries. In fact, it is difficult to find an insect that is not eaten in one form or another by people. Among the most popular are cicadas, locusts, mantises, grubs, caterpillars, crickets, ants, and wasps. Many people support this idea to provide a source of protein in human nutrition. From South America to Japan, people eat roasted insects, like grasshoppers or beetles. |
SciQ | SciQ-5156 | condensed-matter, solid-state-physics, terminology, definition
Title: What is topological material? Recently, topological material has been a hot topic in condensed matter physics, but I don't know what is topological material and how to distinguish topological material from band diagram. And how does it divide the types of topological materials according to band diagram, such as Topological Insulators,Topological Semimetal.... Traditionally, in solid state physics we classify materials into metals, insulators, and semimetals.
In metals, the Fermi energy is in the conduction band, such that pure metals are good electrical conductors.
Insulators (and with them semiconductors, which are insulators with a relatively small bandgap) have their Fermi level at zero temperature in the middle of the bandgap between valence and conduction band. This means, they do not conduct electrical currents very well, because electrons have to be excited above the band gap in order to propagate freely through the crystal.
In semimetals, the conduction and valence band states overlap in energy (hence no bandgap), and the Fermi energy intersects them both. This means that they conduct, but even at zero temperature there are conduction band electrons and valence band holes (unoccupied valence band states) that contribute to the electrical conductance.
As it turned out about 15 years ago, there is yet another class of materials called topological insulators. These materials have a band gap like insulators. At zero temperature, the Fermi level is in the band gap, so the bulk of the material does not conduct electrical current. However, due to the particular lattice symmetry of these materials, there exist surface states at the Fermi energy, which are said to be “topologically protected”. This means that these materials are insulating in the bulk, but they conduct very well at the surface.
The following is multiple choice question (with options) to answer.
In contrast to metals, electrical insulators are materials that conduct electricity poorly because their valence bands are what? | [
"full",
"large",
"half-full",
"empty"
] | A | Insulators In contrast to metals, electrical insulators are materials that conduct electricity poorly because their valence bands are full. The energy gap between the highest filled levels and the lowest empty levels is so large that the empty levels are inaccessible: thermal energy cannot excite an electron from a filled level to an empty one. The valence-band structure of diamond, for example, is shown in part (a) in . Because diamond has only 4 bonded neighbors rather than the 6 to 12 typical of metals, the carbon 2s and 2p orbitals combine to form two bands in the solid, with the one at lower energy representing bonding molecular orbitals and the one at higher energy representing antibonding molecular orbitals. Each band can accommodate four electrons per atom, so only the lower band is occupied. Because the energy gap between the filled band and the empty band is very large (530 kJ/mol), at normal temperatures thermal energy cannot excite electrons from the filled level into the empty band. Thus there is no pathway by which electrons can move through the solid, so diamond has one of the lowest electrical conductivities known. Figure 12.23 Energy-Band Diagrams for Diamond, Silicon, and Germanium. |
SciQ | SciQ-5157 | nuclear-physics, atomic-physics, stability, elements
Now, according to Coulomb's law, if the electron orbits about the nucleus the centripetal motion can be described by $$\frac{Ze^2}{4\pi\epsilon_or}=m_ev^2, $$ where $Z$ denotes the number of protons in the nucleus (the atomic number), and $e$ the elementary charge. Solving for $Z$ and substituting in $r$ from above yields $$Z=\frac{4\pi\epsilon_o \hslash v}{e^2}. $$ But what is $v$? Well, the maximum velocity an electron could ever have is the speed of light, and we wish to find the atomic number associated with an orbiting electron traveling at this speed, so we set $v=c$ and obtain our final result of $$Z=\frac{4\pi\epsilon_o\hslash c}{e^2}\approx 137.521,$$ which implies that for $Z>137$, the electrons at a position of $n=1$ in the Bohr model would have a velocity $>c$; and thus the highest atomic number achievable on the periodic table is 137.
Again, I just want to make sure this is a correct method for deriving element-137 before presenting. Perhaps one could explain how relativity plays a role here. I know Feynman used the Dirac equation to get this result...so could anyone (subsequently of course) expatiate on this in a simplistic manner? Thanks! No, electrons cannot impose any upper limit on the maximum $Z$ of atoms.
The whole research of heavy elements is the research of the nuclei, not the electrons that orbit them. Nuclear physics is about protons, neutrons (or quarks, gluons) and forces in between them and the typical speeds of the constituents are always rather close to the speed of light. Some nuclei classified by $(A,Z)$ are stable, some are short-lived, some are long-lived, some don't exist, and there are islands of stability etc.
For an arbitrarily charged nucleus, however, it's always possible to place an arbitrarily high number of electrons to the orbits.
The following is multiple choice question (with options) to answer.
What model postulates that electrons orbit the nucleus at fixed energy levels? | [
"bohr",
"coreolis",
"Newton's model",
"atomic model"
] | A | The Bohr model postulates that electrons orbit the nucleus at fixed energy levels. |
SciQ | SciQ-5158 | homework-and-exercises, newtonian-mechanics, angular-momentum
Title: Example of Torque, Center of Precession So here's the set up, we have a fence of length $2L$, and a support strut a distance $l$ from the axis (think of a railroad crossing gate). We need to find the best position for the support rod, so that the pivot takes minimum wear. We analyze the forces on the gate, and find that there are three vertical forces (we are ignoring the radial components). The force $\mathbf F _s$ is the force due to the support, $\mathbf W$, the weight, acting at center of mass (position $L$) and the force at the axis of rotation, which we will call $\mathbf F _{\rho} $
The following is multiple choice question (with options) to answer.
In the case of the wheelbarrow, the output force or load is between the pivot and the what? | [
"density force",
"Driving Force",
"velocity force",
"input force"
] | D | Figure 9.24 (a) In the case of the wheelbarrow, the output force or load is between the pivot and the input force. The pivot is the wheel’s axle. Here, the output force is greater than the input force. Thus, a wheelbarrow enables you to lift much heavier loads than you could with your body alone. (b) In the case of the shovel, the input force is between the pivot and the load, but the input lever arm is shorter than the output lever arm. The pivot is at the handle held by the right hand. Here, the output force (supporting the shovel’s load) is less than the input force (from the hand nearest the load), because the input is exerted closer to the pivot than is the output. |
SciQ | SciQ-5159 | inorganic-chemistry, physical-chemistry, electrochemistry, electrons, electronic-configuration
one proton's positive charge attracts one electron.
The "neutral" in a neutral atom means electrically neutral.
How can a neutral atom attract electrons when it's supposed to have zero charge ? The answer lies in electronegativity. When a proton attracts an electron, the electron doesn't magically suck out the charge of the proton. The proton's charge is still distributed in all directions. The reason why 1 proton on average can attract only 1 electron is because electrons push each other out.
Now let's first take H - it has 1 proton which attracts 1 electron. If another electron jumps in, only 1 electron stays in the end. Then He - it has 2 protons, so it attracts electrons even more. So even though electrons are fighting for the place, the nucleus charge is enough to hold them.
It gets interesting with Li. It should have 3 electrons, right? But 1st shell can take only 2 electrons, so the 3d electron must go to the 2nd shell which is further away. In such case the inner shell of electrons has a much greater effect on the outer electron, this is called electron screening, not to mention that the further you are from nucleus - the weaker the attraction. So even though Li has more protons than He, it's too weak to hold electrons on the 2nd shell, so some other atom will take the electron away and Li will be ionized and become Li$^+$ with only 2 electrons.
How strongly an atom wants new electrons is called electronegativity. It increases to the right of the periodic table because nucleus gets larger and larger and can hold on more and more electrons. In the last columns atoms want electrons so much that they can mug other atoms with weaker electronegativity.
But then the row of the table finishes and new row starts. At this point previous shell is completely filled and a new shell starts, and the electron screening kicks in again.
You can see these trends here. Electronegativity is the reason why Na & Cl can't form a molecule (covalent bond) - Cl (strong electronegativity) simply takes Na's (weak electronegativity) electron and both become ions: Cl$^-$ and Na$^+$. In the end they form an ionic bond instead.
The following is multiple choice question (with options) to answer.
What type of electrons are attracted to the positive nucleus? | [
"particular electrons",
"passive electrons",
"turbulent electrons",
"negative electrons"
] | D | Avoid close contact with people who are sick. This includes kissing, hugging, shaking hands, and sharing cups or eating utensils. |
SciQ | SciQ-5160 | 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.
Present-day plants that have a complex vascular tissue system are called what kind of plants? | [
"cirulatory plants",
"pinworm plants",
"vasculated plants",
"vasuluar plants"
] | D | |
SciQ | SciQ-5161 | acoustics, applied-physics, medical-physics, instrument
Title: How does ultrasound imaging localize points in the $x$-$y$ plane? Lots of sources describe how ultrasound imaging uses the time differences between wave emission and reception to calculate distances to points in the body. This makes sense for how localization works in the $z$-direction. But how does it localize points in the $x$-$y$ plane, forming a detailed 2D image? The ultrasound transducer transmits a very short focused pulse (less than a mm in width--and also in length) say at a 45 degree angle to the transducer face and then records the echoes as a function of time. Each recorded echo becomes an image pixel. It then repeats this at say a 44.5 degree angle, next a 44 degree angle, ect... until it has scanned out a pie shaped slice image into the body.
But how does it localize points in the x-y plane, forming a detailed
2D image?
Typically the transducer is a phased array and the pulsed beam is formed by adjusting the delays between array elements before pulsing the scan head when transmitting, or before summing the echoes together when receiving. (Goggle: beam forming and phased arrays)
The following is multiple choice question (with options) to answer.
What tool, used to locate underwater objects, utilizes ultrasound in a way that is similar to echolocation? | [
"sonar",
"GPS",
"scanning",
"radar"
] | A | Sonar uses ultrasound in a way that is similar to echolocation. Sonar stands for so und na vigation and r anging. It is used to locate underwater objects such as sunken ships or to determine how deep the water is. A sonar device is usually located on a boat at the surface of the water. The device is both a sender and a receiver (see Figure below ). It sends out ultrasound waves and detects reflected waves that bounce off underwater objects or the bottom of the water. If you watch the video at the URL below, you can see how sonar is used on a submarine. |
SciQ | SciQ-5162 | ecology, population-dynamics, ecosystem, antipredator-adaptation, predation
I would also like to talk about other things that might be of interest in your model (two of them need you to allow evolutionary processes in your model):
1) lineage selection: predators that eat too much end up disappearing because they caused their preys to get extinct. This hypothesis has nothing to do with some kind of auto-regulation for the good of species. Of course you'd need several species of predators and preys in your model. This kind of hypothesis are usually considered as very unlikely to have any explanatory power.
2) Life-dinner principle. While the wolf runs for its dinner, the rabbit runs for its life. Therefore, there is higher selection pressure on the rabbits which yield the rabbits to run in average slightly faster than wolves. This evolutionary process protects the rabbits from extinction.
3) You may consider..
more than one species of preys or predators
environmental heterogeneity
partial overlapping of distribution ranges between predators and preys
When one species is absent, the model behave just like an exponential model. You might want to make a model of logistic growth for each species by including $K_x$ and $K_y$ the carrying capacity for each species.
Adding a predator (or parasite) to the predator species of interest
... and you might get very different results.
The following is multiple choice question (with options) to answer.
What kind of competition often leads to extinction because the species that is less well adapted gets fewer of the resources that both species need? | [
"parasitism",
"interspecific competition",
"intraspecific competition",
"mutualism"
] | B | Interspecific competition often leads to extinction. The species that is less well adapted may get fewer of the resources that both species need. As a result, members of that species are less likely to survive, and the species may go extinct. |
SciQ | SciQ-5163 | physiology, senescence, organs
Kidney: 7.2 years
Liver: 16.9 years
Lung: 2.1 years
Heart: 14.5 years
Kidney-Pancreas: 12.9 years
These numbers are not definite, since the life style of the donor and the receiver as well as infections of the transplated patient (who has a severely suppressed immune system – this is critical) also play an important role in determining the lifetime of the organ.
The following is multiple choice question (with options) to answer.
A nephrologist studies and deals with diseases of what organ? | [
"kidneys",
"brains",
"lungs",
"stomach"
] | A | Nephrologist A nephrologist studies and deals with diseases of the kidneys—both those that cause kidney failure (such as diabetes) and the conditions that are produced by kidney disease (such as hypertension). Blood pressure, blood volume, and changes in electrolyte balance come under the purview of a nephrologist. Nephrologists usually work with other physicians who refer patients to them or consult with them about specific diagnoses and treatment plans. Patients are usually referred to a nephrologist for symptoms such as blood or protein in the urine, very high blood pressure, kidney stones, or renal failure. Nephrology is a subspecialty of internal medicine. To become a nephrologist, medical school is followed by additional training to become certified in internal medicine. An additional two or more years is spent specifically studying kidney disorders and their accompanying effects on the body. |
SciQ | SciQ-5164 | fluid-dynamics, acoustics, measurements, turbulence, noise
The author continues by providing approximate wavenumber bounds for each subrange, and a corresponding formula for each. For the peaked energy-containing subrange:
"The range of energy containing eddies, having wave numbers comparable to $k_{\ell} = \frac{1}{\ell}$. In homogenous and isotropic turbulence there is no production and these eddies simply lose their energy as they pass it to smaller eddies. However, in shear flows, the energy containing eddies would continuously receive energy from the mean flow. An empirical expression is the von Kármán interpolation formula."
Which they give as:
$$E(k) = \frac{A \epsilon^{2/3} k^{4}}{{[k^2 + \ {k_0}^2]}^{17/6}}$$
I wanted to see how the shape of the von Kármán interpolation formula compared to the empirically observed spectrum.
Using
$A \approx 1.7$ (given by the authors as typical)
$\epsilon = 6 \times 10^{-8} \frac{m^2}{s^3}$
$k_0 = 9.2$ (equivalent to the $f = 500 Hz$ peak that we already saw on the empirical plot - a dissatisfying circular choice)
We can make the following comparison:
I'm not sure how to get the final energy dissipation spectrum into Sound Pressure Level units, but the peaked spectrum appears at least roughly similar to the summertime conditions. I've also added the winter conditions (dashed line on upper plot) from the same location to show how much less pressure energy exists in the environment when the river is frozen.
Additionally, neither $A$, $\epsilon$, nor $k_0$ are easily quantified in the field.
The following is multiple choice question (with options) to answer.
Where is the potential energy of a river the highest at? | [
"the ocean",
"the source",
"the bank",
"the middle"
] | B | Electrical circuits are often modeled by using water in a river. The potential energy of the water is the highest at the source of the river and decreases as the water flows down the river toward the end. When the water reaches the ocean, its potential energy has become zero. The circuit shown below has a similar situation. The current in this circuit is drawn in the direction of the electron flow. It starts at the battery on the left, where electrons leave the negative terminal and travel around the circuit. Since all of the current travels across each resistor, these resistors are said to be in series . A series circuit is one in which all of the current must pass through every resistor in the circuit. Returning to the water analogy, there is only one riverbed from the top of the mountain to the ocean. |
SciQ | SciQ-5165 | biochemistry
Title: educational sources for learning biochemistry I just finished high school and am going into a biology undergraduate degree, I'm getting into biochemistry too and would like to learn more about it through online platforms or even non-fiction books to use my time effectively this summer. So far I've been using online flash cards to learn more about the jargon and would like to hear some suggestions of platforms or books to read that teach concepts strongly tied to biochemistry beyond what a basic high school curriculum would teach. There are several reference books for biochemistry, some more readable than others. I personally recommend two of them: (1) Lehninger et al. Principles of Biochemistry and (2) Voet, D., Voet, J., et al. Fundamentals of Biochemistry: Life at the molecular level. Both books contain the most important and basic features of each subject. The chapters are generally well written. I have to say that, from my own experience, I consider that Voet's book is more enjoyable, given that some of the sections of Lehninger's can be a bit tricky. Whichever book you choose, make sure you get relatively new editions. Good luck!
As a side note, even though biochemistry is one the first proper biology classes one takes in undergrad, there are some background requirements. Taking organic and inorganic chemistry courses before is important and some understanding of thermodynamics will certainly come in handy.
The following is multiple choice question (with options) to answer.
What are the most numerous and diverse biochemical compounds? | [
"lipids",
"proteins",
"acids",
"Carbohydrates"
] | B | Proteins are the most numerous and diverse biochemical compounds, and they have many different functions. Some of their functions include:. |
SciQ | SciQ-5166 | species-identification, botany
Title: Identification of a plant Please help me to identify this plant
The plants can be found on italian balconies and I would like to buy one, but I do not know what I should look for.
The habit of the plant is trailing. This is likely to be a stone plant (Aizoaceae), depending on habit, it could well be the ice plant (Carpobrotus edulis). Stone plants are a quite diverse family of succulents from southern Africa, but are widespread throughout the western world as stabilizers of sand-dunes and in gardens as they are very tolerant of lack of watering and high salinity.
Ice plants are very common in the Mediterranean region, having become an invasive pest on much of the coastline.
If it is ice plant, then you can sub-cultivate it by taking a small part of the plant, usually leaves with a bit of stem, but even a leaf by itself may work, and placing it in water or on sandy soil. With regular watering, it should grow roots and then be plantable.
Apparently the leaves of ice plant are edible (hence the edulis part of the name), similar to Aloe I suspect.
The following is multiple choice question (with options) to answer.
Where are most plants firmly rooted? | [
"mineral",
"soil",
"rock",
"grass"
] | B | Like all living things, plants detect and respond to stimuli in their environment. Unlike animals, plants can't run, fly, or swim toward food or away from danger. They are usually rooted firmly in the soil, like the tree in Figure below . |
SciQ | SciQ-5167 | inorganic-chemistry, acid-base, everyday-chemistry
$$\ce{H2O + CO2(aq) <=> H2CO3}$$
and the protolysis of true $\ce{H2CO3}$
$$\ce{H2CO3 <=> H+ + HCO3-}$$
For a weak acid
$$\begin{align}
\log[\ce{H+}]&\approx\frac12\left(\log K_\mathrm a+\log[\ce{H2CO3^*}]\right)\\
&=\frac12\left(-6.3-5.0\right)\\
&=-5.65\\
\mathrm{pH}&=5.65
\end{align}$$
Thus, pure rain in equilibrium with the atmosphere has about $\mathrm{pH}=5.65$. Any acid rain with lower $\mathrm{pH}$ would be caused by additional acids.
The following is multiple choice question (with options) to answer.
What type of rain dissolves limestone and marble? | [
"acid",
"carbon",
"natural",
"sulfur"
] | A | Figure below shows some of the damage done by acid rain. Acid rain ends up in soil and bodies of water. This can make them very acidic. The acid strips soil of its nutrients. These changes can kill trees, fish, and other living things. Acid rain also dissolves limestone and marble. This can damage buildings, monuments, and statues. |
SciQ | SciQ-5168 | electricity, electric-circuits, electrical-resistance, instrument
Title: Why do we prefer using materials of high resistivity in laboratory instruments? I know that :$$R=\rho\frac{l}{A}$$ where $R$ is the resistance of the wire, $\rho$ is its specific resistance (resistivity), $l$ is its length, and $A$ is the area of cross-section of the wire.
Why do we prefer using materials of high resistivity (like manganin, constantan etc.) in laboratory instruments like potentiometer or Metre Bridge?
I searched everywhere online, but all I always get is the definition of resistivity, which I already know. Manganin, like constantin, are alloys invented in the late 1800s to solve a specific problem: resistance varies with temperature, and every resistor passing a current is subject to Joule heating. So if you are building precise electrical metering equipment their is a design advantage to using materials that show a stable resistance with temperature variations.
The follow-on to your question could be: how are precision resistors made? One way is to simply cut strips of high resistance metals to measure; modern surface mount devices use a ceramic core with a metal coating that is laser-trimmed. Carbon film resistors are similar in design, but typically less precise. Or you can grind up the resistance metal and mix it with clay - this gives a resistor that can dissipate heat, and is suitable for high voltage/current applications.
These and more are described here: http://www.learnabout-electronics.org/Resistors/resistors_08.php
The following is multiple choice question (with options) to answer.
What are materials that have a low resistance to electrical current called? | [
"fast conductors",
"electrons",
"resistors",
"electrical conductors"
] | D | Materials that have low resistance to electric current are called electric conductors. Many metals are good electric conductors. |
SciQ | SciQ-5169 | cellular-respiration
Title: Do cold blooded animals generate any heat? In explaining energy and work to an 8 year-old I said that all conversion of energy generates heat as a by-product. For example, cars generate heat in their engines and running generates heat in our bodies. Then the 8 year-old said, except for cold-blooded animals.
So my question is, do cold-blooded animals generate any heat in their conversion of stored energy (food, fat, etc) into motion? If they generate heat, why are they cold-blooded? They do generate heat. They just do not SPEND energy specifically on heating their bodies by raising their metabolisms. This is a form of energy conservation. The metabolic rate they need to live is not nearly enough to heat their bodies.
An example of spending energy to heat the body is seen in humans shivering. Here muscle is activated not for its usual purpose, but to function as a furnace. "Warm-blooded" and "cold-blooded" is somewhat a misnomer. The correct way to think of it is...
Endotherm or ectotherm. Does the heat primarily come from within (endo) or from the surroundings (ecto). Endothermic animals include mammals. Most of their body heat is generated by their own metabolisms. Ectothermic animals include reptiles and insects. They absorb most of their body heat from the surroundings. This is not the same as saying they let their body temperature fluctuate with their surroundings, some avoid this by moving around to accomodate themselves.
Homeotherm or poikilotherm. Homeotherms want to maintain homeostasis for their body temperatures. They don't want it to change. Poikilotherms do not exhibit this behaviour, instead their body temperatures vary greatly with the environment.
We can have endotherm poikilotherms, such as squirrels, who let their body temperature drop while hibernating. Endotherm homeotherms, such as humans, where temperature is constant by means of complex thermoregulation. Ectotherm homeotherms, such as snakes (moving into shadow or into the sun to regulate temperature), and ectotherm poikilotherms, such as maggots.
The following is multiple choice question (with options) to answer.
What mammalian feature serves functions such as filtration and keeping the body warm? | [
"sweat",
"sensory organs",
"shivering",
"hair"
] | D | Hair serves many functions such as acting as a filter and keeping the body warm. |
SciQ | SciQ-5170 | pressure
Title: How to increase pressure in a bottle? Imagine a plastic bottle half full of water,
what are some cheap ways to increase pressure?
I'm trying to dissolve carbon dioxide in water, it doesn't happen very well at normal atmospheric pressure. I read online somewhere that you need 4 times normal atmospheric pressure (about ~60 psi) for carbon dioxide to really dissolve well in water. So I'm trying to increase the pressure in a water container.
What are some ways this can be achieved? You can use electrolysis (two wires from a battery through a cork in the bottle - water will dissociate into oxygen and hydrogen, creating high pressure). However, beware: this is dangerous (as it is almost always the case with high pressure), as the bottle can explode and harm you or other people. Please be reasonable.
EDIT: And high pressure is not the only hazard in this case: the mixture of oxygen and hydrogen can explode if ignited.
The following is multiple choice question (with options) to answer.
Higher pressures increase the solubility of what? | [
"gases",
"molecules",
"fuels",
"bases"
] | A | Higher pressures increase the solubility of gases. You are probably familiar with this concept as it relates to carbonated beverages. Before opening the container, the inside is pressurized, so a large amount of CO 2 is dissolved in the liquid. After opening, the pressure decreases (to the ambient pressure), so the solubility of CO 2 drops, causing it to bubble out of solution. Because they are not compressible like gases, solid and liquid solutes do not have noticeable changes in solubility at different external pressures. |
SciQ | SciQ-5171 | evolution, cell-biology
What do you mean by multicellularity?
The evolution of multicellularity can be discussed in the context where sister cells form an organism together or when unrelated cells (among the same species or even cells from different species) come together to form an organism. Also, the multicellularity can be discussed at a different level depending on how we want to define multicellularity. Is a stack of cells reproducing individually, working for their own benefit a multicellular? Do we need a division of labor? Do we need a division between germline (reproductive caste) and soma line (non-reproductive case)?
How many times did multicellularity evolve independently?
Some people consider that there are multicellular bacteria (biofilms) but we will avoid discussions that are based on limit-case definitions. Let's talk about eukaryotes. Most Eukaryotes are unicellular and multicellularity evolved many times independently in eukaryotes. To my knowledge, complex multicellularity however evolved only (only?) 6 times independently in eukaryotes.
The following is multiple choice question (with options) to answer.
What is an important level of organization in ecology and the unit of microevolution? | [
"organization",
"population",
"system",
"macro"
] | B | The population is an important level of organization in ecology. It is also the unit of microevolution. |
SciQ | SciQ-5172 | thermodynamics, fluid-dynamics, bubbles
Title: Why do steam bubbles increase in size as they rise? In the following video (a customer's review of a glass kettle), we can observe water boiling: http://youtu.be/jByY5I7Xk7w?t=2m55s
As the kettle starts to boil at around 2:55, we can see large steam bubbles being formed at the bottom, where the heating element is, and these bubbles shrink as they rise. Presumably this is because they are coming into contact with cooler water. Then we get a crazy convection current for a bit before the element switches off again.
After the chaotic motion has died down (and the fluid is presumably very well mixed) we see small steam bubbles being forming at the bottom, which grow as they rise. I can think of two possible explanations for this, and I'm curious as to which is correct:
The water is superheated. Nucleation sites exist on the bottom of the kettle, so that's where steam bubbles form. Steam is produced at the interface between steam and water, which causes the bubbles to grow as they rise.
The pressure at the bottom is slightly higher than at the top. Assuming a depth of 15cm, the boiling point at the bottom of the water is about $100.3^\circ \mathrm{C}$, compared to $100.0^\circ \mathrm{C}$ at the top. Bubbles form at the bottom because the heating element is still slightly hotter than $100.3^\circ \mathrm{C}$, and as they rise they drag hot water up into the slightly lower-pressure area, where it turns to steam because its boiling point lowers, and this increases the size of the bubble.
The following is multiple choice question (with options) to answer.
When hot water gently rises to the surface, it creates a what? | [
"fissure",
"steam cloud",
"volcano",
"hot spring"
] | D | When hot water gently rises to the surface, it creates a hot spring . A hot spring forms where a crack in the Earth allows water to reach the surface after being heated underground. Many hot springs are used by people as natural hot tubs. Some people believe that hot springs can cure illnesses. Hot springs are found all over the world, even in Antarctica!. |
SciQ | SciQ-5173 | human-biology, cellular-respiration
Title: ATP production via aerobic respiration Just started learning about aerobic respiration today, specifically Glycolysis.
We were told that aerobic respiration produces 38 ATP, while anaerobic respiration produces only 2.
However, we're also told that:
Glycolysis produces 2 ATP
Link reaction produces 6 ATP
Krebs cycle produces 24 ATP (18 from NADH, 4 from FADH, and an extra 2)
This only adds up to 32 ATP, so where is this other 6 coming from? Or is this information incorrect. In short, the difference stems from different values regarding the number of ATP attributed to the electron carriers in the electron transport chain (ETC).
My guess is that your class didn't go too far in depth on the subject, and also that your class or text is using mixed sources of information.
I have overviewed (general) glucose metabolism here, but feel free to skip this section if you don't need it.
Glucose metabolism is generally composed of 4* processes:
The following is multiple choice question (with options) to answer.
What is the final stage of aerobic respiration, when energy from the krebs cycle is transferred to atp? | [
"glycolysis",
"cytoplasm transport",
"acetyl-CoA",
"electron transport"
] | D | Electron transport is the final stage of aerobic respiration. In this stage, energy from NADH and FADH 2 , which result from the Krebs cycle, is transferred to ATP. Can you predict how this happens? ( Hint: How does electron transport occur in photosynthesis?). |
SciQ | SciQ-5174 | mass, density, volume
Title: Confused about volume, density and mass, help! I got into an argument with my friend, which cast confusion on my understanding of density and its relationship to volume. I'm hoping to get some clarity. The argument involved describing density in terms of volume. Let's say you define a sphere in empty space. You choose a point, apply the formula for a sphere, and now you have a sphere. Not a sphere OF anything other than space, just a spacial, theoretical sphere. No particles, massless or otherwise (this is a thought experiment). What is the density of that sphere? Is it zero, or is it undefined? I know density can be defined as p = m/v. But in a theoretical sphere, which HAS volume, should we call mass zero, because there is none? Or is it undefined because a theoretical sphere really isn't related to mass at all? If it IS undefined, does that mean it makes no sense to relate density to volume because density is only a property of mass?
The answer, to me, seems to be that in fact it makes no sense to talk about the density of a massless object. Sorry if I answered my own question, but I would still like clarity. If someone could help guide me through the assumptions I'm making about reality and math and how they relate, I'd really appreciate it. Theoretically speaking, in order for something (usually particles) to be massless, it has to be travelling in the speed of light. In quantum theory, uncertainty principle states that the position and momentum of such particle cannot be accurately determined, therefore it is not possible to measure the volume of the particle. So it is generally assumed that the volume is too small and/or insignificant.
Regarding your question, I think that the simple answer would be; a massless object would have no volume nor density, or immeasurable. Take your pick.
The following is multiple choice question (with options) to answer.
What state of matter has a definite volume, but not a definite shape? | [
"solid",
"gas",
"mixture",
"liquid"
] | D | Liquids have a definite volume, but no definite shape. A gallon of milk will keep the same volume whether it is stored in a one-gallon milk jug or a ten-gallon barrel. The volume is the same, but the fluid will either fill the jug or spread out over the bottom of the barrel. |
SciQ | SciQ-5175 | zoology, circulatory-system, heart-output, amphibians
I would add to this my notes from when I was a biochem student (but studied Zoology), mentioning the arterial cone and a spiral valve. This is better described in Britannica:
The conus arteriosus is muscular and contains a spiral valve. Again, as in lungfishes, this has an important role in directing blood into the correct arterial arches. In the frog, Rana, venous blood is driven into the right atrium of the heart by contraction of the sinus venosus, and it flows into the left atrium from the lungs. A wave of contraction then spreads over the whole atrium and drives blood into the ventricle, where blood from the two sources tends to remain separate. Separation is maintained in the spiral valve, and the result is similar to the situation in lungfishes. Blood from the body, entering the right atrium, tends to pass to the lungs and skin for oxygenation; that from the lungs, entering the left atrium, tends to go to the head. Some mixing does occur, and this blood tends to be directed by the spiral valve into the arterial arch leading to the body.
The following is multiple choice question (with options) to answer.
Blood leaves the left ventricle via the what? | [
"dorsal chamber",
"atrium",
"capillary",
"aorta"
] | D | |
SciQ | SciQ-5176 | antarctica, continent, history
Large areas of Antarctica is ice-free, eg. this valley in Vestfold Hills, East Antarctica. The area was first explored in the mid to late 1900's but sightings of outcrop would assure explorers that they actually saw the continent they were expecting and not floating ice.
Geologists could also early correlate the rare findings from Antarctica with surrounding continents and started to reconstruct the Gondwana assembly, a work that is still ongoing and due to the lack of outcrops in Antarctica is to a large extent based on geophysical data. Still, geologists and geophysicists are looking for similarities in Africa, India and Australia to understand the nature of the Antarctic geology under the ice cover.
With aviation, it was finally possible to map the hinterland of the continent, and great discoveries were made as late as 1946–47 during Operation Highjump and during the Soviet's expeditions in the 50's.
(Don't miss this short footage of the discovery of Bunger Hills:
Youtube)
As far as I know, it was not until the International Geophysical Year (IPY) 1957-58 an international effort deploy scientists and collect data firmly defined the physical shape of the continent, that we are still refining today. International collaboration appears to be the key to successful research in Antarctica.
Seismic data is indeed very important to understand the Antarctic lithosphere, but the resolution is low due to the low seismicity and especially the limited number of deployed seismometers. This is, however, improving during recent years and a number of new studies are using seismic tomography and receiver functions to measure the continental shape of Antarctica. See e.g. An et al (2015a) and An et al (2015b). Seismic data is also used to understand the ice sheets and to derive the heat flux that causes basal melting.
Also very important is satellite potential field data. Gravity data e.g. GOCE from ESA is and important constraints, but the resolution is low.
Magnetic data especially from airplanes but also satellites as the flight lines are still sparse is used to map and understand geological terranes covered by ice. The ICECAP project is collecting high-resolution data from flights to improve our understanding of the ice sheets, glaciers and also the bedrock under.
The following is multiple choice question (with options) to answer.
What type of animal can be found on every continent except antarctica? | [
"amphibians",
"reptiles",
"insects",
"mammals"
] | B | Reptiles can be found on every continent except Antarctica. They may live in terrestrial, freshwater, or marine habitats. Most reptiles are carnivores, and large reptiles are the top predators in their ecosystems. Many species of reptiles, especially marine reptiles, are at risk of extinction. |
SciQ | SciQ-5177 | virus, life, philosophy-of-science
Title: Is there any definition of life which makes viruses undeterminable? There are many different definitions of life (RNA, something that comes through evolution) but not one I have seen which could not determine wheter viruses are living things (even though there are many definitions both for YES and NO). Are there any such definitions (I'm looking for cases where it's really fundamental debate, not only struggling for the correct dictionary definition)?
Thank you. Your last sentence is the key: defining life really is just finding a dictionary definition that we can agree upon. Biology is something that defies discrete definitions at times: "What is it to be alive?" "What is a species?" maybe even "What is the wild type allele of a gene?"
I would recommend not looking at viruses as a challenge to determine if they are alive or not so much as an excellent opportunity to discuss what we think are important characteristics of life.
Life can alternately be described as:
"Comprised of self-replicating cells" (a paraphrase of the "Cell Theory of Life"
or
As things that embody at least most of the following characteristics:
1. Self-Replicating
2. Metabolizing
3. Growing
4. Showing signs of adaptation
5. Being organized
6. Respond to their environment
7. Being comprised of cells
I like to think that we should focus on extraterrestrial forms when we define life. i.e. what would we want to see in an extraterrestrial in order to call it 'life'? While some are troubled by calling viruses alive here on earth, the same people might be willing to say that we have found extraterrestrial life on another planet if it was similar (granted, it's hard to imagine this kind of life existing without a host...)
as an aside: You might also ask whether this question is fit for this stack as it can not be supported by literature references (at least none that would actually support a conclusion). So should this be posted as 'Biology' or 'Philosophy'?
The following is multiple choice question (with options) to answer.
Though viruses are not considered living, they share two important traits with living organisms: they have genetic material and they can undergo what process? | [
"generation",
"sexual reproduction",
"evolution",
"learning"
] | C | Though viruses are not considered living, they share two important traits with living organisms. They have genetic material like all cells do (though they are not made of cells), and they can evolve. The genetic material of a virus can change (mutate), altering the traits of the virus. As the process of evolution has resulted in all life on the planet today, the classification of viruses has been controversial. It calls into question the very definition of life. |
SciQ | SciQ-5178 | the-sun
Title: What is the current estimation for how much time the Sun will function properly? Eventually, the Sun will run out of fuel, go dark, and other bad things will happen. About how much long is it predicted that we will have a sun functioning as it is currently? Just to add to Undo's answer, after the expansion to a red giant, the sun will become a planetary nebula, where (according to the link) the fusion reactions inside the star are 'overtaken' by the gravitational collapse, in turn causing the inner layers to condense and heat up causing the outer layers to be blown away. After which, the hot core forms the remnant, a White Dwarf star (NASA source), which is likely to last for several more billions of years.
The image below depicts the current ideas of the expected lifecycle and timeline of the life of the sun:
Image source
How do we know what will happen to the sun?
Currently, the main method to determine the solar lifecycle is described by the article "The Future of the Sun" (Cowing, 2013) is to:
Studying stars with the same mass and composition as the Sun, the so-called "solar twins," can give us more information about our own Sun; solar twins of various ages offer snapshots of the Sun's evolution at different phases
Where the mass and chemical composition of a star provide the information needed to determine its lifecycle.
The following is multiple choice question (with options) to answer.
What is our sun's next stage called? | [
"super nova",
"red giant",
"blue giant",
"white giant"
] | B | A star like our Sun will become a red giant in its next stage. When a star uses up its hydrogen, it begins to fuse helium atoms. Helium fuses into heavier atoms like carbon. At this time the star’s core starts to collapse inward. The star's outer layers spread out and cool. The result is a larger star that is cooler on the surface, and red in color. |
SciQ | SciQ-5179 | acid-base, lewis-structure
Title: Why is carbon dioxide a Lewis acid? I know this has been asked before, but can anyone explain me in simpler terms? Why is $\ce{CO2}$ a Lewis acid? The carbon atom doesn't have any vacant orbitals to accept a lone pair. How can it be a Lewis acid? Suppose one of the doublets of one C=O bond moves to one of these two atoms. It will not be to the Carbon atom. The Oxygen atom is a better choice. And now this Oxygen atom would be negatively charged. As a consequence the Carbon atom is positively charged and has a vacant orbital able to accept a lone pair, for example from an $\ce{OH-}$ ion or from water. This will produce the ion $\ce{HCO3^-}$ (from $\ce{OH-}$) or $\ce{H2CO3}$ (from $\ce{H2O}$).
The following is multiple choice question (with options) to answer.
What type of molecule is carbon dioxide (co2)? | [
"filter",
"non-linear",
"planar",
"linear"
] | D | For molecules with more than two atoms, the molecular geometry must also be taken into account when determining if the molecule is polar or nonpolar. The Figure below shows a comparison between carbon dioxide and water. Carbon dioxide (CO 2 ) is a linear molecule. The oxygen atoms are more electronegative than the carbon atom, so there are two individual dipoles pointing outward from the C atom to each O atom. However, since the dipoles are of equal strength and are oriented in this way, they cancel each other out and the overall molecular polarity of CO 2 is zero. |
SciQ | SciQ-5180 | organic-chemistry, everyday-chemistry, aromatic-compounds, aromaticity, decomposition
Title: How to neutralize the stink of decomposed fish? Recently I discovered for myself an interesting way to easily produce home made plant fertilizer that is quite effective (tested myself on the plants). It's fish emulsion (so can be used also in a hydroponic system) - 1 part fish wastes(skin/bowels) to 2 parts water placed in an airtight container in a sunny spot for ca. 1-2 weeks. The problem - it stinks unbearably. Both - the gas that is produced during the decomposition and the liquid(/fats).
Is it possible to neutralize the stench somehow without loosing the fertilizing qualities of the emulsion? Especially of phosphorus.
1.1 Ideally of both - the gas and the liquid. But at least of the liquid - as that is what is used actually and then continues to spread the smell after being added to the plants.
1.2 Ideally it should be done using some usual household substances/wastes - maybe adding of lemon/orange peels along with the fish wastes? Or maybe ash/charcoals?
The following is multiple choice question (with options) to answer.
Trimethylamine is one of the substances responsible for the what of spoiled fish? | [
"smell",
"appearance",
"feel",
"decay"
] | A | yellow liquid used in the production of synthetic rubber. Its condensed structural formula is ClSSCl. Ethylene glycol is the major ingredient in antifreeze. Its condensed structural formula is HOCH2CH2OH. Trimethylamine is one of the substances responsible for the smell of spoiled fish. Its condensed structural formula is (CH3)3N. Given: condensed structural formula Asked for: molecular formula Strategy: A Identify every element in the condensed structural formula and then determine whether the compound is organic or inorganic. B As appropriate, use either organic or inorganic convention to list the elements. Then add appropriate subscripts to indicate the number of atoms of each element present in the molecular formula. Solution: The molecular formula lists the elements in the molecule and the number of atoms of each. |
SciQ | SciQ-5181 | zoology, behaviour, mammals, rodents
Title: Why do Guinea Pigs chirp / sing? Ok, so this appears to be quite a mystery. Me and my girlfriend have 2 Guinea Pigs, 1 male and 1 female.
My girlfriend once picked up the female one and took her outside into our garden. The Guinea got scared for some unknown reason and jumped out of my girlfriend's arms and fell down hard.. That night, the female Guinea woke us up with some very strange sounds. She sounded like a chirping bird.
Since then, she sometimes repeats these sounds (most often at night, but not always). Mostly, we are puzzled as to why as there is often no apparent reason for her sounds. Also, when she makes the sounds, she appears to be in a trance-like state, making no movements at all.
Looking for the answer online I found many discussions on the subject like this one or this one. Mostly, the sounds (and the often mentioned trance like behavior) appear to be interpreted as either (1) alarm sounds, (2) loneliness sounds or (3) happiness sounds.
There are also recordings of it one Youtube, like this one.
What I was wondering:
Does anybody know about some actual research that has been committed on this subject? If so, what were the results?
I'm just so very curious to find out! I found this question very interesting so I did some research. Here's a brief summary of what I've found:
Researchers have found that there are 11 different call types. Some of these include a "sharp alarm cry", "sociable clucking", chutter, whining, purring etc. Using body position and behaviour, researchers attempted to associate these vocalizations with behaviour. Some vocalizations had no apparent associated action including what researchers designated the "chirrup" ( I think this is similar to what your guinea pig might have emitted.)
For more information you can read the results section of this paper by Berryman. You can find a full description of each of the 11 calls and their assumed cause or purpose. Some involve social interaction, reproduction, and distress. Much of the research regarding Guinea pig vocalization involves communication and response between mothers and pups.
In short, it seems as though this chirping behaviour your Guinea pig is exhibiting is normal, but not of any known cause.
The following is multiple choice question (with options) to answer.
Making ultrasonic clicks is a clever way that some moths respond to attacks by what flying mammals? | [
"bees",
"locusts",
"bats",
"birds"
] | C | |
SciQ | SciQ-5182 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
What do plants respond to in their environment? | [
"changes in temperature or water",
"changes in sunlight or pressure",
"changes in sunlight or water",
"changes in metal or water"
] | C | Like all organisms, plants detect and respond to stimuli in their environment. Their main response is to change how they grow. |
SciQ | SciQ-5183 | human-biology, red-blood-cell
Title: How do people who have lost both of their legs produce red blood cells? As far as I know, just leg bones produce red blood cells. So, how people who lost their both legs produce red blood cells? Red blood cells are produced in the red marrow which...
"is found mainly in the flat bones, such as the pelvis, sternum,
cranium, ribs, vertebrae and scapulae, and in the cancellous
("spongy") material at the epiphyseal ends of long bones such as the
femur and humerus." - Wikipedia
So you are partly right; the femur is associated with red blood cell production, or Erythropoiesis to give it it's technical name, but there are other bones within the human body that also do this job. The process of erythropoiesis is stimulated when the kidneys detect low levels of oxygen in the blood stream and stimulate production of the hormone erythropoietin. Further, the role of the tibia and femur in erythropoiesis also decreases with age whereas...
"the vertebrae, sternum, pelvis and ribs, and cranial bones continue
to produce red blood cells throughout life." - again from the wiki page
So I'd suggest it is unlikely that loss of the legs would have a major impact on the production of red blood cells in adults. I imagine that with the loss of legs comes some reduction in functionality of erythropoiesis but also a lower requirement of red blood cell production (less blood capacity = less blood cells needed = less blood cells need to be produced). I can't find any studies which explore the ability or needs of amputees and non-amputees with regards to red blood cell production.
The following is multiple choice question (with options) to answer.
Bone marrow is found inside many bones and produces what? | [
"sugar",
"apoptosis",
"lymphocytes",
"tumors"
] | C | Bone marrow is found inside many bones. It produces lymphocytes. |
SciQ | SciQ-5184 | evolution, life-history
the relatedness of the actor to the recipient (note a relatedness is not necessarily symmetric)
The competition this recipient causes on the actor
The cost (energy cost, risk of being injured or killed) of killing
Many species (ants, wolves) might kill or injured individuals of the same species, when for example there is competition for reaching a status in the hierarchy.
I think that the definition of k-selected species is not very accurate. First because there are limit cases. But also because r and k can relate to the function that describes the population growth of a species or might describe the amount of energy the parents spend into one offspring which is not necessarily the same thing. If we think of the parental care, we can think of the lions. When a male win the right to access to the females of another male, he will kill the babies that might be potential competitors to his progeny (because they take energy from the females or because females are not fertile before having lost their babies).
Killing its own offsprings is certainly not less common in k-selected species. You might think it is such a big cost to kill one of its own offspring when one has few offspring but what is important is to think in percentage. Killing 50% of the progeny has the same cost of an r-selected species than for a k-selected species.
If one has a probability of 10% to be able to raise its offspring to adult age. But this probability raised to more than 20% if it accepts to kill an offspring to save energy for the next offspring, then it wins by doing so. THen we might ask: "so would one make an offspring if it intends to kill it?"
Well it does not necessarily intend to kill it. It might need to decide late in the season whether or not it has better to kill its own offspring.
Then, maybe offspring might be used as a reserve of energy and matter for its siblings or for its parents.
The following is multiple choice question (with options) to answer.
One species benefits while the host species is harmed in what type of relationship? | [
"mutualism",
"amensalism",
"parasitism",
"fungal"
] | C | In a parasitism, the parasitic species benefits, while the host species is harmed. |
SciQ | SciQ-5185 | molecular-structure, covalent-compounds
Title: How to know it when I see a covalent network? This is a well-known (better said: well-discussed) question in the internet. When you look for answers for popular questions, you usually see them with a variable degree of reliability and complexity. Unfortunately, for this one, I only observed very very crude and general rules of thumb. So let's get a real answer:
A network solid or covalent network solid is a chemical compound (or element) in which the atoms are bonded by covalent bonds in a continuous network extending throughout the material. In a network solid there are no individual molecules, and the entire crystal may be considered a macromolecule. Formulas for network solids, like those for ionic compounds, are simple ratios of the component atoms represented by a formula unit. Covalent network, wikipedia
Diamond and SiO$_2$ are really great examples of covalent networks-lattices. So enough with stories:
If you face a new chemical formula, how would you assume it's a covalent network? (In case it is) Is it somehow done by drawing the Lewis structure? Is there a rule for this? Or is it only possible to know such thing with experimental data?
The following is multiple choice question (with options) to answer.
What is a compound in which all of the atoms are connected to one another by covalent bonds? | [
"covalent mixture",
"compound metal",
"covalent network solid",
"covalent bond element"
] | C | One type of molecular compound behaves quite differently than that described so far. A covalent network solid is a compound in which all of the atoms are connected to one another by covalent bonds. Diamond is composed entirely of carbon atoms, each bonded to four other carbon atoms in a tetrahedral geometry. Melting a covalent network solid is not accomplished by overcoming the relatively weak intermolecular forces. Rather, all of the covalent bonds must be broken, a process that requires extremely high temperatures. Diamond, in fact, does not melt at all. Instead, it vaporizes to a gas at temperatures above 3500°C. |
SciQ | SciQ-5186 | statistical-mechanics, atmospheric-science, density
A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which dissolved carbon dioxide (CO2) suddenly erupts from deep lake waters, forming a gas cloud that can suffocate wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water. Scientists believe earthquakes, volcanic activity, or explosions can be a trigger for such phenomenon. Lakes in which such activity occurs may be known as limnically active lakes or exploding lakes.
Picture 1: one of a number of cattle killed by a limnic eruption at Lake Nyos, Cameroon.
We can occasionally prevent the buildup of carbon dioxide by degassing the body of water.
Picture 2: a siphon used by French scientists to de-gas Lake Nyos. The carbon dioxide emerges from its deposits and bubbles into the water, floating to the top.
The following is multiple choice question (with options) to answer.
What kind of lakes form when volcanic eruptions create massive holes that fill with water? | [
"lava lakes",
"eruption bowls",
"volcanic cavities",
"crater lakes"
] | D | Other lakes are crater lakes or rift lakes, which are pictured in Figure below . Crater lakes form when volcanic eruptions create craters that fill with water. Rift lakes form when movements of tectonic plates create low places that fill with water. |
SciQ | SciQ-5187 | molecular-biology, molecular-genetics, development, sex
Quote from a Review (Yao 2005):
We have just begun to glimpse into the mechanisms underlying ovarian development. Convincing evidence challenges us to reconsider the existing paradigm that describes ovarian development as a default system. The default concept was first proposed in the early 1950s when Jost performed the groundbreaking experiments to demonstrate mechanisms of sex differentiation of reproductive tracts (Jost, 1947, 1953, 1970). The term “default” was not originally intended to describe the developmental status of the ovary. Instead, it is referred to the female reproductive tract or the Mullerian duct based on the fact that the female reproductive tract forms in both XX and XY individuals in the absence of gonads. Indeed, now it has become evident that early ovarian development is an active process involving intrinsic cell fate decisions and complex crosstalks between germ cells and somatic cells. Most intriguingly, the appearance of testicular structures in XX individuals where Sry and its downstream components are absent further raises the improbable question: Could the testicular development be default after all?
The following is multiple choice question (with options) to answer.
The ovaries produce estradiol and progesterone, which cause secondary sex characteristics and prepare the body for? | [
"movement",
"adulthood",
"breathing",
"childbirth"
] | D | cells. The ovaries produce estradiol and progesterone, which cause secondary sex characteristics and prepare the body for childbirth. |
SciQ | SciQ-5188 | electrochemistry, ions
Cells with salt bridge
None of the cells in my three examples had salt bridges. If half-reactions have separate solutions connected by a salt bridge, ions don't travel the entire way between electrodes; instead, redox-inert ions such as potassium cations and chloride anions negotiate the charge transport between solutions of the half cells.
The following is multiple choice question (with options) to answer.
Ions move through what to maintain electrical neutrality in the cell? | [
"the substrate",
"the plasma",
"the membrane",
"the protein"
] | C | 4. Ions move through the membrane to maintain electrical neutrality in the cell. In the cell illustrated above, sulfate ions will move from the copper side to the zinc side to compensate for the decrease in Cu 2+ and the increase in Zn 2+ . |
SciQ | SciQ-5189 | cell-signaling, chemical-communication
Title: How many molecules are generally required for cell signallng processes for given cases? I know its really a broad topic but I am interested in just few cases:
Quorum sensing
neurotransmitters for the communication of images/ general information
hormones/pheromones
I actually want to know that does a single or hundreds of molecules are needed to communicate information from one cell to another.
I searched but approx number of molecules, I can't find anywhere. A cell can interact with other cells in zillions of ways. You can send information from one cell to other cells via neurotransmitters, hormones, pheromones, electric signals, magnetic resonance ,leukotrines etc.
In general a single type of molecule is enough to send such information. Like you require only Acetylcholine(Ach) as neurotransmitter to transmit various nerve impulses.
But, even for a single type, you require thousands of molecules. Like 1 molecule of Ach can do almost nothing and would immediately be broken by Acetylcholinesterase. You require 1000s of such molecules.
You can modify the communicating information via different types of transmitters. You can use GABA or glycine to supress any information exchange or use dopamine to enhance it. But again you will need many molecules of GABA or Glycine.
For visual pathway, you can use no. of types of transmitters like glutamate, glycine, gaba, dopamine, acetylcholine, substance P etc.
Neurotransmitters for visual pathway.
Hormones are transmitters that are required in small quantities. But, again you require certain concentration. There is normal blood concentration of various hormones like 80 pg/ml for calcitonin.
Quorum sensing use transmitters like AHLs. Again a certain threshold value is required for them to act.
Again, to produce these transmitters you have to go through a rigorous process of transcription, translation and post-translational modifications.
So, for cell to communicate a rigorous process is used.
The following is multiple choice question (with options) to answer.
What are the messenger molecules of the endocrine system? | [
"neurons",
"acids",
"enzymes",
"hormones"
] | D | Hormones are the messenger molecules of the endocrine system. Endocrine hormones travel throughout the body in the blood. However, each hormone affects only certain cells, called target cells. A target cell is the type of cell on which a hormone has an effect. A target cell is affected by a particular hormone because it has receptor proteins that are specific to that hormone. A hormone travels through the bloodstream until it finds a target cell with a matching receptor it can bind to. When the hormone binds to a receptor, it causes a change within the cell. Exactly how this works depends on whether the hormone is a steroid hormone or a non-steroid hormone . At the link below, you can watch an animation that shows how both types of hormones work. http://www. wisc-online. com/objects/ViewObject. aspx?ID=AP13704. |
SciQ | SciQ-5190 | polymers
$$\ce{(CF2CF2)_{n} + 2nF2 -> 2nCF4}$$
Similar things can occur under extreme conditions (temperature and pressure) with:
Boranes
Nitric acid
80% NaOH or KOH
Aluminum chloride
Ammonia, some amines, and some imines
The following is multiple choice question (with options) to answer.
What do you call any substance that opposes coagulation? | [
"antibodies",
"toxin",
"anticoagulant",
"dissolvent"
] | C | Plasma Anticoagulants An anticoagulant is any substance that opposes coagulation. Several circulating plasma anticoagulants play a role in limiting the coagulation process to the region of injury and restoring a normal, clot-free condition of blood. For instance, a cluster of proteins collectively referred to as the protein C system inactivates clotting factors involved in the intrinsic pathway. TFPI (tissue factor pathway inhibitor) inhibits the conversion of the inactive factor VII to the active form in the extrinsic pathway. Antithrombin inactivates factor X and opposes the conversion of prothrombin (factor II) to thrombin in the common pathway. And as noted earlier, basophils release heparin, a short-acting anticoagulant that also opposes prothrombin. Heparin is also found on the surfaces of cells lining the blood vessels. A pharmaceutical form of heparin is often administered therapeutically, for example, in surgical patients at risk for blood clots. |
SciQ | SciQ-5191 | 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 controls every aspect of plant growth and development to some degree? | [
"acids",
"hormones",
"chlorophyll",
"pesticides"
] | B | |
SciQ | SciQ-5192 | lo.logic, ds.data-structures, circuit-complexity, randomized-algorithms, db.databases
Next, one of the traditional principles of logic is ex falso quodlibet: that is, $\bot \to A$ holds for all propositions $A$ — if you assume false, everything follows. If you are thinking about the possibility of believing false things (for example, someone has lied to you, or you have a database with errors in it), this is potentially disastrous. In practical reasoning, you don't want to derive a contradiction and then happily believe everything — you want to find a contradiction, and deduce that you have made an error.
The study of what happens to logic when you drop ex falso is called relevance logic, so named because the idea is that you should only make inferences from hypotheses that are relevant to the conclusion. Again, see the SEP article on relevance logic for more. Also, you might wish to tolerate contradictions in your logic system. In this case, the thing to look at is paraconsistent logic.
Next, you mentioned a worry that individual inferential steps might not be completely reliable. In traditional logic we accept the unrestricted use of modus ponens. That is, inside a proof, if we know $A \to B$ and $A$ hold, we can conclude $B$ holds, any number of times. If you start to consider the idea that individual inferential steps might not be completely reliable, then you might think that proofs depending on long chains of inferential steps are "less reliable" than short ones.
It's a bit tricky to formalize this, but it is one of the (several) motivations for ultrafinitism. See Mannucci and Cherubin's draft Model Theory of Ultrafinitism I: Fuzzy Initial Segments of Arithmetic, for an exploration of this idea (and some explanation of its connection to fuzzy logic).
The following is multiple choice question (with options) to answer.
Making a specific prediction based on a general principle is known as what type of reasoning? | [
"logical reasoning",
"validating reasoning",
"deductive reasoning",
"common sense reasoning"
] | C | In deductive reasoning, I make a specific prediction based on a general principle. One general principle is that acids turn blue litmus paper red. If I have a bottle of liquid labeled “acid,” I expect the litmus paper to turn red when I immerse it in the liquid. |
SciQ | SciQ-5193 | species-identification, botany
Title: Which strange fruit is this? Yesterday, my brother brought a strange fruit resembling Lychee (but much bigger in size). Here is a pic of it:
When cut it, it had smell like banana and fibers were like of the chicken meat, though taste was more or less like banana (sorry have no pic of that).
Can someone kindly help me identify it? This appears to be a jackfruit. Jackfruit are a large, tropical fruit, commonly reported as smelling similar to banana.
The following is multiple choice question (with options) to answer.
Ripe fruits are usually red, orange, yellow, or what? | [
"black",
"white",
"blue",
"purple"
] | D | Primate ancestors also mainly ate fruit. They needed to be able to spot colored fruits in the leafy background of the trees ( Figure below ). They also had to be able to judge which fruits were ripe and which were still green. Ripe fruits are usually red, orange, yellow, or purple. Being able to see in color was important for finding food. It was an adaptation that would help fruit-eating primates survive. |
SciQ | SciQ-5194 | electrostatics, electric-fields, gauss-law
Title: Electric lines of force Why cant electric lines of force pass through the charged sphere? Well, basically that's how a Faraday cage works, but how can it be so? An electric field line follows the direction of change of an electrostatic potential. If you choose a point where the field line start, the line will go where the electrostatic potential changes most. This is equal to the force which is exerted on a charged particle which resides at a particular point.
Example: Assume a system of two infinitely large capacitor plates. If you start your field line (you can really choose where you want to start it!) in the middle between the two capacitors, it will take the shortest possible route to one of the capacitor plates.
Back to your question/comment: If you have a conducting sphere, the potential in it is constant. Because a field line follows the direction of change, you can't have field lines there.
Mathematically, a field line $\mathbf r(t)$ for an electrostatic potential $\Phi(\mathbf r)$ is defined as
$$\frac{d\mathbf r(t)}{dt}\propto \nabla \Phi(\mathbf r(t))$$
That's not so important, but I note it for the sake of completeness.
The following is multiple choice question (with options) to answer.
What are the lines of force in the electric field around a charged particle called? | [
"field lines",
"ionic zone",
"terrain lines",
"voltage lines"
] | A | Field lines represent lines of force in the electric field around a charged particle. The lines bend when two particles interact. What would the lines of force look like around two negatively charged particles?. |
SciQ | SciQ-5195 | electricity, electrical-engineering
So what really is the problem in creating transformers in such a way to reduce losses much more than the current status ?
All relevant opinions and comments appreciated
My original post : http://thinklo.blogspot.in/2013/10/improving-transformers.html Well a problem with your concept is that an "air core" transformer can produce only a limited magnetic flux density; limited by the amount of current you can run through it.
If your transformer is for power conversion/transmission, your scheme would be extremely inefficient at power line frequencies. It can be shown that the efficiency is maximized when the "copper losses" are equal to the "iron losses" or "core losses if you prefer.
Since, your transformer has no iron core, there are very low to near zero core losses, but the copper losses (wire resistance) is very high.
With an "iron" core, you can get magnetic fields of 10-15,000 Gauss (is that 1-1.5 Tesla), because of the high permeability, so you can use fewer turns of thicker wire, so less resistance, and copper losses, but more core losses, eddy currents, hysteresis losses etc.
The design of efficient and cost effective transformers, is a very complex discipline.
Sometimes it can get slightly insane. Problem with iron cores, is that they saturate somewhere in the 15-20,000 Gauss region, so if you want to go higher in flux density than that, you have to get rid of the iron. Someone did that once on an electromagnet for an accelerator. They used just two turns of wire, each a foot in diameter (the wire, not the coil). They put 800 Volts across those two turns and it drew 6 million Amps; but gave them twice the field they could get with iron. Guys name was Marcus Oliphant, in Australia. They called his machine (which worked) the white Oliphant.
The following is multiple choice question (with options) to answer.
An electric transformer connects two circuits with an iron core that becomes what? | [
"inductive",
"electromagnet",
"actuator",
"radioactive"
] | B | An electric transformer connects two circuits with an iron core that becomes an electromagnet. |
SciQ | SciQ-5196 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
What structure connects the pharynx to the trachea? | [
"aorta",
"larynx",
"thyroid",
"sternum"
] | B | Larynx The larynx is a cartilaginous structure inferior to the laryngopharynx that connects the pharynx to the trachea and helps regulate the volume of air that enters and leaves the lungs (Figure 22.7). The structure of the larynx is formed by several pieces of cartilage. Three large cartilage pieces—the thyroid cartilage (anterior), epiglottis (superior), and cricoid cartilage (inferior)—form the major structure of the larynx. The thyroid cartilage is the largest piece of cartilage that makes up the larynx. The thyroid cartilage consists of the laryngeal prominence, or “Adam’s apple,” which tends to be more prominent in males. The thick cricoid cartilage forms a ring, with a wide posterior region and a thinner anterior region. Three smaller,. |
SciQ | SciQ-5197 | solutions
Title: Can the total amount of solution be found as a ratio between molar mass of a component and total mass of solution? I wonder whether the following relation is true:
$$n_\mathrm{solvent} + n_\mathrm{solute} = \frac{M}{m_\mathrm{solvent} + m_\mathrm{solute}},$$
where $M$ is the molar mass of the component, $n$ is the amount of substance and $m$ is the mass.
It was derived assuming $n = m/M,$ $n = n_\mathrm{solvent} + n_\mathrm{solute}$ and $m = m_\mathrm{solvent} + m_\mathrm{solute}.$
I don't think this is true, but I wanted to be sure before doing anything weird on a test. To sum up the comments, only the following relation for the total amount of solution $n_\mathrm{tot}$ is universally true:
$$n_\mathrm{tot} = n_\mathrm{solvent} + n_\mathrm{solute} = \frac{m_\mathrm{solvent}}{M_\mathrm{solvent}} + \frac{m_\mathrm{solute}}{M_\mathrm{solute}}\tag{1}$$
The best you can do is to assume that $n_\mathrm{tot}\approx n_\mathrm{solvent}$ for the diluted solutions of small molecules. Also, if the molar masses are similar $(M_\mathrm{solvent}\approx M_\mathrm{solute}\approx \bar{M}),$ the expression can be lead to a common denominator:
$$n_\mathrm{tot} \approx \frac{m_\mathrm{solvent} + m_\mathrm{solute}}{\bar{M}}\tag{2}$$
The following is multiple choice question (with options) to answer.
The resultant solution will contain the same amount of solute but a greater amount of what? | [
"pigment",
"liquid",
"calcium",
"solvent"
] | D | Many chemicals that we use on a daily basis are transported in a concentrated form but used in a more diluted form. For example, concentrated cleaners are often diluted before they are used. To perform a dilution , pure solvent is added to a concentrated solution in order to make a less concentrated (more dilute) solution. The resultant solution will contain the same amount of solute but a greater amount of solvent. It will therefore have a lower concentration than the original solution. When performing a simple dilution, the concentration and volume of the initial solution are related to the new concentration and volume as follows:. |
SciQ | SciQ-5198 | cell-biology
Title: Structure of Cell Are cells spheres or ovals/circles bound by phospholipidbilayer?
If they are spherical how are we able to see the nucleus through the phospholipid bilayer under a microscope? Not exactly. That is a stereotype of cells. Muscle cells are not round nor oval, but rather elongated rods. If you were to look up epithelia cells, you can quickly see that cells are grouped based on their physical characteristics; simple (round/oval & single layer), columnar, and cuboidal to name a few. Cells come in many shapes and sizes. As Hans stated, stains are vital in viewing cellular components. There is a diverse amount of stains used - which all carry a purpose and benefit in a specific application.
The following is multiple choice question (with options) to answer.
The thin scale-like or flat shape of what cells fits their primary function, to provide a smooth and protective surface? | [
"kind epithelium",
"basic epithelium",
"technique epithelium",
"simple epithelium"
] | D | Simple Epithelium The shape of the cells in the single cell layer of simple epithelium reflects the functioning of those cells. The cells in simple squamous epithelium have the appearance of thin scales. Squamous cell nuclei tend to be flat, horizontal, and elliptical, mirroring the form of the cell. The endothelium is the epithelial tissue that lines vessels of the lymphatic and cardiovascular system, and it is made up of a single layer of squamous cells. Simple squamous epithelium, because of the thinness of the cell, is present where rapid passage of chemical compounds is observed. The alveoli of lungs where gases diffuse, segments of kidney tubules, and the lining of capillaries are also made of simple squamous epithelial tissue. The mesothelium is a simple squamous epithelium that forms the surface layer of the serous membrane that lines body cavities and internal organs. Its primary function is to provide a smooth and protective surface. Mesothelial cells are squamous epithelial cells that secrete a fluid that lubricates the mesothelium. In simple cuboidal epithelium, the nucleus of the box-like cells appears round and is generally located near the center of the cell. These epithelia are active in the secretion and absorptions of molecules. Simple cuboidal epithelia are observed in the lining of the kidney tubules and in the ducts of glands. |
SciQ | SciQ-5199 | human-biology, breathing
Our lungs work off of pressure. Specifically our lungs inflate by using "negative pressure" (a word I've always hated). The pressure is not actually negative it is simply lower than the surroundings. Since there is less air in your lungs the air from the atmosphere rushes in because the pressure is higher outside your lungs. This is Boyle's Law (not the pressure outside being higher, but what happens when your lungs expand). Where an increase in Volume means a decrease in Pressure (if all else remains unchanged). In fact plants pull water up using negative pressure.
However to push out the air from our lungs we supply pressure using our muscles that overcomes the outside pressure and forces the air out.
The reason you feel your breathing change is because when that train passes by you correctly observed the strong gust of wind. This gust of wind has some force behind it that normally is not in the air you are breathing from the atmosphere. It has more force which increases the air's velocity. This actually decreases the pressure, but there's no need to get into that here (Bernoulli's).
The reason it feels like your body is "fighting to breath" is because the air is traveling in a direction with some force that you need to overcome by opening up your lungs just enough to "suck" the air in with negative pressure. This is more than the pressure you usually need to produce in order to breath in air that is "still".
What is funny to think about is we don't really have a muscle that "pulls" air in, even though it feels like you are actively doing that. The air actually rushes in on its own. All you do is expand your rib cage, which your lungs are attached to (look up on how, it's actually pretty cool), thereby making inhalation occur.
Now an interesting question for you to ask yourself is why is cold air harder to breathe?
The following is multiple choice question (with options) to answer.
During what phase of breathing does the pressure inside the lungs drops to below atmospheric pressure? | [
"ingestion",
"exhalation",
"inhalation",
"conduction"
] | C | Pressure Associated with the Lungs The pressure inside the lungs increases and decreases with each breath. The pressure drops to below atmospheric pressure (negative gauge pressure) when you inhale, causing air to flow into the lungs. It increases above atmospheric pressure (positive gauge pressure) when you exhale, forcing air out. Lung pressure is controlled by several mechanisms. Muscle action in the diaphragm and rib cage is necessary for inhalation; this muscle action increases the volume of the lungs thereby reducing the pressure within them Figure 11.39. Surface tension in the alveoli creates a positive pressure opposing inhalation. (See Cohesion and Adhesion in Liquids: Surface Tension and Capillary Action. ) You can exhale without muscle action by letting surface tension in the alveoli create its own positive pressure. Muscle action can add to this positive pressure to produce forced exhalation, such as when you blow up a balloon, blow out a candle, or cough. |
SciQ | SciQ-5200 | entomology, pathology, parasitology
Title: Why is the species-diversity of deadly parasites greatest in the tropics? There are so many parasites living in tropical regions of Africa, South America, or Asia, but very few in Europe or North America.
Is this due to climate, or are there other reasons?
Many of the tropical diseases and parasites are transmitted by insects, such as flies and mosquitoes. Well there are flies and mosquitoes in Europe as well.
There might be malaria-transmitting mosquitoes in the very south of Europe, and there is encephalitis transmitted by ticks. But that's it. Why don't the hundreds of different parasitic species from Africa spread to Europe ? The diversity of parasites shows a gradient with increasing diversity from the poles to the equator. Several reasons have been brought forth to explain the latitude-dependency of parasite diversity:
An increased diversity overall around the equator; species diversity in general is greater in the rain forests and hence more hosts are available and thus more parasitic species can develop that target specific hosts;
Larger amounts of precipitation and higher temperatures around the equator may favor the development and transmission of parasites (Nunn et al., 2005);
Increased available energy overall around the equator (Guernier et al., 2004).
References
- Guernier et al., PLOSone (2004): 0020141
- Nunn et al., Diversity and Distrib (2005); 11: 249–56
The following is multiple choice question (with options) to answer.
What type of climates is malaria commonly found in? | [
"tropical and permafrost",
"tropic and arctic",
"arid and arctic",
"tropical and subtropical"
] | D | Malaria is common in tropical and subtropical climates throughout the world (see Figure below ). In fact, malaria is one of the most common infectious diseases on the planet. Malaria is also a very serious disease. It kills several million people each year, most of them children. |
SciQ | SciQ-5201 | species-identification, botany
Title: Identification of a plant Please help me to identify this plant
The plants can be found on italian balconies and I would like to buy one, but I do not know what I should look for.
The habit of the plant is trailing. This is likely to be a stone plant (Aizoaceae), depending on habit, it could well be the ice plant (Carpobrotus edulis). Stone plants are a quite diverse family of succulents from southern Africa, but are widespread throughout the western world as stabilizers of sand-dunes and in gardens as they are very tolerant of lack of watering and high salinity.
Ice plants are very common in the Mediterranean region, having become an invasive pest on much of the coastline.
If it is ice plant, then you can sub-cultivate it by taking a small part of the plant, usually leaves with a bit of stem, but even a leaf by itself may work, and placing it in water or on sandy soil. With regular watering, it should grow roots and then be plantable.
Apparently the leaves of ice plant are edible (hence the edulis part of the name), similar to Aloe I suspect.
The following is multiple choice question (with options) to answer.
Plants that live in the desert are called? | [
"sporozoans",
"xerozoans",
"heatophiles",
"xerophytes"
] | D | Plants that live in extremely dry environments have the opposite problem: how to get and keep water. Plants that are adapted to very dry environments are called xerophytes . Their adaptations may help them increase water intake, decrease water loss, or store water when it is available. |
SciQ | SciQ-5202 | ethology, mammals, language
Title: Can dolphins actually communicate linguistically? Humans use "language." By language, I mean the thing I am using right now to talk to you.
I know dolphins and orcas have very complex communication systems and also seem to process linguistic and gestural commands.
But do they have their own languages? Where is the evidence for or against? If we take two group of dolphins Group A and Group B, would Group A speak one language and Group B speak another? Dolphins and orcas do have dialects. Of course there are species specific dialects and it has been shown that orcas reared with bottlenose dolphins tend to learn the latter's dialect. Dolphins of the same species also seem to have regional dialects, as mentioned in this BBC post (I personally do not trust in non-research articles much, but nonetheless in this case the article indicates a certain possibility of a phenomenon). However, this page also reports the same finding and this source seems to be much more reliable. There are citations too that are at present inaccessible to me. Both the sources say that bottlenose dolphins from Shannon estuary in Ireland, "speak" different dialect compared to those from Cardigan Bay in Wales.
The actual research work is this:
Hickey, R. (2005) Comparison of whistle repertoire and characteristics between Cardigan Bay and the Shannon estuary
populations of Bottlenose dolphins (Tursiops truncatus) with
implications for passive and active survey techniques. School of
Biological Sciences, University of Wales, Bangor
Apart from having regional dialects, the cetacean communication also seems to have other features of a "language". I am pasting excerpts from this article which basically reports a study on the acoustic communication or codas in sperm whales. This may apply to dolphins as well.
Individuals within social units have preferred associates among
members (Gero et al. 2008), indicating differences in the way an
individual interacts with other members of its unit. These preferred
associations among unit members suggest the possibility of an
individual discrimination system.
The following is multiple choice question (with options) to answer.
Dolphins are what type of animal? | [
"mammal",
"whale",
"reptile",
"fish"
] | A | Dolphins are mammals that have adapted to swimming and reproducing in water. |
SciQ | SciQ-5203 | gravity, energy, mass, mass-energy
Title: How does energy convert to matter? To my understanding, matter and energy are one and the same. Shifting from $E$ to $M$ in Einstein's famous equation requires only a large negative acceleration. If $M$ really is $E/c^2$, does that make matter the solid state of energy? I've read a lot about positron-electron collisions at high energies creating larger particles, and there is obvious matter conversion in fusion and fission reactions, but I can't find anything describing the physics of the conversion from energy to matter, rather than the interactions of what is already matter.
Specifically, the thing I'm getting hung up on is the reason energy would take on a solid state in the first place. If energy is represented by waves, how does it become particles? If gravity is determined by mass, and mass is nothing more than static energy, does that make gravity a static-electromagnetic force? Energy and matter are not the same. Matter is a type of thing, whereas energy is a property of a thing, like velocity or volume. So your premise is flawed. In particular:
there's no such thing as "a solid state of energy" - hopefully it makes sense that a property of something does not have states
energy is not represented by waves, though it is a property of a wave. It's also a property of a particle (which, in quantum field theory, is really just a tightly bunched wave).
Note that mass can be converted to energy, because mass actually is energy. It is one of various types of energy: kinetic energy, potential energy, mass energy, and so on. Different types of energy get converted into each other all the time.
I'd suggest looking at several of the questions under the "Related" heading at the right for more information about this. (I actually thought this had been asked here before, but I didn't find an exact duplicate.)
The following is multiple choice question (with options) to answer.
What is the energy of moving matter? | [
"residual energy",
"binary energy",
"potential energy",
"kinetic energy"
] | D | Kinetic energy is the energy of moving matter. Things with kinetic energy can do work. Kinetic energy depends on an object’s mass and velocity. |
SciQ | SciQ-5204 | biochemistry, botany, plant-physiology, photosynthesis
Title: Independence of Light independent reaction in photosynthesis? Inspired by a question asked to me by a classmate, I have the following question about Light-independent (dark phase) reactions in photosynthesis:-
Let us suppose an algae sample was exposed to light for a considerable
time so that maximum( if there is a limit) NADPH concentration was
achieved. Now if the sample is placed in dark and radioactive
¹⁴CO₂ bubbled, will the cell be radiolabelled after some time of
bubbling continuously?
The following is multiple choice question (with options) to answer.
The two parts of photosynthesis photosynthesis takes place in two stages: the light-dependent reactions and which cycle? | [
"dark cycle",
"colors cycle",
"klein cycle",
"calvin cycle"
] | D | The Two Parts of Photosynthesis Photosynthesis takes place in two stages: the light-dependent reactions and the Calvin cycle. In the light-dependent reactions, which take place at the thylakoid membrane, chlorophyll absorbs energy from sunlight and then converts it into chemical energy with the use of water. The light-dependent reactions release oxygen from the hydrolysis of water as a byproduct. In the Calvin cycle, which takes place in the stroma, the chemical energy derived from the light-dependent reactions drives both the capture of carbon in carbon dioxide molecules and the subsequent assembly of sugar molecules. The two reactions use carrier molecules to transport the energy from one to the other. The carriers that move energy from the light-dependent reactions to the Calvin cycle reactions can be thought of as “full” because they bring energy. After the energy is released, the “empty” energy carriers return to the light-dependent reactions to obtain more energy. |
SciQ | SciQ-5205 | 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.
In an atom, what two major types of particles are located in the nucleus? | [
"protons and neutrons",
"molecules and neutrons",
"electrons and neutrons",
"ions and electrons"
] | A | Rutherford’s atomic model became known as the nuclear model . In the nuclear atom, the protons and neutrons, which comprise nearly all of the mass of the atom, are located in the nucleus at the center of the atom. The electrons are distributed around the nucleus and occupy most of the volume of the atom. It is worth emphasizing just how small the nucleus is compared to the rest of the atom. If we could blow up an atom to be the size of a large professional football stadium, the nucleus would be about the size of a marble. |
SciQ | SciQ-5206 | human-anatomy
Title: Difference between Appendix and the Cecum? What's the difference between an appendix and a cecum, and what are their functions? In herbivores the Cecum is an area that stores plant matter and helps digest it via symbiotic bacteria. Carnivores have smaller Cecums because meat is easier to digest than plant matter. In humans the Cecum is also an anatomical landmark that delineates the change from small intestine (a digesting organ) to the large intestine (mostly a capacity/storage organ).
The Appendix is a small, previously thought "superfluous" fleshy worm-shaped organ at the junction between the small and large intestines. Recent research posits that the appendix is sort of a harbor for a person's gut flora that can re-populate the intestines should the existing bacteria die or get removed (diarrhea being the most common cause). It can also become infected, inflamed, and require surgery to remove (Appendicitis).
The following is multiple choice question (with options) to answer.
What is the first part of the large intestine, where wastes enter from the small intestine? | [
"tectum",
"cecum",
"sacrum",
"spleen"
] | B | The cecum is the first part of the large intestine, where wastes enter from the small intestine. The wastes are in a liquid state. As they pass through the colon , which is the second part of the large intestine, excess water is absorbed. The remaining solid wastes are called feces . Feces accumulate in the rectum , which is the third part of the large intestine. As the rectum fills, the feces become compacted. After a certain amount of feces accumulate, they are eliminated from the body. A sphincter controls the anus and opens to let feces pass through. |
SciQ | SciQ-5207 | botany, mathematical-models, statistics, biostatistics, migration
Title: Biostatistics: Pollen dispersal directionality What Information am I looking for?
Think about a tree that is sending pollen all over the place. Because of wind, most pollen grain will go toward one direction. Imagine, we split the 2D area around the tree where pollen grains fall into two half disks of equal size. We chose the disks so that the number of pollen grains falling into one half-disk is minimized and the quantity of pollen falling in the other half-disk is maximized.
The information I need is what proportion of pollen grain falls into each disk? Is it $\frac{0.5}{0.5}$ (in which case the wind would have no effect) or is it something like $\frac{0.8}{0.2}$?
Where to get the information from?
I was reading this paper about pollen dispersal directionality and was trying to extract the info I need.
On pages 4 and 5 they explain their analysis under the section statistical procedure. More specifically, in the first paragraph of the 5th page, they seem to describe the meaning of the parameters that are trying to estimate. One of them is the so-called directionality parameter $\delta$. I don't understand how to interpret this parameter $\delta$. This parameter is part of a logistic regression I think (although the authors do not characterize it as such) of "mating success" $y$ against variables $d$ ("distance") and $h$ ("height") and an angular variable $a = \cos(\alpha_0 - \alpha)$. ($\alpha_0$ is the "presumed prevailing direction of effective pollen dispersal," which apparently is not estimated from these data.) The corresponding parameters of the model are $\beta$, $\gamma$, and $\delta$, respectively, hence
$$\phi_j = \Pr(y_j = 1) = \frac{\exp\left(\beta d_j + \gamma h_j + \delta a_j\right)}{\sum_{k=1}^r \exp\left(\beta d_k + \gamma h_k + \delta a_k\right)}$$
The following is multiple choice question (with options) to answer.
Each pollen grain has two coverings: the exine (thicker, outer layer) and the what? | [
"tube nucleus",
"cytoplasm",
"intine",
"pollen tube"
] | C | Each pollen grain has two coverings: the exine (thicker, outer layer) and the intine (Figure 32.7). The exine contains sporopollenin, a complex waterproofing substance supplied by the tapetal cells. Sporopollenin allows the pollen to survive under unfavorable conditions and to be carried by wind, water, or biological agents without undergoing damage. Female Gametophyte (The Embryo Sac) While the details may vary between species, the overall development of the female gametophyte has two distinct phases. First, in the process of megasporogenesis, a single cell in the diploid megasporangium—an area of tissue in the ovules—undergoes meiosis to produce four megaspores, only one of which survives. During the second phase, megagametogenesis, the surviving haploid megaspore undergoes mitosis to produce an eight-nucleate, seven-cell female gametophyte, also known as the megagametophyte or embryo sac. Two of the nuclei—the polar nuclei—move to the equator and fuse, forming a single, diploid central cell. This central cell later fuses with a sperm to form the triploid endosperm. Three nuclei position themselves on the end of the embryo sac opposite the micropyle and develop into the antipodal cells, which later degenerate. The nucleus closest to the micropyle becomes the female gamete, or egg cell, and the two adjacent nuclei develop into synergid cells (Figure 32.8). The synergids help guide the pollen tube for successful fertilization, after which they disintegrate. Once fertilization is complete, the resulting diploid zygote develops into the embryo, and the fertilized ovule forms the other tissues of the seed. |
SciQ | SciQ-5208 | nuclear-physics, astrophysics, sun, fusion, stellar-physics
Basically, the Sun is a ball of hydrogen and helium, but this is not all there is. Being a Population I star, the Sun contains heavier elements (called metals in stellar astrophysics; anything lithium and heavier is considered metal in this sense). These elements already came with the gas cloud the Sun has formed from, and were produced by previously burst older stars. Despite low abundance, the metallicity plays an important role in the Sun's core power stability.
At some depth the gas ball compresses its inner area enough to heat it up so much that hydrogen fusion into helium begins. This area is called the core. This is where practically all fusion happens, and what is responsible for the star's energy production. For a Sun-mass star and below, the proton-proton chain dominates. The pp-chain energy output is approximately proportional to $T^4$. The good news is, if reaction rate drops, then the outer layer of the star will compress the core, so it heats up, and the renewed energy output compensates for the compression. So this highly-sensitive dependency on the temperature is what gives the star its long term stability.
It is also notable that the center of the core is hotter and therefore more energetic than its periphery, and turns hydrogen into helium faster. Absent any mixing, the core would develop an inert helium ball in the middle (helium cannot be fused by a Sun-mass star, its core is too cold for that): A pp-chain core is entirely non-convective. However, there is another multistage reaction that fuses protons into helium nuclei, the CNO cycle. This cycle requires metals ($C$, $N$ and $O$, naturally) be present in the core. They are not consumed, but participate in stages of the reaction and are ultimately recycled. The rate of this reaction depends on the temperature as $T^{20}$. It's a huge dependency! The CNO-dominant core has so much temperature gradient that it's fully convective, so it mixes the material very thoroughly.
The following is multiple choice question (with options) to answer.
In stars like our sun, hydrogen atoms join together to create what? | [
"iron atom",
"water molecule",
"helium atom",
"oxygen atom"
] | C | A nuclear fusion reaction is so named because the nuclei (center) of atoms fuse (join) together in the process. In stars like our Sun, hydrogen atoms join together to create a helium atom. Nuclear fusion reactions need a lot of energy to get started. Once they begin, they produce even more energy. ( Figure below ). |
SciQ | SciQ-5209 | 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.
How do bacteria reproduce? | [
"natural fission",
"binary fission",
"residual fission",
"multiple fission"
] | B | New mitochondria and chloroplasts are produced through a process similar to binary fission . Bacteria also reproduce through binary fission. |
SciQ | SciQ-5210 | thermodynamics, air, buoyancy, gas, lift
The "why":
Simply put, I'm just wondering if there could be a way of making floating platforms to lift rockets, so they don't need their first stage. Or, at least, to make Zeppelins (a dirigible with rigid structure) to be smaller than conventional helium/hydrogen Zeppelins (but even so, I doubt it).
Of course, I can imagine that if such thing was even efficient, nations would already be using that. You will not get a huge advantage by heating the gas, after all you would need to carry the considerable weight of the heater. Even at very high altitudes, provided the gas inside the balloon is not at a higher pressure than the surrounding air, due to the tension in the balloon envelope, the ratio of the weight of the displaced air causing the buoyancy, to that of the gas inside the balloon will be the same as at ground level.
The net buoyancy is the weight of the displaced air minus that of the internal gas, envelope and payload combined. So the real limit on the ability to gain altitude is the weight of the envelope and payload. When the gasses both inside and outside the balloon are rarefied, you need an envelope of enormous surface area, so it needs to be incredibly thin and light. Perhaps you need graphene for the next world record.
The following is multiple choice question (with options) to answer.
What sort of gas is found in balloons and blimps, and is used to make them float in the sky? | [
"radon",
"oxygen",
"helium",
"hydrogen"
] | C | Helium has long been used in balloons and blimps. Since it is much less dense than air, it will float above the ground. We can buy small balloons filled with helium at stores, but large ones (such as the balloon seen above) are much more expensive and take up a lot more helium. |
SciQ | SciQ-5211 | bond, ionic-compounds, transition-metals, covalent-compounds
Title: Is pyrite (FeS₂) an ionic or a covalent compound? I have searched all over the web and found a lot of diverse explanations, but none of them are concluding exactly whether $\ce{FeS2}$ (solid - pyrite) is a covalent or an ionic compound.
From electronegativity, it should be covalent as the $\Delta\chi=0.7$ which is less than $1.5$ and thus said to make covalent bonds and therefore be a covalent compound.
From the definition of ionic bonds, which are bonds between a metal and a non-metal element (whereas covalent bonds are bonds between non-metal elements), it should be an ionic compound.
Does someone know which of those is 'true', or better, if there is another, more detailed explanation? You seem to have fallen into the trap of thinking that ionic and covalent bonds are fundamentally different. They are not - they are just two ends of a spectrum, which has an arbitrary division somewhere in the middle into an ionic and covalent regime. This is explained in the answers to this question.
In the case of pyrite we have a relatively hard cation, with a small ionic radius and charge of +2, and a rather large anion, with a charge of -2. Therefore there will be a significant degree of covalent character in the Fe-S bonds due to the polarising effect of the cation on the anion. This is confirmed by experimental results and theoretical calculations which suggest that the charge on Fe is about +2/3 and the charge on S is about -1/3. This is significantly less than the expected charges of +2 and -1 from a purely ionic model and so indicates that there is significant sharing of electrons. This is supported by measurements and calculations of the electron density, which show significant electron density between the atoms.
Reference: http://pubs.rsc.org/en/content/articlepdf/2014/sc/c3sc52977k
The following is multiple choice question (with options) to answer.
What color is pyrite? | [
"gold",
"silver",
"black",
"blue"
] | A | Pyrite has a similar color to gold. The appearance of the striations make pyrite different from gold. |
SciQ | SciQ-5212 | civil-engineering
Other things that can be done is to place hay bales, or rocks, on the soil slope and on the slope above the deposited soil. These can help to reduce the speed of surface water running down the slope.
If hay bales are used they should be placed in a staggered, off-set pattern, so that long drainage channels, which would lead to the formation of erosion gullies, are not created by the bales.
Moonscaping of the upper natural slope, above the deposited soil slope would also help in preserving the deposited soil slope.
The following is multiple choice question (with options) to answer.
Planting a row of trees around a field or erecting a fence on a sand dune helps prevent what form of erosion? | [
"fire",
"rain",
"wind",
"water"
] | C | Planting rows of trees around fields is another way to reduce wind erosion. The trees slow down the wind, so it doesn’t cause as much erosion. Fences like the one in Figure below serve the same purpose. The fence in the figure is preventing erosion and migration of sand dunes on a beach. |
SciQ | SciQ-5213 | pregnancy, children
Title: What leads to the different types of navels? Obviously, there are "innies" and "outies" in the human belly button world. Both are the result of a knot tied in the umbilical cord just after birth.
But why do some belly buttons become outies while others become innies? Is it related to how the doctor ties the knot, or is it related to how the knot heals? After childbirth, the umbilical cord is either tied (similar to a tourniquet - the cord itself is not tied into a knot) or clamped to cut off the blood supply. It is then cut distal to the clamp/tie, separating the child from the rest of the cord and the attached placenta. The remaining cells die and dessicate, and the stump eventually falls off, forming the umbilicus or belly button. The default result, barring any issues, is an "innie". However, an "outie" may form if the child was born with a tiny umbilical hernia, or there was a small unnoticed infection at the base of the umbilical cord. Either of these could lead to the formation granulation tissue, described colloquially as an "outie". People can also have combination navels, with the indentation of an "innie" but a small amount of protruding granulation tissue inside.
The following is multiple choice question (with options) to answer.
What structure connects the fetus to the placenta, allowing the exchange of gases? | [
"skin cord",
"umbilical cord",
"sediment cord",
"belly button"
] | B | Within seconds of birth, the umbilical cord is cut. Without this connection to the placenta, the baby can’t exchange gases, so carbon dioxide quickly builds up in the baby’s blood. This stimulates the baby’s brain to trigger breathing, and the newborn takes her first breath. |
SciQ | SciQ-5214 | materials, chemical-engineering, plastic, safety
Title: Why do glass windows still exist? (Why haven't they been replaced by plastics?) Glass is fragile and impractical to transport, install and repair. Even worse, glass kills and hurts people when it breaks. Falling to the streets like guillotines during earthquakes and bomb raids. During wars people put tape on their windows to prevent shattering. When that meteor exploded over Chelyabinsk, people got hurt by standing inside of a window watching the sky when the shock wave hit them.
There are perfectly transparent plastics, for example the PET material used to make coca cola bottles. Why aren't windows made out of that instead of glass (fragile ceramics)? It seems to be much cheaper, safer and more practical to handle. Is there any advantage at all to make windows out of glass? Is this a billion dollar business idea, and if so, why haven't anyone realized it yet? There are two main reasons why glass is still preferred over say PMMA.
The first is durability. As long as it isn't broken, the glass in a window can easily last for hundreds of years in good condition. In particular it is a lot more resistant to scratches than comparable plastics and isn't really subject to much in the way of environmental degradation. Windows are very prone to getting scratched when they are washed as they accumulate small particles of grit on their surface which gets rubbed around the surface during cleaning. Even with scratch resistant coatings no transparent plastics get anywhere near the hardness of glass.
Most glasses are also much more resistant to environmental degradation from sunlight and various chemicals in the environment. Even the most resistant plastics start to discolour and become brittle over time.
The second factor is stiffness. Glass has a much higher Young's Modulus than PMMA. In bottles etc which are stiffened by their shape this doesn't matter much but, as windows tend to be large, flat, thin panels stiffness is a big issue, affecting their ability to be sealed into their frames and their optical properties. So a plastic window would need to be substantially thicker than a glass one to have the same stiffness with consequences for optical quality and cost.
There may also be issues with gas permeability in the context of double glazed windows.
The following is multiple choice question (with options) to answer.
Glass, rubber, and plastics are examples of which type of solids? | [
"dubious",
"porous",
"aqueous",
"amorphous"
] | D | Examples of amorphous solids include glass, rubber, and plastics. |
SciQ | SciQ-5215 | bacteriology, antibiotic-resistance, research-process
Title: How do scientists kill the bacteria they themselves made resistant? I was reading this article on researching bacteria resistance to silver by removing some of their genes.
Researchers then used "colony-scoring" software to measure the differences in growth and size of each plate's bacterial colony. E. coli strains with genes deleted involved in producing sensitivity, or toxicity, to silver grew larger colonies. Strains with genes deleted involved with resistance grew smaller colonies.
Once you end up with some resistant bacteria and you're done researching it, you can't just flush it down the toilet. How do you safely dispose those colony plates in a way that ensures those bacteria don't get out into the wild and reproduce? You are absolutely right, flushing down the toilet (or the sink) or simply throwing them into the normal waste doesn't work for biosafety reasons. And it is also not allowed, depending on the country you would do this in, this can lead to hefty fines.
Biologically contaminated lab waste can be inactivated (=all potential dangerous organisms are destroyed) by two ways: Either by heat or chemically. Which ways is used, depends on the kind of waste.
The most commonly used way is autoclaving, meaning treating the waste with steam at high temperatures at higher pressure. The temperature used here is usually 121°C, the exposure time depends on the volume of the waste, since the temperature needs to be reached and kept for at least 20 minutes. See the references for more details.
Liquid wastes (like culture media) can also be inactivated chemically by adding chlorine bleach to decompose the cells. Bleach can also be used to decontaminate surfaces, although here more often alcoholic solutions (70% Ethanol or Isopropanol) are used. After chemical inactivation, the remaining solutions should not be autoclaved as the emerging fumes are either unhealthy (bleach) or explosive (alcoholic solutions) and this is unnecessary, too.
Liquid wastes can also be autoclaved to inactivate them.
Autoclaving has the main advantage that it is rather simple (put the waste into the autoclave, close it and run a appropriate program), the waste can afterwards simply be discarded as normal waste, which may not be the case for chemically inactivated waste, which may need special precaution for disposal.
References:
The following is multiple choice question (with options) to answer.
What is the process bacteria use to break down chemicals into food? | [
"biosynthesis",
"cellular respiration",
"gametogenesis",
"chemosynthesis"
] | D | The bacteria that make food from chemicals are also primary producers. These organisms do not do photosynthesis since there is no light at the vents. They do something called chemosynthesis. They break down chemicals to make food. |
SciQ | SciQ-5216 | human-biology, eggs
In order to form a zygote (fertilized egg) to develop properly into a fetus it has to be an environment to meet it needs. In a female uterus all these needs are met but replicating them might be difficult. An artificial womb would have to be able to provide nutrients, oxygen, and channels for the development process of a fetus as well as system to expel (birth) the fetus once its development is complete. So can today's technology and science do all this? In theory yes, if resources and time where dedicated (and red tape cut) it would be possible to develop a fertilized egg in an artificial environment within the foreseeable future. There have been multiple experiment where artificial wombs were implanted with fertilized eggs and began to grow but were stopped due to legality.
I encourage you to read the following Wikipedia and motherboard articles regarding artificial wombs and ectogenesis.
https://en.wikipedia.org/wiki/Artificial_uterus
http://motherboard.vice.com/read/artificial-wombs-are-coming-and-the-controversys-already-here
*Note there is a lot of biology I did not mention regarding zygote to fetus development which is the biggest question/obstacle that ectogenesis might face
The following is multiple choice question (with options) to answer.
A fully developed placenta is made up of a large mass of what? | [
"plant cells",
"brain tissues",
"estrogen hormones",
"blood vessels"
] | D | A fully developed placenta, like the one in Figure below , is made up of a large mass of blood vessels from both mother and fetus. The maternal and fetal vessels are close together but separated by tiny spaces. This allows the mother’s and fetus’s blood to exchange substances across their capillary walls without the blood actually mixing. |
SciQ | SciQ-5217 | material-science
Title: Optimal material for a hammer head I was watching a TV show in which a gold hammer was mentioned. It was not serious but caused me to wonder whether gold would be a good material and, if not, what else might be. An attraction of gold is that it has a high density but that advantage is probably negated by being more malleable than steel. So, I started to wonder what properties I need to consider. Some materials may be hard but liable to shatter on impact.
Let's suppose that the dimensions of the hammer are fixed: a fixed handle and a fixed size and shape for the head. The objective is to drive steel nails into a variety of hard substances.
Cost is not a factor, nor ease of construction, nor safety. It will need to last long enough to be used so francium and various heavy elements are not suitable. If depleted uranium is a good material then this would be acceptable. It is used for armour piercing shells presumably because of its density but there are denser materials. Is it that it is cheaper than gold or osmium?
What properties should I be researching?
Additional: to make the question more manageable, I will require a homogenous pure material for the head not an alloy. I hope that this makes me more a question of physics rather than engineering. This is a thought experiment rather than a real project. What the optimal hammer head material is depends on what we are optimizing for.
A standard hammer has a hard head that has high density, held by a strong but usually light handle. If it has length $l$ and is accelerated at some acceleration $a$ set by user muscle strength it will reach a velocity $v$ after having traversed a distance $\sim l$; that is, $l=at^2/2$ gives $t=\sqrt{2l/a}$ and $v=\sqrt{2la}$. The kinetic energy will be $K_e\approx mla$. So a long and heavy hammer will be able to drive a nail more deeply (to a depth $K_e/F$ where $F$ is the resisting force). So more mass and length seems good... but obviously not too much either.
The following is multiple choice question (with options) to answer.
What is an element that tend to be malleable? | [
"lanthanide",
"metal",
"actinide",
"mixture"
] | B | Metals tend to be malleable. This means that they can be formed into thin sheets without breaking. An example is aluminum foil, also pictured in the Figure below . |
SciQ | SciQ-5218 | human-biology, breathing
Our lungs work off of pressure. Specifically our lungs inflate by using "negative pressure" (a word I've always hated). The pressure is not actually negative it is simply lower than the surroundings. Since there is less air in your lungs the air from the atmosphere rushes in because the pressure is higher outside your lungs. This is Boyle's Law (not the pressure outside being higher, but what happens when your lungs expand). Where an increase in Volume means a decrease in Pressure (if all else remains unchanged). In fact plants pull water up using negative pressure.
However to push out the air from our lungs we supply pressure using our muscles that overcomes the outside pressure and forces the air out.
The reason you feel your breathing change is because when that train passes by you correctly observed the strong gust of wind. This gust of wind has some force behind it that normally is not in the air you are breathing from the atmosphere. It has more force which increases the air's velocity. This actually decreases the pressure, but there's no need to get into that here (Bernoulli's).
The reason it feels like your body is "fighting to breath" is because the air is traveling in a direction with some force that you need to overcome by opening up your lungs just enough to "suck" the air in with negative pressure. This is more than the pressure you usually need to produce in order to breath in air that is "still".
What is funny to think about is we don't really have a muscle that "pulls" air in, even though it feels like you are actively doing that. The air actually rushes in on its own. All you do is expand your rib cage, which your lungs are attached to (look up on how, it's actually pretty cool), thereby making inhalation occur.
Now an interesting question for you to ask yourself is why is cold air harder to breathe?
The following is multiple choice question (with options) to answer.
As a diver descends, the increase in pressure causes the body’s air pockets in the ears and lungs to do what? | [
"expand",
"blow up",
"compress",
"heat up"
] | C | from the atmosphere at sea level. As a diver descends, the increase in pressure causes the body’s air pockets in the ears and lungs to compress; on the ascent, the decrease in pressure causes these air pockets to expand, potentially rupturing eardrums or bursting the lungs. Divers must therefore undergo equalization by adding air to body airspaces on the descent by breathing normally and adding air to the mask by breathing out of the nose or adding air to the ears and sinuses by equalization techniques; the corollary is also true on ascent, divers must release air from the body to maintain equalization. Buoyancy, or the ability to control whether a diver sinks or floats, is controlled by the buoyancy compensator (BCD). If a diver is ascending, the air in his BCD expands because of lower pressure according to Boyle’s law (decreasing the pressure of gases increases the volume). The expanding air increases the buoyancy of the diver, and she or he begins to ascend. The diver must vent air from the BCD or risk an uncontrolled ascent that could rupture the lungs. In descending, the increased pressure causes the air in the BCD to compress and the diver sinks much more quickly; the diver must add air to the BCD or risk an uncontrolled descent, facing much higher pressures near the ocean floor. The pressure also impacts how long a diver can stay underwater before ascending. The deeper a diver dives, the more compressed the air that is breathed because of increased pressure: If a diver dives 33 feet, the pressure is 2 ATA and the air would be compressed to one-half of its original volume. The diver uses up available air twice as fast as at the surface. |
SciQ | SciQ-5219 | dna, reproduction, dna-replication, dna-damage
cells basically create copies of DNA all the time in our body. ... Why does inbreeding cause genetic defects, but cell division in one's own body does not?
During normal cell division AaBB cells should produce only AaBB copies which have at least one functional copy A and B gene and thus are fine.
Big picture
In a real population imagine every individual has tens of thousands of genes and each of them can be made nonfunctional by random mutation. The nonfunctional copy often does not have effect since the individual has another functional copy. When two non-related individuals procreate, chances are mutations they carry are in different genes and their progeny are fine as illustrated above. When related individuals procreate chances are thay both have the same deterious mutation(s) and not all their progeny will be fine.
But bed bugs for instance, have managed with inbreeding without any problem (goddamned creatures!).
Species for which inbreeding is normal have much less recessive deleterious mutations prevalence in populations for simple reason. If new deleterious mutation appears the inbreeding leads in two generations to aa homozygots that die or fail to procreate and the "bad" mutations are selected out fairly fast. Inbreeding is normal state for some species. Today inbreeding-resistant species are descendants of individuals who have survived many generations of inbreeding.
The following is multiple choice question (with options) to answer.
Many deleterious alleles have such severe effects that a homozygous embryo spontaneously aborts long before what? | [
"couple",
"LIfe",
"birth",
"baby"
] | C | |
SciQ | SciQ-5220 | astrophysics, exoplanets, stellar-physics
Both very massive stars and low mass stars (especially when younger) can have strong ultraviolet radiation fields that may preclude life (as we know it).
The calculation assumes that all the heat required comes from the star. But it could also come from the radioactive decay of rocks or by tidal heating in the case of a moon orbiting a larger planet (think Io, Europa).
The following is multiple choice question (with options) to answer.
What kind of reaction, in general, keeps stars shining? | [
"fusion",
"magnetism",
"evolution",
"fission"
] | A | The energy from fusion reactions keeps the star shining. |
SciQ | SciQ-5221 | geology, soil, mapping, regional-geology
Title: What is the average color of soil? Where I live the soil is red.
Is there a map or chart where you can see the average color of the dirt according to geographical location? What would the color be if all of the dirt on Earth was added equally to a pallet?
I understand that composition of minerals determines dirt color but what makes dirt its color is not the question I am asking.
Kata Tjuta, Northern Territory, Australia
Sagada, Mountain Province, Philippines
https://eugeneexplorer.wordpress.com/2016/11/22/blue-soil-hills/
Gentry County, Missouri, United States
http://www.airphotona.com/image.asp?imageid=11944 This gif, prepared by the United States Department of Agriculture - Natural Resources Conservation Services (USDA-NRCS) soil scientists at the National Soil Survey Center, has soil colors based on the Munsell Color System for the United States at different depths:
The soil colors nearest the surface are darker due to more organic matter and are lighter at depth with varying colors by region.
Source: http://munsell.com/color-blog/soil-colors-national-parks-anniversary/
This link also has soil colors of select United States National Parks. For example:
The following is multiple choice question (with options) to answer.
What is the most important factor determining soil type? | [
"ecology",
"landscape",
"plant life",
"climate"
] | D | Formed when elements either gain or lose electrons. |
SciQ | SciQ-5222 | human-anatomy
Title: Why is a penis an organ? According to Wikipedia an "An organ is a group of tissues with similar functions". I don't know anything about anatomy but it doesn't seem to me that a penis can be delimited somewhere to form a "group". Therefore I do not understand why a penis is considered an organ.
Can you explain it to me ? Frankly, that's a terrible definition by Wikipedia.
Merriam-Webster defines an organ as:
a differentiated structure (such as a heart, kidney, leaf, or stem) consisting of cells and tissues and performing some specific function in an organism
or
bodily parts performing a function or cooperating in an activity
The important defining feature of an organ is not that the tissues have similar functions but that, together, the tissues comprise a functional whole that achieves some end goal.
For the penis, it consists of multiple tissues with different functions:
(from https://www.ncbi.nlm.nih.gov/books/NBK525966/figure/article-20668.image.f1/ - original from Gray's Anatomy)
The different tissues pictured here: the fibrous envelope, the corpora cavernosa, the septum pectiniforme, the urethra and blood vessels, the nervous tissue in the skin: all of these tissues have different individual functions: structural, erectile, carrying urine or semen, etc.
The key that unifies them into an organ is that the functions of the penis at the organism level (principally sexual function) are not served by any of these tissues alone, but rather by their combination in a full structure: an organ.
Ultimately, organ definitions are somewhat opinion-based: people are lumpers and splitters, so you might find conflicting definitions for which groupings of tissues reflect distinct organs, but I think by most standards you would find the penis to be considered a distinct organ, affiliated with but distinct from the primary sex organs and associated glands.
The following is multiple choice question (with options) to answer.
What are the structural and functional units of the kidney called? | [
"nephrons",
"aeons",
"Ions",
"caldrons"
] | A | Each kidney has more than a million nephrons, which are the structural and functional units of the kidney. Each nephron is like a tiny filtering plant. |
SciQ | SciQ-5223 | mitochondria, chloroplasts
Title: Origin of the double membrane of mitochondria and chloroplasts Most websites and textbooks say that the double membrane of mitochondria and chloroplasts are a result of the endocytosis of ancient prokaryotes (the outer membrane is from the vesicle containing the prokaryote, the inner membrane is from the prokaryote itself).
However, some sources say that this is not the case. The precursor to the mitochondrion (alphaproteobacteria) was a gram-negative bacteria, which has a double membrane. This site says that the reasoning for the double membrane that is often taught is a lie, and that the mitochondrial precursor had a double membrane already to generate ATP through the ETC.
So, if this is the case, why do mitochondria now have two membranes, and not three (two from the prokaryote and one from the vesicle)? The answer lies in the protein composition of mitochondrial membranes, which undoubtedly prove that the outer membrane (OM) is of alphaproteobacterial origin, and the phagosomal membrane (if there was any) is lost. Though the endosymbiotic origin is without question, bear in mind that the phagocytotic origin is still debated (cf. López-García & Moreira 2015). And if the symbiont has entered the host some other ways than phagocytosis (cf. papers of Tom Cavalier-Smith) or syntrophic engulfment (cf. papers by Bill Martin; Searcy; López-García & Moreira) (e.g. puncturing the plasma membrane as a pathogen), then there never was a third membrane.
From Symbiogenesis Wikipedia:
Porins (transport proteins) are found in the OM of mitochondria and
chloroplasts, are also found in bacterial cell membrane (Fischer et
al. 1994Zeth & Thein 2010Fairman et al. 2011). The
membrane lipid cardiolipin is exclusively found in the inner membrane
of mitochondria and bacterial cell membrane Mleykovskaya & Dowhan
2009.
The following is multiple choice question (with options) to answer.
What structure, containing many internal membranes, is the site of photosynthesis? | [
"chloroplast",
"genome",
"ribosome",
"mitochondria"
] | A | The chloroplast is the site of photosynthesis. Part of the photosynthesis reactions occur in an internal membrane within the organelle. The chloroplast contains many of these internal membranes, making photosynthesis very efficient. These internal membranes stack on top of each other, just like a stack of pancakes. |
SciQ | SciQ-5224 | atmosphere, ocean, hydrology, climate-change
Comment: I strongly endorse the use of wind and hydropower as sources of energy over the further use of fossil fuels. However, I still think it is important to do research into the actual renewability of presumed-renewable energy sources, as we don't want to end up with another fossil fuel-type situation, in which we become aware of dependency on these energy sources and their malignant environmental side-effects long after widespread enthusiastic adoption. Electricity from waves, from hydro (both run-of-river and storage) and from wind, are all indirect forms of solar power. Electricity from tides is different, and we can deal with that in a separate question. Global tidal electricity generation is not yet at the scale of gigawatts, so it's tiny for now.
Winds come about from the sun heating different parts of the planet at different rates, due to insolation angles, varying cloud cover, varying surface reflectivity, and varying specific heat of surface materials. Temperature differentials create wind currents.
Waves come about from wind, so they're a twice-indirect form of solar power.
Sunlight on water speeds up evaporation, lifting the water vapour into clouds, giving them lots of gravitational potential. That rain then falls, sometimes onto high land, from where it can be gathered into storage reservoirs that are tapped for electricity, or where it flows into rivers that are then harnessed in run-of-river hydro.
How much power is there? Well, the insolation from the sun is, at the outer boundary of the Earth's atmosphere, at an intensity of about 1400 Watts per square metre. The Earth's albedo is roughly about 30% - i.e. on average about 400 Watts are reflected back into space, giving an average irradiation into the Earth of about 1000 Watts per square metre. Picture the Earth's surface as seen from the Sun: wherever the Earth is in its orbit on its own axis, and around the Sun, the Sun sees a disc that has the Earth's diameter, so the surface area exposed to the Sun is just $\pi$ times the square of Earth's radius, which is about 6 300 kilometres.
So the incoming solar radiation is $1000 \times 6,300,000^2 \times \pi \approx 125 \times 10^{15} \rm \ W$
The following is multiple choice question (with options) to answer.
During the day, what type of energy is transferred from the air over the land to the air over the water? | [
"nuclear",
"thermal",
"magnetic",
"atmospheric"
] | B | A: During the day, thermal energy is transferred from the air over the land to the air over the water. During the night, thermal energy is transferred in the opposite direction. |
SciQ | SciQ-5225 | neuroscience
Title: Nervous system : Nerve signals If the electrical signals from all the various organs throughout the body eventually connect to the nerves in the spinal column traveling up to the brain, how does the brain differentiate the different signals. Is the nerve in the spinal column like an electrical conduit with many wires inside? Yes is the simple answer. A nerve will go up to a specific part of the brain which the brain knows corresponds to a certain region of the body. It isn't perfect though e.g. pain in the diaphragm confuses the brain which doesn't recognise that pain must be coming from there so instead tells the body there is shoulder pain, however this is useful in medicine. Another infamous example is pain from heart disease (angina) which causes pain in the jaw and arm. Perhaps even more interestingly, if a nerve is cut and then grows back linking to the wrong nerve it may lead to the completely wrong part of the body being identified when touched. Also if the brain itself is stimulated in these corresponding areas, a person will feel he or she is indeed being touched in a certain part of the body.
The following is multiple choice question (with options) to answer.
Which nerve carries electrical signals from the rods and cones to the brain? | [
"auditory",
"optic",
"neurotransmitter",
"axon"
] | B | The optic nerve carries electrical signals from the rods and cones to the brain. |
SciQ | SciQ-5226 | electromagnetism, resonance, asteroids
Title: Destroy an asteroid by EM waves by making its crystalline meshes enter in resonance? Could we destroy an asteroid made of crystalline materials heading towards the Earth by bombarding it with electromagnetic rays, making its crystalline meshes enter in vibration resonance and decompose it little by little? I estimate at first that the asteroid does not turn on itself.
If you need an example, imagine a ball of 1km radius made entirely of iron heading towards the Earth with a slightly curved trajectory at any variable speed. You can, of course, use EM radiation to break the bonds of a crystal and thus cause damage to the asteroid. In a sense, this is a form of "resonance" because the bonds will react to photons of some wavelengths more than of others - that's why materials have "color", after all. The trick is that you won't be able to completely destroy it without supplying energy approaching the order of the energy required to vaporize the asteroid, since that's pretty much what "vaporize" means - it means to completely dissolve the crystal lattice, so that every atom is separated from every other. Conservation of energy cannot be cheated!
However, a much better strategy is to not "completely destroy" the asteroid, but to only vaporize a little bit, so as to turn it into an exhaust plume that then produces thrust which pushes the asteroid out of its collision trajectory. Given the huge distances and times involved in a Solar orbit, even 0.1 m/s of dV could do a lot - over a year, or ~32 Ms, that's about 3200 km of deflection. If aimed right, that should convert an impact to at least a grazing pass within a few hundred km of Earth's surface for most impact cases.
And yes, a laser (EM radiation) could be an effective means and, indeed, taken literally and in light of what I just said, it pretty much is exactly what you are claiming - the laser photons "resonate" some of the crystal to the breaking point, sending atoms flying into space, and it happens a little at a time, but you'd have to first get one out to the asteroid, and you'd need it to keep running and aimed in the same spot for long enough to deliver the desired momentum change. There is nothing at all physically impossible about this - the challenge is all in engineering.
The following is multiple choice question (with options) to answer.
What is the only thing that can change an asteroid? | [
"a collision",
"weather",
"a situation",
"a wind"
] | A | An asteroid can only change due to a collision. A collision may cause the asteroid to break up. It may create craters on the asteroid’s surface. An asteroid may strike a planet if it comes near enough to be pulled in by its gravity. |
SciQ | SciQ-5227 | phase-transition
Title: Is a single radon-daughter atom in air, such as ${}^{218}\text{Po}$, a solid? Is a single radon-daughter atom in air a solid?
The Wikipedia article on radon says:
Unlike the gaseous radon itself, radon daughters are solids and stick to surfaces, such as dust particles in the air. If such contaminated dust is inhaled, these particles can also cause lung cancer.
The statement made me wonder about the right terminology. Is a single radon-daughter atom in air, like 218Po, a solid or a gas? I would think it is a gas because it resembles a vapor atom, or a sublimated atom from a solid. And maybe it is a 'potential' solid? When the Wikipedia article says that radon daughters are "solids", the authors actually mean, "If you get a bunch of radon daughter atoms together, then they would form a solid." The state of matter is a property of a large number of atoms, so a single atom in isolation doesn't strictly have a well-defined state.
That said, states of matter are primarily a function of the interactions between atoms. Atoms that weakly interact* with themselves and their environment are likely to be gases, while atoms that strongly interact* with other atoms are likely to be liquids or solids. So Wikipedia appears to be using the state of matter as a shorthand for the strength of interactions. Essentially, radon daughters, unlike radon (which is a noble gas), stick to each other and to the walls, which is the same property that makes large collections of radon daughters solids.
*"weakly" and "strongly" don't refer to the fundamental weak and strong nuclear interactions here, of course, but to the general idea of having a small or large coupling constant in whatever interaction you're examining.
The following is multiple choice question (with options) to answer.
Radon is inert and generally unreactive because it is which kind of gas? | [
"noble gas",
"transitive gas",
"ignoble gas",
"ideal gas"
] | A | Because radon is a noble gas, it is inert and generally unreactive. Despite this, exposure to even low concentrations of radon in air is quite dangerous. Describe the physical consequences of exposure to radon gas. Why are people who smoke more susceptible to these effects?. |
SciQ | SciQ-5228 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
What are the two ways animals can manage their internal environment? | [
"sweating or sleeping",
"adaptation or mutation",
"regulating or conforming",
"digestion or excretion"
] | C | |
SciQ | SciQ-5229 | evolution, zoology, anatomy, species
Title: Examples of animals with 12-28 legs? Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list:
snakes have 0
Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs)
Most mammals, reptiles, amphibians have 4 legs
Echinoderms (e.g., sea stars) typically have 5 legs.
Insects typically have 6 legs
Octopi and arachnids have 8 legs
decapods (e.g., crabs) have 10 legs
....But I can't really think of many examples of animals containing more legs until you reach 30+ legs in centipedes and millipedes. Some millipedes even have as many as 750 legs! The lone example I am aware of, the sunflower sea star, typically has 16-24 (though up to 40) limbs.
So my question is: what are some examples of animals with 12-28 legs? As a couple of counterexamples, species in the classes Symphyla (Pseudocentipedes) and Pauropoda within Myriapoda have 8-11 and 12 leg pairs respectively, so between 16 to 24 legs (sometimes with one or two leg pair stronlgy reduced in size).
(species in Symphyla, from wikipedia)
Another common and species-rich group with 14 walking legs (7 leg pairs) is Isopoda.
(Isopod, picture from wikipedia)
You also need to define 'legs' for the discussion to be meaningful. As you say, decapods have 10 legs on their thoracic segments (thoracic appendages), but they can also have appendages on their abdomens (Pleopods/swimming legs), which will place many decapods in the 10-20 leg range.
(Decapod abdominal appendages/legs in yellow, from wikipedia)
So overall, in Arthropoda, having 12-28 legs doesn't seem all that uncommon. There are probably other Arthropod groups besides those mentioned here that also have leg counts in this range.
However, for a general account, the most likely answer (if there is indeed a relative lack of 12-28 legged animals) is probably evolutionary contingencies and strongly conservative body plans within organism groups.
The following is multiple choice question (with options) to answer.
What may the jointed appendages of arthropods be used for? | [
"digging",
"crawling",
"walking",
"jumping"
] | C | The jointed appendages of arthropods may be used as legs for walking. Being jointed makes them more flexible. Try walking or climbing stairs without bending your knees, and you’ll see why joints are helpful. In most arthropods, the appendages on the head have been modified for other functions. Figure below shows some of the head appendages found in arthropods. Sensory organs such as eyes are also found on the head. |
SciQ | SciQ-5230 | genetics, cell-biology, embryology, meiosis, gamete
Title: Fertilization of the human egg- where does our centrosome come from? Is there a centrosome in a human egg cell? Is the reason why the egg cell remains paused before meiosis 2 because there isn't a centrosome, and it only divides when the sperm fertilizes it thus it can have a centrosome? If this is so, then how did oogenesis happen? ? To answer the first part of your question. The sperm actually introduces two centrosomes. The centrosome then nucleates the new microtubule assembly to form the sperm aster — a step essential for successful fertilization. You can visit these sites Simerly, et al as well as Paweltz, et al
The following is multiple choice question (with options) to answer.
A sperm cell and an egg cell fuse to become what? | [
"unfertilized egg",
"fetus",
"embryo",
"fertilized egg"
] | D | The Neural Tube To begin, a sperm cell and an egg cell fuse to become a fertilized egg. The fertilized egg cell, or zygote, starts dividing to generate the cells that make up an entire organism. Sixteen days after fertilization, the developing embryo’s cells belong to one of three germ layers that give rise to the different tissues in the body. The endoderm, or inner tissue, is responsible for generating the lining tissues of various spaces within the body, such as the mucosae of the digestive and respiratory systems. The mesoderm, or middle tissue, gives rise to most of the muscle and connective tissues. Finally the ectoderm, or outer tissue, develops into the integumentary system (the skin) and the nervous system. It is probably not difficult to see that the outer tissue of the embryo becomes the outer covering of the body. But how is it responsible for the nervous system? As the embryo develops, a portion of the ectoderm differentiates into a specialized region of neuroectoderm, which is the precursor for the tissue of the nervous system. Molecular signals induce cells in this region to differentiate into the neuroepithelium, forming a neural plate. The cells then begin to change shape, causing the tissue to buckle and fold inward (Figure 13.2). A neural groove forms, visible as a line along the dorsal surface of the embryo. The ridge-like edge on either side of the neural groove is referred as the neural fold. As the neural folds come together and converge, the underlying structure forms into a tube just beneath the ectoderm called the neural tube. Cells from the neural folds then separate from the ectoderm to form a cluster of cells referred to as the neural crest, which runs lateral to the neural tube. The neural crest migrates away from the nascent, or embryonic, central nervous system (CNS) that will form along the neural groove and develops into several parts of the peripheral nervous system (PNS), including the enteric nervous tissue. Many tissues that are not part of the nervous system also arise from the neural crest, such as craniofacial cartilage and bone, and melanocytes. |
SciQ | SciQ-5231 | 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.
The muscles in arteries and veins that are largely responsible for regulation of blood pressure are known as what type? | [
"vascular muscles",
"smooth muscles",
"opposing muscles",
"elongated muscles"
] | B | Smooth muscles in arteries and veins are largely responsible for regulation of blood pressure. |
SciQ | SciQ-5232 | gravity, astrophysics, meteorite
Actually, the answer is no, because a mountain in the distance would have generated a gravitational field that would have been part of the initial conditions and he was measuring the change from the initial conditions.
And even if somebody had decided to mess up Cavendish's experiment by putting a mountain 12 miles from his house during his experiment, the effect would have been nearly equal on the two balls so it wouldn't have made much difference. It would just have been a tidal force, and a very small specific force on the torque of the wire that Cavendish was interested in. Cavendish's experiment only works under very specific conditions, one 158 kg weight pulling both suspended balls on the wire in the same clockwise direction so the twist can be measured. That doesn't work with a single large mass. It's the wrong kind of setup.
But to answer your question, forces greater than 1 Cavendish are easy for any relatively large body and a meteor could do that. Bennu, which you mentioned in a comment exerts 6 micro-G, or about 22 Cavendishes. It's radius is about 250 meters, so within about 1100 or 1200 meters, an object that size would exert 1 Cavendish of gravitational force.
Ofcourse, if Bennu was to actually strike the Earth, it would likely decrease, not increase gravity at the spot it hits because it would eject material over a wide area, leaving a crater. Likewise, the effect would be very small, but on the edge of the crater, probably several Cavendish's worth of decreased gravity.
Perpendicular forces like this happen on Earth. As land rises and falls. As glaciers shift, the perpendicular gravitational force near those massive objects changes and this is most noticeable on the ocean. The gravity of the Greenland ice sheet or the Antarctic ice sheet is measurable on sea level and calculating sea level rise if those ice sheets melt (which will take some time), but accurate calculation has to take into account the gravitational pull of the mass of glacial ice on the ocean's sea level.
The following is multiple choice question (with options) to answer.
An inversion may result when what kind of mass moves over cold ground? | [
"warm air",
"warm water",
"cold air",
"cold water"
] | A | When a new air mass moves over a region it brings its characteristics to the region. This may change the area's temperature and humidity. Moving air masses cause the weather to change when they contact different conditions. For example, a warm air mass moving over cold ground may cause an inversion. |
SciQ | SciQ-5233 | neuroscience, neurophysiology, hearing, human-ear
Fettiplace, R. (2011). Hair cell transduction, tuning, and synaptic transmission in the mammalian cochlea. Comprehensive Physiology, 7(4), 1197-1227.
The following is multiple choice question (with options) to answer.
The eardrum is part of what part of the ear? | [
"outer",
"thin",
"inner",
"main"
] | A | The outer ear includes the pinna, ear canal, and eardrum. |
SciQ | SciQ-5234 | java, beginner
I would also change the parameters for Album.addSong() and removeSong() to take a Song instance instead of making Album responsible for instantiating Songs.
And a tip. Use final when declaring fields that don't need to change, especially collections. This reduces the number of mutable things you have to keep track of. When you have a non-final List field, it is mutable in two different ways: you could change the contents of the list or replace the list entirely. Keep it simpler by restricting that to one way of modifying it.
The following is multiple choice question (with options) to answer.
What is never lost and just changes forms? | [
"life",
"energy",
"fuel",
"food"
] | B | This platform is about to change energy from potential to kinetic. The energy is not lost; it just changes forms. The is on top of a precipice. The rest of the ride runs on the potential energy the platform has when it is at the top. |
SciQ | SciQ-5235 | physical-chemistry, thermodynamics, heat, mixtures
Where does this come from and what are the assumptions involved in treating it as an ideal mixture?
What deviations from this are observed in non-ideal mixtures? Can you easily predict the deviations based on the mixture and/or predict the actual specific heat capacity? Suppose you have $n_1$ mole of A and $n_2$ mole of B. If they are at temp. $T_1$ and you want to raise the temp. to $T_2$ then the amount of heat you need to add is
$$\Delta H~= n_1 \times c_{pA} \times \Delta T + n_2 \times c_{pB} \times \Delta T$$
$$\Delta H~= (n_1 \times c_{pA} + n_2 \times c_{pB}) \times \Delta T$$
$$\Delta H~= (n_1 +n_2)\times \frac{(n_1 \times c_{pA} + n_2 \times c_{pB})}{(n_1+n_2)} \times \Delta T$$
$$\Delta H~= n_{total} \times(y_1 \times c_{pA} + y_2 \times c_{pB}) \times \Delta T$$
$$\Delta H~= n_{total} \times c_{p,avg} \times \Delta T$$
So basically you are not losing any information in case of ideal situation where molecular interaction of two different species has no effect on each other's heat capacity. But from statistical mechanics we know,
$$C_v=\frac { <E^2>-<E>^2}{k_B \times T^2}$$
Now if we solve the schrodinger equation for individual species, we must include an extra potential energy term to account the interaction from other species, which in turn will result in fluctuation of $C_v$ from it's previous value.
The following is multiple choice question (with options) to answer.
What is the term for a mixture that varies in its composition? | [
"heterogeneous",
"amorphous",
"mixed composition",
"homogeneous"
] | A | The rock in Figure above is an example of a heterogeneous mixture. A heterogeneous mixture varies in its composition. The black nuggets, for example, are not distributed evenly throughout the rock. |
SciQ | SciQ-5236 | bioinformatics, proteins, structural-biology, protein-structure, xray-crystallography
Title: Subset of Protein Crystal Structures (from PDB) Is there a well-accepted subset of the Protein Data Bank set of protein structures that:
Has only "high quality" structures (may be differing metrics of this; e.g. resolution, size, or structural completeness)
Has minimal redundancy (e.g. nothing with exact sequence identity from the same species)
Is still as large as possible, spanning as many molecules and species as possible
[Optionally but better] Is not too biased (e.g. certain classes of proteins are highly over-represented in the PDB)
It is possible to download the entire PDB and make up rules for myself, but this seems like something people might have already considered reasonably extensively. I'm hoping for a dataset I can just download and cite, in the best case. :) Richardsons' Lab has a top8000 list.
See their paper from 2016.
They also have top500 list, but it hasn't been updated for many years.
The following is multiple choice question (with options) to answer.
What are the "building blocks" of proteins? | [
"nucleic acids",
"amino acids",
"hormones",
"enzymes"
] | B | Amino acids are the "building blocks" of proteins. There are 20 different common amino acids. The structural formula of the simplest amino acid, called glycine, is shown in Figure below . Other amino acids have a similar structure. The sequence of amino acids and the number of amino acid chains in a protein determine the protein’s shape. The shape of a protein, in turn, determines its function. Shapes may be very complex. You can learn more about the structure of proteins at the URL below. |
SciQ | SciQ-5237 | newtonian-mechanics, reference-frames, acceleration
It seems to me that the answers to your questions all depend on how one defines the "feeling of weight".
There seems to be general agreement that feeling "weightless" is a feeling associated with the absence of any contact forces on the body, as in the case of free fall. It seems to me that whether or not the presence of any contact force, in any direction on the body, in and of itself is associated with the feeling of weight would depend on just what one means by the "feeling of weight".
The professors's first example of hanging from a string involves a contact force pulling upwards on the body. He said that would give a person a sensation of weight. But it's a different feeling then standing on the ground experiencing a contact force acting upwards on your feet, which I think is more commonly associated with the perception of weight.
Ride a roller coaster and you experience contact forces of various magnitudes and directions on various parts of your body by the structure that restrains you. Do we consider all these contact forces as equivalent to the sensation of weight? If we define the feeling of weight as the feeling associated with any contact force, which the professor seems to be saying with the first example, then I suppose the answer would be yes. As for me, I'm not so sure.
Hope this helps.
The following is multiple choice question (with options) to answer.
What is responsible for our sense of balance? | [
"our ears",
"our limbs",
"our feet",
"our eyes"
] | A | The ears are also responsible for the sense of balance. Balance is the ability to sense and maintain body position. The semicircular canals inside the ear (see Figure above ) contain fluid that moves when the head changes position. Tiny hairs lining the semicircular canals sense movement of the fluid. In response, they send nerve impulses to the vestibular nerve , which carries the impulses to the brain. The brain interprets the impulses and sends messages to the peripheral nervous system. This system maintains the body’s balance by triggering contractions of skeletal muscles as needed. |
SciQ | SciQ-5238 | regulated cell renewal cycle in the colonic crypt provides a good example of how modeling can be used to find out key features. To accomplish t. Many everyday activities require the use of mathematical models, perhaps unconsciously. arXiv is funded by Cornell University, the Simons Foundation and by the member institutions. uk Abstract. The decision to introduce or amend vaccination programmes is routinely based on mathematical modelling. The models are purely deterministic. The department, joint with the Department of Statistics, is ranked 3rd in the US in terms of National Science Foundation (NSF) funding for Mathematical Sciences in 2015. The Department of Applied and Computational Mathematics and Statistics (ACMS) enables statisticians and mathematicians to work alongside biological science, chemistry, economics and econometrics, engineering, political science, psychology, and sociology, among many other disciplines. Section 2-7 : Modeling with First Order Differential Equations. Issued in print and electronic formats. The book is unique as it addresses a focused theme on mathematics education. You can also make use of the search facility at the top of each page to search for individual mathematicians, theorems, developments, periods in history, etc. Course Information: 3 undergraduate hours. If you are a pilot of a rescue helicopter, you need to know the following:. With calculus, we have the ability to find the effects of changing conditions on a system. Statistics can be defined as a type of mathematical analysis which involves the method of collecting and analyzing data and then summing up the data into a numerical form for a given set of factual data or real world observations. Sign in to view your account details and order history. Session 3: Deforming and Recrystallization Abstract Title Mathematical modelling of soft reduction in Abaqus software with the application of tensile testing under crystallization conditions on Gleeble-3800. Catherine Sulem has been awarded a Killam Research Fellowship. This lesson will help you understand mathematical models and how they are used in the context of business. Abstract: The rotating shallow water is one of the simplest mathematical models that can capture features of rapidly rotating and strongly stratified geophysical flows, relevant to the atmosphere and the ocean. Mathematical Applications, Modeling and Technology Michael de Villiers School of Science, Mathematics & Technology Education, Univ. Data will be generated by practical applications arising from science, business, and finance. Computer Modeling. At this formative stage, learning needs to be effective and interests for learning has to be
The following is multiple choice question (with options) to answer.
What technology do scientists use to create models? | [
"patterns",
"computers",
"calculators",
"microscopes"
] | B | Scientists create models with computers. Computers can handle enormous amounts of data. This can more accurately represent the real situation. For example, Earth’s climate depends on an enormous number of factors. Climate models can predict how climate will change as certain gases are added to the atmosphere. To test how good a model is, scientists might start a test run at a time in the past. If the model can predict the present it is probably a good model. It is more likely to be accurate when predicting the future. |
SciQ | SciQ-5239 | organic-chemistry
Title: What are the minimal chemical requirements for a food which we all can eat? I've been puzzled by the following though experiment for the past few days:
I want to make my own food from scratch, but I do not know where to start from.
I want to be 100% sure that what I eat will never contains something that can damage my body. For example: If you buy something from the local market you can not be 100% sure that it's safe to eat. (99.9 % maybe... but that's not 100%)
I want to ask you to tell me, how can I make a food that I can eat, or should I say - live on it, for the rest of my life, that's 100% safe, I can control every aspect of it's creation and has many combinations of taste because I love diversity.
Thank you for your time : )
Edit:
Because I realized my question is very broad and indeed is a little... too much scientific I want to close it. But before I do so, here's what I had in mind:
I wanted to take some chemical elements, put them in a jar, run some electricity, heat, whatever through it, filter it, do some additional processing and eat it.
I wanted to know if the stomach can take it, because I was going to eat food that's not hard to digest. Considering the three basic biomolecules used by the body are carbohydrates, lipids, and proteins, you would need to consume these three molecules only. Now we can choose three substances.
Glucose, one of the most basic carbohydrates, is needed for ATP production, so that would be a food choice there.
Any oil or butter will provide lipids.
Protein comes from a variety of sources. Meat is typically though of as the best, but nuts are a pretty good source too.
Since nuts satisfy proteins and lipids, I'd say honey roasted peanuts are the most basic food you could live off of, if you replace pure glucose for the honey.
The following is multiple choice question (with options) to answer.
What essential molecules can be harmful if ingested in large amounts, especially if they contain saturated fatty acids from animal foods? | [
"lipids",
"oxygen",
"helium",
"hydrogen"
] | A | Lipids provide the body with energy and serve other vital functions. One gram of lipids provides 9 Calories of energy. You need to eat small amounts of lipids for good health. However, large amounts can be harmful, especially if they contain saturated fatty acids from animal foods. |
SciQ | SciQ-5240 | species-identification, zoology, marine-biology, invertebrates
Title: Help with jellyfish species identification Our research group (Evolutionary Genetics Group, University of Zurich) has received a letter from a special needs child who has kindly asked us to identify three jellyfish species.
Unfortunately, the letter does not include anything else except three rather low quality cutouts from what I assume is a childrens book. Nobody in our lab has any knowledge about jellyfish taxonomy so any help is greatly appreciated. Be warned that these are just best guesses - as you said yourself, these aren't great images for identification as they appear to be simple drawings:
1) this looks a lot like Aurelia aurita - though the lack of any internal patterning in the drawing makes me think perhaps otherwise.
image source: https://www.leisurepro.com/blog/wp-content/uploads/2017/05/shutterstock_272438348.jpg, https://holidays-majorca.co.uk/wp-content/uploads/2017/01/Aurelia-Aurita-S-300x225.jpg
2) possibly a Turritopsis dohrnii or nutricala - if so then this is the 'immortal' jellyfish. shape of bell is correct and the lappets seem reasonably close, it's just the internal structures that I'm not sure about.
image source: https://www.cairnsholidayspecialists.com.au/shared_resources/media/irukandji-jellyfish-in-far-north-18836_400x322.jpg
3) Very unsure about this one, but potentially a Atolla wyvillei? definitely has some visual features in common and I can't find anything else that's similar. I can also see how an artist would derive that image from this species.
The following is multiple choice question (with options) to answer.
What are two ways cnidarians are able to reproduce? | [
"asexually and sexually",
"spawning and sexual",
"internally and externally",
"mitosis and meiosis"
] | A | General Cnidarian Life Cycle. Cnidarians may reproduce both asexually and sexually. |
SciQ | SciQ-5241 | human-biology
Title: Is urine dirty as soon as it leaves the human body? Human urine is sterile as long as it is in the human body. But is it dirty after leaving the human body? Could you get sick from it, if you drink it or don't wash your hands, for example? It was believed for a long time that urine stored in the urinary bladder is sterile. However, Wolfe et al(1). recently found evidence of bacterial presence in the urine extracted from bladders of healthy women. In an article just published, Hilt et al. found that at least some bacteria found in the bladder of healthy women are viable and can be grown in a laboratory after extraction from the bladder).2 (Paywall). They expect that the same is the case for men.
From the Hilt et al. paper:
Thirty-five different genera and 85 different species were identified
by EQUC. The most prevalent genera isolated were Lactobacillus (15%),
followed by Corynebacterium (14.2%), Streptococcus (11.9%),
Actinomyces (6.9%), and Staphylococcus (6.9%). Other genera commonly
isolated include Aerococcus, Gardnerella, Bifidobacterium, and
Actinobaculum.
Note that these species for the most part (Actinobaculum being one exception, as a possible uropathogen) appear to be part of the normal microbiome (collection of microorganisms) in healthy people in the same way as bacteria inhabit other parts of healthy persons. Additionally, the recovered organisms required special care to achieve growth:
Most of the bacteria isolated required either increased CO2 or
anaerobic conditions for growth, along with prolonged incubation, and
they often were present in numbers below the threshold of detection
used in routine diagnostic urine culture protocols.
The following is multiple choice question (with options) to answer.
In what human organ system would you find live e. coli bacteria? | [
"respiratory system",
"digestive system",
"skeletal system",
"circulatory system"
] | B | E. coli bacteria are anaerobic bacteria that live in the human digestive tract. |
SciQ | SciQ-5242 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
What carries blood away from the heart? | [
"veins",
"arteries",
"pores",
"capillaries"
] | B | Arteries carry blood away from the heart, while veins return blood to the heart. |
SciQ | SciQ-5243 | thermodynamics, statistical-mechanics, differentiation, mathematics
$$
(\text{# components})-(\text{# phases}) + 2 = 2
$$
This is the number of independent variables we need to describe the intensive properties of the mixture. In principle we can choose any two among $\{p, T, V, U, S \cdots\}$. Pressure and temperature is a very convenient pair because we can easily measure them and control them experimentally. However, any other set can be used. The equation you wrote,
$$
dU =
\left(\frac{\partial U}{\partial S}\bigg)_VdS
+
\right(\frac{\partial U}{\partial V}\bigg)_SdV
$$
is correct and is equivalent to
$$
dU = T dS - p dV
$$
Mixtures
The number of independent variables is always determined by Gibbs's rule. In a two-component one-phase system we have three independent variables. We normally choose the first two to come from $p, T, V, U, S \cdots$ and the third one is the mol fraction of one of the two components. Again, this is the number of variables we need to describe the intensive properties of the mixture. We may also write equations for the extensive properties of mixture but I will not go there unless there is a question about it.
The following is multiple choice question (with options) to answer.
What is the most important characteristic of a homogeneous mixture? | [
"uniform composition throughout",
"very reactive",
"nonreactive",
"high density"
] | A | A homogeneous mixture is a mixture in which the composition is uniform throughout the mixture. The salt water described above is homogeneous because the dissolved salt is evenly distributed throughout the entire salt water sample. Often it is easy to confuse a homogeneous mixture with a pure substance because they are both uniform. The difference is that the composition of the substance is always the same. The amount of salt in the salt water can vary from one sample to another. All solutions would be considered homogeneous because the dissolved material is present in the same amount throughout the solution. |
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