source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-2244 | bacteriology, vision
Title: To what extent can bacteria actually see? I found some popular articles (e.g. nbcnews and iflscience) that bacteria can "see," but I highly doubt it's in the same way as people do just from looking at the limitations in the vision of small animals like insects. So what exactly are bacteria capable of "seeing" or what are the limitations of their vision? Simple answer is that many simple organisms, including bacteria, carry light-sensitive molecules. One example is halorhodopsin (not bacterial but archaeic). This is a molecule, light-gated ion pump, that reacts to light, thus allowing organism to react to photons by changing concentration of certain ions inside the cell.
Study from Stanford described similar molecule found in bacteria.
In conclusion, if by "vision" you understand ability to react to light in the visible part of the spectrum, then a lot of organisms possess such ability. However, they lack other crutial parts of human vision.
The following is multiple choice question (with options) to answer.
What type of organism is a bacteria? | [
"single-celled prokaryotic",
"multicellular organism",
"fungi",
"paramecium"
] | A | The single-celled prokaryotic organism otherwise known as bacteria. And all it takes is one to quickly grow, under just the right conditions, into millions and billions. Luckily, we know how to control bacteria when necessary. But bacteria do serve many important purposes. In fact, we could not survive without them. |
SciQ | SciQ-2245 | inorganic-chemistry, redox, combustion
As M. Farooq pointed out a combustion reaction happens quickly, producing heat, and usually light and fire. For example, lets look at combustion reaction of an alkene (a hydrocarbon). If it is a complete combustion, the fire have a blue flame:
$$\ce{C_nH_{2n} + $\frac{3n}{2}$ O2 -> nCO2 + n H2O}$$
If it is a partial combustion, it can have a multiple $\ce{C}$ compounds as products, and have a yellow flame due to presence of elemental $\ce{C}$:
$$\ce{C_nH_{2n} + x O2 -> m C + p CO + $(n-m-p)$CO2 + n H2O}$$
where $x = \frac{2(n-p-m) +p}{2} = \frac{2n-2p-2m +p}{2} = \frac{2n-p-2m)}{2}$. In your reaction would not produce fire and it didn't use either oxygen or other oxidants ($\ce{CuO}$ is not that type of oxidant). It is true that the reaction is a redox reaction.
The following is multiple choice question (with options) to answer.
What chemical element is required for a combustion reaction ? | [
"oxygen",
"carbon",
"nitrogen",
"helium"
] | A | A combustion reaction is a reaction in which a substance reacts with oxygen gas, releasing energy in the form of light and heat. Combustion reactions must involve O 2 as one reactant. The combustion of hydrogen gas produces water vapor. |
SciQ | SciQ-2246 | fluid-dynamics, flow
Title: Where does the air go behind a wind turbine? A wind turbine receives wind at 10m/s, and slows it to 5m/s to generate electricity.
Does this mean that the wind around the turbine must be diverted to allow twice the cross-section area for the exiting wind?
If not, how does the exiting air escape? To preserve continuity of mass flow across the propeller disc, the slower air exiting the disc downwind swells out to produce a slow-moving wake that is wider than the propeller disc itself. This gets mixed up with the surrounding air and eventually the wake dissipates as the air in it speeds up to match the surrounding velocity.
The following is multiple choice question (with options) to answer.
What do wind turbines turn wind energy into? | [
"carbon",
"electricy",
"oxygen",
"hydrogen"
] | B | Wind energy is energy provided by the blowing wind. Wind turbines, like those in Figure above , can turn wind energy into electricity. The wind blows because of differences in heating of Earth’s atmosphere by the sun. There will never be a shortage of wind. |
SciQ | SciQ-2247 | human-biology, biochemistry, metabolism, food
Which seem to go in different, rather contradictory directions.
Also, Studies partially supporting either viewpoint can be found:
Study considering hemoglobin A1c levels
Study considering peak glucose levels
Study considering snacking
Which leaves the non-biologist asking themselves which is the "major effect" (certainly, there will be some truth to each position, but the question is which one(s) got the "main point"), and if there are any other important effects to be considered, hence this broad question here, so I understand, from a biological standpoint, what happens to the carbohydrates when I eat them, so I can conclude for myself how to adapt my diet for "optimal" health. Scope of Answer
The original poster provided ample context for his question, which related to health considerations. It was perhaps for this reason, among others, that the question had not received an answer at the time of writing: questions relating to medical or health advice are off-topic here. However, his actual question is primarily biochemical:
What are the biological differences between the digestion of sugar and
different types of carbs as constituents of different types of food in
humans?
Although this might be answered with a little internet search, I felt it would be hospitable if someone offered him an answer to this — and this only.
Definitions
The basic sugar unit is a mono-saccharide, those of relevance to this question being hexoses or pentoses, having six or five carbon atoms, respectively.
What in non-technical language is called sugar, refers to a specific molecule, sucrose, which is a disaccharide of covalently-bonded glucose and fructose.
What in non-technical language are referred to as dietary carbohydrates generally refers to the storage polysaccharide of plants such as potato and other root vegetables, rice, and other cereal crops used to make bread. This is a homo-polymer composed solely of glucose units.
Summary of the differences in metabolism
Arising from these definitions, the following differences in metabolism emerge:
Different enzymes (amylase for these polysaccharides, sucrase for saccharose) are used to catalyse the hydrolysis of the linkages between the monomeric units.
Absorption in the gut is different for glucose and fructose, as is transport into cells.
The following is multiple choice question (with options) to answer.
A simple sugar such as fructose or glucose is also called a what? | [
"disaccharide",
"carbohydrate",
"monosaccharide",
"galactose"
] | C | A monosaccharide is a simple sugar such as fructose or glucose. Fructose is found in fruits, whereas glucose generally results from the digestion of other carbohydrates. Glucose (C 6 H 12 O 6 ) is used for energy by the cells of most organisms, and is a product of photosynthesis. |
SciQ | SciQ-2248 | evolution, ornithology, palaeontology, herpetology, dinosaurs
A few words about pterosaurs
Along with birds and bats, pterosaurs are the other clade of vertebrates capable of powered, flapping flight. Pterosaurs fall within Reptilia (and Diapsida and Archosauria) along with Dinosauria, which includes birds. There are a lot of other extinct lineages in the tree that are not shown, e.g., ornithodirans that are not dinosaurs and not pterosaurs. Pterosaurs and birds share anatomical features that all reptiles, diapsids, archosaurs, and ornithodirans have, which is how we know that they are more closely related to each other than to other groups, like crocodiles. But their flight structures evolved independently and are anatomically distinct fro one another. So pterosaurs are flying reptiles but not flying dinosaurs.
These images might help you understand the above explanation.
The following is multiple choice question (with options) to answer.
The fossilized skeleton of archaeopteryx looks like that of a dinosaur, but it had what structures modified for flight, a trait associated only with birds among modern animals? | [
"fingers",
"feathers",
"beaks",
"claws"
] | B | fossils and birds, specifically in the structure of the hip and wrist bones, as well as the presence of the wishbone, formed by the fusing of the clavicles. One important fossil of an animal intermediate to dinosaurs and birds is Archaeopteryx, which is from the Jurassic period (Figure 29.33). Archaeopteryx is important in establishing the relationship between birds and dinosaurs, because it is an intermediate fossil, meaning it has characteristics of both dinosaurs and birds. Some scientists propose classifying it as a bird, but others prefer to classify it as a dinosaur. The fossilized skeleton of Archaeopteryx looks like that of a dinosaur, and it had teeth whereas birds do not, but it also had feathers modified for flight, a trait associated only with birds among modern animals. Fossils of older feathered dinosaurs exist, but the feathers do not have the characteristics of flight feathers. |
SciQ | SciQ-2249 | physiology, metabolism, pregnancy
Title: Do pregnancy and breast feeding increase basal metabolic rate? Since pregnant or breastfeeding women have extra nutritional needs, does that mean they have a higher BMR?
Why I thought the conclusion would be sensible: Since BMR is the energy needed to perform body functions (breathing, respiration, homeostasis, digestion, etc), pregnant woman or breastfeeding women, because of their extra 'activity' (due to the presence of the fetus) will have a higher BMR. Basal metabolic rate for a particular organism is determined by the amount of calories that the organism needs for basal metabolic processes (i.e. basal energy demands). Since pregnant and breastfeeding women have increased caloric requirements (i.e. increased energy demands), then that means by definition their basal metabolic rate is increased.
The following is multiple choice question (with options) to answer.
Blood volume increases substantially during pregnancy, so that by childbirth, it exceeds its preconception volume by 30 percent, or approximately what? | [
"1-2 liters",
"3-5 liters",
"2-3 liters",
"0-1 liters"
] | A | Circulatory System Changes Blood volume increases substantially during pregnancy, so that by childbirth, it exceeds its preconception volume by 30 percent, or approximately 1–2 liters. The greater blood volume helps to manage the demands of fetal nourishment and fetal waste removal. In conjunction with increased blood volume, the pulse and blood pressure also rise moderately during pregnancy. As the fetus grows, the uterus compresses underlying pelvic blood vessels, hampering venous return from the legs and pelvic region. As a result, many pregnant women develop varicose veins or hemorrhoids. |
SciQ | SciQ-2250 | hydrology, gis, watershed
Title: To delineate the drainage basin for a lake, would the pour point be the inlet or the outlet? I am interested in the area draining into and affecting a particular lake. Delineating this drainage basin, should I use the lake's inlet or outlet to best capture the relevant drainage basin? I think including the lake is valuable in this exercise, as events on or in the lake itself also affect the lake.
I'd think outlet, but want to double check with you all. To complicate things, most lakes have more than one inlet and outlet. I guess I'd go with the lowest outlet in order to avoid missing any land which may drain into the lake. I think there are a few things to consider. First, a drainage basin is defined as the area upstream of the point to which all precipitation converges. Flow does not converge at the outlet - flow converges at the lake. Outlets don't contain any additional information of the upstream area draining into the lake. This implies that to find the area draining into a lake, you would necessarily have to proceed beginning from each and every inlet.
Here's another way to see this. Approximately 20% of all land drains to lakes with no outlets. These are referred to as endorheic lakes or endorheic basins. Even though there is no outlet, there is absolutely still a definable drainage basin area.
The following is multiple choice question (with options) to answer.
All of the land drained by a river system is called its basin, or what "wet" term? | [
"groundwater",
"wetlands",
"watershed",
"river bank"
] | C | All of the land drained by a river system is called its basin, or watershed. One river system’s basin is separated from another river system’s basin by a divide. The divide is created by the highest points between the two river basins. Precipitation that falls within a river basin always flows toward that river. Precipitation that falls on the other side of the divide flows toward a different river. |
SciQ | SciQ-2251 | 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 does the gizzard in birds contain that allows them to grind food? | [
"swallowed stones",
"acid",
"teeth",
"bile"
] | A | The digestive system of birds is unique, with a gizzard that contains swallowed stones for grinding food. Birds do not have teeth. What do you think the stones do? They help them digest their food. Defining characteristics of modern birds also include:. |
SciQ | SciQ-2252 | newtonian-mechanics, forces, friction, free-body-diagram
Are there some other steps to follow when I know that the object is definitely accelerating in one direction or another?
I don't think so. Let's work through your example using those steps:
Inertial frame of table
The 10kg block (B) has a weight force downwards, $\vec{W_B} = -mg \ \hat{y}$. A is accelerating into B, compressing it until B provides an equal and opposite reaction on A. We'll call A's force on B $\vec{N_{BA}}$ and it points right.
In an inertial frame (e.g. the table's) we skip this step.
Resultant force on B, $\vec{R_B}$ is the vector sum of all forces on B: $\vec{W_B} + \vec{N_{BA}}$, pointing down-right. Resolving $\vec{R}$ into components perpendicular and parallel to the slope yields
\begin{align}
\vec{R}_{parallel} &= \vec{W_B} \\
\vec{R}_{perpendicular} &= \vec{N_{BA}}
\end{align}
The direction of static friction, $\hat{Fr}_{BA}$ is the opposite to $\vec{R_{parallel}}$ : $$\hat{Fr}_{BA} = -\hat{R}_{parallel} = -\hat{W_B} = -(-\hat{y}) = \hat{y}$$
The following is multiple choice question (with options) to answer.
Equal and oppositely directed forces produce what kind of acceleration? | [
"steady acceleration",
"faster acceleration",
"greater acceleration",
"no acceleration"
] | D | An object will not change its state of motion (i. e. , accelerate) unless a net force acts on it. Equal and oppositely directed forces do not produce acceleration. |
SciQ | SciQ-2253 | 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.
Organs are groups of what working together? | [
"bones",
"tendons",
"muscles",
"tissues"
] | D | |
SciQ | SciQ-2254 | ocean, oceanography, wind, waves, ocean-currents
Taking 10 meters (one of the smallest values in mid-latitudes) for the surface and bottom boundary layer thicknesses, that implies that in water depths shallower than 20 m the two boundary layers overlap. In water depths shallower than that, the transport in the surface layer is no longer perpendicular to the wind direction. The momentum input into the water by the wind (wind stress) is affected by the presence of the bottom and it is directly dissipated by bottom friction. The mixing by the wind (and wave breaking near the surf zone) results in additional mixing through the water column and facilitating well-mixed water columns. Under these conditions the wind-induced currents extend all the way to the bottom with the direction of the flow being a function of bottom depth, wind direction, and bottom slope. The presence of wind-induced currents does not preclude the occurrence of flow in the opposite direction of the wind.
A fantastic article summarizing the different flow conditions under different wind and wave fields in shallow water depths is given in Lentz and Fewings (2012). (Reprint)
Additional factors to consider are:
The following is multiple choice question (with options) to answer.
Deep water filling a void caused by surface winds blowing water north and south is known as? | [
"surface current",
"divergence",
"downwelling",
"upwelling"
] | D | Upwelling also takes place along the Equator. Winds blow the surface water north and south. This leaves a void that deep water can upwell into. The nutrients rise to the surface and support a great deal of life in the equatorial oceans. |
SciQ | SciQ-2255 | optics, geometric-optics, telescopes
For demonstration purposes the spectral lines formed on a screen and measuring the wavelength of the light approximately is useful but for reasonable accurate and simple measurements of wavelength the telescope wins out.
The following is multiple choice question (with options) to answer.
What devices do astronomers use to see objects at wavelengths all across the electromagnetic spectrum? | [
"levels",
"spectrographs",
"telescopes",
"microscopes"
] | C | Many extremely interesting objects can’t be seen with the unaided eye. Astronomers use telescopes to see objects at wavelengths all across the electromagnetic spectrum. Some very hot stars emit light primarily at ultraviolet wavelengths. There are extremely hot objects that emit X-rays and even gamma rays. Some very cool stars shine mostly in the infrared light wavelengths. Radio waves come from the faintest, most distant objects. |
SciQ | SciQ-2256 | fluid-dynamics, turbulence
Title: Does the wind gust over the ocean? It is easy to observe that on a windy day, the wind does not blow for several hours at constant speed, then gradually subside. Instead, on a time scale of seconds or tens of seconds, there are stronger gusts of wind followed by lulls.
Presumably this is an effect of turbulence. If so, is this turbulence due to the complicated geometry around me - buildings, trees, hills, etc.? If we removed these features and had wind blowing over a flat ocean surface or a flat plain for hundreds of miles, would we still observe the wind to blow in the same sorts of gusts, or should I expect a more steady flow? I believe you're exactly right: it's the complexity of hills, buildings, trees, asphalt, water, etc that make surface winds complicated. As you go higher in the atmosphere, these surface effects disappear and the winds become much more steady. You can see this in the winds aloft forecasts issued by the FAA for use in aviation:
http://aviationweather.gov/adds/winds/
In the upper left there is a drop-down box allowing you to select altitudes from the surface (SFC) to 48,000 feet (FL480). As you go up in altitude, the relatively chaotic surface winds blend into a much smoother (and faster!) flow.
I assume the effect is similar at sea, given the simpler boundary conditions.
(I admit this does not directly address your question of, "how variable are the winds at sea"? I too am curious to hear an authoritive answer.)
The following is multiple choice question (with options) to answer.
What type of winds blow only over a limited area? | [
"periodic",
"trade",
"local",
"Planetary"
] | C | Local winds are winds that blow over a limited area. They are influenced by local geography. Nearness to an ocean, lake or mountain range can affect local winds. Some examples are found below. |
SciQ | SciQ-2257 | python, numpy, simulation, clustering, matplotlib
''' This Function generates evenly spaced points within the given
GeoDataFrame. The parameter 'spacing' defines the distance between
the points in coordinate units. '''
# Get the bounds of the polygon
minx, miny, maxx, maxy = polygon.bounds
# Now generate the entire grid
x_coords = list(np.arange(np.floor(minx), int(np.ceil(maxx)), spacing))
y_coords = list(np.arange(np.floor(miny), int(np.ceil(maxy)), spacing))
grid = [Point(x) for x in zip(np.meshgrid(x_coords, y_coords)[0].flatten(), np.meshgrid(x_coords, y_coords)[1].flatten())]
# Finally only keep the points within the polygon
list_of_points = [point for point in grid if point.within(polygon)]
return list(zip([point.x for point in list_of_points],[point.y for point in list_of_points]))
The following is multiple choice question (with options) to answer.
What is the term for the spacing of individuals within a population? | [
"suspension",
"equilibrium",
"population density",
"dispersion"
] | D | Ecologists also study how individuals in a population are spread across an environment. This spacing of individuals within a population is called dispersion . Some species may be clumped or clustered ( Figure below ) in an area. Others may be evenly spaced ( Figure below ). Still others may be spaced randomly within an area. The population density and dispersion have an effect on reproduction and population size. What do you think the relationship is between population density, dispersion and size?. |
SciQ | SciQ-2258 | mechanical-engineering, mechanisms, pulleys
Title: Would the reduction ratio of a pulley drive also be applied to a compound pulley? So, a pulley drive with the drive pulley having 1cm of diameter and the driven pulley 10cm of diameter would have something around a 10:1 reduction ratio.
However, I don't know if the same logic would apply to a compound pulley, assuming that the fixed pulley has 10cm of diameter and the movable pulley has 1cm of diameter, on top of that, the winch driving the system has 1cm of diameter. The size of the sheaves doesn't matter to pulley systems.
Pulleys gain advantage by multiplying the constant tension of the rope by the pulley advantage. Gears and belts give an advantage to the torque of the sheaves/gears, not the tension on the belt.
In your example, there is a ~2:1 advantage because there are two ropes pulling the weight up. Both ropes have the same tension, so there is twice the force on the weight, at the expense of half the motion. The belt example gives advantage because the sheaves turn at different rates.
The following is multiple choice question (with options) to answer.
What is the minimum number of pulleys needed for a compound pulley? | [
"2",
"1",
"zero",
"4"
] | A | Single pulleys may be fixed or moveable. Compound pulleys consist of two or more pulleys. |
SciQ | SciQ-2259 | electromagnetism
Title: Direction of magnetic force when magnetic field and velocity are not in same plane We know from Flaming's Right Hand Rule how to calculate the direction of the magnetic force given the magnetic field and the velocity are in the same plane. Now suppose they are not in the same plane. As an example, consider a uniform magnetic field directed perpendicularly onto the screen and a charged particle moving on an inclined plane with angle X with the horizontal. What will be the direction of the magnetic force here?
I think Flaming's Right Hand Rule can only be applied when they are in the same plane because if they are not we cannot adjust our hand so that our fingers point to both of them. But I'm just a beginner in this field, so please correct me if I am wrong. Two vectors (starting or shifted/imagined to start at the same point) always belong to the same plane, usually one plane. If the vectors are $A\to B$ and $A\to C$, just imagine that you connect $B,C$ by a straight line, thus completing a triangle, $ABC$. This triangle is already a clear "seed" of a plane, isn't it? The plane isn't necessary vertical, horizontal, or parallel to any other plane you may have thought about at the beginning but it is a plane nevertheless. There always exists a vector $\vec n$ that is orthogonal to the whole plane or, equivalently, that is orthogonal both to the vectors $A\to B$ and $A\to C$.
This is not really physics but rather geometry for the 10-year-olds.
The following is multiple choice question (with options) to answer.
Magnetic force is always perpendicular to what? | [
"sunlight",
"speed",
"velocity",
"length"
] | C | So does the magnetic force cause circular motion? Magnetic force is always perpendicular to velocity, so that it does no work on the charged particle. The particle’s kinetic energy and speed thus remain constant. The direction of motion is affected, but not the speed. This is typical of uniform circular motion. The simplest case occurs when a charged particle moves perpendicular to a uniform B -field, such as shown in Figure 22.20. (If this takes place in a vacuum, the magnetic field is the dominant factor determining the motion. ) Here, the magnetic force supplies the centripetal force F c = mv 2 / r . Noting that sin θ = 1 , we see that. |
SciQ | SciQ-2260 | is the same) and the area is [pi]/2*(R 2-r 2). The centroid of the planar curve can be determined by a single integration through sweeping the elemental centroid of the curve fragment along variable angle c circularly. Radii of gyration iy, iz. (In other words, if you made the triangle out of cardboard, and put its centroid on your finger, it would balance. The centroid coincides with the center of mass or the center of gravity only if the material of the body is homogenous (density or specific weight is constant throughout the body). Right Click the X field and click the Calculate Geometry. Quick guide to geometry generator symbol layers. The complexity of the finite element approach is hidden. MATH 30 FORMULA SHEET Triangles c a b 45 ¡ 45 ¡. Centroid of semi-circle is at a distance of 4R/3π. The angle between the axis connecting the centroid of the optic disc and the foveal center and the horizon, called the disc–fovea angle (DFA), is an anatomical parameter that has been found to affect the RNFL course toward the optic disc. Also known as the centroid. CLASS X FORMULAE MATHS Median The median for the grouped data can be found by using the formula: Median =!+!!!!"! ×ℎ l = lower limit of the median class. ) A = bt tb3 sin2 /3 12 tb3 cos2 (3 12 tb3 sin2 (3 — Regular polygon with n sides (Origin of axes at centroid) centroid (at center of polygon) number of sides (n 3) = central angle for a side length of a side interior angle (or vertex angle). 5 By integral formula. Even Numbers (Integers) Odd Numbers (Integers) Divisibility Rules. The region bounded by y = 3−e−x. Jumping right in:. If the angle is 180 degrees then the sector is a semi-circle. Hence, the centroid is given by. Circle Sector Calculator This is an example of doing multiple math calculations to come to a series of results. index: click on a letter : A: B: C: D: E: F: G: H: I : J: K: L: M: N: O: P: Q: R: S: T: U:
The following is multiple choice question (with options) to answer.
What is the region in the center back of the eye that is responsible for acute vision? | [
"fovea",
"lens",
"cornea",
"pupil"
] | A | The fovea is the region in the center back of the eye that is responsible for acute vision. The fovea has a high density of cones. When you bring your gaze to an object to examine it intently in bright light, the eyes orient so that the object’s image falls on the fovea. However, when looking at a star in the night sky or other object in dim light, the object can be better viewed by the peripheral vision because it is the rods at the edges of the retina, rather than the cones at the center, that operate better in low light. In humans, cones far outnumber rods in the fovea. |
SciQ | SciQ-2261 | human-genetics
Title: In our 23 chromosome pairs, do the 2 members of the pair have distinct or virtually identical sequences? I understand that we have 46 DNA molecules in the nucleus of our cells, arranged in 23 pairs: 22 autosomal and 1 sex chromosome pairs.
I have read in different sources that the pairs contain nearly identical members, excluding any mutations. I have also read that the pairs contain 1 member we inherited from our mothers and 1 we inherited from our fathers, which are different due to inheritance.
This seems contradictory, given that genealogical companies match up on the differences on these chromosomes.
My understanding was that meiosis creates sperm and egg cells that each carry 23 chromosomes - they are haploids. During the first steps of meiosis that creates the reproductive cells we have a combining of the parent's chromosome pair from their parents to create 4 daughter cells, each independently viable, where the recombination of the chromosome pair has occurred at somewhat predictable spots (for you perhaps :-) ) and that these spots can be related to genes. It is this step that give us our genetic variation between siblings for example. A new person's DNA is partially formed from any one of these highly varied daughter cell possibilities.
Fertilization combines the reproductive cells to produce the 46 chromosome zygote with is again diploid.
I think this understanding supports the second interpretation that our chromosome pairs are not 2 nearly identical DNA molecules but are distinct.
Have I got this right? Is there a missing process or a misunderstanding in my interpretation? Homologous chromosomes (those that are paired up), excluding the sex pair are almost identical in size, shape and genes (members as you called them) present in them.
Genes determine traits and each homologous chromosome controls the same traits. The level of identity of a gene inside a population varies between genes. There are very conserved ones that do not change even between humans and yeast and others that vary alot event inside a species. This changes can be small in sequence length, a simple base (letter) swap or one deletion, and have a huge effect on the traits. This is how chimps and humans are very different but share 98.6% of their genome and humans are very similar and share 99.9% of their genome.
In summary, on the bigger scale homologous chromosomes are very similar (size, shape, traits inside), on the smaller scale homologous chromosomes have small changes that affect greatly.
The following is multiple choice question (with options) to answer.
What is it called when a human has an extra autosome? | [
"polysomy",
"mosaicism",
"monosomy",
"trisomy"
] | D | Trisomy is a state where humans have an extra autosome. That is, they have three of a particular chromosome instead of two. For example, trisomy 18 results from an extra chromosome 18, resulting in 47 total chromosomes. To identify the chromosome number (including an abnormal number), a sample of cells is removed from an individual or developing fetus. Metaphase chromosomes are photographed and a karyotype is produced. A karyotype will display any abnormalities in chromosome number or large chromosomal rearrangements. Trisomy 8, 9, 12, 13, 16, 18, and 21 have been identified in humans. Trisomy 16 is the most common trisomy in humans, occurring in more than 1% of pregnancies. This condition, however, usually results in spontaneous miscarriage in the first trimester. The most common trisomy in viable births is Trisomy 21 . |
SciQ | SciQ-2262 | organic-chemistry, alcohols
Title: Does ethanol react with potassium to form potassium ethanolate and hydrogen gas? I'm finding information in Google with the keyword (C2H5OH + K) to find the reaction between $\ce{C2H5OH}$ and $\ce{K}$ and found very little information about it. Just 2-3 related results with contradictory pieces of information.
The first one gave
$$
\ce{K + C2H5OH -> KOH + C2H5},
$$
the second one gave
$$
\ce{2C2H5OH + 2K -> 2C2H5OK + H2},
$$
and the third one gave
$$
\ce{C2H5OH + KOH -> C2H5OK + H2O}
$$
There are no trusted public sources so I'm very baffled. I think that $\ce{C2H5OH}$ will react with $\ce{K}$ to form $\ce{C2H5OK}$ because it looks like the reaction with $\ce{Na}$. But I'm not sure and just want to find a trusted source. Can anyone confirm the true result for this reaction? You can view water as the simplest alcohol, and indeed, water reacts with all of the Group 1 metals to form hydrogen gas and the corresponding metal hydroxide according to the following equation
$\ce{2M + 2HOH -> 2MOH + H2}$
where $\ce{M}$ is the metal.
The same reaction occurs with simple alcohols to produce the corresponding metal alkoxide and hydrogen gas
$\ce{2M + 2ROH -> 2MOR + H2}$
As you increase the hydrocarbon portion of the alcohol, or reduce accessibility to the $\ce{OH}$ portion of the alcohol (e.g. make the alcohol less like water), you slow down the rate of the reaction.
Here is a nice link that compares and discusses the relative reactivities of the Group 1 metals with water.
The following is multiple choice question (with options) to answer.
Carboxylic acids can form what with alcohols? | [
"aldehydes",
"lipids",
"ketones",
"esters"
] | D | Carboxylic acids can form esters with alcohols. |
SciQ | SciQ-2263 | spectroscopy, electronic-configuration, materials, semiconductors
Title: Is the photoelectric effect possible for semiconductors? Is the photoelectric effect possible for semiconductors?
I imagine that this might be, if possible, a two-photon process: excitation of an electron from a filled to conductance band, and then on to ejection. Is anyone familiar with such materials, or even whether this is possible?
I can't readily think of a theoretical reason against it. Two-photon events are often less likely than one-photon, however I could imagine irradiation by a laser of bandwith covering both the band-gap wavelength and that necessary for ejection would do it.
If it does indeed happen, I'd be glad to hear a short summary of how it differs from the photoelectric effect of metals. Given that Jaques Pankove's excellent book on 'Optical Processes in Semiconductors' devotes chapter 13 to 'Photoelectric Emission', you can rest assured that the photoelectric effect is alive and well in semiconductors. While somewhat more complex than emission from simple metals, there is no need for two-photon processes. The 'tricky' part is that you have to look at where the electron states are, and then how much energy is needed to take it out of the semiconductor.
The work function is the energy difference from the Fermi energy to the vacuum level. There may not be any states at the Fermi energy though.
The electron affinity is the energy difference from the bottom of the conduction band to the vacuum level.
One has to take the band structure into account, since direct and indirect transitions will likely have different energies required.
Also, surface band bending may make interpretation of experimental results more difficult. Again, perusing Pankove may prove useful.
The following is multiple choice question (with options) to answer.
What are the two types of semiconductors? | [
"n-type and p-type",
"a-type and b-type",
"n-type and m-type",
"o-type and p-type"
] | A | Electronic components consist of semiconductors, which are solid crystals consisting mainly of silicon. There are two types of semiconductors, called n-type and p-type. |
SciQ | SciQ-2264 | thermodynamics, thermal-radiation, physical-chemistry, biophysics, solar-cells
Title: Extreme life - energy source for living tens of kilometers underground? Living cells were found up to at least 12 miles underground (article), and in other extreme places (BBC survey article), for which beside the problem of just surviving in such extreme conditions, a basic physics thermodynamical question is: what energy source it is based on?
And in such extreme temperatures there is needed a lot of energy just to fight 2nd law of thermodynamics - actively protect cell's structures against thermalization.
Such energy source needs to be relatively stable for past billions of years - what seems to exclude chemical energy sources (?)
One stable energy source in such high temperatures are thermal IR photons, and thermophotovoltaics is generally able to harvest energy from them. However, cell living in such extreme conditions would rather have the same temperature, hence 2nd law seem to forbid harvesting energy from such IR photons? Chemical.
As the Wikipedia entry on Lithoautotroph puts it (restricting ourselves to the deep underground forms):
derives energy from reduced compounds of mineral origin
which they do through inorganic oxidation (see, e.g., Lessons from the Genome of a Lithoautotroph: Making Biomass from Almost Nothing) or other reactions, such as the reaction of formate (HCOO-) and water, to form bicarbonate and hydrogen (Extremophile microbes survive only on energy from formate oxidation).
The following is multiple choice question (with options) to answer.
What is the term for organisms that live in extremely hot environments? | [
"exothermic",
"thermophiles",
"hydrophylic",
"thermophobes"
] | B | The thermophiles live in extremely hot environments. For example, they can grow in hot springs, geysers, and near volcanoes. Unlike other organisms, they can thrive in temperatures near 100°C, the boiling point of water!. |
SciQ | SciQ-2265 | blood-circulation, kidney
Title: Why does glomerulus don't allow white blood cells to leave? The glomerulus in nephrons are just a ball of capillaries, so why can't it allow the white blood cells to squeeze though the epithelial cells into Bowman's capsule just like the formation of tissue fluid in other capillaries by filtration? Red blood cells, White blood cells, platelets and proteins with large molecular weight cannot pass through the podocyte and fenestrations in glomerular capillary, but small molecules like water, salts and sugars are filtered out as part of urine.
As these cells and proteins are large to cross through this filter, they remain in the capillary and create osmotic pressure within the capillary. Bowman’s space has osmotic pressure approximately zero. So, only hydrostatic pressure works in this state and help in movement of fluid across the capillary wall.
Via: https://opentextbc.ca/anatomyandphysiology/chapter/25-5-physiology-of-urine-formation/
The following is multiple choice question (with options) to answer.
What is a capillary bed that filters blood principally based on particle size? | [
"glomerulus",
"vein",
"plexus",
"buds"
] | A | 25.4 Microscopic Anatomy of the Kidney The functional unit of the kidney, the nephron, consists of the renal corpuscle, PCT, loop of Henle, and DCT. Cortical nephrons have short loops of Henle, whereas juxtamedullary nephrons have long loops of Henle extending into the medulla. About 15 percent of nephrons are juxtamedullary. The glomerulus is a capillary bed that filters blood principally based on particle size. The filtrate is captured by Bowman’s capsule and directed to the PCT. A filtration membrane is formed by the fused basement membranes of the podocytes and the capillary endothelial cells that they embrace. Contractile mesangial cells further perform a role in regulating the rate at which the blood is filtered. Specialized cells in the JGA produce paracrine signals to regulate blood flow and filtration rates of the glomerulus. Other JGA cells produce the enzyme renin, which plays a central role in blood pressure regulation. The filtrate enters the PCT where absorption and secretion of several substances occur. The descending and ascending limbs of the loop of Henle consist of thick and thin segments. Absorption and secretion continue in the DCT but to a lesser extent than in the PCT. Each collecting duct collects forming urine from several nephrons and responds to the posterior pituitary hormone ADH by inserting aquaporin water channels into the cell membrane to fine tune water recovery. |
SciQ | SciQ-2266 | water, metal
Title: What would be the reaction if melting iron is put in normal water? What would be the reaction if melting iron is put in normal water? Will water be chemically changed? Unlike the other metals we usually see in the reactivity series, such as calcium, magnesium, zinc, etc., hot iron does not form iron hydroxide, instead it forms iron oxide. The reaction is:
$\ce{3Fe + 4H2O <=> FeO.Fe2O3 + 4H2}$
Iron is similar to magnesium and zinc as they react only with hot water (not cold water). But the reaction of iron with hot water is less vigorous than that of magnesium and zinc.
The following is multiple choice question (with options) to answer.
Minerals form when they precipitate from hot fluids that have done what? | [
"dried out",
"heated up",
"cooled down",
"accelerated down"
] | C | Minerals form when they precipitate from hot fluids that have cooled down. |
SciQ | SciQ-2267 | analytical-chemistry, spectrophotometry
While IR and microwave spectroscopies share some of the above advantages, they are far less suited for analysis of solutes, as the solvent absorbance is often much more likely to confound measurements. Further, the instrumentation and sample preparation are generally much more involved.
Mass spec is terrifically expensive and complicated, is an intrinsically destructive method, and is less well suited for direct quantitation since there is no way to know a priori what fraction of the injected sample is actually making it to the detector and thus careful calibration is required.
NMR, though non-destructive, also requires quite expensive equipment that is complicated to operate properly, and interpretation of the spectra requires quite a bit of practice.
I know too little about EPR/ESR, EXAFS, XANES, and others to comment on them here. I believe the above strengths hold in comparison to those methods as well, however.
$^*$ Technically, MS is mass spectrometry, not spectroscopy, since the measurement is of discrete ion impacts on a detector, as opposed to absorbance of portions of the electromagnetic spectrum by a detector.
The following is multiple choice question (with options) to answer.
Mass spectrometry today is used extensively in chemistry and biology laboratories to identify chemical and biological substances according to their ratios of what? | [
"mass to volume",
"ph to charge",
"mass-to-charge",
"volume to charge"
] | C | Mass spectrometry today is used extensively in chemistry and biology laboratories to identify chemical and biological substances according to their mass-to-charge ratios. In medicine, mass spectrometers are used to measure the concentration of isotopes used as tracers. Usually, biological molecules such as proteins are very large, so they are broken down into smaller fragments before analyzing. Recently, large virus particles have been analyzed as a whole on mass spectrometers. Sometimes a gas chromatograph or high-performance liquid chromatograph provides an initial separation of the large molecules, which are then input into the mass spectrometer. |
SciQ | SciQ-2268 | immunology, bacteriology
Title: How do infectious bacteria determine when their numbers are high enough to attack a host? When you get sick, you generally don't contract enough bacteria at once for them to succeed in battling your immune system, right? Their numbers must gradually increase in the host's body before they know that they can attack. How does that work? I think the current answer to this for bacterial infections is quorum sensing. Quorum sensing is a signalling pathway in bacteria which senses a molecule that the bacteria themselves secrete. When the concentration of the quorum signal reaches a certain level, the bacteria interpret this as their population density reaching some threshhold.
Bacteria are always around - even infectious Staph, as described in the other answer, the bacteria are always being cleared out by the immune system, but when they find the right place where they can get critical mass, they dig in, form a biofilm and secrete toxins, which can help them divide more successfully.
This is a description of the process from a paper on Staph infection, a common bacterial infection in humans.
The following is multiple choice question (with options) to answer.
What helps treat bacterial infections in people? | [
"rest",
"antibiotic drugs",
"vaccines",
"respiratory drugs"
] | B | Bacteria in food or water usually can be killed by heating it to a high temperature. Generally, this temperature is at least 71 °C (160 °F). Bacteria on surfaces such as countertops and floors can be killed with disinfectants, such as chlorine bleach. Bacterial infections in people can be treated with antibiotic drugs . These drugs kill bacteria and may quickly cure the disease. If you've ever had strep throat, you were probably prescribed an antibiotic to treat it. |
SciQ | SciQ-2269 | periodic-trends, ionization-energy
Title: Ionization energy of neon vs its cationic counterpart
Which requires more ionization energy: $\ce{Ne}$ or $\ce{Ne+}?$
It seems to me like it should be neon because of noble gas configuration, but the answer given is $\ce{Ne+}.$ Does this anything to do with size of the atom shrinking?
Is this because cationic counterparts always have more ionization energy than their neutral counterparts because it becomes successively more difficult to remove electrons from atoms on successive removals?
Does this anything to do with size of the atom shrinking?
Yes, precisely; this is one way of putting it. Another way is to say that because one electron has been removed, the remaining electrons are less shielded from the nuclear charge: therefore, the effective nuclear charge increases, and the remaining electrons are harder to remove.
Is this because cationic counterparts always have more ionization energy than their neutral counterparts because it becomes successively more difficult to remove electrons from atoms on successive removals?
Yes. This is true for every element in the Periodic Table, with no exceptions, and it doesn't matter what the electronic configuration is.
If all else were equal, then it would indeed be harder to remove an electron from a noble gas configuration than a non-noble gas configuration. However, that is a very big if! Between $\ce{Ne}$ and $\ce{Ne+}$, the electron configurations are indeed different, but all else is not equal: as discussed previously, the effective nuclear charge in $\ce{Ne+}$ is greater than that in $\ce{Ne}$.
The following is multiple choice question (with options) to answer.
Which has more electrons, neon or fluorine? | [
"the same",
"neither",
"neon",
"fluorine"
] | C | Although neon has just one more electron than fluorine in its outer energy level, that one electron makes a huge difference. Fluorine needs one more electron to fill its outer energy level in order to have the most stable arrangement of electrons. Therefore, fluorine readily accepts an electron from any element that is equally “eager” to give one up, such as the metal lithium or sodium. As a result, fluorine is highly reactive. In fact, reactions with fluorine are often explosive, as you can see in the URL below. Neon, on the other hand, already has a full outer energy level. It is already very stable and never reacts with other elements. It neither accepts nor gives up electrons. Neon doesn’t even react with fluorine, which reacts with all other elements except helium. |
SciQ | SciQ-2270 | thermodynamics
I really doubt that, given all the dynamic things happening at the Earth's surface, where one downhill process drives an uphill process. Such as the huge electric potential generated in a thunderstorm when larger ice particles fall and smack into small ice particles being lifted in the updraft, resulting in lightning. I don't think of the generation of electric potentials as being particularly "spontaneous", but I also don't know if the Gibbs free energy function really applies to this case. In this example and others I can think of (such as generation of wind and water power), it is exergy that is increasing, i.e. available work. I would tend to think of a process that increases the exergy of a system as non-spontaneous, but I don't know if it is used that way by physicists. The important distinction is that, in order for a non-spontaneous process to occur, there has to be energy input to the system. So, in your example, the system is just the electrolytic cell; in order for electrolysis to occur, energy must enter the system from outside, e.g. the battery. If you were to consider the cell and the battery as your system, then it would be a spontaneous process.
The question of intelligent agents is irrelevant. Intelligent or not, we still must obey the 2nd law. Consider the edge cases: for your example, what if humans created a machine that automatically does electrolysis? What if someone accidentally knocks a battery into a bowl of salt water and electrolysis occurs? What if an animal did that? You can even concoct a purely natural example of electrolysis occurring- what if lightning strikes the ocean in just the right way?
The following is multiple choice question (with options) to answer.
What kind of process occurs naturally under certain conditions, unlike its opposite, which will not take place unless it is “driven” by the continual input of energy from an external source? | [
"spontaneous process",
"noticeable process",
"controlled process",
"activation process"
] | A | Spontaneous and Nonspontaneous Processes Processes have a natural tendency to occur in one direction under a given set of conditions. Water will naturally flow downhill, but uphill flow requires outside intervention such as the use of a pump. Iron exposed to the earth’s atmosphere will corrode, but rust is not converted to iron without intentional chemical treatment. A spontaneous process is one that occurs naturally under certain conditions. A nonspontaneous process, on the other hand, will not take place unless it is “driven” by the continual input of energy from an external source. A process that is spontaneous in one direction under a particular set of conditions is nonspontaneous in the reverse direction. At room temperature and typical atmospheric pressure, for example, ice will spontaneously melt, but water will not spontaneously freeze. The spontaneity of a process is not correlated to the speed of the process. A spontaneous change may be so rapid that it is essentially instantaneous or so slow that it cannot be observed over any practical period of time. To illustrate this concept, consider the decay of radioactive isotopes, a topic more thoroughly treated in the chapter on nuclear chemistry. Radioactive decay is by definition a spontaneous process in which the nuclei of unstable isotopes emit radiation as they are converted to more stable nuclei. All the decay processes occur spontaneously, but the rates at which different isotopes decay vary widely. Technetium-99m is a popular radioisotope for medical imaging studies that undergoes relatively rapid decay and exhibits a half-life of about six hours. Uranium-238 is the most abundant isotope of uranium, and its decay occurs much more slowly, exhibiting a half-life of more than four billion years (Figure 16.2). |
SciQ | SciQ-2271 | geology, mineralogy, minerals, weathering
To me, supergene has a specific meaning, it may be part of the weathering process in some locations, but weathering involves the breaking down of rocks due to: reactions with atmospheric gasses, water (usually rain), changes brought on by plants, bacteria wind and temperature.
My suggestion to use the term weathering or weathered.
The following is multiple choice question (with options) to answer.
Gradual degradation of a material due to its exposure to the environment is known as what? | [
"erosion",
"corrosion",
"destruction",
"metabolism"
] | B | The driving force to combine with nonmetals to create ionic compounds varies quite a bit between different metals. Some pure metals, like cesium and potassium, are so eager to react that they must be stored under oil to avoid an immediate reaction with the oxygen present in air. Others, like platinum and gold, are stable enough that they can be found in nature as pure metals rather than as the cationic portion of an ionic compound. Gradual degradation of a material due to its exposure to the environment is known as corrosion . Metals like gold and platinum are unusually resistant to corrosion, which makes them especially valuable for both structural and decorative purposes. |
SciQ | SciQ-2272 | geometry, volume
It turns out that the only m-volume that allows a definition simultaneously satisfying all these properties is the 4-volume, which is the one you asked about. It is not self-evident that there is such a definition or what it should be. For a parallelepiped with edges given by vectors $a$, $b$, $c$, and $d$, the 4-volume is defined by
$V=\epsilon_{ijkl}a^ib^jc^kd^l,$
where $\epsilon$ is the Levi-Civita tensor. If the Levi-Civita tensor is defined in one set of coordinates, then its value in other sets of coordinates can be determined by the usual transformation law for a 4-tensor. It does turn out that if you define the Levi-Civita tensor with elements $\pm1$ in one set of Minkowski coordinates, it also has that form after you boost to a different set of Minkowski coordinates. However, this is by no means an obvious property. In general, we have $\epsilon_{ijkl}=\sqrt{|\operatorname{det}g|}$, where $g$ is the metric.
As an example suggested by PM2Ring in a comment, suppose we have a $1\ \text{m}^3$ box, and it exists for 1 s. Since we're working in SI units, the metric is $c^2dt^2-dx^2-...$,. The determinant of the metric is is $-c^2$, and the volume is $3\times10^8\ \text{m}^4$.
The following is multiple choice question (with options) to answer.
What is the name for a matter that has a fixed volume and a fixed shape? | [
"liquid",
"solid",
"gas",
"stable"
] | B | Ice is an example of solid matter. A solid is matter that has a fixed volume and a fixed shape. Figure below shows examples of matter that are usually solids under Earth conditions. In the figure, salt and cellulose are examples of crystalline solids. The particles of crystalline solids are arranged in a regular repeating pattern. The steaks and candle wax are examples of amorphous ("shapeless") solids. Their particles have no definite pattern. |
SciQ | SciQ-2273 | cell-biology
Title: How do we look inside the cell? My sister is in 9th grade biology and her teacher avoided answering the question of how we actually study the inside of a cell. I haven't taken biology in a while but I'd like to give her an answer.
Can someone roughly summarize how we actually learn about what goes on inside a cell? Just mentioning a few of the most common or used techniques would be fine.
Note: I hope this isn't a bad question. It's a bit vague. But I didn't want to leave her without a decent answer. Techniques to look at whole cells are: Light microscopy (cells, large organelles), electron microscopy (detailed analysis of subcellular structures and even proteins) and confocal fluorescence miscroscopy (look at particular cellular planes, reconstruct 3D images).
And of course you can analyze the insides by Biochemistry by breaking the cell membranes and look at individual proteins and DNA/RNA by extraction and electrophoresis followed by Western / Northern / Southern blotting, or isolate organelles by centrifugation.
It is a broad question, and I just gave the most obvious examples of techniques (not anywhere near exhaustive). By googling the bold-out terms you may provide some details to your sis.
The following is multiple choice question (with options) to answer.
German doctor rudolf virchow first discovered what process when studying living cells under a microscope? | [
"radiation",
"photosynthesis",
"cell division",
"evolution"
] | C | Around 1850, a German doctor named Rudolf Virchow was observing living cells under a microscope. As he was watching, one of the cells happened to divide. Figure below shows a cell dividing, like the cell observed by Virchow. This was an “aha” moment for Virchow. He realized that living cells produce new cells by dividing. This was evidence that cells arise from other cells. |
SciQ | SciQ-2274 | geology, earth-history, paleontology, stratigraphy, mass-extinction
Why did this idea develop only in the 1980s? It was known since the 19th century that extinctions had occurred. Even the stratigraphic time is divided into units constrained by different fauna found in the fossil records. What was it that made the change from a "gradualist" perspective of things to the "catastrophic" point of view? The idea of mass extinction is not that recent actually: Cuvier (1798), Buckland (1823) and d'Orbigny (1851) for instance were already talking about global catastrophes in earth history, linked to extinctions. But during the same period, Brocchi (1814) and Lyell (1832) proposed that extinctions of species occurred individually and were a gradual process (either only linked to an intrinsic taxa longevity for Brocchi, or variations in the environment for Lyell). Darwin, following Lyell, also thought that extinctions were gradual and not catastrophic. He also noted the fact that hiatuses in the fossil record or artificial concentration in some strata could show apparent extinction event.
The issue with mass extinction is that to demonstrate their existence you need to be able to demonstrate extinction synchronicity and quantify the amount of species going extinct (to show that it is more than just background noise).
Demonstrating the synchronicity of one mass extinction is what Alvarez et al. 1980 managed to do thanks to the Iridium layer at the K/Pg boundary. More generally, the possibility of correlating extinctions precisely is something that evolved in par with the evolution of stratigraphic tools, and the 1970-1980s is the period during which high-resolution stratigraphic methods arose (chronostratigraphy, magnetostratigraphy, stable isotope stratigraphy for instance).
Quantifying mass extinction is what Jack Sepkoski did with his compendium of marine invertebrates (see Sepkoski 1978, 1979; Raup & Sepkoski 1982, etc.). Today, the PbDb (PaleoBiology DataBase) is the project which focusses on that specific issue (see for instance Alroy et al. 2001). It still remains today the main hurdle in studying mass extinctions.
Alroy, J. et al., 2001. Effects of sampling standardization on estimates of Phanerozoic marine diversification. PNAS, 98(11): 6261-6266.
The following is multiple choice question (with options) to answer.
What was the first mass extinction that occurred on earth? | [
"proterozoic mass extinction",
"late Devonian mass extinction",
"precambrian mass extinction",
"paleozoic mass extinction"
] | C | At the end of the Precambrian, a mass extinction occurred. In a mass extinction , the majority of species die out. The Precambrian mass extinction was the first of six mass extinctions that occurred on Earth. It’s not certain what caused this first mass extinction. Changes in Earth’s geology and climate were no doubt involved. |
SciQ | SciQ-2275 | botany, plant-physiology
Title: Are fairy rings documented as a growth pattern in ferns? I planted an Onoclea sensibilis, a single plant, in my garden. After the first season, there was signs that a fairy ring was forming. A few years later it was mostly complete, but then was obscured in the following years by the growth of the next generation ferns on the ring.
I have not seen any documentation in my field guides that sensibilis or any other fern creates a fairy ring.
I would believe that the fairy rings would be rare in the field.
Where would I find documentation on fern fairy rings? As this was the only result I could find about Onoclea sensibilis fern ring I wanted to add a reference to a wild fern ring I found of the species. This was found in the fall, 2022, in WV during a hike. I do not know the age of the patch of ferns.
This response, I hope, should act as an answer to the question for documentation of a sensibilis fern fairy ring.
As reference and showing ownership of copyright, I originally posted this image on instagram here: https://www.instagram.com/p/CiTl_VvjXq5/
The following is multiple choice question (with options) to answer.
What type of habitat do ferns need to grow? | [
"dry",
"elevated",
"moist",
"cold"
] | C | Ferns 11,000 They have large leaves in fronds. They have stiff stems, so they are tall growing; some are trees. They reproduce with spores. They need a moist habitat. |
SciQ | SciQ-2276 | genetics, cell-biology, gene-expression, cell-cycle
Title: Why don't cells double gene expression after S-Phase? In the cell cycle (G1-S-G2-M), all of the DNA is replicated during the S or Synthesis stage. The cell may then spend some considerable time in the G2 phase before splitting in the M phase. Since there is double the amount of genetic material in the G2 phase, what mechanism if any, prevents the amount of gene expression from also doubling? When the double strand is duplicated, the old strand (or, in other terms, the template) is methylated : this modification is enough to prevent the bind by the RNApol system and, by so, the transcription.
By methylation, DNA-repair systems are able to detect which is the newer strand, to discover and fix replication errors.
Here you can find additional infos
The following is multiple choice question (with options) to answer.
G2 and s are phases in what process that is important in cell division? | [
"mitosis",
"cytokinesis",
"tissues",
"osmosis"
] | A | DNA and the associated proteins, as well as accumulating enough energy reserves to complete the task of replicating each chromosome in the nucleus. S Phase Throughout interphase, nuclear DNA remains in a semi-condensed chromatin configuration. In the S phase (synthesis phase), DNA replication results in the formation of two identical copies of each chromosome—sister chromatids—that are firmly attached at the centromere region. At this stage, each chromosome is made of two sister chromatids and is a duplicated chromosome. The centrosome is duplicated during the S phase. The two centrosomes will give rise to the mitotic spindle, the apparatus that orchestrates the movement of chromosomes during mitosis. The centrosome consists of a pair of rod-like centrioles at right angles to each other. Centrioles help organize cell division. Centrioles are not present in the centrosomes of many eukaryotic species, such as plants and most fungi. G2 Phase In the G2 phase, or second gap, the cell replenishes its energy stores and synthesizes the proteins necessary for chromosome manipulation. Some cell organelles are duplicated, and the cytoskeleton is dismantled to provide resources for the mitotic spindle. There may be additional cell growth during G2. The final preparations for the mitotic phase must be completed before the cell is able to enter the first stage of mitosis. |
SciQ | SciQ-2277 | thermodynamics, energy, photons, astronomy, sun
Title: Do photons lose energy while travelling through space? Or why are planets closer to the sun warmer? My train of thought was the following:
The Earth orbiting the Sun is at times 5 million kilometers closer to it than others, but this is almost irrelevant to the seasons.
Instead, the temperature difference between seasons is due to the attack angle of the rays, so basically the amount of atmosphere they have to pass through.
Actually, it makes sense, heat comes from the photons that collide with the surface of the earth (and a bit with the atmosphere) and gets reflected, and there's nothing between the earth and the sun that would make a photon lose energy over a 5 million km travel on vacuum. Or is it? (Note I'm not wondering about the possible lose of energy related to the redshift of the expanding universe.)
Which made me wonder…
So why then are the planets closer to the sun warmer? It seems silly, the closer you are to a heat source, the warmer it feels, but that's because of the dispersion of the heat in the medium, right? If there's no medium, what dissipates the energy? The reason being closer to a heat source makes you warmer is the inverse square law. Think of it this way: If you have a $1~\mathrm{m}^2$ piece of material facing the Sun and located at Mercury's orbit, it will be quite hot. What does the shadow of this square look like at Earth's orbit (about $2.5$ times further away than Mercury)? Well, it will be $2.5$ times bigger in both directions, covering about $6~\mathrm{m}^2$. So the same amount of power can be delivered either to $1~\mathrm{m}^2$ on Mercury or to $6~\mathrm{m}^2$ on Earth. Every square meter of Earth gets about $6$ times less Solar power than every square meter on Mercury. The light is not losing energy to the surrounding medium, even if the medium exists.
The following is multiple choice question (with options) to answer.
Solar energy travels in what? | [
"ions",
"neurons",
"photons",
"electrons"
] | C | Solar energy travels in photons. Photons travel in waves, which make up electromagnetic radiation. |
SciQ | SciQ-2278 | ros, rostopic, ros-indigo, joint-state
I know this is documented somewhere more officially - I'll try to get a link.
As gvdhoorn mentioned, I made a mistake here, either the gripper joints are there, or the other joints are there.
This is expected behavior. See this Wiki for the reference.
The following is multiple choice question (with options) to answer.
What type of joint is the knee joint? | [
"ball joint",
"hinge joint",
"condyloid joint",
"pivot joint"
] | B | Hinge Joint. The knee joint is a hinge joint. Like a door hinge, a hinge joint allows backward and forward movement. |
SciQ | SciQ-2279 | physical-chemistry, thermodynamics, gas-laws, equation-of-state
I am confused by this argument-- what exactly is the definition of 'volume' here? They seem to be saying that it is the empty space around the gas molecules, but it seems to me that volume should be defined as the space 'taken up' by the gas. Why should the space taken up by the particles themselves be subtracted? This isn't done for solids or liquids as far as I know.
These thoughts have also made me realize that I'm not quite sure what it means for a gas to 'take up' space. Does anyone have a rigorous definition of gas volume?
EDIT: The exchange with Chris in comments has raised further questions. It now seems to me that the $V-nb$ correction actually accounts for repulsions rather than attractions. I think I was incorrect in thinking that the $V-nb$ correction dominated at intermediate volumes and $a(n/V)^2$ at low volumes. If $V-nb$ is for repulsions, then it should dominate at low volumes, but I can't tell from the equation which correction will actually be dominant. Also I am now wondering whether it even makes sense to connect one correction with repulsions and one with attractions.
EDIT: Follow-up questions for F'x:
- I thought that 'density' meant mass/volume. Is the use of it to represent the inverse of molar volume (as you have used it) common?
- Where is the phase-transition in the red van der Waals curve?
- I am still a little unclear on gas volume. Are the 'volume available to the gas' and 'volume of the gas' the same? You say it's the same as the shape of the container, but aren't we subtracting the volume of the actual gas particles from that? The $V$ term represents the volume of the gas, correct? And $V-nb$ represents the 'volume available to the gas'. The van der Waals equation can't be derived from first principles. It is an ad-hoc formula. There is a "derivation" in statistical mechanics from a partition function that is engineered to give the right answer. It also cannot be derived from first principles.
The following is multiple choice question (with options) to answer.
What state of matter takes the shape and volume of whatever container it occupies? | [
"mixture",
"liquid",
"gas",
"solid"
] | C | |
SciQ | SciQ-2280 | biochemistry, dna, protocol
Title: Concentration of DNA by isopropanol I have read that DNA can be concentrated by addition of isopropanol.
What does "concentrated" mean? What does isopropanol do on a molecular level to concentrate DNA? What you are asking about is the precipitation of DNA (or any other nucleic acid) by isopropanol (or ethanol, which is more common). To do so, you add salt (usually slightly acidic sodium acetate) which makes sure that the phosphate backbone of the DNA is saturated with sodium ions to make it less soluble. Then you add the organic solvent, which precipitates the DNA from the solution by changing the polarity of the solution. This makes the ions form salts and the DNA precipites. The principle is explained in the Wikipedia article on ethanol precipitation. Finally the solution is centrifuged to collect the DNA at the bottom of your reaction tube and to be able to take off the supernatant.
The following is multiple choice question (with options) to answer.
What is a high concentrated solution typically referred to as? | [
"share solution",
"stock solution",
"percent solution",
"saline sollution"
] | B | Another common dilution problem involves deciding how much of a highly concentrated solution is requires to make a desired quantity of solution of lesser concentration. The highly concentrated solution is typically referred to as the stock solution. |
SciQ | SciQ-2281 | human-anatomy
[source]
And now, follow along with your own hand!
finger (4 DOF): each finger has 2 interphalangeal joints between the distal, middle and proximal phalanges that allow for flexion/extension (2 DOF); each finger also has a metacarpophalangeal joint between the proximal phalanx and the metacarpal that allows for flexion/extension as well as abduction/adduction (2 DOF)
thumb (5 DOF): an interphalangeal joint between the distal and proximal phalanges allowing flexion/extension (1 DOF); a metacarpophalangeal joint between the proximal phalanx and metacarpal allowing flexion/extension and abduction/adduction (2 DOF); a carpometacarpal joint between the metacarpal and trapezium allowing flexion/extension and abduction/adduction (2 DOF)
wrist (6 DOF): between the carpals and radius allowing flexion/extension, abduction/adduction and supination/pronation (3 DOF); I think when the authors refer to translation of the wrist, they are simply saying that hand can be moved in all planes of 3D space (ie up/down, side to side, forward/backward - 3 DOF)
Since we have 4 fingers, they give 16 DOF. Adding the 5 DOF of the thumb and 6 of the wrist, we get 27. Please nobody question my reasoning. Thank you.
The following is multiple choice question (with options) to answer.
The joints that are between the bones that make up the skull are what kind of joints? | [
"Interphalangeal joints",
"Ball and socket joints",
"immovable joints",
"Gliding ioints"
] | C | Immovable joints do not allow the bones to move at all. In these joints, the bones are fused together by very tough collagen. Examples of immovable joints include the joints between bones of the skull. You can see them in Figure below . |
SciQ | SciQ-2282 | geology, mineralogy, minerals, weathering
To me, supergene has a specific meaning, it may be part of the weathering process in some locations, but weathering involves the breaking down of rocks due to: reactions with atmospheric gasses, water (usually rain), changes brought on by plants, bacteria wind and temperature.
My suggestion to use the term weathering or weathered.
The following is multiple choice question (with options) to answer.
What weather phenomenon increases the rate of weathering in rock and soil? | [
"temperature",
"rainfall",
"landslide",
"earthquake"
] | B | Rainfall in an area is important because it influences the rate of weathering. More rain means that more rainwater passes through the soil. The rainwater reacts chemically with the particles. The top layers of soil are in contact with the freshest water, so reactions are greatest there. High rainfall increases the amount of rock that experiences chemical reactions. High rainfall may also carry material away. This means that new surfaces are exposed. This increases the rate of weathering. |
SciQ | SciQ-2283 | planets, definition, asteroids
Title: What is the current status of Pluto? Pluto has been designated a planet in our solar system for years (ever since it was discovered in the last century), but in 2006 it was demoted.
What caused this decision? And is there a chance that it could be reversed?
Edit: well, http://www.dailygalaxy.com/my_weblog/2017/03/nasas-new-horizon-astronomers-declare-pluto-is-a-planet-so-is-jupiters-ocean-moon-europa.html is interesting; this is science, so anything could (potentially) change. Pluto is now classified as a dwarf planet. The main difference between a planet and a dwarf planet has to do with the requirement that a planet clear out the material in and near its orbit. Planets do this, dwarf planets do not.
The reclassification was triggered by the discovery of many additional object (the Edgeworth-Kuiper Belt) out beyond the orbit of Neptune. Some of the objects are nearly as big as (and is a few cases, possibly bigger than) Pluto and in very similar orbits. Thus it was realized that Pluto was just the largest of a large number of objects in the outer solar system.
This is simply science at work. At the local university, we have an Astronomy textbook from the 1800's that lists the 12 planets: Mercury, Venus, Earth, Mars, Ceres, Pallas, Juno, Vesta, Jupiter, Saturn, Uranus, and Neptune. However, as more objects were detected between Mars and Jupiter, it was realized this was a new class of object and the middle four were downgraded from planet status to asteroids. It is the same process at work today out in the outer solar system.
The following is multiple choice question (with options) to answer.
What is pluto now called? | [
"dwarf planet",
"meteor",
"planet",
"asteroid"
] | A | If the first three are true but not the fourth, then that object is a dwarf planet . We now call Pluto a dwarf planet. There are other dwarf planets in the solar system. They are Eris, Ceres, Makemake and Haumea. There are many other reasons why Pluto does not fit with the other planets in our solar system. |
SciQ | SciQ-2284 | experimental-physics, measurements, medical-physics
Thus, my measurement setup was as follows: I prepared a 7.5 liter water jug just like they did in the video. I used coarse 1 liter steps for the first 5 liters, then made 0.1 liter tick marks until I reached 6.5 liters, and I ignored the rest. I put the jug upside down in a bucket and used a garden hose to breathe air inside the jug. I made lots of different "measurements" to look at normal breathing, deep inhaling and exhaling, etc. but ultimately I was just interested in vital capacity.
I have measured my own vital capacity to be 5.9 liters. It makes sense since I am still pretty young, I am 189 cm tall, and have an active lifestyle. I estimated the systematic error to be on the order of 0.2 liters (handling of the bottle, drawing of the scale, preparing of the setup), and reduced the statistical error by taking several measurements. Once I got the hang of "fully breathing out" (breathing out as much as possible), the value never really fluctuated by more than 0.1 liters. It doesn't seem to me that many people here actually tried something similar or were interested in it, but if someone was interested and stumbled across this post, it would be helpful.
The following is multiple choice question (with options) to answer.
Tidal volume, expiratory reserve volume, inspiratory reserve volume, and residual volume are all types of what kind of measurement? | [
"lung volume",
"emitted volume",
"breathing volume",
"respiratory volume"
] | A | 39.2 Gas Exchange across Respiratory Surfaces The lungs can hold a large volume of air, but they are not usually filled to maximal capacity. Lung volume measurements include tidal volume, expiratory reserve volume, inspiratory reserve volume, and residual volume. The sum of these equals the total lung capacity. Gas movement into or out of the lungs is dependent on the pressure of the gas. Air is a mixture of gases; therefore, the partial pressure of each gas can be calculated to determine how the gas will flow in the lung. The difference between the partial pressure of the gas in the air drives oxygen into the tissues and carbon dioxide out of the body. |
SciQ | SciQ-2285 | botany, microbiology, terminology, etymology
Title: Rhizosphere vs. Endorhiza? In relation to microbiology and the naming of the various areas of the plant as it relates to microbial inhabitance, I am confused as to the difference between the terms endorhiza and rhizosphere.
In this case I see rhizosphere referred simply to as the 'roots', but in this case I also see endorhiza explained simply as 'roots' also.
However in this case, I see a further explanation for endorhiza (which does make sense etymologically): 'internal root tissues'.
Does this mean endorhiza is be a sub-term for the area inside the roots, and the larger area of the rhizome in general represented by rhizosphere, and that is the difference? Healthy plant growth depends on a microbial community that lives around and inside the roots of plants (Bais et al. 2001). Roots secrete from the roots a number of chemical compounds that influences the microbial community around but outside of the roots. The microbial community can include bacteria, fungi, and single-celled parasites, as well as larger organisms like insect larvae and even roots from other plants. Some chemicals attract certain organisms while other chemicals repel organisms. This community of organisms around the roots is called the rhizosphere (Walker et al. 2003). The paper by Walker (open access) describes some of the many types of symbiotic relationships that occur in the rhizosphere.
Endorhiza refers to the internal environment of the root system. The endorhiza contains another microbial community of bacteria and fungi (Backman and Sikora 2008). The organisms of this endorhizal community are collectively called endophytes. Like the rhizosphere, the organisms in the endorhiza are important symbiotic species that benefit the health of the plant.
Similar communities have been identified for other regions of the plant, such as the phyllosphere, the organisms that live on the leaves, stems and other plant parts above the ground (Backman and Sikora 2008).
The following is multiple choice question (with options) to answer.
What kind of a relationship do plants and soil have? | [
"one-way relationship",
"contentious relationship",
"two-way relationship",
"dimorphic relationship"
] | C | |
SciQ | SciQ-2286 | electromagnetism, electricity, magnetic-fields
Title: Why does electricity flowing through a copper coil generate a magnetic field? Can some one please explain to me why electricity flowing though a copper coil generates a magnetic field or where I could possibly find that information? Are there other materials that produce a magnetic field when a current is run through them in a different shape? Thanks!
Can some one please explain to me why electricity flowing though a
copper coil generates a magnetic field or where I could possibly find
that information?
An electric current (a flow of electric charge) has an associated magnetic field regardless of the material (or space) the flow occurs in. This is a fundamental part of electromagnetism, rooted in observation, and quantified in Ampere's Law.
I wish to emphasize that this phenomenon is considered fundamental in nature, which means there cannot be a "more" fundamental explanation (if there were, electromagnetism would not be fundamental).
The following is multiple choice question (with options) to answer.
What is the process of generating electric current with a magnetic field? | [
"electromagnetic induction",
"mechanical induction",
"pole induction",
"molecular induction"
] | A | An electric generator is a device that produces electricity through electromagnetic induction. Electromagnetic induction is the process of generating electric current with a magnetic field. |
SciQ | SciQ-2287 | human-biology, pharmacology, cardiology
The lack of a decrease in the neuroendocrine prognostic markers, norepinephrine and endothelin-1, suggests that the beneficial effects of spironolactone are mainly related to mechanisms independent of the adrenergic and endothelin systems. The escape of AII and aldosterone, probably reflecting activated feedback mechanisms, confirms the specific activity of spironolactone on the renin-angiotensin-aldosterone system and supports the hypothesis that the beneficial effects of spironolactone on the progression of heart failure are mediated by the blockade of aldosterone receptors.
PubChem
Beneficial neurohormonal profile of spironolactone in severe congestive heart failure: Results from the RALES neurohormonal substudy
The following is multiple choice question (with options) to answer.
The adrenal cortex directly influences the function of what organs through the production of the hormone aldosterone to stimulate sodium reabsorption? | [
"kidneys",
"heart",
"tumors",
"lungs"
] | A | On the superior aspect of each kidney is the adrenal gland. The adrenal cortex directly influences renal function through the production of the hormone aldosterone to stimulate sodium reabsorption. |
SciQ | SciQ-2288 | frequency-response, minimum-phase
The pole contributes a phase change of $-\pi/2$ as $\omega$ moves from zero to infinity. The left half-plane zero of $H_1(s)$ contributes a phase change of $\pi/2$, resulting in a net phase change of zero, whereas the right half-plane zero of $H_2(s)$ contributes a phase change of $-\pi/2$, resulting in a total phase change of $-\pi$.
Another way to see the same thing is to note that any causal and stable transfer function can be written as the product of the minimum-phase transfer function with the same magnitude and a causal and stable allpass:
$$H(s)=H_m(s)H_a(s)\tag{4}$$
It can be shown that the phase of a causal and stable allpass is always non-positive for $\omega\in[0,\infty)$, and, consequently, the phase lag of the minimum-phase system is always less than or equal to the phase lag of any other causal and stable system with the same magnitude response.
The following is multiple choice question (with options) to answer.
What type of direction does a phase change depend on? | [
"weight transfer",
"humidity transfer",
"heat transfer",
"power transfer"
] | C | Remember that a phase change depends on the direction of the heat transfer. If heat transfers in, solids become liquids, and liquids become solids at the melting and boiling points, respectively. If heat transfers out, liquids solidify, and gases condense into liquids. |
SciQ | SciQ-2289 | acid-base, ph
Title: Why can't the strength of superacids be measured in water? I learned about acid strength, that the strength of an acid increases with it's degree of ionization when solvated. So, in water, a strong acid is one where $\ce{[H_3O^+]}$ is large, which is equal to a low pH: $\mathrm{pH=-log[H_3O^+]}$.
Considering extreme cases, such as superacids, I have found out that other methods are used to measure their acidity (methods I don't really understand). My question is why is it impossible to simply get super high concentrations of $\ce{[H_3O^+]}$ in aqueous solutions of superacids, and use this to determine the acid strength. Also, is pH used as a measure of acidity outside of aqueous solutions?
I have come over the leveling effect, but I don't think I fully understand it. The way I understand it (for the case with water as solvent) is that basically any acid in water will protolyze $\ce{H2O}$ to $\ce{H3O+}$, making this the effective acid. I don't understand why this would affect the measured pH, as it is $\ce{[H_3O^+]}$ you are measuring. Any acid-base reaction is always an equilibrium:
$$\ce{HA^1 + (A^2)- <=> (A^1)- + HA2}\tag{1}$$
and for each pair of acids $\ce{HA^1}$ and $\ce{HA^2}$ you could calculate a $K_\mathrm{a}$ value to determine one acid’s strength with respect to the other. This $K_\mathrm{a}$ value is typically calculated according to equation $(2)$ if $\ce{(A^2)-}$ (which does not have to feature a negative charge; I just wanted to avoid different descriptions for the two acids) is the solvent.
The following is multiple choice question (with options) to answer.
The strength of what depends on the concentration of hydrogen ions it produces when dissolved in water? | [
"the solution",
"electricity",
"acid",
"the base"
] | C | The strength of an acid depends on the concentration of hydrogen ions it produces when dissolved in water. A stronger acid produces a greater concentration of ions than a weaker acid. For example, when hydrogen chloride is added to water, all of it breaks down into H + and Cl - ions. Therefore, it is a strong acid. On the other hand, only about 1 percent of acetic acid breaks down into ions, so it is a weak acid. |
SciQ | SciQ-2290 | 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 are the largest phylum in the animal kingdom? | [
"crustaceans",
"mammals",
"arthropods",
"cephalopods"
] | C | Arthropods are the largest phylum in the animal kingdom. |
SciQ | SciQ-2291 | bacteriology, metabolism, mycology, vitamins, gut-bacteria
Title: Where in the biological realm is vitamin B5 chiefly produced? Can yeast produce pantothenic acid (vitamin B5)?
Do bacteria efficiently produce it?
Or does it only come from plants?
The Wikipedia page for pantothenic acid doesn’t seem to answer the question (other than mentioning that small amounts are found in, i.e. used by, every organism, and hinting at the facts that animals concentrate it and yeasts are, at the very least, inefficient at producing it). General Considerations
Pantothenic acid is a precursor for the synthesis of Coenzyme A which is essential for most, if not all, living organisms. As bacteria appeared on earth before plants, and can currently live in environments where there are no plants, it is difficult to envisage their being unable to synthesize pantothenic acid. The situation with yeasts is less obvious, but as independent free-living single-cell organisms, the expectation would be that they had retained this synthetic ability of their evolutionary precursors.
Pantothenic acid synthesis in different organisms
Pantothenic acid is produced by a wide range of bacteria, with the structure of the enzymes of the pathway of its synthesis, e.g. the final enzyme, pantothenate synthetase, available from many different species, as can be seen from a search of the Protein Data Bank.
Indeed far more detail is known about the process than in higher plants, because of the greater ease of conducting molecular genetics on the former.
One way to check for the existence of a pathway in a particular organism is using KEGG, and this approach shows the pathway for the synthesis of pantothenic acid is present in Saccharomyces cerevisiae.
Efficiency
The following is multiple choice question (with options) to answer.
What kind of organisms are yeasts? | [
"single-celled",
"bacteria",
"protozoa",
"viruses"
] | A | The aim of basic science is to discover new knowledge. It leads to a better understanding of the natural world. It doesn’t necessarily have any practical use. An example of basic research in life science is studying how yeast cells grow and divide. Yeasts are single-celled organisms that are easy to study. By studying yeast cells, life scientists discovered the series of events called the cell cycle. The cell cycle works not only in yeasts but in all other organisms with similar cells. Therefore, this basic research made a major contribution to our understanding of living things. Watch the following animation to learn more about the basic yeast research and the cell cycle. You can also see yeast cells dividing. |
SciQ | SciQ-2292 | bond, covalent-compounds, valence-bond-theory
Title: Why are pi bonds only formed when sigma bonds are formed? While studying about bonding there was one statement that "pi bonds can only be formed only with sigma bonds" as we know that in double bond there is 1 sigma bond and 1 pi bond but then one question arises: Why is a pi bond formed only when a sigma bond is formed? Is it possible to form a pi bond without any formation of a sigma bond? A $\pi$ bond has a plane of symmetry along the bond axis. It cannot be formed by s-orbitals; it needs at least p-orbitals to be created. $90\,\%$ of all bonds described some time or another are somehow involving carbon, nitrogen or oxygen. (In fact, I probably underestimated). But these elements can only use p-orbitals to create $\pi$ bonds. To do that, one needs a p-orbital that is ortohogonal to the bond axis. So you run into the problem that you have an orbital pointing in one direction, but want to bond into another direction — hardly optimal, especially since there likely is already another orbital pointing in the direction you need to give a $\sigma$ bond.
Transition metals can use d-orbitals for $\pi$ bonding. They can actually point towards the atom they want to bond with so there is a greater chance of using them due to higher overlap. However, there will usually also be a different orbital pointing directly in the bonding direction which again will bond earlier and would give a $\sigma$ bond.
The following is multiple choice question (with options) to answer.
What kind of bond consists of one sigma bond and one pi bond? | [
"covalent bond",
"double bond",
"beta bond",
"ionic bond"
] | B | Recall that a double bond consists of one sigma bond and one pi bond. In order for a double bond to be formed, each participating carbon atom must have at least one unhybridized p orbital. In a carbon-carbon double bond where both carbons are bonded to two additional atoms, each carbon is sp 2 hybridized. The double bond includes a sigma bond between a hybrid orbital from each carbon and a pi bond between the leftover p orbital from each carbon. The angles between any two bonds for an sp 2 hybridized carbon are approximately 120°. |
SciQ | SciQ-2293 | agriculture
Title: What does "permanent field" mean in agriculture? I am reading a book that in a paragraph talks about the agricultural methods used in prehistoric Finland.
The further north and east, the more extensive the amount of
burn-beat cultivation, which was a far from primitive form of
agriculture. The yield was many times higher (twenty- to thirty-fold)
than on permanent fields (five- to ten-fold), and there were multiple
varieties of the technique
A history of Finland by Henrik Meinander.
One of them is burn-beating. Like I understand, in burn-beating people cut down the trees in the forests and burn the topsoil. This way they can use that soil for 3 to 6 years for cultivation.
The other method is permanent field. I have searched the internet and the result I got was "permanent crops", like here. In which case people planted trees once in a field and harvested them multiple times.
But in another research about prehistoric Finland it was saying:
The site of Orijärvi shows that permanent field cultivation, with
hulled barley as the main crop was conducted from approximately cal AD 600 onwards.
The following is multiple choice question (with options) to answer.
What is the purpose of utilizing careful farming practices such as rotating crops or planting nutrient rich crops? | [
"improve photosynthesis quality",
"improve sediment quality",
"improve soil quality",
"improve soil texture"
] | C | Careful farming helps to keep up soil quality each season. One way is to plant different crops each year. Another is to alternate the crops planted in each row of the field. These techniques preserve and replenish soil nutrients. Planting nutrient rich cover crops helps the soil. Planting trees as windbreaks, plowing along contours of a field, or building terraces into steeper slopes all help to hold soil in place ( Figure below ). No-till or low-till farming disturbs the ground as little as possible during planting. |
SciQ | SciQ-2294 | soft-question
Aside: The biggest beneficiary of ion propulsion is not interplanetary space probes. There just aren't very many interplanetary space probes to begin with, and many of them need high thrust. The biggest beneficiary is commercial space. Space has been partly commercial ever since the 1962 launch of Telstar. There are several hundred birds in geosynchronous orbits, and a good proportion of these now use ion propulsion.
Getting a satellite into geosynchronous orbit is a very expensive proposition. A commercial communications satellite doesn't start turning a profit until after multiple years in orbit. The longer the satellite remains viable, the more profit. Communications satellites occasionally have to use thrusters to perform stationkeeping operations. Depleting all of its propellant spells the end of a communication satellite's useful life. (In fact, having a satellite deplete 100% of its propellant while still in a geosynchronous orbit is highly frowned upon. Operators of a geosynchronous satellite that is approaching the end of its useful life are supposed to make the satellite use the last little dregs of its fuel to boost the satellite out of its geostationary orbit into a satellite graveyard.)
Communications satellites that used chemical propulsion for stationkeeping only had a few years of profitability because of the low specific impulse of chemical propulsion. Ion thrusters enable communications satellites to turn a profit for a far longer period time. The vast majority of new communications satellites now use ion propulsion rather than chemical propulsion for stationkeeping.
The following is multiple choice question (with options) to answer.
What do communication satellites carry and use to provide energy during their missions? | [
"batteries",
"infrared panels",
"solar panels",
"geothermal panels"
] | C | Communications satellites carry solar panels to provide energy for their missions. |
SciQ | SciQ-2295 | geochemistry, earth-history, co2, carbon-cycle
Source: Wikimedia Commons.
I heard this argument at the University of Zaragoza. However, I am uncertain if both my teacher and I have a comprehensive understanding of this matter. One of my concerns is that CO2 dissolves below the Calcite Compensation Depth. I'm unsure if all sediments dissolve or just the top layers. This uncertainty leaves me pondering whether my argument could be refuted on this basis. I couldn't find any clarifications on Science Direct either.
Could someone elucidate this matter for both my friend (who will read this) and me?
Are the Phanerozoic CO2 levels indeed linked with the Wilson Cycle? If so, why?
Bonus Question:
If humans wouldn't exist, would we run out of CO2? (To me, this seems like an absurd query, especially in the context of that Nobel Prize article, because we'll likely gain control over Earth's geochemistry and climate long before then.) To rephrase: if we exclude human influence, would shell organisms eventually consume all the CO2 by the end of the Phanerozoic era, leading to a mass extinction and the emergence of a distinct form of life? Would this scenario transpire in this cycle or the next? On geological timescales, yes, the Wilson cycle (opening and closing of ocean basins) is bound to have an effect on atmospheric CO2 levels, if only because it will affect rainfall patterns, which in turn will affect chemical weathering of rocks, which is one of the things that removes CO2 from the air on very long timescales.
This obviously doesn't explain the post-industrial rise in atmospheric CO2 though, which has occurred on the scale of a century or so, rather than tens to hundreds of millions of years. So it seems like a grain of truth, but the argument is a non-sequitur.
"In the forthcoming million years, CO2 stored by organisms will be
released."
The following is multiple choice question (with options) to answer.
What is the biogeochemical cycle that recycles water called? | [
"Water Table",
"water cycle",
"Liquid Cycle",
"water theory"
] | B | The biogeochemical cycle that recycles water is the water cycle. The water cycle involves a series of interconnected pathways involving both the biotic and abiotic components of the biosphere. Water is obviously an extremely important aspect of every ecosystem. Life cannot exist without water. Many organisms contain a large amount of water in their bodies, and many live in water, so the water cycle is essential to life on Earth. Water continuously moves between living organisms, such as plants, and non-living things, such as clouds, rivers, and oceans ( Figure below ). |
SciQ | SciQ-2296 | ethology, sociality, animal-psychology
Title: Frogs stop croaking at same time I know frogs start croaking at the same time to attract a female.
Why do they all stop at the same time? Calling is a risky activity because it makes the frog conspicuous to predators. When calling in a group, the risk to any given individual is minimized to the point that the minimal risk is outweighed by the advantage of attracting a mate. However, a single frog calling on his own is assuming all of the predation risk. So, the frogs are playing a bit of game theory and when too few are calling simultaneously to make the risk worthwhile, they will all tend to stop.
The following is multiple choice question (with options) to answer.
What type of behavior is frogs croaking or deer clashing antlers an example of? | [
"instincts",
"learned behavior",
"courtship",
"mating"
] | C | Courtship behaviors occur in many other species. For example, males in some species of whales have special mating songs to attract females as mates. Frogs croak for the same reason. Male deer clash antlers to court females. Male jumping spiders jump from side to side to attract mates. |
SciQ | SciQ-2297 | atoms, phase
Title: What is the physical state of a single atom? Can a single atom on its own be either a solid, liquid, or a gas? Or is it none of them? This answer has been written so it hopefully can be understood by people that do not have a degree. If something is not correct, let me know, but be aware that throwing around fancy words will not help anyone understanding this any better. Consider the other posts here concerning liquids and solids, I don't want to be redundant and repeat what has been said already.
The answer is a bit complicated. One would intuitively say no, but that doesn't tell the whole story.
Take the interstellar medium. We have about 1 atom per cm³ in there and it is called a "gas". Now that's what I would call an isolated atom in the gas phase.
An atom is an object that belongs into the realms of quantum mechanics. A solid, liquid or gas is something that belongs into our classical world. If you zoom in close enough, that means if we look at a problem microscopically, words like "solid" or "liquid" no longer make sense. If you now begin to zoom out, the quantum effects vanish. This is sometimes called quantum decoherence and we enter the world of classical physics where solids and and liquids exist again.
So I would argue it all depends on how closely you look at the problem. Isolated atoms in a large volume? A gas if you ask me. But if you have to zoom in to talk about an individual atom within a larger compound consisting of many more atoms, let's say one atom within a piece of iron, you no longer can say that this single atom is "solid".
Think of it like this:
Can a single person have a political system?
The following is multiple choice question (with options) to answer.
An atom can be classified as a particular element based solely on its what? | [
"spectrum",
"ability",
"atomic number",
"light number"
] | C | The atomic number of an element is the number of protons in the nucleus of each atom of that element. An atom can be classified as a particular element based solely on its atomic number. For example, any atom with an atomic number of 8 (its nucleus contains 8 protons) is an oxygen atom, and any atom with a different number of protons would be a different element. The periodic table ( Figure below ) displays all of the known elements and is arranged in order of increasing atomic number. In this table, an element’s atomic number is indicated above the elemental symbol. Hydrogen, at the upper left of the table, has an atomic number of 1. Every hydrogen atom has one proton in its nucleus. Next on the table is helium, whose atoms have two protons in the nucleus. Lithium atoms have three protons, beryllium atoms have four, and so on. Since atoms are neutral, the number of electrons in an atom is equal to the number of protons. Therefore, hydrogen atoms all have one electron occupying the space outside of the nucleus. |
SciQ | SciQ-2298 | ## 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.
In the body, what essential substance is pumped from the heart into arteries and then eventually into capillaries? | [
"water",
"lymphatic Fluid",
"blood",
"spinal fluid"
] | C | The solution to the last part of the example shows that speed is inversely proportional to the square of the radius of the tube, making for large effects when radius varies. We can blow out a candle at quite a distance, for example, by pursing our lips, whereas blowing on a candle with our mouth wide open is quite ineffective. In many situations, including in the cardiovascular system, branching of the flow occurs. The blood is pumped from the heart into arteries that subdivide into smaller arteries (arterioles) which branch into very fine vessels called capillaries. In this situation, continuity of flow is maintained but it is the sum of the flow rates in each of the branches in any portion along the tube that is maintained. The equation of continuity in a more general form becomes ¯. |
SciQ | SciQ-2299 | inorganic-chemistry, nomenclature, coordination-compounds
$\ce{CaCl2.8NH3} \equiv \quad$ calcium chloride—ammonia (1/8)
Therefore the systematic names for the compound $\ce{[Co(NH3)5Cl]Cl2.NH3}$ would be:
pentaamminechloridocobalt(III) chloride—ammonia (1/1)
pentaamminechloridocobalt(3+) chloride—ammonia (1/1)
pentaamminechloridocobalt(III) dichloride—ammonia (1/1)
pentaamminechloridocobalt(3+) dichloride—ammonia (1/1)
The following is multiple choice question (with options) to answer.
What (nh3) is one of the few thermodynamically stable binary compounds of nitrogen with a nonmetal? | [
"ammonia",
"nitrous oxide",
"liquid nitrogen",
"acetic acid"
] | A | Note the Pattern Few binary molecular compounds of nitrogen are formed by the direct reaction of the elements. At elevated temperatures, nitrogen reacts with highly electropositive metals to formionic nitrides, such as Li3N and Ca3N2. These compounds consist of ionic lattices formed by M n+ and N3− ions. Just as boron forms interstitial borides and carbon forms interstitial carbides, with less electropositive metals nitrogen forms a range ofinterstitial nitrides, in which nitrogen occupies holes in a close-packed metallic structure. Like the interstitial carbides and borides, these substances are typically very hard, high-melting materials that have metallic luster and conductivity. Nitrogen also reacts with semimetals at very high temperatures to produce covalent nitrides, such as Si3N4 and BN, which are solids with extended covalent network structures similar to those of graphite or diamond. Consequently, they are usually high melting and chemically inert materials. Ammonia (NH3) is one of the few thermodynamically stable binary compounds of nitrogen with a nonmetal. It is not flammable in air, but it burns in an O2 atmosphere: Equation 22.30. |
SciQ | SciQ-2300 | thermodynamics, heat, ideal-gas
Title: Combined gas law in an open atmosphere The question was asked about pressure vs. Volume increasing in an ideal gas as temperature is increased. My question then is this. What is the formula to determine how much volume and pressure will increase as temperature is increased?
Let me frame the question this way. PV/T=P2V2/T2 this formula works for a controlled system where more than one of these values can be maintained. If we apply a known amount of heat, say n, to the atmosphere, what formula would be used to calculate volume and pressure as the temperature is increased? Technically speaking, If you managed to create a planet with an ideal gas atmosphere, the atmosphere would just float away. Why?
One of the approximations of an ideal gas is
There are no attractive or repulsive forces between the molecules or the surroundings
This means that the gas wouldn't feel the force of gravity!
So if I had a jar of ideal gas, the pressure wouldn't increase as I went to a greater depth in the jar(It does increase in gasses too, just like it does in liquids).
I know this sounds strange but all it really means is that you cannot apply the ideal gas approximation to a system the size of our atmosphere. This approximation works well for small systems(A jar of ideal gas), because the effects of gravity are pretty negligible.
So to analyse effects of change in temperature on the whole atmosphere, you'll need a better model. Maybe considering the atmosphere a non-viscous fluid can help, I don't know. You should research on this.
Note that other approximations like the Van der Waals equation wouldn't help too because they too neglect the effect of gravity.
The following is multiple choice question (with options) to answer.
What does increased temperature cause the volume to do in a gas? | [
"increase",
"disappear",
"decrease",
"halve"
] | A | Equal volumes of four different gases at the same temperature and pressure contain the same number of gaseous particles. Because the molar mass of each gas is different, the mass of each gas sample is different even though all contain 1 mol of gas. The relationships among the volume of a gas and its pressure, temperature, and amount are summarized in Figure 10.10 "The Empirically Determined Relationships among Pressure, Volume, Temperature, and Amount of a Gas". Volume increases with increasing temperature or amount but decreases with increasing pressure. |
SciQ | SciQ-2301 | meteorology, climate-change, poles, vorticity
In the northern hemisphere most vertically propagating Rossby waves arise due to the topography. In the southern hemisphere the sudden stratospheric warmings are a rarity due to lack of such topographical features. The last sudden stratospheric warming over the southern hemisphere was in 2002.
The resulting stratospheric anomalies can in return influence surface climate but the mechanism on how exactly this occurs is the still the matter of scientific research. One of the theories that is currently popular is the wave mean flow interactions. This can be easily summarized as concerning how planetary scale Rossby waves influence the circulating zonal flows around a planet. The other main theory is wave reflections at the tropopause.
So what is the net result of either of the above two possibilities? Either way they affect mid-latitude storms. Storms could either become more intense, shift equatorward, or there could be extremely cold air advection spells as the stratospheric air gets mixed into the troposheric air.
As to the rarity of polar vortex splits - they are coupled to those sudden stratospheric warmings. If you look towards the climatology of SSWs, observations show that they occur more during El Niños and La Niñas than during neutral conditions. Sudden stratospheric warmings happen almost every other year in the NH. However sometimes the polar vortex isn't split during these events but is merely pushed equatorward.
The long term effect a polar vortex split could be extended spells of extremely cold weather in the affected areas, and when the vortex reforms on into summer it would be shrunk in size from the dispersed energy giving rise to greater easterly wind circulation near the poles.
UPDATE
Now that the reanalysis data is available from January 2019 I want to add some visuals for the Dec-2018/Jan 2019 polar vortex split and ongoing cold wave.
The following is multiple choice question (with options) to answer.
Which effect causes winds to strike the polar front at an angle? | [
"coriolis effect",
"axial tilt",
"Lake Effect",
"centrifugal effect"
] | A | Mid-latitude cyclones form at the polar front. Two very different air masses blow past each other in opposite directions. The Coriolis effect causes winds to strike the polar front at an angle. Warm and cold fronts form next to each other. |
SciQ | SciQ-2302 | evolution, ornithology, palaeontology
One thing those many, many bird and proto-bird fossils also made clear is that the traits of modern birds (feathers, wings, toothless beaks, etc) didn't evolve in a simple line from non-bird to bird. Many of those traits evolved convergently in several lineages, were lost in some, maybe regained in others, and feathers in particular turn out to be a widespread dinosaur feature that cannot be considered a uniquely bird trait anymore (unless we want to call T-rexes "birds"). Still, saying "beaks evolved several times" or "feathers evolved several times" doesn't mean that birds, let alone modern birds, evolved from several different ancestors. It can mean that the common ancestor of birds had lots of variously bird-like more-or-less distant cousins living around the same time.
The following is multiple choice question (with options) to answer.
Birds evolved from what type of ancestor? | [
"apes",
"insect",
"fish",
"reptile"
] | D | Birds evolved from a reptile ancestor, but modern birds and reptiles are very different. Birds are now the most numerous four-limbed reptiles on Earth. |
SciQ | SciQ-2303 | cell-biology, hematology, red-blood-cell
Title: Why are red blood cells considered to be cells? Wikipedia states that a cell is
the basic structural, functional and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently.
It then goes on to state that
All cells (except red blood cells which lack a cell nucleus and most organelles to accommodate maximum space for hemoglobin) possess DNA.
Then why are red blood cells still considered cells, while they can't replicate? Is the definition on Wikipedia just a bad definition? Or are red blood cells wrongly considered cells, but remain so for historical reasons? Or are they considered cells for some other reason, such as this answer which states that red blood cells do contain a nucleus at some point? A very good question, and it is most likely because of the last option. It had a nucleus for part of its life. After the RBC jettisons its nucleus, it still remains very metabolically active for approximately 3 months. It maintains its cell membrane integrity, it metabolizes glucose, it interacts constantly with its environment, numerous cellular functions and structure remain intact... It is extremely specialized for a primary purpose, and no longer requires the nucleus to provide more proteins. It has limited capacity to heal from injury, so it has a limited life span.
Speculation: I wonder if it might lose the nucleus early on so that when it is destroyed in the spleen at the end of its life as RBCs are, the spleen macrophages are not overwhelmed with additional processing of nucleic acids? Macrophage type cells are already working hard in there to clear infectious agents and some immune cells from the blood.
The following is multiple choice question (with options) to answer.
Which blood cells serve to defend the body in various ways? | [
"red blood cells",
"helper blood cells",
"blue blood cells",
"white blood cells"
] | D | White blood cells are larger than red blood cells, but there are far fewer of them. Their role is to defend the body in various ways. For example, white blood cells called phagocytes engulf and destroy microorganisms and debris in the blood. |
SciQ | SciQ-2304 | brain
Title: When a thought 'crosses your mind', does it literally cross between left and right cerebral hemispheres? I've heard that part of cognitive processing is information passing between left and right cerebral hemispheres.
This is what happens in the Cerebral Cortex which is divided into two hemispheres,
left brain and right brain connected by a thick layer of nerve fibers called the corpus callosum. These nerve fibers allow messages to pass between the left and right brain
hemispheres
My question is When a thought 'crosses your mind', does it literally cross between left and right cerebral hemispheres?
Assumptions:
I'm making a big leap from 'electronic impulses of neurons' to 'thoughts'. Neuroscience doesn't really have a clear model for what a "thought" consists of exactly. Certain processes that are involved in thought have begun to be mapped--for example, this recent paper talks about a model for how the brain associates location in space with it's own mental map (http://www.ncbi.nlm.nih.gov/pubmed/24462102, I'll try to find something related that's not behind a paywall...). This one doesn't address your particular problem though, they only measured activity on one side of the brain. So basically, it might be possible to partially answer your question for more specific brain processes, but different kinds of "thoughts" are processed in different ways.
And of course I am also conflating impulses crossing the corpus callosum with the thoughts themselves, but I don't think this is really accurate. The most popular models in the labs I'm familiar with suggest that a "thought" is composed of a bunch of neural activity taken together rather than the activities of a few neurons on their own. But that might ultimately just be arguing semantics.
The following is multiple choice question (with options) to answer.
Eutherian mammals possess a specialized structure called the corpus callosum that links what hemispheres? | [
"cerebral",
"appendages",
"spatial",
"cortical"
] | A | possess a single, undivided lobe. Eutherian mammals also possess a specialized structure that links the two cerebral hemispheres, called the corpus callosum. |
SciQ | SciQ-2305 | neuroscience, neuroanatomy
Title: Why is the anterior pituitary not considered part of the diencephalon? According to the wikipedia page on the diencephalon, the posterior pituitary gland is considered part of the diencephalon, but the anterior is not. Is there a reason that these two lobes of the same gland are considered different enough not to be part of the same brain region? Worth going to the wikipedia page on the pituitary:
In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary, which is an extension of the hypothalamus.
The anterior pituitary arises from an invagination of the oral ectoderm (Rathke's pouch). This contrasts with the posterior pituitary, which originates from neuroectoderm.
The posterior lobe develops as an extension of the hypothalamus, from the floor of the third ventricle.
In other words, the different parts of the pituitary are, developmentally, entirely separate. The posterior lobe is actually part of the hypothalamus. The anterior lobe is not even part of the brain.
Lumping them together with one label happened because the anatomists who originally named the thing didn't know much about it, which is not surprising because anatomical names are quite old and understanding of the functions of any parts of the brain is quite new. Old names stick.
The following is multiple choice question (with options) to answer.
Which part of the brain secretes hormones that tell the pituitary gland either to secrete or to stop secreting its hormones? | [
"hypothalamus",
"hippocampus",
"cerebrum",
"thalamus"
] | A | The hypothalamus is actually part of the brain (see Figure below ), but it also secretes hormones . Some of its hormones “tell” the pituitary gland either to secrete or to stop secreting its hormones. In this way, the hypothalamus provides a link between the nervous and endocrine systems. The hypothalamus also produces hormones that directly regulate body processes. These hormones travel to the pituitary gland, which stores them until they are needed. The hormones include antidiuretic hormone and oxytocin. |
SciQ | SciQ-2306 | evolution, zoology, taxonomy, phylogenetics
The apomorphy that defines the tetrapods is "paired limbs". You have Amphibia to the left and Amniota to the right, whose apomorphy is " egg with extraembrionic membranes". Inside them, you have Reptilia, whose apomorphies are "skull with upper and lower fenestra and beta-keratin in epidermis". Turtles came from an ancestor with these characteristics. So, turtles belong to the monophyletic group of "Reptiles".
Post scriptum: You wrote that "turtles (specifically sea turtles) live on both land and water, very much like amphibians". Just a curiosity: the reason why sea turtles leave the water (sea) from time to time shows exactly that they are not amphibians! Amphibians, being non-amniotes, have eggs that survive under water (actually, with few exceptions, they need to be under water). Turtles, on the other hand, are amniotes, and the amniotic egg cannot be laid under water. That's why the turtles have to leave the water to lay eggs: because, contrary to the amphibians, they cannot lay eggs under water.
The following is multiple choice question (with options) to answer.
Most reptile eggs can be laid on land, not in water and they are called what? | [
"umbilical",
"amniotic",
"Transitional",
"aqueous"
] | B | Most reptiles reproduce sexually and have internal fertilization. Their eggs are amniotic, so they can be laid on land instead of in water. Reptiles do not have a larval stage, and their hatchlings are relatively mature. Reptile parents provide little if any care to their young. |
SciQ | SciQ-2307 | ### Show Tags
30 Oct 2009, 17:22
6
1
juukkk wrote:
Bunuel wrote:
How many zeros are in the end (after which no other digits follow) of 32!?
$$\frac{32}{5}+\frac{32}{5^2}=6+1=7$$ (denominator must be less than 32, $$5^2=25$$ is less)
So there are 7 zeros in the end of 32!
If you actually go and check 32! in Excel the result will be 263130836933694000000000000000000000
So more like 21 zeros... I really hope Excel is making a mistake because of how neat is your formula but someone please explain!?
32! = 263130836933693530167218012160000000 This is what 32! really equals to.
32!= 263130836933694000000000000000000000 Accoroding to Excell. Don't worry it's just rounded, so formula is correct.
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Joined: 08 Sep 2009
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### Show Tags
30 Oct 2009, 17:28
2
Bunuel wrote:
32! = 263130836933693530167218012160000000 This is what 32! really equals to.
32!= 263130836933694000000000000000000000 Accoroding to Excell. Don't worry it's just rounded, so formula is correct.
Kudos given and formula memorized already. From where did you got the what "32! really equals to"?
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### Show Tags
31 Oct 2009, 04:19
1
juukkk wrote:
Bunuel wrote:
The following is multiple choice question (with options) to answer.
What do you call a small whole number placed in front of a formula in an equation in order to balance it? | [
"coefficient",
"function",
"divisible",
"correlation"
] | A | A coefficient is a small whole number placed in front of a formula in an equation in order to balance it. The 2 in front of the H 2 means that there are a total of atoms of hydrogen as reactants. Visually, the reaction looks like the Figure below . |
SciQ | SciQ-2308 | oceanography, geochemistry
Title: Why is NaCl so hyper abundant in the ocean? Why is sodium chloride far and away the most abundant salt dissolved in ocean water? Its two constituent ions do have a very high frequency in the crust of the earth, but they are far from the most common. Chlorine is (according to Wikipedia) the 21st most abundant element, and sodium 6th.
I certainly understand that a combination of their solubility and reasonably high frequency would lead one to expect them to be abundant in sea water, but they are hyper abundant, completely dominating all other salt ions. Iron, for example, is twice as abundant, and potassium only a little less abundant, and fluorine more abundant than chlorine.
Moreover, if the salts are deposited in the ocean through weathering of rocks and deposition via rivers, why does the salinity not simply grow and grow? I understand that some is lost due to tectonic activity, but it seems extraordinarily unlikely that these two forces should be equally balanced, and so we would see a significant change in average salinity over time.
(Please note I am migrating this question from the Chemistry SE at their recommendation.) Fluoride salts tend to be not particularly soluble in water. Chloride salts are. The same goes for salts containing sodium versus those containing calcium. Sodium chloride is ridiculously easy to dissolve.
Regarding your second question, it is geological forces that keep salinity more or less constant. People formerly argued that the Earth can't be more than a few hundred million years old because otherwise the river waters running into the oceans would eventually result in an insanely high salinity. It turns out that the Earth's oceans are young (young compared to the 4.5 billion year age of the Earth). The vast majority of oceanic crust is less than 100 million years old. We see huge salt deposits sprinkled across the world because those are the dried up remnants of former seas and oceans. Salt is also drawn into the Earth at subduction zones, where it combines chemically with basalt.
The following is multiple choice question (with options) to answer.
Because the earth is covered with vegetation, cellulose is the most abundant of all what? | [
"vegetables",
"carbohydrates",
"rocks",
"impurities"
] | B | Cellulose Cellulose, a fibrous carbohydrate found in all plants, is the structural component of plant cell walls. Because the earth is covered with vegetation, cellulose is the most abundant of all carbohydrates, accounting for over 50% of all the carbon found in the vegetable kingdom. Cotton fibrils and filter paper are almost entirely cellulose (about 95%), wood is about 50% cellulose, and the dry weight of leaves is about 10%–20% cellulose. The largest use of cellulose is in the manufacture of paper and paper products. Although the use of noncellulose synthetic fibers is increasing, rayon (made from cellulose) and cotton still account for over 70% of textile production. Like amylose, cellulose is a linear polymer of glucose. It differs, however, in that the glucose units are joined by β-1,4-glycosidic linkages, producing a more extended structure than amylose (part (a) of Figure 16.11 "Cellulose"). This extreme linearity allows a great deal of hydrogen bonding between OH groups on adjacent chains, causing them to pack closely into fibers (part (b) of Figure 16.11 "Cellulose"). As a result, cellulose exhibits little interaction with water or any other solvent. Cotton and wood, for example, are completely insoluble in water and have considerable mechanical strength. |
SciQ | SciQ-2309 | energy, waves
Title: Calculating Energy of a Wave So my physics examinations are coming up and I was going through my notes on waves, but I realized that there were some discrepancies.
In my notes, the energy of a wave is directly proportional to the square of the amplitude, ie. $E \propto A^2$
However, I recalled that, in one of my physics lessons, our physics teacher told us that the energy of a wave can be calculated using $E=hf$, where $h$ is the Planck constant and $f$ the frequency.
Hence I was rather confused and tried searching google for answers but couldn't find any suitable ones. To the best extent of that research, what I found out was (apparently) (for visible light), the frequency of the wave could be used to calculate the energy of the wave, while the amplitude was used to determine the intensity of the wave.
So I was wondering, firstly, whether the above statement was correct, and secondly, in the event it is correct, whether it would be applicable to all kinds of waves, (ie. Sound waves, water waves, other EM waves, etc.), and thirdly, back to the original question, how do we calculate the energy of a wave?
Thanks. :) Both the equations you cite are correct.
The energy carried by a wave is indeed proportional to the amplitude squared. for what it's worth, you don't even need a propagating wave, any harmonic oscillator (e.g. a pendulum) will follow that rule. The validity of this rule remains unaffected even in quantum mechanics (actually, since in QM everything can be described by a wave function, it is even more fundamental there).
The second formula expresses the energy of a single photon. A photon is the smallest quantity of radiation that can exist at that frequency. This is completely unrelated to the total energy of the wave! For instance even a small light bulb will emit something like $10^{20}$ photons each second. Each carries an energy of $hf$. Together they sum up to the total power of the beam.
The following is multiple choice question (with options) to answer.
The energy of a photon is directly proportional to the frequency of the electromagnetic what? | [
"evaporation",
"convection",
"absorption",
"radiation"
] | D | The energy of a photon is directly proportional to the frequency of the electromagnetic radiation. |
SciQ | SciQ-2310 | physical-chemistry, thermodynamics, gas-laws, equation-of-state
I am confused by this argument-- what exactly is the definition of 'volume' here? They seem to be saying that it is the empty space around the gas molecules, but it seems to me that volume should be defined as the space 'taken up' by the gas. Why should the space taken up by the particles themselves be subtracted? This isn't done for solids or liquids as far as I know.
These thoughts have also made me realize that I'm not quite sure what it means for a gas to 'take up' space. Does anyone have a rigorous definition of gas volume?
EDIT: The exchange with Chris in comments has raised further questions. It now seems to me that the $V-nb$ correction actually accounts for repulsions rather than attractions. I think I was incorrect in thinking that the $V-nb$ correction dominated at intermediate volumes and $a(n/V)^2$ at low volumes. If $V-nb$ is for repulsions, then it should dominate at low volumes, but I can't tell from the equation which correction will actually be dominant. Also I am now wondering whether it even makes sense to connect one correction with repulsions and one with attractions.
EDIT: Follow-up questions for F'x:
- I thought that 'density' meant mass/volume. Is the use of it to represent the inverse of molar volume (as you have used it) common?
- Where is the phase-transition in the red van der Waals curve?
- I am still a little unclear on gas volume. Are the 'volume available to the gas' and 'volume of the gas' the same? You say it's the same as the shape of the container, but aren't we subtracting the volume of the actual gas particles from that? The $V$ term represents the volume of the gas, correct? And $V-nb$ represents the 'volume available to the gas'. The van der Waals equation can't be derived from first principles. It is an ad-hoc formula. There is a "derivation" in statistical mechanics from a partition function that is engineered to give the right answer. It also cannot be derived from first principles.
The following is multiple choice question (with options) to answer.
What term means the amount of space matter takes up? | [
"density",
"mass",
"volume",
"weight"
] | C | The amount of space matter takes up is its volume . How the volume of matter is measured depends on its state. |
SciQ | SciQ-2311 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
All of the stages that a cell goes through make up what? | [
"photosynthesis",
"the cell cycle",
"glycolysis",
"cytokineses"
] | B | Cell division is just one of the stages that a cell goes through during its lifetime. All of the stages that a cell goes through make up the cell cycle . |
SciQ | SciQ-2312 | species-identification, ornithology
Title: Help me find out what this bird is (description, no picture) A while ago I read about this bird(s) whose species status was not confirmed. This was because they had a very large distribution and birds in adjacent population could breed with each other but birds at each end of the distribution (western Europe and South Asia I think) couldn't. I am pretty sure that they were some kind of gull and from Europe to Asia their wings got lighter, from black to grey. I think I might have read about them in a Richard Dawkins book.
Does anyone know the species I'm talking about? You're describing a Ring Species: "a connected series of neighbouring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene flow between each "linked" population".
The classic ring species is the Herring Gull complex, and that's probably what you read about:
The classical example of the ring species model was originally based upon the herring gull complex (Mayr 1942). This group comprises more than 20 taxa of large gulls (Haffer 1982) which together occupy a circumpolar breeding range in the northern hemisphere. ... Mayr envisioned all taxa of the circumpolar chain to be connected by gene flow, while herring and lesser black-backed gulls in Europe, the hypothetical endpoints of the ring, have reached full reproductive isolation and now coexist as distinct species.
--The Herring Gull Complex (Larus argentatus - fuscus - cachinnans) as a Model Group for Recent Holarctic Vertebrate Radiations
However, recent genetic work shows that the situation is even more complicated than this, and it's questionable whether they really are "ring species":
Contrary to the ring-species model, we find no genetic evidence for a closure of the circumpolar ring through colonization of Europe by North American herring gulls. However, closure of the ring in the opposite direction may be imminent, with lesser black-backed gulls about to colonize North America.
--The herring gull complex is not a ring species.
The following is multiple choice question (with options) to answer.
What term is used to describe birds that mate for an entire season or even stay paired for their entire life? | [
"polygamous",
"monogamous",
"asexual",
"homogeneous"
] | B | These birds are pairing up so that they can produce offspring. Many birds are monogamous , keeping the same mate for an entire season. In some species, they even stay paired for their entire life. |
SciQ | SciQ-2313 | neuroscience, physiology, neurophysiology, action-potential
All the content in this answer is material like you would find in a basic undergraduate neuroscience textbook. The ones I usually recommend are Purves or Kandel.
The following is multiple choice question (with options) to answer.
What branch of science offers an overview of the physiology of humans? | [
"engineer",
"human biology",
"geology",
"marine biology"
] | B | Human Biology provides an overview of the physiology of humans, from the skin inward. In addition to the skin, the skeletal, muscular, nervous, circulatory, respiratory, digestive, excretory, immune, and reproductive systems are described. |
SciQ | SciQ-2314 | cardiology, fat-metabolism
Title: Can fats clog veins or capillaries? I know that so much fats running in the bloodstream could deposit in arteries, harden forming a plaque and cause atherosclerosis. But what about veins (which are formed from same types of layers as arteries) and capillaries?
I googled a bit but everything was regarding arteries.
Is it because veins have a much wider diameter than arteries that even if some fats deposit they won't clog it?
And for capillaries, they are much smaller so shouldn't they be more vulnerable to this?
In addition, I guess since one of the lymphatic vessels functions are to transport fats from capillaries in villi to bloodstream, how are they adapted to prevent deposit of fats as they carry out the transportation?
N:B I'm just an OL biology student, and also horrible at chemistry
I know that so much fats running in the bloodstream could deposit in arteries, harden forming a plaque and cause atherosclerosis. But what about veins (which are formed from same types of layers as arteries) and capillaries?
Wikipedia says this:
Veins do not develop atheromata, because they are not subjected to the same haemodynamic pressure that arteries are,[8] unless surgically moved to function as an artery, as in bypass surgery.
The cited study isn't freely available, but seems to have tested in rabbits by surgically modifying their blood flow and giving them a high fat diet.
As for capillaries, they are continuously remodeled, so while they do become clogged for a variety of reasons, once flow stops they're disassembled and new capillaries formed if the tissue becomes hypoxic.
The following is multiple choice question (with options) to answer.
In atherosclerosis, thickening of an arterial wall due to this can restrict blood flow through the artery? | [
"digestion",
"high blood pressure",
"plaque formation",
"low blood pressure"
] | C | |
SciQ | SciQ-2315 | ethology, herpetology
The 'taping the surface they are on' seems like an attempt to induce vibrations, which is a method of communication.(2)
Some chameleon species communicate with one another by vibrating the substrate that they are standing on, such as a tree branch or leaf. Animals that use vibrational communication exhibit unique adaptations in morphology (i.e., body form) that enable them to detect vibration and use it in communication. These include unique adaptations in ear and jaw morphology that give the animal direct contact with the surface they are standing on, and enable them to detect subtle vibrations. Lizards that live on substrates that can be easily moved (such as thin tree branches or leaves) are probably more likely to use vibrational communication than lizards that live on substrates that do not transmit vibrations as easily, such as the ground or thick tree trunks.
1- https://www.scielo.br/scielo.php?script=sci_arttext&pid=S1676-06032011000400031#:~:text=The%20most%20commonly%20reported%20mating,Bull%202000%2C%20Ribeiro%20et%20al.
2- https://en.wikipedia.org/wiki/Lizard_communication
The following is multiple choice question (with options) to answer.
Moist skin distinguishes frogs from what animal with dry, bumpy skin? | [
"newts",
"turtles",
"snakes",
"toads"
] | D | Although there is actually little difference between toads and frogs, this animal would most often be called a toad. Frogs have moist skin, while toads have dry, bumpy skin. |
SciQ | SciQ-2316 | experimental-physics, energy-conservation, conservation-laws
This is what science is all about: Taking the vast landscape of possible ideas about how the world works - take as a simple example Aristoteles' idea that everything wants to be at rest vs. Newton's idea that everything continues uniform motion unless acted upon - looking at the predictions these different ideas about the laws of nature make and then performing experiments eliminating those ideas that are false. Thus, we make a gradual progress towards the underlying truth, which is empirically inaccessible. The longer we perform experiment, and think of new hypothesis, the more refined will our laws of nature be, the greater our confidence can be that these are really good approximations to the way the world really works.
To say "We cannot prove it, we really don't know" is to vastly underestimate the power of falsificationism, and shows a callous disregard for the scientific method, whose success is reflected in every bit of technology around us.
[One may also find my answer to Why should a (physical) principle be applicable to different systems in different positions in space and time? to be relevant in this context.]
The following is multiple choice question (with options) to answer.
Scientists perform experiments to test their hypotheses because sometimes the nature of natural universe is what? | [
"become obvious",
"not obvious",
"very obvious",
"this obvious"
] | B | Scientists perform experiments to test their hypotheses because sometimes the nature of natural universe is not obvious. |
SciQ | SciQ-2317 | visible-light, quantum-electrodynamics, terminology
Title: Name for phasor model of light I'm looking for the name of the model of light "exploring" every path to a given point, and reaching that point with a probability proportional to the square of the resultant phasor's amplitude. (Yes, that's why I need something more concise.)
I'm thinking that Quantum Electrodynamics is too general, and after some googling, "phasor model" doesn't seem to refer to light specifically.
If you can tell me that I'm wrong, or suggest a better name, it'd be appreciated. what you are referring is just the Feymann path integral, and you obtain probabilities only after you finished summing all the contributions And then, you square the final result - Finally, you divide the result by a suitable constant that guarantees that the probabilities of all possible outcomes sum exactly 1. This is what is called the normalization factor
The following is multiple choice question (with options) to answer.
What is the term for movement toward light? | [
"autolysis",
"gravitational pull",
"phototaxis",
"phototropism"
] | C | Motility The majority of protists are motile, but different types of protists have evolved varied modes of movement (Figure 23.8). Some protists have one or more flagella, which they rotate or whip. Others are covered in rows or tufts of tiny cilia that they coordinately beat to swim. Still others form cytoplasmic extensions called pseudopodia anywhere on the cell, anchor the pseudopodia to a substrate, and pull themselves forward. Some protists can move toward or away from a stimulus, a movement referred to as taxis. Movement toward light, termed phototaxis, is accomplished by coupling their locomotion strategy with a light-sensing organ. |
SciQ | SciQ-2318 | spectroscopy, electrons, ionization-energy, electromagnetic-radiation
In order to excite a valence electron, the longest wavelength or lowest energy radiation is usually in the visible region, not longer than ~700 nm. I'm not sure if there is a lower limit to this energy, or what the observed lowest energy electronic transition is, but certainly in this region, there is some overlap with the energy required to excite molecular vibrations. For some nice cases you can perform vibrational-electronic spectroscopy (usually called "vibronic" spectroscopy), where you resolve a number of vibrational transitions (peaks) as fine splitting or fine structure for a single electronic transition:
$\hspace{20ex}$
However, we do not say that "infrared radiation can excite electrons", though there is a range of frequencies where the types of excitation couple together. See also rotational-vibrational (rovibrational) spectroscopy; a nice example is hydrogen chloride in the gas phase.
The reason coordination complexes are often colored is because there are valence electronic excitations that correspond to the absorption of electromagnetic radiation in the visible region. The reason many molecules or complexes are white is because their lowest energy electronic transition is in the ultraviolet region. This is more general than losing degeneracy, and holds true for any macroscopic or microscopic system. It is not different from the color we see for conjugated systems. If the lowest energy available transition of a system is in the visible region, the system will appear colored. If it absorbs red-orange light, the opposite side of a color wheel will show you that it should appear green-blue. What you see as the system's color is the remaining color after subtracting the absorbed color. Yes, the kinds of orbitals involved are different (d-d transitions or metal-to-ligand charge transfer versus $\pi\rightarrow\pi^{*}$), but the transition energy matching is the most important thing.
For the "limit of ionizing radiation", ionization refers not to the excitation of an electron, but its removal:
$$
\ce{X + energy -> X+ + e-}
$$
The following is multiple choice question (with options) to answer.
Ultraviolet radiation has the highest energy; which has the lowest? | [
"thermal",
"kinetic",
"nuclear",
"infrared"
] | D | Ultraviolet radiation has the highest energy; infrared the lowest. |
SciQ | SciQ-2319 | gene-expression, transcription, gene-regulation
Title: Transcription of Genes: Are Specific Transcription Factors + Enhancers Necessary? I learned about transcription in my AP Biology class and we discussed how transcription occurs, but I was wondering whether transcription always requires the enhancers, activators (specific transcription factors), DNA-bending proteins, etc. to be present, or if this is only used for higher-level production of RNA transcripts?
Can transcription occur if only the RNA Polymerase (I, II, or III) and the General Transcription Factors are present?
Thanks! enhancers, activators, silencers, repressors are necessary in controlling of the transcriptional process. Utilization of enhancers/silencers plays a part in differentiation of developmental processes (i.e. maturation, growth)
https://en.wikipedia.org/wiki/Enhancer_(genetics)
The following is multiple choice question (with options) to answer.
What kind of proteins either activate or deactivate the transcription of other genes? | [
"master regulatory proteins",
"master complex proteins",
"carbon proteins",
"perfect regulatory proteins"
] | A | What makes the heart form during development? What makes the skin form? What makes a structure become an arm instead of a leg? These processes occur during development because of a highly specific pattern of gene expression. This intensely regulated pattern of gene expression turns genes on in the right cell at the right time, such that the resulting proteins can perform their necessary functions to ensure proper development. Transcription factors play an extremely important role during development. Many of these proteins can be considered master regulatory proteins , in the sense that they either activate or deactivate the transcription of other genes and, in turn, these secondary gene products can regulate the expression of still other genes in a regulatory cascade. Homeobox genes and gap genes are important classes of transcription factors utilized during development. |
SciQ | SciQ-2320 | h. Evaluate C.
i. Compute Q(7), the amount of glucose produced during the day.
Exercise 10.3.5 “Based on studies using isolated animal pancreas preparations
maintained in vitro, it has been determined that insulin is secreted in a biphasic manner in response to a marked increase in blood glucose. There is an initial burst of insulin secretion that may last 5-15 minutes, a result of secretion of preformed insulin secretory granules. This is followed by more gradual and sustained insulin secretion that results largely from biosynthesis of new insulin molecules. ” (Rhoades and Tanner, P 710)
a. A student eats a candy bar at 10:20 am. Draw a graph representative of the rate of insulin secretion between 10:00 and 11:00 am.
b. Draw a graph representative of the amount of serum insulin between 10:00 and 11:00. Assume that insulin is degraded throughout 10 to 11 am at a rate equal to insulin production before the candy is eaten, and that serum insulin at 10:00 was Iq.
CHAPTER 10. THE FUNDAMENTAL THEOREM OF CALCULUS
468
c. Write an expression for the amount of serum insulin, I(t), for t between 10:00 and 11:00 am.
Exercise 10.3.6 Equal quantities of gaseous hydrogen and iodine are mixed resulting in the reaction
which runs until I 2 is exhausted [H 2 is also exhausted). The rate at which I 2 disappears is ^°’^ 2 gm/sec. How much I 2 was initially introduced into the mixture?
a. Sketch the graph of the reaction rate, r(t) = jp^yi-
b. Approximately how much I 2 combined with H 2 during the first second?
c. Approximately how much I 2 combined with H 2 during the second second?
d. Let Q(x) be the amount of I 2 that combines with H 2 during time 0 to 2; seconds. Write an integral that is Q(x).
e. What is Q\x)l
f. Compute W'{x) for W(x) = =^.
g. Show that there is a number, C, for which Q(x) = W(x) + C.
h. Show that C = 0.2 so that Q(x) = 0.2 – g.
The following is multiple choice question (with options) to answer.
What occurs when the pancreas doesn’t make enough insulin or else the body’s cells are resistant to the effects of insulin? | [
"hepatitis",
"anemia",
"colitis",
"diabetes"
] | D | Diabetes is another type of noninfectious disease. Diabetes occurs when the pancreas doesn’t make enough insulin or else the body’s cells are resistant to the effects of insulin. Insulin is a hormone that helps cells absorb glucose from the blood. |
SciQ | SciQ-2321 | orbitals, atoms
Title: Why are atoms with eight electrons in the outer shell extremely stable? Atoms that have eight electrons in their outer shell are extremely stable. It can't be because both the $s$ and the $p$ orbitals are full, because then an atom with 13 or 18 valence electrons would be extremely stable. ($d$ has 10, and 5 is also stable).
Why is it that atoms with eight electrons in the outer shell are extremely stable? First, this isn't quite true. It is true for the first row of the periodic chart (from lithium to neon). It is almost true for the second row (from sodium to argon. But there are exceptions there. Beyond that it really isn't true at all for the elements beyond the first two columns.
The reason for the increased stability for the first two rows lies in quantum mechanics. Classically we can note that there are no $d$ electrons there. Another ways of looking at it from a classical point of view is that the early elements are too small to allow too many other atoms or groups of atoms around them. That tends to go away as you go down the periodic chart and the atoms get "fatter". A typical example is chloroplatinic acid which has six chlorines around it.
Most transition metals also can have more than four groups around them as well.
I suspect that this isn't an exceptionally useful explanation. As I said, the answer really lies in quantum mechanics. In looking up "molecular orbital theory", one reference can be found here.
The following is multiple choice question (with options) to answer.
According to the octet rule, magnesium is unstable because its valence shell has just two of what? | [
"protons",
"quarks",
"neutrons",
"electrons"
] | D | Chapter 2 1 The mass number is the total number of protons and neutrons in the nucleus of an atom. 3 The water hydrolyses, or breaks, the glycosidic bond, forming two monosaccharides. 4 D 6 A 8 B 10 C 12 B 14 A 16 C 18 A 20 B 22 D 24 B 26 A 28 B 30 D 32 B 33 These four elements—oxygen, carbon, hydrogen, and nitrogen—together make up more than 95 percent of the mass of the human body, and the body cannot make elements, so it is helpful to have them in consumables. 35 Magnesium’s 12 electrons are distributed as follows: two in the first shell, eight in the second shell, and two in its valence shell. According to the octet rule, magnesium is unstable (reactive) because its valence shell has just two electrons. It is therefore likely to participate in chemical reactions in which it donates two electrons. 37 Water is a polar molecule. It has a region of weakly positive charge and a region of weakly negative charge. These regions are attracted to ions as well as to other polar molecules. Oils are nonpolar, and are repelled by water. 39 It is not. An exchange reaction might be AB + CD → AC + BD or AB + CD → AD + BC . In all chemical reactions, including exchange reactions, the components of the reactants are identical to the components of the products. A component present among the reactants cannot disappear, nor can a component not present in the reactants suddenly appear in the products. 41 Lemon juice is one hundred times more acidic than orange juice. This means that lemon juice has a one hundred-fold greater concentration of hydrogen ions. 43 Maltose contains 12 atoms of carbon, but only 22 atoms of hydrogen and 11 atoms of oxygen, because a molecule of water is removed during its formation via dehydration synthesis. |
SciQ | SciQ-2322 | geometry, distance, perception
Title: Why do objects appear smaller when viewed from a distance? Yes, I know all about perspective (I'm an artist). I even have some basic knowledge of descriptive geometry. I know how it works. My question is more about why it works.
I have a sneaking suspicion it has something to do with the curvature of space. However, I'm not certain whether the two concepts are related.
Another thing that's been bothering me for a while (this may or may not be related to the question: please enlighten me) is the relation of the vanishing point to the horizon:
Strictly speaking, the geometrical horizon is where the vanishing point is. The actual horizon is a bit lower, but the difference is negligible.
Thus, if you sketch a perfectly straight street lined with buildings of equal size stretching all the way to the horizon, you shouldn't even be able to see anything beyond 2.9 miles (the distance to the horizon): all parallel lines will merge - and vanish. And yet, if the buildings are large enough, they will be visible beyond that point.
The following is multiple choice question (with options) to answer.
What make distant objects appear both nearer and larger? | [
"mirrors",
"telescopes",
"lasers",
"astrolabes"
] | B | Telescopes make distant objects appear both nearer and larger. You can see many more stars through a telescope than with the unaided eye. |
SciQ | SciQ-2323 | atmospheric-science, density, air
Title: Why does the composition of the air does not change with altitude? Air contains about 78% nitrogen and 21% oxygen independent of altitude (up to 100 km). Why is this? Shouldn't the concentration of nitrogen increase with higher altitudes since nitrogen has a lower density than oxygen?
Shouldn't the concentration of nitrogen increase with higher altitudes since nitrogen has a lower density than oxygen?
No, it shouldn't, at least not up to 100 km or so. Look at your graph, which shows that even argon is well-mixed throughout the lower atmosphere (the troposphere, stratosphere, and mesosphere). Argon atoms are considerably more massive than are carbon dioxide molecules, which in turn are considerably more massive than oxygen and nitrogen molecules, and yet all of these (along with all of the long-lived gases in the atmosphere) are well-mixed throughout the lower atmosphere.
The reason is that the lower atmosphere is dense enough to support turbulence while the upper atmosphere is not. The turbopause marks the somewhat fuzzy boundary below which turbulent mixing dominates over diffusion and above which it's diffusion that dominates.
The following is multiple choice question (with options) to answer.
The atmosphere consists of oxygen, nitrogen, carbon dioxide, which exerts a certain pressure referred to as what? | [
"atmospheric pressure",
"gravity pressure",
"tidal pressure",
"nitrogen pressure"
] | A | Gas Laws and Air Composition Gas molecules exert force on the surfaces with which they are in contact; this force is called pressure. In natural systems, gases are normally present as a mixture of different types of molecules. For example, the atmosphere consists of oxygen, nitrogen, carbon dioxide, and other gaseous molecules, and this gaseous mixture exerts a certain pressure referred to as atmospheric pressure (Table 22.2). Partial pressure (Px) is the pressure of a single type of gas in a mixture of gases. For example, in the atmosphere, oxygen exerts a partial pressure, and nitrogen exerts another partial pressure, independent of the partial pressure of oxygen (Figure 22.21). Total pressure is the sum of all the partial pressures of a gaseous mixture. Dalton’s law describes the behavior of nonreactive gases in a gaseous mixture and states that a specific gas type in a mixture exerts its own pressure; thus, the total pressure exerted by a mixture of gases is the sum of the partial pressures of the gases in the mixture. |
SciQ | SciQ-2324 | neuroscience, pathology, human-physiology, breathing
Title: In scuba diving, are nitrogen narcosis and high pressure nervous syndrome the same thing? In training for scuba diving, they tell you that when you're bellow 100 ft or so you have to watch out for changes in mental state that resemble drunkenness. The cause of these mental disturbances is called nitrogen narcosis, and it has something to do with the increased pressure on the nitrogen component of the gas that you're breathing out of your tank. I just read this article from the what-if section of XKCD (halfway down the page, under the header about Michael Phelps) that mentioned a very similar sounding disorder called high pressure nervous syndrome. Are nitrogen narcosis and high pressure nervous syndrome related, or are the effects of high pressure nitrogen and high pressure by itself separable? These are different things.
Nitrogen Narcosis or more commonly Gas Narcosis is the narcotic effect of gasses like Oxygen and Nitrogen under pressure. The effects are most prominent under 30m and commercial/technical dives doing dives to 40/50m on air tend to experience the effects most. (Narcosis is managed by adding an inert gas - in most gases Helium - to air to form a mixture referred to as Trimix (Helium/Oxygen/Nitrogen) this then produces an effect as if the diver is diving to a shallower depth and is referred to as Equivalent Narcotic Depth, in some cases Heliox (Helium & Oxygen) was also used)
High Pressure Nervous Syndrome is an interesting aspect of deep diving and used to be called Helium Jitters/Tremors as the accepted standard was that it was caused by breathing Helium mixtures under 150m. Some people hold this to be true and others claim that it has nothing to do with Helium but rather the pressure disrupting the flow of electric signals thru the nervous system.
What is interesting is that they found that if you used Trimix (Helium/Nitrogen/Oxygen) rather than Heliox (Helium/Oxygen) the onset happened later or not as severe. And the slower your descent is the slower the onset of the symptoms.
Some Docs to Read:
Narcosis - Relatively simple document on Narcosis
The following is multiple choice question (with options) to answer.
What is the oxygen-storing protein found in diving mammals' muscles called? | [
"pheromone",
"pigment",
"myoglobin",
"hemoglobin"
] | C | |
SciQ | SciQ-2325 | atoms, phase
Title: What is the physical state of a single atom? Can a single atom on its own be either a solid, liquid, or a gas? Or is it none of them? This answer has been written so it hopefully can be understood by people that do not have a degree. If something is not correct, let me know, but be aware that throwing around fancy words will not help anyone understanding this any better. Consider the other posts here concerning liquids and solids, I don't want to be redundant and repeat what has been said already.
The answer is a bit complicated. One would intuitively say no, but that doesn't tell the whole story.
Take the interstellar medium. We have about 1 atom per cm³ in there and it is called a "gas". Now that's what I would call an isolated atom in the gas phase.
An atom is an object that belongs into the realms of quantum mechanics. A solid, liquid or gas is something that belongs into our classical world. If you zoom in close enough, that means if we look at a problem microscopically, words like "solid" or "liquid" no longer make sense. If you now begin to zoom out, the quantum effects vanish. This is sometimes called quantum decoherence and we enter the world of classical physics where solids and and liquids exist again.
So I would argue it all depends on how closely you look at the problem. Isolated atoms in a large volume? A gas if you ask me. But if you have to zoom in to talk about an individual atom within a larger compound consisting of many more atoms, let's say one atom within a piece of iron, you no longer can say that this single atom is "solid".
Think of it like this:
Can a single person have a political system?
The following is multiple choice question (with options) to answer.
The modern atomic theory states that all matter is composed of what? | [
"quarks",
"atoms",
"molecules",
"ions"
] | B | The modern atomic theory states that all matter is composed of atoms. |
SciQ | SciQ-2326 | physical-chemistry, solubility
Title: At what point does decreasing solvent temperature cause a decrease in gas solubility? Example: At constant pressure, carbon dioxide becomes less soluble in water as temperature increases. We also know that carbon dioxide becomes more soluble in water as temperature decreases.
Does introduction of order and loss of kinetic energy of solvent molecules eventually lead to a decrease in a solvent's ability to accommodate gas molecules? It is hard for me to believe that ice cubes can hold gas more effectively than the same volume of a glass of water. Rules such as "solubility of A in B rises with lower temperature" are only meant to be used if there is no phase transition of the participating substances.
The following is multiple choice question (with options) to answer.
Pressure has a significant effect on the solubility of what state of matter? | [
"mixtures",
"gases",
"solids",
"water"
] | B | Pressure has very little effect on the solubility of solids or liquids, but has a significant effect on the solubility of gases. Gas solubility increases as the partial pressure of a gas above the liquid increases. Suppose a certain volume of water is in a closed container with the space above it occupied by carbon dioxide gas at standard pressure. Some of the CO 2 molecules come into contact with the surface of the water and dissolve into the liquid. Now suppose that more CO 2 is added to the space above the container, causing a pressure increase. More CO 2 molecules are now in contact with the water and so more of them dissolve. Thus the solubility increases as the pressure increases. As with a solid, the CO 2 that is undissolved reaches an equilibrium with the dissolved CO 2 , represented by the following equation. |
SciQ | SciQ-2327 | cell-biology, nutrition, blood-circulation, liver
Title: How do nutrients get to the cells they need to get to? I understand the basics of digestion. I know that nutrients get absorbed by the microvilli, enter the bloodstream and travel to the liver but after all that, what is the biological mechanism that guides these nutrients to the proper receiving location? Broadly speaking, nutrients that enter the blood from the gut, and those that are released into the blood by the liver, are available to any cells that require them. So there is no "guiding to the correct location" in the sense that you suggest.
Lipids for example are present in the various lipoproteins and can be acquired from these by all cells. Iron is bound to transferrin, and any cell with transferrin receptors can internalise the transferrin and take the iron. Glucose is available in solution in the plasma, and free fatty acids are bound to serum albumin in the blood. During starvation the liver produces ketones ("ketone bodies") which are taken up by many different tissues/cell types.
The following is multiple choice question (with options) to answer.
The site of some nutrient absorption, the ileum is the third part of what digestive organ? | [
"rectum",
"stomach",
"large intestine",
"small intestine"
] | D | The ileum is the third part of the small intestine. A few remaining nutrients are absorbed here. Like the jejunum, the inner surface of the ileum is covered with villi that increase the surface area for absorption. |
SciQ | SciQ-2328 | bond, electronegativity, polarity
Title: Why are bonds ionic when the electronegativity difference between bonded atoms is greater than 1.7? I'm learning about how to recognise whether a bond is ionic or covalent, based on the difference in electronegativity between the two bonding partners, $\Delta \chi$.
What I have now is a formula:
If $\Delta \chi = 0$, then the bond is nonpolar
If $0 < \Delta\chi \leq 1.7$, then the bond is polar covalent
If $\Delta \chi > 1.7$, then the bond is ionic
But I don't know how scientists determined that formula, the history of it and which experiment indicates that formula. The first thing to consider is the difference between covalent and ionic bonding, from the UCDavis ChemWiki site Ionic and Covalent Bonds,
In ionic bonding, atoms transfer electrons to each other. Ionic bonds require at least one electron donor and one electron acceptor. In contrast, atoms that have the same electronegativity share electrons in covalent bonds since donating or receiving electrons is unfavorable.
The electron donor has a low electronegativity and the electron acceptor has a higher elelctronegativity - so there is a difference in electronegativity $\Delta{EN}$, effectively creating a positive and negative end, an example is below:
Image source: Japan Synchrotron Radiation Research Institute (JASRI)
When the differences in electronegativities of various compounds are graphed against % ionic character, as shown below:
Image source: University of Florida Chemical Bonding page
Values of $\Delta{EN}$ greater than 1.7 correspond to an ionic character of greater than 50%, from the University of Florida website:
What determines how the electrons are shared is the relative electronegativity (electron greed) of the bonding atoms. The degree of polarity or degree of ionic bonding of any given bond can vary continuosly zero to nearly 100%. We normally say that bonds between atoms with electronegativity difference ($\Delta{EN}$) greater than 1.7 are ionic, although this really means only more than about half ionic in character.
Another resource is from the University of Washington Lecture 23: Ionic to Covalent Bonds.
The following is multiple choice question (with options) to answer.
If both atoms are the same, they have the same electronegativity and share what type of bond? | [
"metabolic",
"isotopic covalent",
"ionic",
"nonpolar covalent"
] | D | |
SciQ | SciQ-2329 | geophysics, plate-tectonics, earth-history, continent
Title: Why Do Supercontinents Form? It would seem, on the face of it, improbable that the continental land-masses would accumulate into a single composite, yet it has happened numerous times, and is expected to again in the future.
There must likely then be some aspect of plate tectonics which favors these arrangements.
Can anyone provide an explanation?
EDIT: This is not, as I see it, a duplicate of the 'What are the causes of the supercontinent cycle?' question. This question goes to what process drives the formation of any & all supercontinent formations, which I assert should be improbable, made more improbable by their recurrence, not so much the cycle itself. The other question did not address this more fundamental aspect, or in any case receive a pertinent account of its resolution. If anyone wants to engage on this, or doesn't see the distinction, please do so in the comments or a chat. I think the mechanisms that you're looking for are subduction, paired with the "stickiness" of continental crust.
The subduction of oceanic crust under continental crust inevitably creates a net movement of crustal material toward a continental plate. Any oceanic plate that is carrying continental material will therefore always drag that continent toward the continental plate that it is subducting underneath, always resulting in eventual collision.
If an oceanic plate has subduction occurring on both sides, the ocean will inevitably narrow until it closes, thereby causing the continental plates on either side to collide.
In every case, subduction inevitably pulls continents together.
Furthermore, once continental plates collide, they have a tendency to stick together for long periods of time, increasing the likelihood that all continental material will eventually accumulate there.
The following is multiple choice question (with options) to answer.
What forms when oceanic crust subducts into the mantle at convergent plate boundaries? | [
"tsunamis",
"glaciers",
"volcanic mountain ranges",
"coral"
] | C | Volcanic mountain ranges form when oceanic crust subducts into the mantle at convergent plate boundaries. The Andes Mountains are a chain of coastal volcanic mountains. They are forming as the Nazca plate subducts beneath the South American plate ( Figure below ). |
SciQ | SciQ-2330 | physiology, respiration
Title: Why does a worm's skin need to be wet for oxygen to diffuse across it? Pages I've read about worms' respiratory systems says that the skin needs to be wet (covered in mucus) or oxygen won't diffuse across the skin. Why? If there is more oxygen outside the worm's skin than inside, what prevents it from diffusing across the skin, even if the skin is dried out? The quick answer: When the skin dries, the lipids in the cell membranes of the skin tissue undergo a phase transition which makes the membranes less permeable for oxygen.
Explanation: The lipids of the cell membrane can exist in different phase states. In the liquid disordered phase the lipids are relatively flexible and mobile, making this phase more oxygen permeable compared to the liquid ordered phase, in which the lipids are more rigidly packed.
The phase transition temperature of lipids increases upon dehydration (another reference), meaning that at the same ambient temperature, a dry lipid membrane is in the liquid ordered state and a wet lipid membrane is in the liquid disordered state.
Therefore, a dry cell membrane is less oxygen permeable than a wet one.
The following is multiple choice question (with options) to answer.
The skin plays an important role in preventing the escape of what commonly found liquid from the body? | [
"urine",
"stomach acid",
"water",
"hormones"
] | C | The skin has multiple roles in the body. Many of these roles are related to homeostasis. The skin’s main functions are preventing water loss from the body and serving as a barrier to the entry of microorganisms. In addition, melanin in the skin blocks UV light and protects deeper layers from its damaging effects. |
SciQ | SciQ-2331 | human-biology, physiology, cardiology, anatomy
Title: Can humans live without their right atrium? The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated blood from the superior and inferior venae cavae, the coronary sinus, and the anterior and smallest cardiac veins, and pumps it into the right ventricle through the tricuspid valve.
Can humans survive without right atrium? In this condition blood would fill the right ventricle directly, comparable to some animals like frogs, toads, snakes and lizards. What advantages does the normal human heart have to this anatomy ? If we had this anatomy, where would the best place for pacemakers be, like the sinus node? This is an interesting theoretical question, but several things would need to be clarified:
Does removing the R atrium relocate the SA node to the R ventricle or remove it completely from the picture?
Does the remaining R ventricle have a tricuspid valve?
Technically, the R atrium is the home of the sino-atrial node, which provides natural pacing of the human heart between 60-80 beats/min. Without this natural pacing, our hearts would rely on back-up pacer systems such as atrioventricular node, His-Purkinje systems or the intrinsic but ectopic pacing of individual atrial or ventricular cells.
The following is multiple choice question (with options) to answer.
Which area of the human heart pumps the blood to the right ventricle? | [
"true atrium",
"right atrium",
"left atrium",
"left ventricle"
] | B | Blood from the body enters the right atrium of the heart. The right atrium pumps the blood to the right ventricle, which pumps it to the lungs. |
SciQ | SciQ-2332 | volcanoes, pyroclastic-flows
Edit: In a research* it is suggested that a turbidite current can flow over barriers, if the thickness of the flow exceeds %65 of the barrier. One may interpret this that, after a pyroclastic current dives to shallow water it may come back to the surface again.
The following is multiple choice question (with options) to answer.
What moves sediments after they have formed? | [
"migration",
"photosynthesis",
"perspiration",
"erosion"
] | D | Erosion moves sediments after they have formed. The sediments are transported away from the place where they form. There are several agents of erosion. Flowing water moves and deposits sediments. Water erodes far more material than any other erosional agent. Wind is important as an agent of erosion. This is especially true in arid climates. Ice, in glaciers, can erode enormous quantities of sediments. Gravity as a force of erosion pulls material downhill. |
SciQ | SciQ-2333 | quantum-mechanics
Title: Timing of photon emission by electron in bound state A photon is emitted by an electron (which is in a bound state). Is the energy of the electron lost immediately, or is the energy emitted during the complete transition time? I think my second assumption is correct but confirmation would be greatly appreciated.
In other words, should I view photon emission as part of the transition process or as merely the cause of it? I am aware that during the transition the election can be viewed as transitioning through a multitude of highly unstable orbitals until it finally settles into the lower level.
This post What is the Quantum Transition Time for Photon Emission? is very useful and really brings home the subtleties involved in quantum mechanics, but I don't think it addresses my question directly.
A photon is emitted by an electron (which is in a bound state). Is the energy of the electron lost immediately, or is the energy emitted during the complete transition time? I think my second assumption is correct but confirmation would be greatly appreciated
One has to let go of the classical framework. Immediately in time has a meaning for a ball falling in the Newtonian gravitational field and mathematics can give you the rate of energy loss per delta(t) because in principle every (x,y,z) point is reached at a specific t. This does not hold in the quantum mechanical framework of an electron bound to an atom.
An individual atom with its electron in an excited state may emit the photon at an arbitrary time t. One has to take a large sample of atoms with the electrons at that energy level and measure the time the photon hits the detector . One then will have a curve characterizing the lifetime of that bound state's collective time behavior
Now in the post you have quoted the answers are indicating the mathematical formulation within the theory of Quantum Mechanics that reproduce this experimental observation. Quantum mechanical calculations give probability distributions for the variables under consideration, time in this instance, to fit the experimental observations.
What is really happening at the individual atom's decay from a higher energy level to a lower one is random to first order ( it is the assumption of calculating the half life curves) . The time will be within the Heisenberg Uncertainty of delta(E)*delta(t) is all that can be safely claimed , and can be presumed "instantaneous" , in the sense that there are no experimental tools to explore further, other than the mathematical ones discussed in the answers of the other question.
The following is multiple choice question (with options) to answer.
What involves the emission of a particle and/or energy as one atom changes into another? | [
"radioactive decay",
"enthalpy",
"atomic transformation",
"spontaneous mutation"
] | A | Radioactive decay involves the emission of a particle and/or energy as one atom changes into another. In most instances, the atom changes its identity to become a new element. There are four different types of emissions that occur. |
SciQ | SciQ-2334 | zoology, species-identification, entomology
Title: Identification of a segmented black insect in France
Found in the Lot department of southern France. I think this is some sort of soldier fly larva (family Stratiomyidae). That would explain lack of legs. There are thousands of species world wide, with both aquatic and terrestrial larvae, so it might be possible to narrow it down a bit more.
Image from bugguide.net for comparison:
Thanks to @bli for reminding me of dipteran larvae!
The following is multiple choice question (with options) to answer.
Certain anaerobic parabasalid species exist in the digestive tracts of termites and wood-eating cockroaches, where they contribute an essential step in the digestion of this? | [
"fiber",
"nutrients",
"carbonate",
"cellulose"
] | D | Protists do not create food sources only for sea-dwelling organisms. For instance, certain anaerobic parabasalid species exist in the digestive tracts of termites and wood-eating cockroaches, where they contribute an essential step in the digestion of cellulose ingested by these insects as they bore through wood. |
SciQ | SciQ-2335 | cell-biology, cancer, cloning
Title: Difference between clonal and subclonal mutations I'm a physicist writing a proposal that has to do with cancer as a disease driven by evolutionary selection. As far as I understand, all tumors start with a single precursor (single cell or group of cells), and the other cells derive from this precursor by cycles of alterations and selection processes.
Reading recent articles, such as this, I learned that the derived cells include both clones and subclones. Since I'm not sure I understood things correctly, I have a few questions on the difference between the two words:
Is it OK to call clones the cells derived from the precursors?
When should I use subclones?
In the case of heterogeneity, is it fine to call clonal population a group of clones with the same characteristics? clones means when a cell has the same DNA characteristics as his predecessor so in that case of yours you could say that those cells are clones while for sub-clones I am not that sure, the difference of clone and sub-clone is that a sub-clone is basically a clone who is then remade with a different characteristic(an upgrade if you will) , since cancer are mutated cells you could call them like that but only if you study its DNA, meaning you have to study deep to find out if there are sub-clones in there. AS for the 3 question I didn't quite understood what you meant cuz you just used 2 words with opposite meaning because heterogeneity means a group of organismes with different characteristics and clonal population means organismes with same DNA ( much like a colony of bacteria).
The following is multiple choice question (with options) to answer.
What do you call a group of cells of the same kind that performs the same function? | [
"organ system",
"tissue",
"molecule",
"nucleus"
] | B | Specialized cells may be organized into tissues. A tissue is a group of cells of the same kind that performs the same function. For example, muscle cells are organized into muscle tissue. The function of muscle tissue is to contract in order to move the body or its parts. |
SciQ | SciQ-2336 | enzymes
Title: Origin of enzyme names Sometimes I get confused about why this or that enzyme was named in this or that particular way.
1) TCA: Why was not isocitrate dehydrogenase named isocitrate decarboxylase?
Wouldn't it have been at least as accurate to name the enzyme in question isocitrate decarboxylase as to call it isocitrate dehydrogenase? It does remove the -COOH, doesn't it?
2) Glycolysis: PEP (phosphoenolpyruvate) carboxykinase. Why isn't it oxaloacetate carboxykinase? Isn't it agreed upon that enzyme substrate be used in the name of enzyme?
3) Why name enzymes by reverse reactions (especially when the reaction is irreversible)? Pyruvatekinase makes pyruvate from PEP. Why not use another name, PEP phosphatase, for example?
I understand that this is the way the enzymes were named and I just have to accept it. But I would also like to understand the logic behind these names. As @Chris commented, when assayed in vitro with a single substrate (which may not even be the physiological one) most enzymes can catalyse a reaction in either direction. And enzymes such as pyruvate kinase were discovered before the pathways they are constituents of were worked out in full. Furthermore, the ways of naming enzymes only became more sophisticated as more were discovered and characterized. (Try googling for ‘old yellow enzyme’.)
Let us take pyruvate kinase as an example. The name kinase is clearly not chemically descriptive but was applied to any reaction using ATP. But, never mind, go to the Wikipedia page for pyruvate kinase and click on the EC (Enzyme Commission) number — 2.7.1.40 — in the box on the right. You will come to a page where you will see that, like TS Eliot’s cat, the enzyme has three different names:
Accepted Name: pyruvate kinase
(because that’s what everyone uses and is in all the text books)
Other names: phosphoenolpyruvate kinase; phosphoenol transphosphorylase
The following is multiple choice question (with options) to answer.
What is the name of a reactant in an enzymatic reaction? | [
"tissues",
"substrate",
"Scar",
"membrane"
] | B | Proteins Function as Enzymes If you were trying to type a paper, and every time you hit a key on your laptop there was a delay of six or seven minutes before you got a response, you would probably get a new laptop. In a similar way, without enzymes to catalyze chemical reactions, the human body would be nonfunctional. It functions only because enzymes function. Enzymatic reactions—chemical reactions catalyzed by enzymes—begin when substrates bind to the enzyme. A substrate is a reactant in an enzymatic reaction. This occurs on regions of the enzyme known as active sites (Figure 2.27). Any given enzyme catalyzes just one type of chemical reaction. This characteristic, called specificity, is due to the fact that a substrate with a particular shape and electrical charge can bind only to an active site corresponding to that substrate. |
SciQ | SciQ-2337 | gas-laws
Ideal Gas Law
You can find the volume of the system because you have the total moles $n_T$ and the total pressure $P_T$:
$$V=\frac{n_T RT}{P_T}$$
You can then replace the number of moles with $n_A$ and solve for $P_A$;
$$P_A=\frac{n_A RT}{V}$$
This approach is basically equivalent to the previous except:
Using the ideal gas law you have to do two calculation (volume and partial pressure), while you only need to do one with Dalton's Law
Fewer math steps means less rounding, which means less error and higher precision.
If you use Dalton's Law, you don't have to worry about the units of temperature or pressure. Temperature is not in the equation, and the pressures are a ratio. You can use whatever pressure unit you want without converting.
You don't need to worry about $R$ and its units in the Dalton's Law approach.
Solve problems as ratios whenever you have the chance.
The following is multiple choice question (with options) to answer.
The ideal gas law is used like any other gas law, with attention paid to the unit and making sure that temperature is expressed in kelvin. however, the ideal gas law does not require a change in the conditions of a gas sample. the ideal gas law implies that if you know any three of the physical properties of a gas, you can calculate this? | [
"fourth",
"second",
"unrelated",
"third"
] | A | The ideal gas law is used like any other gas law, with attention paid to the unit and making sure that temperature is expressed in Kelvin. However, the ideal gas law does not require a change in the conditions of a gas sample. The ideal gas law implies that if you know any three of the physical properties of a gas, you can calculate the fourth property. |
SciQ | SciQ-2338 | organic-chemistry, terminology, hydrocarbons
Title: Is alkene reaction with hydrogen to form an alkane an addition reaction? I have seen in some textbooks that such a reaction is listed under reduction of alkenes.
I understand that the double bond is getting reduced to single bond and one hydrogen atom is added to each of the carbons.
Should I classify this reaction as an addition reaction or a reduction reaction? Yes, the hydrogenation reaction of alkenes is typically classified as an addition reaction. See here and there, for example.
The following is multiple choice question (with options) to answer.
What is a reaction in which an atom or molecule is added to an unsaturated molecule, making a single product? | [
"homeostasis",
"single reaction",
"an addition reaction",
"complete reaction"
] | C | An addition reaction is a reaction in which an atom or molecule is added to an unsaturated molecule, making a single product . An addition reaction can be thought of as adding a molecule across the double or triple bond of an alkene or alkyne. Addition reactions are useful ways to introduce a new functional group into an organic molecule. |
SciQ | SciQ-2339 | history, autoimmune, diabetes-mellitus
Title: When was it determined that Type 1 Diabetes is an autoimmune disease? I just found out today that type 1 diabetes is an autoimmune disease. When was this discovered? This question has two answers: The difference was first described in 1936 by Harold Percival Himsworth, which described it in this article.
At this time it was established that there are two forms of Diabetes, one sensitive to insuline while the other is not.
The terms Diabetes type 1 and 2 where established somewhere between 1974 and 1976, for details see the review "The discovery of type 1 Diabetes".
The following is multiple choice question (with options) to answer.
What is the main problem in both types of diabetes? | [
"blood concentration",
"metabolism",
"insulin production",
"blood pressure"
] | C | Diabetes is a disease in which insulin fails to keep blood glucose levels within a healthy range. In type 1 diabetes, the pancreas doesn’t produce insulin. In type 2 diabetes, body cells do not respond normally to insulin. |
SciQ | SciQ-2340 | evolution, biochemistry, mitochondria
Title: Is there any advantage of having mitochondria for aerobic respiration? If we consider the pathway of breakdown of glucose which includes glycolysis, the citric acid cycle and the electron transport chain, all these processes takes place in some prokaryotes and eukaryotes. In prokaryotes all these processes take place in cytoplasm while in eukaryotes the last two processes take place in mitochondria.
So is there any advantage of performing the last two processes in the mitochondria? Does it yield more energy? If there is no advantage, what is the point of having a mitochondria (at least for this process)? From the evolutionary point of view, the eukaryotes acquired these metabolisms (except glycolysis) from their prokaryotic endosymbionts. Not all prokaryotes have the ETC. The free living ancestor of mitohondria is supposed to be the alpha-proteobacterium.
Now, glycolysis is a common pathway in lot of lifeforms perhaps because of abundance of glucose. TCA cycle is coupled with ETC at certain steps which makes it essentially a part of aerobic metabolism.
The reason for having a dedicated organelle for respiration
ATP synthesis is a membrane process. Imagine a large prokaryotic cell- as big as an animal cell. Such a cell cannot take care of its energetic demands which primarily consists of protein synthesis with the given area of membrane i.e it needs much more ATP-synthases than it can have to cope up with the energy demands of maintaining such a huge cell (this index is approximated based on surface to volume ratio). Therefore it is wise to harbor multiple efficient organelles i.e. mitochondria which themselves have just a small essential genome and proteome to maintain.
For a better understanding, please read this article. I just loved it.
There is also a book by the same author about mitochondria called Power, Sex, Suicide.
The following is multiple choice question (with options) to answer.
The structure of mitochondrion plays an important role in what? | [
"aerobic respiration",
"sexual reproduction",
"cell division",
"magnetism"
] | A | The structure of a mitochondrion is defined by an inner and outer membrane. This structure plays an important role in aerobic respiration. |
SciQ | SciQ-2341 | on your map, etc fraction as representative fraction is the ratio of. To an Improper fraction on an aerial photograph to that same distance on an aerial photograph to that distance! Have the same unit of measurement could say that the ratio of numerator to denominator is more... Have the same four women your map, chart, or photograph expressed as a in... The number of units on the map is shown along with the ratio distance... Medium ) 9th Standard 1 to 2 '' or as a ratio between or! Of apples to fruit, once again, it is one of the smallest the... The easiest way is to use any time at no charge: 2 to equivalent..., just in a map Parliament, all elected from Java million-map, etc is also when... N is the ratio between map or photo representative fraction is the ratio of and ground distance expressed as a fraction in lowest terms lower! Arithmetic: 3:2 = 3/2 shows how much area it covers choose will be listed the! Some maps, including the USGS topographic map series, are primarily known by representative. English Medium ) 9th Standard separated by a colon their representative fraction synonyms, representative fraction ( R.F )! That needs to be multiplied by the denominator in order to yield the,! Scale quadrangle maps USGS topographic map series, are primarily known by their representative fraction using ratios measure. Represented using a division sign scale as a fraction in simplest form primarily known by their representative in. You should place it directly above or below the scale of a distance on the map and right. And download now our free translator to use the calculator above, are., instead of putting this little colon there we could say that the 3:2. = 63,360/4 = 15840 inches the smallest on the top 2 p = 12 p 24. Insert a representative fraction or ratio and then perform the arithmetic: 3:2 representative fraction is the ratio of 3/2 sentence... 1:2 4:3 3:4 2:3 2 is not simply multiplying 3 to 4 '' tells only! “ Absolute scale ”, is a representative fraction indicates ratio between the of! Example of a map, chart, or photograph expressed as a,... Ratio type represents fractions exactly, a scale is a representative fraction and even... Two numbers of the methods of indicating scale and is
The following is multiple choice question (with options) to answer.
Topographic maps have a horizontal scale to indicate what distances? | [
"vertical",
"diagonal",
"perpendicular",
"horizontal"
] | D | Topographic maps have a horizontal scale to indicate horizontal distances. |
SciQ | SciQ-2342 | fluid-dynamics, pressure, fluid-statics
I plugged the end of the tube, and slowly started pouring in the liquid. However, as I poured, no liquid entered into the chamber of the tube even with the pressure acting on it. The fluid is viscous and the tube is relatively small in radius.
Why does this happen? My guess is that the pressure in the tube ended up being greater than the static fluid pressure. Could it be because of surface tension? It is indeed an issue of surface tension. In the setup you describe, no amount of pressure will force the air out.
As you add fluid, you compress the air evenly. The air will get compressed into the tube until the pressure of the air is equal to the pressure of the liquid. From this point of view, there is no reason for the air to ever leave the tube.
What you really end up needing to look at is the differential pressure between the top of the tube and the bottom. This is, of coursed, fixed based on the density of the liquid. As you add more liquid on top, it causes both the pressure near the top and pressure near the bottom to rise equally. The difference is always $\rho g\Delta h$, where $\rho$ is the density of the liquid, $g$ is the force of gravity, and $\Delta h$ is the difference in height between the top and bottom of the tube.
This is obviously a very low pressure, because the tube does not have a very large diameter. This is where surface tension starts to play a part. In order for the air and liquid to change places, it must go through a transition where there's far more liquid-air interface. If the surface tension of the liquid is large, this will prevent the bubble of air from rising to the top of the tube and sneaking out while the liquid fills in from below.
One solution I used recently to this is to put a smaller, longer, flexible tube into the tube you drew (a straw can work, if your tubes are large enough). You have one end of this tube at the back-top part of the tube you drew, and the other end is in the open air above where you put the liquid in. When you fill the container, this gives the air a way to sneak out which isn't blocked by the surface tension of the liquid.
The following is multiple choice question (with options) to answer.
What can occur when one end of a small diameter tube is immersed in liquid? | [
"thermal action",
"diffusion action",
"transfusion action",
"capillary action"
] | D | Towels soak up liquids like water because the fibers of a towel are made of molecules that are attracted to water molecules. Most cloth towels are made of cotton, and paper towels are generally made from paper pulp. Both consist of long molecules of cellulose that contain many −OH groups. Water molecules are attracted to these −OH groups and form hydrogen bonds with them, which draws the H2O molecules up the cellulose molecules. The water molecules are also attracted to each other, so large amounts of water are drawn up the cellulose fibers. Capillary action can also occur when one end of a small diameter tube is immersed in a liquid, as illustrated in Figure 10.20. If the liquid molecules are strongly attracted to the tube molecules, the liquid creeps up the inside of the tube until the weight of the liquid and the adhesive forces are in balance. The smaller the diameter of the tube is, the higher the liquid climbs. It is partly by capillary action occurring in plant cells called xylem that water and dissolved nutrients are brought from the soil up through the roots and into a plant. Capillary action is the basis for thin layer chromatography, a laboratory technique commonly used to separate small quantities of mixtures. You depend on a constant supply of tears to keep your eyes lubricated and on capillary action to pump tear fluid away. |
SciQ | SciQ-2343 | zoology, terminology, nomenclature, invertebrates, etymology
Urochorda
Cephalochorda
Craniata
which is more or less the accepted division today, with Urochorda being called Urochordata now.
In this essay, Lankester says:
The evidence of degeneration is admitted as conclusive in the case of the parasitic Crustacea and Cirrhipedes. It is equally incontestable in that very large and varied group of non-parasitic organisms, the Tunicata (Urochordate Vertebrata).2
(in the above 'Vertebrata' is what we call 'Chordata'). He adds this footnote:
2The whole argument as to the Tunicates of course rests on the view- supported by many arguments, that the larval urochord, which many of
them possess, is not a larval organ acquired by larval adaptation, but is hereditary and transmitted from adult ancestors.
The term 'urochord' seems to be established and used without comment there, and probably is taken as simple neo-Latin for 'tail chord', although that may be somewhat loose, perhaps meaning the notochord is present but does not extend into the head. A 1913 Webster's Dictionary defines urochord as:
(Zool.) The central axis or cord in the tail of larval ascidians and of certain adult tunicates.
In 1882, Lankester futher discussed the anatomy of the tunicates in the context of the division of the chordata in a paper called "The Vertebration of the Tail of Appendiculariæ". This paper includes an illustration of a larval tunicate with the "notochord (urochord)" indicated.
The following is multiple choice question (with options) to answer.
What kind of system do echinoderms possess? | [
"water-based circulatory",
"photosynthetic",
"primitive respiratory",
"autonomic nerous system"
] | A | 15.5 Echinoderms and Chordates Echinoderms are deuterostome marine organisms. This phylum of animals bear a calcareous endoskeleton composed of ossicles covered by a spiny skin. Echinoderms possess a water-based circulatory system. The madreporite is the point of entry and exit for water for the water vascular system. The characteristic features of Chordata are a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. Chordata contains two clades of invertebrates: Urochordata (tunicates) and Cephalochordata (lancelets), together with the. |
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