source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-4044 | newtonian-mechanics, forces, mass, definition
\begin{align}
m_1=-c_{01}m_0
\end{align}
In this way, every object's mass is defined in terms of the reference mass.
We are now ready to define force. Suppose that we observe an object $O$ of mass $m$ from a local inertial frame, and suppose that it is not isolated; it is exposed to some interaction $I$ to which we would like to associate a "force." We observe that in the presence of only this interaction, the mass $m$ accelerates, and we define the force $\mathbf F_{I}$ exerted by $I$ on $O$ to be the product of the object's mass and its observed acceleration $\mathbf a$;
\begin{align}
\mathbf F_{I} \equiv m\mathbf a
\end{align}
In other words, we are defining the force exerted by a single interaction $I$ on some object of mass $m$ as the mass times acceleration that a given object would have if it were exposed only to that interaction in a local inertial frame.
Second Law. If an object $O$ of mass $m$ in a local inertial frame simultaneously experiences interactions $I_1, \dots, I_N$, and if $\mathbf F_{I_i}$ is the force that would be exerted on $O$ by $I_i$ if it were the only interaction, then the acceleration $\mathbf a$ of $O$ will satisfy the following equation:
\begin{align}
\mathbf F_{I_1} + \cdots +\mathbf F_{I_N} = m \mathbf a
\end{align}
The following is multiple choice question (with options) to answer.
Observations suggest that a force applied to an object is always applied by what? | [
"gravity",
"itself",
"another object",
"dark matter"
] | C | Where do forces come from? Observations suggest that a force applied to an object is always applied by another object. A hammer strikes a nail, a car pulls a trailer, and a person pushes a grocery cart. Newton realized that forces are not so one-sided. When the hammer exerts a force on the nail, the nail also exerts a force on the hammer—after all, the hammer comes to rest after the interaction. This led to Newton’s Third Law of Motion , which states that whenever one object exerts a force on a second object, the second object also exerts a force on the first object, equal in magnitude and opposite in direction. |
SciQ | SciQ-4045 | metabolism, nutrition
Title: What are calories and how to burn them? What exactly is a calorie? When burning calories, do we always lose fat?
I have tried many apps to measure calories, do they give exact amounts? How many calories should be taken a day? A calorie is a measure of energy. In nutrition, we usually mean the kilocalorie (kcal), which is the same as about 4.2 kJ (kilojoule). A average person needs about 2,000--2,500 kcal per day, but this of course varies quite a bit between people, depending on size (muscle mass, particularly) and level of physical activity (physical work, exercise).
Nutrition guidelines found on the labels of food products give a pretty good summary of the amount of energy they contain. I'm not sure what applications you have been using, but they most likely rely on the same basic data, so the values should be similar. You can use these values to figure out roughly what your calorie intake is, and to spot very calorie-rich foods. But counting calories exactly is actually quite difficult --- you need to carefully weigh everything you eat and keep track of lots of numbers, and it's easy to make mistakes.
Burning calories does not always mean burning fat. Fat is a long-term energy storage form in the body. When exercising, the body tends to burn stored carbohydrates (glycogen) first, and turns to burning fat when carbohydrates are exhausted. Therefore, prolonged, low-intensity exercise like long walks are usually better for burning fat than short "sprint" type of exercise. The body also burns fat during normal daily activity if your energy intake is lower than the daily need (when dieting). But it is also possible that some muscle mass is degraded (to amino acids) and used for energy as well.
See also Wikipedia articles on food energy and exercise. Please note that "how to burn calories" is a heavily debated issue, there is an entire industry of weight loss methods, and various claims about "easy" methods or products to lose weight quickly are generally not true. The only reliable method to lose weight is to reduce food intake and increase exercise, for a long period of time.
The following is multiple choice question (with options) to answer.
How much exercise should a person ideally get during a single day? | [
"six hours",
"hour",
"fifteen minutes",
"three hours"
] | B | Physical activity is an important part of balanced eating. It helps you use up any extra Calories in the foods you eat. You should try to get at least an hour of exercise just about every day (see Figure below ). Exercise has many health benefits in addition to balancing the energy in food. For example, it strengthens the bones and muscles and may improve your mood. |
SciQ | SciQ-4046 | inorganic-chemistry, electrochemistry, electrons, water
Title: Extraction of hydrogen and oxygen from water The apparatus that I am using is a glass container, with two electrodes,two glass cylinders, water, and a battery. In the glass container will be filled with water and two electrodes kept inside the glass cylinder and then dipped in water.
The two electrodes are then connected with the positive and negative terminals of the battery and the container is sealed. As the current is started the water will be separated into hydrogen and oxygen. After extraction of the gas, the two gases are passed separately.
In this process, will the hydrogen gas start burning immediately as soon as produced? If yes, then what to do to make it pass without burning? The separated gas is passed through glass pipes, will the extraction work properly? No, it won’t burn immediately. As your electrodes are generally separated by some distance, you should be able to isolate the produced oxygen and hydrogen gas by catching the respective bubble streams under a submerged test tube or the like. Alone, neither oxygen nor hydrogen will burn, however combining the oxygen and hydrogen gas will produce an explosive mixture. Mixing the hydrogen with air will also produce an explosive mixture as the atmosphere is about 22 % oxygen.
To get the hydrogen to burn, you need to supply the necessary activation energy, which can be supplied by a spark or flame. After this, the reaction will be self-sustaining due to its exothermicity. There are in fact entirely self-contained apparatus which can be purchased from scientific teaching shops that can electrolytically split water and then combust the hydrogen and oxygen using a piezoelectric ignition system, the ensuing tiny explosion causing water to spurt out of a small hole. Wikipedia mentions that the autoignition temperature of hydrogen in air is 500 degrees Celsius.
On a small scale, this reaction is quite safe, however you should always take safety precautions such as wearing protective eyewear and having fire-suppression equipment at hand.
Here’s an illustration of a reasonable water-splitting setup. Remember that your water should contain an electrolyte such as dissolved salt. Keep in mind that if your potential difference is high enough you will start to produce small quantities of chlorine gas and aqueous sodium hydroxide, both of which are hazardous in high concentrations.
The following is multiple choice question (with options) to answer.
The electrolysis of what substance produces hydrogen and oxygen gases | [
"water",
"hydrocarbon",
"carbon dioxide",
"cholesterol"
] | A | The electrolysis of water produces hydrogen and oxygen gases. The electrolytic cell consists of a pair of platinum electrodes immersed in water containing a small amount of an electrolyte, such as H 2 SO 4 . The electrolyte is necessary because pure water does not contain enough ions to effectively conduct a current. At the anode, water is oxidized to oxygen gas and hydrogen ions. At the cathode, water is reduced to hydrogen gas and hydroxide ions. |
SciQ | SciQ-4047 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
What is the shorter loop of the cardiovascular system? | [
"pulmonary circulation",
"pulmonary edema",
"venous circulation",
"metabolic circulation"
] | A | Pulmonary circulation is the shorter loop of the cardiovascular system. It carries blood between the heart and lungs. Oxygen-poor blood flows from the heart to the lungs. In the lungs, the blood absorbs oxygen and releases carbon dioxide. Then the oxygen-rich blood returns to the heart. |
SciQ | SciQ-4048 | mineralogy, petrology
Title: How do you use the streckeisen (QAPF) classification ternary diagram to identify igneous rocks based on chemical rock composition? I have been given the following diagrams:
and
and a database that is structured like this:
ROCK NAME |SIO2 |TIO2| AL2O3| CR2O3| FEOT| CAO| MGO| MNO| K2O| NA2O| P2O5|
WEHRLITE |45.42| 0.17| 2.57| 0.32| 11.3384| 7.54| 31.93| 0.17| 0.01| 0.24| 0.01|
I want to know how to normalize the data and use these diagrams to identify the rock name based on the IUGS specification. I then am tasked to write a program that will do this automatically meaning that I have to come up with some semi-mathematically-based process to identify these rocks. Any ideas? Why you should not do it
The QAPF and related diagrams are intended for classification of rocks in the field, or preliminary classification with modal proportions as seen in the optical microscope. They are not designed with the chemical composition of the rocks in the mind. Furthermore, these diagrams are merely descriptive and not genetic. They do not take into account many factors affecting the various characteristics of the rocks. While doing something like this may be interesting for homework exercise, it is not something I would expect to see in a recent research article.
If you want to do it anyway
Your solution should consist of two steps.
The following is multiple choice question (with options) to answer.
What is the first classification of igneous rocks? | [
"weight",
"size",
"composition",
"color"
] | C | Igneous rocks are classified first by composition. Categories go from from felsic to ultramafic. Color can indicate composition. |
SciQ | SciQ-4049 | homework-and-exercises, kinematics, projectile, displacement
Title: Displacement related question So you have two tracks of different inclines meeting at a point. Two stones are released from this point each one along the direction of one incline, from rest.
Which stone reaches the ground faster? The one on the steeper incline? I don't understand why. By the kinematic equations of motion displacement in the y direction is equal to -gt^2 for both the motions, and since they are released from the same height, they should reach at the same time. I feel like i'm missing something very important... You are forgetting the fact that here normal reaction acting from the track changes the direction of motion the object and only a smaller component of acceleration due to gravity is acting along the direction of motion ($\leq g$).
The following is multiple choice question (with options) to answer.
What is the very slow movement of rock and soil down a hillside? | [
"creep",
"drop",
"evaporate",
"landslide"
] | A | Creep is the very slow movement of rock and soil down a hillside. Creep occurs so slowly you can’t see it happening. You can only see the effects of creep after years of movement. This is illustrated in Figure below . The slowly moving ground causes trees, fence posts, and other structures on the surface to tilt downhill. |
SciQ | SciQ-4050 | circulatory-system, lymphatic-system, veins
Title: How does most of lymph get back into the blood stream? (I don't mean the lymphatic system) I once read that it was because of osmotic pressure that it returns to the blood stream, by entering the venules. But why? If lymph originated as plasma how come that the solute concentration is higher in the venule? Doesn't plasma contain solutes such as salts, nutrients, oxygen, etc. ? Technically 'lymph' is used to refer to the fluid found within the lymphatic system. If it's not in the lymphatic system, it is not lymph fluid. Thus, your question is really asking about interstitial fluid or the plasma that was filtered out of blood capillaries.
The answer to your question is based on the Starling equation. Normally fluid leaves a capillary due to a net pressure that favors the interstitium. This net pressure is based on the hydrostatic pressure within the capillary being greater than the interstitial pressure of the surrounding tissues, and the oncotic pressure of the capillary (that draws fluid in) being weaker than the hydrostatic pressure of the capillary (that pushes fluid out). At the venule end of this system, the capillary oncotic pressure is stronger than the capillary hydrostatic pressure, drawing fluid back into the circulatory system.
Remember that albumin is the most important component which establishes the oncotic pressure within a vessel, and that this protein is normally NOT released out of a vessel during filtration. Thus, it passes from the capillary into its corresponding venule directly.
The following is multiple choice question (with options) to answer.
Which type of pressure forces fluid out of the capillary? | [
"air",
"gas",
"hydrostatic",
"combustion"
] | C | Osmotic Pressure The net pressure that drives reabsorption—the movement of fluid from the interstitial fluid back into the capillaries—is called osmotic pressure (sometimes referred to as oncotic pressure). Whereas hydrostatic pressure forces fluid out of the capillary, osmotic pressure draws fluid back in. Osmotic pressure is determined by osmotic concentration gradients, that is, the difference in the solute-to-water concentrations in the blood and tissue fluid. A region higher in solute concentration (and lower in water concentration) draws water across a semipermeable membrane from a region higher in water concentration (and lower in solute concentration). As we discuss osmotic pressure in blood and tissue fluid, it is important to recognize that the formed elements of blood do not contribute to osmotic concentration gradients. Rather, it is the plasma proteins that play the key role. Solutes also move across the capillary wall according to their concentration gradient, but overall, the concentrations should be similar and not have a significant impact on osmosis. Because of their large size and chemical structure, plasma proteins are not truly solutes, that is, they do not dissolve but are dispersed or suspended in their fluid medium, forming a colloid rather than a solution. |
SciQ | SciQ-4051 | physiology, hearing, human-ear
It also seems like this type of noise can happen with conditions such as Tonic Tensor Tympani Syndrome.
The tensor tympani connects directly to the handle of the malleus, so I'd assume that's why it can be heard by the person doing it. Apparently this also causes the eardrum to move. This means it's classified as objective tinnitus.
Here are some relevant studies I found:
Voluntary contraction of the tensor tympani muscle
and its audiometric effects
Voluntary Eardrum Movement : A Marker for Tensor Tympani Contraction? (paywall)
Tonic contractions of the tensor tympani muscle: a key to some
non-specific middle ear symptoms? Hypothesis and data from
temporal bone experiments (paywall)
The following is multiple choice question (with options) to answer.
What hits the eardrum and causes it to vibrate? | [
"cilia",
"decibels",
"microwaves",
"sound waves"
] | D | The eardrum is like the head of a drum. It is a thin membrane stretched tight across the end of the ear canal. The eardrum vibrates when sound waves strike it, and it sends the vibrations on to the middle ear. |
SciQ | SciQ-4052 | biophysics, theoretical-biology, ecosystem
Systems ecology, especially with regard to energy and nutrient flow.
This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem Ecology: Understanding Element Cycles by Ågren & Bosatta (Ågren was originally a physicist)
Physical limitations to growth and transport
This can include for instance mechanical contraints on plant growth (see e.g. the book Plant Physics by Nicklas & Spatz), water transport in trees (see e.g. this BioSE question) or the biomechanics of movement (see e.g. Hudson et al (2012) on the speed and movement of cheetahs or Wikipedia: Biomechanics).
Allometric relationships between organisms, e.g. with regard to metabolism
To explain these types of relationships knowledge in physics is useful. See e.g. Kleiber's law for more.
MAXENT as a general approach to ecological patterns or to model species distributions
This is basically a tool lifted from physics that can be applied to ecological problems. There are many papers to look at, but Harte & Newman (2014) (Harte is another previous physicist) and Elith et al (2010) are two good starting points.
Dynamical modelling of populations and communities
This field use many of the same tools for analysis as physics, e.g. systems of differential equations. One of the pioneers in this field (among many) were Robert May (also started with a PhD in physics), and his classical book Theoretical Ecology: Principles and Applications is still a good starting point.
Energy harnessing and conversion by organisms
This can refer both to how organsims convert prey to energy (e.g. conversion efficiencies) and the physics of photosynthesis (which is an interesting intersection between physics and molecular biology). See Jang et al (2004) and O'Reilly & Olaya-Castro (2013) for examples of the how quantum mechanics can inform us about photosynthesis.
Hopefully this will give you a sense of some different ways that knowledge in physics can be useful for biology.
The following is multiple choice question (with options) to answer.
What type of ecologists work to identify and manipulate the processes that most limit recovery of ecosystems from disturbances? | [
"restoration ecologists",
"conservation ecologists",
"quality ecologists",
"environmental"
] | A | |
SciQ | SciQ-4053 | r
[17] "LP6008337-DNA_H06_vs_LP6008338-DNA_D06" "LP6008460-DNA_A04_vs_LP6008340-DNA_D05__pv"
[19] "LP6008460-DNA_D01_vs_LP6008340-DNA_E02__pv" "LP6008460-DNA_F02_vs_LP6008340-DNA_E05"
[21] "LP6008460-DNA_G03_vs_LP6008340-DNA_C05__pv"
>
The following is multiple choice question (with options) to answer.
Name the two types of nucleic acids. | [
"dna (deoxyribonucleic acid) and rna (ribonucleic acid)",
"isoleucin and leucine",
"lysine and methionine",
"dna ( trigraph acid ) and rna ( ribonucleic acid )"
] | A | Living cells need organic molecules, known as nucleic acids . Nucleic acids are molecules that store genetic information. They pass that genetic information to the next generation. Deoxyribonucleic acid (DNA) is the nucleic acid that carries information for nearly all living cells today. DNA has done this for most of Earth's history. Ribonucleic acid (RNA) delivers genetic instructions to the location in a cell where protein is synthesized. RNA regulates protein synthesis. Some scientists think that RNA was the first replicating molecule. |
SciQ | SciQ-4054 | nitrogen
Step three is when plants and the animals that live of the plants die and breaks down into ammonia and other waste products (this is where many explanations of the nitrogen cycle usually starts). The waste products gets converted into ammonia by bacteria and the ammonia gets converted to nitrite and the entire cycle starts all over again.
Legumes have a symbiotic relationship with some bacteria that can fixate nitrogen (N2) https://aces.nmsu.edu/pubs/_a/A129/
sources:
https://science.howstuffworks.com/life/biology-fields/nitrogen-cycle.htm
https://www.britannica.com/science/denitrifying-bacteria
The rest is from my memory.
The following is multiple choice question (with options) to answer.
Interactions between plants and other organisms result in cycling of chemical nutrients within what? | [
"water",
"air",
"habitat",
"ecosystem"
] | D | |
SciQ | SciQ-4055 | terminology, meteorology
I've tried to illustrate the relationships with insolation and temperature here:
There are some other ways too:
Ecological. Scientists who study the behaviour of organisms (hibernation, blooming, etc.) adapt to the local climate, sometimes using 6 seasons in temperature zones, or only 2 in polar and tropical ones.
Agricultural. This would centre around the growing season and therefore, in North America and Europe at least, around frost.
Cultural. What people think of as 'summer', and what they do outdoors (say), generally seems to line up with local weather patterns. In my own experience, there's no need for these seasons to even be 3 month long; When I lived in Calgary, summer was July and August (hiking), and winter was December to March (skiing). Here's another example of a 6-season system, and a 3-season system, from the Aboriginal people of Australia, all based on weather.
Why do systems with later season starting dates prevail today? Perhaps because at mid-latitudes, the seasonal lag means that the start of seasonal weather is weeks later than the start of the 'insolation' period. In a system with no heat capacity, there would be no lag. In systems with high heat capacity, like the marine environment, the lag may be several months (Ibid.). Here's what the lag looks like in three mid-latitude cities:
The exact same effect happens on a diurnal (daily) basis too — the warmest part of the day is often not midday (or 1 pm in summer). As with the seasons, there are lots of other factors too, but the principle is the same.
These aren't mutually exclusive ways of looking at it — there's clearly lots of overlap here. Cultural notions of season are surely rooted in astronomy, weather, and agriculture.
The following is multiple choice question (with options) to answer.
In places where crops grow only during part of the year, the land may be bare for a few? | [
"minutes",
"months",
"weeks",
"days"
] | B | The problem doesn’t stop with plowing. Crops are usually planted in rows, with bare soil in between the rows. In places where crops grow only during part of the year, the land may be bare for a few months. |
SciQ | SciQ-4056 | 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 does bowman's capsule form by surrounding the glomerulus? | [
"ions",
"pores",
"lipids",
"lumen"
] | D | Renal Corpuscle As discussed earlier, the renal corpuscle consists of a tuft of capillaries called the glomerulus that is largely surrounded by Bowman’s (glomerular) capsule. The glomerulus is a high-pressure capillary bed between afferent and efferent arterioles. Bowman’s capsule surrounds the glomerulus to form a lumen, and captures and directs this filtrate to the PCT. The outermost part of Bowman’s capsule, the parietal layer, is a simple squamous epithelium. It transitions onto the glomerular capillaries in an intimate embrace to form the visceral layer of the capsule. Here, the cells are not squamous, but uniquely shaped cells ( podocytes) extending finger-like arms ( pedicels) to cover the glomerular capillaries (Figure 25.11). These projections interdigitate to form filtration slits, leaving small gaps between the digits to form a sieve. As blood passes through the glomerulus, 10 to 20 percent of the plasma filters between these sieve-like fingers to be captured by Bowman’s capsule and funneled to the PCT. Where the fenestrae (windows) in the glomerular capillaries match the spaces between the podocyte “fingers,” the only thing separating the capillary lumen and the lumen of Bowman’s capsule is their shared basement membrane (Figure 25.12). These three features comprise what is known as the filtration membrane. This membrane permits very rapid movement of filtrate from capillary to capsule though pores that are only 70 nm in diameter. |
SciQ | SciQ-4057 | string-theory, education
Title: What is your simplest explanation of string theory? How would you explain string theory to non-physicists such as myself? I'm especially interested in how plausible is it and what is needed to successfully prove it? I've noticed that none of these answers actually answer the question.
The simplest explanation of string theory I can think of:
Particles we currently consider "point particles" (electrons, quarks, photons, etc.) are actually tiny pieces of string with each a characteristic vibration. They interact in a sort of harmony that results in/manifests as the physical laws we observe.
If anyone with more knowledge in the field can correct me, I ask for improvements. This is just how I personally explain it to people who ask, and I'd hate to give out false information.
The following is multiple choice question (with options) to answer.
What do scientists use to help explain objects or systems in simpler ways? | [
"models",
"plants",
"theories",
"measurements"
] | A | Scientists use models to help them understand and explain ideas. Models explain objects or systems in a more simple way. Models often only show only a part of a system. The real situation is more complicated. Models help scientists to make predictions about complex systems. Some models are something that you can see or touch. Other types of models use an idea or numbers. Each type is useful in certain ways. |
SciQ | SciQ-4058 | air-pollution
Title: Less pollution: moving hurricane debris to other regions for use, or burning? When a big hurricane hits, it can create debris on the scale of $\mathrm{10^8 yd^3}$. Cities in Florida, Texas, and other affected areas are struggling to hire enough trucks and drivers to pick it up quickly. But aside from that, I noticed many of the areas have started to burn the debris once it starts building up.
Got to wondering... typically mulch comes in modestly pricey, and when free mulch is offered, it often goes quickly.
So assuming a fair portion of debris is mulchable and is of interest to other areas, and that we can acquire typical transportation resources, then we'll set up transfer from collection sites to those other regions rather than burning it. What would be the net pollution result?
If removed for mulch and such: trucking pollution + decomposition (- trees saved locally??)
If burned: the burning pollution.
Obviously it's about approximation rather than exacts, it's probably hard to appraise the different byproducts from burning versus decomposition, and a lot probably depends upon the way it is burned. But as a whole, can we get a rough estimate of comparable quantities/damage done... is it less pollution/damage even to truck it an average of 3000 miles? 1000 miles? 100 miles? 10 miles? Should it be burned on the spot (if done safely)? Would think there's got to be some way to get a very rough idea.
Certainly the best option if viable might be leaving it in place to decompose. But considering how upset people are getting at having debris around these parts a month later, exclude that option from the possibilities.
Trucking or burning, how do they compare? As the question was changed, my answer attempts to evaluate only the difference between burning and transporting. Please correct my values if my quickly found sources are inaccurate or you find more representing. I know there is quite a few unwritten assumptions that simplify this problem.
The following is multiple choice question (with options) to answer.
Burning trees produces most of the same pollutants as burning what? | [
"fossil compounds",
"carbon",
"fossil fuels",
"coal fuels"
] | C | Millions of acres of forest have been cut and burned to make way for farming. Figure below shows an example. Burning trees produces most of the same pollutants as burning fossil fuels. |
SciQ | SciQ-4059 | mutations, genomes
Title: Bacterial division and mutation rate When a bacteria A divides it produces two cells A', A''. Each of them receives a copy of the chromosome/plasmids. Now, DNA replication occurs way before division in a semiconservative manner. That is, each new chromosome has an 'old' strand and a 'new' strand. Since the polymerase is error prone, my belief is that both genomes can potentially have mutations. Now when people refer to the mutation rate/genome/replication, e.g. 3x10-4 , Does this mean that:
The following is multiple choice question (with options) to answer.
During which process in bacteria do the chromosome replicates and the two daughter chromosomes actively move apart? | [
"matter fission",
"binary fission",
"function fission",
"secondary fission"
] | B | |
SciQ | SciQ-4060 | quantum-mechanics, particle-physics, photons, atomic-physics
Title: Too much photon energy required to excite an atom Apologies if I have done this wrong, it's my first post.
To my understanding, atoms can be excited by a collision of an electron or photon with sufficient energy to excite the electron into a higher energy level.
With an electron collision, it just needs enough kinetic energy to transfer into the atom for the electron to get into a higher energy level. With a photon collision, it needs exactly the amount of energy as the difference of energies between energy levels in the atom. If it has too little energy, the electron wouldn't be excited and hence the photon wouldn't interact, and the same with if it had too much.
My question is why cant the photon, similarly to the electron collision, collide with the atom with more energy than the difference in energy levels in order to excite the atom and then, to conserve momentum (similarly to how the electron continues with less momentum following a collision), why can't a new photon be emitted with a lower frequency?
Is this because momentarily the system would not conserve energy? If so, why cant a lower frequency photon be emitted instantly when the particles interact, similarly to how an excited electron instantly jumps to a higher energy level? There is an important concept of the oscillator called resonance. For example you can place an energized "c" note tuning fork on the "c" piano string .... and the string will oscillate .... However if you place the fork on the C sharp or B flat string these strings will NOT oscillate.
The photon has energy-frequency and it is pure vibration (wave) in the EM field ... when a suitable electron can resonant at the frequency it can absorb the pure energy. When the photon is at a different frequency-energy the suitable electrons just don't resonate or absorb the energy.
All of quantum mechanics is based on the oscillator model for the atom/electron orbital behaviour.
The following is multiple choice question (with options) to answer.
What is emitted by atoms that have been excited by thermal excitation, electron collision, or collisions with photons of exactly the right frequency? | [
"light",
"gravity",
"electricity",
"radioactivity"
] | A | Light is emitted by atoms that have been excited by thermal excitation, electron collision, or collisions with photons of exactly the right frequency. Light is emitted by an incandescent source at many different wavelengths and in all directions. Light produced by an atomic gas consists of only a few different wavelengths but still in all directions. Both of these light sources produce light waves that are not in step or at the same point in their cycle. Groups of light waves that are not at the same point in their cycle are called incoherent light . |
SciQ | SciQ-4061 | genetics, biochemistry, proteins, rna
Title: Where do amino acids get attached to tRNA and where is it synthesized? Some very basic parts of transcription/translation seem to be left out in various literature. I can't find the answer to this anywhere:
How exactly is tRNA synthesized? I realize that mRNA is synthesized through transcription and I know a lot about that. However tRNA is supposedly synthesized the same way but every time you read about transcription they just talk about how the mRNA then gets this and that...?
Where do the amino acids get attached? Is it in the nucleus or outside the nucleus?
Thanks. A pre-tRNA is transcribed from tRNA genes in DNA by RNA polymerase III. Processing occurs in the nucleus, where a 5' sequence is cleaved by RNase P, the 3's CCA motif is added, and ~10% of the nucleotides are substituted. The tRNA are transported out via the pore complexes. Aminoacyl-tRNA synthetase enzymes attach amino acids in the cytoplasm in a 2-step reaction that requires ATP. You'll find there's a unique splicing mechanism in tRNA that additionally splices out an anticodon intron which is abesnt in mature tRNA's:
The wikipedia article notes RNA Pol III generally recognizes internal control elements rather than upstream control elements as in a normal gene.
Source: Qiagen
Source: Molecular Cell Biology. 4th edition.
Addendum: I said in my post that tRNA is charged in the cytoplasm, this is somewhat true. In mammalian cells, we also see that tRNA are charged in the nucleus as well, and it might aid in the export of some of these charged tRNAs. (Source)
The following is multiple choice question (with options) to answer.
Translation is the process of ordering the amino acids in the assembly of a? | [
"lipid",
"vitamin",
"protein",
"carbohydrate"
] | C | Translation is the process of ordering the amino acids in the assembly of a protein. The word ribosome comes from ribo nucleic acid and the Greek soma (meaning body). Two Nobel Prizes have been awarded for work relating to the ribosome. The 1974 Nobel Prize in Physiology or Medicine was awarded to Albert Claude, Christian de Duve and George Emil Palade for the discovery of the ribosome, and the 2009 Nobel Prize in Chemistry was awarded to Venkatraman Ramakrishnan, Thomas A. Steitz and Ada E. Yonath for discovering the detailed structure and mechanism of the ribosome. |
SciQ | SciQ-4062 | species-identification, zoology, entomology
Title: Species identification; clusters of big plump red bugs in Taipei I saw these red insects in Taipei near XinBeitou MRT station in the last week of April 2017, around lunch time. They were fairly active and would keep checking each other out with their antennae for a moment and then move on to the next. What struck me was the wide range of sizes and development in the groups. I didn't notice any feeding or mating that I could recognize, just a lot of walking around and checking each other out.
There are plenty of birds around (this is quite a green area) but I didn't notice any interest by birds in eating them.
I've also included a screenshot from google maps so you can see the location and the trees growing in these concrete structures.
The body of the largest individual is probably 2.5 centimeters long. I'm fairly certain these true bugs belong to the species Leptocoris vicinus, and carry the nickname of "soapberry bugs", which is specific to the subfamily Serinethinae. They're quite common in urban areas of Southeast Asia, which coincides nicely with where you encountered them.
Also, you had mentioned,
There are plenty of birds around (this is quite a green area) but I didn't notice any interest by birds in eating them.
Soapberry bugs, as well as many other types of insects, are able to freely congregate in large numbers, and in such exposed places, due to their bright coloration. Having such a bright color may indicate to some predators that the prey in consideration is toxic, a phenomenon referred to as aposematism.
source
source
And then, here's a map of their distribution, with Taipei holding marker #37. (source)
An interactive version of this map can be found here.
The following is multiple choice question (with options) to answer.
What is the name of the group that rats are apart of called? | [
"Mammels",
"Animals",
"primates",
"rodents"
] | D | Rats are mammals, but this class can be divided into more specific groups. Rats are in a group known as rodents. Rodents are gnawing animals that include beavers, mice, and squirrels. |
SciQ | SciQ-4063 | reproduction, asexual-reproduction
Title: can self-fertilization in flowers be called asexual reproduction? Suppose a flower having both male and female reproductive parts is self-fertilized then can this be called asexual reproduction...?I'm quite confused cause in this case the fusion of male and female gametes do take place but again the gametes are from the same parent....please help. According to this article from Berkeley, asexual reproduction is:
Any reproductive process that does not involve meiosis or syngamy
Using this definition of asexual reproduction and knowing self-fertilization involves meiosis and syngamy, it is not asexual.
The following is multiple choice question (with options) to answer.
Fertilization occurs when what material from one flower reaches the female gametes in the same or a different flower? | [
"ova",
"nitrogen",
"pollen",
"sperm"
] | C | Pea plants reproduce sexually. The male gametes are released by tiny grains of pollen. The female gametes lie deep within the flowers. Fertilization occurs when pollen from one flower reaches the female gametes in the same or a different flower. This is called pollination . Mendel was able to control which plants pollinated each other. He transferred pollen by hand from flower to flower. |
SciQ | SciQ-4064 | energy, photons, semiconductor-physics, solar-cells
In down-conversion one high energy photon promotes an electron from 1 to 3, and by falling to energy level 2 and then 1, two photons can be emitted. Thus one high energy photon in and two low energy photons out.
Of course the next step would be to use a solar cell to collect the converted photons. The up and down converters themselves don't generate power.
Other approaches
There are other approaches to reaching higher efficiency. In specially engineered materials high energy photons can generate multiple electron-hole pairs which provides more current per photon than normal solar cells.
Then there are the hot-carrier approaches. If a material and maintain a thermal gradient then this provides an additional thermodynamic potential allowing higher efficiencies to be achieved.
You can even use hot-carrier materials as a spectral converters! I've worked on this approach over the last few years.
The following is multiple choice question (with options) to answer.
What are the tiny packets of energy the sun gives off called? | [
"neutrons",
"electrons",
"photons",
"ions"
] | C | The Sun gives off energy in tiny packets called photons . Photons travel in waves. Figure below models a wave of light. Notice the wavelength in the figure. Waves with shorter wavelengths have more energy. |
SciQ | SciQ-4065 | molecular-genetics, human-genome
Title: Criteria for the numbering of human chromosomes What were the criteria devised for the numbering convention employed in human chromosomes? When was it fixed?
Correct me if I am wrong; it appears that chromosome pairs 1 to 22 were originally ordered in terms of perceived structural size, which ended up fitting neatly with the quantity of base pairs (but not with the quantity of genes).
The sex chromosomes in turn were arbitrarily assigned as "pair 23".
Is this sound?
Thanks in advance. Why do you think it was "fixed?" Here's a nice review of the history of human cytogenetics, which included not only the original image from 1956 but points out a report which comments on the standardization of chromosome number. The autosomes were indeed numbered by length, and the sex chromosomes are traditionally put at the end as they are "numbered" 23 but clearly function quite differently. Gene content was decades away from being known at the time, and honestly isn't even known now. It's also just as arbitrary; simple size is easy enough and makes for rather nice pictures.
The following is multiple choice question (with options) to answer.
In humans, each set of chromosomes contains 22 of these and 1 sex chromosome? | [
"centrosomes",
"autosomes",
"chromatids",
"genes"
] | B | In humans, each set of chromosomes contains 22 autosomes and 1 sex chromosome . Autosomes are chromosomes that are not directly involved in determining the sex of an individual. The sex chromosomes contain genes that determine the sex of an individual. |
SciQ | SciQ-4066 | cell-biology, microbiology
Title: Are there any organisms that are made of more than one (~5-12) cell? Prokaryotes and eukaryotes are unicellular, made of one cell. Great. Eukaryotes are unicellular or multicellular. But the typical examples of multicellular eukaryotes we have are made of, often, trillions of cells, like us humans. Ants must still be made of many millions of cells. Are there known eukaryotes with very few cells that make them up? Like, 5, or something? Or maybe a dozen cells making up the whole organism in its fully developed state? There's Trichoplax adhaerens, a Placozoa, made of a few thousand cells. Then there is Dicyema japonicum, a simple mesozoan, made up of 9 to 41 cells. Arguably, the simplest multicellular organism is the algae Tetrabaena socialis, whose body consists of 4 cells. Then, there's the parasitic Myxozoa which have 7 cells.
The following is multiple choice question (with options) to answer.
What eukaryotic organisms cannot make their own food and do not technically eat? | [
"fungi",
"plankton",
"proteins",
"cells"
] | A | Protists and Fungi are two types of eukaryotic organisms. What do they have in common? Protists are the earliest eukaryotes, and this kingdom contains some of the simplest eukaryotes. Many are single-celled organisms. Protists consist of animal-like, plant-like, and fungus-like species. Protists evolved into the other three types of eukaryotes, including fungi. Other than that, these two types of eukaryotes are very different. Fungi are eukaryotic organisms that cannot make their own food and do not "eat. " They must absorb their nutrients, usually from decaying organisms. |
SciQ | SciQ-4067 | ethology, behaviour, sociality, ant
Title: Do ant colonies prioritize survival of particular members above others? In some (perhaps small) human communities people may starve because they have no income. This could be interpreted as a consequence of them not participating in the community, hence they don't get any income and are left to their fate of starvation. Also, we can imagine that important members of the community are less likely to starve, as they are given priority treatment (e.g. a royal family will less likely starve to death during a given famine).
Do ants in a given colony allow members to starve when they don't serve the colony, even if there is no scarcity of food?
Secondly, do ants follow a chain of importance and are members of least importance allowed to starve first in times of shortage? I couldn't find any information about ants starving in times of plenty, most likely since it's difficult to determine whether an ant colony is "letting" certain members starve or whether the ants have just died for whatever reason. To your second question, though, yes! This paper, The Effect of Colony Size and Starvation on Food Flow in the Fire Ant by Howard and Tschinkel, shows the effects of different lengths of starvation on the passing of radioactive food through different sized ant colonies. First, the queen:
Generally, queens received radioactive food earlier in starved colonies than in well-fed ones
Starved foraging ants distributed food more quickly than forager ants who had not been starved:
And interestingly, in large colonies, larger worker ants were more likely to receive food (radioactivity) than smaller ants. Very cool paper.
The following is multiple choice question (with options) to answer.
What do ants and termites eat to help them digest wood and leaves? | [
"yeast",
"pollen",
"fungi",
"berries"
] | C | Ants and termites grow fungi in underground “fungus gardens” that they create. When the ants or termites have eaten a big meal of wood or leaves, they also eat some fungi from their gardens. The fungi help them digest the wood or leaves. The fungi secrete certain enzymes that the ants or termites cannot produce on their own. |
SciQ | SciQ-4068 | human-biology, cell-biology
Title: What kinds of cells does human saliva contain? I have heard that our saliva contains cells. What cell types can be found in human saliva? It contains white blood cells (leukocytes) and cells from the inner lining of the mouth (buccal epithelial cells). The DNA obtained from these cells is the basis of DNA profiling based on saliva samples.
Source: Salimetrics
The following is multiple choice question (with options) to answer.
How many types of glands does the dermis contain? | [
"ten",
"three",
"two",
"six"
] | C | The dermis also contains hair follicles and two types of glands. You can see some of these structures in Figure below . |
SciQ | SciQ-4069 | newtonian-mechanics, reference-frames, acceleration, buoyancy, fluid-statics
Title: What will be the buoyant force on an object in an accelerating container? Our teacher taught us it is vρ(g+a) when accelerating upward. But I can't understand the reason for it. Isn't it vρg as buoyant force is equal to the weight of displaced fluid. Please help me with this. Think of it like this: By accelerating upwards with an acceleration $a$, you introduce an inertial force in the direction of $g$. This leads to an effective increase of the specific weight of the water: $\rho g\rightarrow \rho(g+a)$ So the buoyant force is still equal to the weight of the displaced fluid.
The following is multiple choice question (with options) to answer.
What is an upward force that fluids exert on any object that is placed in them? | [
"gravity force",
"warm force",
"buoyant force",
"efficient force"
] | C | Buoyant force is an upward force that fluids exert on any object that is placed in them. The ability of fluids to exert this force is called buoyancy . What explains buoyant force? A fluid exerts pressure in all directions, but the pressure is greater at greater depth. Therefore, the fluid below an object, where the fluid is deeper, exerts greater pressure on the object than the fluid above it. You can see in the Figure below how this works. Buoyant force explains why the girl pictured above can float in water. |
SciQ | SciQ-4070 | human-biology, hematology, human-physiology, blood-circulation
Title: What are the effects of oxygen toxicity in human blood? I was reading some text on deep sea Physiology, and for to know that diving to do could cause oxygen toxicity in the blood. This was the exact text from the book Textbook of Medical Physiology by Arthur Guyton and John E. Hall:
A column of seawater 33 feet (10.1 meters) deep exerts the same pressure at its bottom as the pressure of the atmosphere above the sea. Therefore, a person 33 feet beneath the ocean surface is exposed to 2 atmospheres pressure, with 1 atmosphere of pressure caused by the weight of the air above the water and the second atmosphere caused by the weight of the water.
When the PO2 in the blood rises above 100 mm Hg, the amount of O2 dissolved in the water of the blood increases markedly. Note that in the normal range of alveolar PO2 (below 120 mm Hg), almost none of the total O2 in the blood is accounted for by dissolved O2, but as the O2 pressure rises into the thousands of millimeters of mercury, a large portion of the total O2 is then dissolved in the water of the blood, in addition to that bound with hemoglobin.
I understand that high pressure causes more oxygen to dissolve in blood, but cannot figure out how excess dissolved oxygen in the blood disturbs the normal physiological balance of the body.
I'd be grateful if someone knowing the answer can help me. This is from a Wikipedia article:
Central nervous system oxygen toxicity manifests as symptoms such as visual changes (especially tunnel vision), ringing in the ears (tinnitus), nausea, twitching (especially of the face), behavioural changes (irritability, anxiety, confusion), and dizziness.
Oxygen toxicity - Wikipedia
https://en.wikipedia.org/wiki/Oxygen_toxicity
It says there's hemolysis of red blood cells - i.e., they lyse = break open.
The following is multiple choice question (with options) to answer.
Atmospheric pressure is increased, causing a greater amount of oxygen than normal to diffuse into the bloodstream of the patient, in what type of therapy? | [
"hyperbaric chamber therapy",
"Distinct Chamber Therapy",
"ventilation chamber therapy",
"politic chamber therapy"
] | A | Hyperbaric chamber treatment is based on the behavior of gases. As you recall, gases move from a region of higher partial pressure to a region of lower partial pressure. In a hyperbaric chamber, the atmospheric pressure is increased, causing a greater amount of oxygen than normal to diffuse into the bloodstream of the patient. Hyperbaric chamber therapy is used to treat a variety of medical problems, such as wound and graft healing, anaerobic bacterial infections, and carbon monoxide poisoning. Exposure to and poisoning by carbon monoxide is difficult to reverse, because hemoglobin’s affinity for carbon monoxide is much stronger than its affinity for oxygen, causing carbon monoxide to replace oxygen in the blood. Hyperbaric chamber therapy can treat carbon monoxide poisoning, because the increased atmospheric pressure causes more oxygen to diffuse into the bloodstream. At this increased pressure and increased concentration of oxygen, carbon monoxide is displaced from hemoglobin. Another example is the treatment of anaerobic bacterial infections, which are created by bacteria that cannot or prefer not to live in the presence of oxygen. An increase in blood and tissue levels of oxygen helps to kill the anaerobic bacteria that are responsible for the infection, as oxygen is toxic to anaerobic bacteria. For wounds and grafts, the chamber stimulates the healing process by increasing energy production needed for repair. Increasing oxygen transport allows cells to ramp up cellular respiration and thus ATP production, the energy needed to build new structures. |
SciQ | SciQ-4071 | classical-mechanics
Title: Help me find flaws on my simple machines invention I have a work to make an invention on simple machines. First of all I am sorry if my English is not very good or clear. As we all know, simple machines are used to simplify things in life and use less work (mechanical advantage). My concept is using a pulley to pull things up, but I want to use like a machine that needs to be stepped (lever type 3) to move the pulley. But I feel like there is a flaw to my invention, and feel very frustated. This is my concept visualization:
P.S: Sorry for the language usage (Image is semi-English and semi-Indonesian language)
Thank you for the help. The idea of simple machines is usually "sacrifice length to gain force". Or the opposite, but more rarely. You have incorporated a level and pulleys in your design. Let's analyze those.
The lever
The first problem is that you have made a lever that, if you step on it, the weight will go down. But, it would already go down by gravity, this is not useful. You probably want to counteract gravity and make it go up, so something like this:
The other problem is the general idea of using a level with your foot. The thing is, you can't move your foot much. This means do not really have length to sacrifice to gain force. So, to use a lever with your foot, you have to either:
Use it to lift something very light with a single motion of the foot. It's hard to find a use for this, though. Also, it means that the edge of the lever would be really long a take much space.
Use it to lift a heavy weight, but your foot won't have enough room. To gain multiple times one floor's height, you'd probably want to jump from some roof:
Now that we got the lever "solved", let's discuss the pulley (which is much easier for you to do without being unrealistic).
Note that just having a pulley somewhere doesn't provide you an advantage. You have to use something like a snatch block:
This will indeed allow you to use a long rope to raise the weight with less effort:
The following is multiple choice question (with options) to answer.
An axe head and a doorstop are types of what simple machine? | [
"lever",
"blade",
"wedge",
"pulley"
] | C | The axe head and the doorstop are both examples of a wedge, a type of simple machine. |
SciQ | SciQ-4072 | genetics, homework
Title: "structural and regulatory elements of genes" Can anyone please explain a little about these two elements of genes? My main problem is with "which ‘switch on’ instructions".
genes have structural elements (which code for a particular protein) and regulatory elements (which ‘switch on’ instructions) The expression of protein coding genes happens by the process of transcription. So promoters facilitate access of the RNA polymerase complex to DNA to begin transcribing a locus on the genome. The promoter of a gene often contains sequences that bind proteins called transcription factors, which play a role in various parts of the transcriptional process as well as components of RNA polymerase themselves (Such as a Pribnow box in prokaryotes, or a TATA box or an initiator element in animals).
So whether a gene is turned on and if so, how much it is turned on, is a property of how many transcription factor binding sites exist in the promoter, the nature of the transcription factors themselves in terms of their influence on transcription, and in eukaryotes and some archaea, epigenetic processes that control the access of transcriptional machinery to the locus being transcribed.
So when you think about the two elements in a gene, think of a light (the bit of a gene that codes for proteins) and a dimmer (which controls how much RNA is made by the protein-coding bit)
The following is multiple choice question (with options) to answer.
Dna encodes instructions for what kind of molecules? | [
"acids",
"cells",
"fats",
"proteins"
] | D | DNA encodes instructions for proteins. RNA copies the genetic code in DNA and carries it to a ribosome. There, amino acids are joined together in the correct sequence to make a protein. |
SciQ | SciQ-4073 | evolution, natural-selection, human-genetics, artificial-selection
natural selection is the result of natural variance in fitness linked to traits
artificial selection leads to a change in traits, in a specifically targeted direction, decided and imposed by another organism (usually humans, I know of no other species which does this)
eugenics is practice of artificial selection on humans enacted by humans with the specific aim of improving quality: often for social, economic, or political reasons and is generally accepted as being against human rights these days.
The following is multiple choice question (with options) to answer.
Who coined the term natural selection? | [
"shaw",
"Mendel",
"darwin",
"Pasteur"
] | C | Darwin coined the term fitness to refer to an organism’s relative ability to survive and produce fertile offspring. Nature selects the variations that are most useful. Therefore, he called this type of selection natural selection . |
SciQ | SciQ-4074 | ocean, waves
Title: What causes waves to form the characteristic "breaking" shape as they approach the shoreline? We all know that as waves approach the shallow shores, the waves begin to form a characteristic shape. The upper portion of these breaking waves appears to curl forward and downwards over the bottom segment of the wave, before breaking into "white wash". The image below illustrates what this characteristic shape looks like:
The following is multiple choice question (with options) to answer.
When sand is deposited along a shoreline, what is created? | [
"dunes",
"bay",
"beach",
"island"
] | C | Sand deposited along a shoreline creates a beach. |
SciQ | SciQ-4075 | evolution, human-evolution
Apes
The split between the line leading to modern humans and the line leading to modern chimpanzees occured somewhere around 4 to 7 million years ago. The clade is called Hominini. The split between those and the line leading to modern gorillas occured around 8 to 19 million years ago (yes, the dates are getting fuzzier). A fossil coming close to this ancestor may be Nakalipithecus nakayamai, however, we only have a fossil jaw from that species.
Going back, we get to the split between modern-day humans/chimpanzees/gorillas and modern-day orang-utans. This is the "ape" family, Hominidae. The largest ape that we know of, Gigantopithecus, that grew to about 3 meters, is classified as an orang-utan. Note that this is not a direct ancestor of humans. Even if our ancestors were larger than modern humans at this point it's unlikely that we are talking about anything larger than a big gorilla.
Primates
Going a bit in the reverse order here: The first true primates evolved around 55 million years ago. Fossils from that time are about the size of squirrels. Humans are "old world monkeys" who first appeared around 40 million years ago - the fossils from that clade we know, for example Apidium or Aegyptopithecus are a bit larger, some as large as a dog.
Primate-like mammals
The first primate-like mammals, called Plesiadapiformes appeared around 60 million years ago. We don't know all that much about them, but the most famous Purgatorius was the size of a rat or mouse.
Mammals / placenta mammals
Going back even further, things become even murkier, but early mammals were small. Placentalia, placental mammals appeared around 90 million years ago. They were small, arboreal (tree-dwelling) animals. Early mammals appeared around 160 million years ago and fossils we have from that time place them around the size of a shrew.
Now, is it possible that there were larger mammals in there somewhere, that then "shrunk" again? Sure. Just unlikely.
Therapsid
The following is multiple choice question (with options) to answer.
Prosimians are thought to be more similar to the earliest of these? | [
"insects",
"fish",
"primates",
"rodents"
] | C | Primates called prosimians are generally smaller. There are also far fewer of them. Prosimians include lemurs, such as the mouse lemur in Figure above , and lorises. Prosimians are thought to be more similar to the earliest primates. |
SciQ | SciQ-4076 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
What arteries carry oxygen-poor blood away from the heart to the lungs? | [
"femoral",
"aorta",
"subclavian",
"pulmonary"
] | D | There are specific veins and arteries that are more significant than others. The pulmonary arteries carry oxygen-poor blood away from the heart to the lungs. These are the only arteries that carry oxygen-poor blood. The aorta is the largest artery in the body. It carries oxygen-rich blood away from the heart. |
SciQ | SciQ-4077 | botany, species-identification, mycology
Title: What are those huge plants / fungi on trees called? I've seen them in Scotland in August 2015:
The plants / fungi were quite high (over 2m) on the tree. They are almost circular if you view them from the top, I guess (except for the part where they are connected to the tree). I guess the diameter of them might be over 14cm.
What are they called? Well I will agree with fileunderwater, it is a Fomes fomentarious. For more info check this: Fomes fomentarius is a tough perennial polypore that usually becomes hoof-shaped with age; it is found on standing and fallen hardwoods. Its woody upper surface develops grayish zones, and its brown pore surface features tiny round pores. When sliced open (no easy task, given its toughness) it is usually composed more of vaguely layered tubes than flesh.
Along with Piptoporus betulinus, Fomes fomentarius is one of two mushrooms that the Tyrolean Iceman was carrying around 5000 years ago. He apparently used Fomes fomentarius as tinder.
Description:
Ecology: Parasitic and saprobic on the wood of hardwoods (especially birches and beech); causing a white rot; growing alone or gregariously; perennial; fairly widely distributed in northern and north-temperate North America
Cap: Up to about 20 cm across; shell-shaped to hoof-shaped; with a dull, woody upper surface that is zoned with gray and brownish gray.
Pore Surface: Brownish; 2-5 round pores per mm; tube layers indistinct, brown, becoming stuffed with whitish material.
Stem: Absent.
Flesh: Brownish, thin, hard.
The following is multiple choice question (with options) to answer.
What are the mass of threadlike filaments on the body of a fungus called? | [
"dendrites",
"cuticle",
"hyphae",
"cytoplasm"
] | C | body of a fungus that consists of a mass of threadlike filaments called hyphae. |
SciQ | SciQ-4078 | bond, ions, metal
Title: Can we picture metallic bonding as an equilibrium between electrons and cations? Can we picture metallic bonding as an equilibrium between electrons and cations?
Suppose:
$$\ce{Al^3+ + 3e- <=> Al}$$ In metals, electrons are non-localized, forming a "sea" of electrons, rather than having them localized, as in the $\ce{Na+Cl-}$ lattice of crystalline salt. See Metallic bonding for a more complete description.
It is, of course, a matter of degree, as covalent, ionic and metallic bonding can "blend" from one to the other. A bond can be considered partially ionic and covalent, for example; see these helpful graphics
The following is multiple choice question (with options) to answer.
Ionic bonds between two atoms require one metal and one what? | [
"gas",
"liquid",
"metallic",
"nonmetal"
] | D | Ionic bonds tend to form between atoms for which the electronegativity differences are 2.0 and above. In general, ionic bonds between two atoms require one metal and one nonmetal. |
SciQ | SciQ-4079 | general-relativity, forces, gravity, earth, atmospheric-science
Title: How does Earth hold its atmosphere? According to Einstein's theory of relativity, gravity is not pulling us down but space is pushing us down. This mean there is no gravity and its an illusion. So, in this scenario how does Earth hold its atmosphere? Since there is no force to pull it down.
This mean there is no gravity and its an illusion
This is a very common statement in popular science accounts of general relativity, and while it's true it's also misleading.
If you release an object above the Earth then that object will immediately start accelerating towards the Earth. Isaac Newton would say this is because there is a force pushing the object towards the Earth and that's what we mean by the gravitational force. Albert Einstein would say there is no force pushing the object towards the Earth and the object accelerates towards the Earth due to the curvature of spacetime. It is in this sense that we say gravity isn't really a force.
But in both cases the object accelerates towards the Earth, and if the object is an air molecule then that air molecule accelerates towards the Earth. So the Earth's atmosphere stays with the Earth because the air molecules that make up the atmosphere are all individually accelerating towards the Earth just like any other object does. The fact the atmosphere is bound to the Earth is no more surprising than the fact you and I are also bound to the Earth.
I suppose the surprising thing is why the atmosphere doesn't all fall immediately to the Earth's surface to form a thin dense layer of air molecules. The reason this doesn't happen is that air molecules are all whizzing around at surprisingly high speeds - typically hundreds of metres per second depending on the temperature. The air molecules bash into each other and knock each other around, and the air molecules near the ground bash into the air molecules above them and stop them falling down.
The following is multiple choice question (with options) to answer.
The pressurized gas of earth's atmosphere is contained by what force? | [
"gravity",
"light",
"plasma",
"variation"
] | A | All gases exert pressure; it is one of the fundamental measurable quantities of this phase of matter. Even our atmosphere exerts pressure—in this case, the gas is being “held in” by the earth’s gravity, rather than the gas being in a container. The pressure of the atmosphere is about 14.7 pounds of force for every square inch of surface area: 14.7 lb/in2. Pressure has a variety of units. The formal, SI-approved unit of pressure is the pascal (Pa), which is defined as 1 N/m2 (one newton of force over an area of one square meter). However, this is usually too small in magnitude to be useful. A common unit of pressure is the atmosphere (atm), which was originally defined as the average atmospheric pressure at sea level. However, “average atmospheric pressure at sea level” is difficult to pinpoint because of atmospheric pressure variations. A more reliable and common unit is millimeters of mercury (mmHg), which is the amount of pressure exerted by a column of mercury exactly 1 mm high. An equivalent unit is the torr, which equals 1 mmHg. (The torr is named after Evangelista Torricelli, a seventeenth-century Italian scientist who invented the mercury barometer. ) With these definitions of pressure, the atmosphere unit is redefined: 1 atm is defined as exactly 760 mmHg, or 760 torr. We thus have the following equivalences: 1 atm=760 mmHg=760 torr. |
SciQ | SciQ-4080 | human-biology, genetics, cell-biology, terminology
and according to Wikipedia,
A mitogen is a chemical substance that encourages a cell to commence cell division, triggering mitosis.
What’s the difference between them? I suppose a mitogen specifically refers to mitosis, but if something is stimulating mitosis, isn’t it stimulating growth? Are mitogens all growth factors? Are all growth factors mitogens? There is a lot of confusion and conflicting / imprecise definitions of these terms. It's biology after all :)
A mitogen is an agent that causes a cell to enter mitosis. This definition is pretty clear, and there is a good consensus about it. (Well technically, mitosis is not the same as cell division, but we will gloss over this distinction.)
The term growth factor has at least two different definitions: (1) a factor that causes growth of tissues, organs or entire individuals; or (2) a factor that causes growth of cells (increase in cell size). These two versions are often mixed up, and this causes no end of confusion. Let's consider them both in turn.
Definition (1) is more common and probably older. Since growth of whole tissues usually (but not always) implies both cell growth and division, according to this definition, a growth factor is also a mitogen. But the reverse is not true: there are cases where cells divide without growing, for example the first few cell divisions of a fertilized egg. But note that, since this definition concerns the level of tissues or individuals, it's meaning is not entirely clear in terms of cell growth and division. Muscle growth in the adult stage usually does not involve cell division, for example.
Definition (2) is better suited to cell biology (in my opinion), because it actually concerns cells, not tissues. This definition is more common when studying cell growth and division; see for example this review. Cell growth is a separate phenomenon from cell division: cells can grow without dividing (fat cells, muscle fibers and neuron do this, for example), or divide without growing (as mentioned above). So with this definition, growth factor and mitogen are two completely unrelated concepts. Now, it is certainly true that many proteins can act both as growth factors and mitogens; Matej Pribis gives some nice examples in the other answer. But that is an empirical fact, not a question of definitions.
The following is multiple choice question (with options) to answer.
Cytokinins promote cell division and prevent what? | [
"mutations",
"senescence",
"deficiency",
"apoptosis"
] | B | Cytokinins Promote cell division; prevent senescence. |
SciQ | SciQ-4081 | 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.
Dna transcription is controlled by what type of proteins? | [
"digested",
"regulatory",
"essential",
"genetic"
] | B | As shown in Figure below , transcription is controlled by regulatory proteins . The proteins bind to regions of DNA, called regulatory elements , which are located near promoters. After regulatory proteins bind to regulatory elements, they can interact with RNA polymerase, the enzyme that transcribes DNA to mRNA. Regulatory proteins are typically either activators or repressors. |
SciQ | SciQ-4082 | life, extremophiles
Title: How close to Earth's core can organisms live? We don't to know much about organisms living deep below the Earth's crust. Recently a team led by S. Giovanni discovered some microbes 300 m below the ocean floor. The microbes were found to be a completley new and exotic species and apparently they feed off hydrocarbons like methane and benzene. Scientists speculate that life may exist in our Solar System far below the surface of some planets or moons. This raises some questions:
What is the theoretical minimum distance from Earth's core where life can still exist. Please explain how you came up with this number. For example, there are temperature-imposed limits on many biochemical processes.
Is there the potential to discover some truly alien life forms in the Earth's mantle (by this I mean, life which is not carbon based, or life which gets its energy in ways we have not seen before, or non DNA-based life, or something along these lines)?
What is the greatest distance below the Earth's crust that life has been discovered? I believe it is the 300 m I cited above, but I am not 100% sure. There's a lot we don't know about life in deep caves, but we can bound the deepest living organism to at least 3.5 kilometers down, and probably not more than 30 kilometers down.
The worms recovered from deep mining boreholes are not particularly specifically adapted to live that far down: they have similar oxygen/temperature requirements as surface nematodes.
The Tau Tona mine is about 3.5 kilometers deep and about 60˚ C at the bottom. Hydrothermal vent life does just fine up to about 80˚C, and the crust gets warmer at "about" 25˚C per kilometer. It's entirely reasonable to expect life to about 5 kilometers down, but further than that is speculation.
Increasing pressure helps to stabilize biological molecules that would otherwise disintegrate at those temperatures, so it's not impossible there could be life even deeper. It may even be likely, given that the Tau Tona life breathes oxygen.
I am certain no life we might recognize as life exists in the upper mantle.
The following is multiple choice question (with options) to answer.
Tubeworms deep in the galapagos rift get their energy from what type of bacteria? | [
"chemosynthetic",
"asexual",
"filamentous",
"sprillia"
] | A | Tubeworms deep in the Galapagos Rift get their energy from chemosynthetic bacteria. Tubeworms have no mouth, eyes, or stomach. Their survival depends on a symbiotic relationship with the billions of bacteria that live inside them. These bacteria convert the chemicals that shoot out of the hydrothermal vents into food for the worm. |
SciQ | SciQ-4083 | human-biology, genetics, human-genetics, chromosome, sex-chromosome
Title: Why are X-linked illnesses less common in females if females have X-chromosome inactivation anyway? I have read this post but am still slightly confused about this. Do tissues in the human body not all develop from the same cell(s) in the embryo? If so, I do not see how the cell 'mosaic' would be grainy enough to mask the fact that half of the female's cells are not working properly. For example, all liver cells come from the same cell in the embryo which has an inactivated X. In that case, there is a 50% chance that the females liver is dysfunctional. So I would predict that some females would exhibit X-linked disorers even if they are heterozygous, but I haven't heard of this being the case... Barr bodies (X-chromosome inactivation) don't form in the initial fertilized embryo — it's not that one X-chromosome is inactivated, and then that same inactivation is passed down to daughter cells. Rather, X-chromosome inactivation occurs on a cell-by-cell basis in differentiated cells. Note how the accepted answer to the question you linked mentions that different cell lineages will have different X-chromosome inactivation patterns — in other words, inactivation occurs later in the differentiation and proliferation processes than I think you might be assuming.
To use your example: the liver cells do not all derive from a pluripotent (undifferentiated) cell with one inactivated X-chromosome, but instead derive from said pluripotent cell, and then undergo X-chromosome inactivation.
Although the jury is out, scientifically speaking, on the mechanisms of selection of the X-chromosome to be inactivated, it's been postulated that some sort of decision-making may occur on this cellular level, resulting in a higher likelihood of inactivating the damaged or deleterious chromosome, if one is present.
Regardless, as the accepted answer to the question you linked mentions, the 50% of functional cells that would result from chance or random X-chromosome inactivation tends to be sufficient for the body's needs.
The following is multiple choice question (with options) to answer.
When female mammalian embryos consist of just a few thousand cells, one x chromosome in each cell inactivates by condensing into a structure called what? | [
"barr body",
"baker body",
"lewy's body",
"morton body"
] | A | Humans display dramatic deleterious effects with autosomal trisomies and monosomies. Therefore, it may seem counterintuitive that human females and males can function normally, despite carrying different numbers of the X chromosome. In part, this occurs because of a process called X inactivation. Early in development, when female mammalian embryos consist of just a few thousand cells, one X chromosome in each cell inactivates by condensing into a structure called a Barr body. The genes on the inactive X chromosome are not expressed. The particular X chromosome (maternally or paternally derived) that is inactivated in each cell is random, but once the inactivation occurs, all cells descended from that cell will have the same inactive X chromosome. By this process, females compensate for their double genetic dose of X chromosome. In so-called “tortoiseshell” cats, X inactivation is observed as coat-color variegation (Figure 7.10). Females heterozygous for an X-linked coat color gene will express one of two different coat colors over different regions of their body, corresponding to whichever X chromosome is inactivated in the embryonic cell progenitor of that region. When you see a tortoiseshell cat, you will know that it has to be a female. |
SciQ | SciQ-4084 | geophysics, oceanography, topography
Title: What are the striations or ridges in the eastern Pacific Ocean? Messing around on Google Earth recently I noticed a number of striations in the Eastern Pacific. These appear in an East-West orientation and seem to start on the North and South American continental shelves, and extend for roughly half the Pacific Ocean. For example one of these striations start in Santa Rosa Island off California and ends at Hawaii. These striations also appear to be roughly equally spaced at 8 degree intervals. The North and South American striations are angled with respect to each other and seem to converge at roughly Tahiti.
What causes these? I'm a fascinated novice.
EDIT
Some images to make things clearer (North Pole is top left):
Note the regularly spaced East-West parallel striations starting from the Equator and stepping north. In fact the striation on the Equator covers the entire Pacific.
Here a closer shot also shows fainter striations fanning out from Los Angeles: They are fracture zones.
I've annotated your image with the names of these very long, tectonically important features. They even have names, such as the Mendocino Fracture Zone:
I also labelled some survey tracks (rather subtle, very straight, very regular in width), which are data artifacts — these are the things you noticed radiating from the vicinity of Los Angeles.
There are yet other types of linear feature on the sea floor:
Transform faults are strike-slip faults connecting segments of spreading centres in the oceanic crust.
The spreading centres themselves.
Roughly linear archipelagos like Hawaii.
The long, curved trenches at convergent plate margins.
Images from Google Maps. Note: I edited this answer substantially after the OP clarified the question... and I learned about the difference between transform faults and fracture zones.
The following is multiple choice question (with options) to answer.
Oceans are divided into zones bases on distance from shore and what other factor? | [
"salinity",
"water depth",
"temperature",
"animal species"
] | B | In addition to the amount of salts, other conditions in ocean water vary from place to place. One is the amount of nutrients in the water. Another is the amount of sunlight that reaches the water. These conditions depend mainly on two factors: distance from shore and depth of water. Oceans are divided into zones ( Figure below ) based on these two factors. The ocean floor makes up another zone. |
SciQ | SciQ-4085 | cell-biology, dna, molecular-genetics
Title: During the process of correcting mutations via gene therapy, is the defective gene removed? Just recently started learning about gene therapy, many websites explain that the corrected DNA can be added to the genome using a vector and all that. I just don't understand what happens to the other sequence of nitrogenous bases that codes for the incorrect protein.
Thanks in advance for any answers :) To be specific: I am talking about adult, somatic gene therapy here, and germline gene therapy experiments is still a landmine when considering ethical reasons.
The defective gene codes for a defective protein, that usually plays a part in pathways. Since the protein is also defective, that pathway is also rendered defective because of this protein, and usually when pathways go defective, bad things happen.
There are three target approaches to gene therapy:
Gene silencing by Antisense Oligonucleotide Therapy
Genome Surgery by ZFN, Crispr/Cas9 etc..
Gene Replacement by viral vectors
The only method that corrects the defective gene here is the genome surgery method. By using Zinc Finger Nucleases, or Crispr/Cas9s, TALENS or other methods like that, the defective protein is corrected at the genome level, which automatically corrects the mRNA and protein, and everything works as it should.
Other methods like Antisense, just prevent the incorrect protein from forming. This is really useful if the defective protein is itself toxic to the body, and a replacement protein can be achieved by masking the defective region to produce a truncated but functional protein.
Gene replacement usually puts in a healthy copy of the gene in, that functions along with the defective copy, and this solves majority of the problems as the affected pathway is no longer rendered inactive, as the healthy protein takes over the defective pathway. The defective protein is still produced, but doesnt do anything (or rather, is rendered moot as the healthy protein takes over) and gets removed during regular maintenance of the cell.
The following is multiple choice question (with options) to answer.
If a mistake is made by dna polymerase while adding nucleotides, incorrect bases are removed and replaced by the correct base, and the process of what continues? | [
"hybridization",
"polymerization",
"digestion",
"fermentation"
] | B | DNA Repair DNA polymerase can make mistakes while adding nucleotides. It edits the DNA by proofreading every newly added base. Incorrect bases are removed and replaced by the correct base, and then polymerization continues (Figure 9.13a). Most mistakes are corrected during replication, although when this does not happen, the mismatch repair mechanism is employed. Mismatch repair enzymes recognize the wrongly incorporated base and excise it from the DNA, replacing it with the correct base (Figure 9.13b). In yet another type of repair, nucleotide excision repair, the DNA double strand is unwound and separated, the incorrect bases are removed along with a few bases on the 5' and 3' end, and these are replaced by copying the template with the help of DNA polymerase (Figure 9.13c). Nucleotide excision repair is particularly important in correcting thymine dimers, which are primarily caused by ultraviolet light. In a thymine dimer, two thymine nucleotides adjacent to each other on one strand are covalently bonded to each other rather than their complementary bases. If the dimer is not removed and repaired it will lead to a mutation. Individuals with flaws in their nucleotide excision repair genes show extreme sensitivity to sunlight and develop skin cancers early in life. |
SciQ | SciQ-4086 | entomology
Title: The death of Earthworm In rainy season when children sprinkle salt on earthworm ,it dies.But salt is not dangerous.We use it daily.Then why earthworm dies? It's because on the earth worm skin's special mucous. Acording to this article: Why do earthworms die when salt is sprinkled on them? the mucous makes moist to the worm's skin, which is vital for their survival. Moreover, the worms don't have a respiratory organs, like lungs, gills, etc. This means that Carbon Dioxide and other characterized as "dump" gases can not be exchanged with the Oxygen. But worms breath through their skin, with the help of these special mucous that are developed on its skin. If their skin dries out the result will be death, because the gas exchange will not last without the mucous help. Similarly, the circulatory system won't function, because its main role is to trade gasses with the cells via red blood cells.
What about salinity?
Salinity is a very important factor for the earthworms health, because high salinity destroy their valunable and sensitive skin and kills the mucous that in fact help the worm to "breathe". Low salt concentrations are very beneficial for the worm, because not only their mortarity level is increaced, there are size changes to the worm's body (noticeable bigger size).
Here are and some photos of a worm that its enviroment has low salinity and high salinity:
High salinity:
Low-to-medium salinity
Source: Why do earthworms die when salt is sprinkled on them?.
The following is multiple choice question (with options) to answer.
The common earthworm and leeches are examples of what type of worm? | [
"castrated",
"encapsulated",
"segmented",
"elongated"
] | C | Segmented worms include the common earthworm and leeches. |
SciQ | SciQ-4087 | nuclear-physics, physical-chemistry, mass-energy, binding-energy
Nuclear reactions are kind of in the middle between the two extremes of chemical reactions and elementary particle reactions. In an atomic nucleus, the binding energy contributes anywhere from 0.1% up to about 1% of the total energy of the nucleus. This is a lot less than with the color force in the proton, but it's still enough that it needs to be counted as a contribution to the mass of the nucleus. So that's why we say that mass is converted to energy in nuclear reactions: the "mass" that is being converted is really just binding energy, but there's enough of this energy that when you look at the nucleus as a particle, you need to factor in the binding energy to get the right mass. That's not the case with chemical reactions; we can just ignore the binding energy when calculating masses, so we say that chemical reactions do not convert mass to energy.
The following is multiple choice question (with options) to answer.
Elements involved in nuclear reactions are what? | [
"radioactive",
"detectable",
"inert",
"static"
] | A | Elements involved in nuclear reactions are radioactive. How do you think radioactive elements differ from other elements?. |
SciQ | SciQ-4088 | behaviour, language, genetic-code
Title: How does DNA encode high level features like animal behaviour and language? We know there are complex features which animals supposed to develop based on their genes as opposed to learning from the environment and the collective, also sometimes being very specific to certain species:
Concepts how to build homes
Animal languages including social insect interactions responsible for information transmission (or do they have to learn them through an acquisition process, let's exclude languages of ape tribes where "term" creation has been demonstrated?)
Valid answer: if already known, one or to examples to corresponding research.
Constraint: we are not talking about genes responsible for some sort of tendencies in behaviour but situations where there seems to be a more or less complex "blue print". I suppose we are yet very far from understanding these things. Relation of genotype to phenotype is teh subject of much contemporary research, but it is mainly limited to simple phenotypic features, explainable by action of a few genes, such as the colors of zebra fish mutants: see, e.g., this paper and the related publications by Nüsseln-Vollhardt group. Perhaps closer to your question is circadian rythms, which also have genetic determinants.
The complex behaviors are likely a result of the complex interactions of many genes, which are a very interesting, but also a very difficult problem to solve.
The following is multiple choice question (with options) to answer.
Circadian rhythms and migration are examples of what kind of behaviors in animals? | [
"continual",
"fluid",
"cyclic",
"finite"
] | C | Many animal behaviors occur in a regular cycle. Two types of cyclic behaviors are circadian rhythms and migration. |
SciQ | SciQ-4089 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
The articular cartilage is thickest in the upper and back part of the acetabulum, the socket portion of what? | [
"shoulder joint",
"kneecap",
"hip joint",
"elbow"
] | C | Chapter 9 1 Although they are still growing, the carpal bones of the wrist area do not show an epiphyseal plate. Instead of elongating, these bones grow in diameter by adding new bone to their surfaces. 3 Gout is due to the accumulation of uric acid crystals in the body. Usually these accumulate within joints, causing joint pain. This patient also had crystals that accumulated in the space next to his spinal cord, thus compressing the spinal cord and causing muscle weakness. 5 The immune system malfunctions and attacks healthy cells in the lining of your joints. This causes inflammation and pain in the joints and surrounding tissues. 7 The first motion is rotation (hinging) of the mandible, but this only produces about 20 mm (0.78 in) of mouth opening. 9 The glenoid labrum is wedge-shaped in cross-section. This is important because it creates an elevated rim around the glenoid cavity, which creates a deeper socket for the head of the humerus to fit into. 11 The articular cartilage functions to absorb shock and to provide an extremely smooth surface that makes movement between bones easy, without damaging the bones. 13 The articular cartilage is thickest in the upper and back part of the acetabulum, the socket portion of the hip joint. These regions receive most of the force from the head of the femur during walking and running. 15 The anterior cruciate ligament prevents the tibia from sliding too far forward in relation to the femur and the posterior cruciate ligament keeps the tibia from sliding too far backward. 17 The ligaments of the lateral ankle are the anterior and posterior talofibular ligaments and the calcaneofibular ligament. These ligaments support the ankle joint and resist excess inversion of the foot. 19 An inversion ankle sprain may injure all three ligaments located on the lateral side of the ankle. The sequence of injury would be the anterior talofibular ligament first, followed by the calcaneofibular ligament second, and finally, the posterior talofibular ligament third. 20 C 22 A 24 A 26 D 28 B 30 A 32 A 34 C 36. |
SciQ | SciQ-4090 | food, decomposition
Title: Worm compost cannot have cooked food I live in the Netherlands and it is getting fashionable to compost with worms. After investigating a few websites I noticed that most websites suggested that I cannot feed the worms leftovers from citrus fruits. This seems logical. I then started noticing that people advise against feeding the worms cooked food.
I'm no biologist but I cannot imagine a reason why cooked food is bad for the worms. Could anybody explain why this might be in layman’s terms? There are a few reasons for not feeding cooked foods to worms (Eisenia spp.) in a smaller household size worm farm. It's not because the food is cooked but what it often contains.
The earthworm used in vermiculture is usually Eisenia fetida (red wigglers) though other Eisenia species are sometimes used. All Eisenia are epigeic species meaning they live in the junction of decomposing organic matter (such as leaf litter, aging manure, rotted fallen trees) and their natural food is decaying plant matter and bacteria that are also digesting the organic matter. They don't make use of small dead animals (meat and fat).
In large scale commercial vermiculture operations, leftover and past-due-date foods from restaurants, institutions, nursing homes and schools are used along with plant matter and carboard and paper. I'm not sure how they balance cooked foods but possibly much less is used than plant matter.
The fact food is cooked isn't the problem but what's in it and/or what happens to it when added to the bin. If you have leftover vegetables and fruit that's been cooked with no added salt, it's perfectly acceptable. A certain amount of sweetened cooked fruit is also fine as the worms will eat that too. But ready-made foods usually have preservatives, salt, fats and spices added. Either worms won't eat it, leading to odour caused by mouldy rotten food, or it can make them unthrifty and even killing off your worms if it's fed them repeatedly.
The following is multiple choice question (with options) to answer.
What are decomposers that feed on the organic matter left over from other decomposers? | [
"saprotrophs",
"algae",
"fungi",
"protozoa"
] | A | Saprotrophs are decomposers that feed on any remaining organic matter that is left after other decomposers do their work. Examples of saprotrophs include fungi and protozoa. |
SciQ | SciQ-4091 | nuclear-physics, nuclear-engineering, explosions
Title: Does plutonium need to be squeezed to produce an uncontrolled chain reaction? I guess what I am asking is if in theory you could start with a certain amount of plutonium would it explode with out being squeezed together as is done in an atomic bomb ?
Normally what happens ( and this is an assumption on my part , I am not an atomic bomb scientist ) two or more sections of the isotope in question are rammed together in a very controlled implosion caused by chemical explosives.
But what would happen if the isotope was just manufactured as one large chunk of material? Would it spontaneously detonate or would you still have to squeeze it? The "trick" to a nuclear chain reaction is that each fission triggers more than one other fission event. That requires the emitted neutrons to hit enough other atoms to have a chance of causing fission. But in an ordinary block of plutonium the density of atoms is not enormous, and there are edges where neutrons get lost to the environment. A sufficiently big block would presumably produce a nuclear "fizzle" as chain reactions would release some of the energy (enough to destroy it) but not enough to actually explode.
The solution in a fission bomb is both to compress the material, but also to surround it with a neutron reflector. This makes each fission event likely to trigger several more events producing a boom rather than a fizzle.
Alex Wellerstein has a great writeup about why "critical mass" is the wrong concept (it should be "critical condition") and a very fun interactive visualisation of the process. Notice how piling up a lot of extra atoms makes the chain reaction longer but still relatively inefficient and dirty, while compressing inside a neutron reflector gets most of the energy out of the atoms. Just having a reflector does little on its own here.
The following is multiple choice question (with options) to answer.
Heavier isotopes of plutonium are also produced when lighter plutonium nuclei capture what? | [
"neutrons",
"protons",
"electrons",
"molecules"
] | A | Heavier isotopes of plutonium—Pu-240, Pu-241, and Pu-242—are also produced when lighter plutonium nuclei capture neutrons. Some of this highly radioactive plutonium is used to produce military weapons, and the rest presents a serious storage problem because they have half-lives from thousands to hundreds of thousands of years. Although they have not been prepared in the same quantity as plutonium, many other synthetic nuclei have been produced. Nuclear medicine has developed from the ability to convert atoms of one type into other types of atoms. Radioactive isotopes of several dozen elements are currently used for medical applications. The radiation produced by their decay is used to image or treat various organs or portions of the body, among other uses. The elements beyond element 92 (uranium) are called transuranium elements. As of this writing, 22 transuranium elements have been produced and officially recognized by IUPAC; several other elements have formation claims that are waiting for approval. Some of these elements are shown in Table 21.3. Preparation of Some of the Transuranium Elements Name. |
SciQ | SciQ-4092 | cell-biology, development
Title: What determines the fate of a cell with respect to differentiation? I have been reading about Townes and Holtfreter's work in 1955, in which cells are dissociated from a blastocyst in an alkaline solution then mixed together and spontaneously reaggregates based on type, so epidermal cells around the outside and neural plate cells in the middle.
I understand enough about cell adhesion to understand why the cells will seem to attract cells of their own type, but would like to know how they can initially detect what to become and where they are needed in a specialised form, without something acting like a brain telling them what to become and where to go.
If the selection from the available types is random, as I suspect, what happens to blastocysts with too much epidermal tissue or vice versa? I'm struggling to imagine how organisms like this can develop without something taking the lead and actively coordinating what goes where. Cell differentiation, cell fate and cell mapping is an interplay of accessible evolutionary strategies/programmes and responses to dynamic environmental cues such as specialized hormones (e.g. morphogens) and physical parameters and constraints. That is putting it very broadly. It is a complex issue, if L. Wolpert's PLOS assays are any indication. I compiled a few links to get you started.
Specifically, reappraising the topic of your cited classical experiment are R.Moore et al:
The classical cell sorting experiments undertaken by Townes and
Holtfreter described the intrinsic propensity of dissociated embryonic
cells to self-organize and reconcile into their original embryonic
germ layers with characteristic histotypic positioning. Steinberg
presented the differential adhesion hypothesis to explain these
patterning phenomena.....
The following is multiple choice question (with options) to answer.
What parts of the cell does cell differentiation involve changes in? | [
"cystine and cell wall",
"cell membrane and nucleus",
"endoderm and epidermis",
"cytoplasm and cell wall"
] | D | |
SciQ | SciQ-4093 | entomology, physiology, bio-mechanics, morphology
Title: Why do wasps have "wasp waists"? What's been optimized? I photographed these (unidentified) wasps on a sunny but cool winter day in northern Taiwan because they were conspicuously hanging out on a hand railing and had much lighter coloring than I'd ever seen before.
But after I took the time to look at a close-up I realized "Wow, they really have long, very thin waists!" Mechanically, it looks like they are two large masses connected by a very long thin beam, which must have quite a tiny canal in the center to let all the "juices" flow through.
While other insects and spiders may have segments separated by a tiny connection, this one is both small in diameter and quite long.
Why? Does this specific configuration provide some benefits to them?
click for full size Why do humans have such a flexible shoulder? Our ancestors relied on throwing things so the ones who could throw things better did better. What is the wasp's equivalent weapon? The stinger. Wasps have such thin "waists" to facilitate maneuverability of the stinger. This is especially important in wasps because for many, and for the ancestors who first evolved this feature, a flexible thorax with an ovipositor capable of depositing eggs into grubs and caterpillars was fundamental to their reproduction. The path to their current form seems to have been as follows: 1) early stingless wasps develop an ovipositor and begin implanting their eggs into other insects, 2) the thorax evolves to be thin and flexible to facilitate this method of reproduction, 3) the ovipositor modifies into a stinger and, combined with that flexible thorax, the wasp becomes the Zorro of the skies.
See New Scientist's 20 November 2019 Hourglass figure: Why do wasps have such narrow waists?
The following is multiple choice question (with options) to answer.
The head, thorax, and abdomen comprise what type of body structure, possessed by arthropods? | [
"segmented",
"elongated",
"vertebrate",
"permeable"
] | A | Arthropods range in length from about 1 millimeter (0.04 inches) to 4 meters (about 13 feet). They have a segmented body with a hard exoskeleton. They also have jointed appendages. The body segments are the head, thorax, and abdomen (see Figure below ). In some arthropods, the head and thorax are joined together as a cephalothorax. |
SciQ | SciQ-4094 | 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.
The renal hilum is the entry and exit site for structures servicing which organs? | [
"kidneys",
"lungs",
"brains",
"ovaries"
] | A | Renal Hilum The renal hilum is the entry and exit site for structures servicing the kidneys: vessels, nerves, lymphatics, and ureters. The medial-facing hila are tucked into the sweeping convex outline of the cortex. Emerging from the hilum is the renal pelvis, which is formed from the major and minor calyxes in the kidney. The smooth muscle in the renal pelvis funnels urine via peristalsis into the ureter. The renal arteries form directly from the descending aorta, whereas the renal veins return cleansed blood directly to the inferior vena cava. The artery, vein, and renal pelvis are arranged in an anterior-to-posterior order. |
SciQ | SciQ-4095 | photosynthesis, botany
Title: Photosynthesis - Light Intensity Say I was conducting an experiment for photosynthesis. If I moved light closer to the plant, what effect would this have on the process of photosynthesis? The rate of photosynthesis varies from plant to plant. Some plants require more light and some require less. If you move light closer to the plant, in most scenarios the rate of photosynthesis is likely to be increased. For some plants a minimal light is enough for their photosynthesis, so for those plants, moving light source closer or further will have less effect.
The following is multiple choice question (with options) to answer.
Photosynthesis changes light energy to what type of energy? | [
"chemical",
"radiation",
"potential",
"solar"
] | A | Photosynthesis changes light energy to chemical energy. The chemical energy is stored in the bonds of glucose molecules. Glucose is used for energy by the cells of almost all living things. Plants make their own glucose. Other organisms get glucose by consuming plants (or organisms that consume plants). How do living things get energy from glucose? The answer is cellular respiration. |
SciQ | SciQ-4096 | organic-chemistry, biochemistry, home-experiment, mixtures, colloids
Sugars. Milk is rich a variety of di- and oligo-saccharides such as the eponymous lactose, as well as many other more complex molecules:
[Free oligosaccharides are natural constituents of all placental mammals' milk. Human milk contains 7–12 g/L oligosaccharides, making the oligosaccharide fraction a major component of human milk. Compared with human milk, the concentration of oligosaccharides in the milk of the most relevant domestic mammals is smaller by a factor of 10 to 100.]
The following is multiple choice question (with options) to answer.
Fructose and lactose are types of sugars broken down by the body to form what, which is the simplest sugar of all? | [
"sucrose",
"glutamate",
"carbohydrate",
"glucose"
] | D | Sugars are small, simple carbohydrates that are found in foods such as fruits and milk. The sugar found in fruits is called fructose. The sugar found in milk is called lactose. These sugars are broken down by the body to form glucose (C 6 H 12 O 6 ), the simplest sugar of all. |
SciQ | SciQ-4097 | dna, chromosome
Title: Are the complementary base pairs known as genes? In my text book ,it is written that a chromosome has 1000s of genes and it is distributed throughout the chromatids except in the centromere. But we know that the chromosomes have DNAs inside them which have complementary base pairs. Then are these base pairs known as genes?? Don't assume a chromosome to be some X-shaped box that contains DNA inside it and DNA as a container of genes.
DNA, genes, Chromatid, Chromosomes are just different names at different levels of the same thing.
In molecular biology, you'll find multiple definitions of certain terms because as new insights are gained by any researcher, the definition gets modified. So one has to always make their concept clear so that they don't get confused between the same yet uniquely different terms.
So, Let's first look at how different their definitions can be:
DNA is a molecule inside cells that contains the genetic information responsible for the development and function of an organism. DNA molecules allow this information to be passed from one generation to the next. DNA is made up of a double-stranded helix held together by weak hydrogen bonds between purine-pyrimidine nucleotide base pairs: adenine (A) paired with thymine (T), and guanine (G) paired with cytosine (C). Also called deoxyribonucleic acid.
GENE, For many years the HGNC has maintained the definition of a gene as “a DNA segment that contributes to phenotype/function. In the absence of demonstrated function a gene may be characterized by sequence, transcription, or homology”. As there is still no universally agreed alternative we continue to use this definition.
Chromosome is a highly coiled structure of DNA molecule. Often observed in X-shaped only. Along with DNA, some proteins are also make up chromosomes.
The following is multiple choice question (with options) to answer.
A complementary pair of chromosomes have genes for the same characteristics in the same location on the chromosome are known as? | [
"endroctyne chromosomes",
"symbiotic chromosomes",
"analogous chromosomes",
"homologous chromosomes"
] | D | From Genotype to Phenotype Each human body cell has a full complement of DNA stored in 23 pairs of chromosomes. Figure 28.24 shows the pairs in a systematic arrangement called a karyotype. Among these is one pair of chromosomes, called the sex chromosomes, that determines the sex of the individual (XX in females, XY in males). The remaining 22 chromosome pairs are called autosomal chromosomes. Each of these chromosomes carries hundreds or even thousands of genes, each of which codes for the assembly of a particular protein—that is, genes are “expressed” as proteins. An individual’s complete genetic makeup is referred to as his or her genotype. The characteristics that the genes express, whether they are physical, behavioral, or biochemical, are a person’s phenotype. You inherit one chromosome in each pair—a full complement of 23—from each parent. This occurs when the sperm and oocyte combine at the moment of your conception. Homologous chromosomes—those that make up a complementary pair—have genes for the same characteristics in the same location on the chromosome. Because one copy of a gene, an allele, is inherited from each parent, the alleles in these complementary pairs may vary. Take for example an allele that encodes for dimples. A child may inherit the allele encoding for dimples on the chromosome from the father and the allele that encodes for smooth skin (no dimples) on the chromosome from the mother. |
SciQ | SciQ-4098 | organic-chemistry, biochemistry
But what happens with badly ventilated heaters is not that. Leakage of CO into the room is the dominant problem not a lack of oxygen. CO is very poisonous because it forms a relatively stable compound with haemoglobin, blocking the blood's ability to move oxygen around the body. This happens at very low levels of CO, long before any external shortage of oxygen has happened. When town gas supplies consisted of hydrogen/CO mixtures (phased out in favour of natural gas which is mostly methane in the 1960s in the UK) "putting you head in the oven" was a favoured method of suicide. As was piping a car exhaust into the car (which became harder post catalytic converters which remove CO and some other gases).
The point is that a small level of CO in a space where there is plenty of oxygen is deadly. And the deadly levels are far lower that the levels of carbon dioxide that would trigger any physiological warnings in the body.
The following is multiple choice question (with options) to answer.
What dangerous oxygen compound is found in ground level smog? | [
"sulfur dioxide",
"argon",
"ozone",
"neon"
] | C | Photochemical smog consists mainly of ozone (O 3 ). The ozone in smog is the same compound as the ozone in the ozone layer,(O 3 ). But ozone in smog is found near the ground. Figure below shows how it forms. When nitrogen oxides and VOCs are heated by the Sun, they lose oxygen atoms. The oxygen atoms combine with molecules of oxygen to form ozone. Smog ozone is harmful to humans and other living things. |
SciQ | SciQ-4099 | evolution, life-history
Title: Has there been any observation of species adapting the evolution process? I am very interested in the evolution of the evolution process itself. There are of course a lot of things that influence how evolution will work, but for this question, I am interested in things that are only related to the evolution process. Examples could be increase chance of mutations in newborns, change in reproduction age, and similar. I am specifically interested in observation where the evolution process itself has adapted to a change in the environment. Bacteria such as E. coli are known to increase their mutation rate (by switching to a more error prone polymerase among other things) when under stress. This can mean being placed in a medium where it's not adapted to grow (http://www.micab.umn.edu/courses/8002/Rosenberg.pdf) or when treated with antibiotics (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088971/?tool=pmcentrez).
The following is multiple choice question (with options) to answer.
Large increases in the diversity of life have resulted from adaptive radiations that followed what? | [
"mass mutations",
"mass extinctions",
"glaciers",
"mass migrations"
] | B | |
SciQ | SciQ-4100 | electricity
Title: Electricity production Are there alternate means to produce electricity than magnetic induction?
I observe that all places this method is used .Do other methods exist even if this being the most profitable way. Magnetic induction is by far the most efficient way to generate electricity, but there are other methods. The obvious common method is photoelectricity, as used in solar panels. This is around 10% - 20% efficient.
There are plenty of other ways of generating small amount of electricy that have found specialist niches. For example the Voyager spacecraft use the Seebeck effect to generate electricity from heat. This type of electricity generation is generically known as thermoelectricity. Voyager uses a radioactive source to generate the heat, but any source of heat will work.
Alternatively mechanical forces can generate electricity using piezoelectricity. This is used to generate electric sparks in gas lighters.
Or another method is triboelectricity, of which the most famous example is that schoolchild's favourite the Van de Graaff generator.
And I'm sure there are many others I haven't thought of but commenters will add :-)
The following is multiple choice question (with options) to answer.
What is the source of most electricity? | [
"coal",
"methane",
"the Sun",
"air"
] | A | Coal is the source of most electricity. |
SciQ | SciQ-4101 | waves
Title: Is wave motion the combined motion of the disturbance and the medium? Using a textbook slinky as an example, if the disturbance propagates through the slinky from left to right and the particles of the slinky vibrate up and down, does that mean 'wave motion' is also associated with the medium? Since the motion of the wave that we perceive is the combined motion of the disturbance and the medium? This answer is maybe not the most straightforward satisfactory answer to your stated question, but I think it anticipates ways of thinking that are used in more advanced areas of physics.
There are two pictures of what a wave is.
A wave is coherent motion in a medium; as time progresses energy moves through the medium and vibrations occur in different locations.
A wave is a propagating disturbance. It is not made of anything, the word "wave" refers a disturbance which propagates energy from one place to another.
Your question kind of implies that a wave is some combination of 1 and 2. I would say that either 1 or 2 are valid pictures, but you should treat them as distinct pictures of the same physical phenomenon and not reason about both simultaneously.
The advantage of the first picture is that it gives you a clear mechanical model of what is going on at a fundamental level; if you zoom in there are particles in the material, and the particles are oscillating back and forth in tandem -- that coherent motion is a wave. However, the disadvantage is that wave phenomena occur in many circumstances, and there are features of any particular example that will not generalize and can lead you astray if you take them too seriously. For example, light traveling in vacuum cannot be accurately visualized as motion of particles.
The advantage of the second picture is that it is more abstract and general -- wave phenomena occur in all kinds of materials, and so there is no need to specify which specific material you are thinking of, because we can make very general statements about waves that apply to any material. The disadvantage is that it can be hard to wrap your head around a disturbance without a medium, and also sometimes trying to be too general means you miss special aspects of the particular situation you might be interested in (for example, cool behavior like solitons can occur in water but not in light propagating in vacuum).
The following is multiple choice question (with options) to answer.
What kind of motion characterizes waves? | [
"breathing",
"bending",
"round",
"repetitive"
] | D | Waves are characterized by their repetitive motion. Imagine a toy boat riding the waves in a wave pool. As the water wave passes under the boat, it moves up and down in a regular and repeated fashion. While the wave travels horizontally, the boat only travels vertically up and down. The Figure below shows two examples of waves. |
SciQ | SciQ-4102 | biochemistry, botany, plant-physiology, photosynthesis
Title: Independence of Light independent reaction in photosynthesis? Inspired by a question asked to me by a classmate, I have the following question about Light-independent (dark phase) reactions in photosynthesis:-
Let us suppose an algae sample was exposed to light for a considerable
time so that maximum( if there is a limit) NADPH concentration was
achieved. Now if the sample is placed in dark and radioactive
¹⁴CO₂ bubbled, will the cell be radiolabelled after some time of
bubbling continuously?
The following is multiple choice question (with options) to answer.
Light reactions occur during which stage of photosynthesis? | [
"first stage",
"third stage",
"final stage",
"intermediate stage"
] | A | The light reactions occur in the first stage of photosynthesis. This stage takes place in the thylakoid membranes of the chloroplast. In the light reactions, energy from sunlight is absorbed by chlorophyll. This energy is temporarily transferred to two molecules: ATP and NADPH. These molecules are used to store the energy for the second stage of photosynthesis. The light reactions use water and produce oxygen. |
SciQ | SciQ-4103 | the-sun, distances, equinox
Note that, because we're at the moment of the equinox, the azimuths are now parallel to the equator and separated by 180.00°, as we expect.
The parenthesized numbers are the first digits of the actual elevations the NOAA calculator is using extracted from the JavaScript debugger (their full values are 24.396176229009612° and 45.65502300416843°, respectively), while the unparenthesized numbers are the rounded values it displays.
The distance between the two longitudes is 120°-10°=110°, which is 110°/360°≈30.56% of the way around the Earth.
Using NOAA's formula for refraction here (see also their main.js:330) and inverting the 5°–85° band both zeniths fall into numerically, we get 24.361⋯° and 45.639⋯°. Though small, this difference is significant; it changes the difference between the elevations by almost 0.02°, which as we saw above is as big as the entire discrepancy we're trying to measure!
import math
import scipy
def refract_adjust_5to85deg( true_elev_deg ):
#https://gml.noaa.gov/grad/solcalc/calcdetails.html
T = math.tan( math.radians(true_elev_deg) )
adjust_deg = (1.0/3600.0)*(
58.1/T - 0.07/(T*T*T) + 0.000086/(T*T*T*T*T)
)
return true_elev_deg + adjust_deg
def refract_unadjust( apparent_elev_deg ):
true_elev_deg = scipy.optimize.fsolve(
lambda true_elev_deg:
refract_adjust_5to85deg(true_elev_deg[0]) - apparent_elev_deg,
apparent_elev_deg
)[0]
return true_elev_deg
The following is multiple choice question (with options) to answer.
What is used to measure, in degrees, the distance north or south of the equater? | [
"latitude",
"elevation",
"equator",
"magnitude"
] | A | Latitude is the distance north or south of the Equator. It’s measured in degrees, from 0° to 90°. Several climate factors vary with latitude. |
SciQ | SciQ-4104 | nuclear-engineering, gamma-rays, medical-physics
Title: X-ray shielding X-ray shielding, why is lead used to shield us when taking X-ray images?
As far as I remember (but can't find it on wikipedia ... ), the deflection on (high energy) photons increases the more heavier the nuclei are. (Don't remember and don't find if it's really the mass or rather the proton number.)
In either case, there are heavier, more dense materials with higher proton numbers.
The material is not consumed nor altered by exposure to X-rays. So why don't we use gold or depleted uranium (just to name some alternatives)?
(Not sure about tags, if anyone knows better, please feel free to suggest/add some others.)
Edit: as the answers and comments here helped me to clear my mind to change the question, but the new question is sufficiently different, I've asked a follow-up here: Formula for scattering and energy change of photons on (naked) nuclei I pulled out my notes from a shielding class and found that the absorption cross section per atom follows a rule: $$\sigma_a\sim\frac{Z^p}{E^3},$$
where $z$ is the atomic number of the absorber atom, $E$ is the energy of the photon, and $p$ is an energy dependent value between 3 and 5. For most x-rays, $p\simeq 4$.
While the cross-section per atom does indeed get larger for increasing $Z$, the density of the material is important, too. The density peaks at osmium ($Z=76$), then drops off, then climbs again in the actinides, but never reaches densities near osmium and iridium ($Z=77$).
When considering the effectiveness of an shield/absorber, one must consider the combined effects of cross-section per atom and density. The result of this is a quantity known as the linear attenuation coefficient, $\mu$, which is typically quoted in $\mathrm{cm}^{-1}$. This is used to calculated the intensity of radiation after travelling through a thickness, $x$ of a material: $$I(x)=I_0 e^{-\mu x}.$$
The following is multiple choice question (with options) to answer.
Radiation can be absorbed or shielded by materials, particularly what material used to make protective aprons worn by x-ray administrators? | [
"carbon",
"cotton",
"lead",
"steel"
] | C | Radiation can be absorbed or shielded by materials, such as the lead aprons dentists drape on us when taking x rays. Lead is a particularly effective shield compared with other materials, such as plastic or air. How does the range of radiation depend on material? Ionizing radiation interacts best with charged particles in a material. Since electrons have small masses, they most readily absorb the energy of the radiation in collisions. The greater the density of a material and, in particular, the greater the density of electrons within a material, the smaller the range of radiation. Collisions Conservation of energy and momentum often results in energy transfer to a less massive object in a collision. This was discussed in detail in Work, Energy, and Energy Resources, for example. Different types of radiation have different ranges when compared at the same energy and in the same material. Alphas have the shortest range, betas penetrate farther, and gammas have the greatest range. This is directly related to charge and speed of the particle or type of radiation. At a given energy, each α , β , or γ will produce the same number of ionizations in a material (each ionization requires a certain amount of energy on average). The more readily the particle produces ionization, the more quickly it will lose its energy. The effect of charge is as follows: The α has a charge of +2q e , the β has a charge of −q e , and the γ. |
SciQ | SciQ-4105 | zoology, ecology, species-distribution, migration
Title: How do animals end up in remote areas? I was thinking specifically about random marshy water holes on farmers fields. It seems that you can visit just about any one of these and you will find frogs if you look hard enough.
They usually don't seem to be connected to each other. If it were any other land animal I would figure they walk from one spot to another, but in the case of frogs, I don't imagine their range is very vast. But often these marshy spots can be separated by fairly large distances to a frog.
So this brings me to my question: how do each of these spots end up with frogs in them? I don't imagine a frog is going to go hopping over a hill to get to a marsh on the other side, is it? This question pertains to organism dispersal, which is a very active field of study with relation to it's impact on conservation efforts. Much of what I will say below has been covered in this wiki.
Definition: From the Wiki
Technically, dispersal is defined as any movement that has the
potential to lead to gene flow.
It can be broadly classified into two categories:
Density dependent dispersal
Density independent dispersal
The question of frogs and fishes both refer to Density independent dispersal, while an example of density independent dispersal can be the competition for habitat space between big cats and humans (this is a WWF pdf)
From the wiki:
Density-independent dispersal
Organisms have evolved adaptations for dispersal that take advantage
of various forms of kinetic energy occurring naturally in the
environment. This is referred to as density independent or passive
dispersal and operates on many groups of organisms (some
invertebrates, fish, insects and sessile organisms such as plants)
that depend on animal vectors, wind, gravity or current for dispersal.
Density-dependent dispersal
Density dependent or active dispersal for many animals largely depends
on factors such as local population size, resource competition,
habitat quality, and habitat size.
Currently, some studies suggest the same.
This study in particular studied the movement and habitat occupancy patterns within ephemeral and permanent water bodies in response to flooding. They found that during flooding these frogs moved out to flooded ephemeral water bodies and later on moved back again to the permanent ones.
Other suggested readings for those highly interested in the subject may include this (a phd thesis) and this (a project report)
The following is multiple choice question (with options) to answer.
What is the name for something that consists of all the population in a given area together with the nonliving environment? | [
"ecosystem",
"habitat",
"totality",
"web"
] | A | An ecosystem consists of all the populations in a given area, together with the nonliving environment. |
SciQ | SciQ-4106 | human-biology, evolution, taxonomy
Title: Human evolution: Where *exactly* did the first human come from, whose parents were not? Layman here. So I have never really quite understood this facet of human evolution, (or any other for that matter), in that, I understand the evolutionary process, but I get lost on the 'border' cases.
For example, we, as humans, evolved from monkeys, (to use the colloquial term, I am not a biologist by any measure).
My question is, doesn't this mean that at some, discrete point, there had to have been a human, whose parents were not? If that is true, how does that work, in the sense that we now have species1 giving birth to species2.
If not, then how exactly does this border case work? The only other alternative I see, is that the borders are 'fuzzy', but then that necessarily means that the definition of a species is itself fuzzy, which I understand is not the case.
Thanks!
but I get lost on the 'border' cases.
Not surprisingly, since there are no borders, and this is probably the greatest misunderstanding: Evolution is gradual. It’s not generally possible to say where a complex feature (or a species) starts and another one ends. We could in theory say, for individual mutations on the genetic level, in which generation they first occurred, or when they became fixed in the population. But we cannot infer from these atomic changes where our ancestors started becoming humans. So the whole concept of “first human” is not biologically meaningful.
The best analogy remains a gradient between two colours. Going from the left, where does blue end and red start?
By the way, you spotted this very well by yourself:
[if there is no first human] then that necessarily means that the definition of a species is itself fuzzy
Exactly, that’s the case. For more details on definitions of species, refer to MCM’s answer. But it’s indeed crucial to note that the definition of species (or any other biological classification) is an ever-changing approximation which tries to fit a definitive yes/no answer onto a gradually changing scale.
The following is multiple choice question (with options) to answer.
The amniotic egg first evolved in what species? | [
"birds",
"mammals",
"reptiles",
"amphibians"
] | C | Amniotic Egg. The amniotic egg is an important adaptation in fully terrestrial vertebrates. It first evolved in reptiles. The shells of reptile eggs are either hard or leathery. |
SciQ | SciQ-4107 | species-identification, ichthyology, limnology, aquatic-biology, freshwater-biology
Title: What kind of fish is this? Spotted or largemouth? I don't know if this is a weird looking largemouth bass or a spotted bass. It was caught in southern Oklahoma. Please help! Thanks. This looks like a spotted bass (Micropterus punctulatus).
Here's an image showing some quick differences between some common bass species:
Using the above photo and this source to guide our judgment we can see your specimen appears to:
Have a jaw that does not go posterior to the eye (as it otherwise would in a largemouth).
Have rows of pigment towards its ventral side (below the "lateral line").
Not have the typical darker horizontal line of scales characteristic of the largemouth bass .
Have smaller-sized cranial scales (those around the eye) characteristic of the spotted bass.
If you can provide additional pictures of the following, I can provide a more definitive ID:
Both dorsal fins -- if the 2 dorsal fins are connected, it would further suggest a spotted bass (as largemouth bass dorsal fins are not typically connected)
Tongue -- evidence of a tooth patch is more likely on the spotted bass.
According to the International Game Fish Association:
Spotted bass can be found throughout the central and lower Mississippi basin to the Gulf of Mexico (from Texas to the Florida panhandle), including Georgia, Alabama, Tennessee, Kentucky and other nearby states where it occurs naturally or has been introduced.
The following is multiple choice question (with options) to answer.
A largemouth bass is an example of a cold-blooded animal that conforms to what aspect of the lake it inhabits? | [
"oxygen",
"depth",
"temperature",
"precipitation"
] | C | |
SciQ | SciQ-4108 | particle-physics, mass-energy, higgs, quarks, subatomic
Title: Where does the mass of a nucleon originate in an atom? The mass of the three quarks in the nucleons make up only about one to two percent of the mass of the nucleons. What makes up the other 98 percent? From this wikipedia article:
In quantum chromodynamics, the modern theory of the nuclear force, most of the mass of the proton and the neutron is explained by special relativity. The mass of the proton is about 80–100 times greater than the sum of the rest masses of the quarks that make it up, while the gluons have zero rest mass. The extra energy of the quarks and gluons in a region within a proton, as compared to the rest energy of the quarks alone in the QCD vacuum, accounts for almost 99% of the mass. The rest mass of the proton is, thus, the invariant mass of the system of moving quarks and gluons that make up the particle, and, in such systems, even the energy of massless particles is still measured as part of the rest mass of the system.
Also, at about 5:00 of this youtube video by Veritasium is your same question answered.
This other physics.se question is also related.
The following is multiple choice question (with options) to answer.
What makes up the mass number of an atom? | [
"atoms and neutrons",
"electrons and neutrons",
"protons and neutrons",
"molecules and electrons"
] | C | The mass number is the number of protons plus the number of neutrons in an atom. For example, most atoms of helium have 2 neutrons, so their mass number is 2 + 2 = 4. This mass number means that an atom of helium has a mass of about 4 amu. |
SciQ | SciQ-4109 | plant-anatomy
Title: Are bryophyte sporangia multicellular? My research on the matter can be summarized in a sentence: "It [sporangium] can be composed of a single cell or can be multicellular" (Source: https://en.wikipedia.org/wiki/Sporangium). Yet there shouldn't be a reply placed between "They are" and "They aren't" test options, speaking of "Are bryophyte sporangia multicellular?". A link to the source where I could ascertain whether the bryophyte sporangia is multicellular (if I could ascertain) is highly appreciated. In Embryophyta (land plants), including bryophytes, the sporangium is usually a multicellular structure.
Perhaps you meant to ask about the number of spore mother cells (SMCs) in each sporangium? That varies across groups. In bryophytes, each sporangium has many SMCs, and accordingly produces a large number of spores. (Contrast this with angiosperms, where a megasporangium [called an ovule] has only one megaspore mother cell.)
References and further reading:
https://courses.lumenlearning.com/boundless-biology/chapter/bryophytes/
https://www.britannica.com/science/plant-development
Image attribution:
By LadyofHats. (Public domain;
https://commons.wikimedia.org/wiki/File:Hornwort_structures.jpg)
The following is multiple choice question (with options) to answer.
Clubmosses are not true mosses, though, because they have what? | [
"cambrium",
"vascular tissue",
"hydrothermal tissue",
"smooth tissue"
] | B | Clubmosses are so named because they can look similar to mosses ( Figure below ). Clubmosses are not true mosses, though, because they have vascular tissue. The “club” part of the name comes from club-like clusters of sporangia found on the plants. One type of clubmoss is called the "resurrection plant" because it shrivels and turns brown when it dries out but then quickly turns green when watered again. |
SciQ | SciQ-4110 | planet, natural-satellites, nomenclature
Title: Is the satellite of a small star in a binary solar system a moon or a planet? What exaclty distinguishes a moon from a planet?
In a binary solar system that has a large star in the center and a smaller star - among some planets - orbiting that large star, and the smaller star has natural satellites - are these satellites called moons or planets?
Or asked in a different way - if Jupiter would ignite and become a star (which it can't because its mass doesn't suffice, but let's assume it was larger and could ignite), would its moons then be considered planets? A planetary mass object (also callled a planemo) is an astronomical object large enough to be pulled into a roughly spherical shape by its gravity compressing its matter. A planetary mass object must also have less than about 13 times the mass of Jupiter or about 4,131.4 times the mass of Earth.
If a planetary mass object orbits around the Sun in our solar system it is called a planet (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, & Neptune) or a dwarf planet (Ceres, Pluto, Eris, Hamaea, and Makemake, plus of number of candidate objects).
If a planetary mass object orbits around a planet in our solar system it is considered to be a natural satellite or a moon. Smaller objects which orbit around planets are also considered to be moons.
Any object smaller than a planetary mass object that orbits the Sun in our solar system is a small solar system body. They include all comets, asteroids, etc. that orbit the Sun ddirectly instead of orbiting one of the planets, moons, asteroids etc. that orbit the sun.
Any astronomical body with a mass greater than about 75 times the mass of Jupiter, or about 23,835 times the mass of the Earth, is a star are the stellar remnant of a star which has completed its "life cycle".
Any planetary mass object which directly orbits a star which is not the Sun, in another star system, is usually considered to be planet. So far there has been no effort to classify exoplanets (planets orbiting other stars) in other star systems as planets or dwarf planets. If they are large enough to be detected they are considered to be explanets. That might possibly change sometime in the future.
The following is multiple choice question (with options) to answer.
Europa and titan are names of what kind of celestial objects? | [
"moons",
"stars",
"asteroids",
"galaxies"
] | A | Saturn’s largest moon, Titan, is about one and a half times the size of Earth’s moon. Titan is even larger than the planet Mercury. The picture below compares the size of Titan to Earth ( Figure below ). Scientists are very interested in Titan. The moon has an atmosphere that is thought to be like Earth’s first atmosphere with nitrogen and methane. This atmosphere was around before life developed on Earth. Like Jupiter's moon, Europa, Titan may have a layer of liquid water under a layer of ice. Scientists now think that there are lakes on Titan's surface. Don't take a dip, though. These lakes contain liquid methane and ethane instead of water! Methane and ethane are compounds found in natural gas. |
SciQ | SciQ-4111 | hydrology, groundwater
Title: Hydrology - Depression cone VS transmissivity My question concerns the depression cone of a pumping well in a confined aquifer: Say the transmissivity of the aquifer is 1200 m^2/day how will the cone change if the transmissivity is 600 m^2/day? All the aquifers parameters stay constant in both scenarios and so is the pumping rate (say- 300 cm/hr).
The main interest is what happens to the radius of influence (where there will be no change in head from the aquifers regional head)? and also what happens to the head at the well it self?
Thanks, Asher Based on the Theis equation, increasing the transmissivity will increase the radius of influence and decrease the total drawdown. Drawdown is directly proportional to the pumping rate and inversely proportional to aquifer transmissivity and storativity.
$$s = \frac{Q}{4T\pi}\int_u^\infty \frac{e^{-y}}y dy$$
and $$u = \frac{r^{2}s}{4Tt}$$
Where s is drawdown, r is radius from well, t is time, T is transmissivity, Q is pumping rate, and u is the well function.
Applying this equation, you can produce plots like this:
for these plots, I used Q = 500, S = 0.01, and t = 4
The following is multiple choice question (with options) to answer.
What develops in depressions where water flow is low or nonexistent? | [
"ponds",
"bogs",
"swamps",
"sinkholes"
] | B | Freshwater marshes and swamps are characterized by slow and steady water flow. Bogs develop in depressions where water flow is low or nonexistent. Bogs usually occur in areas where there is a clay bottom with poor percolation. Percolation is the movement of water through the pores in the soil or rocks. The water found in a bog is stagnant and oxygen depleted because the oxygen that is used during the decomposition of organic matter is not replaced. As the oxygen in the water is depleted, decomposition slows. This leads to organic acids and other acids building up and lowering the pH of the water. At a lower pH, nitrogen becomes unavailable to plants. This creates a challenge for plants because nitrogen is an important limiting resource. Some types of bog plants (such as sundews, pitcher plants, and Venus flytraps) capture insects and extract the nitrogen from their bodies. Bogs have low net primary productivity because the water found in bogs has low levels of nitrogen and oxygen. |
SciQ | SciQ-4112 | genetics, botany, seeds
Title: What DNA does a self-fertile plant's seedling have? Some plants are said to be self-fertile. An example is Prunus tomentosa.
Assuming that no cross-pollination happened with other plants, if a self-fertile plant such as prunus tomentosa produces a seedling, what DNA will the seedling have? Is the seedling's DNA an exact copy of the parent plant's DNA, or do the genes get rearranged? Selfing (aka self-fertilizing) differs from cloning. When selfing occurs, the offspring is not an exact copy of the parent. When cloning occurs, the offspring is an exact copy (except for a few mutations) of the parent.
Selfing implies that an individual will produce two gametes (typically a spermatozoid and an ovule but that might be a bit more complicated) and these two gametes are fusing to give the zygote (egg or offspring if you prefer).
As a consequence, when selfing, meiosis is occurring (and therefore segregation and recombination) so that the offspring is not an exact clone of the parent but rather some kind of a rearrangement of the parent genome (with a few mutations of course).
The following is multiple choice question (with options) to answer.
All prokaryotic and some eukaryotic organisms reproduce through what method, where a parent passes all of its genetic material to the next generation? | [
"sexual reproduction",
"asexual reproduction",
"microscopic reproduction",
"organic reproduction"
] | B | Are there male and female bacteria? How could you tell? Remember, bacteria have just one chromosome; they do not have an X or Y chromosome. So they probably have a very simplified form of reproduction. Asexual reproduction, the simplest and most primitive method of reproduction, involves a single parent and produces a clone , an organism that is genetically identical to the parent. Haploid gametes are not involved in asexual reproduction. A parent passes all of its genetic material to the next generation. All prokaryotic and some eukaryotic organisms reproduce asexually. |
SciQ | SciQ-4113 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
Where does photosynthesis occur in plants? | [
"golgi bodies",
"in chloroplasts",
"nucleus",
"cell membrane"
] | B | Figure 8.6 Photosynthesis takes place in chloroplasts, which have an outer membrane and an inner membrane. Stacks of thylakoids called grana form a third membrane layer. |
SciQ | SciQ-4114 | gas-laws, kinetic-theory-of-gases
The size of the force will be proportional to the product of the number of molecules /unit area and the size of the inward force. Both of these will be be proportional to the density ($Nm/V$) or equivalently molar concentration. The reduction in pressure can thus be written as $-a(n/V)^2$ where $a$ is a positive constant that depends on the gas and is determined only by experiment.
The following is multiple choice question (with options) to answer.
What is defined as force per unit area? | [
"momentum",
"energy",
"pressure",
"resistance"
] | C | Pressure is defined as force per unit area, . |
SciQ | SciQ-4115 | evolution, life-history
Title: Has there been any observation of species adapting the evolution process? I am very interested in the evolution of the evolution process itself. There are of course a lot of things that influence how evolution will work, but for this question, I am interested in things that are only related to the evolution process. Examples could be increase chance of mutations in newborns, change in reproduction age, and similar. I am specifically interested in observation where the evolution process itself has adapted to a change in the environment. Bacteria such as E. coli are known to increase their mutation rate (by switching to a more error prone polymerase among other things) when under stress. This can mean being placed in a medium where it's not adapted to grow (http://www.micab.umn.edu/courses/8002/Rosenberg.pdf) or when treated with antibiotics (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088971/?tool=pmcentrez).
The following is multiple choice question (with options) to answer.
What word describes a change in behavior that occurs as a result of experience? | [
"learning",
"taking",
"applying",
"heredity"
] | A | Learning is a change in behavior that occurs as a result of experience. |
SciQ | SciQ-4116 | human-anatomy
In the wrist, you can have palmar flexion, dorsiflexion (extension), ulnar flexion (abduction) and radial flexion (adduction) (Teachmeanatomy).
In the ankle, you can have plantar flexion, dorsiflexion (extension), inversion (inward rotation, adduction) and eversion (outward rotation, abduction). (ScienceDirect).
In the shoulder and hip, raising a limb to the same side as the limb is, is abduction (lateral extension) and raising it to the opposite side is adduction.
Moving the thumb toward the palm (in the same plane as palm) is flexion (adduction) and moving it away from it is extension (abduction).
You can read about flexion and extension and other movements here: Types of Body Movements (BCcampus)
The following is multiple choice question (with options) to answer.
What term means the abnormal or excessive extension of a joint - particularly a hinged joint - beyond its normal range of motion, thus resulting in injury? | [
"tear",
"sprain",
"hypercorrection",
"hyperextension"
] | D | These include anterior-posterior movements of the arm at the shoulder, the forearm at the elbow, the hand at the wrist, and the fingers at the metacarpophalangeal and interphalangeal joints. For the thumb, extension moves the thumb away from the palm of the hand, within the same plane as the palm, while flexion brings the thumb back against the index finger or into the palm. These motions take place at the first carpometacarpal joint. In the lower limb, bringing the thigh forward and upward is flexion at the hip joint, while any posterior-going motion of the thigh is extension. Note that extension of the thigh beyond the anatomical (standing) position is greatly limited by the ligaments that support the hip joint. Knee flexion is the bending of the knee to bring the foot toward the posterior thigh, and extension is the straightening of the knee. Flexion and extension movements are seen at the hinge, condyloid, saddle, and ball-and-socket joints of the limbs (see Figure 9.12a-d). Hyperextension is the abnormal or excessive extension of a joint beyond its normal range of motion, thus resulting in injury. Similarly, hyperflexion is excessive flexion at a joint. Hyperextension injuries are common at hinge joints such as the knee or elbow. In cases of “whiplash” in which the head is suddenly moved backward and then forward, a patient may experience both hyperextension and hyperflexion of the cervical region. |
SciQ | SciQ-4117 | bond
Title: Breaking bonds with energy I'm learning about breaking molecular bonds currently and I'm wondering what are the methods to actually use the amount of bond energy to break the bond. What I'm saying is, knowing the bond energy, how can you actually use this information to break the bond? Do you heat it up the equivalent amount as the Kj/mol or something similar to that? Yes, the energy showed that is needed to break bonds is usually in the form of heat. I don't believe there is another common way to do it, but don't quote me on it. I haven't learned about lasers and other such technologies :). Keep in mind that as bonds are broken, they release energy themselves. As bonds are created, they take in energy on their own. Often, you will just need to start a reaction with some outside energy source (A bunsen burner for example) and it will be able to continue on its own because it produces energy from breaking bonds. If you look at the formation of Magnesium Oxide, all you really have to do is light a small end of a piece of Magnesium ribbon, and the whole thing burns because it creates energy as it reacts. I hope that helps!
The following is multiple choice question (with options) to answer.
Burning of methane is a type of what, which involves the breaking and forming of bonds? | [
"toxic reaction",
"chemical reaction",
"physical reaction",
"liquid reaction"
] | B | An example of a chemical reaction is the burning of methane. In this chemical reaction, the reactants are methane (CH 4 ) and oxygen (O 2 ), and the products are carbon dioxide (CO 2 ) and water (H 2 O). A chemical reaction involves the breaking and forming of chemical bonds. When methane burns, bonds break in the methane and oxygen molecules, and new bonds form in the molecules of carbon dioxide and water. |
SciQ | SciQ-4118 | optics, radiation, superposition
Title: Calculate transparency from Beer-Lambert Law I want to calculate a transparency parameter for a superposition of several volumes containing media using the Beer-Lambert Law, which states that
$$I/I_0=exp(-\tau)$$
where $I$ is the transmitted intensity, $I_0$ is the incident radiation intensity, and $\tau$ is the optical depth of the medium.
My question here is: Can I replace $\tau$ with $\tau_1 + \tau_2 + ... + \tau_n$ when dealing with n media of same/different optical depths? Does it matter whether the volumes overlap (assuming that they do not interact with each other)? If the light passes first through medium $\tau_1$, then through medium $\tau_2$, the optical depths add up to $\tau = \tau_1 + \tau_2$ , as you can see from applying the Beer-Lambert-Formula twice.
Does it matter whether the media overlap (if the media don't interact and light propagation is linear)? No, it doesn't.
The optical depth comprises the factors $\tau = \sigma N l$, the cross section $\sigma$ of the absorbers (molecules, atoms, ..) [unit m$^2$], the density of the absorbers $N$ [m$^{-3}$], and the optical path $l$ [m].
For example, if two media ($\sigma_1, N_1, \sigma_2, N_2$) overlap within the optical path, the effect of this absorbers just adds up, $\sigma N = \sigma_1 N_1+ \sigma_2 N_2$, where the product $\sigma N$ is the inverse absorption length.
The following is multiple choice question (with options) to answer.
Transparent, translucent, or opaque are properties of matter based on an interaction with what? | [
"light",
"air",
"electricity",
"gravity"
] | A | Matter can be classified on the basis of its interactions with light. Matter may be transparent, translucent, or opaque. An example of each type of matter is pictured in the Figure below . |
SciQ | SciQ-4119 | safety, gas
Title: Rotten Egg Gas Smell Background context for question
When I was young, we'd go fishing. And Dad would put a camper on the back of the truck. One time we came back in after fishing and the camper smelled like rotten eggs. He used that as an opportunity to teach us how some gases are tasteless/odorless. And as a result that sort of rotten egg smell is added as a safety measure.
Question:
My question is this: What are those gases that are odorless that then have that rotten egg smell added to them? Rotten eggs happen much less frequently than 50-60 years ago because of better hen-consumer refrigeration. Most people today have not had the pleasure of smelling them. H2S and low molecular weight mercaptans [AKA thiols] have distinct more or less unpleasant odors tho at low concentrations they can smell sweet, and we can develop tolerances to many at higher concentrations when they can be deadly. H2S is supposedly the active ingredient in rotten eggs; Methylsulfide CH3SH the active gas in human feces, and thioglycolic acid in eau de skunk.
Manufactured gas, no longer used, was a mix of H2 and CO and is toxic. It was flavored with mercaptan at rather high levels; smelling gas then was almost a death sentence, we were trained to open windows and leave immediately. There was also the explosion hazard. Manufactured gas was replaced by "natural", really fossil fuel, gas that is mostly methane CH4. Methane is odorless, not toxic, but it can be soporific, and it can explode. A warning is still necessary tho it seems to me the odorant is now less noxious and less intense than before [It could be my sense of smell has waned.]. It is to protect from explosion, again evacuate and ventilate. Odorants are added to propane and LPG, I do not know about hydrogen. Perfumes are added to many products to overcome odors or enhance odors and Bitrex is added to some drugs to make them less palatable so it works both ways.
The following is multiple choice question (with options) to answer.
Hydrogen sulfide is a noxious and toxic gas produced from decaying organic matter that contains what? | [
"sulfur",
"helium",
"tin",
"methane"
] | A | Hydrogen sulfide is a noxious and toxic gas produced from decaying organic matter that contains sulfur. A lethal concentration in rats corresponds to an inhaled dose of 715 molecules per million molecules of air. How many molecules does this correspond to per mole of air? How many moles of hydrogen sulfide does this correspond to per mole of air?. |
SciQ | SciQ-4120 | human-biology, digestive-system, immune-system, microbiome
The next level of defense comes from the cells of the innate immune system (14). In innate immunity, specialized cells monitor the area they are in for Pathogen-Associated Molecular Patterns (PAMPs). PAMPs can be sugars that make up the cell walls of the microbe or proteins that get expressed on the surface of the organism, such as Flagellin, a protein only found in the flagella of certain pathogen. The innate immune cells have pattern recognition receptors (PRR) that have a general specificity for recognizing and responding to the PAMPs. Our cells even have PRRs for DNA and Double Stranded RNA's, however those are usually found in vesicles on the inside of the cell. These interactions are very general, however once PRRs bind to the PAMP, they are able to signal into the cytoplasm, which can lead to the production of proteins, among other possible responses.
Here you can think of PRRs like a motion detector in a security system; the dog, or your two year old, or an intruder are going to set off the alarm just the same. It is not specific. The motion sensor "knows" that something that it is supposed to recognize, i.e. a moving object larger than a mouse passed by and it triggered the response, but it cannot tell you which moving object triggered it, only that it was triggered.
The innate immune cells are also able to respond by "eating" the pathogen in a process called phagocytosis. Here, they break up the bacteria, yeast, or the remnants of other dead host cells or large pathogens, things like worms, and put the broken up pieces on protein molecules on their surface.
When innate immune cells do this, they are presenting molecules to specialized immune cells (adaptive immune cells (14)), B-Cells and T-Cells, that are highly specific as to what they will react to. These cells can also cause a lot of damage to the host, so they are tightly regulated. Think of the interactions as keys and locks. A protein from a bacteria should turn a few of these cells on, but a protein from the host should not fit the lock.
The following is multiple choice question (with options) to answer.
What is the name of the body system that fights to protect the body from specific pathogens? | [
"immune system",
"infectious system",
"allergic response",
"warning system"
] | A | The immune system is the body system that fights to protect the body from specific pathogens. The immune system’s specific reaction to a pathogen is called an immune response. The immune system includes several organs and a system of vessels that carry lymph. |
SciQ | SciQ-4121 | population-genetics, allele
$h$
Dominance Type
Scenario
0<h<1
Incomplete dominance
The heterozygote ($A_1A_2$) more fit than $A_2A_2$ and less fit than $A_1A_1$
h<0
Overdominance
The heterozygote ($A_1A_2$) more fit than homozygotes ($A_1A_1$ and $A_2A_2$)
h>1
Underdominance
The heterozygote ($A_1A_2$) less fit than homozygotes ($A_1A_1$ and $A_2A_2$)
In each of these cases, the phenotype of the heterozygote is something different than either of the homozygotes (hence the term incomplete dominance). What the value $h$ is measuring here is not the difference in phenotypes, it's the effect it has on fitness- which might be different in different contexts.
Let's think about the classic example of overdominance, sickle cell disease. In terms of fitness, individuals with one copy of the sickle cell allele have the sickle cell trait. The sickle cell trait offers resistance to malaria, and therefore higher fitness in regions with endemic malaria. An individual with two copies of the sickle cell allele are less fit because they have sickle cell disease. An individual with no copies of the sickle cell allele is less fit because they don't have resistance to malaria infection.
But this measure of dominance, where we define dominance as the fitness associated with a the expression of a characteristic, is context-dependent- individuals with the sickle cell trait are prone to other diseases, and in the absence of endemic malaria it might be they have lower fitness than an individual with no copies of the sickle cell allele ($0<h<1$).
If we think about dominance as simply the expression of a characteristic, we would actually describe the sickle cell heterozygote as co-dominant- when you look at the blood of individuals with sickle cell trait (heterozygotes), they have a mix of normal-shaped red blood cells and sickle-shaped red blood cells.
So to conclude:
The following is multiple choice question (with options) to answer.
Incomplete dominance and epistasis are both terms that define what? | [
"genetic habits",
"genetic relationships",
"learned behaviors",
"genetic difficulties"
] | B | |
SciQ | SciQ-4122 | transcription, translation
Ralston, A. (2008) Operons and prokaryotic gene regulation. Nature Education
From Genes to Genomes: Concepts and Applications of DNA Technology
Molecular cell biology
Analysis of Genes and Genomes
The following is multiple choice question (with options) to answer.
What branch of biology focuses on heredity? | [
"cell biology",
"zoology",
"genetics",
"botany"
] | C | When zinc reacts with hydrochloric acid, the reaction bubbles vigorously as hydrogen gas is produced. The production of a gas is also an indication that a chemical reaction is occurring. |
SciQ | SciQ-4123 | cell-biology, proteins, transcription, cell-signaling, intracellular-transport
Time is in minutes, and zeroed at first contact between the two cells. I've put a red dot on the T-cell and a blue one on the APC in the DIC images (left panes); hopefully that proves more informative than annoying. The right panes show GFP fluorescence and thus CD3 localization. As time progresses, CD3 is re-localized from one part of the membrane to another (the synapse). There is supposedly a video of this is in the supplementary information of the article, though I was unable to open it.
The rate and directionality of the movement implies that an active process is occurring, rather than simple diffusion. However, they did not find the actual mechanism for movement and I haven't found any follow-up papers in a brief search (though many subsequent papers implicate the cytoskeleton in this movement). Just to show that movement of transmembrane proteins can, in fact, be actively directed by the cytoskeleton, I refer you to this paper:
Grabham PW, Foley M, Umeojiako A, Goldberg DJ. 2000. Nerve growth factor stimulates coupling of beta1 integrin to distinct transport mechanisms in the filopodia of growth cones. J Cell Sci 113:3003-3012.
They show that membrane-spanning integrins are moved along actin filaments of the cytoskeleton by myosin motor proteins. Expectedly, the abstract does a good job of summarizing the paper:
The cycling of membrane receptors for substrate-bound proteins via their interaction with the actin cytoskeleton at the leading edge of growth cones and other motile cells is important for neurite outgrowth and cell migration. Receptor delivered to the leading edge binds to its ligand, which induces coupling of the receptor to a rearward flowing network of actin filaments. This coupling is thought to facilitate advance... [T]ransport was dependent on an intact actin cytoskeleton and myosin ATPase...
The following is multiple choice question (with options) to answer.
The axon contains microtubules and neurofilaments that are bounded by a plasma membrane known as what? | [
"axolenon",
"xerophyte",
"exolemal",
"axolemma"
] | D | View the University of Michigan WebScope at http://virtualslides. umich. edu/Histology/EMsmallCharts/ 3%20Image%20Scope%20finals/054%20-%20Peripheral%20nerve_001. svs/view. apml?listview=1& (http://openstaxcollege. org/l/nervefiber) to see an electron micrograph of a cross-section of a myelinated nerve fiber. The axon contains microtubules and neurofilaments that are bounded by a plasma membrane known as the axolemma. Outside the plasma membrane of the axon is the myelin sheath, which is composed of the tightly wrapped plasma membrane of a Schwann cell. What aspects of the cells in this image react with the stain to make them a deep, dark, black color, such as the multiple layers that are the myelin sheath?. |
SciQ | SciQ-4124 | thermodynamics, atoms, phase-transition
But let's look at how the states change. In a solid, you have a bunch of atoms that can be thought of as masses connected by springs. As heat is added to the system, the atoms begin to vibrate in the lattice of springs. As more heat is added, they vibrate enough to break the springs. This is when the solid begins to melt and turn to a liquid.
Now you have a liquid where the atoms are all moving around but they aren't free to move wherever they want. More heat is added to the system and the atoms begin to translate faster and faster. Eventually they translate fast enough to overcome the forces that are holding them together in a liquid. Now they fly free and are a gas.
So ultimately, heat is energy that makes atoms and molecules move in some way. They may translate, rotate, vibrate, or the electrons may begin moving around depending on how much heat is there and what configuration the molecule has.
The following is multiple choice question (with options) to answer.
What is the process by which a liquid changes to a solid? | [
"boiling",
"freezing",
"vaporizing",
"melting"
] | B | The process in which a liquid changes to a solid is called freezing . The temperature at which a liquid changes to a solid is its freezing point. The freezing point of water is 0°C (32°F). Other types of matter may have higher or lower freezing points. For example, the freezing point of iron is 1535°C. The freezing point of oxygen is -219°C. |
SciQ | SciQ-4125 | bond, electrons, covalent-compounds
Sharing (and stealing) is cheaper
So, if two atoms (e.g. two hydrogen atoms) each have an outer orbital that contains only one electron, those two electrons can sort of look each other over and say, "you know, if you spin downwards and I spin upwards, we could both share this space for almost no energy cost at all!" And so they do, with a net release of energy, producing a covalent bond if the resulting spin-pair cancels out positive nuclear charges equally on both atoms.
However, in some cases the "attractive force" of spin-pairing is so overwhelming greater for one of the two atoms that it can pretty much fully overcome (!) the powerful electrostatic attraction of the other atom for its own electron. When that happens, the electron is simply ripped away from the other atom. We call that an ionic bond, and we act as it if it's no big deal. But it is truly an amazing thing, one that is possible only because the pseudo force of spin-pairing.
Bottom line: Pseudo forces are important!
My apologies for having given such a long answer, but you happened to ask a question that cannot be answered correctly without adding in some version of Pauli "repulsion" and spin-pair "attraction." For that matter, the size of an atom, the shape of its orbitals, and its ability to form bonds similarly all depend on pseudo forces.
The following is multiple choice question (with options) to answer.
How are electrons shared in covalent bonds? | [
"equally",
"randomly",
"orderly",
"unequally"
] | A | In other covalent bonds, electrons are shared equally. These bonds are called nonpolar covalent bonds. Neither atom attracts the shared electrons more strongly. As a result, the atoms remain neutral in charge. The oxygen (O 2 ) molecule in the Figure below has two nonpolar bonds. The two oxygen nuclei have an equal force of attraction for their four shared electrons. |
SciQ | SciQ-4126 | acid-base, equilibrium, ph, electronic-configuration
Title: Why is it that weak bases usually contain nitrogen? Why do weak bases usually contain nitrogen? I know there are two electrons on top for a bond of $\ce{H}$ but why is it mostly nitrogen? I know there are other elemental bases too but why do I keep seeing $\ce{N}$'s mostly?
Is there something special about nitrogen in this respect? The short answer is that yes, the fact that many weak bases contain nitrogen does have to do with nitrogen itself. However, it's not really accurate to say that weak bases "usually" contain nitrogen.
For simplicity, I'm limiting my explanation to aqueous solutions, the Brønsted-Lowry definition, and main-group compounds. A base must do one of two things: either remove a proton ($\ce{H+}$) from water or dissociate to produce something else (typically $\ce{OH-}$) that can remove a proton from water. Most compounds that produce $\ce{OH-}$ directly are ionic; even if they don't dissolve much (like alkaline earth hydroxides), these ionic compounds dissociate completely and are therefore strong bases.
A base that removes protons from water must have a free pair of electrons for the proton to bond to. In period 2, boron tends to form compounds that tie up all three of its electrons. Carbon compounds, likewise, tend to have no free electron pairs. Oxygen and fluorine compounds (e.g., water and hydrogen fluoride) have free electron pairs, but because of their high electronegativity these elements keep their electrons to themselves and are unlikely to grab protons from water if they already have a full octet. Nitrogen is the only element in this period that balances two factors: it has a free electron pair in many of its compounds (e.g., ammonia and organic amines) and has a low enough electronegativity that it can share those electrons with a proton to form a cation (e.g., ammonium, $\text{NH}_3$).
The following is multiple choice question (with options) to answer.
What is the most electron-pair bonds a nitrogen atom can participate in? | [
"seven",
"four",
"three",
"five"
] | B | Reactions and Compounds of Nitrogen Like carbon, nitrogen has four valence orbitals (one 2s and three 2p), so it can participate in at most four electron-pair bonds by using sp3 hybrid orbitals. Unlike carbon, however, nitrogen does not form long chains because of repulsive interactions between lone pairs of electrons on adjacent atoms. These interactions become important at the shorter internuclear distances encountered with the smaller, second-period elements of groups 15, 16, and 17. (For more information on internuclear distance, see Chapter 7 "The Periodic Table and Periodic Trends", Section 7.2 "Sizes of Atoms and Ions" and Chapter 8 "Ionic versus Covalent Bonding", Section 8.2 "Ionic Bonding". ) Stable compounds with N–N bonds are limited to chains of no more than three N atoms, such as the azide ion (N 3−). Nitrogen is the only pnicogen that normally forms multiple bonds with itself and other second-period elements, using π overlap of adjacent np orbitals. Thus the stable form of elemental nitrogen is N 2, whose N≡N bond is so strong (DN≡N = 942 kJ/mol) compared with the N–N and N=N bonds (DN–N = 167 kJ/mol; DN=N = 418 kJ/mol) that all compounds containing N–N and N=N bonds are thermodynamically unstable with respect to the formation of N2. In fact, the formation of the N≡N bond is so thermodynamically favored that virtually all compounds containing N–N bonds are potentially explosive. Again in contrast to carbon, nitrogen undergoes only two important chemical reactions at room temperature: it reacts with metallic lithium to form lithium nitride, and it is reduced to ammonia by certain microorganisms. (For more information lithium, seeChapter 21 "Periodic Trends and the ". ) At higher temperatures, however, N2 reacts with more electropositive elements, such as those in group 13, to give binary nitrides, which range from covalent to ionic in character. Like the corresponding compounds of carbon, binary compounds of nitrogen with oxygen, hydrogen, or other nonmetals are usually covalent molecular substances. Few binary molecular compounds of nitrogen are formed by direct reaction of the elements. At elevated temperatures, N2 reacts with H2 to form ammonia, with O2 to form a mixture of NO and NO2, and with carbon to form cyanogen (N≡C–C≡N); elemental nitrogen does not react with the halogens or the other chalcogens. Nonetheless, all the binary nitrogen halides (NX3) are known. Except for NF3, all are toxic,. |
SciQ | SciQ-4127 | 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.
The hypothalamus and pituitary gland are located near the base of this organ? | [
"the liver",
"the heart",
"the brain",
"the lungs"
] | C | The hypothalamus and pituitary gland are located close together at the base of the brain. |
SciQ | SciQ-4128 | human-biology, cancer
Title: Why do most breast cancers occur in women? According to Korde et al. (2010):
Male breast cancer accounts for less than 1% of all cancers in men and less than 1% of breast cancers.
This raises the question: Why do most breast cancers occur in women?
Two plausible explanations I can think of:
A male is less likely to get breast cancer for anatomical reasons (such as a smaller quantity of breast tissue, or breast tissue that is less susceptible to cancer),
Women have higher significantly levels of estrogen, which is linked to mutations that cause breast cancer (see Cavalieria et al. (2006)).
Although, I have no evidence to suggest that either of these is predominant factor. Yes, this is mostly about estrogen. Most breast cancers rely on endogenous estrogen to sustain proliferation.
Some general reading: Cancer Medicine, Chapter 18
More in-depth reading: Endogenous Hormones as a Major Factor in Human Cancer
Requested summary of mentioned readings:
First of all, there is an established link between breast cancer cell proliferation and concentration of estrogens and progesterone, which is logical, because normal breast cells divide in response to those hormones (e.g. puberty, pregnancy, even luteal phase of the menstrual cycle). Secondly, the incidence of breast cancer in women correlates with major changes in their hormonal profile - girls and elderly women (i.e. women with lower levels of sex hormones) don't get breast cancer.
Many factors, that influence the risk of developing breast cancer are in fact tightly connected to the hormones' levels. For example - early age of menarche (or, more importantly, first ovulation, because physical activity at young age disturbs ovulation AND is protective against breast cancer) and Hormone Replacement Therapy raise the risk, early age of first full-term pregnancy or any form of artificial menopause (such as preventive oophorectomy for women with mutations in BRCA1 or 2) reduce the risk.
The first table from the book chapter lists known risk and preventive factors. The review article explains the same ideas, but connects them to other types of cancer (e.g. ovarian cancer) and suggests mechanisms, which might be the cause of those risk changes.
The following is multiple choice question (with options) to answer.
What is the most common type of cancer in adult males? | [
"prostate",
"leukemia",
"stomach",
"lung"
] | A | The most common type of cancer in adult males is cancer of the prostate gland. The prostate gland is part of the male reproductive system. About one third of all cancers in men are prostate cancers. |
SciQ | SciQ-4129 | We can keep this up, but we'll never really know the exact answer if we simply compute more and more examples. Let's instead look at a "typical'' approximation. Suppose we divide the time into $$n$$ equal intervals, and imagine that on each of these the object travels at a constant speed. Over the first time interval we approximate the distance traveled as $$(0.0)(1/n)=0$$, as before. During the second time interval, from $$t=1/n$$ to $$t=2/n$$, the object travels approximately $$3(1/n)(1/n)=3/n^2$$ centimeters. During time interval number $$i$$, the object travels approximately $$(3(i-1)/n)(1/n)=3(i-1)/n^2$$ centimeters, that is, its speed at time $$(i-1)/n$$, $$3(i-1)/n$$, times the length of time interval number $$i$$, $$1/n$$. Adding these up as before, we approximate the distance traveled as $$(0){1\over n}+3{1\over n^2}+3(2){1\over n^2}+ 3(3){1\over n^2}+\cdots+3(n-1){1\over n^2}$$ centimeters. What can we say about this? At first it looks rather less useful than the concrete calculations we've already done. But in fact a bit of algebra reveals it to be much more useful. We can factor out a 3 and $1/n^2$ to get $${3\over n^2}(0+1+2+3+\cdots+(n-1)),$$ that is, $$3/n^2$$ times the sum of the first $$n-1$$ positive integers. Now we make use of a fact you may have run across before: $$1+2+3+\cdots+k={k(k+1)\over2}.$$ In our case we're interested in
The following is multiple choice question (with options) to answer.
Distance traveled divided by time is equal to what? | [
"frequency",
"direction",
"speed",
"momentum"
] | C | Average speed is calculated by dividing the total distance travelled by the time interval. For example, someone who takes 40 minutes to drive 20 miles north and then 20 miles south (to end up at the same place), has an average speed of 40 miles divided by 40 minutes, or 1 mile per minute (60 mph). Average velocity, however, involves total displacement, instead of distance. It is calculated by dividing the total displacement by the time interval. In this example, the driver's displacement is zero, which makes the average velocity zero mph. |
SciQ | SciQ-4130 | observational-astronomy
Title: What study profiles could land me the job of astronomer? I realize there are very few to none universities that offer direct specialization of astronomy. If I aspired to be make astronomy my career choice, I'd likely have to pick something like physics and specialize later - or something similar - but that's just my hunch, and I'd prefer to know for sure.
What educational and professional paths optimize one's education and skill set for the occupation of astronomer? How do I become one? What you need would be at least the following:
Physics: astronomy is physics in the end, and you'll need strong basis in physics;
Math: as for any good education in physics, you'll need a reasonable amount of math to be able to become an astronomer;
Programming: it's almost impossible nowadays to get away from it. Being an astronomer today implies lots of data processing (to reduce the data, to interpret it etc.), and it involves a lot of coding.
And, as far as I know, in lots of countries/universities, you can find at least few astronomy & astrophysics courses. In some countries, you can even find dedicated master degrees.
With all of that, you'll be ready to start a PhD in astronomy to become a professional astronomer.
The following is multiple choice question (with options) to answer.
What are people called that choose to study science? | [
"lab technicians",
"scientists",
"engineers",
"doctors"
] | B | Scientists are regular people who chose to study science. They are experts in done or more fields of science. |
SciQ | SciQ-4131 | meteorology, climate-change, gas, pollution
Title: Regarding various types of atmospheric pollution Does all the car pollution (from about 150 million cars at least in the U.S. and a lot more in all of North America and the rest of the world) all the smoke-stack pollution of various factories and all the Airline pollution running day after day have a deleterious and damaging effect on the general atmosphere and, over time, the climate?
Given all the observed pollution that China has caused itself and some of the resulting weird weather events there this certainly seems to be evidence of the damaging effects of car and factory pollution. Has anyone calculated how much exhaust from cars is produced in one day on average in a 'moderate' sized city?
Of course it seems with all the increased oil production in the U.S. and elsewhere we, human beings are going to keep are love-affair with gas-powered cars for the next 200 or 300 years. That is if we don't use up all the oil and gas in the ground before then. As a USA resident, the EPA is the best place to start when wondering about the emissions inventory of atmospheric pollutants or pollutant precursors that affect the National Ambient Air Quality Standards (e.g. Particulate Matter, Carbon Monoxide, Sulfur Dioxide, Lead, Nitrogen Oxides, Volatile Organic Compounds). The EPA compiles a comprehensive emissions inventory of all criteria pollutants at the county level which is available in the National Emissions Inventory (compiled once every 3 years). You can see the summary of your county at http://www.epa.gov/air/emissions/where.htm. As for the effects of atmospheric pollution, it is important to consider the lifetime of said pollutants in the atmosphere in order to put their environmental impacts into perspective. For instance, the air pollutants covered by the National Ambient Air Quality Standards have immediate health effects when high concentrations are breathed in regularly. Both animals and plants are adversely affected by these irritating and sometimes toxic chemicals, but these pollutants are also reactive and do not last long in the atmosphere unless they are constantly being replenished (e.g. daily traffic). Air quality also impacts critical nitrogen loads on ecosystems and possible production of acid rain.
The following is multiple choice question (with options) to answer.
What is the main cause of outdoor air pollution? | [
"methane from livestock",
"aerosol spray",
"burning of fossil fuels",
"chimneys"
] | C | The main cause of outdoor air pollution is the burning of fossil fuels. Outdoor air pollution causes human health problems, acid rain, and global climate change. |
SciQ | SciQ-4132 | human-biology, immunology
Title: Are there any viruses or bacteria which have evolved to withstand higher temperatures due to fever My question was raised after receiving this information:
The primary reason the body raises its temperature (via the Hypothalamus in this case) is that bacteria and viruses tend to optimally thrive at 98.6F, which is also your body's optimal operating temperature.
I am just wondering if there are any viruses or bacteria that have gained the ability to prosper under fever temperatures through evolution? If not, why not? Is there any biological restriction stopping such viral evolution?
Update:
I will try to explain my question. As far as I know, evolution helps species to adapt to their environment. For example, when people started using antibiotics we got new bacteria resistant to those antibiotics.
If fever is part of the innate immune reaction to viruses and bacteria, why hasn't this resulted in selection for fever-resistant variants? Why has evolution apparently stopped in this case? Fever is just one of the many ways of the body's defense mechanism work. Under infection, human body can raise body temperature, release cytokins and activate white blood cells etc. Sometimes the bacteria can evade immune suppression or immune complement fixation so that they can stay inside a "fever-ish" body like they just don't care. Example: Pseudomonas aeruginosa. They can grow in 42 degree Celsius which surpass the normal fever temperature.
My answer may not be the best for your question. All I'm trying to say is that fever acts as a supportive role during an infection. Human body relies on heavy artilleries such as white blood cells and cytokin to clear the infection. That's why it will be more beneficial for the bacteria to evolve abilities to evade immune suppression and immune complement fixation. And bacteria know how to do those.
The following is multiple choice question (with options) to answer.
What is the term for organisms that can maintain a stable body temperature even in the face of large fluctuations in the environmental temperature? | [
"ectotherms",
"pachyderm",
"homeotherm",
"endotherms"
] | D | |
SciQ | SciQ-4133 | artificial-intelligence, word-combinatorics
Title: How should i guide a program to perform correct things? I want to make a small model of A.I. which can learn itself. I am inspired by 1000+ monkey theorem which states that if 1000+ monkey bangs a keyboard for enough long, then they will eventually produce a Shakespeare's play. So, if you give a banana to one monkey when he produce a correct word, then he would eventually learn to do correct things. I think it is related to neural network.
So, practically i want to start with basic alphabets and digits and then my program would permutate and combine those to form words. Now, if the words they form matches with those in English Dictionary, i want to reward the program. However i couldn't think of any possible approach to this. How could this be implemented? The "Infinite Monkey Theorem" doesn't say that monkeys will learn. On the contrary: it says that if monkeys keep typing random stuff long enough (i.e. not using any sort of learning), the works of Shakespeare will eventually come out purely by chance. It is the Law of Truly Large Numbers.
So you're right: you need to build feedback into the system. The program should change its behavior based on your feedback. This is known as reinforcement learning and it is used a lot in AI. An overarching term for this, I believe, is machine learning.
The following is multiple choice question (with options) to answer.
What is the term for learning by watching and copying the behavior of someone else? | [
"classical conditioning",
"consequential learning",
"observational learning",
"associative learning"
] | C | Observational learning is learning by watching and copying the behavior of someone else. Human children learn many behaviors this way. When you were a young child, you may have learned how to tie your shoes by watching your dad tie his shoes. More recently, you may have learned how to dance by watching a pop star dancing on TV. Most likely, you have learned how to do math problems by watching your teachers do problems on the board at school. Can you think of other behaviors you have learned by watching and copying other people?. |
SciQ | SciQ-4134 | meteorology, weather-forecasting, united-states
Title: How is a weather forecast really done? I am trying to understand the concrete process of how a meteorologist at a weather forecast office produces the different types of weather forecasts.
I understand how numerical weather models work, but I would like to learn how the model output is turned into a forecast and to what extend it is improved by a skilled meteorologist.
I have found an older reference from 1993 that has some information on the workflow,
https://esrl.noaa.gov/gsd/eds/gfesuite/pubs/AWIPS-Forecast-Preparation-System.pdf
but this is probably outdated and doesn't talk about the meteorological side.
There are a lot of different forecast products from text to graphical products, so my question might be an overly broad one, but I haven't found much information so far, so I don't want to be too restrictive.
What concrete model outputs do forecasters look at and to what extend do they use local observations and experience? The National Weather Service actually has a nice forecast summary page that answers your question:
Our scientists thoroughly review current observations using technology such as radar, satellite and data from an assortment of ground-based and airborne instruments to get a complete picture of current conditions. Forecasters often rely on computer programs to create what’s called an “analysis,” which is simply a graphical representation of current conditions. Once this assessment is complete and the analysis is created, forecasters use a wide variety of numerical models, statistical and conceptual models, and years of local experience to determine how the current conditions will change with time. Numerical modeling is fully ingrained in the forecast process, and our forecasters review the output of these models daily. Often, the models yield different results, and in these circumstances, forecasters will determine which models perform best for the given situation or seek a blended solution.
They also have a good "About Page" that discusses the regional offices and a Virtual Tour of the Forecast Process.
The following is multiple choice question (with options) to answer.
What do we call scientists who study and forecast the weather? | [
"TV hosts",
"forecasters",
"Climate predictors",
"meteorologists"
] | D | Did you ever have a picnic ruined by a surprise rainstorm? People often complain when the weather forecast is wrong. But in fact, weather forecasts today are much more accurate than they were just 20 years ago. Scientists who study and forecast the weather are called meteorologists . How do they predict the weather?. |
SciQ | SciQ-4135 | electromagnetism, electrostatics, electricity
Title: Why is the charge of an electron taken to be the negative of the charge of a proton and vice versa? Let us assume that all we know till now is that two types of charges exist. One of them is possessed by an elementary particle called an electron and the other by another elementary particle called a proton. We also know that the effect of a proton on another proton is the same as that of an electron on another electron in terms of the force of repulsion and an electron and proton also have a similar effect on each other other than the fact that they attract each other, and not repel.
Now, let us say that the charge of an electron is $1 \text{ e}$. Why do we take the charge of a proton as $-1 \text{ e}$ only based on the information that they have similar but opposite effects? Now, if we define the charge of a proton as $-1 \text{ e}$, the net charge of a body with $n_1$ electrons and $n_2$ protons becomes $n_1e+n_2(-e) = (n_1-n_2)e$. How do we know that the results obtained from these mathematical operations will be what the actual effects will be?
I don't know if I was able to express my question properly. I'm finding it hard to express what I have in mind. Please let me know if it is not clear, I will try my best to improve it.
Thanks! I think your question is a little unclear, so let me know if I've misunderstood what you were asking.
If your question is about how we know that the electron and the proton have the same magnitude but opposite signs, it's simple (at least in theory): create a Hydrogen atom. It has one proton and one electron, and it's neutral overall, meaning it has a net charge of zero. Since charges simply add up, the proton and the electron must have opposite charges.
On the other hand, if your question is about why one of them is "called" negative and the other positive, I refer you to E.M. Purcell's excellent text. From Chapter 1.1 (Electric Charge):
The following is multiple choice question (with options) to answer.
What are atoms called when they have the same number of negative electrons as positive protons in an electrical charge? | [
"positive",
"neutral",
"static",
"negative"
] | B | Atoms are neutral in electrical charge because they have the same number of negative electrons as positive protons. Therefore, the atomic number of an atom also tells you how many electrons the atom has. This, in turn, determines many of the atom’s properties. |
SciQ | SciQ-4136 | electromagnetic-radiation, visible-light, thermal-radiation, absorption, photon-emission
For example, hydrogen gas emits light primarily at a wavelength of 656 nm (in the red region of the spectrum) when it makes transitions from the n=3 energy level to the n=2 energy level. However, at a high enough temperature, hydrogen atoms may be excited to higher energy levels and will emit light at a different set of wavelengths. Similarly, each element and molecule may have their own unique set of emission spectra based on its energy level transitions.
The following is multiple choice question (with options) to answer.
Neon, krypton and argon are examples of what kind of gases, which produce light by electroluminescence? | [
"radiation gases",
"irradiation gases",
"ionic gases",
"halogen gases"
] | D | A neon light produces visible light by electroluminescence. In this process, neon or some other gas gives off light when an electric current passes through it. Other halogen gases besides neon—including krypton and argon—also produce light in this way. The word “OPEN” in the sign below is a neon light. It is a long glass tube that contains neon gas. When electricity passes through the gas, it excites electrons of neon atoms, and the electrons jump to a higher energy level. As the excited electrons return to their original energy level, they give off visible light. Neon produces red light. Other gases produce light of different colors. For example, krypton produces violet light, and argon produces blue light. |
SciQ | SciQ-4137 | everyday-life, biophysics
Title: What's Optimal About Six Legs According to Physical Laws? In many respects the insects can be regarded as the most successful class of animals in evolutionary terms. And one of the most common features of insects is that they (mostly) all have six legs.
Not discounting other traits, is there something about six legs that has helped insects achieve this success?
Can we use physical laws to analyze and determine an optimality of having six legs - perhaps such as stability? I can think of two possible reasons: first, you can have half your legs up in the air at one time (as in walking - two on one side and one on the other, then change) and still be perfectly stable (3 legs = most stable, like a tripod); and second, if a predator chews off a leg on either side, you still have two legs (so you can still walk). I think those arguments are borderline biomechanical, rather than physical...
The first argument has some solid scientific backing - see for example http://web.neurobio.arizona.edu/gronenberg/nrsc581/powerpoint%20pdfs/cpg.pdf . It doesn't take a lot of brains to walk with six legs... I fact it can be done almost entirely with "local" neurons. That's a good thing when you don't have a lot of brains.
Quoting from https://answers.yahoo.com/question/index?qid=20090418111020AA75mgR :
Generalizing, insects walk with a metachronal gait and, with speed, a tripod gait - which involves a tripod stance - 2 legs on one side of the body and one on the other remain stationary while the other legs move forward, then the stationary legs walk as the others take a stance. In this way, walking involves maximum stability with a minimum of neural coordination. In fact, ganglia and other nerves and sensors located on each leg may contribute as much to the actual walking movement as the brain does. It's a very easy, stable and adaptable locomotory system which evolved from the basic arthropod body plan with 2 pairs of limbs on each body segment.
The following is multiple choice question (with options) to answer.
What might arthropods use as legs for walking? | [
"flagella",
"cloven hooves",
"antennae",
"jointed appendages"
] | D | The jointed appendages of arthropods may be used as legs for walking. Being jointed makes them more flexible. Try walking or climbing stairs without bending your knees, and you’ll see why joints are helpful. In most arthropods, the appendages on the head have been modified for other functions. Figure below shows some of head appendages found in arthropods. Sensory organs such as eyes are also found on the head. |
SciQ | SciQ-4138 | 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.
What kind of bonds, where electrons are transferred rather than shared, are considered the ultimate in polarity? | [
"covalent bonds",
"ionic bonds",
"soluble bonds",
"magnetic bonds"
] | B | polar, while others are strongly polar. Ionic bonds can be considered the ultimate in polarity, with electrons being transferred rather than shared. To judge the relative polarity of a covalent bond, chemists use electronegativity, which is a relative measure of how strongly an atom attracts electrons when it forms a covalent bond. There are various numerical scales for rating electronegativity. Figure 4.4 "Electronegativities of Various Elements" shows one of the most popular—the Pauling scale. The polarity of a covalent bond can be judged by determining the difference in the electronegativities of the two atoms making the bond. The greater the difference in electronegativities, the greater the imbalance of electron sharing in the bond. Although there are no hard and fast rules, the general rule is if the difference in electronegativities is less than about 0.4, the bond is considered nonpolar; if the difference is greater than 0.4, the bond is considered polar. If the difference in electronegativities is large enough (generally greater than about 1.8), the resulting compound is considered ionic rather than covalent. An electronegativity difference of zero, of course, indicates a nonpolar covalent bond. |
SciQ | SciQ-4139 | everyday-chemistry
Title: How does a fire start? I know that fire in a few words is the exothermic reaction of a fuel with an oxidizing agent, but I can't fully understand what exactly happens to piece of wood when it is ignited. How do molecules start producing a flame? In other words, what is the chemistry behind the production of flame? https://www.youtube.com/watch?v=B0E4PX3e3RE It feels somewhat weird to answer my own question but I think this video describes exactly what I wanted. As it supports, when heat is applied to a piece of wood, some bonds of the molecules that make up wood, break and thus different compounds are formed. These compounds are not held back by some force and so they are released in the air. When these compounds meet atmospheric oxygen, under heat (=energy), they burn and thus more heat is released along with carbon dioxide and water. That stage can be described as ignition. Finally, this produced heat is able to preserve the fire.
The following is multiple choice question (with options) to answer.
What happens when chemical bonds in a burning log break? | [
"remove heat",
"hold heat",
"decrease heat",
"release heat"
] | D | Energy is a measure of the amount of or potential for movement in something. The total amount of energy in the universe is always the same. This symmetry is called a conservation law. Conservation of energy is one of five conservation laws that govern our universe. A group of things (we’ll use the word system ) has a certain amount of energy. Energy can be added to a system; for instance, when chemical bonds in a burning log break, they release heat. Energy can be lost from a system; for instance, when a spacecraft “burns up” its energy of motion during re-entry, it loses energy and the surrounding atmosphere gains the lost energy. A closed system is one for which the total energy does not change, or is conserved . In this chapter, we will often consider closed systems, for which the total amount of energy stays the same, but transforms from one kind to another. The transfer of energy from one system to another is called Work . Work is equal to the amount of energy transferred in (positive work) or out (negative work) of a system. Work is equal to the distance the object is moved multiplied by the amount of force in the direction of its motion. The rate at which work is done is called Power . |
SciQ | SciQ-4140 | bond, periodic-trends, molecular-structure, vsepr-theory
All of the Group IV hydrides will have perfect tetrahedral geometry due to having four bonds to the same atom and no lone pairs. Thus $\ce{CH4}$, $\ce{SiH4}$, $\ce{GeH4}$, $\ce{SnH4}$, and $\ce{PbH4}$ all have bond angles of $109.5^\circ$.
The following is multiple choice question (with options) to answer.
When what common element forms single bonds with other atoms, the shape is tetrahedral, and when its atoms form a double bond, the shape is planar? | [
"carbon",
"hydrogen",
"oxygen",
"silicon"
] | A | Figure 2.22 When carbon forms single bonds with other atoms, the shape is tetrahedral. When two carbon atoms form a double bond, the shape is planar, or flat. Single bonds, like those found in ethane, are able to rotate. Double bonds, like those found in ethene cannot rotate, so the atoms on either side are locked in place. |
SciQ | SciQ-4141 | visible-light, material-science, reflection, metals
The other materials (plastic, glass, apples) have one thing in common: they have a relatively low absorptivity (while for metals the wave only enters a few nanometers, the other materials range from transparent to waves entering at least several micrometers; the absorption caused by pigments in the material is typically much weaker than the one in metals). This means that the reflection is caused by the change of the real part of the index of refraction. As most materials are only slightly dispersive in the optical range, this means that all frequencies are reflected more or less equally, therefore the reflection is not tinted.
The following is multiple choice question (with options) to answer.
What objects are made from highly reflective metal that is applied to a curved or flat piece of glass? | [
"mirrors",
"vases",
"frames",
"machines"
] | A | Mirrors are made from highly reflective metal that is applied to a curved or flat piece of glass. Converging mirrors can be used to focus light – headlights, telescopes, satellite TV receivers, and solar cookers all rely on this principle. Like lenses, mirrors can create images. |
SciQ | SciQ-4142 | human-biology, physiology, endocrinology, vitamins, homeostasis
Title: Counterintuitive action of Vitamin D? Vitamin D acts in a way which to me is counterintuitive. It functionally supplemets Parathormone. It in the intestinal tract steps up calcium absorption by altering nuclear gene expression and also prevents calcium excretion in kidneys. All of this is understandable. But it also, like parathormone, steps up osteoclast action in bone (actually steps up both osteoclast and osteoblast, but the osteoclast action is increased more to result in net bone resorption). This means that Vitamin D increases blood calcium level by increasing bone resorption.
Then how does Vitamin D help in improving bone density, bone strength and prevent rickets or osteoporosis? All of these would require bone deposition rather than resorption. There are two pieces to this question:
a) How does bone resorption (movement of Ca/Phos out of bone into the blood) result in net improvement in bone structure?
Bones are constantly remodeling, primarily in response to mechanical stressors. Although you clearly already realize this, I will make it explicit: osteoblasts are the cells that create new bone; osteoclasts break down (resorb) bone.
Quoting Harrison’s Internal Medicine1:
Radioisotope studies indicate that as much as 18% of the total skeletal calcium is deposited and removed each year. Thus, bone is an active metabolizing tissue.…The cycle of bone resorption and formation is a highly orchestrated process carried out by the basic multicellular unit, which is composed of a group of osteoclasts and osteoblasts
The following is multiple choice question (with options) to answer.
Fractures, osteoarthritis, and rickets are problems of which body system? | [
"skeletal system",
"circulatory system",
"cardiovascular system",
"digestive system"
] | A | Skeletal system problems include fractures, osteoarthritis, and rickets. |
SciQ | SciQ-4143 | neuroscience, neurophysiology, action-potential
Title: Stimulating an axon causes impulses to travel both ways?
A diagram is presented as such above.
The question given states What would be the effect of stimulation to cause a nerve impulse with a microelectrode at the middle of the axon?
I thought the nerve impulse only travels in one direction to the muscle fibres, but the book says "A nerve impulse would pass in both directions."
Why is that the case? Allow me to do a silly analogy: think about the electric wire going from your outlet to your computer, conducting electricity. If you make two cuts in this wire, rotate it 180 degrees and weld it again at the cutting points, what will happen? It will conduct electricity just as it did before.
The same happens to an axon (but please have in mind that this is just an analogy, an action potential is not an electric current). That is, the axon doesn't determine or influence the direction of the action potential. If you cut a piece of that axon, rotate it 180 degrees and join it back in the cutting points, it will conduct the action potential the same way.
That being said, imagine that you stimulate that axon at a given point. There will be two action potentials, going to opposite ways:
unmyelinated (A) and myelinated (B) nerve cells
In your figure (given that is a motor neuron), if you stimulate that axon in the middle, the action potential going to the neuromuscular junction, which is the normal direction, is called orthodromic (from the greek orthos, "proper", and edramon, past of "run"), while the one going to the soma (the perikaryon) is called antidromic (from the greek anti, "against").
According to Oh (2003):
The following is multiple choice question (with options) to answer.
The structure of a neuron allows it to rapidly transmit nerve impulses to other what? | [
"limbs",
"cells",
"proteins",
"muscles"
] | B | The structure of a neuron allows it to rapidly transmit nerve impulses to other cells. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.