source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-5844 | inorganic-chemistry, solubility, analytical-chemistry
Title: Solubility and wetting of substances in water We have seen that, when we pour salt in water then it gets dissolved, that means it is soluble in water. But when we pour sand into water then it doesn't dissolve in water, that means it is insoluble, but still sand gets wet. But there are certain substances which doesn't get wet by water for example, sulfur particles don't get wet by water but wet in oil, as I was studying about froth floatation method.
My question is that:
What is the difference between solubility and wetting in water ?
What is the reason that the sulfur particle doesn't get wet by water? Polar/hydrophilic soluble substances get dissolved, like table salt or sugar.
Polar/hydrophilic insoluble substances get wet, as they attract water, like sand, or limestone.
Nonpolar/hydrophobic insoluble substances do not get wet, as they repulse water, like wax, teflon or silanized glass.
The following is multiple choice question (with options) to answer.
When drinking water is treated, what is the term for when chemicals cause solids in the water to clump together? | [
"coagulation",
"clumping",
"oxidation",
"plasma"
] | A | You can see how water for drinking is treated in Figure below . Treating drinking water requires at least four processes: 1. Chemicals are added to untreated water. They cause solids in the water to clump together. This is called coagulation. 2. The water is moved to tanks. The clumped solids sink to the bottom of the water. This is called sedimentation. 3. The water is passed through filters that remove smaller particles from the water. This is called filtration. 4. Chlorine is added to the water to kill bacteria and other microbes. This is called disinfection. Finally, the water is pure enough to drink. |
SciQ | SciQ-5845 | 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.
What does the urea cycle process? | [
"urine",
"oxygen",
"nitrogen",
"calcium"
] | C | Freely available amino acids are used to create proteins. If amino acids exist in excess, the body has no capacity or mechanism for their storage; thus, they are converted into glucose or ketones, or they are decomposed. Amino acid decomposition results in hydrocarbons and nitrogenous waste. However, high concentrations of nitrogen are toxic. The urea cycle processes nitrogen and facilitates its excretion from the body. |
SciQ | SciQ-5846 | telescopes, camera, sensor
The pupil of an eyepiece lies in the pupil plane, as the name suggests. Its size does not affect magnification. If it becomes smaller than the projected pupil of the telescope however it limits the aperture, because light from the telescope is lost. This changes the f-number and basically reduces the brightness of the images. The magnification is however affected by the eyepiece's focal length, and with it its distance to the focal plane of the telescope.
The CCD/CMOS detector is positioned in a focal plane. Its size limits the field of view of the telescope (the size of the patch of sky that you can see). Its size does not affect the magnification.
Besides aperture, magnification and field of view, a telescope is also characterized by its resolution. For an ideal telescope (diffraction limited), the resolution is limited by the wavelength of the light and its pupil diameter $D$ (Rayleigh criterion). The resolution of the CCD chip, i.e. its pixel size, has to be designed correctly to sample the telescopes resolution correctly.
The following is multiple choice question (with options) to answer.
When using a microscope we do not see the entire extent of the sample. depending on the eyepiece and objective lens we see a restricted region which we say is this? | [
"focal point",
"field of view",
"peripheral view",
"tunnel vision"
] | B | When using a microscope we do not see the entire extent of the sample. Depending on the eyepiece and objective lens we see a restricted region which we say is the field of view. The objective is then manipulated in two-dimensions above the sample to view other regions of the sample. Electronic scanning of either the objective or the sample is used in scanning microscopy. The image formed at each point during the scanning is combined using a computer to generate an image of a larger region of the sample at a selected magnification. When using a microscope, we rely on gathering light to form an image. Hence most specimens need to be illuminated, particularly at higher magnifications, when observing details that are so small that they reflect only small amounts of light. To make such objects easily visible, the intensity of light falling on them needs to be increased. Special illuminating systems called condensers are used for this purpose. The type of condenser that is suitable for an application depends on how the specimen is examined, whether by transmission, scattering or reflecting. See Figure 26.20 for an example of each. White light sources are common and lasers are often used. Laser light illumination tends to be quite intense and it is important to ensure that the light does not result in the degradation of the specimen. |
SciQ | SciQ-5847 | evolution
An Immune Basis for Malaria Protection by the Sickle Cell Trait
Sickle Cell Anaemia and Malaria
If you look further, you will find a number of different examples, where evolution is present after humans went through a genetic bottleneck (meaning the number of humans was drastically reduced).
The following is multiple choice question (with options) to answer.
Sickle cell diseas is caused by what? | [
"bronchiole allele",
"anterior allele",
"posterior allele",
"receccisve allele"
] | D | |
SciQ | SciQ-5848 | life, abiogenesis, artificial-life
Title: Synthetic life creation - status of attempts First I apologize for my incorrect English and for lack of modern knowledge regarding the subject (I studied biology a long time ago).
I'm interested to find out:
if there were successful attempts of life creation from conditions that we suppose were dominant on early Earth
if there were not, are such attempts still being conducted?
To clarify, by "life creation" I mean the accidental creation of entire organism in conditions of organic compounds, water, electricity, radiation etc. being present (Abiogenesis).
If this is already answered here, I'm sorry for asking, I have researched this, this, this and this question with no luck. There have been lot's of attempts, no success so far, a few groups are still working on. However, many steps forward have been done in the last decades.
Starting from the Miller experiment which demonstrated that the building blocks of life chemistry can be obtained starting from fairly simple chemical compounds. Following, Luisi and Szostak showed that 1) nucleic acids can polymerize without the help of enzymes and 2) autocatalytic micelles form spontaneously in many different conditions. It is also important to remember the work of Otto that showed how different molecules can self-replicates.
There are many more examples reported in the literature, still, the complete "creation" of life from matter has not been yet accomplished. However, the results from the experimental work done so far suggest that it is only matter of time and lots of combinatorial work. Unfortunately, there are little to no investments in this field. It's very hard to get the funds needed to start an international cooperation (like the one made to sequence the human genome or to build the CERN's Large Hadron Collider) with the goal of actually making life in the lab. I think that the work of a few (uncoordinated) groups will not get to the goal in the next few years.
The following is multiple choice question (with options) to answer.
What are the most successful organisms on earth? | [
"bacteria",
"trees",
"humans",
"pests"
] | A | Bacteria are the most successful organisms on the planet. They lived on this planet for two billion years before the first eukaryotes and, during that time, evolved into millions of different species. |
SciQ | SciQ-5849 | thermodynamics, statistical-mechanics, temperature, atomic-physics, speed
Title: Is it safe to say that temperature is a measure of molecular activity? In Wikipedia
Temperature is a physical quantity that expresses the hotness of matter or radiation.
There are three types of temperature scale: those, such as the SI scale, that are defined in terms of the average translational kinetic energy per freely moving microscopic particle, such as atom, molecule, or electron, in a body
https://en.wikipedia.org/wiki/Temperature
========
I wonder is it save to say that temperature is a measure of molecular activity? You can say that but it would be rather vague, because there are other physical concepts which might also be called a measure of molecular activity, such as energy, speed, fugacity, etc.
Temperature is property (in formal language, a function of state) of a system in thermal equilibrium, such that two systems at the same temperature will show no net heat flow between them when brought into thermal contact. In microscopic terms, it is a measure of the distribution of energy in the microscopic motions and positions in a system. A higher temperature gives a wider distribution.
The following is multiple choice question (with options) to answer.
The temperature of an object is a measure of what type of energy? | [
"chemical",
"magnetic",
"thermal",
"density"
] | C | Forms of Energy The forms of energy include thermal energy, radiant energy, electrical energy, nuclear energy, and chemical energy (Figure 5.1 "Forms of Energy"). Thermal energy results from atomic and molecular motion; the faster the motion, the greater the thermal energy. The temperature of an object is a measure of its thermal energy content. Radiant energy is the energy carried by light, microwaves, and radio waves. Objects left in bright sunshine or exposed to microwaves become warm because much of the radiant energy they absorb is converted to thermal energy. Electrical energy results from the flow of electrically charged particles. When the ground and a cloud develop a separation of charge, for example, the resulting flow of electrons from one to the other produces lightning, a natural form of electrical energy. Nuclear energy is stored in the nucleus of an atom, and chemical energy is stored within a chemical compound because of a particular arrangement of atoms. (a) Thermal energy results from atomic and molecular motion; molten steel at 2000°C has a very high thermal energy content. (b) Radiant energy (e. , from the sun) is the energy in light, microwaves, and radio waves. (c) Lightning is an example of electrical energy, which is due to the flow of electrically charged particles. (d)Nuclear. |
SciQ | SciQ-5850 | evolution, embryology, chromosome, polyploidy
Polyploidy is an important evolutionary mechanism which was and is probably responsible for a great deal of biological diversity.
Polyploidy arises easily in both animals and plants, but reproductive strategies might prevent it from propagating in certain circumstances, rather than any reduction in fitness resulting from the genome duplication.
Polyploidy may be more prevalent in animals than previously expected, and the imbalance in data arises from the fact that cytogenetics (i.e. chromosome counting) of large populations of wild specimens is a very common practise in botany, and very uncommon in zoology.
In addition, there are now several new suspected factors involved in ploidy which are currently being investigated:
The following is multiple choice question (with options) to answer.
The chromosomal theory of inheritance proposed that what reside on chromosomes? | [
"rna",
"atoms",
"genes",
"molecules"
] | C | Chapter 13 1 Figure 13.3 No. The predicted frequency of recombinant offspring ranges from 0% (for linked traits) to 50% (for unlinked traits). 3 Figure 13.6 B. 4 A 6 C 8 B 10 C 12 D 14 The Chromosomal Theory of Inheritance proposed that genes reside on chromosomes. The understanding that chromosomes are linear arrays of genes explained linkage, and crossing over explained recombination. |
SciQ | SciQ-5851 | reproduction, endocrinology, pregnancy, ovulation
The decline of the corpus luteum is correlated with a decline in serum levels of ovarian hormones including progesterone, estradiol, and inhibin A. Release from negative feedback provided by these hormones at the level of the hypothalamus and pituitary permits FSH to rise, and the cycle begins again.
You should now be able to see that:
Around the time of ovulation, the uterine lining is not fully developed and is stable due to the hormonal milieu. Menstruation does not occur.
Around the time of menstruation, FSH and LH are suppressed in a way that is not conducive to ovulation.
In theory, yes, of course there would be a lower chance of initiating a viable pregnancy (implantation rather than conception is the most obvious problem) were the endometrial lining to be unstable at the time of ovulation. The problem of luteal phase deficiency is along these lines. In this condition, the corpus luteum does not produce adequate progesterone during the luteal phase to develop the endometrial lining in such a way as to support a healthy pregnancy. However, ovulation and menstruation are still time-separated events for the reasons outlined above.
*Note that the first term is with respect to the endometrium; the second is with respect to the ovary.
Abbreviations:
GnRH - Gonadotropin Releasing Hormone; LH - Luteinizing Hormone; FSH - Follicule Stimulating Hormone
References
1. Anatomy & Physiology, Connexions Web site. Illustration is also from here.
2. Jerome Strauss, Robert Barbieri. Yen & Jaffe's Reproductive Endocrinology. September, 2013. Saunders.
The following is multiple choice question (with options) to answer.
What process occurs around day 14 of a 28-day menstrual cycle, triggered by the lh surge? | [
"sedimentation",
"fertilization",
"menstruation",
"ovulation"
] | D | Figure 27.15 Hormone Levels in Ovarian and Menstrual Cycles The correlation of the hormone levels and their effects on the female reproductive system is shown in this timeline of the ovarian and menstrual cycles. The menstrual cycle begins at day one with the start of menses. Ovulation occurs around day 14 of a 28-day cycle, triggered by the LH surge. |
SciQ | SciQ-5852 | evolution
Title: How to define "evolution"? The standard answer found in intro course to evolutionary biology to the question:
what is evolution?
is:
It is a change in allele frequency over time!
I believe a complete definition should encompass the following concepts:
mutations
copy number variation (CNV)
codon usage
chromosome numbers
phenotypic change (whether heritable or not)
Complex phenotypic trait such as plasticity and developmental noise
maybe some other things...
My questions are:
Would it be worth it to talk about phenotype in a definition of evolution?
What are the alternative definitions that have been proposed?
What is your definition?
Note: I would rather talk about genetic evolution, but if you think it is worth making one definition for genetic and cultural (and some other stuff maybe) evolution, you're free to suggest it! What is evolution?
In a non-biological sense, evolution means change:
"a process of [...] change"
Biological evolution (seeing as this is Biology stack exchange) then needs to be tweaked to give a biologically specific context. Many textbooks etc. give definitions of evolution and here are a few good ones from across the history of evolutionary biology:
Charles Darwin:
"Descent with modification".
Mark Ridley1:
"Evolution means change, change in the form and behaviour of organisms between generations. ... When members of a population breed and produce the next generation we can imagine a lineage of populations, made up of a series of populations through time. Each population is ancestral to the descendant population in the next generation: a lineage is an ancestor-descendent series of populations. Evolution is then change between generations within a population lineage."
Brian and Deborah Charlesworth2:
"Evolution means cumulative change over time in the characteristics of a population of living organisms. ... All evolutionary changes require initially rare genetic variants to spread among the members of a population, rising to high frequency..."
All of these have a common theme. Biological information is moving through time, descending with a degree of directionality (e.g. parent $\rightarrow$ offspring), and the information is modified with time.
Personally I would define evolution as:
The following is multiple choice question (with options) to answer.
What term refers to a change in species over time? | [
"spontaneous change",
"generation",
"mutation",
"evolution"
] | D | Evolution can be described as a change in species over time . Dinosaur fossils are significant evidence of evolution and of past life on Earth. |
SciQ | SciQ-5853 | 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.
The nitrogen cycle moves nitrogen back and forth between the atmosphere and what? | [
"organisms",
"Ocean",
"Ozone Layer",
"sediments"
] | A | The nitrogen cycle moves nitrogen back and forth between the atmosphere and organisms. Bacteria change nitrogen gas from the atmosphere to nitrogen compounds that plants can absorb. Other bacteria change nitrogen compounds back to nitrogen gas, which re-enters the atmosphere. |
SciQ | SciQ-5854 | zoology, experimental
Title: Fish "coming back to life" after being frozen I've encountered a clip on Youtube showing a goldfish thrown in liquid nitrogen and immediately after to normal water and swimming normally. In the explanation to the clip it says:
For everyone that is worried about the goldfish, it survived and was perfectly fine until we fed him and a few of his friends to our turtles. (Which is what they were bought for in the first place!)
I am wondering now as to several issues.
If the goldfish wasn't fed to the turtles and was allowed to live out its life, would it suffer any long term damages from the act?
Is time an issue here, if the fish was kept frozen for a longer time, would it suffer more damage and would it be able to be revived?
Is the size and nature of the fish's body a factor? Would a larger animal or an animal with better resistance to frost that would take more time to completely freeze have damage due to gradual freezing of body and systems?
Does the fact that fish have cold blood affect the result of the experiment? I have no idea what's the real reason for the survival of the poor fish, but I would guess this is all in the timing. I know for certain ;-) that one can submerge a hand in liquid nitrogen for a short time or in general one can pour liquid nitrogen on the skin with no harm done whatsoever.
The reason is that the difference in temperature that interface (-180 deg C or so for liquid nitrogen and 20-30 for the skin surface) is so large that nitrogen vaporizes instantly and does not penetrate/affect the tissue. The demonstrator could have pulled the fish with bare hands.
I think that for the goldfish the time was too short and while it was cooled/shocked a bit, it might have been too short to do any serious damage. But -
As a scientist, I can't help but notice that we don't really know the condition of the fish before or after the liquid nitrogen 'treatment'. We only see it flapping for a few seconds when back in water. I wonder what happened to the eyes and the mouth, both quite sensitive tissues for such a shock. Also, the water the fish was in was a factor probably, providing additional buffer between the fish and the liquid nitrogen.
Last but not least, the ethical committee quite certainly did not approve that demonstration.
The following is multiple choice question (with options) to answer.
Eutrophication, or high levels of nutrients, can cause conditions that deprive fish of what vital gas? | [
"nitrogen",
"oxygen",
"dioxide",
"hydrogen"
] | B | High levels of nutrients, called eutrophication, can cause conditions that deprive fish of oxygen. |
SciQ | SciQ-5855 | 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.
What ancestors did caecillians evolve from? | [
"arthropod",
"ornithopod",
"tetrapod",
"hominid"
] | C | Caecilians are most closely related to salamanders. As you can see from Figure below , they have a long, worm-like body without legs. Caecilians evolved from a tetrapod ancestor, but they lost their legs during the course of their evolution. |
SciQ | SciQ-5856 | newtonian-mechanics, friction
Title: Why is kinetic friction less than static friction? Ex: A wooden block is lying on a table.
I am told that because the block is still, the microscopic surface irregularities form more complicated interlocking structures. Is it because the force of the block on the table deforms the molecular structure of the table and wood to eventually reach an equilibrium state? This state then is more connected and harder to change than a block simply gliding over the table?
Also, how fast does this happen? A body in motion tends to stay in motion.
Suppose the peaks of one surface aligned with the valleys of another surface, and you applied enough force to start slipping. One of two things must happen. Either the peaks get shaved off (which takes a lot of force), or the average distance between the two objects increases. Even if there is a little shaving taking place, the distance between the objects is increasing. If the objects start separating, they cannot suddenly return to have the peaks and valleys line up. It takes time, just like it takes time for a ball thrown into the air to return to earth. If the surfaces are kept in motion, the distance between them will reach some average that is greater than the average when they are at rest. Greater separation means that only the peaks of the surfaces are coming into contact at points closer to the tips of the peaks. There will be a reduced attraction between the molecules of the two objects, and a reduced component of the microscopic normal forces parallel to the direction of motion. This results in a lower component of force parallel to the direction of motion, i.e., less friction.
Reference https://www.physicsforums.com/threads/why-is-the-kinetic-friction-always-smaller-than-the-static-friction.140426/
The following is multiple choice question (with options) to answer.
The surfaces of the bones at the joints are covered with a smooth layer of cartilage, which reduces what force between the bones when they move? | [
"friction",
"expulsion",
"gravity",
"vibration"
] | A | Movable joints allow the greatest movement and are the most common. In these joints, the bones are connected by ligaments. The surfaces of the bones at the joints are covered with a smooth layer of cartilage. It reduces friction between the bones when they move. The space between the bones is also filled with a liquid called synovial fluid. It helps to cushion the bones. There are several different types of movable joints. You can see three of them in Figure below . Move these three joints in your own skeleton to experience the range of motion each allows. |
SciQ | SciQ-5857 | immunology, parasitology
Within a few days the protozoans would be recognized and soon eliminated by the immune system except that T. brucei at random times changes the glycoprotein used as its surface coat. The mechanism that does this is called a variant surface glycoprotein (VSG) expression system. The organism has a repertoire of about 1500 different proteins to select from to use for a new glycoprotein coat. The overall effect is that by the time the immune system is able to flood the body with the antibody type it has developed, most of the T. brucei population is not recognizable by those antibodies. T. brucei devotes a significant portion of its genome and its protein production to this immune evasion system.
The following is multiple choice question (with options) to answer.
The infection-fighting complement system consists of roughly 30 proteins in? | [
"blood plasma",
"stomach acid",
"fats",
"stool"
] | A | |
SciQ | SciQ-5858 | biochemistry, biophysics, bioenergetics
Title: Are there known life forms that are able to transform mechanical energy into chemical energy? Are there known life forms that are able to transform mechanical energy into chemical energy?
This question asks a similar subject, but more specific and has no answers.
The background of this question are thoughts about hypothetical life on tidally locked exoplanets of red dwarf stars, where light for photosynthesis is scarce but mechanical energy (storms and/or water currents) aplenty. There are no known life forms that use mechanical energy as a primary form of metabolic energy (i.e., for generic cellular functions). Many life forms are sensitive to mechanical disruption in some way, so they do utilize mechanical energy, but in a very limited fashion (@David's answer touches on this), and of course many organisms have life cycles that somehow depend on mechanical transportation (seed/spore dispersal, traveling on the wind or ocean currents, etc).
I think the main physical problem is that mechanical energy just isn't available to biological cells in a form that can be converted to substantial chemical energy. They are small, and tend to have other great benefits for being small.
To use an ocean wave as an example, there is very little or no perceptible movement for a cell in that wave, besides an apparent increase and decrease in the force of gravity. The top and bottom of the cell are moving together with the flow of water, so there is no differential to operate on.
An E. coli weighs about 1 picogram. If it could capture all of the energy from falling from 1km in the air on earth, assuming no uncaptured aerodynamic drag, that would be about 10-11 joules.
If there are ~3000 kJ/mol of energy available from burning glucose, that means about 5 × 10-21 joules per molecule of glucose, so about 20 billion glucose molecules, which sounds like a lot but it is only 1 femtogram, 0.1% the weight of the cell.
The following is multiple choice question (with options) to answer.
In how many ways ca a living organism obtain chemical energy | [
"seven",
"three",
"four",
"two"
] | D | Living organisms obtain chemical energy in one of two ways. |
SciQ | SciQ-5859 | human-biology, sex, reflexes
Title: In males, why it is difficult to control orgasm? Why it is difficult to control orgasm in male humans? How are orgasms controlled and what is different between males and females?
We can control urine for few minutes, but we can't control orgasm for more than a few seconds, but both are discharging though same organ (penis). The sphincter of the bladder is under voluntary control (that's what toilet training is about). That's why you can hold your urine even when the stretched bladder is sending messages to your brain that you really have to go. That's not to say there aren't involuntary effects on the bladder during orgasm.
Orgasm is a separate entity. It is a complex neurological response with four stages. Orgasm is controlled by the autonomic nervous system and is a response that can be controlled as easily as pupillary dilation/contraction in response to light (that is, not at all). However, there is some measure of voluntary control over the plateau phase of orgasm.
In a bit more detail,
expulsion is a spinal cord reflex that occurs as the ejaculatory process reaches a ‘point of no return’. During expulsion, the smooth muscle fibers of the bladder neck contract to prevent the backward flow of semen into the bladder; the pelvic floor muscles, along with the bulbospongiosus and ischiocavernosus muscles, have primary roles in this function, and display stereotypical rhythmic contractions to propel semen distally throughout the bulbar and penile urethra. During this process, the external urinary sphincter is normally relaxed. The bladder neck and proximal portion of the urethra, which both contain abundant smooth muscle fibers, receive dual sympathetic and parasympathetic innervation. Besides the cholinergic and noradrenergic components, the principal mediators found in these nerve terminals are NPY, VIP, and NO. The external urethral sphincter and pelvic floor striated muscles are solely regulated by the somatic nervous system, but there is no definitive evidence that a voluntary control of the expulsion phase exists in humans.[1]
Human sexual response cycle
Physiology of male sexual function
[1] Ejaculatory Disorders: Pathophysiology and Management: Physiology of Ejaculation
The following is multiple choice question (with options) to answer.
What stage in human males lasts from about ages 12 to 18 years and is controlled by hormones? | [
"maturity",
"puberty",
"childhood",
"adolescence"
] | B | The male reproductive system forms before birth but does not become capable of reproduction until it matures during puberty. Puberty lasts from about ages 12 to 18 years and is controlled by hormones. |
SciQ | SciQ-5860 | forces, spring
Title: Passing limit of proportionality but not elastic limit In my textbook, the limit of proportionality and elastic limit are labelled separately, but quite close to each other. Does this mean that once a spring only just passes the limit of proportionality, but we carefully ensure it doesn't stretch anymore, then once unstretched, it would return to it's original length? Is is even possible to cross limit of proportionality but not reaching the elastic limit? If the spring is stretched beyond the proportionality limit but still within the elastic limit, it recovers its initial length after we remove the stretching force.
However, when unloading the spring, elastic hysteresis can occur, i.e., the path taken by the spring in the load vs deformation plot is different. This means that the work done by the spring to recover its original shape is less than the work needed to stretch it.
The following is multiple choice question (with options) to answer.
Elasticity is the ability of a material to return to its original shape after being stretched or? | [
"Contained",
"compressed",
"combustion",
"correlated"
] | B | Elasticity is the ability of a material to return to its original shape after being stretched or compressed. When an elastic material is stretched or compressed, it exerts elastic force. This force increases the more the material is stretched or compressed. |
SciQ | SciQ-5861 | entomology, invertebrates
Title: Selection for less efficient egg transfer in Human Botfly life cycle I have heard that the Human Botfly transfers its eggs through other invertebrates, and it strikes my curiosity that if an insect could simply land on its host directly to deposit its eggs, then why have intermediate hosts?
I have speculated that the vectors may be better specialized for penetrating hosts, and that penetrating hosts may be difficult, or that approaching hosts is risky. Another speculation on my part is that the Human Botfly may be filling a niche where it does not need to compete. In multi-host complex life cycles (CLCs), an intermediate host often aids in the dispersal of offspring.
In general terms, an animal, say a botfly, have an ultimate "purpose" or 'goal' to spread their genetic information as much as possible. This could mean producing a large number of offspring and hoping some survive or it could mean having one offspring, investing a lot of energy and ensuring it does survive. Regardless, spreading genetic information often requires offspring to disperse (or be spread) a great distance, which may allow the individuals' genetic information to dominate an new region.
In the case of botflies, having an intermediate host means the genetic information can be spread a great distance.
If you're looking for a more thorough explanation of complex life cycles, this paper describes it well. There is also this site more specific to the botfly which is not peer reviewed, but well-researched and descriptive.
The following is multiple choice question (with options) to answer.
Many parasites have complex life cycles involving multiple ? | [
"viruses",
"features",
"diseases",
"hosts"
] | D | |
SciQ | SciQ-5862 | optics, visible-light, polarization
Title: Unpolarized Light: is it always linear or could it be elliptical? Unpolarized light is essentially polarized light in every direction i.e. there are so many waves radiating, that each wave oscillates in a different direction. Polarized light can either be linear or elliptical. Is light from the sun or a lamp all linearly polarized or could they/are they elliptical? Is most polarization in nature linear? It can either be linear, or elliptical... or any other! There are not just 2 possibilities.
The terms "linear" or "elliptical" refer to the basis that we have chosen. If we choose a linear description, we can be lucky and find a beam which has only one-axis component. That's linear light. However, most beams will have both components, because most light isn't purely "linear".
The same happens if we choose a circular basis. We can be lucky to find a clockwise polarized beam, but that's not very probable actually.
So, going to your final question, most light in nature is randomly polarized. This is often called "incoherent light", and it means that the electric field points in a random direction every single time. There's no way to predict where it will be pointing afterwards.
Since the light from the Sun is like this, this is usually called "natural polarisation". Most lamps also emit this way. You can find some screens where pixels make it linearly polarized, but most of it is random. Notice that most light bulbs are made by fluorescence.
To be precise, the atmosphere adds a small linear component. And there are many lightbubs that emit with a certain polarization. Of course, they will if their glass is a polariser.
The following is multiple choice question (with options) to answer.
What type of light is composed of many rays having random polarization directions? | [
"unpolarized light",
"diffracted light",
"reflected light",
"polarized light"
] | A | 27.8 Polarization • Polarization is the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave. • EM waves are transverse waves that may be polarized. • The direction of polarization is defined to be the direction parallel to the electric field of the EM wave. • Unpolarized light is composed of many rays having random polarization directions. • Light can be polarized by passing it through a polarizing filter or other polarizing material. The intensity I of polarized light after passing through a polarizing filter is I = I 0 cos 2 θ, where I 0 is the original intensity and θ is the angle between the direction of polarization and the axis of the filter. • Polarization is also produced by reflection. • Brewster’s law states that reflected light will be completely polarized at the angle of reflection θ b , known as Brewster’s angle, given by a statement known as Brewster’s law: reflected light travel and. |
SciQ | SciQ-5863 | mycology
Title: How do fairy rings propagate? It was somewhat new to me that mushrooms usually aren't individual organisms, but are merely the visible bodies of a bunch of fungi living in the soil. I know that mushrooms emit spores to reproduce, but what has been bizarre to me is how fairy rings form. Why do the fruiting bodies arrange themselves in a more or less circular shape, as opposed to the random scattering one would expect from wind-borne spores? When a fungal spore germinates in a suitable location, the growing mycelium will spread underground in all directions. In the ideal situation, the result is that the mycelium will become circular. Over time, the center of the mycelium will die out whereas the newly formed mycelium (underground) will develop the familiar mushrooms above ground and this will result in a fairy ring.
The following is multiple choice question (with options) to answer.
How do yeasts reproduce? | [
"homosexual",
"asexually",
"bisexual",
"preferentially"
] | B | Yeasts are an exception. They reproduce asexually by budding instead of by producing spores. An offspring cell forms on a parent cell. After it grows and develops, it buds off to form a new cell. The offspring cell is genetically identical to the parent cell. You can see yeast cells budding in Figure below . |
SciQ | SciQ-5864 | Does this help at all? We can keep discussing your thinking on various problems and see what we discover. Let me just say this (which you probably already know, at least in theory): One of the most overlooked steps in problem-solving is the last — to look over your work to see what lessons you can learn from it. Did you see a pattern that turned out to be useful? Or, looking back with the benefit of hindsight, do you see something you could have done that would have gotten you to the goal more quickly? When I asked myself and you why we did certain things above, it was with the idea of abstracting some possibly useful principles for future problems.
The key idea here is that we are trying to make an expression (a) simpler, (b) more familiar, and (c) more like the other side. Each of these short-term goals makes it likely we will be able to move forward.
After some discussion, he demonstrated both methods for this problem, which I’ll include here. The first, which Sarah said worked better for her, started with combining the fractions:
Here’s my work with the first method:
-1 + cos α 1 + cos α
------------- + -------------
sec α + tan α sec α - tan α
(-1 + cos α)(sec α - tan α) + (1 + cos α)(sec α + tan α)
≡ --------------------------------------------------------
(sec α + tan α)(sec α - tan α)
-sec α + tan α + cos α sec α - cos α tan α + sec α + tan α
+ cos α sec α + cos α tan α
≡ ----------------------------------------------------------
sec2 α - tan2 α
The following is multiple choice question (with options) to answer.
In science, what can be described as a set of steps that help us to answer questions? | [
"scientific method",
"scientific controls",
"theory",
"hypothesis"
] | A | The scientific method is a set of steps that help us to answer questions. When we use logical steps and control the number of things that can be changed, we get better answers. As we test our ideas, we may come up with more questions. The basic sequence of steps followed in the scientific method is illustrated in Figure below . |
SciQ | SciQ-5865 | metabolism, diet, carbohydrates
In terms of protein, however, amino acids are either glucogenic, ketogenic, or both. If amino acids are ketogenic, then this means they can be converted into acetyl-CoA for the Krebs Cycle. If amino acids are glucogenic, then it means that they can be broken down into glucose. The breakdown of amino acids can be used to synthesize glucose or for anapleurotic reactions of the Krebs Cycle.
As stated in the editorial noted in the comments of this question (From the American Journal of Clinical Nutrition), there are daily "requirements" for carbohydrates. However, it does not appear that any diseases are unmasked by very low to zero carbohydrate absorption (which is most closely occurs in the Inuit populations whose diet is entirely fat and protein).
So, if you ask the question "are carbohydrates essential components of a human diet?" the answer would be probably not. However, as mentioned above, carbohydrates are ubiquitous and it is impossible to abstain from all carbohydrate intake.
The following is multiple choice question (with options) to answer.
What does the body derive from the breakdown of the carbohydrate-containing foods and drinks we consume? | [
"glucose",
"lipids",
"insulin",
"amino acids"
] | A | Regulation of Blood Glucose Levels by Insulin and Glucagon Glucose is required for cellular respiration and is the preferred fuel for all body cells. The body derives glucose from the breakdown of the carbohydrate-containing foods and drinks we consume. Glucose not immediately taken up by cells for fuel can be stored by the liver and muscles as glycogen, or converted to triglycerides and stored in the adipose tissue. Hormones regulate both the storage and the utilization of glucose as required. Receptors located in the pancreas sense blood glucose levels, and subsequently the pancreatic cells secrete glucagon or insulin to maintain normal levels. |
SciQ | SciQ-5866 | molecular-biology, chromosome, meiosis, mitosis
Which flags are used by the enzymes in the process of making the
centromere to tell them that it is the right spot
There are some centromere associated repeats in the DNA which mark the site for centromere assembly. There is no particular consensus sequence of this repeat. However, this study says that in certain cases stable chromosomes are formed in the absence of centromeric repeats.
are the sister chromatids physically intertwined around each other for
the purpose of joining, or are they simply adjacent?
They are joined by proteins called cohesins. Cohesins looks like rings which form around the sister chromatids. During anaphase, the anaphase promoting complex (APC) activates an enzyme called separase, which in turn degrades cohesin.
what in the centromeres do the spindle fibres attach to, and how do
the tips of the growing fibres notice it to head it its general
direction?
Centromeres serve as a site for the assembly of kinetochore. Kinetochore is a multi-protein complex which forms contact with the spindle fibres (specifically, K-fibres. Refer this previous post). An essential component of kinetochore is the motor protein dynein which makes the kitetochore to crawl along the spindle fibres, towards the pole. The wikipedia article on kinetochore is quite descriptive and you can refer that for details.
The following is multiple choice question (with options) to answer.
A mitotic spindle forms from the centrioles and passes through the nuclear membrane, which remains intact. chromosomes attach to the mitotic spindle, which separates the chromosomes and does what? | [
"migrates the cell",
"manipulates the cell",
"destroys the cell",
"elongates the cell"
] | D | A mitotic spindle forms from the centrioles and passes through the nuclear membrane, which remains intact. Chromosomes attach to the mitotic spindle, which separates the chromosomes and elongates the cell. |
SciQ | SciQ-5867 | acid-base, reaction-mechanism, redox, terminology
Precipitation: Creating a solid
Acid-Base: neutralization
Redox: exchange of electrons
But given a chemical reaction like:
HCl (aq) + NaOH (aq) → H2O (l) + NaCl (aq)
I need to understand how to classify them. Are there any tell-tale signs to look out for when determining. For example, does a precipitation reaction ALWAYS produce a (s) as a product and therefore any reaction with a (s) on the product side is a precipitation reaction? It's true that a precipitation reaction will always yield at least one solid product, but not every reaction that yields a solid is, strictly speaking, properly categorized as a precipitation reaction. Precipitation reactions are ones in which at least one of the reactants is in the aqueous phase (i.e., dissolved in water), and a solid forms on the product side which was not present on the reactant side. If all the reactants are solid, then a solid product forming should not be called a precipitate. To be called a precipitate, an insoluble product must form from within solution, either from a solid and solute interacting, or from an interaction strictly between solutes.
Examples of precipitation reactions:
$\ce{AgNO3_{(aq)} + NaCl_{(aq)} -> AgCl_{(s)} + NaNO3_{(aq)}}$
$\ce{CuCl2_{(aq)} + Zn_{(s)} -> ZnCl2_{(aq)} + Cu_{(s)}}$
Notice that at least one of the reactants was in the aqueous phase, and a new solid chemical species is produced on the product side. $\ce{AgCl_{(s)}}$ and $\ce{Cu_{(s)}}$, respectively, are the precipitates. Incidentally, the second reaction is also an example of a redox reaction, since it involved a change in the oxidation states of the reactants (here, zinc is oxidized while copper is reduced).
Identifying acid-base and redox reactions is a lengthier topic, so I suggest you consult a textbook or any of the numerous online resources.
The following is multiple choice question (with options) to answer.
Substances produced by a reaction are known as? | [
"solutions",
"minerals",
"products",
"compounds"
] | C | Products are substances that are produced in the reaction. |
SciQ | SciQ-5868 | astrophysics, stars, stellar-evolution
Title: Death of Stars and Red Giants As a matter of fact, I was learning stellar astrophysics where I couldn't understand the chain of events at the time of death of stars,
Once the hydrogen fuel core is exhausted, the stars start shrinking until the helium nuclei starts fusing under immense gravitational pressure. Due to powerful radiation pressure the star starts expanding. Like our sun is expected to stretch 200 times it current radius, gobbling up the Mercury and Venus planets.
Here I couldn't understand that helium fusion starts when star is shrinking, but after star starts expanding, so how could star sustain fusion $?$ I mean helium fusion requires even more pressure or temperature than hydrogen, but once star starts expanding, it become cooler and less denser, which should make fusion impossible. And during this phase of Red giant, not only helium, but more heavier nuclei are formed like oxygen which should require even more pressure and temperature.
Is there any flaw in my understanding,then please tell$!$ Please help and thanks in advance $!$ As the hydrogen fuel is exhausted, the core heat that resists gravity diminishes, so gravity takes over and compresses the star. If the star was big enough to start with, then the extra pressure from the compression is enough to enable helium fusion and the heat generated by that is enough to blow parts of the outer envelope off the star and expand it into an immense but cooler sphere. Meanwhile, the remaining inner core of the star continues to fuse helium and remains very hot, and all the heavier elements you mention get fused there as well.
The following is multiple choice question (with options) to answer.
What happens to the core of a star when it begins to run low on hydrogen? | [
"it expands",
"it contracts",
"it disappears",
"it explodes"
] | B | series of stages a sexually reproducing organism goes through from one generation to the next. |
SciQ | SciQ-5869 | meteorology, atmosphere, wind, air-currents
Title: Where does wind come from? Wind is (according to Wikipedia) the flow of gases on a large scale.On the surface of the Earth, wind consists of the bulk movement of air.
What forces would cause such a mass movement of air? Wind is caused by pressure differences. Think of a balloon full of air; poke a hole in it and the air comes out. Why? Because the pressure in the balloon is higher than outside, and so to regain equal pressure, mass moves and that is the wind.
There is a bit more to this in the atmosphere as the Earth rotates and near the surface friction also plays a role. The equation of motion is the Navier-Stokes and in vector form in Cartesian space is:
$$\dfrac{\partial\mathbf u}{\partial t} = - \mathbf u \cdot \nabla \mathbf u -\dfrac{1}{\rho}\nabla p-2 \mathbf \Omega \times \mathbf u + \mathbf g + \mathbf F$$
In this equation, $\mathbf u$ is the vector wind, $(\mathbf u \cdot \nabla)$ is the advection operator, $\rho$ is density, $\mathbf \Omega$ is the vector rotation of the Earth, $\mathbf g$ is effective gravity and $\mathbf F$ is friction.
The LHS is the time rate of change of the wind at a point in space (as opposed to following the parcel). The RHS represent a number of factors that produce a change in the wind. From left to right:
Advection of momentum (non-linear)
Pressure gradient force (this is wind blowing from high to low pressure)
Coriolis force (this turns wind to the right in the NH and left in the SH and causes the wind to flow parallel to isobars)
gravity (provides hydrostatic balance with the PGF in the vertical)
Friction (in the boundary layer you may see this as $\nu\nabla^2\mathbf u$)
The following is multiple choice question (with options) to answer.
What occurs when air masses meet? | [
"tides",
"fronts",
"earthquakes",
"currents"
] | B | Much of the weather occurs at fronts, where air masses meet. |
SciQ | SciQ-5870 | genetics, dna, molecular-genetics, gene
and that employed by the ENCODE project is defined by Gerstein et al. as:
The gene is a union of genomic sequences encoding a coherent set of potentially overlapping functional products
a gene is a genomic sequence (DNA or RNA) directly encoding functional product molecules, either RNA or protein.
In the case that there are several functional products sharing overlapping regions, one takes the union of all overlapping genomic
sequences coding for them.
This union must be coherent — i.e., done separately for final protein and RNA products — but does not require that all products necessarily
share a common sub-sequence
(It is supplemented by an ontological diagram that I shall not reproduce here.)
This is complex, but in relation to the poster’s concern one thing is clear, at no time are the authors concerned with strandedness, and there is no proposal that a gene is confined to a single strand.
Two simple arguments
One might argue that nobody mentions strandedness because everyone assumes a gene is on only one strand. Really? Anyway, I‘ll finish with a couple of mundane arguments that strandedness has no place in defining genes, overlapping or not.
The Transcription Factor/RNA polymerase binding site — the TATA box — is regarded as an integral part of a gene. Both strands of the TATA box are required for binding. Likewise other transcription factor binding sites. Hence the gene cannot be on only one strand.
Single-stranded DNA viruses are found with what are called ‘positive sense’ and ‘negative sense‘ genomes. So clearly among these genomes there are heredity units which read ‘anti-sense’ as well as some that are ‘anti-sense’. On the ‘one-stranded gene’ thesis one of these could not be called genes. One would have to devise some term from them as progenitors of the gene in the complementary strand in the replicative DNA form!
The following is multiple choice question (with options) to answer.
What's the name for a cluster of genes, where one promoter serves adjacent genes? | [
"opteron",
"proton",
"plasma",
"nucleus"
] | A | |
SciQ | SciQ-5871 | genetics, immunology, ecology, biodiversity, fitness
Title: What does genetic diversity in one species have to do with survival rate when an epidemic spreads? I was studying about genes, and soon remembered that the more diverse the genetics of one species, the less the chance of the species to go extinct from natural disaster.
One instance was an epidemic spreads.I don't fully understand why that happens, so I searched for it in Google and books, but all of them only told me that it is true, not why or how.
So my question is : why and how genetic diversity in one species affects the chance of the species's extinction?
I mean, for example, does it relate to antibodies or something else? Genetic diversity could be understood as a variation in alleles (gene variants) and their frequencies in a population. Due to these allelic variations, we would expect an inherent variability in individual genotypes (or genetic codes). Phenotypes (or traits) can and do vary with changes in underlying genotype. (In simple terms: if you change the underlying genetic code, it could result in changes to an individual's traits).
Changes in traits (e.g., color, size, speed, temperature regulation, mobility, etc.) could lead to a variation in energy conservation, survival, reproductive success, and ultimately fitness.
If any member of a population is more fit given a set of environmental circumstances, it is morel likely that they will survive and pass on their genes to subsequent generations.
You would benefit from reviewing evolution and natural selection. (Sexual selection and genetic drift are relevant, too, of course).
However, the environment and resulting ecologies are always changing, and so there is never an "endpoint" of this process. I.e., there's never a perfectly fit individual that will survive all future environmental changes better than all other variants. In fact, all organisms can only tolerate stressful environmental conditions to a point. (See, e.g., principle of allocation).
As a result, any given individual is limited in its ability to survive various environmental conditions, and no individual organism can survive all possible environmental conditions.
The following is multiple choice question (with options) to answer.
The diversity of alleles and genotypes within a population is known as genetic what? | [
"variable",
"density",
"group",
"variance"
] | D | Before Darwinian evolution became the prevailing theory of the field, French naturalist Jean-Baptiste Lamarck theorized that acquired traits could, in fact, be inherited; while this hypothesis has largely been unsupported, scientists have recently begun to realize that Lamarck was not completely wrong. Visit this site (http://openstaxcollege. org/l/epigenetic) to learn more. Heritability is the fraction of phenotype variation that can be attributed to genetic differences, or genetic variance, among individuals in a population. The greater the hereditability of a population’s phenotypic variation, the more susceptible it is to the evolutionary forces that act on heritable variation. The diversity of alleles and genotypes within a population is called genetic variance. When scientists are involved in the breeding of a species, such as with animals in zoos and nature preserves, they try to increase a population’s genetic variance to preserve as much of the phenotypic diversity as they can. This also helps reduce the risks associated with inbreeding, the mating of closely related individuals, which can have the undesirable effect of bringing together deleterious recessive mutations that can cause abnormalities and susceptibility to disease. For example, a disease that is caused by a rare, recessive allele might exist in a population, but it will only manifest itself when an individual carries two copies of the allele. Because the allele is rare in a normal, healthy population with unrestricted habitat, the chance that two carriers will mate is low, and even then, only 25 percent of their offspring will inherit the disease allele from both parents. While it is likely to happen at some point, it will not happen frequently enough for natural selection to be able to swiftly eliminate the allele from the population, and as a result, the allele will be maintained at low levels in the gene pool. However, if a family of carriers begins to interbreed with each other, this will dramatically increase the likelihood of two carriers mating and eventually producing diseased offspring, a phenomenon known as inbreeding depression. Changes in allele frequencies that are identified in a population can shed light on how it is evolving. In addition to natural selection, there are other evolutionary forces that could be in play: genetic drift, gene flow, mutation, nonrandom mating, and environmental variances. |
SciQ | SciQ-5872 | temperature, measurements, error-analysis
So, in summary: the absolute temperature of an everyday substance can be measured to 0.1 mK at the very best, in practice more like 1 mK with significant effort. The change in temperature can however be measured with microkelvin resolution, if sufficiently isolated from the outside environment.
The following is multiple choice question (with options) to answer.
What does temperature measure? | [
"highest potential energy of molecules",
"average potential energy of molecules",
"average kinetic energy of molecules",
"lowest kinetic energy of molecules"
] | C | In this lesson, you read that air density and pressure change with altitude. The temperature of the air also changes with altitude. Air temperature measures the heat energy of air molecules. |
SciQ | SciQ-5873 | fluid-dynamics, simulations, oceanography
Title: Ocean surface mean current flow meaning I tried to simulate the trajectory of an drifting object in the oceans by using the data of the OSCAR project http://www.oscar.noaa.gov/. The dataset actually used consist of grid sampled mean 2d current vectors averaged on a monthly interval indicating the speed and direction of water near the sea surface.
However, moving an object by the gradients shows that the gradient field is riddled with attractors and repellors. There may be several reasons for this, like the water flowing vertically or the mean operation introducing artifacts.
Thus moving an object along trajectories made up by a static snapshot of the dataset isn't very useful, as it usually get stuck in one of the hundreds of sink attractors. This contradicts the usual knowledge of drifting particles to accumulate in very large vortices and eventually reach almost every coastal point on earth.
So how should the mean current be interpreted in respect to drifting object movement? Is there a simple solution to get a coarse drifting simulation that qualitative resembles the expected behavior ? I believe these attractors you are referring to are generally referred to as eddies in the ocean. These features are similar to the hurricanes, and low and high pressure systems in the atmosphere, and just like in the atmosphere they move around.
With monthly mean data (monthly climatology) you can advect particles around in a variety of different ways. The simplest way might be to do a linear interpolation in time between the months and then using that as a time series of velocities. Advecting particles using a single time snap shot of the velocity is not very realistic as the advection of drifters in the real ocean is due to both the velocities and the patterns that these velocities change in. Also by using the monthly mean velocity with linear interpolation you lose the effects of shorter than one month velocity variabilities effect, that have not been sampled by the data.
Quite often the effect of unresolved motions (both in time or space) in the ocean are assumed to be diffusive and you will be able to find a lot of literature on how to parameterize it using some assumptions.
It might be better to post what your ultimate goal is for the trajectory advection experiments and one route over another might be more useful.
The following is multiple choice question (with options) to answer.
What is the term for when the water of the ocean slowly rises and falls? | [
"waves",
"tides",
"dew",
"currents"
] | B | If you’ve ever visited an ocean shore, then you know that ocean water is always moving. Waves ripple through the water, as shown in Figure below . The water slowly rises and falls because of tides. You may see signs warning of currents that flow close to shore. What causes all these ocean motions? Different types of motions have different causes. |
SciQ | SciQ-5874 | zoology, marsupials
Title: Do male marsupials have a pouch? Do male marsupials have a pouch, or is it a female organ only (like the womb)? In most marsupials, only the females have a pouch. However, males of the water opossum and the extinct tasmanian tiger (or thylacine) also have a pouch. The males of both the thylacine and water opposum used/use their pouch to keep their genitalia from getting entangled in vegetation.
The following is multiple choice question (with options) to answer.
Female monotremes lack a uterus and vagina. instead they have what? | [
"urethra",
"endometrium",
"placenta",
"cloaca"
] | D | Female monotremes lack a uterus and vagina. Instead, they have a cloaca with one opening, like the cloacas of reptiles and birds. The opening is used to excrete wastes as well as lay eggs. |
SciQ | SciQ-5875 | visible-light, biophysics, vision
A material absorbing "green" light looks purple, for the impression see the overlapping sections in the following picture. The first image shows what happens if you overlay luminous light (additive colors), the second image shows what happens if you mix paint (subtractive colors).
First image taken from en.wikipedia.org by SharkD, Public Domain; second image taken from de.wikipedia.org by Quark67 CC BY-SA 2.5
If I mix the pigments of paints, each component will absorb its wavelength component(s). In case of "blue" paint mostly "red" light is absorbed, in case of "yellow" paint mostly "blue" light is absorbed, so the dominant remaining color is green. This is the exact reason plants are looking green because plants are mainly absorbing "red" and "blue" light; plant lights are emitting therefore mainly "red" and "blue" light, the color of a plant light looks purple.
If every component is absorbed, mixing yellow, purple and cyan together should give black. In real-life you get a dark brown because the pigments are not mixing perfectly so a color tint is remaining. For that reason we use black ink in our printers for printing grey or black.
The following is multiple choice question (with options) to answer.
Pigments are substances that absorb what? | [
"artificial light",
"visible light",
"synthetic light",
"natural light"
] | B | |
SciQ | SciQ-5876 | organic-chemistry, reaction-mechanism, molecular-structure, alcohols
Title: Predicting product ratio by rearrangement in Dehydration Reactions I came across this question recently, which would have a clear major product. The OP has given satisfactory explanation for the product ratio, but wasn't sure about the major product. When I was looking for reference for better explanation, I show the following question in undergraduate textbook (Ref.1):
Dehydration of 2,2,4-trimethyl-3-pentanol with acid gives a complex mixture of the alkenes in the indicated percentages. Write a mechanism that accounts for each product.
I: 2,3,4-trimethyl-1-pentene, 29%
II: 2,4,4-trimethyl-1-pentene, 24%
III: 3,3,4-trimethyl-1-pentene, 2%
IV: 2,4,4-trimethyl-2-pentene, 24%
V: 2,3,4-trimethyl-2-pentene, 18%
VI: 2-isopropyl-3-methyl-1-butene, 3%
I thought it would be a good practice for our readers to predict the mechanism for the obtained product ratio and give explanation for the major products. Can anybody give a reasonable mechanism for this product ratio and explanation for why $\bf{I} \gt \bf{II} \ge \bf{IV} \gt \bf{V}$, and why $\bf{III}$ and $\bf{VI}$ are in such small amounts?
Late edit: It is evident that the textbook print had an error (Thanks Nisarg Bhavsar for the finding). The compound V is actually 2,3,4-trimethyl-2-pentene, not as 3,3,4-trimethyl-2-pentene in the print. I have corrected it now. Nonetheless, the question is still interesting.
References:
The following is multiple choice question (with options) to answer.
What class of oxygencontaining compounds is formed by the dehydration of alcohols? | [
"reagents",
"ethers",
"sugars",
"nethers"
] | B | Ethanol and resveratrol, a phenol, are representatives of two of the families of oxygencontaining compounds that we consider in this chapter. Two other classes, aldehydes and ketones, are formed by the oxidation of alcohols. Ethers, another class, are made by the dehydration of alcohols. |
SciQ | SciQ-5877 | inorganic-chemistry, molecular-structure
Im Gegensatz zum $\ce{Te(OH)6}$ tritt im Spektrum des $\ce{(H2TeO4)_x}$ eine Frequenz bei $\pu{1618 cm-1}$ auf, die nur von freiem Wasser herrühren kann. Ebenso beobachtet man neben der $\ce{OH}$-Valenzschwingung der $\ce{TeOH}$-Gruppen ($\pu{3200 cm-1}$) die Bande $\pu{3360 cm-1}$ des freien Wassers. Aus den Intensitäten dieser Banden ist zu entnehmen, daß $\ce{H2O}$ und $\ce{TeOH}$-Gruppen in größenordnungsmäßig gleicher Menge vorhanden sind. Eine stöchiometrische Konstitutionsformel wird man dieser Substanz wohl nicht zuordnen können.
The following is multiple choice question (with options) to answer.
Group 16 is called the oxygen group. what is the only metalloid in this group? | [
"gallium",
"tellurium",
"beryllium",
"cadmium"
] | B | Group 16 is called the oxygen group. Tellurium is the only metalloid in this group, which also contains three nonmetals and one metal. |
SciQ | SciQ-5878 | genetics
Title: Can there be medium height(neither tall nor short) pea plants in Mendel's experiment? Can there be medium height(neither tall nor short) pea plants in Mendel's experiment?
All textbooks I have read seem to imply that pea plants have to be either tall or short, nothing in between. Medium height (like in people) and other traits that seem like a mixture of two extremes are often a result of incomplete dominance. For example, a red and white flower are bred to produce an offspring with pink petals.
Mendelian genetics does not include incomplete dominance (which is classified as, surprisingly, non-Mendelian genetics).
Basically, Mendel got very lucky with his choice of plant. Pea plant height is strictly dominant, meaning one dominant allele results in tall plants, regardless of the identity of the second inherited allele. This is a consequence of the genetic makeup of pea plants. Had he tried a similar experiment with snapdragon flower color, he would be very confused.
(See https://www.ndsu.edu/pubweb/~mcclean/plsc431/mendel/mendel2.htm for snapdragon incomplete dominance example.)
The following is multiple choice question (with options) to answer.
In his work with pea plants, mendel performed what, which involves mating two true-breeding individuals that have different traits? | [
"assimilation",
"mutations",
"cross-breeding",
"hybridization"
] | D | These are plants that always produce offspring that look like the parent. By experimenting with true-breeding pea plants, Mendel avoided the appearance of unexpected traits in offspring that might occur if the plants were not true breeding. The garden pea also grows to maturity within one season, meaning that several generations could be evaluated over a relatively short time. Finally, large quantities of garden peas could be cultivated simultaneously, allowing Mendel to conclude that his results did not come about simply by chance. Mendel performed hybridizations, which involve mating two true-breeding individuals that have different traits. In the pea, which is naturally self-pollinating, this is done by manually transferring pollen from the anther of a mature pea plant of one variety to the stigma of a separate mature pea plant of the second variety. Plants used in first-generation crosses were called P, or parental generation, plants (Figure 8.3). Mendel collected the seeds produced by the P plants that resulted from each cross and grew them the following season. These offspring were called the F1, or the first filial (filial = daughter or son), generation. Once Mendel examined the characteristics in the F1 generation of plants, he allowed them to self-fertilize naturally. He then collected and grew the seeds from the F1 plants to produce the F2, or second filial, generation. Mendel’s experiments extended beyond the F2 generation to the F3 generation, F4 generation, and so on, but it was the ratio of characteristics in the P, F1, and F2 generations that were the most intriguing and became the basis of Mendel’s postulates. |
SciQ | SciQ-5879 | geology, oceanography, geochemistry, mineralogy
Title: Will the sea get saltier forever? The sea wasn't always salty. It's been getting saltier over millions of years as minerals dissolve.
Is there a natural limit to this process, or the will the sea keep getting saltier forever?
Is there a natural process which removes salt from the sea at a significant rate?
How long would it take for the sea to get too salty to support life as we know it? No there are natural processes that remove salt as well.
as sea level changes water gets trapped in basins and evaporates leaving the salt behind, this is where many of the salt formation on earth came from. whenever sea levels fall the salinity of the ocean drops. Tectonically isolated basin can remove salt in the same way. The process can even happen repeatedly in the same basin as sea level changes.
There are biological processes that remove it as well the formation of shells and limestone remove some of the ocean salts.
Can it increase yes, but it can also decrease, over earths history there have been saltier and less salty periods.
The following is multiple choice question (with options) to answer.
What type of minerals form when salt water evaporates? | [
"fermite",
"carbonate",
"sulfide",
"halide"
] | D | Halide minerals are salts. They form when salt water evaporates. This mineral class includes more than just table salt. Halide minerals may contain the elements fluorine, chlorine, bromine, or iodine. Some halide minerals combine with metal elements. Common table salt is a halide mineral that contains the elements chlorine and sodium. Fluorite is a type of halide that contains fluorine and calcium. Fluorite can be found in many colors. If you shine an ultraviolet light on fluorite, it will glow!. |
SciQ | SciQ-5880 | orbitals
The principal quantum number (n) can take integer values from 1 to infinity. It describes the different energy levels with increasing distance from the nucleus. As n gets bigger, orbitals within that "shell" also increase in size.
The azimuthal quantum number (l) can take values from 0 to n-1. It describes the type of orbital the electron resides in. It is also call angular momentum quantum number and as I've said above, the angular wave function is responsible for the shape of the orbitals. Makes sense? For each value of l, there is a different type of orbital - 0=s, 1=p, 2=d, 4=f, 5=g (not really seen occupied in the ground state of any element), and these can go on alphabetically.
The magnetic quantum number (ml) describes the direction of the orbital in space with respect to the three Cartesian axis - x, y and z. It can take values from -l to +l. For s orbital, ml can only be 0 and so there is only one s orbital that can exist for a particular principal quantum number. For p orbitals, ml can be -1, 0 and +1 and so there are three p orbitals that can exist - each along different axis - px, py and pz. The axis labeling get more complicated for d and f orbitals.
The spin quantum number (ms) can either be +1/2 or -1/2 and simply describes the direction of the electron's intrinsic angular momentum.
For n=1, l can only be 0 and so there is only an s orbital in that level, referred to as 1s. For n=2, l=0,1 and there can be s and p-types orbitals. For n=3, l=0,1,2 and so you can have s, p and d orbitals in the third shell.
When you're filling up shells with electrons, you go from the lowest energy level to the highest and this can easily be determined by summing up n+l which would give you the relative energies of orbitals. When n+l is the same for two orbitals, the one with the lower n fills up first. One orbital can house 2 electrons which must have opposite spins. There can never be two electrons with the same four quantum numbers in a system (Pauli exclusion principle).
The following is multiple choice question (with options) to answer.
What are identified by the azimuthal quantum number? | [
"covalent bonds",
"sub-energy levels",
"ionic-energy level",
"radioactivity - energy levels"
] | B | The sub-energy levels are identified by the azimuthal quantum number, . |
SciQ | SciQ-5881 | species-identification, botany
Title: Identification of a plant Please help me to identify this plant
The plants can be found on italian balconies and I would like to buy one, but I do not know what I should look for.
The habit of the plant is trailing. This is likely to be a stone plant (Aizoaceae), depending on habit, it could well be the ice plant (Carpobrotus edulis). Stone plants are a quite diverse family of succulents from southern Africa, but are widespread throughout the western world as stabilizers of sand-dunes and in gardens as they are very tolerant of lack of watering and high salinity.
Ice plants are very common in the Mediterranean region, having become an invasive pest on much of the coastline.
If it is ice plant, then you can sub-cultivate it by taking a small part of the plant, usually leaves with a bit of stem, but even a leaf by itself may work, and placing it in water or on sandy soil. With regular watering, it should grow roots and then be plantable.
Apparently the leaves of ice plant are edible (hence the edulis part of the name), similar to Aloe I suspect.
The following is multiple choice question (with options) to answer.
Desert plants have special stems and leaves to conserve what? | [
"air",
"water",
"food",
"habitat"
] | B | Each organism has the ability to survive in a specific environment. Dry desert environments are difficult to live in. Desert plants have special stems and leaves to conserve water. Animals have other ways to live in the desert. The Namib Desert receives only 1.5 inches of rainfall each year. The Namib Desert beetle lives there. How do the beetles get enough water to survive? Early morning fog deposits water droplets. The droplets collect on a beetle's wings and back. The beetle tilts its rear end up. When the droplet is heavy enough, it slides forward. It lands in the beetle’s mouth. There are many other environments that need unique approaches for survival ( Figure below ). |
SciQ | SciQ-5882 | everyday-chemistry, toxicity
Such oxidation reactions are catalyzed both by soluble metals such as iron and by light. Hydrogen sulfide also can combine with metals such as iron (Fe++) to precipitate as black iron sulfide (Figure 1 bottom; FeS and FeS2).
The following is multiple choice question (with options) to answer.
What substance causes oxidation by accepting electrons? | [
"oxidizing agent",
"solvents",
"enzymes",
"thermal agent"
] | A | In the reaction above, the zinc is being oxidized by losing electrons. However, there must be another substance present that gains those electrons and in this case that is the sulfur. In other words, the sulfur is causing the zinc to be oxidized. Sulfur is called the oxidizing agent. The zinc causes the sulfur to gain electrons and become reduced and so the zinc is called the reducing agent. The oxidizing agent is a substance that causes oxidation by accepting electrons. The reducing agent is a substance that causes reduction by losing electrons. The simplest way to think of this is that the oxidizing agent is the substance that is reduced, while the reducing agent is the substance that is oxidized. The sample problem below shows how to analyze a redox reaction. |
SciQ | SciQ-5883 | botany, plant-physiology, reproduction, plant-anatomy, life-history
In dimorphic cleistogamy CL and CH flower differ in the time or place
of production, with CL flowers produced in conditions (underground,
low light levels, early in the season) that are potentially
unfavorable for outcrossing.
In induced cleistogamy potentially CH flowers that experience conditions such as drought or low temperatures fail to open and self-pollinate, becoming, in effect, CL flowers.
You should check out the Culley and Klooster (available online if you make a jstor login) – they discuss complete cleistogamy which addresses your last question. They report several completely CL species in their Table 1, and give references.
More generally, many different plant groups maintain balances of self-pollination and outcrossing (i.e. "real sex"), through an even more diverse set of mechanisms.
Even more generally, many plants and some animals maintain balances of sexual reproduction and clonal reproduction, through an even more diverse set of mechanisms. For instance, vegetative reproduction (e.g., strawberry runners) is very common in many plant groups; facultative and obligate parthenogenesis in animals also occurs.
Culley, Theresa M. and Matthew R. Klooster (2007). The Cleistogamous Breeding System: A Review of Its Frequency, Evolution, and Ecology in Angiosperms. Botanical Review. Vol. 73, No. 1, pp. 1-30
The following is multiple choice question (with options) to answer.
Angiosperm success is a result of two novel structures that ensure reproductive success: flowers and this? | [
"food",
"glass",
"fruit",
"ants"
] | C | Angiosperm success is a result of two novel structures that ensure reproductive success: flowers and fruit. Flowers allowed plants to form cooperative evolutionary relationships with animals, in particular insects, to disperse their pollen to female gametophytes in a highly targeted way. Fruit protect the developing embryo and serve as an agent of dispersal. Different structures on fruit reflect the dispersal strategies that help with the spreading of seeds. |
SciQ | SciQ-5884 | taxonomy, mammals, cladistics
Title: Why aren't mammals and reptiles considered amphibians? We've all heard it: birds descend from dinosaurs, so they're dinosaurs too. But this got me thinking: doesn't this mean that, for instance, all terrestrial vertebrates – including humans – are technically fish? A recent video by MinuteEarth and the Wikipedia article for "Fish" confirmed my shower thought hypothesis.
Interesting. But... all amniotes, i.e. reptiles (and, by extension, birds) and mammals, descend from amphibians, right? If so, then why aren't they considered amphibians too? Mammals and reptiles aren't considered amphibians, because amniotes are not hypothesized to descend from Amphibia. That is to say that Amphibia did not evolve into Amniota. They are sister clades (actually Reptiliomorpha in the Tree of Life tree below).
The following is multiple choice question (with options) to answer.
Squamata is the largest order of what broad animal group, and includes lizards and snakes? | [
"spiny fishes",
"amphibians",
"reptiles",
"mammals"
] | C | Lizards and snakes belong to the largest order of reptiles, Squamata. Lizards are a large group of reptiles, with nearly 5,000 species, living on every continent except Antarctica. Some places are just too cold for lizards. |
SciQ | SciQ-5885 | dna, gene-expression
Title: Complexity in creating transgenic animals (e.g., mice) Many papers I have seen describing transgenic rodent models (and presumably applicable to other model organisms) involve the knock-in, or modification to, a single gene, possibly two genes. With respect to recombineering techniques, what prevents targeting multiple genes in a single organism? For instance, if I wanted to simultaneously knock-in some genes and knock-out others within the same mouse, would I be forced to generate individually modified transgenic lines and then do some "fancy" breeding to generate the multiple-modified mice? One reason is the low likelihood of success. Modifying a gene almost always involves a recombination event of plasmid DNA with a target site in the genome (and I say almost just because there may be some method that I don't know about, but all the ones I'm familiar with do). The likelihood of that decreases exponentially with the number of genes you're trying to modify. If you're trying to make several mutants of individual genes the likelihood of success decreases only linearly.
Another reason is having more knowledge and experimental power. You can learn little from a double mutant if you don't also have the individual mutants to compare. In fact, most reviewers would ask for individual mutant data if you've made a double mutant in your paper. This is especially true with flies and worms, as crosses take less time with them.
Also, the more mutant genes you have, the weaker the animal. Your mutants may not be viable at all with too many mutations.
The following is multiple choice question (with options) to answer.
Animals that have been modified to express recombinant dna are called what? | [
"transgenic animals",
"aquatic animals",
"mammalian animals",
"reproducing animals"
] | A | Transgenic Animals Although several recombinant proteins used in medicine are successfully produced in bacteria, some proteins require a eukaryotic animal host for proper processing. For this reason, the desired genes are cloned and expressed in animals, such as sheep, goats, chickens, and mice. Animals that have been modified to express recombinant DNA are called transgenic animals. Several human proteins are expressed in the milk of transgenic sheep and goats, and some are expressed in the eggs of chickens. Mice have been used extensively for expressing and studying the effects of recombinant genes and mutations. |
SciQ | SciQ-5886 | thermodynamics, boundary-conditions, diffusion
Title: How to formulate a PDE for diffusion between two different materials? Suppose I have two (connected) materials with different diffusion coefficients for which I am modelling diffusion. Consider the one dimensional case. I am not sure what conditions to impose at the point where they are connected. Continuity of concentration makes sense. I am not sure what to impose in terms of the flux. Perhaps counter to intuition, the concentration is not necessarily continuous. Materials tend to segregate impurities to different degrees, and Nature here requires that matter is conserved, not concentration. When formulating the equations, this means that no matter can disappear: the outgoing flux from the left side must equal the incoming flux from the right side.
Thus, for a small* amount of dissolved C near an interface between A and B, for example, we would have
$$J_C|_{0^-}=-D_{CA}\left.\frac{\partial C_C(x)}{\partial x}\right|_{0^-}=-D_{CB}\left.\frac{\partial C_C(x)}{\partial x}\right|_{0^+}=J_C|_{0^+},$$
where $J$ is the flux, $0^-$ and $0^+$ ($=0$) are respectively the left and right sides of the interface, $D$ is the diffusivity of C in the host material, and $C_C$ is the concentration of C.
At steady state, it may also be useful to work with a segregation coefficient $K$ that expresses the equilibrium concentration of C in B, say, given a certain concentration of C in A:
$$KC_C|_{0^-}=C_C|_{0^+}.$$
One could also work with the solubility coefficient $\sigma_{C}$ and permeability $P_{C}=D_{C}\sigma_{C}$; see, for instance, Crank's Mathematics of Diffusion.
The following is multiple choice question (with options) to answer.
In a medium, the closer the distribution of the material gets to what state, the slower the rate of diffusion becomes? | [
"gas",
"elastic",
"erosion",
"equilibrium"
] | D | Each separate substance in a medium, such as the extracellular fluid, has its own concentration gradient, independent of the concentration gradients of other materials. Additionally, each substance will diffuse according to that gradient. Several factors affect the rate of diffusion. • Extent of the concentration gradient: The greater the difference in concentration, the more rapid the diffusion. The closer the distribution of the material gets to equilibrium, the slower the rate of diffusion becomes. • Mass of the molecules diffusing: More massive molecules move more slowly, because it is more difficult for them to move between the molecules of the substance they are moving through; therefore, they diffuse more slowly. • Temperature: Higher temperatures increase the energy and therefore the movement of the molecules, increasing the rate of diffusion. • Solvent density: As the density of the solvent increases, the rate of diffusion decreases. The molecules slow down because they have a more difficult time getting through the denser medium. |
SciQ | SciQ-5887 | biochemistry, cell-biology, metabolism, photosynthesis
Title: How are ions 'pumped' across a membrane during electron transport? A number of sites (including this one) that provide descriptions of photosynthesis state that high energy electrons 'pump' ions across a membrane. What is the actual 'pumping' mechanism? I've looked at Wikipedia and at a number of YouTube lectures/tutorials but so far have only found statements as to the where and when but not the how of this important process. Short answer:
Electrons flow through membranes by floating through kind of channels made out of iron-sulfur clusters.
Long answer:
Let's take a look at the electron transport chain in the inner mitochodrial membrane. There is a proton gradient across the membrane building up a potential difference by pumping protons across the membrane as electeons flow through the respiratory chain. They (electrons) like to flow throught the respiratory chain because they can go from enzyme to enzyme each with a lower standart free energy. These enymes together form one big complex within the inner membrane with Fe-S clusters enabeling electrons to flow through the membrane by giving them a kind of a power stroke (see here).
This as an simplyfied answer on a example.
The following is multiple choice question (with options) to answer.
When substances pass through the cell membrane without needing any energy what is it called? | [
"kinetic transport",
"passive transport",
"active transport",
"energetic transport"
] | B | Passive transport occurs when a substance passes through the cell membrane without needing any energy to pass through. This happens when a substance moves from an area where it is more concentrated to an area where it is less concentrated. Concentration is the number of particles of a substance in a given volume. Let's say you dissolve a teaspoon of salt in a cup of water. Then you dissolve two teaspoons of salt in another cup of water. The second solution will have a higher concentration of salt. |
SciQ | SciQ-5888 | inorganic-chemistry
Title: How do I derive metallic aluminum without electricity? I'm laying the foundation for a project called 21st Century steampunk, where I figure out what the world would look like if electricity was never discovered.
I'm wondering if it's possible to derive usable metallic aluminum from naturally occurring substances without using the Hall–Héroult process. One method, which would also require a non-electrical heating source, involves reduction with carbon. Given a high enough temperature -- meaning over 2000°C -- carbon carries off the oxygen as carbon monoxide and leaves the aluminum behind. See Ref. [1](https://doi.org/10.1016/j.energy.2007.06.002), which includes the equilibrium composition calculation below.
Reference
M.Halmann, A.Frei, A.Steinfeld (2007)."Carbothermal reduction of alumina: Thermochemical equilibrium calculations and experimental investigation". Energy 32, Issue 12, December 2007, Pages 2420-2427. https://doi.org/10.1016/j.energy.2007.06.002
The following is multiple choice question (with options) to answer.
Elements that do not need to conduct electricity are known as what? | [
"silicates",
"carbonates",
"alloys",
"nonmetals"
] | D | Nonmetals are elements that do not conduct electricity. They are the second largest class of elements. Nonmetals are also poor conductors of heat. The majority of nonmetals are gases. Solid nonmetals are dull and brittle. |
SciQ | SciQ-5889 | the-moon, earth, asteroids, impact, rogue-planet
Title: How well would the Moon protect the Earth from an Asteroid? Would the Earth fare better if the Moon blocked the meteor, comet, rogue planet, or otherwise rather than a direct impact? At what point would the Moon's debris would be an extinction event?
The limit of the impactor is the size, angle of attack, or composition in which to moon would no longer be of any protection. The Moon orbits the Earth from $\approx$ 380000 km, but its radius is only $\approx$ 3500 km. The sky has 41253 sq degrees, and the Moon covers only $\approx$ 0.25 sq degree from it.
Thus, the probability that an incoming meteor is blocked by the Moon, is $\approx$ 1:160000. Thus, the Moon is totally unfeasible to protect us from anything.
The debris would work like an "insurance": it will be more likely that some debris will finally end up on the Earth, but their summed damage will be likely negligible, compared to the meteor.
Note also, different meteors regularly cross the orbit of the Moon, but they have still a very small probability to hit us.
The following is multiple choice question (with options) to answer.
What does the moon not have to protect it from extreme temperatures? | [
"oxygen",
"oceans",
"atmosphere",
"metals"
] | C | The Moon has no atmosphere. With no atmosphere, the Moon is not protected from extreme temperatures. The average surface temperature during the day is approximately 107°C (225°F). Daytime temperatures can reach as high as 123°C (253°F). At night, the average temperature drops to -153°C (-243°F). The lowest temperatures measured are as low as -233°C (-397°F). |
SciQ | SciQ-5890 | antimatter, particle-physics
Title: Do particles and anti-particles attract each other? Do particles and anti-particles attract each other?
From the very basic understanding that they are created out of nothing mutually and collide to annihilate each other seems to indicate this happens due to an attraction.
Is it a measurable force?
Plus they are exactly alike except their opposite charge, which would indicate attraction, as this source indicates: http://www.thenakedscientists.com/forum/index.php?topic=36719.0 I'd like more information on this, if possible.
For the record, I'm speaking about them under the construct of time. If you ignore the construct of time, both particles could actually be considered the same particle, one moving backwards through "time" in a loop that occurs "once". Ignore this if you do not know what I'm talking about, or feel free to correct me on it.
From the very basic understanding that they are created out of nothing mutually and collide to annihilate each other seems to indicate this happens due to an attraction.
Why? this just means that if two of them are nearby, they can annihilate. Remember that particles are waves, and thus are quite spread out. They don't have to be directed to collide with each other using any kind of force, they just need to be near each other.
Plus they are exactly alike except their opposite charge
The following is multiple choice question (with options) to answer.
What happens between particles with opposite charges? | [
"they attract",
"they repel",
"they oppose",
"they become static"
] | A | When charged particles are close enough to exert force on each other, their electric fields interact. Particles with opposite charges attract each other. Particles with like charges repel each other. |
SciQ | SciQ-5891 | genetics, botany, senescence, telomere
Do Plants Get Cancer?
It seems to me the next obvious question. One of the first papers I came across (published in 1916 by the Journal of Cancer Research!) talks of Crown Gall in plants and its relation to human cancer (Smith, 1916). Many websites cite galls as being the equivalent to cancer in plants, but it appears that the outgrowths (galls) that appear very tumour-like are in fact caused by bacteria encouraging their surrounding cells to proliferate. (See this question for more detail on galls).
I later found an abstract (I cannot access the full paper) from a paper published in Nature in 2010 called “Walls around tumours — why plants do not develop cancer” (Doonan, 2010). It appears that Plants can and do develop tumours, but they are less frequent and less lethal due to fundamental differences in development between plant and animal cells. Singh and colleagues found that in 2 plant species (Arabidopsis and rice) there were DNA damage repair pathways well conserved but with variation; there were several gene duplications in different DNA repair pathways (Singh, 2010).
Plants Do Not “Age” As We Do
Although I could find no conclusive evidence, it seems to me likely that plants may also have enhanced maintenance against other cellular stresses than DNA damage, such as build-ups of aberrant proteins. It therefore appears that in a protected environment some plants could live indefinitely. I say some, because others deliberately end their lives after reproduction. Traits such as longevity are inherently hard to be selected for, as the advantages come long after reproductive maturity and are therefore under much less selective pressure.
We see plants wither and die, but this is because they are constantly subject to environmental insult. Animals and insects may eat them, there may not be enough food or water, or sunlight, or the plant may become infected. All of which are at the macroscopic level. Due to completely different evolutionary constraints and pressures plants are highly resilient to cellar stresses, possibly due to differences in metabolic rate, and apparently have indefinite replicative potential.
Edit:
The following is multiple choice question (with options) to answer.
Which generation of a plant is generally larger and longer-lived? | [
"dominant generation",
"alpha generation",
"effective generation",
"main generation"
] | A | One of the two generations of a plant’s life cycle is typically dominant to the other generation. Whether it’s the sporophyte or gametophyte generation, individuals in the dominant generation live longer and grow larger. They are the green, photosynthetic structures that you would recognize as a fern, tree, or other plant (see Figure below ). Individuals in the nondominant generation, in contrast, may be very small and rarely seen. They may live in or on the dominant plant. |
SciQ | SciQ-5892 | taxonomy, mammals, cladistics
Title: Why aren't mammals and reptiles considered amphibians? We've all heard it: birds descend from dinosaurs, so they're dinosaurs too. But this got me thinking: doesn't this mean that, for instance, all terrestrial vertebrates – including humans – are technically fish? A recent video by MinuteEarth and the Wikipedia article for "Fish" confirmed my shower thought hypothesis.
Interesting. But... all amniotes, i.e. reptiles (and, by extension, birds) and mammals, descend from amphibians, right? If so, then why aren't they considered amphibians too? Mammals and reptiles aren't considered amphibians, because amniotes are not hypothesized to descend from Amphibia. That is to say that Amphibia did not evolve into Amniota. They are sister clades (actually Reptiliomorpha in the Tree of Life tree below).
The following is multiple choice question (with options) to answer.
Mammals belong to which class of vertebrates? | [
"chondrichthyes",
"placoderms",
"agnathas",
"endothermic"
] | D | Mammals are a class of endothermic vertebrates. They have four limbs and produce amniotic eggs. Examples of mammals include bats, whales, mice, and humans. Clearly, mammals are a very diverse group. Nonetheless, they share many traits that set them apart from other vertebrates. |
SciQ | SciQ-5893 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
Animals that have feeding patterns that are somewhere between that of herbivores and carnivores can be called what? | [
"nematodes",
"megavores",
"omnivores",
"insectivores"
] | C | 34.1 | Digestive Systems By the end of this section, you will be able to: • Explain the processes of digestion and absorption • Compare and contrast different types of digestive systems • Explain the specialized functions of the organs involved in processing food in the body • Describe the ways in which organs work together to digest food and absorb nutrients Animals obtain their nutrition from the consumption of other organisms. Depending on their diet, animals can be classified into the following categories: plant eaters (herbivores), meat eaters (carnivores), and those that eat both plants and animals (omnivores). The nutrients and macromolecules present in food are not immediately accessible to the cells. There are a number of processes that modify food within the animal body in order to make the nutrients and organic molecules accessible for cellular function. As animals evolved in complexity of form and function, their digestive systems have also evolved to accommodate their various dietary needs. |
SciQ | SciQ-5894 | cell-biology, cell, eggs, reproductive-biology, chickens
Title: Why are hard boiled eggs so homogeneous? A eukaryotic animal cell is a complicated piece of biological machinery. Some major structures inside of the cell (see the image below) include: the nucleus, mitochondria, Golgi vesicles, and various tubular structures. Why then is the single-celled, unfertilized chicken egg so homogeneous when it is cooked (or before)? The only major structure I can recognize is the cell nucleus.
*Image Credit: "Animal cell structure en" by LadyofHats (Mariana Ruiz) - Own work using Adobe Illustrator. Image renamed from Image:Animal cell structure.svg. Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Animal_cell_structure_en.svg#mediaviewer/File:Animal_cell_structure_en.svg Disclaimer: This is my understanding of the egg anatomy as a general biologist. There is most certainly better references and sources out there to explain this (please add better references if you know of any).
If I understand you correctly, your question is why we do not see cell organelles in a cracked or boiled egg. If so, your question seems to stem from a misunderstanding of what the egg white and egg yolk represents. A chicken egg is not simply an enlarged cell, and the egg yolk is not the cell nucleus.
When an oocyte matures in the chicken ovary, it stores yolk inside the cell and therefore enlarges. The yolk is therefore part of the oocyte cytoplasm. However, as it enlarges, the yolk is separated from the germinal disc, which holds all the other cell organelles (including the nucleus). The germinal disc is seen as a small white area on the egg yolk. Eventually, when the oocyte has accumulated enought yolk, it disattaches from the ovary (ovulation) and goes into the hens oviduct. This process is happening continuously, and oocytes of different stages of maturation are present on the ovary, which can be seen in this image:
The following is multiple choice question (with options) to answer.
What organs produce eggs? | [
"glands",
"ovaries",
"kidneys",
"testes"
] | B | Like other female vertebrates, all female mammals have ovaries . These are the organs that produce eggs (see Figure below ). Therian mammals also have two additional female reproductive structures that are not found in other vertebrates. They are the uterus and vagina. |
SciQ | SciQ-5895 | organic-chemistry, reaction-mechanism
Title: Mechanism of SN1 reaction Let us say that we have water reacting with t-butyl chloride. When the chlorine atom departs we have a t-butyl cation which becomes an attractive substrate to the nucleophilic oxygen in water. My question is in the reaction that follows, does the hydrogen break off from water first allowing oxygen to attack the carbocation or does water immediately form a bond with the carbocation and then deprotinates the extra hydrogen? Surely there are both $\ce{H2O}$ and $\ce{OH-}$ which attacks the carbocation, as well as, heaven forbid, $\ce{H3O+}$ (and countless other species formed by the auto-ioniziation of water).
Usually textbooks record $\ce{H2O}$ as the attacker because it is much more abundant in the mixture.
After that, usually another $\ce{H2O}$ comes and take away the extra $\ce{H}$ with itself converting to $\ce{H3O+}$, but as I mentioned above, this step could also be done by $\ce{OH-}$ among many more species, but the concentration of those other species are too small that they are not worth mentioning.
PS: the last step can also be done by the product, i.e. t-butyl alcohol.
The following is multiple choice question (with options) to answer.
What kind of reaction adds water to an organic molecule and breaks the large molecule into smaller molecules? | [
"supplementation reaction",
"hydration reaction",
"heat reaction",
"aerobic reaction"
] | B | A hydration reaction is the opposite of a dehydration reaction. A hydration reaction adds water to an organic molecule and breaks the large molecule into smaller molecules. Hydration reactions occur in an acidic water solution. An example of hydration reaction is the breaking of peptide bonds in polypeptides. A hydroxide ion (OH - ) and a hydrogen ion (H + ) (both from a water molecule) bond to the carbon atoms that formed the peptide bond. This breaks the peptide bond and results in two amino acids. |
SciQ | SciQ-5896 | telescope, mars
Have a look at this guide explaining how consumer-grade computer webcams can be used. It contains a neat comparison of a single frame and a stacked image.
Please note that I'm merely speculating as to which techiniques could be used to obtain such images. I can see that the author posted their email on the S&T site and that there's a comments section as well. Feel free to ask them yourself.
The following is multiple choice question (with options) to answer.
How much larger can the most powerful light microscropes make an image? | [
"100 times",
"2000 times",
"10 times",
"500 times"
] | B | Light microscopes allow biologists to see small details of a specimen. Most of the microscopes used in schools and laboratories are light microscopes. Light microscopes use lenses, typically made of glass or plastic, to focus light either into the eye, a camera, or some other light detector. The most powerful light microscopes can make images up to 2,000 times larger. |
SciQ | SciQ-5897 | thermodynamics, everyday-life, cooling, humidity
This is actually a very good question. There appears to be two competing factors involved. Evaporative cooling due to transpiration from the trees cools the air, increasing heat transfer away from the skin making it feel "cooler". But at the same time you would think transpiration increases the humidity in the air, potentially interfering with evaporative cooling of skin perspiration, making you feel "warmer"
The fact that you experienced "cool" rather than "warm" suggests to me that the relative humidity (RH) of the air was low at the time, so that it was capable of absorbing the moisture and cooling the air without significantly raising the RH under the tree to interfere with evaporation of skin perspiration, thus making you feel "cool".
If the RH was high, particularly at or near saturation (100%), transpiration evaporation from the tree, and its cooling effect, ceases. Likewise, evaporative cooling of perspiration ceases, both of which would make you feel "warm". For more information on transpiration of plant, see: https://www.polygongroup.com/en-US/blog/how-humidity-affects-the-growth-of-plants/
Bottom line: The higher the RH the warmer you will feel, whether you are under a tree or not.
Hope this helps.
The following is multiple choice question (with options) to answer.
In mammals, air is warmed and humidified in what? | [
"lungs",
"stomach",
"esophagus",
"nasal cavity"
] | D | 16.3 Circulatory and Respiratory Systems Animal respiratory systems are designed to facilitate gas exchange. In mammals, air is warmed and humidified in the nasal cavity. Air then travels down the pharynx and larynx, through the trachea, and into the lungs. In the lungs, air passes. |
SciQ | SciQ-5898 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
What is the specialized tissue that transports water and nutrients throughout the plant and allows these plants to grow taller? | [
"dioxide tissue",
"vascular tissue",
"blood vessels",
"fiber tissue"
] | B | For these plants, the name says it all. Vascular seedless plants have vascular tissue but do not have seeds. Remember that vascular tissue is specialized tissue that transports water and nutrients throughout the plant. The development of vascular tissue allowed these plants to grow much taller than nonvascular plants, forming ancient swamp forests. Most of these large vascular seedless plants are now extinct, but their smaller relatives still remain. Vascular tissue includes xylem, which transports water from the roots to the rest of the plant; and phloem, which transports sugars and nutrients from the leaves throughout the plant. |
SciQ | SciQ-5899 | acoustics, applied-physics, medical-physics, instrument
Title: How does ultrasound imaging localize points in the $x$-$y$ plane? Lots of sources describe how ultrasound imaging uses the time differences between wave emission and reception to calculate distances to points in the body. This makes sense for how localization works in the $z$-direction. But how does it localize points in the $x$-$y$ plane, forming a detailed 2D image? The ultrasound transducer transmits a very short focused pulse (less than a mm in width--and also in length) say at a 45 degree angle to the transducer face and then records the echoes as a function of time. Each recorded echo becomes an image pixel. It then repeats this at say a 44.5 degree angle, next a 44 degree angle, ect... until it has scanned out a pie shaped slice image into the body.
But how does it localize points in the x-y plane, forming a detailed
2D image?
Typically the transducer is a phased array and the pulsed beam is formed by adjusting the delays between array elements before pulsing the scan head when transmitting, or before summing the echoes together when receiving. (Goggle: beam forming and phased arrays)
The following is multiple choice question (with options) to answer.
What is the term for the method of sending out ultrasound waves to determine the locations of objects? | [
"morphology",
"catabolism",
"echolocation",
"magnetism"
] | C | Animals such as bats and dolphins send out ultrasound waves and use their echoes, or reflected waves, to identify the locations of objects they cannot see. This is called echolocation. Animals use echolocation to find prey and avoid running into objects in the dark. You can see in the Figure below and also at the following URL how a bat uses echolocation to find insect prey. http://www. bsos. umd. edu/psyc/batlab/headaimmovies/nsf_challenge/nsf4. wmv. |
SciQ | SciQ-5900 | genetics, human-genetics, allele
But some illnesses are carried by dominant alleles (from the same article):
Other disorders, such as Huntington disease, occur when an individual inherits only one dominant allele.
My questions are:
How does harm from alleles correlate with their recessiveness? Generally speaking, do harmful alleles tend to be more recessive?
How does benefits from alleles correlate with their dominance? Generally speaking, do "beneficial" alleles tend to be more dominant? Instead of dividing mutations into two classes, dominant vs. recessive, consider categorizing them into classes based on how the mutation affects the gene--or the gene product. This yields loss-of-function (lf) alleles, that reduce the activity of the gene, or its product, and gain-of-function (gf) alleles that act as if they somehow increase the activity of the gene, or its product.
The logic underlying this classification was described in this classic reference: Muller, H. J. 1932. Further studies on the nature and causes of gene mutations. Proceedings of the 6th International Congress of Genetics, pp. 213–255. Since this was before DNA had been shown to be the genetic material his arguments are based solely on the phenotype of animals carrying various combinations of chromosomes. In particular he relies on genetic duplications and deficiencies (or deletions). In this nomenclature + indicates a chromosome carrying a wild-type (wt) allele of the gene, and m indicates a chromosome carrying a mutant allele of the gene. So if an +/m animal appears Wild-Type then that allele is recessive. Similarly, if an +/m animal has a Mutant phenotype then the allele is dominant.
There are two types of lf alleles:
The following is multiple choice question (with options) to answer.
In autosomal dominant inheritance only one "affected" what is necessary to result in an "affected" phenotype? | [
"cells",
"allele",
"molecule",
"trait"
] | B | Autosomal Dominant Inheritance. Only one “affected” allele is necessary to result in the “affected” phenotype. For a genetic disease inherited in this manner, only one mutant allele is necessary to result in the phenotype. Achondroplasia (discussed later) is an example of a dominant disorder. Both homozygous and heterozygous individuals will show the phenotype. Homozygous achondroplasia is usually a lethal condition. |
SciQ | SciQ-5901 | cell-division
Title: Are free-nuclear division and endomitosis the same? As far as I understood it, both are cases of karyokinesis, not followed by cytokinesis. No. If you google the terms you'll get a lot of sites with definitions. For example:
Nuclear division
Definition
noun
The process by which a nucleus divides, resulting in the segregation of the genome to opposite poles of a dividing cell.
source: http://www.biology-online.org/dictionary/Nuclear_division
Edit:
or
free nuclear division mitotic division of nuclei without accompanying cytokinesis, i.e. nuclei divide in a common cytoplasm, the cells walls only forming around each later
source: http://ecflora.cavehill.uwi.edu/bio_courses/bl14apl/Gloss.htm
versus
endomitosis
mitosis taking place without dissolution of the nuclear membrane, and not followed by cytoplasmic division, resulting in doubling of the number of chromosomes within the nucleus.
source: http://medical-dictionary.thefreedictionary.com/endomitosis
or a bit more revealing:
Duplicated chromosomes produced by endomitosis exist as discrete units
in a single polyploid nucleus or may be packaged into separate nuclei,
depending on the phase at which mitosis is aborted
source: http://en.wikipedia.org/wiki/Endoreduplication
So as you see by definition nuclear division is part of a bigger process (cell division), and accoriding to the first source karyokinesis is a synonim for nuclear division (karyo = nucleus kinesis = moving, both come form greek language).
Edit:
If you check the definition above, you can see that free-nuclear division is a mitosis without cytokinesis, thus chromosome separation still occurs.
In endomitosis the can end up with a polyploid nucleus, in contrast to the other two aforementioned mechanism where no polyploidy occurs.
The following is multiple choice question (with options) to answer.
When the nucleus divides, the two chromatids that make up each chromosome separate from each other and move to opposite poles of the cell during this process? | [
"mitosis",
"cytokinesis",
"meiosis",
"spawning"
] | A | During mitosis , when the nucleus divides, the two chromatids that make up each chromosome separate from each other and move to opposite poles of the cell. This is shown in Figure below . You can watch an animation of the process at the following link: http://www. biology. arizona. edu/Cell_bio/tutorials/cell_cycle/MitosisFlash. html . |
SciQ | SciQ-5902 | atmosphere, atmosphere-modelling, air-pollution, air-quality
Title: Why are "ground level" air quality monitors really on rooftops? There are many papers that talk about the air quality at ground-level in cities, observed by air quality monitors. Some monitors are located above the building(not actually on the ground). For example, my lab's equipment was located on the 5th floor of the building (~ 15m).
My questions are:
Is it appropriate to represent air quality using measurement data on a building roof?
What's the difference between air quality on the ground & the roof? And what matters? In order to put your question in perspective, you need to consider atmospheric mixing and the size of the system you are curious about. The troposphere is several kilometers thick and the mixed layer of atmosphere above the ground can occupy a significant fraction of the troposphere. Granted, during cold events, the temperature of the air can be so cold that the lack of convective motion creates a very shallow (e.g. 10s of meters) mixing layer. Though, 15 meters above the ground will virtually always be within the mixed layer near the ground, despite cold weather events.
Some people do measure air quality at the ground level, but it is generally done in the context of studying biogenic emissions (e.g. soil emissions or below-canopy tree emissions). However, those are special field studies, which have different objectives than typical air quality monitor sites.
Typical air quality monitor sites are relatively sparse, and even large cities have just a few monitors. Generally, monitors are located in such a way that they are observing well mixed air, so that it represents air quality in the region. It is imperative that you put your air quality monitor high enough above the ground so that it isn't being directly influenced by emission sources (e.g. your neighbors wood stove, or a car's tailpipe). Otherwise, if you put the monitor literally on the ground, you will often be observing much more variance, with higher peaks that represent that specific location only. See this post for more info on how monitor locations are selected. You can also see this EPA handbook on siting monitors which notes:
The following is multiple choice question (with options) to answer.
What is the layer above the troposphere? | [
"troposphere",
"stratosphere",
"mesosphere",
"thermosphere"
] | B | The stratosphere is the layer above the troposphere. Temperature increases with altitude in this layer. The ozone layer occurs here. |
SciQ | SciQ-5903 | biochemistry, metabolism
The second system, glycolysis, simply refers to the breakdown of carbohydrates (e.g. glucose) to resynthesize ATP from the energy stored in those carbohydrates. Your muscles contain a buffer of glycogen, approx. 300~ gr for the average Joe (give or take). The glycogen can be broken down to glucose-6-phosphate, which can then enter glycolysis. The glucose-6-phosphate is broken down to 2 pyruvate and yields 3 ATP netto (2 when derived from glucose, rather than glycogen, due to a first enzymatic step which requires 1 ATP). The enzymatic steps of glycolysis are controlled by ATP, AMP, ADP and other factors, factually integrating the energy status of the muscle (primarly through allosteric regulation of enzymes, especially phosphofructokinase).
The third system, the oxidative system, refers to the breakdown of carbohydrates and fatty acids, requiring oxygen to 'burn' them (citric acid cycle). The yield of this is much higher than for glycolysis, but the process is way slower.
In essence, all are regulated by the concentration of substrates and products, as well as through allosteric regulation (binding of a molecule at a different site, inhibiting or activating the enzyme, often by intermediates of the pathways themselves). Additionally, there is some long-term regulation through gene expression (e.g. up- or down-regulating expression of genes involved in these pathways), mostly by hormones.
Edit:
Well, I guess this is described in any basic biochemistry book (I'm very fund of the book 'Fundamentals of Biochemistry: Life at the Molecular Level'). If you want to see a description of these energy systems in a more exercise related context (since you were aiming at myocytes) I suggest reading Strength and Condition: Biological Principles and Practical Applications from Marco Cardinale et al., and the NSCA book Essentials of Strength and Conditioning.
The following is multiple choice question (with options) to answer.
Which system consists of organs that break down food and absorb nutrients such as glucose? | [
"circulatory system",
"excretory system",
"digestive system",
"urinary system"
] | C | The digestive system consists of organs that break down food and absorb nutrients such as glucose. Organs of the digestive system are shown in Figure below . Most of the organs make up the gastrointestinal tract. The rest of the organs are called accessory organs. |
SciQ | SciQ-5904 | telescopes, camera, sensor
The pupil of an eyepiece lies in the pupil plane, as the name suggests. Its size does not affect magnification. If it becomes smaller than the projected pupil of the telescope however it limits the aperture, because light from the telescope is lost. This changes the f-number and basically reduces the brightness of the images. The magnification is however affected by the eyepiece's focal length, and with it its distance to the focal plane of the telescope.
The CCD/CMOS detector is positioned in a focal plane. Its size limits the field of view of the telescope (the size of the patch of sky that you can see). Its size does not affect the magnification.
Besides aperture, magnification and field of view, a telescope is also characterized by its resolution. For an ideal telescope (diffraction limited), the resolution is limited by the wavelength of the light and its pupil diameter $D$ (Rayleigh criterion). The resolution of the CCD chip, i.e. its pixel size, has to be designed correctly to sample the telescopes resolution correctly.
The following is multiple choice question (with options) to answer.
What part of the eye controls the size of the pupil? | [
"debis",
"lens",
"avis",
"iris"
] | D | The iris is the colored part of the eye. It controls the size of the pupil. |
SciQ | SciQ-5905 | dna, radiation
Title: How do electrons destroy DNA bonds in radiation? Malignant tumors can be treated by radiation therapy. Most commonly it's radiotherapy with photons, or protons and so on. The common denominator for both types is that the radiation creates electrons inside the body via different effects.
What I haven't quite understood is how these electrons destroy the DNA bonds in the tumor and how this aids in killing off the cancer cells? Is it due to the generation of heat, or otherwise? I think you have a fundamental misunderstanding of the chemical reactions involved in radiation therapy. Neither photon based or proton based therapies "create electrons", but they do cause ionization by adding enough energy to existing electrons around atoms so that the electron is ejected from the atom, creating an ion or free radical, which can then undergo chemical reaction.
Photons, typically gamma rays, X-rays, and high energy UV, typically interact with water molecules and produce free radicals, including the dangerous hydroxyl radical. The hydroxyl radical can interact with proteins and DNA and damage those molecules, but has a very short half-life. Molecular oxygen can help increase the damage by reacting with the hydroxyl radical to produce Reactive Oxygen Species, ROS, which can also damage DNA or protein. However, many tumors have low oxygen concentration that reduces the effectiveness of photon based radiation therapy.
To overcome this, many patients receive proton based radiation therapy. Protons are much heavier than photons (I guess infinitely heavier than a photon, since photons have no mass) and therefore scatter to a much smaller extent. They just sort of plow through tissue and knock electrons out of orbitals as they collide with molecules such as DNA or protein. They don't rely so much on free radical generation or ROS, so low oxygen levels don't reduce their effectiveness.
The goal is damage the DNA to induce double strand breaks which are hard to repair in fast growing cancer cells. Because they grow so quickly, they are already stressed and their DNA repair machinery is less effective than in healthy cells. If their DNA can be sufficiently damaged, the cell will die.
For more information about these processes, please see these wikipedia articles on Radiation Therapy, Radiolysis, Linear Energy Transfer, and Free Radical Damage to DNA.
The following is multiple choice question (with options) to answer.
Depending on a tumor’s location, for example, cancer surgeons may be unable to remove it. radiation and chemotherapy are difficult, and it is often impossible to target only the cancer cells. the treatments inevitably destroy this? | [
"healthy cells",
"fertility",
"carcinogens",
"host cells"
] | A | Cancer treatments vary depending on the disease’s type and stage. Traditional approaches, including surgery, radiation, chemotherapy, and hormonal therapy, aim to remove or kill rapidly dividing cancer cells, but these strategies have their limitations. Depending on a tumor’s location, for example, cancer surgeons may be unable to remove it. Radiation and chemotherapy are difficult, and it is often impossible to target only the cancer cells. The treatments inevitably destroy healthy tissue as well. To address this, researchers are working on pharmaceuticals that can target specific proteins implicated in cancer-associated molecular pathways. |
SciQ | SciQ-5906 | particle-physics, elements
Title: Is it possible to create a new element that doesn't exist in the universe? When I say something new I do not refer to something already made like H,O etc and when I mean something new I do not refer to a transformation like tritium to helium and gold.
If so how ?(I mean is there a specific way to do that ?) Yes, so far, 20 synthetic elements have been created, with atomic numbers 99 (Einsteinium) to 118 (Ununoctium). All these elements are unstable, with half-lives ranging from a year to a few milliseconds.
You can find a list on wikipedia. These elements are produced in specialized nuclear reactors, by bombarding heavy elements like Uranium and Plutonium with neutrons or other elements.
The following is multiple choice question (with options) to answer.
Sodium is an example of what sort of thing that cannot exist by itself in nature? | [
"element",
"compound",
"aspect",
"concept"
] | A | Most of the elements we know about do not exist freely in nature. Sodium cannot be found by itself (unless we prepare it in the laboratory) because it interacts easily with other materials. On the other hand, the element helium does not interact with other elements to any extent. We can isolate helium from natural gas during the process of drilling for oil. |
SciQ | SciQ-5907 | homework-and-exercises, electricity, energy, forces, renewable-energy
Title: Small scale water power, how does water volume and hight convert into electric energy? I was playing a little bit with the basic physics behind water power production but I can't get the numbers right.
Let's say that I put a windmill that pumps water into a watertank on the top of my house,
then I connect some kind of pipe with generator and starts to drain the watertank.
How much electric power (kWh) can I get out from a watertank with size $X\text{ m}^3$ placed $Y\text{ m}$ above the ground?
How does the formulas look like?
Let's put some numbers on this problem, and see where we end up:
Let's say the tank is $1\text{ m}^3$, and it is $10\text{ m}$ off the ground so the water will fall $10\text{ m}$ to the generator.
Let's connect the generator with a standard garden hose that has a 1 inch diameter,
with an area of $2.54\text{ cm}/(2\pi) \sim 5.1\text{ cm}^2$.
And then I guess we would get a $10\text{ m}$ column of water pressure, that could be transformed with the area into the force the hight is putting on the system. Something like the earths gravity (9.82)*density*height = 9.82*1*10 ~ 98 Newton (???).
And then maybe use that we can find that pressure=Force/Area, but how to move from pressure to energy?
The following is multiple choice question (with options) to answer.
What type of resource is water power? | [
"nonrenewable",
"biological",
"renewable",
"geothermal"
] | C | Water power does not burn a fuel. So it causes less pollution than many other kinds of energy. Water power is also a renewable resource. Water keeps flowing downhill. Although we use some of the energy from this movement, we are not using up the water. |
SciQ | SciQ-5908 | botany, terminology, fruit
Title: What is the name of this part in plants, fruits, vegetables? What is the name of this part of the plant, fruit, vegetable? The thing that the plant is connected with the tree and gets nutrients with? The part we usually cut out when eat fruit.
Examples below
Papaya
Banana
Mango 'Stalk' or 'pedicel' would be an appropriate term (see, for example, this paper or this one). Specifically, you could say 'terminal part of the stalk/pedicel', though I don't know if there is a word for that.
Note that the term pedicel is commonly used for the stalk of a flower; it makes sense to use it for fruits too as they are derived from flowers.
The following is multiple choice question (with options) to answer.
Which part of the plant is responsible for seed production? | [
"pistil",
"flower",
"root",
"leaf"
] | B | |
SciQ | SciQ-5909 | meteorology, atmosphere, carbon, co2, rain
Bear in mind that this assumes an enormous rainfall intensity, 100% CO2 saturation of the water and equilibrium chemical dynamics. After the raindrops hit the ground at least half of it will immediately re-evaporate back into the air, leaving, at absolute most, about 3% of the atmospheric CO2 leached out of the atmosphere that will be available to react with the soil, rock or biosphere. Also consider that this is but one of several important processes affecting CO2 transience, such as photosynthesis, respiration, volcanism, industrial pollution, etc. So the CO2 estimates that you read about are average values. Advection and turbulent air mixing should ensure that the CO2 regains approximately normal concentration within an hour or two after rainfall.
The following is multiple choice question (with options) to answer.
The two main agents of soil erosion are water and what else? | [
"humidity",
"steam",
"glaciers",
"wind"
] | D | The main agents of soil erosion are water and wind. |
SciQ | SciQ-5910 | mycology
Title: How do fairy rings propagate? It was somewhat new to me that mushrooms usually aren't individual organisms, but are merely the visible bodies of a bunch of fungi living in the soil. I know that mushrooms emit spores to reproduce, but what has been bizarre to me is how fairy rings form. Why do the fruiting bodies arrange themselves in a more or less circular shape, as opposed to the random scattering one would expect from wind-borne spores? When a fungal spore germinates in a suitable location, the growing mycelium will spread underground in all directions. In the ideal situation, the result is that the mycelium will become circular. Over time, the center of the mycelium will die out whereas the newly formed mycelium (underground) will develop the familiar mushrooms above ground and this will result in a fairy ring.
The following is multiple choice question (with options) to answer.
What do aggregate fruits like raspberries form from? | [
"germinoles fused together",
"carpels fused together",
"chloroplast fused together",
"follicles fused together"
] | B | Figure 32.22 There are four main types of fruits. Simple fruits, such as these nuts, are derived from a single ovary. Aggregate fruits, like raspberries, form from many carpels that fuse together. Multiple fruits, such as pineapple, form from a cluster of flowers called an inflorescence. Accessory fruit, like the apple, are formed from a part of the plant other than the ovary. (credit "nuts": modification of work by Petr Kratochvil; credit "raspberries": modification of work by Cory Zanker; credit "pineapple": modification of work by Howie Le; credit "apple": modification of work by Paolo Neo). |
SciQ | SciQ-5911 | nomenclature, ions
Title: Why Ca 2+ and not Ca +2 I have been learning chemistry for a year or two but I still can't understand this. According to maths we should place the plus or minus sign in front of a number like -2. However, In chemistry we always put the sign behind a number when writing ions like $\ce{Ba^2+}$ ,$\ce{Cu^2+}$, $\ce{O^2-}$ etc. So, I want to know why do we write it that way? Chemistry has an organization called the International Union of Pure and Applied Chemistry (IUPAC), which sets standards for nomenclature (among other things). Chemists usually follow its recommendations.
IUPAC says
Ionic charge is indicated by means of a right upper index, as in $\ce{A^n+}$ or $\ce{A^n-}$ (not $\ce{A^$+n$}$ or $\ce{A^$-n$}$).
and
The ionic charge number is denoted by a right superscript, by the sign alone when the charge number is equal to plus one or minus one.
...
$\ce{Al^3+}$ is commonly used in chemistry and recommended by [74 = see quote above]. The forms $\ce{Al^$+3$}$ and $\ce{S^$-2$}$, although widely used, are obsolete [74], as well as the old notations $\ce{Al^{+++}}$, $\ce{S^=}$, and $\ce{S^{--}}$.
No reason is given, but you'll find a historical account of sign conventions for charge and a defense of IUPAC's choice in this article. He says,
The following is multiple choice question (with options) to answer.
What kind of ions are named by adding the suffix -ide to the end? | [
"particular ions",
"similar ions",
"negative ions",
"positive ions"
] | C | By gaining an electron, the chlorine atom becomes a chloride ion. It now has more electrons than protons and a charge of -1. Negative ions are named by adding the suffix – ide to the first part of the element name. The symbol for chloride is Cl - . |
SciQ | SciQ-5912 | resources, soil
Title: Is soil a renewable resource? My geology textbook tells me that soil is not renewable, and I agree with this, but there was some question in my class as to whether this is true.
Some soils take more than a human lifetime to regenerate. However, in crop production, it seems as if soil can be regenerated with additives.
In the scientific community of soil scientists, is soil considered a renewable resource by most of those scientists? Is there strong evidence to support this? Soil is an interesting case because although it is non-renewable (at any useful rate) as a 'bulk material' once removed from the ground, the nutrient content of soil can be renewed with fertilizers.
What a soil-scientist would understand as 'soil' is ultimately produced from the physical and chemical breakdown of solid bedrock at the base of the soil horizon. The rate at which this happens for natural soil production can vary substantially depending on the climatic conditions and other factors, but typically could range from 0.1 to 2.0 mm/yr.
In many intensively farmed regions, (top)soil is being removed by erosion much faster than it is being replaced by natural process. Removal of vegetation cover is enough to expose bare soil to rainsplash erosion at rates much greater than it is renewed. Once soil is bare, it becomes much more susceptible to erosion.
I think the additives you are referring to replenish the nutrient content of the soil, and not the the bulk material that would be produced by bedrock decomposition. With careful management, the fertility of existing soil can be maintained. But if the soil is allowed to be washed off or erode, for all practical purposes, the rate of replenishment is not fast enough for it to be classed as renewable in that sense.
This site has links to more aspects surrounding this issue.
The following is multiple choice question (with options) to answer.
These resources can be remade quickly, through natural processes | [
"non-renewable",
"fossil fuel",
"renewable",
"electric"
] | C | From a human point of view, natural resources can be classified as either renewable or nonrenewable. Renewable resources, such as sunlight and living things, can be remade quickly by natural processes. Nonrenewable resources, such as fossil fuels and soil, cannot be remade or else take millions of years to remake. |
SciQ | SciQ-5913 | inorganic-chemistry
Read this well written Wikipedia article: https://en.wikipedia.org/wiki/PH#cite_note-2
The following is multiple choice question (with options) to answer.
Inorganic chemical compounds can be broadly classified into two groups: ionic compounds and which other group? | [
"electromagnetic compounds",
"atomic compounds",
"molecular compounds",
"cellular compounds"
] | C | Inorganic chemical compounds can be broadly classified into two groups: ionic compounds and molecular compounds. The structure of all ionic compounds is an extended three-dimensional array of alternating positive and negative ions. Since ionic compounds do not take the form of individual molecules, they are represented by empirical formulas. Now we will begin to examine the formulas and nomenclature of molecular compounds. |
SciQ | SciQ-5914 | taxonomy, mammals, cladistics
Title: Why aren't mammals and reptiles considered amphibians? We've all heard it: birds descend from dinosaurs, so they're dinosaurs too. But this got me thinking: doesn't this mean that, for instance, all terrestrial vertebrates – including humans – are technically fish? A recent video by MinuteEarth and the Wikipedia article for "Fish" confirmed my shower thought hypothesis.
Interesting. But... all amniotes, i.e. reptiles (and, by extension, birds) and mammals, descend from amphibians, right? If so, then why aren't they considered amphibians too? Mammals and reptiles aren't considered amphibians, because amniotes are not hypothesized to descend from Amphibia. That is to say that Amphibia did not evolve into Amniota. They are sister clades (actually Reptiliomorpha in the Tree of Life tree below).
The following is multiple choice question (with options) to answer.
Fish are a diverse and interesting group of organisms in what sub-phylum? | [
"invertebrates",
"organelles",
"vertebrates",
"mammals"
] | C | If the word fish makes you think of cute little goldfish in a tank, check out the anglerfish pictured in Figure below . It’s also called a black sea devil. Surprisingly, goldfish and angler fish aren’t all that different from each other as far as fish diversity goes. Both fish are placed in the same fish class. Clearly, fish are a diverse and interesting group of vertebrates. |
SciQ | SciQ-5915 | human-biology, neuroanatomy, sex, neurology
Title: How spinal cord play its roles in human beings sex? I know most people can't enjoy sex if their spinal cord injured.
How spinal cord play its roles in human beings sex? One of the major functions of the spinal cord is to serve as a "highway" for signals to travel between the brain and the sensory (and motor) organs. Thus, sensory the signals that are generated on the body during sex must travel up through the spinal cord in order to get to the brain, where it will be processed into a pleasurable sensation. If the spinal cord is damaged, the signals will not be able to reach the brain and thus there will be no generation of pleasurable sensations.
Here's an image that shows the general sensory pathways. You can see they travel from the sensory organ to the spinal cord, and up it to the brain.
The following is multiple choice question (with options) to answer.
Spinal cord injuries are notoriously difficult to treat because spinal nerves do not do what? | [
"regenerate",
"cartilage",
"cover",
"moisture"
] | A | Two planets are on a collision course, heading directly towards each other at 0.250c . A spaceship sent from one planet approaches the second at 0.750c as seen by the second planet. What is the velocity of the ship relative to the first planet? 28. When a missile is shot from one spaceship towards another, it leaves the first at 0.950c and approaches the other at ships?. |
SciQ | SciQ-5916 | 1)the average velocity,Average Velocity =(" Total Displacement ")/(" Total Time ")Average Velocity =(d(b)-d(a))/(b-a)2)we ... See the full answer
The following is multiple choice question (with options) to answer.
The ratio of displacement to time interval is the average what? | [
"speed",
"direction",
"velocity",
"acceleration"
] | C | The velocity of an object can be found from a position vs time graph. On a position vs time graph, the displacement is the vertical separation between two points and the time interval is the horizontal separation. The ratio of displacement to time interval is the average velocity. This ratio is also the slope of the line. Therefore, the slope of the straight line is the average velocity. For the motion pictured above,. |
SciQ | SciQ-5917 | python, template, tkinter, gui, factory-method
Title: Python - Tkinter - periodic table of chemical elements Inspired by a question on StackOverflow I decided to code a GUI that is simple, efficent and can be used in other projects as well. I wanted to share this code since it probably is usefull to other people as well. You may want to share some practical hints how to make this code even better.
The code produces a table of frames and shows the information, I did gather for about 5 hours from wikipedia, in the final output. The frames are made clickable to make the usecase wider then without. I hope you enjoy this bit of code.
Database:
symbols = ['H','He','Li','Be','B','C','N','O','F','Ne',
'Na','Mg','Al','Si','P','S','Cl','Ar','K', 'Ca',
'Sc', 'Ti', 'V','Cr', 'Mn', 'Fe', 'Co', 'Ni',
'Cu', 'Zn', 'Ga', 'Ge', 'As', 'Se', 'Br', 'Kr',
'Rb', 'Sr', 'Y', 'Zr', 'Nb', 'Mo', 'Tc', 'Ru',
'Rh', 'Pd', 'Ag', 'Cd', 'In', 'Sn', 'Sb', 'Te',
'I', 'Xe','Cs', 'Ba','La', 'Ce', 'Pr', 'Nd', 'Pm',
'Sm', 'Eu', 'Gd', 'Tb', 'Dy', 'Ho', 'Er', 'Tm',
'Yb', 'Lu', 'Hf', 'Ta', 'W', 'Re', 'Os', 'Ir',
'Pt', 'Au', 'Hg', 'Tl', 'Pb', 'Bi', 'Po', 'At', 'Rn',
The following is multiple choice question (with options) to answer.
What is the modern periodic table based on? | [
"element mass",
"metallic number",
"element density",
"atomic number"
] | D | The modern periodic table is based on atomic number. Elements in each period go from metals on the left to metalloids and then nonmetals on the right. Within groups, elements have similar properties. |
SciQ | SciQ-5918 | quantum-mechanics, quantum-information, superposition
When the compass needle points north, that is like a qubit being in the state $\lvert 0\rangle$, and when the compass needle points east, that is like a qubit being in the state $\lvert 1\rangle$. But a compass needle can also point northeast. The direction northeast is neither north nor east, but it is a superposition of equal parts north and east: if you add a north-pointing vector and an east-pointing vector of equal magnitude, you will get a vector that points northeast. Similarly, the qubit state $\frac{1}{\sqrt{2}}(\lvert 0\rangle + \lvert 1\rangle)$ is neither $\lvert 0\rangle$ nor $\lvert 1\rangle$, but it is a superposition of equal parts $\lvert 0\rangle$ and $\lvert 1\rangle$.
The following is multiple choice question (with options) to answer.
The needle of a compass is made of what element? | [
"aluminum",
"nickel",
"iron",
"tin"
] | C | Calsidyrose. The needle of a compass is made of the element iron . CC BY 2.0. |
SciQ | SciQ-5919 | dna, homework, transcription, translation
Title: How to find the amino acid in the DNA protein 3' A T A G T A C C G C A T G T A C G G G C G A G A C A T T C G A G C A T T C A T 5'
This a Template DNA.
How to find the number of amino acids amino acids in the protein encoded by the above gene?
The answer is $7$.
My Try:
First I converted the above DNA to RNA and got
5' U A U C A U G G C G U A C A U G C C C G C U C U G U A A G C U C G U A A G U A 3'
Then I found the start codon which is A U G
5' U A U C |A U G| G C G U A C A U G C C C G C U C U G U A A G C U C G U A A G U A 3'
From here I am not understanding how to proceed.
Can anyone please explain how to solve this? Then you just have to read the codon until you reach a stop codon. There are three stop codon UAA, UGA and UAG. So, in your example..
Start Stop
5' U A U C | A U G | G C G | U A C | A U G | C C C | G C U | C U G | U A A | G C U C G U A A G U A 3'
Your protein is therefore 7 amino acids long (incuding the starting methionine). The genetic code is
Therefore the 7 amino acids are
Met Ala Tyr Met Pro Ala Leu
In case you are confused about having an AUG codon in the middle of an open reading frame, then you should have a look at the post Effect of a doubling of the start codon in a gene.
Of course, I assumed that the region is indeed transcribed and that the first AUG is indeed the start codon and not just a methionine in the middle of an open reading frame.
The following is multiple choice question (with options) to answer.
What is the process in which the genetic code in mrna is read to make a protein called? | [
"splicing",
"expression",
"modification",
"translation"
] | D | Translation is the second part of the central dogma of molecular biology: RNA → Protein . It is the process in which the genetic code in mRNA is read to make a protein. Figure below shows how this happens. After mRNA leaves the nucleus, it moves to a ribosome, which consists of rRNA and proteins. The ribosome reads the sequence of codons in mRNA. Molecules of tRNA bring amino acids to the ribosome in the correct sequence. |
SciQ | SciQ-5920 | proteins
Title: Speed of protein conformational change? Although the speed may vary a lot based on factors like protein size/scale of conformational change/type of changes (small block change/arm movement,etc), are there examples of experimental results of time scale of such processes? (Only a single conformational change is considered i.e. the time delay between the begain and the end of a single conformational change event of a single protein (or subunit to be more precise?) ) This paper uses "ultrafast 2D-IR vibrational echo chemical-exchange spectroscopy" to track switching between different protein conformations and finds that they take place on the order of 50 pico-seconds ($ 1 \times 10^{-12} $ seconds). Another paper finds something similar but notes that full equilibriation can take on the order or nanoseconds:
Although the main conformational change of the backbone is completed after only 20 ps, the subsequent equilibration in the new region of conformational space continues for times >16 ns.
The following is multiple choice question (with options) to answer.
What type of protein speeds up chemical reactions in cells? | [
"hemoglobin",
"lipids",
"collagen",
"enzyme"
] | D | Proteins are an essential part of all organisms. They play many roles in living things. Certain proteins provide a scaffolding that maintains the shape of cells (structural proteins). Proteins also make up the majority of muscle tissues. Many proteins are enzymes that speed up chemical reactions in cells. Enzymes interact with the substrates (reactants) of a biochemical reaction, helping the reaction proceed at a much faster rate. Other proteins are antibodies that protect you from pathogens. Antibodies bond to foreign substances in the body and target them for destruction. Still other proteins help carry messages or materials in and out of cells (transport proteins) or around the body. For example, the blood protein hemoglobin (see Figure below ) bonds with oxygen and carries it from the lungs to cells throughout the body. |
SciQ | SciQ-5921 | breathing
Title: Why does the pulmonary artery have higher glucose concentration than the pulmonary vein? If the pulmonary artery have higher glucose concentration than the pulmonary vein, does it mean glucose will be consumed during gas exchange?
That confused me because gas exchange is something like diffusion and shouldn't consume any glucose Gas exchange doesn't but the cells of the tissue it occurs in do consume glucose, even the cells in the walls of the artery will consume some. The cells in the lungs still need to be fed and only one of those two vessels has flow going into the tissue so it is the one that has to carry that glucose into the tissue.
The following is multiple choice question (with options) to answer.
In what part of the lungs is pulmonary gas exchanged? | [
"bronchioles",
"bronchi",
"trachea",
"alveoli"
] | D | Pulmonary gas exchange is the exchange of gases between inhaled air and the blood. It occurs in the alveoli of the lungs. Alveoli (singular, alveolus) are grape-like clusters surrounded by networks of thin-walled pulmonary capillaries. After you inhale, there is a greater concentration of oxygen in the alveoli than in the blood of the pulmonary capillaries, so oxygen diffuses from the alveoli into the blood across the capillaries (see Figure below ). Carbon dioxide, in contrast, is more concentrated in the blood of the pulmonary capillaries than in the alveoli, so it diffuses in the opposite direction. |
SciQ | SciQ-5922 | ocean, oceanography, wind, waves, ocean-currents
Taking 10 meters (one of the smallest values in mid-latitudes) for the surface and bottom boundary layer thicknesses, that implies that in water depths shallower than 20 m the two boundary layers overlap. In water depths shallower than that, the transport in the surface layer is no longer perpendicular to the wind direction. The momentum input into the water by the wind (wind stress) is affected by the presence of the bottom and it is directly dissipated by bottom friction. The mixing by the wind (and wave breaking near the surf zone) results in additional mixing through the water column and facilitating well-mixed water columns. Under these conditions the wind-induced currents extend all the way to the bottom with the direction of the flow being a function of bottom depth, wind direction, and bottom slope. The presence of wind-induced currents does not preclude the occurrence of flow in the opposite direction of the wind.
A fantastic article summarizing the different flow conditions under different wind and wave fields in shallow water depths is given in Lentz and Fewings (2012). (Reprint)
Additional factors to consider are:
The following is multiple choice question (with options) to answer.
What phenomenon occurs when strong winds blow surface water away from shore, allowing deeper water to flow to the surface and take its place? | [
"tsunami",
"percolating",
"upwelling",
"hurricane"
] | C | Sometimes deep ocean water rises to the surface. This is called upwelling . The figure below shows why it happens ( Figure below ). Strong winds blow surface water away from shore. This allows deeper water to flow to the surface and take its place. |
SciQ | SciQ-5923 | cell-division
Title: Are free-nuclear division and endomitosis the same? As far as I understood it, both are cases of karyokinesis, not followed by cytokinesis. No. If you google the terms you'll get a lot of sites with definitions. For example:
Nuclear division
Definition
noun
The process by which a nucleus divides, resulting in the segregation of the genome to opposite poles of a dividing cell.
source: http://www.biology-online.org/dictionary/Nuclear_division
Edit:
or
free nuclear division mitotic division of nuclei without accompanying cytokinesis, i.e. nuclei divide in a common cytoplasm, the cells walls only forming around each later
source: http://ecflora.cavehill.uwi.edu/bio_courses/bl14apl/Gloss.htm
versus
endomitosis
mitosis taking place without dissolution of the nuclear membrane, and not followed by cytoplasmic division, resulting in doubling of the number of chromosomes within the nucleus.
source: http://medical-dictionary.thefreedictionary.com/endomitosis
or a bit more revealing:
Duplicated chromosomes produced by endomitosis exist as discrete units
in a single polyploid nucleus or may be packaged into separate nuclei,
depending on the phase at which mitosis is aborted
source: http://en.wikipedia.org/wiki/Endoreduplication
So as you see by definition nuclear division is part of a bigger process (cell division), and accoriding to the first source karyokinesis is a synonim for nuclear division (karyo = nucleus kinesis = moving, both come form greek language).
Edit:
If you check the definition above, you can see that free-nuclear division is a mitosis without cytokinesis, thus chromosome separation still occurs.
In endomitosis the can end up with a polyploid nucleus, in contrast to the other two aforementioned mechanism where no polyploidy occurs.
The following is multiple choice question (with options) to answer.
When does the nucleus divide? | [
"epistasis",
"meiosis",
"mitosis",
"photosynthesis"
] | C | The nucleus divides during mitosis, and the cytoplasm divides during cytokinesis. |
SciQ | SciQ-5924 | neuroscience, physiology, neurophysiology, senses, olfaction
Title: Why does olfactory sensation need lateral inhibition? Why does olfactory sensation need lateral inhibition? If it's not helping in spatial discrimination then why is it needed? Don't we just smell the odour which is more concentrated?
My attempt: It is said that lateral inhibition is an important part of olfaction as it aids in odour discrimination by decreasing firing in response to background odours and differentiating the responses of olfactory nerve inputs in the mitral cell layer. But we also know that sensory perception is based on the pattern of receptors activated by the stimulus. So following questions arise:
Why don't background odours laterally inhibit the target odour? Isn't there more chance of inhibition of target odour being inhibited since its concentration is less? Here is the paper which directly answers your question.
Urban NN. Lateral inhibition in the olfactory bulb and in olfaction. Physiology & behavior. 2002 Dec 31;77(4):607-12.
A few salient points:
It is true that the spatial gradient of sensory attributes is not as clear in the olfactory bulb-neuronal topography as it is at other places with lateral inhibition, but lateral inhibition still seems to serve a similar purpose in all these cases, namely sharpening the perceived stimuli. It is not settled how is this "edge enhancement" brought about in a nontopographical system ( "...Specific inhibitory connections between groups of cells with similar receptive fields may allow for functional lateral inhibition in such nontopographic systems, but no evidence for such specificity has been provided in the olfactory system...").
Unlike say for example in the Retina, where lateral inhibition creates the on/off centres, the lateral inhibition in olfactory bulbs is more widespread. That is, the area inhibited is relatively more expansive. This fact, coupled with the highly localised excitation caused by odours, suggests that "....lateral inhibition will be most effective at suppressing signals with low spatial frequency, in other words, signals that involve activation of broad regions of the olfactory bulb...". This is what I assume was meant by your source while referring to background odours.
The following is multiple choice question (with options) to answer.
Olfactory, optic, and vestibulocochlear nerves are related to what type of function? | [
"sensory",
"digestion",
"respiratory",
"pulmonary"
] | A | Sensory Nerves The olfactory, optic, and vestibulocochlear nerves (cranial nerves I, II, and VIII) are dedicated to four of the special senses: smell, vision, equilibrium, and hearing, respectively. Taste sensation is relayed to the brain stem through fibers of the facial and glossopharyngeal nerves. The trigeminal nerve is a mixed nerve that carries the general somatic senses from the head, similar to those coming through spinal nerves from the rest of the body. Testing smell is straightforward, as common smells are presented to one nostril at a time. The patient should be able to recognize the smell of coffee or mint, indicating the proper functioning of the olfactory system. Loss of the sense of smell is called anosmia and can be lost following blunt trauma to the head or through aging. The short axons of the first cranial nerve regenerate on a regular basis. The neurons in the olfactory epithelium have a limited life span, and new cells grow to replace the ones that die off. The axons from these neurons grow back into the CNS by following the existing axons—representing one of the few examples of such growth in the mature nervous system. If all of the fibers are sheared when the brain moves within the cranium, such as in a motor vehicle accident, then no axons can find their way back to the olfactory bulb to reestablish connections. If the nerve is not completely severed, the anosmia may be temporary as new neurons can eventually reconnect. |
SciQ | SciQ-5925 | solutions, mixtures, fuel, liquids
Title: Can a stoichiometric mixture of oxygen and methane exist as a liquid at standard pressure and some (low) temperature? This answer to the question Pre-mixing cryogenic fuels and using only one fuel tank written by a non-chemist (me) begins with:
At STP:
LOX's boiling point is 90.19 K
Methane's freezing point is 90.7 K
This does not a priori prove that a solution of the two can not exist. However it does mean that they can not be handled as liquids at the same temperature, making mixing the two more difficult.
We know that liquid air exists which shows that LOX and LN2 can mix together. But methane is an organic molecules and we know that heavier $\text{C}_n \text{H}_{2n+2}$ hydrocarbons include oils and waxes don't like to dissolve in non-organic solvents.
A stoichiometric mixture of oxygen and methane would be 2:1 molar:
$$\ce{ 2O2 + CH4 -> CO2 + 2H2O }$$
Though the two can not be conveniently maintained as liquids at the same temperature, can a stoichiometric mixture of the two exist as a liquid at some (low) temperature and standard pressure? There's a NASA report that looks into this: "ON THE SOLUBILITIES AND RATES OF SOLUTION OF GASES IN LIQUID METHANE", Hibbard and Evans, 1968 and concludes that such mixtures are possible.
Starting on page 8:
Figure 5(a) presents the curves for oxygen, argon, carbon monoxide,
and nitrogen. Also shown are the two experimental values for nitrogen.
Agreement is excellent at 99.83K and good at 110.9K. The curves for
these gases show that solubility should decrease with increasing
temperature and the nitrogen data confirm this. This figure shows the
mole fraction solubility of oxygen to be 1.0 at 90K. This means that
oxygen, which has a normal boiling temperature of 90.1K would
continuously condense in, and be miscible in all proportions, with
liquid methane at 90K. This is confirmed by reference 11 where, in a
study of the solubility of methane in liquid oxygen, it was concluded
that these formed a near-ideal solution at -297 F (90K)
The following is multiple choice question (with options) to answer.
What happens when alkanes are mixed with oxygen at room temperature? | [
"combustion",
"redox",
"single replacement",
"no reaction"
] | D | Neither positive ions nor negative ions are attracted to a nonpolar molecule. In fact, the alkanes undergo so few reactions that they are sometimes called paraffins, from the Latin parum affinis, meaning “little affinity. ” Two important reactions that the alkanes do undergo are combustion and halogenation. Nothing happens when alkanes are merely mixed with oxygen (O2) at room temperature, but when a flame or spark provides the activation energy, a highly exothermic combustion reaction proceeds vigorously. For methane (CH4), the reaction is as follows:. |
SciQ | SciQ-5926 | bacteriology
Title: Do sulfate reducing bacteria help during the formation of the mineral dolomite in low temperature environments? Do sulfate reducing bacteria help during the formation of the mineral dolomite in low temperature environments?
Wikipedia says
The actual role of bacteria in the low-temperature formation of
dolomite remains to be demonstrated. The specific mechanism of
dolomitization, involving sulfate-reducing bacteria, has not yet been
demonstrated.
I wonder if someone has any updates on this. The reference given in the Wikipedia article is from 2000, from a source titled suspiciously "Journal of Conference Abstracts". Now it's 2013 and maybe someone else has found out something new. The appropriate answer seems to be that bacteria help somewhat sometimes, maybe.
The evidence for this appears to be mixed, and appears to have been historically controversial.
One old-ish paper claims that bacteria (and more importantly, Archaea) are necessary at least under some conditions. Another somewhat later paper including some of the same authors claims to have found conditions for abiotic dolomite synthesis in the laboratory.
It appears that in terms of mechanisms, the relevant process may involve the proper state of magnesium ions, to which apparently microbes contribute via extracellular polysaccharides:
Literature values for carboxyl group density are not available for all bacteria involved in dolomite formation, however Braissant et al. (2007) demonstrated disordered dolomite phases forming in the presence of the EPS of sulfate reducing bacteria with a carboxyl group density of ~10-3 moles g-1, similar to our values. We suggest that these carboxyl groups promote desolvation of the Mg ion, known to be a kinetic inhibitor in dolomite precipitation (Wright and Wacey, 2004), but are needed in a high density for nucleation to commence.
However, what process exactly is generating geological dolomites appears to be still a matter of debate, and also here, with some suggestive evidence in favor of microbes affecting that process.
The following is multiple choice question (with options) to answer.
At the bottom of lakes and ponds, bacteria in what zone break down dead organisms that sink there? | [
"trophic",
"aphotic zone",
"photic",
"photoreactive zone"
] | B | Lakes and Ponds Lakes and ponds can range in area from a few square meters to thousands of square kilometers. Temperature is an important abiotic factor affecting living things found in lakes and ponds. In the summer, thermal stratification of lakes and ponds occurs when the upper layer of water is warmed by the sun and does not mix with deeper, cooler water. Light can penetrate within the photic zone of the lake or pond. Phytoplankton (algae and cyanobacteria) are found here and carry out photosynthesis, providing the base of the food web of lakes and ponds. Zooplankton, such as rotifers and small crustaceans, consume these phytoplankton. At the bottom of lakes and ponds, bacteria in the aphotic zone break down dead organisms that sink to the bottom. Nitrogen and phosphorus are important limiting nutrients in lakes and ponds. Because of this, they are determining factors in the amount of phytoplankton growth in lakes and ponds. When there is a large input of nitrogen and phosphorus (from sewage and runoff from fertilized lawns and farms, for example), the growth of algae skyrockets, resulting in a large accumulation of algae called an algal bloom. Algal blooms (Figure 44.24) can become so extensive that they reduce light penetration in water. As a result, the lake or pond becomes aphotic and photosynthetic plants cannot survive. When the algae die and decompose, severe oxygen depletion of the water occurs. Fishes and other organisms that require oxygen are then more likely to die, and resulting dead zones are found across the globe. Lake Erie and the Gulf of Mexico represent freshwater and marine habitats where phosphorus control and storm water runoff pose significant environmental challenges. |
SciQ | SciQ-5927 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
What is the name for a heterotroph that eats only or mainly animal foods? | [
"herbivore",
"carnivore",
"omnivore",
"macrophage"
] | B | Some mammals are carnivores. Carnivores are heterotrophs that eat only or mainly animal foods. Depending on their species, carnivorous mammals may eat other mammals, birds, reptiles, amphibians, fish, mollusks, worms, and/or insects. Mammals that are carnivores include anteaters, whales, hyenas, wolves, and seals. The bat in Figure below is also a carnivorous mammal. It eats insects. Carnivores that eat mainly insects are classified as insectivores. |
SciQ | SciQ-5928 | biophysics, cosmic-rays, elementary-particles
The question, then, is to ask not what the fog will do to the locomotive, but what the locomotive will do to the fog -- that fog being your head.
Even a single solid, exactly head-on collision with a nice fat iron nucleus just as an ultra cosmic ray proton enters your head would probably not be a pretty event in terms of the resulting secondary radiation shower. I'm guessing (nothing more, I haven't tried to calculate anything) that outward splattering of a nice little quark plasma, one created as the iron nucleus vaporizes during the transition event, could produce a sufficiently wide cone of particle-zoo ejecta to irradiate a fatal percentage of your brain. Rapid heating of your brain would not be a problem, however, since 1/500 of the approximately 50 Joules of kinetic energy would work out to be only about 0.1 J of heat energy tops. By comparison a standard firecracker releases about 500 J of energy.
And what are the real odds on such a dead-center strike on a large nucleus near the surface of your brain, assuming you were an astronaut unprotected by out atmosphere? Low almost beyond belief. Look at the date on the Oh-My-God particle: 1991. We haven't seen one quite that feisty since. As @dmckee aptly notes, ordinary cosmic rays or their secondary outputs hit us all the time, and astronauts watch direct collision buzz through their retinas without much harm.
The following is multiple choice question (with options) to answer.
What is the name of an extreme form of radiation fog? | [
"aura fog",
"tule fog",
"smelt fog",
"cedar fog"
] | B | Radiation fog forms at night. Skies are clear, and the relative humidity is high. The ground cools as temperature goes down. Air near the ground cools below its dew point. Tule fog is an extreme form of radiation fog. This type of fog strikes the Central Valley of California in winter. |
SciQ | SciQ-5929 | atmosphere, geography
Title: How much atmoshphere is there compared to land and water We know our earth has 71% water and 29% land, but compared to that land and water, how much air do we have in our atmosphere?
I mean:
How big is our atmosphere
Is there any increase or decrease in the amount of atmosphere over time
Is there any change in percentage of oxygen over time 71% of Earth's surface is covered with water and 29% land.
Thinking in that regard, that's saying that on 29% of Earth's "surface" locations you have land below your feet, and in 71% of the locations, you have water. So to continue in such terms, you'd then ask... ok, what percentage of Earth's surface locations would have air above them!?! Well that's all of them. So to if you're comparing it with those percentages, I guess you'd have to say it's another 100%. Or, if we put them together into a full 3-dimensional surroundings at the surface, well it'd basically be 50% air, 36% water, 14% land.
But to compare how much of each there REALLY is, you need to include depth, getting some sort of 3 dimensional understanding of it. But the picture that reveals is certainly not the picture we are used to from daily experience. From the values I was able to find:
In terms of the room each takes up, the volume:
Surface water (oceans+lakes+rivers, glaciers, etc) is 1.4 billion km³
The inside of the Earth is about 1 trillion = 1000 billion km³
For the atmosphere, as mentioned in comments, it's a little more difficult, as the gases only gradually give way to space. You find less and less gas as you go up, but there's no set spot where there is none, as some tiny amount is always floating off into space. So where do you draw the line? A commonly used boundary between the atmosphere and space is the Karman line. This would lead to a volume of 53 billion km³ (using Earth's radius = 6371 km). Note that only about half of that is in the troposphere and stratosphere, which are perhaps the familiar zones of the atmosphere where weather and the ozone layer (and 95% of air molecules) reside.
The following is multiple choice question (with options) to answer.
In what form is most of the earth's freshwater? | [
"gas",
"frozen",
"steam",
"liqued"
] | B | Oceans of salt water cover much of Earth’s surface. Freshwater is water that contains little or no salt. Most of Earth’s freshwater is frozen in ice caps and glaciers. |
SciQ | SciQ-5930 | human-biology, molecular-biology, human-physiology, immune-system, history
Title: Which landmark paper first described the differentiation of T-cells? T-cells are distinguished from B cells in part by their locus of differentiation/maturation (thymus). This is textbook knowledge, but I was wondering which particular person or people were responsible for making this discovery. I'd appreciate any links to their original papers/works. Thanks a lot! This paper appears to be a history of the discovery of B/T differentiation and the role of the thymus. I believe that you should find a number of important references therein.
It describes specifically a series of publications in the 1950s and 1960s that may be relevant (section "Identification of T and B cells"), such as this one by Gowans.
The following is multiple choice question (with options) to answer.
What cells do lymphocytes originate from in the bone marrow? | [
"brain cells",
"stem cells",
"calcium cells",
"kahp cells"
] | B | |
SciQ | SciQ-5931 | waves, harmonic-oscillator, oscillators, string, harmonics
Title: Simple harmonic motion versus oscillations I want to see whether certain oscillations in my daily life, such as the oscillation of violin strings when plucked, are simple harmonic motion or not. Can we identify whether an oscillation is simple harmonic motion or just an oscillation by observing it?
I don't truly understand the difference between the two - mathematically, we know that acceleration should be proportional to negative displacement for simple harmonic motion. Am I right when I say that an oscillation, such as violin strings oscillating when plucked, cannot be identified to be either a regular oscillation or simple harmonic motion until its motion is precisely tracked and analysed? The pure simple harmonic motion is in real life very very rare. There are some cases which are really close (e.g. for engineering purposes). That might be:
Small-amplitude oscillation of a mass on a spring (small enough for spring nonlinearities not to be pronounced) or other kinds of these simple or moreless model oscillators.
Tuning fork. Strictly speaking it has more oscillatory modes but it is hard to effectively excite more than the one.
Speaker membrane when playing a pure sine tone (that's easy to be generated).
For the last but not least case, there is a practical possibility to excite just a harmonic oscillation of the damped system with just pure harmonic driving force. That is what it's done e.g. when the room acoustics is examined using sine sweep tones.
The following is multiple choice question (with options) to answer.
What is the common name for a simple harmonic oscillator, which basically consists of a small object suspended on a wire or string? | [
"pendulum",
"pendant",
"metronome",
"yo-yo"
] | A | Pendulums are in common usage. Some have crucial uses, such as in clocks; some are for fun, such as a child’s swing; and some are just there, such as the sinker on a fishing line. For small displacements, a pendulum is a simple harmonic oscillator. A simple pendulum is defined to have an object that has a small mass, also known as the pendulum bob, which is suspended from a light wire or string, such as shown in Figure 16.14. Exploring the simple pendulum a bit further, we can discover the conditions under which it performs simple harmonic motion, and we can derive an interesting expression for its period. |
SciQ | SciQ-5932 | thermodynamics
I really doubt that, given all the dynamic things happening at the Earth's surface, where one downhill process drives an uphill process. Such as the huge electric potential generated in a thunderstorm when larger ice particles fall and smack into small ice particles being lifted in the updraft, resulting in lightning. I don't think of the generation of electric potentials as being particularly "spontaneous", but I also don't know if the Gibbs free energy function really applies to this case. In this example and others I can think of (such as generation of wind and water power), it is exergy that is increasing, i.e. available work. I would tend to think of a process that increases the exergy of a system as non-spontaneous, but I don't know if it is used that way by physicists. The important distinction is that, in order for a non-spontaneous process to occur, there has to be energy input to the system. So, in your example, the system is just the electrolytic cell; in order for electrolysis to occur, energy must enter the system from outside, e.g. the battery. If you were to consider the cell and the battery as your system, then it would be a spontaneous process.
The question of intelligent agents is irrelevant. Intelligent or not, we still must obey the 2nd law. Consider the edge cases: for your example, what if humans created a machine that automatically does electrolysis? What if someone accidentally knocks a battery into a bowl of salt water and electrolysis occurs? What if an animal did that? You can even concoct a purely natural example of electrolysis occurring- what if lightning strikes the ocean in just the right way?
The following is multiple choice question (with options) to answer.
What kind of process occurs without the need for a continual input of energy from some external source? | [
"spontaneous process",
"induced process",
"Different Process",
"Decay Process"
] | A | Summary 16.1 Spontaneity Chemical and physical processes have a natural tendency to occur in one direction under certain conditions. A spontaneous process occurs without the need for a continual input of energy from some external source, while a nonspontaneous process requires such. Systems undergoing a spontaneous process may or may not experience a gain or loss of energy, but they will experience a change in the way matter and/or energy is distributed within the system. 16.2 Entropy Entropy (S) is a state function that can be related to the number of microstates for a system (the number of ways the system can be arranged) and to the ratio of reversible heat to kelvin temperature. It may be interpreted as a measure of the dispersal or distribution of matter and/or energy in a system, and it is often described as representing the “disorder” of the system. For a given substance, Ssolid < Sliquid < Sgas in a given physical state at a given temperature, entropy is typically greater for heavier atoms or more complex molecules. Entropy increases when a system is heated and when solutions form. Using these guidelines, the sign of entropy changes for some chemical reactions may be reliably predicted. 16.3 The Second and Third Laws of Thermodynamics The second law of thermodynamics states that a spontaneous process increases the entropy of the universe, Suniv > 0. If ΔSuniv < 0, the process is nonspontaneous, and if ΔSuniv = 0, the system is at equilibrium. The third law of thermodynamics establishes the zero for entropy as that of a perfect, pure crystalline solid at 0 K. With only one possible microstate, the entropy is zero. We may compute the standard entropy change for a process by using standard entropy values for the reactants and products involved in the process. 16.4 Free Energy Gibbs free energy (G) is a state function defined with regard to system quantities only and may be used to predict the spontaneity of a process. A negative value for ΔG indicates a spontaneous process; a positive ΔG indicates a nonspontaneous process; and a ΔG of zero indicates that the system is at equilibrium. A number of approaches to the computation of free energy changes are possible. |
SciQ | SciQ-5933 | species-identification, microbiology, microscopy
Title: Identification of protozoa under microscope I observed maybe Protozoa from standing FRESH water and from slowly flowing FRESH water. I am complete dilettante. Can you tell what these creatures are?
https://www.youtube.com/watch?v=6D5ck3zNJzA&t=474s
Thank you.
Added picture for to be more specific At first glance, the organisms may hold the appearance of protozoans like ciliates. However, I am of the belief that these 'totally tubular' micro organisms are in fact diatoms.
The diatoms are a diverse range of eucaryotic microalgae which comprise a large percentage of the phytoplankton group. (Diatomaceous earth is the residual remains of their calcareous walls)
They are likely diatoms because of their apparent hard membrane, and slight brown-green pigment, typical of heterokont diatoms.
I would be unable to specify the organism to family level. However, you may wish to complete your investigation by looking under the order 'Pennales'.
For general information regarding the Diatoms, you may visit https://en.wikipedia.org/wiki/Diatom
Morphology and description available from: https://books.google.co.uk/books?id=xhLJvNa3hw0C&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
Good luck
The following is multiple choice question (with options) to answer.
What are fungus-like protists? | [
"viruses",
"feces",
"molds",
"bacteria"
] | C | Fungus-like protists are molds . They are absorptive feeders on decaying organic matter. They resemble fungi, and they reproduce with spores as fungi do. However, in other ways, they are quite different from fungi and more like other protists. For example, they have cell walls made of cellulose , whereas fungi have cell walls made of chitin. Like other protists, they have complicated life cycles with both asexual and sexual reproduction. They are motile during some stages of their life cycle. Two major types of fungus-like protists are slime molds and water molds. |
SciQ | SciQ-5934 | electrons, quantum-electrodynamics, antimatter
Title: Only one electron? If it is true that an electron can be anywhere in the cosmos at any given time, then is it even theoretically possible that there is only one electron, instead of multiple electrons in the cosmos? If it isn't, I'd appreciate it if someone could point out where I may have misunderstood something as far as the fundamental properties of electrons are concerned.
If it is true that an electron can be anywhere in the cosmos at any given time,
No it is not a true statement. The true quantum mechanical statement is that
there exists a probability that an electron can be anywhere in the cosmos at any given time
This probability is infinitesimally small, and thus the probability that atoms could evolve is practically zero. So it is not even theoretically possible . Your misunderstanding comes from ignoring probabilities coming from the quantum mechanical basic framework.
The following is multiple choice question (with options) to answer.
Electrons exist only where the wave is what? | [
"solid",
"stable",
"seen",
"spinning"
] | B | In the 1920s, physicists discovered that electrons do not travel in fixed paths. In fact, they found that electrons only have a certain chance of being in any particular place. They could only describe where electrons are with mathematical formulas. That’s because electrons have wave-like properties as well as properties of particles of matter. It is the "wave nature" of electrons that lets them exist only at certain distances from the nucleus. The negative electrons are attracted to the positive nucleus. However, because the electrons behave like waves, they bend around the nucleus instead of falling toward it. Electrons exist only where the wave is stable. These are the orbitals. They do not exist where the wave is not stable. These are the places between orbitals. |
SciQ | SciQ-5935 | organic-chemistry, physical-chemistry, combustion
Title: Optimal CFM for kerosene to burn? I am going to be making a kerosene forge, and I need a refresher on calculus-based chemistry.
Given a certain distribution of alkanes, what is the amount of air (21% O$_2$) needed (in cubic feet per minute [CFM]) at 21C to burn kerosene at a rate of X mL/s?
The distribution of alkanes is unknown but from Wikipedia I've got that the molecules have no more than 16 and no less than 6 carbon atoms. The density is $\mathrm{0.795~g~cm^3}$. If any more info or help is needed, I'll be glad to pitch in where I can. This is something of a standard reaction stochiometry question, although the situation is a bit more involved than the ones you normally see in textbooks.
The first step is to work out what the chemical reaction we're talking about actually is. One complication is that "kerosene" doesn't name a single molecular species, but is instead a mix of hydrocarbons. But the hydrocarbons are similar enough that we can probably approximate the mixture as a "typical" hydrocarbon of roughly the right type and mass. Wikipedia approximates kerosene as dodecane, and even gives a combustion reaction (saving us the effort of balancing one):
$$\ce{2 C12H26(l) + 37 O2(g) → 24 CO2(g) + 26 H2O(g)}$$
Now that we have stoichiometry, we just need to convert the quantities of reactants involved to numbers of molecules (moles). We're dealing with rates of consumption for both reactant, so let's just run the numbers for a fixed period of time, say 1 minute.
The following is multiple choice question (with options) to answer.
What are the simplest hydrocarbons? | [
"unsaturated hydrocarbons",
"complex carbohydrates",
"saturated hydrocarbons",
"fossil fuels"
] | C | Saturated hydrocarbons contain only single bonds between carbon atoms. They are the simplest hydrocarbons. They are called saturated because each carbon atom is bonded to as many hydrogen atoms as possible. In other words, the carbon atoms are saturated with hydrogen. You can see an example of a saturated hydrocarbon in Figure below . Each carbon atom is bonded to three hydrogen atoms in this compound, which is named ethane. |
SciQ | SciQ-5936 | waves, atmospheric-science, turbulence
Title: What is the relevant phenomenon behind Undulatus/Radiatus cloud formations? I am seeing many people claiming that cumulus clouds that sometimes form periodic wavy patterns (see images for "altocumulus undulatus" or "Radiatus" for instance) have no explanation aside from being chemtrails, and I'd like to be able to respond with a sound scientific explanation.
I'd like to understand the phenomenon and my guess is that it's about the cloud blanket being forced by winds with the result of a periodic pattern appearing, much like sand waves form in shallow water at the beach.
But is it really the case? Searching for a more detailed explanation I ran into Tollmien-Schlichting waves that are a path to turbulence, but I admit I did not understand much, so here is my question(s):
What is the physics behind such cloud formations? And
Given an estimate of the spatial period of these cloud waves and the cloud height, can one infer the windspeed at that height? There are a variety of cloud wave patterns, including radiatus, undulatus, and gravity wave clouds. Their causes are not mysterious, but fluid mechanics is rarely simple. When air rises and falls in a pattern, clouds form at the high points if the air reaches the lifted condensation level. The spatial period of the clouds does not in general depend just on wind speed and height, so they cannot easily be used to estimate the wind speed at height.
Radiatus clouds (also known as "cloud streets" or "horizontal convective rolls") are lines of thermal-updraft-top clouds which form parallel to the wind direction. The wind lines up the convective cells to form horizontal convective rolls as shown in this image from Wikipedia:
The following is multiple choice question (with options) to answer.
The shield type of what phenomenon commonly forms above hotspots in the oceans? | [
"tsunami",
"hurricane",
"volcano",
"tornado"
] | C | Shield volcanoes commonly form above hotspots in the oceans. |
SciQ | SciQ-5937 | oceanography, geochemistry
Title: Why is NaCl so hyper abundant in the ocean? Why is sodium chloride far and away the most abundant salt dissolved in ocean water? Its two constituent ions do have a very high frequency in the crust of the earth, but they are far from the most common. Chlorine is (according to Wikipedia) the 21st most abundant element, and sodium 6th.
I certainly understand that a combination of their solubility and reasonably high frequency would lead one to expect them to be abundant in sea water, but they are hyper abundant, completely dominating all other salt ions. Iron, for example, is twice as abundant, and potassium only a little less abundant, and fluorine more abundant than chlorine.
Moreover, if the salts are deposited in the ocean through weathering of rocks and deposition via rivers, why does the salinity not simply grow and grow? I understand that some is lost due to tectonic activity, but it seems extraordinarily unlikely that these two forces should be equally balanced, and so we would see a significant change in average salinity over time.
(Please note I am migrating this question from the Chemistry SE at their recommendation.) Fluoride salts tend to be not particularly soluble in water. Chloride salts are. The same goes for salts containing sodium versus those containing calcium. Sodium chloride is ridiculously easy to dissolve.
Regarding your second question, it is geological forces that keep salinity more or less constant. People formerly argued that the Earth can't be more than a few hundred million years old because otherwise the river waters running into the oceans would eventually result in an insanely high salinity. It turns out that the Earth's oceans are young (young compared to the 4.5 billion year age of the Earth). The vast majority of oceanic crust is less than 100 million years old. We see huge salt deposits sprinkled across the world because those are the dried up remnants of former seas and oceans. Salt is also drawn into the Earth at subduction zones, where it combines chemically with basalt.
The following is multiple choice question (with options) to answer.
Bromide is present in brines, which are naturally occurring solutions of what? | [
"iron",
"magnesium",
"calcium",
"salt"
] | D | chlorine is added to an aqueous solution of bromide. iodine crystals are added to a solution of potassium bromide. Bromide is present in naturally occurring salt solutions called brines. Based on your answers, propose an effective method to remove bromide from brine. |
SciQ | SciQ-5938 | • $\mathcal{N}_f = 8$. e.g. a "distorted" octahedron with vertices at 6 points $\pm \vec{A}, \pm \vec{B}, \pm \vec{C}$ where $$\begin{cases} \vec{A} &= (-1,\alpha,1),\\ \vec{B} &= ( 2,0,1),\\ \vec{C} &= (-1,-\alpha,1) \end{cases} \quad\text{ and }\quad \alpha = \frac{\sqrt{3(3+4\sqrt{5} - \sqrt{49+24\sqrt{5}})}}{2} \approx 1.1657187$$ One can cut this "distorted" octahedron along $\vec{A} \to -\vec{C} \to \vec{B} \to -\vec{A} \to \vec{C} \to -\vec{B} \to \vec{A}$ and unfold the surface into two kites.
$\hspace1in$
• $\mathcal{N}_f = 10.$ e.g. a square antiprism mentioned in the question. A concrete example is the one with following 8 vertices at $$\begin{cases} (\pm 1,\pm1,0),\\ (\pm\sqrt{2},0,\beta),\\ (0,\pm\sqrt{2},\beta) \end{cases} \quad\text{ where }\quad\beta = \sqrt{2(\sqrt{2}-1)} \approx 0.9101797$$
The following is multiple choice question (with options) to answer.
What shape are the eight sides of an octahedra? | [
"hexagon",
"square",
"rectangles",
"triangles"
] | D | Cubes have six sides that are all the same size square. All of the angles in a cube are equal to 90°. Rhombohedra also have six sides, but the sides are diamond-shaped. Octahedra have eight sides that are all shaped like triangles. |
SciQ | SciQ-5939 | taxonomy
Title: Why are sponges sometimes not considered multicellular? I read somewhere (I can't find where) that there is no scientific consensus whether sponges should be considered multicellular organisms.
It seems I don't understand where is the line between unicellular and multicellular life.
I am not able to find a more elaborate explanation of that doubt. What are the reasons for it? Sponges are generally considered as colonial organisms because there is little cell specialization and little separation of function/role. All cells do pretty much the same thing; it looks more like a pile of individual cells than an actual multicellular organism. In reality it is a little bit in between.
In any case, what one wants to call multicellular or unicellular is a matter of definition and preferences. You cannot find the line between unicellular and multicellular because there is no such line that would not be very arbitrary and filled with special cases.
You can study a little more the physiology of sponges and then decide for yourself if it looks sufficiently like a multicellular organism or more like a colony of cells (a colonial organism).
The following is multiple choice question (with options) to answer.
Unlike an adult sponge, what stage is motile due to cilia that propel it through water? | [
"zygote",
"parasite",
"larva",
"pupa"
] | C | Sperm are released into the surrounding water through the osculum. If they enter a female sponge through a pore, they may be trapped by collar cells. Trapped sperm are delivered to eggs inside the female body, where fertilization takes place. The resulting zygote develops into a larva. Unlike the adult, the larva is motile. It is covered with cilia that propel it through the water. As the larva grows, it becomes more similar to an adult sponge and loses its ability to swim. |
SciQ | SciQ-5940 | waves, atmospheric-science, turbulence
The clouds form if the rising air reaches the lifted condensation level before the updrafts are stopped by an inversion or stable layer. The air is (relatively) clear above the downdrafts. If the convection rolls were perfectly circular, the cloud row spacing would be twice the height of the inversion/stable layer.
Mathematically, there are many wavelength solutions to convection, but the wavelength that dominates is the fastest growing one. In the Boussinesq approximation, which is reasonably valid here, this turns out to have a wavelength of $2\sqrt{2}\sim 3$ times the height of the convecting layer, i.e. slightly flattened. (See, for example, Eq. 21 of Kuettner (1971) "Cloud bands in the earth's atmosphere: Observations and Theory".)
For typical cumulus cloud heights of $\sim 2$ km, we expect typical spacings of about $6$ km.
Wave, lee, or mountain clouds are lines of clouds downwind of an obstacle (such as a mountain range). The lines are parallel to the wind direction. These are buoyancy waves where wind pushes denser air over an obstacle (e.g. a mountain range) and it ends up above less dense air on the other side. This dense air starts to fall but it overshoots into even higher density air at lower altitude, which forces it back up, and the air ends up bouncing up and down until the oscillations die out. If the vertical temperature profile of the air then is known, it is possible to estimate the vertical buoyancy angular frequency
$$N=\sqrt{\frac{g}{\theta}\frac{d\theta}{dz}}$$
The following is multiple choice question (with options) to answer.
What weather phenomenon, which may bring clouds and precipitation, is created by stalled air masses? | [
"susceptible front",
"stationary front",
"Horizontal Front",
"cool front"
] | B | Sometimes two air masses stop moving when they meet. These stalled air masses create a stationary front . Such a front may bring clouds and precipitation to the same area for many days. |
SciQ | SciQ-5941 | thermodynamics, temperature
Title: Non uniform freezing of lakes Here's a problem from my physics textbook:
Why do lakes freeze first at the surface?
I'm not sure why this should happen, and my guess is that the only reason for this could be the temperature distribution with depth, inside water bodies. You need to know that water at $4^{\circ}$C achieve its highest density. So naturally, water at $4^{\circ}$C will tend to move to the bottom of the lake as it is heavier. When the temperature is cool enough to freeze the lake, eventually there will be some layer of ice forming at the surface but there is still liquid water below the ice layer. The ice also works as an insulation to keep the water below it from freezing to ice completely. Also, ice has a lower density than water so any ice forming will float to the surface. There are other factor like Earth's internal heating that constantly maintaining the water at the bottom of lake from freezing.
The following is multiple choice question (with options) to answer.
What keeps glaciers from forming in water? | [
"warmth",
"movement",
"salt",
"skin"
] | A | Glaciers form only on land because water is too warm. When a glacier flows into water, it usually breaks up into icebergs. Those icebergs eventually melt into the water. |
SciQ | SciQ-5942 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
The human skeleton is an endoskeleton that consists of 206 bones in the adult. it has five main functions: providing support to the body, storing minerals and lipids, producing blood cells, protecting internal organs, and this? | [
"enough movement",
"Forward movement",
"more movement",
"allowing movement"
] | D | The human skeleton is an endoskeleton that consists of 206 bones in the adult. It has five main functions: providing support to the body, storing minerals and lipids, producing blood cells, protecting internal organs, and allowing for movement. The skeletal system in vertebrates is divided into the axial skeleton (which consists of the skull, vertebral column, and rib cage), and the appendicular skeleton (which consists of the shoulders, limb bones, the pectoral girdle, and the pelvic girdle). |
SciQ | SciQ-5943 | botany, reproduction
Title: Are the seeds in a single capsicum fruit genetically identical? Hopefully not a too-basic question for the venue. I'm a chile pepper growing hobbyist and have spent some time searching around and reading up on pepper (angiosperm) reproduction, but I'm not getting a clear picture of the details.
It seems like flowers have multiple ovules and it seems like one pollen-grain landing on the stigma leads to fertilization of a single ovule. And it seems like that process produces a single seed.
But that fertilization also prompts fruit growth and flower death and capsicum fruits have many seeds, never just one (that I've ever seen).
So, does each seed have a potentially different father? Or are the multiple seeds generated through a reproductive/cloning process that I'm not seeing written about? Or something else? No, the seeds are not genetically identical. Each seed come from the fertilization of an ovum with a sperm from a separate pollen grain. Since each pollen grain can come from a different plant, the seeds will generally differ from one another.
Additionally, even ova from a single plant will not usually be genetically identical to one another. This is because the process that creates the ova (meiosis) shuffles the genes of the parent plant on then places only half into the ovum. The same kind of shuffling goes on in the creation of pollen grains.
In the chili pepper genus (Capsicum), plants are predominantly self-pollinating. This means the majority of the pollen for the seeds in a fruit will come from the very same plant. This generally reduces the amount of variation seen in the offspring compared to complete cross-plant pollination. Some cross-pollination can nevertheless occur if there are other varieties in the neighborhood. The fruit will not show the effects of the new genetic combinations present in its seed, but only a plant grown from the seed will make the differences evident.
The following is multiple choice question (with options) to answer.
What's the name for the process where pollen is transferred to the ovules of a seed plant? | [
"hibernation",
"condensation",
"pollination",
"combination"
] | C |
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