source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-6144 | matter
Proton Degenerate matter where only the repulsion of the protons is holding the nuclei apart. Keep adding pressure, and you'll form:
Neutron Degenerate matter where the electrons and protons join and cancel, leaving you with basically a huge neutral atom full of mostly neutrons, being held apart by the quarks. Keep adding pressure, and you'll (in theory) form:
Quark Degenerate matter where the quarks, or at least the standard up/down quarks, can no longer hold the pressure and perhaps combine/change form. Keep adding pressure, and in theory you might form:
Preon Degenerate matter which would sort of be like one big subatomic particle (though you might skip this one), and finally:
A singularity aka Black Hole
The following is multiple choice question (with options) to answer.
The two main fundamental particles that make up neutrons are quarks and what else? | [
"leptons",
"gluons",
"prions",
"atoms"
] | B | Neutrons consist of fundamental particles known as quarks and gluons. Gluons carry the strong nuclear force that binds together the quarks in a neutron. |
SciQ | SciQ-6145 | bio-mechanics, flight, dinosaurs
The Wikipedia article on the Microraptor is quite long and includes a lengthy, technical discussion on just how these four wings might have been used. It seems that it is (currently) generally believed that these dinosaurs had the capability of powered flight, and that they could actually take off from the ground, rather than climb trees, jump, and simply glide.
This is with four wings.
There are many variety of insects with four wings and the two pair are used in a variety of different ways. But these dinosaurs are much larger, of the order of a kilogram.
Question: Have there been any complete simulations of the mechanics of four-winged dinosaur flight, showing how the wings would have been used to take off from the ground and gain altitude? A movie or animation of the coordinated flapping of the front versus rear pair of wings would be great. These days the numerical models and computing power are within reach, but it would still be a substantial effort, so I'm not sure if this has been done yet or not.
I'm assuming that this is not currently believed to be the branch of dinosaur that eventually evolved into modern birds, but it's a fascinating branch nonetheless.
below: from here. Note nowhere in the article does it mention the rear wings flapping. The rear wings do not provide lift, they are acting as control surfaces to improve stability and maneuverability. (think of the tail of a plane).earlier/proto flies have far more demand for control surfaces than developed/derived fliers due to lacking more precise control of flight surfaces.
They basically take off just like any other bird, if they could fly. Flight in dinosaurs likely did not even evolve from gliding as we commonly think of it but instead from raptorian pouncing, the sprawled posture of microraptor you sometimes see, with its hind legs spread wide, is anatomically impossible, you literally have to dislocate both legs to do it. Dinosaur hip joints do not allow for much lateral extension unlike mammalian or varanid ones, more like a hinge than a ball and socket.
The animal in flight would have looked like this.
Hall, Justin, et al. "A new model for hindwing function in the four-winged theropod dinosaur Microraptor gui." JOURNAL OF VERTEBRATE PALEONTOLOGY. Vol. 32. 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA: TAYLOR & FRANCIS INC, 2012.
The following is multiple choice question (with options) to answer.
Birds have evolved a respiratory system that enables them to fly. flying is a high-energy process and requires a lot of this? | [
"weight",
"nitrogen",
"oxygen",
"adaptation"
] | C | Avian Respiration Birds have evolved a respiratory system that enables them to fly. Flying is a high-energy process and requires a lot of oxygen. Furthermore, many birds fly in high altitudes where the concentration of oxygen in low. How did birds evolve a respiratory system that is so unique? Decades of research by paleontologists have shown that birds evolved from therapods, meat-eating dinosaurs (Figure 39.14). In fact, fossil evidence shows that meat-eating dinosaurs that lived more than 100 million years ago had a similar flow-through respiratory system with lungs and air sacs. Archaeopteryx and Xiaotingia, for example, were flying dinosaurs and are believed to be early precursors of birds. |
SciQ | SciQ-6146 | enzymes
Title: Function of coenzymes: do they act as substrate shuttles? My biochemistry textbook, "Harper's Illustrated Biochemistry", states:
Coenzymes serve as recyclable shuttles that transport many substrates
from one point within the cell to another. The function of these
shuttles is twofold. First, they stabilize species such as hydrogen
atoms (FADH2) or hydride ions (NADH) that are too reactive
to persist for any significant time in the presence of the water,
oxygen, or the organic molecules that permeate cells.
Second, they increase the number of points of contact between
substrate and enzyme, which increases the affinity and specificity
with which small chemical groups such as acetate (coenzyme A), glucose
(UDP), or hydride (NAD+) are bound by their target
enzymes."
To be specific I don't understand the meaning of the words in bold, above:
The following is multiple choice question (with options) to answer.
Lysosomes have what type of enzymes that break down old molecules into parts that can be recycled? | [
"probiotics",
"digestive",
"corrosive",
"bacterial"
] | B | Lysosomes are like the recycling trucks that carry waste away from the factory. Lysosomes have digestive enzymes that break down old molecules into parts that can be recycled. |
SciQ | SciQ-6147 | human-biology, nutrition
Title: Do we know a complete list of nutrients that humans must ingest to live? When the people who are making "nutritionally complete" foods like Soylent are developing their product, how do they know that they've covered all their bases? You need to have protein, carbohydrates, fats etc., but what about vitamins or minerals?
Has science produced a commonly accepted list of all the nutrients that humans need to live? For babies there is certainly a formula available for a complete menu for survival: formula*
Here are the nutrition facts from Nestlé's "Good Start":
Formula nutrition facts. source: Nestlé
Comparable lists are available for people that cannot eat normally (e.g. people in a comatose state) and are fed enteral or parenteral nutrition.
*. Remember though, breast is best :)
The following is multiple choice question (with options) to answer.
The breasts contain what to give milk to feed a baby? | [
"fetal glands",
"mammary glands",
"sebaceous glands",
"primordial glands"
] | B | The female reproductive organs include the vagina, uterus, fallopian tubes, and ovaries ( Figure below ). The breasts are not shown in this figure. They are not considered reproductive organs, even though they are involved in reproduction. They contain mammary glands that give milk to feed a baby. The milk leaves the breast through the nipple when the baby sucks on it. |
SciQ | SciQ-6148 | optics, water, evaporation, gas
Title: How are water vapors not visible? This site says that water vapor isn't visible.
However, take a look at this picture:
Isn't that water vapor? Water vapour is a clear and colourless gas, so it can't be seen by the naked eye.
What you see in the photo in your second link is (partially) condensed water vapour, i.e. fog (or mist). Fog contains tiny, discrete water droplets and light bounces off their surface in random directions, causing the visibility.
Water vapour by contrast only contain free molecules, too small for light to bounce off, so pure water vapour (without any condensate) is invisible, like most gases (some gases are clear but coloured like chlorine gas).
The following is multiple choice question (with options) to answer.
What form when water vapor condenses in the air around specs of matter? | [
"storms",
"condensation",
"humidity",
"clouds"
] | D | Clouds form when water vapor condenses in the air around specs of matter. Clouds are classified on the basis of where and how they form. Types of clouds include cirrus, stratus, and cumulus clouds. |
SciQ | SciQ-6149 | cell-biology, microbiology
Title: Are there any organisms that are made of more than one (~5-12) cell? Prokaryotes and eukaryotes are unicellular, made of one cell. Great. Eukaryotes are unicellular or multicellular. But the typical examples of multicellular eukaryotes we have are made of, often, trillions of cells, like us humans. Ants must still be made of many millions of cells. Are there known eukaryotes with very few cells that make them up? Like, 5, or something? Or maybe a dozen cells making up the whole organism in its fully developed state? There's Trichoplax adhaerens, a Placozoa, made of a few thousand cells. Then there is Dicyema japonicum, a simple mesozoan, made up of 9 to 41 cells. Arguably, the simplest multicellular organism is the algae Tetrabaena socialis, whose body consists of 4 cells. Then, there's the parasitic Myxozoa which have 7 cells.
The following is multiple choice question (with options) to answer.
All other forms of life, including plants and animals, are composed of what kind of cells? | [
"synthetic",
"bacterial",
"cytoplasmic",
"eukaryotic"
] | D | |
SciQ | SciQ-6150 | botany, microbiology, terminology, etymology
Title: Rhizosphere vs. Endorhiza? In relation to microbiology and the naming of the various areas of the plant as it relates to microbial inhabitance, I am confused as to the difference between the terms endorhiza and rhizosphere.
In this case I see rhizosphere referred simply to as the 'roots', but in this case I also see endorhiza explained simply as 'roots' also.
However in this case, I see a further explanation for endorhiza (which does make sense etymologically): 'internal root tissues'.
Does this mean endorhiza is be a sub-term for the area inside the roots, and the larger area of the rhizome in general represented by rhizosphere, and that is the difference? Healthy plant growth depends on a microbial community that lives around and inside the roots of plants (Bais et al. 2001). Roots secrete from the roots a number of chemical compounds that influences the microbial community around but outside of the roots. The microbial community can include bacteria, fungi, and single-celled parasites, as well as larger organisms like insect larvae and even roots from other plants. Some chemicals attract certain organisms while other chemicals repel organisms. This community of organisms around the roots is called the rhizosphere (Walker et al. 2003). The paper by Walker (open access) describes some of the many types of symbiotic relationships that occur in the rhizosphere.
Endorhiza refers to the internal environment of the root system. The endorhiza contains another microbial community of bacteria and fungi (Backman and Sikora 2008). The organisms of this endorhizal community are collectively called endophytes. Like the rhizosphere, the organisms in the endorhiza are important symbiotic species that benefit the health of the plant.
Similar communities have been identified for other regions of the plant, such as the phyllosphere, the organisms that live on the leaves, stems and other plant parts above the ground (Backman and Sikora 2008).
The following is multiple choice question (with options) to answer.
A mycorrhiza refers to what kind of relationship between a fungus and the roots of a plant? | [
"familial",
"semantic",
"predator-prey",
"symbiotic"
] | D | A mycorrhiza (Greek for "fungus roots") is a symbiotic association between a fungus and the roots of a plant. In a mycorrhizal association, the fungus may colonize the roots of a host plant by either growing directly into the root cells, or by growing around the root cells. This association provides the fungus with relatively constant and direct access to glucose, which the plant produces by photosynthesis. The mycelia of the fungi increase the surface area of the plant’s root system. The larger surface area improves water and mineral nutrient absorption from the soil. |
SciQ | SciQ-6151 | geothermal-heat
Title: What Keeps the Earth Cooking? If radioactive decay supplies only about half the Earth’s heat, what are the remaining sources of heat?
If radioactive decay supplies only about half the Earth’s heat, what are the remaining sources of heat?
Mostly it is residual heat energy from when the Earth was very young. The biggest source came from the kinetic energy of all the bodies, big and small, that collided to form the Earth being converted to heat. The differentiation of the Earth added even more heat energy to the Earth.
In addition to radioactive decay, the on-going freezing of the outer core material onto to the inner core adds a bit more heat to the system, but neither one compensates for heat transported through the mantle and crust and then out into space. Note that this heating from below is but a tiny portion of the overall energy budget for the Earth's surface.
Even the Earth's surface was very hot shortly after the formation and differentiation of the Earth. While the surface cooled quickly (geologically speaking), the interior has not. The key reason is that 2,890 km of rock makes for a fairly thick blanket.
The following is multiple choice question (with options) to answer.
What is earth's main source of energy? | [
"the core",
"the sun",
"the atmosphere",
"the moon"
] | B | The Sun is Earth’s main source of energy. The Sun gives us both light and heat. The Sun changes hydrogen into helium through nuclear fusion. This releases huge amounts of energy. The energy travels to the Earth mostly as visible light. The energy is carried through the empty space by radiation . We can use sunlight as an energy resource, called solar energy ( Figure above ). |
SciQ | SciQ-6152 | electric-circuits, electric-current
Title: Can Kirchhoff laws be applied to any circuit? Kirchhoff's loop/current rule is just law of conservation of energy and Kirchhoff's junction rule is just law of conservation of charge.So, I think that these can be applied to any circuits unlike Ohm's law. Is there any exceptions? Kirchhoff's loop rule is also called Kirchhoff's voltage law (KVL). Which is different from Kirchhoff's current rule which is also called Kirchhoff's current law (KCL). KVL is derived from Maxwell–Faraday equation for static magnetic field (i.e. the derivative of B with respect to time is zero). KCL is derived from charge continuity equation which is equation 3 here.
A well known case in which KVL doesn't apply is when having a varying magnetic field enclosed by the circuit being studied. The presence of time varying magnetic field makes the measured voltage non-unique (depends on the branch used to measure the voltage). Have a look at page 3 of this presentation.
A well known case in which KCL is limited is when having a voltage source with very high frequency such that effects like parasitic capacitance can no longer be ignored. In those cases wires (or conducors) are treated as transmission lines. In such a case a current can flow even in an open circuit..
For further information have a look at limitations sections of KCL and KVL here.
The following is multiple choice question (with options) to answer.
Kirchhoff’s second rule (the loop rule) is an application of conservation of what? | [
"mineral",
"energy",
"Rock",
"heating"
] | B | Kirchhoff’s Second Rule Kirchhoff’s second rule (the loop rule) is an application of conservation of energy. The loop rule is stated in terms of potential, V , rather than potential energy, but the two are related since PE elec = qV . Recall that emf is the potential difference of a source when no current is flowing. In a closed loop, whatever energy is supplied by emf must be transferred into other forms by devices in the loop, since there are no other ways in which energy can be transferred into or out of the circuit. Figure 21.23 illustrates the changes in potential in a simple series circuit loop. Kirchhoff’s second rule requires emf equals the sum of the. |
SciQ | SciQ-6153 | 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.
Evolution over a short period of time at the level of the population is called what? | [
"redistributions",
"grammaticalization",
"macroevolution",
"microevolution"
] | D | The time scale of evolution can vary. Evolution over a short period of time at the level of the population is called microevolution. Evolution over a long period of time above the level of the species is called macroevolution. |
SciQ | SciQ-6154 | thermodynamics
Based on this page in a “Blaze” book, my six year old asked “which would win?” between water and lava. On further investigation, we refined the question to: which would turn solid first in similar conditions, a liter of room temperature water or a liter of volcanic lava? You've got the right idea — you want to simplify the problem — but I don't think you're using quite the right simplification. Take a look at the book's set-up of the situation, and ask yourself how the water is stopping the lava. You'll see the idea is that we're using liquid water, not ice, to solidify the lava.
So your question should really be: How much heat do we need to absorb from a liter of lava to turn it into a solid, and how much heat can a liter of water at room temperature absorb before it turns to steam? If the latter is larger than the former, then a liter of water can cool a liter of lava to the point where it solidifies before the water all changes into steam.
[I'm using "heat" when I should really be using "thermal energy", but this is for a $6$ y.o., so I'm keeping it simple.]
First, let's do the calculation for water. Here (since it's for a $6$ y.o.), I'm not going to show all the steps in the calculations:
Energy to heat $\pu{1 L}$ liquid water at room temp ($25 \,\pu{^{\circ}C}$ ) to $100 \,\pu{^{\circ}C}$ = $\pu{75 kcal}$
Energy to turn $\pu{1 L}$ liquid water to steam at $100 \,\pu{^{\circ}C}$ = $\pu{533 kcal}$
Total = $\pu{608 kcal}$
According to https://en.wikipedia.org/wiki/Lava, lava is typically $700 \,\pu{^{\circ}C}$ to $1200 \,\pu{^{\circ}C}$, so let's call it $1000 \,\pu{^{\circ}C}$.
The following is multiple choice question (with options) to answer.
When water is heated by magma and makes it's way to the surface what is created? | [
"volcanic",
"trough",
"eruption",
"geyser"
] | D | Water works its way through porous rocks or soil. Sometimes this water is heated by nearby magma. If the water makes its way to the surface, it forms a hot spring or a geyser. |
SciQ | SciQ-6155 | cell-biology, nutrition, blood-circulation, liver
Title: How do nutrients get to the cells they need to get to? I understand the basics of digestion. I know that nutrients get absorbed by the microvilli, enter the bloodstream and travel to the liver but after all that, what is the biological mechanism that guides these nutrients to the proper receiving location? Broadly speaking, nutrients that enter the blood from the gut, and those that are released into the blood by the liver, are available to any cells that require them. So there is no "guiding to the correct location" in the sense that you suggest.
Lipids for example are present in the various lipoproteins and can be acquired from these by all cells. Iron is bound to transferrin, and any cell with transferrin receptors can internalise the transferrin and take the iron. Glucose is available in solution in the plasma, and free fatty acids are bound to serum albumin in the blood. During starvation the liver produces ketones ("ketone bodies") which are taken up by many different tissues/cell types.
The following is multiple choice question (with options) to answer.
The mechanical and digestive processes have one goal: to convert food into molecules small enough to be absorbed by the epithelial cells of what? | [
"intestinal villi",
"bile ducts",
"stomach cilia",
"alveoli"
] | A | Absorption The mechanical and digestive processes have one goal: to convert food into molecules small enough to be absorbed by the epithelial cells of the intestinal villi. The absorptive capacity of the alimentary canal is almost endless. Each day, the alimentary canal processes up to 10 liters of food, liquids, and GI secretions, yet less than one liter enters the large intestine. Almost all ingested food, 80 percent of electrolytes, and 90 percent of water are absorbed in the small intestine. Although the entire small intestine is involved in the absorption of water and lipids, most absorption of carbohydrates and proteins occurs in the jejunum. Notably, bile salts and vitamin B12 are absorbed in the terminal ileum. By the time chyme passes from the ileum into the large intestine, it is essentially indigestible food residue (mainly plant fibers like cellulose), some water, and millions of bacteria (Figure 23.32). |
SciQ | SciQ-6156 | biochemistry, molecular-biology, coronavirus
Mechanics of membrane fusion/pore formation
Membrane tension and membrane fusion
The hydrophobic force: measurements and methods
Reconciling the understanding of ‘hydrophobicity’ with physics-based models of proteins
The following is multiple choice question (with options) to answer.
Influenza virus is packaged in a viral envelope, which fuses with the what? | [
"cell wall",
"plasma membrane",
"nucleus",
"bacteria"
] | B | Influenza virus is packaged in a viral envelope, which fuses with the plasma membrane. This way, the virus can exit the host cell without killing it. What advantage does the virus gain by keeping the host cell alive?. |
SciQ | SciQ-6157 | desert
Title: When was the first not-icy desert formed? For how long have deserts existed and which one would be the first to be created? I'm talking about arid, dry deserts, not the Antarctic or Arctic or any other icy deserts. Deserts have existed since at least the Permian period (299-251 million years ago) when the world's continents had combined into the Pangaea supercontinent. Stretching from pole to pole, this land mass was large enough that portions of its interior received little or no precipitation, according the University of California Museum of Paleontology.
Pangaea broke into smaller land masses which were moved across the surface by tectonic forces, a process that both changed global climate patterns and the climate those continents were exposed to. As a result, current desert regimes date back to no more than 65.5 million years, according to this Encyclopedia Britannica article:
The desert environments of the present are, in geologic terms,
relatively recent in origin. They represent the most extreme result of
the progressive cooling and consequent aridification of global
climates during the Cenozoic Era (65.5 million years ago to the
present), which also led to the development of savannas and scrublands
in the less arid regions near the tropical and temperate margins of
the developing deserts. It has been suggested that many typical modern
desert plant families, particularly those with an Asian centre of
diversity such as the chenopod and tamarisk families, first appeared
in the Miocene (23 to 5.3 million years ago), evolving in the salty,
drying environment of the disappearing Tethys Sea along what is now
the Mediterranean–Central Asian axis.
Which would put the oldest of "modern" desert somewhere in the region of what later became North Africa or South Asia.
The following is multiple choice question (with options) to answer.
A desert is a type of what community in an ecosystem? | [
"culture",
"population",
"biome",
"colony"
] | C | This scene is from Anza-Borrago California Desert Park. However, deserts exist around the globe. You might find a similar picture of a desert in Africa. The desert is one type of biome. |
SciQ | SciQ-6158 | physical-chemistry, phase
Title: Properties of plasmas In chemistry one can recognize that the four states of matter are solid, liquid, gas and plasma. The first is rigid, and has a definite shape and volume. The second doesn't have a shape, and assumes the shape of its container, but it has a fixed volume. The third doesn't have either a shape or a fixed volume and assumes the volume and shape of its container. What about the fourth one (plasma)? Plasma is made up of ionized gas, so molecules have a positive electric charge and valency electrons are totally or partially separated by their nuclei.
Plasma is different from a gas since it has a high temperature and is radiation emitting; think of the Sun and other stars, which are made up of plasma and show both these properties.
Plasma hasn't got a proper volume, like gases; e.g. stars can expand or contract under the opposite effects of gravity and nuclear fusion. For example, this property is important to comprehend the formation of white dwarfs and neutron stars, process caused by high pression due to gravity.
Little trivia: there is also a fifth state of matter, whose name is Bose-Einstein Condensate (BEC).
The following is multiple choice question (with options) to answer.
What are the two types of properties that matter has? | [
"composition and weight",
"nature and purpose",
"size and shape",
"physical and chemical"
] | D | Matter has both physical and chemical properties. Physical properties can be measured or observed without matter changing to a different substance. |
SciQ | SciQ-6159 | endocrinology
Excitement or stress response, including fast heart rate and breathing and anxiety: short term response: adrenaline; long-term response: cortisol
Appetite: ghrelin, leptin, adiponectin, cholecystokinin, insulin, glucagon-like peptide, gastrointestinal peptide...
Sexual drive: sex hormones, mainly testosterone and estradiol
Sleepiness: melatonin, cortisol
Depression: cortisol, sex hormones (mainly in women)
The point of this answer is to show that some of your feelings can be simply affected by hormones, which are note some ultimate forces, and that being aware of that can help you to control them to some extent.
The following is multiple choice question (with options) to answer.
What is the hormone produced in high-stress situations? | [
"testosterone",
"thyroxine",
"somatostatin",
"adrenalin"
] | D | In the health sciences, the concentration of a solution is typically expressed asparts per thousand (ppt), indicated as a proportion. For example, adrenalin, the hormone produced in high-stress situations, is available in a 1:1000 solution, or one gram of adrenalin per 1000 g of solution. The labels on bottles of commercial reagents often describe the contents in terms of mass percentage. Sulfuric acid, for example, is sold as a 95% aqueous solution, or 95 g of H2SO4 per 100 g of solution. Parts per million and parts per billion are used to describe concentrations of highly dilute solutions. These measurements correspond to milligrams and micrograms of solute per kilogram of solution, respectively. For dilute aqueous solutions, this is equal to milligrams and micrograms of solute per liter of solution (assuming a density of 1.0 g/mL). |
SciQ | SciQ-6160 | gas-phase-chemistry
Title: Is there any kind of reaction with two types of reactants (gases) and one product (also gas) such that the total volume after the reaction increases? I would like to think of the following equation:
$$\ce{aA(g) + bB(g) -> cC(g)}$$
where $a + b < c$ and $\ce{A},$ $\ce{B}$ and $\ce{C}$ are different gases.
Is there such chemical reaction? This is a fun question. The essence of what makes it challenging is that you're doing a synthesis -- combining two different species into one -- yet ending up with more particles, not (as is typical) less. This limits the number of possible reactions significantly. Here, however, is one that meets the conditions:
Octasulfur ($\ce {S_8}$) boils at 444.6 $^\circ \text{C}$ at standard pressure. So, above that temperature, one could have:
$$\ce{ S_{8(g)} + 4O_{2(g)}-> 8SO_{(g)}},$$
where $1+4 < 8$.
Of course, if octasulfur were combusted with oxygen, it's likely that many other species of sulfur oxides (i.e., compounds of the form $\ce {S_xO_y}$) would be produced as well.
The following is multiple choice question (with options) to answer.
What type of reaction causes two substances to combine to make a single substance? | [
"composition reaction",
"spontaneous mutation",
"metabolism",
"component reaction"
] | A | In this equation, two substances combine to make a single substance. This is a composition reaction. Two different substances react to make two new substances. This does not fit the definition of either a composition reaction or a decomposition reaction, so it is neither. In fact, you may recognize this as a double-replacement reaction. A single substance reacts to make multiple substances. This is a decomposition reaction. |
SciQ | SciQ-6161 | reproduction, digestion, sexual-reproduction
Hazardous components of pollen:
Trace amounts of hepatotoxic pyrrolizidine alkaloids were found in pollen of Echium vulgare, E. plantagineum, Senecio jacobaea, S. ovatus, and Eupatorium cannabinum (Boppre et al., 2008). In Middle and Northern Europe these pollens are not among the main pollen grains gathered by bees, however in Southern Europe the two Echium plants are more diffused and are gathered by bees in larger amounts (Campos et al., 1994; Serra Bonvehi, 1997). [Source 1] (Page 5)
Therefore, it should undergo tests to approve it's purity as allergies can be caused.
References:
1 : Future of bee pollen(Research gate)
2 : Pollen composition and standardisation of analytical methods(Research gate)
3 : Hollow pollen shells to enhance drug delivery(NCBI)
4 : Bee pollen: chemical composition and therapeutic application(NCBI)
5 : Biological activities of commercial bee pollens: antimicrobial, antimutagenic, antioxidant and anti-inflammatory(NCBI)
6 : Biological and therapeutic properties of bee pollen: a review(NCBI)
The following is multiple choice question (with options) to answer.
Hay fever is actually an allergy to what substance, vital to plant reproduction? | [
"fungi",
"pollen",
"grass",
"nitrogen"
] | B | Did you ever hear of hay fever? It’s not really a fever at all. It’s an allergy to plant pollens. People with this type of allergy have symptoms such as watery eyes, sneezing, and a runny nose. A common cause of hay fever is the pollen of ragweed. Many people are also allergic to poison ivy ( Figure below ). Skin contact with poison ivy leads to an itchy rash in people who are allergic to the plant. |
SciQ | SciQ-6162 | cellular-respiration
Title: Do cold blooded animals generate any heat? In explaining energy and work to an 8 year-old I said that all conversion of energy generates heat as a by-product. For example, cars generate heat in their engines and running generates heat in our bodies. Then the 8 year-old said, except for cold-blooded animals.
So my question is, do cold-blooded animals generate any heat in their conversion of stored energy (food, fat, etc) into motion? If they generate heat, why are they cold-blooded? They do generate heat. They just do not SPEND energy specifically on heating their bodies by raising their metabolisms. This is a form of energy conservation. The metabolic rate they need to live is not nearly enough to heat their bodies.
An example of spending energy to heat the body is seen in humans shivering. Here muscle is activated not for its usual purpose, but to function as a furnace. "Warm-blooded" and "cold-blooded" is somewhat a misnomer. The correct way to think of it is...
Endotherm or ectotherm. Does the heat primarily come from within (endo) or from the surroundings (ecto). Endothermic animals include mammals. Most of their body heat is generated by their own metabolisms. Ectothermic animals include reptiles and insects. They absorb most of their body heat from the surroundings. This is not the same as saying they let their body temperature fluctuate with their surroundings, some avoid this by moving around to accomodate themselves.
Homeotherm or poikilotherm. Homeotherms want to maintain homeostasis for their body temperatures. They don't want it to change. Poikilotherms do not exhibit this behaviour, instead their body temperatures vary greatly with the environment.
We can have endotherm poikilotherms, such as squirrels, who let their body temperature drop while hibernating. Endotherm homeotherms, such as humans, where temperature is constant by means of complex thermoregulation. Ectotherm homeotherms, such as snakes (moving into shadow or into the sun to regulate temperature), and ectotherm poikilotherms, such as maggots.
The following is multiple choice question (with options) to answer.
Endotherms are warmed mostly by heat generated by what? | [
"the sun",
"metabolism",
"movement",
"electricity"
] | B | |
SciQ | SciQ-6163 | newtonian-mechanics, friction, drag, oscillators, dissipation
Title: What is the physical interpretation of the linear coefficient in this ODE for projectile motion? For the second order ODE governing the position of a projectile subject to air resistance
$$ m\frac{d^2x}{dt^2} +k\frac{dx}{dt}+mg=0 \quad k>0, \> x(0)=0, \> x'(0)=V>0 $$
a non-dimensionalization can me made so that the system is then
$$ \frac{d^2X}{d\tau^2} +\beta\frac{dX}{d\tau}+1=0 \quad k>0 $$
for non-dimensional variables $X,\tau$. It turns out $ \beta=\frac{kV}{mg}$. What is the physical interpretation of $\beta$? I was inclined to say that it is the terminal velocity, but examining the ODE shows that terminal velocity is actually $\frac{mg}{k}$. I know that $\beta$ is the ratio between the the resistance it feels when fired and the total downward force.
So the question remains: What is $\beta$? You almost answered it on your own!
Essentially it's the ratio of the viscous force to the gravitational force. As $\beta \rightarrow 0$, the gravitational force dominates and the damping due to air friction is very small. Likewise, as $\beta \rightarrow \infty$, the air friction dominates the solution.
This isn't really all that illustrative physically, but it doesn't always have to be. What it does allow you do to is use only $\beta$ to determine trends. For example, if $\beta = 0.5$, the solution is the same whether you are on Mars, or under water on Earth, or your mass is huge or small, etc.. It's a similiarity parameter that reduces the number of variables in your problem from 4 ($k$, $V$, $m$, $g$) to a single variable, $\beta$.
The following is multiple choice question (with options) to answer.
If a ball is released from rest when air resistance is negligible, velocity is seen to increase linearly, while what related property is a constant? | [
"acceleration",
"time",
"density",
"speed"
] | A | Figure 2.43 Positions and velocities of a metal ball released from rest when air resistance is negligible. Velocity is seen to increase linearly with time while displacement increases with time squared. Acceleration is a constant and is equal to gravitational acceleration. |
SciQ | SciQ-6164 | thermodynamics, physical-chemistry, combustion
Title: Is there an 'intuitive' explanation for "Which burns more?" In helping a friend's son with his grade 10 science homework, I came across a question that essentially asked the following:
"If two objects of equal mass but different specific heat capacities are touched, which will burn more?"
The wording of the question implied that this was meant to be a thought experiment rather than anything calculation-based.
My first reaction was that this question was probably quite a bit more complex than it was made out to be; a quick search online and on this site confirms this, however ideas like conductivity (which I'm familiar with), diffusivity & effusivity (which I'm not) and others are well beyond the student's understanding at the moment. I also felt "burn more" was rather vague.
To address these concerns, I made the following two assumptions:
since the question made no reference to time, I took the phrase "burn more" to mean "transfer the most energy by the time equilibrium has been reached"
all parameters like mass (mentioned in the question), density, conductivity, area of contact, etc., other than specific heat capacity and time would be equal.
The following is multiple choice question (with options) to answer.
What term is used to describe the ability of matter to burn? | [
"volatility",
"permeability",
"reactivity",
"flammability"
] | D | Flammability is the ability of matter to burn. When matter burns, it combines with oxygen and changes to different substances. Wood is an example of flammable matter, as seen in Figure below . |
SciQ | SciQ-6165 | evolution
bacteria
cyanobacteria
archaea
protists
fungi
algae
plants
nematodes
arthropods
vertebrates
Bacterial and archaean colonisation
The first evidence of life on land seems to originate from 2.6 (Watanabe et al., 2000) to 3.1 (Battistuzzi et al., 2004) billion years ago. Since molecular evidence points to bacteria and archaea diverging between 3.2-3.8 billion years ago (Feng et al.,1997 - a classic paper), and since both bacteria and archaea are found on land (e.g. Taketani & Tsai, 2010), they must have colonised land independently. I would suggest there would have been many different bacterial colonisations, too. One at least is certain - cyanobacteria must have colonised independently from some other forms, since they evolved after the first bacterial colonisation (Tomitani et al., 2006), and are now found on land, e.g. in lichens.
Protistan, fungal, algal, plant and animal colonisation
Protists are a polyphyletic group of simple eukaryotes, and since fungal divergence from them (Wang et al., 1999 - another classic) predates fungal emergence from the ocean (Taylor & Osborn, 1996), they must have emerged separately. Then, since plants and fungi diverged whilst fungi were still in the ocean (Wang et al., 1999), plants must have colonised separately. Actually, it has been explicitly discovered in various ways (e.g. molecular clock methods, Heckman et al., 2001) that plants must have left the ocean separately to fungi, but probably relied upon them to be able to do it (Brundrett, 2002 - see note at bottom about this paper). Next, simple animals... Arthropods colonised the land independently (Pisani et al, 2004), and since nematodes diverged before arthropods (Wang et al., 1999), they too must have independently found land. Then, lumbering along at the end, came the tetrapods (Long & Gordon, 2004).
Note about the Brundrett paper: it has OVER 300 REFERENCES! That guy must have been hoping for some sort of prize.
References
The following is multiple choice question (with options) to answer.
What is the evolutionary history of group of related organisms | [
"history",
"iteration",
"phylogeny",
"substructure"
] | C | Phylogeny is the evolutionary history of group of related organisms. It is represented by a phylogenetic tree that shows how species are related to each other through common ancestors. |
SciQ | SciQ-6166 | organic-chemistry, redox
As you can see, the ketone gets oxidised, more precisely the carbonyl carbon gets oxidised as increases its oxidation state. On the other side, the peroxide oxygens get reduced as they decrease their oxidation state.
The following is multiple choice question (with options) to answer.
What forms a ketone when oxidized? | [
"enzyme",
"secondary alcohol",
"carbolic acid",
"aldehyde"
] | B | A secondary alcohol forms a ketone when oxidized. The secondary alcohol cannot be further oxidized to produce a carboxylic acid. Tertiary alcohols cannot be oxidized in this way, because the carbon atom bonded to the OH group is not also bonded to any hydrogens. |
SciQ | SciQ-6167 | thermodynamics, energy, terminology
You are absolutely correct. Heat is not a form of energy. It is a mechanism by which energy is transferred from one substance, object, etc., to another due solely to temperature difference.
When I was learning about thermodynamics I found a particular description that, at least for me, help differentiate between the energy of something and the transfer of energy (by work or heat) from one thing to another. In this case the transfer of energy by heat. I'd like to share it with you in case it might be helpful. For simplicity, the description is for heat conduction.
Consider two solid objects, one having a higher temperature than the other. Which means the molecules of the higher temperature object 1 have a higher average translational kinetic energy than the molecules of the lower temperature object 2.
The objects are placed in contact with each other. At the interface between the objects the molecules of the higher temperature object collide with the molecules of the lower temperature object. On average, this results in the transfer of kinetic energy from the molecules of the higher temperature object to molecules of the lower temperature object causing the temperature of the higher temperature object to decrease, and the temperature of the lower temperature object to increase.
This transfer of kinetic energy from the molecules of the higher temperature object to the molecules of the lower temperature object is what we mean by heat. But the increase in the average kinetic energy of the molecules of the lower temperature object and decrease in the average kinetic energy of the molecules of the higher temperature object is what we mean by a change in the internal (kinetic) energy of the two objects. Thus the difference between the transfer of energy and the energy itself.
Hope this helps.
The following is multiple choice question (with options) to answer.
What is the energy that flows as a result of a difference in temperature? | [
"electricity",
"magnetism",
"polarity",
"heat"
] | D | Heat is the energy that flows as a result of a difference in temperature. We use the symbol for heat. Heat, like all forms of energy, is measured in joules. |
SciQ | SciQ-6168 | cardiology, embryology, pain, central-nervous-system
Title: At what stage is the nervous system developed enough to interpret neuronal signals as 'pain'? According to this article in Live Science, one of the reasons the fetus can't feel pain until 19 weeks is because the nervous system isn't fully developed.
But according to this article, the heart starts beating at day 16.
And according to this article, the nervous system controls the rate beating of the heart.
Then my question is, **how can it be assured that the nervous system isn't developed until 19 weeks, when the nervous system controls the heart beating rate since day 16? First, there is some confusion on your part about heart cells and pain perception. Heart cells generate an action potential intrinsically; they do not need the central nervous system to beat (your second article explains this; read the part about the importance of calcium.) So yes, long before a fetus can feel pain, the heart is beating, because there must be circulation of nutrients throughout the embryo.
Secondly, the vagus nerve and sympathetic nerves can affect heart rate (the former by slowing it down when firing). These nerves start to reach their endpoints late in week 4 of development. So 19 days is not correct.
Cardiac sympathetic system
Although the primitive human heart starts to beat at 21 to 22 d, heart development continues to day 50, and it is near the end of this period, during the fifth week, that thoracic neural crest cells migrate from the neural tube through the somites and form aggregations (ganglia) near the dorsal aorta. [emphasis mine]
To experience pain, however, requires maturation of certain parts of the brain, most importantly, part of the thalamus and the cerebral cortex:
Current theories of pain consider an intact cortical system to be both necessary and sufficient for pain experience. In support are functional imaging studies showing that activation within a network of cortical regions correlate with reported pain experience. Furthermore, cortical activation can generate the experience of pain even in the absence of actual noxious stimulation. These observations suggest thalamic projections into the cortical plate are the minimal necessary anatomy for pain experience. These projections are complete at 23 weeks' gestation. [emphasis mine]
The following is multiple choice question (with options) to answer.
Exposure to toxins is most damaging during weeks 4 through 8 of the embryonic stage due to development of what during this period? | [
"organs",
"faith",
"pain",
"samples"
] | A | Embryonic Development (Weeks 4–8). Most organs develop in the embryo during weeks 4 through 8. If the embryo is exposed to toxins during this period, the effects are likely to be very damaging. Can you explain why? (Note: the drawings of the embryos are not to scale. ). |
SciQ | SciQ-6169 | human-biology, evolution, human-genetics
So, if the trait you consider has genetic variance in the population and that this trait influence the fitness with a given selection differential you can provide estimates of how the trait will change through time in the human population. Now if the variance does not already exist in the population but you have to wait for mutations to occur, then you cannot really provide an estimate of when will this occur.
Discussion on the future evolution of nail size
Also, when you think about some traits such as our nails. You may consider that they are of no use but do you really think that those people that have no nail would really have a better fitness. At first I would tend to think that I would rather chose a partner that have nails, it is much more sexy! If many people are like me and appreciate nails, nailless people will have difficulties to reproduce or in other words, they will have a lower fitness that nailed people.
I don't think we have data on what loci (positions on the chromosomes) influence the size of the nails and about how much of the variance in nail size is explained by the genetic additive variance. And how do the size of our nails influence fitness. So we don't know about how this trait will evolve through time.
Future evolution of other traits
There are several traits that we can/could more or less predict their evolution. Those are the traits for which we know the ratio of the genetic additive variance over the phenotypic variance and how it influences fitness. I can think of genes that are linked with resistance to new diseases such as HIV for example. If malaria comes to a new area you might expect the allele (=variant of a gene) allowing a better resistance to malaria will increase in frequency (note that this allele is advantageous in heterozyotes (protects from malaria) but it is highly disadvantegous in homozygote because it causes sickle-cel disease). We could estimate the change in frequency of alleles linked with obesity in some countries also. Probably several studies exist on the subject but I don't know them. One might improve this answer by giving some information about how HIV resistant variants is likely to change in frequency through time.
What were the last evolutionary changes in human history?
The following is multiple choice question (with options) to answer.
What evolutionary process may affect the distribution of a polygenic trait? | [
"characteristic selection",
"natural selection",
"artificial selection",
"flow selection"
] | B | Natural Selection for a Polygenic Trait. Natural selection may affect the distribution of a polygenic trait. These graphs show three ways this can happen. |
SciQ | SciQ-6170 | newtonian-mechanics, forces, free-body-diagram
Title: Does the normal force require other forces to exist? Let's say we have two blocks resting over a frictionless surface. The two blocks are next to each other and there is contact between them. Even though there is no force trying to push them closer to each other, is there a normal force between the two blocks? In this case, there wouldn't be a normal force between the blocks. Much like friction, the normal force only acts in opposition to other forces. From a logical real-world perspective, this makes sense too, since if the normal force acted between, say, two billiard balls sitting on a surface, they would start rolling away from each other, which isn't what we observe to happen.
The following is multiple choice question (with options) to answer.
What type of force exists between two touching surfaces? | [
"tension",
"centrifugal",
"friction",
"opposing"
] | C | Friction is the force that resists motion. In most beginning physics classes, friction is ignored. Concepts can be understood and calculations made assuming friction to be nonexistent. Whenever physics intersects with the real world, however, friction must be taken into account. Friction exists between two touching surfaces because even the smoothest looking surface is quite rough on a microscopic scale. |
SciQ | SciQ-6171 | neuroscience, physiology, human-physiology, reflexes
Title: Are there neuron mediated reactions faster than reflexes? I'm interested in how fast the human body can respond to a stimulus. I know the fastest reflex, the blink reflex, operates around 100ms from stimulus to reaction. I also know that the blink reflex is known as the fastest reflex in the human body. My interest is in the fastest responses to stimuli I can find in the body.
Are there any faster responses to stimuli within the human body which use neurons but are not categorized as a reflex (due to some technicality), meaning they could be faster than the fastest reflex? To the best of my understanding a reflex is defined by the use of neurons to convey the information, I'm just wondering if there are any grey areas which don't qualify as a reflex but may be faster. I don't want to potentially write off an entire class of neurological behavior in my research simply because I stopped at the blink reflex. A reflex as fast as the blink in a neural circuit:
I would consider suppression of outer hair cells in the cochlea to be a reflex; the faster component of this reflex is about the same as the blink reflex, around 100 ms. The hair cells themselves aren't considered neurons, but the pathway that suppresses their motility certainly is.
A much much faster non-neuronal "reflex":
That said, the outer hair cells themselves also dance along quite fast in response to sensory input, even faster than the typical hearing range for humans, faster than 20kHz! In some ways, this is a reflex because you are taking sensory (specifically, auditory) information and turning it into a motor response, but all the "action" is taking place within one cell, and it isn't a neuron.
A more classical reflex that is substantially faster than 100 ms
Reflexes in the periphery can be much faster than 100 ms. The myotatic reflex, or stretch reflex, can be as fast as 30 ms in the knee - this is the reflex that is tested when a physician smacks you on the knee with a hammer (used as a test of spinal and peripheral nerve function, not as a punishment). It's likely there are other stretch reflexes that are faster just because distances to the spinal cord are shorter, but these might be more difficult to test (in this paper they report latencies as fast as 20 ms).
The following is multiple choice question (with options) to answer.
A short reflex is completely what and only involves the local integration of sensory input with motor output? | [
"physiological",
"peripheral",
"neuronal",
"central"
] | B | Short and Long Reflexes Somatic reflexes involve sensory neurons that connect sensory receptors to the CNS and motor neurons that project back out to the skeletal muscles. Visceral reflexes that involve the thoracolumbar or craniosacral systems share similar connections. However, there are reflexes that do not need to involve any CNS components. A long reflex has afferent branches that enter the spinal cord or brain and involve the efferent branches, as previously explained. A short reflex is completely peripheral and only involves the local integration of sensory input with motor output (Figure 15.8). |
SciQ | SciQ-6172 | organs, lifespan
Title: Organs lifespan out of the body What organ can be conserved outside of the body for the longest time and still function when reimplanted? Depends what you consider an organ. Typically though it's the cells which require the most metabolic activity which have the shortest life span. The kidney is the most of the major internal organs with up to 36 hours with liver coming second at up to 16 hours.
The following is multiple choice question (with options) to answer.
The urea cycle, a set of biochemical reactions that produces urea from ammonium ions to prevent toxicity, occurs to some extent in the kidney, but primarily in what organ? | [
"spleen",
"skin",
"liver",
"colon"
] | C | Urea Cycle The urea cycle is a set of biochemical reactions that produces urea from ammonium ions in order to prevent a toxic level of ammonium in the body. It occurs primarily in the liver and, to a lesser extent, in the kidney. Prior to the urea cycle, ammonium ions are produced from the breakdown of amino acids. In these reactions, an amine group, or ammonium ion, from the amino acid is exchanged with a keto group on another molecule. This transamination event creates a molecule that is necessary for the Krebs cycle and an ammonium ion that enters into the urea cycle to be eliminated. In the urea cycle, ammonium is combined with CO2, resulting in urea and water. The urea is eliminated through the kidneys in the urine (Figure 24.18). |
SciQ | SciQ-6173 | evolution, biochemistry, mitochondria
Title: Is there any advantage of having mitochondria for aerobic respiration? If we consider the pathway of breakdown of glucose which includes glycolysis, the citric acid cycle and the electron transport chain, all these processes takes place in some prokaryotes and eukaryotes. In prokaryotes all these processes take place in cytoplasm while in eukaryotes the last two processes take place in mitochondria.
So is there any advantage of performing the last two processes in the mitochondria? Does it yield more energy? If there is no advantage, what is the point of having a mitochondria (at least for this process)? From the evolutionary point of view, the eukaryotes acquired these metabolisms (except glycolysis) from their prokaryotic endosymbionts. Not all prokaryotes have the ETC. The free living ancestor of mitohondria is supposed to be the alpha-proteobacterium.
Now, glycolysis is a common pathway in lot of lifeforms perhaps because of abundance of glucose. TCA cycle is coupled with ETC at certain steps which makes it essentially a part of aerobic metabolism.
The reason for having a dedicated organelle for respiration
ATP synthesis is a membrane process. Imagine a large prokaryotic cell- as big as an animal cell. Such a cell cannot take care of its energetic demands which primarily consists of protein synthesis with the given area of membrane i.e it needs much more ATP-synthases than it can have to cope up with the energy demands of maintaining such a huge cell (this index is approximated based on surface to volume ratio). Therefore it is wise to harbor multiple efficient organelles i.e. mitochondria which themselves have just a small essential genome and proteome to maintain.
For a better understanding, please read this article. I just loved it.
There is also a book by the same author about mitochondria called Power, Sex, Suicide.
The following is multiple choice question (with options) to answer.
Cellular respiration is the reverse or opposite of what? | [
"spermatogenesis",
"reproduction",
"glycolysis",
"photosynthesis"
] | D | Specifically, during cellular respiration, the energy stored in glucose is transferred to ATP ( Figure below ). ATP , or adenosine triphosphate, is chemical energy the cell can use. It is the molecule that provides energy for your cells to perform work, such as moving your muscles as you walk down the street. But cellular respiration is slightly more complicated than just converting the energy from glucose into ATP. Cellular respiration can be described as the reverse or opposite of photosynthesis. During cellular respiration, glucose, in the presence of oxygen, is converted into carbon dioxide and water. Recall that carbon dioxide and water are the starting products of photosynthesis. What are the products of photosynthesis?. |
SciQ | SciQ-6174 | newtonian-mechanics, forces, newtonian-gravity, free-body-diagram, string
Title: How does a weight connected to a string over a pulley pulling a cart apply force onto the cart? How does the mass hanging down on the bottom (Assuming frictionless environment) apply a pull force to the car? How does the weight of the object transfer to the string (tension force and maybe the pulley does something?) which pulls the car? I wonder if the following diagram is helpful:
There is a force from the pulley on the string - that is what allows the tension to "turn the corner" so the force from the weight (which is downwards) is turned into a horizontal force (tension that can pull the cart).
The following is multiple choice question (with options) to answer.
What force pulls object downwards to the earth? | [
"kinetic energy",
"motion",
"gravity",
"momentum"
] | C | Gravity near the Earth pulls an object downwards toward the surface of the Earth with an acceleration of . In the absence of air resistance, all objects will fall with the same acceleration. The letter is used as the symbol for the acceleration of gravity. When talking about an object's acceleration, whether it is due to gravity or not, the acceleration of gravity is sometimes used as a unit of measurement where . So an object accelerating at 2g's is accelerating at or. |
SciQ | SciQ-6175 | plate-tectonics, crust, mantle, cavern
Title: How likely are caverns inside the mantle? Almost everyone wrongly assumes that the Earth's mantle is liquid, but it isn't (only the outer core is). Is it possible then that there are hollow spaces within the mantle, similar to caves in the crust? What could they look like and up to how much of the mantle could be hollow? What might be inside mantle caverns? Would they be filled with gas or rather vacuum? It is extremely unlikely that any hollow volumes exist in the mantle.
The mantle is a convecting solid which can deform over long timescales. Let's assume that such a cavern did somehow form. Whatever it is filled it, would be of lower density than the surrounding rock. It would slowly rise upwards through the solid-yet-deformable mantle until it reaches a place where the rocks are brittle, not ductile. That place is the crust. And as you know, the crust is full of caverns and there is no problem with that.
The following is multiple choice question (with options) to answer.
How does deeper material cause convection in the mantle? | [
"remains stable",
"sinks then rises",
"folds",
"rises then sinks"
] | D | Not long after Wegener's death, scientists recognized that there is convection in the mantle. Deeper material is hotter and so it rises. Near the surface, it becomes cooler and denser so it sinks. This creates a convection cell in the mantle. |
SciQ | SciQ-6176 | cancer, gene
Title: Why do we have oncogenes? Oncogene is a gene which in certain circumstances can transform a cell
into a tumour cell.
Everything we have has reason and meaning.
Or there was some use in past.
What's the reason for we have oncogenes? From wikipedia
A proto -oncogene
is a normal gene that could become an oncogene due
to mutations or
increased expression. The
resultant protein encoded by an
oncogene is termed oncoprotein.
Proto - oncogenes code for
proteins that help to regulate cell
growth and differentiation.
So, we actually do not have oncogenes. Instead we have proto-oncogenes.
Due to mutation or virus, these are converted into oncogenes.
Since, proto-oncogenes are required for normal cell division and differentiation, they are necessary. Also, these can change to oncogenes any time. So, we always have to live with probability of this conversion.
The following is multiple choice question (with options) to answer.
From what did the first proto-oncogenes arise? | [
"carcinogens",
"viral infections",
"spores",
"bacteria"
] | B | |
SciQ | SciQ-6177 | materials
Title: Is there a lighter-than-air foam material? Soap bubble foam made with helium floats up, but due to extreme fragility hardly counts as "material". There are many solid foam materials though - PUR foam, or styrofoam to name the most common. They typically use carbon dioxide for inflation though (usually produced from precursors of the foam, as a desirable side effect of their reaction).
But it shouldn't be too difficult to make solid foam filled with helium (or hydrogen) in proportions assuring positive buoyancy in air, and I can imagine desirability of it, at least as a filler in applications where mass costs a premium (transport, aviation) even if its structural properties were to be too poor for any other purpose.
Is such material produced? Is it used anywhere? Or if not, why? No matter how good you seal it, when you inflate a balloon with Helium it will stay up for a while, but after a few days, it will lose its pressure.
Enough to realise that in solids, there is also a phenomenon of mass diffusivity, and therefore your foam will not retain the gas. This phenomenon is also called Permeation
Diffusivity in solids is very complex, and 'mostly' cannot be described with an equation as simple as with Fick's laws, and, in many cases, is not even isotropic. But there is still a condition that needs to be met to diffuse: the particle/atom you consider can place itself within the crystallography/pattern of your material. unfortunately for Helium, it is too small and will diffuse through all reasonable materials.
Diffusivity in solids is unfortunately making us unable to isolate a gaz but it
is also positively used in a lot of fields.
The most investigated is probably in microelectronics to make local implants of ions in semiconductors and therefore change locally its electrical properties.
The following is multiple choice question (with options) to answer.
What material used for helium-filled balloons is dense, strong and opaque, with a high molecular mass that forms films that have many fewer pores than rubber? | [
"fiberglass",
"cellophane",
"foil",
"mylar"
] | D | times faster than air. For this reason, high-quality helium-filled balloons are usually made of Mylar, a dense, strong, opaque material with a high molecular mass that forms films that have many fewer pores than rubber. Mylar balloons can retain their helium for days. |
SciQ | SciQ-6178 | cell-biology, nutrition, blood-circulation, liver
Title: How do nutrients get to the cells they need to get to? I understand the basics of digestion. I know that nutrients get absorbed by the microvilli, enter the bloodstream and travel to the liver but after all that, what is the biological mechanism that guides these nutrients to the proper receiving location? Broadly speaking, nutrients that enter the blood from the gut, and those that are released into the blood by the liver, are available to any cells that require them. So there is no "guiding to the correct location" in the sense that you suggest.
Lipids for example are present in the various lipoproteins and can be acquired from these by all cells. Iron is bound to transferrin, and any cell with transferrin receptors can internalise the transferrin and take the iron. Glucose is available in solution in the plasma, and free fatty acids are bound to serum albumin in the blood. During starvation the liver produces ketones ("ketone bodies") which are taken up by many different tissues/cell types.
The following is multiple choice question (with options) to answer.
What do erythrocytes carry and deliver to tissues in the body? | [
"Helium",
"carbon",
"oxygen",
"oxide"
] | C | The cell found in greatest abundance in blood is the erythrocyte. Erythrocytes are counted in millions in a blood sample: the average number of red blood cells in primates is 4.7 to 5.5 million cells per microliter. Erythrocytes are consistently the same size in a species, but vary in size between species. For example, the average diameter of a primate red blood cell is 7.5 µl, a dog is close at 7.0 µl, but a cat’s RBC diameter is 5.9 µl. Sheep erythrocytes are even smaller at 4.6 µl. Mammalian erythrocytes lose their nuclei and mitochondria when they are released from the bone marrow where they are made. Fish, amphibian, and avian red blood cells maintain their nuclei and mitochondria throughout the cell’s life. The principal job of an erythrocyte is to carry and deliver oxygen to the tissues. Leukocytes are the predominant white blood cells found in the peripheral blood. Leukocytes are counted in the thousands in the blood with measurements expressed as ranges: primate counts range from 4,800 to 10,800 cells per µl, dogs from 5,600 to 19,200 cells per µl, cats from 8,000 to 25,000 cells per µl, cattle from 4,000 to 12,000 cells per µl, and pigs from 11,000 to 22,000 cells per µl. Lymphocytes function primarily in the immune response to foreign antigens or material. Different types of lymphocytes make antibodies tailored to the foreign antigens and control the production of those antibodies. Neutrophils are phagocytic cells and they participate in one of the early lines of defense against microbial invaders, aiding in the removal of bacteria that has entered the body. Another leukocyte that is found in the peripheral blood is the monocyte. Monocytes give rise to. |
SciQ | SciQ-6179 | quantum-mechanics, particle-physics
Title: Anything special about the internal structure of Carbon-12? In trying to understand the various structures carbon forms, I'm wondering what, if anything, is so special about having 6 neutrons and 6 protons in the nucleus. I'm aware there are permutations possible (in general) with respect to the specific arrangement of nucleons.
On the surface of the issue it seems like there is something about the internal structures possible that is peculiar... It isn't a rational train of thought but it is tempting to ask if there is something more to the internal structure - a lot of 3's and 2's appearing suggesting a geometric or numeric answer...
I've tried to think of it as a sphere packing problem, knowing that the analogy wouldn't be entirely appropriate, haven't gotten far yet. Also wondering if there is any relation to icosahedra, having 12 vertices and a plethora of interesting geometrical properties.
In short, is there anything to be said about the internal structure of Carbon-12 that's remarkable or distinct to that isotope? Carbon-12 is an "alpha-cluster nucleus," with even proton number $Z$, even neutron number $N$, and $N=Z$. The alpha-cluster nuclei up to argon or so are slightly more stable than than their "mirror nuclei" neighbors at $Z-2,N+2$, and tend to be concentrated in stellar nucleosynthesis.
Nuclear structure is a big subject where lots of different approaches are good at explaining various phenomena.
The cluster model is one approach (or at least, a phenomenon that should arise from a good microscopic nuclear model).
The shell model follows the same sort of four-quantum-number ruleset that leads to the electron structure of the periodic table. For subtle reasons the nucleon shells fill differently that electron shells do: the noble gases have $2,10,18,36,\cdots$ electrons, while the "magic nuclei" have $8,20,28,50,\cdots$ protons and/or neutrons.
For heavy nuclei you can kind of gloss over the details of what's happening inside and model the nucleus as a liquid drop.
The following is multiple choice question (with options) to answer.
How many neutrons do 99% of carbon atoms have? | [
"five",
"six",
"eight",
"sixteen"
] | B | All the atoms of a given element have the same number of protons and electrons. The number of neutrons, however, may vary for atoms of the same element. For example, almost 99 percent of carbon atoms have six neutrons, but the rest have either seven or eight neutrons. Atoms of an element that differ in their numbers of neutrons are called isotopes. The nuclei of these isotopes of carbon are shown in the Figure below . The isotope called carbon-14 is used to find the ages of fossils. You can learn how at this URL: http://science. howstuffworks. com/environmental/earth/geology/carbon-14. htm . |
SciQ | SciQ-6180 | electrochemistry, redox, electrons, electricity
I sent this (as well as a list of other sources that I won't quote here) to my chemistry professor and received the following reply:
The question states electrons. Period. There are no "free" electrons in a battery (there can be delocalized electrons, but that's not the question). Batteries are made of atoms. Atoms are made of protons, neutrons and electrons. As a battery is used, through the flow of electrons, electrons are lost to the environment (fyi - there is energy/electron loss, albeit small to "run" the voltmeter and even in the flow of electrons through a conducting wire). Those electrons are no longer in the battery. Thus, the battery has the same number of protons and neutrons, but less electrons. This also means more unreactive metal cations exist in a used battery.
I appreciate all your research to make a point, but hopefully you now see the answer is true. Even your physics professor agrees because there is loss/leakage. Thus, less electrons in the battery.
Story: I have a family friend, who is a full professor of electrical engineering at Caltech. She is clearly on the cutting-edge of this field. In one of our discussions, she shared displeasure in online information. She told me her grad students often cited sources that were not true. There is more to this story, but I think the point has been made. Keep it simple. Electrons are energy. They flow. That energy goes elsewhere, leaving the initial system with less energy/electrons.
The following is multiple choice question (with options) to answer.
What are the two metals within a battery called? | [
"anode and sheath",
"anode and a cathode",
"sheath and a cathode",
"anode and diode"
] | B | These values suggest that water should be oxidized at the anode because a smaller potential would be needed—using reaction (ii) for the oxidation would give a less-negative cell potential. When the experiment is run, it turns out chlorine, not oxygen, is produced at the anode. The unexpected process is so common in electrochemistry that it has been given the name overpotential. The overpotential is the difference between the theoretical cell voltage and the actual voltage that is necessary to cause electrolysis. It turns out that the overpotential for oxygen is rather high and effectively makes the reduction potential more positive. As a result, under normal conditions, chlorine gas is what actually forms at the anode. Now consider the cathode. Three reductions could occur:. |
SciQ | SciQ-6181 | thermodynamics, visible-light, perpetual-motion
Needless to say, perpetual motion of an untouched body is useless in terms of extraction of mechanical energy.
The following is multiple choice question (with options) to answer.
What is one thing that can not happen to energy? | [
"it cannot stay the same",
"it cannot increase",
"it can not be destroyed",
"it cannot decrease"
] | C | If energy cannot be destroyed, what happens to the energy that is absorbed in an endothermic reaction? The energy is stored in the chemical bonds of the products. This form of energy is called chemical energy. In an endothermic reaction, the products have more stored chemical energy than the reactants. In an exothermic reaction, the opposite is true. The products have less stored chemical energy than the reactants. The excess energy in the reactants is released to the surroundings when the reaction occurs. The graphs in Figure below show the chemical energy of reactants and products in each type of reaction. |
SciQ | SciQ-6182 | biochemistry, bioenergetics
Having got those out of the way, I can now attempt to answer your question (slightly rephrased). Can a reaction in a metabolic pathway be at equilibrium?
To be extremely pedantic, if there is a flux through the pathway (net conversion of first substrate to end product) then the answer is no (Newsholme & Start, 1973, p 11). That is, if there is a flux through the pathway, ΔG' cannot be exactly zero for any individual reaction. However, reactions in a metabolic pathway may be very close to equilibrium (Newsholme & Start, 1973, chapter 1).
Let’s (once again) rephrase your question. Are there any examples of reactions in metabolic pathways that are close to equilibrium, and how can we determine this?
To again quote Newsholme & Start (1973, p11) “In a series of reactions that constitute a metabolic pathway, a few may be displaced far from equilibrium, whereas the majority of reactions may be close to equilibrium”.
So how can this be determined? One way would be to measure the ratio of products to substrates (or the ratio of product to substrate pairs) in the cell, and compare this with the equilibrium constant. Note that it is only the ratio of substrate/product pairs we are interested in, not the absolute concentrations. We might be interested in the NAD+/NADH ratio in the cell, for example.
That is, we measure the mass action ratio and compare this with the equilibrium constant.
Such measurements are fraught with difficulties, but let’s agree that they can be made. We could rapidly freeze the tissue sample to -190°C (using liquid nitrogen), for example, and then measure the ratio of metabolites. Finally, it should be pointed out that comparison of mass-action ratio with the equilibrium constant is not the only way of deducing that a reaction is near equilibrium, and agreement between alternative methods is highly desirable before any firm conclusions are drawn.
Let’s consider glycolysis as an example. It is generally agreed that the reactions catalyzed by phosphoglucoisomerase, phosphoglycerate mutase and enolase are all close to equilibrium: the mass action ratios and the equilibrium constants are about the same (see Newsholme & Start, 1973, p 98).
The following is multiple choice question (with options) to answer.
Where do most biochemical reactions take place? | [
"within cells",
"stomach",
"outside of cells",
"upper atmosphere"
] | A | Most biochemical reactions take place within cells. Cells are the microscopic building blocks of organisms. |
SciQ | SciQ-6183 | evolution, dna, cell-biology, senescence, chromosome
Title: Is there an advantage to linear chromosomes? The DNA copying enzymes have a hard time working to the end of a chromosome. For circular chromosomes this is not a problem, since there is not a sharp 'end'. However, for a linear chromosome, without extra mechanisms in place, a bit of DNA is lost off the end of the chromosome after each replication. Because of this, eukaryotes have a telomere to cap off their chromosomes.
In most cells of a mutli-cellular organism, this telomere is slowly worn away after each reproduction leading to apoptosis. Cells that need to reproduce indefinitely such as germ and stem cells have to invest in extra mechanisms to replenish the telomere. For multi-cellular eukaryotes I can see how this might be usefull (for instance as a cancer counter mechanism). However, multi-cellular organisms evolved from single-cell eukaryotes.
I cannot see a reason for wanting apoptosis in a single-cell organism. However, single cell eukaryotes (say yeast) still have linear chromosomes with telomere caps. What advantage did linear chromosomes provide single-cell eukaryotes to offset the extra investment in reparing the telomere?
Related questions
What is the advantage of circular DNA in bacteria? I think it is the wrong question. You assume that eukaryotes developed from a single-cell organism with circular DNA. Then, clearly, there must have been an advantage of (newly) developing a linear genome. But eukaryotes could have developed from an organism with linear DNA, too. There are still a few bacterial species with linear chromosomes, so this is not unlikely. We don't know, however.
On the other hand, if linearisation developed independently, you can learn from bacteria why it might have occurred:
J. N. Volff, J. Altenbuchner: A new beginning with new ends: linearisation of circular chromosomes during bacterial evolution. In: FEMS microbiology letters. 186, 2, May 2000, 143–150, PMID 10802162. (Review).
Abstract:
The following is multiple choice question (with options) to answer.
The ends of linear chromosomes are maintained by the action of which enzyme? | [
"pepsin",
"telomerase",
"insulin",
"cytokine"
] | B | Figure 9.11 The ends of linear chromosomes are maintained by the action of the telomerase enzyme. |
SciQ | SciQ-6184 | aqueous-solution, kinetics
Title: Diffusion of CO2 and O2 in Water/Atmosphere System Consider the following experiment:
One reservoir of pure water is interfacing the atmosphere at standard condition.
Both are at rest and at the same temperature.
Both have no internal gradients (ie: constant concentrations, temperature, ...)
The interface between them is a perfect flat surface (for sake of simplicity).
The dissolved $\ce{CO2}$ in the water has a concentration somewhere between 0-50ppm.
The dissolved $\ce{O2}$ in the water has a concentration somewhere between 0-11ppm.
Questions
in order of importance
How to mathematically model the $\ce{CO2}$ and $\ce{O2}$ rate of change per unit area (flux) in the water and in the atmosphere considering only diffusion?
Suppose the atmosphere is at constant velocity relative to the water reservoir. How this would change the mathematical model above?
The following is multiple choice question (with options) to answer.
Through which process does water from the oceans enter the atmosphere? | [
"absorption",
"oxidation",
"perspiration",
"evaporation"
] | D | |
SciQ | SciQ-6185 | thermodynamics
Title: Misunderstanding of kinetic energy turning into heat Imagine a block sliding on a surface including friction. Gradually, it'll stop. If we touch both the surface and the block, they are hotter, their temperatures have increased. I've read that kinetic energy has turned into heat, which doesn't sound accurate to me. I handle the next heat definition that is very common: Heat is the transfer of energy due to a diference of temperatures between to two systems. Regarding only about the fact that heat is a flow of energy, so it doesn't appear correct to argue kinetic energy is now heat, since kinetic energy is something you have, but heat isn't. I read a very nice answer that holds this: kinetic energy is transfered as heat, and now is thermal energy. Thermal energy has to do with internal energy. But internal energy may depend on very variables, but thermal energy is only related with temperature, right? Yet I find it confusing. Anyway, so, the total energy can be distributed to increase the temperature of both objtects in many ways, right? Does the same thing happen with collitions?
On the other hand, would it be equivalent saying the work that friction performs is now thermal energy?
Finally, since heat is transfer of energy, (any kind of energy), if two systems are in contact, one hotter than the other, transfer of energy takes place, what kind of energy is transfered?. That's it. The confusion comes between concepts of thermodynamics, and concepts of mechanics. Temperature was originally defined as a thermodynamic variable, but it can be shown that it emerges from the underlying molecular structure of matter. Studying the kinetic theory of gases one can get an intuition on how thermodynamic variables emerge from the microscopic world of atoms and molecules.
It can be shown that temperature, emerges from an average over the kinetic energy of the individual molecules bouncing against each other in the volume of the gas.
$$\large{T= \frac{m\bar{v^2}}{3k_B}}$$
When the gas is heated, the average kinetic energy of the molecules in the gas goes up.
The following is multiple choice question (with options) to answer.
In what type of process does heat flow into its surroundings and cause an increase in kinetic energy? | [
"oscillating process",
"chemical process",
"exothermic process",
"biochemical process"
] | C | In general, the process of interest is taking place in the system, and there are no changes in the composition of the surroundings. However, the temperature of the surroundings does generally change. Entropy changes in the surroundings are determined primarily by the flow of heat into or out of the system. In an exothermic process, heat flows into the surroundings, increasing the kinetic energy of the nearby particles. For an exothermic reaction, ΔS surr is positive. Conversely, heat flows from the surroundings into the system during an endothermic process, lowering the kinetic energy available to the surroundings and resulting in a negative value for ΔS surr . |
SciQ | SciQ-6186 | osmosis, prokaryotes
Title: Does osmosis take place in prokaryotic cells? As far as I know, osmosis occurs in Eukaryotic cells, and I'm wondering if it could take place in prokaryotic cells too. Osmosis works across every cell membrane along a concentration gradient as its a physico-chemical principle. Water can cross the membrane (or cell wall), while the substance dissolved in it (for example salts) can not. Because eukaryotic cells only have a cell membrane, they will burst eventually, while bacteria (and also plant cells) have a more rigid cell wall, which will mostly prevent bursting. However the influx (or outflux) of water creates a pressure which is called turgor pressure. How this works is shown below (figure from here), bacterial cells and plant cells work pretty much the same way:
The following is multiple choice question (with options) to answer.
Prokaryotic organisms, like bacteria, reproduce through what process, where they grow and divide in half? | [
"multiple fission",
"singular fission",
"binary fission",
"symbiotic fission"
] | C | Prokaryotic organisms, like bacteria. Bacteria reproduce through binary fission , where they grow and divide in half ( Figure below ). First, their chromosome replicates and the cell enlarges. The cell then divides into two cells as new membranes form to separate the two cells. After cell division, the two new cells each have one identical chromosome. This simple process allows bacteria to reproduce very rapidly. |
SciQ | SciQ-6187 | kinematics, vectors, calculus
Title: Direction of velocity vector in two dimensions I'm having some problems understanding the velocity vector in two dimensions.
Any given trajectory it's expressed by a curve.
Here we have two metrics to calculate how much the point has traveled:
Displacement: a vector that only takes into account the initial position and the final position.
Distance: a scalar that tells us about the amount of space the point has traveled.
In one dimension the velocity can be expressed simply as $v = \frac{dx}{dt}$ because we're moving along one axis and the two are the same.
However, in two or more dimensions we have a problem with the definition of velocity because, since it's a scalar we have no clue about its direction.
The displacement vector is like this:
if we define velocity as $\vec{v} = \frac{\Delta\vec{r}}{dt}$ we make an error but taking the limit we get that error close to $0$.
My books explains how essentially $d\vec{r} = ds\ \hat{u_T}$, where $\hat{u_T}$ is a versor tangent to the trajectory.
This makes sense because if the displacement is infinitesimal then it must be tangent to the trajectory so it's like if we move an infinitesimal step along the tangent direction.
Here confusion kicks in, because it also says that now the velocity vector can be expressed as $\vec{v} = \frac{ds}{dt}\hat{u_T}$ so it means that the velocity vector can be expressed as a vector tangent to the trajectory that has the magnitude of the instantaneous velocity.
I don't get why this is the case, if we consider pointwise the vector $d\vec{r}$
The following is multiple choice question (with options) to answer.
Displacement is a vector quantity, which means it has both direction and what else? | [
"waves",
"radiation",
"rate",
"magnitude"
] | D | What is the difference between distance and displacement? Whereas displacement is defined by both direction and magnitude, distance is defined only by magnitude. Displacement is an example of a vector quantity. Distance is an example of a scalar quantity. A vector is any quantity with both magnitude and direction. Other examples of vectors include a velocity of 90 km/h east and a force of 500 newtons straight down. The direction of a vector in one-dimensional motion is given simply by a plus. |
SciQ | SciQ-6188 | human-biology, cell-biology
Title: Body's decomposition Does a human body decompose in a completely sterile environment ? If yes, what decomposes it ? And how fast ? What happens in vacuum ? Can it remain exactly the same ?
Thanks
Does a human body decompose in a completely sterile environment ?
No it wont. Unstable molecules like ATP will quickly degrade spontaneously. The stable ones like many proteins and lipids wont degrade spontaneously. Enzymes are essential to degrade them and are to be supplied extraneously.
What happens in vacuum ?
Body will dry up :P
The following is multiple choice question (with options) to answer.
Waste leaves the body in the form of what? | [
"impurities",
"saliva",
"stomach acid",
"feces"
] | D | |
SciQ | SciQ-6189 | radiation, gamma-rays
Title: How does gamma radiation ionise atoms? I am having trouble understanding how gamma radiation can ionise atoms. I think it is due to a lack of understanding about how photons work. My basic understanding is that gamma radiation doesn't directly ionise atoms like alpha and beta particles by 'knocking' electrons out of their orbitals. Gamma radiation causes atoms to emit other particles which then cause ionisation.
But then I read about how photons can hit electrons and transfer energy. Does this mean the electron gets removed and the atom gets ionised? Gamma radiation can interact in a number of different ways with matter. the 3 main phenomena are
1-photoelectric effect: a photon hits an electron in an atom and disappears giving to the electron all its energy ($E=h\nu$, where $h$ is a constant and $\nu$ the frequency of the radiation).
For this to happen the energy of the photon must be exactly equal to the amount required for the electron to transition to another bound state(ie. still being under the influence of the atomic nucleus), or more that the amount required to completely free the electron from the atom. In this case we have photoionization
2-compton scattering: basically scattering between photon and a weakly bonded (ie. is on the outmost levels of the atom) electronic atom which frees the latter from the atom. In general this scattering can happen in the presence of any electron that can be considered approximately free.
3-couple creation: a (high energy) photon decays into an electron and a positron, these beta particles can then ionize atoms. Note that for this to happen the energy of the photon must be greater or equal to the mass energy of an electron and a positron (1.02 MeV)
The following is multiple choice question (with options) to answer.
What process can occur when atoms are exposed to high levels of radiation or when atoms transfer electrons to or from other atoms? | [
"oxidation",
"ionization",
"fusion",
"diffusion"
] | B | The process in which an atom becomes an ion is called ionization. It may occur when atoms are exposed to high levels of radiation or when atoms transfer electrons to or from other atoms. |
SciQ | SciQ-6190 | parasitology
Title: Tapeworms and their effect on humans I've read that some people in some countries actually use tapeworms as a form of losing weight. What are the dangers to these people? I haven't really found much on this topic (besides popular sites) but I can summarize it here:
There are quite some tapeworms (or cestoda), I found numbers of up to 3500 species. They attach to the intestinal wall of the humans and then start to take up predigested food through their skin. With that, they reduce food from their host and start to grow, some get as long as 15 meters!
Some of the worms seem to be relatively harmless (besides stealing food), but this is more true for the first world. In poor countries, where there is not enough food, tapeworms can cause severe malnutrition.
Some tapeworms can migrate into the blood stream and from there into other tissues or organs like muscles, eye and brain. There they can cause cysts which can lead to organ failure and death.
For more information see this CDC webpage and this article: "Biochemistry and physiology of tapeworms.". This popular article is probably also interesting.
The following is multiple choice question (with options) to answer.
Who should an obese person with an eating disorder seek for help? | [
"health professional",
"psychiatrist",
"social worker",
"body builder"
] | A | Some people who are obese have an eating disorder. Eating disorders are mental illnesses that require treatment by health professionals. |
SciQ | SciQ-6191 | cell-division
Title: Why doesn't cellular, replicative senescence (or the hayflick limit) constrain the normal development of an organism? The wikipedia article on cellular senescence states:
Cellular senescence is the phenomenon by which normal diploid cells cease to divide. In culture, fibroblasts can reach a maximum of 50 cell divisions before becoming senescent. This phenomenon is known as "replicative senescence", or the Hayflick limit.
The following is multiple choice question (with options) to answer.
The period of life between the start of puberty and the beginning of adulthood is called? | [
"adolescence",
"prenatal",
"old age",
"youth"
] | A | Adolescence is the period of life between the start of puberty and the beginning of adulthood. Adolescence includes the physical changes of puberty. It also includes many other changes, including significant mental, emotional, and social changes. During adolescence:. |
SciQ | SciQ-6192 | toxicity
A general rule for all compounds is:
As long as you smell them, they can affect you.
The desired effect of painting a door with kerosene is, however, that the kerosene penetrates the door and stays there. The least-volatile constituents will remain on the door itself, protecting it from damage. If all the kerosene diffused away, the method would not be used because it would be worthless. Therefore, after the door has vented properly, letting the volatile components disappear, there is practically nothing left that will be harmful to any noteworthy extent.
In fact, I am include to proclaim that your average coloured paint may well contain more harmful chemicals that the kerosene does.
Yes, you can touch it, no you do not need space suits to be safe.
The following is multiple choice question (with options) to answer.
What element once commonly used in paint and gasoline has now been found to have dangerous effects? | [
"plastic",
"niacin",
"lead",
"chromium"
] | C | lead: An element that was once commonly used in gasoline and paint, is now found to have dangerous effects, such as brain damage. Lead contamination has many harmful effects on the body. |
SciQ | SciQ-6193 | genetics, mutations
Title: Are there any mutagens that can undo the mutations they cause? I was reading a section from my textbook about tautomeric shifts, and it seems to suggest that there are some mutagens that can be directly responsible for the phenomenon. The section is mainly describing spontaneous mutations as opposed to induced mutations, and examples of mutagens are mentioned. However, the author explicitly states that the sort of changes made to DNA due to spontaneous mutations also occur at a higher rate during induced mutagenesis.
If a tautomeric shift can occur due to mutagenic activity, is it possible for the mutagen to undo and "correct" the mutation by reversing the shift? If so, what kind of chemicals or physical mutagens (e.g. radiation) would be involved? It is possible but extremely unlikely.
When a base undergoes tautomeric shift the DNA does not contain a mutation yet, just an unmatched pair. The mutation will only becomes inscribed into the DNA permanently after the DNA is replicated or wrongly repaired.
In order to reverse the mutation you would need to provoke a chemical change to that specific base using the same or another mutagen and as most of them are unspecific the likelihood of obtaining both the correct mutation to reverse the effect AND at that specific location is extremely low. Just for the location itself (i.e. that base pair), in human you have ~0.000000033% chances (1/3 billions) to mutate that base. This is assuming equal probabilities across the genome and a single modification event which is of course not true but shouldn't modify much the conclusion. I am not even speaking about provoking the chemical modification that will reverse it which will even further reduce that probability.
Such induced or natural mutations will actually only rarely appear in the genome permanently as the cell has multiple DNA repair mechanisms (see this wiki). So in this case the modified base does not need to be reverse as the cell will make sure to repair it directly but using mechanisms not based on mutagenesis.
The following is multiple choice question (with options) to answer.
What can happen spontaneously or as a result of mutagens in the environment? | [
"traits",
"mutations",
"combustion",
"lesions"
] | B | Many mutations are not caused by errors in replication. Mutations can happen spontaneously, and they can be caused by mutagens in the environment. Some chemicals, such as those found in tobacco smoke, can be mutagens. Sometimes mutagens can also cause cancer. Tobacco smoke, for example, is often linked to lung cancer. |
SciQ | SciQ-6194 | physiology, muscles
Title: Why Doesn’t Hypercalcemia Cause Muscle Spasms? If you have more calcium in the cell, wouldn’t more attach to troponin and initiate muscle contraction? Why does hypercalcemia cause muscle weakness instead of spasms? Hypercalcemia does indeed cause muscle spasm, but as someone else wrote, hypercalcemia indicates the calcium levels in blood and not in the sarcoplasmic reticuli.
One example where you can observe that increased calcium leads to increased contraction is when you take the cardiac glycoside, digoxin. Digoxin inhibits the Na+/K+ ATPase causing an increased concentration of intracellular sodium ions. Indirectly, the increased levels of sodium will disturb the sodium gradient (because of the accumulation of sodium ions inside the cell) and stop the Na+/Ca2+ exchanger. The consequence of the disturbance of the sodium/calcium exchanger will lead to the increased levels of calcium and the increased storage of calcium in the sarcoplasmic reticulum and thus cause positive inotropy of the myocytes.
You can read more about it here:
Gheorghiade, Mihai, Kirkwood F. Adams, and Wilson S. Colucci. "Digoxin in the management of cardiovascular disorders." Circulation 109.24 (2004): 2959-2964.
The following is multiple choice question (with options) to answer.
Abnormally high activity or low activity of the parathyroid gland can cause disorders related to levels of what bone mineral? | [
"collagen",
"magnesium",
"calcium",
"potassium"
] | C | Abnormally high activity of the parathyroid gland can cause hyperparathyroidism, a disorder caused by an overproduction of PTH that results in excessive calcium reabsorption from bone. Hyperparathyroidism can significantly decrease bone density, leading to spontaneous fractures or deformities. As blood calcium levels rise, cell membrane permeability to sodium is decreased, and the responsiveness of the nervous system is reduced. At the same time, calcium deposits may collect in the body’s tissues and organs, impairing their functioning. In contrast, abnormally low blood calcium levels may be caused by parathyroid hormone deficiency, called hypoparathyroidism, which may develop following injury or surgery involving the thyroid gland. Low blood calcium. |
SciQ | SciQ-6195 | evolution, zoology, taxonomy, phylogenetics
The apomorphy that defines the tetrapods is "paired limbs". You have Amphibia to the left and Amniota to the right, whose apomorphy is " egg with extraembrionic membranes". Inside them, you have Reptilia, whose apomorphies are "skull with upper and lower fenestra and beta-keratin in epidermis". Turtles came from an ancestor with these characteristics. So, turtles belong to the monophyletic group of "Reptiles".
Post scriptum: You wrote that "turtles (specifically sea turtles) live on both land and water, very much like amphibians". Just a curiosity: the reason why sea turtles leave the water (sea) from time to time shows exactly that they are not amphibians! Amphibians, being non-amniotes, have eggs that survive under water (actually, with few exceptions, they need to be under water). Turtles, on the other hand, are amniotes, and the amniotic egg cannot be laid under water. That's why the turtles have to leave the water to lay eggs: because, contrary to the amphibians, they cannot lay eggs under water.
The following is multiple choice question (with options) to answer.
Unlike other tetrapod vertebrates (reptiles, birds, and mammals), amphibians do not produce what type of eggs? | [
"prokaryotic",
"epithelial",
"umbilical",
"amniotic"
] | D | Unlike other tetrapod vertebrates (reptiles, birds, and mammals), amphibians do not produce amniotic eggs. Therefore, they must lay their eggs in water so they won’t dry out. Their eggs are usually covered in a jelly-like substance, like the frog eggs shown in Figure below . The jelly helps keep the eggs moist and offers some protection from predators. |
SciQ | SciQ-6196 | hydrology, mountains, rivers
Title: Why do rivers have 'wells' in mountains? Why/how can rivers have sources in places high above the sea level? The presence of water underground has nothing to do with sea level in mountainous country.
When rain fails on a mountain, or snow falls on a mountain and the snow eventually melts, the water from the rain or snow melt mostly travels downhill via rivers to the sea.
In getting to a river some of the water will fall on the ground. In places where the ground is covered by soil, water can travel through the soil via the pore spaces between the grains of soil. Similarly if porous rock, such as sandstone lies beneath the soil water can travel through the pores in the rock.
If a layer of impervious rock lies under the porous rock or soil, the water cannot move downwards, due to gravity, any further. This can lead to water accumulating in the soil or porous rock and saturating the soil or rock. In such situations an aquifer can form. The top of the saturated zone in an aquifer is called a water table.
The ground beneath a river is saturated and the surface of the river shows the water table exposed to atmosphere. Thus in mountainous regions the ground beneath rivers will be saturated and capable of supporting a well developed from the bank of a river.
The following is multiple choice question (with options) to answer.
What is the name for an underground layer of rock that is saturated with groundwater? | [
"aqueous cavity",
"artesian well",
"gradient",
"aquifer"
] | D | An underground layer of rock that is saturated with groundwater is called an aquifer . A diagram of an aquifer is pictured below ( Figure below ). Aquifers are generally found in porous rock, such as sandstone. Water infiltrates the aquifer from the surface. The water that enters the aquifer is called recharge . |
SciQ | SciQ-6197 | organic-chemistry, experimental-chemistry, redox, synthesis, alcohols
References:
The majority of the chemical information here comes from Comprehensive Organic Synthesis, Vol. 7. A whole chapter is dedicated to DMSO based oxidations and their examples in total synthesis: see Lee, T. V. Oxidation Adjacent to Oxygen of Alcohols by Activated DMSO Methods. DOI: 10.1016/B978-0-08-052349-1.00191-8.
The following is multiple choice question (with options) to answer.
What are prepared by the oxidation of secondary alcohols? | [
"protons",
"ketones",
"ions",
"more alcohol"
] | B | The carbonyl group, a carbon-to-oxygen double bond, is the defining feature ofaldehydes and ketones. In aldehydes at least one bond on the carbonyl group is a carbon-to-hydrogen bond; in ketones, both available bonds on the carbonyl carbon atom are carbon-to-carbon bonds. Aldehydes are synthesized by the oxidation of primary alcohols. The aldehyde can be further oxidized to a carboxylic acid. Ketones are prepared by the oxidation of secondary alcohols. Mild oxidizing agents oxidize aldehydes to carboxylic acids. Ketones are not oxidized by these reagents. A thiol is a compound with an SH functional group. |
SciQ | SciQ-6198 | organic-chemistry, food-chemistry, fats
Title: Saturated vs unsaturated fats - Structure in relation to room temperature state? I'm sure most of us have heard that saturated fats are solid at room temperature, and unsaturated fats are liquid at room temperature. I'm wondering how this relates to their chemical structure -- saturated fats contain only single bonds between carbons, yet to qualify as an unsaturated fat a C=C double bond must exist.
Since a double bond is stronger than a single bond, and the length of the C=C double bond is shorter than that of the single bond, why is it that the fat containing a double bond is a liquid and saturated fats are solids at room temperature? Seems like the double bond would inhibit movement and the resulting substance would be less like olive oil and more like butter. In the solid state, the individual triacylglycerol molecules are interacting with each other primarily through Van der Waals interaction. These weak bonds between molecules are broken at the solid-liquid transition. The amount of energy needed to disrupt these interactions (which determines the melting point of the fat or oil) is determined by the energy associated with all of these bonds added together. In a saturated fat, the acyl chains are able to align perfectly right along their length, maximizing intermolecular interactions. This effect is reflected in the fact that the melting temperature of a pure triacylglycerol increases as the chain length increases.
You can see this effect clearly in the melting temperatures of individual fatty acids. (C18:0 means an 18 carbon molecule with zero double bonds in the acyl chain):
C18:0 (stearic acid) 70°C
C16:0 (palmitic acid) 63°C
C14:0 (myristic acid) 58°C
So the addition of a single -CH2- group in the acyl chain increases melting temperature by a few degrees.
When a cis double bond is introduced into the acyl chain this creates a kink in the structure. Because of this, the acyl chains cannot align completely along their length - they don't pack together as well. Because of this, the sum of the energy associated with intermolecular Van der Waals interactions is reduced. Again this is seen clearly in the melting temperatures of fatty acids:
stearic acid C18:0 70°C
oleic acid C18:1 16°C
The following is multiple choice question (with options) to answer.
Saturated and unsaturated are the two main kinds of what? | [
"fats",
"sugars",
"polymers",
"acids"
] | A | There are two main types of fats, saturated and unsaturated. |
SciQ | SciQ-6199 | evolution, zoology, taxonomy, phylogenetics
The apomorphy that defines the tetrapods is "paired limbs". You have Amphibia to the left and Amniota to the right, whose apomorphy is " egg with extraembrionic membranes". Inside them, you have Reptilia, whose apomorphies are "skull with upper and lower fenestra and beta-keratin in epidermis". Turtles came from an ancestor with these characteristics. So, turtles belong to the monophyletic group of "Reptiles".
Post scriptum: You wrote that "turtles (specifically sea turtles) live on both land and water, very much like amphibians". Just a curiosity: the reason why sea turtles leave the water (sea) from time to time shows exactly that they are not amphibians! Amphibians, being non-amniotes, have eggs that survive under water (actually, with few exceptions, they need to be under water). Turtles, on the other hand, are amniotes, and the amniotic egg cannot be laid under water. That's why the turtles have to leave the water to lay eggs: because, contrary to the amphibians, they cannot lay eggs under water.
The following is multiple choice question (with options) to answer.
Most reptiles lay what kind of eggs? | [
"hard-shelled",
"umbilical",
"amniotic",
"roe"
] | C | All reptiles have a cloaca , a single exit and entrance for sperm, eggs, and waste, located at the base of the tail. Most reptiles lay amniotic eggs covered with leathery or hard shell. These eggs can be placed anywhere as they don't have to be in a moist environment, like the eggs of amphibians. However, not all species lay eggs, as certain species of squamates can give birth to live young. |
SciQ | SciQ-6200 | 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.
Sulfur can combine with oxygen to produce what? | [
"sulfur dioxide",
"sulfur oxide",
"sulfur bioxide",
"sulfur trioxide"
] | D | When nonmetals react with one another, the product is a molecular compound. Often, the nonmetal reactants can combine in different ratios and produce different products. Sulfur can also combine with oxygen to produce sulfur trioxide. |
SciQ | SciQ-6201 | 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 that enters living systems by nitrogen fixation is successively converted from organic nitrogen back into nitrogen gas by what? | [
"pollen",
"algae",
"viruses",
"bacteria"
] | D | The Nitrogen Cycle Getting nitrogen into the living world is difficult. Plants and phytoplankton are not equipped to incorporate nitrogen from the atmosphere (which exists as tightly bonded, triple covalent N2) even though this molecule comprises approximately 78 percent of the atmosphere. Nitrogen enters the living world via free-living and symbiotic bacteria, which incorporate nitrogen into their macromolecules through nitrogen fixation (conversion of N2). Cyanobacteria live in most aquatic ecosystems where sunlight is present; they play a key role in nitrogen fixation. Cyanobacteria are able to use inorganic sources of nitrogen to “fix” nitrogen. Rhizobium bacteria live symbiotically in the root nodules of legumes (such as peas, beans, and peanuts) and provide them with the organic nitrogen they need. Free-living bacteria, such as Azotobacter, are also important nitrogen fixers. Organic nitrogen is especially important to the study of ecosystem dynamics since many ecosystem processes, such as primary production and decomposition, are limited by the available supply of nitrogen. As shown in Figure 46.17, the nitrogen that enters living systems by nitrogen fixation is successively converted from organic nitrogen back into nitrogen gas by bacteria. This process occurs in three steps in terrestrial systems: ammonification, nitrification, and denitrification. First, the ammonification process converts nitrogenous waste from living animals or from the remains of dead animals. |
SciQ | SciQ-6202 | solutions
Title: Can the total amount of solution be found as a ratio between molar mass of a component and total mass of solution? I wonder whether the following relation is true:
$$n_\mathrm{solvent} + n_\mathrm{solute} = \frac{M}{m_\mathrm{solvent} + m_\mathrm{solute}},$$
where $M$ is the molar mass of the component, $n$ is the amount of substance and $m$ is the mass.
It was derived assuming $n = m/M,$ $n = n_\mathrm{solvent} + n_\mathrm{solute}$ and $m = m_\mathrm{solvent} + m_\mathrm{solute}.$
I don't think this is true, but I wanted to be sure before doing anything weird on a test. To sum up the comments, only the following relation for the total amount of solution $n_\mathrm{tot}$ is universally true:
$$n_\mathrm{tot} = n_\mathrm{solvent} + n_\mathrm{solute} = \frac{m_\mathrm{solvent}}{M_\mathrm{solvent}} + \frac{m_\mathrm{solute}}{M_\mathrm{solute}}\tag{1}$$
The best you can do is to assume that $n_\mathrm{tot}\approx n_\mathrm{solvent}$ for the diluted solutions of small molecules. Also, if the molar masses are similar $(M_\mathrm{solvent}\approx M_\mathrm{solute}\approx \bar{M}),$ the expression can be lead to a common denominator:
$$n_\mathrm{tot} \approx \frac{m_\mathrm{solvent} + m_\mathrm{solute}}{\bar{M}}\tag{2}$$
The following is multiple choice question (with options) to answer.
What term describes the amount of solute in a given amount of solution? | [
"cloudiness",
"concentration",
"temperature",
"density"
] | B | The concentration of a solution is the amount of solute in a given amount of solution. A dilute solution has a low concentration of solute. A concentrated solution has a high concentration of solute. |
SciQ | SciQ-6203 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
Which process helps absorptive protists absorb food molecules across their cell membranes? | [
"diffusion",
"secretion",
"metabolism",
"activation"
] | A | Absorptive protists absorb food molecules across their cell membranes. This occurs by diffusion. These protists are important decomposers. |
SciQ | SciQ-6204 | newtonian-mechanics, mass, momentum, conservation-laws
Title: Losing mass in space So I came across a question while studying laws of motion. Roughly, this is how it goes:
There are two astronauts in a space shuttle, who together have mass 200 kg. If by doing exercise, they manage to lose 80 kg, what will be the percentage increase in speed of the shuttle. The question is pretty straight forward, if thought about directly. However, my instant reaction was that by conservation of mass, the mass that the astronauts lose will still be contained within the space ship in the form of water, CO2, etc. So technically there won't be any change in mass, thus no change in speed.
I would like to know if this assumption is correct and in what forms is the mass we lose released. I'll attempt an answer, though someone knowing the precise ground realities will most likely improve on my answer.
You make a very good point about the speed staying constant IF the space ship can be treated as a closed system. That's the sole point that we need to worry about.
Naturally, the atmosphere within a space ship has to be maintained (at the values that can support human beings). If it was just a case of filling up the shuttle once with $21 \%$ oxygen and being done with it, astronauts would keep consuming it so that its levels would fall, and percentage of ${\rm CO}_2$ would keep increasing. That's undesirable and in a simplified description, one can get around this by removing ${\rm CO}_2$ via a chemical reaction with Lithium Hydroxide ${\rm LiOH}$. (By the way, this is a fairly common use of ${\rm LiOH}$, as a Carbon Dioxide Scrubber in breathing purification systems, as can be seen here.) Upon the reaction, these ''canisters'' can be stored and disposed off later. All the excess water (i.e. discounting the potable variety) is directed to tanks, which can again be disposed later. Excess heat is handled by converting to ammonia vapor and subsequent STORAGE. (Though somewhat simplified, a description of this process can be found in the first link of this article.)
The following is multiple choice question (with options) to answer.
When matter recycles and changes state what does it gain or lose by doing so? | [
"fuel",
"energy",
"volume",
"density"
] | B | Matter can exist in one of several different states, including a gas, liquid, or solid state. States of matter differ in the amount of energy their molecules have. When matter recycles, it changes state by gaining or losing energy. |
SciQ | SciQ-6205 | biochemistry, gas-laws
Title: What is the state of aggregation (gas, liquid) of oxygen in blood? Atmospheric oxygen is in O2 and a gas. Then we inhale the air, our efficient lungs do the magic to filter out the oxygen and push them into the blood stream.
When we say hemo and globin transport the oxygen using the iron ions. In what state oxygen is transported in the blood? as a gas or a liquid or an ion? It is hard for me to conceive of the idea that oxygen would be in gaseous form in the blood. "GAS in blood?" e.g. Arterial Blood Gas Test
Also, how does the lungs convert the gas into something that is compatible to be in blood?
References:
Amount of Oxygen in the Blood Regarding the state of oxygen in blood: It is in solution in the blood plasma (which mostly consists of water), in the form of single molecules. Think of water which you leave exposed to air: carbon dioxide will be captured and dissolved (along with the other gases in air), but these molecules are not gaseous or liquid, but rather "in solution", which is different from the "classical" states.
Back to oxygen: As your reference already states, most of the oxygen in solution will bind to hemoglobin. The actual state of oxygen in that complex has been debated, but it is believed to be reduced by the hemoglobin iron to the superoxide anion, coordinated to Fe$^{3+}$. See Wikipedia on this.
Also, the lungs do not "convert" the atmospheric oxygen to anything, they rather allow, due to their very large surface area, the quick exchange of oxygen/carbon dioxide in solution and in the air.
The following is multiple choice question (with options) to answer.
Where does oxygen enter the blood? | [
"in the lungs",
"in the veins",
"in the liver",
"in the heart"
] | A | |
SciQ | SciQ-6206 | inorganic-chemistry, coordination-compounds, transition-metals, color
Title: How can we predict the colour of transition metal complexes? I am facing problems in indentifying colour of complex compunds just by seeing the their molecular formula. Is there any method or concept to predict the colour of complex compunds? The basic principle of coloured compounds is that there is some kind of electronic transition whose energy difference corresponds to a photon whose wavelength is in the visible region ($\pu{400nm}<\lambda<\pu{700nm}$). Thus, to determine the colour of a compound we should always be looking at the molecular orbital scheme; for reference, I have attached the MO scheme of a typical octahedral $\ce{[ML6]^n+}$ compound in figure 1.
The following is multiple choice question (with options) to answer.
What kind of compounds change color when bases come into contact with them, so they can be used to detect bases? | [
"liquid",
"metals",
"parameters",
"indicators"
] | D | Certain compounds, called indicators, change color when bases come into contact with them, so they can be used to detect bases. An example of an indicator is a compound called litmus. It is placed on small strips of paper that may be red or blue. If you place a few drops of a base on a strip of red litmus paper, the paper will turn blue. You can see this in the Figure below . Litmus isn’t the only detector of bases. Red cabbage juice can also detect bases, as you can see in this video: http://www. youtube. com/watch?v=vrOUdoS2BtQ . |
SciQ | SciQ-6207 | fluid-dynamics, everyday-life
Title: Branching lemon drop "smoke rings" This might be hard to ask, but here goes nothing.
I recently poured a cup of water into a black coffee cup. There was a light source--not very bright--above the cup. Anyways, I was squeezing a lemon into my water mindlessly, and to make sure I got every last drop of lemon juice into the water, I watched the lemon juice hit the water. Then I looked closer as something pretty neat was happening.
When a single lemon drop hit the water, it dissipated into a shape that many would describe as a "smoke ring." Knowing some physics/fluids, I understood what was happening here was nothing out of the ordinary. But then I kept watching. As the ring dissipated, it eventually broke off into about 5 other smaller "smoke rings." I couldn't see further down, so who knows if it continued; but I would assume that the 5 smaller rings would turn into 5 + X amount more, etc.
At what point would they stop breaking up into smaller rings? Whats causing this to happen? Does this movement/shape have a scientific term? Does anything else do this that can be easily seen?
I'm more interested in what the movement/pattern that is happening here, not the chemistry aspect. Edit:
The original explanation focused on the vortex production. For a description of what's happening when the vortex breaks off into child vortices, I've added this new section.
The breakup of a single vortex ring into many smaller rings looks sounds like it should be driven by an azimuthal instability. Indeed, under certain conditions, azimuthal waves can grow around a ring's circumference, with instabilities showing as many as 20 peaks around a circumference [1A].
With this in mind, consider what happens when these instabilities drive two vortex filaments closer together. In an inviscid fluid, the filaments could pass through each other and continue developing. But in a viscous fluid, diffusion can cause the overlapping filaments to reconnect into different topologies, spawning child vortices. Such behavior is explained in [2A, 3A] for an elliptical vortex ring splitting into two vortices, but the same mechanism could drive the breakup for higher-frequency instabilities.
The following is multiple choice question (with options) to answer.
Concentric circles that spread out through the water around the droplets are actually types of what moving through the water? | [
"troughs",
"waves",
"winds",
"lines"
] | B | No doubt you’ve seen this happen. Droplets of water fall into a body of water, and concentric circles spread out through the water around the droplets. The concentric circles are waves moving through the water. |
SciQ | SciQ-6208 | quantum-gravity, physical-constants
Title: What is the smallest existing thing in theory and law? What is the smallest existing thing in theory and law?
"What is the smallest existing thing in theory and law?"
The Merriam Webster Dictionary defines a "thing" as:
: an object or entity not precisely designated or capable of being
designated
a: an inanimate object distinguished from a living being
b: a separate and distinct individual quality, fact, idea, or usually
entity
c: the concrete entity as distinguished from
...
A Photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles). Mass: 0 < 1×10−18 eV/c^2.
The photon has zero rest mass and always moves at the speed of light within a vacuum. Since the Photon is a Point Particle and has a size of zero you might say it's not a thing, nothing; that leaves us with:
The smallest real thing is the Neutrino. Mass: ≤ 0.120 eV/c^2.
The smallest theoretical thing is the Planck Particle. Radius: 5.72947×10−35 m, Mass: 3.85763×10−8 kg.
The following is multiple choice question (with options) to answer.
The smallest units of matter that retain the unique properties of an element are known as what? | [
"neutrons",
"atoms",
"protons",
"molecules"
] | B | All matter is made of tiny particles. Protons, neutrons, and electrons form atoms that bond together to create molecules. Atoms are the smallest units that have the properties of an element. Molecules are the smallest units of a compound. Chemical bonds hold molecules together. Molecules form the different types of minerals. The silicates make up most of Earth's crust. Minerals come together to create the three major rock types. They are igneous, sedimentary, and metamorphic. Igneous rocks form from cooled magma. Sedimentary rocks form from compacted or cemented sediments. Metamorphic rocks are those that have been altered by heat and pressure. These three rock types are the material part of the rock cycle. They are connected by different processes. Different processes convert any type of rock into any other type of rock. These processes are weathering and erosion, crystallization, and burial and pressure, among others. Each rock contains a story of how it formed. For most rocks it is possible to know what it formed from. |
SciQ | SciQ-6209 | physical-chemistry, acid-base
Title: Could a strong acid become a strong base? Is it technically possible for a strong acid to change into a strong base, through a chemical reaction?
Example: if an acid with pH 1 became a base with pH 12. Take nitric acid for instance. Reduce the nitrate until ammonia forms. Then using a stronger base than amide ion, you can generate amide base.
Therefore, it is required to make a number of reactions to get a strong base from a strong acid. If you meant that could a strong acid be changed to a strong base by one step reaction, it might be possible with complex big organic or organoboron molecules by replacement of acid functional group with a basic one, but I am unsure about this part.
The following is multiple choice question (with options) to answer.
What is a process that changes some chemical substances into other chemical substances? | [
"cellular respiration",
"a chemical reaction",
"spontaneous mutation",
"a bio reaction"
] | B | A chemical reaction is a process that changes some chemical substances into other chemical substances. The substances that start a chemical reaction are called reactants . The substances that form as a result of a chemical reaction are called products . During the reaction, the reactants are used up to create the products. For example, when methane burns in oxygen, it releases carbon dioxide and water. In this reaction, the reactants are methane (CH 4 ) and oxygen (O 2 ), and the products are carbon dioxide (CO 2 ) and water (H 2 O). |
SciQ | SciQ-6210 | homework-and-exercises, conventions, geometric-optics, lenses
A distance to image $s$ is positive if it is on the same side of the mirror as that which the light originated (i.e., a real image). (again, relative to the mirror).
For lenses, the distance to image $s$ is negative if it is on the same side of the lens from that which the light originated… etc. and the opposite for positive.
With these conventions, you can rather easily solve for the focal length:
$\frac{1}{o_1} + \frac{1}{o_2} = \frac{1}{f}$,
$\left[\frac{1}{0.365}+\frac{1}{.117}\right]^{-1} = f$,
and we know that the radius of curvature is given by:
$f=\frac{R}{2}$. Thus,
$R = 2\left[\frac{1}{0.365}+\frac{1}{.117}\right]^{-1}$.
Now, if the object is moved to a new distance 21.7cm, we have:
$\frac{1}{.217} + \frac{1}{o_2} = \frac{1}{f}$,
and we now know $f$ from our above calculation. The rest is simple.
[EDIT: For the record, notice that my convention is consistent with your observation that you got the correct answer in the second case with a negative image coordinate… you are in fact correct, in that regard. :) ]
The following is multiple choice question (with options) to answer.
What type of lens and mirrors have a negative focal length? | [
"converging",
"subverging",
"diverging",
"convexing"
] | C | The focal length , , of a lens or mirror is the distance from the surface of the lens or mirror to the place where the light is focused. This is called the focal point or focus . For diverging lenses or mirrors, the focal length is negative. |
SciQ | SciQ-6211 | embryology
Title: Is endoderm visible in the germ layer? This picture is my drawing about germ layer - not embryonic folding as I wrote initially.
Where exactly is the endoderm here in the picture?
The known things
Ectoderm
Neural tube
Notochord
Endoderm - Where is this?
Somite
Somite leg
Intraembryonic coelom
Embryonic somatopleura
Embryonic splanchopleura (lateral mesoderm)
Endoderm
Mesoderm (intraembryonic) I think you're going for a view of tube formation, in which case, here's a good image:
Lateral plate mesoderm
Intermediate mesoderm
Somite mesoderm
Chorda
Endoderm
(Reference)
Again in your drawing I think you correctly have it labeled as 10, and don't really need to put it twice.
The following is multiple choice question (with options) to answer.
What is the formation of organs from the germ layers called? | [
"biosynthesis",
"synaptogenesis",
"photosynthesis",
"organogenesis"
] | D | 43.7 Organogenesis and Vertebrate Formation Organogenesis is the formation of organs from the germ layers. Each germ layer gives rise to specific tissue types. The first stage is the formation of the neural system in the ectoderm. The mesoderm gives rise to somites and the notochord. Formation of vertebrate axis is another important developmental stage. |
SciQ | SciQ-6212 | nuclear-physics, kinetic-theory
Title: Usefulness of high molecular speeds in nuclear fusion reactions How do molecules having speeds many times greater than mean speed help in making nuclear fusion reactions in a laboratory? Nuclear fusion is a process in which two or more nuclei are combined to form a different atomic nucleus.
It takes a lot of energy to force nuclei to fuse, even with the lightest elements, like hydrogen in the Sun.
Now the release of energy and the fusion iself goes down between two forces:
strong force (residual strong force, that is the nuclear force), that keeps the neutrons and protons together
EM repulsion, that keeps protons away
When you accelerate nuclei to high enough speeds, they can overcome this EM repulsion, so they can be brought close enough, where the nuclear force is strong enough to hold them together.
At large distances, two naked nuclei repel one another because of the repulsive electrostatic force between their positively charged protons. If two nuclei can be brought close enough together, however, the electrostatic repulsion can be overcome by the quantum effect in which nuclei can tunnel through coulomb forces.
When a nucleon such as a proton or neutron is added to a nucleus, the nuclear force attracts it to all the other nucleons of the nucleus (if the atom is small enough), but primarily to its immediate neighbours due to the short range of the force.
https://en.wikipedia.org/wiki/Nuclear_fusion
The following is multiple choice question (with options) to answer.
What must two nuclei do for fusion to occur? | [
"repel each other",
"melt",
"collide",
"explode"
] | C | Two nuclei must collide for fusion to occur. High temperatures are required to give the nuclei enough kinetic energy to overcome the very strong repulsion resulting from their positive charges. A nuclear reactor consists of the following: 1. A nuclear fuel. A fissionable isotope must be present in large enough quantities to sustain a controlled chain reaction. The radioactive isotope is contained in tubes called fuel rods. A moderator. A moderator slows neutrons produced by nuclear reactions so that they can be absorbed by the fuel and cause additional nuclear reactions. A coolant. The coolant carries heat from the fission reaction to an external boiler and turbine where it is transformed into electricity. |
SciQ | SciQ-6213 | soil
An analogous hypothesis proposed by RUSSEL3 for increases in the number of bacteria after partial sterilization by heat, frost, or other means is that by such partial sterilization the protozoa are killed, thus permitting the unhindered development of bacteria which under normal conditions is held in check by protozoa.
BROWN and SMITH (loc. cit.) in their investigations dealt mainly with the physiological activities of bacteria under conditions of low temperature and frost, although they also made some determinations of the number of bacteria in frozen soil. Their principal conclusions regarding the ammonifying, nitrifying, denitrifying, and nitrogen fixing powers of frozen soils are as follows: (1) that "frozen soils possess a much greater ammonifying power than unfrozen soils"; (2) that "during the fall season, the ammonifying power of the soil increases until the temperature of the soil almost reaches zero, when a decrease occurs, and this is followed by a gradual increase and the ammonifying power of the soil reaches a maximum at the end of the frozen period"; (3) that "the nitrifying power of frozen soils is weak and shows no tendency to increase with extension of the frozen period"; (4) that "frozen soils possess a decided denitrifying power which seems to diminish with the continuance of the frozen period"; (5) that "during the fall season, the denitrifying power of the soil increases until the soil freezes, after which a decrease occurs"; (6) that "frozen soils possess a nitrogen fixing power which increases with the continuance of the frozen period, being independent of moderate changes in the moisture conditions, but restricted by large decreases in moisture"; and (7) that "in the fall, the nitrogen fixing power of the soil increases until the soil becomes frozen, which in almost ceases, after which a smaller nitrogen fixing power is established."
The following is multiple choice question (with options) to answer.
What determines the ability of soil particles to bind many nutrients? | [
"surface charges",
"layer charges",
"surface pulses",
"currents charges"
] | A | |
SciQ | SciQ-6214 | physical-chemistry, thermodynamics, heat, enthalpy
Title: Difference between thermodynamic terms heat and enthalphy What is the difference between heat and enthalphy? Heat is defined as the energy that flow into or out of a system because of difference in temperature between the system and its surrounding. Give special attention to the word 'flow'. It is not the energy that is stored in the body in the form of temperature. It is the energy that is transferred due to temperature difference.
Now, Enthalpy is the energy stored in the body at constant pressure. And here the energy is stored.
The following is multiple choice question (with options) to answer.
Enthalpy is a measure of the total energy of what kind of system? | [
"macroscopic",
"planetary",
"hypodermic",
"thermodynamic"
] | D | Reactions can proceed by themselves if they are exergonic or exothermic, that is if they release energy. The associated free energy of the reaction is composed of two different thermodynamic quantities, enthalpy and entropy. Enthalpy is a measure of the total energy of a thermodynamic system. The change in enthalpy is positive in endothermic reactions, and negative in exothermic processes. |
SciQ | SciQ-6215 | proteins, translation, mrna, ribosome
Title: What is the advantage of the way eukaryotes initiate translation? The eukaryote and prokaryote mechanism for translation is slightly different. Is there any advantage of the eukaryote translation mechanism ?
Edit : I specifically want to know why eukaryotic ribosome first attaches to tRNA and then to mRNA but prokaryotic ribosome can do this in either order. Is there any advantage of the former ? As far as I understand it (and I'll preface this by saying that initiation is not my strongest point), but prokaryotes utilize the beautiful AGGAGG Shine-Dalgarno sequence. Usually around 8bp upstream of the start codon, it is this sequence that the prokaryotic ribosome seeks out to initiate translation. It does this through a complementary region in the 3' sequence of the ribosomal RNA. Upon complementary binding, the ribosome and mRNA are correctly bound. Convenient!
In eukaryotes, however, there is no consensus SD sequence, so a different mechanism must be used; the complex of 40S and Methionine tRNA serves this purpose. The two together scan the mRNA, looking for an AUG start codon which the tRNA is complementary to. This eventually brings the full ribosome (40S + 60S) together to start translation.
The following is multiple choice question (with options) to answer.
In eukaryotes, the new mrna is not yet ready for translation. it must go through more processing before it leaves where? | [
"protons",
"Electrons",
"nucleus",
"molecules"
] | C | In eukaryotes, the new mRNA is not yet ready for translation. It must go through more processing before it leaves the nucleus. This may include splicing, editing, and polyadenylation. These processes modify the mRNA in various ways. Such modifications allow a single gene to be used to make more than one protein. |
SciQ | SciQ-6216 | quantum-mechanics, nuclear-physics, atomic-physics, atoms
Title: Could I turn into a nuclear bomb? Just out of curiousity, could the nuclei of our atoms split via quantum tunnelling, thereby leading to nuclear reactions and ultimately turning us into atomic bombs? I know that this is near-impossible, but wondering if it was technically possible. The thing is, we're made of mostly stable matter of low atomic number. In a nuclear bomb, unstable nuclei split, releasing a number of energetic neutrons which strike other unstable nuclei, and the reactions chain uncontrollably. Splitting a small nucleus actually costs energy, so even if a carbon atom in your body did split, it would only split into smaller, still low-energy atoms, which would interact normally with other atoms in your body. A couple extra lithium or helium atoms isn't going to do anything drastic.
The following is multiple choice question (with options) to answer.
What term describes the splitting of the nucleus of an atom into two smaller nuclei? | [
"atomic reaction",
"nuclean fusion",
"nuclear fission",
"critical fission"
] | C | Nuclear fission is the splitting of the nucleus of an atom into two smaller nuclei. This type of reaction releases a great deal of energy from a very small amount of matter. It begins when the nucleus of a radioactive atom gains a neutron. |
SciQ | SciQ-6217 | pathology
Title: Why are some bodily fluids more of an infection risk than others? Whilst on a recent refresher course it was highlighted that when considering risk of exposure to infection from bodily fluids we should be aware of two distinct risk levels:
High Risk:
Blood
Semen
Vaginal Secretions
Diarrhea
Low Risk:
Saliva
Vomit
Urine
CSF (Cerebrospinal fluid)
Why is it that some bodily fluids are a greater infection risk than others? Is it related to the fluids themselves or the species of pathogen that are located within them? This is just about where the pathogens can be found that are dangerous to people.
Vomit is highly acidic and less accommodating to microbe growth. Similarly saliva has many immune components in it as well as digestive enzymes that keep most microorganisms down.
Urine and CSF are actually quite sterile as they come from environments that are highly filtered - the kidney is an osmotic processor that essentially is a molecular filter and does not allow cells to pass, the spine is highly insulated from the blood and other direct exposure to microorganisms.
Compare that with the 'dangerous' list and you have organs that are open to human pathogens. Venerial disease like HPV is so common that what - about 1 in 5 people under a certain age carry it. That is a pretty high expectation of a biohazard. most infections and viruses are blood bourne - influenza, cold, as well as any bacterial infections.
Feces is always a dangerous thing to handle as the digestive tract is rich in nutrients and essentially directly open to external bacteria and fungi. (and its not acidified like the stomach). Also parasites like tape worms and other multicelled animals! yum!
Diarrhea is often caused by an infection of some sort, so its just more likely a hazard, but feces is always a place where you might find a pathogen.
This is not to say that the 'safe' list is totally safe. Its just less likely to bear disease causing agents.
The following is multiple choice question (with options) to answer.
What type of contamination causes almost 90% of diarrheal disease worldwide? | [
"food contamination",
"ground contamination",
"air contamination",
"water supply contamination"
] | D | Unsafe water supplies have drastic effects on human health. Waterborne diseases are diseases due to microscopic pathogens in fresh water. These diseases can be caused by protozoa, viruses, bacteria, and intestinal parasites. In many parts of the world there are no water treatment plants. If sewage or animal manure gets into a river, then people downstream will get sick when they drink the water. According to the World Health Organization (WHO), diarrheal disease is responsible for the deaths of 1.8 million people every year. It was estimated that 88% of the cases of diarrheal disease are caused by unsafe water supplies. |
SciQ | SciQ-6218 | human-anatomy, respiration, health
Is perpetual liquid breathing possible? ...And healthy?
So this is where we stand with the case studies; mice can breath liquids indefinitely and stay in good health, rabbits with ARDS survive where breathable gas would not help, and there is a contingency in the biomedical community that it can be better than gas ventilation for medical treatment. To me it seems that there is nothing to suggest a fully grown adult would suffer from breathing liquids. The inertness of the fluorocarbons implies any toxicity would only reveal itself in a timescale of years, and everything else about the compounds pose no danger and may make gas transfer across the lungs easier.
This relatively modest success is perhaps no surprise. The exchange interface of our lungs relies on a mucous (liquid) so the gases can permeate the lung tissue. Expanding on that idea should certainly not rule out the possibility of liquid breathing.
The biggest drawback, besides the cost of a long term experiment and being dependent on a mechanical ventilator, is that these are very small case studies of success. Given the massive amounts of unknowns (particularly for long term studies), switching to purely liquid ventilation in an adult human could have unforeseen risks and would be considered dangerous by any ethics board (or insurance company)!
On a lighter note, here is a YouTube video of what Maddie, a biology podcaster from the BBC, had to say on the matter of living in total submersion. Lots of skin problems, risk of infection after a few days etc.
Again, a very interesting, albeit understudied, topic!
The following is multiple choice question (with options) to answer.
Why is respiratory acidosis considered to be problematic? | [
"causes acid stomach",
"causes suffocation",
"excess oxygen in blood",
"excess co2 in blood"
] | D | Metabolic acidosis is problematic, as lower-than-normal amounts of bicarbonate are present in the blood. The pCO2 would be normal at first, but if compensation has occurred, it would decrease as the body reestablishes the proper ratio of bicarbonate and carbonic acid/CO2. Respiratory acidosis is problematic, as excess CO2 is present in the blood. Bicarbonate levels would be normal at first, but if compensation has occurred, they would increase in an attempt to reestablish the proper ratio of bicarbonate and carbonic acid/CO2. Alkalosis is characterized by a higher-than-normal pH. Metabolic alkalosis is problematic, as elevated pH and excess bicarbonate are present. The pCO2 would again be normal at first, but if compensation has occurred, it would increase as the body attempts to reestablish the proper ratios of bicarbonate and carbonic acid/CO 2. Respiratory alkalosis is problematic, as CO2 deficiency is present in the bloodstream. The bicarbonate concentration would be normal at first. When renal compensation occurs, however, the bicarbonate concentration in blood decreases as the kidneys attempt to reestablish the proper ratios of bicarbonate and carbonic acid/CO2 by eliminating more bicarbonate to bring the pH into the physiological range. |
SciQ | SciQ-6219 | biochemistry, molecular-biology, receptor
Title: If a cell has two different GPCRs, how does the cell differentiate between the phosphorylation cascade caused by each? In my biochem course, we learned that GPCR receptors trigger a phosphorylation cascade, with the end result being a large amplification of the signal in the form of cAMP. We never studied any particular GPCR individually, but we were told that GPCRs always end in the formation of a large amount of cAMP, which will go on to phosphorylate key targets that achieve the end result.
My question is as follows: If there are two GPCRs on the same cell membrane (let's say GPCR-A and GPCR-B triggered by substrates A and B respectively), how does the cell "know" which GPCR triggered the phosphorylation cascade if the end result is the same (large amount of cAMP). In theory, couldn't substrate B bind to GPCR-B and cause a phosphorylation cascade identical to that of GPCR-A, thus triggering GPCR-A's cellular response?
Is there some deeper specialization/uniqueness to each type of GPCR receptor that we didn't cover in my course? Does each GPCR produce a slightly different cascade that ends in something similar, but not exactly cAMP? Or is there some restriction, like each cell limited to only one GPCR (I would find this surprising, if this is the case)? First, it would be an oversimplification to say that GPCRs act only through increases in cytosolic cAMP. This is true for receptors coupled to Gs proteins, but there are other G proteins like Gi, Go and Gq which act differently [1].
Now, a cell can have receptors coupled to many different G proteins. Vascular smooth muscle, for instance, has Gs, Gi and Gq-coupled receptors [2]. Further, a cell can have different receptors coupling to G proteins of the same type (e.g., hepatocytes have glucagon and beta adrenergic receptors [3], which both couple to Gs).
The following is multiple choice question (with options) to answer.
When light strikes rhodopsin, the g-protein transducin is activated, which in turn activates what? | [
"phosphodiesterase",
"aldosterone",
"photosynthesis",
"hydrolysis"
] | A | Figure 36.20 When light strikes rhodopsin, the G-protein transducin is activated, which in turn activates phosphodiesterase. Phosphodiesterase converts cGMP to GMP, thereby closing sodium channels. As a result, the membrane becomes hyperpolarized. The hyperpolarized membrane does not release glutamate to the bipolar cell. |
SciQ | SciQ-6220 | photosynthesis, cellular-respiration, energy, sugar
Basically, points 4-7 convey that Calvin-Benson cycle not only produces sugar but what it actually does is fix inorganic carbon (as CO2) to organic form (in the form of sugar). So, most (practically all) of the carbon that a photosynthetic plant has, comes from this carbon fixation process and that's how plants are photoautotrophic.
The following is multiple choice question (with options) to answer.
In what stage of photosynthesis does the calvin cycle occur? | [
"fourth",
"first",
"third",
"second"
] | D | The Calvin cycle occurs in the second stage of photosynthesis. This stage takes place in the stroma of the chloroplast. In the Calvin cycle, carbon dioxide is used to produce glucose (sugar) using the energy stored in ATP and NADPH. The energy is released from these molecules when ATP loses phosphate (P i ) to become ADP and NADPH loses hydrogen (H) to become NADP + . |
SciQ | SciQ-6221 | planet, rotation
Title: What is the axial tilt of a planet measured relative to? I am very much a beginner on the astronomy front but I understand about planets having different axial tilts, hence why Venus turns the opposite direction from the Earth and Uranus turns sideways.
However, I am confused as to what the axial tilt bearing is measured from. For example, if all planets were in a perfect line from the sun, would they spin perfect in alignment on their own various axial tilts? Would some still be 'off-set' by a few degrees to one side or the other?
Do we actually know please? If you look at the Astronomical Almanac for the year 2011 as an example, in the table at the top of page E3, you find two measures of axial tilt. The third column is the declination of the planet's north pole for the mean equinox and equator of date 2011 January 0, 0 hours terrestrial time. So this is measured with respect to the Earth's orbit. The last column is the inclination of the planet's equator to the planet's orbit.
If you look at the right ascension column in the same table, you see that on that particular date the right ascensions are all different.
The following is multiple choice question (with options) to answer.
All of the planets rotate on their axes in the same direction that they move around the sun, except for which one? | [
"Saturn",
"Jupiter",
"venus",
"uranus"
] | D | All of the planets rotate on their axes in the same direction that they move around the Sun. Except for Uranus. Uranus is tilted on its side. Its axis is almost parallel to its orbit. So Uranus rolls along like a bowling ball as it revolves around the Sun. How did Uranus get this way? Scientists think that the planet was struck and knocked over by another planet-sized object. This collision probably took place billions of years ago. |
SciQ | SciQ-6222 | evolution, life-history
Title: Has there been any observation of species adapting the evolution process? I am very interested in the evolution of the evolution process itself. There are of course a lot of things that influence how evolution will work, but for this question, I am interested in things that are only related to the evolution process. Examples could be increase chance of mutations in newborns, change in reproduction age, and similar. I am specifically interested in observation where the evolution process itself has adapted to a change in the environment. Bacteria such as E. coli are known to increase their mutation rate (by switching to a more error prone polymerase among other things) when under stress. This can mean being placed in a medium where it's not adapted to grow (http://www.micab.umn.edu/courses/8002/Rosenberg.pdf) or when treated with antibiotics (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088971/?tool=pmcentrez).
The following is multiple choice question (with options) to answer.
What is the process by which organisms change in small ways over time? | [
"spontaneous mutation",
"adaptation",
"microevolution",
"natural selection"
] | C | Microevolution is the process by which organisms change in small ways over time. |
SciQ | SciQ-6223 | biochemistry, physiology, cell-biology
Title: What triggers meiosis in gonadal cells? What specific biochemical processes are involved in inducing meiosis rather than mitosis? Why are gonadal cells the only cells in the human body which do undergo meiosis?
What specific biochemical processes are involved in inducing meiosis rather than mitosis?
It's a difficult question because every step in the development of a germ cell is ultimately necessary for the final differentiation, which includes a meiotic division. Meiosis requires a lot of specialized components to pair and segregate homologues, to induce and resolve recombination, etc. What starts it all is still largely unknown. There are plenty of mutants that halt the process, but these are required along the way, so damaging the pathway ultimately stops it from progressing. At least one study has been able to initiate the program of meiosis in yeast:
Induction of meiosis in Saccharomyces cerevisiae depends on conversion of the transcriptional represssor Ume6 to a positive regulator by its regulated association with the transcriptional activator Ime1. I Rubin-Bejerano, S Mandel, K Robzyk, and Y Kassir
Basically, they turned on a transcription factor, which activated an entire suite of downstream genes necessary for meiosis. In essence, they turned on the "meiosis pathway." Bear in mind this is yeast, so does't have separate germ cells, but the concept is probably the same.
Why are gonadal cells the only cells in the human body which do undergo meiosis?
All other cells are diploid. Only in germ cells does the organism induce reductional divisions (to make haploid gametes for ultimate fusion in the zygote of the next generation). Creation of haploid somatic cells would uncover recessive lethal mutations and cells would die. In sperm and eggs, which do not express any genes until after fertilization and karyogamy, this is not a problem.
The following is multiple choice question (with options) to answer.
What regulates the cell cycle only when they are tightly bound to cdks? | [
"hormones",
"subclades",
"kinases",
"cyclins"
] | D | Cyclins regulate the cell cycle only when they are tightly bound to Cdks. To be fully active, the Cdk/cyclin complex must also be phosphorylated in specific locations. Like all kinases, Cdks are enzymes (kinases) that phosphorylate other proteins. Phosphorylation activates the protein by changing its shape. The proteins phosphorylated by Cdks are involved in advancing the cell to the next phase. (Figure 10.12). The levels of Cdk proteins are relatively stable throughout the cell cycle; however, the concentrations of cyclin fluctuate and determine when Cdk/cyclin complexes form. The different cyclins and Cdks bind at specific points in the cell cycle and thus regulate different checkpoints. |
SciQ | SciQ-6224 | electromagnetism, relativity
Title: Einsteins thought experiment on travelling with a light wave This might be better suited to the science.history.SE; but I thought I would try here first.
Einstein reportedly considered a thought experiment where one considers travelling alongside a light wave; is this an apocrophyl story? Or a question that he considered in one of his papers; if so which?
The physical content of the story is that travelling alongside a light wave would mean that one would see an unvarying EM field; but there is no such solution to the EM equations - light always travels at c. You can find some information about that on John D. Norton's website. Einstein thought of this at the age of sixteen. Here's another article:
"If I pursue a beam of light with the velocity c (velocity of light in a vacuum), I should observe such a beam of light as an electromagnetic field at rest though spatially oscillating. There seems to be no such thing, however, neither on the basis of experience nor according to Maxwell's equations. From the very beginning it appeared to me intuitively clear that, judged from the standpoint of such an observer, everything would have to happen according to the same laws as for an observer who, relative to the earth, was at rest. For how should the first observer know or be able to determine, that he is in a state of fast uniform motion? One sees in this paradox the germ of the special relativity theory is already contained.".
That's from Einstein's Autobiographical notes
The physical content of the story is that travelling alongside a light wave would mean that one would see an unvarying EM field; but there is no such solution to the EM equations - light always travels at c.
Yes, but do note that all this preceded the wave nature of matter. When we put that light through pair production, we then obtain an electron and a positron. We see an unvarying EM field.
The following is multiple choice question (with options) to answer.
Einstein developed a theory about how electromagnetic radiation can behave as both a wave and what else? | [
"bacteria",
"particle",
"energy",
"sound"
] | B | In 1905, the physicist Albert Einstein developed a new theory about electromagnetic radiation. The theory is often called the wave-particle theory . It explains how electromagnetic radiation can behave as both a wave and a particle. Einstein argued that when an electron returns to a lower energy level and gives off electromagnetic energy, the energy is released as a discrete “packet” of energy. We now call such a packet of energy a photon . According to Einstein, a photon resembles a particle but moves like a wave. You can see this in the Figure below . The theory posits that waves of photons traveling through space or matter make up electromagnetic radiation. |
SciQ | SciQ-6225 | molecular-biology, cell-biology, experiment
Title: Transmembrane Protein Problem Problem
A transmembrane protein has 1000 aa. The 5th aa is found on the external side of the cell membrane. It interacts with the aqueous environment outside the cell. Amino acid 90 is inside the membrane bilayer. Aa 100-600 are intracellular, and 200-400 make a tight ball with minimal exposure to the aqueous cytoplasm. Amino acid 979 is found on the extracellular side of the protein where it forms a weak ionic bond with Cl-.
a. Can you draw the protein and mark positions of all mentioned aa in it?
b. What are the properties of these amino acids?

I dont necessarily want/need the exact answers to these questions, rather i would like some guidance in what principles i would need to understand and conceptualize to attack this problem. Thanks all ! I made a quick sketch on the basis of the information you gave (this is not to scale):
Aminoacid 5 (aa5) of the protein is on the outside, aa90 is inside the membrane. What we don't know here where the transmembrane part starts (directly with aa6 or later) and how it is organised (I indicated this as a transmembrane helix, but this can of course be different). Then we know that the border between the transmembrane part and the cytosolic part is somewhere between aa90 and aa100, that aa100 to aa200 seems to be some connecting part. The aa200 to aa400 is a globular domain which shields hydrophobic amino acids from the cytosol, so this part has to contain a high percentage of hydrophobic amino acids.
The part from 400 to 600 is again cytosolic but with no further information about the structure. After aa600 starts a second transmembrane part of the protein, but here we don't know how long it is. The maximum possibility would be until aa977, since we know the aa978 is outside of the membrane.
The following is multiple choice question (with options) to answer.
What type of proteins are only temporarily associated with the membrane? | [
"peripheral membrane proteins",
"sensitive rod proteins",
"peripheral oxidation proteins",
"visual membrane proteins"
] | A | Peripheral membrane proteins are proteins that are only temporarily associated with the membrane. They can be easily removed, which allows them to be involved in cell signaling. Peripheral proteins can also be attached to integral membrane proteins, or they can stick into a small portion of the lipid bilayer by themselves. Peripheral membrane proteins are often associated with ion channels and transmembrane receptors. Most peripheral membrane proteins are hydrophilic. |
SciQ | SciQ-6226 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
Which organisms break down either organic or inorganic molecules to supply energy for the cell? | [
"chemotrophic organisms",
"photoreactive organisms",
"asexual organisms",
"spicule organisms"
] | A | Chemotrophic organisms break down either organic or inorganic molecules to supply energy for the cell. Some chemotrophic organisms can also use their organic energy-supplying molecules as a carbon supply, which would make them chemoheterotrophs. |
SciQ | SciQ-6227 | earth-rotation, geologic-layers
Title: Do Earth's layers move at different speeds? I don't have a background in Geology but this question popped in my head the other day and can't find an answer anywhere else.
If I remember science class correctly, Earth's layers have different element compositions. Would it be correct to assume that they have different densities and different frictions as a result? And if they do, does it follow from it that they rotate at different speeds?
Thanks. Im am currently doing my masters in geophysics (last semester) and before that I did a bachelor in geoscience.
I assume by layers you mean the crust, the mantle and the core.
These all have different composition and also different densities. But the earth rotates as a whole, not the individual layers, all layers have the same angular velocity. That means they all make one rotation per day.
These layers are also not the perfect boundaries we like to imagine, but more a change in properties around a finite depth. This depth can even change at different places.
The following is multiple choice question (with options) to answer.
What are the things moving under the earth's mantle that move the crust? | [
"lava channels",
"ridges",
"plates",
"crystals"
] | C | What portion of Earth makes up the “plates” in plate tectonics? Again, the answer came about in part due to war. In this case, the Cold War. The scientists set up seismometer networks during the 1950s and early 1960s. The purpose was to see if other nations were testing atomic bombs. Since seismometers measure ground shaking, they also recorded earthquakes. |
SciQ | SciQ-6228 | species-identification, zoology, marine-biology, arthropod
Title: What is this large, lively barnacle? Yesterday I found this creature in a rocky cove in central California, around mid tide (+ 3 feet). It's about 3-4 inches long. At first I thought it was dead, but it closed its mouth when I removed the tiny white pebble, and rotated the operculum rapidly when I poked the bit of exposed yellowish flesh underneath. I think it's some sort of acorn barnacle, but haven't been able to identify a species with the white shell and distinctive red-and-white color and texture differences on the opercular plates. What could it be? Update: this is a giant acorn barnacle, Balanus nubilis. Between Pacific Tides mentions that they can vary widely in coloration, and there's a picture of a similarly colored one here.
We had our ID confirmed by email by a representative of the Monterey Bay Aquarium, who added this info:
You beat me to it. That is indeed a giant acorn barnacle (Balanus
nubilus). Unfortunately, barnacles can’t survive long after being
detached from their rocks and they’re unable to reattach on their own.
Rocky intertidal zones are harsh environments and animals living in
these areas must deal with both water and air, rapidly changing
temperatures, exposure to sunlight, desiccation, high wave energy, and
predators from both land and sea.
The stringy threads attached to the barnacle in your photo are the
byssal threads of California mussels. Mussels secrete these threads
to anchor themselves to rocks, each other, barnacles, etc. It’s very
common to see mussels and barnacles clumped together in high surf
zones.
The following is multiple choice question (with options) to answer.
Although they look like big rocks, what structures that serve as habitats for many different types of ocean life are actually alive? | [
"coral reefs",
"southern reefs",
"natural reefs",
"new forming reefs"
] | A | Coral reefs ( Figure below ) look like big rocks, but they are actually alive. They are built from cnidarians called corals. The corals are sessile (non-moving) polyps that can use their tentacles to feed on ocean creatures that pass by. Their skeletons are made up of calcium carbonate, which is also known as limestone. Over long periods of time, their skeletons build on each other to produce large structures known as coral reefs. Coral reefs are important habitats for many different types of ocean life. |
SciQ | SciQ-6229 | reaction-mechanism
It is generally said that reactants react so that they can achieve a
lower energy state. Then why does a reversible reaction occur in the
first place?
Good question. Remember that we can always add energy to make an unfavorable reaction proceed. For example, the sodium ion, which is isoelectronic with neon, is stable with a full octet of electrons. However, we can still take away more electrons. It just takes a rather sizable application of energy.
The following is multiple choice question (with options) to answer.
What type of reactions are chemical reactions that release energy? | [
"sulfuric reactions",
"biochemical reactions",
"exothermic reactions",
"ozonic reactions"
] | C | Chemical reactions that release energy are called exothermic reactions . An example is the combustion of methane described at the beginning of this lesson. In organisms, exothermic reactions are called catabolic reactions . Catabolic reactions break down molecules into smaller units. An example is a decomposition reaction, such as the breakdown of glucose molecules for energy. Exothermic reactions can be represented by the general chemical equation:. |
SciQ | SciQ-6230 | energy, fuel, environmental-chemistry
Title: Effect of coal and natural gas burning on particulate matter pollution I sometimes hear people talking about how we should replace coal burning plants with natural gas ones, to alleviate the case of particulate matter pollution. What exactly is the difference between coal fuel and natural gas that makes the latter seem "cleaner"?
At the same energy outcome, natural gas produces less carbon dioxide than coal. In a way, natural gas is half way between coal and hydrogen.
Coal produces smelly smoke, solid particles, sulfur dioxide and minor or trace heavy metal pollutants.
It is less known to common people, but power plants burning coal are more significant source of radioactive pollution than nuclear plants. This pollution is very diluted, but rather significant in absolute amount. Coal ash, used in past as a filler for some construction materials, has lead in some cases to significantly increased content of radium-226 in building walls. This radium is a product of long term decay of natural uranium. It further decays while producing radioactive gaseous radon-222, which is dangerous in long term inhalation because of lung cancer. As it stays in lungs as polonium-218 and its decay products.
See e.g. Uranium produced from coal ash
... the uranium concentration in the ash pile is about 150-180 parts per million, about 1/4th of the concentration often thought of as commercially viable for ISL[In Situ Leaching] mining. However, coal ash piles have some physical characteristics that might help overcome that disadvantage since they may be easier to drill and it might be easier to protect the local groundwater from contamination. ...
See Radon in building materials by Czech government agency for radiation protection.
The following is multiple choice question (with options) to answer.
Fossil fuels and coal are examples of what kind of resources? | [
"valuable",
"nonrenewable",
"reusable",
"renewable"
] | B | Nonrenewable resources exist in fixed amounts. They can be used up. Examples include fossil fuels such as coal. |
SciQ | SciQ-6231 | stability, molecular-structure, isomers
[Abstract] ...While the ring isomer is predicted to be the most stable structure on the
hypersurface, the barrier to dissociation is most likely between 1 and 2 kcal mol-1 (including zero-point vibrational
energy [ZPVE], the existence of any barrier becomes questionable) making isolation theoretically possible but
experimentally difficult. This small barrier also detracts from the attractiveness of the N4O ring structure as a high energy-density material. The trans-chain isomer, however, lies in an energy valley with higher sides, consistent
with its previous experimental observation.
[full text]...In an ideal five-membered ring
with 6 $\pi$ electrons, the $\pi$ electrons would be distributed evenly
among all the bonds. In the present case, the highly electronegative
O atom prefers to keep electrons around itself, leading
to a partial negative charge on the oxygen. Energetically, there
is a certain degree of stability associated with the ring isomer,
although not on the order of common aromatic systems. The
ring isomer is predicted to be at most (DZP CISD) 20.9 kcal
mol-1 more stable than the trans-chain isomer; however, this
value decreases to 13.2 kcal mol-1 with TZ2P CCSD.
The ring isomer TS to dissociation into N2 and N2O is shown
in Figure 5. ... Energetically, the barrier to dissociation
is at most 15.3 kcal mol-1 (DZP CISD) and drops lower
with improvements in both basis set and correlation scheme.
In going from a DZP to a TZ2P basis set, for example, this
barrier drops by 5.2 kcal mol-1 for CISD and 4.3 kcal mol-1
for CCSD. Assuming a similar trend in moving from DZP
CCSD(T) to TZ2P CCSD(T), the ring dissociation barrier is
expected to drop to 1-2 kcal mol-1 with the addition of f-type
functions possibly making it even lower. A barrier of this size
lies below the ZPVE, throwing doubt on the existence of the
N4O ring isomer.
The following is multiple choice question (with options) to answer.
What type of compound contains atoms of two or more different elements in its ring structure? | [
"polymer",
"heterocyclic",
"hydrocarbon",
"aldehyde"
] | B | In some amines, the nitrogen atom replaces a carbon atom in an aromatic hydrocarbon. Pyridine (Figure 20.17) is one such heterocyclic amine. A heterocyclic compound contains atoms of two or more different elements in its ring structure. |
SciQ | SciQ-6232 | solubility, precipitation
$$\ce {Fe^{3+} + 2H2O <=> [FeOH]^{2+} + H3O+ }$$
Thus, $\ce{H3O+}$ ions in solution can react with added $\ce{CO3^{2-}}$ ions to form carbonic acid $(\ce{H2(CO3)3})$,which can decomposed to form $\ce{CO2}$ and $\ce{H2O}$. Remaining $\ce{Fe^{3+}}$ will combine with left behind $\ce{OH-}$ ions to make $\ce{Fe(OH)3}$, which would decomposed to $\ce{Fe2O3}$. Thus, when $\ce{Na2CO3}$ is added to an aqueous solution of $\ce{FeCl3}$, one can expect the following sequence of reactions to be taken place:
$$\ce {FeCl3 (aq) + Na2CO3 (aq) -> [Fe2(CO3)]^{3+} (aq) -> Fe2O3 (s) + CO2 (g) + H2O (l)}$$
The following is multiple choice question (with options) to answer.
What is formed when atoms of different elements combine in a chemical reaction? | [
"crystals",
"dust",
"compounds",
"toxins"
] | C | For each of the following situations, tell whether the rate of the reaction would increase or decrease, and explain your answer in terms of collision theory. The concentration of a reactant is doubled. |
SciQ | SciQ-6233 | electricity, charge
Of course, objects CAN become electrically charged, gaining or losing electrons. So something is wrong with my reasoning or my premises. I just don't know what it is. Where am I going wrong? What you have described is the reason that conductors (such as metals) will act to reduce any polarisation within their structure. Polarisation is an imbalance of charge. In an object with a neutral charge overall, one region of the object may have a surplus of electrons, and thus have a net negative charge, and therefore another region will have a deficit of electrons, and thus have a net positive charge.
Now, what you say about metals is true, they conduct electricity and therefore current will flow in order to neutralise any imbalance in charge. However, this does not prevent them losing electrons by friction. The standard classroom experiment where you rub a balloon against your shirt in order to pull electrons from one to the other will still work with metals. Copper, for example, is often used as a conductor in wire form, but a copper rod may also be rubbed against another object to transfer electrons. This is called the Triboelectric Effect.
Also, although conductors when left on their own will act to spread charge out across their structure through current flow, it is still possible to polarise them (i.e. create imbalances of charge) using an external means. One such method is called Electrostatic Induction. In the picture below, moving a positively charged object near to the conductor in the electroscope pulls the electrons toward the top end, and as a result causes a local net negative charge here, and a local net positive charge at the bottom.
"Electroscope showing induction" by Sylvanus P. Thompson - Downloaded from Sylvanus P. Thompson (1881) Elementary Lessons in Electricity and Magnetism, MacMillan, New York, p.16, fig. 12. Licensed under Public domain via Wikimedia Commons.
Now imagine you were to suddenly cut the conducting material in the electroscope in half. The top half would be a completely independent object, and would have more negative charge than positive charge, a surplus of electrons. The bottom half would be similar, but would have more positive charge than negative charge, a deficit of electrons.
I hope this helps.
The following is multiple choice question (with options) to answer.
What type of electricity is formed when a negative charge builds up and are transferred? | [
"direct current",
"static electricity",
"neutron energy",
"alternating current"
] | B | Static electricity is a buildup of electric charges on objects. Charges build up when negative electrons are transferred from one object to another. The object that gives up electrons becomes positively charged, and the object that accepts the electrons becomes negatively charged. This can happen in several ways. |
SciQ | SciQ-6234 | physical-chemistry, thermodynamics
In space, both the temperature and pressure are very low. That would put beyond the bottom left corner of the diagram, well within the ice field. So simply speaking, water would be ice.
However, there is the concept of vapour pressure. Any condensed material (just a fancy word for both solids and liquids) has that same material in the vapour around it. That's why you can smell alcohol, even though it's liquid as one example. That's why a puddle of water will eventually dry out even though it's below the boiling point of water.
The way vapour pressure works is that if you look on the phase diagram, for a certain temperature, the liquid-vapour and the solid-vapour lines have certain pressures associated with them. For example, if you look on 50 C, then the pressure on the curve is 10 kPa. Roughly speaking, this means that in atmospheric pressure, one tenth of the air (which is at 100 kPa) has to be water vapour. If it's any less, water will keep evaporating until it reaches that amount. On Earth, wind and diffusion will disperse the water so it will basically evaporate until there are no more liquid water left.
Now let's think what would happen in space. The temperature is very low, so the vapour pressure is very low. Thus, it should evaporate also in space. However, because the vapour pressures at such low temperatures are extremely low, you might end up with a situation where the gravitation of that ice blob is enough to overcome evaporation, so that will be an agonizingly slow process.
The following is multiple choice question (with options) to answer.
What important liquid is stored throughout the earth in the oceans, underground, and in ice? | [
"water",
"air",
"lava",
"oil"
] | A | Water cycling is extremely important to ecosystem dynamics. Water has a major influence on climate and, thus, on the environments of ecosystems, some located on distant parts of the Earth. Most of the water on Earth is stored for long periods in the oceans, underground, and as ice. Figure 46.13 illustrates the average time that an individual water molecule may spend in the Earth’s major water reservoirs. Residence time is a measure of the average time an individual water molecule stays in a particular reservoir. A large amount of the Earth’s water is locked in place in these reservoirs as ice, beneath the ground, and in the ocean, and, thus, is unavailable for short-term cycling (only surface water can evaporate). |
SciQ | SciQ-6235 | thermodynamics, air, thermal-conductivity
Update 1: I imagine MATLAB model as a combination of room A, B, and the ventialtor between them. Room A has a volume, and temp, room B as well, during each point in time after ventilator starts working with a certain speed I would see drop of temperature in room A and an increase in room B.
Update 2: There should also be a second tube with a ventilator that would take cold air from room B to room A. If you have a volume of air $V$ at temperature $T_B$, then you replace a part of that air with air of volume $\Delta V$ and temperature $T_A$, then the new average temperature is a weighted average of the temperatures of the room's air and the new air.
$$T_B(t+\Delta t) = \frac{(V-\Delta V) T_B(t) + \Delta V T_A(t)}{V}$$
We get a symmetrical expression for the air in the other room:
$$T_A(t+\Delta t) = \frac{(V-\Delta V) T_A(t) + \Delta V T_B(t)}{V}$$
Simplifying...
$$T_B(t+\Delta t) - T_B(t) = \frac{\Delta V}{V} (T_A(t) - T_B(t))$$
$$T_A(t+\Delta t) - T_A(t) = \frac{\Delta V}{V} (T_B(t) - T_A(t))$$
If we divide both sides by the time interval $\Delta t$ it takes for this volume $\Delta V$ to transfer,
$$\frac{T_B(t+\Delta t) - T_B(t)}{\Delta t} = \frac{\Delta V}{\Delta t} \frac 1 V (T_A(t) - T_B(t))$$
The following is multiple choice question (with options) to answer.
What results when a warm air mass runs into a cold air mass? | [
"cool front",
"warm front",
"rough front",
"dry front"
] | B | When a warm air mass runs into a cold air mass, it creates a warm front ( Figure below ). The warm air mass is moving faster than the cold air mass. The warm air mass then flows up over the cold air mass. As the warm air rises, it cools. This brings about clouds and sometimes light precipitation. Warm fronts move slowly and cover a wide area. After a warm front passes, the warm air mass behind it brings warmer temperatures. The warm air is also likely to be more humid. |
SciQ | SciQ-6236 | bond, covalent-compounds, valence-bond-theory
Title: Why are pi bonds only formed when sigma bonds are formed? While studying about bonding there was one statement that "pi bonds can only be formed only with sigma bonds" as we know that in double bond there is 1 sigma bond and 1 pi bond but then one question arises: Why is a pi bond formed only when a sigma bond is formed? Is it possible to form a pi bond without any formation of a sigma bond? A $\pi$ bond has a plane of symmetry along the bond axis. It cannot be formed by s-orbitals; it needs at least p-orbitals to be created. $90\,\%$ of all bonds described some time or another are somehow involving carbon, nitrogen or oxygen. (In fact, I probably underestimated). But these elements can only use p-orbitals to create $\pi$ bonds. To do that, one needs a p-orbital that is ortohogonal to the bond axis. So you run into the problem that you have an orbital pointing in one direction, but want to bond into another direction — hardly optimal, especially since there likely is already another orbital pointing in the direction you need to give a $\sigma$ bond.
Transition metals can use d-orbitals for $\pi$ bonding. They can actually point towards the atom they want to bond with so there is a greater chance of using them due to higher overlap. However, there will usually also be a different orbital pointing directly in the bonding direction which again will bond earlier and would give a $\sigma$ bond.
The following is multiple choice question (with options) to answer.
Which type of double bond has a sigma bond and a pi bond? | [
"dioxide - oxygen bond",
"carbon-oxygen bond",
"sodium - oxygen bond",
"Covalent Bonds"
] | B | Has a double-bonded carbon-oxygen bond (one sigma bond and one pi bond). The carbon to which the oxygen is attached has one hydrogen atom connected to it. |
SciQ | SciQ-6237 | ocean, climate-change
During the 20th century, sea level rise was estimated from tide-gauges, which raises the problem of 'are we measuring rising sea or sinking land?' For the last decade or so we have been able to measure absolute mean sea levels by satellite. That is, independent of land levels. Now we can re-evaluate old data, and come up with 'real' average rates of rising sea level. They turn out to be about 2.5 +/- 1.5 mm/year for most of the last century. Now they have accelerated to more than twice that amount. See, for example:
https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level
This is the global average, and yes, there are all manner of positive and negative anomalies. Now consider sediment displacement. Measuring the global sediment flux from rivers to oceans is extraordinarily difficult, for reasons which would take several pages to explain. But of the diverse range of estimates the consensus seems to be between 20 and 60 Gtonnes per year for the world's major rivers. Leaning towards the upper bound, and adding in a factor for the minor rivers, and assuming an average sediment density of about 2.5, we arrive at about 40 billion cubic metres of sediment entering the oceans each year. There are about 360 million square kilometres of ocean, so on average, the annual increase in ocean sediment is about 1.1 mm. In reality, this is an upper bound with the a more realistic estimate being about 0.6 mm. So, even without taking oceanic subduction into account, the observed sea level is at least an order of magnitude more than can be accounted for by sediment displacement. Or to answer your question, no, the ocean floor isn't rising at any rate that we can measure. Conversely, sea level is rising at a rate that is consistent with thermal expansion of the ocean surface, combined with nett global ice melt.
The following is multiple choice question (with options) to answer.
Has the average annual temperature on earth been rising or falling for the past 100 years? | [
"falling",
"unchanged",
"fluctuating",
"rising"
] | D | The average annual temperature on Earth has been rising for the past 100 years. |
SciQ | SciQ-6238 | adaptation
Title: How do longleaf pine trees adapt to the florida keys rainforest? I know that longleaf pine trees can be found in rainforests, but I can't find anything. This is sort of a too broad question but here are a few ideas. The second most fragile part of plants are the leaves. In the latitudes and elevations that experience freezing, plants have learned to abscise their leaves and go dormant for the winter season. Conifers have thick, waxy, very thin leaves that most conifers do not need to shed.
In a rainforest there is no danger of too cold temperatures. That is why there is an abundance of broadleaf trees and plants in the rainforest. Most of our indoor plants are tropical rainforest species.
There is also an awful lot of rain in a rainforest. There is a problem with leaves covered with water, as it inhibits the absorption of CO2. Beneath the leaf, O2 is released as a by-product of photosynthesis. Broad leafed plants that have adapted to an environment with lots of rain, little wind, and being crowded together have leaves designed to 'wick' the rain water off the leaf to run down the midrib and off the pointy tip or lobed or curled under leaf margins. This clears off the water and allows the plant to take up CO2, or it would not be able to do photosynthesis to make its own food for energy.
The other cool thing I can remember, is that broad leafs of plants are able to 'adjust' to the light. Similar to a 'solar sail' in outer space. If in full sun, those leaves get thick and stay smaller. If in shade, very normal in a rainforest, those leaves can thin and get larger in order to capture as much light as possible.
A better wording for your question would be, 'why is there an abundance of broad leaf species versus conifers in a rainforest'? If I've been able to translate your question correctly?
Hope this helps.
The following is multiple choice question (with options) to answer.
The majoirty of modern gymnosperms belong to what group, which includes pine trees? | [
"conifers",
"clusters",
"stems",
"Pinophytes"
] | A | There are only about 1,000 living species of gymnosperms, whereas there are hundreds of thousands of living species of angiosperms. Living gymnosperms are typically classified in the divisions described in the Table below . Most modern gymnosperms are trees with woody trunks. The majority are conifers such as pine trees. |
SciQ | SciQ-6239 | electricity, electric-circuits, electrons, electric-current, charge
Title: Electrons in an electric circuit , its movement and power delivered Does an electrical appliance convert electrons into its respective work , I mean is electron being consumed by appliance (say bulb ) and then this mass gives us energy.
or the same number of electron , just revolve around the circuit, then from where does power comes from, Electrons have charge and so when there is a potential difference across a circuit, this charge moves through it. In an incandescent light bulb, there is a high resistance, meaning that there are many atoms with which the charges collide, transferring some of their kinetic energy. No electrons are being "consumed" by the light bulb, i.e. the number of electrons in the circuit does not change. The ability of the charges to do work is because of a potential difference, which can be achieved through a number of means, e.g. using voltaic cells or electromagnetic induction.
To gain a better idea of why potential difference moves charges, consider two isolated point charges of opposite charges, one positive and one negative. If you pull the negative charge away from the positive one, you are doing work on it in the form of potential energy, as you are opposing the electric field of the positive charge. If you let go, the negative charge will convert this potential energy into kinetic energy, as it is attracted to the positive test charge. A potential difference across a circuit, albeit simplified, essentially does this – it brings electrons from a higher potential to a lower potential, converting potential energy into the kinetic energy in the process.
The following is multiple choice question (with options) to answer.
A circuit must be what in order for electric devices such as light bulbs to work? | [
"open",
"down",
"closed",
"cyclical"
] | C | A circuit must be closed for electric devices such as light bulbs to work. The arrows in the diagram show the direction in which electrons flow through the circuit. The current is considered to flow in the opposite direction. |
SciQ | SciQ-6240 | homework-and-exercises, radiation, earth, sun
Title: How much radiation does the Earth receive from the Sun's total radiation? I was thinking how to solve this problem. $1\,\mathrm{AU}$ is roughly the distance from the Earth to the Sun, $1.4960 \times 10^{11}\,\mathrm{m}$.
The radius of Earth is approximately $6.4 \times 10^{6}\,\mathrm{m}$, and the radius of the Sun is approximately $6.96 \times 10^{8}\,\mathrm{m}$.
How could we estimate the percent of radiation which the Earth receives, ignoring astrophysical "noise" like dust?
The radiation emitted by the Sun roughly follows the Stefan-Boltzmann law and the radiation emitted is roughly $\propto T^4$, and the surface area of the Earth is roughly $\propto r^2$.
Would you simply take the ratio between the Sun's surface area divided by the Earth's surface area?
All the Sun's power $P$ passes uniformly through a sphere with radius of 1 AU. Calculate the total surface area of this sphere and call it $S$.
The Earth's disc also has a surface area that can be calculated from its radius. Call this surface $S_E=\pi R_E^2$.
The fraction of the Sun's power received by the Earth is thus:
$f=P\frac{S_E}{S}$.
The following is multiple choice question (with options) to answer.
What type of radiation from the sun reaches earth across space striking everything on earth’s surface? | [
"particle",
"static",
"electromagnetic",
"seismic"
] | C | Electromagnetic radiation from the sun reaches Earth across space. It strikes everything on Earth’s surface, including these volleyball players. |
SciQ | SciQ-6241 | cosmology, nuclear-physics, space-expansion, universe, binding-energy
Title: What happens when the universe runs out of fuel? After some X billion years, one would think the stars in the entire universe will run out of hydrogen. What would happen next? Is there any way to get hydrogen out of heavy metals (extreme fission)? Just curious. Then star formation ceases and the universe goes dark. At this stage of the universe's evolution, there'll still be plenty of hydrogen, they just don't form stars.
In theory you can create hydrogen out of heavy metals, but it's a process that requires energy. If you have the energy banked somewhere (and you'll need a LOT of energy to make enough hydrogen for a new star) then it's possible.
The following is multiple choice question (with options) to answer.
What happens if a catalyst runs out? | [
"variety increases",
"reaction slows",
"variety slows",
"reaction increases"
] | B | Chemistry in Everyday Life Transition Metal Catalysts One of the most important applications of transition metals is as industrial catalysts. As you recall from the chapter on kinetics, a catalyst increases the rate of reaction by lowering the activation energy and is regenerated in the catalytic cycle. Over 90% of all manufactured products are made with the aid of one or more catalysts. The ability to bind ligands and change oxidation states makes transition metal catalysts well suited for catalytic applications. Vanadium oxide is used to produce 230,000,000 tons of sulfuric acid worldwide each year, which in turn is used to make everything from fertilizers to cans for food. Plastics are made with the aid of transition metal catalysts, along with detergents, fertilizers, paints, and more (see Figure 19.26). Very complicated pharmaceuticals are manufactured with catalysts that are selective, reacting with one specific bond out of a large number of possibilities. Catalysts allow processes to be more economical and more environmentally friendly. Developing new catalysts and better understanding of existing systems are important areas of current research. |
SciQ | SciQ-6242 | evolution, human-evolution
Apes
The split between the line leading to modern humans and the line leading to modern chimpanzees occured somewhere around 4 to 7 million years ago. The clade is called Hominini. The split between those and the line leading to modern gorillas occured around 8 to 19 million years ago (yes, the dates are getting fuzzier). A fossil coming close to this ancestor may be Nakalipithecus nakayamai, however, we only have a fossil jaw from that species.
Going back, we get to the split between modern-day humans/chimpanzees/gorillas and modern-day orang-utans. This is the "ape" family, Hominidae. The largest ape that we know of, Gigantopithecus, that grew to about 3 meters, is classified as an orang-utan. Note that this is not a direct ancestor of humans. Even if our ancestors were larger than modern humans at this point it's unlikely that we are talking about anything larger than a big gorilla.
Primates
Going a bit in the reverse order here: The first true primates evolved around 55 million years ago. Fossils from that time are about the size of squirrels. Humans are "old world monkeys" who first appeared around 40 million years ago - the fossils from that clade we know, for example Apidium or Aegyptopithecus are a bit larger, some as large as a dog.
Primate-like mammals
The first primate-like mammals, called Plesiadapiformes appeared around 60 million years ago. We don't know all that much about them, but the most famous Purgatorius was the size of a rat or mouse.
Mammals / placenta mammals
Going back even further, things become even murkier, but early mammals were small. Placentalia, placental mammals appeared around 90 million years ago. They were small, arboreal (tree-dwelling) animals. Early mammals appeared around 160 million years ago and fossils we have from that time place them around the size of a shrew.
Now, is it possible that there were larger mammals in there somewhere, that then "shrunk" again? Sure. Just unlikely.
Therapsid
The following is multiple choice question (with options) to answer.
What type of mammals are humans? | [
"placental mammals",
"somatic mammals",
"marsupial mammals",
"respiratory mammals"
] | A | Human beings are mammals. Like other mammals, we have hair and mammary glands. The subclass in which the human species is classified is the placental mammals. |
SciQ | SciQ-6243 | A graph of the position of the object for times $t$ in $[-0.5,3]$ is shown in Figure 9.7.6. Suppose further that the object is at the point $(1.5,-1,0)$ at time $t=0\text{.}$
1. Determine $\va(t)\text{,}$ the acceleration of the object at time $t\text{.}$
2. Determine $\vr(t)\text{,}$ position of the object at time $t\text{.}$
3. Compute and sketch the position, velocity, and acceleration vectors of the object at time $t=1\text{,}$ using Figure 9.7.6.
4. Finally, determine the vector equation for the tangent line, $\vL(t)\text{,}$ that is tangent to the position curve at $t = 1\text{.}$
### Subsection9.7.5Projectile Motion
Any time that an object is launched into the air with a given velocity and launch angle, the path the object travels is determined almost exclusively by the force of gravity. Whether in sports such as archery or shotput, in military applications with artillery, or in important fields like firefighting, it is important to be able to know when and where a launched projectile will land. We can use our knowledge of vector-valued functions in order to completely determine the path traveled by an object that is launched from a given position at a given angle from the horizontal with a given initial velocity.
The following is multiple choice question (with options) to answer.
The shape of the path of an object undergoing projectile motion in two dimensions is a what? | [
"radius",
"circle",
"parabola",
"orbit"
] | C | The shape of the path of an object undergoing projectile motion in two dimensions is a parabola. |
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