source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-444 | inorganic-chemistry, periodic-trends, periodic-table
Title: Comparing Electron affinity and electron gain enthalpy at 0 K In my book it is given that first electron gain enthalpy is greater than second for elements. Should we compare the magnitudes in such cases or the actual numbers with signs? Does the same comparision hold with Electron Affinity at 0K?
For example Be has positive Electron Affinity and F has negative Electron Affinity. So should I consider signs and say Be has more Electron Affinity than F or consider magnitude and say F has more Electron Affinity than Be?
How to compare their Electron gain enthalpies also at 0K?
In my book it is given that first electron gain enthalpy is greater than second for elements. Should we compare the magnitudes in such cases or the actual numbers with signs?
Successive Electron Gain Enthalpies
After the addition of one electron atom becomes negatively charged and second electron is to be added to a negatively charged ion. Thus, due to electrostatic repulsion energy is always required for addition of second electron. First electron gain enthalpy is always more negative than second electron gain enthalpy (which is essentially positive). Author made an ambiguous statement, as we can't just compare the magnitudes. For more clarity see:
$$\ce{S_{(g)} + e- -> S- _{(g)}} \Delta_{eg} H^- _1 = \pu{-200kJ mol^{-1}}$$
$$\ce{S- _{(g)} + e- -> S^{2-}_{(g)}} \Delta_{eg} H^- _2 = \pu{600kJ mol^{-1}}$$.
Does the same comparision hold with Electron Affinity at 0K?
The following is multiple choice question (with options) to answer.
What is the name of the second most electronegative element? | [
"oxygen",
"nitrogen",
"carbon",
"Hydrogen"
] | A | Oxygen has an oxidation state of -2 in most of its compounds. Oxygen is the second most electronegative element, so it also tends to be assigned all shared electrons. Exceptions include O 2 (oxidation state = 0), peroxides, in which two oxygen atoms are connected by a single bond (oxidation state usually = -1), and any compound in which oxygen is bonded to fluorine (pretty rare and reactive). |
SciQ | SciQ-445 | evolution, definitions, artificial-selection
It does not lead to new species
In short, 1) it does lead to new species 2) the concept of species is often meaningless as poorly defined 3) evolution > speciation. In more details, below..
It does lead to new species. Different lineages of cabbage are considered different species. Cows and ox are different species. Pigs and boars are often considered different species. While wolves and dogs are considered same species, some lineages within this species (such as a Chihuahua and a Great Dane) are, I think, reproductively isolated. You might also want to have a look at the post Have we ever observed two drosophila lineages that evolved reproductive isolation in labs?
The question of whether selective breeding lead to speciation or not does not matter much on the question of whether it leads to evolution. Speciation is one outcome of evolution but is definitely not the same as evolution. Evolution does not need to lead to speciation. For example, evolution of the lactase gene in humans (see this post) did not lead to any speciation. It is still an evolutionary process.
The concept of species is mainly arbitrary. If you want to understand the concept of species, have a look at the post How could humans have interbred with Neanderthals if we're a different species?.
It decreases, rather than increases, the size of the gene pool (is this actually true?)
The following is multiple choice question (with options) to answer.
What is the term for species evolving together? | [
"interconnection",
"conjuration",
"specmutation",
"coevolution"
] | D | Coevolution occurs when species evolve together. This often happens in species that have symbiotic relationships. Examples include flowering plants and their pollinators. |
SciQ | SciQ-446 | genetics, cell-biology, embryology, meiosis, gamete
Title: Fertilization of the human egg- where does our centrosome come from? Is there a centrosome in a human egg cell? Is the reason why the egg cell remains paused before meiosis 2 because there isn't a centrosome, and it only divides when the sperm fertilizes it thus it can have a centrosome? If this is so, then how did oogenesis happen? ? To answer the first part of your question. The sperm actually introduces two centrosomes. The centrosome then nucleates the new microtubule assembly to form the sperm aster — a step essential for successful fertilization. You can visit these sites Simerly, et al as well as Paweltz, et al
The following is multiple choice question (with options) to answer.
Where do the eggs develop? | [
"the glands",
"the uterus",
"the ovaries",
"the follicles"
] | C | |
SciQ | SciQ-447 | fluid-dynamics, flow
Title: Where does the air go behind a wind turbine? A wind turbine receives wind at 10m/s, and slows it to 5m/s to generate electricity.
Does this mean that the wind around the turbine must be diverted to allow twice the cross-section area for the exiting wind?
If not, how does the exiting air escape? To preserve continuity of mass flow across the propeller disc, the slower air exiting the disc downwind swells out to produce a slow-moving wake that is wider than the propeller disc itself. This gets mixed up with the surrounding air and eventually the wake dissipates as the air in it speeds up to match the surrounding velocity.
The following is multiple choice question (with options) to answer.
What's the other term for your wind pipe? | [
"esophagus",
"cochlea",
"trachea",
"cornea"
] | C | The trachea , or wind pipe, is a long tube that leads down to the chest. |
SciQ | SciQ-448 | cell-biology, proteins, transcription, cell-signaling, intracellular-transport
Time is in minutes, and zeroed at first contact between the two cells. I've put a red dot on the T-cell and a blue one on the APC in the DIC images (left panes); hopefully that proves more informative than annoying. The right panes show GFP fluorescence and thus CD3 localization. As time progresses, CD3 is re-localized from one part of the membrane to another (the synapse). There is supposedly a video of this is in the supplementary information of the article, though I was unable to open it.
The rate and directionality of the movement implies that an active process is occurring, rather than simple diffusion. However, they did not find the actual mechanism for movement and I haven't found any follow-up papers in a brief search (though many subsequent papers implicate the cytoskeleton in this movement). Just to show that movement of transmembrane proteins can, in fact, be actively directed by the cytoskeleton, I refer you to this paper:
Grabham PW, Foley M, Umeojiako A, Goldberg DJ. 2000. Nerve growth factor stimulates coupling of beta1 integrin to distinct transport mechanisms in the filopodia of growth cones. J Cell Sci 113:3003-3012.
They show that membrane-spanning integrins are moved along actin filaments of the cytoskeleton by myosin motor proteins. Expectedly, the abstract does a good job of summarizing the paper:
The cycling of membrane receptors for substrate-bound proteins via their interaction with the actin cytoskeleton at the leading edge of growth cones and other motile cells is important for neurite outgrowth and cell migration. Receptor delivered to the leading edge binds to its ligand, which induces coupling of the receptor to a rearward flowing network of actin filaments. This coupling is thought to facilitate advance... [T]ransport was dependent on an intact actin cytoskeleton and myosin ATPase...
The following is multiple choice question (with options) to answer.
When food is scarce, starving cells secrete a molecule that stimulates neighboring cells to do what? | [
"aggregate",
"die off",
"compete",
"hoard energy"
] | A | |
SciQ | SciQ-449 | biochemistry, endocrinology, cell-signaling
Title: Effect of steroid hormone on specific cells? As steroid hormones can pass through the plasma membrane by simple diffusion because they are lipid derived hormones, it means that they are capable of passing through every cell of our body, BUT why are only specific cells responsive against steroid hormones?
For example, all of our body cells almost contains the genes for the development of secondary sexual characters but why do only specific cells show a response against these steroid hormones because the development of secondary sexual characters occur only in specific region of our body, that is, beard formation occur only in a specific region of the face, etc.
IN SUMMARY: When steroid hormones can pass through every cell of our body then why do they show only a localized response? Unlike other types of hormones, steroid hormones do not have to bind to plasma membrane receptors. Instead, they can interact with intracellular receptors that are themselves transcription activators. Steroid hormones too hydrophobic to dissolve readily in the blood travel on specific carrier proteins from their point of release to their target tissues. In the target tissue, the hormone passes through the plasma membrane by simple diffusion and binds to its specific receptor protein in the cytoplasm. The receptor-hormone complex then translocates into the nucleus where it acts by binding to highly specific DNA sequences called hormone response elements (HREs), thereby altering gene expression.
Hormone binding triggers changes in the conformation of the receptor proteins so that they be- come capable of interacting with additional transcription factors. The bound hormone-receptor complex can either enhance or suppress the expression of adjacent genes.
The DNA sequences (HREs) to which hormone- receptor complexes bind are similar in length and arrangement, but differ in sequence, for the various steroid hormones. Each receptor has a consensus HRE sequence to which the hormone-receptor complex binds well, with each consensus consisting of two six-nucleotide sequences, either contiguous or separated by three nucleotides,
The ability of a given hormone to act through the hormone-receptor complex to alter the expression of a specific gene depends on the exact sequence of the HRE, its position relative to the gene, and the number of HREs associated with the gene.
The following is multiple choice question (with options) to answer.
What do cells secrete that binds to receptors? | [
"factor",
"endorphans",
"stress",
"proteins"
] | A | |
SciQ | SciQ-450 | thermodynamics, acoustics, wavelength, resonance
Title: Why an open tube at both ends suffers resonance? Why an open tube at both ends suffers resonance when subjected to a sound that propagates through the air with length of where $L / 2$?
I already know the methodology to calculate the harmonics in an open tube. So, I'm not expecting an answer that is based on the calculations. I want to know why this phenomenon occurs from the molecular point of view of the air, taking into account that air could be considered as an ideal gas whose molecules have no interaction with each other. The gas molecules in air do indeed interact with each other, by colliding against each other with surprising speed at room temperature. This means a volume of gas will possess compliance (it can act like a spring). Those gas molecules possess mass too, and hence a volume of air can transmit compression waves through it at a speed that depends on this characteristic compliance and mass, and as a transmissive medium free air in an open space will therefore possess a certain characteristic impedance.
Now the air inside a tube possesses a certain characteristic impedance for waves traveling long its length as well, but this impedance is different from that of free air, which means there is a significant impedance mismatch at the open ends of the tube. When an acoustic wave in a tube meets that mismatch, part of the wave gets reflected off the mismatch (with a 180 degree phase reversal) and travels backwards up the tube, and part of the wave escapes into free space.
The fact that this reflection occurs off the open ends means that even a tube with two open ends will still support a resonance.
The following is multiple choice question (with options) to answer.
What is the term for the tube that carries sound waves into the ear? | [
"ear canal",
"flap canal",
"sound canal",
"tone canal"
] | A | The ear canal is a tube that carries sound waves into the ear. The sound waves travel through the air inside the ear canal to the eardrum. |
SciQ | SciQ-451 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
In the cardiovascular system, what blood vessels carry blood away from the heart? | [
"cilia",
"arteries",
"veins",
"capillaries"
] | B | The blood vessels are an important part of the cardiovascular system. They connect the heart to every cell in the body. Arteries carry blood away from the heart, while veins return blood to the heart ( Figure below ). |
SciQ | SciQ-452 | surface-tension, ideal-gas, kinetic-theory
Title: Collision frequency at surfaces Collision frequency for particles in gases is well known, and collision theory is used to derive chemical reaction rates in gases, (and particles in liquid solutions as well). Using the mean velocity as a function of temperature, one arrives at
$Z = N_A \sigma_{AB}\sqrt{\frac{8k_BT}{\pi\mu_{AB}}}$.
I need something similar where the collisions/interactions can only occur at the surface between two areas. I understand phenomenologically the collision frequency will be proportional to the area, but I am looking for something a little more rigorous. I have two types of particles, A and B. They occupy separate volumes of space and do not mix. One can assume no mixing because the time window I am interested in is too small compared to the average velocities or because of surface tension. I haven't thought it out completely yet.
The only thing I've thought of yet is to define some sort of mixing depth, and then just use the traditional collision frequency, multiplying by the mixing depth to arrive at collision frequency per unit surface area. But then the mixing depth should itself be derived from the average velocities of the particles and it should not really have sharp boundaries.
What is the canonical kind of model used for similar problems, such as reactions on liquid/liquid or liquid/gas boundaries? Collision theory will not help for calculating chemical rates in the liquid phase since the mass transport there is governed by diffusion. It is not perfectly clear from your question, so I will have to assume that you are interested in a two-phase gas/liquid system.
First, liquid phase is much denser, molecules there are always in contact and don't have to wait for collision so reaction rates in the liquid phase are much higher. This means that the major reaction pathway has these steps
Molecule A in the gas phase collides with the surface (defined by the collision theory)
The molecule has a certain chance $\alpha$ to be absorbed by the liquid and transferred to the bulk phase.
Molecule A diffuses through the solution, reacting with molecule B.
The following is multiple choice question (with options) to answer.
Molecules in the gas phase can collide with the liquid surface and reenter the liquid via what? | [
"combustion",
"liquidation",
"condensation",
"fermentation"
] | C | pressure above the liquid. Molecules in the gas phase can collide with the liquid surface and reenter the liquid via condensation. Eventually, a steady state is reached in which the number of molecules evaporating and condensing per unit time is the same, and the system is in a state of dynamic equilibrium. Under these conditions, a liquid exhibits a characteristic equilibrium vapor pressure that depends only on the temperature. We can express the nonlinear relationship between vapor pressure and temperature as a linear relationship using the Clausius–Clapeyron equation. This equation can be used to calculate the enthalpy of vaporization of a liquid from its measured vapor pressure at two or more temperatures. Volatile liquids are liquids with high vapor pressures, which tend to evaporate readily from an open container; nonvolatile liquids have low vapor pressures. When the vapor pressure equals the external pressure, bubbles of vapor form within the liquid, and it boils. The temperature at which a substance boils at a pressure of 1 atm is its normal boiling point. |
SciQ | SciQ-453 | human-biology, physiology, cardiology, anatomy
Title: Can humans live without their right atrium? The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated blood from the superior and inferior venae cavae, the coronary sinus, and the anterior and smallest cardiac veins, and pumps it into the right ventricle through the tricuspid valve.
Can humans survive without right atrium? In this condition blood would fill the right ventricle directly, comparable to some animals like frogs, toads, snakes and lizards. What advantages does the normal human heart have to this anatomy ? If we had this anatomy, where would the best place for pacemakers be, like the sinus node? This is an interesting theoretical question, but several things would need to be clarified:
Does removing the R atrium relocate the SA node to the R ventricle or remove it completely from the picture?
Does the remaining R ventricle have a tricuspid valve?
Technically, the R atrium is the home of the sino-atrial node, which provides natural pacing of the human heart between 60-80 beats/min. Without this natural pacing, our hearts would rely on back-up pacer systems such as atrioventricular node, His-Purkinje systems or the intrinsic but ectopic pacing of individual atrial or ventricular cells.
The following is multiple choice question (with options) to answer.
What guards the opening between the right atrium and the right ventricle? | [
"tricuspid valve",
"aorta",
"brachiocephalic trunk",
"superior vena cava"
] | A | Right Atrium The right atrium serves as the receiving chamber for blood returning to the heart from the systemic circulation. The two major systemic veins, the superior and inferior venae cavae, and the large coronary vein called the coronary sinus that drains the heart myocardium empty into the right atrium. The superior vena cava drains blood from regions superior to the diaphragm: the head, neck, upper limbs, and the thoracic region. It empties into the superior and posterior portions of the right atrium. The inferior vena cava drains blood from areas inferior to the diaphragm: the lower limbs and abdominopelvic region of the body. It, too, empties into the posterior portion of the atria, but inferior to the opening of the superior vena cava. Immediately superior and slightly medial to the opening of the inferior vena cava on the posterior surface of the atrium is the opening of the coronary sinus. This thin-walled vessel drains most of the coronary veins that return systemic blood from the heart. The majority of the internal heart structures discussed in this and subsequent sections are illustrated in Figure 19.9. While the bulk of the internal surface of the right atrium is smooth, the depression of the fossa ovalis is medial, and the anterior surface demonstrates prominent ridges of muscle called the pectinate muscles. The right auricle also has pectinate muscles. The left atrium does not have pectinate muscles except in the auricle. The atria receive venous blood on a nearly continuous basis, preventing venous flow from stopping while the ventricles are contracting. While most ventricular filling occurs while the atria are relaxed, they do demonstrate a contractile phase and actively pump blood into the ventricles just prior to ventricular contraction. The opening between the atrium and ventricle is guarded by the tricuspid valve. |
SciQ | SciQ-454 | thermodynamics, evaporation, gas, liquid-state
On the water surface, knowing the temperature, we can estimate the vapor pressure and vapor mixture fraction. Then there will be an diffusion process for the water vapor to move out and for the ambient air to move in. Because the water surface doesn't allow the air to further move, a circulation forms. When the water vapor moves out, the water vapor pressure drops, so more liquid water evaporates to fill up the loss of water vapor. The evaporation associates latent heat so water surface area temperature drops (you may see dew on the bowl wall). Then a heat transfer process starts which may initiate water circulation as well.
As this is complex, doing test might be a quick way to get the K value if you assume it is a constant, which is questionable.
The following is multiple choice question (with options) to answer.
The water cycle involves movement of water between air and what? | [
"tree",
"animals",
"land",
"air"
] | C | |
SciQ | SciQ-455 | physical-chemistry, reaction-mechanism, free-energy
How does it come, that in one case the activity of the whole product AB is important and in another the single activities of the components of the product?
Equation (1) refers to a molar free energy of formation of $\ce{AB}$ from reagents $A$ and $B$, all under the same constant (P,T, composition) conditions, whereas (2) refers to the free energy of formation of a solid solution of $n_A$ moles of A and $n_B$ moles of B from pure components. Equation (1) refers to combination of A and B at a 1:1 mole ratio, or equivalently reaction to form 1 mole of $\ce{AB}$ from $n_A=n_B=\pu{1 mol}$. Reaction (2) refers to mixture of A and B at any arbitrary ratio or total number of moles. Therefore equation (2) is in a way more general. Also, equation (1) refers to a differential process (transformation to form 1 mole of product under contant conditions) whereas (2) refers to an integral (mixing) process.
For the given reaction:
$$\Delta G = \Delta G^⦵ + RT\ln{\frac{a_\ce{AB}}{a_\ce{A}\cdot a_\ce{B}}} $$
Since all components are pure solid substances, all activities equal 1 and therefore, $\Delta G = \Delta G^⦵$.
The following is multiple choice question (with options) to answer.
When we consider a chemical reaction, we need to take into account both the system and what? | [
"time",
"sorroundings",
"date",
"fluctuations"
] | B | When we consider a chemical reaction, we need to take into account both the system and the surroundings. The system includes the components involved in the chemical reaction itself. These will often take place in a flask, a beaker, a test tube, or some other container. The surroundings include everything that is not part of the system. When potassium reacts with water, part of the heat energy generated in the reaction is released into the surroundings. The boundary between system and surroundings is arbitrary, and it is generally chosen in a way that makes observations and calculations easier. |
SciQ | SciQ-456 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
What is a layer of tissue that lies between the shell and the body? | [
"silt",
"stem",
"mantle",
"node"
] | C | Two unique features of mollusks are the mantle and radula (see Figure above ). The mantle is a layer of tissue that lies between the shell and the body. It secretes calcium carbonate to form the shell. It forms a cavity, called the mantle cavity, between the mantle and the body. The mantle cavity pumps water for filter feeding. The radula is a feeding organ with teeth made of chitin. It is located in front of the mouth in the head region. Herbivorous mollusks use the radula to scrape food such as algae off rocks. Predatory mollusks use the radula to drill holes in the shells of their prey. |
SciQ | SciQ-457 | chemistry-in-fiction, geochemistry
Title: Which crystals can exist permanently (and do not break down) under normal earth like outside conditions? Hi I am looking for crystals I can use in the world of my novel but I have no idea what types to use or what there are.
So my question is what kind of crystals fit these criteria:
They must be able to exist “permanently” without breaking down in normal earth conditions/atmosphere.
They must be able to grow quite large. (I’m thinking about large hexagonal crystal columns)
I would be very happy if you could list any crystals you know that fist the criteria. With the name I should be able to research further myself and narrow it down.
Thanks in advance.
-
P.s. some of you might have some feeling of déjà vu reading my question as I asked a similar question before but that one was marked as to brought so I am asking it again but trimmed down.
link: How do i create a significantly correct world with large crystal formations in my novel?
P.p.s. if this question is to brought as well please leave a comment explaining how I can make it better because I otherwise really have no idea how to fix it. Quartz (silicon dioxide) sounds like a good bet. It is inert, safe to be around, and insoluble in water. Some examples of naturally occurring quartz crystals are really huge - visit the National Museum of Natural History if you are near DC - or any other natural history museum near you. There you will likely see many other naturally occurring minerals of defined chemical composition that form large crystals. Or go online and look for pictures.
The following is multiple choice question (with options) to answer.
In what country can some of the largest natural crystals be found? | [
"mexico",
"canada",
"germany",
"spain"
] | A | Some of the largest, and most beautiful, natural crystals can be found in the Naica mine, in Mexico. These gypsum crystals were formed over thousands of years. Groundwater that is rich in calcium and sulfur flowed through an underground cave. Check it out:. |
SciQ | SciQ-458 | photosynthesis, respiration, ecosystem, decomposition
Title: What does the difference between GPP - NPP represent? Overview
Researchers have been studying a temperate grassland ecosystem with the view to understand it's current status with regard to carbon inputs and outputs and to identify whether the grassland is currently a sink or source of carbon.
The aim of this self-study is to become more familiar with different energy fluxes within the terrestrial carbon ecosystems.
The idea is to calculate energy fluxes in various scenarios, and I am feeling a little confused about the scientific theory of gross primary productivity (GPP), net primary productivity (NPP), net ecosystem production (NEP), net ecosystem exchange (NEE), RT = Total respiration, RA = animal respiration, and RS = soil respiration,
If anyone can help, I would be deeply appreciative.
The relationship between production fluxes and other fluxes summarised by these key equations:
NPP = GPP - (plant respiration)
NEE = NPP - (heterotrophic respiration)
NEP = NEE - (carbon losses from leaching, disturbance, and other inputs, and outputs)
Table of flux values
The following is multiple choice question (with options) to answer.
What are the primary producers in terrestrial biomes? | [
"animals",
"plants",
"soil",
"gases"
] | B | Plants are the primary producers in terrestrial biomes. They make food for themselves and other organisms by photosynthesis. The major plants in a given biome, in turn, help determine the types of animals and other organisms that can live there. |
SciQ | SciQ-459 | airflow, cfd, wind-power, meshing, wind-tunnels
Title: Efficient 3D mesh topology for CFD simulation of turbine blade I´m developing a tool to generate an openFoam wind tunnel case of a wind turbine. I already have the blade geometry constructed, but I'm really new to CFD and parametric meshing. I found some articles where they mention a C topology to mesh the airfoil and also some software (bladedesigner) that mentions a topology named O10H, but none of these has a reference about how to implement these topologies and if there are others. They also do not specify what the best use cases for each one.
Can someone help me to get started making an efficient mesh for my tool?
EDIT: At the end I want to have a domain like the picture below, with other blade orientation, but first I need to define the mesh topology around the blade.
My example Blade:
Some of the mesh topologies that I found:
Bladedesigner O10H topology
Various C topologies I modeled a vertical axis turbine back in 2010 in a two dimensional rotating reference frame in OpenFOAM with good results. I am not up to date with the new tools available, but you want to make sure that your geometry is in fact rotating according to the model (perhaps your periodic boundaries are handling this for you).
I used gmsh (http://geuz.org/gmsh/) for my mesh generation. You want to make sure your boundary layer on the blade surface is hexahedral and the remaining volume can be filled with tetrahedrals as they are very forgiving of complex geometery.
I would highly recommend reposing your question on cfd-online. Lots of experts on there with specific OpenFOAM experience.
http://www.cfd-online.com/Forums/openfoam/
The following is multiple choice question (with options) to answer.
Where are aerofoils found? | [
"airplanes and plants",
"birds and busses",
"birds and airplanes",
"birds and cars"
] | C | Birds also have wings that function as an aerofoil . The surface of the aerofoil is curved to help the bird control and use the air currents to fly. Aerofoils are also found on the wings of airplanes. |
SciQ | SciQ-460 | units, si-units
Title: What would be the standard for the unit of pressure Pa or MPa? Me and my friend are doing a project and in our result we shall provide a plot, and on our axes we are going to write out the units. My friend wrote "xx MPa", claiming it was standard in reports to write Pascal with the prefix Mega. Well, I claim that there is no such thing, you simply write it with the SI-unit, hence Pa. What would you say? Both are correct. It is a matter of personal preference which you decide to use. It makes the graph easier to understand if axes are labelled in small numbers; it also makes the graph less cluttered. So either you would label the x axis "Pressure in units of 10^6 Pa" or "Pressure in MPa". Labelling the x axis as "Pressure in Pa" and using marker values 1x10^6, 2x10^6, 3x10^6, etc is ugly and looks unprofessional.
So it all comes down to the same thing. Not worth spoiling a friendship to argue about!
The following is multiple choice question (with options) to answer.
What is the si unit for pressure? | [
"laurent",
"le",
"watt",
"pascal"
] | D | Summary Four quantities must be known for a complete physical description of a sample of a gas: temperature, volume, amount, and pressure. Pressure is force per unit area of surface; the SI unit for pressure is the pascal (Pa), defined as 1 newton per square meter (N/m2). The pressure exerted by an object is proportional to the force it exerts and inversely proportional to the area on which the force is exerted. The pressure exerted by Earth’s atmosphere, called atmospheric pressure, is about 101 kPa or 14.7 lb/in.2 at sea level. Atmospheric pressure can be measured with abarometer, a closed, inverted tube filled with mercury. The height of the mercury column is proportional to atmospheric pressure, which is often reported in units ofmillimeters of mercury (mmHg), also called torr. Standard atmospheric pressure, the pressure required to support a column of mercury 760 mm tall, is yet. |
SciQ | SciQ-461 | ichthyology, homeostasis, osmoregulation
Pillans, R.D. and C.E. Franklin, 2004. Plasma osmolyte concentrations and rectal gland mass of bull sharks Carcharhinus leucas, captured along a salinity gradient. Comparative Biochemistry and Physiology, Part A 138: 363-371.
The following is multiple choice question (with options) to answer.
Marine fishes take in divalent ions by incessantly drinking what? | [
"seawater",
"oxygen",
"algae",
"sand"
] | A | |
SciQ | SciQ-462 | 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 simplest and smallest particle of matter that still has chemical properties of the element is called? | [
"an atom",
"a molecule",
"an isotope",
"a nucleus"
] | A | Inside of elements, you will find identical atoms. An atom is the simplest and smallest particle of matter that still has chemical properties of the element. Atoms are the building block of all of the elements that make up the matter in your body or any other living or non-living thing. Atoms are so small that only the most powerful microscopes can see them. |
SciQ | SciQ-463 | image-processing, frequency-spectrum, computer-vision
Title: what is $1/f$ property of the visual world? I was watching a talk by Edward H. Adelson on the perception of materials and surfaces. He mentions a $1/f$ property of the visual world. He says:
low frequencies are prevalent than high frequencies.
Also,
the simplest model of the world is that it is random noise with a $1/f$ spectrum.
I didn't understand what he meant. Anyone willing to explain the concept he is talking about?
"Essentially, all models are wrong, but some are useful" (attributed to G. Box)
One of the simplest morphological model for 2D images decomposes objects into structure and texture. Both can be used to detect or understand objects. Even though image formation models are still complicated, objects often appear as smooth intensity gradient, filled with decoration, bounded by edges (some being false).
Smooth intensity gradients are often the most energetic, thus low frequencies can be prominent. Edges, though energetic, are sparser and local, thus possibly less present in a spectrum.
So, a simple "low frequencies are prevalent than high frequencies" model is a decreasing spectrum. Now what would be the decreasing simplest model in terms of elementary functions? Possibly $1/f$. And yes, $\exp^{- |f`|}$ could seem better, especially with the singularity at $0$. More involved models involve $1/f^p$ or $\exp^{- p |f|}$ shapes. Indeed, such models are dependent of the transformations used to reshape the data, and Fourier is a very simple reshaping tool. More local tools like wavelets use Generalized Gaussian Distributions: $\exp^{-\alpha x^\beta}$ in the time/space domain.
Simpler can also be seen from a computational point of view, see Frequency Synthesis of Landscapes (and clouds):
Frequency synthesis is based upon the observation that many "natural"
forms and signals have a 1/fp frequency spectra, that is, their
spectra falls off as the inverse of some power of the frequency where
the power is related to the fractal dimension.
This leads naturally to a method of generating such fractals:
Generate a random (white noise) signal.
Transform this into the frequency domain.
Scale the resulting spectra by the desired $1 / f^p$ function.
Inverse transform.
The following is multiple choice question (with options) to answer.
Frequency and intensity are two measurable properties of what? | [
"heat",
"lines",
"troughs",
"wave"
] | D | All waves can be defined in terms of their frequency and intensity. |
SciQ | SciQ-464 | evolution, mammals, marine-biology
The question remains: why? The most likely explanation is that cetaceans evolved to exploit an unfilled ecological niche or adapted to new niches that formed as a result of plate tectonics or other types of environmental changes that occurred 50-55 million years ago. The niche describes all of the living and non-living resources needed by an organism to survive. Although land-based mammals were increasing in diversity, few or none were present in the oceans. The basic hypothesis is that the early whale-like artiodactyls, like Indohyus and Pakicetus were land-based (terrestrial) mammals that spent most of their time near the water's edge. Over time, they adapted to the niches in the ocean. Fossils like Ambulcetus and Rodhocetus showed clear evidence of swimming ability, with flattened tails and the enlarged rear feet. In addition, the nostrils shifted from the front of the face to the top of the head, which we recognize as the blowhole.
The shift to the aquatic habitat allowed these species to exploit resources that were not available to land-based mammals, thereby reducing competition for the resources. Reduced competition allows more individuals to survive and reproduce.
Similar scenarios are very likely for other marine mammals, such as seals or manatees. They evolved to take advantage of ecological niches that were not filled by other organisms. This basic concept, evolving to fill available niches, is a common outcome of the evolutionary process.
The of adaptation of cetaceans and other mammals to the oceans may be similar to that of the hippopotamus. Hippos spend most of their time in the water, and they show many adaptations that allow them to live in the aquatic environment. The eyes and nostrils of the hippo are high on the head, which allows them to remain almost entirely submerged but still see and smell, as shown below.
(Hippo photo by Johannes Lunberg, Flickr Creative Commons.)
Hippos feed underwaters, they are heavy enough to walk on the bottom of the river, and the mate and give birth underwater. The young can suckle underwater. Clearly, hippos seem to be another mammal that is "returning to water." Similar types of processes must have occurred in cetaceans for them to adapt to the marine habitat.
The following is multiple choice question (with options) to answer.
While most mammals give birth to live young, monotremes can do what? | [
"lay eggs",
"reproduce asexually",
"steal eggs",
"adopt offspring"
] | A | Monotremes can lay eggs, but most mammals give birth to live young. |
SciQ | SciQ-465 | plate-tectonics, mountains, tectonics
Title: What is the impact of divergent tectonic plates on old mountain ranges? I found this question, which is similar to what I'm wondering, but my question is slightly different:
What happens if a new divergent boundary forms in a way that bisects a mountain range, especially one formed by converging plates -- and is that even possible?
Purely for the sake of example, if a divergent rift somehow formed on the North American plate, dividing the Appalachians [ETA: apparently I circled a valley, please pretend I'm not a geography-illiterate dork and that it's actually some old mountains.]:
What would happen to the circled area? Anything? Would the mountain range be recognizable after an ocean formed between them? Considering the timescale involved, perhaps an older range would be unrecognizably eroded? I've tried to find examples in the real world, but my Google-fu fails me.
Somewhere I picked up the idea that the Appalachian and Welsh coal seams were once connected or formed together (I think it may have been from an offhand comment in a movie about Welsh miners, so a] maybe I understood wrong and b] who knows how accurate it was), so I initially wondered if that might be an example of what I'm curious about. Unfortunately, some light research seems to indicate that's not the case (if I'm understanding this and this correctly, the connection ends at "both formed, at least partially, during the Carboniferous.)
I'm most interested in what the effects (if any) would be on older mountain ranges such as the Urals or Appalachians, but if anyone knows what kind of effects it might have on younger, taller ranges, I'd love to hear about it.
If anyone has sources I could look into for a deeper understanding, I'd love to have those as well! My lack of knowledge is distressing me to no end. The example of the East African Rift was given in a different answer.
Splitting of mountain ranges in two becomes even more apparent as you go up north from there.
The Red Sea between Egypt and Saudi Arabia is a young new spreading ocean, that cuts through Precambrian mountains.
The following is multiple choice question (with options) to answer.
What happens to old oceanic crust at convergent boundaries? | [
"destroyed",
"dissolves",
"created",
"emerges"
] | A | It’s much easier to precisely make mirrors than to precisely make glass lenses. For that reason, reflectors can be made larger than refractors. Larger telescopes can collect more light. This means that they can study dimmer or more distant objects. The largest optical telescopes in the world today are reflectors. Telescopes can also be made to use both lenses and mirrors. |
SciQ | SciQ-466 | bond, molecules, noble-gases
Title: How do atoms of noble gases bond with each other? Noble gases have full electron shells, which virtually blocks any other element from bonding with it. However, I've heard about cases where they bond to each other - for example, helium can apparently form a dimer $\ce{He2}$.
How is this possible? Noble gases usually do not form strong bonds between their atoms - it takes a fair amount of energy to dimerise them into excimers, but those are short-lived excited molecules. Thanks to excitation, shells of the atoms aren't closed and they react, but very quickly they lose energy and become separate atoms.
With exception of weakly bound $\ce{Xe2^+}$ cation, stable compounds created from noble gases (mainly xenon) only feature bonds with other elements, typically fluorine or oxygen, but there are also, for example, organoxenon compounds.
As mentioned in the comments, you may have heard about detection of so called van der Waals molecules of helium, which aren't "true" molecules, but very weakly bound pairs of atoms. In fact helium vdW dimer may have weakest bond even among them, and it was an achievement to observe it.
The following is multiple choice question (with options) to answer.
When electrons are shared between two atoms, they make a bond called a what? | [
"metallic bond",
"ionic bond",
"covalent bond",
"hydrogen bond"
] | C | Ionic bonding typically occurs when it is easy for one atom to lose one or more electrons and another atom to gain one or more electrons. However, some atoms won’t give up or gain electrons easily. Yet they still participate in compound formation. How? There is another mechanism for obtaining a complete valence shell: sharing electrons. When electrons are shared between two atoms, they make a bond called a covalent bond. Let us illustrate a covalent bond by using H atoms, with the understanding that H atoms need only two electrons to fill the 1s subshell. Each H atom starts with a single electron in its valence shell:. |
SciQ | SciQ-467 | thermodynamics, energy, temperature, kinetic-theory
If you shine a bright light - or microwave oven, or laser, or maser or incandescent light, or other strong EM energy source - onto or through an object, the photons have an opportunity to interact with the electrons in the object. If they don't interact with the object, they pass through it without reflection or absorption and the object is clear at that wavelength. If the incoming photons have wavelengths / energies which happen to be resonant with allowed transitions in the atoms / molecules they hit, some of the photons' energy will be absorbed into the atoms. The details depend on which transitions are stimulated by the radiation, but generally you can either raise electrons' potential energy on absorption or add energy to rotational and vibrational states. Rotational and vibrational energy are directly components of kinetic energy, so immediately increase the temperature of the absorbing substance. Energy absorbed into electronic energy states may either be re-emitted or get redistributed into rotational/vibrational modes, depending on the structure of the absorbing molecules, how much they interact with neighboring atoms, and overlap between the electronic and rovibrational transitions. If the incident light is re-emitted immediately at the same wavelength, it's reflected. Metals are shiny because they have large numbers of free electrons that efficiently re-emit incident light at many wavelengths. If all the light is reflected or transmitted without being absorbed or redistributed among molecular motions, no heating occurs. The details of what happens (absorption vs reflection vs transmission and which mechanical mode is stimulated) are going to depend on things like the density of "free" electrons, the polarizability of the atoms' / molecules' electron clouds, the frequency of the incident light, the masses of the atoms, the polarization of the incident photons, etc. However, the core physics involved is that an EM wave ("light" / "photon") contains an oscillating electric field (and an oscillating magnetic field, but usually the electric component is more important). When it hits a molecule, the electrons and protons feel opposing forces due to the electric field. This sets up an electric dipole in the individual atoms, and that dipole then feels a force in response to the still-present, still-changing electromagnetic wave. The electrons have much lower masses than the nuclei, so respond more quickly, but still not instantaneously - resulting in the electron
The following is multiple choice question (with options) to answer.
What happens to the temperature of matter as light is absorbed? | [
"it stays the same",
"it triples",
"it drops",
"it increases"
] | D | http://www. chem. ufl. edu/~itl/2045/lectures/lec_d. html. |
SciQ | SciQ-468 | fluid-dynamics, waves, water
Title: Wave with mass transport? I don't think this question has been asked on this forum before (at least I didn't find it).
In the case of a tsunami, an earthquake generates a wave which will travel with the sea/ocean as the medium. However, what I remember from high school is that mechanical waves transfer energy but energy only. On a sectional view we represented molecules of water going up and down as the wave travels but the molecules never moved horizontally.
Then why does a tsunami can flood half of a country? in that case the water does move horizontally. what am I missing?
I have read that for regular waves, the problem is different and their momentum comes from wind streams, but I don't think this is the case for tsunami.
I would appreciate some pieces of answer. Far away from shore the water is moving in a roughly circular motion. If you put a ping pong ball or some other warker on the water you'll find it flows towards the approaching wave and away from the retreating wave. There are loads of animations of this out there; a quick Google found http://www.youtube.com/watch?v=7yPTa8qi5X8 and this is a pretty good description. As you move down in the water the size of the circles decreases until at about one wavelength down the water is no longer moving. Again courtesy of Google, a more technical discussion is http://www.ihad.tmd.go.th/lect18.html.
The problem comes when the depth gets shallower than one wavelength because the sideways oscillation becomes larger and larger as the water gets shallower. When any wave (a tsunami is just an extreme example) hits the shore the oscillation means the water first moves away from the shore then back onto the shore as evey peak hits the shore. In the case of the tsunami the wave is so big that you get first the characteristic sea withdrawal, then the flooding over the shore and onto the land.
The following is multiple choice question (with options) to answer.
By shocking ocean water, earthquakes can cause what deadly ocean waves? | [
"typhoons",
"ebb tides",
"tsunamis",
"deep currents"
] | C | Earthquakes can cause tsunamis . These deadly ocean waves may result from any shock to ocean water. A shock could be a meteorite impact, landslide, or a nuclear explosion. But most come from large underwater earthquakes. |
SciQ | SciQ-469 | cell-biology
Title: Structure of Cell Are cells spheres or ovals/circles bound by phospholipidbilayer?
If they are spherical how are we able to see the nucleus through the phospholipid bilayer under a microscope? Not exactly. That is a stereotype of cells. Muscle cells are not round nor oval, but rather elongated rods. If you were to look up epithelia cells, you can quickly see that cells are grouped based on their physical characteristics; simple (round/oval & single layer), columnar, and cuboidal to name a few. Cells come in many shapes and sizes. As Hans stated, stains are vital in viewing cellular components. There is a diverse amount of stains used - which all carry a purpose and benefit in a specific application.
The following is multiple choice question (with options) to answer.
Where are the desmosome found in a cell? | [
"neuron",
"coating",
"epithelial",
"epithelium"
] | D | A desmosome is a cell junction specialized for cell-to-cell adhesion. They are found in simple and stratified squamous epithelium, and in muscle tissue where they bind muscle cells to one another. These junctions are composed of complexes of cell surface adhesion proteins and linking proteins. These proteins have both an intracellular and extracellular region. Inside the cell, they attach to intracellular filaments of the cytoskeleton. Outside the cell, they attach to other adhesion proteins. |
SciQ | SciQ-470 | neuroscience, neurophysiology, action-potential
Title: Stimulating an axon causes impulses to travel both ways?
A diagram is presented as such above.
The question given states What would be the effect of stimulation to cause a nerve impulse with a microelectrode at the middle of the axon?
I thought the nerve impulse only travels in one direction to the muscle fibres, but the book says "A nerve impulse would pass in both directions."
Why is that the case? Allow me to do a silly analogy: think about the electric wire going from your outlet to your computer, conducting electricity. If you make two cuts in this wire, rotate it 180 degrees and weld it again at the cutting points, what will happen? It will conduct electricity just as it did before.
The same happens to an axon (but please have in mind that this is just an analogy, an action potential is not an electric current). That is, the axon doesn't determine or influence the direction of the action potential. If you cut a piece of that axon, rotate it 180 degrees and join it back in the cutting points, it will conduct the action potential the same way.
That being said, imagine that you stimulate that axon at a given point. There will be two action potentials, going to opposite ways:
unmyelinated (A) and myelinated (B) nerve cells
In your figure (given that is a motor neuron), if you stimulate that axon in the middle, the action potential going to the neuromuscular junction, which is the normal direction, is called orthodromic (from the greek orthos, "proper", and edramon, past of "run"), while the one going to the soma (the perikaryon) is called antidromic (from the greek anti, "against").
According to Oh (2003):
The following is multiple choice question (with options) to answer.
An action potential that starts at the axon hillock moves along the axon only toward what? | [
"nerve endings",
"polar synapses",
"ionic pathways",
"the synaptic terminals"
] | D | |
SciQ | SciQ-471 | nuclear-physics, radioactivity, binding-energy, elements, isotopes
So spontaneous droplet fission will happen when you have a charged ball for which 30% of the surface tension energy is less than 20% of the charge energy. Since charge goes up almost as the volume (not quite, but close) while the surface tension goes up as the area, there is a crossover, and charged droplets will spontaneously separate when they are too big.
The surface tension can be found from the binding energy curve of nuclei, and these simple considerations limit stable nuclear size to about that of Uranium. The U nucleus can spontaneously fission at an extremely low rate, but the transuranics become progressively more unstable because their electrostatic energy is increasing as the volume to a power greater than 2/3, while their surface tension energy is increasing as the surface area, which grows as the 2/3 power of the volume.
These considerations, in much more sophisticated form, are due to Niels Bohr in the seminal liquid drop model of the 1940s. This model explained the nuclear binding energy curve quantitatively, and accounted well for fission phenomena. The only major thing left out of this was the shell model and magic numbers, which was supplied by Mayer.
The following is multiple choice question (with options) to answer.
Fission is a type of radioactivity in which large nuclei spontaneously break apart into what? | [
"faster nuclei",
"smaller nuclei",
"active nuclei",
"light nuclei"
] | B | Fission is a type of radioactivity in which large nuclei spontaneously break apart into smaller nuclei. |
SciQ | SciQ-472 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
Bones are the main organs of what system, which also includes cartilage and ligaments? | [
"digestive system",
"skeletal system",
"lymphatic system",
"endocrine system"
] | B | Bones are the main organs of the skeletal system. The skeletal system also includes cartilage and ligaments. |
SciQ | SciQ-473 | ocean, waves
Title: What causes waves to form the characteristic "breaking" shape as they approach the shoreline? We all know that as waves approach the shallow shores, the waves begin to form a characteristic shape. The upper portion of these breaking waves appears to curl forward and downwards over the bottom segment of the wave, before breaking into "white wash". The image below illustrates what this characteristic shape looks like:
The following is multiple choice question (with options) to answer.
Most waves strike the shore at an angle. this causes what? | [
"longshore drift",
"fontaine drift",
"tide",
"erosion"
] | A | Below the topsoil is the “B“ horizon. This is also called the subsoil . Soluble minerals and clays accumulate in the subsoil. Because it has less organic material, this layer is lighter brown in color than topsoil. It also holds more water due to the presence of iron and clay. There is less organic material in this layer. |
SciQ | SciQ-474 | javascript, performance
const todayDayIndex = new Date().getDay(); // Zero-indexed and starts at Sunday
const todayDayOfMonth = new Date().getDate();
const inputDays = giorni.map(({ giorno }) => giorno);
const itemDates = giorni.map((g) => {
const itemDayIndex = dayIndiciesByDayName[g.giorno.toLowerCase()];
// Below will be 0 to 6:
const itemDayDifferenceFromToday = (itemDayIndex - todayDayIndex + 7) % 7;
const itemDateObj = new Date();
itemDateObj.setDate(todayDayOfMonth + itemDayDifferenceFromToday);
return itemDateObj;
});
const output = itemDates
.sort((a, b) => a - b)
.map((date) => {
const match = date.toString().match(/(\w+ )(\w+) (\d+ )/);
return match[1] + match[3] + match[2];
});
console.log(output);
The following is multiple choice question (with options) to answer.
What is the difference between the daily high and the daily low? | [
"weather forecast",
"tidal change",
"margin of error",
"sunrise and sunset"
] | B | The difference between the daily high and the daily low is the tidal range. |
SciQ | SciQ-475 | homework, reproduction, embryology
Title: Which process is needed to complete male reproductive development? In order to properly complete male reproductive development:
A. primordial germ cells must begin Meiosis I in utero.
B. Sertoli cells must produce testosterone.
C. Dihydrotestosterone must masculinize Wolffian duct derivatives
D. the paramesonephric ducts must degenerate
E. the metanephros must form the genital epithelium
My attempt: I think the answer is C because testosterone turns into DHT which then masculinzing the wolffian duct. Other people I am studying with claim the answer is D (which is true) except that I dont think the loss of the paramesonephric duct is needed to complete male repro development. Regarding option C:
Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ducts:
Between 8 and 12 weeks, the initial secretion of testosterone stimulates mesonephric ducts to transform into a system of organs—the epididymis, vas deferens, and seminal vesicle—that connect the testes with the urethra.*
DHT (dihydrotestosterone) is produced in the Leydig cells by the 5α-Reductase enzyme. It is required for induction of the external male genitalia (urethra, penis, and scrotum) and prostate from the embryonic ureteral groove, and for testicular descent into scrotum.
Regarding option D:
Sertoli cells secrete Anti Müllerian Hormone (AMH), which causes degeneration of the müllerian (a.k.a. paramesonephric) ducts between weeks 8 and 10. It is normal to speak about degeneration of the müllerian ducts as a defining aspect of male embryology, and thus I believe answer D is correct. Your point is taken, however:
Nevertheless, small müllerian duct remnants can be detected in the adult male, including a small cap of tissue associated with the testis, called the appendix testis, and an expansion of the prostatic urethra, called the prostatic utricle.*
The following is multiple choice question (with options) to answer.
Spermatogonia are the stem cells of what male sex organs? | [
"Prostate",
"Epididymis",
"ovaries",
"testes"
] | D | Germ Cells The least mature cells, the spermatogonia (singular = spermatogonium), line the basement membrane inside the tubule. Spermatogonia are the stem cells of the testis, which means that they are still able to differentiate into a variety of different cell types throughout adulthood. Spermatogonia divide to produce primary and secondary spermatocytes, then spermatids, which finally produce formed sperm. The process that begins with spermatogonia and concludes with the production of sperm is called spermatogenesis. |
SciQ | SciQ-476 | neuroscience
Title: Nervous system : Nerve signals If the electrical signals from all the various organs throughout the body eventually connect to the nerves in the spinal column traveling up to the brain, how does the brain differentiate the different signals. Is the nerve in the spinal column like an electrical conduit with many wires inside? Yes is the simple answer. A nerve will go up to a specific part of the brain which the brain knows corresponds to a certain region of the body. It isn't perfect though e.g. pain in the diaphragm confuses the brain which doesn't recognise that pain must be coming from there so instead tells the body there is shoulder pain, however this is useful in medicine. Another infamous example is pain from heart disease (angina) which causes pain in the jaw and arm. Perhaps even more interestingly, if a nerve is cut and then grows back linking to the wrong nerve it may lead to the completely wrong part of the body being identified when touched. Also if the brain itself is stimulated in these corresponding areas, a person will feel he or she is indeed being touched in a certain part of the body.
The following is multiple choice question (with options) to answer.
Sensory neurons transmit nerve impulses from sense organs and internal organs to the brain via the? | [
"nervous system",
"spinal column",
"spinal cord",
"nerve endings"
] | C | Sensory neurons transmit nerve impulses from sense organs and internal organs to the brain via the spinal cord. In other words, they carry information about the inside and outside environment to the brain. |
SciQ | SciQ-477 | mammals, sex-chromosome, gender
Title: What processes regulate the sex of offspring? It is known that some species are more likely to born male than female (and some maybe vice versa). I understand that it is due to evolutionary perspective (average number of adult males is close to that of females), I want to know about how it is regulated.
What I thought is that spermatozoa are made by half as Y and half as X chromosome. Then mitosis and meiosis and the probability that one of them will die is equal for both types. So, somewhere I feel lost.
Also, can it be regulated by female body or not? According to this paper claiming that hormone levels in women affect the likelyhood to born son. Possibly it is just because they choose males that are more likely to have more Y spermatozoa than X, but if it is some chemical mechanism to regulate that I'd like to know.
I'm not asking only about humans, mechanisms can be similar in almost all mammals. I'm not asking about other species: I know some are regulated by temperature, etc. This question is only about mammals.
What processes regulate the sex of offspring?
The processes rulating the sex of offspring may occur in both males and females and be direct or indirect.
What I thought is that spermatozoa are made by half as Y and half as X chromosome. Then mitosis and meiosis and the probability that one of them will die is equal for both types. So, somewhere I feel lost.
This may not be entirely true. The phenomenon called "Meiotic drive" may change the ratio from 1:1. Meiotic Drive occurs through selfish genes. See "Selfish-gene theory" for more info.
Also, can it be regulated by female body or not?
if it is some chemical mechanism to regulate that I'd like to know.
Possibly, there is such in mammals. There is a bunch of mechanisms called "Cryptic female choice". Some of them are chemical. Although, the article is about birds, it can be the case similar mechanism is present in mammals.
Given that higher androgen level exposure in mothers affect make their offspring more male-typical in playing behavior we might consider that in general makes offsrpings more masculine. This would be a good reason for female organisms with higher androgen levels to favor sperm with Y chromosome present.
The following is multiple choice question (with options) to answer.
Sexually reproducing organisms alternate between which stages? | [
"binary and diploid",
"haploid and diploid",
"binary and haploid",
"diploid and traploid"
] | B | CHAPTER SUMMARY 7.1 Sexual Reproduction Nearly all eukaryotes undergo sexual reproduction. The variation introduced into the reproductive cells by meiosis appears to be one of the advantages of sexual reproduction that has made it so successful. Meiosis and fertilization alternate in sexual life cycles. The process of meiosis produces genetically unique reproductive cells called gametes, which have half the number of chromosomes as the parent cell. Fertilization, the fusion of haploid gametes from two individuals, restores the diploid condition. Thus, sexually reproducing organisms alternate between haploid and diploid stages. However, the ways in which reproductive cells are produced and the timing between meiosis and fertilization vary greatly. There are three main categories of life cycles: diploid-dominant, demonstrated by most animals; haploid-dominant, demonstrated by all fungi and some algae; and alternation of generations, demonstrated by plants and some algae. |
SciQ | SciQ-478 | acid-base, reaction-mechanism
Title: Litmus paper - turning red, blue and even bleached I have blue litmus paper, and if I put it in an acid it turns red. I also have red litmus paper, and if I put it in a base, it turns blue.
I know the question about litmus was asked and answered and I like the answer:
How does the litmus pH indicator work?
However, damp litmus paper also becomes bleached in presence of chlorine gas. I believe it has nothing to do with the mechanism described in aforementioned question. I wonder what the mechanism is. Wikipedia actually suggests:
For instance, chlorine gas turns blue litmus paper white – the litmus dye is bleached, because of presence of hypochlorite ions. This reaction is irreversible, so the litmus is not acting as an indicator in this situation.
I also found an equation which describes formation of hypochloric acid (source):
$$\ce{Cl2 (g) + H2O (l) -> HClO (aq) + HCl (aq)}$$
The problem that I have now is as follows: We know that litmus paper gets discolored because of contact with hypochloric acid. But what is actually the chemical reaction for that? I can supply some details now, and hopefully this ought to qualify as an answer.
As I mentioned earlier litmus is a mixture of 10-12 dyes (CAS number: 1393-92-6).
The acid-base indicator properties of litmus are primarily due to 7-hydroxyphenoxazone chromophore (pictured below)
The answer you linked to discusses the acid-base indication mechanism in some detail, so I shall skip over that.
Anyway, what this serves to establishing that it is indeed a extended $\pi$-conjugated system that we are dealing with in the chromophore.
Now, $\ce{HOCl}$ would bring about halohydrination (basically an electrophilic addition) across the $\pi$ bonds, thus disrupting the conjugated system.
Halohydrins are compounds that contain an $\ce{-OH}$ and $\ce{-X}$ groups on adjacent carbons.
This image describes the general mechanistic scheme in a simpler case:
The following is multiple choice question (with options) to answer.
Acids turn blue litmus paper which color? | [
"grey",
"purple",
"red",
"white"
] | C | Certain indicator compounds, such as litmus, can be used to detect acids. Acids turn blue litmus paper red. |
SciQ | SciQ-479 | evolution, brain, development
Title: Why does it take so long for the human brain to develop from an evolutionary point of view?
I have read that it takes about 25 years for the brain to be fully developed.
Coincidentally, humans from the Neolithic and Bronze Age had a very short life expectancy, in fact most of their life their brain wasn't fully developed.
My question is:
from an evolutionary point of view, is there a reason why humans spend so much of their life not being fully developed even long after being sexually fully developed? We can say that brain and our nerve system is the first system in embryo that starts to develop and as you said this system is continuing to develop until after birth.
So here is a question that why our brain don't develop completely before the birth ? Evolution has gone so far as to limit the development of the brain in the human embryonic phase and to allow it to continue into the postnatal phase. This helps the infant to be born and ease the birth both for mother and the new born because if the brain had fully grown, the size of the head would have made problem in birth. Now, after birth, the brain continues to grow and develop majorly between ages 2-3 and becomes more mature after that . The ability of the brain to grow over the years gives us the ability to adapt to different environments , learnings and new issues and other capabilities That happens with the subsequent creation and pruning of dendritic spines.
The following is multiple choice question (with options) to answer.
The development of a head region is called what? | [
"trichina",
"cocklebur",
"spore",
"cephalization"
] | D | Most flatworms have a distinct head region that includes nerve cells and sensory organs, such as eyespots. The development of a head region, called cephalization , evolved at the same time as bilateral symmetry in animals. This process does not occur in cnidarians, which evolved prior to flatworms and have radial symmetry. |
SciQ | SciQ-480 | 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.
Which hormone helps cells absorb sugar from the blood? | [
"estrogen",
"adrenaline",
"cortisol",
"insulin"
] | D | Endocrine system: A high concentration of sugar in the blood triggers secretion of insulin by an endocrine gland called the pancreas. Insulin is a hormone that helps cells absorb sugar from the blood. |
SciQ | SciQ-481 | atoms, terminology
Title: What is a neutral atom? I was told that an atom's atomic number is defined as follows:
The number of electrons or protons present in a neutral atom is called atomic number. It is represented by Z.
What does neutral mean here? Why isn't it just "..present in an atom..."? Electrons and protons are charged particles. The electrons have negative charge, while protons have positive charge. A neutral atom is an atom where the charges of the electrons and the protons balance. Luckily, one electron has the same charge (with opposite sign) as a proton.
Example: Carbon has 6 protons. The neutral Carbon atom has 6 electrons. The atomic number is 6 since there are 6 protons.
The following is multiple choice question (with options) to answer.
What is the number of electrons equal to in every electrically neutral atom? | [
"Electrons",
"protons",
"nucleus",
"molecules"
] | B | Electron Shells and the Bohr Model It should be stressed that there is a connection between the number of protons in an element, the atomic number that distinguishes one element from another, and the number of electrons it has. In all electrically neutral atoms, the number of electrons is the same as the number of protons. Thus, each element, at least when electrically neutral, has a characteristic number of electrons equal to its atomic number. An early model of the atom was developed in 1913 by Danish scientist Niels Bohr (1885–1962). The Bohr model shows the atom as a central nucleus containing protons and neutrons, with the electrons in circular orbitals at specific distances from the nucleus, as illustrated in Figure 2.6. These orbits form electron shells or energy levels, which are a way of visualizing the number of electrons in the outermost shells. These energy levels are designated by a number and the symbol “n. ” For example, 1n represents the first energy level located closest to the nucleus. |
SciQ | SciQ-482 | evolution
Not that I can think of or find easily. While there are detriments associated with being born prematurely, and some evidence that women waiting until they're late 30's and men until they're 60 or older can negatively affect their gametes and consequently the development of any children born from them - it's been such a short time since the introduction of hormonal contraception and modern medicine that we may not see results tangible results for hundreds of years. Although condoms have been around for several hundred years, and there's been no associations with condom use that I can think of.
In the short term, what it has done is affect the ethnic diversity of countries. For the first time ever, Hispanic births have outnumbered Caucasian births in 2012 in the United States. Other countries, mostly European countries, are seeing declines in birth rates - which means their populations will decline with age or be compensated for by immigration. Higher birth rates, however, are associated with lower income brackets or very religious communities - both of which are associated with ethnic Minorities, at least in the United States. So while minority populations have more kids, they do so on fewer resources which may negatively affect their children in the long-term, whereas higher-earning segments of the population might have fewer children later in their lives, but can provide a much more stable environment and opportunities to continue that success.
One thing that hormone-centered birth control has done, however, is eliminate rape as a viable form of passing on one's genes. As gruesome as it might be to consider, pregnancies as a result of rape can produce "fit" offspring. It is a legitimate reproductive strategy in nature, and is in humans... unless the woman is using contraception. In the long-term this will probably show some interesting results (nominally an enhanced "Female Choice" effect - which is already evident in human evolution), but nothing right now.
The following is multiple choice question (with options) to answer.
Does climate change have a positive or negative effect on reproductive success? | [
"both",
"neither",
"negative",
"positive"
] | C | |
SciQ | SciQ-483 | human-biology, human-anatomy, human-genetics
Title: Are males taller than females in humans? Is there any scientific evidence that in humans males are taller than females? And if so, what is the reason that they are taller (please include genes or hormones that accounts for human growth and how they are affected in males and females)? Are males taller than females?
Best data I could find come from the Statistical Abstract of the United States (1999) > Section 3. Here is a table reporting the percentage of the male and female population which height is lower than a given threshold
Note that this data collection was done among students in US universities and is therefore not representative of the whole world or even the whole country.
Does height follow a bimodal distribution?
A difference in height between males and females is often used as a classical example in introductory statistic class to exemplify a bimodal distribution as seen in this picture
and on these (a priori fake) data
However, Schilling et al. 2002 argued that while the difference in mean height between the sexes is real, this difference is too small relative to the variance in height within each sex to be clearly depicted on a graph.
Note that I found this non-peer-reviewed paper which shows real data that display a truly bimodal distribution of height.
Genetics of height
The question why are they taller? is very broad. I will just focus to give you some hints about the genetics of height in humans. First, you want to make sure you understand the concept of heritability.
Evoy and Vissher 2009 report a heritability coefficient of 0.8. This estimate is impressively high - only a few phenotypic traits have such high heritability. They also review articles discussing that 50 loci are correlated with variation in height (actually, today, more than 500 loci are known to contribute to height, see the link in AlexDeLarge's comment to this answer). However, these loci are not sufficient to explain the whole heritability observed (common missing heritability issue). Yang et al. 2010 provide evidence that the remaining heritability is due to incomplete linkage
disequilibrium between causal variants and loci of weak effects. In short, height is a highly polygenic trait.
Related post
You should have a look at Is there a genetic reason explaining the difference of the height of male and female? for more information.
The following is multiple choice question (with options) to answer.
What is the most common form of dwarfism in humans? | [
"malnutrition",
"anemia",
"achondroplasia",
"alopecia"
] | C | It can be. Achondroplasia is the most common form of dwarfism in humans, and it is caused by a dominant mutation. The mutation can be passed from one generation to the next. Over 95% of unrelated individuals with Achondroplasia have the same mutation, making it one of the most common mutations in the human genome. Why?. |
SciQ | SciQ-484 | dna, terminology
Title: Is a DNA molecule a single strand of polynucleotide or two of them linked together? Our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds. The thing is, until now, I always thought a DNA molecule was composed of two strands, those being polynucleotides, both of them being linked together. I can't find a link which is saying the same as my teacher, even if it seems technically correct to call a double helix a dimer of two DNA molecules.
I was curious to know what was the exact terminology. As you pointed out, though this may be basic biology, seeking clarification when receiving conflicting information is a good thing. Don't feel embarrassed for asking. :)
.. our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds.
Respectfully, your teacher is incorrect. A single, double-stranded DNA molecule is comprised of two helical shaped polynucleotides, and are connected together via hydrogen bonding.
Highlight of each polynucleotide
Highlight of hydrogen bonding
And just for further validation, according to Molecular Biology of the Cell, 4th ed., by Alberts B, Johnson A, Lewis J, et al.:
A DNA molecule consists of two long polynucleotide chains composed of four types of nucleotide subunits. Each of these chains is known as a DNA chain, or a DNA strand. Hydrogen bonds between the base portions of the nucleotides hold the two chains together.
So, it would seem that your teacher is referring to each polynucleotide, a.k.a. DNA strand, as a DNA molecule. Instead, she should use the verbiage: a single DNA molecule is composed of two DNA strands, which are helical-shaped polynucleotides.
The following is multiple choice question (with options) to answer.
What is the term for groups of three successive nucleotide bases in dna? | [
"triple play",
"triads",
"triplets",
"tertiary bases"
] | C | Overview of Transcription. Transcription uses the sequence of bases in a strand of DNA to make a complementary strand of mRNA. Triplets are groups of three successive nucleotide bases in DNA. Codons are complementary groups of bases in mRNA. |
SciQ | SciQ-485 | marine-biology, vestigial
Title: Modern Whales with Vestigial legs Myth? Is it a myth that modern whales have been found with hind legs sticking out of their sides and full formed tibias, fibias, and toe bones? I keep finding assertions, but no citations. For example, the wikipedia page has no citation for it.
http://en.wikipedia.org/wiki/Whales#Appendages The link you give doesn't mention limbs sticking out of the body wall, but only vestigial hind limb elements. Many whales do retain pelves and femora, as this page at the Bergen Museum shows. Given the variation in limb development across vertebrates, it would not be surprising to find more distal elements (but I would be very surprised if they extended past the body wall).
The following is multiple choice question (with options) to answer.
The coccyx, or tailbone, results from the fusion of four small what? | [
"coccygeal vertebrae",
"alangulam vertebrae",
"rib vertebrae",
"arsine vertebrae"
] | A | Regions of the Vertebral Column The vertebral column originally develops as a series of 33 vertebrae, but this number is eventually reduced to 24 vertebrae, plus the sacrum and coccyx. The vertebral column is subdivided into five regions, with the vertebrae in each area named for that region and numbered in descending order. In the neck, there are seven cervical vertebrae, each designated with the letter “C” followed by its number. Superiorly, the C1 vertebra articulates (forms a joint) with the occipital condyles of the skull. Inferiorly, C1 articulates with the C2 vertebra, and so on. Below these are the 12 thoracic vertebrae, designated T1–T12. The lower back contains the L1–L5 lumbar vertebrae. The single sacrum, which is also part of the pelvis, is formed by the fusion of five sacral vertebrae. Similarly, the coccyx, or tailbone, results from the fusion of four small coccygeal vertebrae. However, the sacral and coccygeal fusions do not start until age 20 and are not completed until middle age. An interesting anatomical fact is that almost all mammals have seven cervical vertebrae, regardless of body size. This means that there are large variations in the size of cervical vertebrae, ranging from the very small cervical vertebrae of a shrew to the greatly elongated vertebrae in the neck of a giraffe. In a full-grown giraffe, each cervical vertebra is 11 inches tall. |
SciQ | SciQ-486 | organic-chemistry, mixtures
Title: Would Oxygen Gas and Ozone be a pure substance together? If I have oxygen gas and ozone ($\ce{O2 + O3}$) together would it be considered a pure substance or a mixture?
And would pure substances always have the same molecular structure? Ozone is highly reactive and unstable, while dioxygen is stable. There do not combine to form a compound. So, clearly it is a mixture.
To answer the second part of the question, "And would pure substances always have the same molecular structure?", first a Wikipedia definition on substances, to quote:
A chemical substance is a form of matter having constant chemical composition and characteristic properties.[1][2]...
Chemical substances can be simple substances[4], chemical compounds, or alloys. Chemical elements may or may not be included in the definition, depending on expert viewpoint.[4]
Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water...
However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical.
And further:
A chemical substance may well be defined as "any material with a definite chemical composition" in an introductory general chemistry textbook.[5] According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. But, there are exceptions to this definition; a pure substance can also be defined as a form of matter that has both definite composition and distinct properties.[6] The chemical substance index published by CAS also includes several alloys of uncertain composition.[7] Non-stoichiometric compounds are a special case (in inorganic chemistry) that violates the law of constant composition, and for them, it is sometimes difficult to draw the line between a mixture and a compound, as in the case of palladium hydride. Broader definitions of chemicals or chemical substances can be found, for example: "the term 'chemical substance' means any organic or inorganic substance of a particular molecular identity, including – (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature".[8]
The following is multiple choice question (with options) to answer.
What is a pure substance that cannot be separated into any other substances called? | [
"light",
"Spears",
"element",
"Cells"
] | C | An element is a pure substance that cannot be separated into any other substances. There are 92 naturally occurring elements. |
SciQ | SciQ-487 | mechanical-engineering
Title: Approximately how many types of stress are there? Approximately how many types of stress are known/defined? Ex. Piola stress, Cauchy stress ... Your examples aren't really "types" of stress, but different ways to measure stress. The real world structure just responds the way it responds - it doesn't worry about what sort of math you used when you tried to model its behaviour.
https://en.wikipedia.org/wiki/Stress_measures lists a handful different stress measures that have acquired "names". Cauchy stress ("true stress") and Second Piola-Kirchhoff stress are probably the most commonly used.
It doesn't really make sense to talk about a measure of stress in isolation, without also considering how to measure strain, and how to model the constitutive equations that give the relationship between stress and strain.
For example 2-PK stress works nicely with Green strain, which is a convenient way to define the behavior of a body which has "small" elastic deformations superimposed on arbitrary large rigid body motions - in particular, large rigid body rotations, where approximations like $\sin \theta \approx \theta$ are not appropriate.
The following is multiple choice question (with options) to answer.
How many different types of stresses are there? | [
"four",
"three",
"five",
"seven"
] | A | Stress is the force applied to a rock. There are four types of stresses:. |
SciQ | SciQ-488 | dna, terminology
Title: Is a DNA molecule a single strand of polynucleotide or two of them linked together? Our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds. The thing is, until now, I always thought a DNA molecule was composed of two strands, those being polynucleotides, both of them being linked together. I can't find a link which is saying the same as my teacher, even if it seems technically correct to call a double helix a dimer of two DNA molecules.
I was curious to know what was the exact terminology. As you pointed out, though this may be basic biology, seeking clarification when receiving conflicting information is a good thing. Don't feel embarrassed for asking. :)
.. our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds.
Respectfully, your teacher is incorrect. A single, double-stranded DNA molecule is comprised of two helical shaped polynucleotides, and are connected together via hydrogen bonding.
Highlight of each polynucleotide
Highlight of hydrogen bonding
And just for further validation, according to Molecular Biology of the Cell, 4th ed., by Alberts B, Johnson A, Lewis J, et al.:
A DNA molecule consists of two long polynucleotide chains composed of four types of nucleotide subunits. Each of these chains is known as a DNA chain, or a DNA strand. Hydrogen bonds between the base portions of the nucleotides hold the two chains together.
So, it would seem that your teacher is referring to each polynucleotide, a.k.a. DNA strand, as a DNA molecule. Instead, she should use the verbiage: a single DNA molecule is composed of two DNA strands, which are helical-shaped polynucleotides.
The following is multiple choice question (with options) to answer.
A molecule has two structures that can be generated. what is this called? | [
"resonance hybrids",
"congruence",
"ethnocentrism",
"isomerism"
] | D | The cis isomer has the two single hydrogen atoms on the same side of the molecule, while the trans isomer has them on opposite sides of the molecule. In both molecules, the bonding order of the atoms is the same. In order for geometric isomers to exist, there must be a rigid structure in the molecule to prevent free rotation around a bond. If the double bond in an alkene was capable of rotating, the two geometric isomers above would not exist. In addition, the two carbon atoms must each have two different groups attached in order for there to be geometric isomers. Propene has no geometric isomers because one of the carbon atoms has two single hydrogens bonded to it. |
SciQ | SciQ-489 | molecular-biology, immunology
Title: A few questions regarding immunology I know that there is a variable region on antibodies which can recognize a wide variety of antigens, and that germinal centers create more "fit" antibodies to respond to an infection.
So I was just wondering:
The following is multiple choice question (with options) to answer.
An antigen is a molecule that reacts with some component of the what response? | [
"digestion",
"hormones",
"fight or flight",
"immune"
] | D | Chapter 42 1 Figure 42.11 C 3 Figure 42.16 If the blood of the mother and fetus mixes, memory cells that recognize the Rh antigen can form late in the first pregnancy. During subsequent pregnancies, these memory cells launch an immune attack on the fetal blood cells. Injection of anti-Rh antibody during the first pregnancy prevents the immune response from occurring. 4 D 6 A 8 D 10 B 12 D 14 C 16 C 18 D 20 C 22 If the MHC I molecules expressed on donor cells differ from the MHC I molecules expressed on recipient cells, NK cells may identify the donor cells as “non-self” and produce perforin and granzymes to induce the donor cells to undergo apoptosis, which would destroy the transplanted organ. 24 An antigen is a molecule that reacts with some component of the immune response (antibody, B cell receptor, T cell receptor). An epitope is the region on the antigen through which binding with the immune component actually occurs. 26 The TH1 response involves the secretion of cytokines to stimulate macrophages and CTLs and improve their destruction of intracellular pathogens and tumor cells. It is associated with inflammation. The TH2 response is involved in the stimulation of B cells into plasma cells that synthesize and secrete antibodies. 28 T cells bind antigens that have been digested and embedded in MHC molecules by APCs. In contrast, B cells function themselves as APCs to bind intact, unprocessed antigens. 30 Cross reactivity of antibodies can be beneficial when it allows an individual's immune system to respond to an array of similar pathogens after being exposed to just one of them. A potential cost of cross reactivity is an antibody response to parts of the body (self) in addition to the appropriate antigen. |
SciQ | SciQ-490 | virology, infection
Title: Why don't viruses cause wounds? A simple mental model of a viral infection is that an infected cell emits a lot of virions and eventually dies. The emitted virions have a chance of infecting other cells. Nearby cells are at a higher risk of infection.
Based on this model, if one cell in my nose gets infected, I would expect a large part of my nose to be destroyed, as the infection spreads and destroys more and more cells in the same area.
This does not happen! I survived a number of infections and still have my nose. Why?
I know there are "flesh eating" bacteria. Why isn't this the norm for infections? Does a common cold virus or SARS-CoV-2 not infect a lot of cells within the same area? A virus does not destroy that many cells before it is exterminated by the immune system or before the host dies.
Perhaps even more crucially, viruses typically target a very specific type of cell — those on the inner mucal surface of the nose in the case of cold or flu, those of the gastrointestinal tract in the case of stomach viruses, CD4 immune cells in the case of HIV, etc.
Update
As an example of how much time it takes for a virus to eat a noticeable wound, one could take the extermination of the immune cells by HIV - although it does not look as a physical wound, it is one, in the sense that enough of the specific tissue is destroyed to cause a life-threatening condition. It takes about a decade(!) - from the initial infection to the immune system failure.
On the other hand, the lethal effect of typical respiratory viruses is typically via obstructions of the respiratory ways due to inflammation or secretions resulting from the immune response, or via creating suitable conditions for a more serious bacterial infection.
The following is multiple choice question (with options) to answer.
What bodily system is primarily responsible for fighting pathogens in the body? | [
"Muscular",
"immune",
"digestion",
"Cardiovascular"
] | B | 21.5 | The Immune Response against Pathogens By the end of this section, you will be able to: • Explain the development of immunological competence • Describe the mucosal immune response • Discuss immune responses against bacterial, viral, fungal, and animal pathogens • Describe different ways pathogens evade immune responses Now that you understand the development of mature, naïve B cells and T cells, and some of their major functions, how do all of these various cells, proteins, and cytokines come together to actually resolve an infection? Ideally, the immune response will rid the body of a pathogen entirely. The adaptive immune response, with its rapid clonal expansion, is well suited to this purpose. Think of a primary infection as a race between the pathogen and the immune system. The pathogen bypasses barrier defenses and starts multiplying in the host’s body. During the first 4 to 5 days, the innate immune response will partially control, but not stop, pathogen growth. As the adaptive immune response gears up, however, it will begin to clear the pathogen from the body, while at the same time becoming stronger and stronger. When following antibody responses in patients with a particular disease such as a virus, this clearance is referred to as seroconversion (sero- = “serum”). Seroconversion is the reciprocal relationship between virus levels in the blood and antibody levels. As the antibody levels rise, the virus levels decline, and this is a sign that the immune response is being at least partially effective (partially, because in many diseases, seroconversion does not necessarily mean a patient is getting well). An excellent example of this is seroconversion during HIV disease (Figure 21.26). Notice that antibodies are made early in this disease, and the increase in anti-HIV antibodies correlates with a decrease in detectable virus in the blood. Although these antibodies are an important marker for diagnosing the disease, they are not sufficient to completely clear the virus. Several years later, the vast majority of these individuals, if untreated, will lose their entire adaptive immune response, including the ability to make antibodies, during the final stages of AIDS. |
SciQ | SciQ-491 | terminology, vectors, units
Title: If a force is a vector quantity, thus having direction and magnitude, why do we express pounds/newtons, a unit of weight, as a scalar? It is in my understanding that forces are vector quantities, and thus have both magnitude and direction. Since weight is a force of gravity, it also must have magnitude and direction. Why do we define the weight of an object (through SI newtons or customary pounds) as a scalar, such as 5 newtons? Why, despite weight being a force/vector quantity, is the direction not specified? It's just lazy language, the direction is implicit.
If I say "the weight is 4 Newtons", then it's implied, because we're talking about weight, that the direction is "toward the center of the Earth".
Similarly, if we say "the thrust on the airplane from the engines is 11,000 lbs", it's implied that the direction is "in the direction the airplane is going".
The following is multiple choice question (with options) to answer.
Displacement, velocity, acceleration, and force are examples of what type of quantity that has magnitude and direction? | [
"vector",
"frequency",
"wave",
"cycles"
] | A | Vectors in Two Dimensions A vector is a quantity that has magnitude and direction. Displacement, velocity, acceleration, and force, for example, are all vectors. In one-dimensional, or straight-line, motion, the direction of a vector can be given simply by a plus or minus sign. In two dimensions (2-d), however, we specify the direction of a vector relative to some reference frame (i. , coordinate system), using an arrow having length proportional to the vector’s magnitude and pointing in the direction of the vector. Figure 3.9 shows such a graphical representation of a vector, using as an example the total displacement for the person walking in a city considered in Kinematics in Two Dimensions: An Introduction. We shall use the notation that a boldface symbol, such as D , stands for a vector. Its magnitude is represented by the symbol in italics, D , and its direction by θ . Vectors in this Text In this text, we will represent a vector with a boldface variable. For example, we will represent the quantity force with the vector F , which has both magnitude and direction. The magnitude of the vector will be represented by a variable in italics, such as. |
SciQ | SciQ-492 | earth-history
Common elements in space, such as CO2, H20, CH4 and NH3 are gaseous at Earth's distance from the sun and as a result, are unlikely to stick to anything in the Earth's formation region. This is true for all 4 inner planets and likely all rocky worlds. Rocky planets likely can only form close to their star, just as gas giants, ice giants or other icy abundant bodies like comets and low-density moons, can only form further out.
Gases like the 4 above can begin to be retained around a planet after it reaches a sufficiently large mass with low enough surface temperature to retain those gases by gravity.
The boundaries where CO2, H20, CH4, NH3 and other gases can be found in the protoplanetary disk is called the frost line. Different gases have different frost lines depending on their freezing point.
It's thought that much of Earth's water, CO2, CH4 and NH3 came to the Earth by comet after the planet formed. There's still some uncertainty on the percentages, as some of those elements could have been trapped during formation.
Just to add, hydrogen and helium are obviously abundant, but will only begin to accrue around a planet of a certain mass. In our solar-system, only Jupiter and Saturn are massive enough to accrue hydrogen and helium. That's why Uranus and Neptune are relatively low on hydrogen and helium compared to the universal abundance.
Argon is in Earth's atmosphere because it forms from gradual radioactive decay of Potassium-40. Earth's Helium is also present as a result of radioactive decay.
The following is multiple choice question (with options) to answer.
Gases such as co2 and methane can trap what energy in earth's atmosphere, before radiating it into space? | [
"sunlight energy",
"mechanical energy",
"potential energy",
"thermal energy"
] | D | Thermal energy can be trapped in Earth’s atmosphere by gases such as CO2, water vapor, methane, and chlorofluorocarbons before it can be radiated into space—like the effect of a greenhouse. It is not yet clear how large an increase in the temperature of Earth’s surface can be attributed to this phenomenon. Venus is an example of a planet that has a runaway greenhouse effect. The atmosphere of Venus is about 95 times denser than that of Earth and contains about 95% CO2. Because Venus is closer to the sun, it also receives more solar radiation than Earth does. The result of increased solar radiation and high CO2 levels is an average surface temperature of about 450°C, which is hot enough to melt lead. Data such as those in Figure 5.22 "Changes in Atmospheric CO" indicate that atmospheric levels of greenhouse gases have increased dramatically over the past 100 years, and it seems clear that the heavy use of fossil fuels by industry is largely responsible. It is not clear, however, how large an increase in temperature (global warming) may result from a continued increase in the levels of these gases. Estimates of the effects of doubling the preindustrial levels of CO2 range from a 0°C to a 4.5°C increase in the average temperature of Earth’s surface, which is currently about. |
SciQ | SciQ-493 | equilibrium, water
Title: Can water synthesis and decomposition be in a dynamic equilibrium? When heated at extreme temperatures, water can spontaneously decompose.
According to Wikipedia (https://en.wikipedia.org/wiki/Water_splitting):
In thermolysis, water molecules split into their atomic components hydrogen and oxygen. For example, at 2200 °C about three percent of all H2O are dissociated into various combinations of hydrogen and oxygen atoms, mostly H, H2, O, O2, and OH. Other reaction products like H2O2 or HO2 remain minor. At the very high temperature of 3000 °C more than half of the water molecules are decomposed, but at ambient temperatures only one molecule in 100 trillion dissociates by the effect of heat.[15] The high temperatures and material constraints have limited the applications of this approach.
The following is multiple choice question (with options) to answer.
What happens when heated water is released into a body of water? | [
"thermal pollution",
"gaseous pollution",
"crystalline pollution",
"geysers"
] | A | If heated water is released into a body of water, it may cause thermal pollution. Thermal pollution is a reduction in the quality of water because of an increase in water temperature. A common cause of thermal pollution is the use of water as a coolant by power plants and factories. This water is heated and then returned to the natural environment at a higher temperature. |
SciQ | SciQ-494 | psychology, animal-models, mouse, behaviour
Title: Does isolation have any effect upon mouse behavior? I work with a lot of mice. I don't do any behavioral analysis, I just inject DNA or RNA and do imaging assays. However, I have noticed some effect of isolation on mouse behavior. Normally, the mice are housed in our university's animal facility with no more than 5 mice to a cage. Sometimes, 1 mouse will be put in a cage by itself. When I go to get these lone mice from their cages, they seem more skittish, harder to grab, and more likely to bite me than mice kept in groups.
Additionally, our Office of Animal Resources, which is responsible for getting in the mouse shipments and putting them into cages, has recently changed how our mice are caged, with a group of 4 mice being normal, any leftover mice are put into cages with other mice, making a 5 mouse cage. This means I haven't seen a single mouse in a cage for a while. So I might not be the only one to have noticed an effect of isolation on the animal's health.
I have heard of studies on monkeys by B.F. Skinner, where he induced very severe depression and other psychological issues by isolating them, so I suspect similar studies have been attempted on mice using far more quantitative methods than I've been able to do. Yeah, it's not good:
Social isolation (SI) rearing in rodents causes a variety of behavioral changes, including hyperlocomotion, anxiety, impulsivity, aggression, and learning and memory deficits. These behavioral abnormalities in rodents may be related to the symptoms in patients with neuropsychiatric disorders, such as attention-deficit hyperactivity disorder, obsessive-compulsive disorder, autism, schizophrenia and depression...
Also:
Our findings suggest that [social isolation]-induced behavioral abnormality is a psychobehavioral complex relevant to various clinical symptoms observed in neuropsychiatric disorders, including ADHD, schizophrenia and depression, and that SI-reared mice are a useful animal model to study the pathophysiology/pathogenesis of these diseases.
There's this:
The following is multiple choice question (with options) to answer.
What term is used to describe a chemical released by an animal that affects the behavior or physiology of animals of the same species? | [
"pheromone",
"isolate",
"amino",
"enzyme"
] | A | The amount of material left over after a certain number of half-lives can be easily calculated. |
SciQ | SciQ-495 | biophysics, theoretical-biology, ecosystem
Systems ecology, especially with regard to energy and nutrient flow.
This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem Ecology: Understanding Element Cycles by Ågren & Bosatta (Ågren was originally a physicist)
Physical limitations to growth and transport
This can include for instance mechanical contraints on plant growth (see e.g. the book Plant Physics by Nicklas & Spatz), water transport in trees (see e.g. this BioSE question) or the biomechanics of movement (see e.g. Hudson et al (2012) on the speed and movement of cheetahs or Wikipedia: Biomechanics).
Allometric relationships between organisms, e.g. with regard to metabolism
To explain these types of relationships knowledge in physics is useful. See e.g. Kleiber's law for more.
MAXENT as a general approach to ecological patterns or to model species distributions
This is basically a tool lifted from physics that can be applied to ecological problems. There are many papers to look at, but Harte & Newman (2014) (Harte is another previous physicist) and Elith et al (2010) are two good starting points.
Dynamical modelling of populations and communities
This field use many of the same tools for analysis as physics, e.g. systems of differential equations. One of the pioneers in this field (among many) were Robert May (also started with a PhD in physics), and his classical book Theoretical Ecology: Principles and Applications is still a good starting point.
Energy harnessing and conversion by organisms
This can refer both to how organsims convert prey to energy (e.g. conversion efficiencies) and the physics of photosynthesis (which is an interesting intersection between physics and molecular biology). See Jang et al (2004) and O'Reilly & Olaya-Castro (2013) for examples of the how quantum mechanics can inform us about photosynthesis.
Hopefully this will give you a sense of some different ways that knowledge in physics can be useful for biology.
The following is multiple choice question (with options) to answer.
Producers at the base of ecological food webs are also known as? | [
"symbiotic",
"endoscopic",
"autotrophic",
"mutualistic"
] | C | |
SciQ | SciQ-496 | meteorology, climate-change, gas, pollution
Title: Regarding various types of atmospheric pollution Does all the car pollution (from about 150 million cars at least in the U.S. and a lot more in all of North America and the rest of the world) all the smoke-stack pollution of various factories and all the Airline pollution running day after day have a deleterious and damaging effect on the general atmosphere and, over time, the climate?
Given all the observed pollution that China has caused itself and some of the resulting weird weather events there this certainly seems to be evidence of the damaging effects of car and factory pollution. Has anyone calculated how much exhaust from cars is produced in one day on average in a 'moderate' sized city?
Of course it seems with all the increased oil production in the U.S. and elsewhere we, human beings are going to keep are love-affair with gas-powered cars for the next 200 or 300 years. That is if we don't use up all the oil and gas in the ground before then. As a USA resident, the EPA is the best place to start when wondering about the emissions inventory of atmospheric pollutants or pollutant precursors that affect the National Ambient Air Quality Standards (e.g. Particulate Matter, Carbon Monoxide, Sulfur Dioxide, Lead, Nitrogen Oxides, Volatile Organic Compounds). The EPA compiles a comprehensive emissions inventory of all criteria pollutants at the county level which is available in the National Emissions Inventory (compiled once every 3 years). You can see the summary of your county at http://www.epa.gov/air/emissions/where.htm. As for the effects of atmospheric pollution, it is important to consider the lifetime of said pollutants in the atmosphere in order to put their environmental impacts into perspective. For instance, the air pollutants covered by the National Ambient Air Quality Standards have immediate health effects when high concentrations are breathed in regularly. Both animals and plants are adversely affected by these irritating and sometimes toxic chemicals, but these pollutants are also reactive and do not last long in the atmosphere unless they are constantly being replenished (e.g. daily traffic). Air quality also impacts critical nitrogen loads on ecosystems and possible production of acid rain.
The following is multiple choice question (with options) to answer.
What is the term for the gas in smog that can damage plants? | [
"carbon",
"sulphur",
"ozone",
"dioxide"
] | C | The ozone in smog may damage plants. The effects of ozone add up over time. Plants such as trees, which normally live a long time, are most affected. Entire forests may die out if ozone levels are very high. Other plants, including crop plants, may also be damaged by ozone. You can see evidence of ozone damage in Figure below . |
SciQ | SciQ-497 | ions
Title: How does Phosphorus Pentachloride bond? The thing I am having trouble with: why does $\small\ce{PCl4}$ form a +1 ion and $\small\ce{Cl}$ a -1 ion? There is no ionic bonding that occurs, the phosphorus is able to make a hybrid orbital out of its $\small3s$ and $\small3p$ electrons, along with an empty $\small d$ orbital to form 5 $sp^3d$ molecular orbitals, of equal energy, which yields 5 spots for bonding electrons.
This is a known exception to the octet rule.
(graciously borrowed from here)
The following is multiple choice question (with options) to answer.
What must happen for two ions to form an ionic bond? | [
"two ions need to have opposite charges",
"two ions need to have neutral charges",
"two ions need to have the same charge",
"Two ions need to be the same size"
] | A | |
SciQ | SciQ-498 | evolution
Title: Is there any genetic similarity that defy evolution theory? For example,
say species A is common ancestor of B, and C. Species B is a common ancestor of D and E.
We would expect that there will be more genetic similarity between D and E than D and C. And those genetic similarity must exist in B.
In other word, we won't expect genetic similarity that don't "cross" the common ancestor or the evolutionary tree.
The exception is probably genetically engineered bacteria.
That being said, am I correct?
Some people say that we have similarity with pigs and chimps even though our common ancestors may be to far off. That won't happen right?
To summarize
I expect that evolutionary tree will form a well, tree. Genetic similarity would infect "nearby" trees and can't jump between trees without connectors, such as common ancestors.
Is that what we observe for ALL species? You have an excellent answer from Remi.b already but I just wanted to add/emphasise this (because there is always more than one way of explaining something and IMO the site benefits from having many answers to the questions)...
The tree we construct does not necessarily accurately reflect what happened in evolution. If B & C evolved from A, and D & E came from B, we would create this tree if we measured using the correct indicator. But the methods we have are not perfect. The first evolutionary trees were based on morphological descriptions etc. and clearly some of the classifications were going to be wrong. These days we use molecular methods, which are probably more accurate but could also be wrong some times. For example if we based our phylogeny on one SNP variant we could have some idea about the phylogeny between a few species, but if we based it on millions of SNPs we would have a much better idea - as technology & models improve that is becoming more realistic. The key point here being there is a difference between the trees we can draw from evidence, and the real evolutionary tree.
The following is multiple choice question (with options) to answer.
What is the study of the similarities and differences in the embryos of different species? | [
"prenatal biology",
"diversified embryology",
"example embryology",
"comparative embryology"
] | D | Comparative embryology is the study of the similarities and differences in the embryos of different species. Similarities in embryos are evidence of common ancestry. All vertebrate embryos, for example, have gill slits and tails. Most vertebrates, except for fish, lose their gill slits by adulthood. Some of them also lose their tail. In humans, the tail is reduced to the tail bone. Thus, similarities organisms share as embryos may be gone by adulthood. This is why it is valuable to compare organisms in the embryonic stage. See http://www. pbs. org/wgbh/evolution/library/04/2/pdf/l_042_03. pdf for additional information and a comparative diagram of human, monkey, pig, chicken and salamander embryos. |
SciQ | SciQ-499 | human-biology, cancer, systems-biology
Title: How does cancer of the larynx (laryngeal cancer) affect the respiratory system? The larynx is part of the respiratory system and is responsible for producing sound (our voices). My question is how cancer in the larynx (voice box) affect the respiratory system overall? I appreciate any answer, but if it's not too inconvenient, please don't use too complex terminology (I'm in grade 10 Canada).
Thanks According to this website:
http://www.spirometry.guru/fvc.html
it causes difficulty with inhalation but exhalation is normal...
"Typically the expiratory part of the F/V-loop is normal: the
obstruction is pushed outwards by the force of the expiration."
"During inspiration the obstruction is sucked into the trachea with
partial obstruction and flattening of the inspiratory part of the
flow-volume loop."
the exact symptoms of a laryngeal tumor depends on where it is located on the larynx... above the vocal cords, on the vocal cords, or below the vocal cords...
but more generally:
anatomy:
mouth/nose-->pharynx-->larynx-->trachea-->bronchi-->lungs
a tracheostomy may be necessary... basically the surgeon makes a connection between the skin outside the throat and the trachea... this bypasses the larynx (as well as pharynx and nose/mouth)...
The following is multiple choice question (with options) to answer.
What are the main organs of the respiratory system? | [
"kidneys",
"ovaries",
"intestines",
"lungs"
] | D | The lungs are the main organs of the respiratory system. This is where gases are exchanged between the air and the blood. Gases are also transported by the blood and exchanged between the blood and all the cells of the body. |
SciQ | SciQ-500 | ecology
Title: How to define a 'trait' objectively? I'm coming across an increasing number of papers that use trait-based approaches for risk assessment, like this one . This paper defines a trait as follows:
Traits are the physiological, morphological, and ecological attributes
of species or other taxonomic entities, which describe their physical
characteristics, ecological niche, and functional role within an
ecosystem.
I've wondered about using this sort of approach during some analyses of invasiveness potential in vector insects before and it's likely to come up during a systematic literature review I'm coordinating, but I'm concerned that devising my own trait classification system is likely to introduce confirmation bias into a study. Is there either a recognised methodology for trait definition, or alternatively some sort of accepted list or classification of traits that I could use, to minimise the chances of this? Is there a generally-accepted method to correct for phylogenetic correlation?
I've tried Google but the results mostly appear to be about trait theory, which is an approach used in psychology to study human personality. I think you this paper is what you need. The many concepts of trait are discussed in the functional ecology background. But basically, a "trait" can be defined as
" 'Functional traits’ are defined as morpho-physiophenological
traits which impact fitness indirectly via their effects on growth, reproduction and survival, the three components of individual performance." (Violle et al. 2007)
Which are not so different from the definition you posted.
Some organisms have an improved methodology to collect and measure traits, like plants. But this is not common to all organisms.
As for the method to correct for phylogenetic correlation, this is a whole different field called Phylogenetic Comparative Methods. To choose the method you need to know the kind of data you have and the question being asked.
The following is multiple choice question (with options) to answer.
What do you call the traits that allow a plant, animal, or other organism to survive and reproduce in its environment? | [
"advantages",
"settings",
"additions",
"adaptations"
] | D | Every plant and animal depends on its traits to survive. Survival may include getting food, building homes, and attracting mates. Traits that allow a plant, animal, or other organism to survive and reproduce in its environment are called adaptations . |
SciQ | SciQ-501 | 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.
The products of photosynthesis are glucose and what else? | [
"oxygen",
"hydrogen",
"carbon",
"nitrogen"
] | A | The products of photosynthesis are glucose and oxygen. |
SciQ | SciQ-502 | mutations, genomes
Title: Bacterial division and mutation rate When a bacteria A divides it produces two cells A', A''. Each of them receives a copy of the chromosome/plasmids. Now, DNA replication occurs way before division in a semiconservative manner. That is, each new chromosome has an 'old' strand and a 'new' strand. Since the polymerase is error prone, my belief is that both genomes can potentially have mutations. Now when people refer to the mutation rate/genome/replication, e.g. 3x10-4 , Does this mean that:
The following is multiple choice question (with options) to answer.
In what way do bacteria reproduce? | [
"cellular respiration",
"sexual reproduction",
"fragmentation",
"binary fission"
] | D | Bacteria reproduce by binary fission, resulting in two daughter cells identical to the parent cell. |
SciQ | SciQ-503 | biochemistry, proteins, enzymes
Title: Is chitin actually protein? Recently insects are featured as a protein rich source for human nutrition. That humans can really digest chitin through chitinase enzym has been only recently confirmed.
But, does the chitin shell of their body actually count to the protein family?
Wikipedia does not state a clear yes or no. It says it is derivative of glucose, and may be compared by function to keratin protein. I'd really like to exclude any ambuguity and undersrand why. Chitin and protein are completely unrelated.
The only common thing is that they are polymers.
Chitin is a polymer of amino sugars while protein is a polymer of amino acids.
Both monomers are very different and are not converted one to the other.
In fact, chitin, like cellulose, is not fragmented by animals, so it is not absorbed.
Moreover, chitin is a homopolymer, so even if it where absorbed and transformed to amino acids, it would yield only one (or maybe a few ones) but all the others would have to be obtained through a different source.
So chitin is not a source of protein or amino acids.
The following is multiple choice question (with options) to answer.
What type of fibers are made mostly of protein in living things? | [
"muscle fibers",
"organ fibers",
"liver fibers",
"connective tissue fibers"
] | A | Muscle fibers are made mostly of protein. |
SciQ | SciQ-504 | glaciology
Title: Typical values of Glen flow law for glaciers? The Glen flow law for glaciers is a common relationship linking stress to strain. At its simplest,
$\Sigma = k\tau^n$
where $\tau$ is stress, $\Sigma$ is strain, and $n$ is roughly 3.
I understand that $k$ depends on temperature and material properties of the ice, and that it can vary over two or three orders of magnitude.
I have been searching the literature to find some example values of $k$ (also called $B$ and $A$) but so far I've had a surprisingly hard time. Is there somewhere that has a compilation of $k$ values from various studies? For glaciology related doubts, the first place to look is The Physics of Glaciers by Kurt M. Cuffey, W. S. B. Paterson. Going through the section 3.4.5 Controls on Creep Parameter A, should give you a good insight on the topic. It also includes example values.
As well as recommendations for values of A as a function of temperature.
This section is included in the preview of the book on Google books.
The following is multiple choice question (with options) to answer.
What force is responsible for erosion by flowing water and glaciers? | [
"gravity",
"weight",
"kinetic",
"electromagnetic"
] | A | Gravity is responsible for erosion by flowing water and glaciers. That’s because gravity pulls water and ice downhill. These are ways gravity causes erosion indirectly. But gravity also causes erosion directly. Gravity can pull soil, mud, and rocks down cliffs and hillsides. This type of erosion and deposition is called mass wasting . It may happen suddenly. Or it may occur very slowly, over many years. |
SciQ | SciQ-505 | species-identification, microbiology, microscopy
Title: Identification of protozoa under microscope I observed maybe Protozoa from standing FRESH water and from slowly flowing FRESH water. I am complete dilettante. Can you tell what these creatures are?
https://www.youtube.com/watch?v=6D5ck3zNJzA&t=474s
Thank you.
Added picture for to be more specific At first glance, the organisms may hold the appearance of protozoans like ciliates. However, I am of the belief that these 'totally tubular' micro organisms are in fact diatoms.
The diatoms are a diverse range of eucaryotic microalgae which comprise a large percentage of the phytoplankton group. (Diatomaceous earth is the residual remains of their calcareous walls)
They are likely diatoms because of their apparent hard membrane, and slight brown-green pigment, typical of heterokont diatoms.
I would be unable to specify the organism to family level. However, you may wish to complete your investigation by looking under the order 'Pennales'.
For general information regarding the Diatoms, you may visit https://en.wikipedia.org/wiki/Diatom
Morphology and description available from: https://books.google.co.uk/books?id=xhLJvNa3hw0C&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
Good luck
The following is multiple choice question (with options) to answer.
Nearly all protists exist in some type of aquatic environment, including freshwater and marine environments, damp soil, and even snow. several protist species are parasites that infect animals or plants. a few protist species live on dead organisms or their wastes, and contribute to what? | [
"their decay",
"greenhouse gas",
"spontaneous mutation",
"habitat loss"
] | A | Habitats Nearly all protists exist in some type of aquatic environment, including freshwater and marine environments, damp soil, and even snow. Several protist species are parasites that infect animals or plants. A few protist species live on dead organisms or their wastes, and contribute to their decay. |
SciQ | SciQ-506 | geology, volcanology, geochemistry, petrology, magmatism
I'm not exactly sure what do you mean by 'mature' but I will address the timing of alkali magmatic activity. Here is a very simplified depiction of what happens:
At first (A), a young plume will still be deep. The melts that it forms are low degree and deep. Then, when the plume 'matures' (B), it causes shallow melting producing voluminous tholeiitic basalts. The margins of the plumes still produce low degrees alkali melts. When the plume wanes (or just migrates somewhere else), you get only alkali melts again (sorry, I was too lazy to draw C in the figure, but it should look not too different than A). This is similar to what's happening at the moment in Hawaii. The newest (still underwater) volcano, Loihi, erupts alkali magmas. This corresponds to stage A in the figure. This is also what the oldest rock on Hawaii (the island) are made of: alkali rocks. Most of the rocks by volume on Hawaii (again, the island) are tholeiitic basalts erupted some hundred thousands year ago, corresponding to stage B in the figure. Recent (geologically) eruptions are yet again alkaline, similar to stage C.
For some extra reading about alkali rocks and related subjects, see these other questions and answers:
What are the high field strength and large ion lithophile (HFS or HFSE & LIL or LILE) elements?
What are rare earths and why do they cluster near alkaline magmatism?
Are there significant amounts of rare earth elements on Iceland?
The following is multiple choice question (with options) to answer.
What type of rocks form from cooled magma or lava? | [
"granite",
"igneous",
"metamorphic",
"sedementary"
] | B | Igneous rocks form from cooled magma or lava. |
SciQ | SciQ-507 | physical-chemistry, electrochemistry, electrolysis, reduction-potential, electricity
Title: what are the differences between reversible cells and rechargeable cells? My chemistry textbook says daniel cells are reversible, but not rechargeable.
Why is it that all reversible cells are not rechargeable?
Are all rechargeable cells reversible? why/why not? Per Wikipedia on Electrolytic Cells, to quote:
Galvanic cells compared with electrolytic cells
In an electrolytic cell a current is passed through the cell by an external voltage, causing an otherwise nonspontaneous chemical reaction to proceed. In a galvanic cell the progress of a spontaneous chemical reaction causes an electric current to flow. An equilibrium electrochemical cell is at the state between an electrolytic cell and a galvanic cell. The tendency of a spontaneous reaction to push a current through the external circuit is exactly balanced by an external voltage that is called a counter electromotive force or counter e.m.f. so that no current flows. If this counter voltage is increased the cell becomes an electrolytic cell and if it is decreased the cell becomes a galvanic cell.[1]
I do also, operationally, agree with Aben Philip comments, where apparently, attempting to recharge (aka, chemically reverse) a galvanic cell, may undesirably further introduce hydrogen gas. The problematic $\ce{H2}$ gas evolution can result in bursting and the usual safety concerns working with hydrogen (as in an explosion hazard).
More technically from a electrochemistry perspective, per another source, rechargeable batteries are again distinctly claimed again to an "Electrolytic Cell", characterized as having non-spontaneous oxidation-reduction reaction versus spontaneous for a galvanic cell. But further, in addition, they may also have a semipermeable membrane governing the flow of ions, which are not found in a galvanic cell.
I hope this helps.
The following is multiple choice question (with options) to answer.
What kind of cells have positive cell potentials, and all the reduction reactions are reversible? | [
"inhibited cells",
"galvanic cells",
"neutral cells",
"new cells"
] | B | Galvanic cells have positive cell potentials, and all the reduction reactions are reversible. The reaction at the anode will be the half-reaction with the smaller or more negative standard reduction potential. Reversing the reaction at the anode (to show the oxidation) but not its standard reduction potential gives: Anode (oxidation):. |
SciQ | SciQ-508 | fluid-dynamics, flow, propulsion
Title: Fluid Virtual Mass In this paper of Lighthill, the author studies the motion of a fish in a constant flow field $U$, modelling the movement of the fish as a deforming, rotationally symmetric, rigid surface in an inviscid fluid. The cross section of the solid volume delimited by the surface, is called $S_x$ and depends on $x$, along the body of the fish.
The fish is supposed to be Slender, that is the displacements and the transversal dimensions of the surface are small compared to the length of the fish in the $x$-direction.
At a certain point, Lighthill says:
Locally, the body shape differs little from that of an infinite
cylinder $C$, whose cross-section is $S_x$, all the way along.
Accordingly, to the slender-body approximation, the flow component
due to the displacements of the cross section near $S_x$, is identical
with the two-dimensional potential flow that would result from the
motion of the cylinder $C$, through fluid at rest with velocity $V(x,
> t)$.
We suppose now that this flow has momentum $$\rho\ A(x)\ V(x,t)$$
per unit length of cylinder, where $\rho$ is the density of the water.
In the usual terminology, $\rho A(x)$ is the ‘virtual mass’ of the
cylinder $C$, per unit length for motions in the $z$-direction. Thus,
the coefficient $A(x)$ has the dimensions of area; for example, it is
equal to the area of the cross-section $S_x$, when the latter is
circular, while for an ellipse with minor axis in the z-direction
$A(x)$ is the area of its circumscribing circle.
My questions are basically two:
The following is multiple choice question (with options) to answer.
A fish's stream-lined body that reduces water resistance is an example of what kind of response to an aquatic lifestyle? | [
"retraction",
"adaptation",
"evolution",
"natural selection"
] | B | Many structures in fish are adaptations for their aquatic lifestyle. For example, fish have a stream-lined body that reduces water resistance while swimming. |
SciQ | SciQ-509 | atmosphere, climate-change, climate
Title: Why is the temperature *still* rising? 2015 is the hottest year on record, and the average temperature continues to rise.
I don't understand why this continues, as (over the past twenty years) so much work was put into reducing Global Warming over the past 40 years, yet not only does the temperature not fall, it continues to rise more than it did between 1870-1960.
I don't understand something. The amount of industry went through the roof (literally) between 1870 to 1960, and no one cared about the environment
Now that we do care about it, and (at least somewhat) legislate cleaner cars, factories, etc, I would expect the temperature to even out, yet it doesn't
Why not? "So much work"? Actually, compared to the global rate of greenhouse gas emissions, it's a case of "so little work"! From a scientific perspective the 'economists' solution' of carbon trading was always unlikely to achieve the required carbon cuts, as has been verified by their ineffectiveness over the last decade or so. As farrenthorpe points out, the rate of increase of CO2 is largely population-driven, and hence there is still an inexorable rise in mean atmospheric CO2. The acid test of human efforts to limit global warming is whether the Hawaiian CO2 monitoring graph is flattening off:
It clearly isn't going to flatten anytime soon. In fact, if anything, it is getting steeper. So all the hot air from 'Paris', and previous talkfests, is evidently too little, too late. Realistically, limiting the average temperature rise to less than 2 °C, is now effectively unattainable. We have yet to see what 'all this work' can achieve. So far, almost nothing.
The following is multiple choice question (with options) to answer.
Emissions of what gas into the atmosphere from fossil fuel burning have been rising for the past several decades? | [
"carbon dioxide",
"sulphur",
"neon",
"oxygen"
] | A | Carbon dioxide emissions into the atmosphere from fossil fuel burning have been rising for the past several decades. |
SciQ | SciQ-510 | evolution, botany, proteins
tl;dr: the egg contains more proteins than the seed because the chicken that made the egg ate a whole lot of seeds, and all the protein in those seeds ended up concentrated in that one egg.
EDIT: running into this much later I realized I missed a pretty vital half of the question, because there is a difference between fruits and seeds. The difference is the following: nitrogen is precious for plants so they'll try and use it for very important things. Seeds are very important to the plant, so while a seed has less protein than an egg it will still have lots of protein by plant standards. Fruits now, that's another story. Like the sugary nectar, fruits are a bribe for animals, a bit of food offered to them so that they'll spread the plant's seeds. And like with the sugary nectar, the plant has every incentive to pack that bribe full of cheap carbohydrates and as few precious proteins as it can manage.
The following is multiple choice question (with options) to answer.
Gymnosperms have seeds but do not have what? | [
"roots",
"stems",
"flowers",
"leaves"
] | C | Gymnosperms have seeds but do not have flowers. |
SciQ | SciQ-511 | ecology, database, biodiversity, species-distribution
Title: Database of Geographic Range of Species Is there a database of organisms which would contain their queriable geographic location?
I would need to perform a rather simple query, such as Animals of <Location>, where Location is some well defined geographic area such as Czech Republic or Europe.
So far I have found multiple lists on Wikipedia and other webpages, however they seem to be quite incomplete as their intersect is quite small. Moreover, I have found EOL (Encyclopedia of Life) collections but they appear to struggle the same way. This is to a large extent a question of how reliable the data in the database needs to be. Reliability (and spatial scale) will differ between datasets and between species groups within datasets, and it is difficult to give a general recommendation. I doubt that you will find a single database with good coverage over all taxonomic groups, even if it is in the form of country checklists. For the most reliable information, curated country checklists for specific taxonomic groups will probably be best, but these have to be searched for individually for each taxonomic group of interest.
As a starting point, you might want to look at the occurence data that can be found in gbif.org (The Global Biodiversity Facility). The data found there is certainly not complete, and it will be misleading for many species. However, for the current distribution of relatively well-known groups of species it will give you a good idea of their distribution. This has to be evaluated on a case-by-case basis though. You can access the data in gbif using external tools, for instance using R through rgbif (there is also tools for python or other languages). At the blog recology.info you can find a tutorial on how to get a species list for a particular country using rgbif (more specifically the function density_spplist).
The following is multiple choice question (with options) to answer.
Modern members of what broad animal group live in many different habitats and are found on every continent except antarctica? | [
"amphibians",
"reptiles",
"parasites",
"arachnids"
] | B | Modern reptiles live in many different habitats. They can be found on every continent except Antarctica. |
SciQ | SciQ-512 | zoology, circulatory-system, heart-output, amphibians
I would add to this my notes from when I was a biochem student (but studied Zoology), mentioning the arterial cone and a spiral valve. This is better described in Britannica:
The conus arteriosus is muscular and contains a spiral valve. Again, as in lungfishes, this has an important role in directing blood into the correct arterial arches. In the frog, Rana, venous blood is driven into the right atrium of the heart by contraction of the sinus venosus, and it flows into the left atrium from the lungs. A wave of contraction then spreads over the whole atrium and drives blood into the ventricle, where blood from the two sources tends to remain separate. Separation is maintained in the spiral valve, and the result is similar to the situation in lungfishes. Blood from the body, entering the right atrium, tends to pass to the lungs and skin for oxygenation; that from the lungs, entering the left atrium, tends to go to the head. Some mixing does occur, and this blood tends to be directed by the spiral valve into the arterial arch leading to the body.
The following is multiple choice question (with options) to answer.
The right ventricle pumps what type of blood toward the lungs? | [
"plasma",
"oxygen-rich",
"oxygenated",
"oxygen-poor"
] | D | The right ventricle pumps oxygen-poor blood toward the lungs, where it receives oxygen. |
SciQ | SciQ-513 | organic-chemistry, organometallic-compounds
Title: Organic reaction of dry ice and Grignard reagent
Which of the following product is formed in the reaction $\ce{CH3MgBr}$ in DryIce/acid?
A) $\ce{CH3COOH}$
B) $\ce{CH4}$
C) $\ce{CH3OH}$
D) $\ce{CH3CH2CHO}$
My answer is A, since dry ice is $\ce{CO2}$ and it has one carbon atom and reactant has one carbon, so in all the product should have two carbon atoms, which is option A.
Am I correct? You are correct. Grignard reagents $\ce{RMgX}$ (where $\ce{R}$ stands for some hydrocarbon group and $\ce{X}$ is a halogen, usually $\ce{Cl}$, $\ce{Br}$, or $\ce{I}$) react with carbon dioxide to produce carboxylic acids after acidic workup:
$$\ce{RMgX ->[1)\ \ce{ CO2}][2)\ \ce{ H3O+}] RCO2H}$$
$$\ce{RMgX + CO2 -> RCO2- MgX+}$$
$$\ce{RCO2- + H3O+ -> RCO2H + H2O}$$
In general your reasoning when approaching this problem is a good one. If you are reacting two 1-carbon reagents, then you probably have a 2-carbon product.
The following is multiple choice question (with options) to answer.
Some 96% of the dry mass consists of organic compounds produced by what? | [
"photosynthesis",
"erosion",
"reproduction",
"electrolysis"
] | A | |
SciQ | SciQ-514 | newtonian-mechanics, rotational-dynamics, rotation
This is something that happens very often with all sorts of constraints, constraints very often have forces that only apply if your motion is trying to violate the constraint. So if one is trying to find out when a car falls off of a loop-de-loop, one would indirectly look for a vanishing normal force, the normal force enforces the constraint that the car does not fly outward through the loop-de-loop surface, when this vanishes it implies that the car is just barely holding on and any lower speed falls off of it.
The following is multiple choice question (with options) to answer.
What is it called when something is unable to move from place to place? | [
"obovate",
"ovate",
"Undrate",
"sessile"
] | D | Sponges come in a variety of shapes and sizes. For example, they may be shaped like tubes, fans, cones, or just blobs. They range in diameter from about a centimeter (0.4 inches) to over a meter (3.3 feet). Many species live in colonies that may be quite large. Adult sponges are sessile . This means they are unable to move from place to place. Root-like projections anchor them to solid surfaces such as rocks and reefs. |
SciQ | SciQ-515 | visible-light, laser, home-experiment, frequency
Title: Beam of electromagnetic wave, with radius of 3cm or less I need to create a beam of electromagnetic wave, with radius of 3cm or less, for distance about few meters. What is the minimum frequency (maximum wavelength) that it is really possible? Assuming you're talking about propagation through free space, the beam will be diffracted by the aperture you pass it through (3cm in this case) and that will cause the beam to diverge. The far field angular divergence, $\theta$, is approximately given by the equation for the Airy disk:
$$ \sin\theta \approx 1.22 \frac{\lambda}{d} \tag{1} $$
where $d$ is the diameter of the aperture (3cm) and $\lambda$ is the wavelength you're using. So you just need to decide what angular divergence is acceptable and plug it into equation (1).
The following is multiple choice question (with options) to answer.
What waves are the broad range of electromagnetic waves with the longest wavelengths and lowest frequencies? | [
"microwaves",
"radio",
"sound",
"light"
] | B | Radio waves are the broad range of electromagnetic waves with the longest wavelengths and lowest frequencies. They are used for radio and television broadcasts, microwave ovens, cell phone transmissions, and radar. |
SciQ | SciQ-516 | geology, rocks, sedimentology, geomorphology, terminology
Title: What do you call boulders of non sedimentary rock that were lithified into sandstone? I'm convinced there is a word for this. I was in the Hoodoos at Writing on Stone this weekend and kept noticing what looked like reddish quartzite boulders laying around in the sand, or sometimes sticking partially out of the hoodoos.
When a non-sedimentary rock gets washed out into silt which later lithifies, what's it called? It's kind of like a conglomerate, except there's only a couple of really big rocks, which eventually fall out out the rock because all the sandstone around them eroded away. The technical term for a sedimentary rock that has a lithified fine-grained sediment with larger pieces of rocks suspended in it upon lithification is a conglomerate. The fine-grained interstitial part is called the matrix, and the large pieces suspended in it are called clasts. Clasts can range from gravel- to boulder-size. These are technical terms used by sedimentologists.
It is tempting to refer to these fragments as xenoliths but as that word has a very specific meaning in igneous petrology, it is best to avoid it to remove any confusion.
The following is multiple choice question (with options) to answer.
What are the two main types of sedimentary rocks? | [
"clastic and chemical",
"basalt and dolomite",
"sandstone and shale",
"shale and limestone"
] | A | There are two main types of sedimentary rocks: clastic and chemical. Clastic rocks are made of sediments, which are sometimes called clasts. Creating rocks from sediments is called lithification . Chemicals precipitate from liquid to form chemical sedimentary rocks. |
SciQ | SciQ-517 | electromagnetism, waves, laser, maxwell-equations, interference
Title: Is there a reflection when light destrucively interferes on a surface? Imagine the following setup:
I have a coherent single frequency electromagnetic wave (laser beam) that is imaged on a surface. It is reflected onto a detector (photodiode). I can easily take measurements there.
The question is: What happens when there is a second wave with similar, but not identical frequency, traveling the same path? There will be constructive and destructive interference along the propagating path. If I place the reflecting surface at a position, where it happens to interfere destructive, the electric field strength is zero on the surface.
I imagine, there is still an electric field composed of both beams. However, the physical interactions that lead to reflection or scattering are based on electric field which is zero at the interface.
Can I still measure the reflected light as both beams independently will have energy? What happens if I filter one of the frequencies after the reflection happened (assuming there is reflection)? Is there a difference between a reflecting and scattering surface?
Many thanks! Interference doesn't destroy energy. The energy in the incoming like will go somewhere. This means that if destructive interference produces no or less light in one place, it produces more light through constructive interference in another.
Suppose you have monochromatic light at normal incidence on a plate of glass with a single layer antireflection coating. Without the coating a small amount is reflected.
With the coating, some light reflects from the top surface of the coating and some from the bottom surface. The thickness of the coating has been arranged so that the extra distance traveled to the bottom surface and back is $1/2$ wavelength. This means destructive interference will complete cancel the reflected wave. It also means all the light will be transmitted into the glass.
In reality it is more complex. Multiple reflections must be accounted for, there can be different phase shifts on reflection at the bottom and top, and there can be multiple layers.
The following is multiple choice question (with options) to answer.
Light waves which interfere with themselves after interaction with a small aperture or target are said to what? | [
"adduce",
"refract",
"reflect",
"diffract"
] | D | Waves are characterized by their ability to constructively and destructively interfere . Light waves which interfere with themselves after interaction with a small aperture or target are said to diffract . |
SciQ | SciQ-518 | kmph. com/2016/01/01/speed-distance-timeVideos, worksheets, 5-a-day and much more. If a car traveled 50 miles over the course of one hour then its average speed will be 50 mph. Distance, Time and Speed Word Problems | GMAT GRE Maths. Exercise: Problems on Speed Time and Distance. org/time-speed-distanceTime, Speed and Distance (popularly known as TSD) is an important topic for written round of placements for any company. sg//sol_04_distance_speed_and_time. Let the time taken to cover the distance downstream = t hrs. Distance Time Speed. Time is entered in minutes, speed in knots and distance in nautical miles (the same formula will work for statute miles and kilometres). Time = Distance / speed = 20/4 = 5 hours. Speed, Time, and Distance Worksheet. Equations: Acccceelleerraattiioonn = Final speed–Initial TTiimme = Final Speed–Initial Time Acceleration. When dealing with distance, rate and time, we always want to remember the nifty little formula, D = R x T, in which D stands for the distance, R stands for the rate (or speed), and T stands for the time. b. Acceleration – change in velocity over time. 4 Calculate speed, distance, and time I . Distance (D) = Speed (S) × Time (T) X kmph = X × 5/18 m/s X m/s = X × 18/5 kmph. He drives 150 meters in 18 seconds. Distance (D) = Speed (S) × Time (T) X kmph = X × 5/18 m/s X m/s = X × 18/5 kmph. Aptitude Reasoning TRAINS DISTANCE SPEED TIME QUANTITATIVE APTITUDE . We define speed as distance divided by time. A train travels at a speed of 30mph and travel a distance of 240 miles. It can cross a pole in 10 seconds. The speeds are indicated in the rate column. Toon Train is traveling at the speed of 10 m/s at the top of a hill. If you run around the house randomly, and then end up back where you started, moving a total of 44 meters, what is your distance? Average speed for the entire trip is going to be equal to the total
The following is multiple choice question (with options) to answer.
Distance traveled divided by time yields what measurement, which is another word used to describe the speed of a chemical reaction? | [
"flow",
"rate",
"displacement",
"acceleration"
] | B | Chemists need to be concerned with the rates at which chemical reactions occur. Rate is another word for speed. If a sprinter takes 11.0 s to run a 100 m dash, his rate or speed is given by the distance traveled divided by the time. |
SciQ | SciQ-519 | aqueous-solution, analytical-chemistry, precipitation
Title: Magnesium vs calcium vs barium ions from these 3 tests How do I pick up the difference between barium, calcium, and magnesium ions? I had to do a quantitative analysis practical exam: I was given an aqueous solution of a salt, and when adding separately dilute sulphuric acid, magnesium chloride, and sodium carbonate to the solution, a white precipitate formed in each tube. The notes say that all three ions make insoluble precipitates, so I don’t know how to get the difference. The unfortunate thing is that salts of these ions are white and can't be differentiated by just looking. But you can take solubility to your advantage.
The solubility of the sulfates of alkaline earth metal decreases down the group. So, you can form their sulfates and differentiate based on their solubility.
\begin{array}{c|c}
\mathbf{Salt} & \mathbf{Solubility~at~r.t.} & \mathbf{Inference}\\\hline
\text{Magnesium sulfate} & \text{$\ce{35.1 g/100 ml}$} & \text{Very Soluble} \\
\text{Calcium sulfate} & \text{$\ce{0.26 g/100ml}$} & \text{$\ce{Slightly Soluble}$}\\
\text{Strontium sulfate} & \text{$\ce{97 mg/l}$} & \text{$\ce{Almost Insoluble but not negligible}$}\\
\text{Barium sulfate} & \text{$\ce{2.5 mg/l}$}& \text{Insoluble}\end{array}
You can make oxalates of ions and then dissolve in hot acetic acid. Barium oxalate is readily dissolved in acetic acid while calcium and magnesium oxalate are practically insoluble in acetic acid (calcium and magnesium oxalates can still be separated as described here)
The following is multiple choice question (with options) to answer.
Beryllium, magnesium, calcium, strontium, and barium are classified as what type of metals? | [
"alkaline aligned metals",
"alkaline support metals",
"acid earth metals",
"alkaline earth metals"
] | D | The alkaline earth metals include beryllium, magnesium, calcium, strontium, and barium. Strontium and barium react with air and must be stored in oil. |
SciQ | SciQ-520 | biochemistry, entomology
Title: How do ants follow each other? I was observing ants in my house.They all were going in a straight line and also some of the ants were coming back through the the same line.
I took some water and rubbed the line with my finger, then the ants were not able to follow each other. Looks like they were confused.
My assumption is that they may had secreted some chemical .
Am I right ?
If yes, then which chemical is that and how it is secreted? The chemical we are talking about here is called pheromone, trail pheromone to be specific.
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individuals.1
Pheromones are of mainly 9 types (13 exactly, but 4 not so common) which are:
Aggregation pheromones
Alarm pheromones
Epideictic pheromones
Releaser pheromones
Signal pheromones
Primer pheromones
Territorial pheromones
Trail pheromones
Sex pheromones
Nasonov pheromones
Royal pheromones
Calming pheromones
Necromones2
Ants, and many other animals, use trail pheromones to mark their trail as a guide for others in their gang. Other ants, catching the signal of trail pheromone, follow the way it goes and reach their gang leader. Trail pheromones are volatile compounds, so it is not very likely that you would see ants following the exactly same path tomorrow or a week later. All ants release trail pheromones, so as long as ants are going through that path, the trail signal will keep getting stronger and will also tell lost ants "Hey, bro! We are going this way. Don't you want to join us?" See, for example, here3:
The following is multiple choice question (with options) to answer.
Common among mammals and insects, pheromones are often related to what type of behavior? | [
"aggressive",
"cardiac",
"immune",
"reproductive"
] | D | |
SciQ | SciQ-521 | condensed-matter, nuclear-physics, neutron-stars, white-dwarfs
Title: Free decompression of white dwarf or neutron star matter -- what do we end up with? (Possibly related: What would happen to a teaspoon of neutron star material if released on Earth?)
Suppose that we somehow produced or obtained a small amount of neutron star matter or white dwarf matter compressed to nearly the degeneracy limit and released it into free space uncompressed by gravitational fields or surrounding matter.
That it would explode with nuclear force is well known. What I ask, is, how precisely is it known what it would explode into, and what that would be? Would you get exclusively light nucleii, or heavier ones? If it is just neutronic matter - i.e. mostly neutrons with a small fraction of protons and electrons to maintain "$\beta$ equilibrium", then to first order, all that would happen is the particles would expand very quickly (relativistically) to low densities and the free neutrons would decay into protons, electrons and anti-neutrinos over the course of an hour.
A slow expansion would be more interesting, because you would in a sense be working your way up through density regimes occupied by the neutron star crust. If you could arrange such an expansion, whereby nuclear statistical equilibrium was maintained, then you start with nuclear pasta, move on to very heavy, very neutron-rich nuclei, then lighter (but still $A>100$) neutron-rich nuclei and finally end up with "normal" iron-peak nuclei. At the same time, as the material become less neutron-rich it must create lots of anti-neutrinos and electrons.
An intermediate case is represented by colliding neutron stars. There you have a distinctly non-equilibrium process where material is rich in free-neutrons and there are lots of seed heavy nuclei that can be built into heavy neutron-rich nuclei through r-process neutron capture.
The following is multiple choice question (with options) to answer.
Neutron stars are the corpses of left over what? | [
"stellar explosions",
"planet explosions",
"supernova explosions",
"gravitational explosions"
] | C | Neutron stars are the corpses of stars left over after supernova explosions. They are the size of a small city, but can spin several times per second. (Try to imagine this in your head. ) Consider a neutron star of radius 10 km that spins with a period of 0.8 seconds. Imagine a person is standing at the equator of this neutron star. Calculate the centripetal acceleration of this person and compare it to the acceleration due to gravity on Earth. |
SciQ | SciQ-522 | life, replication
Title: What is the name of the smallest self-replicating thing? Some time last year, I found an article on Wikipedia about the smallest something to be able to reproduce.
I don't remember exactly what it was, but I am fairly certain that after the initial discovery another of the previous organism (this one slightly smaller) was discovered.
I think that the smallest something might have been the smallest self-replicating protein, or smallest self-replicating molecule, or something like that.
It was not mentioned in this thread: Which organism has the smallest genome length?
It had a strange, stand-out name and I believe it was discovered in the 90s. You're probably thinking of the Spiegelman Monster. It was actually discovered in 1965, but it was discovered that it became shorter over time in 1997.
It also wasn't included in that thread, and it has a strange name.
http://en.wikipedia.org/wiki/Spiegelman_Monster
The following is multiple choice question (with options) to answer.
In recent years, however, researchers have discovered that microsporidia actually have tiny organelles derived from what? | [
"proteins",
"mitochondria",
"plasma",
"carbohydrates"
] | B | |
SciQ | SciQ-523 | acid-base, ph
Title: When an acid is added to water, why does the hydroxide ion concentration decrease? At equilibrium in pure water, we have
$$\ce{[H_3O+][OH-]} = 10^{-14}$$
Since $\ce{H3O+}$ and $\ce{OH-}$ ions are produced in pairs, we may conclude
$$\ce{[H_3O+]}=\ce{[OH-]} = 10^{-7}$$
So far so good. But shouldn't things change when we introduce a new substance into water ? I mean why does the first equation above hold no matter what ?
Also when I introduce $\ce{H2SO4}$ into the water, it doesn't just give a $\ce{H+}$ ion, it also gives $\ce{HSO4-}$ ion. Shouldn't these new negative ions change the behavior of water? Why does my textbook never talk about these new negative ions? Help appreciated. Thanks! Your question title is a bit misleading, but i try to answer all the small questions in you question text.
The equation $[\ce{H3O^+}][\ce{OH^-}]$ holds true, if other parameters (like T) are constant. Keep in mind, the power of hydroxide decreases, whereas the power oxonium increases. Being equal in the equation and considering how logs are being computed,bthey will add up to 14 every time.
Regarding the introduced $\ce{HSO4^-}$, they don't contribute to pH by definition. On the other hand, they alter the behaviour of the water, by increasing its conductivity.
Your textbooks don't talk about the other negative ions in acidic or alkaline solutions, because they don't directly contribute to the values of pH or pOH by definition. In cases of polyacids like sulfuric acid, ions like $\ce{HSO4^-}$ are accounted for by using a different formula to calculate the actual pH value, but the "not-hydrogen" part is largely irrelevant in the behaviour of the solution itself.
The following is multiple choice question (with options) to answer.
The negative logarithm of the hydroxide-ion concentration of a solution is called? | [
"the hop",
"the piel",
"the hil",
"the poh"
] | D | As with the hydrogen-ion concentration, the concentration of the hydroxide ion can be expressed logarithmically by the pOH. The pOH of a solution is the negative logarithm of the hydroxide-ion concentration. |
SciQ | SciQ-524 | dna, zoology, radiation, entomology
1.-3. Therefore, the only sensitive part of insects is the intestinal epithelium which gets renewed on a regular basis (similar to that of humans, also a known target of radiation), but...
Insects (and generally the arthropodes) are known to have exoskeleton. This potentially serves as a good "armor" for vulnerable intestine cells, filtering out the most heavy particles (like alpha- and in some respect also the beta-particles).
EDIT: This seems not to be real protection, see the discussion in comments.
Therefore it is not a surprise that insects generally show much higher resistance against radiation.
EDIT:
As it was correctly added in the comments, there are also gamets, that are most sensitive to radiation (because they bear only the half of the normal genetic information and cannot repair mutations). Even though the lesions in gamets do not lead to immediate death, the potential sterility can easily cause the extinction.
However, cockroaches (and insects generally) are known to be r-animals, meaning that they favor the quantity (r) over quality (K) of their off-spring. This strategy is optimal when dealing with radiation-induced changes in gametes: the high number of offsprings compensates for the genetic imperfections in gametes.
[a] -- meaning that is has secreted peptides in their hemolymph that protect them
[b] -- there are phagocytes, somewhat similar to tissue magrophages in humans, but the rest of the cell chains in immune response in vertrebrates, like T- and B-cells, are completely missing. Those are responsible for the mediation and amplification of the immune response in vertebrates and are the cells that are most susceptible to radiation damage.
The following is multiple choice question (with options) to answer.
What is the greatest contribution of arthropods to human food supply? | [
"reproduction",
"pollination",
"vegetation",
"hibernation"
] | B | The intentional cultivation of arthropods and other small animals for human food, referred to as minilivestock, is now emerging in animal husbandry as an ecologically sound concept. However, the greatest contribution of arthropods to human food supply is by pollination. Three-fourths of the world’s flowering plants and about 35% of the world’s food crops depend on animal pollinators to reproduce and increase crop yields. More than 3,500 species of native bees pollinate crops. Some scientists estimate that one out of every three bites of food we eat exists because of animal pollinators, including birds and bats and arthropods like bees, butterflies and moths, and beetles and other insects. |
SciQ | SciQ-525 | radiation
Now, this paragraph is particularly devious. El Nino's tend to warm the earth, La Nina's cool it. The effect is temporary and not huge, but enough to cause yearly variation. A strong El Nino drove the big spike in global temperature for 1998 and we're in an El Nino now (edited my answer, since 2014 they've been talking about entering an El Nino, I gather it's officially started now).
We had more La Nina years than El Nino 2006-2013 with the only small El Nino coinciding with 2010, which set records for temperature. A lot of the hiatus in warming that is often talked about is related to there being only 1 small El Nino over 7 years.
Predicting 2017 as the time when the cooling will "begin" is devious because that could be around the time the El Nino has ended and the oceans could switch back to a La Nina (which usually follows El Nino). This will create a temporary cooling for a year or two, which he, no doubt, will take credit for if it happens. Now, he also predicts 2021 which could go either way and he gives an amount, but that doesn't change the fact that he's making a prediction and hoping the El Nino of 2015 will end and make it prediction look good.
Real global warming or cooling can't be measured in 1 year anyway, unless, maybe, if it's ocean current and the occasional mega-volcano adjusted - then, maybe you can get some measure of warming/cooling based on one year, but it's still only one year. That's a really really short period to make any predictions on and not something I'd trust very far at all.
and on the "scientists have predicted a mini ice age in 2030", that's not actually true. There was a study on sun-spots and they predicted that we could see a sun-spot low period around 2030, perhaps similar to the Maunder Minimum that may have caused the mini ice age, but the scientists who predicted that were very clear that they were not predicting a new mini ice age, they said the effect would be smaller than the effect of CO2.
Here's the mini ice age prediction, which a few people made (but not the scientists who did the research).
Here's an article that explains why it isn't true.
The following is multiple choice question (with options) to answer.
What kind of weather change do la nina years usually bring? | [
"heat",
"drought",
"moisture",
"Mass amounts of snow"
] | B | El Niño and La Niña bring about dramatic changes in climate for a year or two. In some locations, one brings rain and the other brings drought. In California, for example, El Niño years are full of snow and rain. La Niña years tend toward drought. These variations can bring tremendous changes to living creatures. Humans are also affected; for example, erosion from storms may be very high some years. |
SciQ | SciQ-526 | newtonian-mechanics, thermodynamics, energy-conservation, potential-energy, dissipation
Title: Potential, Kinetic, Thermal Energy? When things move, potential energy turns into Kinetic energy, right? Then how does Kinetic energy convert to thermal energy? "Thermal energy" is just kinetic energy.
When people talk about temperature, a typically good (but largely classical) idea is that tenperature is a measure of the average kinetic energy of the particles. When people talk about an increase or decrease of thermal energy, they usually mean something has gotten hotter or colder. This suggests that thermal energy is really just kinetic energy.
The following is multiple choice question (with options) to answer.
In physics, _______ is defined as the average kinetic energy of the particles in an object? | [
"temperature",
"potential energy",
"heat",
"climate"
] | A | No doubt you already have a good idea of what temperature is. You might define it as how hot or cold something feels. In physics, temperature is defined as the average kinetic energy of the particles in an object. When particles move more quickly, temperature is higher and an object feels warmer. When particles move more slowly, temperature is lower and an object feels cooler. |
SciQ | SciQ-527 | bioinformatics, gene-expression, rna-sequencing
Title: Where to find a list of genes coding for protein in human I have raw read counts extracted by htseq from STAR alignment
I have both data with both Ensembl IDs and gene symbols, but I need only a latest list of protein coding genes in human; I googled but I did not find
Any suggestion please? Submit your ensembl IDs to biomart, and get the "gene biotype". "protein-coding" is one of the options there.
The following is multiple choice question (with options) to answer.
What are proteins encoded by? | [
"genes",
"DNA",
"codons",
"RNA"
] | A | |
SciQ | SciQ-528 | cellular-respiration, fermentation
Fermentation: An ATP-generating process in which organic compounds act as both donors and acceptors of electrons. Fermentation can take place in the absence of O2. Discovered by Louis Pasteur, who described fermentation as “la vie sans l’air” (“life without air”).
So the biochemical lawyers have produced a definition that very few readers will be able to take in at first sight. What is this business about electron donors and acceptors? Well what it means in relation to the fermentation process in which lactic acid is produced (note my legalistic choice of words) is that one organic compound is reduced (glyceraldehyde 3-phosphate) — by NAD+ — and one organic compound is oxidized (pyruvate) — by NADH. And as the production of ATP is included in the definition this means that Berg et al. include glycolysis in this definition of fermentation.
…except that on the same page there is the following statement:
pyruvate is converted, or fermented, into lactic acid in lactic acid fermentation or into ethanol in alcoholic fermentation
So here it seems that the word is being used for the conversion of pyruvate to lactate or ethanol, i.e. it excludes glycolysis.
Pasteur managed to talk about fermentation without being aware of glycolysis or ATP, and it is clear to me that you can write whatever carefully phrased definitions you like, but people are going to continue to use venerable terms like fermentation in whatever way seems natual to them.
The following is multiple choice question (with options) to answer.
In alcoholic fermentation , which acid changes to alcohol and carbon dioxide? | [
"lipoic",
"chloride",
"pyruvic",
"rain"
] | C | In alcoholic fermentation , pyruvic acid changes to alcohol and carbon dioxide. This is shown in Figure below . NAD + also forms from NADH, allowing glycolysis to continue making ATP. This type of fermentation is carried out by yeasts and some bacteria. It is used to make bread, wine, and biofuels. |
SciQ | SciQ-529 | species-identification
Title: What species is this worm? I was at the park lying on the grass and its the third time I have seen them, I used to think they were parasites when I was like 7. It is the very small brown worm on the green leaf. It moves by squiggling. It comes in different colors but same size.
http://postimg.org/image/ea3x2nw95/
http://postimg.org/image/zfawh9pr1/ For me it looks like an inchworms which are the larvae of geometer moth or Geometridae.
By your picture it is almost impossible to see of which type it is.
I took picture of one in Switzerland (but likely not the same as yours).
Full resolution here: https://flic.kr/p/utFsiU
The following is multiple choice question (with options) to answer.
What is another term for scale worms? | [
"spirogyra",
"wormidanopis",
"halkieria",
"trichina"
] | C | Halkieria, or scale worms, are an example of a fossil life from the Cambrian. |
SciQ | SciQ-530 | meteorology, wind, remote-sensing
Title: How do weather services measure wind I'm curious to know where commercial weather services like the Weather Channel and Weather Underground get their wind speed and direction measurements, to produce maps like this one (http://www.wunderground.com/maps/us/WindSpeed.html?MR=1):
A model is probably used, but how does the station measure or acquire real measurements to assimilate the data into the model? Is it by regularly placed anemometers on the ground? Or data measured by satellites? Weather stations and airports around the world almost always include an anemometer. Because of ground friction, the wind speed varies with height, so instrumental deployment is set at a standard height of 10 metres in open rural areas. This may require some adjustment in urban or forested areas. In fact, measuring accurate wind speeds above tree canopies is particularly difficult. There is quite an art in correctly positioning the instrumentation.
Thousands of such anemometers and direction sensors are deployed on nearly every continent, and the results are part of the routine reporting. Such reporting may be every 24, 12, or 6 hours, or even shorter periods down to and including 'continuous'. Then comes the number crunching, in which the strength and direction is gridded and plotted on what appears to be a uniform distribution of points. In reality it is very far from a uniform distribution.
With the introduction of increasing numbers of wind farms higher elevation wind measurements are becoming more important.
The following is multiple choice question (with options) to answer.
What type of device do scientist use to determine wind speed? | [
"barometer",
"anemometer",
"dynamometer",
"photometer"
] | B | |
SciQ | SciQ-531 | solar-system, coordinate, stellar-astrophysics
Can you see either in the sky now. Do they look the same? If yes you are in the same hemisphere you normally live in. If they look strange - upside down. You are in the hemisphere opposite to where you normally live.
You've just spent the rest of the night looking at the sky and the Sun is up. Observe the path Sun, in the sky, during the course of the day. If it is low, it winter. If it is high, it's summer. The daytime temperature will also confirm this.
The following is multiple choice question (with options) to answer.
Which constellation looks like a rectangle high in winter's south-southeastern sky? | [
"orion",
"Andromeda",
"Apus",
"Caelum"
] | A | The star constellation “Orion, The Hunter”. Orion is one of the most beautiful of all constellations, and one of the easiest to find. It looks like a large (slightly twisted) rectangle high in winter's south-southeastern sky. Two of the brightest stars in the evening sky lie at opposite corners of the rectangle: bright orange-red Betelgeuse at the northeastern corner (upper left in the photo) and even brighter Rigel at the southwest (lower right in the photo). Betelgeuse is at least 300 times the Sun's diameter, and perhaps much more. It puts out about 100,000 times more energy than the Sun does. When Betelgeuse dies, it will create a fireball that will briefly outshine billions of normal stars. Betelgeuse is a red giant and Rigel is a blue giant. |
SciQ | SciQ-532 | species-identification, entomology
Title: Big Bug from Peru I'd like to have a name for this guy. There were 5 or 6 of them zipping around the flower bed on the coast of Peru about 120 kms south of Lima. That is a hawkmoth, probably Hyles annei (Guerin-Meneville, 1839). It is one of a number of moth species commonly called "hummingbird," "sphinx," or "hawk" moths in the family Sphingidae.
Beautiful, isn't it? :)
edit - sorry, I originally misidentified this as Hyles lineata - the pattern is slightly different.
The following is multiple choice question (with options) to answer.
What mammal is often a pollinator of nocturnal flowers? | [
"bat",
"rabbits",
"sunbirds",
"hummingbirds"
] | A | Pollination by Bats In the tropics and deserts, bats are often the pollinators of nocturnal flowers such as agave, guava, and morning glory. The flowers are usually large and white or pale-colored; thus, they can be distinguished from the dark surroundings at night. The flowers have a strong, fruity, or musky fragrance and produce large amounts of nectar. They are naturally large and wide-mouthed to accommodate the head of the bat. As the bats seek the nectar, their faces and heads become covered with pollen, which is then transferred to the next flower. |
SciQ | SciQ-533 | dna, virology, human-genetics, human-genome
Title: What is the contribution of viruses to the evolution of mankind? I'm interested in horizontal gene transfer in bacteria, viruses, and organisms such as Bdelloid Rotifers. I've just read in Carl Zimmer's 'A Planet of Viruses' the following passage:
As a host cell manufactures new viruses, it sometimes accidentally adds some of its own genes to them. The new viruses carry the genes of their hosts as they swim through the ocean, and they insert them, along with their own, into the genomes of their new hosts. By one estimate, viruses transfer a trillion trillion genes between host genomes in the ocean every year.
It's interesting to consider the scale of DNA-swapping that has occurred given the frequency by which it happens and the evolutionary timescale.
Are there any examples of genes in the human genome that we know were deposited by viruses that would have given an evolving human a physical/mental advantage? Where did they come from? What benefit did they provide?
I'm interested in genetic additions from non-human-ancestor species, rather than the transfer of genes that occurred as mutations from other humans. The processes that control the germline of metazoans (multicellular animals) are highly regulated compared to single cell bacteria and eukaryotes as well as plants.
At this point there are no clear stories of gene transfer into a complex animal, though there are some for plants:
"animals and fungi seem to be largely unaffected, with a few exceptions, while lateral gene transfer frequently occurs in protists with phagotrophic lifestyles, possibly with rates comparable to prokaryotic organisms."
Bacteria fungi and plants are more permissive and more susceptible to gene transfer and it probably is more important to their evolutionary path.
Its been estimated that as much as eight percent of the human genome has been affected by viral integration. But viral genomes are highly selected against carrying non essential material - other genes rarely come along for the ride it seems. What is probably more influential is that viral insertions could participate in rewiring the regulatory network of animal cells, not adding genes, but modifying the conditions under which they are active.
The following is multiple choice question (with options) to answer.
What can reproduce by infecting the cell of a living host? | [
"virus",
"carcinogens",
"bacteria",
"mucus"
] | A | A virus cannot reproduce on its own. However, a virus can reproduce by infecting the cell of a living host. Inside the host cell, the virus uses the cell’s structures, materials, and energy to make copies of itself. |
SciQ | SciQ-534 | atoms, phase
Title: What is the physical state of a single atom? Can a single atom on its own be either a solid, liquid, or a gas? Or is it none of them? This answer has been written so it hopefully can be understood by people that do not have a degree. If something is not correct, let me know, but be aware that throwing around fancy words will not help anyone understanding this any better. Consider the other posts here concerning liquids and solids, I don't want to be redundant and repeat what has been said already.
The answer is a bit complicated. One would intuitively say no, but that doesn't tell the whole story.
Take the interstellar medium. We have about 1 atom per cm³ in there and it is called a "gas". Now that's what I would call an isolated atom in the gas phase.
An atom is an object that belongs into the realms of quantum mechanics. A solid, liquid or gas is something that belongs into our classical world. If you zoom in close enough, that means if we look at a problem microscopically, words like "solid" or "liquid" no longer make sense. If you now begin to zoom out, the quantum effects vanish. This is sometimes called quantum decoherence and we enter the world of classical physics where solids and and liquids exist again.
So I would argue it all depends on how closely you look at the problem. Isolated atoms in a large volume? A gas if you ask me. But if you have to zoom in to talk about an individual atom within a larger compound consisting of many more atoms, let's say one atom within a piece of iron, you no longer can say that this single atom is "solid".
Think of it like this:
Can a single person have a political system?
The following is multiple choice question (with options) to answer.
The theory that establishes the concepts of atoms and how they compose matter is called what? | [
"unified matter theory",
"contemporary atomic theory",
"modern particle theory",
"modern atomic theory"
] | D | The modern atomic theory establishes the concepts of atoms and how they compose matter. |
SciQ | SciQ-535 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
How does the heart transport blood? | [
"muscles",
"blood pellets",
"nerves",
"blood vessels"
] | D | A screw is an inclined plane wrapped around a cylinder. When on a screw, inclined planes are called threads, which can be seen in the image above. The mechanical advantage of a screw increases with the density of the threads. The calculations to determine the IMA for a screw involve the circumference of the head of the screw and the thread width. When the screw is turned completely around one time, the screw penetrates by one thread width. So, if the circumference of the head of a screw is 3.0 cm and the thread width is 0.60 cm, then the IMA would be calculated by. |
SciQ | SciQ-536 | human-biology, genetics, sex-chromosome
Title: Can a Turner syndrome patient develop male characteristics artificially? From an answer to the question Can stem cells from male convert to cells of female-only organs, and vice versa?
Y chromosome is the sex determining chromosome with SRY gene that determines testes development. Absence of the Y chromosome leads to female development by default. That is why XX forms women and there are people with only one X chromosome which are women. (Turner's syndrome)
and Why are mice with a single X chromosome and no Y chromosome males?
The Y has only a few genes (less than all other chromosomes), but it has genes that occur only on the Y. One of these in particular, the one called SRY, is the main gene that causes the individual to develop male characteristics. It mostly does its job indirectly, by making a protein that affects many other genes on other chromosomes that in turn do the work of building and maintaining the male form... they managed to cause mice without a Y chromosome to develop many male characteristics. They did this by faking one or two of the actions of SRY. One of the many actions of SRY is to turn on a gene called Sox9 (which is on a non-Y chromosome), and it turns out Sox9 causes most of the things that make the male mouse form.
My question: Is it possible to make a Turner syndrome patient develop male characteristics by artificial stimulation? Has it ever been tried? After a lot of research, I've finally found an answer.
In the case of humans, it is practically impossible. See this article from wikipedia:
During gestation, the cells of the primordial gonad that lie along the urogenital ridge are in a bipotential state, meaning they possess the ability to become either male cells (Sertoli and Leydig cells) or female cells (follicle cells and Theca cells)...Once proper SOX9 levels are reached, the bipotential cells of the gonad begin to differentiate into Sertoli cells.
The following is multiple choice question (with options) to answer.
The gender of a baby is determined by what special pair of chromosomes? | [
"reflection chromosomes",
"sex chromosomes",
"diploid chromosomes",
"sister chromatids"
] | B | One of the exciting things about expecting a child is wondering if the baby will be a boy or a girl. There are many superstitions about how one might influence or predict the outcome. But what really determines if a baby is male or female? We now know that the gender of a baby is determined by a special pair of chromosomes known as the sex chromosomes. |
SciQ | SciQ-537 | homework-and-exercises, radiation, radioactivity
$$ \frac{\mathrm{d}N(t)}{\mathrm{d}t} = -\kappa\, N(t) $$ and thus
$$ \kappa = \frac{\mathrm{d} N_{\mathrm{D}}(t)}{\mathrm{d}t} /N(t) \quad . \tag{2}$$
We can see that $\kappa$ is the decay rate (activity) relative to the existent population $N(t)$.
Note that this is basically the definition given in your book. Since by definition $\kappa$ is constant, the right-hand side cannot depend on $t$ and we are free to evaluate it at $t=t_0$.
The following is multiple choice question (with options) to answer.
What does the activity of an organism depend on the totality of? | [
"chemical attraction",
"adaptations",
"interdependence",
"independent cells"
] | D | the activity of an organism depends on the total activity of independent cells,. |
SciQ | SciQ-538 | thermodynamics, evaporation, gas, liquid-state
On the water surface, knowing the temperature, we can estimate the vapor pressure and vapor mixture fraction. Then there will be an diffusion process for the water vapor to move out and for the ambient air to move in. Because the water surface doesn't allow the air to further move, a circulation forms. When the water vapor moves out, the water vapor pressure drops, so more liquid water evaporates to fill up the loss of water vapor. The evaporation associates latent heat so water surface area temperature drops (you may see dew on the bowl wall). Then a heat transfer process starts which may initiate water circulation as well.
As this is complex, doing test might be a quick way to get the K value if you assume it is a constant, which is questionable.
The following is multiple choice question (with options) to answer.
What is solid water that forms when water vapor undergoes deposition? | [
"distillate",
"dew",
"frost",
"glacier"
] | C | Frost is solid water that forms when water vapor undergoes deposition. |
SciQ | SciQ-539 | meteorology, atmosphere, carbon, co2, rain
Bear in mind that this assumes an enormous rainfall intensity, 100% CO2 saturation of the water and equilibrium chemical dynamics. After the raindrops hit the ground at least half of it will immediately re-evaporate back into the air, leaving, at absolute most, about 3% of the atmospheric CO2 leached out of the atmosphere that will be available to react with the soil, rock or biosphere. Also consider that this is but one of several important processes affecting CO2 transience, such as photosynthesis, respiration, volcanism, industrial pollution, etc. So the CO2 estimates that you read about are average values. Advection and turbulent air mixing should ensure that the CO2 regains approximately normal concentration within an hour or two after rainfall.
The following is multiple choice question (with options) to answer.
What gets released into the atmosphere when fossil fuels are burned? | [
"hydrogen",
"oxygen",
"chemical dioxide",
"carbon dioxide"
] | D | Using fossil fuels and nuclear energy creates other problems as well. The burning of fossil fuels releases carbon dioxide into the atmosphere. This is one of the major greenhouse gases causing global climate change. Nuclear power creates another set of problems, including the disposal of radioactive waste. |
SciQ | SciQ-540 | newtonian-mechanics, fluid-statics, density, buoyancy
Title: Measure liquids density: hydrometer It is possible to measure liquids density with an hydrometer:
The following is multiple choice question (with options) to answer.
What is the term for the measure of a fluid's thickness? | [
"elasticity",
"friction",
"salinity",
"viscosity"
] | D | Characteristics of Blood When you think about blood, the first characteristic that probably comes to mind is its color. Blood that has just taken up oxygen in the lungs is bright red, and blood that has released oxygen in the tissues is a more dusky red. This is because hemoglobin is a pigment that changes color, depending upon the degree of oxygen saturation. Blood is viscous and somewhat sticky to the touch. It has a viscosity approximately five times greater than water. Viscosity is a measure of a fluid’s thickness or resistance to flow, and is influenced by the presence of the plasma proteins and formed elements within the blood. The viscosity of blood has a dramatic impact on blood pressure and flow. Consider the difference in flow between water and honey. The more viscous honey would demonstrate a greater resistance to flow than the less viscous water. The same principle applies to blood. The normal temperature of blood is slightly higher than normal body temperature—about 38 °C (or 100.4 °F), compared to 37 °C (or 98.6 °F) for an internal body temperature reading, although daily variations of 0.5 °C are normal. Although. |
SciQ | SciQ-541 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
Plant cells have structures that animal cells? | [
"drink",
"lack",
"eat",
"have"
] | B | Plant cells have structures that animal cells lack. What important process takes place in plant cells but not in animal cells that might explain their differences?. |
SciQ | SciQ-542 | environmental-protection, agriculture
Title: How much does the productivity of modern agriculture depend on Glyphosate? Glyphosate is the most important herbicide in agriculture by quantity. A committee of the European Union just recently voted against a ban of the substance, after much debate around possible negative effects on human health. I now see a lot of petitions popping up on social media, calling for an immediate ban. This got me wondering: if Glyphosate would be banned in the near future, say in the course of next year, what problems would arise for farmers? Are there viable alternative weed killers, and would productivity be significantly reduced without using one? Chemistry is not a bad thing; life depends on it. And just because a pesticide or herbicide is natural or synthetic has practically nothing to do with its toxicity. Many so-called natural or organic pesticides are many times more potent than widely-used synthetic ones, as this article mentions.As to whether or not Glyphosate is necessary, this article explains some of the economic impacts from an outright Glyphosate ban. Some of the effects include:...French research institute Arvalis suggested a ban would cost that country’s agriculture industry 976 million euros ($1.1 billion). And in Germany, the Kleffmann Group said restrictions could hurt barley and corn output—with profit margin shrinkage between 40 and 70 percent–as farmers start planting alternative, more profitable crops.
The following is multiple choice question (with options) to answer.
What reduces the need for pesticides and other toxic chemicals? | [
"pollen",
"helium",
"fungi",
"yeast"
] | C | Harmless fungi can be used to control pathogenic bacteria and insect pasts on crops. Fungi compete with bacteria for nutrients and space, and they parasitize insects that eat plants. Fungi reduce the need for pesticides and other toxic chemicals. |
SciQ | SciQ-543 | states-of-matter, matter
Title: What distinguishes the difference states of matter from solid to BEC and perhaps fermionic condensate? Is it something to do with the behavior of electrons? How many states are there either discovered or predicted? 無
'States of matter' is a question of taxonomy, not of reality, and moreover, it's a result of the conditions surrounding the matter, not its internal properties. Certain combinations of properties give us a hint towards calling something 'solid' or 'liquid', but in truth there are no lines, just a continuous spectrum, and under certain conditions, matter transitions seamlessly through all sorts of states, both mundane and exotic:
Behold: Jupiter
A perfect example of this is Jupiter. Composed primarily of hydrogen, this gas giant consists (conjecturally) of a core of high-temperature hydrogen ice, floating in liquid hydrogen, enveloped in hydrogen gas, moving through interplanetary medium composed of hydrogen plasma.
Except not really: Under these conditions, the classical notions of states of matter break down entirely: Between these states of matter there are no interfaces, just a gradual, continuous transition.
In other words: The distinctive line to separate one state from another you are after doesn't really exist.
The following is multiple choice question (with options) to answer.
Matter can be described with what two encompassing types of properties? | [
"color and distance",
"thermal and magnetic",
"velocity and energy",
"physical and chemical"
] | D | Matter can be described with both physical properties and chemical properties. |
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