source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-1744 | cell-biology, microbiology
Title: Are there any organisms that are made of more than one (~5-12) cell? Prokaryotes and eukaryotes are unicellular, made of one cell. Great. Eukaryotes are unicellular or multicellular. But the typical examples of multicellular eukaryotes we have are made of, often, trillions of cells, like us humans. Ants must still be made of many millions of cells. Are there known eukaryotes with very few cells that make them up? Like, 5, or something? Or maybe a dozen cells making up the whole organism in its fully developed state? There's Trichoplax adhaerens, a Placozoa, made of a few thousand cells. Then there is Dicyema japonicum, a simple mesozoan, made up of 9 to 41 cells. Arguably, the simplest multicellular organism is the algae Tetrabaena socialis, whose body consists of 4 cells. Then, there's the parasitic Myxozoa which have 7 cells.
The following is multiple choice question (with options) to answer.
Single-celled eukaryotes that share some traits with animals are also called? | [
"microorganisms",
"eukaryotes",
"prokaryotes",
"monomers"
] | B | Protozoa are single-celled eukaryotes that share some traits with animals. |
SciQ | SciQ-1745 | virus, antibiotics
Title: What are the positive effects of wrongful antibiotic use on a viral infection? I categorically accept that bacteria differ from viruses; so antibiotics DON'T help in viral infections. I also read this and this; so no need to explain this. I've read about the negative effects (eg exacerbation of antibiotic resistance); I ask only about the positive effects here, and NOT for reasons to exploit antibiotics for infections not due bacteria.
Yet I myself have witnessed that some people with viral infections feel better after wrongly taking antibiotics? and so asked about this first on Cognitive Sciences SE.
Initially, I suspected only some placebo effect, but this enlightened me on the side benefits of antibiotic consumption for a viral infection and motivated this question, now that my original question on psychology has revealed the relevance of biology. There are indeed antibiotics which have immunomodulatory side-effects, these are mostly from the class of macrolide antibiotics (erythromycin, clarithromycin, roxithromycin, azithromycin) and to some degree from the tetracyclines. Beta-lactam antibiotics (as Penicillin or Ampicillin) have not been shown to be immunomodulatory, but they are among the most commonly used. See reference 1 for more details.
The biggest effect has been shown on pulmonary diseases such as cystic fibrosis or diffuse panbrochiolitis (see reference 2).
Although the exact mechanism of action is not known, Macrolides are know to downregulate the inflammatory cascade and that the reduce the strong cytokine expression of some viral infections. However, these regulatory effects are relatively weak if you compare them to the anti-inflammatory properties of corticosteroids. So the question here is if the advantages are really sufficient compared to the problems, which an unnecessary use of antibiotics may cause. See reference 3 and the references in the paper for more details here.
Antibiotics may be useful to fight bacterial secondary or superinfections which accompany a virus infection.
References:
Immunomodulatory Properties of Antibiotics
Macrolide activities beyond their antimicrobial effects: macrolides
in diffuse panbronchiolitis and cystic fibrosis
Macrolide Therapy in Respiratory Viral Infections
The following is multiple choice question (with options) to answer.
Antibiotics can be used to fight what, in general? | [
"bacteria",
"pathogens",
"viruses",
"fever"
] | A | In summary, society is facing an antibiotic crisis. Some scientists believe that after years of being protected from bacterial infections by antibiotics, we may be returning to a time in which a simple bacterial infection could again devastate the human population. Researchers are working on developing new antibiotics, but few are in the drug development pipeline, and it takes many years to generate an effective and approved drug. Naimi, T. , LeDell, K. , Como-Sabetti, K. , et al. , “Comparison of community- and health care-associated methicillin-resistant Staphylococcus aureus infection,” JAMA 290 (2003): 2976-2984, doi: 10.1001/jama.290.22.2976. |
SciQ | SciQ-1746 | 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.
An organism that carries pathogens from one individual to another is called what? | [
"vector",
"germ cell",
"virus",
"host"
] | A | Still other pathogens are spread by vectors. A vector is an organism that carries pathogens from one person or animal to another. Most vectors are insects such as ticks or mosquitoes. They pick up pathogens when they bite an infected animal and then transmit the pathogens to the next animal they bite. Ticks spread the bacteria that cause Lyme disease. Mosquitoes spread the protozoa that cause malaria. |
SciQ | SciQ-1747 | biochemistry, skin, pigmentation
The picture shows that the stain occurs on both fingernails and skin. The most abundant protein that's common to those two tissues is keratin. Like other examples of protein staining, the mechanism is complicated and poorly understood, but the basic outline is that parts of keratin are greasy (the non-polar amino acids) that associate with other greasy things. (EDIT: AliceD's answer also depicts the well-known staining of teeth, which are not keratinized, showing that the staining mechanism is likely a nonspecific adsorption of greasy things onto surfaces.)
The stain can be fixed through the involvement of free radicals and other reactive species in cigarette smoke, like formaldehyde. In this sense, reactive oxygen species are active participants. I don't think oxygen deprivation plays a role here. I don't think this can be described as a melanosis, as the skin isn't producing melanin in response to smoking but is simply being coated in tar.
Even if the stain was completely fixed, the coloring would fade away as the exterior skin cells are sloughed off, consistent with normal skin physiology. This is the explanation for the fading of any stained epidermis. The persistence of tar stains on teeth (which do not exfoliate) further evinces that the stain is removed through the replacement of skin cells.
The following is multiple choice question (with options) to answer.
What fills the epidermal cells that make up fingernails and toenails? | [
"keratin",
"amino acids",
"cellulose",
"chromatin"
] | A | Fingernails and toenails consist of specialized epidermal cells that are filled with keratin . The keratin makes them tough and hard, which is important for the functions they serve. Fingernails prevent injury by forming protective plates over the ends of the fingers. They also enhance sensation by acting as a counterforce to the sensitive fingertips when objects are handled. Nails are similar to claws in other animals. They cover the tips of fingers and toes. Fingernails and toenails both grow from nail beds. As the nail grows, more cells are added at the nail bed. Older cells get pushed away from the nail bed and the nail grows longer. There are no nerve endings in the nail. Otherwise cutting your nails would hurt a lot!. |
SciQ | SciQ-1748 | parasitology
Title: Tapeworms and their effect on humans I've read that some people in some countries actually use tapeworms as a form of losing weight. What are the dangers to these people? I haven't really found much on this topic (besides popular sites) but I can summarize it here:
There are quite some tapeworms (or cestoda), I found numbers of up to 3500 species. They attach to the intestinal wall of the humans and then start to take up predigested food through their skin. With that, they reduce food from their host and start to grow, some get as long as 15 meters!
Some of the worms seem to be relatively harmless (besides stealing food), but this is more true for the first world. In poor countries, where there is not enough food, tapeworms can cause severe malnutrition.
Some tapeworms can migrate into the blood stream and from there into other tissues or organs like muscles, eye and brain. There they can cause cysts which can lead to organ failure and death.
For more information see this CDC webpage and this article: "Biochemistry and physiology of tapeworms.". This popular article is probably also interesting.
The following is multiple choice question (with options) to answer.
What is the name for a parasite that causes disease? | [
"fungi",
"enfluenza",
"pathogen",
"microbes"
] | C | |
SciQ | SciQ-1749 | ocean, ocean-currents, sea-level, topography, bathymetry
Title: Does bathymetry affect ocean topography/height? Here is a map of ocean surface height or topography:
The following is multiple choice question (with options) to answer.
What type of map shows the elevation and features in an area? | [
"geographic",
"topographic",
"meteorological",
"gradient"
] | B | Relief , or terrain, includes all the landforms of a region. A topographic map shows the height, or elevation , of features in an area. This includes mountains, craters, valleys, and rivers. For example, Figure below shows the San Francisco Peaks in northern Arizona. Features on the map include mountains, hills and lava flows. You can recognize these features from the differences in elevation. We will talk about some different landforms in the next section. |
SciQ | SciQ-1750 | cell-biology
Title: Are ribosomes assembled in rough ER and Golgi body, or in the nucleolus? I mean all the components, such as ribosomal RNA (rRNA) are synthesized in the nucleolus, but is the whole ribosome structure assembled in the nucleolus or is it also done in the rough endoplasmic reticulum and Golgi apparatus? Ribosome assembly starts in the nucleolus (of eukaryotes) and finishes in the cytoplasm. However, in the cytoplasm the Golgi apparatus is certainly not involved, and, as some cells have little rough endoplasmic reticulum, assembly does not require that. Thus, the abstract of a review by Fromont-Racine et al. in Gene (2003) vol 313 pp. 17–42 starts with the statement:
Ribosome synthesis is a highly complex and coordinated process that occurs not only in the nucleolus but also in the nucleoplasm and the cytoplasm of eukaryotic cells.
In the 26 pages of this review there is not a single mention of the words ‘endoplasmic reticulum’ or ‘Golgi’.
A more recent (and freely available) review by Thomson et al. in Journal of Cell Science (2013) vol 126 pp. 4815-4820 is in accord with this. It has a pretty poster insert which presents the assembly as a succession of events, starting in the nucleolus, proceeding to the nucleoplasm, and with some final polishing in the cytoplasm.
The following is multiple choice question (with options) to answer.
What are organelles made of protein and ribosomal rna (rrna)? | [
"ribosomes",
"chromosomes",
"carbons",
"electrons"
] | A | The nucleus of many cells also contains a non-membrane bound organelle called a nucleolus , shown in Figure below . The nucleolus is mainly involved in the assembly of ribosomes. Ribosomes are organelles made of protein and ribosomal RNA (rRNA), and they build cellular proteins in the cytoplasm. The function of the rRNA is to provide a way of decoding the genetic messages within another type of RNA (called mRNA), into amino acids. After being made in the nucleolus, ribosomes are exported to the cytoplasm, where they direct protein synthesis. |
SciQ | SciQ-1751 | terminology, meteorology
I've tried to illustrate the relationships with insolation and temperature here:
There are some other ways too:
Ecological. Scientists who study the behaviour of organisms (hibernation, blooming, etc.) adapt to the local climate, sometimes using 6 seasons in temperature zones, or only 2 in polar and tropical ones.
Agricultural. This would centre around the growing season and therefore, in North America and Europe at least, around frost.
Cultural. What people think of as 'summer', and what they do outdoors (say), generally seems to line up with local weather patterns. In my own experience, there's no need for these seasons to even be 3 month long; When I lived in Calgary, summer was July and August (hiking), and winter was December to March (skiing). Here's another example of a 6-season system, and a 3-season system, from the Aboriginal people of Australia, all based on weather.
Why do systems with later season starting dates prevail today? Perhaps because at mid-latitudes, the seasonal lag means that the start of seasonal weather is weeks later than the start of the 'insolation' period. In a system with no heat capacity, there would be no lag. In systems with high heat capacity, like the marine environment, the lag may be several months (Ibid.). Here's what the lag looks like in three mid-latitude cities:
The exact same effect happens on a diurnal (daily) basis too — the warmest part of the day is often not midday (or 1 pm in summer). As with the seasons, there are lots of other factors too, but the principle is the same.
These aren't mutually exclusive ways of looking at it — there's clearly lots of overlap here. Cultural notions of season are surely rooted in astronomy, weather, and agriculture.
The following is multiple choice question (with options) to answer.
What are major temperature zones primarily based on? | [
"longitude",
"altitude",
"latitute",
"gps"
] | C | Temperature falls from the equator to the poles. Therefore, major temperature zones are based on latitude . They include tropical, temperate, and arctic zones (see Figure below ). However, other factors besides latitude may also influence temperature. For example, land near the ocean may have cooler summers and warmer winters than land farther inland. This is because water gains and loses heat more slowly than does land, and the water temperature influences the temperature on the coast. Temperature also falls from lower to higher altitudes. That’s why tropical zone mountain tops may be capped with snow. |
SciQ | SciQ-1752 | human-physiology, digestion, stomach
The stomach accomplishes much of its function by mechanically breaking down the swallowed food particles and mixing them with acid and enzymes into a sort of slurry. To do this, there are three major layers of muscle surround the stomach - from the outside, the longitudinal layer, the circular layer, and the oblique layer. The stomach also has two holes in it - the gastroesophageal opening, coming from the esophagus with the swallowed food/saliva mix, and the pylorus, where the food/acid/enzyme slurry exits into the duodenum, which is the beginning of the small intestine.
Due to the three layers of (rather strong) muscle, the stomach doesn't have a lot of expansion capability once it is filled completely to capacity. Fortunately, this almost never occurs (despite how we may feel after a large meal) because material is always leaving the stomach on its way to enzymatic digestion in the intestines. Additionally, once the stomach is filled to a certain extent, hormones such as leptin are secreted that give you the feeling of being sated, or full, triggering the brain to make you stop eating.
Of course, as we can see with the current epidemic of obesity around the world, the stomach can change its size over time. However, this is a rather slow process (weeks to months to years) of adapting to continuously consuming large meals.
But what would happen if you completely ignored these internal warnings, or were being force-fed, or whatever? Instead of rupturing (the biological equivalent of "exploding"), food would most likely be expelled either into the small intestine or back into the esophagus and back up the way it came down, i.e. causing vomiting.
The following is multiple choice question (with options) to answer.
What type of muscle is found in the walls of other internal organs such as the stomach? | [
"smooth muscle",
"inorganic muscle",
"Tube Muscle",
"Fiber Muscle"
] | A | Smooth muscle is found in the walls of other internal organs such as the stomach. It isn’t striated because its muscle fibers are arranged in sheets rather than bundles. Contractions of smooth muscle are involuntary. When smooth muscles in the stomach contract, they squeeze food inside the stomach. This helps break the food into smaller pieces. |
SciQ | SciQ-1753 | optics, everyday-life
Title: Light reflected in a cylinder I was cooking and noticed a funny pattern appearing when i was looking in on of my pans. When light fell into a pan with high edges, it seemed to reflect into a hart-shaped pattern. Can anyone explain how the light gets warped into this shape, and does anyone know why the light gets reflected into a sharp line, rather then a hart-shaped plane?
I have added some pictures to make it more clear. You want to look up Caustics in optics.
The specifics of your example boil down to the way the geometry works out. In this case the simplest model would be something like a Nephroid, where you have a circular shape which ( in terms of illumination ) is similar to a half circle, and that makes that particular caustic.
The following is multiple choice question (with options) to answer.
A visual "copy" of an object that is formed by reflected or refracted light is called what? | [
"mirror",
"instance",
"photo",
"image"
] | D | Almost all surfaces reflect some of the light that strikes them. The still water of the lake in Figure above reflects almost all of the light that strikes it. The reflected light forms an image of nearby objects. An image is a copy of an object that is formed by reflected or refracted light. |
SciQ | SciQ-1754 | 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.
From the pharynx, air next passes through what structure, also known as the voice box because it contains vocal cords? | [
"pancreas",
"trachea",
"larynx",
"diaphram"
] | C | From the pharynx, air next passes through the larynx , or voice box. The larynx contains vocal cords, which allow us to produce vocal sounds. |
SciQ | SciQ-1755 | 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.
Vertebrates are all chordates that have a what? | [
"backbone",
"circulatory system",
"brain",
"fossil"
] | A | Living species of chordates are classified into three major subphyla: Vertebrata, Urochordata, and Cephalochordata. Vertebrates are all chordates that have a backbone. The other two subphyla are invertebrate chordates that lack a backbone. Members of the subphylum Urochordata are tunicates (also called sea squirts). Members of the subphylum Cephalochordata are lancelets . Both tunicates and lancelets are small and primitive. They are probably similar to the earliest chordates that evolved more than 500 million years ago. |
SciQ | SciQ-1756 | eyes, vision, human-eye
Ideas so far
Does the eye try focusing either a little nearer or further and then if that doesn't help to make the object clearer then the eye focuses in the opposite direction?
Or is there some light-sensitive apparatus that is always a focused a little nearer or further than the rest of the eye, and so for instance if the cells which are focused further out are giving a clearer picture than the other cells then the eye knows to focus further out?
Or is the blurriness of a object closer than the focal point a distinguishably different sort of blurriness than an object beyond than the focal point?
Or is there some other mechanism altogether? Interesting question! Determining the focus of a visual image is carried out in the visual association area of the brain. Ultimately, this process results in focusing of the retinal image by adjustment of the shape of the lens in the eye. Lens shaping to focus the image is called accommodation
The neuronal circuitry involved in accommodation includes the following structures:
The input to the accommodation response is provided by the retina, optic nerve, thalamus, and visual cortex. The visual cortex projects to the association cortex.
The (simplified) output scheme is the following: The association cortex projects to the supraoculomotor nuclei, which in turn generates motor control signals that initiate the accommodation response. The signal is then sent bilaterally to the oculomotor complex, and hence input from one eye is enough to focus both eyes.
The motor output regulates the ciliary muscles that control the shape of the crystalline lens. Negative accommodation adjusts the eye for long distances by relaxation of the ciliary muscles. Positive accommodation adjustment of the eye for short distances by contraction of the ciliary muscles Medical Dictionary.
As to the second part of your question: how out-of-focus images are functionally recognized:
There are at least three mechanisms responsible for accommodation:
The following is multiple choice question (with options) to answer.
What do structures of the human eye collect and focus? | [
"sugars",
"light",
"air",
"electricity"
] | B | The structures of the human eye collect and focus light. They form a reduced, upside-down image on the retina at the back of the eye. |
SciQ | SciQ-1757 | standard-model
Title: What if the stationary mass of fundamental particular were different? My question is the following:
Consider the possibility of existing variations of the elementary particles whose stationary mass were 100 times smaller. I mean, electrons and other fundamental particles with 1/100 (or 1/1000) the stationary mass they have. All other things remaining equal, my questions are:
Such particles would be able to form atoms?
Said atoms could form molecules and macroscopic bodies?
Which different properties would we expect that such bodies could have? They obviously would be much lighter, but would they interact with light differently? Would we be able to see them? Would we be able to touch and feel them?
Such particles would enable the existence of stable elements with higher atomic numbers, like stable versions of low half-life elements? I suppose by stationary mass you mean what is usually called
rest mass or invariant mass.
So let us assume the rest masses of all elementary particles
(electrons, quarks, ...) are $100$
times smaller than they are in our universe.
Such particles would be able to form atoms?
Yes, because the electromagnetic interaction between charges
is still there. But according to quantum mechanics
the atoms would be $100$ times larger.
Said atoms could form molecules and macroscopic bodies?
Yes, but the molecules and macroscopic bodies
would also be $100$ times larger, because they are
governed by the electromagnetic interaction as well.
Which different properties would we expect that such bodies
could have? They obviously would be much lighter, but would
they interact with light differently? Would we be able to see
them? Would we be able to touch and feel them?
The atomic and molecular binding energies
would be $100$ times smaller.
Therefore the energy of photons emitted/absorbed by
atoms and molecules would also be $100$ times smaller.
And hence the light frequencies would be $100$ times smaller
and the light wavelengths would be $100$ times larger.
So the world experienced by us would be essentially the
same, just scaled differently.
Such particles would enable the existence of stable elements
with higher atomic numbers, like stable versions of low half-life elements?
The following is multiple choice question (with options) to answer.
Different elements differ in the size, mass, and other properties of what fundamental structures? | [
"compounds",
"ions",
"particles",
"atoms"
] | D | Atoms of different elements differ in size, mass, and other properties. |
SciQ | SciQ-1758 | human-anatomy
Title: Why is a penis an organ? According to Wikipedia an "An organ is a group of tissues with similar functions". I don't know anything about anatomy but it doesn't seem to me that a penis can be delimited somewhere to form a "group". Therefore I do not understand why a penis is considered an organ.
Can you explain it to me ? Frankly, that's a terrible definition by Wikipedia.
Merriam-Webster defines an organ as:
a differentiated structure (such as a heart, kidney, leaf, or stem) consisting of cells and tissues and performing some specific function in an organism
or
bodily parts performing a function or cooperating in an activity
The important defining feature of an organ is not that the tissues have similar functions but that, together, the tissues comprise a functional whole that achieves some end goal.
For the penis, it consists of multiple tissues with different functions:
(from https://www.ncbi.nlm.nih.gov/books/NBK525966/figure/article-20668.image.f1/ - original from Gray's Anatomy)
The different tissues pictured here: the fibrous envelope, the corpora cavernosa, the septum pectiniforme, the urethra and blood vessels, the nervous tissue in the skin: all of these tissues have different individual functions: structural, erectile, carrying urine or semen, etc.
The key that unifies them into an organ is that the functions of the penis at the organism level (principally sexual function) are not served by any of these tissues alone, but rather by their combination in a full structure: an organ.
Ultimately, organ definitions are somewhat opinion-based: people are lumpers and splitters, so you might find conflicting definitions for which groupings of tissues reflect distinct organs, but I think by most standards you would find the penis to be considered a distinct organ, affiliated with but distinct from the primary sex organs and associated glands.
The following is multiple choice question (with options) to answer.
Breasts are considered accessory organs of what body system? | [
"female reproductive system",
"nervous system",
"lymphatic system",
"digestive system"
] | A | The Breasts Whereas the breasts are located far from the other female reproductive organs, they are considered accessory organs of the female reproductive system. The function of the breasts is to supply milk to an infant in a process called lactation. The external features of the breast include a nipple surrounded by a pigmented areola (Figure 27.17), whose coloration may deepen during pregnancy. The areola is typically circular and can vary in size from 25 to 100 mm in diameter. The areolar region is characterized by small, raised areolar glands that secrete lubricating fluid during lactation to protect the nipple from chafing. When a baby nurses, or draws milk from the breast, the entire areolar region is taken into the mouth. Breast milk is produced by the mammary glands, which are modified sweat glands. The milk itself exits the breast through the nipple via 15 to 20 lactiferous ducts that open on the surface of the nipple. These lactiferous ducts each extend to a lactiferous sinus that connects to a glandular lobe within the breast itself that contains groups of milk-secreting cells in clusters called alveoli (see Figure 27.17). The clusters can change in size depending on the amount of milk in the alveolar lumen. Once milk is made in the alveoli, stimulated myoepithelial cells that surround the alveoli contract to push the milk to the lactiferous sinuses. From here, the baby can draw milk through the lactiferous ducts by suckling. The lobes themselves are surrounded by fat tissue, which determines the size of the breast; breast size differs between individuals and does not affect the amount of milk produced. Supporting the breasts are multiple bands of connective tissue called suspensory ligaments that connect the breast tissue to the dermis of the overlying skin. |
SciQ | SciQ-1759 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
Because plants lack what kind of system, their first line of defense is usually the death of cells surrounding infected tissue to prevent spread of infection? | [
"digestion system",
"nervous system",
"hormones system",
"immune system"
] | D | Plants don't have an immune system, but they do respond to disease. Typically, their first line of defense is the death of cells surrounding infected tissue. This prevents the infection from spreading. |
SciQ | SciQ-1760 | cancer, mutations
Here is another great paper that specifically addresses your question, linking increased cell division with the accumulation of both significant and insignificant mutations, which over time, lead to an accumulation of mutations needed for cancer to develop.
The following is multiple choice question (with options) to answer.
What type of cells make up tumors? | [
"white blood cells",
"consumption cells",
"boyle cells",
"cancer cells"
] | D | |
SciQ | SciQ-1761 | species-identification, botany, ecology, trees
Title: Identifying a shrub with unusual "many shoots" growth behavior While recently hiking in the southern mountains of New Hampshire, we came across a plant, and some of them were exhibiting what we interpreted to be a disease, or least unusual growth. On some of the nodes, there were a large number of extra stalks:
On each plant, the number and locations of these things varied, and not all of them had it. And we first assumed it was some ivy, or parasite, or separate plant, but it seemed pretty clear to us that it was coming right from the same branch.
We soon saw there were dead versions of this plant, and all of them had this "extra shoot" variation:
So we reasoned that no matter what this thing was -- natural variation or some kind of disease -- it was killing the plants.
Google image search was no help. It possibly identified the plant as a "viburnum", but was unable to help with the growth.
Anyone know what plant this is, or what this growth behavior is the result of? Possibly an example of a "Witch's Broom."
Witch's Broom is a deformity in plants (typically woody species) which typically causes dense patches of stems/shoots to grow from a single point on the plant. The name comes from the broom-like appearance of the stems.1
Witch's broom may be caused by many different types of organisms, including fungi, oomycetes, insects, mistletoe, dwarf mistletoes, mites, nematodes, phytoplasmas, or viruses.2
Sources:
1. Wikipedia
2. Book of the British Countryside. Pub. London : Drive Publications, (1973). p. 519
Image1. Gardeningknowhow.com
Image2. Iowa state University
The following is multiple choice question (with options) to answer.
When leaves wilt, what plant process ceases? | [
"reactions",
"hydration",
"photosynthesis",
"carbonation"
] | C | Photosynthesis ceases when leaves wilt, mainly because. |
SciQ | SciQ-1762 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
What type of tissue makes up much of the inside of a plant? | [
"leaf tissue",
"stem tissue",
"ground tissue",
"working tissue"
] | C | Ground tissue makes up much of the inside of a plant. The cells of ground tissue carry out basic metabolic functions and other biochemical reactions. Ground tissue may also store food or water. |
SciQ | SciQ-1763 | malaria, mosquitoes
Title: How do sporozoites travel into the human host when the mosquito is sucking blood? I mean how are the sporozoites able to swim in the reverse direction of blood flow through the proboscis of the mosquito into the human body? Nice question! Basically, the mosquito does not only suck; it also injects some saliva into the host with its saliva glands. From National Geographic:
The mosquito starts salivating as soon as it probes the [host]’s skin, releasing substances that prevent blood vessels from constricting, stop blood from clotting, and prevent inflammation. Sometimes, Choumet could see the saliva as small bubbles that hung around the tips of the mouthparts. And even after the mosquito stops feeding, pockets of saliva linger in the lower layers of the skin.
And from cdc.gov:
After 10-18 days, the parasites are found (as "sporozoites") in the mosquito's salivary glands. When the Anopheles mosquito takes a blood meal on another human, the sporozoites are injected with the mosquito's saliva and start another human infection when they parasitize the liver cells.
The probiscus is actually equipped to inject saliva as well as to suck blood. And once the saliva has entered the victim, it can spread to the whole body since the blood is constantly moving. From mosquitnoband.com:
Mosquitoes also have special hematophagous arthropod saliva in their proboscis. Hematophagous arthropod saliva is a scientific way of saying “spit from a blood-sucking creature with an exoskeleton.” This specific type of saliva has chemicals and proteins in it that prevents blood from clotting. So what do mosquitoes do with their hematophagous arthropod saliva? They inject it into their victim before they start sucking its blood to prevent any clotting while they slurp.
Hope this helps!
The following is multiple choice question (with options) to answer.
Saliva can carry the hiv virus, but it won't spread it, unless the saliva gets into what? | [
"bloodstream",
"liver",
"kidneys",
"lungs"
] | A | HIV spreads through contact between an infected person’s body fluids and another person's bloodstream or mucus membranes, which are found in the mouth, nose, and genital areas. Body fluids that may contain HIV are blood, semen, vaginal fluid, and breast milk. The virus can spread through sexual contact or shared drug needles. It can also spread from an infected mother to her baby during childbirth or breastfeeding. Saliva can carry the HIV virus, but it won't spread it, unless the saliva gets into the bloodstream. Other body fluids such as urine and sweat do not contain the virus. HIV does not spread in any fluid in which the host cells cannot survive. |
SciQ | SciQ-1764 | human-biology, neuroscience, physiology, anatomy
Title: Why does sympathetic activity constrict pulmonary vessels? I don't know understand why sympathetic stimulation constricts pulmonary vessels?
I thought that the sympathetic nervous system activated the body for physical activity. Physical activity would need more oxygen supply. Doesn't constriction of pulmonary vessels reduce the gas exchange? Short answer
The sympathetic nervous system mediates the fight, flight and fright response. It constricts the arteries and arterioles to increase blood pressure, in turn pushing the blood to the muscles and other organs vital for physical activity.
Background
The sympathetic nervous system functions triggers the fight, fright, flight (FFF) response (Fig. 1). It provides the body with a burst of energy so that it can respond to danger (source: Harvard Medical School).
The FFF response is initiated in the hypothalamus by activating the sympathetic nervous system through the adrenal glands. These glands release epinephrine (adrenaline) into the bloodstream. Epi increases heart rate and blood pressure to push blood to the muscles, heart, and other vital organs. The person also starts to breathe more rapidly and the small airways in the lungs open up. This way, the lungs can take in as much oxygen as possible with each breath. Extra oxygen is sent to the brain, increasing alertness (source: Harvard Medical School).
In blood vessels, as you say, sympathetic activation constricts arteries and arterioles (resistance vessels), which increases vascular resistance and decreases distal blood flow. When this occurs throughout the body, the increased vascular resistance causes arterial pressure to increase (Klabunde, 2012). This enhances the distribution of oxygen already present in the blood. I don't think the pulmonary circulation responds differently than that in the rest of the body. The stress response is meant to support the evasion of acute dangers. But indeed, chronic exposure to adrenaline may eventually lead to impaired oxygen exchange in the lungs (Krishnamoorthy et al., 2012).
Fig. 1. Fight, flight, fright response. source: Freelap USA
References
- Klabunde, Cardiovascular Physiology Concepts, 2nd ed. (2012). Lippincott Williams & Wilkins
- Krishnamoorthy et al., Anesthesiology (2012); 117(10): 745-54
The following is multiple choice question (with options) to answer.
Does blood flow increase or decrease when blood vessels constrict? | [
"decrease",
"it's not affected",
"increases",
"it stops"
] | A | When a blood vessel constricts, less blood can flow through it. |
SciQ | SciQ-1765 | planets
Title: What is Venus's core made of? As we all know Venus's surface is so hot that it can probably melt lead.
What would be in it's in core?
Is it in the liquid or solid state?
What would be it's temperature?
How many cores does it have? Scientists think that Venus' internal structure is somewhat like Earth's, as shown below:
In other words, a crust, mantle, and core. The evidence points to Venus not having plate tectonics like Earth or a magnetic field. Venus also probably has a partially molten core, like Earth, as it has been cooling at the same rate.
Honestly, we don't know much else. We can tell you the atmosphere composition, but we don't know what the core is made up of. The Venus Wikipedia page (here) is very helpful and has more information and explanations of why we don't know these things.
The following is multiple choice question (with options) to answer.
What is venus covered in a thick layer of? | [
"clouds",
"storms",
"fog",
"gases"
] | A | Viewed through a telescope, Venus looks smooth and featureless. The planet is covered by a thick layer of clouds. You can see the clouds in pictures of Venus ( Figure below ). |
SciQ | SciQ-1766 | hydrology, mountains, rivers
Title: Why do rivers have 'wells' in mountains? Why/how can rivers have sources in places high above the sea level? The presence of water underground has nothing to do with sea level in mountainous country.
When rain fails on a mountain, or snow falls on a mountain and the snow eventually melts, the water from the rain or snow melt mostly travels downhill via rivers to the sea.
In getting to a river some of the water will fall on the ground. In places where the ground is covered by soil, water can travel through the soil via the pore spaces between the grains of soil. Similarly if porous rock, such as sandstone lies beneath the soil water can travel through the pores in the rock.
If a layer of impervious rock lies under the porous rock or soil, the water cannot move downwards, due to gravity, any further. This can lead to water accumulating in the soil or porous rock and saturating the soil or rock. In such situations an aquifer can form. The top of the saturated zone in an aquifer is called a water table.
The ground beneath a river is saturated and the surface of the river shows the water table exposed to atmosphere. Thus in mountainous regions the ground beneath rivers will be saturated and capable of supporting a well developed from the bank of a river.
The following is multiple choice question (with options) to answer.
What type of aquifer is trapped between two impermeable rock layers? | [
"abandoned",
"confined",
"segmented",
"solid"
] | B | Sometimes an aquifer is confined. A confined aquifer is trapped between two impermeable rock layers. Pressure from the rock layer on top forces the water out where the aquifer reaches the ground surface. Water that flows up to the surface naturally is an artesian spring . If people drill a well into a confined aquifer, the water may flow to the surface without assistance. This is an artesian well ( Figure below ). |
SciQ | SciQ-1767 | cell-division
Title: Are free-nuclear division and endomitosis the same? As far as I understood it, both are cases of karyokinesis, not followed by cytokinesis. No. If you google the terms you'll get a lot of sites with definitions. For example:
Nuclear division
Definition
noun
The process by which a nucleus divides, resulting in the segregation of the genome to opposite poles of a dividing cell.
source: http://www.biology-online.org/dictionary/Nuclear_division
Edit:
or
free nuclear division mitotic division of nuclei without accompanying cytokinesis, i.e. nuclei divide in a common cytoplasm, the cells walls only forming around each later
source: http://ecflora.cavehill.uwi.edu/bio_courses/bl14apl/Gloss.htm
versus
endomitosis
mitosis taking place without dissolution of the nuclear membrane, and not followed by cytoplasmic division, resulting in doubling of the number of chromosomes within the nucleus.
source: http://medical-dictionary.thefreedictionary.com/endomitosis
or a bit more revealing:
Duplicated chromosomes produced by endomitosis exist as discrete units
in a single polyploid nucleus or may be packaged into separate nuclei,
depending on the phase at which mitosis is aborted
source: http://en.wikipedia.org/wiki/Endoreduplication
So as you see by definition nuclear division is part of a bigger process (cell division), and accoriding to the first source karyokinesis is a synonim for nuclear division (karyo = nucleus kinesis = moving, both come form greek language).
Edit:
If you check the definition above, you can see that free-nuclear division is a mitosis without cytokinesis, thus chromosome separation still occurs.
In endomitosis the can end up with a polyploid nucleus, in contrast to the other two aforementioned mechanism where no polyploidy occurs.
The following is multiple choice question (with options) to answer.
Name the multi-phase process in which the nucleus of a eukaryotic cell divides? | [
"symbiosis",
"mitosis",
"meiosis",
"cytokinesis"
] | B | Mitosis in the Eukaryotic Cell Cycle. Mitosis is the multi-phase process in which the nucleus of a eukaryotic cell divides. In this diagram, prometaphase is not included as a separate phase, but incorporated into prophase. |
SciQ | SciQ-1768 | muscles
Title: What is meant by a muscle fiber being glycerinated? I was popped this questions today, "what is a glycerinated muscle fiber, and what is required for its contraction," and had little idea. I'm assuming the question is "what's required for its contraction as compared to normal muscle tissue?"
There's a limited amount of information out there about this. It appears that it is a type of in vitro system requiring special preparation of typical muscle tissue. I was wondering if anyone here had a little more information. Is this something that's just used in teaching lab exercises? From: http://www.acad.carleton.edu/curricular/BIOL/classes/bio126/Documents/Lab_5.pdf
Glycerination disrupts the membranes of the muscle cells, ruptures mitochondria, and leaches out soluble constituents such as ATP and inorganic ions. However, glycerinated muscle retains the organized structural array of myosin thick filaments and actin thin filaments, actin-associated proteins like troponin and tropomyosin which regulate contraction, and the functional capacity for contraction.
I would expect that because the sample has lost ATP and inorganic ions, you would need to supply ATP (the source of energy), $Mg^{2+}$ (which is necessary for ATP hydrolysis) and $Ca^{2+}$ (to induce the contraction).
The following is multiple choice question (with options) to answer.
What is the term for the basic contractile unit of the muscle? | [
"sphincter",
"sarcomere",
"bandimere",
"filament"
] | B | |
SciQ | SciQ-1769 | 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.
What are chemical messengers that control sexual development and reproduction? | [
"lipids",
"neurotransmitters",
"sex hormones",
"proteins"
] | C | Sex hormones are chemical messengers that control sexual development and reproduction. The male reproductive system consists of structures that produce male gametes called sperm and secrete the male sex hormone testosterone. |
SciQ | SciQ-1770 | homework, ecology, population-biology, conservation-biology
Title: Difference between biological control and introducing species for conservation? I have a biology assignment and we have to explain various methods and strategies for conservation, two of which are:
Biological control
Introduced Species
What is the difference between these? I was under the impression that they are essentially the same thing – biological control being the introduction of species to predate pests (eg. the abysmal failure of the cane toad).
Any clarification would be great. After talking to my teacher, he said that biological control is the introduction of species to control another species, however species may be introduced for other reasons (the "Introduced Species" method), such as to "assist an ecosystem cope, flourish or re-establish itself."
The example he gave was the introduction of South African veldt grass to Western Australia in order to stabilise sand dunes, so that they can later be built upon further (eg. plants which may not perform well in sandy, unstable soil can then be planted).
Hopefully this helps anyone else with the same problem.
The following is multiple choice question (with options) to answer.
What are species that are first to colonize a disturbed area called? | [
"exploratory species",
"pioneer species",
"brave species",
"novel species"
] | B | The first species to colonize a disturbed area such as this are called pioneer species (see Figure below ). They change the environment and pave the way for other species to come into the area. Pioneer species are likely to include bacteria and lichens that can live on bare rock. Along with wind and water, they help weather the rock and form soil. Once soil begins to form, plants can move in. At first, the plants include grasses and other species that can grow in thin, poor soil. As more plants grow and die, organic matter is added to the soil. This improves the soil and helps it hold water. The improved soil allows shrubs and trees to move into the area. |
SciQ | SciQ-1771 | star, planet, telescope, light, space
Title: How do I know what I'll be able to see? So I live in a suburb in Victoria, Australia. Less than an hour away from the city and I guess there is a bit of light pollution because from my backyard I can probably only see about 15 - 20 stars (probably less), I'm wondering what these stars are, and what I'll see when I get this telescope:
https://www.opticscentral.com.au/saxon-707az2-refractor-telescope.html?___SID=U#.WXQNMtN940r
This is going to sound stupid but how do I know when there are planets in the sky that I can see? I don't think I've ever actually seen a planet other than the moon.
Thank you. Firstly, if you're planet spotting, don't worry too much about light pollution. The planets are some of the brightest objects in the sky and some (especially Jupiter) can easily be observed even with a full Moon - the full Moon (along with the Sun!) is the biggest contributor to light pollution!
Take a look at the list of brightest stars ( https://en.wikipedia.org/wiki/List_of_brightest_stars ), which also contains estimates for the brightness of the Sun, Moon and major planets. There aren't typically any stars brighter from Earth than Venus, Jupiter, Mars and Mercury and precious few brighter than Saturn. I'm going to suggest you probably have seen many of the planets - but just didn't recognise them.
+1 for Stellarium ( http://www.stellarium.org/en_GB/ ). It's free, intuitive and very visual to use. You can put in your local viewing location and it gives you a view for any time of the night, future or past. At the time of writing (23 July 2017), Saturn and Jupiter should be looking good for the Southern Hemisphere. This rotates throughout the year, and Stellarium will help with this.
Do a web search for "the sky at night in the southern hemisphere" and you'll find a number of examples of websites with highlights to look for when you get out.
Couple of final suggestions:
The following is multiple choice question (with options) to answer.
What planet is the easiest to observe? | [
"uranus",
"mars",
"mercury",
"pluto"
] | B | Mars is the easiest planet to observe. As a result, it has been studied more than any other planet besides Earth. People can stand on Earth and observe the planet through a telescope. We have also sent many space probes to Mars. A car-sized robotic rover, Curiosity, arrived on the Red Planet in August 2012. Curiosity joins Opportunity, which has been active since 2004. |
SciQ | SciQ-1772 | 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.
Where does the heartbeat originate in vertebrates? | [
"the pulse",
"the blood",
"the heart",
"the tissue"
] | C | |
SciQ | SciQ-1773 | organic-chemistry, inorganic-chemistry, acid-base, solvents, molecules
Title: How can one find products when one knows the reagents? I'm going to use an example (I could have used a different one);
On the document it is about the study of the chemical balance of an acid-basic solution.
The chemists have written the chemical reaction equation to make a table of the evolution of pH during the reaction.
If I understand with this equation I'll be able to understand others.
$\ce{CH3COOH + H2O ->CH3COO- + H3O+}$
Here is what I already understand:
This is the equation of methanoic acid with water
I understood why the general formula of methanoic acid is $\ce{CH3COOH}$
What I want to know is how do we know that
$\ce{CH3COOH}$ changes into $\ce{CH3COO-}$ ?
$\ce{H2O}$ changes into $\ce{H3O+}$?
The following is multiple choice question (with options) to answer.
What is a process where some substances called reactants change chemically into different substances called products? | [
"chemical reaction",
"non-chemical reaction",
"crystals reaction",
"carbon reaction"
] | A | The student athlete in Figure below is practically flying down the track! Running takes a lot of energy. But you don’t have to run a race to use energy. All living things need energy all the time just to stay alive. The energy is produced in chemical reactions. A chemical reaction is a process in which some substances, called reactants, change chemically into different substances, called products. Reactants and products may be elements or compounds. |
SciQ | SciQ-1774 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
Cellulose is the main structural component of what part of the plant cell, and makes up over thirty percent of plant matter? | [
"cell wall",
"roots",
"proteins wall",
"flowers"
] | A | Figure 31.3 Cellulose, the main structural component of the plant cell wall, makes up over thirty percent of plant matter. It is the most abundant organic compound on earth. Plants are able to make their own cellulose, but need carbon from the soil to do so. |
SciQ | SciQ-1775 | newtonian-mechanics, forces, free-body-diagram
Title: How can I actually push heavier objects? I've been thinking about Newton's third law lately because I couldn't understand a few things and I think I actually answered my own question. Could someone confirm if my reasoning is right or show me my mistakes?
So the question is: If force and reaction force are always the same, and less mass means greater acceleration, how can I actually push heavier objects? Then I got my idea of an answer that I will try to show with a picture:
I exert $F_{\text{action}}$ force on a Box (much heavier than me) and an equal $F_{\text{reaction}}$ is exerted on me in the opposite direction, but $F_{\text{action}}$ is caused by the $F_{\text{muscle}}$ force which is exerted on me and has the same direction as $F_{\text{action}}$
The box changes position but I don't change position myself because $F_{\text{muscle}}$ still acts and prevents it.
Step 1 is repeated and that way I can push much heavier objects.
(I am sorry that box looks little different in every step. It was hand-drawn - the box in steps 2 and 3 is meant to be in the same position)
The following is multiple choice question (with options) to answer.
What is a push or a pull acting on an object? | [
"energy",
"action",
"pulse",
"force"
] | D | Force is a push or a pull acting on an object. Examples of force include friction and gravity. Force is a vector because it has both size and direction. The SI unit of force is the newton (N). |
SciQ | SciQ-1776 | human-biology
Title: Is urine dirty as soon as it leaves the human body? Human urine is sterile as long as it is in the human body. But is it dirty after leaving the human body? Could you get sick from it, if you drink it or don't wash your hands, for example? It was believed for a long time that urine stored in the urinary bladder is sterile. However, Wolfe et al(1). recently found evidence of bacterial presence in the urine extracted from bladders of healthy women. In an article just published, Hilt et al. found that at least some bacteria found in the bladder of healthy women are viable and can be grown in a laboratory after extraction from the bladder).2 (Paywall). They expect that the same is the case for men.
From the Hilt et al. paper:
Thirty-five different genera and 85 different species were identified
by EQUC. The most prevalent genera isolated were Lactobacillus (15%),
followed by Corynebacterium (14.2%), Streptococcus (11.9%),
Actinomyces (6.9%), and Staphylococcus (6.9%). Other genera commonly
isolated include Aerococcus, Gardnerella, Bifidobacterium, and
Actinobaculum.
Note that these species for the most part (Actinobaculum being one exception, as a possible uropathogen) appear to be part of the normal microbiome (collection of microorganisms) in healthy people in the same way as bacteria inhabit other parts of healthy persons. Additionally, the recovered organisms required special care to achieve growth:
Most of the bacteria isolated required either increased CO2 or
anaerobic conditions for growth, along with prolonged incubation, and
they often were present in numbers below the threshold of detection
used in routine diagnostic urine culture protocols.
The following is multiple choice question (with options) to answer.
Which organ will bladder infections commonly damage if untreated? | [
"lungs",
"tissue",
"kidney",
"heart"
] | C | Bacterial infections of the urinary tract, especially the bladder, are very common. Bladder infections can be treated with antibiotics prescribed by a doctor. If untreated, they may lead to kidney damage. |
SciQ | SciQ-1777 | biochemistry, cell-biology, proteins, enzymes, digestive-system
So, while maybe something like $\ce{H2SO4}$ or $\ce{HNO3}$ could work too, hydrochloric acid is just more convenient to use? Parietal cells use ion pumps to expel protons and chlorine ions into the lumen, which create the necessary acidic environment to denature pepsinogen into pepsin.
It is the low pH environment that reconfigures or denatures pepsinogen into pepsin. The acid used does not matter. For example, one experiment in classifying properties of pepsinogen used a 3.5 pH solution of 0.5 N sulfuric acid to activate pepsin.
We evolved stomachs with parietal cells that use an energetically expensive process to maintain the acidic gradient necessary for digestion and protection from pathogens.
It may be that biochemical pathways to generate other acids did not evolve, because it is either energetically cheaper for these cells to make HCl, compared with other pathways that would generate other acids of sufficient strength; or the relevant chemical components involved are more abundant than others in what we eat and drink, and thus easier to make in quantities needed for digestion and defense. Chloride ions also serve a role in maintaining intra- and extracellular fluid pressure and thus play a larger part as electrolytes in the normal function of the body — they are available and cells use them.
But to answer your main question, an acidic environment activates pepsin, and it is not chemically necessary for this to be created by hydrochloric acid.
The following is multiple choice question (with options) to answer.
What is the acid that is released by the stomach that kills most pathogens that enter the stomach? | [
"hydrochloric acid",
"Sulfuric Acid",
"Hydrofluoric Acid",
"Nitric Acid"
] | A | The stomach also releases a very strong acid, called hydrochloric acid. This acid kills most pathogens that enter the stomach in food or water. Urine is also acidic, so few pathogens can grow in it. |
SciQ | SciQ-1778 | newtonian-mechanics, forces, newtonian-gravity, acceleration
Title: What does an applied force on an already accelerating object do? I'm a big beginner having only taken Grade 11 high-school physics.
Imagine this situation: an object is accelerating north, and while it's accelerating, it's 'hit' by a northward force.
To me it would make sense that the acceleration of the object would increase - something like this:
aNew = aOld + (f/m)
I got the (f/m) from f=ma.
But then think of gravity - while an object is accelerating downward at 9.8m/s2, it has the force of gravity pulling it too. So then, based on my previous logic, it's acceleration would constantly be increasing!
aNew = aOld + (fGravity/mass)
And I know that you don't increase your acceleration while you fall, so now I'm confused.
In a nutshell: What exactly are the rules for how an already accelerating object reacts to forces? Am I wrong that your acceleration would increase?
EDIT: I realized I've made a big mistake; I never knew that the acceleration drops to 0 the second the net force is 0. This makes sense now. The acceleration of an object is a result of the sum of all the forces. If it was accelerating before you hit it, there must have been a force. If an object is falling in air, there are forces of gravity and air friction on it. When all forces even out the object continues with the same velocity.
Simply take the vector sum of all forces - that will tell you what is going on.
The following is multiple choice question (with options) to answer.
What occurs when force is applied to a moving object? | [
"acceleration",
"inertia",
"stimulation",
"transmission"
] | A | Acceleration occurs when a force is applied to a moving object. |
SciQ | SciQ-1779 | rust, simulation
// There are some terms reused between smooth, grad_smooth and laplacian_smooth, this could be optimised
// Not to mention, some of these terms are constants...
fn smooth(current_position: Vector4<f32>, other_position: Vector4<f32>) -> f32
{
return (315.0/(64.0*PI*(SMOOTHING_RADIUS.powi(9)))) * (SMOOTHING_RADIUS.powi(2) - (current_position - other_position).magnitude2()).powi(3);
}
fn grad_smooth(current_position: Vector4<f32>, other_position: Vector4<f32>) -> Vector4<f32>
{
return (-45.0/(PI*(SMOOTHING_RADIUS.powi(6)))) * (SMOOTHING_RADIUS - (current_position - other_position).magnitude2()).powi(2) * ((current_position - other_position) / (current_position - other_position).magnitude2());
}
fn laplacian_smooth(current_position: Vector4<f32>, other_position: Vector4<f32>) -> f32
{
return (45.0/(PI*(SMOOTHING_RADIUS.powi(6)))) * (SMOOTHING_RADIUS - (current_position - other_position).magnitude());
}
fn setup() -> SimulationData {
let sim_space = SimulationSpace{
positions: get_initial_positions(),
velocities: get_initial_velocities(),
accelerations: get_initial_accelerations()
};
let sim_data = SimulationData {
simulation_space: sim_space,
//voxel_pixel_map: HashMap::new()
};
return sim_data;
}
The following is multiple choice question (with options) to answer.
Smooth, cardiac, and skeletal are all types of what? | [
"hormones",
"teeth",
"muscle",
"bone"
] | C | The three types of muscles in the body include skeletal muscle, smooth muscle, and cardiac muscle. |
SciQ | SciQ-1780 | inorganic-chemistry, reaction-mechanism, ions
Weiss, A. W. Theoretical Electron Affinities for Some of the Alkali and
Alkaline-Earth Elements. Phys. Rev., 1968, 166 (1), 70-74
Tehan, F. J.; Barnett, B. L.; Dye, J. L. Alkali anions. Preparation and Crystal Structure of a Compound which contains the Cryptated Sodium Cation and the Sodium Anion. J. Am. Chem. Soc., 1974, 96 (23), 7203–7208
Dye, J. L. Compounds of Alkali Metal Anions. Angew. Chem., 1979, 18 (8), 587-598
Dye, J. L.; Ceraso, J. M.; Lok, M. T.; Barnett, B. L.; Tehan, F. J. A Crystalline Salt of the Sodium Anion (Na-). J. Am. Chem. Soc., 1974, 96 (2), 608-609
The following is multiple choice question (with options) to answer.
What group of elements does sodium belong to? | [
"metalloids",
"alkali metals",
"halogens",
"noble gases"
] | B | Sodium belongs to the group of elements called the alkali metals. An alkaline solution is another name for a solution that is basic. All alkali metals react readily with water to produce the metal hydroxide and hydrogen gas. The resulting solutions are basic. |
SciQ | SciQ-1781 | electromagnetism, waves, electromagnetic-radiation, interference, superposition
Title: Constructive Interference of Electromagnetic Waves So I was wondering if Electromagnetic wave has the same property of interference as normal waves. I understand that both the electric and magnetic parts of the wave would have to be in the same position at the same time. To negotiate the fact that only one part of the wave would match up at one time due to the fact that light can't go faster than it's self I had the idea for three waves all intersecting at the same point. All of these waves would be of different wavelengths so that they do not interfering with each other before the main point. If I knew of a good easy way off making a fbd I would but i am rather new to really doing physics Ioutside of a high school classroom. So I was wondering if constructive interference worked on electromagnetic waves and if it does whether or not is decrease's the wavelength (increasing the energy). The electric and magnetic parts of an electromagnetic wave have the same wavelength and the same spatial relationship, so if the electric parts line up the magnetic ones do, too. There is only one wave, not three. If they are traveling in the same direction (as in a laser) they will stay in phase. Constructive interference works fine-that is what makes lasers work and interference patterns in light.
The following is multiple choice question (with options) to answer.
Pure constructive interference and pure destructive interference are distinguished by whether or not identical waves are what? | [
"before phase",
"in equilibrium",
"after phase",
"in phase"
] | D | Figure 27.11 The amplitudes of waves add. (a) Pure constructive interference is obtained when identical waves are in phase. (b) Pure destructive interference occurs when identical waves are exactly out of phase, or shifted by half a wavelength. |
SciQ | SciQ-1782 | photosynthesis
Title: Photosystem I and the ETC In the light reactions of photosynthesis, Photosystem I receives electrons from the ETC after Photosystem II sends them to the ETC. Then, when Photosystem I receives light, the electron becomes excited and passes the electron back to the ETC. This leads me to my question: In the following question, are both $B$ and $E$ correct?
Which of the following are directly associated with photosystem I?
$A)$ harvesting of light energy by ATP
$B)$ receiving electrons from the thylakoid membrane electron transport chain
$C)$ generation of molecular oxygen
$D)$ extraction of hydrogen electrons from the splitting of water
$E)$ passing electrons to the thylakoid membrane electron transport chain It appears the author of the question is trying to use "thylakoid electron transport chain" in an overly specific way. The chain from which PS I receives electrons has far more components and is different from the shorter chain to which PS I passes its electrons. But according to my copy of Biology, Campbell & Reece 7th edition, both are called "electron transport chains" and both reside in, or on, the thylakoid membrane. Perhaps the "directly" in the question refers to the fact that PS I's electron is first captured by a "primary receptor" before being passed to ferredixon, the first member of the chain to which PS I passes electrons. But, again according to Campbell, this primary acceptor is considered part of the photosystem.
I used to teach this stuff. I'd toss out the question.
The following is multiple choice question (with options) to answer.
The process of photosynthesis uses chlorophyll, which is located in organelles called what? | [
"nucleus",
"fibroblasts",
"chloroplasts",
"mitochondria"
] | C | Plants are a large and varied group of organisms. There are close to 300,000 species of catalogued plants. Of these, about 260,000 are plants that produce seeds. Mosses, ferns, conifers, and flowering plants are all members of the plant kingdom. The plant kingdom contains mostly photosynthetic organisms; a few parasitic forms have lost the ability to photosynthesize. The process of photosynthesis uses chlorophyll, which is located in organelles called chloroplasts. Plants possess cell walls containing cellulose. Most plants reproduce sexually, but they also have diverse methods of asexual reproduction. Plants exhibit indeterminate growth, meaning they do not have a final body form, but continue to grow body mass until they die. |
SciQ | SciQ-1783 | everyday-chemistry, metal, transition-metals, smell
Also, it turns out that $\ce{Fe^{2+}}$ ions (but not $\ce{Fe^{3+}}$) are capable of oxidizing substances present in oils produced by the skin, namely lipid peroxides. A small amount of $\ce{Fe^{2+}}$ ions are produced when iron comes into contact with acids in sweat. These then decompose the oils releasing a mixture of ketones and aldehydes with carbon chains between 6 and 10 atoms long. In particular, most of the smell of metal comes from the unsaturated ketone 1-octen-3-one, which has a fungal/metallic odour even in concentrations as low as $1\ \mu g\ m^{-3}$ . In short:
Sweaty skin corrodes iron metal to form reactive $\ce{Fe^{2+}}$ ions that are oxidized within seconds to $\ce{Fe^{3+}}$ ions while simultaneously reducing and decomposing existing skin lipid peroxides to odorous carbonyl hydrocarbons that are perceived as a metallic odor.
In the supporting information for the article (also free-access), the authors describe experiments performed with other metals, including copper:
The following is multiple choice question (with options) to answer.
What kind of oily substance is secreted from sebaceous glands? | [
"progesterone",
"Blood",
"sebum",
"pus"
] | C | Sebaceous glands produce an oily substance called sebum. Sebum is secreted into hair follicles and makes its way to the skin surface. It waterproofs the hair and skin and helps prevent them from drying out. Sebum also has antibacterial properties, so it inhibits the growth of microorganisms on the skin. |
SciQ | SciQ-1784 | physical-chemistry, reaction-mechanism, everyday-chemistry, experimental-chemistry
Title: Need reactants for a rocket I am doing a project in chemistry at the moment to build a rocket out of materials that can be easily bought and that react strongly to create thrust.
I was wondering if anyone knew a good chemical formula for my rocket fuel? I know lots of good fuels and reactants used in amateur rocketry however commercial fuels have been banned from the project.
Any help would be appreciated. Put some potassium nitrate $\ce{KNO3}$ plus powdered charcoal and sulfur in a mortar. Wet it carefully and grind the whole until you get a black homogeneous paste. Let it dry overnight in the mortar. The obtained black gun powder may be detached from the mortar with a wooden spoon. It is a safe rocket fuel. The proportions of the powders are defined by stoichiometry. They must allow the chemical reaction : $$\ce{2 KNO3 + 3 C + S -> K2S + 3 CO2 + N2}$$
I have done it many times with my students. It's a good exercice of stoichiometry. Never had an accident ! And remember : Never ! Never grind dry powders ! Grind as wet powders as possible ! In case of doubt add more water ! Pastes are even a better choice for grinding purposes !
The following is multiple choice question (with options) to answer.
Some reactions need extra help to occur quickly. they need another substance called what? | [
"a catalyst",
"protein",
"hormone",
"neurotransmitter"
] | A | Some reactions need extra help to occur quickly. They need another substance called a catalyst. A catalyst is a substance that increases the rate of a chemical reaction. A catalyst isn’t a reactant, so it isn’t changed or used up in the reaction. Therefore, it can catalyze many other reactions. |
SciQ | SciQ-1785 | electrons, nuclear-physics, radiation, radioactivity, neutrons
For example, if we have $
\newcommand{\U}{\mathrm U}
\newcommand{\Mo}{\mathrm{Mo}}
\newcommand{\Xe}{\mathrm{Xe}}
\newcommand{\n}{\mathrm n}$
$
^{235}_{92}\U$, which decays into $^{98}_{42}\Mo$ and $^{136}_{54}\Xe$, then can we uniquely tell which particles would have been emitted?
The equation would be $$^{235}_{92}\U+ {^{1}_{0}\n} \rightarrow {^{98}_{42}\Mo}+ {^{136}_{54}\Xe} + {}?$$
Now, we know the unknown particles would have a mass of $235+1-98-136=2 $ units and the total charge would be $-4$.
Surely, this could mean $4$ electrons + $2$ neutrons or $5$ electrons + $1$ proton + $1$ neutron and similarly multiple more possibilities.
It was a subpart of a problem asked in a textbook, in which they have taken the case of $4 ~e^{-1}+2 ~^1_0 \n $ and ignored others.
The following is multiple choice question (with options) to answer.
What have approximately the same mass as protons but no charge? | [
"electrons",
"neutrons",
"reactions",
"atoms"
] | B | Neutrons have approximately the same mass as protons but no charge. They are electrically neutral. The mass of a proton or a neutron is about 1836 times greater than the mass of an electron. Protons and neutrons constitute by far the bulk of the mass of atoms. The discovery of the electron and the proton was crucial to the development of the modern model of the atom and provides an excellent case study in the application of the scientific method. In fact, the elucidation of the atom’s structure is one of the greatest detective stories in the history of science. |
SciQ | SciQ-1786 | human-biology, genetics, pathology, chromosome, history
The success of any genetic linkage project depends in large part on
the quality of family material available for study. We initially
invested considerable effort in identifying a useful family from the
National Research Roster for Huntington's Disease Patients and
Families at Indiana University. An American family of reasonable size
was selected and blood samples were obtained (...). Subsequently, a
substantially larger Huntington's disease family was located. This
pedigree stem from a unique community of interrelated Huntington's
disease gene carriers living along the shores of Lake Maracaibo,
Venezuela. (...)For the past three years an expedition has spent one
month annually in Venezuela collecting pedigree information, tissue
samples, and clinical data. (...) In Venezuela, many family members
were examined for three consectuvie years. Permanent lymphoblastoid cell lines were
again established for each individual to act as a permanent source of
genomic DNA. In both families each individual was examined by at least
one neurologist experienced and knowledgable about Huntington's
disease.
The Scitable page also summarizes the approach and results described in the paper. For the RFLP analysis, several DNA probes were tried, of which one, "G8", resulted in a HD-linked pattern:
James F. Gusella and colleagues carried out a study to determine
whether they could identify a DNA probe that would show an
HD-associated restriction fragment length polymorphism (RFLP) when
used in Southern blot analyses of chromosomal DNA digested with the
restriction enzyme HindIII (palindromic recognition sequence
5'-AAGCTT-3'). The team identified one probe out of 12 tested, called
G8, that showed a specific RFLP pattern associated with HD in two
large families with a history of the disease (Gusella et al., 1983).
Using the G8 probe, they next identified two HindIII sites (called H1
and H2) that were palindromic within this chromosomal region. DNA
fragments at these sites vary in length among different HD lineages.
Because researchers used two large pedigrees in these experiments,
they were able to obtain statistical support for their discovery
(Figure 3).
The following is multiple choice question (with options) to answer.
Amniocentesis and chorionic villus sampling can indicate whether a suspected genetic disorder is present at what stage? | [
"adult",
"fetal",
"infant",
"toddler"
] | B | |
SciQ | SciQ-1787 | ocean, ocean-currents, tides
Direct disruption of seabed habitats by physical interference, e.g. from moorings
Disruption of ecological niches: Some organisms have evolved to survive in areas where others cannot - e.g. high current speed environments. Changes in seabed conditions, e.g. from greater or lesser current speeds, may cause them to be out-competed by other species that can then settle there.
Similarly, changes to sediment distribution represent changes to seabed habitats.
Alteration of flow patterns could have implications for species with a dispersive juvenile stage (e.g. larvae that rely on currents to spread) or those that rely on current flow for nutrient or waste transport.
The following is multiple choice question (with options) to answer.
What do you call aquatic biomes in the ocean? | [
"freshwater biomes",
"ocean dwellers",
"coastal biomes",
"marine biomes"
] | D | Anglerfish live in the ocean. Aquatic biomes in the ocean are called marine biomes . Organisms that live in marine biomes must be adapted to the salt in the water. For example, many have organs for excreting excess salt. Two ocean zones are particularly challenging to marine organisms: the intertidal zone and the deep ocean. |
SciQ | SciQ-1788 | human-biology, digestive-system, food
Title: Does sour food cause sweating? While eating sour food or candy, I start to sweat if it's sour enough. My body feels much hotter although my actual temperature is the same, my forehead starts sweating a lot and I feel like it just got twice as hot wherever I am.
Is this a biological phenomena or is my DNA just stupid? Is it somehow related to the digestive system, that sour food is harder to digest? In general, sweating is caused by too much heat, even if you're not aware of the heat. This can happen if the bowel moves and so raises the core temperature. Such movement is often accompanied with sweating, and since you only feel the normal temperature on the skin, it is cold sweat. But at the same time your core is hot so you think it's cold, but it will later mix to normal.
Anyway, it points to unusual bowel movement. This can be due to food allergy or, in a milder form, in food intolerances which are quite common. When it comes to sour ingredients, they are often in fruits, so I'll make a shot in the blue and say that you have a food intolerance against some fruits. You can check this hypothesis by trying chemically pure acetic acid to sour your food. If that doesn't result in sweat/hotness then it's probably the fruits.
http://en.wikipedia.org/wiki/Food_intolerance
The Wikipedia points even directly to salicylate in fruits but I think you cannot exclude allergies against essential oils like limonene and such. Plants are really chemistry factories and not all is well that you can get with them.
The following is multiple choice question (with options) to answer.
The reaction of which body system causes food allergies? | [
"immune system",
"nervous system",
"lymphatic system",
"cardiac system"
] | A | Food allergies are like other allergies. They occur when the immune system reacts to harmless substances as though they were harmful. Almost ten percent of children have food allergies. Some of the foods most likely to cause allergies are shown below ( Figure below ). |
SciQ | SciQ-1789 | terminology, human-physiology, organs
Title: Medical term for "holding urine for a long time" Sometimes I get/feel pain in my stomach because of holding urine for long time. Is there any medical terminology describing: "holding urine for a long time", or pain associated with this activity? A swollen organ may be described as distended if the swelling is symptomatic of a medical disfunction.
The purpose of most bladders is to collect and retain a fluid; if that fluid needs to be discharged periodically, and is not able to do so, then there is usually pain as a result of the distension.
Inability to urinate is known as ischuria or urinary retention, and could be the result of obstruction to the urethra, could be a failure of the bladder to fully contract during urination, or could many other possible causes.
The following is multiple choice question (with options) to answer.
Leaving tampons in for too long can put you at risk of what syndrome? | [
"Vaginismis",
"Scalded Skin Syndrome",
"toxic shock",
"Endometrial Cancer"
] | C | If you are a girl and use tampons, be sure to change them every four to six hours. Leaving tampons in for too long can put you at risk of toxic shock syndrome . This is a serious condition. Signs and symptoms of toxic shock syndrome develop suddenly, and the disease can be fatal. The disease involves fever, shock, and problems with the function of several body organs. |
SciQ | SciQ-1790 | human-anatomy, muscles
Title: Contracting muscles in humans I study biology at school, and unfortunately for me, my program skips the muscles in humans chapter.
I know (and mainly, feel) that the movement in one direction isn't created by the same muscle as the movement in the opposite direction, e.g the Triceps ("front") and Biceps ("back").
I know that the triceps straightens the elbow, while the biceps contracts the elbow.
I also know that, instead of actually moving the arm, I can contract these two muscles (when I show off, for example...) without actually moving the arm. That area becomes hard. Both muscles, as I feel, are contracting. I cannot statically contract only one of them.
My question is whether this action is something "special", or simply both muscles working against each other, resulting in zero movement? The situation you are describing where muscles are situated on opposites sides of a joint and produce opposing movements is called "antagonism." Most joints are set up where one or more muscles on either sides will produce such movements (e.g., flexors vs. extensors). Here's a question about muscles without antagonists.
When you contract all the muscles crossing a joint (i.e., when you are "showing off"), the muscles balance each other. If not, the bones would move and the joint angles would change. So taking the elbow as an example, in the image below, Arnold is contracting the elbow flexors (biceps brachii, brachialis) as well as the elbow extensors (triceps brachii). In order for the bones to remain static, the forces must be equal and opposite.
The following is multiple choice question (with options) to answer.
There are three flat skeletal muscles in the antero-lateral wall of what? | [
"shoulder socket",
"hip joint",
"thoracic cavity",
"abdomen"
] | D | There are three flat skeletal muscles in the antero-lateral wall of the abdomen. The external oblique, closest to the surface, extend inferiorly and medially, in the direction of sliding one’s four fingers into pants pockets. Perpendicular to it is the intermediate internal oblique, extending superiorly and medially, the direction the thumbs usually go when the other fingers are in the pants pocket. The deep muscle, the transversus abdominis, is arranged transversely around the abdomen, similar to the front of a belt on a pair of pants. This arrangement of three bands of muscles in different orientations allows various movements and rotations of the trunk. The three layers of muscle also help to protect the internal abdominal organs in an area where there is no bone. The linea alba is a white, fibrous band that is made of the bilateral rectus sheaths that join at the anterior midline of the body. These enclose the rectus abdominis muscles (a pair of long, linear muscles, commonly called the “sit-up” muscles) that originate at the pubic crest and symphysis, and extend the length of the body’s trunk. Each muscle is segmented by three transverse bands of collagen fibers called the tendinous intersections. This results in the look of “six-pack abs,” as each segment hypertrophies on individuals at the gym who do many sit-ups. The posterior abdominal wall is formed by the lumbar vertebrae, parts of the ilia of the hip bones, psoas major and iliacus muscles, and quadratus lumborum muscle. This part of the core plays a key role in stabilizing the rest of the body and maintaining posture. |
SciQ | SciQ-1791 | physiology, respiration
Title: Why does a worm's skin need to be wet for oxygen to diffuse across it? Pages I've read about worms' respiratory systems says that the skin needs to be wet (covered in mucus) or oxygen won't diffuse across the skin. Why? If there is more oxygen outside the worm's skin than inside, what prevents it from diffusing across the skin, even if the skin is dried out? The quick answer: When the skin dries, the lipids in the cell membranes of the skin tissue undergo a phase transition which makes the membranes less permeable for oxygen.
Explanation: The lipids of the cell membrane can exist in different phase states. In the liquid disordered phase the lipids are relatively flexible and mobile, making this phase more oxygen permeable compared to the liquid ordered phase, in which the lipids are more rigidly packed.
The phase transition temperature of lipids increases upon dehydration (another reference), meaning that at the same ambient temperature, a dry lipid membrane is in the liquid ordered state and a wet lipid membrane is in the liquid disordered state.
Therefore, a dry cell membrane is less oxygen permeable than a wet one.
The following is multiple choice question (with options) to answer.
The dead, dry stratum corneum is the most superficial layer of what and is the layer exposed to the outside environment? | [
"dermis",
"epidermis",
"lungs",
"intestinal"
] | B | Stratum Corneum The stratum corneum is the most superficial layer of the epidermis and is the layer exposed to the outside environment (see Figure 5.5). The increased keratinization (also called cornification) of the cells in this layer gives it its name. There are usually 15 to 30 layers of cells in the stratum corneum. This dry, dead layer helps prevent the penetration of microbes and the dehydration of underlying tissues, and provides a mechanical protection against abrasion for the more delicate, underlying layers. Cells in this layer are shed periodically and are replaced by cells pushed up from the stratum granulosum (or stratum lucidum in the case of the palms and soles of feet). The entire layer is replaced during a period of about 4 weeks. Cosmetic procedures, such as microdermabrasion, help remove some of the dry, upper layer and aim to keep the skin looking “fresh” and healthy. |
SciQ | SciQ-1792 | immunology, immunoglobin
Title: Does class switching occur both in B cells and Plasma cells? I understand that the cell class switches to change the type of immunoglobulin it is producing. The B-cell produces the membrane bound B-cell receptor (BCR) while the plasma cell produces the the secreted form of Ig, the antibody. Now, the isotypes are different in their constant regions and I'm assuming switching only matters if it is an antibody. (differences in avidity, permeability, antibody receptors, etc.)
How would a B-cell receptor (membrane bound Ig) even benefit from class switching? Does class switching even happen in activated B-cells? Or is it a process limited to plasma cells? I read up that BCR also has the 5 isotypes.
What are the specific chronological milestones at which class switching happens in plasma cells and B-cells (if it does)? Short Answer : B-cells class switch to become Plasma cells in the germinal centre of the lymph node.
Long Answer :
There are two important concepts addressed in the question. One is the Immunoglobulin structure - isotype and membrane/soluble type. And the other is the germinal centre B-cell paradigm. Understanding both the concepts are a prerequisite to understand the answer to the issue.
First of all, immunoglobulin synthesized by the lymphocyte can either be membrane bound (known as the B-cell receptor (BCR)) or soluble antibody. After gene rearrangements, the B-cell (still immature) begins to produce membrane bound IgM/IgD. This continues even in the mature B-cell. The membrane bound Ig or mIg has an extra sequence (refer image) on the carboxyl end adding a few hydrophobic amino acid sequences so that it gets anchored well in the hydrophobic part of the membrane. Also at the end is a series of hydrophilic residues involved in downstream cell signalling.
The following is multiple choice question (with options) to answer.
What protein is produced when a plasma cell is stimulated by antigens? | [
"dystrophin",
"immunoglobulin",
"collagen",
"keratin"
] | B | 42.3 | Antibodies By the end of this section, you will be able to: • Explain cross-reactivity • Describe the structure and function of antibodies • Discuss antibody production An antibody, also known as an immunoglobulin (Ig), is a protein that is produced by plasma cells after stimulation by an antigen. Antibodies are the functional basis of humoral immunity. Antibodies occur in the blood, in gastric and mucus secretions, and in breast milk. Antibodies in these bodily fluids can bind pathogens and mark them for destruction by phagocytes before they can infect cells. |
SciQ | SciQ-1793 | newtonian-mechanics, forces, vectors
Title: What are the vector forces that cause a high side accident? I was accelerating my bicycle around a corner and leaning hard to the left. I felt my rear wheel hop and looked back to see what I had just hit. What I saw was that the bicycle had rotated such that the wheel had flipped from leaning to the left to leaning horizontally to the right. The next moment I slammed into the sidewalk. From tire hop to crash happened in a second.
When I saw the rear wheel had flipped from left to right, my immediate reaction was "How did that possibly happen?" I then hit the sidewalk.
Since the accident, I've been trying to understand how the forces the bike and I were experiencing ended up rotating the bicycle such that it rotated some 120 degrees to the right. The 120 degree is a guess assuming I was initially leaning 30 degrees leftward and ended up horizontal with my head to the right.
I described the accident to a motorcycling friend the other day and he said "Sounds like a high side to me." Looking at some motorcycle videos I would agree except they appear to involve braking issues and I was accelerating when the accident happened. Both accidents entail the rear wheel losing contact.
So two questions:
The following is multiple choice question (with options) to answer.
An unbalanced force on an object in motion causes what? | [
"agitation",
"acceleration",
"vibration",
"velocity"
] | B | An object will not change its state of motion (i. e. , accelerate) unless an unbalanced force acts on it. Equal and oppositely directed forces on the same object do not produce acceleration. |
SciQ | SciQ-1794 | homework, reproduction, allele
Title: Albinism inheritance problem: what are the father's alleles if he got an albino kid?
Albinism is caused by a recessive gen "c". A normal man marries an
albino woman. The first son happened to be albino. What are the
possible phenotypes of the parents? What is the chance that their
other kids will be albino?
Alright, since "c" is recessive and the woman is albino, then the woman must be "c c" right? And since the son is albino, he must be "c c" too. Hence the father must have at least one "c". But since he is normal, then the other allele must NOT be "c" too (otherwise he would be albino).
My question is, when writing the Mendel table, how do I express that allele of the father (the one that is not "c")?
$$\begin{bmatrix} & c & c\\
? & ?c & ?c\\
c & cc & cc\end{bmatrix}$$
I marked it with $?$ because I'm not sure what to put there. My first thought was "well, it could be a capital C I guess..." - but that doesn't sound right to me. A capital C would mean there is a dominant albinism allele (but I am told that albinism is recessive only...)
I can see clearly that there is a 50-50 chance of having albino kids. I just don't know how to draw that inheritance table. Super oober short answer: The father is Cc, the mother is cc, there is a 50% chance the children will be albino (as you predicted).
An explination on Mendelian genetics:
First let's look at (what a lot of people consider) the normal Mendel table from here:
The following is multiple choice question (with options) to answer.
Partial albinism results from a mutation in an enzyme that is involved in the production of what? | [
"cancer",
"hair",
"melanin",
"cytoplasm"
] | C | The pointed pattern is a form of partial albinism, which results from a mutation in an enzyme that is involved in melanin production. The mutated enzyme is heat-sensitive; it fails to work at normal body temperatures. However, it is active in cooler areas of the skin. This results in dark coloration in the coolest parts of the cat's body, such as the lower limbs and the face, as shown in Figure above . The cat’s face is cooled by the passage of air through the nose. Generally adult Siamese cats living in warm climates have lighter coats than those in cooler climates. |
SciQ | SciQ-1795 | pregnancy, children
Title: What happens to the umblical cord inside the mother? After giving birth to a child, the umblical cord is cut (and stored if they want). The end connected to the child's navel will fell off eventually but what happens to the end inside the mother?
Will it be removed right after birth by doctors or what happens? Labor is typically divided into 3 stages:
Stage 1: From the onset of contractions (true labor pains) to full dilatation of the cervix (which is about 10 cm) - this takes about 12 to 18 hours
Stage 2: From full dilatation of cervix to expulsion of fetus - This takes about ~ 30 minutes
Stage 3. From expulsion of fetus to expulsion of placenta - this takes about ~ 15 minutes. During the third stage, the umblical cord which is attached to placenta is expelled along with the placenta. This would be the answer to your question.
Source:Hympath.com
The following is multiple choice question (with options) to answer.
Where does a baby travel to after leaving the uterus? | [
"ear canal",
"nasal canal",
"tissue canal",
"birth canal"
] | D | Some processes in the body are regulated by positive feedback. Positive feedback is when a response to an event increases the likelihood of the event to continue. An example of positive feedback is milk production in nursing mothers. As the baby drinks her mother's milk, the hormone prolactin, a chemical signal, is released. The more the baby suckles, the more prolactin is released, which causes more milk to be produced. Other examples of positive feedback include contractions during childbirth. When constrictions in the uterus push a baby into the birth canal, additional contractions occur. |
SciQ | SciQ-1796 | python, parsing, numpy, scipy
if 'electric' in producer.energy:
recipe = self.produce(cls, producer, **kwargs)
recipe.rates['Energy'] = energy
yield recipe
elif 'heat' in producer.energy:
recipe = self.produce(cls, producer, **kwargs)
recipe.rates['Heat'] = energy
yield recipe
elif 'burner' in producer.energy:
for fuel_name in producer.valid_fuel.split('+'):
fuel_name = fuel_name.strip().lower()
fuel = all_items[fuel_name]
fuel_value = parse_power(fuel.fuel_value)
new_kwargs = dict(kwargs)
if self.title:
title = self.title
else:
title = f'{self.resource} ({producer})'
new_kwargs['title'] = f'{title} fueled by {fuel_name}'
recipe = self.produce(cls, producer, **new_kwargs)
recipe.rates[fuel.title] = energy / fuel_value
yield recipe
else:
raise NotImplementedError()
tree_re = re.compile(r'(\d+) .*?\|([^}|]+)\}')
def wood_mining(self) -> Iterable[MiningRecipe]:
miners = tuple(
ManualMiner(tool)
for tool in all_items.values()
if tool.prototype_type == 'mining-tool'
)
for m in self.tree_re.finditer(self.resource.mining_time):
mining_time, source = int(m[1]), m[2]
for miner in miners:
yield self.produce(
MiningRecipe, miner,
mining_hardness=float(self.resource.mining_hardness),
mining_time=mining_time,
title=f'{self.resource} ({miner} from {source})')
The following is multiple choice question (with options) to answer.
Name an important natural resource in and of itself. | [
"food chain",
"water",
"biodiversity",
"habitat"
] | C | It’s obvious that living things are important natural resources needed by human beings. After all, other species provide us with all of the food we eat. We couldn’t survive without them. But that’s far from the only reason that other species are important for human survival. Biodiversity is an important natural resource in and of itself. |
SciQ | SciQ-1797 | terminology, htm
Title: Biological analogy for boosting and inhibition idea in Hierarchical Temporal Memory (HTM) I've just watched the 9th episode of HTM school about the "boosting" and "inhibition" ideas. However, I couldn't find the neuroscience counterpart of these terms and concepts. Since HTM is a biologically-constrained theory, the "boosting" and "inhibition" concepts must have a neuroscience counterpart. What are they?
The video also discusses homeostasis and homeostatic regulation of neuronal excitability. Do these concepts have something to do with "boosting" and "inhibition"? After doing some research, I found that "boosting" and "inhibition", in the context of HTM, are Numenta's implementation of homeostasis.
The following is multiple choice question (with options) to answer.
In classical conditioning, a response called the conditioned response is associated with what? | [
"conditioned stimulus",
"external inhibition",
"blocking effect",
"unconditioned stimulus"
] | A | Conditioned Behavior Conditioned behaviors are types of associative learning, where a stimulus becomes associated with a consequence. During operant conditioning, the behavioral response is modified by its consequences, with regards to its form, strength, or frequency. Classical Conditioning In classical conditioning, a response called the conditioned response is associated with a stimulus that it had previously not been associated with, the conditioned stimulus. The response to the original, unconditioned stimulus is called the unconditioned response. The most cited example of classical conditioning is Ivan Pavlov’s experiments with dogs (Figure 45.40). In Pavlov’s experiments, the unconditioned response was the salivation of dogs in response to the unconditioned stimulus of seeing or smelling their food. The conditioning stimulus that researchers associated with the unconditioned response was the ringing of a bell. During conditioning, every time the animal was given food, the bell was rung. This was repeated during several trials. After some time, the dog learned to associate the ringing of the bell with food and to respond by salivating. After the conditioning period was finished, the dog would respond by salivating when the bell was rung, even when the unconditioned stimulus, the food, was absent. Thus, the ringing of the bell became the conditioned stimulus and the salivation became the conditioned response. Although it is thought by some scientists that the unconditioned and conditioned responses are identical, even Pavlov discovered that the saliva in the conditioned dogs had characteristic differences when compared to the unconditioned dog. |
SciQ | SciQ-1798 | bond, ionic-compounds, covalent-compounds, boron-family
The answer given was 4.
I get that there might be an exception but I'm not able to find it anywhere. If there exists an ionic compound of boron, could someone please mention that to me? Boron can form ions but there is some fine print. You won't get monatomic cations like the metals below it. Instead, ionic boron structures are formed from clusters where the ionic bonding is driven by the molecular orbital structures in these clusters, not by electronegativity (cf. This answer).
Such clusters are internally held together by covalent bonds between the boron atoms, so in this sense boron is still forming covalent bonds. The ionic bonds would be with atoms of other elements outside the boron cluster. Since the valence shells of a neutral boron atom are less than half filled the clusters will likely have low-energy, bonding orbitals that require electrons from outside atoms. Thus the boron clusters will be anionic and the ionic bonds will be most likely formed with electropositive metals. As suggested in the comments, magnesium diboride, $\ce{MgB2}$, is one of the most widely studied compounds containing such boron clusters. It has drawn much research interest because of its relatively high critical temperature (39 K) for superconductivity, which may be related to the impact of ionic magnesium-boron bonding on the eletronic interactions that lead to superconduction.
Magnesium diboride has a layered structure in which magnesium layers alternate with boron layers. The latter are covalently bonded into a hexagonal honeycomb, resembling a carbon layer in graphite. However, in the boron layers each atom supplies only three electrons per atom instead of four, so the layers may act as electron-accepting structures to form macro-anion having the formula $\ce{B^-}$. An ionic model for the diboride would then have the empirical formula $\ce{Mg^{2+}(B^-)2}$. Here I discuss two references I have examined, in which the bonding is examined and the results may be compared with this model.
The following is multiple choice question (with options) to answer.
What kind of bonds does boron form rather than metallic lattices? | [
"multicenter",
"bilateral",
"electron bonds",
"magnetic bonds"
] | A | Boron forms multicenter bonds rather than metallic lattices with delocalized valence electrons. Why does it prefer this type of bonding? Does this explain why boron behaves like a semiconductor rather than a metal? Explain your answer. |
SciQ | SciQ-1799 | 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 broad group of living things serves as the major producers in terrestrial biomes? | [
"animals",
"vases",
"plants",
"flowers"
] | C | Plants are the major producers in terrestrial biomes. They have five basic needs: air, warmth, sunlight, water, and nutrients. How well these needs are met in a given location depends on the growing season and soil quality, both of which are determined mainly by climate. |
SciQ | SciQ-1800 | botany, mathematical-models, statistics, biostatistics, migration
Title: Biostatistics: Pollen dispersal directionality What Information am I looking for?
Think about a tree that is sending pollen all over the place. Because of wind, most pollen grain will go toward one direction. Imagine, we split the 2D area around the tree where pollen grains fall into two half disks of equal size. We chose the disks so that the number of pollen grains falling into one half-disk is minimized and the quantity of pollen falling in the other half-disk is maximized.
The information I need is what proportion of pollen grain falls into each disk? Is it $\frac{0.5}{0.5}$ (in which case the wind would have no effect) or is it something like $\frac{0.8}{0.2}$?
Where to get the information from?
I was reading this paper about pollen dispersal directionality and was trying to extract the info I need.
On pages 4 and 5 they explain their analysis under the section statistical procedure. More specifically, in the first paragraph of the 5th page, they seem to describe the meaning of the parameters that are trying to estimate. One of them is the so-called directionality parameter $\delta$. I don't understand how to interpret this parameter $\delta$. This parameter is part of a logistic regression I think (although the authors do not characterize it as such) of "mating success" $y$ against variables $d$ ("distance") and $h$ ("height") and an angular variable $a = \cos(\alpha_0 - \alpha)$. ($\alpha_0$ is the "presumed prevailing direction of effective pollen dispersal," which apparently is not estimated from these data.) The corresponding parameters of the model are $\beta$, $\gamma$, and $\delta$, respectively, hence
$$\phi_j = \Pr(y_j = 1) = \frac{\exp\left(\beta d_j + \gamma h_j + \delta a_j\right)}{\sum_{k=1}^r \exp\left(\beta d_k + \gamma h_k + \delta a_k\right)}$$
The following is multiple choice question (with options) to answer.
Birds that move pollen from flower to flower are called what? | [
"carnivores",
"spores",
"pollinators",
"frogs"
] | C | Nectar-feeding birds are important pollinators , meaning they move the pollen from flower to flower to help fertilize the sex cells and create new plants. Hummingbirds, sunbirds, and the honey-eaters are common pollinators. |
SciQ | SciQ-1801 | air-pollution
Title: Less pollution: moving hurricane debris to other regions for use, or burning? When a big hurricane hits, it can create debris on the scale of $\mathrm{10^8 yd^3}$. Cities in Florida, Texas, and other affected areas are struggling to hire enough trucks and drivers to pick it up quickly. But aside from that, I noticed many of the areas have started to burn the debris once it starts building up.
Got to wondering... typically mulch comes in modestly pricey, and when free mulch is offered, it often goes quickly.
So assuming a fair portion of debris is mulchable and is of interest to other areas, and that we can acquire typical transportation resources, then we'll set up transfer from collection sites to those other regions rather than burning it. What would be the net pollution result?
If removed for mulch and such: trucking pollution + decomposition (- trees saved locally??)
If burned: the burning pollution.
Obviously it's about approximation rather than exacts, it's probably hard to appraise the different byproducts from burning versus decomposition, and a lot probably depends upon the way it is burned. But as a whole, can we get a rough estimate of comparable quantities/damage done... is it less pollution/damage even to truck it an average of 3000 miles? 1000 miles? 100 miles? 10 miles? Should it be burned on the spot (if done safely)? Would think there's got to be some way to get a very rough idea.
Certainly the best option if viable might be leaving it in place to decompose. But considering how upset people are getting at having debris around these parts a month later, exclude that option from the possibilities.
Trucking or burning, how do they compare? As the question was changed, my answer attempts to evaluate only the difference between burning and transporting. Please correct my values if my quickly found sources are inaccurate or you find more representing. I know there is quite a few unwritten assumptions that simplify this problem.
The following is multiple choice question (with options) to answer.
The major cause of outdoor air pollution is the burning of? | [
"fossil fuels",
"trash",
"charcoal briquettes",
"trees"
] | A | The major cause of outdoor air pollution is the burning of fossil fuels. |
SciQ | SciQ-1802 | newtonian-mechanics, work, string
Title: Why pulley systems give mechanical advantage? In a system with 2 pulleys, to lift a x kg object y meters I would need half the force that the object exerts due to gravity but pull the rope double the distance, why does this happen this way? This can be viewed as a requirement of the work-energy theorem and the conservation of energy. Assuming you alter the system slowly enough that parts don't gain a significant kinetic energy, the work you do by pulling the rope must be equal to the work done against gravity or any other forces that may be applicable. If you pull the rope with a force $F$ by a distance $a$, and the object of interest with weight $W$ is lifted a distance of $b$, we have
$$ F a \ge W b, $$
where equality holds in idealized systems where work is only being done by pushing the weight $W$ against gravity. For a pulley system, this means having no friction, massless strings and massless pulleys. If $ a = 2b $ in such an idealized system, then $ F = W/2 $.
The following is multiple choice question (with options) to answer.
What is the ideal mechanical advantage in the single fixed pulley? | [
"2",
"1",
"4",
"zero"
] | B | In the single fixed pulley, only one rope segment pulls up on the load, so the ideal mechanical advantage is 1. In other words, this type of pulley doesn’t increase the force that is applied to it. However, it does change the direction of the force. This allows you to use your weight to pull on one end of the rope and more easily raise the load attached to the other end. |
SciQ | SciQ-1803 | computability, turing-machines, physics
Title: Can normal physics laws be simulated in Digital physics? Physics is defined as the study of an object {matter or energy} with its interaction with other objects:
Physics is the study of matter, energy, and the interaction between them.
On the other hand, Digital physics is based on computations and information.
Digital physics is a collection of theoretical perspectives based on the premise that the universe is, at heart, describable by information, and is therefore computable.
The following is multiple choice question (with options) to answer.
What science is the study of matter and the changes it undergoes? | [
"biology",
"chemistry",
"astronomy",
"geology"
] | B | Chemistry is the study of matter and the changes it undergoes. |
SciQ | SciQ-1804 | the-sun, solar-wind
Title: How much water on the earth is made from hydrogen comes with solar wind? A great fraction of solar wind is protons or Hydrogen ions. Some part of it is captured by Earth. I am wondering how much water in my half a liter cup is made of hydrogen from the Sun. Here is a way of getting a rough upper bound: the density $\rho$ of the solar wind is about 4 atoms per cm$^3$ (that we can assume are hydrogen), and it travels at $v=400-500$ km/s. That means that were the Earth to catch every atom directed at it it would gain $\pi R_\oplus^2 \rho v$ atoms per second, $2.0$ to $2.5\cdot10^{14}$. Which gives us a mass flow of $3.4$ to $4.3\cdot 10^{-13}$ kg/s. Earth has been around for 4.5 billion years, so over that time at most about 49 to 61 tons of hydrogen have arrived.
The total amount of liquid water on Earth is $V=1.386\cdot 10^9$ km$^3$ (which doesn't count the sizeable amount of water bound in rocks). About 11.19% of this mass is hydrogen, so the weight of hydrogen is $0.1119 V\rho_{water}=1.55\cdot 10^{20}$ kg. So the ratio between hydrogen from Earth and from the sun is about $2$ or $3\cdot 10^{15}$.
Still, in a half liter (about 27.7 mol water) there are $3.33\cdot 10^{25}$ hydrogen atoms, so there should be about 11 to 16 billion solar hydrogen atoms in the cup if this estimate is right.
Maybe Earth's magnetic field captures more atoms, which might increase the value. Likely most solar wind is instead pushed away and the true value is much lower. But I am pretty confident there are some solar atoms in the cup.
The following is multiple choice question (with options) to answer.
What is driven by the sun's energy and moves water over the surface of earth? | [
"sun cycle",
"the water cycle",
"tides",
"weather cycle"
] | B | The Sun heats some areas more than others, which causes wind. The Sun's energy also drives the water cycle, which moves water over the surface of the Earth. Both wind and water power can be used as renewable resources. |
SciQ | SciQ-1805 | electrical-engineering, materials, heat-transfer
Title: Material which can be used for resistive heating and simultaneous temperature measurement I want to embed a wire inside a plastic and heat it to specific temperatures (80$^\circ$C 100$^\circ$C 130$^\circ$C 180$^\circ$C). I want to find a material that is resistive enough for resistive heating, but also I want the wire's resistivity to vary fairly strongly with temperature - this way I can know the actual temperature that I'm getting by looking at the resistance during the heating process.
My problem is that I cannot seem to find a material with the properties I want. I tried nichrome wire and carbon fibers, and while they are resistive enough to give me heat, their resistance does not change enough (for my desired temperature ranges) to be measurable with my setup. Just about anything you can find will exhibit a temperature dependence on its resistivity. The first hit looking up nichrome says it's temperature dependence is 0.004/°C.
A better model for resistivity is the Steinhardt-Hart(sp?) equation, but you probably don't need something that elaborate. Since you only want to control the temperature to 4 discrete values, you can figure out ahead of time what the total resistance of a particular diameter and length of wire will be at each of those 4 temperatures.
To measure the resistance, you need to measure the voltage across the wire and the current thru it, then divide. With the right analog electronics, these values can be presented to A/D inputs of a microcontroller, which can compute the resistance, determine the temperature, then vary the current via a controller accordingly.
I'd probably implement the resistance to temperature function as a piecewise-linear table lookup. That's quick to compute and can model any non-linearities without lots of cycles.
The following is multiple choice question (with options) to answer.
What are materials that are poor thermal conductors called? | [
"pollution insulators",
"warmth insulators",
"sunlight insulators",
"thermal insulators"
] | D | Particles of gases are farther apart and have fewer collisions, so they are not good at transferring thermal energy. Materials that are poor thermal conductors are called thermal insulators . Figure below shows several examples. Fluffy yellow insulation inside the roof of a home is full of air. The air prevents the transfer of thermal energy into the house on hot days and out of the house on cold days. A puffy down jacket keeps you warm in the winter for the same reason. Its feather filling holds trapped air that prevents energy transfer from your warm body to the cold air outside. Solids like plastic and wood are also good thermal insulators. That’s why pot handles and cooking utensils are often made of these materials. |
SciQ | SciQ-1806 | inorganic-chemistry, redox, stoichiometry
Title: Balancing disproportionation reactions How to balance the following disproportionation reaction
$$\ce {XeF2 + H2O → Xe + XeO3 + HF + O2} $$
My attempt: I tried by making total number of reductions equal to total number of oxidation but I couldn't do because Xe is both oxidised and reduced also the solvent is water so what should I do to balance protons and oxygen on both sides?. Please help by solving it on the basis of same procedure that is making oxidation equal to reduction It can't be balanced unambiguously, for this is not a single reaction, but a mechanical sum of two reactions, and these can be formally mixed in arbitrary proportion.
The first reaction is indeed a disproportionation. To balance it, use the common trick: consider these two xenons different elements for a while.
$$\ce{\underbrace{XeF2}_{for\;reduction} + \underbrace{XeF2}_{for\;oxidation} +H2O->Xe + XeO3 + HF}$$
The second is a typical redox:
$$\ce{XeF2 + H2O -> Xe + O2 + HF}$$
The following is multiple choice question (with options) to answer.
Balanced chemical reactions are balanced in what? | [
"molecular bonds",
"terms of moles",
"atoms",
"electrical charge"
] | B | Balanced chemical reactions are balanced in terms of moles. |
SciQ | SciQ-1807 | physiology, cardiology, blood-circulation
Title: What is the quality rate of intrinsic autoregulation in the heart? Autoregulation is the maintenance of constant blood flow to an organ in spite of fluctuations in Blood pressure.
It involves the relaxation of myocardium and contraction.
It is local.
I know that autoregulation is best done in the brain, well in kidneys and badly in skeletal muscle.
I am interested how it is in the heart.
I think it should be at least good.
Brain can be thought more important.
However, I am not sure.
How good is the autoregulation of the blood flow in the heart? My conjecture: Intrinsic regulation is done in the heart the second best, after the brain.
This idea is based on the fact that the brain controls heart's some autonomic functions.
It is an open research question how the autonomic nervous system affects the intrinsic functions of the heart - and the reverse is true too.
To answer this question, we need to understand the autonomic regulation of the heart better i.e. the inner-physiology of the heart's electrical activity.
The following is multiple choice question (with options) to answer.
The autonomic nervous system serves as the relay between what and the internal organs? | [
"central nervous system",
"hormones",
"somatic system",
"peripheral nervous system"
] | A | The autonomic nervous system serves as the relay between the CNS and the internal organs. It controls the lungs, the heart, smooth muscle, and exocrine and endocrine glands. The autonomic nervous system controls these organs largely without conscious control; it can continuously monitor the conditions of these different systems and implement changes as needed. Signaling to the target tissue usually involves two synapses: a preganglionic neuron (originating in the CNS) synapses to a neuron in a ganglion that, in turn, synapses on the target organ (Figure 16.24). There are two divisions of the autonomic nervous system that often have opposing effects: the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system is responsible for the immediate responses an animal makes when it encounters a dangerous situation. One way to remember this is to think of the “fight-or-flight” response a person feels when encountering a snake (“snake” and “sympathetic” both begin with “s”). Examples of functions controlled by the sympathetic nervous system include an accelerated heart rate and inhibited digestion. These functions help prepare an organism’s body for the physical strain required to escape a potentially dangerous situation or to fend off a predator. |
SciQ | SciQ-1808 | ecology
Title: Do invasive species cause long-term damage to ecosystems they invade? Growing up in the U.S., I was warned at various times of the dire consequences of a variety of introduced pests (usually insects).
Japanese beetles, gypsy moths, and most recently the brown marmorated stink bug are all introduced pests that, at various times, were described as serious threats to our ecology.
These threats aren't confined to arthropods, either. The giant African land snail is causing a stir in Florida (indeed, Florida seems to suffer from an excessive variety of introduced species.
"Lack of native predators" is frequently cited as the primary reason many invasive species are considered such a risk to the ecology.
I understand that these introduced species can place tremendous pressure on native species that fill similar ecological niches, and may even push these species out of the region due to competition for food and habitat. However, do the overall ecologies that these species are introduced to adjust over long periods of time?
The numbers of Japanese beetles and gypsy moths don't seem anywhere as high as when I was a child. Has the ecosystem adjusted, or has the overpopulation self-corrected as the species ran low on food through over-consumption? Or are the populations still just as problematic now as they were 30 years ago, and I just am not seeing the bigger picture?
What is the long-term impact that we've seen from invasive, introduced species? Is there a significant difference on the long-term impact between introduced flora, arthropods, or mammals? The answer really depends on how you think of invasive. One extreme answer is to say that all things are relative, and that the concepts of local and invasive are all relative. This matters to a certain extent because ecologists draw a fuzzy line between invasive and naturalized. You could start with some basic species that we all think of as either good, local, or neutral. Take the earthworm. Most people think of it as a common native species, but the earthworm is actually an invasive species that has radically changed much of North America that came over with the Europeans. Similarly, brown trout are also invasive, coming to the US in the 1800's.
The following is multiple choice question (with options) to answer.
The role that a particular species plays in its ecosystem is also known as what? | [
"unique",
"type",
"niche",
"market"
] | C | Niche is the role that a particular species plays in its ecosystem. This role includes all the ways that the species interacts with the biotic and abiotic factors in the ecosystem. |
SciQ | SciQ-1809 | particle-physics, elements
Title: Is it possible to create a new element that doesn't exist in the universe? When I say something new I do not refer to something already made like H,O etc and when I mean something new I do not refer to a transformation like tritium to helium and gold.
If so how ?(I mean is there a specific way to do that ?) Yes, so far, 20 synthetic elements have been created, with atomic numbers 99 (Einsteinium) to 118 (Ununoctium). All these elements are unstable, with half-lives ranging from a year to a few milliseconds.
You can find a list on wikipedia. These elements are produced in specialized nuclear reactors, by bombarding heavy elements like Uranium and Plutonium with neutrons or other elements.
The following is multiple choice question (with options) to answer.
What element has the atomic number 16? | [
"sulfur",
"neon",
"oxygen",
"helium"
] | A | |
SciQ | SciQ-1810 | solar-system, history
Earth at the center.
Moon orbiting the Earth.
Mercury orbiting the Earth farther than the Moon.
Venus orbiting the Earth farther than Mercury.
Sun orbiting the Earth farther than Venus.
Mars orbiting the Earth farther than Sun.
Jupiter orbiting the Earth farther than Mars.
Saturn orbiting the Earth farther than Jupiter.
The celestial sphere of stars rotating around the Earth, being the outermost sphere.
The following is multiple choice question (with options) to answer.
Name the most famous satellite of the earth? | [
"the moon",
"skylab",
"sputnik",
"demos"
] | A | |
SciQ | SciQ-1811 | optimization, digital-circuits
Title: Determining whether a digital circuit is optimal Are there any techniques that can be used to determine whether a digital logic circuit is optimal, or if it has extraneous operations that don't contribute to the output?
I'm especially curious in the case where the circuit is defined in terms of XOR and AND gates.
I know I could make a karnaugh map and create a circuit from that, but that doesn't really tell me about the circuit I had, it just gives me another circuit.
Thanks for any info! Use one of the standard techniques for circuit minimization. As far as I know, verifying that a candidate circuit is minimal is as hard as finding the minimal circuit in the first place (I know of no faster algorithm for verifying minimality than finding a minimal circuit in the first place).
Circuit minimzation is NP-hard (in fact it's even harder than that, in some sense), so you shouldn't expect an efficient algorithm for it that handles all functions efficiently.
The following is multiple choice question (with options) to answer.
What is the minimum number of loops a circuit can have? | [
"1",
".1",
"3",
"2"
] | A | An electric circuit consists of at least one closed loop through which electric current can flow. Every circuit has a voltage source such as a battery and a conductor such as metal wire. A circuit may have other parts as well, such as lights and switches. In addition, a circuit may consist of one loop or two loops. |
SciQ | SciQ-1812 | species-identification, microbiology, microscopy
Title: Identification of protozoa under microscope I observed maybe Protozoa from standing FRESH water and from slowly flowing FRESH water. I am complete dilettante. Can you tell what these creatures are?
https://www.youtube.com/watch?v=6D5ck3zNJzA&t=474s
Thank you.
Added picture for to be more specific At first glance, the organisms may hold the appearance of protozoans like ciliates. However, I am of the belief that these 'totally tubular' micro organisms are in fact diatoms.
The diatoms are a diverse range of eucaryotic microalgae which comprise a large percentage of the phytoplankton group. (Diatomaceous earth is the residual remains of their calcareous walls)
They are likely diatoms because of their apparent hard membrane, and slight brown-green pigment, typical of heterokont diatoms.
I would be unable to specify the organism to family level. However, you may wish to complete your investigation by looking under the order 'Pennales'.
For general information regarding the Diatoms, you may visit https://en.wikipedia.org/wiki/Diatom
Morphology and description available from: https://books.google.co.uk/books?id=xhLJvNa3hw0C&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
Good luck
The following is multiple choice question (with options) to answer.
What type of organism is algae? | [
"bacteria (cyanobacteria)",
"yeast",
"virus",
"amoeba"
] | A | Describe why algae is a good source of biofuel. |
SciQ | SciQ-1813 | soil, minerals, terminology, soil-science
Title: "Down wash" as a source for mineral particles in the soil In a previous IGCSE examination paper$^1$, the following question was asked and answer provided:
State one source of mineral particles in soil.
Marking Scheme:
Accept any one of:
rock;
down wash;
What's "down wash" and how is it responsible for providing minerals to soil? Googling the term lead me to an aerodynamics definition, which I doubt is the one referred to by the marking scheme.
$^1$ UCLES. Environmental Management, 0680/12, Paper 1. Cambridge International General Certificate of Secondary Education, February/March 2017. Downwash can be part of some erosion environments where minerals are moved down from their host rock environment to another location.
Black Snake Range - Granite Slopes, Victoria, Australia
The crest of the divide rises to almost 400 metres and at this site there are numerous exposed granite slopes and large boulders near the ridge crest. The lower slopes have a cover of granite downwash and the minor valleys have become partly infilled with this granitic sand wash, and hence they are swampy
Southdowns, UK, page 4
Overlying the bedrock geology are drift deposits of alluvium (along the numerous
streams) and ‘head’ (downwash deposits at the base of the Greensand Hills around
Liss and Petersfield).
In the Discussion section of Slope Stability and Slope Formation in the Flysch Zone of the Vienna Forest (Austria)
The downwash of the basal clays and marls, uncovering the solid bedrock, has to be regarded as the main aspect of this phase
The following is multiple choice question (with options) to answer.
When water slows down, it starts depositing sediment, starting with which particles first? | [
"largest",
"lightest",
"smallest",
"finest"
] | A | How water transports particles depends on their size. When water slows down, it starts depositing sediment, starting with the largest particles first. |
SciQ | SciQ-1814 | endocrinology, glucose, homeostasis, insulin, hypothalamus
Title: Role of the Hypothalmus in the control of Blood Sugar In homeostatic regulation of blood glucose, the receptor and effector is the Pancreas, but how does the control centre — the Hypothalamus — connect and link into this process? Your question doesn’t make it clear whether you think that the pancreas must be under the control of the hypothalmus, or whether you are asking whether it has an influence on the pancreas in relation to the secretion of insulin and glucagon, which control the concentration of blood glucose.
First, it has been long known that secretion of insulin can be influenced by the concentration of glucose in isolated pancreatic islets in vitro, so it can not be true that the effects must involve the hypothalmus. This is implicit in most book or general information articles you might find on the web, but for an original reference a review by W.J. Malaisse in Diabetologia 9, 167–173 (1973) seems highly cited.
I know almost nothing about physiology, but on searching the web for the role of the hypothalmus in glucose homeostasis, found a most readable prize-winning postgraduate essay on the topic by Syed Hussein of Imperial College London. I trust that it is in order to append an edited extract of this:
The following is multiple choice question (with options) to answer.
Because they control many cell activities - as well as being controlled by feedback mechanisms - what substances are very important for homeostasis? | [
"enzymes",
"hormones",
"acids",
"proteins"
] | B | Hormones control many cell activities, so they are very important for homeostasis. But what controls the hormones themselves? Most hormones are regulated by feedback mechanisms. A feedback mechanism is a loop in which a product feeds back to control its own production. Most hormone feedback mechanisms involve negative feedback loops . Negative feedback keeps the concentration of a hormone within a narrow range. |
SciQ | SciQ-1815 | muscles, lungs, human-physiology
Title: Why is there smooth muscle in our bronchioles? Having muscle tissue in our bronchioles that can constrict seems like a poor choice for tissue. Why would our airway want to ever close up? Wouldn't it be more beneficial for our bronchioles to just remain open? There are at least two things to consider.
First, ability to limit airflow is a defense mechanism for animal. Imagine getting into area of some sort of toxic evaporation, e.g. CO2 cloud near volcano , then it makes sense to decrease delivery of toxin via lungs to minimum. As I understand, that is what an allergic asthma attack. (Sorry for not providing good enough source of that)
Secondly, you are incorrect in assuming that normal state is "dilated". Dilation of branchioles is sympathetic ("fight-and-fly") response of the nervous system to something like danger, that requires short-term boost in energy production. That is, by default, your airflow is limited. Probably, to limit amount of energy you effectively burn via oxygenation. But most importantly, you leave yourself a reserve in terms of oxygen supply for critical moments.
Some more information you might find here.
The following is multiple choice question (with options) to answer.
Contraction of what large, sheet-like muscle results in inhalation? | [
"pelvic floor",
"uterus",
"diaphragm",
"deltoid"
] | C | Inhaling is an active movement that results from the contraction of a muscle called the diaphragm. The diaphragm is large, sheet-like muscle below the lungs (see Figure below ). When the diaphragm contracts, the ribcage expands and the contents of the abdomen move downward. This results in a larger chest volume, which decreases air pressure inside the lungs. With lower air pressure inside than outside the lungs, air rushes into the lungs. When the diaphragm relaxes, the opposite events occur. The volume of the chest cavity decreases, air pressure inside the lungs increases, and air flows out of the lungs, like air rushing out of a balloon. |
SciQ | SciQ-1816 | acid-base, ionic-compounds, erratum
Title: Are all ionic compounds salts? According to Wikipedia:
A salt is an ionic compound that can be formed by the neutralization
reaction of an acid and a base.
Are all ionic compounds salts? Are all salts ionic compounds? Interestingly, IUPAC states that a "salt" is "a chemical compound consisting of an assembly of cations and anions". Under this definition, all ionic compounds are salts, and all salts are ionic compounds.
Therefore, something like sodium hydroxide ($\ce{Na+OH-}$, definitely an ionic compound) could actually be correctly called a salt. This clashes with the commonly taught high-school level definition of a salt ("the product of an acid-base reaction"), unless you consider very general definitions of acids and bases such as the Usanovich definition, whereby sodium metal $\ce{Na^0}$ is an electron donor (and therefore a base) and water is an electron acceptor (and therefore an acid).
That said, the high-school definition is too simplistic. It is common for compounds to be an acid, a base and a salt all at the same time; consider for example sodium bicarbonate ($\ce{Na+HCO3-}$). It is made of cations and anions, and therefore is definitely a salt. Furthermore, it can act as both a Brønsted–Lowry acid ($\ce{NaHCO3 + OH- -> H2O + Na+ + CO3^2-}$) and as a Brønsted–Lowry base ($\ce{NaHCO3 + H+ -> Na+ + H2CO3}$). Another amusing example is hydrazinium sulfate, a salt, acid and base, where both the cation and anion are also both acids and bases!
The following is multiple choice question (with options) to answer.
What type of ionic compound is formed from acid and bases reacting with each other? | [
"isolated",
"salt",
"dry",
"common"
] | B | Acids have some properties in common. They turn litmus, a plant extract, red. They react with some metals to give off H2 gas. They react with carbonate and hydrogen carbonate salts to give off CO2 gas. Acids that are ingested typically have a sour, sharp taste. (The name acid comes from the Latin word acidus, meaning “sour. ”) Bases also have some properties in common. They are slippery to the touch, turn litmus blue, and have a bitter flavor if ingested. Acids and bases have another property: they react with each other to make water and an ionic compound called a salt. A salt, in chemistry, is any ionic compound made by combining an acid with a base. A reaction between an acid and a base is called a neutralization reaction and can be represented as follows: acid + base → H2O + salt The stoichiometry of the balanced chemical equation depends on the number of H+ions in the acid and the number of OH− ions in the base. |
SciQ | SciQ-1817 | biochemistry, transition-metals, oxidation-state, proteins
15. Goddard, W. A., III; Olafson, B. D. Ozone Model for Bonding of an O2 to Heme in Oxyhemoglobin. Proc. Natl. Acad. Sci. 1975, 72 (6), 2335–2339. DOI: http://10.1073/pnas.72.6.2335.
16. Chen, H.; Ikeda-Saito, M.; Shaik, S. Nature of the Fe−O2 Bonding in Oxy-Myoglobin: Effect of the Protein. J. Am. Chem. Soc. 2008, 130 (44), 14778–14790. DOI: 10.1021/ja805434m.
17. Grinstaff, M. W.; Hill, M. G.; Labinger, J. A.; Gray, H. B. Mechanism of catalytic oxygenation of alkanes by halogenated iron porphyrins. Science 1994, 264 (5163), 1311–1313. DOI: 10.1126/science.8191283.
18. Wilson, S. A.; Kroll, T.; Decreau, R. A.; Hocking, R. K.; Lundberg, M.; Hedman, B.; Hodgson, K. O.; Solomon, E. I. Iron L-Edge X-ray Absorption Spectroscopy of Oxy-Picket Fence Porphyrin: Experimental Insight into Fe–O2 Bonding. J. Am. Chem. Soc. 2013, 135 (3), 1124–1136. DOI: 10.1021/ja3103583
19. Wilson, S. A.; Green, E.; Mathews, I. I.; Benfatto, M.; Hodgson, K. O.; Hedman, B.; Sarangi, R. X-ray absorption spectroscopic investigation of the electronic structure differences in solution and crystalline oxyhemoglobin. Proc. Natl. Acad. Sci. 2013, 110 (41), 16333–16338. DOI: 10.1073/pnas.1315734110.
The following is multiple choice question (with options) to answer.
The iron ion used to bind oxygen is on what type of "ring"? | [
"reagent ring",
"petrarchan ring",
"DNA ring",
"porphyrin ring"
] | D | The yellow subunits are identical in structure, as are the gray subunits. A smaller organic structure called a porphyrin ring is attached to each protein subunit and contains the iron ion used to bind oxygen. |
SciQ | SciQ-1818 | electromagnetism, frequency, radio-frequency, sensor, radar
Title: Why do sensors that emit higher frequency signals give more accurate data? I am doing a technical presentation about RADAR and LiDAR. I understand that LiDAR is several times more accurate and capable of producing really detailed 3-D maps of their surroundings, while RADARs tend to lag behind in accuracy.
Several sources indicate that the shorter wavelength signals from LiDAR contribute to its higher accuracy, but they don't really explain why.
This webpage explains that higher frequency signals yield more accurate data in RADARs, but does not really explain why either:
http://www.radartutorial.eu/07.waves/Waves%20and%20Frequency%20Ranges.en.html
There are some posts that mention the Heisenberg Uncertainty Principle, but I don't think an explanation at the atomic level is really relevant nor required to explain this phenomenon.
Can anybody give an equation or state a scientific concept as to why sensors/apparatuses that use higher frequency signals yield more accurate data? In the article that anna v mentioned:
robotsforroboticists.com/lidar-vs-radar
there is a segment which states:
"The down side [of the RADAR] is that if an object is much smaller than the RF wave being used, the object might not reflect back enough energy to be detected. For that reason many RADAR’s in use for obstacle detection will be “high frequency” so that the wavelength is shorter (hence why we often use mm-wave in robotics) and can detect smaller objects."
This does provide some intuitive understanding as to why devices emitting higher frequency signals provide high-resolution data. Small objects and the small/fine details of large objects (ie. protrusions of a wall, a pedestrian's facial features, and bumps/cracks/curves that make up the texture of any surface) do not reflect enough low-frequency EM wave energy back to the RADAR. Thus, such fine details are not detected by RADAR.
If the generated signals were of higher frequency, then the EM wave oscillates faster, and a greater percentage of the wave would hit and be reflected by small objects and the fine details of large objects (ie. protrusions/bumps/curves). Thus, a sensor emitting waves at a higher frequency can detect such details.
The following is multiple choice question (with options) to answer.
In police radar, a radar gun sends out short bursts of which waves? | [
"electrodes",
"soundwaves",
"photons",
"microwaves"
] | D | Radar stands for ra dio d etection and r anging. In police radar, a radar gun sends out short bursts of microwaves. The microwaves reflect back from oncoming vehicles and are detected by a receiver in the radar gun. The frequency of the reflected waves is used to compute the speed of the vehicles. Radar is also used for tracking storms, detecting air traffic, and other purposes. |
SciQ | SciQ-1819 | inorganic-chemistry, acid-base
The amphoteric character of chromium(III) is stated in its Wikipedia article:
Chromium(III) oxide is amphoteric. Although insoluble in water, it
dissolves in acid to produce hydrated chromium
ions, $\ce{[Cr(H2O)6]^3+}$ which react with base to give salts
of $\ce{[Cr(OH)6]^{3−}}$. It dissolves in concentrated alkali to yield
chromite ions $(\ce{[CrO2]^{-}})$.
So, the rule of thumb is as oxidation number increases, charge on metal increases, acidic character increases. Also, basic oxide is soluble in water, acidic oxide is insoluble in water. This can be used to differentiate between acidic and basic oxide.
The following is multiple choice question (with options) to answer.
Oxides of small, highly charged ions of what type tend to be acidic? | [
"plastic",
"liquid",
"steel",
"metal"
] | D | Summary The transition metals are characterized by partially filled d subshells in the free elements and cations. The ns and (n − 1)d subshells have similar energies, so small influences can produce electron configurations that do not conform to the general order in which the subshells are filled. In the secondand third-row transition metals, such irregularities can be difficult to predict, particularly for the third row, which has 4f, 5d, and 6s orbitals that are very close in energy. The increase in atomic radius is greater between the 3d and 4d metals than between the 4d and 5d metals because of the lanthanide contraction. Ionization energies and electronegativities increase slowly across a row, as do densities and electrical and thermal conductivities, whereas enthalpies of hydration decrease. Anomalies can be explained by the increased stabilization of half-filled and filled subshells. Transition-metal cations are formed by the initial loss of ns electrons, and many metals can form cations in several oxidation states. Higher oxidation states become progressively less stable across a row and more stable down a column. Oxides of small, highly charged metal ions tend to be acidic, whereas oxides of metals with a low charge-to-radius ratio are basic. |
SciQ | SciQ-1820 | acid-base, lewis-structure
Title: Why is carbon dioxide a Lewis acid? I know this has been asked before, but can anyone explain me in simpler terms? Why is $\ce{CO2}$ a Lewis acid? The carbon atom doesn't have any vacant orbitals to accept a lone pair. How can it be a Lewis acid? Suppose one of the doublets of one C=O bond moves to one of these two atoms. It will not be to the Carbon atom. The Oxygen atom is a better choice. And now this Oxygen atom would be negatively charged. As a consequence the Carbon atom is positively charged and has a vacant orbital able to accept a lone pair, for example from an $\ce{OH-}$ ion or from water. This will produce the ion $\ce{HCO3^-}$ (from $\ce{OH-}$) or $\ce{H2CO3}$ (from $\ce{H2O}$).
The following is multiple choice question (with options) to answer.
A lewis acid is a substance that accepts a pair of electrons to form what? | [
"accretion bond",
"functionality bond",
"covalent bond",
"ambivalent bond"
] | C | Gilbert Lewis (1875-1946) proposed a third theory of acids and bases that is even more general than either the Arrhenius or Brønsted-Lowry theories. A Lewis acid is a substance that accepts a pair of electrons to form a covalent bond. A Lewis base is a substance that donates a pair of electrons to form a covalent bond. So, a Lewis acid-base reaction is represented by the transfer of a pair of electrons from a base to an acid. A hydrogen ion, which lacks any electrons, accepts a pair of electrons. It is an acid under both the Brønsted-Lowry and Lewis definitions. Ammonia consists of a nitrogen atom as the central atom with a lone pair of electrons. The reaction between ammonia and the hydrogen ion can be depicted as shown in the Figure below . |
SciQ | SciQ-1821 | air
Title: Air Bearing pressure vs area I'm interested in hovering 100 lbs.
I'm interested in knowing what pressure of air and what surface area is needed and how they relate to each other. You need $444.52016 N$ force to support that load, and that force is given as force $F=P*A$,
where $P$ is the pressure of air and $A$ is the area of the supporting platform. Please use whatever value for $P$ and $A$ is convenient for you.
The following is multiple choice question (with options) to answer.
What is the amount of force pushing against a given area? | [
"energy",
"inertia",
"pressure",
"power"
] | C | Pressure is defined as the amount of force pushing against a given area. How much pressure a gas exerts depends on the amount of gas. The more gas particles there are, the greater the pressure. |
SciQ | SciQ-1822 | botany, terminology, nomenclature
Regnum Animale: the animals;
Regnum Vegetabile: the plants;
Regnum Lapideum: the minerals (you read it right).
Note that, in this classification, "animals" correspond to what nowadays we call animals and protozoans, and "plants" correspond to what nowadays we call plants, algae, fungi and bacteria.
You have to keep in mind that this book was first published in 1735, well before the evolutionary biology being proposed in the XIX century and established in the XX century. Therefore, it is a book published when fixism was the current paradigm, full of mentions to the scala naturae.
So, the plants (as well as the animals) showed a continuum of species, going to the lower plants (the bacteria) to the higher plants (the flowering ones). It's worth mentioning again that, by that time, bacteria were plants: Phylum Schyzophyta, to be more precise.
Thus, we have "lower plants" and "higher plants", "lower animals" and "higher animals", as well as "lower minerals" and "higher minerals"!
Unfortunately, this terminology is so embedded in the biological sciences that even today, as I mentioned, we struggle to get rid of it.
Just drop "higher plants", whatever it means
As your Wikipedia link says, "higher plants" is a synonym of vascular plants. However, there are a lot of problems here:
First, this is a remnant of the scala naturae and, just because of that, should be avoided. Think of it as a meaningless term, just like "more evolved organism".
Second, there is no clear and indisputable definition of what is a "higher" plant. Some authors used to define the "higher plants" as the Angiosperms only, or the seed plants (Angiosperms + Gymnosperms), or the vascular plants (Angiosperms, Gymnosperms and Pteridophyta).
For instance, in lusophone biology books, it was very common a division in three groups:
lower plants: bacteria and algae;
intermediate plants: bryophytes and pteridophytes;
higher plants: gymnosperms and angiosperms.
The following is multiple choice question (with options) to answer.
What is another word for seed plants? | [
"gymnosperm",
"echinoderm",
"phyla",
"protosperm"
] | A | The most basic division is between nonvascular plants and vascular plants . Vascular plants are further divided into those that reproduce without seeds and those that reproduce with seeds. Seed plants, in turn, are divided into those that produce seeds in cones and those that produce seeds in the ovaries of flowers. Seed plants are called gymnosperms . Seed plants called angiosperms produce seeds in the ovaries of flowers . |
SciQ | SciQ-1823 | entomology, parasitology, parasitism
The male (microgametocytes) and female (macrogametocytes) gametocytes are ingested by a female Anopheles mosquito during a blood meal (8) - only female mosquitoes (of pretty much any species) drink blood. The parasites' multiplication in the mosquito is known as the sporogonic cycle (stage C). While in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes (9). The zygotes in turn become motile and elongated (ookinetes) (10) which invade the midgut wall of the mosquito where they develop into oocysts (11). The oocysts grow, rupture, and release sporozoites (12), which make their way to the mosquito's salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle (1).
Sources
The following is multiple choice question (with options) to answer.
What process takes place when echinoderms release their gametes into the water? | [
"isolation",
"migration",
"stimulation",
"fertilization"
] | D | The echinoderm nervous system has a nerve ring at the center and five radial nerves extending outward along the arms. There is no centralized nervous control. Echinoderms have separate sexes and release their gametes into the water where fertilization takes place. Echinoderms may also reproduce asexually through regeneration from body parts. |
SciQ | SciQ-1824 | equilibrium, aqueous-solution, hydrolysis
$\ce {Mg^2+ + 2H2O <=> Mg(OH)2 + 2H+}$
(We usually call this as hydrolyzation of salt.)
And because $\ce {Mg^2+}$ is a weak base, you may expect that there will be not a lot $\ce {Mg(OH)2}$ and it's still soluable. Also there will be not a lot $\ce {H+}$ so the solution is just a bit more acidic then water.
The following is multiple choice question (with options) to answer.
Salt hydrolysis is a reaction in which one of the ions from a salt reacts with what? | [
"proteins",
"air",
"water",
"fat"
] | C | The fluoride ion is acting as a weak Brønsted-Lowry base. The hydroxide ion that is produced as a result of the above reaction makes the solution slightly basic. Salt hydrolysis is a reaction in which one of the ions from a salt reacts with water, forming either an acidic or basic solution. |
SciQ | SciQ-1825 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
Do motile cilia usually occur in small or large numbers on the cell surface? | [
"mixed",
"large",
"small",
"neither"
] | B | |
SciQ | SciQ-1826 | inorganic-chemistry, reactivity
Title: Why does potassium react more violently with water than lithium? Recently, I was telling my friends about the violent reaction that takes place when you throw potassium into water. Soon after, a friend of mine claimed that lithium would react more violently than potassium.
I disagreed with him, because potassium is more electropositive than lithium and thus more reactive.
My friend claimed lithium to be more reactive than potassium due to its position in the reactivity series of metals:
$$\ce{Li > Cs > Rb > K > Ba > Sr > Ca > Na > Mg}$$
Then we found out that potassium reacts indeed more violently in water.
But what about his argument? Why isn't he right? For the reaction,
$$\ce{M -> M+ + e-}$$
the heat liberated is highest for lithium owing to its high negative $E^\circ$ value so one would think that the reaction must be most vigorous.
The reason behind the more violent reactivity of potassium rather than lithium lies in kinetics and not in thermodynamics.
No doubt, maximum energy is evolved with lithium but the vaporization and ionization will also consume maximum energy (the melting point and ionization energy of lithium are the highest) and so the reaction proceeds gently. On the other hand, potassium has a lower melting point and ionization enthalpy. The heat of reaction is sufficient to melt it. The molten metal spreads over the water and exposes a larger surface to water. Also, the hydrated radius of lithium is the greatest out of all alkali metals. This reduces the ionic mobility which in turn reduces the speed of the molten metal.
That's why potassium gives a more violent reaction with water.
Reference:
Kumar, Prabhat Conceptual Inorganic Chemistry; Shri Balaji Publications: Muzaffarnagar, U.P., 2014.
The following is multiple choice question (with options) to answer.
Potassium is a soft, silvery metal that ignites explosively in what? | [
"cold",
"air",
"water",
"acid"
] | C | Potassium is a soft, silvery metal that ignites explosively in water. It easily loses its one valence electron to form positive potassium ions (K + ), which are needed by all living cells. Potassium is so important for plants that it is found in almost all fertilizers, like the one shown here. Potassium is abundant in Earth’s crust in minerals such as feldspar. |
SciQ | SciQ-1827 | physical-chemistry
Title: How can the concentration of a solid be constant during a reaction? The molar concentration is given by the ratio between density and molar mass. I understand the proof.
But how does this remain true during a reaction?
For example consider the reaction,
$$\ce{4Al(s) + 3O2 (g) -> 2Al2O3(s)}$$
If the amount of Al and O2 moles are equal, according to stoichiometry Al ought to be the reactant to end first. But, being a solid, Al’s concentration must be constant.
How can this be? What is wrong in my reasoning?
**Please note that I mistakenly assumed that the amount of Al and O2 are equal, without stating it, leading to the confusion that Al ends first at all times, I have edited the question appropriately In physical chemistry one does not use the concentration of a chemical but its activity (see https://en.m.wikipedia.org/wiki/Thermodynamic_activity)
In a solid the standard condition is the pure chemical. In case of the solid block of aluminum it is therefore in its standard condition which leads to the fact that the activity is 1 (the chemical potential is equal to the chemical potential in the standard condition as the block of aluminium is in its standard condition - see the link I provided for the definition of the activity).
Therfore it doesn't need to be considered in calculations like the law of mass action as multiplying or diving by 1 does not affect the result.
However in "real chemistry" one does not calculate with activities too often and uses concentrations instead and in order to apply the same trick one simply says that the concentration is constant.
So in the end it's just a result of sloppiness because one doesn't want to work with activities.
The following is multiple choice question (with options) to answer.
When a solid substance is involved in a chemical reaction, only the matter from which part of the solid is exposed to other reactants? | [
"the surface",
"the base",
"the top",
"the interior"
] | A | When a solid substance is involved in a chemical reaction, only the matter at the surface of the solid is exposed to other reactants. If a solid has more surface area, more of it is exposed and able to react. Therefore, increasing the surface area of solid reactants increases the reaction rate. For example, crushing a solid into a powder exposes more of the substance to other reactants. This may greatly speed up the reaction. You can see another example in Figure below . Iron rusts when it combines with oxygen in the air. The iron hammer head and iron nails will both rust eventually. Which will rust faster?. |
SciQ | SciQ-1828 | chemical-potential, osmosis
Our models and theories require the introduction of a parameter that
explicitly represents structure in liquids, which until now has had no
place in the thermodynamic description of solutions. This lack is
surprising, when one remembers that experimental results from the
broad range of fields of colloid, clay and biological sciences have
clearly established the marked effect of solutes on the structural
properties of water, globally called ‘hydration phenomena’.
The introduction of such a parameter can help explain the direction in
which energy flows during osmosis, which has been so puzzling to those
of us interested in mechanism since the time of Pfeffer, more than a
century ago. Further, elementary work cycles show, that changes in
this parameter correspond to changes in the energy associated with
solvent structure which can be used to produce useful work. The
ability of osmotic systems to do work is familiar to all of us
(indeed, a nuisance to many!), and is the basis of cytomechanics,
i.e., the physical processes observed in the living cell. The fact
that it still has no satisfactory explanation is clearly an urgent
problem for us all.
In his article "Quantum Worlds", James Watson reviews osmotic theory of Watterson:
The following is multiple choice question (with options) to answer.
Which word describes how an extracellular solution can change the volume of a cell by affecting osmosis? | [
"velocity",
"instability",
"tonicity",
"trichina"
] | C | Tonicity Tonicity describes how an extracellular solution can change the volume of a cell by affecting osmosis. A solution's tonicity often directly correlates with the osmolarity of the solution. Osmolarity describes the total solute concentration of the solution. A solution with low osmolarity has a greater number of water molecules relative to the number of solute particles; a solution with high osmolarity has fewer water molecules with respect to solute particles. In a situation in which solutions of two different osmolarities are separated by a membrane permeable to water, though not to the solute, water will move from the side of the membrane with lower osmolarity (and more water) to the side with higher osmolarity (and less water). This effect makes sense if you remember that the solute cannot move across the membrane, and thus the only component in the system that can move—the water—moves along its own concentration gradient. An important distinction that concerns living systems is that osmolarity measures the number of particles (which may be molecules) in a solution. Therefore, a solution that is cloudy with cells may have a lower osmolarity than a solution that is clear, if the second solution contains more dissolved molecules than there are cells. Hypotonic Solutions Three terms—hypotonic, isotonic, and hypertonic—are used to relate the osmolarity of a cell to the osmolarity of the extracellular fluid that contains the cells. In a hypotonic situation, the extracellular fluid has lower osmolarity than the fluid inside the cell, and water enters the cell. (In living systems, the point of reference is always the cytoplasm, so the prefix hypo- means that the extracellular fluid has a lower concentration of solutes, or a lower osmolarity, than the cell cytoplasm. ) It also means that the extracellular fluid has a higher concentration of water in the solution than does the cell. In this situation, water will follow its concentration gradient and enter the cell. Hypertonic Solutions As for a hypertonic solution, the prefix hyper- refers to the extracellular fluid having a higher osmolarity than the cell’s cytoplasm; therefore, the fluid contains less water than the cell does. Because the cell has a relatively higher concentration of water, water will leave the cell. Isotonic Solutions In an isotonic solution, the extracellular fluid has the same osmolarity as the cell. If the osmolarity of the cell matches that of the extracellular fluid, there will be no net movement of water into or out of the cell, although water will still move in and out. Blood cells and plant cells in hypertonic, isotonic, and hypotonic solutions take on characteristic appearances (Figure 5.12). |
SciQ | SciQ-1829 | soil, minerals, terminology, soil-science
Title: "Down wash" as a source for mineral particles in the soil In a previous IGCSE examination paper$^1$, the following question was asked and answer provided:
State one source of mineral particles in soil.
Marking Scheme:
Accept any one of:
rock;
down wash;
What's "down wash" and how is it responsible for providing minerals to soil? Googling the term lead me to an aerodynamics definition, which I doubt is the one referred to by the marking scheme.
$^1$ UCLES. Environmental Management, 0680/12, Paper 1. Cambridge International General Certificate of Secondary Education, February/March 2017. Downwash can be part of some erosion environments where minerals are moved down from their host rock environment to another location.
Black Snake Range - Granite Slopes, Victoria, Australia
The crest of the divide rises to almost 400 metres and at this site there are numerous exposed granite slopes and large boulders near the ridge crest. The lower slopes have a cover of granite downwash and the minor valleys have become partly infilled with this granitic sand wash, and hence they are swampy
Southdowns, UK, page 4
Overlying the bedrock geology are drift deposits of alluvium (along the numerous
streams) and ‘head’ (downwash deposits at the base of the Greensand Hills around
Liss and Petersfield).
In the Discussion section of Slope Stability and Slope Formation in the Flysch Zone of the Vienna Forest (Austria)
The downwash of the basal clays and marls, uncovering the solid bedrock, has to be regarded as the main aspect of this phase
The following is multiple choice question (with options) to answer.
The process where eroded material is dropped somewhere is called? | [
"diffusion",
"deposition",
"diffusion",
"maturation"
] | B | Erosion and deposition are responsible for many landforms. Erosion is the transport of sediments. Agents of erosion include flowing water, waves, wind, ice, or gravity. Eroded material is eventually dropped somewhere else. This is called deposition . |
SciQ | SciQ-1830 | biotechnology, restriction-enzymes
Title: Which was the first restriction endonuclease to be isolated? I kind of have confusion between the first restriction endonuclease to be isolated and discovered.
In class XII NCERT, it says that,
"In the year 1963, the two enzymes responsible for restricting the growth of bacteriophage in Escherichia coli were discovered. One of these added methyl groups to the DNA, while the other cut DNA. The latter was called restriction endonuclease".
Now, "one of these added methyl groups to the DNA" refers to DNA methylase clearly and "the other cut DNA" must refer to EcoR1, I think?
In the next paragraph it is given that,
"The first restriction endonuclease, Hind II, whose functioning depended on a specific DNA nucleotide sequence was isolated and characterised five years later".
What I understand from this is that,
Hind II was the first restriction endonuclease to be discovered but EcoR1 the first to be isolated?
I went on many sites, but they all use these terms interchangeably. The restriction endonuclease (RE) isolated from E. coli K strain was a type I restriction endonuclease, identified/characterized by Meselson and Yuan1 in 1968. Type I REs are site specific, but cleave DNA randomly.
The one isolated from Haemophilus influenzae by Smith and Wilcox2 in 1968 was the first type II RE and is now known by the name HindII - the isolate they had was actually a heterogenous mixture with HindIII, for which there are no sites in the one of the viruses they were digesting, so they were able to work out the specific site of digestion for HindII, but not HindIII. Type II REs are site specific and cleave at specific sites too, which makes them useful in molecular biology, as opposed to type I REs, which aren't so useful.
EcoRI (type II RE) wasn't isolated until 1971, and was done by Yoshimori as his PhD thesis at University of California, San Francisco (see reference 27 in Roberts; ref 3 below).
Roberts (2005) a succinct history of it all3. See sections on Restriction Enzymes and Polyacryamide Gel Electrophoresis for information about the discovery of type I and II REs respectively.
Refs:
The following is multiple choice question (with options) to answer.
What was the first amino acid to be isolated? | [
"histon",
"histamine",
"glutathione",
"asparagine"
] | D | The first amino acid to be isolated was asparagine in 1806. It was obtained from protein found in asparagus juice (hence the name). Glycine, the major amino acid found in gelatin, was named for its sweet taste (Greek glykys, meaning “sweet”). In some cases an amino acid found in a protein is actually a derivative of one of the common 20 amino acids (one such derivative is hydroxyproline). The modification occurs after the amino acid has been assembled into a protein. |
SciQ | SciQ-1831 | organic-chemistry, everyday-chemistry, experimental-chemistry, biochemistry, food-chemistry
Title: How Bread is made with yeast, sugar and luke warm milk? Materials and Apparatus:
wheat flour
sugar
dry yeast
glass bowl
covering plate
milk
Procedure:
Lukewarm milk is taken in the glass bowl and sugar is added to it. Then, yeast is added to the same.
The mixture is left undisturbed for 10-12 minutes to activate the yeast
3 cups of wheat flour are added to the bowl containing the milk mixture.
The mixture is mixed thoroughly with 100ml of added water and the dough is kneaded well
The dough is placed in a bowl, covered with a plate and left undisturbed for 2 hours.
My query/confusion:
Why is milk needed?
"activated yeast"- what's the difference?
Can yeast work without sugar or milk.
Detail out the stages of the anaerobic oxidative process which takes place as a common first step in both aerobic and anaerobic respiration.
Finally, feel free to share anything I may be missing which should be here.
If you have any confusion regarding what I want to ask, please ask in the comments. Please upvote if you are curious about it too
milk is not needed, 'pure' bread is without milk
yeast is a fungus, therefore, it is alive. Its best to work with fresh yeast, which you find as small cubes in the refrigerated section. This one does not have to be activated. non-fresh yeast is dried, so in order for it to work properly, it has to be undried by adding water, which is called activation.
and 4. As said before, milk is not needed. Sugar however is the food for the yeast, without it, it does nothing. In aerobic breathing, the yeast metabolizes the sugar as we would: sugar + oxygen -> water + CO2. Without oxygen, the yeast resorts to ethanol fermentation: sugar -> alcohol + CO2 (this is, why it is used to make beer or wine). For making bread, we have a mixture of both respirations, which does not really matter, since we are only interested in the CO2, which makes the dough fluffy =) But without sugar, there is no CO2.
The following is multiple choice question (with options) to answer.
Where is the food stored before being mixed with the chyme? | [
"hemispherical of the stomach",
"histopathology of the stomach",
"top of the stomach",
"fundus of the stomach"
] | D | Chemical Digestion The fundus plays an important role, because it stores both undigested food and gases that are released during the process of chemical digestion. Food may sit in the fundus of the stomach for a while before being mixed with the chyme. While the food is in the fundus, the digestive activities of salivary amylase continue until the food begins mixing with the acidic chyme. Ultimately, mixing waves incorporate this food with the chyme, the acidity of which inactivates salivary amylase and activates lingual lipase. Lingual lipase then begins breaking down triglycerides into free fatty acids, and mono- and diglycerides. The breakdown of protein begins in the stomach through the actions of HCl and the enzyme pepsin. During infancy, gastric glands also produce rennin, an enzyme that helps digest milk protein. Its numerous digestive functions notwithstanding, there is only one stomach function necessary to life: the production of intrinsic factor. The intestinal absorption of vitamin B12, which is necessary for both the production of mature red blood cells and normal neurological functioning, cannot occur without intrinsic factor. People who undergo total gastrectomy (stomach removal)—for life-threatening stomach cancer, for example—can survive with minimal digestive dysfunction if they receive vitamin B12 injections. The contents of the stomach are completely emptied into the duodenum within 2 to 4 hours after you eat a meal. Different types of food take different amounts of time to process. Foods heavy in carbohydrates empty fastest, followed by highprotein foods. Meals with a high triglyceride content remain in the stomach the longest. Since enzymes in the small intestine digest fats slowly, food can stay in the stomach for 6 hours or longer when the duodenum is processing fatty chyme. However, note that this is still a fraction of the 24 to 72 hours that full digestion typically takes from start to finish. |
SciQ | SciQ-1832 | life, extremophiles
Title: How close to Earth's core can organisms live? We don't to know much about organisms living deep below the Earth's crust. Recently a team led by S. Giovanni discovered some microbes 300 m below the ocean floor. The microbes were found to be a completley new and exotic species and apparently they feed off hydrocarbons like methane and benzene. Scientists speculate that life may exist in our Solar System far below the surface of some planets or moons. This raises some questions:
What is the theoretical minimum distance from Earth's core where life can still exist. Please explain how you came up with this number. For example, there are temperature-imposed limits on many biochemical processes.
Is there the potential to discover some truly alien life forms in the Earth's mantle (by this I mean, life which is not carbon based, or life which gets its energy in ways we have not seen before, or non DNA-based life, or something along these lines)?
What is the greatest distance below the Earth's crust that life has been discovered? I believe it is the 300 m I cited above, but I am not 100% sure. There's a lot we don't know about life in deep caves, but we can bound the deepest living organism to at least 3.5 kilometers down, and probably not more than 30 kilometers down.
The worms recovered from deep mining boreholes are not particularly specifically adapted to live that far down: they have similar oxygen/temperature requirements as surface nematodes.
The Tau Tona mine is about 3.5 kilometers deep and about 60˚ C at the bottom. Hydrothermal vent life does just fine up to about 80˚C, and the crust gets warmer at "about" 25˚C per kilometer. It's entirely reasonable to expect life to about 5 kilometers down, but further than that is speculation.
Increasing pressure helps to stabilize biological molecules that would otherwise disintegrate at those temperatures, so it's not impossible there could be life even deeper. It may even be likely, given that the Tau Tona life breathes oxygen.
I am certain no life we might recognize as life exists in the upper mantle.
The following is multiple choice question (with options) to answer.
What kind of biome or climate might you find very close to the earth's poles, as well as up on high mountains? | [
"desert",
"taiga",
"tropical",
"tundra"
] | D | Tundra is found near the poles and up on high mountains. |
SciQ | SciQ-1833 | waves, acoustics, atmospheric-science, planets, dispersion
and links to the April 1, 2022 paper in Nature In situ recording of Mars soundscape
Abstract:
Prior to the Perseverance rover landing, the acoustic environment of Mars was unknown. Models predicted that: (i) atmospheric turbulence changes at centimeter scales or smaller at the point where molecular viscosity converts kinetic energy into heat1, (ii) the speed of sound varies at the surface with frequency2,3, and (iii) high frequency waves are strongly attenuated with distance in CO22–4. However, theoretical models were uncertain because of a lack of experimental data at low pressure, and the difficulty to characterize turbulence or attenuation in a closed environment. Here using Perseverance microphone recordings, we present the first characterization of Mars’ acoustic environment and pressure fluctuations in the audible range and beyond, from 20 Hz to 50 kHz. We find that atmospheric sounds extend measurements of pressure variations down to 1,000 times smaller scales than ever observed before, revealing a dissipative regime extending over 5 orders of magnitude in energy. Using point sources of sound (Ingenuity rotorcraft, laser-induced sparks), we highlight two distinct values for the speed of sound that are ~10 m/s apart below and above 240 Hz, a unique characteristic of low-pressure CO2-dominated atmosphere. We also provide the acoustic attenuation with distance above 2 kHz, allowing us to elucidate the large contribution of the CO2 vibrational relaxation in the audible range. These results establish a ground truth for modelling of acoustic processes, which is critical for studies in atmospheres like Mars and Venus ones. Why exactly do higher frequency (>240 Hz) sounds on Mars travel ~4% faster than lower frequencies? What's the physics and are there optical analogies?
Yes sound is generally a scalar wave under normal conditions and for optics/EM we usually use vector waves, so I've asked only for possible analogies rather than a 1:1 correspondence.
The discussion in Nature is likely to have the basis of an answer, but it's pretty in-depth and thorough and I'm hoping there's a way to explain the physics in simpler terms and draw an analogy to some optical dispersion phenomenon I might be more familiar with.
Potentially related sound on Mars questions in Space SE:
What would sounds on Mars be like?
The following is multiple choice question (with options) to answer.
What type of waves travel through the body of a planet? | [
"gas waves",
"energy waves",
"vacuum waves",
"body waves"
] | D | Body waves travel through the body of a planet. Surface waves travel along the surface. |
SciQ | SciQ-1834 | fusion
Title: Where does the energy produced by fusion come from? Fission, in layman's (or "initiate's") terms, is easy enough to understand; a large atom with a lot of protons and neutrons requires a large amount of force provided by the strong interaction to overcome electromagnetism and keep the nucleus together. The necessary energies were imparted to the atom during its formation, which we can replicate to some degree within a nuclear reactor; a combination of heat and fast-moving free protons/neutrons recaptured by the atoms of the fuel turns uranium into plutonium, even as the actual atom-splitting produces much lighter krypton and barium isotopes (or a host of other possibilities, some more likely than others, as with many other types of reactions). That atom-splitting, by the way, reduces the size of the resulting nuclei, and therefore reduces the amount of strong interaction force required to contain them; the leftover energy is released as a high-frequency gamma photon.
Fusion, however, is an odder beast. A fusion reaction requires a large amount of starting energy; enough to strip the electrons off of the deuterium/tritium nuclei and form plasma. That heat is also enough to accelerate the particles fast enough that when they collide, the initial electromagnetic repulsion is overcome and the strong interaction binds them together.
Now, that's a lot of energy required; the Sun's inner core where most of the fusion occurs is estimated to be about 15 million Kelvin. The reaction, however, doesn't seem to release any energy, based at least on this simplistic explanation. Now, obviously that's wrong; pretty much all the energy we have available to us right now is, however indirectly, a result of the Sun bathing us in the energy from nuclear fusion. The rest of it, such as from nuclear fission, is also star-based, via creation of superheavy elements in stellar nucleogenesis.
The following is multiple choice question (with options) to answer.
What type of energy occurs by splitting the nuclei of radioactive uranium? | [
"kinetic",
"microwave",
"atomic",
"nuclear"
] | D | Nuclear energy is produced by splitting the nuclei of radioactive uranium. This doesn’t release air pollution or carbon dioxide, but it does produce dangerous radioactive wastes. |
SciQ | SciQ-1835 | biochemistry, physiology, muscles, bioenergetics
Title: Location of t tubule in muscle Why do mammalian skeletal muscles have t-tubules at the junction of the anisotropic and isotropic band, whereas non-mammalian muscles and cardiac muscles have it at Z-line? What could have been the functional significance?
If skeletal muscle would have it at the Z-line then I think it would have been more effective in contraction of muscle fibre. So which arrangement is more efficient?
Also, why is a common arrangement (the more efficient one) not seen in all those muscle types? Interesting question. Indeed it is related to the working of cardiac muscles. First of all, lets have a look at the structure of a sarcomere of a cardiac muscle from here:
Here, what we can see is that the t-tubule is a depression formed in myocyte. It is important to know this fact here. Why? See this:
In contrast to skeletal muscle, cardiac muscle requires extracellular calcium ions for contraction to occur. Like skeletal muscle, the initiation and upshoot of the action potential in ventricular cardiomyocytes is derived from the entry of sodium ions across the sarcolemma in a regenerative process. However, an inward flux of extracellular calcium ions through L-type calcium channels sustains the depolarization of cardiac muscle cells for a longer duration. The reason for the calcium dependence is due to the mechanism of calcium-induced calcium release (CICR) from the sarcoplasmic reticulum that must occur during normal excitation-contraction (EC) coupling to cause contraction.
First, cardiac muscles don't work by external action potentials, they work on a cycle governed by themselves, known as the cardiac cell cycle.
Second, as is clear from above paragraph, these cells depend on extracellular Ca2+ ions for initiating contraction, a clear difference from skeletal muscles which need Ca2+ stored in SR. Hence, they require t-tubule at a place where a sarcomere ends. Obviously, having a depression in the middle of a sarcomere (i.e. between I- and A-band) would not work here.
Also, the structure of t-tubules is also different between the two. Compare my first image with the image below from here:
The following is multiple choice question (with options) to answer.
Like skeletal muscle, cardiac muscle is what? | [
"striated",
"atrophied",
"cylindrical",
"tissue"
] | A | |
SciQ | SciQ-1836 | reproduction, endocrinology, pregnancy, ovulation
The decline of the corpus luteum is correlated with a decline in serum levels of ovarian hormones including progesterone, estradiol, and inhibin A. Release from negative feedback provided by these hormones at the level of the hypothalamus and pituitary permits FSH to rise, and the cycle begins again.
You should now be able to see that:
Around the time of ovulation, the uterine lining is not fully developed and is stable due to the hormonal milieu. Menstruation does not occur.
Around the time of menstruation, FSH and LH are suppressed in a way that is not conducive to ovulation.
In theory, yes, of course there would be a lower chance of initiating a viable pregnancy (implantation rather than conception is the most obvious problem) were the endometrial lining to be unstable at the time of ovulation. The problem of luteal phase deficiency is along these lines. In this condition, the corpus luteum does not produce adequate progesterone during the luteal phase to develop the endometrial lining in such a way as to support a healthy pregnancy. However, ovulation and menstruation are still time-separated events for the reasons outlined above.
*Note that the first term is with respect to the endometrium; the second is with respect to the ovary.
Abbreviations:
GnRH - Gonadotropin Releasing Hormone; LH - Luteinizing Hormone; FSH - Follicule Stimulating Hormone
References
1. Anatomy & Physiology, Connexions Web site. Illustration is also from here.
2. Jerome Strauss, Robert Barbieri. Yen & Jaffe's Reproductive Endocrinology. September, 2013. Saunders.
The following is multiple choice question (with options) to answer.
Rising and falling levels of what will result in progression of the ovarian and menstrual cycles? | [
"red blood cells",
"hormones",
"oxygen",
"blood pressure"
] | B | Figure 43.17 Rising and falling hormone levels result in progression of the ovarian and menstrual cycles. (credit: modification of work by Mikael Häggström). |
SciQ | SciQ-1837 | statistical-mechanics, partition-function
where $S_D(R)$ is the surface area of the hypersphere.
Fun fact: if we are dealing with non-interacting particles, i.e.
$$H=\sum_i^N \frac{p_i^2}{2m}$$
we have
$$\int_{E<\sum p_i^2/2m<E+E_0} d^{3N}p \ d^{3N}q = V^N \int_{E<\sum p_i^2/2m<E+E_0} d^{3N}p $$
and this integral is exactly an hyperspherical shell.
References: M. E. Tuckerman, Statistical Mechanics: Theory and Molecular Simulation
The following is multiple choice question (with options) to answer.
What is the term for how much matter is packed into a given space? | [
"opacity",
"density",
"volume",
"mass"
] | B | Density is a quantity that expresses how much matter is packed into a given space. The amount of matter is its mass, and the space it takes up is its volume. To calculate the density of an object, then, you would use this formula:. |
SciQ | SciQ-1838 | photosynthesis
Title: Photosystem I and the ETC In the light reactions of photosynthesis, Photosystem I receives electrons from the ETC after Photosystem II sends them to the ETC. Then, when Photosystem I receives light, the electron becomes excited and passes the electron back to the ETC. This leads me to my question: In the following question, are both $B$ and $E$ correct?
Which of the following are directly associated with photosystem I?
$A)$ harvesting of light energy by ATP
$B)$ receiving electrons from the thylakoid membrane electron transport chain
$C)$ generation of molecular oxygen
$D)$ extraction of hydrogen electrons from the splitting of water
$E)$ passing electrons to the thylakoid membrane electron transport chain It appears the author of the question is trying to use "thylakoid electron transport chain" in an overly specific way. The chain from which PS I receives electrons has far more components and is different from the shorter chain to which PS I passes its electrons. But according to my copy of Biology, Campbell & Reece 7th edition, both are called "electron transport chains" and both reside in, or on, the thylakoid membrane. Perhaps the "directly" in the question refers to the fact that PS I's electron is first captured by a "primary receptor" before being passed to ferredixon, the first member of the chain to which PS I passes electrons. But, again according to Campbell, this primary acceptor is considered part of the photosystem.
I used to teach this stuff. I'd toss out the question.
The following is multiple choice question (with options) to answer.
Phototrophic organisms capture light energy from the sun and convert it into what type of energy inside their cells? | [
"radiation energy",
"chemical energy",
"solar power",
"mechanical energy"
] | B | Phototrophic organisms capture light energy from the sun and convert it into chemical energy inside their cells. |
SciQ | SciQ-1839 | entomology, parasitology, parasitism
The male (microgametocytes) and female (macrogametocytes) gametocytes are ingested by a female Anopheles mosquito during a blood meal (8) - only female mosquitoes (of pretty much any species) drink blood. The parasites' multiplication in the mosquito is known as the sporogonic cycle (stage C). While in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes (9). The zygotes in turn become motile and elongated (ookinetes) (10) which invade the midgut wall of the mosquito where they develop into oocysts (11). The oocysts grow, rupture, and release sporozoites (12), which make their way to the mosquito's salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle (1).
Sources
The following is multiple choice question (with options) to answer.
What is an animal that picks up pollen on its body and carries it to another flower called? | [
"rodent",
"lizard",
"pollinator",
"fungi"
] | C | The showy petals of flowers evolved to help attract pollinators. Wind-blown pollen might land just anywhere and be wasted. A pollinator is an animal that picks up pollen on its body and carries it directly to another flower of the same species. This helps ensure that pollination occurs. Pollinators are usually small animals such as bees, butterflies, and bats. You can see an example in Figure below . |
SciQ | SciQ-1840 | neuroscience, neurophysiology, neuroanatomy, neurology
Conceptually, rather than thinking about extra parts, all of your same questions apply just as much to what is "normal". There is no evidence that brain development has any assumption built in that there will be 4 limbs or 5 digits on a hand, rather, connections are made with the nervous system as the limbs and digits develop, and these connections carry information between the CNS and sensory neurons and motor neurons, and the brain develops in response to those connections.
The following is multiple choice question (with options) to answer.
How many bones make up an adult human skeleton? | [
"130",
"186",
"206",
"244"
] | C | The adult human skeleton includes 206 bones and other tissues. It supports the body, protects internal organs, produces blood cells, and maintains mineral homeostasis. |
SciQ | SciQ-1841 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
The process in which a sperm unites with an egg is called? | [
"migration",
"fertilization",
"absorption",
"infection"
] | B | This image depicts a true wonder of nature. This tiny human sperm is penetrating a much larger egg. These two cells will unite to become a brand new human being. The process in which they unite is called fertilization. |
SciQ | SciQ-1842 | waves, interference, wavelength, superposition
The wavelength is the distance of a "cycle". Take the horizontal length between any two crests, or any two troughs, and what you get is called the wavelength. In physics, this is notated with the $\lambda$ symbol (the Greek letter Lambda). In the plot above, the wavelength has a value of $\pi$.
The amplitude is the height from the centre line to either the crest or the trough.
Destructive interference happens when the squared amplitude of the sum of the waves is lower than the sum of the squared amplitudes of the waves.
Therefore, the interference between two waves is the "most destructive" when the phase difference is an odd number of half-wavelengths, as shown in the plot above with the "$\pi/2$", "$3\pi/2$", "$5\pi/2$" points on the horizontal axis.
The following is multiple choice question (with options) to answer.
What is the term for the height of the wave? | [
"amplitude",
"vibration",
"frequency",
"magnitude"
] | A | (A) A wave consists of alternation crests and troughs. The wavelength (λ) is defined as the distance between any two consecutive identical points on the waveform. The amplitude is the height of the wave. (B) A wave with a short wavelength (top) has a high frequency because more waves pass a given point in a certain amount of time. A wave with a longer wavelength (bottom) has a lower frequency. |
SciQ | SciQ-1843 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
When a plant has what deficiency, guard cells may lose turgor and close stomata? | [
"light",
"water",
"air",
"cold"
] | B |
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