source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-1944 | 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.
What is a group of organs that work together to do the same job? | [
"an organ battery",
"an organ assembly",
"an organ colony",
"an organ system"
] | D | Organs may be organized into organ systems. An organ system is a group of organs that work together to do the same job. For example, the heart is part of the cardiovascular system. This system also includes blood vessels and blood. The job of the cardiovascular system is to transport substances in blood to and from cells throughout the body. |
SciQ | SciQ-1945 | cell-signaling, chemical-communication
Title: How many molecules are generally required for cell signallng processes for given cases? I know its really a broad topic but I am interested in just few cases:
Quorum sensing
neurotransmitters for the communication of images/ general information
hormones/pheromones
I actually want to know that does a single or hundreds of molecules are needed to communicate information from one cell to another.
I searched but approx number of molecules, I can't find anywhere. A cell can interact with other cells in zillions of ways. You can send information from one cell to other cells via neurotransmitters, hormones, pheromones, electric signals, magnetic resonance ,leukotrines etc.
In general a single type of molecule is enough to send such information. Like you require only Acetylcholine(Ach) as neurotransmitter to transmit various nerve impulses.
But, even for a single type, you require thousands of molecules. Like 1 molecule of Ach can do almost nothing and would immediately be broken by Acetylcholinesterase. You require 1000s of such molecules.
You can modify the communicating information via different types of transmitters. You can use GABA or glycine to supress any information exchange or use dopamine to enhance it. But again you will need many molecules of GABA or Glycine.
For visual pathway, you can use no. of types of transmitters like glutamate, glycine, gaba, dopamine, acetylcholine, substance P etc.
Neurotransmitters for visual pathway.
Hormones are transmitters that are required in small quantities. But, again you require certain concentration. There is normal blood concentration of various hormones like 80 pg/ml for calcitonin.
Quorum sensing use transmitters like AHLs. Again a certain threshold value is required for them to act.
Again, to produce these transmitters you have to go through a rigorous process of transcription, translation and post-translational modifications.
So, for cell to communicate a rigorous process is used.
The following is multiple choice question (with options) to answer.
What are specialized cells that are capable of sending electrical as well as chemical signals? | [
"ions",
"neurons",
"enzymes",
"hormones"
] | B | 16.6 Nervous System The nervous system is made up of neurons and glia. Neurons are specialized cells that are capable of sending electrical as well as chemical signals. Most neurons contain dendrites, which receive these signals, and axons that send signals to other neurons or tissues. Glia are non-neuronal cells in the nervous system that support neuronal development and signaling. There are several types of glia that serve different functions. Neurons have a resting potential across their membranes and when they are stimulated by a strong enough signal from another neuron an action potential may carry an electrochemical signal along the neuron to a synapse with another neuron. Neurotransmitters carry signals across synapses to initiate a response in another neuron. The vertebrate central nervous system contains the brain and the spinal cord, which are covered and protected by three meninges. The brain contains structurally and functionally defined regions. In mammals, these include the cortex (which can be broken down into four primary functional lobes: frontal, temporal, occipital, and parietal), basal ganglia, thalamus, hypothalamus, limbic system, cerebellum, and brainstem—although structures in some of these designations overlap. While functions may be primarily localized to one structure in the brain, most complex functions, like language and sleep, involve neurons in multiple brain regions. The spinal cord is the information superhighway that connects the brain with the rest of the body through its connections with peripheral nerves. It transmits sensory and motor input and also controls motor reflexes. The peripheral nervous system contains both the autonomic and sensory-somatic nervous systems. The autonomic nervous system provides unconscious control over visceral functions and has two divisions: the sympathetic and parasympathetic nervous systems. The sympathetic nervous system is activated in stressful situations to prepare the animal for a “fight-orflight” response. The parasympathetic nervous system is active during restful periods. The sensory-somatic nervous system is made of cranial and spinal nerves that transmit sensory information from skin and muscle to the CNS and motor commands from the CNS to the muscles. |
SciQ | SciQ-1946 | newtonian-mechanics, newtonian-gravity, history
Newton's genius was also in realizing that this force is not limited to describing the dynamics of celestial bodies but also applies to the dynamics of objects falling to the Earth on ground. He could verify this by confirming that the acceleration of freely falling objects near the ground was in agreement with the prediction from his universal law of gravitation.
The following is multiple choice question (with options) to answer.
What did sir isaac newton's famous law help people understand? | [
"motion",
"radio waves",
"light",
"gravity"
] | D | People have known about gravity for thousands of years. After all, they constantly experienced gravity in their daily lives. They knew that things always fall toward the ground. However, it wasn’t until Sir Isaac Newton developed his law of gravity in the late 1600s that people really began to understand gravity. Newton is pictured in Figure below . |
SciQ | SciQ-1947 | organic-chemistry, structural-formula, amines, identification
Title: Identify two amines I was reading a random text about the surface chemistry of YBaCuO superconductors. In the text, there was a table. The table had a list of several chemical compounds, including these two:
Alkyl Amine: FcC(O)NH(CH2)4NH2
Aryl Amine: p-Fc-C6H4-NH2
Two amines. After extensive search, I was unable to find a structural formula for it (the closest I've found was this). I even tried to draw all structural formulas I could think off in a piece of paper. But I couldn't draw a single one satisfying the second one (the easiest probably).
Can you identify these amines? What's their structural formula? The proposed strucutre of these compound are, correct me if i am wrong.
The following is multiple choice question (with options) to answer.
Compounds containing an atom of what element, bonded in a hydrocarbon framework, are classified as amines? | [
"ammonia",
"oxygen",
"nitrogen",
"hydrogen"
] | C | 20.2 Alcohols and Ethers Many organic compounds that are not hydrocarbons can be thought of as derivatives of hydrocarbons. A hydrocarbon derivative can be formed by replacing one or more hydrogen atoms of a hydrocarbon by a functional group, which contains at least one atom of an element other than carbon or hydrogen. The properties of hydrocarbon derivatives are determined largely by the functional group. The –OH group is the functional group of an alcohol. The –R–O–R– group is the functional group of an ether. 20.3 Aldehydes, Ketones, Carboxylic Acids, and Esters Functional groups related to the carbonyl group include the –CHO group of an aldehyde, the –CO– group of a ketone, the –CO2H group of a carboxylic acid, and the –CO2R group of an ester. The carbonyl group, a carbon-oxygen double bond, is the key structure in these classes of organic molecules: Aldehydes contain at least one hydrogen atom attached to the carbonyl carbon atom, ketones contain two carbon groups attached to the carbonyl carbon atom, carboxylic acids contain a hydroxyl group attached to the carbonyl carbon atom, and esters contain an oxygen atom attached to another carbon group connected to the carbonyl carbon atom. All of these compounds contain oxidized carbon atoms relative to the carbon atom of an alcohol group. 20.4 Amines and Amides The addition of nitrogen into an organic framework leads to two families of molecules. Compounds containing a nitrogen atom bonded in a hydrocarbon framework are classified as amines. Compounds that have a nitrogen atom bonded to one side of a carbonyl group are classified as amides. Amines are a basic functional group. Amines and carboxylic acids can combine in a condensation reaction to form amides. |
SciQ | SciQ-1948 | cartography, coordinate-system
The first antipodal point (Pacific Ocean) seems slightly more logical to me than the second one (Indian Ocean), but both differ from what my ungeometric brain was expecting before I delved into this, which was a point "south" (actually "negative north," I guess*) of the South Pole, "beyond" Antarctica (if ya know whaddi mean).
As it is impossible to go "south" of the South Pole.
UPDATE 2
I posted a substack article tangentially/partially about this here. I think you are too into the numbers. When talking about longitude and latitude they are two different things. Longitude goes east and west from a point on the earth from 0 to 180 degrees east and 0 to 180 degrees west and describe semicircles of equal length running from the north pole to the south pole. Latitude however is in degrees north or south of the equator and describe circular lines around the earth that get smaller as you get closer to the poles. See this image:
The following is multiple choice question (with options) to answer.
What line of latitude is an equal distance from both the north and south poles? | [
"meridian",
"divider",
"equator",
"mid-part"
] | C | Lines of latitude circle around Earth. The Equator is a line of latitude right in the middle of the planet. Latitude is divided into degrees: 90° north of the Equator and 90° south of the Equator. One degree is subdivided into 60 minutes. One minute is subdivided into 60 seconds. The Equator is at 0°. The Equator is an equal distance from both the North and South Poles. If you know your latitude, you know how far you are north or south of the Equator. |
SciQ | SciQ-1949 | visualization, social-network-analysis, metadata
for ie=sortWe(:,2)',
i=mod(ie-1,N)+1;
j=floor((ie-1)/N)+1;
if (j>i)
h=plot(x([i,j]),y([i,j]),'k-');
% set(h,'linewidth',str(i,j))
set(h,'color',[.5 .5 .5]*(1-str(i,j)));
end
end
for i=1:length(gnu)
nodes_percom = length(find(gnu(i)==gn));
idx=find(gnu(i)==gn);
radius=15*(((nodes_percom)^(.25))*(pi/sqrt(nodes*length(gnu))));
comcolors=scores2(idx);
comcolorsu=unique(comcolors);
for j=1:length(colorsu)
percents(j)=length(find(comcolors==colorsu(j)))/length(idx);
end
drawpie(percents,XY(i,:),radius,idcolors);
end
hold off
end
function drawpie(percents,pos,radius,colors)
The following is multiple choice question (with options) to answer.
What type of graph is useful for showing percents of a whole? | [
"circle graphs",
"bar graphs",
"gnomic graphs",
"shift graphs"
] | A | Circle graphs are especially useful for showing percents of a whole. The circle graph in Figure below shows the percent of all vehicles counted that were of each type. |
SciQ | SciQ-1950 | human-biology, neuroscience, cell-biology, general-biology, neurology
Title: Effects of exercise on the brain I am well aware of the phenomenon of neurogenesis induced by exercise, as well as the dopamine release that results from exercise. I am really interested in neuropsychology and the effects of exercise on personality. What are some other biological processes that are stimulated by exercise, does it activate our parasympathetic nervous system? Is there any cool research out there for me to read? I am grateful for any input. Any information about exercise and its effects on human biology is appreciated.
UPDATE
While this answer was appreciated, i'm interested in other biological processes... What happens to stress and anxiety? Do our adrenal glands stop secreting as much corticosteroids? What effect does exercise have on circadian rhythms? With exercise, can you circumvent the problem of not getting enough light in the winter? What effect does exercise have on memory? It should probably help, since it would lead to decreased damage to the hippocampus. How does exercise effect sleep, learning, memory, metabolic processes??? I'm searching for the comprehensive list of different primary and secondary effects of exercise from a biological standpoint. I'm really interested in what the short term and long term effects of exercise are on the brain. Although current research has little to say about the effects of exercise on personality, there has been recent correlations demonstrated between personality and the "drive" to exercise--specifically, aggression as a personality trait has been linked to higher metabolic rate. See http://phys.org/news206006380.html for more information about this.
The causation in exercise-induced neurogenesis is not well understood. A correlation that has been found (in mice) is the presence of a hormone called beta-endorphin, which is attributed to positive affect (a boost in mood). Exercising mice that demonstrated the presence of beta-endorphin in their hippocampal region did experience exercise-induced neurogenesis, while those that naturally lacked beta-endorphin did not experience neurogenesis.
The following is multiple choice question (with options) to answer.
What substances affect the brain and influence how a person feels, thinks, or acts? | [
"amphetamines",
"primeval drugs or drugs",
"H2 blockers",
"psychoactive drugs or drugs"
] | D | Psychoactive drugs affect the brain and influence how a person feels, thinks, or acts. They include medicines and other legal drugs as well as illegal drugs. They may stimulate or depress the central nervous system. Abuse of such drugs may lead to drug addiction, overdose, and death. |
SciQ | SciQ-1951 | reaction-mechanism, kinetics, catalysis, surface-chemistry, reaction-coordinate
Figure Autocatalysis $\ce{A + B $\to$ P + 2B}$. Initially species A decreases slowly as the concentration of B is small. As the reaction proceeds, more B is produced and although A is reduced overall, the rate increases and A is consumed even more rapidly. At longer times, the concentration of A becomes so small that even though that of B is large the reaction rate is slow.
The following is multiple choice question (with options) to answer.
The reaction rate usually increases as the concentration of what increases? | [
"generators",
"complexes",
"mutations",
"reactants"
] | D | Concentration Effects Two substances cannot possibly react with each other unless their constituent particles (molecules, atoms, or ions) come into contact. If there is no contact, the reaction rate will be zero. Conversely, the more reactant particles that collide per unit time, the more often a reaction between them can occur. Consequently, the reaction rate usually increases as the concentration of the reactants increases. One example of this effect is the reaction of sucrose (table sugar) with sulfuric acid, which is shown in Figure 14.1 "The Effect of Concentration on Reaction Rates". |
SciQ | SciQ-1952 | atoms, terminology
Title: What is a neutral atom? I was told that an atom's atomic number is defined as follows:
The number of electrons or protons present in a neutral atom is called atomic number. It is represented by Z.
What does neutral mean here? Why isn't it just "..present in an atom..."? Electrons and protons are charged particles. The electrons have negative charge, while protons have positive charge. A neutral atom is an atom where the charges of the electrons and the protons balance. Luckily, one electron has the same charge (with opposite sign) as a proton.
Example: Carbon has 6 protons. The neutral Carbon atom has 6 electrons. The atomic number is 6 since there are 6 protons.
The following is multiple choice question (with options) to answer.
Atoms are composed of negatively charged electrons and a positively charged what? | [
"DNA segment",
"neutron",
"nucleus",
"bond"
] | C | 30.2 Discovery of the Parts of the Atom: Electrons and Nuclei • Atoms are composed of negatively charged electrons, first proved to exist in cathode-ray-tube experiments, and a positively charged nucleus. • All electrons are identical and have a charge-to-mass ratio of. |
SciQ | SciQ-1953 | ethology, mammals, language
Title: Can dolphins actually communicate linguistically? Humans use "language." By language, I mean the thing I am using right now to talk to you.
I know dolphins and orcas have very complex communication systems and also seem to process linguistic and gestural commands.
But do they have their own languages? Where is the evidence for or against? If we take two group of dolphins Group A and Group B, would Group A speak one language and Group B speak another? Dolphins and orcas do have dialects. Of course there are species specific dialects and it has been shown that orcas reared with bottlenose dolphins tend to learn the latter's dialect. Dolphins of the same species also seem to have regional dialects, as mentioned in this BBC post (I personally do not trust in non-research articles much, but nonetheless in this case the article indicates a certain possibility of a phenomenon). However, this page also reports the same finding and this source seems to be much more reliable. There are citations too that are at present inaccessible to me. Both the sources say that bottlenose dolphins from Shannon estuary in Ireland, "speak" different dialect compared to those from Cardigan Bay in Wales.
The actual research work is this:
Hickey, R. (2005) Comparison of whistle repertoire and characteristics between Cardigan Bay and the Shannon estuary
populations of Bottlenose dolphins (Tursiops truncatus) with
implications for passive and active survey techniques. School of
Biological Sciences, University of Wales, Bangor
Apart from having regional dialects, the cetacean communication also seems to have other features of a "language". I am pasting excerpts from this article which basically reports a study on the acoustic communication or codas in sperm whales. This may apply to dolphins as well.
Individuals within social units have preferred associates among
members (Gero et al. 2008), indicating differences in the way an
individual interacts with other members of its unit. These preferred
associations among unit members suggest the possibility of an
individual discrimination system.
The following is multiple choice question (with options) to answer.
Communication is any way that animals share what? | [
"water",
"food",
"information",
"genes"
] | C | Communication is any way that animals share information. For animals that live in social groups, communication is essential. Animals may use a range of senses for communicating. The most important way that humans communicate is with language. |
SciQ | SciQ-1954 | 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 do the muscles of the gastrointestinal tract do? | [
"stop digestion",
"break down food",
"secrete stomach acid",
"keep food moving"
] | D | Organs of the GI tract are covered by muscles that contract to keep food moving along. A series of involuntary muscle contractions moves rapidly along the tract, like a wave travelling through a spring toy. The muscle contractions are called peristalsis. The diagram in Figure below shows how peristalsis works. |
SciQ | SciQ-1955 | human-anatomy
In the wrist, you can have palmar flexion, dorsiflexion (extension), ulnar flexion (abduction) and radial flexion (adduction) (Teachmeanatomy).
In the ankle, you can have plantar flexion, dorsiflexion (extension), inversion (inward rotation, adduction) and eversion (outward rotation, abduction). (ScienceDirect).
In the shoulder and hip, raising a limb to the same side as the limb is, is abduction (lateral extension) and raising it to the opposite side is adduction.
Moving the thumb toward the palm (in the same plane as palm) is flexion (adduction) and moving it away from it is extension (abduction).
You can read about flexion and extension and other movements here: Types of Body Movements (BCcampus)
The following is multiple choice question (with options) to answer.
What is the fan-like superior region that forms the largest part of the hip bone and is united to the sacrum at the largely immobile sacroiliac joint? | [
"spine",
"pica",
"ilium",
"septum"
] | C | The ilium is the fan-like, superior region that forms the largest part of the hip bone. It is firmly united to the sacrum at the largely immobile sacroiliac joint (see Figure 8.12). The ischium forms the posteroinferior region of each hip bone. It supports the body when sitting. The pubis forms the anterior portion of the hip bone. The pubis curves medially, where it joins to the pubis of the opposite hip bone at a specialized joint called the pubic symphysis. |
SciQ | SciQ-1956 | species-identification, zoology, marine-biology, invertebrates
Title: Help with jellyfish species identification Our research group (Evolutionary Genetics Group, University of Zurich) has received a letter from a special needs child who has kindly asked us to identify three jellyfish species.
Unfortunately, the letter does not include anything else except three rather low quality cutouts from what I assume is a childrens book. Nobody in our lab has any knowledge about jellyfish taxonomy so any help is greatly appreciated. Be warned that these are just best guesses - as you said yourself, these aren't great images for identification as they appear to be simple drawings:
1) this looks a lot like Aurelia aurita - though the lack of any internal patterning in the drawing makes me think perhaps otherwise.
image source: https://www.leisurepro.com/blog/wp-content/uploads/2017/05/shutterstock_272438348.jpg, https://holidays-majorca.co.uk/wp-content/uploads/2017/01/Aurelia-Aurita-S-300x225.jpg
2) possibly a Turritopsis dohrnii or nutricala - if so then this is the 'immortal' jellyfish. shape of bell is correct and the lappets seem reasonably close, it's just the internal structures that I'm not sure about.
image source: https://www.cairnsholidayspecialists.com.au/shared_resources/media/irukandji-jellyfish-in-far-north-18836_400x322.jpg
3) Very unsure about this one, but potentially a Atolla wyvillei? definitely has some visual features in common and I can't find anything else that's similar. I can also see how an artist would derive that image from this species.
The following is multiple choice question (with options) to answer.
What do jellyfish lack in their nervous system? | [
"Cortex",
"true brain",
"stimulus",
"Response"
] | B | Nervous systems throughout the animal kingdom vary in structure and complexity, as illustrated by the variety of animals shown in Figure 35.2. Some organisms, like sea sponges, lack a true nervous system. Others, like jellyfish, lack a true brain and instead have a system of separate but connected nerve cells (neurons) called a “nerve net. ” Echinoderms such as sea stars have nerve cells that are bundled into fibers called nerves. Flatworms of the phylum Platyhelminthes have both a central nervous system (CNS), made up of a small “brain” and two nerve cords, and a peripheral nervous system (PNS) containing a system of nerves that extend throughout the body. The insect nervous system is more complex but also fairly decentralized. It contains a brain, ventral nerve cord, and ganglia (clusters of connected neurons). These ganglia can control movements and behaviors without input from the brain. Octopi may have the most complicated of invertebrate nervous systems—they have neurons that are organized in specialized lobes and eyes that are structurally similar to vertebrate species. |
SciQ | SciQ-1957 | 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.
Ingestive protists extend their cell wall and cell membrane around the food item, forming a what? | [
"protective bubble",
"food pocket",
"food vacuole",
"fuel vacuole"
] | C | Ingestive protists ingest, or engulf, bacteria and other small particles. They extend their cell wall and cell membrane around the food item, forming a food vacuole . Then enzymes digest the food in the vacuole. |
SciQ | SciQ-1958 | species-identification, entomology
Title: Trying to identify an insect Toady a friend saw an insect in his garden, in the UK (England).
It looks like a combination of a hover wasp, a wasp and a dragonfly. Whist flying, I'd describe it more similar to a dragonfly.
I've used Google images to try and identify it, and come close, but the creature was about 3 inches long and up to 1 inch wide. I thought it was a broad-bodied chaser but he assures me (possibly incorrectly) it wasn't big enough I would agree with you on this one - looks like a female or young male Libellula depressa (the 'broad bodied chaser') to me. It has the characteristic broad, flattened abdomen and the distinctive brown-yellow abdomen with bright yellow patches and the dark wing bases are both visible (the latter only just, to be fair). The broad abdomen differentiates it from the other Chaser and Skimmer dragonflies while the colour is quite distinctive (the species is sexually dimorphic; mature males have a blue abdomen while females and young males have a yellow abdomen). Not sure what you friend is talking about regarding the size; 3in long is about right for L. depressa. It's in the right geographical region too.
(thanks to @RHA for pointing out to me that young males also have yellow abdomens!)
Citation from Wikimedia Commons: By No machine-readable author provided. Bogdan assumed (based on copyright claims). - No machine-readable source provided. Own work assumed (based on copyright claims)., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=754252
The following is multiple choice question (with options) to answer.
What type of flowers offer no reward, such as nectar, to a male wasp? | [
"perennials",
"roses",
"ophrys",
"vines"
] | C | |
SciQ | SciQ-1959 | cancer
Title: do tumour cells begin with abnormal characteristics? At what point in the cell cycle do cells start to become tumorous? Do they have abnormal characteristics to begin with; if so what are they? Cancer cells don't start to become cancerous at a specific stage of the cell cycle; you will find that while uncontrolled proliferation is a hallmark of cancer, different cancers acquire alterations in different phases of the cell cycle. BRCA-deficient cancers for example have a compromised G2-M checkpoint [1], while Rb deficient cancers have a compromised G1-S [2] checkpoint in the cell cycle.
The cell cycle is simply a property of proliferating cells and the same broad phases of the cell cycle are universal to both normal and malignant cells.
As for when abnormally growing cells actually become a cancer - this has nothing to do with phases of the cell cycle, and everything to do with the ability to break through the basement membrane of the original site (indicating the potential to be invasive/spread), because the ability to invade is a hallmark of cancer [3]
References
[1] http://cancerres.aacrjournals.org/content/67/13/6286
[2] https://www.ncbi.nlm.nih.gov/pubmed/16936740
[3] https://www.ncbi.nlm.nih.gov/pubmed/21376230
The following is multiple choice question (with options) to answer.
If an abnormal cell is not prevented from dividing and it divides uncontrollably, what forms? | [
"cyst",
"inflammation",
"tumor",
"edema"
] | C | In panel A, an abnormal cell (2) is prevented from dividing, and the abnormal cell dies (1). In panel B, an abnormal cell is not prevented from dividing. Instead, it divides uncontrollably, leading to the formation of a tumor. |
SciQ | SciQ-1960 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
Vertebrates have evolved more complex digestive systems, with some species having multi-chambered types of what organ? | [
"heart",
"stomach",
"respiratory",
"skin"
] | B | Vertebrate Digestive Systems Vertebrates have evolved more complex digestive systems to adapt to their dietary needs. Some animals have a single stomach, while others have multi-chambered stomachs. Birds have developed a digestive system adapted to eating unmasticated food. Monogastric: Single-chambered Stomach As the word monogastric suggests, this type of digestive system consists of one (“mono”) stomach chamber (“gastric”). Humans and many animals have a monogastric digestive system as illustrated in Figure 34.6ab. The process of digestion begins with the mouth and the intake of food. The teeth play an important role in masticating (chewing) or physically breaking down food into smaller particles. The enzymes present in saliva also begin to chemically break down food. The esophagus is a long tube that connects the mouth to the stomach. Using peristalsis, or wave-like smooth muscle contractions, the muscles of the esophagus push the food towards the stomach. In order to speed up the actions of enzymes in the stomach, the stomach is an extremely acidic environment, with a pH between 1.5 and 2.5. The gastric juices, which include enzymes in the stomach, act on the food particles and continue the process of digestion. Further breakdown of food takes place in the small intestine where enzymes produced by the liver, the small intestine, and the pancreas continue the process of digestion. The nutrients are absorbed into the blood stream across the epithelial cells lining the walls of the small intestines. The waste material travels on to the large intestine where water is absorbed and the drier waste material is compacted into feces; it is stored until it is excreted through the rectum. |
SciQ | SciQ-1961 | genetics
Title: Law of Segregation (Genetics) What if the two factors/different factors of a character did not segregate during gametogenesis and blended together? The factors that segregate according segregation law are the two alleles of any gene (https://en.wikipedia.org/wiki/Mendelian_inheritance). The only way to avoid that two alleles segregate at meiosis is to have them inherited in the same gamete, as shown in the picture below . Thus, if the two alleles would not segregate you will double you number of alleles (and chromosomes) at each generation. The effect on any given allele would depend on the level of dominance (dominant, recessive, additive), but that would be the least, since at each meiosis the offspring would have twice the number of chromosomes compared to the parents.
The following is multiple choice question (with options) to answer.
A trait controlled by a single gene that has two alleles is given what name, after the scientist who studied inheritance? | [
"mendelian trait",
"carlinian trait",
"darwinian trait",
"rosilin trait"
] | A | A Mendelian trait is a trait that is controlled by a single gene that has two alleles. One of these alleles is dominant and the other is recessive. Many inheritable conditions in humans are passed to offspring in a simple Mendelian fashion. Medical professionals use Mendel’s laws to predict and understand the inheritance of certain traits in their patients. Also, farmers, animal breeders, and horticulturists who breed organisms can predict outcomes of crosses by understanding Mendelian inheritance and probability. |
SciQ | SciQ-1962 | thermodynamics, energy, work
Title: Is energy the ability to do work? Here was my argument against this, the second law of thermodynamics, in effect says that, there is no heat engine that can take all of some energy that was transferred to it by heat and do work on some object. So, if we can not take a 100% the thermal energy of an object, and use it to do work, what about the thermal energy that is rejected to the environment, can we use all of that energy to do work on an object? No, if energy is supposed to be the ability to do work, well that’s a contradiction. "The ability to do work" is certainly a lousy definition of energy.
Is it "merely" a lousy definition, or is it actually an incorrect definition? I think it could be either, depending on precisely how the word "ability" is interpreted. But if the words are interpreted as they would be in everyday speech and everyday life, I would say it's an incorrect definition.
UPDATE -- What is a definition of energy that is not lousy?
This is a tricky issue. Defining a thing that exists in the real world (like you do in physics) is quite different than defining a concept within an axiomatic framework (like you do in math).
For example, how do you "define" Mount Everest? Well, you don't exactly define it, you merely describe it! You describe where it is, you describe what it looks like, you describe how tall it is, etc. Since there is only one mountain that has all these properties, you wind up with a "definition".
Likewise, if I start describing energy (i.e. listing out various properties of energy), I will eventually wind up with a definition of energy (because nothing except energy has all these properties). Here goes:
The following is multiple choice question (with options) to answer.
What law states that energy cannot be created or destroyed? | [
"difference of energy",
"deposit of energy",
"conservation of force",
"conservation of energy"
] | D | In any chemical reaction, there is no overall change in the amount of energy. Energy cannot be created or destroyed. This is the law of conservation of energy. |
SciQ | SciQ-1963 | cellular-respiration
Title: Do cold blooded animals generate any heat? In explaining energy and work to an 8 year-old I said that all conversion of energy generates heat as a by-product. For example, cars generate heat in their engines and running generates heat in our bodies. Then the 8 year-old said, except for cold-blooded animals.
So my question is, do cold-blooded animals generate any heat in their conversion of stored energy (food, fat, etc) into motion? If they generate heat, why are they cold-blooded? They do generate heat. They just do not SPEND energy specifically on heating their bodies by raising their metabolisms. This is a form of energy conservation. The metabolic rate they need to live is not nearly enough to heat their bodies.
An example of spending energy to heat the body is seen in humans shivering. Here muscle is activated not for its usual purpose, but to function as a furnace. "Warm-blooded" and "cold-blooded" is somewhat a misnomer. The correct way to think of it is...
Endotherm or ectotherm. Does the heat primarily come from within (endo) or from the surroundings (ecto). Endothermic animals include mammals. Most of their body heat is generated by their own metabolisms. Ectothermic animals include reptiles and insects. They absorb most of their body heat from the surroundings. This is not the same as saying they let their body temperature fluctuate with their surroundings, some avoid this by moving around to accomodate themselves.
Homeotherm or poikilotherm. Homeotherms want to maintain homeostasis for their body temperatures. They don't want it to change. Poikilotherms do not exhibit this behaviour, instead their body temperatures vary greatly with the environment.
We can have endotherm poikilotherms, such as squirrels, who let their body temperature drop while hibernating. Endotherm homeotherms, such as humans, where temperature is constant by means of complex thermoregulation. Ectotherm homeotherms, such as snakes (moving into shadow or into the sun to regulate temperature), and ectotherm poikilotherms, such as maggots.
The following is multiple choice question (with options) to answer.
How do mammals generate heat? | [
"eating spicy foods",
"maintaning low metabolism",
"maintaining high metabolism",
"running around fast"
] | C | Mammals generate heat mainly by maintaining a high rate of metabolism. Compared with the cells of other animals, the cells of mammals have more mitochondria. Mitochondria are the cell organelles that generate energy. Mammals may also produce little bursts of heat by shivering. Shivering occurs when many muscles all contract slightly at the same time. The muscle contractions generate a small amount of heat. |
SciQ | SciQ-1964 | planets, orbital-motion, stars
Title: Could there be a star orbiting around a planet? I wonder if there ever could be a star (really small) which may orbit around a planet (really big)? One thing to keep in mind is that objects that are bound gravitationally actually revolve around each other around a point called a barycenter. The fact that the earth looks like its revolving around the sun is because the sun is much more massive and its radius is large enough that it encompasses the barycenter. This is a similar situation with the Earth and Moon. If there were three bodies, where two bodies were of similar size (like a binary star system plus a massive planet) then an analysis of three body systems shows that there are stable configurations where the objects will be in very complicated orbits where it would be difficult to say one orbits the other.
Update: The short answer is yes, it is possible when you look at the complete dynamical system, for the reasons stated above. More evidence of this can be found in the study of regular star orbits where very complicated orbits are possible and can be stable. Currently the cut off for classification of a planet and a brown dwarf is 13 Jupiter masses, which is arbitrary to some degree. The lightest main sequence stars have a mass of 75 Jupiters. This will put the barycenter well outside the radius of either body for binary systems.
A quick check of the two body system using the equation:
$$R = \dfrac{1}{m_1 + m_2}(m_1r_1 + m_2r_2)$$
Setting $m_1 = 75$, $r_1 = 1$, $m_2 = 13$, $r_2 = 2$ gives:
$$\dfrac{75 + 26}{75+13} = 1.147$$
Indicating a barycenter at roughly $\dfrac{1}{7}$ the distance between the objects. More bodies will cause more complicated orbits, where again, it would be difficult to say which object orbits which. It should be noted that if the system was composed of 3 objects, 2 of which had similar mass, it would be possible to develop a system that appears to have two larger objects orbiting a third smaller object. A quick check reveals:
The following is multiple choice question (with options) to answer.
What are small, icy objects that have very elliptical orbits around the sun? | [
"craters",
"meteors",
"comets",
"asteroids"
] | C | Comets are small, icy objects that have very elliptical orbits around the Sun. Their orbits carry them from the outer solar system to the inner solar system, close to the Sun. Early in Earth’s history, comets may have brought water and other substances to Earth during collisions. |
SciQ | SciQ-1965 | thermodynamics, energy, work
The following are examples of energy: Kinetic energy, electric potential energy, gravitational potential energy, ...
The fundamental laws of physics are the same at every moment in time -- they were the same yesterday as they are today. This fact implies, by Noether's theorem, that there is a conserved quantity in our universe... This quantity is energy.
Special relativity relates energy to mass / inertia.
General Relativity relates energy to the curvature of spacetime.
In quantum mechanics, the energy of a system is its eigenvalue with respect to the Hamiltonian operator.
Whatever other things I'm forgetting or haven't learned...
All these properties are interrelated, and out of them bubbles a completely precise and unambiguous understanding of what energy is.
(I'm sure that some people will claim that one bullet point is the fundamental definition of energy, while the other bullet points are "merely" derived consequences. But you should know that this is a somewhat arbitrary decision. The same thing is true even in mathematics. What aspects of "differentiable manifold" are part of its definition, and what aspects are proven by theorems? Different textbooks will disagree.)
But can you boil that understanding of energy down into a one sentence "definition" that is technically correct and easy to understand? Well, I can't, and I doubt anyone on earth can.
The following is multiple choice question (with options) to answer.
Is the most basic what is the most basic of the sciences, concerning itself with energy, matter, space and time, and their interactions? | [
"physics",
"biology",
"genetics",
"experiments"
] | A | Section Summary 1.1 Physics: An Introduction • Science seeks to discover and describe the underlying order and simplicity in nature. • Physics is the most basic of the sciences, concerning itself with energy, matter, space and time, and their interactions. • Scientific laws and theories express the general truths of nature and the body of knowledge they encompass. These laws of nature are rules that all natural processes appear to follow. |
SciQ | SciQ-1966 | everyday-chemistry, biochemistry, food-chemistry, terminology
Vitamin D is not strictly a vitamin, rather it is the precursor of one
of the hormones involved in the maintenance of calcium homeostasis and
the regulation of cell proliferation and differentiation, where it has
both endocrine and paracrine actions.
The name vitamin D1 was originally given to the crude product of irradiation of ergosterol,
which contained a mixture of ergocalciferol with inactive lumisterol (an isomer of ergosterol) and suprasterols. When ergocalciferol was identified
as the active compound, it was called vitamin D2. Later, when cholecalciferol was identified as the compound formed in the skin and found in foods, it was
called vitaminD3.
Remarks
The "Vitamin B" naming of these compounds must have been through discovery, and no clear experiments had accurately produced identity of these compounds, there were named as they were discovered but since they have been identified they they now have systematic names
abeit vitamin B still being used today and are formulated as "vitamin B complexes" in pharmaceutical products (perhaps to avoid confusion) hence systematic names are used (folic acid, pantonthenic acid, biotin, thiamin, niacin, cobalamin etc) I have never come across complexes of other Vitamins. Remember for a compound to be named a vitamin it must fit the description above, but I am not disputing the fact that other compounds with similar biological activities exist as "K" group.
References
Nutritional Biochemistry of Vitamins (Bender)
Nutritional biochemistry (Brody)
Modern Nutrition in Health and Disease (Rosset al)
The following is multiple choice question (with options) to answer.
Which is the active ingredient of cereal crop disease, ergot? | [
"pixelation acid",
"byblis acid",
"amino acid",
"lysergic acid"
] | D | Plant Parasites and Pathogens The production of sufficient good-quality crops is essential to human existence. Plant diseases have ruined crops, bringing widespread famine. Many plant pathogens are fungi that cause tissue decay and eventual death of the host (Figure 24.25). In addition to destroying plant tissue directly, some plant pathogens spoil crops by producing potent toxins. Fungi are also responsible for food spoilage and the rotting of stored crops. For example, the fungus Claviceps purpurea causes ergot, a disease of cereal crops (especially of rye). Although the fungus reduces the yield of cereals, the effects of the ergot's alkaloid toxins on humans and animals are of much greater significance. In animals, the disease is referred to as ergotism. The most common signs and symptoms are convulsions, hallucination, gangrene, and loss of milk in cattle. The active ingredient of ergot is lysergic acid, which is a precursor of the drug LSD. Smuts, rusts, and powdery or downy mildew are other examples of common fungal pathogens that affect crops. |
SciQ | SciQ-1967 | evolution, trees
Title: How related are trees? I was surprised to see how far apart macadamia and hazelnuts are from each other. I always thought all trees had a common ancestor that was also a tree. But that doesn't seem to be the case? Did wood evolve multiple times? The word "tree" is a not a taxonomic classification, but a human perceptual clustering based on form and size. The word "fish" has a similar problem, covering a vast collection of taxa, some of which are less closely related to one another than they are to us.
Becoming tree-like often has a strong evolutionary value, because plants compete for sunlight and taller plants shade shorter plants. Thus, we should not be surprised that "tree" forms have evolved independently in a number of different lineages.
The common evolutionary lineage for all of these, however, is tracheophyta, the vascular plants. These are plants that have differentiated xylem (which is the wood of a tree) and phloem tissues for transport of water and minerals. Most such plants are not trees, of course, but these tissues provide an effective means of vertical transport and the basis for hard woody material, which appears to have been the key differentiator between plants capable of evolving into trees and plants that are not able do to so.
The following is multiple choice question (with options) to answer.
What type of structures evolved to do the same job by unrelated organisms? | [
"analogous structures",
"symmetrical structures",
"primal structures",
"dioxide structures"
] | A | Scientists compare the anatomy, embryos, and DNA of living things to understand how they evolved. Evidence for evolution is provided by homologous structures. These are structures shared by related organisms that were inherited from a common ancestor. Other evidence is provided by analogous structures. These are structures that unrelated organisms share because they evolved to do the same job. |
SciQ | SciQ-1968 | asteroids, mars, comets, impact, crater
What’s more, the meteoroid excavated boulder-size chunks of ice buried closer to the Martian equator than ever found before – a discovery with implications for NASA’s future plans to send astronauts to the Red Planet.
PIA25583 Credit: NASA/JPL-Caltech/University of Arizona
How do we know that this ice is from Mars and not from the impactor, which would then be a comet and not an asteroid?
I guess it all comes down to inferring the density of the impactor, but its dimensions and mass seems to be poorly constrained. The NASA press release says "5 to 12 meters", without precising the shape. This IPGP press release (in French) says the object was between "250 and 650 tonnes". Assuming a spherical shape, combining these numbers can yield any density between 0.28 g cm$^{-3}$ (12 m sphere weighting 250 tonnes) and 10 g cm$^{-3}$ (5 m sphere weighting 650 tonnes). (I won't consider this Imperial College press release, as it is full of "units" even worse than the imperial system: "one and a half times the size of Trafalgar Square", "van-sized", "the area inside London’s M25 motorway" [sic]...)
Comets have a density of about 0.6 g cm$^{-3}$, while iron meteorites can be as dense as 8 g cm$^{-3}$, with rocky bodies in between, so they all seem to fall in the possible range.
I've glanced over the two Science papers associated with the story (#1, #2), but the ice is barely mentioned, and I could not find any mass or dimension of the impactor. From Richardson et. al, all the small, high-speed debris gets ejected from an impact first, and ends up furthest from the impact point. This would include any intermixing of the impactor with Martian material at the center of the crater, supposing the impactor wasn't entirely vaporized on impact.
The last of the ejecta to exit the crater are the largest pieces of existing planetary material, which come from the very outside edges of the crater at the lowest speed. The paper has a nice figure that I've referenced in a number of other answers:
The following is multiple choice question (with options) to answer.
What explains the spherical shape of ceres, once thought to be the largest asteroid? | [
"high gravity",
"low gravity",
"orbital plane",
"space debris"
] | A | Ceres ( Figure below ) is a rocky body that orbits the Sun. It could be an asteroid or a planet. Before 2006, Ceres was thought to be the largest asteroid. Is it an asteroid? Ceres is in the asteroid belt. But it is by far the largest object in the belt. Ceres has such high gravity that it is spherical. |
SciQ | SciQ-1969 | earthquakes, waves, scale
Title: If a very huge Earthquake occured anywhere on Earth could waves emerge to come together again on the opposite side? Suppose that a super-powerful earthquake occurred anywhere on Earth, say one with the value 10 on Richter's scale. The quake can have any value but as can be read in a comment below the highest value ever measured was 32 on a superdense star. In that case, it's much more difficult to tear the star apart. The Earth, in contrast, could be torn apart by a quake with value 10 because she is highly less massive.
Suppose the quake was mainly transversal (in a vertical direction). Could it be that correspondingly waves emerged from the center of the quake, traveling the Earth around to come together and reinforced again on the opposite side of the center, with the effect that the quake was felt more strongly on the opposite side of the center than at places halfway from the center (or halfway to the opposite side of the center), to say it in one long breath? Or would too much energy be absorbed from the waves by the Earth to reach the opposite side? It is called "antipodal focusing". See for example Antipodal focusing of seismic waves observed with the USArray.
We present an analysis of the M-w = 5.3 earthquake that occurred in the Southeast Indian Ridge on 2010 February 11 using USArray data. The epicentre of this event is antipodal to the USArray, providing us with an opportunity to observe in details the antipodal focusing of seismic waves in space and time. We compare the observed signals with synthetic seismograms computed for a spherically symmetric earth model
The above paper deals with "body waves" that travel through the interior of the Earth.
There are also Rayleigh waves that travel on the surface and can travel around the Earth several times before dissipating (Wikipedia). Antipodal focusing of seismic waves due to large meteorite impacts on Earth does numerical simulations of surface waves at the antipode of the Chicxulub impact. The waves do not arrive at the antipode at the same time because of Earth’s ellipsoidal shape and different rock properties along their paths.
Isosurfaces of the norm of the peak displacement vector after a vertical impact for the impact hemisphere (left-hand side) and antipodal hemisphere (right-hand side).
The following is multiple choice question (with options) to answer.
What measures the height of the largest seismic wave or earth quakes? | [
"magnitude scale",
"richter scale",
"The EF Scale",
"tremor scale"
] | B | The intensity of an earthquake can be determined in many ways. The Mercalli Scale identifies the damage done and what people feel, the Richter Scale measures the height of the largest seismic wave, and the moment magnitude scale measures the total energy released by an earthquake. |
SciQ | SciQ-1970 | ocean, ocean-currents, antarctic
Title: Why don't Antarctic waters have more upwellings, when Arctic waters are so rich in upwellings? Formation of ice and hence more dense saltwater sinking happens in both polar regions, creating downwellings. Meanwhile, only a few spots in Antarctica have upwellings
I refer to this image:
https://en.wikipedia.org/wiki/Upwelling#/media/File:Upwelling_image1.jpg First, we might want to distinguish between the different types of upwelling:
Coastal upwelling: It is the best known form of upwelling. Winds in these systems flow parallel to the coast (with the coast to the left in the northern hemisphere or to the right in the southern hemisphere) and generate upwelling dynamics. Surface Ekman balance is setup (in deep enough waters) with water transport being to the right (left) of the wind in the northern (southern) hemisphere. The result is a deficit along the coast that requires a compensating flow in the deeper part of the water column bringing usually colder waters to the surface. If the wind blows in the opposite direction, then downwelling occurs.
The figure from the question refers to coastal upwelling (here in its original website with explaining caption). There is definitely more coastal upwelling in the northern hemisphere because of the abundance of shorelines as a greater amount of landmass is present in that hemisphere.
Source Commons Wikipedia.
Equatorial upwelling: Winds from the east blow and converge along the equator as part of the Intertropical Convergence Zone (ITCZ). While the magnitude of the Coriolis acceleration is zero along the equator, Ekman transport takes place immediately north and south of the equator resulting in surface ocean divergence that requires a compensating flow of denser (nutrient-rich) water upwelled from below.
Source
The following is multiple choice question (with options) to answer.
What type of winds are created when more solar energy strikes the equator than the polar regions? | [
"global winds",
"arctic winds",
"domestic winds",
"equatorial winds"
] | A | Winds on Earth are either global or local. Global winds blow in the same directions all the time. They are created when more solar energy strikes the Equator than the polar regions. More about global wind patterns is described in detail in the concept "Global Wind Belts. ". |
SciQ | SciQ-1971 | evolution, taxonomy, ornithology
Title: Birds and Dinosaurs This came up in an argument with some friends. I know that birds are direct descendants of dinosaurs, shown pretty clearly through the fossil record. However, is it proper to say that birds are dinosaurs, or is there an actual distinction? I bet you'll be interested about the concept monophyly. Any human-made group of species (or taxon) like birds dinosaurs, primate, bacteria, angiosperm, reptiles, … are either monophyletic, polyphyletic or paraphyletic. This picture explain the concept When the taxon is monophyletic it is called a clade.
Monophyletic taxon are those groups of species that can be considered to be objective in the sense that it represents a group of species where each species in the taxon is more related (in terms of time to common ancestor, not according to their genetic similarity) to any other species within the same taxon than to any other species outside this taxon. This is obviously not the case for paraphyletic or polyphyletic taxon.
Typically, we do not consider a parrot or a deer to be reptiles. Therefore, the ususal understanding of "reptiles" makes this taxon paraphyletic. Now, one should not confound the common understanding (what is a reptile in our everyday life) with the strict definition of the taxon Reptilia, which is a monophyletic taxon (or a clade in other words). Probably the best source for exploring the tree of life is tolweb.org. Here, you will find the clade Reptilia (who include birds, snakes, turtles and lizards). Note: Mammals are within the Reptiliomorpha, not the Reptilia.
It is exactly the same issue with the dinosaurs. When we talk about dinosaurs in our everyday life we do not mean birds. But there is a clade called Dinosauria, which include both dinosaurs and birds.
In short, I would say that a bird is a Dinosauria (monophyletic taxon) but is not a dinosaur (paraphyletic taxon). But this little play on word is not a scientific issue but an issue of english usage.
You will also find in this post an introduction to phylogeny
The following is multiple choice question (with options) to answer.
Reptiles and birds are the only known living descendants of what? | [
"dinosaurs",
"fossils",
"mammals",
"dragons"
] | A | Crocodilia, containing both alligators and crocodiles, is an order of large reptiles. Reptiles belonging to Crocodilia are the closest living relatives of birds. Reptiles and birds are the only known living descendants of the dinosaurs. Some would day that alligators and crocodiles actually look like small dinosaurs. Dinosaurs that evolved wings are the ancestors of birds. |
SciQ | SciQ-1972 | evolution
Title: How to define "evolution"? The standard answer found in intro course to evolutionary biology to the question:
what is evolution?
is:
It is a change in allele frequency over time!
I believe a complete definition should encompass the following concepts:
mutations
copy number variation (CNV)
codon usage
chromosome numbers
phenotypic change (whether heritable or not)
Complex phenotypic trait such as plasticity and developmental noise
maybe some other things...
My questions are:
Would it be worth it to talk about phenotype in a definition of evolution?
What are the alternative definitions that have been proposed?
What is your definition?
Note: I would rather talk about genetic evolution, but if you think it is worth making one definition for genetic and cultural (and some other stuff maybe) evolution, you're free to suggest it! What is evolution?
In a non-biological sense, evolution means change:
"a process of [...] change"
Biological evolution (seeing as this is Biology stack exchange) then needs to be tweaked to give a biologically specific context. Many textbooks etc. give definitions of evolution and here are a few good ones from across the history of evolutionary biology:
Charles Darwin:
"Descent with modification".
Mark Ridley1:
"Evolution means change, change in the form and behaviour of organisms between generations. ... When members of a population breed and produce the next generation we can imagine a lineage of populations, made up of a series of populations through time. Each population is ancestral to the descendant population in the next generation: a lineage is an ancestor-descendent series of populations. Evolution is then change between generations within a population lineage."
Brian and Deborah Charlesworth2:
"Evolution means cumulative change over time in the characteristics of a population of living organisms. ... All evolutionary changes require initially rare genetic variants to spread among the members of a population, rising to high frequency..."
All of these have a common theme. Biological information is moving through time, descending with a degree of directionality (e.g. parent $\rightarrow$ offspring), and the information is modified with time.
Personally I would define evolution as:
The following is multiple choice question (with options) to answer.
Organism's changing over time is called? | [
"generation",
"heterogenicity",
"evolution",
"variation"
] | C | Evolution means change over time. Darwin’s theory of evolution says that organisms change over time ( Figure below ). Evolution is seen in the fossil record. It is seen in the way organisms develop. Evolution is evident in the geographic locations where organism are found. It is evident in the genes of living organisms. Evolution has a mechanism called natural selection . The organism that is best suited to its environment is most likely to survive. Evolution is described in the chapter Life on Earth . |
SciQ | SciQ-1973 | mass, conservation-laws
Title: Is there any deeper reason behind the conservation of mass? I have read that behind the conservation of energy or momentum is the Noether theorem with its intimidating maths.
Is there any similar deeper foundation behind the conservation of mass? Mass is not a conserved quantity, except in classical mechanics and its derivatives. As classical mechanics emerges from quantum mechanics and special relativity the conservations laws on energy and momentum, Noether's theorem in quantum mechanical terms, define also the mass. Everything has energy and momentum and is described by a fourvector, and the "length" of that four vector is the invariant mass of a particle . Vector algebra has to be used for systems of particles, and the summed vector's length gives the invariant mass of the system
The following is multiple choice question (with options) to answer.
The law of conservation mass states that matter cannot be created or what? | [
"changed",
"destroyed",
"moved",
"observed"
] | B | The law of conservation of mass states that matter cannot be created or destroyed. |
SciQ | SciQ-1974 | biochemistry
Title: Bradford Reagent Disposal I am a graduate student volunteering in a professor's lab being tasked with finding out how to dispose of certain hazardous materials. I have encountered a problem with disposing of Bradford's Reagent. I have checked online, but am running into problems due to the methanol component of this compound. Can someone help me with the proper disposal procedure? Thank you in advance. I would strongly suggest to ask someone in your lab about this, they will have a better idea about the different waste disposal methods you have available.
In general you would dispose anything that contains organic solvents like methanol in a waste container for generic solvent waste. You should have something like that somewhere in the lab.
One thing you always have to keep in mind is to never put anything still reactive into your waste container. A popular example would be a strong oxidizing agent, putting that into a solvent waste container is dangerous and could e.g. ignite the waste. This is not an issue in this case, but you should always keep that in mind.
Another aspect is the pH of the waste, in many cases the waste disposal facility will only accept reasonably neutral waste, so you should neutralize your waste before putting it into a container. Neutralizing it inside the container can be much more annoying. This might not be necessary if you have a dedicated acidic waste, you'll have to ask someone in your lab about that. The Bradford reagent is strongly acidic, so you'll have to pay attention to this aspect.
The following is multiple choice question (with options) to answer.
What help should you use for disposing hazardous products? | [
"call poison control",
"biohazard unit",
"guidelines on label",
"first aid kit"
] | C | Proper disposal depends on the waste. Many hazardous products have disposal guidelines on the label. That’s one reason why you should keep the products in their original containers. The labels also explain how to use the products safely. Follow the instructions to protect yourself and the environment. Most communities have centers for disposing of household hazardous waste (see Figure below ). Do you know how to dispose of hazardous waste in your community?. |
SciQ | SciQ-1975 | fluid-dynamics
Title: Are waves affected by an under-water barrier? Given a wave propagating at the surface of still water towards a barrier that is below the surface, but at a distance that is of the order of the dimensions of the wave (such as depicted in the scheme below).
How will the course of the wave be affected ?
Will it be blind to it and pursue its course unaffected ?
Will it only partially pursue and a part of it will bounce back ?
Something else ?
<
wave
/~~~
/~~~~\ ->
~~~~/~~~~~~`~~~~~~~~~~~~~~~~~~~~~~~~ water surface
____
| |
| |
____________________| |__________
barrier Ocean surface waves that are said to 'feel' bottom are known as shallow water waves which are categorically differentiated from deep water waves according to wavelength and depth, and which are not as affected by the depth of the sea floor.
Ocean surface waves are a movement of energy, not a bulk forward motion of water but do result in local circular orbits of the water particles. With depth the circular orbits flatten into elliptical orbits and eventually vanish, and it's at this depth obstacles will no longer influence surface wave motion. For obstacles that do intrude into this space, the circular or elliptical motions are disturbed and energy is dissipated towards the upper water layers, building up wave height. IN very shallow water the build up can get high enough that the wave can no longer sustain its shape and you have a breaking wave.
The property that actually leads to the loss of energy from obstacles is the viscosity of the water, the ability for layers of water to flow over one another.
The following is multiple choice question (with options) to answer.
Although surface waves are slowest, they do most of the damage of what event? | [
"volcano",
"earthquake",
"tsunami",
"hurricane"
] | B | Surface waves are the slowest, but they do the most damage in an earthquake. |
SciQ | SciQ-1976 | biochemistry, botany
Title: Ripening bananas artificially: What is the biological theory behind? I am a resident of the tropical island of Sri Lanka, and we have a strange traditional method to ripen our banana harvest quickly.
What we do is this: We dig a pit in earth that is enough to put the whole banana cluster in. Then, after safely laying the bananas in the pit, we cover up the pit with a sheet such that only a small hole from a side remains: visualize a small 3-4 inch door to the pit.
After that, we light a fire with semi-dry leaves just outside the pit's door. (Semi-dry leaves are used to get as much smoke as possible. Dry leaves do not give that much smoke, because they completely oxidize quickly). And the smoke is sent through the door by blowing it with the aid of a bamboo.
This sends a good amount of smoke and warms the inside of the pit considerably. And by experience I can tell you that this makes the bananas to ripen really quickly. I have done a controlled experiment where half of the cluster was not put into the pit. Bananas in the pit ripen overnight and the control sample took days to ripen.
Can anybody explain what are the bio-mechanisms that are working here? Ripening of bananas (and other fruits) is induced by acetylene and ethylene (Ethyne and Ethene) (see reference 1), which acts as a hormone and induces the ripening process. The incomplete combustion of the leaves produces ethylene, additionally the warmth of the process will help the enzymes as well. There is even a paper about this technique (although it is unfortunately not accessible), see reference 2 for more information. Smoking Chambers are routinely used in this process, see reference 3 and 4.
References:
Role of Ethylene in Fruit Ripening
Effects of smoking on some physiological changes in bananas.
Fruit Ripening
Technology for ripening fruits as important as marketing them
The following is multiple choice question (with options) to answer.
Fruit begins to ripen because what gas is released? | [
"hydrogen",
"ethylene",
"sulfur",
"chloride"
] | B | |
SciQ | SciQ-1977 | meteorology, tornado, coriolis
And then conversely, Australia doesn't have a lot of land Poleward yet is still a reasonably busy tornado spot.
Mountain ranges Poleward also generally aren't a big deal... even pretty large ones; one of the biggest tornado areas is Bangladesh\India, despite the disruption the Himalayas presents. Because enough cold air can filter into the region in spite of the blockage.
The only thing that would be a real large scale geographic issue to the needed cold air would be a warm sea Poleward that modifies the incoming cold air significantly.
But that's pretty tough to have geographically. Perhaps more possible in the Autumn... maybe the Great Lakes serves as a slight dampener on fall season tornadoes in parts of the US? Though their effect is still mostly pretty small overall. Bring too near any large body of water, in any direction, is really a downer on supercellular tornadoes, as it modifies temperature gradients and instability.
To your direct question... there actually is a very good example of what Tornado Alley would look like in the Southern Hemisphere already: the Pampas Lowlands of Argentina.
It has that big mountain range to the west, in the midlatitudes, and does have fairly warm water a ways northward.
But it doesn't have quite as large of a region east of the mountains to have the tornadoes in, the cold air (and storm system strength) is probably modified due to the closed nature of the Antarctic vortex and the widespread oceans of the SH modifying air masses, and the source water isn't probably as well located being so far north (and is it warm?).
But even still, Pampas area might be the second most consistent tornado region on Earth. Such that some US storm chasers have traveled down there in our winter.
In the end, local effects play a huge role too, creating mesoscale ingredients (seabreezes\temperature boundaries, upsloping, local vortex flow, etc) to add plenty of rotation to the ledger (see Florida, one of highest tornadoes per square mile in US, in large part due to seabreeze water spouts and hurricanes). But all things equal, being east of mountains in the midlatitudes is a jackpot ingredient to climatological tornado formation (regardless of hemisphere).
The following is multiple choice question (with options) to answer.
Winter storms develop from what, which form at high altitudes and are associated with hurricanes as well? | [
"droughts",
"currents",
"fronts",
"cyclones"
] | D | Like hurricanes, winter storms develop from cyclones. But in the case of winter storms, the cyclones form at higher latitudes. In North America, cyclones often form when the jet stream dips south in the winter. This lets dry polar air pour south. At the same time, warm moist air from the Gulf of Mexico flows north. When the two air masses meet, the differences in temperature and pressure cause strong winds and heavy precipitation. Two types of winter storms that occur in the U. S. are blizzards and lake-effect snow storms. |
SciQ | SciQ-1978 | botany
Title: Do plants absorb toxins from the soil? Consider a plant like Aloe Vera that grows up in a toxic environment where the concentration of pesticides, and materials like lead, mercury, cadmium, arsenic etc is very high(e.g. Marshland dumping yard ). Would that mean that the extract from these plants would contain all these toxic elements. Not "all of them". But yes, plants suck up water from the soil, with everything dissolved in this water - nutrients, heavy metals, poisons. And also they breathe air, and absorb stuff via this route.
There probably are some toxins which will not enter the plant, because their molecules are too large and/or fragile. For example, should a plant root come in contact with snake venom, I cannot imagine that any venom will end up stored in the plant leaves.
Plants also have their own metabolism, so they will change/deactivate some toxins. I've seen claims that some plants "purify" formaldehyde, although I don't trust the sources enough to be sure of that.
But the smaller the poison molecule, and the less similar to stuff which is usually digested in nature, the more likely that it will enter the plant and stick around instead of being broken down. The heavy metals you mentioned are prime candidates. If they are present in the groundwater - or also lead from air pollution, before we banned leaded gasoline - they end up in plants, including food plants. And mushrooms are even more at risk.
Growing food near waste dumps is a known problem in farming, and sometimes makes the news, for example here:
http://bigstory.ap.org/article/mafia-toxic-waste-dumping-poisons-italy-farmlands
The following is multiple choice question (with options) to answer.
Fungi absorb nutrients from the environment through what? | [
"spores",
"hymenium",
"apothecia",
"mycelia"
] | D | Fungal mycelia. Fungi absorb nutrients from the environment through mycelia. The branching mycelia have a high surface-area-to-volume ratio which allows for efficient absorption of nutrients. Some fungi digest nutrients by releasing enzymes into the environment. |
SciQ | SciQ-1979 | evolution, mammals
Title: Why haven't land animals evolved beyond urination? It occurred to me (while urinating) that this would seem to be selected against because water is a scarce resource. Why are we constantly losing water we don't need to through urination? What is it about the chemistry of urine and the waste products eliminated that make urination necessary as opposed to eliminating them through defecation and recovering the water on the way out? It is probably true that toilets and other resting-ish area are always a great place to think about biology, I agree $\ddot \smile$.
Why do we urinate?
In short, urine contains the waste from our blood while defecation is just the stuff that we haven't digested. Kidneys are the organs responsible for draining wastes (mostly nitrogen-containing, or nitrogenous, wastes) from our blood.
Trade-off: energy cost vs. water loss
You're correct that the loss of water through urination is a considerable cost for an organism (especially those living in dry environments). But the amount of water used to excrete nitrogenous wastes is negatively correlated with the energy it costs to perform this excretion. In other words, there is a trade-off between water and energy loss during nitrogen excretion. Also, the question of toxicity is important.
Three ways to excrete nitrogenous wastes
Animals basically have three choices to excrete nitrogenous wastes:
Uric acid (excreted by uricotelic organisms)
Solid (crystal) with low water solubility
Low toxicity
Little water is needed
Lots of energy is needed
Ammonia (excreted by aminotelic organisms)
Highly soluble in water
High toxicity
Lots of water is needed to dilute it because of the toxicity
Not much energy is needed
Urea (excreted by ureotelic organisms)
Solid but highly soluble in water
"medium" amount of water is needed
"medium" toxicity
"medium" amount of energy is needed
The following is multiple choice question (with options) to answer.
What do you call any process in which excess water or wastes are removed from the body? | [
"depletion",
"excretion",
"diffusion",
"digestion"
] | B | Excretion is any process in which excess water or wastes are removed from the body. Excretion is the job of the excretory system. Organs of excretion include the large intestine, liver, skin, lungs, and kidneys. |
SciQ | SciQ-1980 | the-sun, earth, heat
Hopefully you can fully appreciate the point I'm getting at which is that Earth actually is inside the atmosphere of the Sun and that atmosphere is really hot! The reason we of course aren't boiled to death is that the atmosphere is incredibly sparse. Only a handful of particles per cubic centimeter. So what you're really proposing is to increase the density of this atmosphere by an insane amount. You want to make it approximately $10^{20}$ times more dense! If we just extrapolate properties, that's going to turn the already hot atmosphere of the Sun (around the Earth) into something incredibly hot. And the huge density means we'll really feel the effects. The Earth will likely be vaporized in a flash, before the cataclysmic explosion which I alluded to above can even happen.
So, long answer short: About a billion degrees.
The following is multiple choice question (with options) to answer.
Earth's temperature will increase further as more of what colorfully nicknamed gases are put into the atmosphere? | [
"greenhouse gases",
"blue dioxide gases",
"bluehouse gases",
"green dioxide gases"
] | A | Current Situation : Currently the heating effect of extra greenhouse gases (since the start of the industrial revolution) is equal to about . Thus the recent period has recorded parallel increases in concentration of carbon dioxide and average global temperature. As more greenhouse gases are put into the atmosphere the temperature will increase further. There are certain effects of a warmer Earth (discussed more in optional section), which could accelerate the process, even if no more greenhouse gases are put into the atmosphere (an unlikely prospect for the foreseeable future). |
SciQ | SciQ-1981 | 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.
What happens to cells in a hypertonic solution as water leaves the cell via osmosis? | [
"self destruction",
"get larger",
"evaporation",
"shrinkage"
] | D | The movement of water molecules is not itself regulated by cells, so it is important that cells are exposed to an environment in which the concentration of solutes outside of the cells (in the extracellular fluid) is equal to the concentration of solutes inside the cells (in the cytoplasm). Two solutions that have the same concentration of solutes are said to be isotonic (equal tension). When cells and their extracellular environments are isotonic, the concentration of water molecules is the same outside and inside the cells, and the cells maintain their normal shape (and function). Osmosis occurs when there is an imbalance of solutes outside of a cell versus inside the cell. A solution that has a higher concentration of solutes than another solution is said to be hypertonic, and water molecules tend to diffuse into a hypertonic solution (Figure 3.8). Cells in a hypertonic solution will shrivel as water leaves the cell via osmosis. In contrast, a solution that has a lower concentration of solutes than another solution is said to be hypotonic, and water molecules tend to diffuse out of a hypotonic solution. Cells in a hypotonic solution will take on too much water and swell, with the risk of eventually bursting. A critical aspect of homeostasis in living things is to create an internal environment in which all of the body’s cells are in an isotonic solution. Various organ systems, particularly the kidneys, work to maintain this homeostasis. |
SciQ | SciQ-1982 | 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.
Digestion and respiration are both facilitated by the pharynx, more commonly called the what? | [
"nose",
"esophagus",
"throat",
"sinus"
] | C | The Pharynx The pharynx (throat) is involved in both digestion and respiration. It receives food and air from the mouth, and air from the nasal cavities. When food enters the pharynx, involuntary muscle contractions close off the air passageways. A short tube of skeletal muscle lined with a mucous membrane, the pharynx runs from the posterior oral and nasal cavities to the opening of the esophagus and larynx. It has three subdivisions. The most superior, the nasopharynx, is involved only in breathing and speech. The other two subdivisions, the oropharynx and the laryngopharynx, are used for both breathing and digestion. The oropharynx begins inferior to the nasopharynx and is continuous below with the laryngopharynx (Figure 23.12). The inferior border of the laryngopharynx connects to the esophagus, whereas the anterior portion connects to the larynx, allowing air to flow into the bronchial tree. |
SciQ | SciQ-1983 | 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.
What muscle is found only in the walls of the heart? | [
"skeletal muscle",
"abdominal muscle",
"respiratory muscle",
"cardiac muscle"
] | D | Cardiac muscle is found only in the walls of the heart. When cardiac muscle contracts, the heart beats and pumps blood. Cardiac muscle contains a great many mitochondria, which produce ATP for energy. This helps the heart resist fatigue. Contractions of cardiac muscle are involuntary like those of smooth muscle. |
SciQ | SciQ-1984 | classical-mechanics, waves, frequency, string
At (a), a single pulse it traveling to the right. It partially reflects at the boundary, and a pulse of half the amplitude (and 1/3 of the wavelength) continues to the right, while the remainder is reflected and inverted at (b). At (c), the wave on the left has returned, while the one on the right is still traveling to the right. Another transmission/reflection happens, and you get an even smaller fraction of the wave on the left and a second pulse on the right at (d). If you continued this diagram, you would see that the motion on left and right is an infinite summation of waves of different amplitudes and timings; a steady state solution can only exist for certain frequencies, which we will compute below.
This diagram is what it would look like if you could give a short "kick" to the left end of the string, and watched the waves propagate. As these pulses travel back and forth, it will usually happen that the higher frequencies are damped and you are left with a standing wave. In principle you can do the same diagram with sine waves, but it would quickly look very mess - so let's go to the mathematical treatment instead:
It is known that the propagation velocity of the wave is proportional to the inverse square root of the mass per unit length; so if you have half the string at density $\rho$ and the other half at density $9\rho$, then the wave travels 3x faster in the thinner part of the string - and there should be more waves in the thick part.
To draw this, you need to find a function that is continuous in both amplitude (so string doesn't break) and the first derivative (otherwise there will be infinite acceleration at the "kink" until it's smooth again). This means that to the left of the center, it's of the form
$$y = A_1 \sin(k x)$$
while to the right it is
$$y = A_2 \sin(3k (2L-x))$$
(Using the $\sin$ basis function like this we enforce the boundary conditions at x=0 and x=2L).
Continuity of amplitude implies that
$$A_1 \sin(kL)=A_2\sin(3 kL)$$
and continuity of first derivative:
The following is multiple choice question (with options) to answer.
The wave on a guitar string is transverse. the sound wave rattles a sheet of paper in a direction that shows the sound wave is what? | [
"longitudinal",
"magnetic",
"lateral",
"obtuse"
] | A | Figure 16.33 The wave on a guitar string is transverse. The sound wave rattles a sheet of paper in a direction that shows the sound wave is longitudinal. |
SciQ | SciQ-1985 | photosynthesis, cellular-respiration, energy, sugar
Basically, points 4-7 convey that Calvin-Benson cycle not only produces sugar but what it actually does is fix inorganic carbon (as CO2) to organic form (in the form of sugar). So, most (practically all) of the carbon that a photosynthetic plant has, comes from this carbon fixation process and that's how plants are photoautotrophic.
The following is multiple choice question (with options) to answer.
How do leaves export sugar to roots and other nonphotosynthetic parts of the plant? | [
"chloroplasts",
"veins",
"stems",
"glands"
] | B | |
SciQ | SciQ-1986 | electrochemistry, metal
Title: Corrosion of a galvanic couple made with silver and gold If a bangle is made out of gold and silver, connected with each-other would there be corrosion happening?
If so, can it be explained using the galvanic series?
Also do those metals undergo oxidation under normal conditions? As you state, though silver is not very reactive, silver jewelry would corrode more rapidly when in contact with gold and a bit of sweat as electrolyte. Though the difference in electronegativity of pure gold and pure silver is 0.15V, and is considered acceptably corrosion resistant, commercial jewelry contains copper and other metals in the alloys. There is clearly evident corrosion in photos of copper/silver jewelry. According to the Victoria and Albert Museum staff, "All metals, with the exception of 24 carat gold, suffer the effects of corrosion."
However, in a bangle, physical abrasion is likely to cause more damage and loss of material than galvanic corrosion. Wear the jewelry and enjoy it, but it will not last forever.
The following is multiple choice question (with options) to answer.
Some metals, such as gold and platinum, do not corrode easily because they are very resistant to what? | [
"oxidation",
"precipitation",
"evaporation",
"heat"
] | A | Some metals, such as gold and platinum, do not corrode easily because they are very resistant to oxidation by common substances. Some other metals begin to be oxidized, but are further protected from additional corrosion by a coating formed on the surface. Aluminum reacts with oxygen to form aluminum oxide, which remains tightly packed on the surface. The aluminum oxide prevents the interior of the aluminum from corroding. Not all corrosion is a result of reaction with oxygen. Copper corrodes by reaction with carbon dioxide to form copper(II) carbonate. This distinctive green compound is also called patina and prevents the copper underneath from further corrosion (see Statue of Liberty in the Figure below ). |
SciQ | SciQ-1987 | water, flow
Title: How is it that a cistern can collect rainfall, but a well cannot, even though both of them are holes? I imagined that a regular downpour or flood of rain would fall into the well directly, so I did a search on Google and was surprised to find this answer. But the article didn't make sense other than that the water would seep through the ground and in ten years, it would be at the water table, where it might, perhaps, refill the well. Still, I'm not sure what sets a cistern apart at being able to collect rainwater, since the gravity should be able to pull rain down.
If there is a better SE site for this question, feel free to move it. Without directing runoff rainwater into an open well it can only catch the rain that lands on its exposed surface area. This could only add a few inches at most in a single rainfall. A cistern directs runoff from a larger area into it, so it is fed by a much larger area than just the surface area of the tank.
The following is multiple choice question (with options) to answer.
What are floods a source of on a floodplain? | [
"acids",
"nutrients",
"salt",
"minerals"
] | B | Floods are a source of nutrients on a floodplain. |
SciQ | SciQ-1988 | biochemistry
Title: Is glutamate always involved in the deamination and amination of the other amino acids? For example, are there pathways for the deamination of phenylalanine that simply produce ammonia or pathways for it to be synthesized from phenylpyruvate with ammonia being utilized to form the amine group?
Preferably, I want to know how it is with human metabolism mainly. For most amino acids, the removal of the α-amino group involves α-ketoglutarate and glutamate. The amino group is first transferred to a-ketoglutarate by transaminases, and the resulting glutamate is then deaminated (via glutamate dehydrogenase) to yield ammonia.
The same is true for amination. Glutamate and glutamine are the two major amino group-donors. Most ketoacids are converted to their respective amino acids by transamination involving glutamate or glutamine. Glutamine can be synthesized by amination of glutamate with ammonia without transamination (via a synthetase enzyme) and glutamate can be aminated with ammonia too.
Exceptions do exist, of course. For example, Not all transaminations involve glutamate/glutamine (as this user has replied), and serine and threonine can be directly deaminated (via dehydratase enzymes, as opposed to the dehydrogenase used for glutamate).
The following is multiple choice question (with options) to answer.
Which process helps deaminate amino acids? | [
"deactivation",
"caramelization",
"transamination",
"bromination"
] | C | The Fate of the Carbon Skeleton Any amino acid can be converted into an intermediate of the citric acid cycle. Once the amino group is removed, usually by transamination, the α-keto acid that remains is catabolized by a pathway unique to that acid and consisting of one or more reactions. For example, phenylalanine undergoes a series of six reactions before it splits into. |
SciQ | SciQ-1989 | brain, terminology, neuroanatomy, etymology
anterior to or involving the anterior part of a frontal structure
Anterior meaning
situated before or toward the front
Indeed Siddiqui et al (2008) mention:
The anterior part of the frontal lobe referred in the literature as ‘pre’-frontal lobe has been simultaneously referred to as ‘frontal granular cortex’ and ‘frontal association cortex.’ The anterior most portion of the frontal lobe is occupied by the PFC...
Reference
- Siddiqui et al., Indian J Psychiatry (2008); 50(3): 202–8
Fig. 1. The frontal lobe includes the prefrontal cortex (PFC). source: Socratic
The following is multiple choice question (with options) to answer.
What is each half of the cerebrum called? | [
"a describe",
"a biplane",
"a hemisphere",
"demisphere"
] | C | The cerebrum is divided into a right and left half ( Figure above ). Each half of the cerebrum is called a hemisphere. The two hemispheres are connected by a thick bundle of axons called the corpus callosum . It lies deep inside the brain and carries messages back and forth between the two hemispheres. |
SciQ | SciQ-1990 | cell-biology, proteins, mitosis
Title: Purpose of intensive protein synthesis in G1 phase of mitosis What is the purpose of intensive protein synthesis in G1 phase of mitosis, and what purposes do these synthesized proteins serve? Why are lipids and carbohydrates not synthesized intensively as well? The G1 phase of eukaryotic cell cycle is part of interphase, which is when the cell is replicating its DNA ready for division. To understand the need for intense protein synthesis, we first need to understand how DNA is organised during mitosis.
Before DNA is condensed into chromosomes ready for nuclear division it is in the form of chromatin, a long fiber-like structure inside the nucleus. In order to condense into chromosomes, this chromatin must undergo a process of coiling and folding in order to create the chromosome 'X' structure we are familiar with.
A major part of this DNA 'miniaturization' is the folding of the double helix around proteins called Histones - this creates new structures called nucleosomes.
In order to fully condense the roughly 3 meters of DNA in the average human cell down to a singular chromosome, millions upon millions of these Histone proteins are required.
And that answers your question; intense protein synthesis during the G1 phase is required in order to produce the extremely large amount of Histone proteins that are needed for packaging DNA into chromosomes ready for cellular division.
As for carbohydrates, these are constantly being processed by the body in order for the production of ATP for use as energy. The use of said energy for mitosis is a just another constantly required use of ATP within the body. Therefore there isn't any noticeable increase in carbohydrate processing/production, as it is happening regardless of the cell's stage in its cycle.
-See the image below (from shmoop.com) that explains the process of getting DNA into a chromosome.
The following is multiple choice question (with options) to answer.
During interphase, the cell undergoes normal growth processes while also preparing for what, by accumulating energy and building blocks of dna? | [
"technology division",
"chromosome division",
"cell division",
"proteins division"
] | C | The population is an important unit in ecology as well as other biological sciences. How is a population defined, and what are the strengths and weaknesses of this definition? Are there some species that at certain times or places are not in populations?. |
SciQ | SciQ-1991 | 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.
What type of species have a large effect on the balance of organisms in an ecosystem? | [
"secondary consumers",
"producers",
"decomposers",
"keystone"
] | D | Predators play an important role in an ecosystem. For example, if they did not exist, then a single species could become dominant over others. Grazers on a grassland keep grass from growing out of control. Predators can be keystone species . These are species that can have a large effect on the balance of organisms in an ecosystem. For example, if all of the wolves are removed from a population, then the population of deer or rabbits may increase. If there are too many deer, then they may decrease the amount of plants or grasses in the ecosystem. Decreased levels of producers may then have a detrimental effect on the whole ecosystem. In this example, the wolves would be a keystone species. |
SciQ | SciQ-1992 | 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.
Which type of skeleton supports the animal, protects internal organs, and allows for movement? | [
"shell",
"internal",
"external",
"mechanical"
] | B | An internal skeleton. The internal skeleton supports the animal, protects internal organs, and allows for movement. |
SciQ | SciQ-1993 | development
Title: How detachment/separation works in biology? It might be a strange question, but I'm interested in the mechanics of separation/detachment during asexual reproduction, for example when an organism reproduces by budding (I don't mean cellular budding like baker's yeast). When the newly formed body is fully matured it detaches itself from the parent / original body.
It might not be caused by a specific tissue, as animals with not so differentiated bodies are (also) capable of such, but I could easily be wrong. Is this (the detachment) triggered by changes in the cell membrane? I can't really think of other explanations. Reproductive budding and what you call 'cellular budding' are really highly related processes. Budding as a form of reproduction essentially partitions protein aggregates and damaged cellular components into the host or mother and builds fresh or 'young' cells on the opposite side of a partition. To begin understanding this look at Saccharomyces cerevisiae (budding yeast) which forms protein rings (from the septin proteins) at the membrane, around the bud neck which separates the mother and daughter cells Hartwell 1971. This ring acts a partition that in part, withholds protein aggregates and certain proteins from diffusing from the mother to the daughter. This protein ring is an example of how cells limit diffusion of proteins and cellular components to the daughter cell. Another good example that comes to mind is Linder 2007, though it is done in E Coli, not budding yeast, where mother cells maintain protein aggregates and age, while the daughter cells are given fresh components and are therefore more fresh and 'young'.
Now like you mention, imagine this process in a multicellular organism to be fundamentally the same. At some point the multicellular organism will start an outgrowth of cells, while restricting what materials are given to the daughter cells to maintain their youth. And eventually a new organism will have been created. Some of the details will be different, but the fundamental process is is quite similar. In that you start with an old cell that creates a new cell from scratch, but rather than splitting all cellular components equally between mother and daughter, the daughter cells is made in peak condition while the mother cell retains much of the cell 'junk' like protein aggregates.
Hopefully that starts to answer your question.
The following is multiple choice question (with options) to answer.
After cell division what are the two new cells called? | [
"offspring cells",
"daughter cells",
"step cells",
"production cells"
] | B | Cell division is the process in which a cell divides to form two new cells. The original cell is called the parent cell. The two new cells are called daughter cells. All cells contain DNA. DNA is the nucleic acid that stores genetic information. Before a cell divides its DNA must be copied. That way, each daughter cell gets a complete copy of the parent cell’s genetic material. |
SciQ | SciQ-1994 | evolution
bacteria
cyanobacteria
archaea
protists
fungi
algae
plants
nematodes
arthropods
vertebrates
Bacterial and archaean colonisation
The first evidence of life on land seems to originate from 2.6 (Watanabe et al., 2000) to 3.1 (Battistuzzi et al., 2004) billion years ago. Since molecular evidence points to bacteria and archaea diverging between 3.2-3.8 billion years ago (Feng et al.,1997 - a classic paper), and since both bacteria and archaea are found on land (e.g. Taketani & Tsai, 2010), they must have colonised land independently. I would suggest there would have been many different bacterial colonisations, too. One at least is certain - cyanobacteria must have colonised independently from some other forms, since they evolved after the first bacterial colonisation (Tomitani et al., 2006), and are now found on land, e.g. in lichens.
Protistan, fungal, algal, plant and animal colonisation
Protists are a polyphyletic group of simple eukaryotes, and since fungal divergence from them (Wang et al., 1999 - another classic) predates fungal emergence from the ocean (Taylor & Osborn, 1996), they must have emerged separately. Then, since plants and fungi diverged whilst fungi were still in the ocean (Wang et al., 1999), plants must have colonised separately. Actually, it has been explicitly discovered in various ways (e.g. molecular clock methods, Heckman et al., 2001) that plants must have left the ocean separately to fungi, but probably relied upon them to be able to do it (Brundrett, 2002 - see note at bottom about this paper). Next, simple animals... Arthropods colonised the land independently (Pisani et al, 2004), and since nematodes diverged before arthropods (Wang et al., 1999), they too must have independently found land. Then, lumbering along at the end, came the tetrapods (Long & Gordon, 2004).
Note about the Brundrett paper: it has OVER 300 REFERENCES! That guy must have been hoping for some sort of prize.
References
The following is multiple choice question (with options) to answer.
What are bacteria and archaea examples of? | [
"fungi",
"prokaryotes",
"plants",
"eukaryotes"
] | B | Prokaryotes include Bacteria and Archaea. An individual prokaryote consists of a single cell without a nucleus. |
SciQ | SciQ-1995 | electromagnetism, electricity, magnetic-fields
Title: Why does electricity flowing through a copper coil generate a magnetic field? Can some one please explain to me why electricity flowing though a copper coil generates a magnetic field or where I could possibly find that information? Are there other materials that produce a magnetic field when a current is run through them in a different shape? Thanks!
Can some one please explain to me why electricity flowing though a
copper coil generates a magnetic field or where I could possibly find
that information?
An electric current (a flow of electric charge) has an associated magnetic field regardless of the material (or space) the flow occurs in. This is a fundamental part of electromagnetism, rooted in observation, and quantified in Ampere's Law.
I wish to emphasize that this phenomenon is considered fundamental in nature, which means there cannot be a "more" fundamental explanation (if there were, electromagnetism would not be fundamental).
The following is multiple choice question (with options) to answer.
What gives a coil of copper wire the ability to conduct electricity well? | [
"metallic ions",
"metallic electrons",
"optical bonds",
"metallic bonds"
] | D | Image copyright SergiyN, 2014. Coil of copper wire, which conducts electricity well due to metallic bonds . Used under license from Shutterstock. com. |
SciQ | SciQ-1996 | physiology
Title: Why does dehydration lead to low blood pressure I understand that the two leading causes of death from dehydration is imbalance in electrolytes and loss of blood pressure. I'm trying to understand what role water is playing in these cases and how the loss of it causes these imbalances, focusing for now on the blood pressure angle.
While I understand that blood is made up heavily of water, I'm still a little confused why dehydration so quickly leads to drop in blood pressure. Why can't the body continue to pump the already existing blood through the body, where is it using the water to keep the blood pressure up and what vital function is no longer being performed that causes that pressure to drop? The blood pressure is the exertion of force upon the blood vessels by the blood fluids. Thus having less fluids will results in decreased pressure.
The following is multiple choice question (with options) to answer.
Blood helps maintain homeostasis by stabilizing ph, temperature, osmotic pressure, and by eliminating this? | [
"water",
"acid",
"toxins",
"excess heat"
] | D | The Role of Blood in the Body Blood, like the human blood illustrated in Figure 40.5 is important for regulation of the body’s systems and homeostasis. Blood helps maintain homeostasis by stabilizing pH, temperature, osmotic pressure, and by eliminating excess heat. Blood supports growth by distributing nutrients and hormones, and by removing waste. Blood plays a protective role by transporting clotting factors and platelets to prevent blood loss and transporting the disease-fighting agents or white blood cells to sites of infection. |
SciQ | SciQ-1997 | development
Title: How detachment/separation works in biology? It might be a strange question, but I'm interested in the mechanics of separation/detachment during asexual reproduction, for example when an organism reproduces by budding (I don't mean cellular budding like baker's yeast). When the newly formed body is fully matured it detaches itself from the parent / original body.
It might not be caused by a specific tissue, as animals with not so differentiated bodies are (also) capable of such, but I could easily be wrong. Is this (the detachment) triggered by changes in the cell membrane? I can't really think of other explanations. Reproductive budding and what you call 'cellular budding' are really highly related processes. Budding as a form of reproduction essentially partitions protein aggregates and damaged cellular components into the host or mother and builds fresh or 'young' cells on the opposite side of a partition. To begin understanding this look at Saccharomyces cerevisiae (budding yeast) which forms protein rings (from the septin proteins) at the membrane, around the bud neck which separates the mother and daughter cells Hartwell 1971. This ring acts a partition that in part, withholds protein aggregates and certain proteins from diffusing from the mother to the daughter. This protein ring is an example of how cells limit diffusion of proteins and cellular components to the daughter cell. Another good example that comes to mind is Linder 2007, though it is done in E Coli, not budding yeast, where mother cells maintain protein aggregates and age, while the daughter cells are given fresh components and are therefore more fresh and 'young'.
Now like you mention, imagine this process in a multicellular organism to be fundamentally the same. At some point the multicellular organism will start an outgrowth of cells, while restricting what materials are given to the daughter cells to maintain their youth. And eventually a new organism will have been created. Some of the details will be different, but the fundamental process is is quite similar. In that you start with an old cell that creates a new cell from scratch, but rather than splitting all cellular components equally between mother and daughter, the daughter cells is made in peak condition while the mother cell retains much of the cell 'junk' like protein aggregates.
Hopefully that starts to answer your question.
The following is multiple choice question (with options) to answer.
During sexual reproduction, the macronucleus dissolves and is replaced by what? | [
"fluctuations",
"micronucleus",
"sporozoans",
"chromosomes"
] | B | Figure 23.16 The complex process of sexual reproduction in Paramecium creates eight daughter cells from two original cells. Each cell has a macronucleus and a micronucleus. During sexual reproduction, the macronucleus dissolves and is replaced by a micronucleus. (credit “micrograph”: modification of work by Ian Sutton; scale-bar data from Matt Russell). |
SciQ | SciQ-1998 | nomenclature, elements
0 = nil, 1 = un, 2 = bi, 3 = tri, 4 = quad, 5 = pent, 6 = hex, 7 = sept, 8 = oct, 9 = enn
(Pure & Appl. Chem. 51, 1979, 381-384, open access)
Thus it was until specific agreement that unnilunium ($\ce{_{101}Unu}$) eventually was named mendelevium ($\ce{_{101}Md}$), and IUPAC continues to publish how to name the new elements (example).
Despite this report, however, the roots are neither pure Latin, nor Greek, but convention. Because there no tenners (like decem, vīgintī), or hundreds (like centum, ducentī), etc. Even spelling the numeri only by position, you would expect unus, duo, tres, quattuor, quinque, sex, septem, octo, novem for $1\dots9$ for the former.
For the names eventually adopted, IUPAC set the rules that these
"In keeping with tradition, elements are named after
a mythological concept or character (including an astronomical object);
a mineral, or similar substance;
a place or geographical region;
a property of the element; or
a scientist.
[...] The names of all new elements should have an ending that reflects and maintains historical and chemical consistency. This would be in general “-ium” for elements belonging to groups 1–16, “-ine” for elements of group 17 and “-on” for elements of group 18. N.B. The present recommendation is here more specific than that
written in the 2002 document."
(Pure & Appl. Chem., 88, 2016, 401-505, open access)
The following is multiple choice question (with options) to answer.
When naming this type of ion the ending of the element’s name is dropped and replaced with the – ide suffix? | [
"amines",
"cations",
"oxides",
"anions"
] | D | Naming anions is slightly different than naming cations. The ending of the element’s name is dropped and replaced with the – ide suffix. For example, F - is the fluoride ion, while O 2- is the oxide ion. As is the case with cations, the charge on the anion is indicated by a superscript following the symbol. Common anions are listed in the Table below :. |
SciQ | SciQ-1999 | gene-expression
Title: How does a gene "know" what to change to? Excuse my ignorance but I've always been curious about this...
For example, a frog is red, but it starts living in a green forest. Over time the frog becomes green to camouflage. But a gene can't see and I'm sure there's no mechanism for color info to be transmitted to individual genes from the brain. So how does a gene know to pick green over, say, blue? Using your example, the gene doesn't know anything. Mutations cause some of the offspring of the red frog to turn green, some to turn blue, some to turn fluorescent yellow, and some stay red. Birds can't see the green ones as well as the others, so more green frogs survive and make more green frogs. The red frogs, the fluorescent yellow ones, the blue ones, mostly get eaten. After a few generations, almost all the frogs are green -- not because the gene knew anything, not because the mutations went in any direction, but because all the other changes were counterproductive and got eaten.
The gene doesn't know anything. It's just a bunch of chemicals that randomly react with cosmic rays, chance, whatever. Most of the changes are irrelevant or actively bad, and the frog that's carrying those particular chemicals doesn't survive. But sometimes the change benefits the frog carrying the particular chemicals and then the frog sends those chemicals down to its progeny.
Obviously this is hugely over-simplified. A short and simple intro to the basics of evolution is Understanding Evolution, by UC Berkeley.
The following is multiple choice question (with options) to answer.
What is a random change in an organism's genes? | [
"mutation",
"accumulation",
"meiosis",
"infection"
] | A | At some time in the past, a variation probably came from a mutation. A mutation is a random change in an organism's genes ( Figure below ). Mutations are natural. Some are harmful, but many are neutral. If a mutation is harmful, the organism may not live to reproduce. If the mutation is beneficial, that organism may have a better chance to survive. An organism that survives is likely to have offspring. If it does, it may pass the mutation on to its offspring. The offspring may be more likely to survive. |
SciQ | SciQ-2000 | 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.
Osseous tissue - the connective tissue that includes specialized cells, mineral salts, and collagen fibers - makes up what? | [
"ligaments",
"spine",
"muscles",
"bone"
] | D | 38.2 Bone Bone, or osseous tissue, is connective tissue that includes specialized cells, mineral salts, and collagen fibers. The human skeleton can be divided into long bones, short bones, flat bones, and irregular bones. Compact bone tissue is composed of osteons and forms the external layer of all bones. Spongy bone tissue is composed of trabeculae and forms the inner part of all bones. Four types of cells compose bony tissue: osteocytes, osteoclasts, osteoprogenitor cells, and osteoblasts. Ossification is the process of bone formation by osteoblasts. Intramembranous ossification is the process of bone development from fibrous membranes. Endochondral ossification is the process of bone development from hyaline cartilage. Long bones lengthen as chondrocytes divide and secrete hyaline cartilage. Osteoblasts replace cartilage with bone. Appositional growth is the increase in the diameter of bones by the addition of bone tissue at the surface of bones. Bone remodeling involves the processes of bone deposition by osteoblasts and bone resorption by osteoclasts. Bone repair occurs in four stages and can take several months. |
SciQ | SciQ-2001 | neuroscience, neuroanatomy
Likewise, the spinal chord is structured into sensory and motor regions. In summary, the spinal chord consists of: 1) cell bodies (motor, sensory, inter; grey in the picture), 2) ascending axons (blue), 3) descending axons (red). Similar to nerves, axons going up or down the spinal chord are bundled into "tracts". Sensory axons are never bundled with motor axons, making it possible to create a map of the spinal chord in cross-section.
The tracts' names might be a bit confusing at first, but on second look are actually pretty self-explanatory. They usually contain where the axons come from and where they are going in order to synapse with other neurons. E.g. the spinocerebellar tract is formed of axons coming from the spine and going to the cerebellum. Given that the cerebellum is near the brain and the spine is further down, this is obviously an ascending tract - and ascending tracts are always sensory (because sensory information never needs to be carried downwards due to the brain being at the top).
Where it gets blurry
The sensory/motor separation isn't always as clear as I've described above. In fact, nerves (bundles of axons anywhere in the body outside of the CNS) will usually contain both sensory and motor pipelines. In particular, the cranial nerves (12 of the most important nerves) all include sensory and motor components for the respective part of the body that they manage. E.g. the facial nerve contains both the sensory connections for parts of the tongue and the motor connections that control facial muscles.
Another more complex example is pain sensation, where interneurons in the spinal chord can feed back onto sensory neurons and inhibit their signals, or axons can inhibit those packed in the same nerve bundle simply due to electrical effects.
The following is multiple choice question (with options) to answer.
What is the name of the hollow nerve cord along the back of chordates? | [
"mesoderm",
"notochord",
"phloem",
"zetacord"
] | B | |
SciQ | SciQ-2002 | statistical-mechanics, entropy, phase-space
The volume of phase space can be seen as the number of microstates a system can occupy (given some constraints, like energy in your case).
Say I have two systems; one can take 2 microstates and the other 3. Then, a combination of these two systems will allow for $2 \times 3$ microstates and not $2 + 3$.
The following is multiple choice question (with options) to answer.
What term is used to describe the amount of space occupied by a sample of matter? | [
"volume",
"mass",
"liquid",
"growth"
] | A | Volume is the amount of space occupied by a sample of matter. |
SciQ | SciQ-2003 | proteins, enzymes, cellular-respiration
Earlier models proposed simple rotational diffusion of a rigid c12 ring, possibly driven by electrostatic forces. The structural data on protonation-linked conformational changes in subunit c indicate that the process may be more mechanical, with local rotations within subunit c driving larger-scale rotations of the c12 oligomer as a whole, in a `wheels within wheels' type of mechanism.
The whole paper's a good read. But this is as current as I am on the topic, and it's likely that a more detailed mechanism has been determined for the action of ATP synthase since 1999.
The following is multiple choice question (with options) to answer.
What are responsible for the bending movements of the organelle? | [
"muscles",
"sporozoans",
"dyneins",
"pores"
] | C | |
SciQ | SciQ-2004 | inorganic-chemistry, redox
Title: What is formed when you leave iron(II) sulfate in plain air? What is formed when you leave iron(II) sulfate in plain air?
Knowing that iron(II) is easily oxidised to iron(III), and assuming that the reactive component of air is oxygen, I solved it this way:
$$\ce{FeSO4 + O2 -> Fe2O3 + SO2}$$
But in my textbook it's given that iron(III) sulfate, $\ce{Fe2(SO4)3}$, is formed. Is this because $\ce{Fe2O3 + SO2}$ react to form $\ce{Fe2(SO4)3}$? Usually, the original iron(II) sulfate is present as green $\ce{FeSO4.7H2O}$.
Oxygen can oxidize $\ce{Fe(II)}$ salts to $\ce{Fe(III)}$ salts; for example, at $\mathrm{pH}=0$:
$$\begin{alignat}{2}
\ce{[Fe(H2O)6]^3+ + e- \;&<=> [Fe(H2O)6]^2+}\quad &&E^\circ = +0.771\ \mathrm{V}\\
\ce{O2 + 4H+ + 4e- \;&<=> 2H2O}\quad &&E^\circ = +1.229\ \mathrm{V}
\end{alignat}$$
$\ce{Fe(II)}$ is even easier oxidized under alkaline conditions; for example, at $\mathrm{pH}=14$:
$$\begin{alignat}{2}
\ce{FeO(OH) + H2O + e- \;&<=> Fe(OH)2 + OH-}\quad &&E^\circ = -0.69\ \mathrm{V}\\
\ce{O2 + 2H2O + 4e- \;&<=> 4OH-}\quad &&E^\circ = +0.401\ \mathrm{V}
The following is multiple choice question (with options) to answer.
What are formed when primary pollutants interact with sunlight, air, or each other? | [
"typical pollutants",
"secondary contaminants",
"cross pollutants",
"secondary pollutants"
] | D | Secondary pollutants are formed when primary pollutants interact with sunlight, air, or each other. They do not directly cause pollution. However, when they interact with other parts of the air, they do cause pollution. For example, ozone is created when some pollutants interact with sunlight. High levels of ozone in the atmosphere can cause problems for humans. |
SciQ | SciQ-2005 | virology, infection
Title: Why don't viruses cause wounds? A simple mental model of a viral infection is that an infected cell emits a lot of virions and eventually dies. The emitted virions have a chance of infecting other cells. Nearby cells are at a higher risk of infection.
Based on this model, if one cell in my nose gets infected, I would expect a large part of my nose to be destroyed, as the infection spreads and destroys more and more cells in the same area.
This does not happen! I survived a number of infections and still have my nose. Why?
I know there are "flesh eating" bacteria. Why isn't this the norm for infections? Does a common cold virus or SARS-CoV-2 not infect a lot of cells within the same area? A virus does not destroy that many cells before it is exterminated by the immune system or before the host dies.
Perhaps even more crucially, viruses typically target a very specific type of cell — those on the inner mucal surface of the nose in the case of cold or flu, those of the gastrointestinal tract in the case of stomach viruses, CD4 immune cells in the case of HIV, etc.
Update
As an example of how much time it takes for a virus to eat a noticeable wound, one could take the extermination of the immune cells by HIV - although it does not look as a physical wound, it is one, in the sense that enough of the specific tissue is destroyed to cause a life-threatening condition. It takes about a decade(!) - from the initial infection to the immune system failure.
On the other hand, the lethal effect of typical respiratory viruses is typically via obstructions of the respiratory ways due to inflammation or secretions resulting from the immune response, or via creating suitable conditions for a more serious bacterial infection.
The following is multiple choice question (with options) to answer.
The first reaction of the body to tissue damage or infection is called the what response? | [
"inflammatory",
"retaliatory",
"harmful",
"defensive"
] | A | The cut on your hand may become red, warm, and swollen. These are signs of an inflammatory response. This is the first reaction of the body to tissue damage or infection. As explained in Figure below , the response is triggered by chemicals called cytokines and histamines , which are released when tissue is injured or infected. The chemicals communicate with other cells and coordinate the inflammatory response. You can see an animation of the inflammatory response at this link: http://www. sumanasinc. com/webcontent/animations/content/inflammatory. html . |
SciQ | SciQ-2006 | human-biology
Title: Stopping the effect of hormone Many hormones released by endocrine organs travel down in the blood and bind to specific receptors on the target cells. What then breaks that binding of the molecule with the receptor ? ( thus inactivating further stimulation of the target cell ) The binding is reversible typically; part of the potency of a drug is ow well and for how long it binds to its target. There's a natural equilibrium of binding and dissociation. Many drugs, once bound to their cognate receptor, cause a down regulation of their cognate receptor on the target cell. The bound/activated downstream signalling pathways may be inhibited by ubiquitination of the downstream signals themselves or upregulation of antagonists etc. The hormone itself has a half life, which is very important, thus levels naturally decrease and for some hormones this is incredibly rapid. Levels may decrease due to breakdown or excretion. Increase of binding hormones may decrease free hormone thus it's effect also.
The following is multiple choice question (with options) to answer.
Because these components of the endocrine system are transported via blood, they get diluted and are present in low concentrations when they act on their target cells. | [
"antibodies",
"enzymes",
"minerals",
"hormones"
] | D | Endocrine Signaling Signals from distant cells are called endocrine signals, and they originate from endocrine cells. (In the body, many endocrine cells are located in endocrine glands, such as the thyroid gland, the hypothalamus, and the pituitary gland. ) These types of signals usually produce a slower response but have a longer-lasting effect. The ligands released in endocrine signaling are called hormones, signaling molecules that are produced in one part of the body but affect other body regions some distance away. Hormones travel the large distances between endocrine cells and their target cells via the bloodstream, which is a relatively slow way to move throughout the body. Because of their form of transport, hormones get diluted and are present in low concentrations when they act on their target cells. This is different from paracrine signaling, in which local concentrations of ligands can be very high. Autocrine Signaling Autocrine signals are produced by signaling cells that can also bind to the ligand that is released. This means the signaling cell and the target cell can be the same or a similar cell (the prefix auto- means self, a reminder that the signaling cell sends a signal to itself). This type of signaling often occurs during the early development of an organism to ensure that cells develop into the correct tissues and take on the proper function. Autocrine signaling also regulates pain sensation and inflammatory responses. Further, if a cell is infected with a virus, the cell can signal itself to undergo programmed cell death, killing the virus in the process. In some cases, neighboring cells of the same type are also influenced by the released ligand. In embryological development, this process of stimulating a group of neighboring cells may help to direct the differentiation of identical cells into the same cell type, thus ensuring the proper developmental outcome. Direct Signaling Across Gap Junctions Gap junctions in animals and plasmodesmata in plants are connections between the plasma membranes of neighboring cells. These water-filled channels allow small signaling molecules, called intracellular mediators, to diffuse between the two cells. Small molecules, such as calcium ions (Ca2+), are able to move between cells, but large molecules like proteins and DNA cannot fit through the channels. The specificity of the channels ensures that the cells remain independent but can quickly and easily transmit signals. The transfer of signaling molecules communicates the current state of the cell that is directly next to the target cell; this allows a group of cells to coordinate their response to a signal that only one of them may have received. In plants, plasmodesmata are ubiquitous, making the entire plant into a giant, communication network. |
SciQ | SciQ-2007 | theoretical-biology, population-dynamics, population-biology
\frac{dN_C}{dt} = \nu_B N_B(t - \tau_B) - \gamma_C N_C \\
$$
So constants $\beta, \gamma, \nu, \tau$ represent constants for the birth rate, death rate, migration-maturation rate, and time lag. In my actual model I have 2 species that compete, but this model above gives a flavor of the dynamics. I would like to include some carrying capacity constraints too, but that can come later.
Like I said, it is easy enough to express this model in a discrete form as well. But I was hoping someone might be able to reference articles or something that shows someone analyzing discete multi-generational models--so that I can see a flavor of how they deal with the nondimensionalization, bifurcations, chaotic dynamics, etc.
I was hoping to see if other biologists or ecologists had studied this kind of continuous system, and how they had analyzed it. It seems like the first thing to do is nondimensionalize it, as I have way too many parameters. But I am not sure of a good scheme or equilibrium condition to use to do that. You use the word "evolution" here to mean "change in populations over time", as is typical in (say) astrophysics (or, I guess, economics?). My initial comments and suggestions were based on a misreading of "evolution" having its biological meaning, i.e. change of genetic make-up of a population over time.
With that out of the way: delay differential equations are slightly less common than ordinary DEs in population biology, but still very common. I wouldn't say there are any special mathematical tricks that aren't also used by mathematical analysts or people studying dynamics in other fields ...
The following is multiple choice question (with options) to answer.
Which theory explains how populations of organisms can change over time? | [
"changes by natural selection",
"evolution by natural selection",
"intelligent selection",
"free by natural selection"
] | B | The theory of evolution by natural selection explains how populations of organisms can change over time. As environments change, so must the traits of organisms if they are to survive in the new conditions. Evolution by natural selection explains how this happens. It also explains why there are so many different species of organisms on Earth today. You can see examples of the incredible diversity of living animals in Figure below . You can read more about the theory of evolution in the chapter Evolution. |
SciQ | SciQ-2008 | dna, sequence-analysis, nucleic-acids
Some of the nucleotides force the DNA polymer molecule to take on different shapes, or to be stiffer or more flexible, because of their underlying chemical shape.
A polyacrylamide gel is basically a big tangle of polyacrylamide molecules and bonds. So think of DNA moving through it like trying to drag a rope through a forest. A very long rope will tangle more than a short one and will take more effort/time to pull through the trees. However, a rope of the same length that has a different structure (maybe it has lots of knots tied in it, or it is stiff rather than flexible) may also be harder to pull through the forest, even though it's not any longer.
The following is multiple choice question (with options) to answer.
What forms when the dna in the nucleus wraps around proteins? | [
"chromosomes",
"genes",
"ribosomes",
"rna"
] | A | To begin mitosis, the DNA in the nucleus wraps around proteins to form chromosomes . Each organism has a unique number of chromosomes. In human cells, our DNA is divided up into 23 pairs of chromosomes. Replicated DNA forms a chromosome made from two identical sister chromatids , forming an "X" shaped molecule ( Figure below ). The two chromatids are held together on the chromosome by the centromere . The centromere is also where spindle fiber microtubules attach during mitosis. The spindles separate sister chromatids from each other. |
SciQ | SciQ-2009 | medicine
Kiekeboe 21: the Piri-Piri Pills, Page 17, strip 30. Author: Merho. Publisher: J.Hoste NV (currently part of Standaard Uitgeverij). Picture taken by Nate Kerkhofs on 16 september 2014.
It is in Dutch, but the names of the illenesses are clearly readable (since they're Latin anyway).
The doctor asks "what are you here for, madame? a cold, reumathism, headache?" right before this. The woman answers "no, doctor, I'm struggling with ... and also ... not to mention ... and a really annoying .... The doctor then replies "but madame, where did you get all those illnesses?" the woman replies "in my medical encyclopaedia!". Erythema multiforme (minor) can and does occur in a lot of people; while it is usually self-limited, it can recur, especially when the trigger is an unsuspected food.[1] How common is it? It is very common.
Necrobiosis Lipoidica is not uncommon in diabetics, less common but still found in non-diabetics. It can occur at any age, including the eighth decade. It also shows a sex predilection, being 3 times more common in women than in men.[2] How common is it? It is not rare.
Phlegmasia Alba and Cerulea Dolens[3] is serious and associated with deep vein thrombosis, which is an acute event. It is not uncommon, but it's not chronic. (More than 600,000 cases of venous thromboembolism are estimated to occur each year in the United States, all of which can lead to Phlegmasia Alba and Cerulea Dolens. How common is it? Luckily, not very. If the author is referring to garden-variety thrombophlebitis, though, that's a chronic problem, and not uncommon in the elderly. Thrombophlebitis is chronic and common enough.
I'm not going to address Metropathia Haemorrhagica, because, as you have noted, it's found in menstruating women.
The following is multiple choice question (with options) to answer.
What is the condition called where pimples form on the skin? | [
"acne",
"cramping",
"blushing",
"dermatitis"
] | A | About 85 percent of teens develop acne, like the boy in Figure below . Acne is a condition in which pimples form on the skin. It is caused by a bacterial infection. It happens when the sebaceous glands secrete too much sebum. The excess oil provides a good place for bacteria to grow. Keeping the skin clean helps prevent acne. Over-the-counter products or prescription drugs may be needed if the problem is serious or doesn’t clear up on its own. |
SciQ | SciQ-2010 | newtonian-mechanics, kinematics
Title: Newton's laws of motion in kinematics I know that there are 3 laws of motion given by Newton, but are there any other laws which govern the motion of the bodies? The three laws of Newton basically tell you about the movement of bodies that have a mass if a force acts on them.
There are two ways to answer your question based on this.
Newton's laws don't work if the bodies move at very high speed (you'd need laws from Special Relativity for this), or if the masses involved are very large (this is the realm of General Relativity) or if you get to very small scales (Quantum Mechanics). So, in these special extreme cases, Newton's laws are not sufficient (in fact wrong) and you need other laws to describe motion.
Nothing is said in Newton's laws about what the force is. Depending on the context you might need additional laws such as the law of gravity, Coulomb law, Lorentz force,... in order to do calculations using Newton's laws.
Also, there are alternative ways to describe motion such as the Lagrangian/Hamiltonian mechanics, which can replace Newton's laws.
The following is multiple choice question (with options) to answer.
Whose laws of motion are the foundation of dynamics? | [
"einstein",
"bell",
"newton",
"aristotle"
] | C | Introduction to Dynamics: Newton’s Laws of Motion Motion draws our attention. Motion itself can be beautiful, causing us to marvel at the forces needed to achieve spectacular motion, such as that of a dolphin jumping out of the water, or a pole vaulter, or the flight of a bird, or the orbit of a satellite. The study of motion is kinematics, but kinematics only describes the way objects move—their velocity and their acceleration. Dynamics considers the forces that affect the motion of moving objects and systems. Newton’s laws of motion are the foundation of dynamics. These laws provide an example of the breadth and simplicity of principles under which nature functions. They are also universal laws in that they apply to similar situations on Earth as well as in space. Isaac Newton’s (1642–1727) laws of motion were just one part of the monumental work that has made him legendary. The development of Newton’s laws marks the transition from the Renaissance into the modern era. This transition was characterized by a revolutionary change in the way people thought about the physical universe. For many centuries natural philosophers had debated the nature of the universe based largely on certain rules of logic with great weight given to the thoughts of earlier classical philosophers such as Aristotle (384–322 BC). Among the many great thinkers who contributed to this change were Newton and Galileo. |
SciQ | SciQ-2011 | botany, plant-physiology, ecology, virology, host-pathogen-interaction
Note about symbiosis - comes in reaction to @Gerhard's comment
Different authors use the word symbiosis differently. From wikipedia:
The definition of symbiosis is controversial among scientists. Some believe symbiosis should only refer to persistent mutualisms, while others believe it should apply to any type of persistent biological interaction (i.e. mutualistic, commensalistic, or parasitic).4 After 130+ years of debate,5 current biology and ecology textbooks now use the latter "de Bary" definition or an even broader definition (i.e. symbiosis = all species interactions), with the restrictive definition no longer used (i.e. symbiosis = mutualism)
The following is multiple choice question (with options) to answer.
Mutualism is a symbiotic relationship in which both species do what? | [
"die",
"suffer",
"reproduce",
"benefit"
] | D | Mutualism is a symbiotic relationship in which both species benefit. An example of mutualism is pictured in Figure below . The clownfish in the photo is hiding among the tentacles of a sea anemone. The tentacles have stingers that can inject poison in the anemone’s prey. The clownfish is protected from the stingers by mucus that covers its body. |
SciQ | SciQ-2012 | organic-chemistry, mixtures
Title: Would Oxygen Gas and Ozone be a pure substance together? If I have oxygen gas and ozone ($\ce{O2 + O3}$) together would it be considered a pure substance or a mixture?
And would pure substances always have the same molecular structure? Ozone is highly reactive and unstable, while dioxygen is stable. There do not combine to form a compound. So, clearly it is a mixture.
To answer the second part of the question, "And would pure substances always have the same molecular structure?", first a Wikipedia definition on substances, to quote:
A chemical substance is a form of matter having constant chemical composition and characteristic properties.[1][2]...
Chemical substances can be simple substances[4], chemical compounds, or alloys. Chemical elements may or may not be included in the definition, depending on expert viewpoint.[4]
Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water...
However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical.
And further:
A chemical substance may well be defined as "any material with a definite chemical composition" in an introductory general chemistry textbook.[5] According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. But, there are exceptions to this definition; a pure substance can also be defined as a form of matter that has both definite composition and distinct properties.[6] The chemical substance index published by CAS also includes several alloys of uncertain composition.[7] Non-stoichiometric compounds are a special case (in inorganic chemistry) that violates the law of constant composition, and for them, it is sometimes difficult to draw the line between a mixture and a compound, as in the case of palladium hydride. Broader definitions of chemicals or chemical substances can be found, for example: "the term 'chemical substance' means any organic or inorganic substance of a particular molecular identity, including – (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature".[8]
The following is multiple choice question (with options) to answer.
What do you call a substance that cannot be broken down to other substances by chemical reactions.? | [
"an element",
"a molecule",
"a participate",
"a compound"
] | A | |
SciQ | SciQ-2013 | meteorology, wind
Is this the correct definition? I'm a bit confused, since this contradicts the company support guys (which are specialist for this thing). They insist, there is not time-averaging-period attached to the definition of "Wind gust" which is, in my understanding, not sensible. There must be some time information attached to any definition of "wind gust" as far as I understand? But then again I'm not a meteorologist and might miss something basic.
Obliged for any help to clarify this respectively lets me understand this better. The WMO definition of wind gust for observing stations is,
The following is multiple choice question (with options) to answer.
What weather term describes what the temperature feels like when the wind is taken into account? | [
"windshield",
"humidity",
"freezing point",
"windchill"
] | D | Blizzards are dangerous storms. The wind may blow the snow into deep drifts. Along with the poor visibility, the snow drifts make driving risky. The wind also makes cold temperatures more dangerous. The greater the wind speed, the higher the windchill. Windchill is what the temperature feels like when the wind is taken into account. It depends on air temperature and wind speed ( Figure below ). Higher windchill will cause a person to suffer frostbite and other harmful effects of cold sooner than if the wind isn't blowing. |
SciQ | SciQ-2014 | electromagnetic-induction
Title: Working principle of inverter I got project on the working of inverter from school. I know this that DC inverter has an alternator switch which constantly changes its direction so that magnetic field is produced in primary coil due to which current is induced in secondary coil and we get output AC. So according to all this Electromagnetic induction should be the working principle behind the working of DC inverter. But DC can't take part in EMI, I know alternator is being used but it doesn't feels right. I hope I am right till this point I am taking following image as reference:
Please don't get mad at me if I got everything wrong. You are right. The alternator turns the DC of the battery into AC, which allows for changing magnetic fields in the primary. A transformer need a changing magnetic flux (which is why "DC doesn't work") - the alternating switch keeps changing the direction of the current, so the flux keeps changing. This induces e.m.f. in the secondary, and the result is an AC voltage on the output of the circuit.
The voltage wave form on the primary will be a square wave: the output waveform will be more complicated, depending on details of the resistance of the coils and the load. Obviously, the higher the switching frequency, the more regular the shape of the output: at very low frequencies, the output will "decay" between switching of the input alternator.
The following is multiple choice question (with options) to answer.
What device uses electromagnetic induction to change the voltage of electric current? | [
"electric combustion",
"electric transformer",
"electric conductor",
"convection device"
] | B | An electric generator is a device that changes kinetic energy to electrical energy through electromagnetic induction. An electric transformer is a device that uses electromagnetic induction to change the voltage of electric current. |
SciQ | SciQ-2015 | geophysics, sedimentology
Title: Does dirt compact itself over time? If so, how does this happen? If I were to bury something 10 feet (~3 metres) underground, with loose soil on top, would the ground naturally compact itself over time, until whatever I had buried has dirt tightly pressing against it on all sides?
What if I buried it 50 feet (~15 metres) underground?
If it exists, what is this compaction process called and how does it happen? Soil is a collection of various sized minerals grains, of various types of minerals produced by the weathering of rock. Typical soil minerals are clays, silts and sands.
The properties and behavior of different soil types depends of the composition of the soil: the proportion of clays, silts and sand in a soil. Sandy soils are well draining and clayey soils are sticky.
Between the grains of minerals that comprise a soil are spaces, called pores or pore spaces. The pores can be filled with either water or air, depending the location of water tables and wetting events like rain, snow melts or other forms of water inundation.
The density of a soil is dependent on the degree of compaction of the soil. For to a soil to be compacted, a stress has to be applied to the soil to realign the grains of soil which reduces the total volume of the pores and reduces the amount of air within the pores.
Consolidation of a soil occurs when pore space is reduced and water in a soil is displaced due to an applied stress.
Regarding having something buried and soil compacting around it over time, yes that will occur but it is a question of how much stress the soil experiences, the duration of time and the nature of the soil - sandy or clayey. Something buried for a day without any stresses not much will happen. But, something buried for thousands of years with people and animals walking over it, rain falling on the soil, vibrations from nearby human activity and an occasional earthquake all add to the stresses the soil will experience and increases the degree of compaction or consolidation over time.
The following is multiple choice question (with options) to answer.
What layer of soil usually does not have very small particles like clay? | [
"undersoil",
"sediment",
"topsoil",
"silt"
] | C | Topsoil usually does not have very small particles like clay. Clay-sized particles are carried to lower layers as water seeps down into the ground. Many minerals dissolve in the fresh water that moves through the topsoil. These minerals are carried down to the lower layers of soil. |
SciQ | SciQ-2016 | hydrology, rivers, geomorphology
Mountain ranges are often formed from orogeny, where tectonic plates collide. Rivers starts at high altitude, radiating out in all directions from mountains, but as collisions in the present continental settings are often on the rim of large plates (e.g Andes, Alps, Himalaya), and the rivers can't cross the range, it will have to travel the whole continental plate to reach ocean level. In the case of Asia, most large rivers starts in Himalaya (or other tectonic active regions, as Altai), in Europe large rivers starts in the Alps. In Africa, they start in the tectonic active rift zone.
This map shows the ocean drainage dividers. The border between the drainage areas are the line where rivers start.
The following is multiple choice question (with options) to answer.
Which type of glaciers form in high mountains and travel through valleys? | [
"seaside glaciers",
"altitude glaciers",
"alpine glaciers",
"rocky glaciers"
] | C | Continental glaciers form in a central location with ice moving outward in all directions. Alpine glaciers form in high mountains and travel through valleys. Ice caps cover large areas. |
SciQ | SciQ-2017 | physiology, cell-biology
Title: Polarized epithelium and localization of ion channels I'm trying to learn more about polarized epithelial cells of the gut. I am familiar with classic brush border transporters localized to the apical memebrane to facilitate nutrient absorption. I am wondering though, where are ion channels located? I would guess basolaterally since they would be exposed to the extracellular space. I would appreciate a primary reference showing the location of voltage-gated channels in particular as I could not find them myself. Well, that's a first for me. I wouldn't have guessed gut cells would have voltage-gated channels.
This article describes voltage-gated sodium channels on both the luminal and basolateral membranes:
Barshack, I., Levite, M., Lang, A., Fudim, E., Picard, O., Ben Horin, S., & Chowers, Y. (2008). Functional voltage-gated sodium channels are expressed in human intestinal epithelial cells. Digestion, 77(2), 108-117.
http://www.ncbi.nlm.nih.gov/pubmed/18391489
The following is multiple choice question (with options) to answer.
What two types of junctions do animal cells have? | [
"tight and gap",
"loose and tight",
"standard and specialized",
"gap and solid"
] | A | |
SciQ | SciQ-2018 | metabolism, nutrition, digestive-system
Title: Do I have to chew for digestion to kick in? Liquid nutrient-rich products (such as Soylent) are consumed without chewing. But if I have to chew to initiate digestion, are those nutrients really "processed"? If you had to chew to digest, then beverages like sugary sodas would never be digested or provide calories or nutrients, as you (generally) don't chew when you drink them. No, chewing is not required for digestion or nutrient absorption. Chewing is important when eating solid foods, as the chewing action breaks down and begins to solublize the food, and stimulates the production of saliva, which contains enzymes that begin to break down the food prior to digestion in the stomach and intestines.
The following is multiple choice question (with options) to answer.
Where does digestion take place within an incomplete digestive system? | [
"lumbar region",
"central nervous system",
"abdomen",
"gastrovascular cavity"
] | D | Flatworms have an incomplete digestive system. This means that the digestive tract has only one opening. Digestion takes place in the gastrovascular cavity. |
SciQ | SciQ-2019 | evolution, dna, natural-selection
It seems plausible to me that we (advanced life) could have a biological mechanism to "write" needed alterations into either our own DNA or our reproductive DNA over time, triggering the very specific evolutionary developments necessary to our survival without relying on random mutation.
My question:
Is this possible? Does any similar mechanism exist that we know of? If not, how can so many specific (advanced) evolutionary leaps be otherwise explained? This entire answer will be long, so read the short part first, then read the rest if you (or anyone else) is curious. Citations are included in the long section. I can include additional citations in the short section if needed.
Long Story Short
Your question touches on some common misconceptions about how the evolutionary process. Organisms don't "want" to evolve traits. Traits evolve through the biological processes of random mutation and natural selection.
Organisms do not "want" to evolve traits. (Well, OK, I'd love to evolve an extra pair of hands but that is not possible.) Natural selection works by modifying existing traits. Your turtle can stare all she wants at food out of reach but she will not evolve a longer neck. Instead, natural variation exists among neck lengths of the turtles because of variation of the genes that determine features related to overall boxy size. Those individuals with longer necks may be able to get a bit more food, live a little longer, and reproduce a little more. They will pass along their genes to their offspring, so perhaps more of their offspring will also have longer necks. Over many generations, the turtles may have somewhat longer necks.
A common misconception is that the traits of organisms are precisely adapted for a specific need. They are not, for a few reasons. First, natural selection occurs relative to the current environment. Adaptations that work well in one environment may not be so useful in another environment. Environments are rarely stable over evolutionary time so traits are subject to constant change.
Next, as mentioned above, natural selection can only work on what traits are present. While an extra set of arms would be handy, I am a tetrapod. My four appendages, along with the appendages of all other tetrapods, trace back to our common ancestor. The appendages of all tetrapods are modifications of that ancestral trait.
The following is multiple choice question (with options) to answer.
Natural selection cannot create new variations in organisms - these new variations must be created by what, which are usually associated with some sort of abnormality? | [
"infection",
"mutation",
"radiation",
"pollution"
] | B | Introduction All life on Earth is related. Evolutionary theory states that humans, beetles, plants, and bacteria all share a common ancestor, but that millions of years of evolution have shaped each of these organisms into the forms seen today. Scientists consider evolution a key concept to understanding life. Natural selection is one of the most dominant evolutionary forces. Natural selection acts to promote traits and behaviors that increase an organism’s chances of survival and reproduction, while eliminating those traits and behaviors that are to the organism’s detriment. But natural selection can only, as its name implies, select—it cannot create. The introduction of novel traits and behaviors falls on the shoulders of another evolutionary force—mutation. Mutation and other sources of variation among individuals, as well as the evolutionary forces that act upon them, alter populations and species. This combination of processes has led to the world of life we see today. |
SciQ | SciQ-2020 | gene-expression, genomics, gene-regulation
Title: Percentage of genome devoted to regulating gene expression Recently I've been studying the p53 tumor suppressor gene as a model for regulation of gene expression. It's amazing how many different post-translational modifications are known to regulate p53 activity, and how many different factors are involved in this regulation.
It is postulated that there are between 20,000 and 30,000 genes in the human genome. Is there an estimate for the percentage of these genes whose primary function is related to regulation of gene expression? Okay, I'll take this out of the comments and put in an answer for all of us to work on.
To directly answer your question:
"Is there an estimate for the percentage of these genes whose primary
function is related to regulation of gene expression?"
It depends on how you define "gene expression." And what cellular processes you want to include in that definition.
Larry's answer is the usual standard response, especially for people (such as me, ha) that have spent significant time studying transcription factors. About 1% of human genes have DNA binding domains and are thought to be directly involved in regulating the transcription of genes into mRNA - these are transcription factors (TFs). Closely related are cofactors, which regulate expression by binding to TFs or RNA polymerase machinery, but not directly to DNA.
Regulation of gene expression could also include modifications at the chromatin level - here you would include chromatin remodelers, histone acetylases, deacetylases, methylases and the histones themselves.
mRNA transcripts can also be regulated by miRNAs: post-transcriptional regulators that bind to complementary sequences on target mRNAs, which leads to translational repression or target degradation and gene silencing. So you would also include the proteins involved in this process, most notably the RNA-induced silencing complex, which includes Dicer.
There are also proteins involved in mRNA stabilization and turnover, which effects gene expression.
I'm not sure if anyone has added up all of the genes above to determine an overall percentage of the genome.
If you include in your definition of "gene regulation" post-transcriptional modification, folding chaperones, intra-cellular transport, extra-cellular and intra-cellular signaling, and so on - then Shigeta is right, you begin approaching 100%. In the most basic sense, life itself is gene regulation.
The following is multiple choice question (with options) to answer.
Gene expression is regulated primarily at the what level? | [
"manufacturing",
"translational",
"transcriptional",
"binding"
] | C | Gene expression is regulated primarily at the transcriptional level. |
SciQ | SciQ-2021 | organic-chemistry, inorganic-chemistry, physical-chemistry
Liquid Water - We still know so little about the molecular level interactions of water molecules with themselves and other species. The great extent of hydrogen bonding networks in liquid water make it hard to model. Just how many water molecules are solvating a proton in acid? Why are organic reactions between hydrophobic molecules accelerated in the presence of water?
Molecular origins of life, especially homochirality. The formose reaction is believed to be the origin of carbohydrates. Amino acids, lipids, and nucleic acids have similar hypothetical origins. However, how did these molecules come together to create living organisms? Why are most (not all) biomolecules present as one enantiomer and not the other?
Protein folding. Can we predict the three-dimensional shape of a protein simply from the order of the amino acids? If so, then we could design proteins to do whatever we wanted.
True designer proteins. Once we solve the folding problem, then we can design proteins with active sites of specific geometries and specific amino acids in those active sites to do whatever reaction we need.
High Temperature superconductors. Although room temperature superconductors would be nice, inexpensive superconductors that operate at liquid nitrogen temperature (77 K) instead of liquid helium (5 K) temperatures would make NMR, MRI, and a host of other important techniques much cheaper.
The Energy Crisis. We need a chemical solution to replace fossil fuels as the world's primary energy source. Hydrogen, fuel cells, biomass, and solar power all have serious drawbacks currently.
Replacement of petrochemical feedstocks. The petroleum industry remains the primary source of organic compounds. What will we do when the petroleum runs out?
Bonding theory. Modern bonding theories have developed into bloated mathematical formalisms that have removed any resemblance of intuition from the study of the structure of molecules. Can a unified modern bonding theory be developed that retains only the best features of valence bond and molecular orbital theories?
Improved ideality and efficiency of synthesis. Can the synthesis of compounds be improved so as to remove wasteful steps (like adding and removing protecting groups) or complex purifications to better adhere to the principles of Green Chemistry?
Structure-Property Relationship. All established relations between structure and activity is empirical, especially when the desired activity is biochemical. Can we design the best drug with the fewest side effects on the first try?
The following is multiple choice question (with options) to answer.
What nullified the idea that all biological catalysts are proteins? | [
"discovery of ribozymes",
"discovery of enzymes",
"amino acid theory",
"discovery of metabolites"
] | A | |
SciQ | SciQ-2022 | taxonomy, mammals, cladistics
Title: Why aren't mammals and reptiles considered amphibians? We've all heard it: birds descend from dinosaurs, so they're dinosaurs too. But this got me thinking: doesn't this mean that, for instance, all terrestrial vertebrates – including humans – are technically fish? A recent video by MinuteEarth and the Wikipedia article for "Fish" confirmed my shower thought hypothesis.
Interesting. But... all amniotes, i.e. reptiles (and, by extension, birds) and mammals, descend from amphibians, right? If so, then why aren't they considered amphibians too? Mammals and reptiles aren't considered amphibians, because amniotes are not hypothesized to descend from Amphibia. That is to say that Amphibia did not evolve into Amniota. They are sister clades (actually Reptiliomorpha in the Tree of Life tree below).
The following is multiple choice question (with options) to answer.
A tadpole turns into what land mammal? | [
"a frog",
"a morph",
"A tortoise.",
"a pod"
] | A | |
SciQ | SciQ-2023 | newtonian-mechanics, energy, work
Title: Types of energy and work I am learning about energy and work, and am a beginner to this topic. Energy is defined as the ability to do work. In some cases, the ability to do work directly follows the type of energy. For instance, heat energy can be used to do work through isothermal expansion of gas, for instance.
Is there a relationship/concept between how easy it is to get a type of energy to do work? Some types of energy might make them more suitable to do work, whereas others might involve a more indirect/contrived route. Energy defined as the ability to do work; this does not mean that only work is done, it means that work can be done.
Here is an expanded definition that should help.
The energy of a system is a property of the system that is increased (decreased) by the following mechanisms:
work done on (or done by) the system from its surroundings
heat added to (or removed from) the system from its surroundings
mass transfer into (or from) the system to its surroundings.
"How easy it is to get a type of energy to do work" depends how the system interacts with the surrounding.
For example, if a system comprised of a gas has a higher pressure than its surroundings and can move a boundary (say a piston), the system can lose energy by doing work on the surroundings as the gas expands. Or if the gas is in a closed container (fixed volume) and has a higher temperature than its surroundings, the gas can lose energy by transferring heat to the surroundings. A liquid can have a decrease in its energy, with a decrease in its temperature, by evaporation (mass transfer from the liquid).
The details of energy transfer is addressed by the laws of thermodynamics (e.g., the first and second laws).
The following is multiple choice question (with options) to answer.
In physics, what do you call devices that make work easier? | [
"circuits",
"levers",
"machines",
"tools"
] | C | In this chapter, you saw how pressure and buoyancy of fluids can be used to make work easier — from raising a car on a lift to floating a ship on the ocean. Devices that make work easier are called machines in physics. |
SciQ | SciQ-2024 | earth, mars
Title: Does Mars contain more iron than the Earth? Is the reason Mars is red because its surface contains a lot of iron? (When dirt is red on Earth, it is sometimes caused by a high amount of iron).
If so, does Mars contain more iron than the earth? Mars definitely has far less Iron than Earth. Mars has 10.7% of Earth's mass. On the other hand, Iron comprises 32% of Earth since there is so much Iron in its inner core, outer core, and the mantle. That means if Mars was made entirely of Iron (which it is not), Earth would still have more than 3 times as much Iron.
You are right that Mars has more Iron at its surface than Earth so it looks very red. Earth has many other metals on its surface (not to mention water to make it look blue and plants to make it look green).
The following is multiple choice question (with options) to answer.
Mars appears red because of large amounts of which element in the soil? | [
"mercury",
"coal",
"carbon",
"iron"
] | D | Viewed from Earth, Mars is red. This is due to large amounts of iron in the soil. The ancient Greeks and Romans named the planet Mars after the god of war because the planet's red color reminded them of blood. Mars has only a very thin atmosphere made up mostly of carbon dioxide. |
SciQ | SciQ-2025 | geology
Title: Where do riverbed stones come from? Have they always been here since the river was formed? Are some newer than others? Riverbed 'stones' - I assume you mean things like pebbles, boulders, etc. are pieces of rock that have weathered out and been deposited in the river. Some come from rock that is very close to where they are located and some have been transported from very far away. In general (and it is a very broad generalization) the rounder the stone, the longer it has been in the river and the more likely it is to have come from far away. Of course that depends on the hardness of the rock, and other factors, too.
Some rocks are newer than others. Some have been formed quite recently and some are billions of years old.
The following is multiple choice question (with options) to answer.
What type of rocks are laid down horizontally with the oldest at the bottom? | [
"igneous",
"crystalline",
"metamorphic",
"sedimentary"
] | D | Sedimentary rocks are laid down horizontally with the oldest at the bottom. |
SciQ | SciQ-2026 | acid-base, reaction-mechanism, redox, terminology
Precipitation: Creating a solid
Acid-Base: neutralization
Redox: exchange of electrons
But given a chemical reaction like:
HCl (aq) + NaOH (aq) → H2O (l) + NaCl (aq)
I need to understand how to classify them. Are there any tell-tale signs to look out for when determining. For example, does a precipitation reaction ALWAYS produce a (s) as a product and therefore any reaction with a (s) on the product side is a precipitation reaction? It's true that a precipitation reaction will always yield at least one solid product, but not every reaction that yields a solid is, strictly speaking, properly categorized as a precipitation reaction. Precipitation reactions are ones in which at least one of the reactants is in the aqueous phase (i.e., dissolved in water), and a solid forms on the product side which was not present on the reactant side. If all the reactants are solid, then a solid product forming should not be called a precipitate. To be called a precipitate, an insoluble product must form from within solution, either from a solid and solute interacting, or from an interaction strictly between solutes.
Examples of precipitation reactions:
$\ce{AgNO3_{(aq)} + NaCl_{(aq)} -> AgCl_{(s)} + NaNO3_{(aq)}}$
$\ce{CuCl2_{(aq)} + Zn_{(s)} -> ZnCl2_{(aq)} + Cu_{(s)}}$
Notice that at least one of the reactants was in the aqueous phase, and a new solid chemical species is produced on the product side. $\ce{AgCl_{(s)}}$ and $\ce{Cu_{(s)}}$, respectively, are the precipitates. Incidentally, the second reaction is also an example of a redox reaction, since it involved a change in the oxidation states of the reactants (here, zinc is oxidized while copper is reduced).
Identifying acid-base and redox reactions is a lengthier topic, so I suggest you consult a textbook or any of the numerous online resources.
The following is multiple choice question (with options) to answer.
What are two types of frozen percipitation? | [
"ice and frost",
"icycles and icebergs",
"snow and hail",
"rain and hail"
] | C | Snow falls when water vapor condenses as ice crystals. The air temperature is below freezing all the way to the ground, so the ice crystals remain frozen. They fall as flakes. Sleet forms when snow melts as it falls through a layer of warm air and then refreezes. It turns into small, clear ice pellets as it passes through a cold layer near the ground. Freezing rain falls as liquid water. It freezes on contact with cold surfaces near the ground. It may cover everything with a glaze of ice. If the ice is thick, its weight may break tree branches and pull down power lines. Hail is another type of frozen precipitation. Hail forms in thunderstorms when strong updrafts carry rain high into the troposphere. The rain freezes into balls of ice called hailstones. This may happen over and over again until the hailstones are as big as baseballs. Hail forms only in cumulonimbus clouds. |
SciQ | SciQ-2027 | bond, hydrogen-bond
Title: What are the prerequisites in hydrogen bonding? I know when a hydrogen bond is, but - can hydrogen bonds only occur between two molecules containing hydrogen? Or, only one of the molecules should contain hydrogen and the other one may not contain hydrogen, but should have a large electronegative difference between two of its sides? Actually, theoretically speaking hydrogen bond is the attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atom of a different molecule. Usually the electronegative atom is oxygen, nitrogen, or fluorine, which has a partial negative charge. A hydrogen bond may occur between $\ce{H-O}$, $\ce{H-N}$, $\ce{H-F}$ (first two are more common). Apart from that, these hydrogen-bond attractions can occur between molecules (intermolecular) or within different parts of a single molecule (intramolecular)
See also the Wikipedia article about hydrogen bonding
A hydrogen atom attached to a relatively electronegative atom will play the role of the hydrogen bond donor An electronegative atom such as fluorine, oxygen, or nitrogen will be the hydrogen bond acceptor, irrespective of whether it is bonded to a hydrogen atom or not. An example of a hydrogen bond acceptor that does not have a hydrogen atom bonded to it is the oxygen atom in diethyl ether.
http://chemwiki.ucdavis.edu/@api/deki/files/4680/image115.png?revision=1
The following is multiple choice question (with options) to answer.
The bond between the two nitrogen atoms is a what? | [
"quadruple bond",
"triple bond",
"single bond",
"double bond"
] | B | Solution 1. The bond between the two nitrogen atoms is a triple bond. The Lewis diagram for N2 is as follows:. |
SciQ | SciQ-2028 | inorganic-chemistry, crystal-structure, geochemistry, glass, minerals
You are correct. The main difference is that sand is crystalline and glass is not—it is amorphous.
The main component (> 95%) of common yellow sand is quartz (the mineral whose composition is SiO2). Note that not all sand is quartz. There are white sands containing calcite (CaCO3) and black sand (containing various heavy minerals). But the most common sand is indeed quartz sand: SiO2.
Glass, the type you see in your everyday life, on the other hand, is not composed of pure SiO2. It has a bunch of other additives such as Na, K, B, and others. This is done to modify the properties of the glass and make it more suitable for human use. It doesn't matter much though for our discussion.
So if they are made of the same thing, why the difference? The answer is cooling rate. If you cool molten SiO2 slow enough, the atoms have enough time to organize themselves into a crystalline structure. In the case of pure SiO2, this is a network of SiO4 tetrahedra: One silicon atom surrounded by four oxygens. If it cools too fast, then the crystalline structure does not form. It may be completely amorphous, or form into a sub-microscopic array of SiO2 crystals in various structures (CT-opal for example).
What determines the cooling rate? Well, in the case of glass it is a matter of minutes. You've seen glass making: The glass is molten and very quickly it solidifies to a solid. In contrast, most of the quartz sand you're seeing is actually broken fragments of rocks called granite. This type of rock has abundant quartz in it, and it forms deep underground (as in 10s of kilometers) at very slow cooling rates. While a glass maker can take his glass and let it cool in the atmosphere or in water, molten silicate magma ("glass") deep in the Earth is surrounded by rocks that are in the hundreds of degrees. This slow cooling facilitates crystallization of the SiO2 into quartz rather than glass. How slow is this? At least tens of years, more commonly hundreds or even thousands of years. This is much slower than the seconds and minutes in glass making.
The following is multiple choice question (with options) to answer.
What are the two most common silicates? | [
"Petalite and Quartz",
"Petalite and Analcime",
"Analcime and Feldspar",
"feldspar and quartz"
] | D | Feldspar and quartz are the two most common silicates. In beryl, the silicate pyramids join together as rings. Biotite is mica. The silicate pyramids come together to create thin, flexible sheets. Compare the beryl and the biotite pictured below ( Figure below ). |
SciQ | SciQ-2029 | biochemistry
Title: Why can't amylase break down glycogen? Amylase is an enzyme that breaks down starch in the form of amylopectin and amylose. Both amylose and amylopectin are formed by alpha glucose joined together by (1-4) and (1-6) glycosidic bonds. Glycogen is no exception, just that it has more branching. However, why is it that a google search shows that it is hydrolyzed by Glycogen Phosphorylase rather than amylase? Also, how can amylase digest both (1,6) and (1,4) glycosidic bonds?
Any help would be greatly appreciated. At an approximation the active sites of enzymes can be considered as having two aspects. The first relates to the catalysis — in this case the breaking of the glycosidic linkage. The second relates to binding the substrate. This review of the α-amylases by MacGregor et al. shows that there is a range of a-amylases, differing in this latter respect — their substrate specificity. In general there are binding sites for a varying numbers of glucose residues at either side of the bond being cleaved. This is shown in Fig. 3 of that review:
The important difference in the structure of glycogen and starch (amylopectin) — seldom mentioned in general biochemical or biology texts — is their patten of branching:
As this previous answer of mine to a different question explains, this results in a globular structure for glycogen granules in which only the ends of the chains are accessible. (The image below, from Protopedia, illustrates this better, especially if you imagine it in three dimensions.)
The following is multiple choice question (with options) to answer.
Starch is a large, complex carbohydrate made of thousands of _____ joined together? | [
"glucose orders ( monomers )",
"glucose divisions ( monomers )",
"glucose units (monomers)",
"glucose partitions ( monomers )"
] | C | Starch is a large, complex carbohydrate made of thousands of glucose units (monomers) joined together. Starches are found in foods such as vegetables and grains. Starches are broken down by the body into sugars that provide energy. Breads and pasta are good sources of complex carbohydrates. |
SciQ | SciQ-2030 | meiosis
Title: Aneuploidy in meiosis I am quite confused about nondisjuction in anaphase II. If the double chromosome is not segregated, isn't it double. On pictures they are drawn as single but I don't understand why, and if they are double do they duplicate themselves in the S phase?
What is confusing me in picture above is cell (n+1) , why are all chromosomes single? I thought, after end of division in the third cell (labeled as n+1) there should be 3 chromosomes with single chromatid, and 1 chromosome with 2 chromatid joined at centromeric region, as it is drawn in picture above that show nondisjunction in cell during anaphase ii . When and how do these 2 chromatids get physically separated? From Study.com >>
On the off chance that nondisjunction happens amid anaphase II of meiosis II, it implies that no less than one set of sister chromatids did not isolate.
In this situation, two cells will have the typical haploid number of chromosomes. Additionally, one cell will have an additional chromosome (n + 1) and one will miss a chromosome (n - 1) due to the nondisjunction of the chromosomes.
Here is a picture reference taken from Google.ca >>
In the image provided in the question, the chromosomes are not indicated clear and concisely, so it is very hard to follow through the logic of segregation of the daughter cells to (n + 1) and (n - 1) chromosomes.
As you can see from the updated image reference in the answer, we can notice that the cell that underwent nondisjunction in anaphase 2 gives rise to 2 daughter cells, in which, one cell receives the non-segregated chromosome plus one copy of a sister chromatid which makes it (n + 1) and the other daughter cell receives one segregated sister chromatid ONLY which makes it (n - 1).
On an additional note, from Biology Exams 4 U >>
The following is multiple choice question (with options) to answer.
Newly duplicated chromosomes are divided into two daughter nuclei during what stage? | [
"symphysis",
"meiosis",
"mitosis",
"prophase"
] | C | During mitosis, the newly duplicated chromosomes are divided into two daughter nuclei. |
SciQ | SciQ-2031 | human-biology, biochemistry, hematology, red-blood-cell, human-physiology
Title: Besides hemoglobin, what proteins are present in red blood cells? I knew that mature red blood cells (RBCs) lacked nuclei, but I wasn't aware until just now that they also lacked ribosomes and mitochondria. Most cells in the human body all contain a common laundry list of housekeeping proteins and RNAs (including mitochondrial proteins and ribosomal RNAs), but I guess RBCs lack a number of them. Do they still have all of the other organelles? Obviously hemoglobin (and to a lesser extent carbonic anhydrase) makes up a large portion of the dry weight of RBCs, but are other proteins still present? If so, what are their relative abundances?
For example, do red blood cells have any of the normal metabolic (i.e. ATP producing) proteins? Obviously they don't have any of the TCA cycle proteins, but do they still have the glycolysis ones? Reticulocyte stage is when the ribosomes are still present and after that no new protein synthesis occurs. However RBCs have a lot of proteins and major proteins other than haemoglobin are cytoskeletal proteins and ion channels/pumps (In fact, cytoskeletal proteins are more abundant than haemoglobin). It is the Na+-K+-ATPase that consumes most ATP. As you correctly identified the RBCs produce ATP via glycolysis and glycolytic enzymes are also present. Note that deficiency of pyruvate kinase leads to haemolytic anaemia.
For a detail on the proteins present in human RBSs, see this paper. They have studied the RBC proteome by ion-trap MS. The top 5 proteins (from Table-1) are:
No. Protein description Molecular mass (Da) Gi Number Sequence No. of identified
coverage(%) peptides
1 Spectrin α chain, erythrocyte 279,916.5 1174412 48.0 77*
2 Spectrin β chain, erythrocyte 246,468.1 17476989 48.0 76*
3 Ankyrin 1, splice form 2 206,067.9 105337 45.0 55
The following is multiple choice question (with options) to answer.
As an erythrocyte matures in the red bone marrow, it extrudes its nucleus and most of its other what? | [
"organelles",
"energy",
"moisture",
"electrons"
] | A | Shape and Structure of Erythrocytes As an erythrocyte matures in the red bone marrow, it extrudes its nucleus and most of its other organelles. During the first day or two that it is in the circulation, an immature erythrocyte, known as a reticulocyte, will still typically contain remnants of organelles. Reticulocytes should comprise approximately 1–2 percent of the erythrocyte count and provide a rough estimate of the rate of RBC production, with abnormally low or high rates indicating deviations in the production of these cells. These remnants, primarily of networks (reticulum) of ribosomes, are quickly shed, however, and mature, circulating erythrocytes have few internal cellular structural components. Lacking mitochondria, for example, they rely on anaerobic respiration. This means that they do not utilize any of the oxygen they are transporting, so they can deliver it all to the tissues. They also lack endoplasmic reticula and do not synthesize proteins. Erythrocytes do, however, contain some structural proteins that help the blood cells maintain their unique structure and enable them to change their shape to squeeze through capillaries. This includes the protein spectrin, a cytoskeletal protein element. Erythrocytes are biconcave disks; that is, they are plump at their periphery and very thin in the center (Figure 18.6). Since they lack most organelles, there is more interior space for the presence of the hemoglobin molecules that, as you will see shortly, transport gases. The biconcave shape also provides a greater surface area across which gas exchange can occur, relative to its volume; a sphere of a similar diameter would have a lower surface area-to-volume ratio. In the capillaries, the oxygen carried by the erythrocytes can diffuse into the plasma and then through the capillary walls to reach the cells, whereas some of the carbon dioxide produced by the cells as a waste product diffuses into the capillaries to be picked up by the erythrocytes. Capillary beds are extremely narrow, slowing the passage of the erythrocytes and providing an extended opportunity for gas exchange to occur. However, the space within capillaries can be so minute that, despite their own small size, erythrocytes may have to fold in on themselves if they are to make their way through. Fortunately, their structural proteins like spectrin are flexible, allowing them to bend over themselves to a surprising degree, then spring back again when they enter a wider vessel. In wider vessels, erythrocytes may stack up much like a roll of coins, forming a rouleaux, from the French word for “roll. |
SciQ | SciQ-2032 | nuclear-physics, radiation, radioactivity
Title: Fluorescent lamp to detect ionizing radiation like a scintillator? As far as I understand the mercury vapor inside the tubes of CFL's can be ionized using electricity but can it be ionized by ionizing radiation like alpha, beta or gamma rays. If it ionizes would it be enough to make the tube glow when brought near a radiation source?
We can also measure the tiny change in current/voltage/resistance between the terminals of the tube (by taking apart the lamp circuit and exposing the cathode and anode).
Is this method of ionizing radiation detection feasible or has anyone tried? This is the basic operating principle behind most radiation detectors, but an off-the-shelf fluorescent lamp tube isn't very well-optimized for few-particle detection.
As you have read, a fluorescent lamp works by passing electrical current through a vapor of mercury atoms, which produce a line spectrum with a mixture of visible and ultraviolet light as they de-ionize and relax back towards their ground state.
This light is absorbed by a fluorescent paint on the inside of the bulb, which generally absorbs the ultraviolet photons and re-emits the energy as visible photons.
The biggest issue with using an off-the-shelf fluorescent tube for radiation detection is efficiency. A typical lamp operates with (milli)ampere-scale currents, or of order $10^{19}$ fundamental charges per second.
For comparison, a common radiation unit is the curie, which is roughly $10^{10}$ decays per second --- a billion times slower. A curie is an enormous amount of radioactivity. A typical americium smoke detector has an activity somewhere under a microcurie.
If you could somehow get a smoke detector source inside the tube of a fluorescent lamp, there probably wouldn't be enough activity for you to see the fluorescence with the naked eye. Not a great detector.
You're on a better track with detecting the ionization produced as the radioactive particles lose energy. In fact, this is how those americium smoke detectors work: the radioactive source ionizes a small volume of air, which conducts an electrical current. When smoke enters this air volume, the alpha radiation from the americium captures on the smoke particles, and the ionization/conductivity of the air is reduced. An americium smoke detector is a lack-of-radioactivity alarm.
The following is multiple choice question (with options) to answer.
What is the tube-like device used to reliably measure lower levels of radiation? | [
"MRI machine",
"geiger counter",
"Richter scale",
"weber counter"
] | B | These devices are not very sensitive to low levels of radiation, but more sensitive devices are also available that reliably measure the frequency of radioactive events. One such device is the Geiger counter. A Geiger counter is a tube filled with an inert gas that will conduct electricity when exposed to charged radiation, such as alpha or beta particles. When a charged particle enters the tube, it changes the electrical potential between the anode and the cathode, and this change in potential is registered by an electrical circuit as a single radioactive event. Geiger counters are fairly inexpensive and reliable, so they are useful in a wide range of applications. More complicated types of counters are also available, but are generally used only in sophisticated experiments. |
SciQ | SciQ-2033 | 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.
The conducting zone of the respiratory system includes the organs and structures not directly involved in what? | [
"helium exchange",
"gold exchange",
"gas exchange",
"copper exchange"
] | C | Functionally, the respiratory system can be divided into a conducting zone and a respiratory zone. The conducting zone of the respiratory system includes the organs and structures not directly involved in gas exchange. The gas exchange occurs in the respiratory zone. |
SciQ | SciQ-2034 | microbiology, cancer, toxicology
Title: Molds associated with Aflatoxin? I've been reading how some molds may be carcinogenic. In particular, molds associated with the fungus metabolite, Aflatoxin.
Are the types of mold that produce this toxin, present in buildings/showers/domestic environments, or do they only grow on food-stuffs? Strictly speaking the common bread mould Rhizopus sp. does not produce aflatoxin.
The fungus Aspergillus flavus which belongs to the class Ascomycetes secretes aflatoxin. It attacks cereal grains , legumes, tree nuts. The fungi are green in colour and 'mould' like in appearance.
The fungus attacks the food stuffs and storage grains. So under favourable conditions it may grow in your store room if it finds food for its growth. Also Aspergillus can grow at temperatures as high as 48°C and even at low temperatures like 5-8°C.
Edit: On being asked for sources I include some which strongly support my claim
1. For suitable conditions of growth of the fungi visit https://en.m.wikipedia.org/wiki/Aspergillus_flavus and read under the Environment heading.
2. Visit https://bioweb.uwlax.edu/bio203/s2013/ernst_ale2/habitat.htm and read from " Aspergillus flavus is omnipresent " upto " Aspergillus may also grow on or inside walls in homes, especially if the house is damp or has been damaged by flooding. "
3.https://www.moldbacteria.com/mold-types.html this site provides a list of different fungi found in our homes. Here you can find Aspergillus flavus to grow in flower pot soil. Moreover other species of Aspergillus are found in kitchens and bathrooms.
The following is multiple choice question (with options) to answer.
Aflatoxins are toxic, carcinogenic compounds released by fungi of this? | [
"protist group",
"genus sporozoa",
"arthropod class",
"genus aspergillus"
] | D | Aflatoxins are toxic, carcinogenic compounds released by fungi of the genus Aspergillus. Periodically, harvests of nuts and grains are tainted by aflatoxins, leading to massive recall of produce. This sometimes ruins producers and causes food shortages in developing countries. |
SciQ | SciQ-2035 | biochemistry, physiology, cell-biology
Title: What triggers meiosis in gonadal cells? What specific biochemical processes are involved in inducing meiosis rather than mitosis? Why are gonadal cells the only cells in the human body which do undergo meiosis?
What specific biochemical processes are involved in inducing meiosis rather than mitosis?
It's a difficult question because every step in the development of a germ cell is ultimately necessary for the final differentiation, which includes a meiotic division. Meiosis requires a lot of specialized components to pair and segregate homologues, to induce and resolve recombination, etc. What starts it all is still largely unknown. There are plenty of mutants that halt the process, but these are required along the way, so damaging the pathway ultimately stops it from progressing. At least one study has been able to initiate the program of meiosis in yeast:
Induction of meiosis in Saccharomyces cerevisiae depends on conversion of the transcriptional represssor Ume6 to a positive regulator by its regulated association with the transcriptional activator Ime1. I Rubin-Bejerano, S Mandel, K Robzyk, and Y Kassir
Basically, they turned on a transcription factor, which activated an entire suite of downstream genes necessary for meiosis. In essence, they turned on the "meiosis pathway." Bear in mind this is yeast, so does't have separate germ cells, but the concept is probably the same.
Why are gonadal cells the only cells in the human body which do undergo meiosis?
All other cells are diploid. Only in germ cells does the organism induce reductional divisions (to make haploid gametes for ultimate fusion in the zygote of the next generation). Creation of haploid somatic cells would uncover recessive lethal mutations and cells would die. In sperm and eggs, which do not express any genes until after fertilization and karyogamy, this is not a problem.
The following is multiple choice question (with options) to answer.
Four haploid spermatids form during meiosis from what? | [
"the primary spermatocyte",
"the ova",
"the zygote",
"the sister chromatic"
] | A | Maturation of the ovum. Notice only 1 mature ovum, or egg, forms during meiosis from the primary oocyte. Three polar bodies may form during oogenesis. These polar bodies will not form mature gametes. Conversely, four haploid spermatids form during meiosis from the primary spermatocyte. |
SciQ | SciQ-2036 | history, autoimmune, diabetes-mellitus
Title: When was it determined that Type 1 Diabetes is an autoimmune disease? I just found out today that type 1 diabetes is an autoimmune disease. When was this discovered? This question has two answers: The difference was first described in 1936 by Harold Percival Himsworth, which described it in this article.
At this time it was established that there are two forms of Diabetes, one sensitive to insuline while the other is not.
The terms Diabetes type 1 and 2 where established somewhere between 1974 and 1976, for details see the review "The discovery of type 1 Diabetes".
The following is multiple choice question (with options) to answer.
Like people with type 1 diabetes, people with type 2 diabetes must frequently check what level? | [
"glucose",
"blood sugar",
"pulse",
"heartbeat"
] | B | Some cases of type 2 diabetes can be cured with weight loss. However, most people with the disease need to take medicine to control their blood sugar. Regular exercise and balanced eating also help, and should be a regular part of the treatment for these people. Like people with type 1 diabetes, people with type 2 diabetes must frequently check their blood sugar. |
SciQ | SciQ-2037 | species-identification, botany, ecology
Title: Algae or Lichen identification. Coastal BC, Canada I have tried all books and internet resources I know of, but I still have no idea what this might be — a lichen or something else.
At first glimpse, I thought it was something man-made and unnatural, but then I looked closer and saw how it appears to be attached and growing. It grows on exposed rocks well above the high tide. The photo is taken in late March, on northern Vancouver Island. It's loosely attached to the rock.
It was somewhat abundant around the general area (within of a few km), but I haven't seen it elsewhere - although I'm not from BC so there might be a lot of this around.
The water droplet in the lower right corner give a rough sense of scale.
Edit:
Adding another photo in which I just noticed a streak of white, which I included in original resolution. I want to propose you expand your search to a broader taxonomic scope. Specifically, I think you might be looking at a species of "red" green algae (family: Trentepohliaceae).
From Nelson et al. (2011):
All Trentepohliaceae have filamentous growth forms and often contain large amounts of carotenoid pigments (ß-carotene and hematochrome), causing the algae to appear yellow orange in color (Thompson and Wujek 1997, Lo´pez-Bautista et al. 2002).
The Trentepohliaceae contains five genera: (Trentepohlia, Printzina, Phycopeltis, Cephaleuros and Stomatochroon) and 70+ species worldwide.
For example, the following algae (picture from England) looks fairly similar to your specimen:
Trentepohlia aurea
Source: David Fenwick
If your specimen is a species in this family of algae, it is most likely in the Trentepohlia genus (or possibly Printzina genus).
Trentepohlia is a genus of filamentous chlorophyte green algae in the family Trentepohliaceae.
Typically orange or yellow in color.
Live on tree trunks and wet rocks or symbiotically in lichens.
Here's a picture of a free-living Trentepohlia species from coastal Oregon, USA:
Source: Richard C. Hoyer (2015)
The following is multiple choice question (with options) to answer.
Many species in rhizaria are among the organisms referred to as what? | [
"fungi",
"protozoa",
"prokaryotes",
"amoebas"
] | D | |
SciQ | SciQ-2038 | reaction-mechanism, kinetics
Title: Can we interpret the "extent of reaction" as the number of reactions that happened? Consider this reaction:
$$\ce{\alpha\ A + \beta\ B -> \omega\ C + \delta\ D}$$
Where $\ce A$ and $\ce B$ are the reactants, $\ce C$ and $\ce D$ are the products, and $ \alpha, \beta, \omega, \delta$ their respective stoichiometric constants
We can then define the extent of reaction at instant $t$ as: $\xi (t)$.
My question is: can we interpret the extent of reaction as the number of reactions that happened at an instant $t$ considering that say, for reactant $\ce A$ at instant $t$: $$n_{t}(\ce A) = n_{i}(\ce A) - \alpha\times \xi(t)$$ If I understand this correctly you want to measure $\ce A$ to infer the extent of reaction. I think you should have started with mathmatically defining the extend of reaction:
$$\xi(t) = \left[\frac{n_i(\ce A) -n_t(\ce A)}{n_i(\ce A)}\right]\tag 1$$
Where $n_t$ is the concentration at a given time $t$. Here $n_i(\ce A) -n_t(\ce A)$ gives the consumed concentration of $\ce A$ after time $t$ which is normalized by the initial concentration to yield an extent of conversion.
The following is multiple choice question (with options) to answer.
What is the amount actually produced in a reaction called? | [
"maximum yield",
"individual yield",
"actual yield",
"minimum yield"
] | C | In all the previous calculations we have performed involving balanced chemical equations, we made two assumptions: (1) the reaction goes exactly as written, and (2) the reaction proceeds completely. In reality, such things as side reactions occur that make some chemical reactions rather messy. For example, in the actual combustion of some carbon-containing compounds, such as methane, some CO is produced as well as CO2. However, we will continue to ignore side reactions, unless otherwise noted. The second assumption, that the reaction proceeds completely, is more troublesome. Many chemical reactions do not proceed to completion as written, for a variety of reasons (some of which we will consider in Chapter 13 "Chemical Equilibrium"). When we calculate an amount of product assuming that all the reactant reacts, we calculate the theoretical yield, an amount that is theoretically produced as calculated using the balanced chemical reaction. In many cases, however, this is not what really happens. In many cases, less—sometimes much less—of a product is made during the course of a chemical reaction. The amount that is actually produced in a reaction is called the actual yield. By definition, the actual yield is less than or equal to the theoretical yield. If it is not, then an error has been made. Both theoretical yields and actual yields are expressed in units of moles or grams. It is also common to see something called a percent yield. The percent yield is a comparison between the actual yield and the theoretical yield and is defined as Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-2039 | evolution, cell-biology
What do you mean by multicellularity?
The evolution of multicellularity can be discussed in the context where sister cells form an organism together or when unrelated cells (among the same species or even cells from different species) come together to form an organism. Also, the multicellularity can be discussed at a different level depending on how we want to define multicellularity. Is a stack of cells reproducing individually, working for their own benefit a multicellular? Do we need a division of labor? Do we need a division between germline (reproductive caste) and soma line (non-reproductive case)?
How many times did multicellularity evolve independently?
Some people consider that there are multicellular bacteria (biofilms) but we will avoid discussions that are based on limit-case definitions. Let's talk about eukaryotes. Most Eukaryotes are unicellular and multicellularity evolved many times independently in eukaryotes. To my knowledge, complex multicellularity however evolved only (only?) 6 times independently in eukaryotes.
The following is multiple choice question (with options) to answer.
Each group of organisms went through its own evolutionary journey, called what? | [
"superfamily",
"phylogeny",
"zoology",
"anomalous"
] | B | CHAPTER SUMMARY 20.1 Organizing Life on Earth Scientists continually gain new information that helps understand the evolutionary history of life on Earth. Each group of organisms went through its own evolutionary journey, called its phylogeny. Each organism shares relatedness with others, and based on morphologic and genetic evidence, scientists attempt to map the evolutionary pathways of all life on Earth. Historically, organisms were organized into a taxonomic classification system. However, today many scientists build phylogenetic trees to illustrate evolutionary relationships. |
SciQ | SciQ-2040 | photoelectric-effect
Title: Is the photoelectric effect a type of nuclear decay? If the frequency of light is $f$ and if $f \ge f_t$, where $f_t$ is the threshold frequency, electrons are emitted if light is shined on a metal surface. By my understanding, the light comes in and is absorbed by the atom. The atom then has too much energy and emits an electron. I don't remember much about nuclear decay, but when an atom has too much energy it can emit an alpha particle or a gamma ray or whatever else (something about decaying down to a stable line).
Anyways, so if an atom has too much energy and ejects an electron, is that considered a nuclear decay? Also, does the photoelectric effect then ionize materials? Could I take a metal sheet, shine light on it, and get a metal sheet that is now positive? Could I do this at home? The photoelectric effect involves the shell (electrons) of the atom. Photon energies are typically in the range of electron volts.
To excite the nucleus, you'll need higher energies (MeV or hundreds of keV).
What you are probably looking for is called photonuclear reaction.
Anyways, so if an atom has too much energy and ejects an electron, is that considered a nuclear decay?
If this electron is coming from the shell, then it's NOT a decay of the nucleus (aka nuclear decay). If however, this is coming from a $\beta^-$ decay (bound neutron decays to a bound proton plus an electron and an anti-electron neutrino) of the nucleus, then yes, this is a nuclear decay.
One has to be careful when talking about 'the atom has too much energy': one has to clarify whether it's an electron in the shell which is not in the energetically lowest possible state or whether it's the nucleus which is not in its energetically lowest state.
Could I take a metal sheet, shine light on it, and get a metal sheet that is now positive?
The following is multiple choice question (with options) to answer.
What term refers to the emission of material or energy from an atom's nucleus? | [
"stasis",
"microscopic",
"radioactivity",
"smog"
] | C | Radioactivity involves the spontaneous emission of material and/or energy from the nucleus of an atom. The most common radioactive atoms have high atomic numbers and contain a large excess of neutrons. Some typical radioactive elements are technetium (atomic number 43), promethium (atomic number 61), and all elements atomic number 84 (polonium) and higher. There are four primary types of emission, either involving the release of a particle from the nucleus or the release of energy. In many instances, both energy and a particle are produced by the radioactive event. |
SciQ | SciQ-2041 | navigation, ekf, gps, navsat-transform, robot-localization
Cause
The cause for each of these problems is as follows:
Incorrect datum: I'm not 100% sure about this as I still haven't fixed it, but my imu_link -> base_link tansform occasionally fails, and so what I think is happening is that navsat_transform is getting a bad transform when it subscribes to the /imu/data topic to calculate the LL -> UTM transform, which then ruins the calculation of /map's origin. In addition, there is a bit of natural error in the IMU's heading, so this will only contribute to the problem.
Locked orientation: It is currently impossible for navsat_transform to in any way change the orientation of the /map frame. There are however three parameters that may appear to do so. These parameters do not change the visible orientation of the frame but instead add an angle offset to all the odometry that navsat_transform reports in that frame. So you will never see the 'Y' axis of /map point anywhere but Magnetic North. The parameters are:
heading: This, along with the 'latitude' and 'longitude' values define the datum parameter, which let you re-set the orientation of the /map frame. However, the third parameter 'heading' does not affect the actual heading of the /map frame, instead it simply assumes that your robot starts at that heading within the /map frame.
mag declination: This parameter exists purely so that navsat_transform can calculate where True North is for the purposes of the LL -> UTM conversion, it has no effect on the orientation of /map whatsoever but it does massively affect the odometry in that frame if you get it wrong (see below).
yaw offset: This parameter exists purely to compensate for the fact that most IMUs read 0 when facing North, whereas ROS conventions expect 0 facing East (see REP-105). Again, this parameter has no effect on the orientation of /map but WILL affect the odometry calculated in that frame.
The following is multiple choice question (with options) to answer.
Which feature in maps allows users to make corrections between magnetic north and true north? | [
"inset",
"scale",
"double compass rose",
"key"
] | C | Some maps have a double compass rose. This allows users to make the corrections between magnetic north and true north. An example is a nautical chart that boaters use to chart their positions at sea ( Figure below ). |
SciQ | SciQ-2042 | thermodynamics, fluid-dynamics, energy-conservation, conservation-laws, steady-state
Title: General Definition of Steady State According to many sources (including Wikipedia, Stephani&Kluge, D.J. Acheson) a steady state ist:
In systems theory, a system in a steady state has numerous properties that are unchanging in time. This means that for those properties $p$ of the system, the partial derivative with respect to time is zero:
$$ \frac{\partial p}{\partial t} = 0 $$
But why is it defined like that? Why not ${d \over dt} p=0$ ? If only $ \frac{\partial p}{\partial t} = 0 $ then there will still be change in time if $p=p(\vec r(t))$ !
Since people seem to disagree that this is even a legitimate question here is a motivation for that, Wikipedia about total and partial derivative:
The total derivative of a function is different from its corresponding partial derivative ($\partial$). Calculation of the total derivative of f with respect to t does not assume that the other arguments are constant while t varies; instead, it allows the other arguments to depend on t.
The following is multiple choice question (with options) to answer.
What is the term for the maintenance of a steady state despite internal and external changes? | [
"equilibrium",
"homeostasis",
"consciousness",
"hypothesis"
] | B | |
SciQ | SciQ-2043 | cell-biology
Title: Structure of Cell Are cells spheres or ovals/circles bound by phospholipidbilayer?
If they are spherical how are we able to see the nucleus through the phospholipid bilayer under a microscope? Not exactly. That is a stereotype of cells. Muscle cells are not round nor oval, but rather elongated rods. If you were to look up epithelia cells, you can quickly see that cells are grouped based on their physical characteristics; simple (round/oval & single layer), columnar, and cuboidal to name a few. Cells come in many shapes and sizes. As Hans stated, stains are vital in viewing cellular components. There is a diverse amount of stains used - which all carry a purpose and benefit in a specific application.
The following is multiple choice question (with options) to answer.
Any structure inside a cell that is enclosed by a membrane is called? | [
"an enclave",
"a particle",
"an article",
"an organelle"
] | D | The nucleus is an example of an organelle . An organelle is any structure inside a cell that is enclosed by a membrane. Eukaryotic cells may contain many different organelles. Each does a special job. For example, the mitochondrion is an organelle that provides energy to the cell. You can see a mitochondrion and several other organelles in the animal cell in Figure above . Organelles allow eukaryotic cells to carry out more functions than prokaryotic cells can. |
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