source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-1544 | botany
Title: Do any plants exhibit hormonal changes similar to puberty? Just what the title states.
Are there any plants/trees that exhibit a growth spurt at a definite interval after the shoot appears? In flowering plants (the angiosperms) there are several developmental transitions in the life of the plant. I won't list the plants, because the list includes pretty much all of them (although the magnitude in the change of developmental pace differs widely between taxa and environments).
First there is seed germination, which is controlled hormonally. Absence of germination is usually imposed by abscisic acid, whilst germination is caused at the appropriate time by gibberellic acid and ethylene (among other things; Holdsworth, Bentsink & Soppe, 2008).
Next, in many herbaceous species there is a transition between a spreading growth stage (e.g. rosette growth) and the flowering stage. The 'growth spurt' here is the differentiation and elongation of the flowering stem, and then subsequently the sudden flowering of buds. The transition is also controlled hormonally, by a variety of hormones including auxin (Zhao, 2010), gibberellic acid, ethylene (Schaller, 2012), and the long anticipated, recently confirmed florigen (Choi, 2012). Ethylene and abscisic acid then play important roles in the next developmental transition when seeds and fruits are produced and dehisced.
Small RNAs are also now being revealed to play a large role in controlling the timing of developmental, but they are upstream of the hormonal changes. In particular some key miRNAs are involved in auxin-based regulation of branching, and in embryogenesis (Nodine & Bartel, 2010), and RNA silencing is involved in the switch from rosette growth to flowering growth (reviewed in Poethig, 2009 and Baurle & Dean 2006).
The following is multiple choice question (with options) to answer.
Puberty and other physical changes occurs during which stage of development? | [
"childhood",
"infancy",
"adulthood",
"adolescence"
] | D | Adolescence includes the physical changes of puberty among other changes. |
SciQ | SciQ-1545 | organic-chemistry, inorganic-chemistry
But then, some inorganic compounds do have carbon too, and there may even be some compounds that some call organic, and others call inorganic, like $CO_2$.
As I have felt it, in my learnings so far, it's like inorganic chemistry is the default chemistry and organic chemistry goes a step beyond.
But I don't quite grasp the difference.
What is the real semantics behind the word "organic"?
For example, we humans are made of loads of water, and that's a pretty organic thing to me. But then, water is inorganic.
Diamonds are the carbon top of the cake, and do not transmit the idea of being an "organic" thing.
Another very confusing thing are polymers, chanins of loads of carbons with other elements, in many shapes and textures. To me, a piece of "plastic" is not a very organic thing, but indeed, they are!
That brings the semantics into an even more confusing level.
And of course, there must be historical reasons for those chosen words.
Could someone please point out where this distinction comes from and why it is important?
With all my respect to science and the people who made chemistry a useful thing. This question is not about critics, it's about not knowing the facts, so of course I am the ignorant here.
Related and useful: What is the definition of organic compounds? IUPAC is the International Union of Pure and Applied Chemistry, they make recommendations on the nomenclature. IUPAC mentions that the difference between organic and inorganic is not distinct. To quote "The boundaries between ‘organic’ and ‘inorganic’ compounds are blurred." in Brief Guide to the Nomenclature of Inorganic Chemistry R. M. Hartshorn, K.-H. Hellwich, A. Yerin.
Since the terminology of organic vs. inorganic is all human classification, it is not a binary system 0 or 1. What we can say now is that traditionally, all organic compounds do contain carbon. It can come from natural sources or purely synthetic. There is no such restriction. Plastic is an organic compound because it contains a lot of carbon chains.
Note that this word organic, as used in chemistry, has nothing to with the buzz word used in marketing of organic food, organic fruits, organically grown stuff. The word organic comes from French organique designating the jugular vein, hence related to organs or living beings.
The following is multiple choice question (with options) to answer.
What makes organic compounds ubiquitous is the chemistry of their what? | [
"dioxide core",
"carbon core",
"dioxide shell",
"carbon shell"
] | B | The Chemistry of Carbon What makes organic compounds ubiquitous is the chemistry of their carbon core. Recall that carbon atoms have four electrons in their valence shell, and that the octet rule dictates that atoms tend to react in such a way as to complete their valence shell with eight electrons. Carbon atoms do not complete their valence shells by donating or accepting four electrons. Instead, they readily share electrons via covalent bonds. |
SciQ | SciQ-1546 | organic-chemistry, physical-chemistry, biochemistry, alcohols
Title: Storage of Urine Not all may be favorable to this project, but I will explain what I am trying to do. I work at home, and instead of walking a moderate distance to the bathroom and loosing my focus, I've been, at times, peeing in a 3 Quart Poland Springs water bottle. If you take offense at this, please do not continue reading except to be helpful in the scientific goal. I know this subject won't suit many types of people, so just ignore it if that is your case.
I noticed first of all that urine is not at all as sterile as people say that it is. The rate of growth of bacteria is relatively slow, but as a precaution, I found the need to use additional measures to prevent the growth of bacteria. I settled on the following method: I have two bottles and I add to each bottle about enough salt as can be soluble in the urine and sometimes maybe a little more. The one bottle then fills up throughout the day and is emptied, washed, and refilled with salt. The salt helps to kill the bacteria which would be lingering in the empty bottle. The next day, the bottle stays empty and the other is used.
I would add that I discovered that the bacteria (without the salt) does not usually grow unless the bottle is left with urine for two days. After this, however, that same bottle (without the salt) would retain the bacteria and immediately grow, if used again.
This system works relatively well, so long as it is done every day. It will even withstand 2 days with only moderate growth. (If I should leave it by mistake for longer it can get ugly). Nevertheless, I am still looking to improve upon this. One reason is that, if I drink less water or relieve myself normally, the bottle does not fill in one day. I am looking for someone with knowledge of chemistry to help me find a substance that can be added to this solution which fits a number of common sense criteria. I will also add a list of the substances that I have tried or already considered.
Necessary qualities
The following is multiple choice question (with options) to answer.
What type of drugs can increase water loss by interfering with the recapture of solutes and water from the forming urine? | [
"sedatives",
"diuretics",
"hallucinogens",
"disassociates"
] | B | Antidiuretic Hormone (ADH) Diuretics are drugs that can increase water loss by interfering with the recapture of solutes and water from the forming urine. They are often prescribed to lower blood pressure. Coffee, tea, and alcoholic beverages are familiar diuretics. ADH, a 9-amino acid peptide released by the posterior pituitary, works to do the exact opposite. It promotes the recovery of water, decreases urine volume, and maintains plasma osmolarity and blood pressure. It does so by stimulating the movement of aquaporin proteins into the apical cell membrane of principal cells of the collecting ducts to form water channels, allowing the transcellular movement of water from the lumen of the collecting duct into the interstitial space in the medulla of the kidney by osmosis. From there, it enters the vasa recta capillaries to return to the circulation. Water is attracted by the high osmotic environment of the deep kidney medulla. |
SciQ | SciQ-1547 | botany, plant-physiology, plant-anatomy
*No others are known, but could definitely exist.
Bibliography
Crafts, A. S. “Phloem Anatomy, Exudation, and Transport of Organic Nutrients in Cucurbits.” Plant Physiology 7, no. 2 (1932): 183–225.
Fischer, A. “Das Siebröhrensystem von Cucurbita.” Berichte Deutsche Botanische Gesell 1 (1883): 276–279.
Fischer, A. “Neue Beiträge Zur Kenntniss Der Siebröhren.” Berichte Über Die Verhandlungen Der Königlich-Sächsischen Gesellschaft Der Wissenschaften Zu Leipzig, Mathematisch-Physische Klasse 38 (1886): 291–336.
Fischer, A. Untersuchungen Über Das Siebröhren System Der Cucurbitaceen. Berlin, 1884.
Turgeon, R. and Oparka, K. “The Secret Phloem of Pumpkins.” Proceedings of the National Academy of Sciences 107, no. 30 (2010): 13201 –13202.
Walz, C. and Giavalisco, P. and Schad, M. and Juenger, M. and Klose, J. and Kehr, J. “Proteomics of Curcurbit Phloem Exudate Reveals a Network of Defence Proteins.” Phytochemistry 65, no. 12 (2004): 1795–1804.
Zhang, B. and Tolstikov, V. and Turnbull, C. and Hicks, L. M. and Fiehn, O. “Divergent Metabolome and Proteome Suggest Functional Independence of Dual Phloem Transport Systems in Cucurbits.” Proceedings of the National Academy of Sciences 107, no. 30 (2010): 13532.
The following is multiple choice question (with options) to answer.
This type of tissue consists of bundles of xylem and phloem and transports fluids throughout the plant. | [
"vascular tissue",
"cytoplasm",
"nonvascular tissue",
"dermal tissue"
] | A | Vascular tissue runs through the ground tissue inside a plant. It consists of bundles of xylem and phloem, which transport fluids throughout the plant. |
SciQ | SciQ-1548 | physical-chemistry
Title: Which is hardest: iron, brass or bone? I was hopping around random wikipedia articles when I came across the article for the Behemoth. In the description for the beast it says:
His bones are as strong pieces of brass; his bones are like bars of
iron
So it got me thinking, which of these three substances is hardest: iron, brass or bone?
(I had a quick look at the Mohs scale, which lists iron as 4, but could not find anything for brass or bone.) These two sources both put bone at a hardness of 5:
http://www.chacha.com/question/how-hard-is-bone-according-to-moh's-hardness-scale
https://answers.yahoo.com/question/index?qid=20110310200841AABwtMj
Whether they are trustworthy is questionable though, so take it as you will.
This source put brass at 3 and iron at 4.5:
http://www.jewelrynotes.com/the-mohs-scale-of-hardness-for-metals-why-it-is-important/
and this image puts brass at 4 and iron at 4-5 (Similar to 4.5):
http://patentimages.storage.googleapis.com/WO2001048807A1/imgf000009_0001.png
While these different sources seem to have conflicting data, I think it would be safe to assume that Brass is the softest of these three materials, Iron comes second, and Bone is the hardest.
Edit: In the description of that monster, the adjective used is 'strong'. You may want to consider how much force each of these materials can withstand instead of how hard they each are :)
The following is multiple choice question (with options) to answer.
What is the scientific name of the thighbone, the longest, heaviest, and strongest bone in the body? | [
"humerus",
"fibula",
"femur",
"tibia"
] | C | The femur, or thighbone, is the longest, heaviest, and strongest bone in the body. The femur and pelvis form the hip joint at the proximal end. At the distal end, the femur, tibia, and patella form the knee joint. The patella, or kneecap, is a triangular bone that lies anterior to the knee joint. The patella is embedded in the tendon of the femoral extensors (quadriceps). It improves knee extension by reducing friction. The tibia, or shinbone, is a large bone of the leg that is located directly below the knee. The tibia articulates with the femur at its proximal end, with the fibula and the tarsal bones at its distal end. It is the second largest bone in the human body and is responsible for transmitting the weight of the body from the femur to the foot. The fibula, or calf bone, parallels and articulates with the tibia. It does not articulate with the femur and does not bear weight. The fibula acts as a site for muscle attachment and forms the lateral part of the ankle joint. |
SciQ | SciQ-1549 | meteorology, snow, radar
Also note that winter precipitation adds an extra complication because the particles are lighter in weight and can thus be blown about more by vertical and horizontal winds. Raindrops (and hail) are quite likely to fall unless extreme updrafts exist because they are heavy. But drizzle, snow, and sleet may be blown around quite a bit. Without a time-intensive dual-Doppler analysis, you cannot know the wind motion in the storm thoroughly, and therefore will have varying results at times.
And finally, the big wrench is unfortunate inherent to how radars work. They measure the percentage of their sent energy that is reflected back to them. That's great because that's directly connected to the diameter of the item falling (to the 6th power). But unfortunately the grand problem is that in a storm, there is a huge variety of drop/flake sizes mixed together at once... such that we can't extract which combination of particle sizes created it (and thus can't calculate volume to actually know the rain/snow amount that falls). It could be like 6 medium size flakes causing the 10 dBZ echo... or 2 large flakes and 10 small flakes... and each combination is a different volume/snow total. (to see the nitty-gritty math details on this, read more here.) So we can never know for sure the exact rain/snow falling using just radar. The good news is we've at least done lots of experiments and come up with some fairly useful best-practice formulas for using the Z-R ratio in different scenarios. Good, but not perfect.
The following is multiple choice question (with options) to answer.
What determines which type of precipitation falls? | [
"air pressure",
"air temperature",
"air currents",
"ground temperature"
] | B | Why does it snow instead of rain? Air temperature determines which type of precipitation falls. Rain falls if the air temperature is above freezing (0° C or 32° F). Frozen precipitation falls if the air or ground is below freezing. Frozen precipitation may fall as snow, sleet, or freezing rain. You can see how the different types form in Figure below . |
SciQ | SciQ-1550 | geology, fossil-fuel, petroleum
For some transport applications, the energy density is still a winning attribute of hydrocarbons: most notably, powered flight for freight and travel.
We already have two routes to non-fossil hydrocarbons: biological sources, and direct chemical synthesis. Each involves capturing atmospheric CO2, and combining with water, to generate a blend of hydrocarbons.
Now, we already have means of creating hydrocarbons suitable for flight (e.g. Jet-A and Jet-A1 fuels). And there are already demonstration plants that have closed-loop generation of synthetic hydrocarbons, for use in electricity-grid-balancing, by using surplus electricity to synthesise methane, which is then burnt in gas turbines when required. Similarly, Tony Marmont's team have been synthesising petrol (gasoline) from air, water, and electricity.
However, none of those things mean that hydrocarbons necessarily have much of a future, beyond plastics production. Because hydrocarbon-powered aviation has a lot of environmental problems beyond just CO2 emissions, in particular it makes other contributions to exacerbating global warming. And there are lots of options for energy storage within the electricity supply chain.
The following is multiple choice question (with options) to answer.
Algae is a promising alternative to traditional crops for what type of fuels? | [
"fertilizer",
"fossil",
"non-renewable",
"biofuel"
] | D | Algae is the focus of much research. Algae is a very promising alternative to traditional crops for biofuels. |
SciQ | SciQ-1551 | cell-biology, cancer, cloning
Title: Difference between clonal and subclonal mutations I'm a physicist writing a proposal that has to do with cancer as a disease driven by evolutionary selection. As far as I understand, all tumors start with a single precursor (single cell or group of cells), and the other cells derive from this precursor by cycles of alterations and selection processes.
Reading recent articles, such as this, I learned that the derived cells include both clones and subclones. Since I'm not sure I understood things correctly, I have a few questions on the difference between the two words:
Is it OK to call clones the cells derived from the precursors?
When should I use subclones?
In the case of heterogeneity, is it fine to call clonal population a group of clones with the same characteristics? clones means when a cell has the same DNA characteristics as his predecessor so in that case of yours you could say that those cells are clones while for sub-clones I am not that sure, the difference of clone and sub-clone is that a sub-clone is basically a clone who is then remade with a different characteristic(an upgrade if you will) , since cancer are mutated cells you could call them like that but only if you study its DNA, meaning you have to study deep to find out if there are sub-clones in there. AS for the 3 question I didn't quite understood what you meant cuz you just used 2 words with opposite meaning because heterogeneity means a group of organismes with different characteristics and clonal population means organismes with same DNA ( much like a colony of bacteria).
The following is multiple choice question (with options) to answer.
Cancers derived from epithelial cells are referred to as what? | [
"carcinomas",
"adenomas",
"nodules",
"caricatures"
] | A | Tissues and Cancer Cancer is a generic term for many diseases in which cells escape regulatory signals. Uncontrolled growth, invasion into adjacent tissues, and colonization of other organs, if not treated early enough, are its hallmarks. Health suffers when tumors “rob” blood supply from the “normal” organs. A mutation is defined as a permanent change in the DNA of a cell. Epigenetic modifications, changes that do not affect the code of the DNA but alter how the DNA is decoded, are also known to generate abnormal cells. Alterations in the genetic material may be caused by environmental agents, infectious agents, or errors in the replication of DNA that accumulate with age. Many mutations do not cause any noticeable change in the functions of a cell. However, if the modification affects key proteins that have an impact on the cell’s ability to proliferate in an orderly fashion, the cell starts to divide abnormally. As changes in cells accumulate, they lose their ability to form regular tissues. A tumor, a mass of cells displaying abnormal architecture, forms in the tissue. Many tumors are benign, meaning they do not metastasize nor cause disease. A tumor becomes malignant, or cancerous, when it breaches the confines of its tissue, promotes angiogenesis, attracts the growth of capillaries, and metastasizes to other organs (Figure 4.22). The specific names of cancers reflect the tissue of origin. Cancers derived from epithelial cells are referred to as carcinomas. Cancer in myeloid tissue or blood cells form myelomas. Leukemias are cancers of white blood cells, whereas sarcomas derive from connective tissue. Cells in tumors differ both in structure and function. Some cells, called cancer stem cells, appear to be a subtype of cell responsible for uncontrolled growth. Recent research shows that contrary to what was previously assumed, tumors are not disorganized masses of cells, but have their own structures. |
SciQ | SciQ-1552 | waves, string
Regarding the vibrating drum head: Each tiny portion of the moving drum head (which has springiness and mass!) is connected to a little slab of air right next to it, and each little slab of air is then connected to another little slab of air right next to it- just like the rope example, except now we are in THREE dimensions. Each of those little slabs has springiness (air is compressible) and it has mass too, and so once again you get wave motion being coupled from the 2-dimensions of the drum head to 3-dimensional space. In this case, the waves are compressive and they are free to spread sideways because there are no walls or edges to get in the way.
So wave motion is all about connecting little springs and masses into a continuous network in one, two, or three dimensions, and then shaking one end of it.
The following is multiple choice question (with options) to answer.
Vibrating objects such as drumheads produce what? | [
"negative ions",
"sound energy",
"heat",
"light"
] | B | Vibrating objects such as drumheads produce sound energy. |
SciQ | SciQ-1553 | astrochemistry, infrared, sofia
This is the first molecule to be produced with any important level of abundance. Note, this appears to be a somewhat arbitrary definition, since it is also claimed (e.g. Lepp et al. 2002), that He$_{2}^{+}$ formed the first molecular bond, via He$^+ +$ He, but was too weakly bound to survive in any concentration (the concentration peaks about 100 times lower than HeH$^+$ according to Galli & Palla 2013).
It is also possible to form small quantities of $H_2$ at $z> 2000$ via the reaction of a hydrogen atom with another in an excited state: H + H$^* \rightarrow$ H$_2$; but of course, although the hydrogen molecule is much more strongly bound than HeH$+$ (the dissociation energy of $H_2$ is 4.5 eV, versus about 1.8 eV for HeH$^+$), there is very little atomic hydrogen present and this reaction requires not one, but two hydrogen atoms to get together. It is not until H atoms recombine in quantity some 260,000 years later that hydrogen molecules are formed in various gas phase processes and H$_2$ becomes the dominant molecular species.
The dihydrogen cation, H$_2^{+}$ cannot form directly before either helium hydride or atomic hydrogen are formed as precursors. e.g.
$$ {\rm HeH}^{+} + {\rm H} \rightarrow {\rm H}_2^{+} + {\rm He}$$
$$ {\rm H} + {\rm H}^+ \rightarrow {\rm H}_2^{+}$$
and thus H$_2^{+}$ forms after HeH$^+$.
The following is multiple choice question (with options) to answer.
What two element makes up a hyrdocarbon? | [
"carbon and hydrogen",
"hydrogen and carbonite",
"nitrogen and carbon",
"helium and carbon"
] | A | The simplest organic compounds are hydrocarbons and are composed of carbon and hydrogen. |
SciQ | SciQ-1554 | organic-chemistry, nomenclature
P-102.3.4 Cyclic forms of monosaccharides
Most monosaccharides exist as cyclic hemiacetals or hemiketals. Two aspects of the internal cyclisation must be examined: first, the size of the ring, and secondly, the conformation of the newly created chirality center.
P-102.3.4.1 Ring size
Out of the various possible heterocyclic ring sizes resulting from hemiacetal or hemiketal formation, those with five and six members, including an oxygen atom, prevail and are discussed in this Section. Their names are based on those of the parent heterocycles furan and pyran, respectively. Names are formed by including the terms ‘furan’ and ‘pyran’ before the ending ‘ose’ in the name of a sugar. (…)
Thus, the retained name ᴅ-glucose is changed to ᴅ-glucopyranose to indicate the cyclic form having a six-membered ring.
P-102.3.4.2 Anomeric forms; the stereodescriptors ‘α’ and ‘β’
P-102.3.4.2.1 In the cyclic form, the configuration of the newly created chirality center ‘C-1’ must be expressed. This center is called the ‘anomeric center’. The two stereosiomers are called ‘anomers’; they are designated by the stereodescriptors ‘α’ and ‘β’ according to the configurational relationship between the anomeric center and the so called ‘reference center’.
P-102.3.4.2.2 Configurations ‘α’ and ‘β’ for monosaccharides
The anomeric reference center in a monosaccharide having a retained name is the configurational atom as defined in P-102.3.3. (…)
The anomeric stereodescriptor ‘α’ or ‘β’, followed by a hyphen, is placed immediately before the configurational stereodescriptor ‘ᴅ’ or ‘ʟ’ of the carbohydrate name.
Therefore, the resulting name for the β-pyranose form of ᴅ-glucose is β-ᴅ-glucopyranose.
The following is multiple choice question (with options) to answer.
What are monosaccharides and disaccharides also called? | [
"complex sugars",
"simple sugars",
"basic sugars",
"simple chemicals"
] | B | An example of a disaccharide is sucrose (table sugar), which consists of the monosaccharides glucose and fructose ( Figure below ). Other common disaccharides include lactose ("milk sugar") and maltose. Monosaccharides and disaccharides are also called simple sugars . They provide the major source of energy to living cells. |
SciQ | SciQ-1555 | zoology, ecology, species-distribution, migration
Title: How do animals end up in remote areas? I was thinking specifically about random marshy water holes on farmers fields. It seems that you can visit just about any one of these and you will find frogs if you look hard enough.
They usually don't seem to be connected to each other. If it were any other land animal I would figure they walk from one spot to another, but in the case of frogs, I don't imagine their range is very vast. But often these marshy spots can be separated by fairly large distances to a frog.
So this brings me to my question: how do each of these spots end up with frogs in them? I don't imagine a frog is going to go hopping over a hill to get to a marsh on the other side, is it? This question pertains to organism dispersal, which is a very active field of study with relation to it's impact on conservation efforts. Much of what I will say below has been covered in this wiki.
Definition: From the Wiki
Technically, dispersal is defined as any movement that has the
potential to lead to gene flow.
It can be broadly classified into two categories:
Density dependent dispersal
Density independent dispersal
The question of frogs and fishes both refer to Density independent dispersal, while an example of density independent dispersal can be the competition for habitat space between big cats and humans (this is a WWF pdf)
From the wiki:
Density-independent dispersal
Organisms have evolved adaptations for dispersal that take advantage
of various forms of kinetic energy occurring naturally in the
environment. This is referred to as density independent or passive
dispersal and operates on many groups of organisms (some
invertebrates, fish, insects and sessile organisms such as plants)
that depend on animal vectors, wind, gravity or current for dispersal.
Density-dependent dispersal
Density dependent or active dispersal for many animals largely depends
on factors such as local population size, resource competition,
habitat quality, and habitat size.
Currently, some studies suggest the same.
This study in particular studied the movement and habitat occupancy patterns within ephemeral and permanent water bodies in response to flooding. They found that during flooding these frogs moved out to flooded ephemeral water bodies and later on moved back again to the permanent ones.
Other suggested readings for those highly interested in the subject may include this (a phd thesis) and this (a project report)
The following is multiple choice question (with options) to answer.
Terrestrial biomes are associated with land, while aquatic ones are associated with what? | [
"water",
"air",
"blood",
"plants"
] | A | 20.3 Terrestrial Biomes Earth has terrestrial and aquatic biomes. Aquatic biomes include both freshwater and marine environments. There are eight major terrestrial biomes: tropical rainforests, savannas, subtropical deserts, chaparral, temperate grasslands, temperate forests, boreal forests, and Arctic tundra. The same biome can occur in different geographic locations with similar climates. Temperature and precipitation, and variations in both, are key abiotic factors that shape the composition of animal and plant communities in terrestrial biomes. Some biomes, such as temperate grasslands and temperate forests, have distinct seasons with cold and hot weather alternating throughout the year. In warm, moist biomes, such as the tropical rainforest, net primary productivity is high as warm temperatures, abundant water, and a year-round growing season fuel plant growth. Other biomes, such as deserts and tundra, have low primary productivity due to extreme temperatures and a shortage of water. |
SciQ | SciQ-1556 | 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.
Different shapes often correlate with different what in cells? | [
"enzymes",
"functions",
"systems",
"types"
] | B | Cells with different functions often have different shapes. The cells pictured in Figure below are just a few examples of the many different shapes that cells may have. Each type of cell in the figure has a shape that helps it do its job. For example, the job of the nerve cell is to carry messages to other cells. The nerve cell has many long extensions that reach out in all directions, allowing it to pass messages to many other cells at once. Do you see the tail-like projections on the algae cells? Algae live in water, and their tails help them swim. Pollen grains have spikes that help them stick to insects such as bees. How do you think the spikes help the pollen grains do their job? ( Hint: Insects pollinate flowers. ). |
SciQ | SciQ-1557 | cell-biology, cell, eggs, reproductive-biology, chickens
Title: Why are hard boiled eggs so homogeneous? A eukaryotic animal cell is a complicated piece of biological machinery. Some major structures inside of the cell (see the image below) include: the nucleus, mitochondria, Golgi vesicles, and various tubular structures. Why then is the single-celled, unfertilized chicken egg so homogeneous when it is cooked (or before)? The only major structure I can recognize is the cell nucleus.
*Image Credit: "Animal cell structure en" by LadyofHats (Mariana Ruiz) - Own work using Adobe Illustrator. Image renamed from Image:Animal cell structure.svg. Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Animal_cell_structure_en.svg#mediaviewer/File:Animal_cell_structure_en.svg Disclaimer: This is my understanding of the egg anatomy as a general biologist. There is most certainly better references and sources out there to explain this (please add better references if you know of any).
If I understand you correctly, your question is why we do not see cell organelles in a cracked or boiled egg. If so, your question seems to stem from a misunderstanding of what the egg white and egg yolk represents. A chicken egg is not simply an enlarged cell, and the egg yolk is not the cell nucleus.
When an oocyte matures in the chicken ovary, it stores yolk inside the cell and therefore enlarges. The yolk is therefore part of the oocyte cytoplasm. However, as it enlarges, the yolk is separated from the germinal disc, which holds all the other cell organelles (including the nucleus). The germinal disc is seen as a small white area on the egg yolk. Eventually, when the oocyte has accumulated enought yolk, it disattaches from the ovary (ovulation) and goes into the hens oviduct. This process is happening continuously, and oocytes of different stages of maturation are present on the ovary, which can be seen in this image:
The following is multiple choice question (with options) to answer.
What structure is found at the top of the head of the sperm that helps it penetrate and fertilize the egg? | [
"acrosome",
"centriole",
"axial filament",
"terminal disc"
] | A | of human sperm as well as a diagram of the parts of the sperm. An acrosome is found at the top of the head of the sperm. This structure contains lysosomal enzymes that can digest the protective coverings that surround the egg to help the sperm penetrate and fertilize the egg. An ejaculate will contain from two to five milliliters of fluid with from 50–120 million sperm per milliliter. |
SciQ | SciQ-1558 | tissue
Title: What are the main differences between lab-grown tissues and natural tissues from living animals? What are the main differences between lab-grown tissues and natural tissues from living animals?
Using a biologist's classic "structure (anatomy) and function (physiology)" idea, I thought about the followings:
Structure:
It might be difficult to recreate the composition of different tissues / cells in living things precisely with artificial methods. This may lead to bad results when the tissue is used for tests of medicines and cosmetics.
Function:
Cells might not function and produce as expected (or is harder to make them function) in artificial compositions, as cells need strictly regulated environments to function correctly.
The following is multiple choice question (with options) to answer.
What makes up most of biological tissues? | [
"water",
"bone",
"muscle",
"air"
] | A | Biological tissue consists primarily of water, which absorbs electromagnetic radiation in the infrared region of the spectrum. Suggest a plausible reason for using carbon dioxide lasers in surgery. |
SciQ | SciQ-1559 | organic-chemistry, reaction-mechanism, alcohols
The primary carbon will not, as stated above, form a primary carbocation since it is too unstable. Hence only the bimolecular substitution will occur. If no primary carbocation is generated, no Wagner-Meerwein rearrangement can occur. And the mechanism of an $\mathrm{S_N2}$ reaction does not allow bromide’s (or anything else’s) migration.
The secondary carbon could undergo bimolecular substitution, too. The reaction rate will probably be slower than that of fragmentation and rearrangement, though, since the latter are unimolecular processes. And other shifts (e.g. methyl followed by hydride) are possible but again slower since you need to shift twice. All in all, a higher proportion of side-products may be expected.
In no case will the bromide shift after substitution; any shift would need to occur before.
The following is multiple choice question (with options) to answer.
What occurs when some substances change chemically to other substances? | [
"chemical reaction",
"hormonal reaction",
"spontaneous mutation",
"toxic reaction"
] | A | A chemical reaction occurs when some substances change chemically to other substances. Chemical reactions are represented by chemical equations. |
SciQ | SciQ-1560 | species-identification, zoology, entomology, food, pest-control
Title: Questions about insects eating flour and living in the cracks of a wooden cutting boards I have a large wooden cutting board which is used in my kitchen mainly for preparing egg pasta. The wood type is Populus (poplar or aspen or cottonwood).
The main ingredients used with the cutting board are: flour (mainly soft wheat flour), hens' eggs, white sugar, butter, and baking powder.
After the food preparation, the cutting board is cleaned by scraping away the ingredients remains.
The board has some cracks and some small unknown insects are living inside the cracks.
The board has also a lot of holes due to woodboring beetles but I think the woodworms operated long time ago and they no longer live in the cutting board.
The unknown insect has an approximate length of 1 mm (along the direction of their movements) and a width of 0.3 mm. The unknown insects do not have wings, they just walk. I am not able to see how many pairs of legs they have.
The color of the insect is pale brown.
The cutting board was free from these unknown insects some months ago but then they appeared.
My questions:
What insects are they?
Are these insects poisonous to humans?
How can I get rid of them?
Update
The unknown insects could be Acarus siro, I will try to get a picture of the insects.
Update 2
Here is a picture. The bottom part of the image is a one Euro coin, the top part of the image is a caliper (each bright area is one mm tick).
Some more pictures: This is a species of psocid (of the family Psocoptera, AKA booklice).
The following is multiple choice question (with options) to answer.
What type of butterfly do birds avoid eating since it makes them sick? | [
"sphingidae",
"monarch butterflies",
"noctuidae",
"pyralidae"
] | B | Many birds learn to avoid eating monarch butterflies, like the one pictured in Figure below . Monarch butterflies taste bad and make birds sick. In this case, the behavior is learned because it is punished with a nasty taste and illness. |
SciQ | SciQ-1561 | ornithology, kidney
Back to worrying about the mammal-centric thinking: there is a causal implication in both the original and my edited version that is not warranted, which is that the anatomy of the loops of Henle is somehow determining the nitrogen excretion strategy that birds use. It's equally reasonable to presume that birds don't need long loops of Henle since they evolved an alternative excretion mechanism that makes it unnecessary to concentrate urine to a great degree.
The "trick" of that alternative excretion mechanism is using uric acid and excreting a paste. Because uric acid crystalizes and comes out of solution, it doesn't "count" toward osmolarity of the urine, it's excreted as a solid. Birds don't need to remove water to crystalize uric acid, and don't need to use water to flush it out at all, it falls out of solution on its own because it's not very soluble. You could add a bunch of extra water and it would still stay mostly solid rather than dissolving.
So back to your original question: how do birds concentrate their urine? Well, pretty much the same way we do as far as the kidney goes. They also pull some water back in through the cloaca before urine is released, similar to how mammals pull water in from stool in the large intestine. The important difference is not how birds concentrate their urine (because urine concentration isn't a goal/need in itself), but rather how birds excrete nitrogen waste. By not flushing soluble nitrogenous waste with water in the first place, they don't have as much urine to concentrate, so it's less important for them to be very efficient in doing so.
The following is multiple choice question (with options) to answer.
Birds possess a cloaca, a structure that allows water to be reabsorbed from waste back into this? | [
"intestines",
"skin",
"eggs",
"blood stream"
] | D | Other modifications that reduce weight include the lack of a urinary bladder. Birds possess a cloaca, a structure that allows water to be reabsorbed from waste back into the bloodstream. Uric acid is not expelled as a liquid but is concentrated into urate salts, which are expelled along with fecal matter. In this way, water is not held in the urinary bladder, which would increase body weight. Most bird species only possess one ovary rather than two, further reducing body mass. The air sacs that extend into bones to form pneumatic bones also join with the lungs and function in respiration. Unlike mammalian lungs in which air flows in two directions, as it is breathed in and out, airflow through bird lungs travels in one direction (Figure 29.32). Air sacs allow for this unidirectional airflow, which also creates a cross-current exchange system with the blood. In a cross-current or counter-current system, the air flows in one direction and the blood flows in the opposite direction, creating a very efficient means of gas exchange. |
SciQ | SciQ-1562 | cell-biology, neuroscience, histology
Although the paper mainly talks of the sorting of axonal and somatodendritic vesicles as seen in the picture, they also seem to apply for the RER which actually are the basis for Nissl's granules.
This structure excludes not only somatodendritic vesicles but also larger organelles, such as the Golgi complex and the rough ER, in effect constituting the cytoplasmic boundary for the somatodendritic and axonal domains..... The exclusion of the rough ER and Golgi complex, in addition to somatodendritic vesicles, at the PAEZ suggests that a common restriction mechanism may operate for all of these organelles.
Well, as you might have understood by now, it's not a matter of the size of the axon/ dendrite since same sized vesicles are being diverted in either direction and as previously mentioned, even mitochondria enter the axon.
The following is multiple choice question (with options) to answer.
What contain organelles common to other cells, such as a nucleus and mitochondria, and also have more specialized structures, including dendrites and axons? | [
"blood cells",
"muscle cells",
"follicles",
"neurons"
] | D | Figure 16.19 Neurons contain organelles common to other cells, such as a nucleus and mitochondria. They also have more specialized structures, including dendrites and axons. |
SciQ | SciQ-1563 | meteorology, wind, tropical-cyclone, storms, tornado
Title: Why is there no middle ground between tornadoes and hurricanes? A tornado has an effective area of destruction about the size of a city block.
A hurricane spans several hundred kilometers.
However, there doesn't seem to be a continuum between the two. Why are there no vortex windstorms on the scale of a city? Is it because tornadoes and hurricanes have different formation mechanisms? Or is there a reason why city-sized vortices would be so weak as to be un-newsworthy? Tornadoes are the result of small-scale effects such as the convergence of updraft/downdraft regions in a single thunderstorm, the stretching or entrainment of vertical vorticity, wind shear profiles, and even friction with the ground.
Hurricanes rely on massive amounts of latent heat release from an atmosphere moistened by warm ocean waters causing rising air and lower pressure over a wide area. This allows the Coriolis effect to act, sculpting airflow into a spiral pattern. Under normal conditions, the Coriolis effect is only applicable over a large area (don't get me started on the toilet myth).
There are some intermediate types of circulations. A mesocyclone is roughly city-sized (and these are often associated with tornadoes). A mesoscale convective vortex can form out of a thunderstorm complex and are roughly state-sized (usually more of an Indiana than a Texas). There have been very small hurricanes and typhoons (look up Tropical Storm Marco or Typhoon Tracy).
Extending the scale upward, the normal "synoptic" low pressure systems associated with cold and warm fronts and usually bigger than hurricanes, and upper-level circulations can be continent-sized.
The following is multiple choice question (with options) to answer.
Hurricanes and winter storms both develop from what, which often form when the jet stream dips south in the winter? | [
"waves",
"typhoons",
"cyclones",
"tides"
] | C | 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. Blizzards and lake-effect snow storms are two types of winter storms that occur in the U. S. |
SciQ | SciQ-1564 | neuroscience
Title: Nervous system : Nerve signals If the electrical signals from all the various organs throughout the body eventually connect to the nerves in the spinal column traveling up to the brain, how does the brain differentiate the different signals. Is the nerve in the spinal column like an electrical conduit with many wires inside? Yes is the simple answer. A nerve will go up to a specific part of the brain which the brain knows corresponds to a certain region of the body. It isn't perfect though e.g. pain in the diaphragm confuses the brain which doesn't recognise that pain must be coming from there so instead tells the body there is shoulder pain, however this is useful in medicine. Another infamous example is pain from heart disease (angina) which causes pain in the jaw and arm. Perhaps even more interestingly, if a nerve is cut and then grows back linking to the wrong nerve it may lead to the completely wrong part of the body being identified when touched. Also if the brain itself is stimulated in these corresponding areas, a person will feel he or she is indeed being touched in a certain part of the body.
The following is multiple choice question (with options) to answer.
Which body system controls all the others by sending electrical messages? | [
"the nervous system",
"the endocrine system",
"the localized system",
"the specialized system"
] | A | The nervous system sends electrical messages throughout the body and controls all other body systems. |
SciQ | SciQ-1565 | thermodynamics, evaporation, gas, liquid-state
On the water surface, knowing the temperature, we can estimate the vapor pressure and vapor mixture fraction. Then there will be an diffusion process for the water vapor to move out and for the ambient air to move in. Because the water surface doesn't allow the air to further move, a circulation forms. When the water vapor moves out, the water vapor pressure drops, so more liquid water evaporates to fill up the loss of water vapor. The evaporation associates latent heat so water surface area temperature drops (you may see dew on the bowl wall). Then a heat transfer process starts which may initiate water circulation as well.
As this is complex, doing test might be a quick way to get the K value if you assume it is a constant, which is questionable.
The following is multiple choice question (with options) to answer.
What occurs when water on the surface changes to water vapor? | [
"evaporation",
"oxidation",
"condensation",
"photosynthesis"
] | A | Evaporation occurs when water on the surface changes to water vapor. The sun heats the water and gives water molecules enough energy to escape into the atmosphere. |
SciQ | SciQ-1566 | earth-rotation, geologic-layers
Title: Do Earth's layers move at different speeds? I don't have a background in Geology but this question popped in my head the other day and can't find an answer anywhere else.
If I remember science class correctly, Earth's layers have different element compositions. Would it be correct to assume that they have different densities and different frictions as a result? And if they do, does it follow from it that they rotate at different speeds?
Thanks. Im am currently doing my masters in geophysics (last semester) and before that I did a bachelor in geoscience.
I assume by layers you mean the crust, the mantle and the core.
These all have different composition and also different densities. But the earth rotates as a whole, not the individual layers, all layers have the same angular velocity. That means they all make one rotation per day.
These layers are also not the perfect boundaries we like to imagine, but more a change in properties around a finite depth. This depth can even change at different places.
The following is multiple choice question (with options) to answer.
What is the position of rock layers and the relative ages called? | [
"metamorphism",
"bifurcation",
"diffraction",
"superposition"
] | D | Superposition refers to the position of rock layers and their relative ages. Relative age means age in comparison with other rocks, either younger or older. The relative ages of rocks are important for understanding Earth’s history. New rock layers are always deposited on top of existing rock layers. Therefore, deeper layers must be older than layers closer to the surface. This is the law of superposition . You can see an example in Figure below . |
SciQ | SciQ-1567 | genetics
Title: What distinguishes Mendelian Inheritance from Non-Mendelian Inheritance? I'm having some trouble determining what exactly is the difference between Mendelian inheritance and non-Mendelian inheritance. For instance, I understand that chromosomal abnormalities such as Down's Syndrome fall under non-Mendelian inheritance because they concern chromosomes, not single genes. And I also understand that Mendelian inheritance concerns single genes, as in Sickle-cell anemia (which is an autosomal recessive disorder).
What confuses me is the fact that our textbook discusses dihybrid and trihybrid (concerning 2 genes and 3 genes, respectively) crosses under the Mendelian inheritance chapter, when to me it seems like these crosses are non-Mendelian because they deal with multiple genes. However, Gregor Mendel did in fact use the dihybrid cross to deduce the law of independent assortment, so I'm completely confused. Could someone please clarify this for me? I'm afraid that I'm maybe misinterpreting something. You can discuss multiple genes within the framework of Mendelian inheritance; what you're probably thinking of, though, is the fact that Mendelian inheritance doesn't recognize the idea of multiple genes that contribute to a single trait.
For example, if there is a gene that controls petal color (blue vs. white, with blue = dominant) and a gene that controls height (short vs. tall, with tall = dominant), then Mendelian inheritance predicts that two short plants with white flowers will only produce short plants with white flowers.
But if there are multiple genes that interact to determine height in a complex way, that's outside the scope of Mendelian inheritance.
The following is multiple choice question (with options) to answer.
What is the field of biology that focuses on the study of inheritance in humans? | [
"generational biology",
"relational biology",
"human genetics",
"computational biology"
] | C | Human genetics is the field of biology that focuses on the study of inheritance in humans. |
SciQ | SciQ-1568 | acid-base, ph
Title: Why can't the strength of superacids be measured in water? I learned about acid strength, that the strength of an acid increases with it's degree of ionization when solvated. So, in water, a strong acid is one where $\ce{[H_3O^+]}$ is large, which is equal to a low pH: $\mathrm{pH=-log[H_3O^+]}$.
Considering extreme cases, such as superacids, I have found out that other methods are used to measure their acidity (methods I don't really understand). My question is why is it impossible to simply get super high concentrations of $\ce{[H_3O^+]}$ in aqueous solutions of superacids, and use this to determine the acid strength. Also, is pH used as a measure of acidity outside of aqueous solutions?
I have come over the leveling effect, but I don't think I fully understand it. The way I understand it (for the case with water as solvent) is that basically any acid in water will protolyze $\ce{H2O}$ to $\ce{H3O+}$, making this the effective acid. I don't understand why this would affect the measured pH, as it is $\ce{[H_3O^+]}$ you are measuring. Any acid-base reaction is always an equilibrium:
$$\ce{HA^1 + (A^2)- <=> (A^1)- + HA2}\tag{1}$$
and for each pair of acids $\ce{HA^1}$ and $\ce{HA^2}$ you could calculate a $K_\mathrm{a}$ value to determine one acid’s strength with respect to the other. This $K_\mathrm{a}$ value is typically calculated according to equation $(2)$ if $\ce{(A^2)-}$ (which does not have to feature a negative charge; I just wanted to avoid different descriptions for the two acids) is the solvent.
The following is multiple choice question (with options) to answer.
The acidity of a solution is typically assessed experimentally by measurement of its what? | [
"color",
"ph",
"density",
"mass"
] | B | The acidity of a solution is typically assessed experimentally by measurement of its pH. The pOH of a solution is not usually measured, as it is easily calculated from an experimentally determined pH value. The pH of a solution can be directly measured using a pH meter (Figure 14.4). |
SciQ | SciQ-1569 | energy, electrostatics, potential-energy
Title: where is electrostatic potential energy stored?
Potential energy can be defined as the capacity for doing work which arises from position or configuration.In the electrical case, a charge will exert a force on any other charge and potential energy arises from any collection of charges.
Where is this potential energy stored and how? That actually gets a bit tricky at the advanced level, but at the basic level, you should find somewhere in your textbook the equation $U = \int d^3x \left(\frac{1}{2} |\vec{E}|^2 \right)$ (maybe with a different constant up front, depending on what system of units the book is using). So at any point in space, the electric field $\vec{E}(\vec{x})$ at that point "stores" an amount of potential energy $\frac{1}{2} |\vec{E}|^2$.
The following is multiple choice question (with options) to answer.
Where is chemical energy stored? | [
"ribosomes",
"cell wall",
"nucleus",
"atom bonds"
] | D | 2. Chemical energy is energy that is stored in the bonds between the atoms of compounds. If the bonds are broken, the energy is released and can be converted to other forms of energy. |
SciQ | SciQ-1570 | energy, fuel, environmental-chemistry
Title: Effect of coal and natural gas burning on particulate matter pollution I sometimes hear people talking about how we should replace coal burning plants with natural gas ones, to alleviate the case of particulate matter pollution. What exactly is the difference between coal fuel and natural gas that makes the latter seem "cleaner"?
At the same energy outcome, natural gas produces less carbon dioxide than coal. In a way, natural gas is half way between coal and hydrogen.
Coal produces smelly smoke, solid particles, sulfur dioxide and minor or trace heavy metal pollutants.
It is less known to common people, but power plants burning coal are more significant source of radioactive pollution than nuclear plants. This pollution is very diluted, but rather significant in absolute amount. Coal ash, used in past as a filler for some construction materials, has lead in some cases to significantly increased content of radium-226 in building walls. This radium is a product of long term decay of natural uranium. It further decays while producing radioactive gaseous radon-222, which is dangerous in long term inhalation because of lung cancer. As it stays in lungs as polonium-218 and its decay products.
See e.g. Uranium produced from coal ash
... the uranium concentration in the ash pile is about 150-180 parts per million, about 1/4th of the concentration often thought of as commercially viable for ISL[In Situ Leaching] mining. However, coal ash piles have some physical characteristics that might help overcome that disadvantage since they may be easier to drill and it might be easier to protect the local groundwater from contamination. ...
See Radon in building materials by Czech government agency for radiation protection.
The following is multiple choice question (with options) to answer.
What kind of fuels include coal, oil, and natural gas? | [
"storage",
"ancient",
"sediment",
"fossil"
] | D | Fossil fuels include coal, oil, and natural gas. Fossil fuels are the greatest energy source for modern society. Millions of years ago, plants used energy from the Sun to form carbon compounds. These compounds were later transformed into coal, oil, or natural gas. Fossil fuels take millions of years to form. For this reason, they are non-renewable. We will use most fossil fuels up in a matter of decades. Burning fossil fuels releases large amounts of pollution. The most important of these may be the greenhouse gas carbon dioxide. |
SciQ | SciQ-1571 | geophysics, plate-tectonics, earth-history, continent
Title: Why Do Supercontinents Form? It would seem, on the face of it, improbable that the continental land-masses would accumulate into a single composite, yet it has happened numerous times, and is expected to again in the future.
There must likely then be some aspect of plate tectonics which favors these arrangements.
Can anyone provide an explanation?
EDIT: This is not, as I see it, a duplicate of the 'What are the causes of the supercontinent cycle?' question. This question goes to what process drives the formation of any & all supercontinent formations, which I assert should be improbable, made more improbable by their recurrence, not so much the cycle itself. The other question did not address this more fundamental aspect, or in any case receive a pertinent account of its resolution. If anyone wants to engage on this, or doesn't see the distinction, please do so in the comments or a chat. I think the mechanisms that you're looking for are subduction, paired with the "stickiness" of continental crust.
The subduction of oceanic crust under continental crust inevitably creates a net movement of crustal material toward a continental plate. Any oceanic plate that is carrying continental material will therefore always drag that continent toward the continental plate that it is subducting underneath, always resulting in eventual collision.
If an oceanic plate has subduction occurring on both sides, the ocean will inevitably narrow until it closes, thereby causing the continental plates on either side to collide.
In every case, subduction inevitably pulls continents together.
Furthermore, once continental plates collide, they have a tendency to stick together for long periods of time, increasing the likelihood that all continental material will eventually accumulate there.
The following is multiple choice question (with options) to answer.
What do you call the slope that forms the edge of the continent? | [
"the prevalent slope",
"the cataclysmic slope",
"the continental slope",
"the land slope"
] | C | The continental slope is the slope that forms the edge of the continent. It is seaward of the continental shelf. In some places, a large pile of sediments brought from rivers creates the continental rise. The continental rise ends at the ocean floor. Much of the ocean floor is called the abyssal plain. |
SciQ | SciQ-1572 | The images for the contours shamelessly taken from this and this answer on the site.
• Thank you so much! Is there any way you could attach a diagram depicting the integration path? It would render the explanation far more lucid, as far as I am concerned, and would be most appreciated. – Grtv Jan 20 '14 at 16:10
• I'm terrible with pictures, I'll see if I can figure out how to draw one, but I make no promises. – Daniel Fischer Jan 20 '14 at 16:16
• Here's a suggestion - perhaps you could find a diagram online which represents to some extent the same rationale and provide the link. – Grtv Jan 20 '14 at 16:32
• For your path, the search term would be "keyhole contour". That's pretty standard, should turn up a few items (I guess there's a good chance that you can search better than I, I'll try nevertheless). For the sector, I'm not sure what the terms should be. Let's see if I can find something. – Daniel Fischer Jan 20 '14 at 16:39
• I've found some contours on site, hope the pictures help. If not, tell me what I could explain better. – Daniel Fischer Jan 20 '14 at 17:09
The following is multiple choice question (with options) to answer.
What do contour lines that are close together indicate? | [
"deep slope",
"flat slope",
"close slope",
"steep slope"
] | D | 1. The spacing of contour lines shows the slope of the land . Contour lines that are close together indicate a steep slope. This is because the elevation changes quickly in a small area. Contour lines that seem to touch indicate a very steep slope, like a cliff. When contour lines are spaced far apart, the slope is gentle. So contour lines help us see the three-dimensional shape of the land. |
SciQ | SciQ-1573 | neuroscience, cancer
Title: Can neurons become cancerous? I've been reading about brain cancer lately, and something I've noticed is that the tumors seem to start in all tissues, except neural tissue. Am I missing something, or is there an explanation? Short answer
Neuronal tumors are rare, but they do exist. These cancers develop from neuroblast cells, a population of undifferentiated, dividing precursor cells that will eventually fully differentiate into functional neuronal cells.
Background
Most neuronal cell types have lost their ability to divide, because of their progressed state of differentiation. There are but a few regions in the brains that generate new nerve cells in adulthood, for example in the hippocampus where neuro-regeneration is believed to be involved in memory formation. Because of the rarity of cell division of neuronal cells in adulthood, neural cancers are rare.
The point where neuronal cells actively divide is during development. These cells are basically still stem cells. A prime example here are retinoblastomas. These are tumors in the photosensitive part of the eye, namely the retina. During early development stem cells actively divide to lay down a layered structure in the back of the eye eventually forming the rods and cones and other visual cells. If this division process goes out of control, tumors can develop. Retinoblasomas can now be diagnosed in utero (Paquette et al., 2012).
Tumors with a neuronal origin developing post natally are rare, but do exist. Neuroblastoma being a prime example. This is a rare cancer (prevalence of 1:100,000) most commonly found in children younger than age 5. It affects the sympathetic nervous system, which regulates involuntary bodily functions such as heart rate, blood pressure, breathing, and digestion. Neuroblastoma typically begins in the nerve tissues of the adrenal glands but may also begin in the nerves that are located anywhere along the spinal cord, including the neck, chest, or abdomen. The cancer can metastasize (spread) to other organs.
The following is multiple choice question (with options) to answer.
What is the most common type of cancer developed in children? | [
"lung cancer",
"anemia",
"leukemia",
"stomach cancer"
] | C | Childhood cancer is rare. The main type of cancer in children is leukemia. It makes up about one third of all childhood cancers. It occurs when the body makes abnormal white blood cells. |
SciQ | SciQ-1574 | human-biology, physiology, cardiology, anatomy
Title: Can humans live without their right atrium? The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated blood from the superior and inferior venae cavae, the coronary sinus, and the anterior and smallest cardiac veins, and pumps it into the right ventricle through the tricuspid valve.
Can humans survive without right atrium? In this condition blood would fill the right ventricle directly, comparable to some animals like frogs, toads, snakes and lizards. What advantages does the normal human heart have to this anatomy ? If we had this anatomy, where would the best place for pacemakers be, like the sinus node? This is an interesting theoretical question, but several things would need to be clarified:
Does removing the R atrium relocate the SA node to the R ventricle or remove it completely from the picture?
Does the remaining R ventricle have a tricuspid valve?
Technically, the R atrium is the home of the sino-atrial node, which provides natural pacing of the human heart between 60-80 beats/min. Without this natural pacing, our hearts would rely on back-up pacer systems such as atrioventricular node, His-Purkinje systems or the intrinsic but ectopic pacing of individual atrial or ventricular cells.
The following is multiple choice question (with options) to answer.
How many chambers are in the heart? | [
"four",
"eight",
"five",
"two"
] | A | The atria receive the blood, and the ventricles pump the blood out of the heart. Each of the four chambers of the heart has a specific job. |
SciQ | SciQ-1575 | microbiology, biophysics, cell-membrane, yeast
(We know, Psi S = -Pi) As written above in (1)
Psi W = -Pi + Psi P
(We know, Turgor Pressure is the same thing as Psi P)
Psi W = -Pi + T.P
Suction Pressure is the negative of Total Pressure inside a Cell
(S.P = -Psi W)
(Water flows from high water potential to low potential, but from low Suction Pressure to an area of High Suction Pressure)
Therefore
-S.P = -Pi + T.P
multiplying by -1
S.P = Pi - T.P
The following is multiple choice question (with options) to answer.
The central vacuole maintains turgor pressure against what? | [
"the cell multiplication",
"the cell addition",
"the cell move",
"the cell wall"
] | D | The central vacuole maintains turgor pressure against the cell wall. |
SciQ | SciQ-1576 | biochemistry, physiology, digestive-system, fat-metabolism
Title: How are micelles formed from the byproducts of emulsification in fat digestion? It is known that fat droplets are made into emulsion droplets via the addition of bile salts. It is then said that the emulsion droplets are made into micelles through some sort of lipase, which can be absorbed and transported to different cells through the LDL and HDL pathway.
My question is what is the biochemistry for transforming emulsion droplets into micelles? How does water, lipase, and other factors make these micelles? Fat (triglyceride) enters the small intestine in the form of an emulsion of droplets which are stabilised by surfactants from the diet including proteins and phospholipids.
Bile salts (BS) bind to the surface of these droplets, displacing proteins. The BS-stabilised droplets are the substrate for pancreatic lipase which can adsorb to the BS-stabilised surface and convert the triglycerides to monoglycerides and free fatty acids.
The products of lipolysis then enter micelles that are formed by BS and phosphatidylcholine (PC: also in bile). The prevailing view is that these micelles take the form of discs of bilayer-like structure with BS situated both around the edges protecting the exposed acyl groups, and also embedded within the PC bilayer.
I think that the mechanism by which the products of lipolysis move from BS/PC micelles into enterocytes is not known. However, once they have entered they are re-esterified to form triglycerides which are packaged into chylomicrons (a class of lipoproteins) and exported into the lymphatic system.
Maldonado-Valderrama et al. (2011) The role of bile salts in digestion. Adv Colloid Interface Sci. 165:36-46 doi: 10.1016/j.cis.2010.12.002
The following is multiple choice question (with options) to answer.
In the small intestine, chyme mixes with bile, which emulsifies what substances? | [
"proteins",
"fats",
"acids",
"sugars"
] | B | ART CONNECTION QUESTIONS 1. Figure 34.11 Which of the following statements about the digestive system is false? a. Chyme is a mixture of food and digestive juices that is produced in the stomach. Food enters the large intestine before the small intestine. In the small intestine, chyme mixes with bile, which emulsifies fats. The stomach is separated from the small intestine by the pyloric sphincter. Figure 34.12 Which of the following statements about the small intestine is false? a. Absorptive cells that line the small intestine have microvilli, small projections that increase surface area and aid in the absorption of food. |
SciQ | SciQ-1577 | electromagnetic-radiation
Title: What is the brightest light? I have been to wikipedia about intensity of light, and there are at least 20 different ways to classify it. So I guess it boils down to the formula E = hf, which is the energy of a single photon. Now past gamma rays, is there a maximum frequency, hence energy of a photon? How does what we can create in labs compare to what exists in outer space? I'll suggest GRB 110918A, which had a peak luminosity of $L_{iso} = 4.7 × 10^{47}$ Watts. That a ten to the forty-seven - it isn't a typo.
The following is multiple choice question (with options) to answer.
Which electromagnetic waves are the most energetic of all electromagnetic waves? | [
"gamma rays",
"sunlight rays",
"ultraviolet rays",
"plasma rays"
] | A | Gamma rays are electromagnetic waves that carry photons of energy called gamma particles. They are the most energetic of all electromagnetic waves. |
SciQ | SciQ-1578 | biochemistry
Alright so this is the oxidation of one mole of glucose equation (Without the ATPs) but till now I don't exactly know the correct answer for this question, but to not create any confusion this question is related to the Aerobic respiration (Glycolysis, Krebs Cycle and Electron transport chain).
Here's how I approached this question:
(a) is obviously not correct because the products of glycloysis are 2 pyruvate molecules and 2 ATP molecules so I checked off this choice.
(b) However seems correct because the products of 2 Krebs cycle is 4 CO2 and there is already 2CO2 when the pyruvate acid formed the 2 acetyl CoA molecules so in total that's 6CO2, but still what about the 6 Water molecules?
(c) is a very debating choice because when there is a "Complete occurrence of oxidative phosphorylation process" so that means 2 Krebs cycles had already occurred and formed the 6CO2, and during the oxidative phosphorylation process Water molecules are formed. and ATPs too? I don't exactly know about the ATPs, but aren't they supposed to be in the equation's products in order for this choice to be correct?
(d) This choice indicates to Krebs cycle but the water molecules only are formed during oxidative phosphorylation only.
So basically all the choices seems very debating and confusing and if I were to choose then I'll go with (C) because it's the only choice that makes sense for the water molecules (and the question asks for water), but I want someone to please answer this question with a brief explanation to why he chose this answer,
Thanks :) This reaction only means complete oxidation of glucose to 6 molecules of carbon dioxide and 6 molecules of water.
Reaction presented in question is very generalized, but the presence of six water molecules only means complete cellular respiration. Check out the actual biochemical pathways which take place to oxidize one glucose molecule.
And other options do not represent the complete cellular respiration, so there will not be formation of six water molecules, only option C means complete oxidation of glucose.
The following is multiple choice question (with options) to answer.
Glycolysis harvests chemical energy by oxidizing glucose to what? | [
"chlorophyll",
"cellulose",
"oxygen",
"pyruvate"
] | D | 9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate. |
SciQ | SciQ-1579 | evolution, dna, theoretical-biology, genomes, species
Title: Biodiversity is restricted by genome combinatorics? Me and some friends are interested in opinions for the following:
Conjecture
The maximum number of species must be limited by the maximum
combinatorial/permutational space that can be occupied by DNA. Thus if
there is a maximum physical genome size this is what will determine
the maximum number of species that can possibly exist.
Explanation
E.G. say maximum number of DNA base pairs able to fit in a genome was $3$, each base pair can be one of either ${A,G,T,C}$. Then there are $4^3 = 64$ possible combinations of genomes. Extrapolate to genome sizes of $x$ base pairs, then there are $4^x$ combinations.
Questions
Would it be possible to claim that the underlying "blueprint" that codes for living diversity sets the absolute maximum for the total "diversity space"?
**Does it make sense to define the total number of species life can achieve with the simple function:
$S < 4^x$, where X is the maximum genome size measured in DNA base pairs?**
Notable Comments
The following is multiple choice question (with options) to answer.
What is the term for the most abundant species in a community, characterized by high competitive abilities? | [
"carnivores",
"dominant species",
"keystone species",
"merging species"
] | B | |
SciQ | SciQ-1580 | hydrology, geography, rivers, salinity, estuary
Title: Are there any saltwater rivers on Earth? I'm curious if there are any saltwater rivers on Earth. These would presumably arise if a saltwater lake had a river outlet to the ocean.
However, all the saltwater lakes I looked at (Caspian Sea, Dead Sea, Great Salt Lake Utah), apparently don't have any river outlets.
Do any exist? And the obvious follow up, why or why not?
Edit: For the purposes of this question, undersea flows don't count. They are fascinating, but I'm interested if any "regular surface rivers" exist as saltwater rivers. The water in any river draining the sea is infinitely recycle-able (from rain replenishment), whereas the salt from any terrestrial source is not. So salty rivers, if any, won't exist permanently. Saltwater lakes gain their salinity precisely because they have no outlet, so salt just gets concentrated by evaporation. I don't think there are any truly saline rivers throughout their entire length.
The nearest approximations I can think of are:
Rare ephemeral runoff from emergent salt domes in desert areas.
Freshwater rivers that drain into arid areas where combined evaporation and infiltration gradually reduces the flow to zero. These are more 'very brackish' than truly saline. The Amu Darya in Uzbekistan is one such example. I don't know the salinity of the Jordan as it enters the Dead Sea, but the river is reduced to almost nothing, whilst there are hypersaline springs, and sewage effluent from Amman draining into it.
The only river I can think of that is very highly mineralized from source to sea is only about 3 kilometres long. It is an unnamed river from the volcanic crater on Savo Island, in the Solomon Islands (Southwest Pacific). It is also acidic and boiling hot - quite literally, for most of it's length.
The following is multiple choice question (with options) to answer.
Salt-water biomes in the ocean are called what? | [
"marine species",
"ocean biomes",
"marine organelles",
"marine biomes"
] | D | Aquatic biomes are water-based biomes. They include both freshwater biomes, such as rivers and lakes, and marine biomes, which are salt-water biomes in the ocean. The primary producers in most aquatic biomes are phytoplankton. Phytoplankton consist of microscopic bacteria and tiny algae that make food by photosynthesis. Unlike terrestrial biomes, which are determined mainly by temperature and moisture, aquatic biomes are determined mainly by sunlight and dissolved substances in the water. These factors, in turn, depend mainly on depth of water and distance from shore. |
SciQ | SciQ-1581 | reproduction, endocrinology, pregnancy, ovulation
The decline of the corpus luteum is correlated with a decline in serum levels of ovarian hormones including progesterone, estradiol, and inhibin A. Release from negative feedback provided by these hormones at the level of the hypothalamus and pituitary permits FSH to rise, and the cycle begins again.
You should now be able to see that:
Around the time of ovulation, the uterine lining is not fully developed and is stable due to the hormonal milieu. Menstruation does not occur.
Around the time of menstruation, FSH and LH are suppressed in a way that is not conducive to ovulation.
In theory, yes, of course there would be a lower chance of initiating a viable pregnancy (implantation rather than conception is the most obvious problem) were the endometrial lining to be unstable at the time of ovulation. The problem of luteal phase deficiency is along these lines. In this condition, the corpus luteum does not produce adequate progesterone during the luteal phase to develop the endometrial lining in such a way as to support a healthy pregnancy. However, ovulation and menstruation are still time-separated events for the reasons outlined above.
*Note that the first term is with respect to the endometrium; the second is with respect to the ovary.
Abbreviations:
GnRH - Gonadotropin Releasing Hormone; LH - Luteinizing Hormone; FSH - Follicule Stimulating Hormone
References
1. Anatomy & Physiology, Connexions Web site. Illustration is also from here.
2. Jerome Strauss, Robert Barbieri. Yen & Jaffe's Reproductive Endocrinology. September, 2013. Saunders.
The following is multiple choice question (with options) to answer.
What occurs before the endometrium thickens in estrous cycles? | [
"pregnancy",
"fertilization",
"copulation",
"ovulation"
] | D | |
SciQ | SciQ-1582 | marine-biology, vestigial
Title: Modern Whales with Vestigial legs Myth? Is it a myth that modern whales have been found with hind legs sticking out of their sides and full formed tibias, fibias, and toe bones? I keep finding assertions, but no citations. For example, the wikipedia page has no citation for it.
http://en.wikipedia.org/wiki/Whales#Appendages The link you give doesn't mention limbs sticking out of the body wall, but only vestigial hind limb elements. Many whales do retain pelves and femora, as this page at the Bergen Museum shows. Given the variation in limb development across vertebrates, it would not be surprising to find more distal elements (but I would be very surprised if they extended past the body wall).
The following is multiple choice question (with options) to answer.
Structures like the human tail bone and whale pelvis are called what? | [
"adaptations",
"vestigial structures",
"primordial structures",
"parasitic structures"
] | B | Structures like the human tail bone and whale pelvis are called vestigial structures . Evolution has reduced their size because the structures are no longer used. The human appendix is another example of a vestigial structure. It is a tiny remnant of a once-larger organ. In a distant ancestor, it was needed to digest food. It serves no purpose in humans today. Why do you think structures that are no longer used shrink in size? Why might a full-sized, unused structure reduce an organism’s fitness?. |
SciQ | SciQ-1583 | 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.
Hazardous waste is material that is toxic, chemically active, corrosive, or what? | [
"decomposed",
"flammable",
"organic",
"inactive"
] | B | Hazardous waste is material that is toxic, chemically active, corrosive, or flammable. |
SciQ | SciQ-1584 | respiration
Here is what happens at the molecular level.
The $\rm CN^-$ ions diffuse into the mitochondria. They have high affinity to the ferrous ion of the mitochondrial enzyme cytochrome c oxidase involved in the electron transport chain (ETC), one of the phases of cellular respiration where $\rm ATP$ is generated from $\rm NADH$ and $\rm FADH_2$. And it is this process that actually requires oxygen. The inhibited cytochrome c oxidase is of no good in transporting electrons, thus no $\rm ATP$ molecules are generated. The oxygen molecules waiting for those electrons remain empty handed resulting in the increase in the concentration of molecular oxygen. Remember, ETC occurs in almost all living cells except a few like RBC which get their major share of ATP from the highly inefficient anaerobic glycolysis. Also, $\rm ATP$ is the energy currency of our body and is required in a wide variety of bodily processes like osmotic balance, nerve impulse transmission, muscle contraction etc. With no $\rm ATP$ your heart and respiratory muscles can't contract, your medulla can't regulate breathing, your kidneys can't concentrate urine and the list goes on. Death is imminent if a high concentration of cyanide gets into your blood.
The symptoms of panic like tachypnea and tachycardia (that result due to low oxygen in blood) are not usually seen unless the victim himself knows he is poisoned. The end effects like cardiac and respiratory arrest, seizures and coma, however, are similar to those of suffocation.
For further read:
The Mechanism of Cyanide Intoxication and its Antagonism
The following is multiple choice question (with options) to answer.
Which component of the electron transport chain does cyanide inhibit? | [
"cytochrome c oxidase",
"adenosine diphosphate",
"succinate dehydrogenase",
"mitochondrial matrix"
] | A | Cyanide inhibits cytochrome c oxidase, a component of the electron transport chain. If cyanide poisoning occurs, would you expect the pH of the intermembrane space to increase or decrease? What effect would cyanide have on ATP synthesis?. |
SciQ | SciQ-1585 | pathology
Title: Are all diseases caused by organisms (microorganisms)? Are there other causes? Or is it correct to say that all diseases are in fact caused by organisms (microorganisms)? It is not correct to say that all diseases are caused by foreign organisms. Counterexamples are:
Cancer is caused by random genetic mutations in the cells of our body. The mutations can be caused by many factors such as ionizing radiation, smoking, chemical toxins etc.
Diseases such as stroke or heart attack are caused by blood clots blocking the blood flow to essential organs.
Autoimmune diseases are caused by the immune system falsely recognizing cells of the body as foreign and attacking that tissue leading to a wide variety of symptoms.
Alzheimer's disease is caused by chronic neurodegeneration, meaning that the cells in the brain die. The causes are not quite understood but as Alzheimer's usually appears late in life it is likely related to ageing. Also, it is known that some genetic defects can lead to early-onset Alzheimers.
Prion proteins can cause diseases such as Creutzfeldt–Jakob disease also known as mad-cow disease.
Hereditary diseases such as early-onset Alzheimers or ALS are cause by gene defects inherited from the parents.
Toxins can cause chronic diseases such as lead poisoning.
The list probably goes on...
Please note that the first two on the list are the most common cause of death in developed countries.
The following is multiple choice question (with options) to answer.
Diseases of this system include epilepsy, strokes, and alzheimer’s disease | [
"endocrine system",
"nervous system",
"circulatory system",
"infectious system"
] | B | Diseases of the nervous system include infections, epilepsy, strokes, and Alzheimer’s disease. Injuries include concussions and spinal cord damage that may cause paralysis. Most nervous system diseases can’t be prevented, but many nervous system injuries can be prevented by following safe practices. |
SciQ | SciQ-1586 | coordination-compounds, transition-metals, crystal-field-theory, ligand-field-theory
Title: Deriving population of $t_{2g}$ orbitals in transition metal oxides I have recently studied ligand field theory but there is one thing I do not understand.
Consider an octaedral geometry of ligands around a transition metal with a $t_{2g}$ - $e_g$ splitting of atomic $d$-orbitals due to bonding with the ligands. Suppose that the gap between the two is very large and electrons can only populate $t_{2g}$ orbitals.
My question is: how do I understand how many electrons populate the $t_{2g}$ orbitals knowing the number of electrons in the atomic d orbitals?
Originally I thought they were just the same, but apparently they are not! For example, in this paper https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.107.256401 the authors consider e.g. SrMnO$_3$ and they say that in this case the $t_{2g}$ is half filled with 3 electrons. However Mn has 5 valence electrons.
Why is that?
I am a layman in chemistry, so please be patient if this is a silly question! There is more to this question than meets the eye. First I answer with the OP's assumption that the metal ions are "low spin" — meaning because all the $t_{2g}$ orbitals are fully occupied before any of the hugher $e_g$ orbitals start to be populated. Then I will assess the accuracy of this assumption. (Hint: it's about as accurate as my typing. I had to make a lot of corrections and probably missed some.) In this discussion I assume octahedral coordination, which covers at least most oxides. I'll let the reader work out the corresponding situation with tetrahedral coordination, if that comes up.
There are three $t_{2g}$ orbitals, and in the low-spin case they would hold the first six $d$ electrons from the metal ion. Thus we render the count of $t_{2g}$ electrons based on the number of valence $d$ electrons in the metal ion:
The following is multiple choice question (with options) to answer.
About how full is the outer energy level in metalloids? | [
"half full",
"a quarter full",
"nearly empty",
"three-fourth full"
] | A | Metalloids such as boron have an outer energy level that is about half full. These elements need to gain or lose too many electrons for a full outer energy level to come about easily. As a result, these elements are not very reactive. They may be able to conduct electricity but not very well. |
SciQ | SciQ-1587 | evolution, biochemistry
Title: Why is it thought that silicon based lifeforms never flourished on Earth? Reading the recent ScienceAlert article "For the first time, living cells have formed carbon-silicon bonds", it is stated that despite the relative abundance of silicon in the surface of the Earth, there are no silicon based lifeforms.
Specifically, the article asserts:
Why silicon has never be incorporated into any kind of biochemistry on Earth has been a long-standing puzzle for scientists, because, in theory, it would have been just as easy for silicon-based lifeforms to have evolved on our planet as the carbon-based ones we know and love.
I have read the question and answers "Why are we carbon-based?", which looks at the importance of carbon, what I am seeking information of is why carbon and why not silicon in the first place. So, therefore my question:
Why is it thought that silicon based lifeforms never flourished on Earth? At temperatures above -195C, "C" wins the day. "Si" based chemistry may be more versatile than carbon in some environments, for example in a frozen nitrogen atmosphere.
Silicon accounts for 43% of rocks, Carbon is less than 0.1 percent, except that carbon is similar to water for reactivity and dissolving stuff, and organic "C" compounds are a molecular sludge like flowing-dissolved-stone, room-temperature-lava: tar/margarine/oil/diesel/glucose/alcohols/acetone are sludgy, liquid, the molecules can rotate, flow, coalesce... Carbon molecules are fluid, sludgy, rotating, pivoting, kind of lego material, whereas silicone chemistry doesn't flow, it vaporises and precipitates out of any flowing state.
Carbon reacts with both the molecules of water, O and H, and almost everything else, to make millions and millions of compounds. Silicon can't bond H. It's like the difference in between lego technic and lego. Try making a robot from lego!
That gives life millions of times more chemistry building blocks compared to silicone, and permits life to interact with water. Silicon life can't really interact with water.
10/1 cosmic abundance of carbon vs silicon
The following is multiple choice question (with options) to answer.
Which chemical element is the basis of all life on earth? | [
"hydrogen",
"carbon",
"oxygen",
"nitrogen"
] | B | Carbon is an element. Carbon is the basis of all life on Earth. Since carbon can combine with many other elements it forms a variety of different substances. |
SciQ | SciQ-1588 | physiology, cardiology, blood-circulation
Title: What is the quality rate of intrinsic autoregulation in the heart? Autoregulation is the maintenance of constant blood flow to an organ in spite of fluctuations in Blood pressure.
It involves the relaxation of myocardium and contraction.
It is local.
I know that autoregulation is best done in the brain, well in kidneys and badly in skeletal muscle.
I am interested how it is in the heart.
I think it should be at least good.
Brain can be thought more important.
However, I am not sure.
How good is the autoregulation of the blood flow in the heart? My conjecture: Intrinsic regulation is done in the heart the second best, after the brain.
This idea is based on the fact that the brain controls heart's some autonomic functions.
It is an open research question how the autonomic nervous system affects the intrinsic functions of the heart - and the reverse is true too.
To answer this question, we need to understand the autonomic regulation of the heart better i.e. the inner-physiology of the heart's electrical activity.
The following is multiple choice question (with options) to answer.
What structures of the cardiovascular system help regulate body processes by either constricting or dilating? | [
"capillaries",
"cartilage",
"muscles",
"blood vessels"
] | D | Blood vessels help regulate body processes by either constricting (becoming narrower) or dilating (becoming wider). These actions occur in response to signals from the autonomic nervous system or the endocrine system. Constriction occurs when the muscular walls of blood vessels contract. This reduces the amount of blood that can flow through the vessels (see Figure below ). Dilation occurs when the walls relax. This increases blood flows through the vessels. |
SciQ | SciQ-1589 | evolution, zoology, taxonomy, phylogenetics
The apomorphy that defines the tetrapods is "paired limbs". You have Amphibia to the left and Amniota to the right, whose apomorphy is " egg with extraembrionic membranes". Inside them, you have Reptilia, whose apomorphies are "skull with upper and lower fenestra and beta-keratin in epidermis". Turtles came from an ancestor with these characteristics. So, turtles belong to the monophyletic group of "Reptiles".
Post scriptum: You wrote that "turtles (specifically sea turtles) live on both land and water, very much like amphibians". Just a curiosity: the reason why sea turtles leave the water (sea) from time to time shows exactly that they are not amphibians! Amphibians, being non-amniotes, have eggs that survive under water (actually, with few exceptions, they need to be under water). Turtles, on the other hand, are amniotes, and the amniotic egg cannot be laid under water. That's why the turtles have to leave the water to lay eggs: because, contrary to the amphibians, they cannot lay eggs under water.
The following is multiple choice question (with options) to answer.
What is the term for the class of ectothermic, four-legged vertebrates that produce amniotic eggs? | [
"mammals",
"reptiles",
"Turtles",
"amphibians"
] | B | Reptiles are a class of ectothermic, four-legged vertebrates that produce amniotic eggs. They include turtles, crocodiles, lizards, and snakes. Reptiles were the first vertebrates to live full time on land, and they evolved many terrestrial adaptations. |
SciQ | SciQ-1590 | molecular-biology, proteins, genetics, learning
Title: How do proteins and genes participate in learning? I am a computer scientist that studies biology and bioinformatics.
In the last weeks, I have been trying to study new research directions, and I would like to deepen my knowledge on the role and behavior of genes and proteins in learning.
By learning, I mean the human process: the information I is absent at time T, and present at time T+1.
I would like to study more this problem, and I am wondering: how do proteins and genes behave during learning?
I have read that proteins that participate in learning are called marker proteins. Is it true? Which role do they have?
Where could I find some resources to study this fascinating problem?
Thank you very much! The storage of memories in cells is rarely thought of on the protein level of the cell. Cells are usually given a developmental state, but no memory. A cell may become a liver cell, cancerous, or diabetic, but this is not memory, but a physiological change in the cell which is usually not reversible to a previous state.
For example cancer treatments are entirely focused on identifying the cancerous cells and killing them. Internally the genomes of cancer cells often have deletions and duplications. They are cancerous, they have not learned to be cancerous. Though not as dramatic, it is now thought that cellular differentiation which creates different types of cells is heavily influenced by epigenetic modification of the genome; the DNA is marked by methyl groups which dictates the state of the cell by modifying the gene. This is mediated by proteins for sure, but is quite complex and not well understood at this time. Epigenetic markers can even change gene behavior between generations of offspring as well, though that is not usually called memory.
How is information stored in the brain? This is thought to be reflected in the organization of the neurons in the brain. There are many kinds of neurons. They can be distinguished by the sorts of axons and dendrites that emanate from the cell body. They can also be distinguished by the chemical variety of neurotransmitter they use (there are a score of different molecules). So to a great extent the type of cell and the specific proteins it chooses to use to mediate information is very important.
The following is multiple choice question (with options) to answer.
The goal of proteomics is to identify or compare what substances expressed from a given genome under specific conditions, study the interactions between them, and use the information to predict cell behavior or develop drug targets? | [
"cells",
"rna",
"proteins",
"dna"
] | C | Basic Techniques in Protein Analysis The ultimate goal of proteomics is to identify or compare the proteins expressed from a given genome under specific conditions, study the interactions between the proteins, and use the information to predict cell behavior or develop drug targets. Just as the genome is analyzed using the basic technique of DNA sequencing, proteomics requires techniques for protein analysis. The basic technique for protein analysis, analogous to DNA sequencing, is mass spectrometry. Mass spectrometry is used to identify and determine the characteristics of a molecule. Advances in spectrometry have allowed researchers to analyze very small samples of protein. X-ray crystallography, for example, enables scientists to determine the three-dimensional structure of a protein crystal at atomic resolution. Another protein imaging technique, nuclear magnetic resonance (NMR), uses the magnetic properties of atoms to determine the three-dimensional structure of proteins in aqueous solution. Protein microarrays have also been used to study interactions between proteins. Large-scale adaptations of the basic two-hybrid screen (Figure 17.17) have provided the basis for protein microarrays. Computer software is used to analyze the vast amount of data generated for proteomic analysis. Genomic- and proteomic-scale analyses are part of systems biology. Systems biology is the study of whole biological systems (genomes and proteomes) based on interactions within the system. The European Bioinformatics Institute and the Human Proteome Organization (HUPO) are developing and establishing effective tools to sort through the enormous pile of systems biology data. Because proteins are the direct products of genes and reflect activity at the genomic level, it is natural to use proteomes to compare the protein profiles of different cells to identify proteins and genes involved in disease processes. Most pharmaceutical drug trials target proteins. Information obtained from proteomics is being used to identify novel drugs and understand their mechanisms of action. |
SciQ | SciQ-1591 | radioactivity, archaeology
Title: Do fluctuations in radioactive isotope decay rates affect carbon dating techniques? In 2010, Purdue University published a research paper[1] stating that their researchers had detected slight fluctuations in radioactive isotope decay rates "in synch with the rotation of the sun's core." The article also stated:
The team has not yet examined isotopes used in medical radiation treatments or for dating of ancient artifacts.
Has there been any further research on this, and has it been found to affect carbon dating techniques or other archeological dating methods? Are the fluctuations large enough to call into question currently accepted geological dates?
The following is multiple choice question (with options) to answer.
Radiometric dating methods, such as carbon-14 dating depend on what type of decay? | [
"carbon",
"radioactive",
"nuclear",
"microwave"
] | B | The age of a rock in years is its absolute age. The main evidence for absolute age comes from radiometric dating methods, such as carbon-14 dating. These methods depend on radioactive decay. |
SciQ | SciQ-1592 | star, amateur-observing, constellations
Title: What are the stars/constellations a beginner/enthusiast can easily identify? I was just wondering what are some of the stars, constellations or any other things that one can just identify by looking up at the night sky.
For example, when ever i look up, I immediately see Orion and can identify Betelgeuse, Rigel, Bellatrix. Apart from that i can identify some of the bright stars liike sirius , vega.
So, what other stars are there that one can easily identify and point? It varies throughout the year. A book or a website with maps will help.
In Spring, Leo and Boötes dominate the southern skies, with Coma Berencies between them
In Summer, the summer triangle of Deneb, Altair and Vega is seen, with Cygnus flying along the Milky Way, and the rich star fields of Saggitarius closer to the horizon.
In Autumn there is the square of Pegasus, with Andomeda riding, past Perseus
And in Winter, Orion dominates the southern skies, with his dogs following.
In the North, Cassiopea and the Ursa Major, are on opposite sides of the Pole star.
The following is multiple choice question (with options) to answer.
What is the brightest star in the orion constellation? | [
"natel",
"rigel",
"omicron",
"sol"
] | B | 7. You look through a telescope at Rigel. Rigel is the brightest star in the Orion constellation. Rigel is around 800 light years from Earth. What are you looking at when you look through that telescope? What does Rigel look like today?. |
SciQ | SciQ-1593 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
Which organelle specific to plant cells is responsible for photosynthesis? | [
"the mitochondria",
"the chloroplast",
"the vacuole",
"the lipid"
] | B | Photosynthesis occurs in the chloroplast, an organelle specific to plant cells. |
SciQ | SciQ-1594 | newtonian-mechanics, thermodynamics, energy-conservation, potential-energy, dissipation
Title: Potential, Kinetic, Thermal Energy? When things move, potential energy turns into Kinetic energy, right? Then how does Kinetic energy convert to thermal energy? "Thermal energy" is just kinetic energy.
When people talk about temperature, a typically good (but largely classical) idea is that tenperature is a measure of the average kinetic energy of the particles. When people talk about an increase or decrease of thermal energy, they usually mean something has gotten hotter or colder. This suggests that thermal energy is really just kinetic energy.
The following is multiple choice question (with options) to answer.
What is another word for thermal energy? | [
"temperature",
"heat",
"humidity",
"solar"
] | B | |
SciQ | SciQ-1595 | # Thread: Roots of unity and the length from one root to the other roots
1. ## Roots of unity and the length from one root to the other roots
Hello,
I had an assignment that required me to solve for the roots of unity for various equations of the form $z^n -1 = 0$. Then , I was asked to represent the roots of unity for each equation on an argand diagram in the form of a regular polygon.
I did all of that , however, i have a question:
is there a relation ship between the power n and the length from one root to the other roots?
When n = 3,
The roots are $-0.5 \pm 0.8660i$ and 1. The length from one root to the other roots are both 1.7321 (sqrt of 3)
When n = 4,
The roots are $\pm 1, 0 \pm 1i$. The length from one root to the other roots are (sqrt 2, sqrt and 2)
I am wondering , for the equation $z^3 - 1 = 0$ , is there a formula relating the power of z to the length from one roots to the other roots?
Thanks.
2. ## Re: Roots of unity and the length from one root to the other roots
The nth roots of unity lie at the vertices of a polygon with n sides, each vertex having distance from the center of 1. Drawing a line from the center to each vertex divides the polygon into n isosceles triangles, each having two sides of length 1, vertex angle of 360/n degrees and you want to find the length of the third side. If you draw a line from the vertex of such a triangle to the center of the base, you get two right triangles with hypotenuse length 1 and one angle of 180/n. The opposite side of that triangle has length 1(sin(180)/n) so the side of the polygon is twice that :
2sin(180/n).
3. ## Re: Roots of unity and the length from one root to the other roots
Hi, thank you very much for answering the question first.
The following is multiple choice question (with options) to answer.
Roots grow in length and width from the primary and secondary what? | [
"leaf",
"pistil",
"meristem",
"frill"
] | C | Roots grow in length and width from primary and secondary meristem. |
SciQ | SciQ-1596 | population-genetics, molecular-evolution, microbiome, quantitative-genetics
Microbiome members are often interdependent
As hinted at in the question update, bacteria display a type of community altruism, where an individual cell with a specific gene can influence the fitness of neighboring cells that lack the gene. For an example, see my answer to Will all bacteria become resistant against all antibiotics in the long term? concerning secreted β-lactamases.
Therefore, spatial association is an added factor when considering population dynamics of a genetically heterogeneous bacterial species. Some methods that address cell-cell spatial proximity in microbiomes include sequencing of cryofractured fragments 17 and probe-based spectral imaging.18 Even if microbes are not spatially associated, different microbes may play complementary roles in the iterative metabolism of large carbohydrates into small metabolites.19,20
Surely, this discussion is incomplete, though I hope my answer has given you the footing you need to continue your own exploration to find the appropriate resources for your research. For a more in-depth discussion of the points I've addressed here, see What Is Metagenomics Teaching Us, and What Is Missed?,21 particularly the sections titled Strain-Level Analyses and Ecoevolutionary Modeling.
The following is multiple choice question (with options) to answer.
What often form symbiotic associations with much larger organisms? | [
"prokaryotes",
"protists",
"viruses",
"eukaryotes"
] | A | |
SciQ | SciQ-1597 | phylogenetics, phylogeny, database, covid-19, sars-cov-2
Title: Database with antigens and current vaccines I am seeking virological databases focussing on:
vaccines
antibody interactions
host receptors.
Preferably the data base will host multiple strains/samples of a given virus samples.
Any assistance would be welcome. Given "any virus will do", the viruses that are "head and shoulders" above the rest in terms of volumes of data are HIV and influenza.
The influenza database is here
The influenza viral spike that attaches to the cell receptor is the HA protein – hemagglutinin. The cell receptor is sialic acid – a small sugar that is attached to many different proteins on the cell surface. You can of course simply search PDB for HA or else Genbank.
The following is multiple choice question (with options) to answer.
Name the fever that is caused by a virus that has antigens similar to molecules in human heart tissues. | [
"yellow fever",
"Dengue fever",
"rheumatic fever",
"chronic fever"
] | C | Rheumatic fever is caused by a virus that has antigens similar to molecules in human heart tissues. When the immune system attacks the virus, it may also attack the heart. What type of immune system disease is rheumatic fever? Explain your answer. |
SciQ | SciQ-1598 | star, planet, exoplanet, distances, mass
Title: Minimum distance between planets In our solar system, MOIDs (minimum orbital intersection distance) of different planets reach a minimum of ~30 million miles (Mercury and Venus). However, other star systems have more compact planets. So I am wondering, what is the absolute minimum for planets of different sizes (list below)
1 Earth mass
5 Earth masses
10 Earth masses (Neptune-sized)
50 Earth masses (Super-Neptune)
100 Earth masses or 0.3 Jupiter mass (Sub-Jupiter)
1 Jupiter mass
5 Jupiter masses
The following is multiple choice question (with options) to answer.
What is the smallest planet in our solar system? | [
"mercury",
"Mars",
"Earth",
"Jupiter"
] | A | Mercury is the smallest planet and the closest to the Sun. It has an extremely thin atmosphere so surface temperatures range from very hot to very cold. Like the Moon, it is covered with craters. |
SciQ | SciQ-1599 | thermodynamics, water, phase-transition
Title: What makes water boil? Basically how boiling takes place?
Also like to know...
What makes boiling point alter at various altitudes?
Why bubbles rise through boiling water? I'll give somewhat satisfying answer...
Heat - We know that Heat is a form of energy that is transferred by difference in temperature of regions. Here, it's just the amount of energy required by the $H_2O$ molecules in the liquid state to get converted to gaseous state. As we provide heat, it gets absorbed by water to get converted into water vapors.
Convection - It's the transfer of heat through water (proper term is fluid) caused by molecular motion. You see, Convection can be brought to focus by taking normal experiments into account. Particles (even Chalk) would rise and fall in somewhat rotatory motion due to this flow of heat. The water vapor formed at the bottom of the liquid (water) flows to the top in the form of united water vapor bubbles. 'Cause it's a gas and its so hot down there..! (This explains bubble formation when water is boiled.)
Now, why boiling point differ with altitude:
The atmospheric vapor pressure is 1 atm only for us (I mean, at sea level). For higher elevations, the pressure is too low out there in atmosphere. It should also be noticed that the volume change is too high when a liquid changes to gas.
By Ideal gas equation, For 'n' moles of gas $\implies$ $P=\frac{nRT}{V}$ which shows that pressure is inversely proportional to volume. So, we could relate this expansion with pressure. Expanding against low pressure takes somewhat lower energy than expanding against high pressure. And hence the boiling point would be low at higher altitudes. Wiki says it somewhat clearly with a formula.
Using this water boiling point calculator, Boiling point at sea level (1 atm or 29.92 inches of Hg) is approximately 212 °F whereas at a height of about 5000 ft. (24.9 inches of Hg), it is 203 °F.
The following is multiple choice question (with options) to answer.
What is the term for when a substance boils and changes to gas? | [
"boiling point",
"reaction point",
"activation point",
"changing point"
] | A | The temperature at which a substance boils and changes to a gas is called its boiling point. Boiling point is a physical property of matter. The boiling point of pure water is 100°C. Other substances may have higher or lower boiling points. Several examples are listed in the Table below . Pure water is included in the table for comparison. |
SciQ | SciQ-1600 | 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.
Where are hormones released? | [
"brain",
"lungs",
"liver",
"bloodstream"
] | D | Signaling molecules can belong to two broad groups. Neurotransmitters are released at synapses, whereas hormones are released into the bloodstream. These are simplistic definitions, but they can help to clarify this point. Acetylcholine can be considered a neurotransmitter because it is released by axons at synapses. The adrenergic system, however, presents a challenge. Postganglionic sympathetic fibers release norepinephrine, which can be considered a neurotransmitter. But the adrenal medulla releases epinephrine and norepinephrine into circulation, so they should be considered hormones. What are referred to here as synapses may not fit the strictest definition of synapse. Some sources will refer to the connection between a postganglionic fiber and a target effector as neuroeffector junctions; neurotransmitters, as defined above, would be called neuromodulators. The structure of postganglionic connections are not the typical synaptic end bulb that is found at the neuromuscular junction, but rather are chains of swellings along the length of a postganglionic fiber called a varicosity (Figure 15.5). |
SciQ | SciQ-1601 | reproduction, asexual-reproduction
Title: can self-fertilization in flowers be called asexual reproduction? Suppose a flower having both male and female reproductive parts is self-fertilized then can this be called asexual reproduction...?I'm quite confused cause in this case the fusion of male and female gametes do take place but again the gametes are from the same parent....please help. According to this article from Berkeley, asexual reproduction is:
Any reproductive process that does not involve meiosis or syngamy
Using this definition of asexual reproduction and knowing self-fertilization involves meiosis and syngamy, it is not asexual.
The following is multiple choice question (with options) to answer.
The union of gametes is called? | [
"fertilization",
"fusion",
"pollination",
"migration"
] | A | Sexual reproduction involves two parents. It produces offspring that are all genetically unique. It requires the production of haploid gametes. The union of gametes is called fertilization. It results in a diploid zygote. |
SciQ | SciQ-1602 | behaviour, language, genetic-code
Title: How does DNA encode high level features like animal behaviour and language? We know there are complex features which animals supposed to develop based on their genes as opposed to learning from the environment and the collective, also sometimes being very specific to certain species:
Concepts how to build homes
Animal languages including social insect interactions responsible for information transmission (or do they have to learn them through an acquisition process, let's exclude languages of ape tribes where "term" creation has been demonstrated?)
Valid answer: if already known, one or to examples to corresponding research.
Constraint: we are not talking about genes responsible for some sort of tendencies in behaviour but situations where there seems to be a more or less complex "blue print". I suppose we are yet very far from understanding these things. Relation of genotype to phenotype is teh subject of much contemporary research, but it is mainly limited to simple phenotypic features, explainable by action of a few genes, such as the colors of zebra fish mutants: see, e.g., this paper and the related publications by Nüsseln-Vollhardt group. Perhaps closer to your question is circadian rythms, which also have genetic determinants.
The complex behaviors are likely a result of the complex interactions of many genes, which are a very interesting, but also a very difficult problem to solve.
The following is multiple choice question (with options) to answer.
What type of behavior occurs naturally in all animals of a given species? | [
"innate",
"learned",
"acquired",
"stimulated"
] | A | Innate behavior is any behavior that occurs naturally in all the animals of a given species. It doesn’t have to be learned, and it occurs in the same way in all members of the species. Examples of innate behaviors include the waggle dance in honeybees and the grasp reflex in human babies. |
SciQ | SciQ-1603 | star, observational-astronomy, amateur-observing, asteroids
Title: Do objects that are invisible to the naked eye occlude much of the stars to Earth based observers? I was looking at a star recently and some other object that appeared to be stationary in relation to the star was occluding the light to only one of my eyes. This is why it caught my attention.
I was able to move my head around this shadow and see the star but there was a definite tiny area where the star was clearly hidden. The object hiding the star also appeared to be a similar size to the tiny point of light of the star. Is this common to observe?
For the last few days I have been asking myself how many objects could be hidden like this (though most with shadows that engulf the earth); How thick are asteroid belts etc, that are between our eyes and the rest of the stars.
Is most of it hidden? From your description, an object that blocks out light from a star in only one location cannot be an astronomical object.
Occultations by asteroids are fairly common. You can see a list at http://www.asteroidoccultation.com/. When a star is being occluded by an asteroid there will be a fairly narrow strip from which the star will be hidden. But it is still about 50km wide. The star appears to rapidly fade, and it remains hidden for at most a few seconds, then reappears. Your description of "only hidden to one of my eyes" doesn't fit an asteroid occultation.
The object hiding the star must, therefore, have been local, and not moving. It would be speculation to suggest what it could be.
There are may objects that are hidden in visible light, not by asteroids, but by interstellar dust clouds. We can see them by using other wavelengths.
The following is multiple choice question (with options) to answer.
What parts of comets make them easy to see? | [
"novas and tails",
"craters and tails",
"comas and tails",
"arcs and tails"
] | C | Gases in the coma and tail of a comet reflect light from the Sun. Comets are very hard to see except when they have comas and tails. That is why they appear only when they are near the Sun. They disappear again as they move back to the outer solar system. |
SciQ | SciQ-1604 | newtonian-mechanics, rotational-dynamics, estimation, stability
Title: Human Lean Equation For a medical experiment I am doing, I need an equation to find the angle at which someone will lean before falling. I am not mathematically inclined in terms of advanced stuff, I am more so of a trigonometry person.
I assume factors that will be needed are BMI, including height and weight, but that is really all I have. For example, I am a 5'11" (180.3cm) tall female. I weigh 165 pounds (74.8kg). I want to find out, computationally (because I could measure myself), how far I could lean before I fall.
Any ideas of how I could go upon this? Even though your body is not a simple, homogeneous, rigid object, we can calculate a little... With a lot of assumptions.
I assume, your feet stand next to each other, not in a step-forward-position. And I assume, the question is about leaning forward/backward, not sideways.
And I assume that the arms have to be aligned at the side of the body.
First step, we need to locate your center of gravity (CG). Even if you feel light/heavy hearted, we assume you to be symmetric. We also assume you to be front-back-symmetric, except for your feet.
Now we need the hight-coordinate of CG. You can find it via plancking across a bar. Let's assume your result is that CG is 99cm from floor up.
Next up, we need your shoe size. I guess you at an american women's size of 11.5, which equates to 27cm foot-length.
If you ever took dance classes, you may remember that you were instructed to "put your weight over your heel", or over the center of your feet. Let's assume that this little shift can be done without "leaning".
As you are "more of a trigonometry person", here comes the fun part:
We think of you (having "weight over heel") as a L-shape, with your feet being 27cm, and the stem of the "L" being 99cm (height of CG). Now you gradually lean forward, and when CG passes over your toes, you fall.
The following is multiple choice question (with options) to answer.
What gives the body shape and support? | [
"skeleon",
"muscles",
"organs",
"gravity"
] | A | The skeleton supports the body and gives it shape. It has several other functions as well, including:. |
SciQ | SciQ-1605 | waves, acoustics, frequency
Low frequencies really only get attenuated according to the inverse square law, but higher frequencies are attenuated more strongly.
3 - detecting sound
In order to detect sound, a membrane needs to be moved. This motion then has to somehow be conveyed to the nervous system, which is water-based and therefore has a very different acoustic impedance than air ($z_0 = \rho c$ - so when density increases by 1000x and speed of sound by 4x, you have a mismatch...). The mechanisms in the ear (tympanic membrane, malleus, incus, stapes, oval window, cochlea) is a beautiful piece of engineering to create something of an acoustic match, and works quite well over a range of frequencies. Unfortunately, for very low or very high frequencies, bit of that mechanism stop working so well - the finite mass (inertia) of the components makes them more reluctant to move at high frequencies. This again puts an upper limit on the frequency we can hear. However, the "amplification" that the entire organ provides is exquisite - as I computed in the answer linked above this means you can hear tiny, tiny vibrations.
4 - evolution
The human body is a wonderful machine, refined by aeons of evolution - "she who hears the approaching predator lives to procreate another day". The combination of "everything disturbs the air around it" and "we are designed to detect the slightest sound" is the answer to your question.
The following is multiple choice question (with options) to answer.
What do you call sound that has a wave frequency higher than the human ear can detect? | [
"hypersonic sound",
"ultrasound",
"supersonic sound",
"dynamic sound"
] | B | Ultrasound is sound that has a wave frequency higher than the human ear can detect. It includes all sounds with wave frequencies higher than 20,000 waves per second, or 20,000 hertz (Hz). |
SciQ | SciQ-1606 | botany, ecology, energy
Title: Why do plants create enough energy for the entire ecosystem? In my environmental class, we were recently learning about the $10\%$ law that basically says only $10\%$ of the energy goes from one trophic level to the next.
This got me thinking about why energy flows from one level to the next. Specifically, why do plants create enough energy for the entire ecosystem? Wouldn't they do fine without us, and wouldn't that save them the work of creating all that excess energy? Plants collect energy for themselves via photosynthesis, not for others.
It is used for it's own growth and survival.
It's energy is then redistributed to other organisms when either the plant dies and decomposes or when it is consumed. Many organism cannot collect their energy like plants do, and thus must feed on organisms (like plants) that are able to collect and store energy. This is in many cases detrimental to the plant (it should be intuitive why being eaten might be bad), and many, many plants do have traits to discourage other organisms from eating them (plants with toxins, thorns, etc.).
The following is multiple choice question (with options) to answer.
Plants not only contribute food but what else for organisms? | [
"carbon",
"hydrogen",
"oxygen",
"dioxide"
] | C | The oxygen atoms, however, form oxygen gas, which is a waste product of photosynthesis. The oxygen given off supplies most of the oxygen in our atmosphere. Before photosynthesis evolved, Earth’s atmosphere lacked oxygen altogether, and this highly reactive gas was toxic to the many organisms living at the time. Something had to change! Most contemporary organisms rely on oxygen for efficient respiration. So plants don’t just “restore” the air, they also had a major role in creating it!. |
SciQ | SciQ-1607 | acid-base, corrosion
Title: Are all corrosives either acids or bases? Are all corrosives either acid or a base? From what I could remember from school, strong acids and bases can be corrosive, but can substances be corrosive from reasons other than that? I tried my best to check for the answer with my limited knowledge.
If it is not just acids and bases what is it then, how can we categorize them, if possible in simple terms? Wikipedia lists many corrosive compounds. While a lot of them function as strong acids or bases, there are also these (not an exhaustive list):
Strong oxidizers including concentrated hydrogen peroxide
Fluorides (they say "fluoride ion", so salts as well as the acid are meant)
Organic compounds that can act as alkylating agents such as methyl sulfate
The moral of the story: Hazards can't be pigeonholed into specific types of chemicals. Best to find and read the safety data sheet with any chemical.
The following is multiple choice question (with options) to answer.
Substances that act as both weak acids and bases are said to be what? | [
"atmospheric",
"amphiphilic",
"amphoteric",
"hygroscopic"
] | C | Other applications of carbonates include glass making—where carbonate ions serve as a source of oxide ions—and synthesis of oxides. Hydrogen carbonates are amphoteric because they act as both weak acids and weak bases. Hydrogen carbonate ions act as acids and react with solutions of soluble hydroxides to form a carbonate and water: KHCO 3(aq) + KOH(aq) ⟶ K 2 CO 3(aq) + H 2 O(l) With acids, hydrogen carbonates form a salt, carbon dioxide, and water. Baking soda (bicarbonate of soda or sodium bicarbonate) is sodium hydrogen carbonate. Baking powder contains baking soda and a solid acid such as potassium hydrogen tartrate (cream of tartar), KHC4H4O6. As long as the powder is dry, no reaction occurs; immediately after the addition of water, the acid reacts with the hydrogen carbonate ions to form carbon dioxide: HC 4 H 4 O 6 −(aq) + HCO 3 −(aq) ⟶ C 4 H 4 O 6 2−(aq) + CO 2(g) + H 2 O(l) Dough will trap the carbon dioxide, causing it to expand during baking, producing the characteristic texture of baked goods. |
SciQ | SciQ-1608 | inorganic-chemistry, solubility, metallurgy
Any insights would be much appreciated! Let me give an extreme example of chemical analysis. It is an anecdote. Some analytical chemists were using a very sensitive technique to analyze metals in blood. It is called neutron activation analysis. What they saw was that a very small quantity of molybdenum (Mo) was present in small quantities persistently. Nobody expected that. It turned out after a lot of hard work that Mo was coming from the stainless steel syringe needle used for drawing blood. Lesson of the story: There is nothing which is perfectly insoluble in water. It all depends on the analytical technique. If you try to weigh a hair on a "weighing machine" it will tell you that the mass is zero kg, but if you use a fine analytical balance it will tell you that hair has a mass.
The same goes for lead pipes. Natural water has plenty of minerals, dissolved oxygen anions, cations and don't forget the microorganisms. The bacteria do a lot of chemical transformations in water. As a result, Pb would slowly leach into the water at parts per million or parts per billion levels. Don't assume that Romans were drinking lead salt solutions in high concentration ranges. Not only water lead was present in water, it was also present in alcoholic beverages.
Read more here Lead in ancient Rome’s city waters
Lead in water is still a serious problem in several areas of the modern world. It is not an ancient problem.
The following is multiple choice question (with options) to answer.
What is the medical process of removing wastes and excess water from the blood by diffusion and ultrafiltration called? | [
"tumors",
"dialysis",
"arthritis",
"digestion"
] | B | Dialysis Technician Dialysis is a medical process of removing wastes and excess water from the blood by diffusion and ultrafiltration. When kidney function fails, dialysis must be done to artificially rid the body of wastes. This is a vital process to keep patients alive. In some cases, the patients undergo artificial dialysis until they are eligible for a kidney transplant. In others who are not candidates for kidney transplants, dialysis is a life-long necessity. Dialysis technicians typically work in hospitals and clinics. While some roles in this field include equipment development and maintenance, most dialysis technicians work in direct patient care. Their on-the-job duties, which typically occur under the direct supervision of a registered nurse, focus on providing dialysis treatments. This can include reviewing patient history and current condition, assessing and responding to patient needs before and during treatment, and monitoring the dialysis process. Treatment may include taking and reporting a patient’s vital signs and preparing solutions and equipment to ensure accurate and sterile procedures. |
SciQ | SciQ-1609 | universe, naming, cosmological-horizon
Title: What's the name of outside the cosmic horizon? The word we use to refer to what's inside the cosmic horizon is the 'universe', so what would you call the empty space outside of the horizon? The outside is also the universe, the inside is just the observable universe.
The following is multiple choice question (with options) to answer.
What is the "a" horizon commonly known as? | [
"topsoil",
"sediment",
"crust",
"core"
] | A | The first horizon is the “A“ horizon. It is more commonly called the topsoil . The topsoil is usually the darkest layer of the soil. It is the layer with the most organic material. Humus forms from all the plant and animal debris that falls to or grows on the ground. The topsoil is also the region with the most biological activity. Many organisms live within this layer. Plant roots stretch down into this layer. The roots help to hold the topsoil in place. Topsoil is needed to grow most crops ( Figure below ). |
SciQ | SciQ-1610 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
What are the building blocks of life? | [
"bricks",
"cells",
"seeds",
"muscles"
] | B | Cells are the building blocks of life. This is clear from the photo in Figure below . It shows stacks upon stacks of cells in an onion plant. Cells are also the basic functional units of living things. They are the smallest units that can carry out the biochemical reactions of life. No matter how different organisms may be from one another, they all consist of cells. Moreover, all cells have the same basic parts and processes. Knowing about cells and how they function is necessary to understanding life itself. |
SciQ | SciQ-1611 | thermodynamics, energy, heat
Title: A Calorimetry Problem I have a question in calorimetry from an old competitive exam. The question is:
The temperature of $100$ grams of water is to be raised from $24 ^\circ$C to $90 ^\circ$C by adding steam to it. Find the mass of steam required.
I tried attempting the question by assuming that the added steam would convert back to water and thus lose an amount of heat calculated by the latent heat of vaporization. Additionally, to cool from 100 degrees to 90 degrees, the 'watered steam' will contribute some additional heat. I equated this to the heat gained by the 100 grams of water to reach 90 degrees from 24 degrees. But I am not getting the right answer!
I would appreciate any help on this matter. Thank you :) Your method seems correct. Here are the details:
$Q_{Heat Water}=m\times c\times (T_2-T_1)=100 \times 1 \times 66 = 6600$ calories
From 1 gram of steam, $$Q=L_v+c\times(100-T_2)=540+1 \times 10=550$$
Therefore, grams of steam needed $=\frac{6600}{550}=12$ grams
The following is multiple choice question (with options) to answer.
The amount of energy needed to raise the temperature of one gram of liquid water by 1°c is also known as? | [
"mass",
"specific heat",
"Kelvin",
"calorie"
] | B | State of matter that has a fixed volume and fixed shape. |
SciQ | SciQ-1612 | signal-detection, multipath, ultrasound
Try one or both of those solutions, and put up your results. I expect there to be tangible improvements that we can then iterate on. (Pulse shaping, different/longer PN sequences, etc).
The following is multiple choice question (with options) to answer.
What helps amplify the effects of extracellular signals? | [
"spontaneous cascades",
"enzymatic cascades",
"mutation cascades",
"electrical cascades"
] | B | The effects of extracellular signals can also be amplified by enzymatic cascades. At the initiation of the signal, a single ligand binds to a single receptor. However, activation of a receptor-linked enzyme can activate many copies of a component of the signaling cascade, which amplifies the signal. |
SciQ | SciQ-1613 | thermodynamics, temperature, units
My personal favorite way to do it is to measure entropy in bits, so that $k_B = \frac{1}{\ln 2} \,\mathrm{bits}$ and the units of temperature are $\mathrm{J\cdot bits^{-1}}$. Having entropy rather than temperature as the quantity with the fundamental unit tends to make it much clearer what's going on, and bits are a pretty convenient unit in terms of building an intuition about the relationship to probability theory.
The following is multiple choice question (with options) to answer.
What units are typically used to measure heats of reaction? | [
"degrees Celsius",
"volts",
"kilojoules",
"kilobytes"
] | C | Heats of reaction are typically measured in kilojoules. It is important to include the physical states of the reactants and products in a thermochemical equation as the value of the depends on those states. |
SciQ | SciQ-1614 | acid-base, equilibrium, aqueous-solution, ions
Title: Why does the ionic product of water remain constant after addition of non-neutral solute? In my textbook, it is given that the ionic product of water $K_\mathrm{w}$ remains constant even when a non-neutral solute such as an acid is added to it.
$$K_\mathrm{w} = \ce{[H3O+][OH-]}$$
When a strong acid is added to water, the concentration of $\ce{[H3O+]}$ increases. Yet the $K_\mathrm{w}$ must remain constant. But how? How does the concentration of $\ce{[OH-]}$ decrease? $K_w$ is the equilibrium constant of this reaction:
$$\ce{2H2 O <=> H3O+ +OH-}.$$
So, it's constant at a fixed temperature. It equals $10^{-14}$ at $25~^\circ\mathrm{C}$. At this temperature $\ce{[H3O+]=[OH^{-}]}=10^{-7}~\mathrm{mol/L}$.
If you add acid to water, the above reaction equilibrium is displaced in order to counteract the change in the concentration of ion hydronium, i.e. the reaction is displaced to the left. This means that ions hydroxide will react with the excess of ions hydronium to give water. As a result: the concentration of ion hydroxide will be less than $10^{-7}~\mathrm{mol/L}$, and the concentration of ion hydronium will be more than $ 10^{-7}~\mathrm{mol/L}$. But their product is constant. $\ce{[H3O+] \cdot[OH^{-}]}=10^{-14}$.
The following is multiple choice question (with options) to answer.
What are solutions that maintain a relatively constant ph when an acid or a base is added? | [
"liquids",
"gases",
"water",
"buffer"
] | D | Buffers are solutions that maintain a relatively constant pH when an acid or a base is added. They therefore protect, or “buffer,” other molecules in solution from the effects of the added acid or base. Buffers contain either a weak acid (HA) and its conjugate base (A−) or a weak base (B) and its conjugate acid (BH+), and they are critically important for the proper functioning of biological systems. In fact, every biological fluid is buffered to maintain its physiological pH. |
SciQ | SciQ-1615 | dna, rna, virus, virology, gene
Title: Is there any virus that contains both DNA and RNA in its genome? It is known that viruses contain DNA or RNA- either one and not both.
I came across a question: Which virus contains both DNA and RNA? Here is the results summary of the study that describes the discovery of DNA:RNA hybrid virus:
Results
Bioinformatic analysis of viral metagenomic sequences derived from a hot, acidic lake revealed a circular, putatively single-stranded DNA virus encoding a major capsid protein similar to those found only in single-stranded RNA viruses. The presence and circular configuration of the complete virus genome was confirmed by inverse PCR amplification from native DNA extracted from lake sediment. The virus genome appears to be the result of a RNA-DNA recombination event between two ostensibly unrelated virus groups. Environmental sequence databases were examined for homologous genes arranged in similar configurations and three similar putative virus genomes from marine environments were identified. This result indicates the existence of a widespread but previously undetected group of viruses.
And here is the link to the paper:
https://biologydirect.biomedcentral.com/articles/10.1186/1745-6150-7-13
The following is multiple choice question (with options) to answer.
Along with dna, what is the other main type of nucleic acid? | [
"protein",
"nucleotides",
"cytoplasm",
"rna"
] | D | Nucleic acids are biochemical molecules that contain oxygen, nitrogen, and phosphorus in addition to carbon and hydrogen. There are two main types of nucleic acids. They are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). |
SciQ | SciQ-1616 | mitochondria
Title: Why in some cells is GTP made in citric acid cycle and in some ATP? In many animals GTP is produced in citric acid cycle. While in plants,bacteria and some animals ATP is produced. Why is this so ? What is the advantage ? This step is catalyzed by succinyl-CoA synthase which has two different isoforms- one which produces GTP while the other produced ATP.
It seems from this study that predominantly anabolic tissues prefer the GTP-producing form whereas the predominantly catabolic tissues use the ATP-producing from.
In the same paper they discuss that GTP is important for protein synthesis and it is also involved in production of phospho-enolpyruvate by PEP-carboxykinase in mitochondria; therefore playing an important role in anabolic processes.
The following is multiple choice question (with options) to answer.
Glutathione is a low-molecular-weight compound found in living cells that is produced naturally by what? | [
"amino acids",
"blood",
"liver",
"brain"
] | C | Glutathione is a low-molecular-weight compound found in living cells that is produced naturally by the liver. Healthcare providers give glutathione intravenously to prevent side effects of chemotherapy and to prevent kidney problems. |
SciQ | SciQ-1617 | mechanical-engineering, dynamics, kinematics
Title: Is there a simple trigonometric relationship between these two angles?
The setup shows 3 rigid links (with fixed lengths) constrained by 4 joints. The blue joints are fixed in place and only allow rotation, while the black joints can move and also allow rotation. Initially θ1 < θ2, and the top link is perfectly horizontal.
As θ1 decreases (due to the leftmost link rotating clockwise), it is clear that θ2 will increase, but I would like to get the specific value of θ2 as a function of θ1. Is there a name for this kind of problem? What would be the best software tool to simulate this? Since considering four-bar linkages is a useful tool in my research field, I happen to know of a paper that precisely solves what you want to do. George H. Martin published in 1958 in the journal Machine Design the paper "Four-Bar Linkages", the following equations are taken from that paper:
When you consider a four-bar linkage as shown below, then you know the angle $\theta _2$ and you want to know the angle that is the sum of $\beta$ and $\lambda$.
Considering the triangle OAD, we can write
$$ \beta = \sin^{-1} \left( \frac{b}{l} \sin \theta_2 \right).$$
So that is already the first half. For the triangle ABD, we can write
$$ \psi = \cos^{-1} \left( \frac{c^2+l^2-d^2}{2cl} \right).$$
Using $\psi$, we can write $\lambda$ as
$$ \lambda = \sin^{-1} \left( \frac{c}{d} \sin \psi \right).$$
With these, you should be able to work out a single equation for your problem.
The following is multiple choice question (with options) to answer.
What work together in pairs to bend or straighten a joint? | [
"muscles",
"nerve fibers",
"cartilage tissues",
"collagen bands"
] | A | Muscles work together in pairs to bend or straighten the joint. |
SciQ | SciQ-1618 | orbitals, atoms
Title: Why are atoms with eight electrons in the outer shell extremely stable? Atoms that have eight electrons in their outer shell are extremely stable. It can't be because both the $s$ and the $p$ orbitals are full, because then an atom with 13 or 18 valence electrons would be extremely stable. ($d$ has 10, and 5 is also stable).
Why is it that atoms with eight electrons in the outer shell are extremely stable? First, this isn't quite true. It is true for the first row of the periodic chart (from lithium to neon). It is almost true for the second row (from sodium to argon. But there are exceptions there. Beyond that it really isn't true at all for the elements beyond the first two columns.
The reason for the increased stability for the first two rows lies in quantum mechanics. Classically we can note that there are no $d$ electrons there. Another ways of looking at it from a classical point of view is that the early elements are too small to allow too many other atoms or groups of atoms around them. That tends to go away as you go down the periodic chart and the atoms get "fatter". A typical example is chloroplatinic acid which has six chlorines around it.
Most transition metals also can have more than four groups around them as well.
I suspect that this isn't an exceptionally useful explanation. As I said, the answer really lies in quantum mechanics. In looking up "molecular orbital theory", one reference can be found here.
The following is multiple choice question (with options) to answer.
What are the outer-shell electrons of an atom called? | [
"valence electrons",
"organism electrons",
"outer electrons",
"helium electrons"
] | A | Valence electrons are the outer-shell electrons of an atom. |
SciQ | SciQ-1619 | reproduction, asexual-reproduction
Title: can self-fertilization in flowers be called asexual reproduction? Suppose a flower having both male and female reproductive parts is self-fertilized then can this be called asexual reproduction...?I'm quite confused cause in this case the fusion of male and female gametes do take place but again the gametes are from the same parent....please help. According to this article from Berkeley, asexual reproduction is:
Any reproductive process that does not involve meiosis or syngamy
Using this definition of asexual reproduction and knowing self-fertilization involves meiosis and syngamy, it is not asexual.
The following is multiple choice question (with options) to answer.
What kind of reproduction is vegetative reproduction? | [
"sexual",
"meiosis",
"asexual",
"mitosis"
] | C | Vegetative reproduction is a type of asexual reproduction found in plants. This type of reproduction occurs when new individuals are formed without the production of seeds or spores. The formation of new plants out of rhizomes or stolons is an example of vegetative reproductive, such as in the strawberry plant. Other plants use this type of reproduction to reproduce through bulbs or tubers, or shoots and suckers that form along lateral roots. See the Plant Biology concepts for additional information. |
SciQ | SciQ-1620 | botany, homework, terminology, plant-anatomy, tissue
Interfascicular cambium differentiates from parenchyma or collenchyma cells located between the vascular bundles (mainly in stem)
The following is multiple choice question (with options) to answer.
What type of tissue runs the length of a stem in vascular bundles? | [
"thermal tissue",
"cardiac tissue",
"muscle tissue",
"vascular tissue"
] | D | |
SciQ | SciQ-1621 | zoology, circulatory-system, heart-output, amphibians
I would add to this my notes from when I was a biochem student (but studied Zoology), mentioning the arterial cone and a spiral valve. This is better described in Britannica:
The conus arteriosus is muscular and contains a spiral valve. Again, as in lungfishes, this has an important role in directing blood into the correct arterial arches. In the frog, Rana, venous blood is driven into the right atrium of the heart by contraction of the sinus venosus, and it flows into the left atrium from the lungs. A wave of contraction then spreads over the whole atrium and drives blood into the ventricle, where blood from the two sources tends to remain separate. Separation is maintained in the spiral valve, and the result is similar to the situation in lungfishes. Blood from the body, entering the right atrium, tends to pass to the lungs and skin for oxygenation; that from the lungs, entering the left atrium, tends to go to the head. Some mixing does occur, and this blood tends to be directed by the spiral valve into the arterial arch leading to the body.
The following is multiple choice question (with options) to answer.
Birds have a relatively large heart and a rapid what? | [
"blink rate",
"lifespan",
"digestive process",
"heart rate"
] | D | To keep their flight muscles well supplied with oxygen, birds evolved specialized respiratory and circulatory systems. Birds have special air sacs for storing extra air and pumping it into the lungs. They also have a relatively large heart and a rapid heart rate. These adaptations keep plenty of oxygenated blood circulating to the flight muscles. |
SciQ | SciQ-1622 | synoptic
Why is a front so quick to dissipate? Well, in large part because it's not a level situation; indeed, some storm energy is continually lost away to friction. Because of this, a front actually needs continual reinforcement to even maintain its gradient. Some times the pattern will permit fronts to continue through repeated periods of weakening and intensification as upper troughs pass by. As a trough comes by and then shifts by on east (in tandem with the primary surface low), the front will start to weaken some... perhaps gradually becoming stationary... only to reignite when the next upper system comes in from the west [stationary fronts aren't, as may often be suggested, a cold front and warm front "at war", but instead rather more like a lull in the "battle", where the cold front has run out of steam, but readied next for the warm air to start surging back north should another trough/low move in to re-fire the convergence]. Often you can see quite a long chain of fronts (troughs) connecting together lows pressure systems across continents... (which work into the shape and positioning to the polar jet stream). Other times, when the upper systems come less consistently or the upper flow starts to break down/shift into other regions, the front will quickly fade from existence. So much so that I don't believe you're ever not going to see anything like a true front anywhere near a formative synoptic high pressure... unless maybe a giant meteor or as-of-yet-unseen-in-size nuclear bomb were precisely set loose upon a front. And then... well I suggest trying to witness the brief time that the high pressure is connected to the frontal boundaries... should probably be the least of your concerns!
The following is multiple choice question (with options) to answer.
When a warm air mass becomes trapped between two cold air masses, what type of front occurs? | [
"obscured front",
"storm front",
"stationary front",
"occluded front"
] | D | With an occluded front , a warm air mass becomes trapped between two cold air masses. The warm air is lifted up above the cold air as in Figure below . Cloudy weather and precipitation along the front are typical. |
SciQ | SciQ-1623 | # Mathematical Physics: Differential equation of a raindrop
I hope this is a suited question for this site since it contains a mix of physics and mathematics. In case I should post this on the physics stackexchange site, please let me know.
A spherical raindrop is falling from the sky. Because of the humid atmosphere the raindrop will gain mass during his fall. The increase in mass per time is proportional to the current surface area.
1. Find an equation for the radius of the drop as a function of time ($r(t)$). ($r(0) =r_0$)
2. Find and solve the equation of motion for the raindrop. The equation of motion should depend on $r_0$
My work so far:
Mass: $m(t)=\frac{4}{3} \pi r(t)^3 \rho$
Sufrace Area: $A(t)=4\pi r(t)^2$
\begin{aligned} & \implies \frac{dm(t)}{dt}=\frac{d}{dt}(\frac{4}{3}\pi r(t)^3 \rho)=4 \pi r(t)^2 r'(t)\rho\\ & \iff 4 \pi \rho r(t)^2 r'(t)=\lambda 4 \pi r(t) ^2 \iff r'(t)=\frac{\lambda}{\rho} \iff \frac{dr}{dt}=\frac{\lambda}{\rho} \\ & \iff \int dr = \frac{\lambda}{\rho} \int dt \iff r(t)=\frac{\lambda}{\rho}t+c \\ & \color{blue}{\implies r(t)=\alpha t+r_0} \space \space \space \space \space \space \space \space \space \space \space \text{where}\space \space\alpha=\frac{\lambda}{\rho} \end{aligned}
Equation of motion:
Gravitational Force: $mg$
The following is multiple choice question (with options) to answer.
What is water falling from the sky called? | [
"distillation",
"erosion",
"precipitation",
"vaporization"
] | C | |
SciQ | SciQ-1624 | molecular-orbital-theory, metal, conductivity, electricity
Title: Formation of Bands in Semi-Conductors At school, we are learning about semi-conductors and their applications in modern electronics. One of the features of semi-conductors is that there is a small energy gap between the valence and conduction band. My teacher explains that he bands occur because in the compound, since there are millions of atoms close together, due to the Pauli Exclusion Principle the energy levels of the atoms slightly change in value, forming band. When electrons are excite form the valence to conduction band, the substance is able to conduct an electric current.
However I fairly certain this is a superficial explanation as it doesn't really explain what the conduction and valence band is and doesn't explain why electrons in the conduction band are able to conduct electricity while electrons in the valence band can't.
After some researching on the web this is my rough understanding of semi-conductors now:
The s and p orbitals of the metals combine together to form MOs. As the AOs of millions of atoms combine together, these MOs become a continuum, forming two bands. One band is the valence band which consists of 2s sigma bonding and anti-bonding orbitals while the other band is the conduction band which consists of 2p pi bonding and anti-bonding orbitals. This explains why electrons in the conduction band are able to conduct an electric current since they are conjugated (not sure if this is the correct term) across the entire substance and hence explains why electrons in metals are described as a 'sea of de-localised electrons'.
This is just my understanding which isn't that solid. Could someone please offer a more in-depth explanation into how these bands form and correct any wrong things that I said. Also I still have some questions.
One website stated that 'it is only when these bands become filled with 2p electrons that the elements lose their metallic character'. Which I interpret as that when the conduction band is completely filled with electrons, the substance isn't able to conduct electricity any more. However why is this so? Aren't there still electrons in the pi MOs which are 'de-localised' along the substance?
Also the above explanation using MOs seems to explain why these bands form. Does this mean that the explanation that my teacher gave me about the Pauli Exclusion Principle being responsible for the formation of bands is wrong and not needed?
The following is multiple choice question (with options) to answer.
What forms when atoms share or transfer valence electrons? | [
"levels",
"bonds",
"fusion",
"replicas"
] | B | A chemical bond is a force of attraction between atoms or ions. Bonds form when atoms share or transfer valence electrons. Valence electrons are the electrons in the outer energy level of an atom that may be involved in chemical interactions. Valence electrons are the basis of all chemical bonds. For a video introduction to chemical bonds, go to this URL: http://www. youtube. com/watch?v=CGA8sRwqIFg . |
SciQ | SciQ-1625 | biochemistry
Now we can go on to explain the action potential in the neuron, which is not something I originally wanted to go into, but since the original question has been edited I feel that I have to address this now. Even though the original question now makes no reference to the action potential, it is describing exactly those events that occur during an action potential.
The inside and the outside of the neuron is separated by a cell membrane, which is selectively permeable to ions such as $\ce{Na+}$, $\ce{K+}$, $\ce{Ca^2+}$, and $\ce{Cl-}$. Of these four, sodium and potassium ions are the most important as they are directly involved in depolarisation and repolarisation when an action potential is generated.
The distribution of ions is not symmetrical across the membrane. When at rest, the extracellular concentration of $\ce{Na+}$ is much higher than the intracellular concentration of $\ce{Na+}$; the converse is true for $\ce{K+}$. Due to the membrane having different permeabilities to $\ce{Na+}$ and $\ce{K+}$ (for details of this, one can consult a neuroscience text), the resting membrane potential is -70 mV. Conventionally, the membrane potential is described as the intracellular potential with respect to the potential of the extracellular potential; this means that the inside of the cell is more negative.
Neurons react to certain stimuli by having $\ce{Na+}$ enter the cell, via various means which are not important to the current discussion. Since positively charged ions are entering the cell, this causes the membrane potential to rise. Once the membrane potential has risen to roughly -55 mV, voltage-gated $\ce{Na+}$ channels open, making the membrane permeable to $\ce{Na+}$.
At this stage, we have to consider the two factors that influence the diffusion of $\ce{Na+}$:
Since the potential difference is still negative, it favours influx of $\ce{Na+}$.
Since the extracellular concentration of $\ce{Na+}$ is larger than the intracellular concentration, the concentration gradient also favours influx of $\ce{Na+}$.
The following is multiple choice question (with options) to answer.
Which part of the axon has a higher membrane potential? | [
"muscular hillock",
"axon hillock",
"biofilm hillock",
"canals hillock"
] | B | |
SciQ | SciQ-1626 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
A diploid zygote is formed when one sperm does what? | [
"cracks the egg",
"incapacitates the egg",
"fertilizes the egg",
"repels the egg"
] | C | |
SciQ | SciQ-1627 | thermodynamics, electrochemistry, ph, electrolysis
Title: How does pH change during the electrolysis of water? How does the pH change during electrolysis of a water and magnesium sulphate solution? Also, will this pH change happen every time? Does the pH change differently when there is just water in the anode and cathode? The pH will increase or decrease or stay the same, depending on where and when and how you look.
At the cathode, $\ce{Mg^{2+}}$ ions will be reduced to magnesium metal. The magnesium will immediately react with water to evolve $\ce{H2}$ gas and form $\ce{Mg(OH)2}$, which is a strong base (though not very soluble). The pH increases near the cathode. The $\ce{H+}$ concentration due to the slight acidity of $\ce{MgSO4}$ is negligible but any $\ce{H+}$ which is removed by being turned into $\ce{H2}$ gas results in the same effect: the pH increases at the cathode.
At the anode, $\ce{SO4^{2-}}$ anions are oxidized, $\ce{O2}$ is evolved and the sulfate ion is converted into $\ce{SO3}$ and hydrates to $\ce{H2SO4}$. The pH at the anode decreases as sulfuric acid is formed.
If you stir the solution and then take a pH measurement, the pH will not have changed, because the $\ce{H2SO4}$ will react with the $\ce{Mg(OH)2}$ to produce $\ce{MgSO4}$ again, and the only change will have been that $\ce{H2O}$ was converted into $\ce{H2 and O2}$.
The following is multiple choice question (with options) to answer.
As ph increases what happens to a solution? | [
"stays the same",
"depends on the solution",
"becomes more basic",
"becomes less basic"
] | C | The deprotonated form of an acid is referred to as its conjugate base. Similarly, the protonated form of a base is referred to as its conjugate acid. |
SciQ | SciQ-1628 | newtonian-mechanics
Title: Effects of vertical circular motion to the body weight Our body weight will experience the differences when moving at constant speed in a vertical circular motion such as roller coaster. Why do we feel heavier when at the bottom of the loop and lighter when at the top ? When you are at the bottom of a roller coaster about to move upwards (in say a circular motion), the net force you experience is given by,
$F_{net} = \frac{mv^2}{r}$
The forces acting on you are the normal force of the track $N$, and gravity, $mg$.
Therefore,
$N - mg = \frac{mv^2}{r}$, and thus,
$N = \frac{mv^2}{r} + mg$
This normal force is the force the track is pushing up on you, and it is what makes you feel heavy.
When you are at the top of the roller coaster moving down, again assume in circular motion, the net force is now given by,
$F_{net} = -\frac{mv^2}{r}$
Now we have,
$N - mg = -\frac{mv^2}{r}$
Thus,
$N = mg - \frac{mv^2}{r}$
Therefore the normal force is less at the top of the track than at the bottom.
This can be understood intuitively as when you are moving upwards, gravity is opposing the centripetal motion and thus the normal force must be greater to compensate.
When you are moving downwards in circular motion, gravity is assisting this centripetal acceleration, and thus less normal force is required from the track.
The following is multiple choice question (with options) to answer.
What is the term for changes in speed or direction, changes that make a roller coaster ride so exciting? | [
"oscillation",
"acceleration",
"inclination",
"transmission"
] | B | Imagine the thrill of riding on a roller coaster like this one! The coaster slowly crawls to the top of the track and then flies down the other side. It also zooms around twists and turns at breakneck speeds. These changes in speed and direction are what make a roller coaster ride so exciting. Changes in speed or direction are called acceleration. |
SciQ | SciQ-1629 | botany, marine-biology, salt
Title: Mangroves and desalination of sea water I am not an expert but I guess that mangroves (or some other plants that thrive in sea water) perform some kind of desalination to extract fresh water from sea water.
Is this true? If yes, What biological mechanisms are used to remove salt from sea water?
I am interested in any research about biological desalination. This paper might be of interest to you: https://advances.sciencemag.org/content/6/8/eaax5253.
The researchers created a synthetic mangrove that actually performs desalination, using the principles of natural mangroves.
The introduction has a good overview of the main ways mangroves desalinate saline water, namely:
Physical blockage by suberin within cells walls
Selective permeability of cell membranes in root
Negative pressure caused by evaporation that acts as hydraulic pressure to cause take-up of water by roots
All these combine to turn the mangrove into a kind of natural RO (reverse osmosis) machine.
The following is multiple choice question (with options) to answer.
What do aquatic mollusk species use for respiration? | [
"lungs",
"phototropism",
"gills",
"pores"
] | C | Which of the following statements about the anatomy of a mollusk is false? a. Mollusks have a radula for grinding food. A digestive gland is connected to the stomach. The tissue beneath the shell is called the mantle. The digestive system includes a gizzard, a stomach, a digestive gland, and the intestine. Mollusks have a muscular foot, which is used for locomotion and anchorage, and varies in shape and function, depending on the type of mollusk under study. In shelled mollusks, this foot is usually the same size as the opening of the shell. The foot is a retractable as well as an extendable organ. The foot is the ventral-most organ, whereas the mantle is the limiting dorsal organ. Mollusks are eucoelomate, but the coelomic cavity is restricted to a cavity around the heart in adult animals. The mantle cavity develops independently of the coelomic cavity. The visceral mass is present above the foot, in the visceral hump. This includes digestive, nervous, excretory, reproductive, and respiratory systems. Mollusk species that are exclusively aquatic have gills for respiration, whereas some terrestrial species have lungs for respiration. Additionally, a tongue-like organ called a radula, which bears chitinous tooth-like. |
SciQ | SciQ-1630 | diffusion
The reverse process is also happening with molecules diffusing from right to left at a rate proportional to their concentration in the right side solution. As the concentration on the right side increases to be equal to the concentration on the left, so the diffusion rates become equal and there is zero nett diffusion and the system approaches equilibrium.
Note that this assumes a "perfect" system where there is no chemical reaction occurring between the solutes or between the solutes and the membrane. In practice this means that either the interaction between solutes A and B is the same as the interaction between the solutes and the solvent or that the solute molecules are so greatly outnumbered by the solvent molecules that the solute-solute interactions are not significant.
The rate of diffusion of solute A may be different from B (i.e. the proportionality constant between rate and concentration may be different). This means that before reaching equilibrium the relative concentrations of A and B may change but at equilibrium, the relative concentration will be the same as initially.
If we define "reaching equilibrium" as having some fraction (say 99.99%) of the final concentration then increasing the initial global concentration will increase the lag for both solutes equally and will not change their relative concentrations.
The following is multiple choice question (with options) to answer.
Because the solute is moving down the concentration gradient, and no input of energy is required, facilitated diffusion is considered what type of transport? | [
"passive",
"active",
"adaptive",
"neutral"
] | A | Facilitated diffusion is the diffusion of solutes through integral membrane transport proteins. Facilitated diffusion is a type of passive transport . Even though facilitated diffusion involves transport proteins (and is essentially a transport process), it can still be considered passive transport because the solute is moving down the concentration gradient, and no input of energy is required. Facilitated diffusion utilizes proteins known as uniporters. A uniporter can be either a channel protein or a carrier protein. |
SciQ | SciQ-1631 | food, nutrition
Supplements aren't intended to be a food substitute because they can't replicate all of the nutrients and benefits of whole foods, such as fruits and vegetables.
and there are three main differences:
Greater nutrition. Whole foods are complex, containing a variety of
the micronutrients your body needs — not just one. An orange, for
example, provides vitamin C plus some beta carotene, calcium and
other nutrients. It's likely these compounds work together to produce
their beneficial effect.
Essential fiber. Whole foods, such as whole grains, fruits,
vegetables and legumes, provide dietary fiber. Most high-fiber foods
are also packed with other essential nutrients. Fiber, as part of a
healthy diet, can help prevent certain diseases, such as type 2
diabetes and heart disease, and it can also help manage constipation.
Protective substances. Whole foods contain other substances important
for good health. Fruits and vegetables, for example, contain
naturally occurring substances called phytochemicals, which may help
protect you against cancer, heart disease, diabetes and high blood
pressure. Many are also good sources of antioxidants — substances
that slow down oxidation, a natural process that leads to cell and
tissue damage.
So you could live off of some meal replacement shake for the rest of your life but should you? Probably not.
The following is multiple choice question (with options) to answer.
What does fiber help keep at normal levels in the body? | [
"bloodpressure",
"hydration",
"salt and cholesterol",
"sugar and lipids"
] | D | Fiber is a complex carbohydrate that consists mainly of cellulose and comes only from plants. High-fiber foods include whole grains and legumes such as beans. Fiber can’t be broken down by the digestive system, but it plays important roles in the body. It helps keep sugar and lipids at normal levels in the blood. It also helps keep food waste moist so it can pass easily out of the body. |
SciQ | SciQ-1632 | thermodynamics, evaporation, gas, liquid-state
On the water surface, knowing the temperature, we can estimate the vapor pressure and vapor mixture fraction. Then there will be an diffusion process for the water vapor to move out and for the ambient air to move in. Because the water surface doesn't allow the air to further move, a circulation forms. When the water vapor moves out, the water vapor pressure drops, so more liquid water evaporates to fill up the loss of water vapor. The evaporation associates latent heat so water surface area temperature drops (you may see dew on the bowl wall). Then a heat transfer process starts which may initiate water circulation as well.
As this is complex, doing test might be a quick way to get the K value if you assume it is a constant, which is questionable.
The following is multiple choice question (with options) to answer.
What is it called when plant roots absorb liquid water and release water vapor into the atmosphere? | [
"perspiration",
"transpiration",
"evaporation",
"sedimentation"
] | B | Liquid water is taken up by plant roots. The plant releases water vapor into the atmosphere. This is transpiration. |
SciQ | SciQ-1633 | nuclear-physics, fusion
Title: Nuclear Fusion Fuels I have seen some possible fuels for nuclear fusion.
My questions are:
Are there other fuels available even theoretically or the list of candidates is limited?
What are the requirements that a "substance" should meet in order to be able to be used as fuel for nuclear fusion? As the content of the wiki page shared by you already states,
"Tritium is a natural isotope of hydrogen, but because it has a short half-life of 12.32 years, it is hard to find, store, produce, and is expensive. Consequently, the deuterium-tritium fuel cycle requires the breeding of tritium from lithium".
So yes, the fuel do exist, but some are hard to find while others are produced by certain nuclear.
Any fuel beside that of the link you provided, yes, theoretically it's possible, but I'm not aware if we have really proved any of it practically though experiments, because of the conditions involving. Just like elements of higher mass fuse inside sun during stellar death.
http://abyss.uoregon.edu/~js/ast122/lectures/lec18.html
http://sciencelearn.org.nz/Contexts/Just-Elemental/Science-Ideas-and-Concepts/How-elements-are-formed
So, we can say it's theoretically available and that's how matter is formed in distant galaxies, but when it comes to experiments, the condition involved are quite extreme and out of our reach to manifest or replicate.
The basic requirement of nuclear fuel is the ability of the nucleus to combine with that of another at very high temperature to form stabilized nucleus liberating very high amount of energy in form of heat. So the amount of energy that could be harnessed, how economic is the process, and the availability of the fuel, along with the stability of the output nucleus are some of the basic factors that are kept in consideration while choosing a fusion fuel. There are other factors also, like neutron scattering, radiation(alpha particles) and energy density that comes into play while choosing a fuel.
The following is multiple choice question (with options) to answer.
Fossil fuels and nuclear power are what type of resource? | [
"nonrenewable",
"reusable",
"renewable",
"recurring"
] | A | Nonrenewable resources include fossil fuels and nuclear power. |
SciQ | SciQ-1634 | equilibrium
Title: Chemical equilibrium and stoichiometry In reactions that go until the end the stoichiometric number indicates the exact amounts of reactants and products you will get. However, this is not the case in equilibrium reactions and you will get a different amounts (concentrations) than what exhibits the stoichiometric numbers.
$$\ce{Na + Cl -> NaCl}$$
You will get in the end 1 mole of NaCl from 1 mole of Na and one mole of Cl.
$$\ce{2SO3<=>2SO2 + O2}$$
In equilibrium you will not get 1 molar of $\ce{O2}$ and 2 molar of $\ce{SO2}$ from 2 molar of $\ce{SO3}$.
Then what do the stoichiometric numbers indicate in equilibrium? Let us take the example of your equation:
$$\ce{2SO3<=>2SO2 + O2}$$
The stoichiometric coefficients represent two facts:
If 2 mole $\ce{SO3}$ reacts, it will give 2 mole $\ce{SO2}$ and 1 mole $\ce{O2}$ but one needs to remember here that all of the 2 moles will not react. But the number of moles that do dissociate, give products in the above ratio i.e. if initially have 2 moles of $\ce{SO3}$ and degree of dissociation is 50%, then we will have 1 mole of $\ce{SO3}$ reacting to give 1 mole of $\ce{SO2}$ and half mole of $\ce{O2}$
The stoichiometric coefficients also provide the powers to which the concentrations of each compound will be raised to in the expression for equilibrium constant $$K_\mathrm c = \frac{[\ce{SO2}]^2[\ce{O2}]}{[\ce{SO3}]^2}$$
The following is multiple choice question (with options) to answer.
The stoichiometric coefficients indicate the relative amounts of what? | [
"reactions and products",
"trajectories and products",
"reactants and products",
"exigencies and products"
] | C | stoichiometric coefficient : The letters a, b, c, and d where A and B are reactants, and C and D are products. The stoichiometric coefficients indicate the relative amounts of reactants and products. |
SciQ | SciQ-1635 | zoology, circulatory-system, heart-output, amphibians
I would add to this my notes from when I was a biochem student (but studied Zoology), mentioning the arterial cone and a spiral valve. This is better described in Britannica:
The conus arteriosus is muscular and contains a spiral valve. Again, as in lungfishes, this has an important role in directing blood into the correct arterial arches. In the frog, Rana, venous blood is driven into the right atrium of the heart by contraction of the sinus venosus, and it flows into the left atrium from the lungs. A wave of contraction then spreads over the whole atrium and drives blood into the ventricle, where blood from the two sources tends to remain separate. Separation is maintained in the spiral valve, and the result is similar to the situation in lungfishes. Blood from the body, entering the right atrium, tends to pass to the lungs and skin for oxygenation; that from the lungs, entering the left atrium, tends to go to the head. Some mixing does occur, and this blood tends to be directed by the spiral valve into the arterial arch leading to the body.
The following is multiple choice question (with options) to answer.
Blood enters the heart in what valve? | [
"atria",
"tricuspid",
"aortic",
"mitral"
] | A | Blood flows in only one direction in the heart. Blood enters the atria, which contract and push blood into the ventricles. The atria relax and the ventricles fill with blood. Finally, the ventricles contract and push blood around the body. |
SciQ | SciQ-1636 | geology, mineralogy, minerals, weathering
To me, supergene has a specific meaning, it may be part of the weathering process in some locations, but weathering involves the breaking down of rocks due to: reactions with atmospheric gasses, water (usually rain), changes brought on by plants, bacteria wind and temperature.
My suggestion to use the term weathering or weathered.
The following is multiple choice question (with options) to answer.
What works through chemical reactions that change the rock? | [
"rock weathering",
"chemical breakdown",
"chemical weathering",
"gradual weathering"
] | C | Chemical weathering is different than mechanical weathering. The minerals in the rock change their chemical makeup. They become a different type of mineral or even a different type of rock. Chemical weathering works through chemical reactions that change the rock. |
SciQ | SciQ-1637 | speciation
Title: Does too much Genetical Modification leads to formation of new species? I think Genetical Modification can be termed as 'Artificial Mutation'.
Is it possible that genes can be modified so much that it leads to the introduction of new Species i.e Can integration of large no. of Helpful mutations lead to quick evolution? yes it possible, in one article show a study for Mycoplasma genitalium which have 525 gene, however only 382 genes are essential for biological functions, they take out the nature gene and place the ' artifical gene' which synthsis in vitro, to test if the M. genitalium will survival when the No. of gene lower than 382. If it survival it will be a new species.
The following is multiple choice question (with options) to answer.
What is necessary for new alleles to be created? | [
"new rna",
"new frequencies",
"cross-pollination",
"new mutations"
] | D | No new mutations are occurring. Therefore, no new alleles are being created. |
SciQ | SciQ-1638 | dna
D) Indeed, even when one looks at repeat elements derived from endogenous retroviruses, there are those that are of functional significance; Syncitin (which actually codes for a protein) is responsible for trophoblast fusion + placenta formation (See https://www.ncbi.nlm.nih.gov/pubmed/10693809 ) , and there are multiple repeats that themselves serve as enhancers of interferon response genes. See https://www.ncbi.nlm.nih.gov/pubmed/26941318
The following is multiple choice question (with options) to answer.
What does the placenta sustain during pregnancy? | [
"the heart",
"the fetus",
"the mother",
"the endocrine system"
] | B | Placental mammals are therian mammals in which a placenta develops during pregnancy. The placenta sustains the fetus while it grows inside the mother’s uterus. Placental mammals give birth to relatively large and mature infants. Most mammals are placental mammals. |
SciQ | SciQ-1639 | metabolism, ecology, photosynthesis
Title: Why isn't phosphorus or nitrogen a limiting nutrient for animals? Nitrogen and Phosphorus are usually the limiting nutrient for plants, especially for algae. Phosphorus is used for DNA, ATP and phospholipids, and Nitrogen is used for pretty much every protein a cell might want to produce. That is, their need for biological processes is not tied specifically to photosynthesis: anything that lives is going to need them, pretty much for anything it might want to do. It would make sense for them to be a limiting nutrient for almost anything that's trying to grow, plant or animal.
Yet for animals the limiting "nutrient" seems to always be energy, ie: food. Why aren't animals limited by lack of nutrients in the same way that plants are? Obviously animals need these nutrients, too. Or to reverse the question, why do plants need so much more phosphorus/nitrogen than animals do?
My best guess is that an animal's digestion of plant material is relatively inefficient energy-wise but relatively efficient nutrient-wise. So for an animal to eat enough food to have sufficient energy to survive, it's probably eaten more than enough Nitrogen and Phosphorus for its needs. But I'm just guessing and I can't find any data that would back up that guess. Phosphorus
Your suggestion that if we are meeting our calorific requirement we will be getting enough is true for phosphorus.
Most foods contain lots of phosphorus. The maximum dietary requirement occurs during adolescent growth, estimated at 1250 mg per day. Assuming a calorie intake of 2500 kcal we can calculate a 2500 kcal equivalent phosphorus content for various foods:
skimmed milk contains 7,400 mg phosphorus per 2500 kcal
roasted chicken breast contains 7,500 mg phosphorus per 2500 kcal
cooked white rice contains 3840 mg per 2500 kcal
(Calculations are based upon values obtained via this site.)
Nitrogen
Our requirement for nitrogen is met by our protein intake: inadequate protein intake manifests as kwashiorkor which is essentially due to a dietary deficiency of essential amino acids. In other words, the only way to achieve a nitrogen-deficient diet is to not eat protein, and this would not be alleviated by any inorganic source of nitrogen, even if we could consume enough of such a N source.
The following is multiple choice question (with options) to answer.
Other than nitrogen, which nutrient most often limits marine production? | [
"potassium",
"zinc",
"phosphorus",
"calcium"
] | C | |
SciQ | SciQ-1640 | solar-system, comets
Title: How does a comet form? As the title explains,
How does a comet form?
What are the elements, what is a comet composed of?
Why didn't they become part of planets, moons or asteroids?
Comets are some of the material left over from the formation of the planets. Our entire solar system, including comets, was created by the collapse of a giant, diffuse cloud of gas and dust about 4.6 billion years ago. Much of the matter merged into planets, but some remained to form small lumps of frozen gas and dust in the outer region of the solar system, where temperatures were cold enough to produce ice.
A comet is generally considered to consist of a small nucleus embedded in a nebulous disk called the coma. the nucleus, containing practically all the mass of the comet, is a “dirty snowball” conglomerate of ices and dust.For one, of the observed gases and meteoric particles that are ejected to provide the coma and tails of comets, most of the gases are fragmentary molecules, or radicals, of the most common elements in space: hydrogen, carbon, nitrogen, and oxygen. The radicals, for example, of CH, NH, and OH may be broken away from the stable molecules CH4 (methane), NH3 (ammonia), and H2O (water), which may exist as ices or more complex, very cold compounds in the nucleus.
3.Many astronomers believe that these small objects never became planets or other large objects because of the gravity of the large planets. For example, the pull of Jupiter's kept 'stirring the pot' of the asteroid belt, so that the gravitational pull of the asteroids on each other was constantly being disturbed.
For the Kuiper belt and Oort cloud, there is a popular theory called 'planetary migration.' The main idea behind this theory is that the large outer planets of our Solar System started out much closer to the Sun when the Solar System was formed. As they migrated outward through the cloud of small objects still there, the gravity of these large planets pulled a lot of the small objectsout of their orbits. Some were pulled into the planets, and some were flung far into the outer reaches of the Solar System.
The objects that were flung very far out by Jupiter became the Oort cloud. The object that were not flung out quite as far by the movement of Neptune became the Kuiper belt.
Source
The following is multiple choice question (with options) to answer.
What astronomical phenomenon is often comprised of remnants of the earliest material that formed in the solar system? | [
"asteroids",
"meteorites",
"particles",
"comets"
] | B | Many meteorites are remnants of the earliest material that formed in the solar system. |
SciQ | SciQ-1641 | metallurgy, nuclear-chemistry, geochemistry
Title: Why are rare earth metals and platinum group metals are often found clustered together in ores Rare earth and platinum group metals are often found clustered together in the earth's crust. Mining for platinum, for instance, also yields Rhodium and Ruthenium belonging to the same group. Likewise, rare earth elements such as Neodymium, Europium and Samarium also cooccur in the same ore, so much so, that they are difficult to chemically separate.
It could be reasoned that it's the result of nucleogenesis where elements are formed consecutively based on their atomic number. While it might explain the first row and the second row of each group, where each metal is only one atomic number apart, it doesn't explain why metals from both rows are found together which are much further apart.
Alternatively, the similar chemistry of each group could explain the clustering. The two groups are the only group with this property. It fails to explain, however, how these metals found each other in a molten soup of heterogeneous elements. There may be some geological factors in the clustering, but it's unclear.
Why are the two groups of elements found clustered together? The factors that generate mineral concentrations are complex and often only partly known
Introduction: geology is complicated
The one thing we can be very certain about is is that the distribution of minerals in the earth's crust has very little to do with the primordial origins of the component elements (that is where they came from in the early solar system and how they were originally generated). Most "heavy" elements are originally formed in the cores of supernovae and not in either the big bang or in normal stars.
The distribution of elements in the earth is mostly unrelated to the cosmic origins of elements because the earth's crust is not static but is frequently churned up by a variety of processes on a geological timescale. If we go back far enough in the history of the planet, everything was molten and this allowed some of the denser components to separate out before the surface cooled enough to be solid. The led to the core being mostly metallic (and consisting of mostly iron and nickel). Higher layers contain less dense minerals containing a lot of silicate minerals. At the top there is a thin layer, the crust, which is where we find useful minerals and it is even more concentrated in silicate minerals and even less dense.
The following is multiple choice question (with options) to answer.
Minerals are grouped based on what? | [
"chemical composition",
"carbon composition",
"mineral composition",
"density"
] | A | Minerals are divided into groups. The groups are based on their chemical composition. |
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The following is multiple choice question (with options) to answer.
What is the term for the average number of individuals in a population for a given area? | [
"population structure",
"result density",
"Area Density",
"population density"
] | D | Another sign of a species’ state of health is the density of its populations. Population density is the average number of individuals in a population for a given area. Density is a measure of how crowded or spread out the individuals in a population are on average. For example, a population of 100 deer that live in an area of 10 square kilometers has a population density of 10 deer per square kilometer. |
SciQ | SciQ-1643 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
What is the shape of the thyroid gland? | [
"snake - shaped",
"butterfly-shaped",
"square-shaped",
"triangle-shaped"
] | B | Thyroid Gland The thyroid gland is located in the neck, just below the larynx and in front of the trachea, as shown in Figure 37.16. It is a butterfly-shaped gland with two lobes that are connected by the isthmus. It has a dark red color due to its extensive vascular system. When the thyroid swells due to dysfunction, it can be felt under the skin of the neck. |
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