The main reason for food spoilage is the reproduction of microorganisms, low temperature can inhibit the growth of microorganisms, and retain the original flavor of food to the greatest extent, so the refrigerator is currently the most common way to preserve household food.
It is true that high temperatures kill the vast majority of bacteria, but if you envision sustained high temperatures to preserve food, there are a few other problems you face:
The first is the destruction of the flavor of the food, and the continuous high temperature will destroy the structure of the food and lose the original taste. And a series of by-products from heating can alter the flavor of the food, which is contrary to the heat sought after in cooking.
Secondly, high temperature will degrade, denature, and even produce harmful substances in food. This is best known for the deterioration of acrylamide and grease at high temperatures produced by the Maynard reaction.
Although continuous high temperature is not suitable for food preservation, short-term high temperature sterilization and aseptic sealed packaging can reduce the damage to the flavor quality of food while using high temperature sterilization, which is also the principle of pasteurization with a long history and wide application in the food industry (in fact, UHT, high temperature and high pressure canned food sterilization are this basic principle, but the temperature and conditions have changed).
by a large naked ape
Q.E.D.
Q2
by 柒拾一
Answer:
Before the 2008 Wenchuan magnitude 8 earthquake, the change of geomagnetic field in the extreme seismic region caused irregular disturbance, deflection and even abnormal rotation of the compass. This indicates that before the strong earthquake is about to occur, there is a magnetic field disorder and a magnetic jet anomaly in the epicenter. Freunf's literature shows that the pressure of the rock will produce charge polarization, and the charge movement will produce an electric current, which reaches a maximum before the rock fractures, which is 34 times that of the pressurized rock. The charge in the compression zone of the rock spreads to the non-compression zone, and the in-situ stress compresses or stretches the rock, affecting its electrical conductivity. The sudden increase in electrical conductivity causes a sudden change in the local magnetic field.
Before the earthquake, the surging of underground fluids caused the expansion and closure of faults and fissures in the earthquake-bearing area, and produced a certain frequency of magnetic fluctuations. The natural frequency properties of underground rock formations respond resonantly to the frequency of magnetic vibration, and its intensity decays rapidly with the increase of distance, which is a kind of "magnetic intermittent eruption" before a major earthquake, similar to the "Tesla effect" reflected in the physicist Tesla's supertransmission experiment of reaching a strong output with a small input. This results in an unusually drastic geomagnetic disturbance effect.
Addendum: In fact, the geomagnetic field has four components, namely the main magnetic field, the lithospheric magnetic field, the variable magnetic field, and the induced magnetic field. The traditional analysis of the seismic and magnetic effects is mostly based on the basic field of geomagnetism (the main magnetic field and the lithospheric magnetic field), and the main magnetic field accounts for the vast majority, and most earthquakes occur at the top of the earth's crust and upper mantle, that is, in the lithosphere. According to the author's investigation, the previous seismic analysis mainly used the fundamental field of the geomagnetic field, which accounts for the majority of the main magnetic field, to analyze the seismic and magnetic effects.
However, some researchers later analyzed the correspondence between the total strength, magnetic declination, magnetic inclination angle and earthquake of the lithospheric magnetic field before and after the earthquake. The results show that the influence of the lithosphere is mainly concentrated near the epicenter, and is not reflected in the area far from the epicenter. At the same time, due to the different geological structures and seismic mechanisms, the seismic and magnetic changes in different regions have different manifestations and amplitudes.
Resources:
Freunf Friedemann.Toward a unified solid state theory for pre - earthquake signals [ J] . Acta Geophysica,2010 , 58 ( 5 ) :719 - 766.
Gu Chunlei, Zhang Yi, Xu Rugang, et al. Progress in Geophysics, 2010(2):6.
Zeng Xiaoping, Zheng Ji'an, Wang Caoyi, et al. Pre-earthquake megamagnetic anomaly and its short-term warning significance[J].Strategic Study of Chinese Academy of Engineering,2011,13(04):48-53.)
by Lan Duoduo
Q.E.D.
Q3
by 小玉
Answer:
As a must-have item in shabu-shabu, mutton rolls have won the love of many diners for their delicious taste and unique flavor. Let's briefly analyze why most of the lamb cut out is rolled from a mechanical point of view.
Knives used in the kitchen are generally wedge-shaped, and their cross-section is inverted triangle. It is conceivable that if a downward force is applied to the knife, its sides will be squeezed to both sides at the same time, and the frozen lamb slices will bend and deform when they are squeezed, thus cutting the lamb into rolls.
Can you master the principle of cutting lamb rolls to cut a complete lamb roll? Actually, no, you also need to grasp the temperature of the mutton and the thickness of the meat roll. Generally speaking, do not cut the frozen lamb immediately, because the lamb is too hard at this time. It is easy to break due to uneven force when cutting, and cutting hard things for a long time will also cause more wear and tear on the blade.
Usually put the mutton at room temperature to thaw for a while before cutting, it is not good to leave it for a long time, the completely thawed mutton is very soft, and it naturally cannot be rolled when cutting. In addition, the cut meat roll should not be too thick, otherwise the squeezing force exerted by the knife edge to the sides is too small enough for the lamb to roll up, and the cut meat will be flaky.
Doesn't it mean that the speed of light does not change? Doesn't it "slow down" in the water? No.409
by Sid
Q.E.D.
Q4
by zsh
Answer:
The color streaks on the oily part are due to the interference of the thin film of the wave, because when the light is incident on the oil film, it will be reflected from the upper and lower surfaces respectively, so that two beams of light from the same light source are superimposed and interfered. Their optical path difference is
n refers to the refractive index of the oil film, d refers to the thickness of the oil film, and for different wavelengths of light, if the optical path difference is equal to an integer multiple of the wavelength, the emission interference will be enhanced. If it is an odd multiple of half a wavelength, it is interference cancellation, so interference fringes of different colors will appear.
If you observe carefully, you will also find that soap bubbles can also see colored stripes, and he is also a kind of film interference, I don't know if I have found pinching.
by Lan Duoduo
Q.E.D.
Q5
by 匿名
Answer:
Most portable lighters use liquefied butane as fuel. Butane is a flammable gas that is stored in liquid form at room temperature in a sealed container inside a fire engine. When a lighter is dropped to the ground, if its casing ruptures (as is common in plastic lighters), the liquid butane inside it will rapidly vaporize and expand, creating high-velocity airflow and shell fragments that can cause harm to those around them.
In addition, once the fuel leaks, butane quickly evaporates into a gas that mixes with air to form a flammable mixture. Combustion or explosion can also occur if this gas mixture encounters an ignition source, such as a high-temperature heat source in the environment or a spark from an impact on a metal lighter.
In general, although it is rare for a lighter to cause a serious explosion during daily use, there is a certain risk. Proper use and storage of fires and avoiding exposure to extreme conditions or potentially dangerous environments are key to preventing accidents.
by Fish Not Me
Q.E.D.
Q6
by Wild High School Livestock
Answer:
The velocity at which light enters the medium changes, which can be described in terms of refractive index. But in essence, the speed of electromagnetic waves is still the speed of light in a vacuum, and the changing speed of light in the medium is only an equivalent effect of wave superposition. When light travels through a medium, the charge in the medium is driven by the electric field (magnetic field) of the light and will oscillate back and forth at the same frequency, radiating new electromagnetic waves. This electromagnetic wave has the same frequency as the original light wave, but usually has a phase delay, because the electrons that are forced to oscillate cannot keep up with the driving force of the light field in time.
The following is a dipole-based harmonic oscillator model to discuss the effect of a medium on light, assuming that the electrons in the medium are bound around a stationary atom and are displaced under the light field, and the electrons are subjected to a recovering force trying to return to the equilibrium position, then the electron displacement x satisfies the differential equation:
Doesn't it mean that the speed of light does not change? Doesn't it "slow down" in the water? No.409
is the eigenfrequency at which the electron oscillates near its equilibrium position; is the frequency of light. The solution of the equation is calculated so that the polarization intensity of a medium containing N atoms is:
Doesn't it mean that the speed of light does not change? Doesn't it "slow down" in the water? No.409
According to the electromagnetics-related formula, the polarization intensity satisfies the formula:
Doesn't it mean that the speed of light does not change? Doesn't it "slow down" in the water? No.409
where is the dielectric constant, which is the relative permittivity. So the expression for the refractive index can be obtained:
Doesn't it mean that the speed of light does not change? Doesn't it "slow down" in the water? No.409
The light vibration in the medium satisfies:
Doesn't it mean that the speed of light does not change? Doesn't it "slow down" in the water? No.409
z is the displacement of the direction of light propagation, and c is the speed of light, so the speed of light slows down to c/n.
The light wave in the medium is the superposition of the original wave plus the new electromagnetic wave radiated by all the charges in the medium. When the frequency of the light wave is unchanged, the wavelength of the light wave is compressed due to the phase delay, and the distance traveled by the light after a cycle becomes shorter, so the apparent wave velocity of the light in the medium becomes slower.
Doesn't it mean that the speed of light does not change? Doesn't it "slow down" in the water? No.409
Resources:
[[Official Bilingual] Why does light "slow down", and why is it related to the color of the rainbow? Optical Puzzle Part 3
Refractive index
by Small Line
Q.E.D.
Q7
by @曹芃静
Answer:
The main component of an induction cooker is a coil wound into a disc.
Doesn't it mean that the speed of light does not change? Doesn't it "slow down" in the water? No.409
We know that a toroidal magnetic field can be generated around an energized wire, so a coil with an alternating current can produce an alternating magnetic field. So the magnetic flux of the food container placed on the induction cooker changes, creating an induced electromotive force, and since the container is a conductor, the electrons inside the conductor are driven by an induced electric field, creating eddy currents, which generate heat to heat the food.
As shown in the figure below, there will be a ring magnetic field around the changing alternating current, and the changing magnetic field will produce a changing electric field, because the changing electric field is opposite to the direction of the original current at the center of the wire, resulting in a large resistance to the electrons in the center, so that the electrons in the center will be distributed at the edge of the conductor. In the same way, the eddy currents induced by the container also have a skin-like effect and appear on the surface of the container.
Doesn't it mean that the speed of light does not change? Doesn't it "slow down" in the water? No.409
For induction cooking, the bottom of a suitable container is usually made of steel or iron. These ferromagnetic materials have high permeability, which greatly reduces the skin depth, concentrates the current in a very thin layer on the bottom surface of the metal of the pot, reduces the effective cross-sectional area of the conductor, thereby increasing its effective resistance, effectively heating the pot. However, aluminum has a small magnetic permeability, a deep skin depth (dozens of times that of iron), low energy conversion efficiency, and very slow heating, which is not suitable for induction cooking.
Resources:
Skin effect
Induction cooking
by Small Line
Q.E.D.
Q8
by 狐汁
Answer:
The conclusion is no. There are many reasons for this, and here are just a few simple ones to explain.
The first is the fertilization process, adult males will release hundreds of millions of sperm during a mating process, usually only one lucky sperm will combine with the egg to form a fertilized egg, so the probability of a specific sperm forming a fertilized egg is only 1 in 100 million, and the probability of winning the jackpot in the two-color ball is thousands of times higher than this. So from the perspective of probability, even if the gender does not change and do it again, the probability of giving birth to you is extremely small.
Then there is maternal inheritance, limited by the structure of sperm, the mitochondrial genome in the zygote is all derived from the mother, so when your parents are reversed, the mitochondrial genome you inherit will also change, and the source will change from grandma to grandma, and naturally it will not be you now.
There is also the environment, "trait = gene + environment", when your parents' sex is reversed, their growth environment will change very differently, which will lead to trait changes, and the changes will also be passed on to the offspring (epigenetics), so the probability of producing you is basically zero.
If the questioner is a male, this question is even simpler, originally you inherited your grandfather's Y chromosome, and after the change, you inherited your grandfather's Y chromosome, and the chromosomes are not the same, and it is impossible to give birth to the original you.
If the questioner is a woman, it is impossible to answer. Because regardless of gender, there are rearrangements and exchanges in the process of meiosis, and mutations in the process of DNA replication, so many variables are superimposed, and the probability of producing you is infinitely close to zero.
