Currently, the meaning of the word "drift" can be applied in several fields of science.This term applies to geography, and optics and anatomy, and many other areas.
drift
In 1912, German scientist Alfred Wegener proposed heuristic theory of the infinite movement of continental masses.These findings geologist made based on your own observations and discoveries.What is continental drift?Wegener suggested that the continents are in constant motion, but the rate is so small that it is impossible to feel.In the early 20th century, this report caused a lot of criticism and ridicule from the scientific world.
worth noting that continental drift was opened long before the German geologist.In the 1620s the well-known enthusiast Francis Bacon wrote in his manuscript writings of some matches in outline coast of America and Africa.On the basis of his notes later decades the idea of moving continents pushed the Frenchman Franco Plaka, and then the German Theodore Lilienthal.In 1858, the American theologian Antonio Snyder proposed a more radical theory that after cooling the Earth's surface is not withstand the pressure and split into chasti.Dolgoe during continental drift has not been proven.In much of Europe and the United States, this theory is still rejected.Nevertheless, in the early 1960s, Soviet scientists concluded that Wegener judgments are true.In turn, the concept of fiksizma continued to defend the well-known Russian geologists MA Usov and S. hoop.
theory of continental drift
In the early 20th century, Alfred Wegener travel around the world with the purpose of knowing the nature and origins of all life on the planet.On the basis of data as a result of numerous expeditions German geologist determined that all continents similar structural composition.Moreover, the scientist proved common fossil flora and fauna of the continents in the past.Also, it was possible to carry out parallel and climatic zones.
According to Wegener, on the surface of the planet emerged first layer of granite.Over time, the build-up concentrated in large breed prakontinent called Pangaea.This formation dates to 500 million years BCIt is then formed a single praokean.As a result of tectonic movements Pangaea began to break up into small pieces.So there was a continental drift.
movement of continents is achieved by centrifugal forces of rotation of the Earth.Another important factor is the attraction of the sun and moon.Due to this there was estrangement from Eurasia North America and then Africa.Giant crevice filled Atlantic.The consequence of the split of Pangea began to mountain ranges of the Andes and the Cordillera.
a result of the drift of the continents of Africa and Europe collided with each other, forming the Alps, the Himalayas, the Carpathians and other mountain ranges.According to the hypothesis of Wegener, the main points of rotation of the Earth's continents were poles.
drift ice
no secret that the frozen mass of water moving through the seas and oceans due to internal flow.But what is the drift of the ice?This is not the free movement of the water.In this case, the movement of icebergs in the ocean or the sea by the wind and the various currents.Most ice drifting in the Arctic, where the research does not stop even for a day.Such movements are represented mainly anticyclonic movement, in other words, clockwise.As a result of this cycle of ice out of the Arctic Ocean to the shores of Greenland, three streams.In this way a small iceberg need from 1 to 5 years, depending on the starting point of spalling.The trajectory of movement depends on the flow of Greenland.
first of a unique phenomenon watched scientist F. Nansen in 1893.Then the ship "Fram" drifted from the New Siberian coast to the Greenland Sea.Nansen tracked the connection between the characteristics of the ice throughout the 3-year course of the expedition.As a result, scientists have identified two important rules: iceberg drift velocity is about 2% of the accompanying wind speed and direction of movement is at 30 degrees to the right flow.These Nansen later confirmed the Soviet Professor Vladimir Wiese.
barometric drift ice
This unique natural phenomenon from 1913 to 1940 in the waters of Greenland, studied dozens of expeditions, and every time scientists agree that Nansen was right in his writings and conjecture.In the late 1930s, the Soviet Union launched a network of Arctic weather stations.The project was headed by scientist Zubov.
According to information received him and his team were able to identify a pattern of drift, which occurs along the isobars.As it turned out, for in Greenland waters are extremely weak, but very strong winds.It was he who drove the floes to the shores of the larger islands.So opened the barometric drift.He posted two rules: 1.Driving Directions ice and isobars coincide.When this pressure is significantly elevated in the right pane.
2. Travel speed is inversely proportional to the distance between the isobars.
Regarding angle of 30 degrees, then this deviation is influenced by the Coriolis force and friction.
Gene flow: determination
in the human body at the cellular level occur millions of automated processes.One of the most interesting and unique of them is genetic drift.This is perhaps the only mechanism which is caused by static random phenomena.So what is genetic drift?This chaotic change in allele frequencies of genes, that is, variations in the population.
mechanism of the phenomenon is in the process of reproduction as a result of which produces a huge amount of sex cells called gametes.These cells are unable to form a zygote, but there are rare exceptions.It is because they are formed in a population of unique species.It should be noted that the shift range of frequencies of alleles is possible only with respect to one of the previous generation.
Due to drift the evolution of species in the local populations.It is important to realize that such a change in frequency occurs regardless of any factors.
Gene flow: population waves
This process is not in any way affect the number of species, as for the lifts always follow recessions.Many scientists still wonder about what is on the evolution of genetic drift.On this in their studies tried to answer Russian scientist Chetverikov.He drew attention to the legitimate fluctuations in populations.During the experiments it was found that these processes play a decisive role in the evolution of all life on the planet.Fluctuations in the number of population are called human volny.Geneticheskaya structure is constructed in such a way that at the right moment to give birth to offspring - a new individual of the same species.Animals and plants population waves depend on the territorial basis.In a certain area can appear only species with the initial genetic code.Nevertheless, over the evolution in the fauna and flora of the alleles is responsible.
Gene flow: molecular evolution
The end result is the phenomenon of complete disappearance from the population one allele and the other embodied in it.The higher level of genetic drift, the faster evolution of molecular species.Research has shown that the probability of fixation of alleles equal to the frequency of the moving population.
noteworthy that each such molecule gene originated once by mutation.Evolutionary leaps occur with a frequency of about 10-5 per gene / gamete.It is logical to assume that the smaller the population level, the lower the probability of a new mutation.
Nevertheless, many scientists believe that the degree of evolution does not depend on the number of species and the number of genetic drift.American researchers and Zuckerkandl Polling revealed that neutral alleles are moved at a constant speed.This applies to any species.
electron drift
This process is the movement of charged particles under the influence of a static field.Moving can be a messy and natural.All depends on the electrical conductivity polya.Dreyf particles in gases and metals by the action of the current is determined by the thermal motion.In this case, predict the speed and direction of movement will not succeed.The fact that the thermal effect does not form a single macroscopic flux of charged particles.Here, the electron with the field is characterized by the intensity and density of the medium.The plasma particles are under the influence of a magnetic field, so the motion will be uniform and regular.
drift velocity of charge in the electric field is much higher than ion.It is caused by a strong impulse protection.
drift in DC
The FET amplifier has one major problem - the spontaneous strain relief.This phenomenon is called the zero drift.As a result, disconnection of the amplifier output current value of the index falls to entry.The zero drift is most often seen when there is no input signal.
reasons for this disconnect can be:
- power supply fault;
- instability of resistors or transistors;
- low frequency noise;
- high ambient temperature;
- interferences or pomehi.Naibolee rare and complex consequence of current interruption in the DCA could be galvanic connection between the stages.She quickly sends signals change, so volatility at the entrance hardly traceable.
to neutralize the zero drift can be used termokompensiruyuschie components deep DUS DC converters, detection mechanism states.It is worth to change the balanced circuit DCA.
eyes drift
The process is slow due to the gradual displacement of the eyeball.In other words, it is involuntary fixation of the central part of the retina at a facility.Logically it begs the question of what is the drift of the eyes and what causes it.
To answer this question it is necessary to understand that the human retina has three types of movements that are not even being felt: a constant tremor, snatch fixation and smooth movement.The first state is the norm.The frequency of contraction of the eye muscles to 80 Hz.The second condition is also normal.The mechanism is controlled by a sudden reaction.The third state is allowed only with the first two, but not separately.Its cause may be a denial of the retina of a feedback mechanism.
Ship drift
Offset ship off course it occurs most often under the influence of strong winds.The main characteristic of this drift is the angle between the lines of true and false directions of the route.Demolition of the vessel may occur under the influence of the tide.And offset drift is indicated in the "anchor" when the goods crawling along the bottom.
The most dangerous consequence of the demolition of a likelihood of a ship on the rocks or shoals.To eliminate such a situation it is necessary to send the ship's nose against the wind.
