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Учебное пособие Издание второе, переработанное и дополненное Москва Астрель act 2005
CLASSWORK
READING (17B)
• Read the article by Graham P. Collins from May 2001 and make an appropriate comment on the discovery made. What does the author mean by the title? What dog and what trick docs he mean?
NEW TRICK FROM OLD DOG
A Magnesium Compound Is a Startling Superconductor by Graham P. Collins
You can buy magnesium boride ready-made from chemical suppliers as a black powder. The compound has been known since 1950s and has typically been used as a reagent in chemical reactions. But until this year (2001) no one knew that at 39 degrees above absolute zero it conducts electric current perfectly — it is a superconductor. Although its superconducting temperature is far below that ofthe copper oxide high-temperature superconductors, the compound has set off a flurry of excited activity among researchers. Magnesium boride overturned theorists' expectations and promises technological applications.
Jun Akimitsu of Tokyo University anounced the surprising discovery at a conference in Japan on January 10, after he and his workers stumbled on magnesium boride's properties while trying to make more complicated materials involving magnesium and boron.
Word ofthe discovery spread around the world by e-mail and in three weeks the first research papers by othergroups were posted on the Internet.
In early March, a special session on magnesium boride was hastily put together in Seattle at the American Physical Society's largest annual conference: from 8 p.m. until long after midnight, nearly 80 researchers presented ultrabrief summaries on their results.
Until January, standard wisdom ruled out the possibility of a conventional Superconductor operating above about 30 kelvins. Conventional superconductors are understood by the so-called BCS theory, formulated in 1957. The magnesium boride result seemed to imply that either a new superconducting mechanism had been discovered or that the BCS theory needed to be revised.
Almost all the experimental evidence so far supports the idea that magnesium boride is a standard BCS superconductor, unlike the copper oxides. For example, when researchers use the isotope boron 10 in place of boron 11, the material critical temperature rises slightly, as expected, because the lighter isotope alters vibrations ofthe material's lattice of atoms, a key component of BCS theory. How, then, has the magic 30 kelvins been exceeded?
Perhaps, those predictions were premature. Magnesium boride has a combination of low-mass atoms and favourable electron states, that was overlooked as a possibility.
Physicists are trying to push the BCS' limit even further to produce higher critical temperatures by doping the material with carefully selected impurities. Groups have added aluminium or carbon (neighbours of boron in the periodic table), but these both decrease the critical temperature. Calcium is expected to work better, but no one has succeeded in producing calcium-doped magnesium boride.
Even undoped, magnesium boride has several attractive features for applications. First, the higher operating temperature would allow cooling ofthe superconductor by refrigeration instead of by expensive liquid helium, as is needed for the most widely used superconductors.
The high-temperature copper oxide superconductors beat magnesium boride hands-down on that count but they have proved difficult to manufacture into convenient wires. Also, the supcrcurrent does not flow well across the boundaries of microscopic grains in copper oxides.
Magnesium boride, in contrast, has already been fashioned into wires using simple techniques, and the supercurrent flows effortlessly between grains. One drawback, however, is that magnesium boride loses its superconductivity in relatively weak magnetic fields, fields that are inescapable in applications. But with the progress seen already in a scant few months, researchers are confident they can overcome such problems.
HOMEWORK
(to be done in writing)
1. Translate into Russian. Pay special attention to the word one in different meanings.
1. We could offer you a number of challenging problems, but this one seems to be the most attractive.
One should find a simple and elegant solution ofthe problem.
No one seems to have dealt with this problem yet.
One should mention the problem under investigation in our lab.
No one seems to have formulated this problem in precise terms.
This is one ofthe most confusing and puzzling problems we have ever dealt with.
This problem seemstobc much more complicated than all the previous ones.
8. No one has yet presented it in all its complexity.
2. Translate into English.
Зеркальная (mirror/reflection) симметрия является первым случаем геометрического понятия симметрии, относящейся к таким операциям, как отражение или вращение. Симметрия является той идеей, посредством которой человек на протяжении веков пытался понять и создать порядок, красоту и совершенство (perfection). Первые (early) ученые считали окружность на плоскости и сферу в пространстве наиболее совершенными геометрическими фигурами.
Что можно назвать математической философией левого и правого? Сточки зрения научного мышления, между левым и правым не существует полярной противоположности. Пространство изучается геометрией. Но пространство также служит средой всех физических явлений. Структура физического мира проявляется (reveal) во всеобщих законах природы. Во всей физике нет ничего, что указывало бы на внутреннее различие между левым и правым. Левое и правое эквивалентны так же, как все точки и все направления в пространстве.
UNIT EIGHTEEN
GRAMMAR: ГЛАГОЛ WOULD
Would Глагол обозначает волеизъявление, желание, склонность к выполнению действия. Чаще употребляется в отрицательной форме, означая упорное нежелание совершить действие. Относительно неодушевленных предметов или явлений означает неспособность предмета выполнитьдействие,для которого он предназначен, или недостаточность условий для реализации явления.
Would not We did everything to persuade him but he would not change (Никак) не the procedure of his experiment.
Мыделали все, чтобы убедить его, ноон(никак) не хотел изменить процедуру эксперимента.
Would
1) a) Future in the Past
He wrote he would return in a week. Он писал, что вернется через неделю.
b) The Subjunctive Mood
It would be extremely interesting to attend this conference. Было бы очень интересно присутствовать на этой конференция.
2) a) We tried to open the door but it wouldn't.
Мы пытались открыть дверь, но она никак не открывалась.
Ь) вежливая просьба
Would you give me your English textbook?
He дадите ли мне ваш учебник по английскому языку?
136
3) would = used to — бывало, обычно, имел обыкновение
Не would work (used to work) in his lab for ten hours.
Он имел обыкновение работать всвоей лаборатории по 10 часов.
Note: В научно-технической литературе would в этом значении на русский язык не переводится.
Sometimes the device would fail. Иногда прибор ломался.
• Sentences to be translated.
We asked them whether they would change the conditions of the experiment.
They tried to raise the temperature but it wouldn't.
The device was tested several times and it would always prove correct.
Were the surface of the material highly polished, the friction would be less.
There would be no progress in science without observations.
The density of the medium would change with temperature no matter what measures they took.
There were electron tube devices in our laboratories but now they are replaced by semiconductor ones.
It would be desirable that all necessary calculations be made before the experiment starts.
WORD AND PHRASE STUDY
anypron. — любой, всякий (утверд. предложение)
any kind — всякого рода
in any case (event) - в любом случае
any longer - больше не (syn. any more, no longer, no more)
hardly any — почти ничего
if any - если вообще (таковые имеются), если только
• Sentences to be translated.
If this is the case, it is difficult to measure any internal properties of the plasma by any ofthe conventional methods.
One can obtain very poor, if any, data on this event.
Any of these approaches will hold.
4. Гп any event one should bear in mind that the information obtained may be misleading as to the course ofthe reaction.
READING (18A)
• Read the passage below and find the answer for the following question:
Which symmetries, global or local, hold the greatest interest for physicists today and why?
GAUGE THEORIES1
An understanding of how the world is put together requires a theory of how the elementary particles of matter interact with one another. Equrvalently. it requires a theory of the basic forces-of nature. Four such forces have been identified, and until recently a different kind of theory was needed for each of them. Two ofthe forces, gravitation and elcctromagnetism, have an unlimited range; largely for this reason they arc familiar to everyone. They can be felt directly as agencies that push or pull. The remaining forces, which are called simply the weak force and the strongforce, cannot be perceived directly because their influence extends only over a short range, no larger than the radius of an atomic nucleus. The strong force binds together the protons and the neutrons in the nucleus, and in another context it binds together the particles called quarks that are thought to be the constituents of protons and neutrons. The weak force is mainly responsible forthe decay of certain particles.
A long-standing ambition of physicists has been to construct a single master theory that would incorporate all the known forces. One imagines that such a theory would reveal some deep connection between the various forces while accounting for their apparent diversity. Such a unification has not yet been attained, but in recent years some progress may have been made. The weak force and elcctromagnetism can now be understood in the context of a single theory. Although the two forces remain distinct, in the theory they become mathematically intertwined. What may ultimately prove more important, all four forces are now described by means of theories that have the same general form. Thus if physicists have yet to find a single key that fits all the known locks, at least all the needed keys can be cut from the same blank. The theories in this single favored class are formally designated non-Abelian gauge theories with local symmetry. What is meant by this forbidding label is the main topic of this article. For now, it will suffice to note that the theories relate the properties ofthe forces to symmetries of nature.
Gauge theories — градиентные полевые теории, или калибровочные теории поля
• Look through the passage and And English equivalents for the following Russian terms and phrases:
как построен мир; до недавнего времени; не больше чем; в основном, отвечая зд ...; единым ключ, который подходит ко всем замкам; достаточно заметить; согласно тому же принципу; основные силы природы; слабые/сильные взаимодействия
• Answer some more questions about the passage.
What is a long-standing ambition of physicists?
What do scientists mean by a single master theory and why is it needed?
How many and what basic forces of nature have been identified until recently?
Which of these forces have a limited/an unlimited range?
Which of the basic forces are familiar/unfamiliar to everyone and why is it so?
What are the strong/weak forces responsible for?
What progress has been made recently in developing a theory of the basic forces of nature?
By means of what theories are the basic forces of nature described now?
• Study the block-scheme below and try to discuss or summarize the problem as a whole.
Forces
 weak
strong
intertwined
radioactive beta decay
pull/push
proton/neutron binding
CLASS WORKREADING(18B)• Study the table given below. Read the passage and be prepared to discuss the problem using this table.
THE FORCES IN NATURE
|
TYPE
|
INTENSITY OF FORCES (Decreasing order)
|
BINDING PARTICLE (Field quantum)
|
OCCURS IN
|
STRONG NUCLEAR FORCE
|
1
|
GLUONS (no mass)
|
ATOMIC NUCLEUS
|
ELECTROMAGNETIC FORCE
|
- io-3
|
PHOTON (no mass)
|
ATOMIC SHELL APPL1C.
OF ELECTRICITY
|
WEAK NUCLEAR FORCE
|
io-5
|
BOSONS Z°, W\ W(hcavy)
|
RADIOACTIVE BETA DECAY
|
GRAVITATION
|
io-38
|
GRAVITON?
|
H EAVEN LY BODIES
| THE EXCHANGE OF PARTICLES IS RESPONSIBLE FORTHE FORCES THE FOUR FORCES OF NATURE One of the major achievements of modern physics has been the development over the past 20 years or so of a new class of grand unified theories to describe the forces acting between elementary particles. There arc four different ways in which the various particles that make up the Universe can interact with one another. Each of these is a particular variety of interaction, or to use a more old-fashioned but more common term, a force (the forces are nuclear, electromagnetic, weak, gravitational). Of the four forces, two — the nuclear force and the weak force — make themselves felt only at incredibly tiny distances of 10 13 centimeters or less. This is just about the width of the tiny nucleus that exists at the very center of the atom. It is only within the nucleus, in the immediate neighbourhood of isolated particles, that these forces exist. For this reason the term nuclear force is sometimes given to both, and they are differentiated by their relative strength into the strong nuclear force and the weak nuclear force. The weak force is responsible for such processes as the beta decay of a radioactive atomic nucleus; the strong nuclear force holds the nucleus together. The electromagnetic force governs the interaction of electrically charged particles; and gravity holds the Universe together. Until the theories were introduced the four observable forces of nature seemed to be independent of one another. Two of these forces, the electromagnetic force and the weak nuclear force, arc already linked by the highly successful electrowcak theory, which treats them as different manifestations of a single underlying force. According to the prevailing view ofthe interactions of elementary particles, the force is transmitted between two particles by the exchange of a third, intermediary particle. Such a description is the essence of a quantum field theory. In electromagnetic and weak interactions the exchanged particle is a member ofthe family called the vector bosons, named after the Indian physicist S.N. Bose. This term refers to a classification of particles according to one of their most basic properties: spin angular momentum. A boson is a particle whose spin, when measured in fundamental units, is an integer such asO, 1 or 2. "Vector" designates a boson whose spin value is equal to 1. In the case ofelectromagnetism the exchanged vector boson is the photon, the massless and chargeless "wave packet" of electromagnetic energy that functions as the quantum ofthe electromagnetic field. The other two forces — gravity and st rong nuclear force — are thought to be transmitted by intermediary particles, namely the graviton and the eight particles called gluons.The unified eleotroweak theory is the theory that predicts the existence of the three massive particles called intermediate vector bosons (also known as weakens; "intermediate" simply because of their mediating role between particles). The electroweak theory, which can now be considered the "standard" account of electromagnetic and weak interactions, for the first time made specific and testable predictions about the properties of intermediate vector bosons, including their mass. The goal of attempts to create a grand unified theory is to arrive at a more comprehensive mathematical structure that would incorporate both the electroweak force and the strong nuclear force (omitting only gravity, the fourth known force). Scientific American, August, 1982 • Find equivalents for the following phrases.лают о себе знать; различные проявления одной, лежащей в их основе силы; в соответствии с общепринятым мнением; целое число; обычное объяснение электромагнитных...; слабое взаимодействие; сильное взаимодействие; теория великого объединения; ...в непосредственной бл изости... • Re-read the passage and answer the questions.
What is one of the major achievements of modern physics over the past 20 years?
Where do the nuclear force and the weak force make themselves felt?
What does the term "nuclear force" imply?
What is the weak force responsible for?
What is the strong force responsible for?
What forces are linked by means of the electroweak theory?
What is the exchange particle in the electroweak force?
How many bosons does the unified electroweak theory predict?
What is the goal of creating a grand unified theory?
• Match each word in column I with its synonym in column II.
I
apparent, to attain, to come about, to designate, familiar, decay, with respect to, ultimately, explicit, to reveal
• Choose the proper word.
II
definite, to name, to show, as regards, finally, evident, to achieve, to happen, disintegration, well-known
The strong force (separates/binds together/breaks) the protons and the neutrons in the nucleus.
The gauge theory will (designate/reveal/relate) some deep connection between the various forces.
In the theory the two forces become mathematically (unified/defined/ intertwined).
The theories in this single favored class are formally (designed/ designated/defined) non-Abelian gauge theories with local symmetry.
For a local symmetry to be observed this law of physics must retain its ( value/valence/validity).
It is hard to imagine a state of matter (immediate/intermediate/internal) between the proton and the neutron.
HOMEWORK(to be done in writing) |
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