1. It is necessary that the intensity of radiation should be measured very accurately.
2. The object behaves as if it were given some energy at the start.
3. Keep the temperature lest the substance should be overcooled.
4. In some calculations the air is treated as if it had no viscosity.
5. He suggested that the tunnel diode devices should be constructed from heavily doped semiconductors.
6. The whole weight of a body acts as though it were concentrated at a single point, this point being called the centre of gravity.
7. It is desirable that the errorsignal should be isolated from the detector.
8. The laws of mechanics require that the distance of each body from the center of gravity should be related to its mass.
2. Translate into English.
1. Предлагается, чтобы эксперименты провели в совершенно иных условиях.
2. Как бы мне хотелось принять участие в этой конференции!
3. Будь осторожен, чтобы прибор не сломался снова.
4. Проблемы обсуждалисьтак, какбудто имели большое значение.
5. Было бы трудно завершить исследование без его помоши.
6. Важно, чтобы реакция не прекратилась.
7. Он потребовал, чтобы все вычисления были проведены тщательно.
UNIT TEN GRAMMAR: GERUND
| Forms of Gerund | Active | Passive |
| Indefinite | solving | being solved |
| Perfect | having solved | having been solved |
FUNCTIONS OF GERUND
WORD AND PHRASE STUDY
re- = again + re- + N = N re- + construction = reconstruction
re- + V = V re- + model = remodel
• Translate the following words into Russian:
retake, retrace, reestablish, rearrange, reproduction, redirect, redistribution, recharge, recapture, redefine
READING (10A)
• Read the passage attentively and be prepared to say a few words about "induced" or "artificial" radioactivity.
NUCLEAR FISSION
Following the discovery of neutrons in 1932 due to the English physicist James Chadwick many new types of artificial nuclear transformations have been investigated. Neutrons are the ideal projectiles for nuclear bombardment because they have no electrical charge and thus suffer no repulsion in their approach to atomic nuclei.
In some cases the impact of a neutron may result in the ejection of a proton or an a-particle, as in the reactions:
7NM + 0n1->6C,4 + 1H' 7Nl4 + 0n'->5B"+2H4
In some cases the incident neutron can eject another neutron without being captured itself:
Cl4+ n'-^C" +2 n1
6 О О О
whereas in other cases the incident neutron can be captured by the nucleus with the release of excess energy in the form ofay-quantum. The latter process, known as the radiative capture of neutrons, is of particular importance for heavy nuclear targets, since in this case the ejection of protons and a-particles is strongly hindered by the "outgoing" potential barrier surrounding the nucleus. I fit were not for the radiative capture ofthe neutron no heavier isotope of the bombarded clement would be formed. Sometimes these isotopes are stable so that no further nuclear transformation takes place:
r|6+ п'-^я017 + у
Hon 1
whereas in some other cases the radiative capture of a neutron leads to a (i-emission:
47Ag'w + on'->47Ag"u + Y 47Ag4°->48Cd» + e-
which is necessary to re-establish the proper neutron-to-proton ratio.
In the year 1939, a German radio-chemist, Otto Hahn, with his coworker, Frits Strassman, studied the effect of the neutron bombardment of uranium atoms, expecting to observe the formation of uranium isotopes with atomic weights higher than that of ordinary uranium, i.e., 238. To his great surprise Hahn found that the sample of uranium bombarded by neutrons contained radioactive atoms of a much lighter clement, barium. The mystery of this discovery was soon cleared up by two German physicists, Lisc Meitner and Otto Frisch, who suggested that in Hahn and Strassman's experiments the nuclei of U218 were split by incident neutrons into two nearly equal parts:
П238 + ni_4 Ba144+, ftKr94
32 о 56 36
Since the barium and krypton atoms produced in this process possessed excess neutrons, as compared with ordinary stable atoms of the same atomic weight (60Nd144 and 40Zr94), these so-called fission products emitted negative electrons, makingthem strongly radioactive. Frishand Meitner's interpretation of Hahn and Strassman's experimental finding as the splitting ofthe uranium nucleus into two nearly equal parts opened new vistas in the field of nuclear physics. Instead ofjust "chipping off' small pieces ofthe bombarded nucleus, as was the case in all previous experiments, here was a real breakup ofthe central body of the atom, the fission of a large droplet of the nuclearfluid into two half-size droplets. Instead ofjust the few million electron-volts of energy observed in previous experiments on artificial nucleartransformations, uranium fission liberates 200 MeV per atom.
The detailed theoretical studies ofthe process of nuclear fission were carried out by Niels Bohr and John Wheeler and published in the September 1939 issue of the Physical Review. This was the first and last comprehensive article on the theory of nuclear fission that appeared as "open literature" before the "security curtain" was drawn tight on that subject. According to Bohr and Wheeler, the fission of heavy nuclei resulting from the impact of a neutron is a resolution of a conflict between the opposing tendencies of nuclear (attractive) and Coulomb (repulsive) forces acting in the atomic nucleus.
• Find English equivalents for the following Russian phrases.
не испытывают никакой отталкивающей силы; на две почти равных части; вслед за открытием; загадка этого открытия была вскоре разрешена; как это происходило во всех предыдущих экспериментах; может привести к; идеальные частицы; радиационный захват; по сравнению с обычными устойчивыми атомами; испусканию протонов и альфа-частиц серьезно мешает; последний процесс особенно важен; эти так называемые продукты деления; никакого дальнейшего ядерного превращения не происходит; правильное отношение числа нейтронов к числу протонов; избыточные нейтроны; избыточная энергия; налетающий нейтрон
• Read the passage again and answer the following questions.
1. What problem is the text concerned with?