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Nitroglycerine is a dangerous explosive, still it is used in medicine. , .
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So, the expedition started! , !
I. :
1. We were told, we had built Socialism and created conditions for the onward march to Communism. 2. Our peace proposals are approved and welcomed by all peoples, for they fully correspond to their interests. 3. We are proud of the great contribution that women have already made towards the lessening of world tension. 4. China, like the other great nations, must be represented in the United Nations Organization. 5. China used to suffer from a chronic food storage, but that situation has fundamentally changed since the establishment of new economic approach. 6. Since 1945, immense changes have occurred in the Far East.
2. Only scientific theory can ensure practical achievements. 2. We now know that the atom is divisible. 3. The electric current flows in the circuit only after it is closed. 4. The only resistance in this case is the internal resistance of the cell. 5. The movement of a jet plane is so swift that the eye can follow its flight only with difficulty. 6. Unlike uranium, oxygen is a very light element. 7. Since the weight of a body is a force, it must be expressed in force units. 8. The boiling stopped and the liquid became still. 9. We could not see the ships as they were hidden by a dense fog.
B
1. The declaration of the Council of Peace rightly points out that its demands are quite practical. 2. We want the atomic warfare to be forbidden since the atomic bomb is a weapon of mass destruction. 3. When the Great Patriotic War broke out the Soviet State was still the only socialist country in the world. 4. Scars left by the war are still visible in many cities of Egypt. 5. In the colonies monopoly capital functions parasitically, since it is invested principally in the sphere of circulation and does not contribute to the economic development of these countries.
1. A great amount of energy liberates after the atomic burst. 2. It was believed before that the atom is indivisible. 3. It is difficult to liberate oxygen from a compound, for its compounds are very stable. 4. The Centigrade temperature scale is the only scale used in most countries. 5. Potassium chloride melts at 360 and, as the temperature rises still higher, bubbles of oxygen appear in the liquid and break on its surface. 6. Since one-half of the material of the earths crust is oxygen, its compounds are very common. 7. We expect the chemical properties of pure oxygen to be like those of air. 8. All planes but one returned from the flight. 9. We like all kinds of sport. 10. Unlike Sofia a city of straight avenues, Bucharest has many winding streets.
C
1. The Soviet Union had always had the support of the working people of all countries, for in the Soviet Union they saw a reliable defender of universal peace and security. 2. The growing might of the Soviet State strengthened the cause of peace throughout the world, for it is entirely placed at the service of peace. 3. In the short period since the Chinese Peoples Republic was established, profound historic changes occurred in the country. 4. That policy of force and cold war policy run sharply counter to the national interests of all countries has now become obvious even to many of those who in the past actively supported these policies. 5. The USA still pursues the policy of banning trade with democratic countries.
1. A transformer cannot be called a machine, for it has no moving parts. 2. A mixture of two liquids like milk is called an emulsion. 3. In radar, unlike in communication, the transmitter and the receiver are located at the same place. 4. Like poles of magnet repel each other. 5. Perpetuum mobile is but a naïve dream of the ancient people. 6. As the radio wave travels through the space, the electromagnetic part of its energy rapidly drops in strength. 7. As we should infer from the vigor with which its constituents combine, water is a very stable substance. 8. In the atomic nucleus there are forces of attraction that keep the protons and neutrons together. 9. These two particles are very much alike.
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II. , :
COHESION AND ADHESION
When we consider the magnitude of the forces that must be applied to tear apart portions of solid bodies, it is evident that the particles composing the bodies must be mutually attracted, and by large forces. The particles are said to cohere, and the property is called cohesion. We know further that such forces must be effectively operative but over small distances, for a solid body, after being cut in two, will not re-cohere with cohesive forces that approach something like the original values even after the faces of the cut have been carefully polished.
By great refinement in polishing, and by pressing the surfaces together, still greater force can be developed, but the original value still will not be reestablished.
Adhesion is a similar property, but involving unlike bodies in contact. Cohesions and adhesions are shown not only by liquids but also by solids.
An interesting illustration is found in the phenomena that occur in contacts between solids and liquids. Some liquids wet a given solid, but others do not. For example, an attempt to empty a clean glass vessel after tilling it with water leaves the entire surface of contact wet, since the water has adhered to the glass so that the forces of cohesion of its own particles were unable to tear it away.
This is not the only feasible example, as there are many other liquids with like adhesive properties.
Contrasting behaviour is shown by mercury, that does not wet clean glass. So, a beaker filled with mercury can be completely emptied, as the cohesion of the particles of mercury is greater than adhesion between mercury and glass.
DIRECT CP VIOLATION has been observed at Fermilab by the KTeV collaboration. An important way of apprehending the basic nature of time and space (in the finest tradition of Greek philosophy) is to ask what if questions. For example, will a collision between particles be altered if we view the whole thing in a mirror? Or what if we turn all the particles into antiparticles?
These propositions, called respectively parity (P) and charge conjugation (C) conservation, are upheld by all the forces of nature except the weak nuclear force. And even the weak force usually conserves the compound proposition of CP. In only one small corner of physics the decay of Kmesons has CP violation been observed, although physicists suspect that CP violation must somehow operate on a large scale since it undoubtedly helped bring about the present-day preponderance of matter over antimatter.
K mesons (kaons) are unstable and do not exist outside the interiors of neutron stars and particle accelerators, where they are artificially spawned in K-anti K pairs amidst high energy collisions. Ks might be born courtesy of the strong nuclear force, but the rest of their short lives are under control of the weak force, which compels a sort of split personality: neither the K nor anti-K leads a life of its own. Instead each transforms repeatedly into the other. A more practical way of viewing the matter is to suppose that the K and anti-K are each a combination of two other particles, a short lived entity called K1 which usually decays to two pions (giving K1 a CP value of +1) and a longer-lived entity, K2, which decays into three pions (giving K2 a CP value of -1). This bit of bookkeeping enshrined the idea then current that CP is conserved.
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All of this was overthrown when in 1964 the experiment of Jim Cronin and Val Fitch showed that a small fraction of the time (about one case in every 500, a fraction called epsilon) the K2 turns into a K1, which subsequently decays into two pions. This form of CP violation is said to be indirect since the violation occurs in the way that Ks mix with each other and not in the way that Ks decay. One theoretical response was to say that this lone CP indiscretion was not the work of the weak force but of some other novel superweak force. Most theorists came to believe, however, that the weak force was responsible and, moreover, that CP violation should manifest itself directly in the decay of K2 into two pions. The strength of this direct CP violation, characterized by the parameter epsilon prime, would be far weaker than the indirect version. For twenty years detecting a nonzero value of epsilon prime has been the object of large-scale experiments at Fermilab and for nearly as long at CERN. In each case, beams of Ks are sent down long pipes in which the K-decay pions could be culled in sensitive detectors.
At the APS Centennial meeting in Atlanta last week, both groups discussed their work. The KTeV group at Fermilab reported a definite result: a ratio of epsilon prime to epsilon equal to 28 (+/-4) x 10 4, larger than the theoretical expectation. As for the NA48 group at CERN, Lydia Iconomidou-Fayard said that data analysis was still proceeding and no definite measurement could be reported at this time. The principal conclusion was stated by KTeV co-spokesman Bruce Winstein: Before the new experiments direct CP violation had not been established, owing to the large uncertainty in the early measurements of epsilon prime; the new experiment, by contrast, does succeed in establishing a nonzero value for epsilon prime, thus providing a new way to probe (a parameter that can be measured in the lab) this cosmologically-important and most mysterious feature of particle physics.
CREATING ANTIMATTER WITH LASER LIGHT. Intense light from the Petawatt laser at Livermore, the worlds most powerful laser, has been directed onto a thin gold film where it creates a plasma plume, which acts as a sort of messy wakefield accelerator. In particular the laser electric fields rip electrons from the gold atoms and send the electrons shooting off with energies as high as 100 MeV. Some of these electrons radiate gamma rays which in turn can create electron-positron pairs (the first antimatter made in laser-solid interactions) and can also induce fission. Thus laser photons at the electron-volt level can, by teaming up, initiate the sort of million-electron-volt nuclear reactions that normally take place only at an accelerator. Moreover, the femtosecond laser pulses can be focused to a much smaller spot size then is possible with any conventional particle beam. Tom Cowan reported these results at last weeks APS centennial meeting in Atlanta.
TABLETOP THERMONUCLEAR FUSION. Yet another Livermore photonuclear breakthrough was reported at the APS meeting. Todd Ditmire described an experiment in which laser pulses (35 fsec long and intensities as high as 1017 W/cm2) were absorbed by a gas jet of deuterium molecules. These molecules actually resided in clusters (average size of 5 nm) which exploded under the laser bombardment. Some of the rocketing Ds fused into helium-3 nuclei plus energetic neutrons. The neutrons, showing up with a characteristic energy of 2.45 MeV, were detected (about 10,000 per laser shot) via a time-of-flight technique. Ditmire said that this new approach to promoting fusion reactions (executed with a setup that fits on a 4x11 table) could probably not be scaled up to provide commercial power, but that it might provide a cheap source of neutrons. The whole process is highly efficient: virtually all the laser energy was converted into ion kinetic energy.
MOLECULAR ASTROPHYSICS. To understand how molecules form in space, earthbound scientists are performing laboratory experiments that simulate the cold interstellar dust and gas clouds where molecules are manufactured. Some researchers study the formation of H2, the universes simplest and most abundant molecule. Other researchers study the properties of polycyclic aromatic hydrocarbons (PAHs), flat rings of carbon and hydrogen which seem to exist in the interstellar clouds. At the APS meeting, Gianfranco Vidali of Syracuse presented studies on how two hydrogen atoms join together on an interstellar dust grain. Shooting H atoms onto a solid target (playing the role of an interstellar dust grain, with a temperature of 10 K) and observing how many of the atoms would react on the cold surface to form molecular hydrogen, he and his colleagues found that the rate of H2 formation was higher on amorphous carbon than on olivine (a silicon-oxygen based material), suggesting that the former is a more likely candidate for interstellar dust, whose composition is still unknown. Louis Allamandola and his colleagues at NASA-Ames discussed recent experiments showing that shining UV light on PAHs can convert them to organic compounds that are present in henna, aloe, and St.Johns wort.
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Combined with spectroscopic measurements that support the existence of PAHs in interstellar clouds, these experiments advance the notion that PAHs may be the precursors of biologically important molecules on our planet and possibly others.
B
