A graphical treatment of the tone reproduction problem in television systems satisfactorily answered by extensive experimental work, using the techniques of subjective appraisal which have been increasingly developed in recent years. Direct comparison of a reproduction and an original, with all the parameters of the system accurately known, calls, of course, for a considerable experimental effort. Such limited observations as have been made, however, suggest that the shape of the curves at least gives a good impression of the relative effects of viewing cathode-ray tubes with different values of A, and operating under, different conditions. It is not intended to draw any conclusions or express any as to what form of reproduction characteristic is most desirable. There can, however, be little doubt that there are instances where faithful reproduction is not desirable -where, in fact, the television system can improve on the eye and convey the maximum of information or enhance the asthetic value of a scene by emphasizing certain luminosity differences at the expense of others. To a large extent the value of such distortions must be a matter of personal preference.What constitutes the most desirable form of characteristic is, again, a question which calls for large-scale experiment on a subjective basis; factors such as signal-to-noise ratio and the effect of the characteristic on apparent definition have to be taken into account.Reference may be made in passing to the results of Jones's investigation into the preferences of a large number of observers in the matter of photographic prints.Q) This investigation tends to show that preferred prints are those in which the gradient of the logL,/logL, curve is approximately unity for the medium tones, and that a greater fall in the gradient is acceptable towards black. It would be unwise to assume, however, that the results obtained are necessarily applicable to television practice, where the form of the transfer characteristics and the viewing conditions are different. One general principle which does not seem to be in dispute is that, whereas a considerable tolerance exists when the reproduction is in monochrome, colour calls for a much closer approach to fidelity in luminosity reproduction.Large-area luminance range in modern aluminized cathoderay tubes, in the absence of external light, appears to offer little scope for worth-while improvement. It is worth noting, however, that the importance of good detail luminance range in determining the subjective quality of television pictures has been stressed by Law@) and other writers.Assuming that an optimum characteristic, or range of characteristics, can be defined, practical realization of the optimum raises a number of issues, e.g. the relative contributions of the transmitting and receiving apparatus to the overall result, and whether the desired objective can best be arrived at by selection of the camera or cathode-ray tube characteristic or by suitable circuit design.It is hoped that the present communication may help...

AbsbaCL An alomcdly ordered PdCu&o.p hydride was spthesizcd at 600 K and a hydxogcn p m s m of 3 GPa Irs Netd lanice had B primitive temgonal cell fomcd from the initial K c cell of thc disordcred PdCu alloy due to ordcrbg of the Pd and Cu atoms into allemve la)cn perpendicul;lr to the tetragonal c-ais. Rietveld refinemcat of Ihe neumn diffraction pallem of P d C u b 9 m a u r e d ai 80 K showcd thc H ~o m s to occupy octahedral interstitials within thc Pd layers. The inclastic neumu scanering sNdy at 35 K revealed a broad hydrogen o p i d peak with pcculivlties at energy m s f c n of 79 and 95 meV and of I13 meV uhich wcre zcribed to the H vibrations in the P d H planes and dong thc CU-H chains perpendiculv to the planer, respectively. The paantid for hydmgen *OM in the PdCK+9 ordered phase was thus noticeably diffcrenc even in the Pd-H plane, from that in the h o u n hydrides of pdhdium and palladium alloys. The value of approximly 116 meV was predicted forthc l o d H vibntions in dilute Cu-H solid solutions. E G 1991 Physica B 174 25741 Sov. Phys.-Solid State 33 87-90 Calcu&fions: User Manual (IFF KFA, Jiilich) Jiil-Spa-366 Rev. B 36 8798-801 A I, Bashkin IO, Sinicyn V V and Ponyatovskii E G 1989 Physlca C 162-164 1369-70 Belushkin A V 1993 Phys. Solid Srate 35 99-103

No abstract

A modified version of the IERM approach is applied to electron scattering from hydrogen atoms at intermediate energies to evaluate integrated cross sections for the n = 2 to n = 3 transitions. Results are compared with earlier work which overestimates these cross sections due to the omission of continuum channels. These results have important applications in astrophysics.

The second half of the nineteenth century was marked by the greatest event in the history of organic chemistry-the creation of the chemical structural theory by the Russian scientific genius Aleksandr Mikhailovich Butlerov. This theory from the moment of its origin, and throughout its entire subsequent development has been and still is the firm foundation of all organic chemistry and the sure guide for all the researches of organic chemists. The creation of the structural theory led to an exceptionally rapid and vigorous efflorescence of organic chemistry, and to the development of organic chemical industry indissolubly connected with such growth.The essential content of Butlerov's teaching is the assertion that the chemical structure of molecules is real, and that the chemical properties and mutual relations of compounds are caused by their chemical structures. Butlerov wrote: "Starting with the idea that each of the component chemical atoms of a compound participates in the formation of the latter, and there exerts a definite and specific quantity of chemical force (affinity), I designate as chemical structure the distribution of the action of this force by which the chemical atoms, indirectly or directly influencing one another, are united into a chemical particle" (1). And further:"If, at the present time, we attempt to determine the chemical structure of a substance, and if we succeed in expressing that structure in our formulas, then such formulas will (to a certain though imperfect degree) be 1 Report of the Commission of the Institute of Organic Chemistry of the Academy of Sciences, U.S.S.R., for the investigation of the present state of the theory of chemical structure; approved for publication by the Scientific Council of the Institute of Organic Chemistry of the Academy of Sciences, U.S.S.R.The Bureau of the Division of Chemical Sciences of the Academy of Sciences, U.S.S.R., has deemed it desirable that further discussion of this problem be transferred to the pages of the journals, Izvestiya Akademii Na.uk S.S.S.R. Otdelenie Khitnicheskikh Nauk (Bulletin o) the Academy of Sciences U.