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Soil respiration during the growing season was calculated from CO2 profiles in a heavy clay soil under native grass and on cultivated plots. Soil respiration of the native grass plots was correlated with moisture content and temperature of the surface soil. However, the correlation accounted for only ⅓ of the observed variation in soil respiration and could not explain the large difference between two growing seasons. Addition of mineral N decreased soil respiration and irrigation increased it. Total soil respiration on the cultivated plots was higher than on the native grassland. On the wheat plots, soil respiration was significantly correlated with soil moisture but not with temperature; the reverse was true for the fallowed plots. Soil respiration between 1 May and 1 September on the native grassland was highly correlated with rainfall and the number of days with rain in excess of 5 mm. It was concluded that the number of wetting and drying cycles in the soil was mainly responsible for the annual variation in soil respiration. From comparison with data on shoot production, it appears that soil respiration exceeds net production in wet years and that the opposite is true in dry years.

We show that small‐signal gain reduction in a CO2 laser power amplifier can be achieved by adding to the gain medium deuterated ammonia as a saturable absorber. The saturation energy, and effects of NH2D on the amplifier kinetics and energy extraction were also investigated.

The energy spectrum of a simple many body problem, which is solvable for any finite number of particles, is solved in the infinite particle number limit. The model consists of N fermions, in two N -fold degenerate levels, interacting through a monopole-monopole force of strength V . The Hamiltonian can be written in terms of ordinary angular momentum operators, and for a given N , the finite matrix representation can in principle be diagonalized. In this paper, the limit N → ∞, but NV finite, is investigated from the point of view of diagonalizing the resulting infinite matrix. The complete energy spectrum is obtained, and the first exited state agrees with the results obtained by various other technieques.

Thomson theory of arbitrarily intense elliptically polarized plane electromagnetic wave scattering by free electrons, solving electron equations of motion

The average binding energy and equilibrium density of nuclear matter are calculated in the self-consistent independent pair approximation. The potentials of Gammel and Thaler are used. The hard core is replaced by a pseudo-potential, and the potentials are adjusted to give the same low energy scattering data. The pseudo-potential is of the Huang-Yang type, and hence one can use ordinary Raylwigh-Schroedinger perturbation theory, which is then a joint expansion in the strength of the pseudo-potential plus the central potentials plus the tensor force. The first and second order terms in this expansion have been calculated exactly, but have been made self-consistent only in the effective mass approximation, the self-consistency requirement becoming the solution of a quadratic equation for the effective mass. It is found that a simple S-wave pseudo-potential is not sufficient to produce saturation within a density range corresponding to kF = 1 to 2 fm−1. A more exact treatment of the hard core gas by means of a pseudo-potential is available from the work of Martin and de Dominicis. Incorporating their results into our perturbation calculation yields saturation for nuclear matter with a binding energy per particle of about 18 MeV at a density corresponding to kF = 1.4 fm−1. The main results of this paper are not so much the actual binding energy and equilibrium density of nucleat matter, but the results of the various contributions coming from second order perturbation theory, especially the interference terms between the pseudo-potential and the attractive potentials, and interference terms between direct and exchange matrix elements for the attractive central and tensor forces, which have been calculated exactly.

Various calculations of the binding energy of nuclear matter are discussed. The question of off-the-energy shell propagation is considered in detail. Numerical approximations made in the calculations are investigated and it is shown that they are such as to give too much binding energy, so that the present discrepancy between theoretical and experimental values is worsened.

The preheater and the heat-exchanger possibilities of the coal-hydrogenation process are described. Comparison has been made between the demonstration and the German plant equipment. Emphasis has been placed on the importance of developing applicable high-pressure heat exchangers for commercial-size plants, in order to eliminate the preheaters and increase the thermal efficiency of the process.

Programs for electronic computors should be divided into small parts. If there is a technique for automatic connection of the program parts, then several advantages arise: the small programs can more easily be coded and tested, changes can be achieved by substituting such program parts, several programmers can independently work on the program etc. The necessary techniques are described for the IBM 650 as an example. The program parts are automatically made relocatable by the coding system used and are automatically read into consecutive in areas the store. The programmer need not deal with the connections and absolute addresses of the program parts. The techniques described are especially useful in connection with algorithmic languages.