Population pressure and land use change: from tree crops to sawah in Northwestern Kalimantan,Indonesia

The author describes the role of population pressure in the current transition from tree crops to wet rice cultivation (sawah) in Northwestern Kalimantan, Indonesia. He contends that this change is occurring "because the senescent trees no longer produce enough commodities to exchange for rice to feed an enlarged population." The historical background is described, policies of the Indonesian government are discussed, and data are presented on the rate of population growth     

Systematic reductions of 19th century planetary observations

Systematic reductions of nineteenth century observations to the system of the FK4 are discussed. Reductions made on a nightly basis are described and compared with the results obtained through the use of conventional tables. The series of observations made at the Paris Observatory from 1837 to 1881 was used to compare the two methods, and a combined system of 24 000 FK4, FK4 Sup and AGK 3R positions and proper motions provided the reference stars. The results show that for Uranus the mean error of a single observation in right ascension is ±1..33 when tables are used for the reductions, and ±1.12 when nightly reductions are made, while in declination the corresponding mean errors are ±0.88 and ±0.80. The observations of Neptune show an even greater difference between the two methods; the mean errors for the tabular and nightly reductions are ±1.57 and ±1.09 in right ascension and ±0.88 and ±0.75 in declination. Secular rates in the (0–C)'s of Uranus of –0.029/year in right ascension and ±0.030/year in declination are present when the observations are reduced with tables. These rates are reduced to –0.007/year and +0.015/year, respectively, when nightly reductions are made.Presented at the Symposium Star Catalogues, Positional Astronomy and Celestial Mechanics, held in honor of Paul Herget at the U.S. Naval Observatory, Washington, November 30, 1978.     

A geographical interpretation of an attempt at migratory regionalization in Italy

In the first part, the authors review a group of studies dealing with the identification of regional differences in Italian migratory patterns, especially using the concept of migration field. The second part is devoted to a study of the hierarchical clustering of Italian provinces using 1973 inter-provincial migratory flow data. (summary in ENG, FRE)     

Some comments on the Oort cloud

The arguments used by Lyttleton to prove the nonexistence of the Oort cloud are reviewed, and it is shown that Oort's hypothesis remains consistent with observation. The 1950 model of the cloud cannot be correct and, by use of the results from a number of more recent papers, an improved model is described and compared with observations. It is emphasized that comparison of the predictions of theory with observations should concentrate on thea-distribution, as the 1/a-distribution masks much of the detailed structure of the theory. An order of magnitude argument is given which shows that 20% of so-called new comets have passed through the planetary system before, and the implications of this to the statistics of near-parabolic comet orbits are briefly investigated.     

A model for a structure in the galactic nebula S206

The galactic nebula S206 contains a half shell of high excitation nebulosity which is centred on the associated exciting star. The suggestion has been made that this structure is caused by the interaction of stellar mass loss from the star with nebular gas. A steady state model of such an interaction is investigated quantitatively. The required mass loss rate from the star is about 10^–7 M yr^–1 which is compatible with the observationally derived mass-loss rates from early-type stars.     

Density wave-star interaction in the theory of spiral galaxies

The dispersion relation has been derived for density waves propagating at an arbitrary angle. The analysis has shown the existence of a resonance which for a two-arm galaxy can be stable, neutral or unstable as }2$$ " align="middle" border="0"> , respectively.     

Outward transport of angular momentum by gas convection and the equatorial acceleration of the Sun

A new mechanism for sustaining enhanced rotational velocity of the outer layers of the solar convective envelope is considered.The gas density inside turbulent eddies decreases because of centrifugal scattering of matter. The decrease of density in eddies rotating in the same sense as the Sun on the whole is larger than that in eddies rotating in the opposite sense. As a result, the former ascend while the latter sink down, thus producing a continuous outward flux of angular momentum.A distribution of angular velocity in the radius of the solar convective envelope in the equatorial plane was obtained in the approximation of the mixing length theory of thermal convection. The results agree rather well with observations.     

Energetic properties of interplanetary plasma at the earth's orbit following the August 4, 1972 flare

Solar wind and interplanetary magnetic field data were obtained by the PROGNOZ 1 and PROGNOZ 2 satellites during the period following the August 4, 1972 (0621 UT) solar flare. A thermalized plasma was recorded one hour after the shock followed two hours later by the plasma piston with a bulk velocity higher than 1700 km s^-1. The comparison between the PROGNOZ and PIONEER 9 solar wind data shows an attenuation of the plasma properties with the deflection from the flare's meridian.     

Plasmasphere response to the onset of quiet magnetic conditions: Plasma convection patterns

A whistler study has been made of plasma convection within the plasmasphere during a transition from steady moderate geomagnetic activity to quiet conditions. Continuous whistler data recorded at Sanae, Antarctica (L= 3.98) for the period 0400 UT, 10 July to 0400 UT, 11 July 1973 have been analyzed in 15 min intervals.This study has revealed two distinct bulges in the plasmasphere centred on 1700 and 0100 UT. The bulges appear to result from the outward flow of plasma rather than the addition of new plasma. We tentatively interpret the late bulge at 0100 UT as being the duskside bulge of earlier studies rotated into the midnight region. In this bulge, plasma above L = 3.8 appears to convect outwards to form the bulge whereas plasma at lower L-values is relatively undisturbed. For the early bulge (1700 UT) the plasma convection pattern is similar over all observable L-values and closely reflects the shape of the estimated plasmapause in that region. Comparison of the bulges, with those obtained by Carpenter (1966) suggests that the onset of quiet conditions results in a general displacement of the bulges in an eastward direction by about 3 hr.     

Newtonian cosmology with a varying gravitational constant

Newtonian cosmology is developed with the assumption that the gravitational constantG diminishes with time. The functional form adopted forG(t), a modification of a suggestion of Dirac, isG=A(k+t) ^–1, wheret is the age of the Universe and a small constantk is inserted to avoid a singularity in the two-body problem. IfR is the scale factor, normalized to unity at an epoch time , the differential equation is then . Here ₀ is the mean density at the epoch time. With the above form forG(t), the solution is reducible to quadratures.The scale factorR either increases indefinitely or has one and only one maximum. LetH ₀ be the present value of Hubble's constant /R and _0c the minimum density for a maximum ofR, i.e., for closure of the Universe. The conditions for a maximum lead to a boundary curve of _0c versusH ₀ and the numbers indicate strongly that thisG-variable Newtonian model corresponds to an open universe. An upward estimate of the age of the Universe from 10¹⁰ yr to five times such a value would still lead to the same conclusion.The present Newtonian cosmology appears to refute the statement, sometimes made, that the Dirac model forG necessarily leads to the conclusion that the age of the Universe is one-third the Hubble time. Appendix B treats this point, explaining that this incorrect conclusion arises from using all the assumptions in Dirac (1938). The present paper uses only Dirac's final result, viz,G(k+t)^–1, superposing it on the differential equation .