The association of OH and methanol masers in W3(OH)

We present single-baseline Multi-Element Radio-Linked Interferometer Network (MERLIN) measurements of excited OH 6.0-GHz masers and methanol 6.7-GHz masers for the source W3(OH). These allow us to compare the positions of individual maser spots of these two species to ∼15 mas accuracy for the first time, and to compare these with previously published positions of ground-state OH masers near 1.7 GHz and excited-state OH masers near 4.7 GHz. There is a strong association between OH 6035-MHz and 1665-MHz masers. OH and methanol have very similar distributions, but associations of individual masers are relatively rare: most methanol 6.7-GHz masers are within 100 mas of OH 6.0-GHz masers, but only four methanol masers are within 15 mas of an OH 6.0-GHz maser. There are no correspondences of either species with excited OH 4.7-GHz masers. Zeeman splitting of the 6.0-GHz OH lines indicates an ordered magnetic field ranging from 3.2 to 14.4 mG. The magnetic fields estimated from co-propagating masers such as 6035 and 1665 MHz are generally in good agreement with each other.     

Weak field limit and tests of a relativistic theory of gravity

Static spherically-symmetric solutions to the linearized field equations of a generalized scalartensor theory of gravity are derived. The gravitational potential outside such a source is determined; it is found that this potential can have an intermediate range variation. The question of whether such an intermediate range variation would manifest itself in two experiments is addressed.     

Simulation of deforestation in eastern Amazonia using a high-resolution model

Summary This work evaluates the impact of deforestation on the climate of the eastern portion of the Amazon basin. This region is primarily an area of native tropical rainforest, but also contains several other natural ecosystems such as mangroves and savanna. It is the most densely populated area in Amazonia, and has been significantly affected by deforestation. In this study, numerical simulations were performed with a high spatial resolution, regional model that allows for consideration of mesoscale aspects such as topography, coastlines and large rivers.To evaluate the present situation and to predict potential future effects of deforestation on the climatic conditions of this region, two, one-year model simulations were made. In the first, control simulation, an attempt was made to match the existing surface vegetation. The biophysical parameters used were derived from recent studies of similar Amazon-region ecosystems. In the second run, deforested simulation, the forested-area biophysical parameters were replaced by those corresponding to the pasture areas of the region.The higher-resolution regional modelling revealed important climatic features of the deforestation process, displaying some associated mesoscale effects that are not typically represented in similar Global Circulation Model simulations. Near coastal zones and along large rivers, deforestation resulted in reduced cloud cover and precipitation. However, increased cloud cover and precipitation was predicted over upland areas, especially on slopes facing river valleys. The modelled surface sensible and latent heat fluxes also presented both positive and negative anomalies. The magnitudes of these anomalies were greater during the dry season. Windspeed near the surface was the meteorological variable that presented the most significant change due to deforestation. The reduction in roughness coefficient resulting from the shift from forest to pasture produced increased windspeeds near the Atlantic coast. The greater windspeeds diminished local humidity convergence and consequently reduced rainfall totals in nearby regions.The results obtained from these higher-resolution simulations show that, in general, orography, coastline profile and the distribution of large rivers play important roles in determining anomaly patterns of precipitation, wind, and energy exchange associated with deforestation in eastern Amazonia.     

The circumstellar envelope of S persei

We present MERLIN observations of OH and H₂O masers in the circumstellar envelope of S Per. The results are consistent with a model of a thick shell of H₂O masers in a region which is still accelerating.     

CLIMATIC CHANGE,POPULATION GROWTH,AND THEIR EFFECTS ON GREAT LAKES WATER SUPPLIES*

Two scenarios of CO₂-induced climatic change and projections of population and consumptive use of water to the year 2035 are utilized in a climate impact assessment of future water resources in the Great Lakes basin. When expressed as a streamflow/population index, results indicate a sharp decline of this index. Future index values are projected to be similar to those presently recorded for the Colorado River basin.     

General relativistic rotational properties of stellar models

In this paper we give general relativistic expressions for the angular momentum and rotational kinetic energy of slowly rotating stars. These expressions contain contributions from the presure, gravitational red shift, and Doppler shift, and the motion of inertial frames. These contributions are not negligible, e.g., there are stable neutron star models for which the angular velocity of inertial frames at the center is about 70% the angular velocity of the star. These expressions are useful in the study of pulsars if pulsars are rotating neutron stars.     

New orbital elements for Moon and planets

The results of a simultaneous solution for the orbital elements of Moon and planets are given and their derivation is discussed. A modern Cowell integrator is used for orbit computations, and least-squares fits are made to some 40000 optical observations taken since 1913. The model includes relativistic terms, the leading zonal harmonics of Earth and Moon, the precession of the lunar equator, and the tidal couple between Earth and Moon. The tidal term in the Moon's mean longitude is found to be –19±4 per century squared. The solution also yields an extrapolation of the atomic time scale back to 1912.5. At that time, the difference between atomic and ephemeris time is about 6±2 s. Lunar declinations observed by the Washington transit circles, after receiving limb corrections and thus with respect to the center of Watts' reference sphere, are smaller than computed values by 0.33±0.01. It is found that solar oblateness cannot quite be determined with optical data covering about 50 yr, butJ ₂ is unlikely to be much larger than 10^–5. The advance of Mercury's perihelion is verified to within our resolution of 2 per century to match that predicted by Einstein.The solution presented here is believed to be the only simultaneous improvement of the orbits of Moon and planets. This simultaneity is found to be an essential feature in separating the Moon's mean motion, the lunar tidal deceleration, and the corrections to the Earth rotation rate. It is now possible to refer all astronomical events of the past 60 yr to a time with uniform rate, namely the atomic clock system. Considering the long baseline, this model should facilitate the prediction of fast variables, such as the lunar longitude, with considerably increased confidence. The planetary orbital elements compete with efforts of similar scope and accuracy at the Massachusetts Institute of Technology and the Jet Propulsion Laboratory.     

Numerical experiments on Lynden-Bell's statistics

We performed computer experiments on 13 different initial configurations of one-dimensional self-gravitating systems. The three most and the three least violently relaxed systems were compared with the predictions of Lynden-Bell's statistical mechanics. The agreement between the experimental results and the theoretical predictions became worse as the relaxation became more violent. While all six systems were theoretically nondegenerate, the violent systems invariably flung out a halo that took most of the energy, leaving behind a low-energy degenerate core.