Periodic orbits based on geometric structure of center manifold around Lagrange points

This study proposes an analytical method that determines the center manifold and identifies the reduced system on the center manifold. The proposed method expresses the center manifold through general equations containing only state variables, and not functions with respect to time. This is the so-called geometric structure of the center manifold. The location of periodic or quasi-periodic orbits is identified after the geometric structure of the center manifold is determined. The reduced system on the center manifold is described using ordinary differential equations, so that periodic or quasi-periodic orbits can be computed by numerically integrating the reduced system. The results indicate that the analytical method proposed in this study has higher precision compared with the Lindstedt-Poincaré method of the same order.     

VLBI observations of high-opacity HI gas in NGC 5793

We report on observations, with sub-parsec resolution, of neutral hydrogen seen in absorption in the λ=21 cm line against the nucleus of the active spiral galaxy NGC 5793. The absorption line consists of three components separated in both location as well as velocity. We derive HI column densities of 2×10²² cm⁻² assuming a gas spin temperature of 100 K. For the first time we are able to reliably estimate the HI cloud sizes (≈15 pc) and atomic gas densities (≈200 cm⁻³). Our results suggest that the HI gas is not associated with the <10 pc region which presumably contains the H₂O masers, but it is more distant from the nucleus, and is probably associated with the r1 kpc gas seen in CO.     

Diffuse X-ray background measurements in the energy range 2–18 keV

Rocket measurements, of the diffuse X-ray background in the energy range 2–18 keV, conducted from Thumba Equatorial Rocket Launching Station (TERLS), India, are presented. The estimates of the cosmic background are derived by the method which employs the Earth and its atmosphere as a shutter to intercept the celestial X-rays. The results are shown to be consistent with a power law photon spectrum.13.6 _–3.3 ^+4.3 E ^{–1.73±0.15} photons/cm²-sec-keV-ster the spectrum being much flatter than that observed at higher energies.     

Spectra of simulated lightning on Venus,Jupiter, and Titan

Laser-induced plasmas in various gas mixtures were used to simulate lightning in other planetary atmospheres. This method of simulation has the advantage of producing short-duration, high-temperature plasmas free from electrode contamination. The laser-induced plasma discharges in air are shown to accurately simulate terrestrial lightning and can be expected to simulate lightning spectra in other planetary atmospheres. Spectra from 240 to 880 nm are presented for simulated lightning in the atmospheres of Venus, Earth, Jupiter, and Titan. The spectra of lightning on the other giant planets are expected to be similar to that of Jupiter because the atmospheres of these planets are composed mainly of hydrogen and helium. The spectra of Venus and Titan show substantial amounts of radiation due to the presence of carbon atoms and ions and show CN Violet radiation. Although small amounts of CH₄ and NH₃ are present in the Jovian atmosphere, only emission from hydrogen and helium is observed. Most differences in the spectra can be understood in terms of the elemental ratios of the gas mixtures. Consequently, observations of the spectra of lightning on other planets should provide in situ estimates of the atmospheric and aerosol composition in the cloud layers in which lightning is occuring. In particular, the detection of inert gases such as helium should be possible and the relative abundance of these gases compared to major constituents might be determined.     

A new model for barred spiral galaxies

Computer simulations are used to demonstrate that normal spiral galaxies with symmetrically warped arms can appear to have bar and bar-within-ring structures when viewed from appropriate position angles.     

Spectrophotometry of Saturn and its rings from 60 to 180 microns

We observed Saturn at far-infrared and submillimeter wavelengths during the Earth's March 1980 passage through the plane of Saturn's rings. Comparison with earlier spectroscopic observations by D. B. Ward [Icarus32, 437–442 (1977)], obtained at a time when the tilt angle of the rings was 21.8°, permits separation of the disk and ring contributions to the flux observed in this wavelength range. We present two main results: (1) The observed emission of the disk between 60 and 180 μm corresponds to a brightness temperature of 104 ± 2°K; (2) the brightness temperature of the rings drops approximately 20°K between 60 and 80 μm. Our data, in conjunction with the data obtained by other observers between 1 μm and 1 mm, permit us to derive an improved estimate for the total Saturnian surface brightness of (4.84 ± 0.32) × 10^?4W cm^?2 corresponding to an effective temperature of 96.1 ± 1.6°K. The ratio of radiated to incident power, P_R/P_I, is (1.46 ± 0.08)/(1 - A), where A is the Bond albedo. For A = 0.337 ± 0.029, P_R/P_I = 2.20 ± 0.15 and Saturn's intrinsic luminosity is L_S = (2.9 ± 0.5) × 10^?10L_⊙.     

Auroral boundary variations and the interplanetary magnetic field

This paper describes a DMSP data set of 150 auroral images during magnetically quiet times which have been analyzed in corrected geomagnetic local time and latitudinal coordinates and fit to offset circles. The fit parameters R (circle radius) and (X, Y) (center location) have been compared to the hourly interplanetary magnetic field (IMF) prior to the time of the satellite scan of the aurora. The results for variation of R with B_z, agree with previous works and generally show about a 1° increase of R with increase of southward B_z by 1 nT. The location of the circle center also has a clear statistical shift in the Southern Hemisphere with IMF B_y such that the southern polar cap moves towards dusk (dawn) with B_y > (B_y < 0).     

Partizansky base-metal skarn deposit, Dal’negorsk ore district, Russia: Stages of ore formation, mineral assemblages, and typomorphism of fahlore

As indicated by mineralogical, geochemical, and structural-textural data, the base-metal skarn ore at the Partizansky deposit was formed during two stages (base-metal skarn and silver-sulfosalt), which were separated by intrusion of basaltic dikes. The bulk of the base-metal ore was deposited at the first stage, which comprises four sequential mineral assemblages: skarn-silicate, quartz-arsenopyrite, productive galena-sphalerite, and pyrrhotite-pyrite-chalcopyrite. The mineralization of the second stage was mainly confined to the upper margins of orebodies and pertains to the sulfosalt-galena-chalcopyrite assemblage, which was super-imposed on minerals of the first stage. The vertical mineralogical-geochemical zoning of the deposit is telescopic (related to the formation of the late silver-sulfosalt mineralization) and facies (typical of the early skarn and base-metal assemblages). The zoning of the skarn-silicate assemblage is expressed in the metasomatic replacement of skarn by quartz and calcite in the uppermost zone of skarn bodies and is emphasized by variation of the mineral composition throughout the skarn column, for instance, by the distinct updip enrichment of hedenbergite in manganese. The vertical zoning of the productive assemblage is emphasized by variations in the ratio of sphalerite to galena (the Pb/Zn ratio in the ore increases upward from 0.1 to 1), changes in mineral assemblages, and compositional variation of major ore-forming and minor minerals. In particular, galena from the deep levels is extremely enriched in Bi and Ag, while that from the upper levels is almost completely devoid of isomorphic admixtures. Fahlore displays updip enrichment in Sb, Ag, and Fe and corresponding depletion in Cu and Zn. The vertical chemical variations in fahlore are caused by the specific geological setting of ore deposition, the composition of the ore-forming solutions, and the physicochemical conditions of their transportation and ore deposition.     

INFLUENCE OF A CONDUCTING SHIELD IN THE ONE-LOOP VERSION OF THE TRANSIENT PULSE INDUCTION METHOD*

The transient response of a conductive shell-shell model in the one-loop version was obtained analytically. The results indicate that four zones, namely early, late early, intermediate, and late zone can be identified in the total transient characteristic of the model. In case the measurements are carried out in the late early zone, a conductive target appears as a resistive one. It is suggested that the optimum time of measurement should be so selected as to fall in the intermediate zone.     

Compound and simple lava flows and flood basalts

Compound lava flows, defined as those lavas which are divisible into flowunits, commonly have a shield-like form and are thought to develop when the rate of extrusion of lava is relatively low.Simple lava flows, defined as those lavas which are not divisible into flow-units, are thought to form when the rate of extrusion of lava is relatively high. A logical definition oflava flow must embrace both simple lava sheets and substantial lava shields (compound lava flows) up to 600 m high. Flood basalt piles include both compound and simple flows, but the most extensive and far-reaching flows are simple and they are believed to form when the rate of extrusion of lava is particularly high.