Mesoscale linear streaks on Mars: environments of dust entrainment

Variable surface albedo features on Mars are likely caused by the entrainment and deposition of dust by the wind. Most discrete markings are associated with topographic forms or with regional slopes that serve to alter the effective wind shear stress on the surface. Some of the largest variable features, here termed mesoscale linear streaks, are up to 400 km in length and repeatedly occur in one of the smoothest regions of Mars: Amazonis Planitia. Their orientations and apparent season of variability as observed by Viking and Mars Orbiter cameras indicate linear streak formation by enhanced surface wind stresses during regional or local dust storms and during the initial stages of global dust storms. They provide an example of the ability of large-scale winds, without significant local enhancement, to initiate dust motion on Mars. The sizes and spacing of the linear streaks may be controlled by boundary layer rolls. The repetitive formation of these streaks, over a span of more than 11 Mars years, gives one measure of the stability of Mars’ eolian processes.     

LU Vel (GJ 375): A M3.5Ve Flare and Double-Lined Spectroscopic Binary

High resolution echelle spectroscopic observations taken with the FEROS spectrograph at the 2.2 m telescope ESO confirm the binary nature of the flare M3.5V star LU Vel (GJ 375, RE J0958-462) previously reported by Christian and Mathioudakis (2002). Emission of similar intensity from both components is detected in the Balmer, Na i D₁&D₂, He i D₃, Ca ii H&K, and Ca ii IRT lines. We have determined precise radial velocities by cross correlation with radial velocity standard stars, which have allowed us to obtain for the first time the orbital solution of the system. The binary consists of two near-equal M3.5V components with an orbital period shorter than 2 days. We have analyzed the behaviour of the chromospheric activity indicators (variability and possible flares). In addition, we have determined its rotational velocity and kinematics.     

Inhomogeneous substrate analysis using EM300 backscatter imagery

Backscatter reflectivity from multibeam echo-sounders provides a powerful tool to efficiently characterize seafloor substrates. A comprehensive EM300 bathymetric and backscatter survey has been completed of Cook Strait, in central New Zealand. This paper presents a detailed analysis of the realtime corrections applied to the raw EM300 multibeam data and additional corrections required to compute angular variations of the backscatter strength. The corrections, including the local absorption coefficient, the influence of seafloor topography and sound refraction in the water column, are determined for different Cook Strait seafloor substrates. Modifying MB-System software code, we extracted the backscatter signal parameters in order to quantify the raw backscatter strength and apply additional processing. Profiles of backscatter strength versus incidence angle were computed for a variety of sites characterized by flat seafloor and homogeneous substrates, and for which ground-truth data were available. For each homogeneous site, different but characteristic backscatter profiles are observed that can be interpreted in terms of sediment facies. To analyze heterogeneous substrates, we present a statistical technique, based on a 3-dimensional distribution of (incidence angle, backscatter strength) couples that preserves geological information of the substrate components. This analysis, using backscatter data acquired on a submarine volcano, north of New Zealand, clearly differentiates soft sediments and lava flows within a heterogeneous substrate.     

BACODINE,the real-time BATSE gamma-ray burst coordinates distribution network

The celestial coordinates of gamma-ray burst sources observed with BATSE on GRO are automatically determined and distributed in real time to members of the global scientific community. These data are now being used by more than 20 operations to enable searches for associated transients in a variety of other wavelength or energy regimes to identify the burst source objects. The minimum total delay time from the onset of a burst to the receipt of its coordinates by distant experimenters can be under 4 sec, less than the duration of a typical GRB, and the maximum total delay is 7 sec, or longer, depending on the distribution method. Some improvements to the BACODINE system and a summary of the follow-up observations made by some of the sites are given.     

Spatial factors of differentiation of unemployment in Poland during 1990–2007

An analysis is made of the dynamics of unemployment and of the factors of its spatial differentiation on the territory of Poland. Six stages were identified in the dynamics of employment, which are associated with the character of development of the national economy and its accession to the common European market of manpower. It is stressed that the historical and political-geographical conditions have influence on the character of the spread of unemployment.     

A search for soft X-ray emission from stellar sources

With the soft X-ray detector (0.2–0.284 keV) aboard the Astronomical Netherlands Satellite (ANS) we have searched for X-ray emission from hot star coronae and peculiar stars. On Sirius ( CMa) and Capella ( Aur) X-ray emission has been measured at 6 and 5 level, respectively, above background. In all other cases the search revealed no evidence for soft X-ray emission. Upper limits to the luminosities of about 25 star coronae (main-sequence stars, (sub)giants, and supergiants) and of 4 peculiar stars ( Sco, Lyr, P Cyg, and Car) have been obtained.Paper presented at the COSPAR/IAU Symposium on Fast Transients in X-and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.     

The formation of saturn's satellites and rings,as influenced by saturn's contraction history

We have used Pollack et al.'s 1976 calculations of the quasi-equilibrium contraction of Saturn to study the influence of the planet's early high luminosity on the formation of its satellites and rings. Assuming that the condensation of ices ceased at the same time within Jupiter's and Saturn's primordial nebulae, and using limits for the time of cessation derived for Jupiter's system by Pollack and Reynolds (1974) and Cameron and Pollack (1975), we arrive at the following tentative conclusions. Titan is the innermost satellite at whose position a methane-containing ice could condense, a result consistent with the presence of methane in this satellite's atmosphere. Water ice may have been able to condense at the position of all the satellites, a result consistent with the occurrence of low-density satellites close to Saturn. The systematic decrease in the mass of Saturn's regular satellites with decreasing distance from Saturn may have been caused partially by the larger time intervals for the closer satellites between the start of contraction and the first condensation of ices at their positions and between the start of contraction and the time at which Saturn's radius became less than a satellite's orbital radius. Ammonia ices, principally NH₄SH, were able to condense at the positions of all but the innermost satellites.Water ice may bave been able to condense in the region of the rings close to the end of the condensation period. We speculate that the rings are unique to Saturn because on the one hand, temperatures within Jupiter's Roche limit never became cool enough for ice particles to form before the end of the condensation period and on the other hand, ice particles formed only very early within Uranus' and Neptune's Roche limits, and were eliminated by gas drag effects that caused them to spiral into the planet before the gas of these planets' nebula was eliminated. Gas drag would also have eliminated any rocky particles initially present inside the Roche limit.We also derive an independent estimate of several million years for the time between the start of the quasi-equilibrium contraction of Saturn and the cessation of condensation. This estimate is based on the density and mass characteristics of Saturn's satellites. Using this value rather than the one found for Jupiter's satellites, we find that the above conclusions about the rings and the condensation of methane-and ammonia-containing ices remain valid.     

Morphology and Histology of Lattice-like Ossified Epaxial Tendons in Psittacosaurus (Dinosauria: Ceratopsia)

<正>Epaxial tendons play an important role in the study of the musculoskeletal system and locomotory style of dinosaurs.Although the ossified epaxial tendon lattice is fairly well known in Iguanodontoidea,only recently has knowledge of this complex been extended to ceratopsians.This study concerns the gross morphology and microstructure of the tendon lattice in Psittacosaurus,a basal ceratopsian.As in the neoceratopsian Chasmosaurus,the ossified tendons of Psittacosaurus form a three-layered, lattice-like structure.The microstructure of the tendons in large psittacosaur individuals retains an early stage of ossification,as in juvenile birds and nestling hadrosaurs,suggesting a slow developmental rate of ossification of the tendons in psittacosaur ontogeny.Comparative study indicates that a lattice-like arrangement of three-layered epaxial tendons is widely distributed in Cerapoda.This pattern also extends to Ankylosauria,implying a similar pattern of the epaxial muscles through the ornithischian clade.In addition,comparison with crocodiles implies that the different morphology of ossified tendons in dinosaurs may be associated with adaptive aspects of their paleobiology,not simply a side effect of skeletal ossification.In contrast to the short tendons in quadrupedal Chasmosaurus and Protoceratops,the elongated tendons in Psittacosaurus may be related to the bipedal locomotion characteristic of this taxon.     

Absence of regional stratigraphic hiatus in the late Carboniferous (Asturian - Stephanian) in the northern Variscan foreland: a review of the bio- and lithostratigraphical evidence in central england

An extensive regional stratigraphic hiatus has been proposed in the Asturian to Stephanian foreland basin successions lying to the north of the main Variscan deformation belt, stretching from north west Europe to eastern North America. The hiatus is inferred on megafloral grounds and involves the absence of most if not all of Stephanian Substages B and C. If present it would have great significance for the understanding of regional basin dynamics in the later stages of the Variscan orogeny. However, its existence has been strongly contested. One of the keys to this hypothesis is the correct identification and interpretation of plant fossils from the Warwickshire Coalfield (Central England). The published identifications are here shown to be incorrect, and revised determinations taken in conjunction with other stratigraphic data from Central England suggest that a regional hiatus is not present in the early-mid Stephanian, and that any stratigraphic hiatuses at other horizons in the succession are of purely local extent. A review of known occurrences of the Asturian and Stephanian successions in basins stretching from eastern Canada to Germany suggests that, while facies developments may be similar, there is little uniformity in stratigraphic style and little evidence for a major Stephanian hiatus.