Observations and analysis of the Southern binary R Arae

This paper investigates the nature of the relatively bright ( 7th magnitude) eclipsing variable R Arae (HD 149730A), which has an orbital period of 4^d.42509, from the analysis of photometricUBV observations. The main objective behind such an analysis is to determine whether the system qualifies for a classical Algol of semi-detached status.An analysis has been performed twice on each of theUBV curves as well as the light curve due to Gaposchkin, utilising a light curve optimisation procedure. In the first analysis the presence of the visual companion (HD 1497330B) to R Arae (angular separation = 3'.6), whose light was present in all observations, was not accounted for. The second analysis attempts to account for this third light source.All the analyses indicate the relative radius of the secondary star, is of the order of 0.20. This value is well below the limit which would classify the system as a semi-detached binary.These results do, however, seem to be somewhat discordant with the spectroscopic and general photometric nature of the system, all of which suggest mass transfer processes to be occuring (therefore a possible semi-detached status). This is seen in several features, especially a marked increase in the system's mean orbital period, which tends to corroborate mass transfer from the secondary star.     

Effects of Shoreline Modifications on Supratidal Macroinvertebrate Fauna on Puget Sound,Washington Beaches

In coastal environments, the supratidal zone bridges marine and terrestrial ecosystems and is important for energy exchange. However, it is also subject to extensive anthropogenic disturbance, such as armoring of shorelines. Shoreline armoring is extensive along many coasts, but the impacts on biota are comparatively unknown. Between 2000 and 2002, paired and synoptic sampling regimes were employed to assess armoring effects on insects and benthic macroinvertebrates in the supratidal zone of Puget Sound beaches. Paired sampling showed natural beach sites had significantly more deposited wrack. Infauna was dominated by oligochaetes and nematodes; talitrid amphipods, insects, and collembolans were significantly more numerous at natural beaches, and crustaceans were more abundant at altered beaches. Insect assemblages were diverse, with taxon richness higher at natural beach sites. In the synoptic sampling, where sites with higher elevation modifications were used, there were fewer differences in invertebrate assemblages between armored and nonarmored sites. The results show that, where shoreline armoring lowers the land–sea interface, benthic infauna and insect assemblages are disrupted. Widespread shoreline modifications may decrease the availability of prey resources for fish and wildlife and decrease the contribution of organic material entering the nearshore ecosystem.     

Optimal transfers between unstable periodic orbits using invariant manifolds

This paper presents a method to construct optimal transfers between unstable periodic orbits of differing energies using invariant manifolds. The transfers constructed in this method asymptotically depart the initial orbit on a trajectory contained within the unstable manifold of the initial orbit and later, asymptotically arrive at the final orbit on a trajectory contained within the stable manifold of the final orbit. Primer vector theory is applied to a transfer to determine the optimal maneuvers required to create the bridging trajectory that connects the unstable and stable manifold trajectories. Transfers are constructed between unstable periodic orbits in the Sun–Earth, Earth–Moon, and Jupiter-Europa three-body systems. Multiple solutions are found between the same initial and final orbits, where certain solutions retrace interior portions of the trajectory. All transfers created satisfy the conditions for optimality. The costs of transfers constructed using manifolds are compared to the costs of transfers constructed without the use of manifolds. In all cases, the total cost of the transfer is significantly lower when invariant manifolds are used in the transfer construction. In many cases, the transfers that employ invariant manifolds are three times more efficient, in terms of fuel expenditure, than the transfer that do not. The decrease in transfer cost is accompanied by an increase in transfer time of flight.     

The Galileo star scanner observations at Amalthea

In November of 2002, the Galileo spacecraft passed within 250 km of Jupiter's moon Amalthea. An onboard telescope, the star scanner, observed a series of bright flashes near the moon. It is believed that these flashes represent sunlight reflected from 7 to 9 small moonlets located within about 3000 km of Amalthea. From star scanner geometry considerations and other arguments, we can constrain the diameter of the observed bodies to be between 0.5 m to several tens of kilometers. In September of 2003, while crossing Amalthea's orbit just prior to Galileo's destruction in the jovian atmosphere, a single additional body seems to have been observed. It is suspected that these bodies are part of a discrete rocky ring embedded within Jupiter's Gossamer ring system.     

Numerical modeling of the development of small-scale magmatic emulsions by Korteweg stress driven flow

The occurrence of micron to millimeter size globular heterogeneities in igneous rocks is frequently explained by processes of liquid immiscibility. However, such textures have also been documented in miscible magmatic pairs. In this study, the ability of miscible magmas to develop transient surface tensions and mimic the behavior of immiscible liquids is tested for the whole spectrum of magmatic compositions. We implemented a numerical model that includes the effect of gradient stresses (namely Korteweg stress) in order to investigate the role of such stresses in the evolution of diffusive interfaces. The results show that an initially elongated heterogeneity surrounded by a miscible and compositionally diverse magma will tend to minimize its contact surface by relaxing to a spherical shape, advected by a Korteweg stress driven flow. If the initial aspect ratio of the heterogeneity exceeds a critical value, surface minimization may be achieved by drop breakup. In addition, it is shown that two neighboring heterogeneities may coalesce to a single spherical drop. These results imply that even for fully miscible magmas, rheological barriers may prevent efficient mechanical intermingling and induce the formation of small-scale globular textures, analogous to those commonly observed in immiscible liquids. A better understanding of the role of Korteweg stress may be of the utmost importance for deciphering the textures generated by the interaction of compositionally diverse magmas.     

Comment on “Structural geology of the Upper Cretaceous Chalk Central Mass,Isle of Wight,UK” by Rory Mortimore. Proceedings of the Geologists’ Association,vol. 122 (2), 2012, pp. 298–331

The Chalk Group of the Central Downs of the Isle of Wight forms a relay ramp between two major inverted extensional faults. Mortimore (2011) presented a structural model of this key area based on a geological map constructed from detailed logging of a limited set of exposed sections. The area has been recently mapped at 1:10,000 scale by the British Geological Survey. Our interpretation of the geological structure differs significantly from that proposed by Mortimore, and suggests that Chalk has relatively uniform dips that progressively steepen towards the hanging wall of the E-W oriented basement faults. However, a suite of mapped extensional faults indicates an element of differential movement or transpression along the main basement structures.