The formation of fluidized ejecta on Mars by granular flows

Abstract— A simple granular flow model is used to investigate some of the conditions under which ejecta may flow as a granular media. The purpose of this investigation is to provide some bounds as to when either volatiles or an atmosphere are required to explain the fluid‐like morphology of many Martian ejecta deposits. We consider the ejecta deposition process from when an ejecta curtain first strikes a target surface via ballistics and possibly flows thereafter. A new finding is that either hard‐smooth surfaces or slightly erodible surfaces allow ejecta to flow readily as a granular medium. Neither volatiles nor an atmosphere are required to initiate flow. A low friction coefficient between ejecta grains can also generate flow and would be analogous to adding volatiles to the ejecta. The presence of either a rough or a densely packed erodible surface does not permit easy ejecta flow. High friction coefficients between ejecta grain also prevent flow, while changes in the coefficient of restitution (a measure of how much energy is retained after collisions between particles) plays a minor role in the flow dynamics of ejecta. A hard smooth or a somewhat erodible surface could be generated by past fluvial activity on Mars, which can either indurate a surface, erode and smooth a surface, or generate sedimentary terrains that are fairly easy to erode. No ramparts or layered ejecta morphologies are generated by our model, but this may be because several simplifying assumptions are used in our model and should not be construed as proof that either volatiles or an atmosphere are required to form fluidized ejecta morphologies.     

Characteristics and climatic sensitivities of runoff from a cold‐type glacier on the Tibetan Plateau

Model calculations are made in order to understand the characteristics and response to climate change of runoff from a cold glacier on the Tibetan Plateau. Some 20% of meltwater is preserved at the snow–ice boundary due to refreezing, since the glaciers in mid to northern Tibet are sufficiently cooled during the previous winter. Sensitivity to alterations in meteorological parameters has revealed that a change in air temperature would cause not only an increase in melting by sensible heat, but also a drastic increase in melting due to lowering of the albedo, since some of the snowfall changes to rainfall. In addition, it was suggested that a decrease in precipitation would cause a lowering of the surface albedo, with a resulting increase in the contribution of glacier runoff to the total runoff of river water. This study shows the first quantitative evaluation of the above effects, though they have been suggested qualitatively. The seasonal sensitivity of glacier runoff was examined by changing the dates given for a meteorological perturbation for a period of only 5 days. It was revealed that changes in both air temperature and precipitation during the melting season strongly affected glacier runoff by changing the surface albedo, though these perturbations only slightly altered the annual averages. Copyright © 2006 John Wiley & Sons, Ltd.     

Population dynamics of phytoplankton, heterotrophic bacteria, and viruses during the spring bloom in the western subarctic Pacific

We characterized the community composition of phytoplankton in the western subarctic Pacific from the pre-bloom to the decline phase of the spring bloom with special reference to decreases in the silicic acid concentration in surface waters as an index for diatom bloom development. Furthermore, responses of heterotrophic bacteria and viruses to the spring bloom were also concomitantly investigated. Under pre-bloom conditions when nutrients were abundant but the surface mixed layer depth was relatively deep, chlorophyll (Chl) a concentrations were consistently low and green algae (chlorophytes and prasinophytes), cryptophytes, and diatoms were predominant in the phytoplankton assemblages as estimated by algal pigment signatures. Together with the shallowing of the mixed layer depth and the decrease in silicic acid concentration, diatoms bloomed remarkably in the Oyashio region, though the magnitude of the bloom in the Kuroshio-Oyashio transition (hereafter Transition) region was relatively small. A total of 77 diatom species were identified, with the bloom-forming diatoms mainly consisting of Thalassiosira, Chaetoceros, and Fragilariopsis species. It has become evident that the carotenoid fucoxanthin can serve as a strong indicator of the diatom carbon biomass during the spring diatom bloom. Differences in the species richness of diatoms among stations generally enabled us to separate the Oyashio bloom stations from the Transition and the Oyashio pre-bloom stations. Relatively high values of the Shannon-Wiener index for the diatom species were also maintained during the Oyashio bloom, indicating that a wide variety of species then shared dominance. In the decline phase of the Oyashio bloom when surface nutrient concentrations decreased, senescent diatom cells increased, as inferred from the levels of chlorophyllide a. Although the cell density of heterotrophic bacteria changed little with the development of the diatom bloom, viral abundance increased toward the end of the bloom, suggesting an increased likelihood of mortality among organisms including diatoms resulting from viral infection. This is the first report on the microbial trophodynamics, including viruses, during the spring diatom bloom in the western subarctic Pacific.     

Near-Infrared Photometric And Polarimetric Observations Of Comet Hale-Bopp

Near-infrared photometric and polarimetric observations of comet Hale-Bopp (1995 O1) using KONIC (Kiso Observatory Near-Infrared Camera) are reported. Observations were carried out on March 18 UT and April 26 UT 1997, when the heliocentric distances of the comet were 0.94 and 1.02 AU, and the phase angles were 48.5 deg and 32.9 deg, respectively. In the J, H, and K′ bands, we obtained linear polarization of the near-nucleus region of 16.4 ± 1.2, 18.8 ± 1.3, and 15.1 ± 0.9 percent on March 18UT and 7.1 ± 1.1, 8.9 ± 1.0, and 6.9 ± 0.6 percent on April 26, respectively. These values were higher than those observed for 1P/Halley. The maximum polarization was found at H band on both dates. Polarization maps showed higher polarization regions toward the anti-solar direction in the J and H bands. No distinct correlation was found between high polarization regions and bright regions. The projected expansion velocity of the arc structure of the dust jet was 375 ± 35.7 m/s on 17–19 March. The periodicity was found to be 11.1 ± 2.8 hours. This revised version was published online in July 2006 with corrections to the Cover Date.     

The application of δ13C and C/N ratios as indicators of organic carbon sources and paleoenvironmental change of the mangrove ecosystem from Ba Lat Estuary, Red River, Vietnam

In this study, two sediment cores (~70 cm) were collected from separate mangrove forests straddling the Ba Lat Estuary, Red River of northern Vietnam, to examine the origins of sedimentary organic carbon (SOC) and reconstruct the paleoenvironment. In addition, mangrove leaves and particulate organic matter were collected and measured for δ¹³C to trace the origins of SOC. The cores were analyzed by high-resolution sections for δ¹³C, TOC, C/N ratios, sediment grain size, water content, and porosity, with values of δ¹³C, TOC, and C/N ratios ranging from −28.19 to −22.5‰, 2.14–30.94 mg/g, and 10.29–18.32, respectively. The δ¹³C and TOC relationship indicated that there were some small residual effects of diagenetic processes on TOC and δ¹³C values in mangrove sediments. However, the shifts of δ¹³C and C/N ratios from the bottom to the surface sediment of the cores explained the change in organic matter sources, with values of C/N > 12 and δ¹³C < −25‰, and C/N < 12 and δ¹³C > −25‰ indicated terrestrial (e.g., mangrove litter) and marine phytoplankton sources, respectively. The covarying δ¹³C, C/N ratios, and sediment grain sizes during the past 100 years in sediment cores showed that the paleoenvironment may be reconstructed into three environments (subtidal, tidal flat, and intertidal mangrove). General trends in δ¹³C and C/N followed a gradual increase in the C/N ratio and a concomitant decrease in δ¹³C from the subtidal, through to tidal flat, and to the intertidal mangrove. δ¹³C and C/N ratios are therefore effective in measuring the continuum of environmental change in mangrove ecosystem.     

Financial risk management for energy service project under the Tokyo emission trading system

Recently, energy service providers (ESP) have increased due to deregulation in the power market. They install energy supply equipment at their own cost and supply the necessary energy to the client. The Tokyo Metropolitan Government started Asia’s first cap-and-trade program in April 2010. This program caps energy-related carbon dioxide emissions from some 1,330 offices and factories in Tokyo. Then, ESPs have to manage the many risks of energy service project directly linked to the profits. In this paper, we describes the risk analysis and investment optimization for energy service projects using financial engineering.     

Experiments and Dynamic Finite Element Analysis of a Wire-Rope Rockfall Protective Fence

The imperative need to protect structures in mountainous areas against rockfall has led to the development of various protection methods. This study introduces a new type of rockfall protection fence made of posts, wire ropes, wire netting and energy absorbers. The performance of this rock fence was verified in both experiments and dynamic finite element analysis. In collision tests, a reinforced-concrete block rolled down a natural slope and struck the rock fence at the end of the slope. A specialized system of measuring instruments was employed to accurately measure the acceleration of the block without cable connection. In particular, the performance of two energy absorbers, which contribute also to preventing wire ropes from breaking, was investigated to determine the best energy absorber. In numerical simulation, a commercial finite element code having explicit dynamic capabilities was employed to create models of the two full-scale tests. To facilitate simulation, certain simplifying assumptions for mechanical data of each individual component of the rock fence and geometrical data of the model were adopted. Good agreement between numerical simulation and experimental data validated the numerical simulation. Furthermore, the results of numerical simulation helped highlight limitations of the testing method. The results of numerical simulation thus provide a deeper understanding of the structural behavior of individual components of the rock fence during rockfall impact. More importantly, numerical simulations can be used not only as supplements to or substitutes for full-scale tests but also in parametric study and design.