Prospects for Extrasolar "Earths" in Habitable Zones

We have shown that Earth-mass planets could survive in variously restricted regions of the habitable zones (HZs) of most of a sample of nine of the 102 main-sequence exoplanetary systems confirmed by 19 November 2003. In a preliminary extrapolation of our results to the other systems, we estimate that roughly a half of these systems could have had an Earth-mass planet confined to the HZ for at least the most recent 1000 Ma. The HZ migrates outwards during the main-sequence lifetime, and so this proportion varies with stellar age. About two thirds of the systems could have such a planet confined to the HZ for at least 1000 Ma at sometime during the main-sequence lifetime. Clearly, these systems should be high on the target list for exploration for terrestrial planets. We have reached this conclusion by launching putative Earth-mass planets in various orbits and following their fate with mixed-variable symplectic and hybrid integrators. Whether the Earth-mass planets could form in the HZs of the exoplanetary systems is an urgent question that needs further study.Comment: 7 pages, 2 figure

The Use of Mt. Mazama Volcanic Ash as Natural Pozzolans for Sustainable Soil and Unpaved Road Improvement

Natural pozzolans can be a replacement for portland cement in many applications. Some natural pozzolans are byproducts of industrial processes. Other natural pozzolans, such as volcanic ash, occur naturally. This study determined the suitability of Mt. Mazama volcanic ash as a natural pozzolan and explored innovative uses of the material for roadway improvement. Requirements of natural pozzolans are specified in ASTM C618 – coal fly ash and raw or calcined natural pozzolan for use in concrete. This study concluded that volcanic ash from Mt. Mazama meets chemical requirements of a natural pozzolan. In its unprocessed, natural form, Mt. Mazama volcanic ash does not meet fineness, moisture or strength requirements as a natural pozzolan. An innovative study of the strength of mortar cubes created with increasing replacement of portland cement with Mt. Mazama volcanic ash showed that decreases in strength occur with increased percentage replacements. When the Mt. Mazama volcanic ash is crushed and passed through a No. 200 sieve, this decrease in strength is less than unprocessed material. Slurry mixes of Mt. Mazama volcanic ash, lime and portland cement applied to gravel materials bound material to a greater percentage, and reduced potentially airborne particulates to a greater degree than using portland cement slurry alone. A sustainability analysis concluded that any replacement of portland cement with volcanic ash reduces embodied energy and carbon dioxide emissions

Mount Mazama Ash Offers Sustainable Solution for ADA Accessibility on Unpaved Trails

National Institute for Transportation and Communities (NITC) researcher Matthew Sleep of Oregon Tech investigated whether Mazama ash could be used in place of portland cement, as a natural pozzolan. Results indicate that it can—and unpaved trail surfaces made with Mazama ash are actually firmer and more durable than those made with portland cement alone. Such trails can provide a reliable surface for wheeled mobility devices

The Use of Mt. Mazama Volcanic Ash as Natural Pozzolans for Sustainable Soil and Unpaved Road Improvement

Natural pozzolans can be a replacement for portland cement in many applications. Some natural pozzolans are byproducts of industrial processes. Other natural pozzolans, such as volcanic ash, occur naturally. This study determined the suitability of Mt. Mazama volcanic ash as a natural pozzolan and explored innovative uses of the material for roadway improvement. Requirements of natural pozzolans are specified in ASTM C618 – coal fly ash and raw or calcined natural pozzolan for use in concrete. This study concluded that volcanic ash from Mt. Mazama meets chemical requirements of a natural pozzolan. In its unprocessed, natural form, Mt. Mazama volcanic ash does not meet fineness, moisture or strength requirements as a natural pozzolan. An innovative study of the strength of mortar cubes created with increasing replacement of portland cement with Mt. Mazama volcanic ash showed that decreases in strength occur with increased percentage replacements. When the Mt. Mazama volcanic ash is crushed and passed through a No. 200 sieve, this decrease in strength is less than unprocessed material. Slurry mixes of Mt. Mazama volcanic ash, lime and portland cement applied to gravel materials bound material to a greater percentage, and reduced potentially airborne particulates to a greater degree than using portland cement slurry alone. A sustainability analysis concluded that any replacement of portland cement with volcanic ash reduces embodied energy and carbon dioxide emissions

Origin and thermal evolution of Mars

The thermal evolution of Mars is governed by subsolidus mantle convection beneath a thick lithosphere. Models of the interior evolution are developed by parameterizing mantle convective heat transport in terms of mantle viscosity, the superadiabatic temperature rise across the mantle, and mantle heat production. Geological, geophysical, and geochemical observations of the compositon and structure of the interior and of the timing of major events in Martian evolution are used to constrain the model computations. Such evolutionary events include global differentiation, atmospheric outgassing, and the formation of the hemispherical dichotomy and Tharsis. Numerical calculations of fully three-dimensional, spherical convection in a shell the size of the Martian mantle are performed to explore plausible patterns of Martian mantel convection and to relate convective features, such as plumes, to surface features, such as Tharsis. The results from the model calculations are presented

Applying a Mt. Mazama Volcanic Ash Treatment as a Trail Accessibility Improvement

A procedure has been developed for implementing a topically applied Mt. Mazama volcanic ash trail surface amendment for improving trail firmness and stability. This project involved implementation of previously conducted Mt. Mazama volcanic research by applying a Mazama Ash and Portland Cement solution over a 0.2-mile section of the Geo Trail at the Oregon Institute of Technology Klamath Falls campus. Testing was performed to verify ideal Ash-to-Cement-to-Water ratios. A procedure was developed and applied for batching and mixing the dry materials on-site, spreading and integrating the dry material with the existing trail surface, and wetting and compacting the surface. After the pilot application, visual inconsistencies were observed in the treated trail surface. Firmness and stability were measured at different locations along the treated trail surface and on the untreated surface with a rotational penetrometer apparatus. Roughness was quantified using a modified Wheelchair Pathway Roughness Index at different locations along the treated rail surface and on the untreated surface. At each of the testing locations on the treated surface, stability was shown to have improved, firmness was relatively consistent, and the ability to roll an occupied wheelchair without rutting was markedly improved

Best Practices in Second Stage Labor Care: Maternal Bearing Down and Positioning

Despite evidence of adverse fetal and maternal outcomes from the use of sustained Valsalva bearing down efforts, current second-stage care practices are still characterized by uniform directions to “push” forcefully upon complete dilatation of the cervix while the woman is in a supine position. Directed pushing might slightly shorten the duration of second stage labor, but can also contribute to deoxygenation of the fetus; cause damage to urinary, pelvic, and perineal structures; and challenge a woman’s confidence in her body. Research on the second stage of labor care is reviewed, with a focus on recent literature on maternal bearing down efforts, the “laboring down” approach to care, second-stage duration, and maternal position. Clinicians can apply the scientific evidence regarding the detrimental effects of sustained Valsalva bearing down efforts and supine positioning by individualizing second stage labor care and supporting women’s involuntary bearing down sensations that can serve to guide her behaviors

Coupled Simulation of DNAPL Infiltration and Dissolution in Three-Dimensional Heterogeneous Domains: Process Model Validation

A three-dimensional multiphase numerical model was used to simulate the infiltration and dissolution of a dense nonaqueous phase liquid (DNAPL) release in two experimental flow cells containing different heterogeneous and well-characterized permeability fields. DNAPL infiltration was modeled using Brooks-Corey-Burdine hysteretic constitutive relationships. DNAPL dissolution was simulated using a rate-limited mass transfer expression with a velocity-dependent mass transfer coefficient and a thermodynamically based calculation of DNAPL-water interfacial area. The model did not require calibration of any parameters. The model predictions were compared to experimental measurements of high-resolution DNAPL saturations and effluent concentrations. The predicted concentrations were in close agreement with measurements for both domains, indicating that important processes were effectively captured by the model. DNAPL saturations greatly influenced mass transfer rates through their effect on relative permeability and velocity. Areas with low DNAPL saturation were associated with low interfacial areas, which resulted in reduced mass transfer rates and nonequilibrium dissolution. This was captured by the thermodynamic interfacial area model, while a geometric model overestimated the interfacial areas and the overall mass transfer. This study presents the first validation of the thermodynamic dissolution model in three dimensions and for high aqueous phase velocities; such conditions are typical for remediation operations, especially in heterogeneous aquifers. The demonstrated ability to predict DNAPL dissolution, only requiring prior characterization of soil properties and DNAPL release conditions, represents a significant improvement compared to empirical dissolution models and provides an opportunity to delineate the relationship between source zone architecture and the remediation potential for complex DNAPL source zones

Origin and thermal evolution of Mars

The thermal evolution of Mars is governed by subsolidus mantle convection beneath a thick lithosphere. Models of the interior evolution are developed by parameterizing mantle convective heat transport in terms of mantle viscosity, the superadiabatic temperature rise across the mantle and mantle heat production. Geological, geophysical, and geochemical observations of the composition and structure of the interior and of the timing of major events in Martian evolution, such as global differentiation, atmospheric outgassing and the formation of the hemispherical dichotomy and Tharsis, are used to constrain the model computations. Isotope systematics of SNC meteorites suggest core formation essentially contemporaneously with the completion of accretion. Other aspects of this investigation are discussed