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Sample records for affect slope stability

  1. Arctic Submarine Slope Stability

    NASA Astrophysics Data System (ADS)

    Winkelmann, D.; Geissler, W.

    2010-12-01

    Submarine landsliding represents aside submarine earthquakes major natural hazard to coastal and sea-floor infrastructure as well as to coastal communities due to their ability to generate large-scale tsunamis with their socio-economic consequences. The investigation of submarine landslides, their conditions and trigger mechanisms, recurrence rates and potential impact remains an important task for the evaluation of risks in coastal management and offshore industrial activities. In the light of a changing globe with warming oceans and rising sea-level accompanied by increasing human population along coasts and enhanced near- and offshore activities, slope stability issues gain more importance than ever before. The Arctic exhibits the most rapid and drastic changes and is predicted to change even faster. Aside rising air temperatures, enhanced inflow of less cooled Atlantic water into the Arctic Ocean reduces sea-ice cover and warms the surroundings. Slope stability is challenged considering large areas of permafrost and hydrates. The Hinlopen/Yermak Megaslide (HYM) north of Svalbard is the first and so far only reported large-scale submarine landslide in the Arctic Ocean. The HYM exhibits the highest headwalls that have been found on siliciclastic margins. With more than 10.000 square kilometer areal extent and app. 2.400 cubic kilometer of involved sedimentary material, it is one of the largest exposed submarine slides worldwide. Geometry and age put this slide in a special position in discussing submarine slope stability on glaciated continental margins. The HYM occurred 30 ka ago, when the global sea-level dropped by app. 50 m within less than one millennium due to rapid onset of global glaciation. It probably caused a tsunami with circum-Arctic impact and wave heights exceeding 130 meters. The HYM affected the slope stability field in its neighbourhood by removal of support. Post-megaslide slope instability as expressed in creeping and smaller-scaled slides are

  2. Local slope stability analysis

    NASA Astrophysics Data System (ADS)

    Hattendorf, I.; Hergarten, St.; Neugebauer, H. J.

    Mass movements under the influence of gravity occur as result of diverse disturbing and destabilizing processes, for example of climatic or anthropological origin. The stability of slopes is mainly determined by the geometry of the land-surface and designated slip-horizon. Further contributions are supplied by the pore water pressure, cohesion and friction. All relevant factors have to be integrated in a slope stability model, either by measurements and estimations (like phenomenological laws) or derived from physical equations. As result of stability calculations, it's suitable to introduce an expectation value, the factor-of-safety, for the slip-risk. Here, we present a model based on coupled physical equations to simulate hardly measurable phenomenons, like lateral forces and fluid flow. For the displacements of the soil-matrix we use a modified poroelasticity-equation with a Biot-coupling (Biot 1941) for the water pressure. Latter is described by a generalized Boussinesq equation for saturated-unsaturated porous media (Blendinger 1998). One aim of the calculations is to improve the knowledge about stability-distributions and their temporal variations. This requires the introduction of a local factor-of-safety which is the main difference to common stability models with global stability estimations. The reduction of immediate danger is still the emergent task of the most slope and landslide investigations, but this model is also useful with respect to understand the governing processes of landform evolution.

  3. Slope Stability Analysis Using GIS

    NASA Astrophysics Data System (ADS)

    Bouajaj, Ahmed; Bahi, Lahcen; Ouadif, Latifa; Awa, Mohamed

    2016-10-01

    An analysis of slope stability using Geographic Information System (GIS) is presented in this paper. The methodology is based on the calculation of the safety factor in 2D and 3D using ArcGis. Hovland's Method in 3D and 2D were used in the stability analysis of the slope located at the 34 kilometer point (K.P.34) on the highway in the North of Morocco connecting Tangier to Ksar Sghir. Results shows that the safety factors obtained in 3D are always higher than those obtained in 2D and the slope becomes unstable when the water table level is less than 1 m.

  4. Slope Stability Analysis of Mountain Pine Beetle Impacted Areas

    NASA Astrophysics Data System (ADS)

    Bogenschuetz, N. M.; Bearup, L. A.; Maxwell, R. M.; Santi, P. M.

    2015-12-01

    The mountain pine beetle (MPB), Dendroctonus ponderosae, has caused significant tree mortality within North America. Specifically, the MPB affects ponderosa pine and lodgepole pine forests within the Rocky Mountains with approximately 3.4 million acres of forest impacted over the past 20 years. The full impacts of such unprecedented tree mortality on hydrology and slope stability is not well understood. This work studies the affects of MPB infestation on slope instability. A large-scale statistical analysis of MPB and slope stability is combined with a more in-depth analysis of the factors that contribute to slope stability. These factors include: slope aspect, slope angle, root decay, regrowth and hydrologic properties, such as water table depth and soil moisture. Preliminary results show that MPB may affect a greater number of north- and east-facing slopes. This is in accordance with more water availability and a higher MPB impacted tree density on north-facing slopes which, in turn, could potentially increase the probability of slope failure. Root strength is predicted to decrease as the roots stop transpiring 3-4 years proceeding infestation. However, this effect on the hillslope is likely being counterbalanced by the regrowth of grasses, forbs, shrubs, and trees. In addition, the increase in water table height from the lack of transpiring trees is adding a driving force to the slopes. The combination of all these factors will be used in order to assess the effects of MPB tree mortality on slope stability.

  5. Slope Stability. CEGS Programs Publication Number 15.

    ERIC Educational Resources Information Center

    Pestrong, Raymond

    Slope Stability is one in a series of single-topic problem modules intended for use in undergraduate and earth science courses. The module, also appropriate for use in undergraduate civil engineering and engineering geology courses, is a self-standing introduction to studies of slope stability. It has been designed to supplement standard…

  6. Slope stability of moraines, Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Klimes, J.; Novotny, J.

    2012-12-01

    Landslides originating from inner slopes of moraine dams are often capable of producing glacial lakes outburst floods (GLOFs). Therefore assessing stability conditions of the moraines is important for predicting this potentially damaging phenomenon. Characteristics of the basic mechanical properties of the material and geophysical investigations were applied to collect necessary information for slope stability assessment of the Palcacocha Lake moraine dam, Peru. The lake is situated in the Cordillera Blanca Mts. at the altitude of about 4,500m asl and produced catastrophic GLOF in 1941. Another minor flood originated in 2003 due to landslide impact into the lake. Detailed investigations of this landslide site included geomorphological mapping, geophysical investigations and characterization of basic mechanical properties of the forming material. Geomorphological mapping identified dormant landslide with scarp up to 2m high which developed on the edge of the inner moraine slope. It is conditioned by set of parallel extension trenches which also affected the origin of 2003 landslide. Within its scarp area, significant water bearing layer was noticed around 10 m bellow the moraine surface. Three profiles were investigated using electric resistivity tomography performed on 4poing light instrument with 24 electrodes and with spacing ranging from 1 to 4m. Results helped to verify geometry of the main shear plane of the mapped landslide as well as the spacing and depth of extension trenches. Significant heterogeneity in the moraine resistivity characteristics was found. The high resistivity regions are explained by rock block accumulation whereas the low resistivity may represent wet layers within the moraine body. Grain size distribution of 33 disturbed soil samples originating from moraine material within the Cordillera Blanca Mts., Peru were determined and classified according to the UCSC classification system. The samples were taken from moraine dams and slopes

  7. Ranking Slope Stability in Frozen Terrain

    NASA Astrophysics Data System (ADS)

    Stothoff, S.; Dinwiddie, C. L.; Walter, G. R.; Necsoiu, M.

    2011-12-01

    Motivated by the need to assess the risk of permafrost thaw to infrastructure, such as roads, bridges, and pipelines, a landscape-scale approach was developed to rank the risk of slope failures and thermokarst development in areas of seasonally frozen soils underlain by permafrost. The approach has two parts: (i) identifying locations where permafrost thaw is likely to occur under future climates, and (ii) identifying areas where thaw would have consequences with respect to a disturbance. The developed screening tool uses (i) land classification maps developed from remotely sensed data and (ii) a thermohydrologic hazard risk assessment to identify areas susceptible to slope instability under current and future climate states. The screening tool combines a numerical ground thawing and freezing dynamics model for calculating the thickness of the active layer and depth of permafrost with a simple slope stability model that is based upon the Level I Stability Analysis (LISA) approach of Harrell et al. (1992). Instead of using the numerical models directly within probabilistic sampling, a response function for the factor of safety in slope stability is developed from numerical simulations that systematically vary input parameters across their range of applicability. The response function is used within Monte Carlo sampling for each grid cell in a landscape model, with a probability distribution for each input parameter assigned to each grid cell based on (i) classes defined for each grid cell; (ii) a digital elevation model; (iii) empirical, mathematical, and numerical interpretive models; and (iv) probabilistic descriptions of the parameters in the interpretive models. For example, the root cohesion distribution is defined by vegetation class, with vegetation spread across the landscape using Landsat-derived vegetation classification maps. The probability of slope failure is the fraction of parameter realizations that result in a factor of safety less than 1. Ranking

  8. Regional method to assess offshore slope stability.

    USGS Publications Warehouse

    Lee, H.J.; Edwards, B.D.

    1986-01-01

    The slope stability of some offshore environments can be evaluated by using only conventional acoustic profiling and short-core sampling, followed by laboratory consolidation and strength testing. The test results are synthesized by using normalized-parameter techniques. The normalized data are then used to calculate the critical earthquake acceleration factors or the wave heights needed to initiate failure. These process-related parameters provide a quantitative measure of the relative stability for locations from which short cores were obtained. The method is most applicable to offshore environments of gentle relief and simple subsurface structure and is not considered a substitute for subsequent site-specific analysis. -from ASCE Publications Information

  9. Robustness for slope stability modelling under deep uncertainty

    NASA Astrophysics Data System (ADS)

    Almeida, Susana; Holcombe, Liz; Pianosi, Francesca; Wagener, Thorsten

    2015-04-01

    Landslides can have large negative societal and economic impacts, such as loss of life and damage to infrastructure. However, the ability of slope stability assessment to guide management is limited by high levels of uncertainty in model predictions. Many of these uncertainties cannot be easily quantified, such as those linked to climate change and other future socio-economic conditions, restricting the usefulness of traditional decision analysis tools. Deep uncertainty can be managed more effectively by developing robust, but not necessarily optimal, policies that are expected to perform adequately under a wide range of future conditions. Robust strategies are particularly valuable when the consequences of taking a wrong decision are high as is often the case of when managing natural hazard risks such as landslides. In our work a physically based numerical model of hydrologically induced slope instability (the Combined Hydrology and Stability Model - CHASM) is applied together with robust decision making to evaluate the most important uncertainties (storm events, groundwater conditions, surface cover, slope geometry, material strata and geotechnical properties) affecting slope stability. Specifically, impacts of climate change on long-term slope stability are incorporated, accounting for the deep uncertainty in future climate projections. Our findings highlight the potential of robust decision making to aid decision support for landslide hazard reduction and risk management under conditions of deep uncertainty.

  10. 30 CFR 56.3130 - Wall, bank, and slope stability.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Mining Methods § 56.3130 Wall, bank, and slope stability. Mining methods shall be used that will maintain wall, bank, and slope stability in places where persons work or travel in performing their...

  11. 30 CFR 56.3130 - Wall, bank, and slope stability.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Wall, bank, and slope stability. 56.3130... Mining Methods § 56.3130 Wall, bank, and slope stability. Mining methods shall be used that will maintain wall, bank, and slope stability in places where persons work or travel in performing their...

  12. Slope Stability in the Choco Volcanics.

    DTIC Science & Technology

    The rocks comprising the Choco volcanics, a formation crossed by the proposed Route 25 sea-level canal through northwestern Colombia, have been...found to slake in ethylene glycol. It is concluded that the factors of intermediate unconfined compressive strength and slaking will not cause massive slope failures of crater slopes formed in the Choco volcanic rocks.

  13. Slope Stability of Geosynthetic Clay Liner Test Plots

    EPA Science Inventory

    Fourteen full-scale field test plots containing five types of geosynthetic clay liners (GCLs) were constructed on 2H:IV and 3H:IV slopes for the purpose of assessing slope stability. The test plots were designed to simulate typical final cover systems for landfill. Slides occurr...

  14. The Dynamic Evaluation of Rock Slope Stability Considering the Effects of Microseismic Damage

    NASA Astrophysics Data System (ADS)

    Xu, N. W.; Dai, F.; Liang, Z. Z.; Zhou, Z.; Sha, C.; Tang, C. A.

    2014-03-01

    demonstrate that microseismic activity induced by construction disturbance only slightly affects the stability of the slope. The proposed feedback analysis technique provides a novel method for dynamically assessing rock slope stability and can be used to assess the slope stability of other similar rock slopes.

  15. Geosynthetic clay liners - slope stability field study

    SciTech Connect

    Carson, D.A.; Daniel, D.E.; Koerner, R.M.; Bonaparte, R.

    1997-12-31

    A field research project was developed to examine the internal shear performance of geosynthetic clay liners (GCLs). Several combinations of cross sections were assembled using GCL materials that were available at the time of project initiation. The cross sections utilized were intended to simulate landfill cover applications. Thirteen (13) resulting test plots were constructed on two different slope angles, and each plot is instrumented for physical displacement and soil moisture characteristics. Test plots were constructed in a manner that dictated the shear plane in the clay portion of the GCL product. The project purpose is to assess field performance and to verify design parameters associated with the application of GCLs in waste containment applications. Interim research data shows that test slopes on 2H:1V show global deformation, but little internal shear evidence, and the 3H:1V slopes show little deformation at approximately 650 days. The research is ongoing, and this paper presents the most recent information available from the project.

  16. Linking hydrological, infinite slope stability and land-use change models through GIS for assessing the impact of deforestation on slope stability in high Andean watersheds

    NASA Astrophysics Data System (ADS)

    Vanacker, Veerle; Vanderschaeghe, Michiel; Govers, Gerard; Willems, Edith; Poesen, Jean; Deckers, Jozef; De Bievre, Bert

    2003-06-01

    In the Ecuadorian Andes, episodic slope movements comprising shallow rotational and translational slides and rapid flows of debris and soil material are common. Consequently, not only considerable financial costs are experienced, but also major ecological and environmental problems arise in a larger geographical area. Sediment production by slope movement on hillslopes directly affects sediment transport and deposition in downstream rivers and dams and morphological changes in the stream channels. In developing countries world-wide, slope movement hazards are growing: increasing population pressure and economic development force more people to move to potentially hazardous areas, which are less suitable for agriculture and rangelands. This paper describes the methods used to determine the controlling factors of slope failure and to build upon the results of the statistical analysis a process-based slope stability model, which includes a dynamic soil wetness index using a simple subsurface flow model. The model provides a time-varying estimate of slope movement susceptibility, by linking land-use data with spatially varying hydrologic (soil conductivity, evapotranspiration, soil wetness) and soil strength properties. The slope stability model was applied to a high Andean watershed (Gordeleg Catchment, 250 ha, southern Ecuadorian Andes) and was validated by calculating the association coefficients between the slope movement susceptibility map of 2000 and the spatial pattern of active slope movements, as measured in the field with GPS. The proposed methodology allows assessment of the effects of past and future land-use change on slope stability. A realistic deforestation scenario was presented: past land-use change includes a gradual fragmentation and clear cut of the secondary forests, as observed over the last four decades (1963-2000), future land-use change is simulated based on a binary logistic deforestation model, whereby it was assumed that future land

  17. Geotechnical characteristics and slope stability in the Gulf of Cadiz

    USGS Publications Warehouse

    Lee, H.; Baraza, J.

    1999-01-01

    Sedimentological and geotechnical analyses of thirty-seven core samples from the Gulf of Cadiz continental margin were used to define the regional variability of sediment properties and to assess slope stability. Considering the sediment property data set as a whole, there is an association between grain size, plasticity and water content. Any one of these properties can be mapped regionally to provide an indication of the dominant surface sediment lithology. Based on static sediment strength, a simplified slope stability analysis showed that only steep slopes (> 16??for even the most vulnerable sediment) can fail under static loading conditions. Accordingly, transient loads, such as earthquakes or storms, are needed to cause failure on more moderate slopes. A regional seismic slope stability analysis of the Cadiz margin was performed based on detailed geotechnical testing of four gravity core samples. The results showed that the stability of these slopes under seismic loading conditions depends upon sediment density, the cyclic loading shear strength, the slope steepness, and the regional seismicity. Sediment density and cyclic loading shear strength are dependent upon water content, which can act as a proxy for plasticity and texture effects. Specifically, Sediment in the water content range of 50-56% is most vulnerable to failure under cyclic loading within the Cadiz margin. As a result, for a uniform seismicity over the region, susceptibility to failure during seismic loading conditions increases with increasing slope steepness and is higher if the sediment water content is in the 50-56% range than if it is not. The only sampled zone of failure on the continental slope contains sediment with water content in this critical range. Storm-wave-induced instability was evaluated for the continental shelf. The evaluation showed that a storm having hundreds of waves with a height in the range of 16 m might be capable of causing failure on the shelf. However, no

  18. Relief unity emulator and slope stability simulator applied to mass movement occurrence analysis in slope evolution

    NASA Astrophysics Data System (ADS)

    Colangelo, Antonio C.

    2010-05-01

    This work refers to a part of my "Fellow" thesis "Geomorphosynthesis and Geomorphocinematic applied to slope stability and evolution" (Colangelo, 2007). Relief unity emulator (rue) is a device that permits to synthesize a slope unity by means of a single generatrix profile that determine the initial conditions for application of a set of a geotechnical, hydrological and morphological models. This initial profile is considered in equilibrium with original environmental conditions, and operates in an integrated manner with these models. The aim is to induce a boundary condition on initial profile and produce a new profile: a threshold profile. For this manner and by iterations we generate a set of new profiles that represents, each one, a meta-stable profile, or a descending profile. The evolution of these profiles is in according with the central geomorphologycal concepts of slope retreat, base level change and head retreat. This set of "descending profiles" will be now sliced at topographic equivalent points, that will linked for describe a "topographic equivalence line". The crossing of this kind of isolines with descending profiles composes a 3D slope unity. This descending slope unity is represented by a mesh built for the crossing of these new slope profiles with the topographic equivalence lines and, the result is a four-dimensional meta-stable object integrated to the slope stability simulator (sss). This composite "rue-sss" device operates with 10 main models and 16 variables. The models describe effective stress, shearing resistance, soil saturation level behavior, potential rupture surface depth, critical depth, potential rupture surface critical gradient, critical soil saturation level, top of percolation flow gradient and unit weight of soil. Of this manner, is possible to evaluate effective friction angles and cohesion, critical soil saturation levels, critical gradients for potential rupture surfaces, neutral stress, shear strength, shear stress

  19. Impact of vegetation on stability of slopes subjected to rainfall - numerical aspect

    NASA Astrophysics Data System (ADS)

    Switala, Barbara Maria; Tamagnini, Roberto; Sudan Acharya, Madhu; Wu, Wei

    2015-04-01

    Recent years brought a significant development of soil bioengineering methods, considered as an ecological and economically effective measure for slope stabilization. This work aims to show the advantages of the soil bioengineering solutions for a slope subjected to a heavy rainfall, with the help of a numerical model, which integrates most of the significant plant and slope features. There are basically two different ways in which vegetation can affect stability of a slope: root reinforcement (mechanical impact) and root water uptake (evapotranspiration). In the numerical model, the first factor is modelled using the Cam-Clay model extended for unsaturated conditions by Tamagnini (2004). The original formulation of a constitutive model is modified by introducing an additional constitutive parameter, which causes an expansion of the yield surface as a consequence of an increase in root mass in a representative soil element. The second factor is the root water uptake, which is defined as a volumetric sink term in the continuity equation of groundwater flow. Water removal from the soil mass causes an increase in suction in the vicinity of the root zone, which leads to an increase in the soil cohesion and provides additional strength to the soil-root composite. The developed numerical model takes into account the above mentioned effects of plants and thus considers the multi-phase nature of the soil-plant-water relationship. Using the developed method, stability of some vegetated and non-vegetated slopes subjected to rainfall are investigated. The performance of each slope is evaluated by the time at which slope failure occurs. Different slope geometries and soil mechanical and hydrological properties are considered. Comparison of the results obtained from the analyses of vegetated and non-vegetated slopes leads to the conclusion, that the use of soil bioengineering methods for slope stabilization can be effective and can significantly delay the occurrence of a

  20. Reliability-based Assessment of Stability of Slopes

    NASA Astrophysics Data System (ADS)

    Hsein Juang, C.; Zhang, J.; Gong, W.

    2015-09-01

    Multiple sources of uncertainties often exist in the evaluation of slope stability. When assessing stability of slopes in the face of uncertainties, it is desirable, and sometimes necessary, to adopt reliability-based approaches that consider these uncertainties explicitly. This paper focuses on the practical procedures developed recently for the reliability-based assessment of slope stability. The statistical characterization of model uncertainty and parameter uncertainty are first described, followed by an evaluation of the failure probability of a slope corresponding to a single slip surface, and the system failure probability. The availability of site-specific information then makes it possible to update the reliability of the slope through the Bayes’ theorem. Furthermore, how to perform reliability-based design when the statistics of random variables cannot be determined accurately is also discussed. Finally, case studies are presented to illustrate the benefit of performing reliability-based design and the procedure for conducting reliability-based robust design when the statistics of the random variables are incomplete.

  1. Infinite slope stability under steady unsaturated seepage conditions

    USGS Publications Warehouse

    Lu, N.; Godt, J.

    2008-01-01

    [1] We present a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions. The analytical framework allows the water table to be located at any depth below the ground surface and variation of soil suction and moisture content above the water table under steady infiltration conditions. The framework also explicitly considers the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil. The factor of safety is conceptualized as a function of the depth within the vadose zone and can be reduced to the classical analytical solution for subaerial infinite slopes in the saturated zone. Slope stability analyses with hypothetical sandy and silty soils are conducted to illustrate the effectiveness of the framework. These analyses indicate that for hillslopes of both sandy and silty soils, failure can occur above the water table under steady infiltration conditions, which is consistent with some field observations that cannot be predicted by the classical infinite slope theory. A case study of shallow slope failures of sandy colluvium on steep coastal hillslopes near Seattle, Washington, is presented to examine the predictive utility of the proposed framework. Copyright 2008 by the American Geophysical Union.

  2. Infinite slope stability under steady unsaturated seepage conditions

    NASA Astrophysics Data System (ADS)

    Lu, Ning; Godt, Jonathan

    2008-11-01

    We present a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions. The analytical framework allows the water table to be located at any depth below the ground surface and variation of soil suction and moisture content above the water table under steady infiltration conditions. The framework also explicitly considers the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil. The factor of safety is conceptualized as a function of the depth within the vadose zone and can be reduced to the classical analytical solution for subaerial infinite slopes in the saturated zone. Slope stability analyses with hypothetical sandy and silty soils are conducted to illustrate the effectiveness of the framework. These analyses indicate that for hillslopes of both sandy and silty soils, failure can occur above the water table under steady infiltration conditions, which is consistent with some field observations that cannot be predicted by the classical infinite slope theory. A case study of shallow slope failures of sandy colluvium on steep coastal hillslopes near Seattle, Washington, is presented to examine the predictive utility of the proposed framework.

  3. Slope Stability: Factor of Safety along the Seismically Active Continental Slope Offshore Sumatra

    NASA Astrophysics Data System (ADS)

    Patton, J. R.; Goldfinger, C.; Djadjadihardja, Y.; None, U.

    2013-12-01

    Recent papers have documented the probability that turbidites deposited along and downslope of subduction zone accretionary prisms are likely the result of strong ground shaking from great earthquakes. Given the damaging nature of these earthquakes, along with the casualties from the associated tsunamis, the spatial and temporal patterns of these earthquakes can only be evaluated with paleoseismologic coring and seismic reflection methods. We evaluate slope stability for seafloor topography along the Sunda subduction offshore Sumatra, Indonesia. We use sediment material properties, from local (Sumatra) and analogous sites, to constrain our estimates of static slope stability Factor of Safety (FOS) analyses. We then use ground motion prediction equations (GMPE's) to estimate ground motion intensity (Arias Intensity, AI) and acceleration (Peak Ground Acceleration, PGA), as possibly generated by fault rupture, to constrain seismic loads for pseudostatic slope stability FOS analyses. The ground motions taper rapidly with distance from the fault plane, consistent with ground motion - fault distance relations measured during the 2011 Tohoku-Oki subduction zone earthquake. Our FOS analyses include a Morgenstern method of slices probabilistic analysis for 2-D profiles along with Critical Acceleration (Ac) and Newmark Displacement (Dn) analysis of multibeam bathymetry of the seafloor. In addition, we also use estimates of ground motion modeled with a 2004 Sumatra-Andaman subduction zone (SASZ) earthquake fault slip model, to also compare with our static FOS analyses of seafloor topography. All slope and trench sites are statically stable (FOS < 1) and sensitive to ground motions generated by earthquakes of magnitude greater than 7. We conclude that for earthquakes of magnitude 6 to 9, PGA of 0.4-0.6 to 1.4-2.5 g would be expected, respectively, from existing GMPE's. However, saturation of accelerations in the accretionary wedge may limit actual accelerations to less than 1

  4. Aspect-Driven Changes in Slope Stability Due to Ecohydrologic Feedbacks

    NASA Astrophysics Data System (ADS)

    Poulos, M. J.; Pierce, J. L.; Flores, A. N.; Benner, S. G.; Smith, T. J.; McNamara, J. P.

    2009-12-01

    southwestern batholith, are most sensitive to aspect, with average northern slope angles of 29°, and southern slope angles of 21°. Initial assessment of ecohydrologic factors in Dry Creek finds that annual precipitation for the watershed ranges from 20-35 inches, forestation ranges from ~15% forested on south-facing slopes, to ~80% forested on north-facing slopes, and annual insolation on north-facing slopes is roughly three-fifths that for south-facing slopes. Furthermore, preliminary analysis of soil textures finds soils to contain 29-41% silt on north-facing slopes, and ~12% silt on south-facing slopes. Slope distributions from the Lochsa River basin in the northern Idaho Batholith had little contrast between slope angles; this basin, however, receives 30-70 inches of precipitation and has nearly-homogenous forest cover for all aspects. Ongoing study seeks to 1) use large-scale spatial analysis to correlate the influence of aspect on slope angles to changes in ecohydrologic conditions and 2) understand the spatial distribution and relative influence of processes that affect the weathering of slope materials, erosive processes that reduce slope angles, and cohesive forces that stabilize slopes (e.g. root strength, soil texture, and soil moisture).

  5. Stability of infinite slopes under transient partially saturated seepage conditions

    NASA Astrophysics Data System (ADS)

    Godt, Jonathan W.; ŞEner-Kaya, BaşAk; Lu, Ning; Baum, Rex L.

    2012-05-01

    Prediction of the location and timing of rainfall-induced shallow landslides is desired by organizations responsible for hazard management and warnings. However, hydrologic and mechanical processes in the vadose zone complicate such predictions. Infiltrating rainfall must typically pass through an unsaturated layer before reaching the irregular and usually discontinuous shallow water table. This process is dynamic and a function of precipitation intensity and duration, the initial moisture conditions and hydrologic properties of the hillside materials, and the geometry, stratigraphy, and vegetation of the hillslope. As a result, pore water pressures, volumetric water content, effective stress, and thus the propensity for landsliding vary over seasonal and shorter time scales. We apply a general framework for assessing the stability of infinite slopes under transient variably saturated conditions. The framework includes profiles of pressure head and volumetric water content combined with a general effective stress for slope stability analysis. The general effective stress, or suction stress, provides a means for rigorous quantification of stress changes due to rainfall and infiltration and thus the analysis of slope stability over the range of volumetric water contents and pressure heads relevant to shallow landslide initiation. We present results using an analytical solution for transient infiltration for a range of soil texture and hydrological properties typical of landslide-prone hillslopes and show the effect of these properties on the timing and depth of slope failure. We follow by analyzing field-monitoring data acquired prior to shallow landslide failure of a hillside near Seattle, Washington, and show that the timing of the slide was predictable using measured pressure head and volumetric water content and show how the approach can be used in a forward manner using a numerical model for transient infiltration.

  6. Assessment and mapping of slope stability based on slope units: A case study in Yan'an, China

    NASA Astrophysics Data System (ADS)

    Zhuang, Jianqi; Peng, Jianbing; Xu, Yonglong; Xu, Qiang; Zhu, Xinghua; Li, Wei

    2016-10-01

    Precipitation frequently triggers shallow landslides in the Loess Plateau of Shaanxi, China, resulting in loss of life, damage to gas and oil routes, and destruction of transport infrastructure and farmland. To assess the possibility of shallow landslides at different precipitation levels, a method to draw slope units and steepest slope profiles based on ARCtools and a new method for calculating slope stability are proposed. The methods were implemented in a case study conducted in Yan'an, north-west China. High resolution DEM (Digital Elevation Model) images, soil parameters from in-situ laboratory measurements and maximum depths of precipitation infiltration were used as input parameters in the method. Next, DEM and reverse DEM were employed to map 2146 slope units in the study area, based on which the steepest profiles of the slope units were constructed. Combining analysis of the water content of loess, strength of the sliding surface, its response to precipitation and the infinite slope stability equation, a new equation to calculate infinite slope stability is proposed to assess shallow landslide stability. The slope unit stability was calculated using the equation at 10-, 20-, 50- and 100-year return periods of antecedent effective precipitation. The number of slope units experiencing failure increased in response to increasing effective antecedent rainfall. These results were validated based on the occurrence of landslides in recent decades. Finally, the applicability and limitations of the model are discussed.

  7. Comparison of slope stability in two Brazilian municipal landfills

    SciTech Connect

    Gharabaghi, B. Singh, M.K.; Inkratas, C. Fleming, I.R. McBean, E.

    2008-07-01

    The implementation of landfill gas to energy (LFGTE) projects has greatly assisted in reducing the greenhouse gases and air pollutants, leading to an improved local air quality and reduced health risks. The majority of cities in developing countries still dispose of their municipal waste in uncontrolled 'open dumps.' Municipal solid waste landfill construction practices and operating procedures in these countries pose a challenge to implementation of LFGTE projects because of concern about damage to the gas collection infrastructure (horizontal headers and vertical wells) caused by minor, relatively shallow slumps and slides within the waste mass. While major slope failures can and have occurred, such failures in most cases have been shown to involve contributory factors or triggers such as high pore pressures, weak foundation soil or failure along weak geosynthetic interfaces. Many researchers who have studied waste mechanics propose that the shear strength of municipal waste is sufficient such that major deep-seated catastrophic failures under most circumstances require such contributory factors. Obviously, evaluation of such potential major failures requires expert analysis by geotechnical specialists with detailed site-specific information regarding foundation soils, interface shearing resistances and pore pressures both within the waste and in clayey barrier layers or foundation soils. The objective of this paper is to evaluate the potential use of very simple stability analyses which can be used to study the potential for slumps and slides within the waste mass and which may represent a significant constraint on construction and development of the landfill, on reclamation and closure and on the feasibility of a LFGTE project. The stability analyses rely on site-specific but simple estimates of the unit weight of waste and the pore pressure conditions and use 'generic' published shear strength envelopes for municipal waste. Application of the slope stability

  8. Rock mass characterisation and stability analyses of excavated slopes

    NASA Astrophysics Data System (ADS)

    Zangerl, Christian; Lechner, Heidrun

    2016-04-01

    Excavated slopes in fractured rock masses are frequently designed for open pit mining, quarries, buildings, highways, railway lines, and canals. These slopes can reach heights of several hundreds of metres and in cases concerning open pit mines slopes larger than 1000 m are not uncommon. Given that deep-seated slope failures can cause large damage or even loss of life, the slope design needs to incorporate sufficient stability. Thus, slope design methods based on comprehensive approaches need to be applied. Excavation changes slope angle, groundwater flow, and blasting increases the degree of rock mass fracturing as well as rock mass disturbance. As such, excavation leads to considerable stress changes in the slopes. Generally, slope design rely on the concept of factor of safety (FOS), often a requirement by international or national standards. A limitation of the factor of safety is that time dependent failure processes, stress-strain relationships, and the impact of rock mass strain and displacement are not considered. Usually, there is a difficulty to estimate the strength of the rock mass, which in turn is controlled by an interaction of intact rock and discontinuity strength. In addition, knowledge about in-situ stresses for the failure criterion is essential. Thus, the estimation of the state of stress of the slope and the strength parameters of the rock mass is still challenging. Given that, large-scale in-situ testing is difficult and costly, back-calculations of case studies in similar rock types or rock mass classification systems are usually the methods of choice. Concerning back-calculations, often a detailed and standardised documentation is missing, and a direct applicability to new projects is not always given. Concerning rock mass classification systems, it is difficult to consider rock mass anisotropy and thus the empirical estimation of the strength properties possesses high uncertainty. In the framework of this study an approach based on

  9. Overpressure, Flow Focusing, Compaction and Slope Stability on the continental slope: Insights from IODP Expedition 308

    NASA Astrophysics Data System (ADS)

    Flemings, P. B.

    2010-12-01

    Integrated Ocean Drilling Program Expepedition 308 used direct measurements of pore pressure, analysis of hydromechanical properties, and geological analysis to illuminate how sedimentation, flow focusing, overpressure, and slope stability couple beneath the seafloor on the deepwater continental slope in the Gulf of Mexico. We used pore pressure penetrometers to measure severe overpressures (60% of the difference between lithostatic stress and hydrostatic pressure) that extend from the seafloor for 100’s of meters. We ran uniaxial consolidation experiments on whole core and found that although permeability is relatively high near the seafloor, the sediments are highly compressible. As a result, the coefficient of consolidation (the hydraulic diffusivity) is remarkably constant over a large range of effective stresses. This behavior accounts for the high overpressure that begins near the seafloor and extends to depth. Forward modeling suggests that flow is driven laterally along a permeable unit called the Blue Unit. Calculations suggest that soon after deposition, lateral flow lowered the effective stress and triggered the submarine landslides that we observe. Later in the evolution of this system, overpressure may have pre-conditioned the slope to failure by earthquakes. Results from IODP Expedition 308 illustrate how pore pressure and sedimentation control the large-scale form of continental margins, how submarine landslides form, and provide strategies for designing stable drilling programs.

  10. The role of Soil Water Retention Curve in slope stability analysis in unsaturated and heterogeneous soils.

    NASA Astrophysics Data System (ADS)

    Antinoro, Chiara; Arnone, Elisa; Noto, Leonardo V.

    2015-04-01

    The mechanisms of rainwater infiltration causing slope instability had been analyzed and reviewed in many scientific works. Rainwater infiltration into unsaturated soil increases the degree of saturation, hence affecting the shear strength properties and thus the probability of slope failure. It has been widely proved that the shear strength properties change with the soil water suction in unsaturated soils; therefore, the accuracy to predict the relationship between soil water content and soil water suction, parameterized by the soil-water characteristic curve, has significant effects on the slope stability analysis. The aim of this study is to investigate how the characterization of SWRC of differently structured unsaturated soils affects the slope stability on a simple infinite slope. In particular, the unimodal and bimodal distributions of the soil pore size were compared. Samples of 40 soils, highly different in terms of structure and texture, were collected and used to calibrate two bimodal SWRCs, i.e. Ross and Smettem (1993) and Dexter et al., (2008). The traditional unimodal van Genuchten (1980) model was also applied for comparison. Slope stability analysis was conducted in terms of Factor of Safety (FS) by applying the infinite slope model for unsaturated soils. In the used formulation, the contribution of the suction effect is tuned by a parameter 'chi' in a rate proportional to the saturation conditions. Different parameterizations of this term were also compared and analyzed. Results indicated that all three SWRC models showed good overall performance in fitting the sperimental SWRCs. Both the RS and DE models described adequately the water retention data for soils with a bimodal behavior confirmed from the analysis of pore size distribution, but the best performance was obtained by DE model confirmed. In terms of FS, the tree models showed very similar results as soil moisture approached to the saturated condition; however, within the residual zone

  11. Three-Dimensional Stability of Slopes and Excavations

    DTIC Science & Technology

    2009-12-01

    a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. a...W911NF-08-1-0376 611102 Form Approved OMB NO. 0704-0188 53315-EV.9 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 10. SPONSOR/MONITOR’S ACRONYM(S) ARO 8...To) Standard Form 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 - Three-dimensional stability of slopes and excavations Report Title ABSTRACT

  12. HDMR methods to assess reliability in slope stability analyses

    NASA Astrophysics Data System (ADS)

    Kozubal, Janusz; Pula, Wojciech; Vessia, Giovanna

    2014-05-01

    Stability analyses of complex rock-soil deposits shall be tackled considering the complex structure of discontinuities within rock mass and embedded soil layers. These materials are characterized by a high variability in physical and mechanical properties. Thus, to calculate the slope safety factor in stability analyses two issues must be taken into account: 1) the uncertainties related to structural setting of the rock-slope mass and 2) the variability in mechanical properties of soils and rocks. High Dimensional Model Representation (HDMR) (Chowdhury et al. 2009; Chowdhury and Rao 2010) can be used to carry out the reliability index within complex rock-soil slopes when numerous random variables with high coefficient of variations are considered. HDMR implements the inverse reliability analysis, meaning that the unknown design parameters are sought provided that prescribed reliability index values are attained. Such approach uses implicit response functions according to the Response Surface Method (RSM). The simple RSM can be efficiently applied when less than four random variables are considered; as the number of variables increases, the efficiency in reliability index estimation decreases due to the great amount of calculations. Therefore, HDMR method is used to improve the computational accuracy. In this study, the sliding mechanism in Polish Flysch Carpathian Mountains have been studied by means of HDMR. The Southern part of Poland where Carpathian Mountains are placed is characterized by a rather complicated sedimentary pattern of flysh rocky-soil deposits that can be simplified into three main categories: (1) normal flysch, consisting of adjacent sandstone and shale beds of approximately equal thickness, (2) shale flysch, where shale beds are thicker than adjacent sandstone beds, and (3) sandstone flysch, where the opposite holds. Landslides occur in all flysch deposit types thus some configurations of possible unstable settings (within fractured rocky

  13. Supersonic Wave Interference Affecting Stability

    NASA Technical Reports Server (NTRS)

    Love, Eugene S.

    1958-01-01

    Some of the significant interference fields that may affect stability of aircraft at supersonic speeds are briefly summarized. Illustrations and calculations are presented to indicate the importance of interference fields created by wings, bodies, wing-body combinations, jets, and nacelles.

  14. A multidisciplinary methodological approach for slope stability assessment of an area prone to shallow landslides

    NASA Astrophysics Data System (ADS)

    Bordoni, Massimiliano; Meisina, Claudia; Valentino, Roberto; Bittelli, Marco; Battista Bischetti, Gian; Vercesi, Alberto; Chersich, Silvia; Giuseppina Persichillo, Maria

    2016-04-01

    Rainfall-induced shallow landslides are widespread slope instabilities phenomena in several hilly and mountainous contexts all over the world. Due to their high density of diffusion also in small areas, they can provoke important damages to terrains, infrastructures, buildings, and, sometimes, loss of human lives. Shallow landslides affect superficial soils of limited thickness (generally lower than 2 m), located above weathered or not bedrock levels. Their triggering mechanism is strictly linked to the hydrological response of the soils to rainfall events. Thus, it becomes fundamental a comprehensive analysis of the soil properties which can influence the susceptibility of a slope to shallow landslides. In this study, a multidisciplinary approach was followed for the characterization of the soils and the individuation of the triggering conditions in an area particularly prone to shallow failures, for slope stability assessment. This area corresponded to the hilly sector of North-Eastern Oltrepò Pavese (Lombardy Region, Northern Italy), where the density of shallow landslides is really high, reaching more than 36 landslides per km2. The soils of the study area were analyzed through a multidisciplinary characterization, which took into account for the main geotechnical, mechanical and mineralogical parameters and also for the main pedological features of the materials. This approach allowed for identifying the main features and the horizons which could influence the soil behavior in relation to the conditions that are preparatory to shallow landslides development. In a test-site slope, representative of the main geomorphological, geological and landslides distribution characteristics typical of the study area, a continuous in time monitoring of meteorological (rainfall amount, air temperature, air humidity, atmospheric pressure, net solar radiation, wind speed and direction) and hydrological (soil water content, pore water pressure) parameters was implemented. In

  15. Comprehensive evaluation of high-steep slope stability and optimal high-steep slope design by 3D physical modeling

    NASA Astrophysics Data System (ADS)

    Lai, Xing-ping; Shan, Peng-fei; Cai, Mei-feng; Ren, Fen-hua; Tan, Wen-hui

    2015-01-01

    High-steep slope stability and its optimal excavation design in Shuichang open pit iron mine were analyzed based on a large 3D physical simulation technique. An optimal excavation scheme with a relatively steeper slope angle was successfully implemented at the northwest wall between Nos. 4 and 5 exploration lines of Shuichang Iron Mine, taking into account the 3D scale effect. The physico-mechanical properties of rock materials were obtained by laboratory tests conducted on sample cores from exploration drilling directly from the iron mine. A porous rock-like composite material was formed for the model, and the mechanical parameters of the material were assessed experimentally; specifically, the effect of water on the sample was quantitatively determined. We adopted an experimental setup using stiff modular applied static loading to carry out a visual excavation of the slope at a random depth. The setup was equipped with acoustic emission (AE) sensors, and the experiments were monitored by crack optical acquirement, ground penetrating radar, and close-field photogrammetry to investigate the mechanisms of rock-mass destabilization in the high-steep slope. For the complex study area, the model results indicated a clear correlation between the model's destabilization resulting from slope excavation and the collected monitoring information. During the model simulation, the overall angle of the slope increased by 1-6 degrees in different sections. Dramatically, the modeled excavation scheme saved over 80 million tons of rock from extraction, generating enormous economic and ecological benefits.

  16. Slope stability of bioreactor landfills during leachate injection: effects of heterogeneous and anisotropic municipal solid waste conditions.

    PubMed

    Giri, Rajiv K; Reddy, Krishna R

    2014-03-01

    In bioreactor landfills, leachate recirculation can significantly affect the stability of landfill slope due to generation and distribution of excessive pore fluid pressures near side slope. The current design and operation of leachate recirculation systems do not consider the effects of heterogeneous and anisotropic nature of municipal solid waste (MSW) and the increased pore gas pressures in landfilled waste caused due to leachate recirculation on the physical stability of landfill slope. In this study, a numerical two-phase flow model (landfill leachate and gas as immiscible phases) was used to investigate the effects of heterogeneous and anisotropic nature of MSW on moisture distribution and pore-water and capillary pressures and their resulting impacts on the stability of a simplified bioreactor landfill during leachate recirculation using horizontal trench system. The unsaturated hydraulic properties of MSW were considered based on the van Genuchten model. The strength reduction technique was used for slope stability analyses as it takes into account of the transient and spatially varying pore-water and gas pressures. It was concluded that heterogeneous and anisotropic MSW with varied unit weight and saturated hydraulic conductivity significantly influenced the moisture distribution and generation and distribution of pore fluid pressures in landfill and considerably reduced the stability of bioreactor landfill slope. It is recommended that heterogeneous and anisotropic MSW must be considered as it provides a more reliable approach for the design and leachate operations in bioreactor landfills.

  17. The effect of chestnut coppice forests abandon on slope stability: a case study

    NASA Astrophysics Data System (ADS)

    Vergani, Chiara; Bassanelli, Chiara; Rossi, Lorenzo; Chiaradia, Enrico Antonio; Battista Bischetti, Gian

    2013-04-01

    , as expected, show that management didn't affect root mechanical properties, whereas root distribution within the soil profile did. In terms of additional root cohesion, values are higher in the managed stand, and lower in the abandoned one, at least in the first 50 cm of soil. In the abandoned stand, in fact, roots reach deeper layers of soil (100 cm) than the managed one (50 cm), mainly because of an unexpected greater soil depth. To assess the implication of such results in terms of slope stability, a simple infinite slope model was applied to the two conditions. The results showed that the abandoned stand is prone to instability also with a low level of saturation. On the contrary, by applying the additional root cohesion profile obtained in the managed stand to the steeper slopes, stability should be guaranteed, except in the case of total saturation. In conclusion, although more investigations are required especially to extend the number of stands, coppicing practice seem to be fundamental to prevent shallow landsliding in sweet chestnut forests over cohesionless slopes.

  18. Slope stability improvement using low intensity field electrosmosis

    NASA Astrophysics Data System (ADS)

    Armillotta, Pasquale

    2014-05-01

    The electrosmosis technique has been introduced in the past for slope stabilization. However, its application to real cases has been scarce due to several drawbacks mostly related to the high intensity electric field needed (1.0 V/cm or higher): the rapid degradation of the electrodes, the high system management cost, the heating and cracking of the soil and the reduction of its colloidal fraction. Thanks to the introduction of new materials, the technique is currently applied to decrease the consolidation time of saturated clay soils (forcing the elimination of water), consequently improving its mechanical strength. In clay soils, the volume variation is influenced by the presence of smectites. The clay compressibility decreases with the increasing of electrolytes concentration. Soil containing smectites that have interacted with calcium showed a reduction or the absence of swelling during hydration with distilled water and a positive increase of their shear strength. The different values of pH between the anode (acid) and the cathode (basic), induced by the electrosmosis create the conditions for the precipitation of CaCO3 near the cathode. The injection of solutions containing calcium in soils and their diffusion induced by the electrosmosis, lead to calcium precipitation and consequential increase of the shear strength. The material technological advances and the laboratory experiences described in this paper, demonstrate that the use low electric field (0.1 V/cm or lower) intensity electrosmosis (LEFE in acronym) can be effective for soil dewatering and shear strength increase while reducing its adverse effect. The LEFE can be used to: reduce the potential for swelling of active clay minerals through the introduction of ions and the precipitation of hardening substances; induce the "dewatering" in cohesive soils. Several Lab activities were carried out, using custom made electrosmosis equipment. These activities can be divided in two phases: Phase 1

  19. Regional variability of slope stability: Application to the Eel margin, California

    USGS Publications Warehouse

    Lee, H.; Locat, J.; Dartnell, P.; Israel, K.; Florence, Wong

    1999-01-01

    Relative values of downslope driving forces and sediment resisting forces determine the locations of submarine slope failures. Both of these vary regionally, and their impact can be addressed when the data are organized in a Geographic Information System (GIS). The study area on the continental margin near the Eel River provides an excellent opportunity to apply GIS spatial analysis techniques for evaluation of slope stability. In this area, swath bathymetric mapping shows seafloor morphology and distribution of slope steepness in fine detail, and sediment analysis of over 70 box cores delineates the variability of sediment density near the seafloor surface. Based on the results of ten geotechnical studies of submarine study areas, we developed an algorithm that relates surface sediment density to the shear strength appropriate to the type of cyclic loading produced by an earthquake. Strength and stress normalization procedures provide results that are conceptually independent of subbottom depth. Results at depth are rigorously applicable if sediment lithology does not vary significantly and consolidation state can be estimated. Otherwise, the method applies only to shallow-seated slope failure. Regional density, slope, and level of anticipated seismic shaking information were combined in a GIS framework to yield a map that illustrates the relative stability of slopes in the face of seismically induced failure. When a measure of predicted relative slope stability is draped on an oblique view of swath bathymetry, a variation in this slope stability is observed on an otherwise smooth slope along the mid-slope region north of a plunging anticline. The section of slope containing diffuse, pockmarked gullies has a lower measure of stability than a separate section containing gullies that have sharper boundaries and somewhat steeper sides. Such an association suggests that our slope-stability analysis relates to the stability of the gully sides. The remainder of the

  20. Morphodynamics and slope stability at Mergui Ridge, off western Thailand

    NASA Astrophysics Data System (ADS)

    Schwab, J.; Gross, F.; Krastel, S.; Jintasaeranee, P.; Bunsomboonsakul, S.; Winkelmann, D.; Weinrebe, W.

    2012-04-01

    2D seismic data from the top and the western slope of the Mergui Ridge (200 km off the Thai west coast) have been acquired during MASS cruise III in January 2011 in water depths between 300 and 2200 m. The Mergui Ridge is a part of the outer shelf slope off the Thai-Malay Peninsula and forms the eastern boundary of the East Andaman Basin. Structural features in the working area include faulted older slope sediments at the transition from Mergui Ridge to East Andaman Basin that are onlapping on the (acoustic) basement of Mergui Ridge. At their top these sediments are bordered by a pronounced erosive unconformity. Younger sedimentary units on top include three E-W elongated carbonate platforms. Moreover, drift sediments are deposited on top of the ridge, comprising features such as large scale sediment waves and moats around the platforms indicating transport and reworking of the sediments. These sediments are thinning towards the edge of the ridge where a zone of non-sedimentation prevails. In the East Andaman Basin younger sediments comprise disturbed and partially faulted units that are overlain by plastered drifts with increasing thickness towards south, where pronounced sediment waves within the drifts may indicate slope normal sediment transport by bottom currents. At the basin ridge transition, within the drift sediments on top of Mergui Ridge, and at the edge of the ridge several smaller scale mass transport deposits were identified. These MTDs indicate a general instability of the slope. Instability and general morphology of the slope may result from long-term tectonic processes such as extension due to backarc basin formation in the Andaman Sea basin. Moreover, phases of uplift, erosion and subsidence may have contributed to faulting and deformation of older units in our working area. Ongoing tectonics might still cause deformation and instability. In addition, bottom currents may presently play an important role concerning morphodynamic development by

  1. Stability calculation method of slope reinforced by prestressed anchor in process of excavation.

    PubMed

    Li, Zhong; Wei, Jia; Yang, Jun

    2014-01-01

    This paper takes the effect of supporting structure and anchor on the slope stability of the excavation process into consideration; the stability calculation model is presented for the slope reinforced by prestressed anchor and grillage beam, and the dynamic search model of the critical slip surface also is put forward. The calculation model of the optimal stability solution of each anchor tension of the whole process is also given out, through which the real-time analysis and checking of slope stability in the process of excavation can be realized. The calculation examples indicate that the slope stability is changed with the dynamic change of the design parameters of anchor and grillage beam. So it is relatively more accurate and reasonable by using dynamic search model to determine the critical slip surface of the slope reinforced by prestressed anchor and grillage beam. Through the relationships of each anchor layout and the slope height of various stages of excavation, and the optimal stability solution of prestressed bolt tension design value in various excavation stages can be obtained. The arrangement of its prestressed anchor force reflects that the layout of the lower part of bolt and the calculation of slope reinforcement is in line with the actual. These indicate that the method is reasonable and practical.

  2. Stability Calculation Method of Slope Reinforced by Prestressed Anchor in Process of Excavation

    PubMed Central

    Li, Zhong; Wei, Jia; Yang, Jun

    2014-01-01

    This paper takes the effect of supporting structure and anchor on the slope stability of the excavation process into consideration; the stability calculation model is presented for the slope reinforced by prestressed anchor and grillage beam, and the dynamic search model of the critical slip surface also is put forward. The calculation model of the optimal stability solution of each anchor tension of the whole process is also given out, through which the real-time analysis and checking of slope stability in the process of excavation can be realized. The calculation examples indicate that the slope stability is changed with the dynamic change of the design parameters of anchor and grillage beam. So it is relatively more accurate and reasonable by using dynamic search model to determine the critical slip surface of the slope reinforced by prestressed anchor and grillage beam. Through the relationships of each anchor layout and the slope height of various stages of excavation, and the optimal stability solution of prestressed bolt tension design value in various excavation stages can be obtained. The arrangement of its prestressed anchor force reflects that the layout of the lower part of bolt and the calculation of slope reinforcement is in line with the actual. These indicate that the method is reasonable and practical. PMID:24683319

  3. How does slope form affect erosion in CATFLOW-SED?

    NASA Astrophysics Data System (ADS)

    Gabelmann, Petra; Wienhöfer, Jan; Zehe, Erwin

    2016-04-01

    Erosion is a severe environmental problem in agro-ecosystems with highly erodible loess soils. It is controlled by various factors, e.g. rainfall intensity, initial wetness conditions, soil type, land use and tillage practice. Furthermore slope form and gradient have been shown to influence erosion amounts to a large extent. Within the last fifty years, various erosion models have been developed to describe the erosion process, estimate erosion amounts and identify erosion-prone areas. These models differ in terms of complexity, the processes which are considered, and the data required for model calibration and they can be categorised into empirical or statistical, conceptual, and physically-based models. CATFLOW-SED is a process-based hydrology and erosion model that can operate on catchment and hillslope scales. Soil water dynamics are described by the Richards equation including effective approaches for preferential flow. Evapotranspiration is simulated using an approach based on the Penman-Monteith equation. The model simulates overland flow using the diffusion wave equation. Soil detachment is related to the attacking forces of rainfall and overland flow, and the erosion resistance of soil. Sediment transport capacity and sediment deposition are related to overland flow velocity using the equation of Engelund and Hansen and the sinking velocity of grain sizes respectively. We performed a study to analyse the erosion process on different virtual hillslopes, with varying slope gradient and slope form, using the CATFLOW-SED model. We explored the role of landform on erosion and sedimentation, particularly we look for forms that either maximise or minimise erosion. Results indicate the importance to performing the process implementation within physically meaningful limits and choose appropriate model parameters respectively.

  4. Application of FBG Sensing Technology in Stability Analysis of Geogrid-Reinforced Slope

    PubMed Central

    Sun, Yijie; Xu, Hongzhong; Gu, Peng; Hu, Wenjie

    2017-01-01

    By installing FBG sensors on the geogrids, smart geogrids can both reinforce and monitor the stability for geogrid-reinforced slopes. In this paper, a geogrid-reinforced sand slope model test is conducted in the laboratory and fiber Bragg grating (FBG) sensing technology is used to measure the strain distribution of the geogrid. Based on the model test, the performance of the reinforced soil slope is simulated by finite element software Midas-GTS, and the stability of the reinforced soil slope is analyzed by strength reduction method. The relationship between the geogrid strain and the factor of safety is set up. The results indicate that the measured strain and calculated results agree very well. The geogrid strain measured by FBG sensor can be applied to evaluate the stability of geogrid-reinforced sand slopes. PMID:28294995

  5. Application of FBG Sensing Technology in Stability Analysis of Geogrid-Reinforced Slope.

    PubMed

    Sun, Yijie; Xu, Hongzhong; Gu, Peng; Hu, Wenjie

    2017-03-15

    By installing FBG sensors on the geogrids, smart geogrids can both reinforce and monitor the stability for geogrid-reinforced slopes. In this paper, a geogrid-reinforced sand slope model test is conducted in the laboratory and fiber Bragg grating (FBG) sensing technology is used to measure the strain distribution of the geogrid. Based on the model test, the performance of the reinforced soil slope is simulated by finite element software Midas-GTS, and the stability of the reinforced soil slope is analyzed by strength reduction method. The relationship between the geogrid strain and the factor of safety is set up. The results indicate that the measured strain and calculated results agree very well. The geogrid strain measured by FBG sensor can be applied to evaluate the stability of geogrid-reinforced sand slopes.

  6. Role of slope stability in cumulative impact assessment of hydropower development: North Cascades, Washington

    SciTech Connect

    Lee, R.R.; Staub, W.P.

    1993-08-01

    Two environmental assessments considered the potential cumulative environmental impacts resulting from the development of eight proposed hydropower projects in the Nooksack River Basin and 11 proposed projects in the Skagit River Basin, North Cascades, Washington, respectively. While not identified as a target resource, slope stability and the alteration of sediment supply to creeks and river mainstems significantly affect other resources. The slope stability assessment emphasized the potential for cumulative impacts under disturbed conditions (e.g., road construction and timber harvesting) and a landslide-induced pipeline rupture scenario. In the case of small-scale slides, the sluicing action of ruptured pipeline water on the fresh landslide scarp was found to be capable of eroding significantly more material than the original landslide. For large-scale landslides, sluiced material was found to be a small increment of the original landslide. These results predicted that hypothetical accidental pipeline rupture by small-scale landslides may result in potential cumulative impacts for 12 of the 19 projects with pending license applications in both river basins. 5 refs., 2 tabs.

  7. Application of soil nails to the stability of mine waste slopes

    SciTech Connect

    Tant, C.R.; Drumm, E.C.; Mauldon, M.; Berry, R.M.

    1996-12-31

    The traditional soil nailed structure incorporates grouted or driven nails, and a wire mesh reinforced shotcrete facing to increase the stability of a slope or wall. This paper describes the construction and monitoring of a full-scale demonstration of nailing to stabilize coal mine spoil. The purpose of the investigation is to evaluate the performance of nailed slopes in mine spoil using methods proven for the stabilization of soil walls and slopes. The site in eastern Tennessee is a 12 meter high slope of dumped fill, composed of weathered shale chips, sandstone, and coal. The slope was formed by {open_quotes}pre-regulatory{close_quotes} contour surface mining operations and served as a work bench during mining. The material varies in size from silt to boulders, and has a small amount of cohesion. Portions of the mine spoil slope have experienced slope instability and erosion which have hampered subsequent reclamation activities. Three different nail spacings and three different nail lengths were used in the design. The 12 meter high structure is instrumented to permit measurement of nail strain, and vertical inclinometer readings and survey measurements will be used for the detection of ground movement. The results of this study will aid in the development of design recommendations and construction guidelines for the application of soil nailing to stabilize mine spoil.

  8. Geotechnical characteristics and slope stability on the Ebro margin, western Mediterranean

    USGS Publications Warehouse

    Baraza, J.; Lee, H.J.; Kayen, R.E.; Hampton, M.A.

    1990-01-01

    Sedimentological and geotechnical analyses of core samples from the Ebro continental slope define two distinct areas on the basis of sediment type, physical properties and geotechnical behavior. The first area is the upper slope area (water depths of 200-500 m), which consists of upper Pleistocene prodeltaic silty clay with a low water content (34% dry weight average), low plasticity, and high overconsolidation near the seafloor. The second area, the middle and lower slope (water depths greater than 500 m), contains clay- and silt-size hemipelagic deposits with a high water content (90% average), high plasticity, and a low to moderate degree of overconsolidation near the sediment surface. Results from geotechnical tests show that the upper slope has a relatively high degree of stability under relatively rapid (undrained) static loading conditions, compared with the middle and lower slopes, which have a higher degree of stability under long-term (drained) static loading conditions. Under cyclic loading, which occurs during earthquakes, the upper slope has a higher degree of stability than the middle and lower slopes. For the surface of the seafloor, calculated critical earthquake accelerations that can trigger slope failures range from 0.73 g on the upper slope to 0.23 g on the lower slope. Sediment buried well below the seafloor may have a critical acceleration as low as 0.09 g on the upper slope and 0.17 g on the lower slope. Seismically induced instability of most of the Ebro slope seems unlikely given that an earthquake shaking of at least intensity VI would be needed, and such strong intensities have never been recorded in the last 70 years. Other cyclic loading events, such as storms or internal waves, do not appear to be direct causes of instability at present. Infrequent, particularly strong earthquakes could cause landslides on the Ebro margin slope. The Columbretes slide on the southwestern Ebro margin may have been caused by intense earthquake shaking

  9. Application and analysis of anchored geosynthetic systems for stabilization of abandoned mine land slopes

    SciTech Connect

    Vitton, S.J.; Whitman, F.; Liang, R.Y.; Harris, W.W.

    1996-12-31

    An anchored geosynthetic system (AGS) was used in the remediation of a landslide associated with an abandoned coal mine located near Hindman, Kentucky. In concept, AGS is a system that provides in-situ stabilization of soil slopes by combining a surface-deployed geosynthetic with an anchoring system of driven reinforcing rods similar to soil nailing. Installation of the system of driven reinforcing rods similar to soil nailing. Installation of the system involves tensioning a geosynthetic over a slope`s surface by driving anchors through the geosynthetic at a given spacing and distance. By tensioning the geosynthetic over the slope`s surface, a compressive load is applied to the slope. Benefits of AGS are described to include the following: (1) increase soil strength due to soil compression including increased compressive loading on potential failure surfaces, (2) soil reinforcement through soil nailing, (3), halt of soil creep, (4) erosion control, and (5) long term soil consolidation. Following installation of the AGS and one year of monitoring, it was found that the anchored geosynthetic system only provided some of the reported benefits and in general did not function as an active stabilization system. This was due in part to the inability of the system to provide and maintain loading on the geosynthetic. The geosynthetic, however, did tension when slope movement occurred and prevented the slope from failing. Thus, the system functioned more as a passive restraint system and appeared to function well over the monitoring period.

  10. OBSERVED STABILITY OF NATURAL AND REINFORCED SLOPES DURING THE 2008 WENCHUAN EARTHQUAKE

    NASA Astrophysics Data System (ADS)

    Guo, Deping; Hamada, Masanori

    The 2008 Wenchuan earthquake with a surface wave magnitude of 8.0 induced numerous landslides along the Longmen Mt. zone in Sichuan Province of China. The authors investigated into various influential factors on the slope stability of 119 landslides in Wenchuan prefecture, such as horizontal peak ground acceleration, slope angle, slope height, rock materials and geological structures. The authors developed hanging wall and footwall's acceleration attenuation formulae from 115 seismic stations and the formulae confirmed hanging-foot wall effect had notable influence on landslide distribution density and occurrence probability. The results of multivariable analysis clarified that slope height, horizontal peak ground acceleration and geological structures were more influential to sliding area and volume than slope angle and rock materials. Furthermore, the authors discussed the effectiveness of reinforcements on the slope stability and showed that anchor cable, frame beam and soil nailing wall had good anti-seismic property, however, shotcrete with bolts had limited ability to enhance slope stability during the earthquake.

  11. Using Three-dimensional Plant Root Architecture in Models of Shallow-slope Stability

    PubMed Central

    Danjon, Frédéric; Barker, David H.; Drexhage, Michael; Stokes, Alexia

    2008-01-01

    Background The contribution of vegetation to shallow-slope stability is of major importance in landslide-prone regions. However, existing slope stability models use only limited plant root architectural parameters. This study aims to provide a chain of tools useful for determining the contribution of tree roots to soil reinforcement. Methods Three-dimensional digitizing in situ was used to obtain accurate root system architecture data for mature Quercus alba in two forest stands. These data were used as input to tools developed, which analyse the spatial position of roots, topology and geometry. The contribution of roots to soil reinforcement was determined by calculating additional soil cohesion using the limit equilibrium model, and the factor of safety (FOS) using an existing slope stability model, Slip4Ex. Key Results Existing models may incorrectly estimate the additional soil cohesion provided by roots, as the spatial position of roots crossing the potential slip surface is usually not taken into account. However, most soil reinforcement by roots occurs close to the tree stem and is negligible at a distance >1·0 m from the tree, and therefore global values of FOS for a slope do not take into account local slippage along the slope. Conclusions Within a forest stand on a landslide-prone slope, soil fixation by roots can be minimal between uniform rows of trees, leading to local soil slippage. Therefore, staggered rows of trees would improve overall slope stability, as trees would arrest the downward movement of soil. The chain of tools consisting of both software (free for non-commercial use) and functions available from the first author will enable a more accurate description and use of root architectural parameters in standard slope stability analyses. PMID:17766845

  12. Quantitative correlation of rainfall and earth surface displacements for slope stability studies

    NASA Astrophysics Data System (ADS)

    Steiakakis, Chrysanthos; Agioutantis, Zacharias; Apostolou, Evangelia; Papavgeri, Georgia; Tripolitsiotis, Achilleas

    2015-06-01

    It is common sense that the possibility of a rockfall increases after an intense rainfall and it is well documented that rainfalls accelerate earth surface displacements such as landslides and rockfalls. This qualitative correlation is highly affected by the geology and climate condition of the area under consideration. The research project entitled "Development of an integrated system for rockfall identification in highways", funded by the Operational Program Competitiveness and Entrepreneurship (co-funded by the European Regional Development Fund (ERDF)) aims to develop an operational system for early warning of rockfalls that occur along transportation corridors. To accomplish this goal the influence and the time gap between triggering mechanisms and rockfall incidents is investigated. In this work, previous studies towards quantitative correlation of rainfall magnitude and earth surface displacements are briefly presented. Based on these works, and taking into account that rockfall incidents, in the majority of Mediterranean countries, are not well-documented, data obtained by a slope stability monitoring network are used to quantitatively determine the magnitude of the rainfall that caused the slope's movement.

  13. Assessing Geotechnical Parameters and Slope Stability on the Architecture of Continental Margins

    NASA Astrophysics Data System (ADS)

    Hutton, E. W.; Syvitski, J. P.

    2001-12-01

    slope. As kinematic viscosity increases a debris flow deposit shorten up and become more blocky deposits. Most parameters controlling slope stability appear to affect the internal character of the margin deposits, rather than the gross shape of the continental margin.

  14. The Effects of Differing Sequences of Earthquake Ground-Shaking on Coseismic Slope Stability

    NASA Astrophysics Data System (ADS)

    Brain, M.; Rosser, N. J.; Vann Jones, E. C.; Tunstall, N.

    2015-12-01

    Studies of earthquake-induced landsliding typically consider slope stability during high-magnitude ground shaking events only. During such events, downslope movement of the landslide mass occurs when seismic ground accelerations are sufficient to overcome shear resistance at the landslide shear surface. This approach does not consider the potential effects that sequences of low-magnitude ground shaking events can have on material strength and, hence, coseismic slope stability. Since such events are more common in nature relative to high-magnitude shaking events, it is important to constrain their geomorphic effectiveness. Using an experimental laboratory approach, we present results that address this key issue. We used a bespoke geotechnical testing apparatus, the Dynamic Back-Pressured Shear Box, that permits realistic simulation of earthquake ground-shaking conditions within a hillslope. We tested both cohesive and granular materials that displayed ductile behaviour under standard strain-controlled monotonic shear tests. We applied dynamic stresses of varying amplitude, frequency and sequence, and monitored the resultant strain response to determine which factors, when combined, created notable deviations from standard monotonic shear behaviour. We observed that multiple dynamic stress/shaking events that are largely insufficient to cause large strains (and hence are conventionally deemed geomorphologically ineffective) can affect material stiffness such that the future behaviour of the sediment/landslide differs considerably from that observed in standard monotonic shear tests. In other words, low-magnitude ground shaking events can be effective precursory geomorphic processes. Critically, the sequence of ground-shaking events is an important control; where shaking conditions cause progressive densification of sediment, the frictional strength of the material subsequently increases. In turn, the resultant strain response to high-magnitude ground shaking events

  15. The long-term hydrological effect of forest stands on the stability of slopes

    NASA Astrophysics Data System (ADS)

    Bogaard, T. A.; Meng, W.; van Beek, L. P. H.

    2012-04-01

    Forest is widely known to improve slope stability as a result of mechanical and hydrological effects. While the mechanics underlying the stabilizing process of root reinforcement are well understood and quantified, the influence of forest on the occurrence of critical hydrological conditions in terms of suction or pore pressure remains uncertain. Due to seasonal and inter-annual fluctuations, the stabilizing influence of evaporation and transpiration is difficult to isolate from the overall noise of the hydrological signal. More long-term effects of forest stands on soil development are highly variable and thus difficult to observe and quantify. Often these effects are ambivalent, having potentially a stabilizing or destabilizing influence on a slope under particular conditions (e.g., more structured soils leading to both rapid infiltration and drainage). Consequently, it can be postulated that forests will hydrologically influence the magnitude-frequency distribution of landsliding, not only at the stand level but also on a regional scale through the groundwater system. The overall aim of this research is to understand and quantify the stabilizing hydrological effect of forests on potentially unstable slopes. To this end, we focus on the changes in the magnitude-frequency distribution of landsliding that arise as a result of variations in evapotranspiration losses over the life cycle of stands. Temporal variations in evapotranspiration comprise first of all the interception that can account for an important amount of evaporation from a forest, and that changes with seasonal and annual variations in the interception capacity of the canopy and forest floor. Transpiration also represents an important loss that varies over the various growth stages of a forest stand. Based on a literature review of water consumption by tree species and water balance studies of forested catchments we defined the potential transpiration for different growth stages. This information we

  16. Evaluation of Rainfall Impacts on Groundwater Flow and Land Deformation in an Unsaturated Heterogeneous Slope and Slope Stability Using a Fully Coupled Hydrogeomechanical Numerical Model

    NASA Astrophysics Data System (ADS)

    Kihm, J.; Kim, J.

    2006-12-01

    A series of numerical simulations using a fully coupled hydrogeomechanical numerical model, which is named COWADE123D, is performed to analyze groundwater flow and land deformation in an unsaturated heterogeneous slope and its stability under various rainfall rates. The slope is located along a dam lake in Republic of Korea. The slope consists of the Cretaceous granodiorite and can be subdivided into the four layers such as weathered soil, weathered rock, intermediate rock, and hard rock from its ground surface due to weathering process. The numerical simulation results show that both rainfall rate and heterogeneity play important roles in controlling groundwater flow and land deformation in the unsaturated slope. The slope becomes more saturated, and thus its overall hydrogeomechanical stability deteriorates, especially in the weathered rock and weathered soil layers, as the rainfall increases up to the maximum daily rainfall rate in the return period of one year. However, the slope becomes fully saturated, and thus its hydrogeomechanical responses are almost identical under more than such a critical rainfall rate. From the viewpoint of hydrogeology, the pressure head, and hence the hydraulic head increase as the rainfall rate increases. As a result, the groundwater table rises, the unsaturated zone reduces, the seepage face expands from the slope toe toward the slope crest, and the groundwater flow velocity increases along the seepage face. Particularly, the groundwater flow velocity increases significantly in the weathered soil and weathered rock layers as the rainfall rate increases. This is because their hydraulic conductivity is relatively higher than that of the intermediate rock and hard rock layers. From the viewpoint of geomechanics, the horizontal displacement increases, while the vertical displacement decreases toward the slope toe as the rainfall rate increases. This may result from the buoyancy effect associated with the groundwater table rise as the

  17. Slope Stability Estimation of the Kościuszko Mound in Cracow

    NASA Astrophysics Data System (ADS)

    Wrana, Bogumił; Pietrzak, Natalia

    2015-06-01

    In the paper, the slope stability problem of the Kościuszko Mound in Cracow, Poland is considered. The slope stability analysis was performed using Plaxis FEM program. The outer surface of the mound has complex geometry. The slope of the cone is not uniform in all directions, on the surface of the cone are pedestrian paths. Due to its complicated geometry it was impossible to do computing by Plaxis input pre-procesor. The initial element mesh was generated using Autodesk Autocad 3D and next it was updated by Plaxis program. The soil parameters were adopted in accordance with the detailed geological soil testing performed in 2012. Calculating model includes geogrids. The upper part was covered by MacMat geogrid, while the lower part of the Mound was reinforced using Terramesh Matt geogrid. The slope analysis was performed by successives reduction of φ /c parameters. The total multiplayer ΣMsf is used to define the value of the soil strength parameters. The article presents the results of slope stability before and after the rainfall during 33 days of precipitation in flood of 2010.

  18. Parameterization experiments performed via synthetic mass movements prototypes generated by 3D slope stability simulator

    NASA Astrophysics Data System (ADS)

    Colangelo, Antonio C.

    2010-05-01

    The central purpose of this work is to perform a reverse procedure in the mass movement conventional parameterization approach. The idea is to generate a number of synthetic mass movements by means of the "slope stability simulator" (Colangelo, 2007), and compeer their morphological and physical properties with "real" conditions of effective mass movements. This device is an integrated part of "relief unity emulator" (rue), that permits generate synthetic mass movements in a synthetic slope environment. The "rue" was build upon fundamental geomorphological concepts. These devices operate with an integrated set of mechanical, geomorphic and hydrological models. The "slope stability simulator" device (sss) permits to perform a detailed slope stability analysis in a theoretical three dimensional space, by means of evaluation the spatial behavior of critical depths, gradients and saturation levels in the "potential rupture surfaces" inferred along a set of slope profiles, that compounds a synthetic slope unity. It's a meta-stable 4-dimensional object generated by means of "rue", that represents a sequence evolution of a generator profile applied here, was adapted the infinite slope model for slope. Any slope profiles were sliced by means of finite element solution like in Bishop method. For the synthetic slope systems generated, we assume that the potential rupture surface occurs at soil-regolith or soil-rock boundary in slope material. Sixteen variables were included in the "rue-sss" device that operates in an integrated manner. For each cell, the factor of safety was calculated considering the value of shear strength (cohesion and friction) of material, soil-regolith boundary depth, soil moisture level content, potential rupture surface gradient, slope surface gradient, top of subsurface flow gradient, apparent soil bulk density and vegetation surcharge. The slope soil was considered as cohesive material. The 16 variables incorporated in the models were analyzed for

  19. Influence of magnetic cohesion on the stability of granular slopes.

    PubMed

    Taylor, K; King, P J; Swift, Michael R

    2008-09-01

    We use a molecular dynamics model to simulate the formation and evolution of a granular pile in two dimensions in order to gain a better understanding of the role of magnetic interactions in avalanche dynamics. We find that the angle of repose increases only slowly with magnetic field; the increase in angle is small even for intergrain cohesive forces many times stronger than gravity. The magnetic forces within the bulk of the pile partially cancel as a result of the anisotropic nature of the dipole-dipole interaction between grains. However, we show that this cancellation effect is not sufficiently strong to explain the discrepancy between the angle of repose in wet systems and magnetically cohesive systems. In our simulations we observe shearing deep within the pile, and we argue that it is this motion that prevents the angle of repose from increasing dramatically. We also investigate different implementations of friction with the front and back walls of the container, and conclude that the nature of the friction dramatically affects the influence of magnetic cohesion on the angle of repose.

  20. Rock slope stability assessment by using RMRB and SMR methods for future development around Gunung Lang, Ipoh, Perak

    NASA Astrophysics Data System (ADS)

    Kamaruszaman, Norazliza; Jamaluddin, Tajul Anuar

    2016-11-01

    The unfavourably oriented discontinuities with respect to the slope cutting orientation may results in rock slope failure or instabilities. The main factor that influences the rock slope stability is the geological factors. The role of geology on slope problems and assessment is variable, according to the subsoil constituent and structures itself. Generally, rock masses are contains a plane of weaknesses such as fault, joint, bedding plane, foliation, dyke, folds, etc. Therefore, those structures will drive a rock mass on a slope to break down. Geological processes also play the role in the rock slope stability. These are due to weathering (expose with air and water), surface erosion, seepage occurs along open joints and the chemical reaction in the intact rock with water that produce high porosity (e.g. limestone). To determine the instabilities of rock falls, basic rock mass rating (RMRb) and slope mass rating (SMR) assessment were conducted on rocks slope in Gunung Lang. The study area is divided into three slope zone; GL-1, GL-2 and GL-3. The results indicates that the rock slopes have two possible modes of failure consisting of planar failure and wedge failures. Rock slope GL-1 is relatively in stable condition. Rock slope GL-2 has potential mode of wedge failure. The slope is considered as partially stable and its probability of failure is 40%. Rock slope GL-3 have potential modes of wedge and planar failures. Therefore, the slope is considered as unstable and its probability of failure is 60%.

  1. Environmental Assessment for Slope Stabilization Projects at Fort MacArthur, San Pedro, California

    DTIC Science & Technology

    2012-01-01

    dewatering, earthwork, structural stabilization, and material strengthening. Page 2 of 2 Alternatives Considered: The Alternative One (Proposed Action) and a...The slopes consist mainly of fill material , so it is unlikely that archaeological resources are located within the non-native soils. An...Temporary road closures may be necessary during stabilization to allow construction equipment room to operate, while maintaining a safe perimeter

  2. Analysis of slope stability, Wilmington to Lindenkohl Canyons, US mid-Atlantic margin

    SciTech Connect

    Almagor, G.; Bennett, R.H.; Lambert, D.N.; Forde, E.B.; Shephard, L.E.

    1984-01-01

    The continental slope gradient in the study area averages 7 to 8/sup 0/. Many valleys, canyons, and occasionally large sediment slumped masses occur. Moderate to steep slopes (19 to 27/sup 0/) as well as very steep to precipitous slopes (> 27/sup 0/) are abundant and occupy about 7% of the investigated area. The surficial sediments are predominantly terrigenous silty clays of medium to high plasticity (I/sub p/ = 10 to 35% w/sub L/ = 30 to 70%), but contain varying quantities of sands. Angles of internal friction are anti phi/sub d/ = 27 to 32/sup 0/, anti phi/sub cu/ = 30 to 33/sup 0/, and phi/sub cu/ = 14 to 17/sup 0/. The sediments are normally to slightly overconsolidated, but some unconsolidated sediments also were identified. c/sub u//anti p/sub 0/ values range from 0.12 to 0.78. An analysis of force equilibrium within the sediments reveals that (a) the gentle slopes in the study area are mostly stable; (b) that the stability of some steep slopes (19 to 27/sup 0/) is marginal; and (c) that on precipitous slopes (> 27/sup 0/) only a thin veneer of sediments can exist. Observations of these slopes during steep dives support these results. The analysis shows that additional accumulation of sediments and small shocks caused by earthquakes or internal waves can cause the slopes to fail. Collapse resulting from liquefaction in the uppermost slope along the canyons and valley axes, where fine sands and silt accumulate, also is likely. 22 references, 9 figures, 2 tables.

  3. Probabilistic stability evaluation and seismic triggering scenarios of submerged slopes in Lake Zurich (Switzerland)

    NASA Astrophysics Data System (ADS)

    Strupler, M.; Hilbe, M.; Anselmetti, F. S.; Kopf, A. J.; Fleischmann, T.; Strasser, M.

    2017-01-01

    Subaqueous landslides and their consequences, such as tsunamis, can cause serious damage to offshore infrastructure and coastal communities. Stability analyses of submerged slopes are therefore crucial, yet complex steps for hazard assessment, as many geotechnical and morphological factors need to be considered. Typically, deterministic models with data from a few sampling locations are used for the evaluation of slope stabilities, as high efforts are required to ensure high spatial data coverage. This study presents a simple but flexible approach for the probabilistic stability assessment of subaqueous slopes that takes into account the spatial variability of geotechnical data. The study area ( 2 km2) in Lake Zurich (northern Switzerland) shows three distinct subaquatic landslides with well-defined headscarps, translation areas (i.e. the zone where translational sliding occurred) and mass transport deposits. The ages of the landslides are known ( 2,210 and 640 cal. yr BP, and 1918 AD), and their triggers have been assigned to different mechanisms by previous studies. A combination of geophysical, geotechnical, and sedimentological methods served to analyse the subaquatic slope in great spatial detail: 3.5 kHz pinger seismic reflection data and a 300 kHz multibeam bathymetric dataset (1 m grid) were used for the detection of landslide features and for the layout of a coring and an in situ cone penetration testing campaign. The assignment of geotechnical data to lithological units enabled the construction of a sediment-mechanical stratigraphy that consists of four units, each with characteristic profiles of bulk density and shear strength. The thickness of each mechanical unit can be flexibly adapted to the local lithological unit thicknesses identified from sediment cores and seismic reflection profiles correlated to sediment cores. The sediment-mechanical stratigraphy was used as input for a Monte Carlo simulated limit-equilibrium model on an infinite slope for

  4. Slope Stability Analysis In Seismic Areas Of The Northern Apennines (Italy)

    SciTech Connect

    Lo Presti, D.; Fontana, T.; Marchetti, D.

    2008-07-08

    Several research works have been published on the slope stability in the northern Tuscany (central Italy) and particularly in the seismic areas of Garfagnana and Lunigiana (Lucca and Massa-Carrara districts), aimed at analysing the slope stability under static and dynamic conditions and mapping the landslide hazard. In addition, in situ and laboratory investigations are available for the study area, thanks to the activities undertaken by the Tuscany Seismic Survey. Based on such a huge information the co-seismic stability of few ideal slope profiles have been analysed by means of Limit equilibrium method LEM - (pseudo-static) and Newmark sliding block analysis (pseudo-dynamic). The analysis--results gave indications about the most appropriate seismic coefficient to be used in pseudo-static analysis after establishing allowable permanent displacement. Such indications are commented in the light of the Italian and European prescriptions for seismic stability analysis with pseudo-static approach. The stability conditions, obtained from the previous analyses, could be used to define microzonation criteria for the study area.

  5. Geological Control on Stability of Excavated Rock Slope at Jeruklegi Claystone Quarry, Cilacap Regency, Central Java Province, Indonesia

    NASA Astrophysics Data System (ADS)

    Fukuoka, Hiroshi; Dok, Atitkagna; Pramumijoyo, Subagyo; Faisal Fathani, Teuku

    2010-05-01

    PT. Holcim Indonesia Tbk is a well-known company for cement production in Cilacap, Central Java, Indonesia. In cement manufacturing, certain raw materials such as limestone, claystone and other supplementary materials are required. In a mean time, the company is conducting claystone mining to support the cement industry. Currently, the exploitation has covered the area of approximately 103 ha. Due to the increment need of more claystone to achieve the expecting amount of cement production, the company plans to extend existing mining site up to 250 ha with maximum depth of +10m above the sea level. However, such development may eventually lead to major slope failures which essentially affect the sustainability and the safety of the mine. Understanding that various negative impacts may appear during the mining operation, which possibly result in personal injury, potential life loss, property damage and other socio-economic consequences, it is crucial to assess slope stability conditions of the mining pit to ensure safety of the mine. The study is mainly focused on analysis of the rock mass behaviours under specific geological control and earthquake trigger through the application of finite element method. Based on the assessment result, the zone where covered by discontinuous rock mass, absorbent lithology and steep slope geometry in combination with presence of groundwater, is estimated to be potential to slope movement in form of rock falls and/or rock slides which could be possibly predicted to occur as a consequence of heavy rainfall intensity, un-controlled slope excavation and ground vibration. And, the stable slope inclination is suggested not to be steeper than 60˚, with the maximum width of 3m and maximum height of 6m.

  6. A strategy for GIS-based 3-D slope stability modelling over large areas

    NASA Astrophysics Data System (ADS)

    Mergili, M.; Marchesini, I.; Alvioli, M.; Metz, M.; Schneider-Muntau, B.; Rossi, M.; Guzzetti, F.

    2014-12-01

    GIS-based deterministic models may be used for landslide susceptibility mapping over large areas. However, such efforts require specific strategies to (i) keep computing time at an acceptable level, and (ii) parameterize the geotechnical data. We test and optimize the performance of the GIS-based, 3-D slope stability model r.slope.stability in terms of computing time and model results. The model was developed as a C- and Python-based raster module of the open source software GRASS GIS and considers the 3-D geometry of the sliding surface. It calculates the factor of safety (FoS) and the probability of slope failure (Pf) for a number of randomly selected potential slip surfaces, ellipsoidal or truncated in shape. Model input consists of a digital elevation model (DEM), ranges of geotechnical parameter values derived from laboratory tests, and a range of possible soil depths estimated in the field. Probability density functions are exploited to assign Pf to each ellipsoid. The model calculates for each pixel multiple values of FoS and Pf corresponding to different sliding surfaces. The minimum value of FoS and the maximum value of Pf for each pixel give an estimate of the landslide susceptibility in the study area. Optionally, r.slope.stability is able to split the study area into a defined number of tiles, allowing parallel processing of the model on the given area. Focusing on shallow landslides, we show how multi-core processing makes it possible to reduce computing times by a factor larger than 20 in the study area. We further demonstrate how the number of random slip surfaces and the sampling of parameters influence the average value of Pf and the capacity of r.slope.stability to predict the observed patterns of shallow landslides in the 89.5 km2 Collazzone area in Umbria, central Italy.

  7. Experimental test of theory for the stability of partially saturated vertical cut slopes

    USGS Publications Warehouse

    Morse, Michael M.; Lu, N.; Wayllace, Alexandra; Godt, Jonathan W.; Take, W.A.

    2014-01-01

    This paper extends Culmann's vertical-cut analysis to unsaturated soils. To test the extended theory, unsaturated sand was compacted to a uniform porosity and moisture content in a laboratory apparatus. A sliding door that extended the height of the free face of the slope was lowered until the vertical cut failed. Digital images of the slope cross section and upper surface were acquired concurrently. A recently developed particle image velocimetry (PIV) tool was used to quantify soil displacement. The PIV analysis showed strain localization at varying distances from the sliding door prior to failure. The areas of localized strain were coincident with the location of the slope crest after failure. Shear-strength and soil-water-characteristic parameters of the sand were independently tested for use in extended analyses of the vertical-cut stability and of the failure plane angle. Experimental failure heights were within 22.3% of the heights predicted using the extended theory.

  8. Investigations of slope stability, Savannah River Plant, Aiken, South Carolina. Draft report

    SciTech Connect

    Not Available

    1985-01-01

    Our analysis of slope stability indicates acceptable factors of safety for trenches excavated at a slope inclination of one (horizontal) to one (vertical). Further, without the addition of externally applied loads, such as construction trafficking and the gantry crane, a slope inclination of 0.75 horizontal to 1.0 vertical was found to have an acceptable factor of safety of 1.5. Setback distances were calculated for a slope inclination of one to one, and it was found that the gantry crane loading could safely be applied at a setback distance of approximately 7.5 feet while maintaining a factor of safety of approximately 1.2. Similarly, setback distances required for dump trucks and scrapers would be expected to be approximately 6 feet and 10 feet, respectively, to maintain a factor of safety of 1.2. In order to allow flexibility with construction loadings, parametric studies were utilized for construction trafficking to enable setback distances to be selected consistent with actual equipment to be utilized during construction. The effect of removal of surficial soils was investigated, and it is concluded that a minimum of 4-1/2 feet should be removed from all areas prior to the excavation of slopes.

  9. SLOPE STABILITY EVALUATION AND EQUIPMENT SETBACK DISTANCES FOR BURIAL GROUND EXCAVATIONS

    SciTech Connect

    MCSHANE DS

    2010-03-25

    After 1970 Transuranic (TRU) and suspect TRU waste was buried in the ground with the intention that at some later date the waste would be retrieved and processed into a configuration for long term storage. To retrieve this waste the soil must be removed (excavated). Sloping the bank of the excavation is the method used to keep the excavation from collapsing and to provide protection for workers retrieving the waste. The purpose of this paper is to document the minimum distance (setback) that equipment must stay from the edge of the excavation to maintain a stable slope. This evaluation examines the equipment setback distance by dividing the equipment into two categories, (1) equipment used for excavation and (2) equipment used for retrieval. The section on excavation equipment will also discuss techniques used for excavation including the process of benching. Calculations 122633-C-004, 'Slope Stability Analysis' (Attachment A), and 300013-C-001, 'Crane Stability Analysis' (Attachment B), have been prepared to support this evaluation. As shown in the calculations the soil has the following properties: Unit weight 110 pounds per cubic foot; and Friction Angle (natural angle of repose) 38{sup o} or 1.28 horizontal to 1 vertical. Setback distances are measured from the top edge of the slope to the wheels/tracks of the vehicles and heavy equipment being utilized. The computer program utilized in the calculation uses the center of the wheel or track load for the analysis and this difference is accounted for in this evaluation.

  10. Evidence for Holocene stability of steep slopes, northern Peruvian Andes, based on soils and radiocarbon dates

    USGS Publications Warehouse

    Miller, D.C.; Birkeland, P.W.; Rodbell, D.T.

    1993-01-01

    Radiocarbon dating and soil relationships indicate that landscapes in highaltitude glaciated valleys of the northern Peruvian Andes have been remarkably stable during the Holocene. Radiocarbon dates show that deglaciation was underway by 12 ka, and that slopes and alluvial fans at the bases of slopes were essentially stabilized by at least 8 ka. The soils consist of fine-grained loessial A horizons overlying Bw horizons in gravelly till or alluvial-fan gravel. Following deglaciation, widespread gullying took place in till on the steep (maximum angle: 37??) sideslopes of most valleys; the eroded material was deposited as fans at the bases of the slopes. Loess was then deposited as a fairly uniform blanket across most elements of the landscape. Soil formation began during or following loess deposition, and because soil-profile morphology is sufficiently similar at most sites, soil formation has been a dominant process during much of the Holocene. This remarkable stability, especially for such steep slopes, is attributed to a combination of tight packing of the till, permeability of the capping loess, rapid revegetation following ice retreat, and roots from the present grassland vegetation and possibly former forests. ?? 1993.

  11. Unsaturated slope stability analysis with steady infiltration or evaporation using elasto-plastic finite elements

    NASA Astrophysics Data System (ADS)

    Griffiths, D. V.; Lu, N.

    2005-03-01

    The paper presents results of unsaturated slope stability analyses using elasto-plastic finite elements in conjunction with a novel analytical formulation for the suction stress above the water table. The suction stress formula requires four parameters, three for the soil type and one for the steady infiltration (or evaporation) due to environmental effects. The suction stress approach enables the analysis to proceed in the context of classical effective stress, while maintaining the advantages of a general non-linear finite element approach in which no advance assumptions need to be made about the shape or location of the critical failure surface. The results show the extent to which suctions above the water table can increase the factor of safety of a slope for a variety of different soil types and infiltration rates. All stability analyses that include the effects of suction stresses are contrasted with more traditional approaches in which water pressures above the water table are ignored. Copyright

  12. User’s Guide: Modified Slope Stability Package with Kansas City Analysis (DGSLOPE).

    DTIC Science & Technology

    1984-01-01

    MODIFIED SLOPE STABILITY PACKAGE WITH KANSAS CITY ANALYSIS (DGSLOPE) by Robert L. Hall, Michael E. Pace Automatic Data Processing Center U. S. Army Engineer...endorsement or approval of the use of such commercial products. J W’ Unclassified SECURITY CLASSIFICATION OF THIS PAGE (16.., Dots gntenod) EPAGE AD...report 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR~s) S. CONTRACT OR GRANT NUMBER(S) Robert L. Hall Michael E. Pace S. PERFORMING ORGANIZATION NAME AND

  13. Stability Thresholds and Performance Standards for Flexible Lining Materials in Channel and Slope Restoration Applications

    DTIC Science & Technology

    2012-07-01

    riprap, concrete ), soft or light armoring (e.g., erosion control blankets, ECBs, an early type of so-called rolled erosion control product, reinforced ...slope stabilization. In some applications, reinforced vegetative covers can be used in lieu of rock riprap, concrete paving, or articulated block or...produced in a roll, natural or synthetic, degradable or non-degradable, short- or long-term USEPA, ASTM, ECTC Turf reinforcement mat TRM A type of

  14. Feasibility of biochar application on a landfill final cover-a review on balancing ecology and shallow slope stability.

    PubMed

    Chen, Xun-Wen; Wong, James Tsz-Fung; Ng, Charles Wang-Wai; Wong, Ming-Hung

    2016-04-01

    Due to the increasing concerns on global warming, scarce land for agriculture, and contamination impacts on human health, biochar application is being considered as one of the possible measures for carbon sequestration, promoting higher crop yield and contamination remediation. Significant amount of researches focusing on these three aspects have been conducted during recent years. Biochar as a soil amendment is effective in promoting plant performance and sustainability, by enhancing nutrient bioavailability, contaminants immobilization, and microbial activities. The features of biochar in changing soil physical and biochemical properties are essential in affecting the sustainability of an ecosystem. Most studies showed positive results and considered biochar application as an effective and promising measure for above-mentioned interests. Bio-engineered man-made filled slope and landfill slope increasingly draw the attention of geologists and geotechnical engineers. With increasing number of filled slopes, sustainability, low maintenance, and stability are the major concerns. Biochar as a soil amendment changes the key factors and parameters in ecology (plant development, soil microbial community, nutrient/contaminant cycling, etc.) and slope engineering (soil weight, internal friction angle and cohesion, etc.). This paper reviews the studies on the production, physical and biochemical properties of biochar and suggests the potential areas requiring study in balancing ecology and man-made filled slope and landfill cover engineering. Biochar-amended soil should be considered as a new type of soil in terms of soil mechanics. Biochar performance depends on soil and biochar type which imposes challenges to generalize the research outcomes. Aging process and ecotoxicity studies of biochar are strongly required.

  15. Probabilistic stability evaluation of submerged slopes in Lake Zurich (Switzerland) and seismic triggering scenarios

    NASA Astrophysics Data System (ADS)

    Strupler, Michael; Hilbe, Michael; Anselmetti, Flavio S.; Kopf, Achim J.; Fleischmann, Timo; Strasser, Michael

    2016-04-01

    The consequences of subaquatic slope failures both in the marine and the lacustrine realm can be very serious. For hazard assessments, stability analyses of submerged slopes are therefore crucial steps, yet very complex ones, as they require knowledge of several geotechnical and morphological factors. Traces of subaquatic mass movements are often used to extract paleoseismological information. For Lake Zurich, a perialpine lake in Northern Switzerland, coeval subaquatic landslide occurrences along distinct time-correlative horizons have been previously interpreted as earthquake-triggered. The 'Oberrieden' study area (˜2 km2) shows three distinct, dated subaquatic landslides with well-defined headscarps, translation areas and mass-transport deposits. The respective failures have been assigned to different trigger mechanisms ranging from human-induced shore loading to earthquake shaking. However, the local shaking intensities leading to slope failures are unknown. A 3.5 kHz pinger seismic reflection dataset and a 300 kHz multibeam bathymetric dataset (1 m grid) were used for the detection of landslide features and for the layout of a coring campaign and in situ geotechnical testing. A total of 8 Kullenberg-system piston cores (4 cores /km2) and 22 short gravity cores (11 cores /km2) were taken and 39 in situ Cone Penetration Tests (CPT) (˜20 CPT /km2) were performed. The high density of sediment cores and CPT sites in a well-known area allows us to include the spatial variability in the slope model. With a probabilistic back analysis of the earthquake-triggered ˜2210 BP subaquatic landslide and an assessment of the actual stability of the neighbouring, unfailed sediment drape, we analyse different scenarios of slope stability under static conditions and under seismic shaking in order to quantitatively constrain failure mechanisms and triggers. We apply a Monte Carlo two-dimensional limit-equilibrium infinite-slope stability model that includes a sediment

  16. Using a Remotely Piloted Aircraft System (RPAS) to analyze the stability of a natural rock slope

    NASA Astrophysics Data System (ADS)

    Salvini, Riccardo; Esposito, Giuseppe; Mastrorocco, Giovanni; Seddaiu, Marcello

    2016-04-01

    This paper describes the application of a rotary wing RPAS for monitoring the stability of a natural rock slope in the municipality of Vecchiano (Pisa, Italy). The slope under investigation is approximately oriented NNW-SSE and has a length of about 320 m; elevation ranges from about 7 to 80 m a.s.l.. The hill consists of stratified limestone, somewhere densely fractured, with dip direction predominantly oriented in a normal way respect to the slope. Fracture traces are present in variable lengths, from decimetre to metre, and penetrate inward the rock versant with thickness difficult to estimate, often exceeding one meter in depth. The intersection between different fracture systems and the slope surface generates rocky blocks and wedges of variable size that may be subject to phenomena of gravitational instability (with reference to the variation of hydraulic and dynamic conditions). Geometrical and structural info about the rock mass, necessary to perform the analysis of the slope stability, were obtained in this work from geo-referenced 3D point clouds acquired using photogrammetric and laser scanning techniques. In particular, a terrestrial laser scanning was carried out from two different point of view using a Leica Scanstation2. The laser survey created many shadows in the data due to the presence of vegetation in the lower parts of the slope and limiting the feasibility of geo-structural survey. To overcome such a limitation, we utilized a rotary wing Aibotix Aibot X6 RPAS geared with a Nikon D3200 camera. The drone flights were executed in manual modality and the images were acquired, according to the characteristics of the outcrops, under different acquisition angles. Furthermore, photos were captured very close to the versant (a few meters), allowing to produce a dense 3D point cloud (about 80 Ma points) by the image processing. A topographic survey was carried out in order to guarantee the necessary spatial accuracy to the process of images exterior

  17. Stability of submerged slopes on the flanks of the Hawaiian Islands, a simplified approach

    SciTech Connect

    Lee, H.J.; Torresan, M.E.; McArthur, W.

    1994-12-31

    Undersea transmission lines and shoreline AC-DC conversion stations and near-shore transmission lines are being considered as part of a system for transporting energy between the Hawaiian Islands. These facilities will need to be designed so that they will not be damaged or destroyed by coastal or undersea landslides. Advanced site surveys and engineering design of these facilities will require detailed site specific analyses, including sediment sampling and laboratory testing of samples, in situ testing of sediment and rock, detailed charting of bathymetry, and two- or three-dimensional numerical analyses of the factors of safety of the slopes against failure from the various possible loading mechanisms. An intermediate approximate approach can be followed that involves gravity and piston cores, laboratory testing and the application of simplified models to determine a seismic angle of repose for actual sediment in the vicinity of the planned facility. An even simpler and more approximate approach involves predictions of angles of repose using classification of the sediment along a proposed route as either a coarse volcaniclastic sand, a calcareous ooze, or a muddy terrigenous sediment. The steepest slope that such a sediment can maintain is the static angle of repose. Sediment may be found on slopes as steep as these, but it must be considered metastable and liable to fail in the event of any disturbance, storm or earthquake. The seismic angle of repose likely governs most slopes on the Hawaiian Ridge. This declivity corresponds to the response of the slope to a continuing seismic environment. As a long history of earthquakes affects the slopes, they gradually flatten to this level. Slopes that exceed or roughly equal this value can be considered at risk to fail during future earthquakes. Seismic and static angles of repose for three sediment types are tabulated in this report.

  18. Observations of Radiation Divergence and Stability Driven Slope Flows during the Field Experiment KASCADE

    NASA Astrophysics Data System (ADS)

    Duine, Gert-Jan; Durand, Pierre; Hedde, Thierry; Roubin, Pierre; Augustin, Patrick; Fourmentin, Marc; Lohou, Fabienne; Lothon, Marie

    2014-05-01

    This work is in the frame of the PhD-thesis entitled "Dispersion of pollutants in stable boundary layer conditions in the middle valley of the Durance", financed by the Commissariat à l'Energie Atomique (CEA) and jointly supervised by CEA and Laboratoire d'Aérologie (LA), Toulouse. It takes place in a wider context of R & D work performed at CEA to characterize the site specific atmospheric conditions, with a view to improve the knowledge of the impact of the potential release of pollutants. During the winter of 2013 the intensive field measurement campaign KASCADE (KAtabatic winds and Stability over CAdarache for Dispersion of Effluents) has been carried out at Cadarache, a research centre of CEA, located in South-Eastern France. The stability of the lower atmospheric boundary layer caused by radiative cooling at night, combined with the local orography, strongly affects the conditions for the dispersion of potential pollutants. Understanding the complex patterns of drainage flow and cold pool build up in the smaller valleys confluent to the Durance river is thus a major issue for refining the models used to assess the sanitary and environmental impact of Cadarache. Stability is easily formed in the region and in combination with the orographic complexity, there is a need to study the Stable Boundary Layer (SBL), which potentially can have a large impact on the dispersion of gaseous emissions released by the various facilities of Cadarache. KASCADE was designed to characterize the local SBL in order to feed future planned numerical simulations with WRF and impact studies involving numerical models coping with dispersion. With a focus on night time, a combination of continuous observations (SODAR and a flux-measurement tower of 30 meter [M30]) and 23 Intensive Observational Periods (IOPs) (Tethered Balloon [TB] profiling and radio-soundings) allows to study the relevant phenomena for SBL-formation. M30 was equipped with sonic anemometers at 3 levels for

  19. Calvarial slope affecting accuracy of Ghajar Guide technique for ventricular catheter placement.

    PubMed

    Park, Jaechan; Son, Wonsoo; Park, Ki-Su; Kim, Min Young; Lee, Joomi

    2016-05-01

    OBJECT The Ghajar Guide technique is used to direct a ventricular catheter at a 90° angle to the skull surface at Kocher's point. However, the human calvaria is not completely spherical. Lateral to the sagittal midline, the calvaria slopes downward with individual variation and thereby affects the accuracy of ventricular catheter placement. Accordingly, the authors investigated the accuracy of the orthogonal catheter trajectory using radiographic simulation and examined the effect of the calvarial slope on this accuracy. METHODS A catheter trajectory orthogonal to the skull surface at Kocher's point and the ideal catheter trajectory to the foramen of Monro were drawn bilaterally on coronal head images of 52 patients with hydrocephalus. The correction angle, the difference between the 2 catheter trajectories, was then measured. Meanwhile, the calvarial slope was measured around Kocher's point by using a coronal head image. The correlation between the correction angle and factors such as the calvarial slope and bicaudate index was then assessed using a Pearson correlation analysis. RESULTS The ventricular catheter trajectory orthogonal to the skull at Kocher's point in the patients with hydrocephalus led to a catheter trajectory into the ipsilateral (70.2%) or contralateral (29.8%) lateral ventricles. The correction angles ranged from -3.3° to 16.4° (mean ± SD 5.7° ± 3.7°). In 87 (83.7%) head sides, lateral deviation from the orthogonal trajectory was required to approximate the ideal trajectory, and the correction angle ranged from 2.0° to 16.4° (mean 6.7° ± 2.9°). The calvarial slope in the 104 head sides ranged from 15.6° to 32.5° (mean 24.2° ± 3.1°). Pearson correlation analysis revealed a strong positive correlation (r = 0.733) between the calvarial slope and the correction angle. CONCLUSIONS The accuracy of ventricular catheter placement using the Ghajar Guide technique is affected primarily by the calvarial slope around Kocher's point. A

  20. Using Controlled Landslide Initiation Experiments to Test Limit-Equilibrium Analyses of Slope Stability

    NASA Astrophysics Data System (ADS)

    Reid, M. E.; Iverson, R. M.; Brien, D. L.; Iverson, N. R.; Lahusen, R. G.; Logan, M.

    2004-12-01

    Most studies of landslide initiation employ limit equilibrium analyses of slope stability. Owing to a lack of detailed data, however, few studies have tested limit-equilibrium predictions against physical measurements of slope failure. We have conducted a series of field-scale, highly controlled landslide initiation experiments at the USGS debris-flow flume in Oregon; these experiments provide exceptional data to test limit equilibrium methods. In each of seven experiments, we attempted to induce failure in a 0.65m thick, 2m wide, 6m3 prism of loamy sand placed behind a retaining wall in the 31° sloping flume. We systematically investigated triggering of sliding by groundwater injection, by prolonged moderate-intensity sprinkling, and by bursts of high intensity sprinkling. We also used vibratory compaction to control soil porosity and thereby investigate differences in failure behavior of dense and loose soils. About 50 sensors were monitored at 20 Hz during the experiments, including nests of tiltmeters buried at 7 cm spacing to define subsurface failure geometry, and nests of tensiometers and pore-pressure sensors to define evolving pore-pressure fields. In addition, we performed ancillary laboratory tests to measure soil porosity, shear strength, hydraulic conductivity, and compressibility. In loose soils (porosity of 0.52 to 0.55), abrupt failure typically occurred along the flume bed after substantial soil deformation. In denser soils (porosity of 0.41 to 0.44), gradual failure occurred within the soil prism. All failure surfaces had a maximum length to depth ratio of about 7. In even denser soil (porosity of 0.39), we could not induce failure by sprinkling. The internal friction angle of the soils varied from 28° to 40° with decreasing porosity. We analyzed stability at failure, given the observed pore-pressure conditions just prior to large movement, using a 1-D infinite-slope method and a more complete 2-D Janbu method. Each method provides a static

  1. Methods for assessing the stability of slopes during earthquakes-A retrospective

    USGS Publications Warehouse

    Jibson, R.W.

    2011-01-01

    During the twentieth century, several methods to assess the stability of slopes during earthquakes were developed. Pseudostatic analysis was the earliest method; it involved simply adding a permanent body force representing the earthquake shaking to a static limit-equilibrium analysis. Stress-deformation analysis, a later development, involved much more complex modeling of slopes using a mesh in which the internal stresses and strains within elements are computed based on the applied external loads, including gravity and seismic loads. Stress-deformation analysis provided the most realistic model of slope behavior, but it is very complex and requires a high density of high-quality soil-property data as well as an accurate model of soil behavior. In 1965, Newmark developed a method that effectively bridges the gap between these two types of analysis. His sliding-block model is easy to apply and provides a useful index of co-seismic slope performance. Subsequent modifications to sliding-block analysis have made it applicable to a wider range of landslide types. Sliding-block analysis provides perhaps the greatest utility of all the types of analysis. It is far easier to apply than stress-deformation analysis, and it yields much more useful information than does pseudostatic analysis. ?? 2010.

  2. Sensitivity analysis and calibration of a coupled hydrological/slope stability model (TRIGRS)

    NASA Astrophysics Data System (ADS)

    Zieher, Thomas; Rutzinger, Martin; Perzl, Frank; Meißl, Gertraud

    2014-05-01

    Shallow landslides potentially endanger human living in mountain regions worldwide. In order to prevent impacts of such gravitational mass movements it is necessary to fully understand the processes involved. Shallow landslides are usually understood as gravitational mass movements of the translational, slope-parallel type comprising of a mixture of earth and debris with a maximum depth of 1-2 m. Depending on the degree of saturation the initial sliding can turn into a flow-like movement. Numerous approaches for modelling shallow landslide susceptibility with different degrees of complexity exist. Regardless of the modelling approach it is crucial to provide sufficient field data, mainly on regolith characteristics. As for the TRIGRS (Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability) model, numerous hydraulic and geotechnical parameters have to be known area-wide. Hence, as spatial interpolation of these input parameters is generally problematic in terms of accuracy, calibrating the model accordingly is a crucial step before conducting any simulations. This study presents a sensitivity analysis and the calibration of the coupled hydrological/slope stability model TRIGRS for a study area in Vorarlberg (Austria). The results of the sensitivity analysis show that in case of the stability model cohesion is the driving parameter while for the hydrological model it is the initial depth of the water table and the saturated hydraulic conductivity. The calibration of the stability model was carried out using a landslide inventory assuming completely saturated conditions. The use of geotechnical parameters extracted from literature for mapped soil types generally lead to unlikely stable conditions. In order to simulate mapped landslide initial areas correctly values for soil cohesion had to be adapted. However, the calibration of the stability model generally supports the assumption of saturated conditions. In absence of meteorological or hydrological

  3. Slope stability analysis for Valles Marineris, Mars: a numerical analysis of controlling conditions and failure types

    NASA Astrophysics Data System (ADS)

    Crosta, G.; Castellanza, R.; De Blasio, F.; Utili, S.

    2012-04-01

    Valles Marineris (VM hereafter) in the equatorial area of Mars exhibits several gravitative failures often involving the whole 6-8 km thickness of the valley walls. The failures have resulted in a series of long-runout landslides up to several hundred cubic kilometres in volume (Quantin et al., 2004), and the formation of sub-circular alcoves perched on the top. Several questions arise as to forces at play in the stability of the walls of VM, the geometrical shape of the alcoves and the shape and long-runout of the landslides (see for example Lucas et al., 2011). In this work, we concentrate on the stability analysis of the walls of VM with two precise questions in mind starting from past studies (Bigot-Cormier and Montgomery, 2006; Neuffer and Schultz, 2006, Schultz, 2002). The first concerns the properties of the materials that give origin to instability. We performed several finite element and discrete element calculations tailored to slope stability analysis based on the genuine shape of the walls of VM taken from the MOLA topographic data. We considered stratified and differently altered/degraded materials to define the range of physical mechanical properties required for failure to occur and to explain the discrete distribution of failures along the VM valley flanks. A second question addressed in this work is the geometrical shape of the sub-circular alcoves. Normally, these shapes are commonplace for slopes made of uniform and isotropic properties, and are also observed in subaqueous environment. We performed calculations taking into consideration the progressive failure in the slope showing the final results in terms of surface failure geometry. Bigot-Cormier, F., Montgomery, D.R. (2007) Valles Marineris landslides: Evidence for a strength limit to Martian relief? Earth and Planetary Science Letters, 260, 1-2, 15, 179-186 Lucas, A., Mangeney, A., Mège, D., and Bouchut, F., 2011. Influence of the scar geometry on landslide dynamics and deposits

  4. Soil aggregation and slope stability related to soil density, root length, and mycorrhiza

    NASA Astrophysics Data System (ADS)

    Graf, Frank; Frei, Martin

    2013-04-01

    Eco-engineering measures combine the use of living plants and inert mechanical constructions to protect slopes against erosion and shallow mass movement. Whereas in geotechnical engineering several performance standards and guidelines for structural safety and serviceability of construction exist, there is a lack of comparable tools in the field of ecological restoration. Various indicators have been proposed, including the fractal dimension of soil particle size distribution, microbiological parameters, and soil aggregate stability. We present results of an soil aggregate stability investigation and compare them with literature data of the angle of internal friction ?' which is conventionally used in slope stability analysis and soil failure calculation. Aggregate stability tests were performed with samples of differently treated moraine, including soil at low (~15.5 kN/m³) and high (~19.0 kN/m³) dry unit weight, soil planted with Alnus incana (White Alder) as well as the combination of soil planted with alder and inoculated with the mycorrhizal fungus Melanogaster variegatus s.l. After a 20 weeks growth period in a greenhouse, a total of 100 samples was tested and evaluated. Positive correlations were found between the soil aggregate stability and the three variables dry unit weight, root length per soil volume, and degree of mycorrhization. Based on robust statistics it turned out that dry unit weight and mycorrhization degree were strongest correlated with soil aggregate stability. Compared to the non-inoculated control plants, mycorrhized White Alder produced significantly more roots and higher soil aggregate stability. Furthermore, the combined biological effect of plant roots and mycorrhizal mycelia on aggregate stability on soil with low density (~15.5 kN/m³) was comparable to the compaction effect of the pure soil from 15.5 to ~19.0 kN/m³. Literature data on the effect of vegetation on the angle of internal friction ?' of the same moraine showed

  5. 75 FR 65366 - Recovery Policy RP9524.2, Landslides and Slope Stability Related to Public Facilities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-22

    ... SECURITY Federal Emergency Management Agency Recovery Policy RP9524.2, Landslides and Slope Stability... availability. SUMMARY: This document provides notice of the final Recovery Policy RP9524.2, Landslides and... eligibility of emergency work to protect eligible facilities threatened by landslides or slope failures;...

  6. Prediction of landslide run-out distance based on slope stability analysis and center of mass approach

    NASA Astrophysics Data System (ADS)

    Firmansyah; Feranie, S.; Tohari, Adrin; Latief, F. D. E.

    2016-01-01

    Mitigation of landslide hazard requires the knowledge of landslide run-out distance. This paper presents the application of slope stability analysis and center of mass approach to predict the run-out distance of a rotational landslide model with different soil types. The Morgenstern-Price method was used to estimate the potential sliding zone and volume of landslide material. The center of mass approach used a simple Coulomb friction model to determine the run-out distance. Results of the slope stability analysis showed that the soil unit weight can influence the depth of sliding zone, and the volume of unstable material. The slope model of silty sand and gravel would have the largest volume of unstable mass. From the Coulomb friction analysis, this slope model has higher run-out distance and velocity than other slope models. Thus, the run-out distance will be influenced by soil type and the dimension of unstable soil mass.

  7. Instrumental record of debris flow initiation during natural rainfall: Implications for modeling slope stability

    USGS Publications Warehouse

    Montgomery, D.R.; Schmidt, K.M.; Dietrich, W.E.; McKean, J.

    2009-01-01

    The middle of a hillslope hollow in the Oregon Coast Range failed and mobilized as a debris flow during heavy rainfall in November 1996. Automated pressure transducers recorded high spatial variability of pore water pressure within the area that mobilized as a debris flow, which initiated where local upward flow from bedrock developed into overlying colluvium. Postfailure observations of the bedrock surface exposed in the debris flow scar reveal a strong spatial correspondence between elevated piezometric response and water discharging from bedrock fractures. Measurements of apparent root cohesion on the basal (Cb) and lateral (Cl) scarp demonstrate substantial local variability, with areally weighted values of Cb = 0.1 and Cl = 4.6 kPa. Using measured soil properties and basal root strength, the widely used infinite slope model, employed assuming slope parallel groundwater flow, provides a poor prediction of hydrologie conditions at failure. In contrast, a model including lateral root strength (but neglecting lateral frictional strength) gave a predicted critical value of relative soil saturation that fell within the range defined by the arithmetic and geometric mean values at the time of failure. The 3-D slope stability model CLARA-W, used with locally observed pore water pressure, predicted small areas with lower factors of safety within the overall slide mass at sites consistent with field observations of where the failure initiated. This highly variable and localized nature of small areas of high pore pressure that can trigger slope failure means, however, that substantial uncertainty appears inevitable for estimating hydrologie conditions within incipient debris flows under natural conditions. Copyright 2009 by the American Geophysical Union.

  8. Influence of diatom microfossils on sediment shear strength and slope stability

    NASA Astrophysics Data System (ADS)

    Wiemer, G.; Kopf, A.

    2017-01-01

    Diatom microfossils have been detected in many natural marine sediment deposits around the globe and are held responsible for the disobedience to well-established geotechnical relationships between index-properties and shear strength. We revisit the static shear strength and present the first cyclic undrained shear strength experiments on diatom microfossil—clayey-silt mixtures to study the role of diatoms on submarine slope stability. It is attested that the angle of internal friction (Φ) increases with diatom content, however, we provide evidence for a significant overestimation of Φ in previous studies. Based on direct shear tests at varying normal stresses ≤ 600 kPa we find Φ = 32° in contrast to 43° in pure diatom. Similarly, to static shear strength, cyclic shear strength increases with diatom content, however, in contrast to static shear strength the most drastic increase does not occur from 0% to 25% diatoms but from 75% to 100%. Interestingly, diatomaceous sediments tend to fail by liquefaction although well-established relations between index properties and liquefaction susceptibility predict the opposite. Liquefaction failure is observed solely in samples containing ≥ 50% diatoms whereas samples with lower diatom content fail by cyclic softening. We conclude diatom microfossils in marine sediments significantly contribute to an increased slope stability under static and cyclic loading conditions since diatoms lead to higher resistance independently of the loading mode. The strength increase is interpreted as a result of particle interlocking and surface roughness, which is very efficient given the highly variable habitus of diatom species.

  9. [Sizes of soil macropores and related main affecting factors on a vegetated basalt slope].

    PubMed

    Guan, Qi; Xu, Ze-Min; Tian, Lin

    2013-10-01

    The landslide on vegetated slopes caused by extreme weather has being increased steadily, and the preferential flow in soil macropores plays an important role in the landslide. By using water breakthrough curve and Poiseuille equation, this paper estimated the radius range, amount, and average volume of soil macropores on a vegetated basalt slope of Maka Mountain, Southwest China, and analyzed the distribution of the soil macropores and the main affecting factors. In the study area, the radius of soil macropores ranged from 0.3 to 1.8 mm, mainly between 0.5 and 1.2 mm. The large-radius macropores (1.4-1.8 mm) were lesser, while the small-radius macropores (< 1.4 mm) were more. With the development of soil profile, soil macropores were more in upper layers and lesser in deeper layers. The average volume of the macropores contributed 84.7% to the variance of steady effluent rate. Among the factors affecting the average volume of the large macropores, vegetations root mass had a linear relationship, with the correlation coefficient being 0.70, and soil organic matter content also had a linear relationship, with the correlation coefficient being 0.64.

  10. Integration of complex models for slope stability and landslide runout with GIS

    NASA Astrophysics Data System (ADS)

    Mergili, M.; Schratz, K.; Ostermann, A.; Fellin, W.

    2009-04-01

    Geographic Information Systems (GIS) are common tools for landslide susceptibility and hazard analysis on various spatial scales, from global to local. Complex multivariate statistical methods are successfully used in combination with GIS for studies of landslide susceptibility at the regional scale. In contrast, relatively simple deterministic or semi-deterministic methods are often employed for detailed studies at the local scale (for example infinite slope stability models or two-parameter friction models for runout). These methods, however, are inappropriate in many cases, and more complex approaches would be required instead. The main reasons for the scarcity of more advanced GIS-based deterministic modelling tools are that (a) in contrast to many statistical methods, which, though mathematically complex, rely on the simple overlay of maps, deterministic models for slope stability or landslide motion are often geometrically complex, and (b) that many deterministic models are expressed in non-rectangular coordinate systems. Whilst these, chosen by engineers, physicians, or mathematicians, are adequate for the problems to be solved, they seem to discourage geoinformation scientists. The work presented here is understood as an attempt to overcome these problems by involving geoinformation scientists, engineers, and mathematicians in a common project. The following two gaps were attacked: (1) A GIS-based model for rotational slope failures. Infinite slope stability models, which are frequently used in combination with GIS, are suitable for the identification of shallow translational slope failures. Theoretically, they are only valid for cohesionless soil and a constant inclination of the slope. They fail for deep-seated rotational failures. Being more complex from a geometrical point of view, rotational failures are usually modelled based on a pre-defined longitudinal section, assuming a circular or elliptical slip surface. The most critical slip surface is often

  11. The effect of season on the slope stability analysis: Case study at UNNES building, Semarang - Indonesia

    NASA Astrophysics Data System (ADS)

    Qudus, Nur; Kusumawardani, Rini; Chew, Boon Cheong; Lestari, Nur Dhini

    2017-03-01

    A slope assessment to predict the probability of landslide occurrence and the safety factor of landslide at E9 building, Home Economics Department, Universitas Negeri Semarang was conducted to obtain a safety factor index of slope and structures in study area. A rupture of soil surface appeared in some parts of the study area. It indicated an initial destruction of structure and infrastructure. Differential settlements occurred in north side of building. Therefore, a downward movement of soil, rock mass and debris to the slope direction was identified as an initial hypotheses. The influence of season was analyzed in this paper. A combination of LHZ method and numerical analysis by Plaxis version 9.2 was utilized for the predicted behavior of soil movement and the safety factor. The results of analysis revealed that the safety factor in the wet season reached 1.0635 and in the dry season reached 1.075. From this results, it can be concluded that the influence of season parameter of the season did not affect for the possibility of landslide in this area.

  12. How to model the stability of terraced slopes? The case study of Tresenda (northern Italy)

    NASA Astrophysics Data System (ADS)

    Camera, Corrado; Apuani, Tiziana; Masetti, Marco

    2015-04-01

    Terraces are very common morphological features all around the Mediterranean Basin. They have been built to adapt the natural morphology of the territory to the development of anthropogenic activities, particularly agriculture. However, the increasing land abandonment during the last century is leading to soil degradation and stability issues, mainly due to lack of maintenance of these peculiar environments. The objective of this study was to develop a coupled hydrologic-stability model to identify possible triggering areas of superficial landslides during intense rainfall events. The model was tested on a slope uphill of the village of Tresenda, in Northern Italy, which experienced several superficial landslides in the last 35 years. Distributed stability analyses are usually carried out using an infinite slope approach, but in the case of terraces some basic assumptions of this method fail: the parallelism between topographical surface and potential sliding surface and the high ratio between slope length and failure surface depth are the most important examples. In addition, the interest is more on the stability of the terrace system (dry stone retaining wall and backfill soil) and not on soil alone. For these reasons, a stability analysis based on the global method of equilibrium is applied and soft coupled to a well know hydrological model (STARWARS). Sections of terrace, one cell wide, are recognized from the base of a wall to the top of the closest downstream one, and each cell (1 x 1 m2) is considered as a slice. The method of Sarma for circular and non-circular failure is applied. The very fine horizontal resolution (1 m) is crucial to take into consideration the hydrogeological and mechanical properties of dry stone walls (0.6-1.0 m wide). A sensitivity analysis was conducted for saturated water content, initial volumetric water content, the cohesion and friction angle of soil and walls and soil depth. The results of the sensitivity analysis showed that

  13. Design of anti-slide piles for slope stabilization in Wanzhou city, Three Gorges Area, China

    NASA Astrophysics Data System (ADS)

    Zhou, Chunmei; van Westen, Cees

    2013-04-01

    This study is related to the design of anti-slide piles for several landslides in Wanzhou city located in the Three Gorges area. Due to the construction of the Three Gorges Reservoir the hydro-geological conditions in this area have deteriorated significantly, leading to larger instability problems. China has invested a lot of money in slope stabilization measures for the treatment of landslides in the Three Gorges area. One of the methods for the stabilization of large landslides is the design of anti-sliding piles. This paper focuses on extensive slope stability analysis and modeling of the mechanical behavior of the landslide masses, and the parameters required for designing the number, size and dimensions of reinforced concrete stabilization piles. The study focuses on determining the rock parameters, anchor depth, and the pile and soil interaction coefficient. The study aims to provide guidelines for anti-slide pile stabilization works for landslides in the Wanzhou area. The research work contains a number of aspects. First a study is carried out on the distribution of pressures expected on the piles, using two different methods that take into account the expected pore water pressure and seismic acceleration. For the Ercengyan landslide , the Limit Equilibrium Method and Strength Reduction Method of FEM are compared through the results of the landslide pressure distributions on the piles and stress fields in the piles. The second component is the study of the required anchor depth of antislide piles, which is carried out using a statistical analysis with data from 20 landslides that have been controlled with anti-sliding piles. The rock characteristics of the anchor locations were obtained using laboratory tests, and a classification of rock mass quality is made for the anchors of antislide piles. The relationship between the critical anchor height and the angle of the landslide slip surface is determined. Two different methods are presented for the length

  14. Elucidating the mechanical effects of pore water pressure increase on the stability of unsaturated soil slopes

    NASA Astrophysics Data System (ADS)

    Buscarnera, G.

    2012-12-01

    The increase of the pore water pressure due to rain infiltration can be a dominant component in the activation of slope failures. This paper shows an application of the theory of material stability to the triggering analysis of this important class of natural hazards. The goal is to identify the mechanisms through which the process of suction removal promotes the initiation of mechanical instabilities. The interplay between increase in pore water pressure, and failure mechanisms is investigated at material point level. In order to account for multiple failure mechanisms, the second-order work criterion is used and different stability indices are devised. The paper shows that the theory of material stability can assess the risk of shear failure and static liquefaction in both saturated and unsaturated contexts. It is shown that the combined use of an enhanced definition of second-order work for unsaturated porous media and a hydro-mechanical constitutive framework enables to retrieve bifurcation conditions for water-infiltration processes in unsaturated deposits. This finding discloses the importance of the coupling terms that incorporate the interaction between the solid skeleton and the pore fluids. As a consequence, these theoretical results suggest that some material properties that are not directly associated with the shearing resistance (e.g., the potential for wetting compaction) can play an important role in the initiation of slope failures. According to the proposed interpretation, the process of pore pressure increase can be understood as a trigger of uncontrolled strains, which at material point level are reflected by the onset of bifurcation conditions.

  15. A Preliminary Design of a Calibration Chamber for Evaluating the Stability of Unsaturated Soil Slope

    NASA Astrophysics Data System (ADS)

    Hsu, H.-H.

    2012-04-01

    The unsaturated soil slopes, which have ground water tables and are easily failure caused by heavy rainfalls, are widely distributed in the arid and semi-arid areas. For analyzing the stability of slope, in situ tests are the direct methods to obtain the test site characteristics. The cone penetration test (CPT) is a popular in situ test method. Some of the CPT empirical equations established from calibration chamber tests. The CPT performed in calibration chamber was commonly used clean quartz sand as testing material in the past. The silty sand is observed in many actual slopes. Because silty sand is relatively compressible than quartz sand, it is not suitable to apply the correlations between soil properties and CPT results built from quartz sand to silty sand. The experience on CPT calibration in silty sand has been limited. CPT calibration tests were mostly performed in dry or saturated soils. The condition around cone tip during penetration is assumed to be fully drained or fully undrained, yet it was observed to be partially drained for unsaturated soils. Because of the suction matrix has a great effect on the characteristics of unsaturated soils, they are much sensitive to the water content than saturated soils. The design of an unsaturated calibration chamber is in progress. The air pressure is supplied from the top plate and the pore water pressure is provided through the high air entry value ceramic disks located at the bottom plate of chamber cell. To boost and uniform distribute the unsaturated effect, four perforated burettes are installed onto the ceramic disks and stretch upwards to the midheight of specimen. This paper describes design concepts, illustrates this unsaturated calibration chamber, and presents the preliminary test results.

  16. Scoops3D: software to analyze 3D slope stability throughout a digital landscape

    USGS Publications Warehouse

    Reid, Mark E.; Christian, Sarah B.; Brien, Dianne L.; Henderson, Scott T.

    2015-01-01

    The computer program, Scoops3D, evaluates slope stability throughout a digital landscape represented by a digital elevation model (DEM). The program uses a three-dimensional (3D) method of columns approach to assess the stability of many (typically millions) potential landslides within a user-defined size range. For each potential landslide (or failure), Scoops3D assesses the stability of a rotational, spherical slip surface encompassing many DEM cells using a 3D version of either Bishop’s simplified method or the Ordinary (Fellenius) method of limit-equilibrium analysis. Scoops3D has several options for the user to systematically and efficiently search throughout an entire DEM, thereby incorporating the effects of complex surface topography. In a thorough search, each DEM cell is included in multiple potential failures, and Scoops3D records the lowest stability (factor of safety) for each DEM cell, as well as the size (volume or area) associated with each of these potential landslides. It also determines the least-stable potential failure for the entire DEM. The user has a variety of options for building a 3D domain, including layers or full 3D distributions of strength and pore-water pressures, simplistic earthquake loading, and unsaturated suction conditions. Results from Scoops3D can be readily incorporated into a geographic information system (GIS) or other visualization software. This manual includes information on the theoretical basis for the slope-stability analysis, requirements for constructing and searching a 3D domain, a detailed operational guide (including step-by-step instructions for using the graphical user interface [GUI] software, Scoops3D-i) and input/output file specifications, practical considerations for conducting an analysis, results of verification tests, and multiple examples illustrating the capabilities of Scoops3D. Easy-to-use software installation packages are available for the Windows or Macintosh operating systems; these packages

  17. Species type controls root strength and influences slope stability in coastal Ecuador

    NASA Astrophysics Data System (ADS)

    Anttila, E.; Wray, M. E.; Knappe, E.; Ogasawara, T.; Tholt, A.; Cliffe, B.; Oshun, J.

    2014-12-01

    Tree roots, particular those of old growth trees, provide significant cohesive strength that can prevent shallow landslides. Little is known about the root strength of trees growing in dry tropical forests. In 1997, Bahía de Caráquez, Ecuador experienced a large landslide, which may have been precipitated by massive deforestation along the Ecuadorian coast. We used a tensile spring apparatus combined with root maps to caclulate the cohesive strength of different native species of trees. Whereas the results show the previously reported power law relationship between root diameter and tensile strength, our data also reveals new contributions. First, we find that trees have far stronger and more abundant roots than neighboring bushes, and thus add far more cohesive strength to the hillslope. Furthermore, there is a wide range of tensile strength among the native trees measured, with algarrobo having the strongest roots, and ceibo gernally being weak rooted. Finally, we use a slope stability model to predict failure conditions considering the strength added to a hillslope if vegetation is predominantly composed of bushes, algarrobo, or ceibo. Our results, which are the first of their kind for the Ecuadorian dry tropical forest, will be used to guide the ongoing native reforestation efforts of Global Student Embassy. Our unique partnership with Global Student Embassy connects our field study to practical land use decisions that will lead to increased slope and decreased human danger along coastal Ecuador's dry tropical forest.

  18. Slope and bank erosional stability of the Canonsburg, Pennsylvania, UMTRA disposal site

    SciTech Connect

    Not Available

    1994-12-01

    This report was prepared in response to US Nuclear Regulatory Commission (NRC) comments received in a letter of 8 March 1994. This letter included discussions of the US Department of Energy (DOE) 21 May 1993 geomorphic report for the Canonsburg, Pennsylvania, site. To clarify the NRC`s position, a DOE/NRC conference call was held on 12 April 1994. The NRC clarified that it did not require a preliminary erosion protection design for the Canonsburg site, but directed the DOE to address a ``one-bad-year`` scenario. The NRC wants confirmation that one bad year of stream flooding and landsliding will not release residual radioactive material (RRM) from the Canonsburg site into the creek. The NRC is concerned that a bad year theoretically could occur between postcell-closure inspections. These annual inspections are conducted in September or October. The NRC suggested that the following procedures should be conducted in this analysis: a flooding analysis, including the maximum saturation levels (flood water elevations) anticipated during a 100-year flood; a stream bank erosion analysis to determine how much of the bank adjacent to the site may be removed in a bad year; a slope stability analysis to determine how far back the site would be disturbed by slope instability that could be triggered by a bad year of stream bank erosion; and a ``critical cross section`` study to show the relationship of the RRM located outside the disposal cell to the maximum computer estimated erosion/landslide activity.

  19. Seismic imaging of a slope stability mitigation project at Newby Island Sanitary Landfill, San Jose, California

    NASA Astrophysics Data System (ADS)

    Treece, B.; Catchings, R.; Reed, D.; Goldman, M.

    2013-12-01

    Seismic reflection and refraction data were obtained along a transect through a slope stability mitigation project involving deep soil mixing at Newby Island Sanitary Landfill in San Jose, California. Deep soil mixing involves the simultaneous injection of a cement slurry while rotating augers advance vertically down through the subsurface material, resulting in groups of soil-cement columns (elements) intended to increase the strength and rigidity of the treated area. Seismic data were used to analyze the effectiveness of the mitigation procedure, approximately one month after the completion of the deep soil mixing project. Repeated accelerated-weight-drop (AWD) impacts provided the seismic source at each geophone location. Seismic arrivals were recorded with 40-Hz vertical-component geophones, spaced at 3-m intervals. All shots were recorded on all channels. This shooting geometry was designed to produce tomographic refraction (velocity) and reflection (CDP stacks) images from a yet to be mitigated area into the mitigated area, along the base of a steep slope composed of compacted landfill. The acquired data were generally of good quality, with shots propagating the entire length of the profile. An initial analysis of the data shows an increase in seismic velocity in the treated areas compared with non-treated areas, and a relative seismic velocity increase with curing time for soil-cement elements. Future surveys will be collected to further constrain strength increases with time, and to correlate calculated rates of strength with other subsurface data.

  20. A shallow landslide analysis method consisting of contour line based method and slope stability model with critical slip surface

    NASA Astrophysics Data System (ADS)

    Tsutsumi, D.

    2015-12-01

    To mitigate sediment related disaster triggered by rainfall event, it is necessary to predict a landslide occurrence and subsequent debris flow behavior. Many landslide analysis method have been developed and proposed by numerous researchers for several decades. Among them, distributed slope stability models simulating temporal and spatial instability of local slopes are more essential for early warning or evacuation in area of lower part of hill-slopes. In the present study, a distributed, physically based landslide analysis method consisting of contour line-based method that subdivide a watershed area into stream tubes, and a slope stability analysis in which critical slip surface is searched to identify location and shape of the most instable slip surface in each stream tube, is developed. A target watershed area is divided into stream tubes using GIS technique, grand water flow for each stream tubes during a rainfall event is analyzed by a kinematic wave model, and slope stability for each stream tube is calculated by a simplified Janbu method searching for a critical slip surface using a dynamic programming method. Comparing to previous methods that assume infinite slope for slope stability analysis, the proposed method has advantage simulating landslides more accurately in spatially and temporally, and estimating amount of collapsed slope mass, that can be delivered to a debris flow simulation model as a input data. We applied this method to a small watershed in the Izu Oshima, Tokyo, Japan, where shallow and wide landslides triggered by heavy rainfall and subsequent debris flows attacked Oshima Town, in 2013. Figure shows the temporal and spatial change of simulated grand water level and landslides distribution. The simulated landslides are correspond to the uppermost part of actual landslide area, and the timing of the occurrence of landslides agree well with the actual landslides.

  1. A genetic algorithm for slope stability analyses with concave slip surfaces using custom operators

    NASA Astrophysics Data System (ADS)

    Jurado-Piña, Rafael; Jimenez, Rafael

    2015-04-01

    Heuristic methods are popular tools to find critical slip surfaces in slope stability analyses. A new genetic algorithm (GA) is proposed in this work that has a standard structure but a novel encoding and generation of individuals with custom-designed operators for mutation and crossover that produce kinematically feasible slip surfaces with a high probability. In addition, new indices to assess the efficiency of operators in their search for the minimum factor of safety (FS) are proposed. The proposed GA is applied to traditional benchmark examples from the literature, as well as to a new practical example. Results show that the proposed GA is reliable, flexible and robust: it provides good minimum FS estimates that are not very sensitive to the number of nodes and that are very similar for different replications.

  2. Applying Distributed, Coupled Hydrological Slope-Stability Models for Landslide Hazard Assessments

    NASA Astrophysics Data System (ADS)

    Godt, J. W.; Baum, R. L.; Lu, N.; Savage, W. Z.; McKenna, J. P.

    2006-12-01

    Application of distributed, coupled hydrological slope-stability models requires knowledge of hydraulic and material-strength properties at the scale of landslide processes. We describe results from a suite of laboratory and field tests that were used to define the soil-water characteristics of landslide-prone colluvium on the steep coastal bluffs in the Seattle, Washington area and then use these results in a coupled model. Many commonly used tests to determine soil-water characteristics are performed for the drying process. Because most soils display a pronounced hysteresis in the relation between moisture content and matric suction, results from such tests may not accurately describe the soil-water characteristics for the wetting process during rainfall infiltration. Open-tube capillary-rise and constant-flow permeameter tests on bluff colluvium were performed in the laboratory to determine the soil-water characteristic curves (SWCC) and unsaturated hydraulic conductivity functions (HCF) for the wetting process. Field-tests using a borehole permeameter were used to determine the saturated hydraulic conductivity of colluvial materials. Measurements of pore-water response to rainfall were used in an inverse numerical modeling procedure to determine the in-situ hydraulic parameters of hillside colluvium at the scale of the instrument installation. Comparison of laboratory and field results show that although both techniques generally produce SWCCs and HCFs with similar shapes, differences in bulk density among field and lab tests yield differences in saturated moisture content and saturated hydrologic conductivity. We use these material properties in an application of a new version of a distributed transient slope stability model (TRIGRS) that accounts for the effects of the unsaturated zone on the infiltration process. Applied over a LiDAR-based digital landscape of part of the Seattle area for an hourly rainfall history known to trigger shallow landslides, the

  3. Factors Affecting Lateral Stability and Controllability

    NASA Technical Reports Server (NTRS)

    Campbell, John P; Toll, Thomas A

    1948-01-01

    The effects on dynamic lateral stability and controllability of some of the important aerodynamic and mass characteristics are discussed and methods are presented for estimating the various stability parameters to be used in the calculation of the dynamic lateral stability of airplanes with swept and low-aspect-ratio wings.

  4. Simulation of long-term debris flow sediment transport based on a slope stability and a debris flow routing model

    NASA Astrophysics Data System (ADS)

    Müller, T.; Hoffmann, T.

    2012-04-01

    Debris flows play a crucial role in the coupling of hillslope-sediment sources and channels in mountain environments. In most landscape evolution models (LEMs), the sediment transport by debris flows is (if at all) often represented by simple empirical rules. This generally results from the mismatch of the coarse resolution of the LEMs and the small scale impacts of debris flow processes. To extend the accuracy and predictive power of LEMs, either a higher resolution of LEMs in combination with process-based debris flow models or a better parametrisation of subpixel scale debris flow processes is necessary. Furthermore, the simulation of sediment transport by debris flows is complicated by their episodic nature and unknown factors controlling the frequency and magnitude of events. Here, we present first results using a slope stability model (SINMAP) and an event-based debris flow routing model (SCIDDICA-S4c) to simulate the effects of debris flows in LEMs. The model was implemented in the XULU modelling platform developed by the Department of Computer Science at the University of Bonn. The combination of the slope stability model and the event-based routing and mass balance model enables us to simulate the triggering and routing of debris flow material through the iteration of single events over several thousand years. Although a detailed calibration and validation remains to be done, the resulting debris flow-affected areas in a test elevation model correspond well with data gained from a geomorphological mapping of the corresponding area, justifying our approach. The increased computation speed allows to run high resolution LEM in convenient short time at relatively low cost. This should encourage the development of more detailed LEMs, in which process-based models should be incorporated.

  5. The effects of trait and state affect on diurnal cortisol slope among children affected by parental HIV/AIDS in rural China.

    PubMed

    Chen, Lihua; Chi, Peilian; Li, Xiaoming; Zilioli, Samuele; Zhao, Junfeng; Zhao, Guoxiang; Lin, Danhua

    2016-12-28

    Affect is believed to be one of the most prominent proximal psychological pathway through which more distal psychosocial factors influence physiology and ultimately health. The current study examines the relative contributions of trait affect and state affect to the hypothalamic-pituitary-adrenal axis activity, with particular focus on cortisol slope, in children affected by parental HIV/AIDS. A sample of 645 children (8-15 years old) affected by parental HIV/AIDS in rural China completed a multiple-day naturalistic salivary cortisol protocol. Trait and state affect, demographics, and psychosocial covariates were assessed via self-report. Hierarchical linear modeling was used for estimating the effects of trait affect and state affect on cortisol slope. Confidence intervals for indirect effects were estimated using the Monte Carlo method. Our results indicated that both trait and state negative affect (NA) predicted flatter (less "healthy") diurnal cortisol slopes. Subsequent analyses revealed that children's state NA mediated the effect of their trait NA on diurnal cortisol slope. The same relationships did not emerge for trait and state positive affect. These findings provide a rationale for future interventions that target NA as a modifiable antecedent of compromised health-related endocrine processes among children affected by parental HIV/AIDS.

  6. Workflow for the fast evaluation of rock mass properties and stability of rock slopes along trafficways in Lower Austria

    NASA Astrophysics Data System (ADS)

    Straka, Wolfgang; Zangerl, Christian

    2016-04-01

    In Lower Austria there is a total of 17.000 km of provincial and 24.000 km of communal roads, to be maintained by the province and the municipalities. In addition, there are approx. 1.500 km of railroads, and the Danube as a major waterway. A large part of this infrastructure is, or is potentially, affected by various types of instability of adjacent slopes. Due to insufficient knowledge, as well as slope design and management practice in the past, every year, especially in connection to weather extremes, slopes known to be critical become active landslides again, and unexpected new ones arise, causing damage as well as financial stress. Engineering intervention, if possible, should be quick and effective. Geologists and engineers in public service, not having the means for detailed investigation in most cases, are using guidelines to assess the requirements to be met by slope design on traffic ways. But these guidelines don't reflect many of the newer scientific advances. Therefore, scientists at BOKU and backers in the administration want to gain more insight into causative factors, which, if successful, may render maintenance of traffic lines under critical conditions more effective and predictable. The specific project goal is to produce new guidelines to allow quick assessment of the most likely behaviour of rock masses common in the area, especially when cut into shape along infrastructure lines, using readily available information. The scientific investigations include simple and ready tests (like Schmidt hammer), as well as photogrammetry, laserscanning, and other complex geophysical and numerical techniques, but the final product (guidelines) is expected to work without such difficult methods. It is important to note, on the other hand, that the rock mass stability classification inherent in the new guidelines must allow distinction between conclusions which are safe, and conjectures which are in need of validation by contracted experts. It is planned to

  7. The horizontal transport of pollutants from a slope wind layer into the valley core as a function of atmospheric stability

    NASA Astrophysics Data System (ADS)

    Leukauf, Daniel; Gohm, Alexander; Rotach, Mathias W.; Posch, Christian

    2016-04-01

    Slope winds provide a mechanism for the vertical exchange of air between the valley and the free atmosphere aloft. By this means, heat, moisture and pollutants are exported or imported. However, it the static stability of the valley atmosphere is strong, one part of the up-slope flow is redirected towards the valley center and pollutants are recirculated within the valley. This may limit the venting potential of slope winds severely. The main objective of this study is to quantify the horizontal transport of pollutants from the slope wind layer into the stable valley core and to determine the dependency of this flux as a function of the initial stability of the atmosphere. For this purpose, we conducted large eddy simulations with the Weather Research and Forecasting (WRF) model for a quasi-two-dimensional valley. The valley geometry consists of two slopes with constant slope angle rising to a crest height of 1500 m and a 4 km wide flat valley floor in between. The valley is 20 km long and homogeneous in along-valley direction. Hence, only slope winds but no valley winds can evolve. The surface sensible heat flux is prescribed by a sine function with an amplitude of 125 W m-2. The initial sounding characterized by an atmosphere at rest and by a constant Brunt-Väisälä frequency which is varied between 0.006 s-1 and 0.02 s-1. A passive tracer is released with an arbitrary but constant rate at the valley floor. As expected, the atmospheric stability has a strong impact on the vertical and horizontal transport of tracer mass. A horizontal intrusion forms at the top of the mixed layer due to outflow from the slope wind layer. Tracer mass is transported from the slope towards the center of the valley. The efficiency of this mechanism increases with increasing stability N. For the lowest value of N, about 70% of the tracer mass released at the valley bottom is exported out of the valley. This value drops to about 12% in the case of the strongest stability. Hence, most

  8. Geotechnical properties and preliminary assessment of sediment stability on the continental slope of the northwestern Alboran Sea

    USGS Publications Warehouse

    Baraza, J.; Ercilla, G.; Lee, H.J.

    1992-01-01

    Laboratory analysis of core samples from the western Alboran Sea slope reveal a large variability in texture and geotechnical properties. Stability analysis suggests that the sediment is stable under static gravitational loading but potentially unstable under seismic loading. Slope failures may occur if horizontal ground accelerations greater than 0.16 g are seismically induced. The, Alboran Sea is an active region, on which earthquakes inducing accelerations big enough to exceed the shear strength of the soft soil may occur. Test results contrast with the apparent stability deduced from seismic profiles. ?? 1992 Springer-Verlag New York Inc.

  9. Constraints on mechanisms for the growth of gully alcoves in Gasa crater, Mars, from two-dimensional stability assessments of rock slopes

    USGS Publications Warehouse

    Okubo, C.H.; Tornabene, L.L.; Lanza, N.L.

    2011-01-01

    The value of slope stability analyses for gaining insight into the geologic conditions that would facilitate the growth of gully alcoves on Mars is demonstrated in Gasa crater. Two-dimensional limit equilibrium methods are used in conjunction with high-resolution topography derived from stereo High Resolution Imaging Science Experiment (HiRISE) imagery. These analyses reveal three conditions that may produce observed alcove morphologies through slope failure: (1) a ca >10m thick surface layer that is either saturated with H2O ground ice or contains no groundwater/ice at all, above a zone of melting H2O ice or groundwater and under dynamic loading (i.e., seismicity), (2) a 1-10m thick surface layer that is saturated with either melting H2O ice or groundwater and under dynamic loading, or (3) a >100m thick surface layer that is saturated with either melting H2O ice or groundwater and under static loading. This finding of three plausible scenarios for slope failure demonstrates how the triggering mechanisms and characteristics of future alcove growth would be affected by prevailing environmental conditions. HiRISE images also reveal normal faults and other fractures tangential to the crowns of some gully alcoves that are interpreted to be the result of slope instability, which may facilitate future slope movement. Stability analyses show that the most failure-prone slopes in this area are found in alcoves that are adjacent to crown fractures. Accordingly, crown fractures appear to be a useful indicator of those alcoves that should be monitored for future landslide activity. ?? 2010.

  10. Spatial pattern of soil moisture and its temporal stability within profiles on a loessial slope in northwestern China

    NASA Astrophysics Data System (ADS)

    Jia, Yu-Hua; Shao, Ming-An; Jia, Xiao-Xu

    2013-07-01

    Temporal stability of spatial distributions of soil moisture are usually observed after repeated surveys of soil moisture across an area. To understand how temporal stability of soil moisture varied with soil depth under the combined influences of vegetation and local topography, we collected soil moisture data at intervals of 10 cm within 1-m profiles on a loessial slope in China in four plots (61 m × 5 m) under different types of vegetation (Korshinsk peashrub, KOP; purple alfalfa, ALF; natural fallow, NAF; millet, MIL). Measurements of soil water content were made by neutron probes on 15 occasions between 2010 and 2012. Soil moisture distributions in both the vertical and horizontal dimensions were investigated to describe its spatial pattern and to lay the groundwork for better understanding its temporal stability characteristics. The results indicated that: (1) soil moisture presented different vertical but similar horizontal trends in the four plots, with significant correlations of soil moisture occurring primarily among adjacent soil layers irrespective of vegetation types, mostly in soil profiles under KOP and ALF and less frequently in soil profiles under NAF and MIL; (2) based on Spearman rank correlation coefficients, with increasing depth temporal stability generally increased under KOP and MIL, but first increased and then decreased under ALF, and increased after the first three measurements under NAF; (3) based on the relative difference technique, points with extreme moisture tended to remain representative at more depths than did points with average moisture and their time stability increased with increasing soil depth; and (4) the correlation between MRD (mean relative differences) and the wetness index weakened with soil depth. The relationship between SDRD (the standard deviation of MRD) and the wetness index varied nonlinearly with soil depth. Vegetation type, soil depth and the wetness index, in descending order of influence, had significant

  11. Assessment of rock mechanical properties and seismic slope stability in variably weathered layered basalts

    NASA Astrophysics Data System (ADS)

    Greenwood, William; Clark, Marin; Zekkos, Dimitrios; Von Voigtlander, Jennifer; Bateman, Julie; Lowe, Katherine; Hirose, Mitsuhito; Anderson, Suzanne; Anderson, Robert; Lynch, Jerome

    2016-04-01

    A field and laboratory experimental study was conducted to assess the influence of weathering on the mechanical properties of basalts in the region of the Kohala volcano on the island of Hawaii. Through the systematic characterization of the weathering profiles developed in different precipitation regimes, we aim to explain the regional pattern of stability of slopes in layered basalts that were observed during the 2006 Mw 6.7 Kiholo Bay earthquake. While deeper weathering profiles on the wet side of the island might be expected to promote more and larger landslides, the distribution of landslides during the Kiholo Bay earthquake did not follow this anticipated trend. Landslide frequency (defined as number of landslides divided by total area) was similar on the steepest slopes (> 50-60) for both the dry and the wet side of the study area suggesting relatively strong ground materials irrespective of weathering. The study location is ideally suited to investigate the role of precipitation, and more broadly of climate, on the mechanical properties of the local rock units because the presence of the Kohala volcano produces a significant precipitation gradient on what are essentially identical basaltic flows. Mean annual precipitation (MAP) varies by more than an order of magnitude, from 200 mm/year on the western side of the volcano to 4000 mm/year in the eastern side. We will present results of measured shear wave velocities using a seismic surface wave methodology. These results were paired with laboratory testing on selected basalt specimens that document the sample-scale shear wave velocity and unconfined compressive strength of the basaltic rocks. Shear wave velocity and unconfined strength of the rocks are correlated and are both significantly lower in weathered rocks near the ground surface than at depth. This weathering-related reduction in shear wave velocity extends to greater depths in areas of high precipitation compared to areas of lower precipitation

  12. Integrating the effects of forest cover on slope stability in a deterministic landslide susceptibility model (TRIGRS 2.0)

    NASA Astrophysics Data System (ADS)

    Zieher, T.; Rutzinger, M.; Bremer, M.; Meissl, G.; Geitner, C.

    2014-12-01

    The potentially stabilizing effects of forest cover in respect of slope stability have been the subject of many studies in the recent past. Hence, the effects of trees are also considered in many deterministic landslide susceptibility models. TRIGRS 2.0 (Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability; USGS) is a dynamic, physically-based model designed to estimate shallow landslide susceptibility in space and time. In the original version the effects of forest cover are not considered. As for further studies in Vorarlberg (Austria) TRIGRS 2.0 is intended to be applied in selected catchments that are densely forested, the effects of trees on slope stability were implemented in the model. Besides hydrological impacts such as interception or transpiration by tree canopies and stems, root cohesion directly influences the stability of slopes especially in case of shallow landslides while the additional weight superimposed by trees is of minor relevance. Detailed data on tree positions and further attributes such as tree height and diameter at breast height were derived throughout the study area (52 km²) from high-resolution airborne laser scanning data. Different scenarios were computed for spruce (Picea abies) in the study area. Root cohesion was estimated area-wide based on published correlations between root reinforcement and distance to tree stems depending on the stem diameter at breast height. In order to account for decreasing root cohesion with depth an exponential distribution was assumed and implemented in the model. Preliminary modelling results show that forest cover can have positive effects on slope stability yet strongly depending on tree age and stand structure. This work has been conducted within C3S-ISLS, which is funded by the Austrian Climate and Energy Fund, 5th ACRP Program.

  13. A hybrid method for quasi-three-dimensional slope stability analysis in a municipal solid waste landfill

    SciTech Connect

    Yu, L.; Batlle, F.

    2011-12-15

    Highlights: > A quasi-three-dimensional slope stability analysis method was proposed. > The proposed method is a good engineering tool for 3D slope stability analysis. > Factor of safety from 3D analysis is higher than from 2D analysis. > 3D analysis results are more sensitive to cohesion than 2D analysis. - Abstract: Limited space for accommodating the ever increasing mounds of municipal solid waste (MSW) demands the capacity of MSW landfill be maximized by building landfills to greater heights with steeper slopes. This situation has raised concerns regarding the stability of high MSW landfills. A hybrid method for quasi-three-dimensional slope stability analysis based on the finite element stress analysis was applied in a case study at a MSW landfill in north-east Spain. Potential slides can be assumed to be located within the waste mass due to the lack of weak foundation soils and geosynthetic membranes at the landfill base. The only triggering factor of deep-seated slope failure is the higher leachate level and the relatively high and steep slope in the front. The valley-shaped geometry and layered construction procedure at the site make three-dimensional slope stability analyses necessary for this landfill. In the finite element stress analysis, variations of leachate level during construction and continuous settlement of the landfill were taken into account. The 'equivalent' three-dimensional factor of safety (FoS) was computed from the individual result of the two-dimensional analysis for a series of evenly spaced cross sections within the potential sliding body. Results indicate that the hybrid method for quasi-three-dimensional slope stability analysis adopted in this paper is capable of locating roughly the spatial position of the potential sliding mass. This easy to manipulate method can serve as an engineering tool in the preliminary estimate of the FoS as well as the approximate position and extent of the potential sliding mass. The result that Fo

  14. Coir geotextile for slope stabilization and cultivation - A case study in a highland region of Kerala, South India

    NASA Astrophysics Data System (ADS)

    Vishnudas, Subha; Savenije, Hubert H. G.; Van der Zaag, Pieter; Anil, K. R.

    A sloping field is not only vulnerable to soil erosion it may also suffer from soil moisture deficiency. Farmers that cultivate on slopes everywhere face similar problems. Conservation technologies may reduce soil and nutrient losses, and thus enhance water holding capacity and soil fertility. But although these technologies promote sustainable crop production on steep slopes, the construction of physical structure such as bench terraces are often labour intensive and expensive to the farmers, since construction and maintenance require high investments. Here we studied the efficiency of coir geotextile with and without crop cultivation in reducing soil moisture deficiency on marginal slopes in Kerala, India. From the results it is evident that the slopes treated with geotextile and crops have the highest moisture retention capacity followed by geotextiles alone, and that the control plot has the lowest moisture retention capacity. As the poor and marginal farmers occupy the highland region, this method provides an economically viable option for income generation and food security along with slope stabilization.

  15. Alaskan Beaufort Sea Heat Flow and Ocean Temperature Analysis: Implications for Stability of Climate-Sensitive Continental Slope Gas Hydrates

    NASA Astrophysics Data System (ADS)

    Phrampus, B. J.; Hornbach, M. J.; Ruppel, C. D.; Hart, P. E.

    2013-12-01

    Based on USGS estimates, gas hydrates beneath the continental slope of the US Beaufort Sea sequester several gigatons of methane. Warming of Beaufort Sea intermediate waters has the potential to cause dissociation of upper slope gas hydrates, release of methane to the overlying water column, and the buildup of pore pressure in slope sediments in an area first used by Kayen and Lee (1991) as the archetype for linked gas hydrate dynamics and slope failures. Limited constraints on regional heat flow, ocean temperature variability, and the extent of methane hydrates across the region have made analysis of Beaufort continental slope gas hydrate system difficult. Using legacy USGS seismic data combined with a new 3D thermal refraction model and more than 30 years of ocean temperature measurements, we analyze the stability of Beaufort continental slope methane hydrates. Our analysis provides the first regional heat flow map of the Alaskan shelf and margin, a detailed >30 year assessment of ocean temperature change in this region, and the first map revealing where disequilibrium methane hydrate stability conditions exist in the Western Beaufort Sea. Our results show that heat flow is complex and highly variable across the Beaufort margin, that intermediate ocean temperatures have warmed steadily for more than 30 years, and that the gas hydrates on the upper slope are out of equilibrium with overlying intermediate waters over large parts of the area. The discrepancy between observed and predicted hydrate stability depths is best explained by significant (>1 degC) intermediate ocean warming since the last glacial maximum. Even in the absence of persistent ocean warming conditions in the near future, the results predict destabilization of gas hydrates underlying an area ranging from ~4,750 km2 to ~30,000 km2 on the US Beaufort continental slope over the next 100 years. A fraction of the methane released by these gas hydrates may be emitted at seafloor seeps and contribute to

  16. Assessing deep-seated landslide susceptibility using 3-D groundwater and slope-stability analyses, southwestern Seattle, Washington

    USGS Publications Warehouse

    Brien, Dianne L.; Reid, Mark E.

    2008-01-01

    In Seattle, Washington, deep-seated landslides on bluffs along Puget Sound have historically caused extensive damage to land and structures. These large failures are controlled by three-dimensional (3-D) variations in strength and pore-water pressures. We assess the slope stability of part of southwestern Seattle using a 3-D limit-equilibrium analysis coupled with a 3-D groundwater flow model. Our analyses use a high-resolution digital elevation model (DEM) combined with assignment of strength and hydraulic properties based on geologic units. The hydrogeology of the Seattle area consists of a layer of permeable glacial outwash sand that overlies less permeable glacial lacustrine silty clay. Using a 3-D groundwater model, MODFLOW-2000, we simulate a water table above the less permeable units and calibrate the model to observed conditions. The simulated pore-pressure distribution is then used in a 3-D slope-stability analysis, SCOOPS, to quantify the stability of the coastal bluffs. For wet winter conditions, our analyses predict that the least stable areas are steep hillslopes above Puget Sound, where pore pressures are elevated in the outwash sand. Groundwater flow converges in coastal reentrants, resulting in elevated pore pressures and destabilization of slopes. Regions predicted to be least stable include the areas in or adjacent to three mapped historically active deep-seated landslides. The results of our 3-D analyses differ significantly from a slope map or results from one-dimensional (1-D) analyses.

  17. On how hydrogen bonds affect foam stability.

    PubMed

    Stubenrauch, Cosima; Hamann, Martin; Preisig, Natalie; Chauhan, Vinay; Bordes, Romain

    2017-02-08

    Do intermolecular H-bonds between surfactant head groups play a role for foam stability? From the literature on the foam stability of various surfactants with C12 alkyl chains but different head groups a clear picture emerges: stable foams are only generated when hydrogen bonds can form between the head groups, i.e. when the polar head group has a hydrogen bond donor and a proton acceptor. Stable foams can therefore be generated with surfactants having a sugar unit, a glycine, an amine oxide (at pH~5), or a carboxylic acid (at pH~pKa) as polar head group. On the other hand, aqueous foams stabilized with surfactants having oligo(ethylene oxide), phosphine oxide, quaternary ammonium, sulfate, sarcosine, amine oxide (at pH≠5), or carboxylic acid (at pH≠pKa) are not very stable. These observations suggest that hydrogen bonds between neighbouring molecules at the surface enhance foam stability. Formation of hydrogen bonds between surfactant head groups gives rise to a short-range attractive interaction that may restrict the surfactant's mobility while providing a more elastic surfactant layer which can counteract deformations. To support our hypothesis we carried out a systematic foaming study of two types of surfactants, one of them being capable of forming H-bonds and the other one not. Generating foams of all surfactants mentioned above with the same foaming conditions we found that stable foams are obtained when the head group is capable of forming intersurfactant H-bonds. The outcome of this study constitutes a new step towards the implementation of H-bonds in the future design of surfactants.

  18. Terrestrial Radar Interferometry: The current state-of-the-art demonstrated by real-world slope stability case studies

    NASA Astrophysics Data System (ADS)

    Wooster, Michael; Thomas, Adam; Holley, Rachel

    2013-04-01

    Risk associated with natural terrain is typically mapped and monitored using established geodetic, geotechnical and remote sensing (satellite and airborne) techniques; however such techniques can pose challenges related to health and safety, cost and the density and frequency of measurements. Terrestrial Radar Interferometry (TRI) systems offer users new capabilities in the mapping and monitoring of ground displacements, and more specifically, slope stability. Use of portable radar systems that facilitate quick deployment and data acquisition, rapid and long distance scanning, and the ability to function and operate in most weather conditions, are revolutionising the terrestrial survey industry. This work presents a summary of the capabilities, limitations and applications of a state-of-the-art TRI system. The system is quick to deploy, allowing data acquisition within tens of minutes of arrival on site and requiring little or no permanent site infrastructure. Imaging scans are typically completed in less than 1 minute for a field of view of up to 360°, with repeat scans possible at up to 1-2 minute intervals. The system gives an azimuth resolution of around 8 m at distances of 1 km, with the capability to image slopes at distances of between 50 m and 10 km from the sensor with a deformation accuracy of less than 1 mm. These capabilities represent a significant advance over more traditional stability monitoring methods. The benefits of the TRI technology will be demonstrated through various natural and artificial slope stability case studies. Measurements on artificial slopes in environments such as quarries and open-cast mines allow benchmarking of capabilities across a variety of surface characteristics and failure mechanisms. These results allow an informed consideration of the applicability in various natural slope stability applications, and enable discussion on how TRI can meet the additional challenges encountered in natural environments.

  19. Modelling dual-permeability hydrological system and slope stability of the Rocca Pitigliana landslide using COMSOL Multiphysics

    NASA Astrophysics Data System (ADS)

    Shao, Wei; Bogaard, Thom; Bakker, Mark; Berti, Matteo

    2014-05-01

    The accuracy of using hydrological-slope stability models for rainfall-induced landslide forecasting relies on the identification of realistic landslide triggering mechanisms and the correct mathematical description of these mechanisms. The subsurface hydrological processes in a highly heterogeneous slope are controlled by complex geological conditions. Preferential flow through macropores, fractures and other local high-permeability zones can change the infiltration pattern, resulting in more rapid and deeper water movement. Preferential flow has significant impact on pore water pressure distribution and consequently on slope stability. Increasingly sophisticated theories and models have been developed to simulate preferential flow in various environmental systems. It is necessary to integrate methods of slope stability analysis with preferential flow models, such as dual-permeability models, to investigate the hydrological and soil mechanical response to precipitation in landslide areas. In this study, a systematic modeling approach is developed by using COMSOL Multiphysics to couple a single-permeability model and a dual-permeability model with a soil mechanical model for slope stability analysis. The dual-permeability model is composed of two Richards equations to describe coupled matrix and preferential flow, which can be used to quantify the influence of preferential flow on distribution and timing of pressure head in a slope. The hydrological models are coupled with a plane-strain elastic soil mechanics model and a local factor of safety method. The factor of safety is evaluated by applying the Mohr-Coulomb failure criterion on the effective stress field. The method is applied to the Rocca Pitigliana landslide located roughly 50 km south of Bologna. The landslide material consists of weathered clay with a thickness of 2-4m overlying clay-shale bedrock. Three years of field data of pore pressure measurements provide a reliable description of the dynamic

  20. Spatio-temporal patterns of recurrent slope instabilities affecting undercut slopes in flysch: A dendrogeomorphic approach using broad-leaved trees

    NASA Astrophysics Data System (ADS)

    Šilhán, Karel; Pánek, Tomáš; Turský, Ondřej; Brázdil, Rudolf; Klimeš, Jan; Kašičková, Lucie

    2014-05-01

    The undercut slope of the Skalická Strážnice/Vrchy hill situated in the piedmont of the Carpathian Mountains (Czech Republic) is a regional landslide "hotspot", notorious for its repeated recent and historical sliding reactivations. We performed tree-ring analysis of a large number (n = 274) of broad-leaved trees to reconstruct the spatio-temporal patterns of landslide reactivation for a period spanning more than one hundred years (1884-2011). Although tree rings of broad-leaved trees are less-reliable archives of landslide activity than those of conifers, the application of a methodology based on the weighting of disturbance signals within eccentricity series generated a usable dataset of sliding activity affecting anisotropic flysch bedrock. Although some known landslide years could not be found (or were expressed by only weak signals) in the reconstructed dataset, the majority of landslide events reconstructed from the tree-ring series coincide with hydrometeorological data, revealing a correlation with heavy summer rainfalls lasting from two to ten days. The spatial distribution of landslide recurrence derived from the tree-ring records together with electrical resistivity tomography and a kinematic analysis of slope failures suggest a close link between the concentration of landslide activity and the presence of faulted or fractured flysch bedrock.

  1. Stability and Change in Affect among Centenarians

    ERIC Educational Resources Information Center

    Martin, Peter; da Rosa, Grace; Margrett, Jennifer A.; Garasky, Steven; Franke, Warren

    2012-01-01

    Much information is available about physical and functional health among very old adults, but little knowledge exists about the mental health and mental health changes in very late life. This study reports findings concerning positive and negative affect changes among centenarians. Nineteen centenarians from a Midwestern state participated in four…

  2. Evaluating a slope-stability model for shallow rain-induced landslides using gage and satellite data

    USGS Publications Warehouse

    Yatheendradas, S.; Kirschbaum, D.; Baum, Rex L.; Godt, Jonathan W.

    2014-01-01

    Improving prediction of landslide early warning systems requires accurate estimation of the conditions that trigger slope failures. This study tested a slope-stability model for shallow rainfall-induced landslides by utilizing rainfall information from gauge and satellite records. We used the TRIGRS model (Transient Rainfall Infiltration and Grid-based Regional Slope-stability analysis) for simulating the evolution of the factor of safety due to rainfall infiltration. Using a spatial subset of a well-characterized digital landscape from an earlier study, we considered shallow failure on a slope adjoining an urban transportation roadway near the Seattle area in Washington, USA.We ran the TRIGRS model using high-quality rain gage and satellite-based rainfall data from the Tropical Rainfall Measuring Mission (TRMM). Preliminary results with parameterized soil depth values suggest that the steeper slope values in this spatial domain have factor of safety values that are extremely close to the failure limit within an extremely narrow range of values, providing multiple false alarms. When the soil depths were constrained using a back analysis procedure to ensure that slopes were stable under initial condtions, the model accurately predicted the timing and location of the landslide observation without false alarms over time for gage rain data. The TRMM satellite rainfall data did not show adequately retreived rainfall peak magnitudes and accumulation over the study period, and as a result failed to predict the landslide event. These preliminary results indicate that more accurate and higher-resolution rain data (e.g., the upcoming Global Precipitation Measurement (GPM) mission) are required to provide accurate and reliable landslide predictions in ungaged basins.

  3. Characteristics of low-slope streams that affect O2 transfer rates

    USGS Publications Warehouse

    Parker, Gene W.; DeSimone, Leslie A.

    1991-01-01

    Multiple-regression techniques were used to derive the reaeration coefficients estimating equation for low sloped streams: K2 = 3.83 MBAS-0.41 SL0.20 H-0.76, where K2 is the reaeration coefficient in base e units per day; MBAS is the methylene blue active substances concentration in milligrams per liter; SL is the water-surface slope in foot per foot; and H is the mean-flow depth in feet. Fourteen hydraulic, physical, and water-quality characteristics were regressed against 29 measured-reaeration coefficients for low-sloped (water surface slopes less than 0.002 foot per foot) streams in Massachusetts and New York. Reaeration coefficients measured from May 1985 to October 1988 ranged from 0.2 to 11.0 base e units per day for 29 low-sloped tracer studies. Concentration of methylene blue active substances is significant because it is thought to be an indicator of concentration of surfactants which could change the surface tension at the air-water interface.

  4. Slope aspect affects geomorphic dynamics of coal mining spoil heaps in Belgium

    NASA Astrophysics Data System (ADS)

    Nyssen, Jan; Vermeersch, Dominiek

    2010-11-01

    After the abandonment of coal mining in Belgium in the 1960s-1980s, many coal tips have been left to themselves. Increasingly, these coal tips are regarded as socio-cultural heritage and protected for their environmental value. This research analyses the spatial distribution of the main geomorphic processes (sheet and rill erosion, landsliding, rock fragment movement and root throw) occurring on coal tips in Belgium, through mapping of the processes and their causal factors. Five spoil heaps spread over the major coal basins were studied in detail. The spoil heaps were subdivided in homogeneous land units, especially with regard to slope gradient, vegetation cover and slope aspect. Qualitative and quantitative observations were done on processes and potential causal factors. Regressions showed that generally, the expression of slope processes on the studied coal tips is (1) strongly dependent on westerly aspect of the slopes, (2) independent of slope gradient (which presents a narrow range), (3) impeded by grass cover, and (4) not fully predictable due to variability in type and age of dumped mine spoil.

  5. A hybrid method for quasi-three-dimensional slope stability analysis in a municipal solid waste landfill.

    PubMed

    Yu, L; Batlle, F

    2011-12-01

    Limited space for accommodating the ever increasing mounds of municipal solid waste (MSW) demands the capacity of MSW landfill be maximized by building landfills to greater heights with steeper slopes. This situation has raised concerns regarding the stability of high MSW landfills. A hybrid method for quasi-three-dimensional slope stability analysis based on the finite element stress analysis was applied in a case study at a MSW landfill in north-east Spain. Potential slides can be assumed to be located within the waste mass due to the lack of weak foundation soils and geosynthetic membranes at the landfill base. The only triggering factor of deep-seated slope failure is the higher leachate level and the relatively high and steep slope in the front. The valley-shaped geometry and layered construction procedure at the site make three-dimensional slope stability analyses necessary for this landfill. In the finite element stress analysis, variations of leachate level during construction and continuous settlement of the landfill were taken into account. The "equivalent" three-dimensional factor of safety (FoS) was computed from the individual result of the two-dimensional analysis for a series of evenly spaced cross sections within the potential sliding body. Results indicate that the hybrid method for quasi-three-dimensional slope stability analysis adopted in this paper is capable of locating roughly the spatial position of the potential sliding mass. This easy to manipulate method can serve as an engineering tool in the preliminary estimate of the FoS as well as the approximate position and extent of the potential sliding mass. The result that FoS obtained from three-dimensional analysis increases as much as 50% compared to that from two-dimensional analysis implies the significance of the three-dimensional effect for this study-case. Influences of shear parameters, time elapse after landfill closure, leachate level as well as unit weight of waste on FoS were also

  6. Geotechnical properties of weathered and hydrothermally decomposed granite and their influence on slope stability

    NASA Astrophysics Data System (ADS)

    Thuro, K.; Scholz, M.

    2003-04-01

    processes of weathering. The change of mineral content and the increase of pore volume promotes the action of chemical decomposition. Further, some geotechnical aspects of the different granite weathering and alteration stages and their influence on slope stability are discussed.

  7. Slope stability susceptibility evaluation parameter (SSEP) rating scheme - An approach for landslide hazard zonation

    NASA Astrophysics Data System (ADS)

    Raghuvanshi, Tarun Kumar; Ibrahim, Jemal; Ayalew, Dereje

    2014-11-01

    In this paper a new slope susceptibility evaluation parameter (SSEP) rating scheme is presented which is developed as an expert evaluation approach for landslide hazard zonation. The SSEP rating scheme is developed by considering intrinsic and external triggering parameters that are responsible for slope instability. The intrinsic parameters which are considered are; slope geometry, slope material (rock or soil type), structural discontinuities, landuse and landcover and groundwater. Besides, external triggering parameters such as, seismicity, rainfall and manmade activities are also considered. For SSEP empirical technique numerical ratings are assigned to each of the intrinsic and triggering parameters on the basis of logical judgments acquired from experience of studies of intrinsic and external triggering factors and their relative impact in inducing instability to the slope. Further, the distribution of maximum SSEP ratings is based on their relative order of importance in contributing instability to the slope. Finally, summation of all ratings for intrinsic and triggering parameter based on actual observation will provide the expected degree of landslide in a given land unit. This information may be utilized to develop a landslide hazard zonation map. The SSEP technique was applied in the area around Wurgessa Kebelle of North Wollo Zonal Administration, Amhara National Regional State in northern Ethiopia, some 490 km from Addis Ababa. The results obtained indicates that 8.33% of the area fall under Moderately hazard and 83.33% fall within High hazard whereas 8.34% of the area fall under Very high hazard. Further, in order to validate the LHZ map prepared during the study, active landslide activities and potential instability areas, delineated through inventory mapping was overlain on it. All active landslide activities and potential instability areas fall within very high and high hazard zone. Thus, the satisfactory agreement confirms the rationality of

  8. Mountain permafrost, glacier thinning, and slope stability - a perspective from British Columbia (and Alaska)

    NASA Astrophysics Data System (ADS)

    Geertsema, Marten

    2016-04-01

    The association of landslides with thinning glaciers and mapped, or measured, mountain permafrost is increasing. Glacier thinning debuttresses slopes and promotes joint expansion. It is relatively easy to map. Permafrost, a thermal condition, is generally not visually detectible, and is difficult to map. Much mountain permafrost may have been overlooked in hazard analysis. Identifying, and characterizing mountain permafrost, and its influence on slope instability is crucial for hazard and risk analysis in mountainous terrain. Rock falls in mountains can be the initial event in process chains. They can transform into rock avalanches, debris flows or dam burst floods, travelling many kilometres, placing infrastructure and settlements at risk.

  9. Laboratory investigation of coupled deformation and fluid flow in mudrock: implications for slope stability in the Ursa Basin, Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Flemings, P. B.; Song, I.; Saffer, D. M.

    2012-04-01

    Integrated Ocean Drilling Program (IODP) Expedition 308 was dedicated to the study of fluid flow, overpressure, and slope stability in the Ursa Basin, on the continental slope of the Gulf of Mexico. In this location, turbidite channel levees deposited a wedge-shaped body: the deposition rate in the thick part of the wedge exceeded 12 mm/yr. This rapid deposition of fine grained sediments generated excess pore pressure observed near the seafloor. IODP drilling focused on three Sites: U1322, U1323, and U1324, along the steepest slope (2°) on the eastern section of the Ursa Canyon levee deposits. In this study, we conducted a suite of deformation experiments on samples from Site 1324, to understand the stress-strain behavior and stress history of the recovered core material. Our samples were taken from depths of 30-160 meters below seafloor, and are composed of ~40% silt and ~60% clay, with porosities ranging from ~42-55%. We first conducted uniaxial consolidation tests to determine pre-consolidation stresses and define deformation behavior due to simulated vertical loading. In a subset of tests, we subjected the samples to undrained shearing following consolidation, to define the friction angle and define relationships between stress state and deformation. We find that the lateral effective stress during uniaxial compression is 56-64% of the vertical effective stress (avg. K0=0.6). Pre-consolidation stresses suggest that pore pressure is hydrostatic to 50 mbsf (meters below seafloor), and is overpressured below this, with excess pressures up to 70% of the hydrostatic effective vertical stress (λ*=0.7) at 160 mbsf. The time coefficient of consolidation (cv) in these experiments is ~2.2x10-8 m2/s. Undrained shear tests define a failure envelope with a residual friction angle (φ) of 23° and zero cohesion. In our shearing tests, we observed no pore pressure change during initial (primarily elastic) shear deformation, but note a monotonic increase in pore pressure

  10. Root reinforcement and its contribution to slope stability in the Western Ghats of Kerala, India

    NASA Astrophysics Data System (ADS)

    Lukose Kuriakose, Sekhar; van Beek, L. P. H.

    2010-05-01

    The Western Ghats of Kerala, India is prone to shallow landslides and consequent debris flows. An earlier study (Kuriakose et al., DOI:10.1002/esp.1794) with limited data had already demonstrated the possible effects of vegetation on slope hydrology and stability. Spatially distributed root cohesion is one of the most important data necessary to assess the effects of anthropogenic disturbances on the probability of shallow landslide initiation, results of which are reported in sessions GM6.1 and HS13.13/NH3.16. Thus it is necessary to the know the upper limits of reinforcement that the roots are able to provide and its spatial and vertical distribution in such an anthropogenically intervened terrain. Root tensile strength and root pull out tests were conducted on nine species of plants that are commonly found in the region. They are 1) Rubber (Hevea Brasiliensis), 2) Coconut Palm (Cocos nucifera), 3) Jackfruit trees (Artocarpus heterophyllus), 4) Teak (Tectona grandis), 5) Mango trees (Mangifera indica), 6) Lemon grass (Cymbopogon citratus), 7) Gambooge (Garcinia gummi-gutta), 8) Coffee (Coffea Arabica) and 9) Tea (Camellia sinensis). About 1500 samples were collected of which only 380 could be tested (in the laboratory) due to breakage of roots during the tests. In the successful tests roots failed in tension. Roots having diameters between 2 mm and 12 mm were tested. Each sample tested had a length of 15 cm. Root pull out tests were conducted in the field. Root tensile strength vs root diameter, root pull out strength vs diameter, root diameter vs root depth and root count vs root depth relationships were derived. Root cohesion was computed for nine most dominant plants in the region using the perpendicular root model of Wu et al. (1979) modified by Schimidt et al. (2001). A soil depth map was derived using regression kriging as suggested by Kuriakose et al., (doi:10.1016/j.catena.2009.05.005) and used along with the land use map of 2008 to distribute the

  11. Rock Slope Stability Evaluation in a Steep-Walled Canyon: Application to Elevator Construction in the Yunlong River Valley, Enshi, China

    NASA Astrophysics Data System (ADS)

    Xiao, Lili; Chai, Bo; Yin, Kunlong

    2015-09-01

    A passenger elevator is to be built on a nearly vertical slope in the National Geological Park in Enshi, Hubei province, China. Three steps comprise the construction: excavating the slope toe for the elevator platform, building the elevator on the platform, and affixing the elevator to the slope using anchors. To evaluate the rock slope stability in the elevator area and the safety of the elevator construction, we applied three techniques: qualitative analysis, formula calculation, and numerical simulation methods, based on field investigation and parameter selection, and considering both wet and dry conditions, pre- and post-construction. Qualitative stability factors for sliding and falling were calculated using the limit equilibrium method; the results show that the slope as a whole is stable, with a few unstable blocks, notably block BT1. Formula-based stability factors were calculated for four sections on block BT1, revealing the following: anchors will decrease the stability of certain rock pieces; the lowest average stability factor after anchoring will be K f = 1.36 in wet conditions; block BT1 should be reinforced during elevator construction, up to a first-class slope stability factor of K f = 1.40; and the slope as a whole is stable. Numerical simulation using FLAC3D indicated that the stress distribution will reach equilibrium for all steps before and after construction, and that the factor of safety (FOS) is within the general slope safety range (FOS > 1.05). We suggest that unstable pieces in block BT1 be reinforced during construction to a first-class slope safety range (FOS > 1.3), and that deformation monitoring on the slope surface be implemented.

  12. Plant ecology. Anthropogenic environmental changes affect ecosystem stability via biodiversity.

    PubMed

    Hautier, Yann; Tilman, David; Isbell, Forest; Seabloom, Eric W; Borer, Elizabeth T; Reich, Peter B

    2015-04-17

    Human-driven environmental changes may simultaneously affect the biodiversity, productivity, and stability of Earth's ecosystems, but there is no consensus on the causal relationships linking these variables. Data from 12 multiyear experiments that manipulate important anthropogenic drivers, including plant diversity, nitrogen, carbon dioxide, fire, herbivory, and water, show that each driver influences ecosystem productivity. However, the stability of ecosystem productivity is only changed by those drivers that alter biodiversity, with a given decrease in plant species numbers leading to a quantitatively similar decrease in ecosystem stability regardless of which driver caused the biodiversity loss. These results suggest that changes in biodiversity caused by drivers of environmental change may be a major factor determining how global environmental changes affect ecosystem stability.

  13. Nitrous oxide emissions affected by biochar and nitrogen stabilizers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Both biochar and N fertilizer stabilizers (N transformation inhibitors) are potential strategies to reduce nitrous oxide (N2O) emissions from fertilization, but the mechanisms and/or N transformation processes affecting the N dynamics are not fully understood. This research investigated N2O emission...

  14. Cyclic Fatigue Testing for Application for paraglacial rock slope stability modelling

    NASA Astrophysics Data System (ADS)

    Grämiger, Lorenz; Perras, Matthew A.; Moore, Jeffrey R.; Loew, Simon

    2015-04-01

    In glacial environments, rock mass damage is influenced by stress redistribution caused by glaciation and deglaciation cycles. The intact rock strength, discontinuities, stress regime and environmental factors all contribute to the mechanical behavior of the rock slope. Critically-stressed rock walls are exposed to changing boundary conditions. The effect of stress changes during deglaciation of a major glacial period is not well constrained, neither the influence of smaller stress magnitudes of repeat glacier cycles during an interglacial. In an effort to constrain numerical rock slope model input values, a laboratory testing program has been conducted to address the role of fatigue on the intact rock strength. Baseline unconfined compression and Brazilian tensile testing has been conducted on gneissic rocks from the Aletsch valley in Switzerland. The baseline testing results are used to determine load levels for cyclic fatigue compression and tension testing. In the cyclic tests the intact rock samples are taken to the load levels determined from the baseline tests and cyclic loading and unloading is conducted around the nominal load level. The stress fluctuation chosen is between 2-10 MPa, which is equivalent to a glacial loading and unloading of 200-1000m of ice. Such ice thickness change are typical for the Grosser Aletsch glacier during the Lateglacial and Holocene. During cyclic loading and unloading the amount of damage is estimated by recording the number of acoustic emission events with time. Once the acoustic emission events per cycle decrease well below initial cycling levels the load level is increased and cyclic loading is continued at the new load level. This was done for both cyclic compression and cyclic Brazilian tensile tests. The aim of the cyclic tests is to understand what degree of pre-existing damage is required such that 2-10 MPa stress fluctuations could cause crack propagation and failure of laboratory samples in long-term cyclic fatigue

  15. Slope stability analysis of landslide in Wayang Windu Geothermal Field, Pangalengan, West Java Province, Indonesia

    NASA Astrophysics Data System (ADS)

    Yuhendar, A. H.; Wusqa, U.; Kartiko, R. D.; Raya, N. R.; Misbahudin

    2016-05-01

    Large-scale landslide occurred in Margamukti village, Pangalengan, Bandung Regency, West Java Province, Indonesia. The landslide damaged geothermal gas pipeline along 300 m in Wayang Windu Geothermal Field. Based on field observation, landslide occured in rotational sliding movement. Laboratory analysis were conducted to obtain the characteristics of the soil. Based on the condition of the landslide in this area, the Factor of Safety can be simulated by the soil mechanics approach. Factor of safety analysis based on soil cohesion and internal friction angle was conducted using manual sensitivity analysis for back analysis. The analysis resulted soil cohesion in critical condition (FS<1) is 6.01 kPa. This value is smaller than cohesion of undisturbed slope soil sample. Water from rainfall is the most important instability factors in research area. Because it decreases cohesion in soils and increases weight and pore water pressure in granular media.

  16. Processes affecting the transport of nitrogen in groundwater and factors related to slope position

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrate (NO3-) pollution of water resources has been a major problem for years, causing contaminated water supplies, harmful effects on human health, and widespread eutrophication of fresh water resources. The main objectives of this study were to: 1) understand the processes affecting NO3- transpor...

  17. The influence of the maintenance of terraced areas on slope stability during the November 2014 flood event in Liguria (northwestern Italy)

    NASA Astrophysics Data System (ADS)

    Giordan, Daniele; Poggi, Flavio; Baldo, Marco; Cignetti, Martina

    2016-04-01

    Terraced environments are a widespread feature of the coastal settlement of eastern Liguria (northwestern Italy) and they constitute a well-known favorable role in slope stability. In this region, starting from the twentieth century, the progressive abandonment of agriculture determines a progressively increasing lack of maintenance of the terraces, consequently raising the level of slope instability. Moreover, it should be taken into account not only the level of terraces maintenance, but also their interaction with several factors as i) geological and geomorphological conditions, ii) soil properties, iii) hydrological and hydrogeological conditions, and iv) land use, causing an increase in landslides occurrence. The definition of managed terraces effects on slope stability and their response to external stress like a flood event is rather complicated; a possible approach is a statistical analysis of the effects of a flood event over a large terraced area, distinguishing the maintained sectors from the abandoned ones. After the November 2014 flood event, which affected several sectors of the Liguria region, where a high number of shallow landslides were triggered, an airborne LiDAR survey of the damaged area was carried out. In particular, a high resolution Digital Terrain Model (DTM) resampled to a lower density (1 square meter grid spacing) and a photogrammetric coverage of the area was performed, in order to create a landslide map of the flood event. The surveyed area covered more than 380 square kilometers, and over 1600 shallow landslides triggered by the flood event were identified and inventoried. The high resolution DTM allowed the identification of terraced areas also in wooded sectors and a sharp mapping of the extension of terraced slopes in this portion of Liguria region. By considering: i) the terraced areas recognized through DTM analysis, ii) the mapped landslides, and iii) the land use classification, a correlation between the presence of terraces

  18. The Influence of Plant Root Systems on Subsurface Flow: Implications for Slope Stability

    EPA Science Inventory

    Although research has explained how plant roots mechanically stabilize soils, in this article we explore how root systems create networks of preferential flow and thus influence water pressures in soils to trigger landslides. Root systems may alter subsurface flow: Hydrological m...

  19. Radar-derived asteroid shapes point to a 'zone of stability' for topography slopes and surface erosion rates

    NASA Astrophysics Data System (ADS)

    Richardson, J.; Graves, K.; Bowling, T.

    2014-07-01

    Previous studies of the combined effects of asteroid shape, spin, and self-gravity have focused primarily upon the failure limits for bodies with a variety of standard shapes, friction, and cohesion values [1,2,3]. In this study, we look in the opposite direction and utilize 22 asteroid shape-models derived from radar inversion [4] and 7 small body shape-models derived from spacecraft observations [5] to investigate the region in shape/spin space [1,2] wherein self-gravity and rotation combine to produce a stable minimum state with respect to surface potential differences, dynamic topography, slope magnitudes, and erosion rates. This erosional minimum state is self-correcting, such that changes in the body's rotation rate, either up or down, will increase slope magnitudes across the body, thereby driving up erosion rates non-linearly until the body has once again reached a stable, minimized surface state [5]. We investigated this phenomenon in a systematic fashion using a series of synthesized, increasingly prolate spheroid shape models. Adjusting the rotation rate of each synthetic shape to minimize surface potential differences, dynamic topography, and slope magnitudes results in the magenta curve of the figure (right side), defining the zone of maximum surface stability (MSS). This MSS zone is invariant both with respect to body size (gravitational potential and rotational potential scale together with radius), and density when the scaled-spin of [2] is used. Within our sample of observationally derived small-body shape models, slow rotators (Group A: blue points), that are not in the maximum surface stability (MSS) zone and where gravity dominates the slopes, will generally experience moderate erosion rates (left plot) and will tend to move up and to the right in shape/spin space as the body evolves (right plot). Fast rotators (Group C: red points), that are not in the MSS zone and where spin dominates the slopes, will generally experience high erosion rates

  20. Numerical slope stability simulations of chasma walls in Valles Marineris/Mars using a distinct element method (dem).

    NASA Astrophysics Data System (ADS)

    Imre, B.

    2003-04-01

    NUMERICAL SLOPE STABILITY SIMULATIONS OF CHASMA WALLS IN VALLES MARINERIS/MARS USING A DISTINCT ELEMENT METHOD (DEM). B. Imre (1) (1) German Aerospace Center, Berlin Adlershof, bernd.imre@gmx.net The 8- to 10-km depths of Valles Marineris (VM) offer excellent views into the upper Martian crust. Layering, fracturing, lithology, stratigraphy and the content of volatiles have influenced the evolution of the Valles Marineris wallslopes. But these parameters also reflect the development of VM and its wall slopes. The scope of this work is to gain understanding in these parameters by back-simulating the development of wall slopes. For that purpose, the two dimensional Particle Flow Code PFC2D has been chosen (ITASCA, version 2.00-103). PFC2D is a distinct element code for numerical modelling of movements and interactions of assemblies of arbitrarily sized circular particles. Particles may be bonded together to represent a solid material. Movements of particles are unlimited. That is of importance because results of open systems with numerous unknown variables are non-unique and therefore highly path dependent. This DEM allows the simulation of whole development paths of VM walls what makes confirmation of the model more complete (e.g. Oreskes et al., Science 263, 1994). To reduce the number of unknown variables a proper (that means as simple as possible) field-site had to be selected. The northern wall of eastern Candor Chasma has been chosen. This wall is up to 8-km high and represents a significant outcrop of the upper Martian crust. It is quite uncomplex, well-aligned and of simple morphology. Currently the work on the model is at the stage of performing the parameter study. Results will be presented via poster by the EGS-Meeting.

  1. Stage structure alters how complexity affects stability of ecological networks

    USGS Publications Warehouse

    Rudolf, V.H.W.; Lafferty, Kevin D.

    2011-01-01

    Resolving how complexity affects stability of natural communities is of key importance for predicting the consequences of biodiversity loss. Central to previous stability analysis has been the assumption that the resources of a consumer are substitutable. However, during their development, most species change diets; for instance, adults often use different resources than larvae or juveniles. Here, we show that such ontogenetic niche shifts are common in real ecological networks and that consideration of these shifts can alter which species are predicted to be at risk of extinction. Furthermore, niche shifts reduce and can even reverse the otherwise stabilizing effect of complexity. This pattern arises because species with several specialized life stages appear to be generalists at the species level but act as sequential specialists that are hypersensitive to resource loss. These results suggest that natural communities are more vulnerable to biodiversity loss than indicated by previous analyses.

  2. A Tensile Strength of Bermuda Grass and Vetiver Grass in Terms of Root Reinforcement Ability Toward Soil Slope Stabilization

    NASA Astrophysics Data System (ADS)

    Noorasyikin, M. N.; Zainab, M.

    2016-07-01

    An examination on root characteristics and root properties has been implemented in this study. Two types of bioengineering were chose which are Vetiver grass and Bermuda grass as these grasses were widely applied for slope stabilization. The root samples were taken to the laboratory to investigate its classification, characteristics and strength. The root of both grasses was found grow with fibrous root matrix system. In terms of root anchorage, the root matrix system of Vetiver grass was exhibits more strengthen than the Bermuda grass. However, observation on root image from Scanning Electron Microscope test reveals that the root of Vetiver grass becomes non-porous as the moisture content reduced. Meanwhile, the root tensile strength of Bermuda grass was obtained acquired low value with higher percentage of moisture content, root morphology and bonding strength. The results indicated that the root tensile strength is mainly influence by percentage of moisture content and root morphology.

  3. Rock slope stability analysis along the North Carolina section of the Blue Ridge Parkway: Using a geographic information system (GIS) to integrate site data and digital geologic maps

    USGS Publications Warehouse

    Latham, R.S.; Wooten, R.M.; Cattanach, B.L.; Merschat, C.E.; Bozdog, G.N.

    2009-01-01

    In 2008, the North Carolina Geological Survey (NCGS) completed a five-year geologic and geohazards inventory of the 406-km long North Carolina segment of the Blue Ridge Parkway (BRP). The ArcGIS??? format deliverables for rock slopes include a slope movement and slope movement deposit database and maps and site-specific rock slope stability assessments at 158 locations. Database entries for known and potential rock slope failures include: location data, failure modes and dimensions, activity dates and levels, structural and lithologic data, the occurrence of sulfide minerals and acid-producing potential test results. Rock slope stability assessments include photographs of the rock cuts and show locations and orientations of rock data, seepage zones, and kinematic stability analyses. Assigned preliminary geologic hazard ratings of low, moderate and high indicate the generalized relative probability of rock fall and/or rock slide activity at a given location. Statistics compiled based on the database indicate some general patterns within the data. This information provides the National Park Service with tools that can aid in emergency preparedness, and in budgeting mitigation, maintenance and repair measures. Copyright 2009 ARMA, American Rock Mechanics Association.

  4. Slope stability of proposed ski facilities at the southeast side of Snodgrass Mountain, Gunnison County, Colorado

    USGS Publications Warehouse

    Baum, Rex L.

    1996-01-01

    Part of the proposed expansion of ski facilities at Crested Butte Mountain Resort, Gunnison County, Colorado, is in an area underlain by landslide deposits that are on the southeast side of Snodgrass Mountain. Except for localized movement, the landslides do not appear to be moving at present or to have moved in the past several decades. Shallow sliding and debris flows have occurred in similar materials nearby and are likely to occur in the landslide deposits during the 50-100 year life of the proposed facilities. Hazards related to debris flow, shallow slumping, and expansive soils in the deposits can be reduced by appropriate engineering and remedial measures but maintenance for the proposed facility may become costly. Snow making is likely to aggravate the hazards of shallow slumping, deep-seated sliding, and debris flow. Reactivation and deep-seated movement of a 1.6-million-m3 slide at the east side of the deposits would damage or destroy a proposed gondola, ski lift N-3, and related facilities. Moving the gondola and lift off the slide and prohibiting snow making on the slide will protect the gondola and lift and reduce the chances of debris-flow damage to a proposed development near the toe of the slide. Insufficient data are available to assess the current or future stability of the landslides or to evaluate possible mitigation strategies; detailed stability analyses are needed before developing any facilities on the landslide deposits.

  5. Multi-phase Temporal Seismic Imaging of a Slope Stability Mitigation Project at Newby Island Sanitary Landfill, San Jose, California

    NASA Astrophysics Data System (ADS)

    Treece, B. J.; Catchings, R.; Reed, D.; Goldman, M.

    2014-12-01

    Without slope stability mitigation, liquefaction-induced settlement in bay mud and Pleistocene alluvial deposits may lead to the collapse of levee walls surrounding sanitary landfills that are located adjacent to the San Francisco Bay. To analyze the effectiveness of a slope stability mitigation project involving deep soil mixing at Newby Island Sanitary Landfill in San Jose, California, we acquired P- and S-wave seismic surveys along a transect through the mitigated region during, and two years after, completion of the mitigation project. Deep soil mixing involves the injection of a cement slurry in augered holes, resulting in groups of soil-cement columns (elements) that are intended to increase the strength and rigidity of the subsurface materials. For our seismic investigations, we used accelerated-weight-drop (AWD) and hammer impacts to generate P- and S-wave seismic sources, respectively, at 57 geophone locations, spaced 5 m apart. The resulting seismic data were recorded using 40-Hz, vertical-component (P-wave) and 4.5-Hz, horizontal-component (S-wave) sensors. Initially, we developed tomographic refraction (velocity) images along a progressive transition from a yet-to-be-mitigated area into a more recently mitigated area, located along the base of a steep slope composed of compacted landfill. The initial survey revealed an increase in seismic velocity in the treated area, seismic velocity increases with curing time for soil-cement elements, and a high-velocity zone beneath the active injection zone. The influence of the mitigation was most apparent from increases in Vp/Vs and Poisson's ratios. To assess the long-term effects of the mitigation project, an identical, follow-up survey was acquired in July 2014, 23 months after the initial survey. We present a comparative analysis of the tomographic images from the two surveys, variations in Vp/Vs and Poisson's ratios over time, and a comparison of in situ, time-varying seismic parameters with laboratory

  6. Assessment of Rock Slope Stability in Limestone Quarries in the Tournai's Region (Belgium) Using Structural Data

    NASA Astrophysics Data System (ADS)

    Tshibangu, Jean-Pierre; Deloge, K. Pierre-Alexandre; Deschamps, Benoît; Coudyzer, Christophe

    The Tournais region is characterised by famous outcrops of carboniferous limestone which is mined out for cement and raw material production. The four main quarries found in the Region, i.e. Gaurain-Ramecroix, Milieu, Antoing and Lemay; are owned by the three main cement producers in Belgium: Italcimenti, Holcim and CBR. The global production of limestone is about 20 millions tons per year, giving big pits with depths up to 150 m. With the growth of the pits, the quarries are approaching each other leading to the problem of managing the reserves contained in the separating walls and their mechanical stability. The limestone deposit is composed of different seams having varying thickness, chemical com- position and even mechanical properties. The deposit has an overall horizontal dip and is intersected by two main sets of discontinuities with a spacing of about 10 m or less. It is also crossed by a set of east to west faults but the quarries are implanted in the in between areas, so to not be crossed by these faults. The layers and specially the shallow ones are characterised by a typical karstic weathering giving open or filled cavities. This paper presents the global work quarried out in order to study the stability of the Lemays quarry. First a description of the orientation and spacing of discontinuities is presented, and an attempt made to correlate to the development of weathering. Mechanical laboratory tests have been performed and a qualification of the rock mass assessed. A coupled approach is then presented using a mining planning analysis and mechanical simulation (i.e. Finite Element method).

  7. Modeling 3-D Slope Stability of Coastal Bluffs Using 3-D Ground-Water Flow, Southwestern Seattle, Washington

    USGS Publications Warehouse

    Brien, Dianne L.; Reid, Mark E.

    2007-01-01

    Landslides are a common problem on coastal bluffs throughout the world. Along the coastal bluffs of the Puget Sound in Seattle, Washington, landslides range from small, shallow failures to large, deep-seated landslides. Landslides of all types can pose hazards to human lives and property, but deep-seated landslides are of significant concern because their large areal extent can cause extensive property damage. Although many geomorphic processes shape the coastal bluffs of Seattle, we focus on large (greater than 3,000 m3), deepseated, rotational landslides that occur on the steep bluffs along Puget Sound. Many of these larger failures occur in advance outwash deposits of the Vashon Drift (Qva); some failures extend into the underlying Lawton Clay Member of the Vashon Drift (Qvlc). The slope stability of coastal bluffs is controlled by the interplay of three-dimensional (3-D) variations in gravitational stress, strength, and pore-water pressure. We assess 3-D slope-stability using SCOOPS (Reid and others, 2000), a computer program that allows us to search a high-resolution digital-elevation model (DEM) to quantify the relative stability of all parts of the landscape by computing the stability and volume of thousands of potential spherical failures. SCOOPS incorporates topography, 3-D strength variations, and 3-D pore pressures. Initially, we use our 3-D analysis methods to examine the effects of topography and geology by using heterogeneous material properties, as defined by stratigraphy, without pore pressures. In this scenario, the least-stable areas are located on the steepest slopes, commonly in Qva or Qvlc. However, these locations do not agree well with observations of deep-seated landslides. Historically, both shallow colluvial landslides and deep-seated landslides have been observed near the contact between Qva and Qvlc, and commonly occur in Qva. The low hydraulic conductivity of Qvlc impedes ground-water flow, resulting in elevated pore pressures at the

  8. Free-surface stability criterion as affected by velocity distribution

    USGS Publications Warehouse

    Cheng-Lung, Chen

    1995-01-01

    This paper examines how the velocity distribution of flow in open channels affects the kinematic and dynamic wave velocities, from which the various forms of the Vedernikov number V can be formulated. When V >1, disturbances created in open-channel flow will amplify in the form of roll waves; when V <1, some (though not all) disturbances will attenuate. A study of the Vedernikov stability criterion reveals that it can be readily deduced within the framework of the kinematic and dynamic wave theories by comparing the kinematic wave velocity to the corresponding dynamic wave velocity. -from Author

  9. Assessment of rock properties and slope stability at Pacaya Volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Schaefer, Lauren; Kendrick, Jackie; Oommen, Thomas; Lavallee, Yan

    2014-05-01

    Pacaya is an active stratovolcano located 30 km south of Guatemala City, Guatemala. A large (0.65 km3) sector collapse of the volcano occurred 0.6 - 1.6 ka B.P., producing a debris avalanche that traveled 25 km SW of the edifice. The structural setting of the current cone, along with two recent smaller-volume collapses in 1962 and 2010, suggest gravitational instability of this volcano. Recent measurements of the geomechanical properties of lava and breccia from Pacaya are used to improve our understanding of the destabilizing potential of different volcanic processes. Room-temperature uniaxial and triaxial compressive tests, and total porosity tests, were conducted on 17 breccia and 21 lava samples. The average uniaxial compressive strength (σci) of lava rocks was moderately strong (σci = 72.4 MPa), with breccia rocks being 62.2% weaker (σci = 27.4 MPa). These values can partially be contributed to lava rock's very low porosity (0.054) and breccia rock's higher porosity (0.19). We also find an apparent rate-dependent strengthening of the samples as strain rate is increased from 10-5 to 10-1. Values of Poisson's Ratio (v) and Young's Modulus (E) calculated from triaxial tests, are v= 0.28 and E = 13.9 GPa for breccia and v= 0.31 and E = 17.6 GPa for lava. These experiments highlight the contrasting character of breccia versus lava, and suggest that sector collapse may have initiated in the weaker breccia. Additionally, cohesion (c) and friction angle (φ) calculated from triaxial tests yielded values of c = 1.8 MPa and φ = 19.4° for breccia and c = 4.0 MPa and φ = 41.4° for lava. Following sector collapse, the frictional properties of the rocks partially dictate the flow and deposition of the debris avalanche, and these were studied using high velocity rotary shear experiments on ash and lava rock. Experimental results are combined to understand the historical flank stability and assess the likelihood of future sector collapse at Pacaya.

  10. Factors affecting storage stability of various commercial phytase sources.

    PubMed

    Sulabo, R C; Jones, C K; Tokach, M D; Goodband, R D; Dritz, S S; Campbell, D R; Ratliff, B W; DeRouchey, J M; Nelssen, J L

    2011-12-01

    phytase activity than when phytases were mixed with the vitamin or VTM premixes. Coated phytases stored in any form had greater (P < 0.01) activity retention than the uncoated phytases at all sampling periods. Results indicate that storage stability of commercially available phytases is affected by duration of storage, temperature, product form, coating, and phytase source. Pure products held at 23°C or less were the most stable. In premixes, longer storage times and higher temperatures reduced phytase activity, but coating mitigated some of these negative effects.

  11. Photogrammetry and laser scanning for analyzing slope stability and rock fall runout along the Domodossola-Iselle railway, the Italian Alps

    NASA Astrophysics Data System (ADS)

    Salvini, R.; Francioni, M.; Riccucci, S.; Bonciani, F.; Callegari, I.

    2013-03-01

    In Italy, railways crossing the alpine valleys are a vital means of civil and commercial communications with the rest of Europe. The geomorphologic configuration and the climatic conditions, especially in winter and spring, can cause rock fall events resulting in railway service interruptions and damage to infrastructure and, in the worst case, to people. There were rock fall events at a slope adjacent to the Domodossola-Iselle railway, most recently in 2004. This paper evaluates the stability of a mountain slope and maps rock fall hazards through the modeling of potential runout trajectories. Traditional geological, geomorphological and geo-engineering surveys were combined with data derived from digital terrestrial photogrammetry. Stereo photographic pairs of rocky outcrops in inaccessible areas were acquired from a helicopter. Data from photogrammetry, topographic measurements and laser scanning were then integrated to build a digital model of the slope, to characterize the rock mass and block geometry, and to define possible runout trajectories. The geomatic methods used have yielded oriented stereo-images, orthophotos and precise digital models of rocky wedges. Geometrical and structural characteristics of slopes, such as joint attitude, spacing and persistence, and block volumes, were also derived. The results were used together with a deterministic limit equilibrium method to evaluate slope stability. We assessed the probabilistic distribution of rock fall end points and kinetic energy along the rock falling paths and existing barriers, and created a hazard map based on the spatial distribution of trajectories, rock fall transit density and kinetic energy.

  12. Factors affecting hazardous waste solidification/stabilization: a review.

    PubMed

    Malviya, Rachana; Chaudhary, Rubina

    2006-09-01

    Solidification/stabilization is accepted as a well-established disposal technique for hazardous waste. As a result many different types of hazardous wastes are treated with different binders. The S/S products have different property from waste and binders individually. The effectiveness of S/S process is studied by physical, chemical and microstructural methods. This paper summarizes the effect of different waste stream such as heavy metals bearing sludge, filter cake, fly ash, and slag on the properties of cement and other binders. The factors affecting strength development is studied using mix designs, including metal bearing waste alters the hydration and setting time of binders. Pore structure depends on relative quantity of the constituents, cement hydration products and their reaction products with admixtures. Carbonation and additives can lead to strength improvement in waste-binder matrix.

  13. From mass-wasting to slope stabilization - putting constrains on the transition in slope erosion mode: A case study in the Judea Hills, Israel

    NASA Astrophysics Data System (ADS)

    Ryb, U.; Matmon, A.; Porat, N.; Katz, O.

    2012-04-01

    The geomorphic response of a drainage system to the termination of tectonic uplift includes the stabilization of base level followed by a transition in the mode of hillslope erosion from mass wasting to diffusive processes. We test this transition in the Soreq drainage, Judea Hills, Israel. This study area is characterized by Upper Cretaceous marine carbonate rocks and sub-humid Mediterranean climate, and the drainage hillslopes are typically mantled by thick calcrete crusts. Calcretized remnants of landslide debris and alluvial deposits are evident along the presently stable hillslopes. These remnants indicate that a transition from landslides to dissolution-controlled hillslope erosion had occurred, most likely due to the stabilization of the present base-level which probably followed a significant decrease in tectonic uplift during late Cenozoic. Four deposits were dated using thermally transferred OSL of aeolian quartz grains incorporated in the calcrete which cement the ancient deposits. Three deposits are associated with the present streambed and constrain the hillslope stabilization period; one deposit is associated with a ~100 m higher base-level and puts constrains on the rate of stream incision prior to the stabilization of the current streambed. We conclude that incision of ~100 m occurred between 1056±262 ka to 688±86 ka due to ~0.3° westward tilt of the region; such incision invoked high frequency of landslide activity in the drainage. The ages of a younger landslide remnant, alluvial terrace, and alluvial fan, all situated only a few meters above the present level of the active streambed, range between 688±86 ka and 244±25 ka and indicate that since 688±86 the Soreq base level had stabilized and that landslide activity decreased significantly by the middle Pleistocene. This study demonstrates that colluvial deposits may be used as markers for stream incision and base level stabilization, much like alluvial deposits that are commonly used for

  14. A study on difference and importance of sacral slope and pelvic sacral angle that affect lumbar curvature.

    PubMed

    Choi, Seyoung; Lee, Minsun; Kwon, Byongan

    2014-01-01

    Individual pelvic sacral angle was measured, compared and analyzed for the 6 male and female adults who were diagnosed with lumbar spinal stenosis, foraminal stenosis and mild spondylolisthesis in accordance with spinal parameters, pelvic parameters and occlusion state of sacroiliac joint presented by the author of this thesis based on the fact that the degree of lumbar excessive lordosis that was one of the causes for lumbar pain was determined by sacral slope. The measured values were compared with the standard values of the average normal range from 20 s to 40 s of normal Koreans stated in the study on the change in lumbar lordosis angle, lumbosacral angle and sacral slope in accordance with the age by Oh et al. [5] and sacral slope and pelvic sacral slope of each individual of the subjects for measurement were compared. Comparing the difference between the two tilt angles possessed by an individual is a comparison to determine how much the sacroiliac joint connecting pelvis and sacral vertebrae compensated and corrected the sacral vertebrae slope by pelvic tilt under the condition of synarthrodial joint.Under the condition that the location conforming to the line in which the sagittal line of gravity connects with pelvic ASIS and pubic pubic tuberele is the neutral location of pelvic tilt, sacral slope being greater than pelvic sacral slope means pelvic anterior tilting, whereas sacral slope being smaller than pelvic sacral slope means pelvic posterior tilting. On that account, male B, female A and female C had a pelvic posterior tilting of 16 degrees, 1 degree and 5 degrees respectively, whereas male A, male C and female B had a pelvic anterior tilting of 3 degrees, 9 degrees and 4 degrees respectively. In addition, the 6 patients the values of lumbar lordosis angle, lumbosacral angle and sacral slope that were almost twice as much as the normal standard values of Koreans. It is believed that this is because the pelvic sacral slope maintaining an angle that is

  15. Structural Stabilities of β-Ti Alloys Studied Using a New Mo Equivalent Derived from [ β/( α + β)] Phase-Boundary Slopes

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Dong, Chuang; Liaw, Peter K.

    2015-08-01

    Structural stabilities of β-Ti alloys are generally investigated by an empirical Mo equivalent, which quantifies the stability contribution of each alloying element, M, in comparison to that of the major β-Ti stabilizer, Mo. In the present work, a new Mo equivalent (Moeq)Q is proposed, which uses the slopes of the boundary lines between the β and ( α + β) phase zones in binary Ti-M phase diagrams. This (Moeq)Q reflects a simple fact that the β-Ti stability is enhanced, when the β phase zone is enlarged by a β-Ti stabilizer. It is expressed as (Moeq)Q = 1.0 Mo + 0.74 V + 1.01 W + 0.23 Nb + 0.30 Ta + 1.23 Fe + 1.10 Cr + 1.09 Cu + 1.67 Ni + 1.81 Co + 1.42 Mn + 0.38 Sn + 0.34 Zr + 0.99 Si - 0.57 Al (at. pct), where the equivalent coefficient of each element is the slope ratio of the [ β/( α + β)] boundary line of the binary Ti-M phase diagram to that of the Ti-Mo. This (Moeq)Q is shown to reliably characterize the critical stability limit of multi-component β-Ti alloys with low Young's moduli, where the critical lower limit for β stabilization is (Moeq)Q = 6.25 at. pct or 11.8 wt pct Mo.

  16. Seasonal Effects on the Relationships Between Soil Water Content, Pore Water Pressure and Shear Strength and Their Implications for Slope Stability

    NASA Astrophysics Data System (ADS)

    Hughes, P. N.

    2015-12-01

    A soil's shear resistance is mainly dependent upon the magnitude of effective stress. For small to medium height slopes (up to 10m) in clay soils the total stress acting along potential failure planes will be low, therefore the magnitude of effective stress (and hence soil shear strength) will be dominated by the pore-water pressure. The stability of slopes on this scale through periods of increased precipitation is improved by the generation of negative pore pressures (soil suctions) during preceding, warmer, drier periods. These negative pore water pressures increase the effective stress within the soil and cause a corresponding increase in shearing resistance. The relationships between soil water content and pore water pressure (soil water retention curves) are known to be hysteretic, but for the purposes of the majority of slope stability assessments in partially saturated clay soils, these are assumed to be consistent with time. Similarly, the relationship between shear strength and water content is assumed to be consistent over time. This research presents a laboratory study in which specimens of compacted Glacial Till (typical of engineered slopes within the UK) were subjected to repeated cycles of wetting and drying to simulate seasonal cycles. At predetermined water contents, measurements of soil suction were made using tensiometer and dewpoint potentiometer methods. The undrained shear strength of the specimens was then measured using triaxial strength testing equipment. Results indicate that repeated wetting and drying cycles caused a change in the soil water retention behaviour. A reduction in undrained shear strength at corresponding water contents along the wetting and drying paths was also observed. The mechanism for the change in the relationship is believed to be a deterioration in the soil physical structure due to shrink/swell induced micro-cracking. The non-stationarity of these relationships has implications for slope stability assessment.

  17. The stability of gas hydrate field in the northeastern continental slope of Sakhalin Island, Sea of Okhotsk, as inferred from analysis of heat flow data and its implications for slope failures

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Lee, S.; Jin, Y.; Baranov, B.; Obzhirov, A.; Salomatin, A.; Shoji, H.

    2012-12-01

    The sudden release of methane in shallow water due to ocean warming and/or sea level drop, leading to extensive mass wasting at continental margins, has been suggested as a possible cause of global climate change. In the northeastern continental slope of the Sakhalin Island (Sea of Okhotsk), numerous gas hydrate-related manifestations occur, including hydroacoustic anomaly (gas flare) in the water column, pockmarks and mounds on the seafloor, seepage structures and bottom-simulating reflectors (BSRs). The gas hydrate found at 385 mbsl represents the shallowest occurrence ever recorded in the Okhotsk Sea. In this study, we modeled the gas hydrate stability zone (GHSZ) using methane gas composition, water temperature and geothermal gradient to see if it is consistent with the observed depth of BSR. An important distinction can be made between the seafloor containing seepage features and normal seafloor in terms of their thermal structure. The depth of BSR matches well with the base of GHSZ estimated from the background heat flow (geothermal gradient). A large slope failure feature is found in the northern Sakhalin continental slope. We explore the possibility that this failure was caused by gas hydrate dissociation, based on the past climate change history and inference from the GHSZ modeling. Prediction of the natural landslide is difficult; however, new stratigraphic evidence from subbottom profiles suggests that the landslide occurred at 20 ka which is roughly consistent with the period of sea level drop during the Last Glacial Maximum. Furthermore, this region has witnessed a rapid sea water temperature increase (~0.6°C) in the last 50 years. If such a trend continues, additional slope failure can be expected in the near future in this region.

  18. Geomorphology and Sediment Stability of a Segment of the U.S. Continental Slope off New Jersey.

    PubMed

    Robb, J M; Hampson, J C; Twichell, D C

    1981-02-27

    The morphology of complex deposits of Pleistocene sediments covering the upper continental slope between Lindenkohl Canyon and South Toms Canyon results from both depositional and erosional processes. Small slump or slide features were detected primarily on the flanks of canyons or valleys and were observed to occur only within Pleistocene-aged sediments. Eocene to Miocene sediments are exposed over much of the mid- and lower slope in this area.

  19. Geotechnical characteristics and stability analysis of rock-soil aggregate slope at the Gushui Hydropower Station, southwest China.

    PubMed

    Zhou, Jia-wen; Shi, Chong; Xu, Fu-gang

    2013-01-01

    Two important features of the high slopes at Gushui Hydropower Station are layered accumulations (rock-soil aggregate) and multilevel toppling failures of plate rock masses; the Gendakan slope is selected for case study in this paper. Geological processes of the layered accumulation of rock and soil particles are carried out by the movement of water flow; the main reasons for the toppling failure of plate rock masses are the increasing weight of the upper rock-soil aggregate and mountain erosion by river water. Indoor triaxial compression test results show that, the cohesion and friction angle of the rock-soil aggregate decreased with the increasing water content; the cohesion and the friction angle for natural rock-soil aggregate are 57.7 kPa and 31.3° and 26.1 kPa and 29.1° for saturated rock-soil aggregate, respectively. The deformation and failure mechanism of the rock-soil aggregate slope is a progressive process, and local landslides will occur step by step. Three-dimensional limit equilibrium analysis results show that the minimum safety factor of Gendakan slope is 0.953 when the rock-soil aggregate is saturated, and small scale of landslide will happen at the lower slope.

  20. Geotechnical Characteristics and Stability Analysis of Rock-Soil Aggregate Slope at the Gushui Hydropower Station, Southwest China

    PubMed Central

    Shi, Chong; Xu, Fu-gang

    2013-01-01

    Two important features of the high slopes at Gushui Hydropower Station are layered accumulations (rock-soil aggregate) and multilevel toppling failures of plate rock masses; the Gendakan slope is selected for case study in this paper. Geological processes of the layered accumulation of rock and soil particles are carried out by the movement of water flow; the main reasons for the toppling failure of plate rock masses are the increasing weight of the upper rock-soil aggregate and mountain erosion by river water. Indoor triaxial compression test results show that, the cohesion and friction angle of the rock-soil aggregate decreased with the increasing water content; the cohesion and the friction angle for natural rock-soil aggregate are 57.7 kPa and 31.3° and 26.1 kPa and 29.1° for saturated rock-soil aggregate, respectively. The deformation and failure mechanism of the rock-soil aggregate slope is a progressive process, and local landslides will occur step by step. Three-dimensional limit equilibrium analysis results show that the minimum safety factor of Gendakan slope is 0.953 when the rock-soil aggregate is saturated, and small scale of landslide will happen at the lower slope. PMID:24082854

  1. Development of a GIS-based failure investigation system for highway soil slopes

    NASA Astrophysics Data System (ADS)

    Ramanathan, Raghav; Aydilek, Ahmet H.; Tanyu, Burak F.

    2015-06-01

    A framework for preparation of an early warning system was developed for Maryland, using a GIS database and a collective overlay of maps that highlight highway slopes susceptible to soil slides or slope failures in advance through spatial and statistical analysis. Data for existing soil slope failures was collected from geotechnical reports and field visits. A total of 48 slope failures were recorded and analyzed. Six factors, including event precipitation, geological formation, land cover, slope history, slope angle, and elevation were considered to affect highway soil slope stability. The observed trends indicate that precipitation and poor surface or subsurface drainage conditions are principal factors causing slope failures. 96% of the failed slopes have an open drainage section. A majority of the failed slopes lie in regions with relatively high event precipitation ( P>200 mm). 90% of the existing failures are surficial erosion type failures, and only 1 out of the 42 slope failures is deep rotational type failure. More than half of the analyzed slope failures have occurred in regions having low density land cover. 46% of failures are on slopes with slope angles between 20° and 30°. Influx of more data relating to failed slopes should give rise to more trends, and thus the developed slope management system will aid the state highway engineers in prudential budget allocation and prioritizing different remediation projects based on the literature reviewed on the principles, concepts, techniques, and methodology for slope instability evaluation (Leshchinsky et al., 2015).

  2. Slope stability, triggering factors and threshold conditions. Study of debris flow activity in the Reyðarfjörður fjord, eastern Iceland.

    NASA Astrophysics Data System (ADS)

    Margeirsson, Guðbjörn; Sæmundsson, Þorsteinn; Norðdahl, Hreggviður

    2016-04-01

    Precipitation is one of the main triggering factor for debris flow activity in Eastern Iceland, but the amount needed, duration and the rainfall and its intensity to trigger the flow (e.g. the threshold condition) can vary considerably between areas. There are a few factors that have to be taken into account to determine the threshold condition and slope stability between areas, such as the slope angle and aspect, type and thickness of loose material, vegetation cover and gully distribution. Weather factors such as air and soil temperature, wind speed and wind direction is also crucial. The study area is located in the Reyðarfjörður fjord, one of the longest fjords on the east coast of Iceland. It is a 30 km long glacially eroded fjord, cut into the Tertiary bedrock. The bedrock is mostly made up of jointed basaltic lava flows, individual flows can vary in thickness from 2-30 m and usually separated by lithified sedimentary horizons often red in color. The slopes of the fjord are steep up to 900 m high, often consisting of nearly vertical cliffs, 60°-90°, in the upper parts of the slopes. The lower parts are covered with various glaciogenic landforms and consist of sediments and talus material. Several small hanging valleys and numerous small gullies and streams occur along the both sides of the fjord. The debris flow activity in the Reyðafjörður fjord is mostly constrained to the gullies and streams. Some activity has also been observed on the slopes between the gullies, but such activity is usually connected to extreme conditions, during or following heavy rain storms or a rainfall, especially of long duration. The aim of the study is to map the distribution of loose slope sediments in two areas inside the fjord, collect data about the known debris flow history, analyze various weather patterns which have contributed to these debris flows and understand how variables between the slopes react differently to different factors.

  3. Deterministic estimation of hydrological thresholds for shallow landslide initiation and slope stability models: case study from the Somma-Vesuvius area of southern Italy

    USGS Publications Warehouse

    Baum, Rex L.; Godt, Jonathan W.; De Vita, P.; Napolitano, E.

    2012-01-01

    Rainfall-induced debris flows involving ash-fall pyroclastic deposits that cover steep mountain slopes surrounding the Somma-Vesuvius volcano are natural events and a source of risk for urban settlements located at footslopes in the area. This paper describes experimental methods and modelling results of shallow landslides that occurred on 5–6 May 1998 in selected areas of the Sarno Mountain Range. Stratigraphical surveys carried out in initiation areas show that ash-fall pyroclastic deposits are discontinuously distributed along slopes, with total thicknesses that vary from a maximum value on slopes inclined less than 30° to near zero thickness on slopes inclined greater than 50°. This distribution of cover thickness influences the stratigraphical setting and leads to downward thinning and the pinching out of pyroclastic horizons. Three engineering geological settings were identified, in which most of the initial landslides that triggered debris flows occurred in May 1998 can be classified as (1) knickpoints, characterised by a downward progressive thinning of the pyroclastic mantle; (2) rocky scarps that abruptly interrupt the pyroclastic mantle; and (3) road cuts in the pyroclastic mantle that occur in a critical range of slope angle. Detailed topographic and stratigraphical surveys coupled with field and laboratory tests were conducted to define geometric, hydraulic and mechanical features of pyroclastic soil horizons in the source areas and to carry out hydrological numerical modelling of hillslopes under different rainfall conditions. The slope stability for three representative cases was calculated considering the real sliding surface of the initial landslides and the pore pressures during the infiltration process. The hydrological modelling of hillslopes demonstrated localised increase of pore pressure, up to saturation, where pyroclastic horizons with higher hydraulic conductivity pinch out and the thickness of pyroclastic mantle reduces or is

  4. Mechanical Stability of Stratified Sediments along the upper continental Slope off Vesterålen, northern Norway - Insights from in situ CPTU Tests

    NASA Astrophysics Data System (ADS)

    Voelker, D.; Stegmann, S.; Kreiter, S.; L'Heureux, J. S.; Vanneste, M. W. B.; Baeten, N. J.; Knudsen, S.; Rise, L.; Longva, O.; Brendryen, J.; Haflidason, H.; Chand, S.; Mörz, T.; Kopf, A.

    2015-12-01

    High-resolution single channel-seismic data (3.5 kHz) reveal small-scale submarine landslide structures and superficial deformation features (e.g. tension cracks) along the gently dipping (3°) upper continental slope west of the Vesterålen Archipelago off northern Norway. Previous laboratory-based geotechnical studies attest that the slope is per sestable and that seismic events in an order of magnitude M5.7 may have triggered the slope sediments to fail. Here we present geotechnical in situ data (sedimentary strength, pore pressure), which were obtained with RV Poseidon in summer 2014 using the static CPTU system GOST. The CPTU system provided high-resolution geotechnical profiles of the uppermost sediments to a maximum penetration depth of ~ 20 m at six sites within the landslide features and beside them in undisturbed slope sediments as reference. The CPTU data reveal the occurrence of mechanically weaker zones (MWZ) by the drop of sedimentary strength. These zones are interbedded by coarser, more competent layers. The occurrence of sensitive fine-grained material may be responsible for the loss of strength in the deeper portion (appx. 12 to 18 m below seafloor). An 1D infinite pseudo-static stability analysis attests that the mechanically weaker zones (MWZ) correlate well with portions, where the Factor of Safety (FoS) ≤ 1 (meta-stable to unstable) indicates permanent deformation or failure in case additional dynamic load is induced by an earthquake. Thus, the mechanically weak layers can be considered as one important pre-condition for landslide activity. In conclusion, the integration of in situ CPTU data with geophysical data improves soil characterization and hence foster a better understanding of the pre-conditioning factors for slope instability at the upper continental slope off Vesterålen. Risk assessment for the present-day slope off Vesterålen is particularly crucial, because the opening of the region for offshore oil and gas exploration is

  5. Dynamic stability as affected by the longitudinal moment of inertia

    NASA Technical Reports Server (NTRS)

    Wilson, Edwin B

    1924-01-01

    In a recent Technical Note (NACA-TN-115, October, 1922), Norton and Carrol have reported experiments showing that a relatively large (15 per cent) increase in longitudinal moment of inertia made no noticeable difference in the stability of a standard SE-5A airplane. They point out that G. P. Thomson, "Applied Aeronautics," page 208, stated that an increase in longitudinal moment of inertia would decrease the stability. Neither he nor they make any theoretical forecast of the amount of decrease. Although it is difficult, on account of the complications of the theory of stability of the airplane, to make any accurate forecast, it is the purpose of this report to attempt a discussion of the matter theoretically with reference to finding a rough quantitative estimate.

  6. FACTORS AFFECTING DISINFECTION AND STABILIZATION OF SEWAGE SLUDGE

    EPA Science Inventory

    Effective disinfection and stabilization of sewage sludge prior to land application is essential to not only protect human health, but also to convince the public of its benefits and safety. A basic understanding of the key factors involved in producing a stable biosolid product ...

  7. Physical and geotechnical properties and assessment of sediment stability on the continental slope and basin of the Bransfield Basin (Antarctica Peninsula)

    USGS Publications Warehouse

    Casas, D.; Ercilla, G.; Estrada, F.; Alonso, B.; Baraza, J.; Lee, H.; Kayen, R.; Chiocci, F.

    2004-01-01

    Our investigation is centred on the continental slope of the Antarctic Peninsula and adjacent basin. Type of sediments, sedimentary stratigraphy, and physical and geotechnical characterization of the sediments have been integrated. Four different types of sediments have been defined: diamictons, silty and muddy turbidites, muddy, silty and muddy matrix embedded clast contourites. There is a close correspondence between the physical properties (density, magnetic susceptibility and p-wave velocity) and the texture and/or fabric as laminations and stratification. From a quantitative point of view, only a few statistical correlations between textural and physical properties have been found. Within the geotechnical properties, only water content is most influenced by texture. This slope, with a maximum gradient observed (20??), is stable, according to the stability under gravitational loading concepts, and the maximum stable slope that would range from 22?? to 29??. Nevertheless, different instability features have been observed. Volcanic activity, bottom currents, glacial loading-unloading or earthquakes can be considered as potential mechanisms to induce instability in this area. Copyright ?? Taylor & Francis Inc.

  8. Analyses of fracture pattern and slope stability of road-cut sections in the northwestern Daegu, SE Korea

    NASA Astrophysics Data System (ADS)

    Ko, K.; Choi, J.; Kim, Y.; Geologic Structure; Geohazard Research Group

    2010-12-01

    Recently numerous road-cut sections have been exposed due to national road project in the Daegu area of SE Korea, in which Cretaceous sedimentary layers are widely exposed. Easily recognizable bedding changes are very useful for analysis of geological structures. Therefore, we were able to study the characteristics of fracture patterns in this area based on the analysis of well exposed sections. In this study, we aimed to understand fracture propagation and the controlling factors on slope failure in this kind of sedimentary rocks. For this purpose, we carried out satellite image and aerial photo analyses and detailed mapping on well-exposed road-cut sections, to understand their structural characteristics. From these analyses, we recognized N-S, NNE-SSW and NW-SE trending lineaments. Slickenlines and secondary fractures indicate dominant right-lateral strike-slip movement. Normal faults and dykes have mainly N-S or NNW-SSE trends. In a quarry section, different slip patterns are observed along vertical normal faults that cross different lithologic layers. Slip occurred along pre-existing vertical fractures in sandstone, and it has occurred along lower angle fault planes in shale layers. Although generally proportional relationships between joint spacing and layer thickness are observed, some exposures do not match well with the suggested model. Irregular, high density joint spacing has developed along layers, which are more competent than surrounding layers. This may be the result of different controlling factors rather than lithology and layer thickness alone. At the arc shaped road-cutting, multiple discontinuities have developed with various strikes. At this location, however, only one discontinuity, parallel or sub-parallel to the cutting, is known to have caused slope failure. Therefore, the angular relationship between the discontinuities and the cutting surface appears to be the most important factor in the slope failure in this area.

  9. Deep-water seamounts in the NE Atlantic, sources of landslides-induced tsunamis: Slope stability analysis and tsunami numerical modelling

    NASA Astrophysics Data System (ADS)

    Baptista, M. A.; Omira, R.; Ramalho, I.; Vales, D.; Matias, L. M.; Terrinha, P.

    2015-12-01

    Submarine mass failures (SMFs) present one of the significant marine Geo-hazards. Their importance as contributors to tsunami hazard has been recognized over the last 20-30 years, but they are seldom considered in the evaluation of quantitative tsunami impact or in the design of warning strategies. This study aims to investigate the slope stability of the SMFs in the NE Atlantic, their companion tsunami and the associated hazard at the target coasts. It focuses on two major deep-water seamounts of the NE Atlantic, the Gorringe Bank and the Hirondelle, where evidences of large SMFs have been found. Slope stability analysis is often based on relationships between landslides and earthquakes. Here, within each considered seamount, slope failure potential is investigated through the pseudo-static method. This analysis allows establishing a relationship between the size of the SMF and the critical earthquake peak ground acceleration necessary to initiate it and therefore define the possible SMF scenarios. Numerical modelling of SMF-induced tsunami generation is then employed to test the tsunamigenic potential of each defined scenario. It is performed using a multi-layers viscous shallow-water model, where the lower layer represents the deformable slide that is assumed to be a viscous-incompressible fluid, and bounded by the upper layer of seawater assumed to be inviscid and incompressible. The propagation of tsunami waves is simulated employing non-linear shallow water equations. Results are presented in terms of: 1) slope stability curves that establish the relationship between the probable earthquake magnitudes and the possible sizes of SMFs, 2) possible SMF scenarios within each seamount, 3) potential of tsunami generation for each SMF, 4) tsunami coastal impact at target coasts. Results show that SMFs in the NE Atlantic have the potential of generating large tsunamis with significant impact along the surrounding coasts. Therefore, more attention must be accorded to

  10. Quantifying the effects of root reinforcing on slope stability: results of the first tests with an new shearing device

    NASA Astrophysics Data System (ADS)

    Rickli, Christian; Graf, Frank

    2013-04-01

    The role of vegetation in preventing shallow soil mass movements such as shallow landslides and soil erosion is generally well recognized and, correspondingly, soil bioengineering on steep slopes has been widely used in practice. However, the precise effectiveness of vegetation regarding slope stabilityis still difficult to determine. A recently designed inclinable shearing device for large scale vegetated soil samples allows quantitative evaluation of the additional shear strength provided by roots of specific plant species. In the following we describe the results of a first series of shear strength experiments with this apparatus focusing on root reinforcement of White Alder (Alnus incana) and Silver Birch (Betula pendula) in large soil block samples (500 x 500 x 400 mm). The specimen with partly saturated soil of a maximum grain size of 10 mm were slowly sheared at an inclination of 35° with low normal stresses of 3.2 kPa accounting for natural conditions on a typical slope prone to mass movements. Measurements during the experiments involved shear stress, shear displacement and normal displacement, all recorded with high accuracy. In addition, dry weights of sprout and roots were measured to quantify plant growth of the planted specimen. The results with the new apparatus indicate a considerable reinforcement of the soil due to plant roots, i.e. maximum shear stress of the vegetated specimen were substantially higher compared to non-vegetated soil and the additional strength was a function of species and growth. Soil samples with seedlings planted five months prior to the test yielded an important increase in maximum shear stress of 250% for White Alder and 240% for Silver Birch compared to non-vegetated soil. The results of a second test series with 12 month old plants showed even clearer enhancements in maximum shear stress (390% for Alder and 230% for Birch). Overall the results of this first series of shear strength experiments with the new apparatus

  11. Analysis of rainfall infiltration law in unsaturated soil slope.

    PubMed

    Zhang, Gui-rong; Qian, Ya-jun; Wang, Zhang-chun; Zhao, Bo

    2014-01-01

    In the study of unsaturated soil slope stability under rainfall infiltration, it is worth continuing to explore how much rainfall infiltrates into the slope in a rain process, and the amount of rainfall infiltrating into slope is the important factor influencing the stability. Therefore, rainfall infiltration capacity is an important issue of unsaturated seepage analysis for slope. On the basis of previous studies, rainfall infiltration law of unsaturated soil slope is analyzed. Considering the characteristics of slope and rainfall, the key factors affecting rainfall infiltration of slope, including hydraulic properties, water storage capacity (θs - θr), soil types, rainfall intensities, and antecedent and subsequent infiltration rates on unsaturated soil slope, are discussed by using theory analysis and numerical simulation technology. Based on critical factors changing, this paper presents three calculation models of rainfall infiltrability for unsaturated slope, including (1) infiltration model considering rainfall intensity; (2) effective rainfall model considering antecedent rainfall; (3) infiltration model considering comprehensive factors. Based on the technology of system response, the relationship of rainfall and infiltration is described, and the prototype of regression model of rainfall infiltration is given, in order to determine the amount of rain penetration during a rain process.

  12. Cow biological type affects ground beef colour stability.

    PubMed

    Raines, Christopher R; Hunt, Melvin C; Unruh, John A

    2009-12-01

    To determine the effects of cow biological type on colour stability of ground beef, M. semimembranosus from beef-type (BSM) and dairy-type (DSM) cows was obtained 5d postmortem. Three blends (100% BSM, 50% BSM+50% DSM, 100% DSM) were adjusted to 90% and 80% lean points using either young beef trim (YBT) or beef cow trim (BCT), then packaged in high oxygen (High-O(2); 80% O(2)) modified atmosphere (MAP). The BSM+YBT patties had the brightest colour initially, but discoloured rapidly. Although DSM+BCT patties had the darkest colour initially, they discoloured least during display. Metmyoglobin reducing ability of ground DSM was up to fivefold greater than ground BSM, and TBARS values of BSM was twofold greater than DSM by the end of display (4d). Though initially darker than beef cow lean, dairy cow lean has a longer display colour life and may be advantageous to retailers using High-O(2) MAP.

  13. Towards electrical resistivity soundings in eco-engineering: A non-invasive and fast method to model the near-subsurface characteristics on stabilized alpine slopes.

    NASA Astrophysics Data System (ADS)

    Bast, Alexander; Meyer, Christine; Meier, Wolfgang; Wilcke, Wolfgang; Lüscher, Peter; Graf, Frank; Gärtner, Holger

    2014-05-01

    The observation and monitoring of the aboveground plant development is a common practice in eco-engineering to estimate the plant's influence on the stabilization process. In contrast to this aboveground "sphere", the near subsurface is invisible and therefore difficult to address. To get an impression of the near subsurface and to model slope stability, (soil)samples are taken or a soil profile is dug and root traits (e.g., tensile strength) are determined. Other parameters as rooting depth, root length density, root clustering or the type of root in general are also of interest. However, soil samples or soil profiles only provide limited point-by-point data, alter parts of the study site, and are often time-consuming and expensive. The development of plants results a complex spatial and temporal distribution of the root network along a slope. This network causes shear strength variations and hydrological heterogeneities in the near subsurface within short distances. In contrast to the common point data, geophysical methods provide minimally-invasive, spatial and, via a time-lapse approach (monitoring), also temporal information of the near subsurface conditions. Hence, by measuring physical properties of the near subsurface, the root system, i.e. root distribution and rooting depth can be modeled. Furthermore, if a correlation between root traits and the measured physical properties is determined, the corresponding root trait can be estimated. To test this approach we applied electrical resistivity tomography (ERT) in a subalpine catchment in the Prättigau valley/Eastern Swiss Alps. Different ERT-soundings were conducted using varying electrode spacings (5cm, 25cm, 50cm and 100cm), electrode arrays (Wenner and Wenner-Schlummberger) and locations (eco-engineered slopes, stabilized two, three and 17 years ago; two forest stands of different stand densities). Furthermore, we took soil samples along the electrical profiles, and dug out several soil profiles to

  14. The Saguenay Fjord, Quebec, Canada: Integrating marine geotechnical and geophysical data for spatial seismic slope stability and hazard assessment

    USGS Publications Warehouse

    Urgeles, R.; Locat, J.; Lee, H.J.; Martin, F.

    2002-01-01

    In 1996 a major flood occurred in the Saguenay region, Quebec, Canada, delivering several km3 of sediment to the Saguenay Fjord. Such sediments covered large areas of the, until then, largely contaminated fjord bottom, thus providing a natural capping layer. Recent swath bathymetry data have also shown that sediment landslides are widely present in the upper section of the Saguenay Fjord, and therefore, should a new event occur, it would probably expose the old contaminated sediments. Landslides in the Upper Saguenay Fjord are most probably due to earthquakes given its proximity to the Charlevoix seismic region and to that of the 1988 Saguenay earthquake. In consequence, this study tries to characterize the permanent ground deformations induced by different earthquake scenarios from which shallow sediment landslides could be triggered. The study follows a Newmark analysis in which, firstly, the seismic slope performance is assessed, secondly, the seismic hazard analyzed, and finally an evaluation of the seismic landslide hazard is made. The study is based on slope gradients obtained from EM1000 multibeam bathymetry data as well as water content and undrained shear strength measurements made in box and gravity cores. Ground motions integrating local site conditions were simulated using synthetic time histories. The study assumes the region of the 1988 Saguenay earthquake as the most likely source area for earthquakes capable of inducing large ground motions in the Upper Saguenay region. Accordingly, we have analyzed several shaking intensities to deduce that generalized sediment displacements will begin to occur when moment magnitudes exceed 6. Major displacements, failure, and subsequent landslides could occur only from earthquake moment magnitudes exceeding 6.75. ?? 2002 Elsevier Science B.V. All rights reserved.

  15. Assessments of wildlife viability, old-growth timber volume estimates, forested wetlands, and slope stability. Forest Service general technical report

    SciTech Connect

    Shaw, C.G.; Julin, K.R.

    1997-03-01

    Conceptual Approaches for Maintaining Well-Distributed Viable Wildlife Populations: A Resource Assessment; Options for Defining Old-Growth Timber Volume Strata: A Resource Assessment; Tentative Suitability of Forested Wetlands for Timber Production: A Resource Assessment; and Controlling Stability Characteristics of Steep Terrain With Discussion of Needed Standardization for Mass Movement Hazard Indexing: A Resource Assessment.

  16. Stability Affects of Artificial Viscosity in Detonation Modeling

    SciTech Connect

    Vitello, P; Souers, P C

    2002-06-03

    Accurate multi-dimensional modeling of detonation waves in solid HE materials is a difficult task. To treat applied problems which contain detonation waves one must consider reacting flow with a wide range of length-scales, non-linear equations of state (EOS), and material interfaces at which the detonation wave interacts with other materials. To be useful numerical models of detonation waves must be accurate, stable, and insensitive to details of the modeling such as the mesh spacing, and mesh aspect ratio for multi-dimensional simulations. Studies we have performed show that numerical simulations of detonation waves can be very sensitive to the form of the artificial viscosity term used. The artificial viscosity term is included in our ALE hydrocode to treat shock discontinuities. We show that a monotonic, second order artificial viscosity model derived from an approximate Riemann solver scheme can strongly damp unphysical oscillations in the detonation wave reaction zone, improving the detonation wave boundary wall interaction. These issues are demonstrated in 2D model simulations presented of the 'Bigplate' test. Results using LX-I 7 explosives are compared with numerical simulation results to demonstrate the affects of the artificial viscosity model.

  17. TRIGRS - A Fortran Program for Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Analysis, Version 2.0

    USGS Publications Warehouse

    Baum, Rex L.; Savage, William Z.; Godt, Jonathan W.

    2008-01-01

    The Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Model (TRIGRS) is a Fortran program designed for modeling the timing and distribution of shallow, rainfall-induced landslides. The program computes transient pore-pressure changes, and attendant changes in the factor of safety, due to rainfall infiltration. The program models rainfall infiltration, resulting from storms that have durations ranging from hours to a few days, using analytical solutions for partial differential equations that represent one-dimensional, vertical flow in isotropic, homogeneous materials for either saturated or unsaturated conditions. Use of step-function series allows the program to represent variable rainfall input, and a simple runoff routing model allows the user to divert excess water from impervious areas onto more permeable downslope areas. The TRIGRS program uses a simple infinite-slope model to compute factor of safety on a cell-by-cell basis. An approximate formula for effective stress in unsaturated materials aids computation of the factor of safety in unsaturated soils. Horizontal heterogeneity is accounted for by allowing material properties, rainfall, and other input values to vary from cell to cell. This command-line program is used in conjunction with geographic information system (GIS) software to prepare input grids and visualize model results.

  18. Significance analysis of the leachate level in a solid waste landfill in a coastal zone using total water balance and slope stability alternatives

    SciTech Connect

    Koo, Ja-Kong; Do, Nam-Young

    1996-12-31

    The K site near Seoul began landfilling in 1992. The landfilled wastes include municipal solid waste (66.4%), construction residues (20.4%), water and wastewater sludges (trace levels), and hazardous waste (trace levels). The water content of the municipal solid waste is very high (47.3%); as a result, the leachate level (average E.L.) of the landfill, the design value of which is 7.0 m, was measured at 10.3 m in January 1995 and is increasing. The increase of leachate level in the landfill site causes a problem with slope stability. The leachate level at each disposal stage divided by the intermediate cover layer was calculated with the HELP (Hydrologic Evaluation of Landfill Performance) model and calibrated with the data measured from February 1993 to June 1995. Also, the hydraulic conductivities of the waste layer and the intermediate cover layer in each stage were calibrated continuously with HELP model analysis. To verify these results, the total water balance in the landfill site was calculated using the infiltration rate calculated from HELP modeling. The leachate level was E.L. 10.0 m, which was close to the measured leachate level. To estimate the change of the leachate level in the future, the total water balances with different leachate discharge rates of 3,000, 3,500, and 5,000 m{sup 3}/day were analyzed. When the leachate discharge rate was 5,000 ton/day and the initial water content was decreased below 25%, the average leachate level was 10.8 m. This result satisfies the safety factor requirements (=1.3) for landfill slope stability. 4 refs., 8 figs., 1 tab.

  19. Dermal nanocrystals from medium soluble actives - physical stability and stability affecting parameters.

    PubMed

    Zhai, Xuezhen; Lademann, Jürgen; Keck, Cornelia M; Müller, Rainer H

    2014-09-01

    Nanocrystals are meanwhile applied to increase the dermal penetration of drugs, but were applied by now only to poorly soluble drugs (e.g. 1-10 μg/ml). As a new concept nanocrystals from medium soluble actives were produced, using caffeine as model compound (solubility 16 mg/ml at 20 °C). Penetration should be increased by (a) further increase in solubility and (b) mainly by increased hair follicle targeting of nanocrystals compared to pure solution. Caffeine nanocrystal production in water lead to pronounced crystal growth. Therefore the stability of nanocrystals in water-ethanol (1:9) and ethanol-propylene glycol (3:7) mixtures with lower dielectric constant D was investigated, using various stabilizers. Both mixtures in combination with Carbopol 981 (non-neutralized) yielded stable nanosuspensions over 2 months at 4 °C and room temperature. Storage at 40 °C lead to crystal growth, attributed to too strong solubility increase, supersaturation and Ostwald ripening effects. Stability of caffeine nanocrystals at lower temperatures could not only be attributed to lower solubility, because the solubilities of caffeine in mixtures and in water are not that much different. Other effects such as quantified by reduced dielectric constant D, and specific interactions between dispersion medium and crystal surface seem to play a role. With the 2 mixtures and Carbopol 981, a basic formulation composition for this type of nanocrystals has been established, to be used in the in vivo proof of principle of the new concept.

  20. Atmospheric stability effects on wind fields and scalar mixing within and just above a subalpine forest in sloping terrain

    USGS Publications Warehouse

    Burns, Sean P.; Sun, Jielun; Lenschow, D.H.; Oncley, S.P.; Stephens, B.B.; Yi, C.; Anderson, D.E.; Hu, Jiawen; Monson, Russell K.

    2011-01-01

    Air temperature Ta, specific humidity q, CO2 mole fraction ??c, and three-dimensional winds were measured in mountainous terrain from five tall towers within a 1 km region encompassing a wide range of canopy densities. The measurements were sorted by a bulk Richardson number Rib. For stable conditions, we found vertical scalar differences developed over a "transition" region between 0.05 < Rib < 0.5. For strongly stable conditions (Rib > 1), the vertical scalar differences reached a maximum and remained fairly constant with increasing stability. The relationships q and ??c have with Rib are explained by considering their sources and sinks. For winds, the strong momentum absorption in the upper canopy allows the canopy sublayer to be influenced by pressure gradient forces and terrain effects that lead to complex subcanopy flow patterns. At the dense-canopy sites, soil respiration coupled with wind-sheltering resulted in CO2 near the ground being 5-7 ??mol mol-1 larger than aloft, even with strong above-canopy winds (near-neutral conditions). We found Rib-binning to be a useful tool for evaluating vertical scalar mixing; however, additional information (e.g., pressure gradients, detailed vegetation/topography, etc.) is needed to fully explain the subcanopy wind patterns. Implications of our results for CO2 advection over heterogenous, complex terrain are discussed. ?? 2010 Springer Science+Business Media B.V.

  1. Drainage effects on the transient, near-surface hydrologic response of a steep hillslope to rainfall: Implications for slope stability, Edmonds, Washington, USA

    USGS Publications Warehouse

    Biavati, G.; Godt, J.W.; McKenna, J.P.

    2006-01-01

    Shallow landslides on steep (>25??) hillsides along Puget Sound have resulted in occasional loss of life and costly damage to property during intense or prolonged rainfall. As part of a larger project to assess landslide hazards in the Seattle area, the U.S. Geological Survey instrumented two coastal bluff sites in 2001 to observe the subsurface hydrologic response to rainfall. The instrumentation at one of these sites, near Edmonds, Washington, consists of two rain gauges, two water-content probes that measure volumetric water content at eight depths between 0.2 and 2.0 m, and two tensiometer nests that measure soil-water suction at six depths ranging from 0.2 to 1.5m. Measurements from these instruments are used to test one- and two-dimensional numerical models of infiltration and groundwater flow. Capillary-rise tests, performed in the laboratory on soil sample from the Edmonds site, are used to define the soil hydraulic properties for the wetting process. The field observations of water content and suction show an apparent effect of porosity variation with depth on the hydraulic response to rainfall. Using a range of physical properties consistent with our laboratory and field measurements, we perform sensitivity analyses to investigate the effects of variation in physical and hydraulic properties of the soil on rainfall infiltration, pore-pressure response, and, hence, slope stability. For a two-layer-system in which the hydraulic conductivity of the upper layer is at least 10 times greater than the conductivity of the lower layer, and the infiltration rate is greater than the conductivity of the lower layer, a perched water table forms above the layer boundary potentially destabilizing the upper layer of soil. Two-dimensional modeling results indicate that the addition of a simple trench drain to the same two-layer slope has differing effects on the hydraulic response depending on the initial pressure head conditions. For slope-parallel flow conditions

  2. Drainage effects on the transient, near-surface hydrologic response of a steep hillslope to rainfall: implications for slope stability, Edmonds, Washington, USA

    NASA Astrophysics Data System (ADS)

    Biavati, G.; Godt, J. W.; McKenna, J. P.

    2006-05-01

    Shallow landslides on steep (>25°) hillsides along Puget Sound have resulted in occasional loss of life and costly damage to property during intense or prolonged rainfall. As part of a larger project to assess landslide hazards in the Seattle area, the U.S. Geological Survey instrumented two coastal bluff sites in 2001 to observe the subsurface hydrologic response to rainfall. The instrumentation at one of these sites, near Edmonds, Washington, consists of two rain gauges, two water-content probes that measure volumetric water content at eight depths between 0.2 and 2.0 m, and two tensiometer nests that measure soil-water suction at six depths ranging from 0.2 to 1.5 m. Measurements from these instruments are used to test one- and two-dimensional numerical models of infiltration and groundwater flow. Capillary-rise tests, performed in the laboratory on soil sample from the Edmonds site, are used to define the soil hydraulic properties for the wetting process. The field observations of water content and suction show an apparent effect of porosity variation with depth on the hydraulic response to rainfall. Using a range of physical properties consistent with our laboratory and field measurements, we perform sensitivity analyses to investigate the effects of variation in physical and hydraulic properties of the soil on rainfall infiltration, pore-pressure response, and, hence, slope stability. For a two-layer-system in which the hydraulic conductivity of the upper layer is at least 10 times greater than the conductivity of the lower layer, and the infiltration rate is greater than the conductivity of the lower layer, a perched water table forms above the layer boundary potentially destabilizing the upper layer of soil. Two-dimensional modeling results indicate that the addition of a simple trench drain to the same two-layer slope has differing effects on the hydraulic response depending on the initial pressure head conditions. For slope-parallel flow conditions

  3. The Influence of Shales on Slope Instability

    NASA Astrophysics Data System (ADS)

    Stead, Doug

    2016-02-01

    Shales play a major role in the stability of slopes, both natural and engineered. This paper attempts to provide a review of the state-of-the-art in shale slope stability. The complexities of shale terminology and classification are first reviewed followed by a brief discussion of the important physical and mechanical properties of relevance to shale slope stability. The varied mechanisms of shale slope stability are outlined and their importance highlighted by reference to international shale slope failures. Stability analysis and modelling of anisotropic rock slope masses are briefly discussed and the potential role of brittle rock fracture and damage highlighted. A short review of shale slopes in open pits is presented.

  4. The use of "stabilization exercises" to affect neuromuscular control in the lumbopelvic region: a narrative review.

    PubMed

    Bruno, Paul

    2014-06-01

    It is well-established that the coordination of muscular activity in the lumbopelvic region is vital to the generation of mechanical spinal stability. Several models illustrating mechanisms by which dysfunctional neuromuscular control strategies may serve as a cause and/or effect of low back pain have been described in the literature. The term "core stability" is variously used by clinicians and researchers, and this variety has led to several rehabilitative approaches suggested to affect the neuromuscular control strategies of the lumbopelvic region (e.g. "stabilization exercise", "motor control exercise"). This narrative review will highlight: 1) the ongoing debate in the clinical and research communities regarding the terms "core stability" and "stabilization exercise", 2) the importance of sub-grouping in identifying those patients most likely to benefit from such therapeutic interventions, and 3) two protocols that can assist clinicians in this process.

  5. Effects of ground water, slope stability, and seismic hazard on the stability of the South Fork Castle Creek blockage in the Mount St. Helens Area, Washington

    SciTech Connect

    Meyer, W.; Sabol, M.A.; Glicken, H.X.; Voight, B.

    1984-01-01

    South Fork Castle Creek was blocked by the debris avalanche that occurred during the May 18, 1980, eruption of Mount St. Helens, Washington. A lake formed behind the blockage, eventually reaching a volume of approximately 19,000 acre-feet prior to construction of a spillway - a volume sufficiently large to pose a flood hazard of unknown magnitude to downstream areas if the lake were to break out as a result of blockage failure. Breakout of lakes formed in a similar fashion is fairly common and several such events occurring in recent times have posed hazards around the world. Analyses of blockage stability included determining the effects of gravitational forces and horizontal forces induced by credible earthquakes from the Mount St. Helens seismic zone, which passes within several miles of the blockage. The blockage is stable at September 1983 water levels under static gravitational forces. If an earthquake with magnitude near 6.0 occurred with September 1983 water levels, movement on the order of 5 feet on both upstream and downstream parts of the blockage over much of its length could potentially occur. If the sliding blocks liquified, retrogressive failure could lead to lake breakout, but this is not considered to be probable. 24 refs., 25 figs., 5 tabs.

  6. Water making hot rocks soft: How hydrothermal alteration affects volcano stability

    NASA Astrophysics Data System (ADS)

    Ball, J. L.

    2015-12-01

    My research involves using numerical models of groundwater flow and slope stability to determine how long-term hydrothermal alteration in stratovolcanoes can cause increases in pore fluid pressure that lead to edifice collapse. Or in simpler terms: We can use computers to figure out how and why water that moves through hot rocks changes them into softer rocks that want to fall down. It's important to pay attention to the soft rocks even if they look safe because this can happen a long time after the stuff that makes them hot goes away or becomes cool. Wet soft rocks can go very far from high places and run over people in their way. I want show where the soft wet rocks are and how they might fall down so people will be safer.

  7. Downward Slope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This false-color image from NASA's Mars Exploration Rover Opportunity panoramic camera shows a downward view from the rover as it sits at the edge of 'Endurance' crater. The gradual, 'blueberry'-strewn slope before the rover contains an exposed dark layer of rock that wraps around the upper section of the crater. Scientists suspect that this rock layer will provide clues about Mars' distant past. This mosaic image comprises images taken from 10 rover positions using 750, 530 and 430 nanometer filters, acquired on sol 131 (June 6, 2004).

  8. Gullied Slope

    NASA Technical Reports Server (NTRS)

    2005-01-01

    20 May 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows gullies formed on an equator-facing slope among mounds in Acidalia Planitia. Similar gullies occur in a variety of settings at middle and polar latitudes in both martian hemispheres.

    Location near: 49.8oN, 22.7oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

  9. Hillslope stability and land use (1985). Volume II

    SciTech Connect

    Sidle, R.C.; Pearce, A.J.; O'Loughlin, C.L.

    1985-01-01

    This book emphasizes the natural factors affecting slope stability, including soils and geomorphic, hydrologic, vegetative, and seismic factors and provides information on landslide classification, global damage, and analytical methods. The effects of various extensive and intensive land management practices on slope stability are discussed together with methods for prediction, avoidance, and control. Examples of terrain evaluation procedures and land management practices are presented.

  10. Density-dependent dispersal and relative dispersal affect the stability of predator-prey metacommunities.

    PubMed

    Hauzy, Céline; Gauduchon, Mathias; Hulot, Florence D; Loreau, Michel

    2010-10-07

    Although density-dependent dispersal and relative dispersal (the difference in dispersal rates between species) have been documented in natural systems, their effects on the stability of metacommunities are poorly understood. Here we investigate the effects of intra- and interspecific density-dependent dispersal on the regional stability in a predator-prey metacommunity model. We show that, when the dynamics of the populations reach equilibrium, the stability of the metacommunity is not affected by density-dependent dispersal. However, the regional stability, measured as the regional variability or the persistence, can be modified by density-dependent dispersal when local populations fluctuate over time. Moreover these effects depend on the relative dispersal of the predator and the prey. Regional stability is modified through changes in spatial synchrony. Interspecific density-dependent dispersal always desynchronizses local dynamics, whereas intraspecific density-dependent dispersal may either synchronize or desynchronize it depending on dispersal rates. Moreover, intra- and interspecific density-dependent dispersal strengthen the top-down control of the prey by the predator at intermediate dispersal rates. As a consequence the regional stability of the metacommunity is increased at intermediate dispersal rates. Our results show that density-dependent dispersal and relative dispersal of species are keys to understanding the response of ecosystems to fragmentation.

  11. Characterization of H/V Spectral Ratios for the Assessment of Slope Stability in the Gas Hydrate-rich Area: an Example from Offshore SW Taiwan

    NASA Astrophysics Data System (ADS)

    Lin, J. Y.; Tsia, C. H.; Cheng, W. B.; Chin, S. J.; Lin, S. S.; Liang, C. W.

    2015-12-01

    The Nakamura's method, which calculates the ratios between horizontal and vertical component spectra of seismic signals (H/V), is widely used in the inland area. However, few related estimations were performed for the offshore area and little knowledge for the marine sediments were obtained. From 2013 to 2015, three passive ocean bottom seismometer (OBS) experiments were conducted in gas hydrate-rich area offshore SW Taiwan in the aim of acquiring information related to the physical properties of seafloor sediments. The H/V of the seafloor sediments in the three areas were estimated by using the ambient noise and seismic signal recorded by OBSs. The resonance frequency of each site was estimated from the main peak of H/V distribution and a range between 5 and 10 Hz were obtained. Based on the empirical law, this resonance frequency range should correspond to a sediment thickness of approximately several to ten of meters. This estimation is consistent with the thickness of the sedimentary cover imaged by chirp sonar survey, suggesting that the site response of seafloor is dominantly controlled by the unconsolidated sedimentary layer on the top of the sea bed. Remarkably, the H/V ratios obtained in our study area are much larger than that calculated for the inland areas. The magnification can reach as high as 50 to more than 100. This observation infers that the sea water movement might emphasize the horizontal motion of the marine sediments, which is crucial for the slope stability assessment. Moreover, for most stations located in the active margin, no distinct peak is observed for the H/V pattern calculated during earthquakes. However, in the passive margin, the H/V peak calculated from ambient noise and earthquakes is mostly identical. This phenomenon may suggest that relatively unclear sedimentary boundary exist in the active margin environment. Estimating H/V spectral ratios of data recorded by the OBSs deployed in the southwest Taiwan offshore area offers a

  12. Seat surface inclination may affect postural stability during Boccia ball throwing in children with cerebral palsy.

    PubMed

    Tsai, Yung-Shen; Yu, Yi-Chen; Huang, Po-Chang; Cheng, Hsin-Yi Kathy

    2014-12-01

    The aim of the study was to examine how seat surface inclination affects Boccia ball throwing movement and postural stability among children with cerebral palsy (CP). Twelve children with bilateral spastic CP (3 with gross motor function classification system Level I, 5 with Level II, and 4 with Level III) participated in this study. All participants underwent pediatric reach tests and ball throwing performance analyses while seated on 15° anterior- or posterior-inclined, and horizontal surfaces. An electromagnetic motion analysis system was synchronized with a force plate to assess throwing motion and postural stability. The results of the pediatric reach test (p = 0.026), the amplitude of elbow movement (p = 0.036), peak vertical ground reaction force (PVGRF) (p < 0.001), and movement range of the center of pressure (COP) (p < 0.020) were significantly affected by seat inclination during throwing. Post hoc comparisons showed that anterior inclination allowed greater amplitude of elbow movement and PVGRF, and less COP movement range compared with the other inclines. Posterior inclination yielded less reaching distance and PVGRF, and greater COP movement range compared with the other inclines. The anterior-inclined seat yielded superior postural stability for throwing Boccia balls among children with bilateral spastic CP, whereas the posterior-inclined seat caused difficulty.

  13. Allochthonous subsidy of periodical cicadas affects the dynamics and stability of pond communities.

    PubMed

    Nowlin, Weston H; González, María J; Vanni, Michael J; Stevens, M Henry H; Fields, Matthew W; Valente, Jonathon J

    2007-09-01

    Periodical cicadas emerge from below ground every 13 or 17 years in North American forests, with individual broods representing the synchronous movement of trillions of individuals across geographic regions. Due to predator satiation, most individuals escape predation, die, and become deposited as detritus. Some of this emergent biomass falls into woodland aquatic habitats (small streams and woodland ponds) and serves as a high-quality allochthonous detritus pulse in early summer. We present results of a two-part study in which we (1) quantified deposition of Brood X periodical cicada detritus into woodland ponds and low-order streams in southwestern Ohio, and (2) conducted an outdoor mesocosm experiment in which we examined the effects of deposition of different amounts of cicada detritus on food webs characteristic of forest ponds. In the mesocosm experiment, we manipulated the amount of cicada detritus input to examine if food web dynamics and stability varied with the magnitude of this allochthonous resource subsidy, as predicted by numerous theoretical models. Deposition data indicate that, during years of periodical cicada emergence, cicada carcasses can represent a sizable pulse of allochthonous detritus to forest aquatic ecosystems. In the mesocosm experiment, cicada carcass deposition rapidly affected food webs, leading to substantial increases in nutrients and organism biomass, with the magnitude of increase dependent upon the amount of cicada detritus. Deposition of cicada detritus impacted the stability of organism functional groups and populations by affecting the temporal variability and biomass minima. However, contrary to theory, stability measures were not consistently related to the size of the allochthonous pulse (i.e., the amount of cicada detritus). Our study underscores the need for theory to further explore consequences of pulsed allochthonous subsidies for food web stability.

  14. Stability Limits of Capillary Bridges: How Contact Angle Hysteresis Affects Morphology Transitions of Liquid Microstructures.

    PubMed

    de Ruiter, Riëlle; Semprebon, Ciro; van Gorcum, Mathijs; Duits, Michèl H G; Brinkmann, Martin; Mugele, Frieder

    2015-06-12

    The equilibrium shape of a drop in contact with solid surfaces can undergo continuous or discontinuous transitions upon changes in either drop volume or surface energies. In many instances, such transitions involve the motion of the three-phase contact line and are thus sensitive to contact angle hysteresis. Using a combination of electrowetting-based experiments and numerical calculations, we demonstrate for a generic sphere-plate confinement geometry how contact angle hysteresis affects the mechanical stability of competing axisymmetric and nonaxisymmetric drop conformations and qualitatively changes the character of transitions between them.

  15. Dip-slope and Dip-slope Failures in Taiwan - a Review

    NASA Astrophysics Data System (ADS)

    Lee, C.

    2011-12-01

    Taiwan is famous for dip-slope and dip-slope slides. Dip-slopes exist at many places in the fold-and-thrust belt of Taiwan. Under active cutting of stream channels and man-made excavations, a dip-slope may become unstable and susceptible for mass sliding. Daylight of a bedding parallel clay seam is the most dangerous type for dip-slope sliding. Buckling or shear-off features may also happen at toe of a long dip-slope. Besides, a dip-slope is also dangerous for shallow debris slides, if the slope angle is between 25 to 45 degrees and the debris (colluvium or slope wash) is thick (>1m). These unstable slopes may slide during a triggering event, earthquake or typhoon storm; or even slide without a triggering event, like the 2010 Tapu case. Initial buckling feature had been found in the dip-slope of the Feitsui arch dam abutment after detailed explorations. Shear-off feature have also been found in dip-slope located in right bank of the Nahua reservoir after field investigation and drilling. The Chiufengerhshan slide may also be shear-off type. On the other hand, the Tapu, the Tsaoling slides and others are of direct slide type. The Neihoo Bishan slide is a shallow debris slide on dip-slope. All these cases demonstrate the four different types of dip-slope slide. The hazard of a dip-slope should be investigated to cover these possible types of failure. The existence of bedding parallel clay seams is critical for the stability of a dip-slope, either for direct slide or buckling or shear-off type of failure, and is a hot point during investigation. Because, the stability of a dip-slope is changing with time, therefore, detailed explorations to including weathering and erosion rates are also very necessary to ensure the long-term stability of a dip-slope.

  16. SIRT1 stimulation by polyphenols is affected by their stability and metabolism.

    PubMed

    de Boer, Vincent C J; de Goffau, Marcus C; Arts, Ilja C W; Hollman, Peter C H; Keijer, Jaap

    2006-07-01

    Silent information regulator two ortholog 1 (SIRT1) is the human ortholog of the yeast sir2 protein; one of the most important regulators of lifespan extension by caloric restriction in several organisms. Dietary polyphenols, abundant in vegetables, fruits, cereals, wine and tea, were reported to stimulate the deacetylase activity of recombinant SIRT1 protein and could therefore be potential regulators of aging associated processes. However, inconsistent data between effects of polyphenols on the recombinant SIRT1 and on in vivo SIRT1, led us to investigate the influence of (1) stability of polyphenols under experimental conditions and (2) metabolism of polyphenols in human HT29 cells, on stimulation of SIRT1. With an improved SIRT1 deacetylation assay we found three new polyphenolic stimulators. Epigallocatechin galate (EGCg, 1.76-fold), epicatechin galate (ECg, 1.85-fold) and myricetin (3.19-fold) stimulated SIRT1 under stabilizing conditions, whereas without stabilization, these polyphenols strongly inhibited SIRT1, probably due to H2O2 formation. Using metabolically active HT29 cells we were able to show that quercetin (a stimulator of recombinant SIRT1) could not stimulate intracellular SIRT1. The major quercetin metabolite in humans, quercetin 3-O-glucuronide, slightly inhibited the recombinant SIRT1 activity which explains the lack of stimulatory action of quercetin in HT29 cells. This study shows that the stimulation of SIRT1 is strongly affected by polyphenol stability and metabolism, therefore extrapolation of in vitro SIRT1 stimulation results to physiological effects should be done with caution.

  17. Habitat stability affects dispersal and the ability to track climate change.

    PubMed

    Hof, Christian; Brändle, Martin; Dehling, D Matthias; Munguía, Mariana; Brandl, Roland; Araújo, Miguel B; Rahbek, Carsten

    2012-08-23

    Habitat persistence should influence dispersal ability, selecting for stronger dispersal in habitats of lower temporal stability. As standing (lentic) freshwater habitats are on average less persistent over time than running (lotic) habitats, lentic species should show higher dispersal abilities than lotic species. Assuming that climate is an important determinant of species distributions, we hypothesize that lentic species should have distributions that are closer to equilibrium with current climate, and should more rapidly track climatic changes. We tested these hypotheses using datasets from 1988 and 2006 containing all European dragon- and damselfly species. Bioclimatic envelope models showed that lentic species were closer to climatic equilibrium than lotic species. Furthermore, the models over-predicted lotic species ranges more strongly than lentic species ranges, indicating that lentic species track climatic changes more rapidly than lotic species. These results are consistent with the proposed hypothesis that habitat persistence affects the evolution of dispersal.

  18. Harvest date affects aronia juice polyphenols, sugars, and antioxidant activity, but not anthocyanin stability.

    PubMed

    Bolling, Bradley W; Taheri, Rod; Pei, Ruisong; Kranz, Sarah; Yu, Mo; Durocher, Shelley N; Brand, Mark H

    2015-11-15

    The goal of this work was to characterize how the date of harvest of 'Viking' aronia berry impacts juice pigmentation, sugars, and antioxidant activity. Aronia juice anthocyanins doubled at the fifth week of the harvest, and then decreased. Juice hydroxycinnamic acids decreased 33% from the first week, while proanthocyanidins increased 64%. Juice fructose and glucose plateaued at the fourth week, but sorbitol increased 40% to the seventh harvest week. Aronia juice pigment density increased due to anthocyanin concentration, and polyphenol copigmentation did not significantly affect juice pigmentation. Anthocyanin stability at pH 4.5 was similar between weeks. However, addition of quercetin, sorbitol, and chlorogenic acid to aronia anthocyanins inhibited pH-induced loss of color. Sorbitol and citric acid may be partially responsible for weekly variation in antioxidant activity, as addition of these agents inhibited DPPH scavenging 13-30%. Thus, aronia polyphenol and non-polyphenol components contribute to its colorant and antioxidant functionality.

  19. Homogenization conditions affect the oxidative stability of fish oil enriched milk emulsions: lipid oxidation.

    PubMed

    Let, Mette B; Jacobsen, Charlotte; Sørensen, Ann-Dorit M; Meyer, Anne S

    2007-03-07

    In this study fish oil was incorporated into commercial homogenized milk using different homogenization temperatures and pressures. The main aim was to understand the significance of homogenization temperature and pressure on the oxidative stability of the resulting milks. Increasing homogenization temperature from 50 to 72 degrees C decreased droplet size only slightly, whereas a pressure increase from 5 to 22.5 MPa decreased droplet size significantly. Surprisingly, emulsions having small droplets, and therefore large interfacial area, were less oxidized than emulsions having bigger droplets. Emulsions with similar droplet size distributions, but resulting from different homogenization conditions, had significantly different oxidative stabilities, indicating that properties of significance to oxidation other than droplet size itself were affected by the different treatments. In general, homogenization at 72 degrees C appeared to induce protective effects against oxidation as compared to homogenization at 50 degrees C. The results thus indicated that the actual composition of the oil-water interface is more important than total surface area itself.

  20. Mycorrhizal aspects in slope stabilisation

    NASA Astrophysics Data System (ADS)

    Graf, Frank

    2016-04-01

    In order to re-colonise and stabilise slopes affected by superficial soil failure with plants essential requirements have to be met: the plants must grow the plants must survive sustainably plant succession must start and continuously develop These requirements, however, are anything but easy given, particularly under the often hostile environmental conditions dominating on bare and steep slopes. Mycorrhizal fungi, the symbiotic partners of almost all plants used in eco-engineering, are said to improve the plants' ability to overcome periods governed by strongly (growth) limiting factors. Subsequently, results of investigations are presented of mycorrhizal effects on different plant and soil functions related to eco-engineering in general and soil and slope stabilisation in particular. Generally, inoculation yielded higher biomass of the host plants above as well as below ground. Furthermore, the survival rate was higher for mycorrhized compared to non-mycorrhized plants, particularly under extreme environmental conditions. However, the scale of the mycorrhizal impact may be species specific of both the plant host as well as the fungal partner(s) and often becomes evident only after a certain time lag. Depending on the plant-fungus combination the root length per soil volume was found to be between 0 and 2.5 times higher for inoculated compared to non-inoculated specimens. On an alpine graded ski slope the survival of inoculated compared to non-treated Salix herbacea cuttings was significant after one vegetation period only for one of the three added mycorrhizal fungus species. However, after three years all of the inoculated plantlets performed significantly better than the non-inoculated controls. The analysis of the potential for producing and stabilising soil aggregates of five different ectomycorrhizal fungi showed high variation and, for the species Inocybe lacera, no significant difference compared to untreated soil. Furthermore, inoculation of Salix

  1. Spectrofluorimetric methods of stability-indicating assay of certain drugs affecting the cardiovascular system

    NASA Astrophysics Data System (ADS)

    Moussa, B. A.; Mohamed, M. F.; Youssef, N. F.

    2011-01-01

    Two stability-indicating spectrofluorimetric methods have been developed for the determination of ezetimibe and olmesartan medoxomil, drugs affecting the cardiovascular system, and validated in the presence of their degradation products. The first method, for ezetimibe, is based on an oxidative coupling reaction of ezetimibe with 3-methylbenzothiazolin-2-one hydrazone hydrochloride in the presence of cerium (IV) ammonium sulfate in an acidic medium. The quenching effect of ezetimibe on the fluorescence of excess cerous ions is measured at the emission wavelength, λem, of 345 nm with the excitation wavelength, λex, of 296 nm. Factors affecting the reaction were carefully studied and optimized. The second method, for olmesartan medoxomil, is based on measuring the native fluorescence intensity of olmesartan medoxomil in methanol at λem = 360 nm with λex = 286 nm. Regression plots revealed good linear relationships in the assay limits of 10-120 and 8-112 g/ml for ezetimibe and olmesartan medoxomil, respectively. The validity of the methods was assessed according to the United States Pharmacopeya guidelines. Statistical analysis of the results exposed good Student's t-test and F-ratio values. The introduced methods were successfully applied to the analysis of ezetimibe and olmesartan medoxomil in drug substances and drug products as well as in the presence of their degradation products.

  2. Geology and slope stability in selected parts of The Geysers geothermal resources area: a guide to geologic features indicative of stable and unstable terrain in areas underlain by Franciscan and related rocks

    SciTech Connect

    Bedrossian, T.L.

    1980-01-01

    The results of a 4-month study of various geologic and topographic features related to the stability of Franciscan terrain in The Geysers GRA are presented. The study consisted of investigations of geologic and topographic features, throughout The Geysers GRA, and geologic mapping at a scale of 1:12,000 of approximately 1500 acres (600 hectares) of landslide terrain within the canyon of Big Sulphur Creek in the vicinity of the Buckeye mine (see plate 1). The area mapped during this study was selected because: (1) it is an area of potential future geothermal development, and (2) it illustrates that large areas mapped as landslides on regional scales (McLaughlin, 1974, 1975b; McNitt, 1968a) may contain zones of varying slope stability and, therefore, should be mapped in more detail prior to development of the land.

  3. Post-Biostimulation Biogenic U(IV) Stability and Microbial Community Structure that Affects its Dynamics

    NASA Astrophysics Data System (ADS)

    Jaffe, P. R.; Long, P. E.; Moon, H.; N'Guessan, L.; Peacock, A.; Sinha, M.; Tan, H.; Traub, D.; Williams, K. H.

    2010-12-01

    Flow-through sediment column experiments were conducted to determine the stability of biogenic U(IV) after biostimulation has been discontinued, and to isolate the key biogeochemical processes that affect the post-biostimulation U(IV) stability. Columns, packed with sediments from an UMTRA site (Rifle Colorado) were biostimulated for two months by injecting groundwater containing 3 mM acetate and 20 uM U(VI) at flow rates typically encountered at the Rifle site. After the biostimulation period, acetate injection was discontinued, and groundwater containing dissolved oxygen was allowed to enter the columns. Columns were then sacrificed at two week intervals to examine the sediment geochemistry and associated microbial community. Results showed that iron sulfide precipitates, that formed during the bioreduction phase, acted as a buffer to partially prevent biogenic U(IV) oxidation during the month post stimulation period. Groundwater and sediment microbial community compositions were analyzed over a period of one month post-biostimulation. The results indicate that two distinct biological processes, characterized by oxygen utilization, played important roles during this period. Within two weeks post stimulation, organisms such as Hydrogenophaga sp. and Thiobacillus sp. were observed in the columns. These bacteria, are able to use Fe(II), sulfide, or thiosulfate as their electron donor in the presence of O2. Furthermore, organisms closely related to Lysobacter sp. and Sterolibacterium sp. were also detected in the groundwater and sediment. It was suggested that these organisms may be feeding on decaying biomass and consuming O2 in the process. The presence of these oxidizing and spoilage bacteria is thought to have resulted in the consumption of oxygen, therefore protecting the biogenic U(IV) from being reoxidized in the sediment columns. To simulate the in situ U(IV) stability under post biostimulation conditions, columns bioreduced in the laboratory, as described

  4. Replacement of Val3 in Human Thymidylate Synthase Affects Its Kinetic Properties and Intracellular Stability

    SciTech Connect

    Huang, Xiao; Gibson, Lydia M.; Bell, Brittnaie J.; Lovelace, Leslie L.; Pea, Maria Marjorette O.; Berger, Franklin G.; Berger, Sondra H.; Lebioda, Lukasz

    2010-11-03

    Human and other mammalian thymidylate synthase (TS) enzymes have an N-terminal extension of {approx}27 amino acids that is not present in bacterial TSs. The extension, which is disordered in all reported crystal structures of TSs, has been considered to play a primary role in protein turnover but not in catalytic activity. In mammalian cells, the variant V3A has a half-life similar to that of wild-type human TS (wt hTS) while V3T is much more stable; V3L, V3F, and V3Y have half-lives approximately half of that for wt hTS. Catalytic turnover rates for most Val3 mutants are only slightly diminished, as expected. However, two mutants, V3L and V3F, have strongly compromised dUMP binding, with K{sub m,app} values increased by factors of 47 and 58, respectively. For V3L, this observation can be explained by stabilization of the inactive conformation of the loop of residues 181-197, which prevents substrate binding. In the crystal structure of V3L, electron density corresponding to a leucine residue is present in a position that stabilizes the loop of residues 181-197 in the inactive conformation. Since this density is not observed in other mutants and all other leucine residues are ordered in this structure, it is likely that this density represents Leu3. In the crystal structure of a V3F {center_dot} FdUMP binary complex, the nucleotide is bound in an alternative mode to that proposed for the catalytic complex, indicating that the high K{sub m,app} value is caused not by stabilization of the inactive conformer but by substrate binding in a nonproductive, inhibitory site. These observations show that the N-terminal extension affects the conformational state of the hTS catalytic region. Each of the mechanisms leading to the high K{sub m,app} values can be exploited to facilitate design of compounds acting as allosteric inhibitors of hTS.

  5. [Fire behavior of Mongolian oak leaves fuel-bed under no-wind and zero-slope conditions. I. Factors affecting fire spread rate and modeling].

    PubMed

    Jin, Sen; Liu, Bo-Fei; Di, Xue-Ying; Chu, Teng-Fei; Zhang, Ji-Li

    2012-01-01

    Aimed to understand the fire behavior of Mongolian oak leaves fuel-bed under field condition, the leaves of a secondary Mongolian oak forest in Northeast Forestry University experimental forest farm were collected and brought into laboratory to construct fuel-beds with varied loading, height, and moisture content, and a total of 100 experimental fires were burned under no-wind and zero-slope conditions. It was observed that the fire spread rate of the fuel-beds was less than 0.5 m x min(-1). Fuel-bed loading, height, and moisture contents all had significant effects on the fire spread rate. The effect of fuel-bed moisture content on the fire spread had no significant correlations with fuel-bed loading and height, but the effect of fuel-bed height was related to the fuel-bed loading. The packing ratio of fuel-beds had less effect on the fire spread rate. Taking the fuel-bed loading, height, and moisture content as predictive variables, a prediction model for the fire spread rate of Mongolian oak leaves fuel-bed was established, which could explain 83% of the variance of the fire spread rate, with a mean absolute error 0.04 m x min(-1) and a mean relative error less than 17%.

  6. Use of Structure-from-Motion Photogrammetry Technique to model Danxia red bed landform slope stability by discrete element modeling - case study at Mt. Langshan, Hunan Province, China

    NASA Astrophysics Data System (ADS)

    Simonson, Scott; Hua, Peng; Luobin, Yan; Zhi, Chen

    2016-04-01

    Important to the evolution of Danxia landforms is how the rock cliffs are in large part shaped by rock collapse events, ranging from small break offs to large collapses. Quantitative research of Danxia landform evolution is still relatively young. In 2013-2014, Chinese and Slovak researchers conducted joint research to measure deformation of two large rock walls. In situ measurements of one rock wall found it to be stable, and Ps-InSAR measurements of the other were too few to be validated. Research conducted this year by Chinese researchers modeled the stress states of a stone pillar at Mt. Langshan, in Hunan Province, that toppled over in 2009. The model was able to demonstrate how stress states within the pillar changed as the soft basal layer retreated, but was not able to show the stress states at the point of complete collapse. According to field observations, the back side of the pillar fell away from the entire cliff mass before the complete collapse, and no models have been able to demonstrate the mechanisms behind this behavior. A further understanding of the mechanisms controlling rockfall events in Danxia landforms is extremely important because these stunning sceneries draw millions of tourists each year. Protecting the tourists and the infrastructure constructed to accommodate tourism is of utmost concern. This research will employ a UAV to as universally as possible photograph a stone pillar at Mt. Langshan that stands next to where the stone pillar collapsed in 2009. Using the recently developed structure-from-motion technique, a 3D model of the pillar will be constructed in order to extract geometrical data of the entire slope and its structural fabric. Also in situ measurements will be taken of the slope's toe during the field work exercises. These data are essential to constructing a realistic discrete element model using the 3DEC code and perform a kinematic analysis of the rock mass. Intact rock behavior will be based on the Mohr Coulomb

  7. Stability and Control Harmony in Approach and Landing. [analysis of factors affecting flight characteristics at low airspeeds

    NASA Technical Reports Server (NTRS)

    Anderson, S. B.

    1975-01-01

    A review of the factors which affect stability and control harmony in approach and landing is made to obtain a clearer understanding of the proper relationship, the trade-offs involved, and to show how limits in stability and control harmony are established for advanced aircraft. Factors which influence stability and control harmony include the longitudinal short period response of the aircraft and the level of several pitch control characteristics including control power, control sensitivity, and control feel. At low stability levels for advanced aircraft, less conventional control techniques such as DLC are needed to improve harmony and some form of stability augmentation must be provided to improve precession of flight path control and reduce pilot work load.

  8. Factors affecting the stability and performance of ipratropium bromide; fenoterol hydrobromide pressurized-metered dose inhalers.

    PubMed

    Ninbovorl, Jenjira; Sawatdee, Somchai; Srichana, Teerapol

    2013-12-01

    The aim of the study was to investigate the factors affecting the stability and performance of ipratropium bromide and fenoterol hydrobromide in a pressurized-metered dose inhaler (pMDI). A factorial design was applied to investigate the effects of three parameters (propellant, water, and ethanol) on the performance of 27 designed formulations of a solution-based pMDI. The formulations that contained a hydrofluoroalkane (HFA) propellant lower than 72% v/v and an ethanol concentration higher than 27% v/v remained as clear solutions. Nine formulations that contained the HFA propellant higher than 74% v/v precipitated. The results indicated that it was not only the HFA propellant content of the formulations that was related to the formulation instability but also ethanol content. Only six formulations from the 18 formulations, that did not precipitate, produced drug contents that were within the acceptable range (80-120%). These six formulations generated aerosols with mass median aerodynamic diameters (MMAD) of approximately 2 μm with a fine particle fraction (FPF; particle size, <6.4 μm) between 45% and 52%. The MMAD and FPF did not change significantly after 6 months of storage (P > 0.05).

  9. Navigating Ski Slopes Safely

    MedlinePlus

    ... medlineplus.gov/news/fullstory_162902.html Navigating Ski Slopes Safely National Ski Areas Association offers advice on ... 2017 (HealthDay News) -- Many people head for the slopes at the first sign of snow, but it's ...

  10. Evaluation of TRIGRS (transient rainfall infiltration and grid-based regional slope-stability analysis)'s predictive skill for hurricane-triggered landslides: A case study in Macon County, North Carolina

    USGS Publications Warehouse

    Liao, Z.; Hong, Y.; Kirschbaum, D.; Adler, R.F.; Gourley, J.J.; Wooten, R.

    2011-01-01

    The key to advancing the predictability of rainfall-triggered landslides is to use physically based slope-stability models that simulate the transient dynamical response of the subsurface moisture to spatiotemporal variability of rainfall in complex terrains. TRIGRS (transient rainfall infiltration and grid-based regional slope-stability analysis) is a USGS landslide prediction model, coded in Fortran, that accounts for the influences of hydrology, topography, and soil physics on slope stability. In this study, we quantitatively evaluate the spatiotemporal predictability of a Matlab version of TRIGRS (MaTRIGRS) in the Blue Ridge Mountains of Macon County, North Carolina where Hurricanes Ivan triggered widespread landslides in the 2004 hurricane season. High resolution digital elevation model (DEM) data (6-m LiDAR), USGS STATSGO soil database, and NOAA/NWS combined radar and gauge precipitation are used as inputs to the model. A local landslide inventory database from North Carolina Geological Survey is used to evaluate the MaTRIGRS' predictive skill for the landslide locations and timing, identifying predictions within a 120-m radius of observed landslides over the 30-h period of Hurricane Ivan's passage in September 2004. Results show that within a radius of 24 m from the landslide location about 67% of the landslide, observations could be successfully predicted but with a high false alarm ratio (90%). If the radius of observation is extended to 120 m, 98% of the landslides are detected with an 18% false alarm ratio. This study shows that MaTRIGRS demonstrates acceptable spatiotemporal predictive skill for landslide occurrences within a 120-m radius in space and a hurricane-event-duration (h) in time, offering the potential to serve as a landslide warning system in areas where accurate rainfall forecasts and detailed field data are available. The validation can be further improved with additional landslide information including the exact time of failure for each

  11. Factors affecting the stability of the performance of ambient fine-particle concentrators.

    PubMed

    Kim, S; Sioutas, C; Chang, M C; Gong, H

    2000-01-01

    This article describes a systematic evaluation of factors affecting the stability of the performance of Harvard ambient fine-particle concentrators, an essential requirement for controlled animal and human exposure studies that utilize these technologies. Phenomenological problems during the operation of the concentrator, including pressure drop increase and decrease in concentration enrichment, were statistically correlated with ambient air parameters such as temperature, relative humidity, PM2.5 mass concentration, and mass median diameter. The normalized hourly pressure drop across the concentrator was strongly associated (R2 = .81) with the product of ambient PM2.5 mass concentration and the difference between the vapor pressure downstream of the impactor nozzle and the saturation vapor pressure at the adiabatic expansion temperature (i.e., the temperature of the aerosol immediately downstream of the virtual impactors). From multiple regression analysis, the average enrichment factor was predicted reasonably well (R2 = .67) by aerosol mass median diameter and the normalized hourly pressure drop. Based on these results, we can anticipate in any given day whether an exposure study can be conducted without a considerable increase in the concentrator pressure drop, which might lead to an abrupt or premature termination of the exposure. As particle mass concentration and ambient dewpoint are the two main parameters responsible for raising the pressure drop across the concentrator, efforts should be made to either desiccate the ambient aerosol at days of high dewpoints, or to dilute the ambient PM at days of high concentrations, prior to drawing the aerosol through the virtual impactors. The latter approach is recommended on days of severe ambient pollution conditions because it is simpler and also makes it possible to maintain the appropriate concentration level delivered to the exposure chamber.

  12. Slope sensitivities for optical surfaces

    NASA Astrophysics Data System (ADS)

    Rogers, John R.

    2015-09-01

    Setting a tolerance for the slope errors of an optical surface (e.g., surface form errors of the "mid-spatial-frequencies") requires some knowledge of how those surface errors affect the final image of the system. While excellent tools exist for simulating those effects on a surface-by-surface basis, considerable insight may be gained by examining, for each surface, a simple sensitivity parameter that relates the slope error on the surface to the ray displacement at the final image plane. Snell's law gives a relationship between the slope errors of a surface and the angular deviations of the rays emerging from the surface. For a singlet or thin doublet acting by itself, these angular deviations are related to ray deviations at the image plane by the focal length of the lens. However, for optical surfaces inside an optical system having a substantial axial extent, the focal length of the system is not the correct multiplier, as the sensitivity is influenced by the optical surfaces that follow. In this paper, a simple expression is derived that relates the slope errors at an arbitrary optical surface to the ray deviation at the image plane. This expression is experimentally verified by comparison to a real-ray perturbation analysis. The sensitivity parameter relates the RMS slope errors to the RMS spot radius, and also relates the peak slope error to the 100% spot radius, and may be used to create an RSS error budget for slope error. Application to various types of system are shown and discussed.

  13. Soil aggregate stability as affected by clay mineralogy and polyacrylamide addition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The addition of polyacrylamide (PAM) to soil leads to stabilization of existing aggregates and improved bonding between, and aggregation of adjacent soil particles However, the dependence of PAM efficacy as an aggregate stabilizing agent on soil-clay mineralogy has not been studied. Sixteen soil sam...

  14. Soil-Structural Stability as Affected by Clay Mineralogy, Soil Texture and Polyacrylamide Application

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil-structural stability (expressed in terms of aggregate stability and pore size distribution) depends on (i) soil inherent properties, (ii) extrinsic condition prevailing in the soil that may vary temporally and spatially, and (iii) addition of soil amendments. Different soil management practices...

  15. Stress release, joints, and instability on submarine slopes

    SciTech Connect

    Booth, J.S.; Robb, J.M.

    1984-04-01

    Mass movements related to gradual stress release within a sediment section may be quantitatively important on submarine slopes, particularly when such stress release involves joint sets. The sequence of events that promotes this phenomenon has been established by numerous terrestrial studies. The process involves: mass wasting or erosion to remove vertical stress (overburden) or lateral stress (such as through canyon cutting); consequent elastic rebound of the unloaded section; and opening of existing joints and/or formation of new joint sets. The presence of joints, which constitute planes of weakness within the sediment section, controls and reduces the stability of the affected slope; that is, the stability of the slope may no longer be dependent on the inherent strength of the sediments. The results of this process have been observed on the continental slope off the Mid-Atlantic coast of the United States. There, exposed Tertiary sediments have a well-developed joint pattern that has been observed in sidescan-sonar images, from submersible operations, and in a piston core. The measured preconsolidation stress on an Eocene core sample suggests that more than 100 m (330 ft) of overburden may have been removed from parts of the area. Intact Eocene blocks, which represent apparent failure along joint planes, have fallen from canyon walls on the lower slope and moved onto the upper rise. It is suggested that this process has the potential to operate on most deeply eroded surfaces and that exhumed (overconsolidated) sediments do not necessarily represent stable conditions despite their typical high shear strengths.

  16. Murine startle mutant Nmf11 affects the structural stability of the glycine receptor and increases deactivation

    PubMed Central

    Wilkins, Megan E.; Caley, Alex; Gielen, Marc C.; Harvey, Robert J.

    2016-01-01

    Key points Hyperekplexia or startle disease is a serious neurological condition affecting newborn children and usually involves dysfunctional glycinergic neurotransmission.Glycine receptors (GlyRs) are major mediators of inhibition in the spinal cord and brainstem.A missense mutation, replacing asparagine (N) with lysine (K), at position 46 in the GlyR α1 subunit induced hyperekplexia following a reduction in the potency of the transmitter glycine; this resulted from a rapid deactivation of the agonist current at mutant GlyRs.These effects of N46K were rescued by mutating a juxtaposed residue, N61 on binding Loop D, suggesting these two asparagines may interact.Asparagine 46 is considered to be important for the structural stability of the subunit interface and glycine binding site, and its mutation represents a new mechanism by which GlyR dysfunction induces startle disease. Abstract Dysfunctional glycinergic inhibitory transmission underlies the debilitating neurological condition, hyperekplexia, which is characterised by exaggerated startle reflexes, muscle hypertonia and apnoea. Here we investigated the N46K missense mutation in the GlyR α1 subunit gene found in the ethylnitrosourea (ENU) murine mutant, Nmf11, which causes reduced body size, evoked tremor, seizures, muscle stiffness, and morbidity by postnatal day 21. Introducing the N46K mutation into recombinant GlyR α1 homomeric receptors, expressed in HEK cells, reduced the potencies of glycine, β‐alanine and taurine by 9‐, 6‐ and 3‐fold respectively, and that of the competitive antagonist strychnine by 15‐fold. Replacing N46 with hydrophobic, charged or polar residues revealed that the amide moiety of asparagine was crucial for GlyR activation. Co‐mutating N61, located on a neighbouring β loop to N46, rescued the wild‐type phenotype depending on the amino acid charge. Single‐channel recording identified that burst length for the N46K mutant was reduced and fast agonist application

  17. Geotechnical Characterization and Stability of a Slope in the Marnoso-Arenacea Formation for the Realization of an Underground Car Park in Urbino (Italy)

    NASA Astrophysics Data System (ADS)

    Gori, Umberto; Polidori, Ennio; Tonelli, Gianluigi; Veneri, Francesco

    The plan of an underground car park located near the historical centre of Urbino town, has required characterizing the Marnoso-Arenacea Formation (Tortonian), from a geomechanical point of view. The project implies that the intervention will be insert inside the flank of the hill, in order to mitigate the effect of the environmental impact. It also involves an excavation front 42 m high and 100 m large. To analyze the mechanical behaviour of the soils, many samples both from the Marnoso-Arenacea Formation and from the cover, have been tested in laboratory. The anisotropy index evaluated by point load test in natural water conditions shows a higher value of the arenitic levels in comparison with the marls. On the contrary, the marls level tested in dry condition provides greater anisotropy index data. In the mono-axial compression test the arenaceous sediments show higher results. The stability analysis carried out with distinct element method shows the opportunity to retain the upper part of the cut with anchored bulkhead.

  18. The use of “stabilization exercises” to affect neuromuscular control in the lumbopelvic region: a narrative review

    PubMed Central

    Bruno, Paul

    2014-01-01

    It is well-established that the coordination of muscular activity in the lumbopelvic region is vital to the generation of mechanical spinal stability. Several models illustrating mechanisms by which dysfunctional neuromuscular control strategies may serve as a cause and/or effect of low back pain have been described in the literature. The term “core stability” is variously used by clinicians and researchers, and this variety has led to several rehabilitative approaches suggested to affect the neuromuscular control strategies of the lumbopelvic region (e.g. “stabilization exercise”, “motor control exercise”). This narrative review will highlight: 1) the ongoing debate in the clinical and research communities regarding the terms “core stability” and “stabilization exercise”, 2) the importance of sub-grouping in identifying those patients most likely to benefit from such therapeutic interventions, and 3) two protocols that can assist clinicians in this process. PMID:24932016

  19. Denaturation and Oxidative Stability of Hemp Seed (Cannabis sativa L.) Protein Isolate as Affected by Heat Treatment.

    PubMed

    Raikos, Vassilios; Duthie, Garry; Ranawana, Viren

    2015-09-01

    The present study investigated the impact of heat treatments on the denaturation and oxidative stability of hemp seed protein during simulated gastrointestinal digestion (GID). Heat-denatured hemp protein isolate (HPI) solutions were prepared by heating HPI (2 mg/ml, pH 6.8) to 40, 60, 80 and 100 °C for 10 min. Heat-induced denaturation of the protein isolates was monitored by polyacrylamide gel electrophoresis. Heating HPI at temperatures above 80 °C significantly reduced solubility and led to the formation of large protein aggregates. The isolates were then subjected to in vitro GID and the oxidative stability of the generated peptides was investigated. Heating did not significantly affect the formation of oxidation products during GID. The results suggest that heat treatments should ideally remain below 80 °C if heat stability and solubility of HPI are to be preserved.

  20. Chemical expansion affected oxygen vacancy stability in different oxide structures from first principles calculations

    SciTech Connect

    Aidhy, Dilpuneet S.; Liu, Bin; Zhang, Yanwen; Weber, William J.

    2015-01-21

    We study the chemical expansion for neutral and charged oxygen vacancies in fluorite, rocksalt, perovskite and pyrochlores materials using first principles calculations. We show that the neutral oxygen vacancy leads to lattice expansion whereas the charged vacancy leads to lattice contraction. In addition, we show that there is a window of strain within which an oxygen vacancy is stable; beyond that range, the vacancy can become unstable. Using CeO2|ZrO2 interface structure as an example, we show that the concentration of oxygen vacancies can be manipulated via strain, and the vacancies can be preferentially stabilized. Furthermore, these results could serve as guiding principles in predicting oxygen vacancy stability in strained systems and in the design of vacancy stabilized materials.

  1. Chemical expansion affected oxygen vacancy stability in different oxide structures from first principles calculations

    SciTech Connect

    Aidhy, Dilpuneet S.; Liu, Bin; Zhang, Yanwen; Weber, William J.

    2015-03-01

    We study the chemical expansion for neutral and charged oxygen vacancies in fluorite, rocksalt, perovskite and pyrochlores materials using first principles calculations. We show that the neutral oxygen vacancy leads to lattice expansion whereas the charged vacancy leads to lattice contraction. In addition, we show that there is a window of strain within which an oxygen vacancy is stable; beyond that range, the vacancy can become unstable. Using CeO2|ZrO2 interface structure as an example, we show that the concentration of oxygen vacancies can be manipulated via strain, and the vacancies can be preferentially stabilized. These results could serve as guiding principles in predicting oxygen vacancy stability in strained systems and in the design of vacancy stabilized materials.

  2. Chemical expansion affected oxygen vacancy stability in different oxide structures from first principles calculations

    DOE PAGES

    Aidhy, Dilpuneet S.; Liu, Bin; Zhang, Yanwen; ...

    2015-01-21

    We study the chemical expansion for neutral and charged oxygen vacancies in fluorite, rocksalt, perovskite and pyrochlores materials using first principles calculations. We show that the neutral oxygen vacancy leads to lattice expansion whereas the charged vacancy leads to lattice contraction. In addition, we show that there is a window of strain within which an oxygen vacancy is stable; beyond that range, the vacancy can become unstable. Using CeO2|ZrO2 interface structure as an example, we show that the concentration of oxygen vacancies can be manipulated via strain, and the vacancies can be preferentially stabilized. Furthermore, these results could serve asmore » guiding principles in predicting oxygen vacancy stability in strained systems and in the design of vacancy stabilized materials.« less

  3. Nitrogen transformation and nitrous oxide emissions affected by biochar amendment and fertilizer stabilizers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochar as a soil amendment and the use of fertilizer stabilizers (N transformation inhibitors) have been shown to reduce N2O emissions, but the mechanisms or processes involved are not well understood. The objective of this research was to investigate N transformation processes and the relationship...

  4. Factors Affecting the Stability of Biodiesel Sold in the United States

    SciTech Connect

    McCormick, R. L.; Ratcliff, M.; Moens, L.; Lawrence, R.

    2006-01-01

    As part of a survey of biodiesel quality and stability in the United States, 27 biodiesel (B100) samples were collected from blenders and distributor nationwide. For this sample set, 85% met all of the requirements of the industry standard for biodiesel, ASTM D6751.

  5. AN EVALUATION OF FACTORS AFFECTING THE SOLIDIFICATION/STABILIZATION OF HEAVY METAL SLUDGE

    EPA Science Inventory

    Solidification/stabilization (SIS) of hazardous waste involves mixing the waste with a binder material to enhance the physical properties of the waste and to immobilize contaminants that may be detrimental to the environment. Many hazardous wastes contain materials that are know...

  6. Temporal stability of soil water contents as affected by weather patterns: a simulation study.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Temporal stability of soil water content (TS SWC) is a natural phenomenon that recently attracts attention and finds multiple applications. Large variations in the interannual and interseasonal TS SWC have been encountered among locations studied by various authors. The objective of this work was ...

  7. An Evaluation of Factors Affecting the Solidification/Stabilization of Heavy Metal Sludge

    DTIC Science & Technology

    1993-03-01

    Regression Analysis of UCS and CI ...... ............... .. 63 Wet/ Dry Testing ............... ........................ .. 70 Permeability...wet/ dry test . . . 89 53 Wet/dry cycling for the LFA solidified/stabilized samples with grease interference .......... ................... .. 90 54...one wet/ dry test . Disintegration of over 70 percent of the original sample was recorded as failure of a product. Sample A was carried through this

  8. Sublethal concentrations of silver nanoparticles affect the mechanical stability of biofilms.

    PubMed

    Grün, Alexandra Y; Meier, Jutta; Metreveli, George; Schaumann, Gabriele E; Manz, Werner

    2016-12-01

    Bacterial biofilms are most likely confronted with silver nanoparticles (Ag NPs) as a pollutant stressor in aquatic systems. In this study, biofilms of Aquabacterium citratiphilum were exposed for 20 h to 30 and 70 nm citrate stabilized Ag NPs in low-dose concentrations ranging from 600 to 2400 μg l(-1), and the Ag NP-mediated effects on descriptive, structural, and functional biofilm characteristics, including viability, protein content, architecture, and mechanical stability, were investigated. Viability, based on the bacterial cell membrane integrity of A. citratiphilum, as determined by epifluorescence microscopy, remained unaffected after Ag NP exposure. Moreover, in contrast to information in the current literature, protein contents of cells and extracellular polymeric substances (EPS) and biofilm architecture, including dry mass, thickness, and density, were not significantly impacted by exposure to Ag NPs. However, the biofilms themselves served as effective sinks for Ag NPs, exhibiting enrichment factors from 5 to 8. Biofilms showed a greater capacity to accumulate 30 nm sized Ag NPs than 70 nm Ag NPs. Furthermore, Ag NPs significantly threatened the mechanical stability of biofilms, as determined by a newly developed assay. For 30 nm Ag NPs, the mechanical stability of biofilms decreased as the Ag NP concentrations applied to them increased. In contrast, 70 nm Ag NPs produced a similar decrease in mechanical stability for each applied concentration. Overall, this finding demonstrates that exposure to Ag NPs triggers remarkable changes in biofilm adhesion and/or cohesiveness. Because of biofilm-mediated ecological services, this response raises environmental concerns regarding Ag NP release into freshwater systems, even in sublethal concentrations.

  9. Stability and heavy metal distribution of soil aggregates affected by application of apatite, lime, and charcoal.

    PubMed

    Cui, Hongbiao; Ma, Kaiqiang; Fan, Yuchao; Peng, Xinhua; Mao, Jingdong; Zhou, Dongmei; Zhang, Zhongbin; Zhou, Jing

    2016-06-01

    Only a few studies have been reported on the stability and heavy metal distribution of soil aggregates after soil treatments to reduce the availability of heavy metals. In this study, apatite (22.3 t ha(-1)), lime (4.45 t ha(-1)), and charcoal (66.8 t ha(-1)) were applied to a heavy metal-contaminated soil for 4 years. The stability and heavy metal distribution of soil aggregates were investigated by dry and wet sieving. No significant change in the dry mean weight diameter was observed in any treatments. Compared with the control, three-amendment treatments significantly increased the wet mean weight diameter, but only charcoal treatment significantly increased the wet aggregate stability. The soil treatments increased the content of soil organic carbon, and the fraction 0.25-2 mm contained the highest content of soil organic carbon. Amendments' application slightly increased soil total Cu and Cd, but decreased the concentrations of CaCl2 -extractable Cu and Cd except for the fraction <0.053 mm. The fractions >2 and 0.25-2 mm contained the highest concentrations of CaCl2-extractable Cu and Cd, accounted for about 74.5-86.8 % of CaCl2-extractable Cu and Cd in soil. The results indicated that amendments' application increased the wet soil aggregate stability and decreased the available Cu and Cd. The distribution of available heavy metals in wet soil aggregates was not controlled by soil aggregate stability, but possibly by soil organic carbon.

  10. Balancing protein stability and activity in cancer: a new approach for identifying driver mutations affecting CBL ubiquitin ligase activation

    PubMed Central

    Li, Minghui; Kales, Stephen C.; Ma, Ke; Shoemaker, Benjamin A.; Crespo-Barreto, Juan; Cangelosi, Andrew L.; Lipkowitz, Stanley; Panchenko, Anna R.

    2015-01-01

    Oncogenic mutations in the monomeric Casitas B-lineage lymphoma (Cbl) gene have been found in many tumors, but their significance remains largely unknown. Several human c-Cbl (CBL) structures have recently been solved depicting the protein at different stages of its activation cycle and thus provide mechanistic insight underlying how stability-activity tradeoffs in cancer-related proteins may influence disease onset and progression. In this study, we computationally modeled the effects of missense cancer mutations on structures representing four stages of the CBL activation cycle to identify driver mutations that affect CBL stability, binding, and activity. We found that recurrent, homozygous, and leukemia-specific mutations had greater destabilizing effects on CBL states than did random non-cancer mutations. We further tested the ability of these computational models assessing the changes in CBL stability and its binding to ubiquitin conjugating enzyme E2, by performing blind CBL-mediated EGFR ubiquitination assays in cells. Experimental CBL ubiquitin ligase activity was in agreement with the predicted changes in CBL stability and, to a lesser extent, with CBL-E2 binding affinity. Two-thirds of all experimentally tested mutations affected the ubiquitin ligase activity by either destabilizing CBL or disrupting CBL-E2 binding, whereas about one-third of tested mutations were found to be neutral. Collectively, our findings demonstrate that computational methods incorporating multiple protein conformations and stability and binding affinity evaluations can successfully predict the functional consequences of cancer mutations on protein activity, and provide a proof of concept for mutations in CBL. PMID:26676746

  11. Finite Element analyses of soil bioengineered slopes

    NASA Astrophysics Data System (ADS)

    Tamagnini, Roberto; Switala, Barbara Maria; Sudan Acharya, Madhu; Wu, Wei; Graf, Frank; Auer, Michael; te Kamp, Lothar

    2014-05-01

    Soil Bioengineering methods are not only effective from an economical point of view, but they are also interesting as fully ecological solutions. The presented project is aimed to define a numerical model which includes the impact of vegetation on slope stability, considering both mechanical and hydrological effects. In this project, a constitutive model has been developed that accounts for the multi-phase nature of the soil, namely the partly saturated condition and it also includes the effects of a biological component. The constitutive equation is implemented in the Finite Element (FE) software Comes-Geo with an implicit integration scheme that accounts for the collapse of the soils structure due to wetting. The mathematical formulation of the constitutive equations is introduced by means of thermodynamics and it simulates the growth of the biological system during the time. The numerical code is then applied in the analysis of an ideal rainfall induced landslide. The slope is analyzed for vegetated and non-vegetated conditions. The final results allow to quantitatively assessing the impact of vegetation on slope stability. This allows drawing conclusions and choosing whenever it is worthful to use soil bioengineering methods in slope stabilization instead of traditional approaches. The application of the FE methods show some advantages with respect to the commonly used limit equilibrium analyses, because it can account for the real coupled strain-diffusion nature of the problem. The mechanical strength of roots is in fact influenced by the stress evolution into the slope. Moreover, FE method does not need a pre-definition of any failure surface. FE method can also be used in monitoring the progressive failure of the soil bio-engineered system as it calculates the amount of displacements and strains of the model slope. The preliminary study results show that the formulated equations can be useful for analysis and evaluation of different soil bio

  12. ceRNA crosstalk stabilizes protein expression and affects the correlation pattern of interacting proteins.

    PubMed

    Martirosyan, Araks; De Martino, Andrea; Pagnani, Andrea; Marinari, Enzo

    2017-03-07

    Gene expression is a noisy process and several mechanisms, both transcriptional and post-transcriptional, can stabilize protein levels in cells. Much work has focused on the role of miRNAs, showing in particular that miRNA-mediated regulation can buffer expression noise for lowly expressed genes. Here, using in silico simulations and mathematical modeling, we demonstrate that miRNAs can exert a much broader influence on protein levels by orchestrating competition-induced crosstalk between mRNAs. Most notably, we find that miRNA-mediated cross-talk (i) can stabilize protein levels across the full range of gene expression rates, and (ii) modifies the correlation pattern of co-regulated interacting proteins, changing the sign of correlations from negative to positive. The latter feature may constitute a potentially robust signature of the existence of RNA crosstalk induced by endogenous competition for miRNAs in standard cellular conditions.

  13. ceRNA crosstalk stabilizes protein expression and affects the correlation pattern of interacting proteins

    PubMed Central

    Martirosyan, Araks; De Martino, Andrea; Pagnani, Andrea; Marinari, Enzo

    2017-01-01

    Gene expression is a noisy process and several mechanisms, both transcriptional and post-transcriptional, can stabilize protein levels in cells. Much work has focused on the role of miRNAs, showing in particular that miRNA-mediated regulation can buffer expression noise for lowly expressed genes. Here, using in silico simulations and mathematical modeling, we demonstrate that miRNAs can exert a much broader influence on protein levels by orchestrating competition-induced crosstalk between mRNAs. Most notably, we find that miRNA-mediated cross-talk (i) can stabilize protein levels across the full range of gene expression rates, and (ii) modifies the correlation pattern of co-regulated interacting proteins, changing the sign of correlations from negative to positive. The latter feature may constitute a potentially robust signature of the existence of RNA crosstalk induced by endogenous competition for miRNAs in standard cellular conditions. PMID:28266541

  14. Factors affecting the stability of drug-loaded polymeric micelles and strategies for improvement

    NASA Astrophysics Data System (ADS)

    Zhou, Weisai; Li, Caibin; Wang, Zhiyu; Zhang, Wenli; Liu, Jianping

    2016-09-01

    Polymeric micelles (PMs) self-assembled by amphiphilic block copolymers have been used as promising nanocarriers for tumor-targeted delivery due to their favorable properties, such as excellent biocompatibility, prolonged circulation time, favorable particle sizes (10-100 nm) to utilize enhanced permeability and retention effect and the possibility for functionalization. However, PMs can be easily destroyed due to dilution of body fluid and the absorption of proteins in system circulation, which may induce drug leakage from these micelles before reaching the target sites and compromise the therapeutic effect. This paper reviewed the factors that influence stability of micelles in terms of thermodynamics and kinetics consist of the critical micelle concentration of block copolymers, glass transition temperature of hydrophobic segments and polymer-polymer and polymer-cargo interaction. In addition, some effective strategies to improve the stability of micelles were also summarized.

  15. Rice (Oryza sativa L) plantation affects the stability of biochar in paddy soil.

    PubMed

    Wu, Mengxiong; Feng, Qibo; Sun, Xue; Wang, Hailong; Gielen, Gerty; Wu, Weixiang

    2015-05-05

    Conversion of rice straw into biochar for soil amendment appears to be a promising method to increase long-term carbon sequestration and reduce greenhouse gas (GHG) emissions. The stability of biochar in paddy soil, which is the major determining factor of carbon sequestration effect, depends mainly on soil properties and plant functions. However, the influence of plants on biochar stability in paddy soil remains unclear. In this study, bulk and surface characteristics of the biochars incubated without rice plants were compared with those incubated with rice plants using a suite of analytical techniques. Results showed that although rice plants had no significant influence on the bulk characteristics and decomposition rates of the biochar, the surface oxidation of biochar particles was enhanced by rice plants. Using (13)C labeling we observed that rice plants could significantly increase carbon incorporation from biochar into soil microbial biomass. About 0.047% of the carbon in biochar was incorporated into the rice plants during the whole rice growing cycle. These results inferred that root exudates and transportation of biochar particles into rice plants might decrease the stability of biochar in paddy soil. Impact of plants should be considered when predicting carbon sequestration potential of biochar in soil systems.

  16. Stability of the Octameric Structure Affects Plasminogen-Binding Capacity of Streptococcal Enolase

    PubMed Central

    Law, Ruby H. P.; Casey, Lachlan W.; Valkov, Eugene; Bertozzi, Carlo; Stamp, Anna; Jovcevski, Blagojce; Aquilina, J. Andrew; Whisstock, James C.; Walker, Mark J.; Kobe, Bostjan

    2015-01-01

    Group A Streptococcus (GAS) is a human pathogen that has the potential to cause invasive disease by binding and activating human plasmin(ogen). Streptococcal surface enolase (SEN) is an octameric α-enolase that is localized at the GAS cell surface. In addition to its glycolytic role inside the cell, SEN functions as a receptor for plasmin(ogen) on the bacterial surface, but the understanding of the molecular basis of plasmin(ogen) binding is limited. In this study, we determined the crystal and solution structures of GAS SEN and characterized the increased plasminogen binding by two SEN mutants. The plasminogen binding ability of SENK312A and SENK362A is ~2- and ~3.4-fold greater than for the wild-type protein. A combination of thermal stability assays, native mass spectrometry and X-ray crystallography approaches shows that increased plasminogen binding ability correlates with decreased stability of the octamer. We propose that decreased stability of the octameric structure facilitates the access of plasmin(ogen) to its binding sites, leading to more efficient plasmin(ogen) binding and activation. PMID:25807546

  17. How Does Functional Soccer Training on Uneven Ground Affect Dynamic Stability of Lower Limbs in Young Soccer Players

    PubMed Central

    Plenzler, Marcin; Mrozińska, Natalia; Mierzwińska, Anna; Korbolewska, Olga; Mejnartowicz, Daria; Popieluch, Marcin; Śmigielski, Robert

    2014-01-01

    the supporting limb after the preparatory period, during which a stability and proprioception training was completed. The significance of these results is even greater when the parallel substantial increase of the physical body height of these young players is taken into account (the taller the player is, the harder it is for him to keep the balance). The players’ tests results are, also, statistically lower than the control group’s data. That, in turn, means that the players had better stability in comparison to the control group. This co-dependence regarding the overall stability was mainly affected by the A/P stability indexes taken in a sagittal plane. Also, no new injuries were recorded within the young players group. Conclusion: 1. The exercised functional training significantly improved stability results of the supporting limb among the young players. 2. The results encourage to continue the study, and, in the later stage, check whether there is an actual relationship between the dynamic stability results and sports achievements combined with the frequency of injuries.

  18. Stability of the Stevia-Derived Sweetener Rebaudioside A in Solution as Affected by Ultraviolet Light Exposure.

    PubMed

    Zhang, Jiewen; Bell, Leonard N

    2017-04-01

    Rebaudioside A is a natural noncaloric high-potency sweetener extracted from the leaves of Stevia rebaudiana. With rebaudioside A use increasing in foods, understanding the factors affecting its stability is necessary. This project evaluated the degradation rate constants of rebaudioside A in water, 0.1 M phosphate buffer, and 0.1 M citrate buffer at pH 3 and 7 as a function of ultraviolet (UV) light intensity (365 nm, 0 μW/cm(2) for dark conditions, 27 μW/cm(2) for low intensity, and 190 μW/cm(2) for high intensity) at 32.5 °C. Rebaudioside A stability was adversely affected by light exposure. The pseudo-1st-order degradation rate constants increased significantly (P < 0.05) with increasing light intensity in all solutions. Under dark conditions, rebaudioside A in phosphate buffers was more susceptible to breakdown than in water and citrate buffers at both pH levels. However, exposure to UV light resulted in rebaudioside A degradation occurring approximately 10 times faster in citrate than in phosphate buffers at both pH levels. The sensitivity of rebaudioside A to UV light was greater in citrate buffers than in water or phosphate buffers. The use of light-protective packaging for beverages containing rebaudioside A will improve its stability.

  19. Fiber Bragg grating-based performance monitoring of a slope model subjected to seepage

    NASA Astrophysics Data System (ADS)

    Zhu, Hong-Hu; Shi, Bin; Yan, Jun-Fan; Zhang, Jie; Zhang, Cheng-Cheng; Wang, Bao-Jun

    2014-09-01

    In the past few years, fiber optic sensing technologies have played an increasingly important role in the health monitoring of civil infrastructures. These innovative sensing technologies have recently been successfully applied to the performance monitoring of a series of geotechnical structures. Fiber optic sensors have shown many unique advantages in comparison with conventional sensors, including immunity to electrical noise, higher precision and improved durability and embedding capabilities; fiber optic sensors are also smaller in size and lighter in weight. In order to explore the mechanism of seepage-induced slope instability, a small-scale 1 g model test of the soil slope has been performed in the laboratory. During the model’s construction, specially fabricated sensing fibers containing nine fiber Bragg grating (FBG) strain sensors connected in a series were horizontally and vertically embedded into the soil mass. The surcharge load was applied on the slope crest, and the groundwater level inside of the slope was subsequently varied using two water chambers installed besides the slope model. The fiber optic sensing data of the vertical and horizontal strains within the slope model were automatically recorded by an FBG interrogator and a computer during the test. The test results are presented and interpreted in detail. It is found that the gradually accumulated deformation of the slope model subjected to seepage can be accurately captured by the quasi-distributed FBG strain sensors. The test results also demonstrate that the slope stability is significantly affected by ground water seepage, which fits well with the results that were calculated using finite element and limit equilibrium methods. The relationship between the strain measurements and the safety factors is further analyzed, together with a discussion on the residual strains. The performance evaluation of a soil slope using fiber optic strain sensors is proved to be a potentially effective

  20. Factors affecting the thermal shock behavior of yttria stabilized hafnia based graphite and tungsten composites.

    NASA Technical Reports Server (NTRS)

    Lineback, L. D.; Manning, C. R.

    1971-01-01

    Hafnia-based composites containing either graphite or tungsten were investigated as rocket nozzle throat inserts in solid propellant rocket engines. The thermal shock resistance of these materials is considered in terms of macroscopic thermal conductivity, thermal expansion, modulus of elasticity, and compressive fracture stress. The effect of degree of hafnia stabilization, density, and graphite or tungsten content upon these parameters is discussed. The variation of the ratio of elastic modulus to compressive fracture stress with density and its effect upon thermal shock resistance of these materials are discussed in detail.

  1. Intermonomer Interactions in Hemagglutinin Subunits HA1 and HA2 Affecting Hemagglutinin Stability and Influenza Virus Infectivity

    PubMed Central

    DeFeo, Christopher J.; Alvarado-Facundo, Esmeralda; Vassell, Russell

    2015-01-01

    ABSTRACT Influenza virus hemagglutinin (HA) mediates virus entry by binding to cell surface receptors and fusing the viral and endosomal membranes following uptake by endocytosis. The acidic environment of endosomes triggers a large-scale conformational change in the transmembrane subunit of HA (HA2) involving a loop (B loop)-to-helix transition, which releases the fusion peptide at the HA2 N terminus from an interior pocket within the HA trimer. Subsequent insertion of the fusion peptide into the endosomal membrane initiates fusion. The acid stability of HA is influenced by residues in the fusion peptide, fusion peptide pocket, coiled-coil regions of HA2, and interactions between the surface (HA1) and HA2 subunits, but details are not fully understood and vary among strains. Current evidence suggests that the HA from the circulating pandemic 2009 H1N1 influenza A virus [A(H1N1)pdm09] is less stable than the HAs from other seasonal influenza virus strains. Here we show that residue 205 in HA1 and residue 399 in the B loop of HA2 (residue 72, HA2 numbering) in different monomers of the trimeric A(H1N1)pdm09 HA are involved in functionally important intermolecular interactions and that a conserved histidine in this pair helps regulate HA stability. An arginine-lysine pair at this location destabilizes HA at acidic pH and mediates fusion at a higher pH, while a glutamate-lysine pair enhances HA stability and requires a lower pH to induce fusion. Our findings identify key residues in HA1 and HA2 that interact to help regulate H1N1 HA stability and virus infectivity. IMPORTANCE Influenza virus hemagglutinin (HA) is the principal antigen in inactivated influenza vaccines and the target of protective antibodies. However, the influenza A virus HA is highly variable, necessitating frequent vaccine changes to match circulating strains. Sequence changes in HA affect not only antigenicity but also HA stability, which has important implications for vaccine production, as well

  2. Redefining a Bizarre Situation: Relative Concept Stability in Affect Control Theory

    ERIC Educational Resources Information Center

    Nelson, Steven M.

    2006-01-01

    I analyze the process by which we react cognitively to information that contradicts our culturally held sentiments in the context of affect control theory. When bizarre, unanticipated events come to our attention and we have no opportunity to act so as to alter them, we must reidentify at least one event component: the actor, the behavior, or the…

  3. Heat stability and acid gelation properties of calcium-enriched reconstituted skim milk affected by ultrasonication.

    PubMed

    Chandrapala, Jayani; Bui, Don; Kentish, Sandra; Ashokkumar, Muthupandian

    2014-05-01

    The aggregation of proteins after heating of calcium-fortified milks has been an ongoing problem in the dairy industry. This undesirable effect restricts the manufacture of calcium rich dairy products. To overcome this problem, a completely new approach in controlling the heat stability of dairy protein solutions, developed in our lab, has been employed. In this approach, high intensity, low frequency ultrasound is applied for a very short duration after a pre-heating step at ⩾70 °C. The ultrasound breaks apart whey/whey and whey/casein aggregates through the process of acoustic cavitation. Protein aggregates do not reform on subsequent post-heating, thereby making the systems heat stable. In this paper, the acid gelation properties of ultrasonicated calcium-enriched skim milks have also been investigated. It is shown that ultrasonication alone does not change the gelation properties significantly whereas a sequence of preheating (72 °C/1 min) followed by ultrasonication leads to decreased gelation times, decreased gel syneresis and increased skim milk viscosity in comparison to heating alone. Overall, ultrasonication has the potential to provide calcium-fortified dairy products with increased heat stability. However, enhanced gelation properties can only be achieved when ultrasonication is completed in conjunction with heating.

  4. Dissecting the Factors Affecting the Fluorescence Stability of Quantum Dots in Live Cells.

    PubMed

    Wang, Zhi-Gang; Liu, Shu-Lin; Hu, Yuan-Jun; Tian, Zhi-Quan; Hu, Bin; Zhang, Zhi-Ling; Pang, Dai-Wen

    2016-04-06

    Labeling and imaging of live cells with quantum dots (QDs) has attracted great attention in the biomedical field over the past two decades. Maintenance of the fluorescence of QDs in a biological environment is crucial for performing long-term cell tracking to investigate the proliferation and functional evolution of cells. The cell-penetrating peptide transactivator of transcription (TAT) is a well-studied peptide to efficiently enhance the transmembrane delivery. Here, we used TAT peptide-conjugated QDs (TAT-QDs) as a model system to examine the fluorescence stability of QDs in live cells. By confocal microscopy, we found that TAT-QDs were internalized into cells by endocytosis, and transported into the cytoplasm via the mitochondria, Golgi apparatus, and lysosomes. More importantly, the fluorescence of TAT-QDs in live cells was decreased mainly by cell proliferation, and the low pH value in the lysosomes could also lower the fluorescence intensity of intracellular QDs. Quantitative analysis of the amount of QDs in the extracellular region and whole cells indicated that the exocytosis was not the primary cause of fluorescence decay of intracellular QDs. This work facilitates a better understanding of the fluorescence stability of QDs for cell imaging and long-term tracking in live cells. Also, it provides insights into the utility of TAT for transmembrane transportation, and the preparation and modification of QDs for cell imaging and tracking.

  5. Vestibular ablation and a semicircular canal prosthesis affect postural stability during head turns.

    PubMed

    Thompson, Lara A; Haburcakova, Csilla; Lewis, Richard F

    2016-11-01

    In our study, we examined postural stability during head turns for two rhesus monkeys: one animal study contrasted normal and mild bilateral vestibular ablation and a second animal study contrasted severe bilateral vestibular ablation with and without prosthetic stimulation. The monkeys freely stood, unrestrained on a balance platform and made voluntary head turns between visual targets. To quantify each animals' posture, motions of the head and trunk, as well as torque about the body's center of mass, were measured. In the mildly ablated animal, we observed less foretrunk sway in comparison with the normal state. When the canal prosthesis provided electric stimulation to the severely ablated animal, it showed a decrease in trunk sway during head turns. Because the rhesus monkey with severe bilateral vestibular loss exhibited a decrease in trunk sway when receiving vestibular prosthetic stimulation, we propose that the prosthetic electrical stimulation partially restored head velocity information. Our results provide an indication that a semicircular canal prosthesis may be an effective way to improve postural stability in patients with severe peripheral vestibular dysfunction.

  6. Vestibular ablation and a semicircular canal prosthesis affect postural stability during head turns

    PubMed Central

    Thompson, Lara A.; Haburcakova, Csilla; Lewis, Richard F.

    2016-01-01

    In our study, we examined postural stability during head turns for two rhesus monkeys: one, single animal study contrasted normal and mild bilateral vestibular ablation and a second animal study contrasted severe bilateral vestibular ablation with and without prosthetic stimulation. The monkeys freely stood, unrestrained on a balance platform and made voluntary head turns between visual targets. To quantify each animals’ posture, motions of the head and trunk, as well as torque about the body’s center-of-mass, were measured. In the mildly ablated animal, we observed less foretrunk sway in comparison to the normal state. When the canal prosthesis provided electric stimulation to the severely ablated animal, it showed a decrease in trunk sway during head turns. Because the rhesus monkey with severe bilateral vestibular loss exhibited a decrease in trunk sway when receiving vestibular prosthetic stimulation, we propose that the prosthetic electrical stimulation partially restored head velocity information. Our results provide an indication that a semicircular canal prosthesis may be an effective way to improve postural stability in patients with severe peripheral vestibular dysfunction. PMID:27405997

  7. NASA Now: SLOPE

    NASA Video Gallery

    Welcome to the SLOPE facility at NASA’s Glenn Research Center in Cleveland, Ohio. In this building, NASA engineers experiment with different wheel designs for lunar rovers. They use a simulated c...

  8. Mars Exploration Rover Landing Site Hectometer Slopes

    NASA Astrophysics Data System (ADS)

    Haldemann, A. F.; Anderson, F. S.

    2002-12-01

    The Mars Exploration Rover (MER) airbag landing system imposes a maximum slope of 5 degrees over 100 m length-scales. This limit avoids dangerous changes in elevation over the horizontal travel distance of the lander on its parachute between the time of the last radar altimeter detection of the surface and the time the retro-rockets fire and the bridle to the airbags is cut. Stereo imagery from the MGS MOC can provide information at this length scale, but MOC stereo coverage is sparse, even when targeted to MER landing sites. Additionally, MGS spacecraft stability issues affect the DEMs at precisely the hectometric length-scale1. The MOLA instrument provides global coverage pulse-width measurements2 over a single MOLA-pulse footprint, which is about 100 m in diameter. However, the pulse spread only provides an upper bound on the 100 m slope. We chose another approach. We sample the inter-pulse root-mean-square (RMS) height deviations for MOLA track segments restricted to pixels of 0.1 deg latitude by 0.1 deg longitude. Then, under the assumption of self-affine topography, we determine the scale-dependence of the RMS deviations and extrapolate that behavior over the range of 300 m to 1.2 km downward to the 100 m scale. Shepard et al.3 clearly summarize the statistical properties of the RMS deviation (noting that it also goes by the name structure function, variogram or Allan deviation), and we follow their nomenclature. The RMS deviation is a useful measure in that it can be directly converted to RMS-slope for a given length-scale. We map the results of this self-affine extrapolation method for each of the proposed MER landing sites as well as Viking Lander 1 (VL1) and Pathfiner (MPF). In order of decreasing average hectometer RMS-slopes, Melas (about 4.5 degrees) > Elysium EP80 > Gusev > MPF > Elysium EP78 > VL1 > Athabasca > Isidis > Hematite (about 1 degree). We also map the scaling parameter (Hurst exponent); its behavior in the MER landing site regions is

  9. [Fire behavior of Mongolian oak leaves fuel bed under no-wind and zero-slope conditions. II. Analysis of the factors affecting flame length and residence time and related prediction models].

    PubMed

    Zhang, Ji-Li; Liu, Bo-Fei; Di, Xue-Ying; Chu, Teng-Fei; Jin, Sen

    2012-11-01

    Taking fuel moisture content, fuel loading, and fuel bed depth as controlling factors, the fuel beds of Mongolian oak leaves in Maoershan region of Northeast China in field were simulated, and a total of one hundred experimental burnings under no-wind and zero-slope conditions were conducted in laboratory, with the effects of the fuel moisture content, fuel loading, and fuel bed depth on the flame length and its residence time analyzed and the multivariate linear prediction models constructed. The results indicated that fuel moisture content had a significant negative liner correlation with flame length, but less correlation with flame residence time. Both the fuel loading and the fuel bed depth were significantly positively correlated with flame length and its residence time. The interactions of fuel bed depth with fuel moisture content and fuel loading had significant effects on the flame length, while the interactions of fuel moisture content with fuel loading and fuel bed depth affected the flame residence time significantly. The prediction model of flame length had better prediction effect, which could explain 83.3% of variance, with a mean absolute error of 7.8 cm and a mean relative error of 16.2%, while the prediction model of flame residence time was not good enough, which could only explain 54% of variance, with a mean absolute error of 9.2 s and a mean relative error of 18.6%.

  10. Modified Stability Charts for Rock Slopes Based on the Hoek-Brown Failure Criterion / Zmodyfikowane Diagramy Stabilności Skalistych Zboczy Otrzymane W Oparciu O Warunek Wytrzymałości Hoeka-Browna

    NASA Astrophysics Data System (ADS)

    Nekouei, Mahdi; Ahangari, Kaveh

    2013-09-01

    Only an article rendered by Lia et al. in 2008 has represented charts based on Hoek-Brown criterion for rock slopes, however, these charts are not precise and efficient. Because of this problem, a modification is suggested for the mentioned charts in this study. The new charts are calculated according to four methods. Among the methods, one relates to finite element method using Phase2 software. The other three methods are Janbu, Bishop and Fellenius that belong to limit equilibrium method by using Slide software. For each slope angle, the method having high correlation coefficient is selected as the best one. Then, final charts are rendered according to the selected method and its specific equations. Among forty equations, twenty-five ones or 62.5% relate to numerical method and Phase2 software, six ones or 15% belong to Fellenius limit equilibrium, six ones or 15% relate to Bishop limit equilibrium, and three ones or 7.5% belong to Janbu limit equilibrium. In order to validate new charts, slope stability analysis is carried out for several sections of Chadormalu iron ore open pit mine, Iran. The error percentage of new charts in limit equilibrium method using Slide software and in Bishop method for slopes of Chadormalu iron ore mine are rendered and compared. The charts on a basis of Hoek-Brown failure criterion for rock slopes show less than ±4% error. This indicates that these charts are appropriate tools and their safety factor is optimal for rock slopes. Diagramy stabilności skalistych zboczy otrzymane w oparciu o warunek wytrzymałości Hoeka- Browna znaleźć można jedynie w pracy Lia et al. (2008), choć wykresy te nie są absolutnie dokładne i jasne. Dlatego też w niniejszym artykule zaproponowano pewną modyfikację diagramów. Nowe wykresu sporządzono w oparciu o cztery metody. Jedna z metod opiera się na metodzie elementów skończonych i wykorzystuje oprogramowanie Phase2. Pozostałe trzy podejścia to metody Janbu, Bishopa i Felleniusa bazuj

  11. Stability of micronutrients and phytochemicals of grapefruit jam as affected by the obtention process.

    PubMed

    Igual, M; García-Martínez, E; Camacho, M M; Martínez-Navarrete, N

    2016-04-01

    Fruits are widely revered for their micronutrient properties. They serve as a primary source of vitamins and minerals as well as of natural phytonutrients with antioxidant properties. Jam constitutes an interesting way to preserve fruit. Traditionally, this product is obtained by intense heat treatment that may cause irreversible loss of these bioactive compounds responsible for the health-related properties of fruits. In this work, different grapefruit jams obtained by conventional, osmotic dehydration (OD) without thermal treatment and/or microwave (MW) techniques were compared in terms of their vitamin, organic acid and phytochemical content and their stability through three months of storage. If compared with heating, osmotic treatments lead to a greater loss of organic acids and vitamin C during both processing and storage. MW treatments permit jam to be obtained which has a similar nutritional and functional value than that obtained when using a conventional heating method, but in a much shorter time.

  12. Gemini surfactants affect the structure, stability, and activity of ribonuclease Sa.

    PubMed

    Amiri, Razieh; Bordbar, Abdol-Khalegh; Laurents, Douglas V

    2014-09-11

    Gemini surfactants have important advantages, e.g., low micromolar CMCs and slow millisecond monomer ↔ micelle kinetics, for membrane mimetics and for delivering nucleic acids for gene therapy or RNA silencing. However, as a prerequisite, it is important to characterize interactions occurring between Gemini surfactants and proteins. Here NMR and CD spectroscopies are employed to investigate the interactions of cationic Gemini surfactants with RNase Sa, a negatively charged ribonuclease. We find that RNase Sa binds Gemini surfactant monomers and micelles at pH values above 4 to form aggregates. Below pH 4, where the protein is positively charged, these aggregates dissolve and interactions are undetectable. Thermal denaturation experiments show that surfactant lowers RNase Sa's conformational stability, suggesting that surfactant binds the protein's denatured state preferentially. Finally, Gemini surfactants were found to bind RNA, leading to the formation of large complexes. Interestingly, Gemini surfactant binding did not prevent RNase Sa from cleaving RNA.

  13. Electricity and colloidal stability: how charge distribution in the tissue can affects wound healing.

    PubMed

    Farber, Paulo Luiz; Hochman, Bernardo; Furtado, Fabianne; Ferreira, Lydia Masako

    2014-02-01

    The role of endogenous electric fields in wound healing is still not fully understood. Electric fields are of fundamental importance in various biological processes, ranging from embryonic development to disease progression, as described by many investigators in the last century. This hypothesis brings together some relevant literature on the importance of electric fields in physiology and pathology, the theory of biologically closed electric circuits, skin battery (a phenomenon that occurs after skin injury and seems to be involved in tissue repair), the relationship between electric charge and interstitial exclusion, and how skin tissues can be regarded as colloidal systems. The importance of electric charges, as established in the early works on the subject and the relevance of zeta potential and colloid stability are also analyzed, and together bring a new light for the physics involved in the wound repair of all the body tissues.

  14. Phosphine passivated gold clusters: how charge transfer affects electronic structure and stability.

    PubMed

    Mollenhauer, Doreen; Gaston, Nicola

    2016-11-02

    A systematic evaluation of small phosphine ligand-protected gold clusters with six to nine gold atoms using density functional theory with dispersion correction has been performed in order to understand the major factors determining stability, including its size, shape, and charge dependence. We show that the charge per atom of the cluster is much more important for the interaction between the ligand shell and gold cluster than the system size. Thus, strong charge transfer effects determine the binding strength between the ligand shell and cluster. The clusters in this series are all non-spherical and exhibit large HOMO-LUMO gaps (above 2.7 eV). Analysis of the delocalized nature of the electronic states at the centre of the clusters demonstrates the presence of nascent superatomic states. However the number of delocalized electrons in these systems is significantly influenced by the charge transfer from the phosphine ligands, contrary to the usual accounting rule for superatom complex systems. Thus, not only electron withdrawing but also charge transfer effects should be considered to influence the superatomic structure of charged ligand surrounded clusters. In consequence in the phosphine gold cluster series under consideration the systems Au7(PPh3)7(+) and Au8(PPh3)8(2+) exhibit nearly fully filled S and P states and the HOMO-LUMO gap increases by 0.2 eV and 0.9 eV, respectively. The interpretation for the stability of the gold phosphine systems is in agreement with experimental results and demonstrates the importance of the superatomic concept.

  15. Desirable plant root traits for protecting unstable slopes against landslides

    NASA Astrophysics Data System (ADS)

    Stokes, A.; Atger, C.; Bengough, G.; Fourcaud, T.; Sidle, R. C.

    2009-04-01

    determine slope stability. Rooting depth is species dependent when soil conditions are not limiting and the number of horizontal lateral roots borne on the vertical roots usually changes with depth. Therefore, the number and orientation of roots that the shear surface intersects will change significantly with rooting depth for the same plant, even for magnitudes of only several cm. Similarly, depending on the geometry of the root system, the angle at which a root crosses the shear surface can also have an influence on its resistance to pullout and breakage. The angle at which a root emerges from the parent root is dependent on root type, depth and species (when soil conditions are not limiting). Due to the physiology of roots, a root branch can be initiated at any point along a parent root, but not necessarily emerge fully from the parent root. These traits, along with others including size, relative growth rate, regeneration strategies, wood structure and strength will be discussed with regard to their influence on slope stability. How each of these traits is influenced by soil conditions and plantation techniques is also of extreme importance to the landslide engineer. The presence of obstacles in the soil, as well as compaction, affects root length and branching pattern. Roots of many species of woody plants on shallow soils also tend to grow along fractures deep into the underlying bedrock which allows roots to locate supplies of nutrient and water rich pockets. Rooting depths of herbaceous species in water-limited environments are highly correlated with infiltration depth, but waterlogged soils can asphyxiate tree roots, resulting in shallow root systems. The need to understand and integrate each of these traits for a species is not easy. Therefore, we suggest a hierarchy whereby traits are considered in order of importance, along with how external factors influence their expression over time.

  16. Chemical properties and oxidative stability of perilla oils obtained from roasted perilla seeds as affected by extraction methods.

    PubMed

    Jung, Dong Min; Yoon, Suk Hoo; Jung, Mun Yhung

    2012-12-01

    The chemical properties and oxidative stability of perilla oils obtained from roasted perilla seeds as affected by extraction methods (supercritical carbon dioxide [SC-CO(2)], mechanical press, and solvent extraction) were studied. The SC-CO(2) extraction at 420 bar and 50 °C and hexane extraction showed significantly higher oil yield than mechanical press extraction (P < 0.05). The fatty acid compositions in the oils were virtually identical regardless of the extraction methods. The contents of tocopherol, sterol, policosanol, and phosphorus in the perilla oils greatly varied with the extraction methods. The SC-CO(2) -extracted perilla oils contained significantly higher contents of tocopherols, sterols, and policosanols than the mechanical press-extracted and hexane-extracted oils (P < 0.05). The SC-CO(2) -extracted oil showed the greatly lower oxidative stability than press-extracted and hexane-extracted oils during the storage in the oven under dark at 60 °C. However, the photooxidative stabilities of the oils were not considerably different with extraction methods.

  17. Negative energy balance affects imprint stability in oocytes recovered from postpartum dairy cows.

    PubMed

    O'Doherty, Alan M; O'Gorman, Aoife; al Naib, Abdullah; Brennan, Lorraine; Daly, Edward; Duffy, Pat; Fair, Trudee

    2014-09-01

    Ovarian follicle development in post-partum, high-producing dairy cows, occurs in a compromised endogenous metabolic environment (referred to as negative energy balance, NEB). Key events that occur during oocyte/follicle growth, such as the vital process of genomic imprinting, may be detrimentally affected by this altered ovarian environment. Imprinting is crucial for placental function and regulation of fetal growth, therefore failure to establish and maintain imprints during oocyte growth may contribute to early embryonic loss. Using ovum pick-up (OPU), oocytes and follicular fluid samples were recovered from cows between days 20 and 115 post-calving, encompassing the NEB period. In a complimentary study, cumulus oocyte complexes were in vitro matured under high non-esterified fatty acid (NEFA) concentrations and in the presence of the methyl-donor S-adenosylmethionine (SAM). Pyrosequencing revealed the loss of methylation at several imprinted loci in the OPU derived oocytes. The loss of DNA methylation was observed at the PLAGL1 locus in oocytes, following in vitro maturation (IVM) in the presence of elevated NEFAs and SAM. Finally, metabolomic analysis of postpartum follicular fluid samples revealed significant differences in several branched chain amino acids, with fatty acid profiles bearing similarities to those characteristic of lactating dairy cows. These results provide the first evidence that (1) the postpartum ovarian environment may affect maternal imprint acquisition and (2) elevated NEFAs during IVM can lead to the loss of imprinted gene methylation in bovine oocytes.

  18. Habitat stability and predation pressure affect temperament behaviours in populations of three-spined sticklebacks.

    PubMed

    Brydges, Nichola M; Colegrave, Nick; Heathcote, Robert J P; Braithwaite, Victoria A

    2008-03-01

    1. There is growing interest in the causes and consequences of animal temperaments. Temperament behaviours often have heritable components, but ecological variables can also affect them. Numerous variables are likely to differ between habitats, and these may interact to influence temperament behaviours. 2. Temperament behaviours may be correlated within populations (behavioural syndromes), although the underlying causes of such correlations are currently unclear. 3. We analysed three different temperament behaviours and learning ability in three-spined sticklebacks, Gasterosteus aculeatus, to determine how different ecological variables influence them both within and between populations. We selected populations from four ponds and four rivers that varied naturally in their exposure to predators. 4. High-predation river populations were significantly less bold than a high-predation pond and low-predation river populations, and low-predation pond populations were significantly less bold than a high-predation pond population. Within populations, temperament behaviours were correlated in one high-predation river population only. 5. These results suggest that multiple ecological factors can interact to affect temperament behaviours between populations, and also correlations in those behaviours within populations.

  19. Uner Tan syndrome caused by a homozygous TUBB2B mutation affecting microtubule stability.

    PubMed

    Breuss, Martin W; Nguyen, Thai; Srivatsan, Anjana; Leca, Ines; Tian, Guoling; Fritz, Tanja; Hansen, Andi H; Musaev, Damir; McEvoy-Venneri, Jennifer; James, Kiely N; Rosti, Rasim O; Scott, Eric; Tan, Uner; Kolodner, Richard D; Cowan, Nicholas J; Keays, David A; Gleeson, Joseph G

    2016-12-23

    The integrity and dynamic properties of the microtubule cytoskeleton are indispensable for the development of the mammalian brain. Consequently, mutations in the genes that encode the structural component (the α/β-tubulin heterodimer) can give rise to severe, sporadic neurodevelopmental disorders. These are commonly referred to as the tubulinopathies. Here we report the addition of recessive quadrupedalism, also known as Uner Tan syndrome (UTS), to the growing list of diseases caused by tubulin variants. Analysis of a consanguineous UTS family identified a biallelic TUBB2B mutation, resulting in a p.R390Q amino acid substitution. In addition to the identifying quadrupedal locomotion, all three patients showed severe cerebellar hypoplasia. None, however, displayed the basal ganglia malformations typically associated with TUBB2B mutations. Functional analysis of the R390Q substitution revealed that it did not affect the ability of β-tubulin to fold or become assembled into the α/β-heterodimer, nor did it influence the incorporation of mutant-containing heterodimers into microtubule polymers. The 390Q mutation in S. cerevisiae TUB2 did not affect growth under basal conditions, but did result in increased sensitivity to microtubule-depolymerizing drugs, indicative of a mild impact of this mutation on microtubule function. The TUBB2B mutation described here represents an unusual recessive mode of inheritance for missense-mediated tubulinopathies and reinforces the sensitivity of the developing cerebellum to microtubule defects.

  20. Limiting equilibrium and liquefaction potential in infinite submarine slopes

    USGS Publications Warehouse

    Denlinger, R.P.; Iverson, R.M.

    1990-01-01

    Stability evaluation of submarine slopes is hampered by the difficulty of making field measurements. Owing to the scarcity of detailed field data, stability is commonly assessed by assuming homogenous infinite slopes with steady seepage. For these conditions, it is necessary to measure only the slope angle, friction angle, cohesion, and pore pressure at some distance into the sediment to evaluate stability. Examination of available data shows that conditions close to those required for liquefaction are necessary for Coulomb failure in many continental shelf areas. This favors long landslide runouts and flow of sediment subsequent to failure. -from Authors

  1. Phytochemical stability in dried tomato pulp and peel as affected by moisture properties.

    PubMed

    Lavelli, Vera; Kerr, William; Sri Harsha, P S C

    2013-01-23

    Phytochemical stability was studied in dried tomato pulp and dried tomato peel stored at 30 °C with various water activity (a(w)) levels and related to glass transition temperature (T(g)) and water mobility. At a(w) < 0.32, the values for T(g) were >30 °C for both the pulp and peel, indicating that they were in the glassy state, with little molecular mobility. At a(w) = 0.56, T(g) was <30 °C, indicating the samples were in the rubbery state, with decreased viscosity and increased molecular mobility. The hydrophilic antioxidants (hydroxycinnamic acids and naringenin) were stable for samples in the glassy state, but were unstable for samples in the rubbery state. In contrast, the lipophilic antioxidants lycopene and α-tocopherol were mostly unstable for samples in the glassy state. These results could be used to optimize phytochemical contents in tomato products that must be dried prior to further processing.

  2. Enzyme bread improvers affect the stability of deoxynivalenol and deoxynivalenol-3-glucoside during breadmaking.

    PubMed

    Vidal, Arnau; Ambrosio, Asier; Sanchis, Vicente; Ramos, Antonio J; Marín, Sonia

    2016-10-01

    The stability of deoxynivalenol (DON) and deoxynivalenol-3-glucoside (DON-3-glucoside) during the breadmaking process was studied. Some enzymes used in the bakery industry were examined to evaluate their effects on DON and DON-3-glucoside. The level of DON in breads without added enzymes was reduced (17-21%). Similarly, the addition of cellulase, protease, lipase and glucose-oxidase did not modify this decreasing trend. The effect of xylanase and α-amylase on DON content depended on the fermentation temperature. These enzymes reduced the DON content by 10-14% at 45°C. In contrast, at 30°C, these enzymes increased the DON content by 13-23%. DON-3-glucoside levels decreased at the end of fermentation, with a final reduction of 19-48% when no enzymes were used. However, the presence of xylanase, α-amylase, cellulase and lipase resulted in bread with greater quantities of DON-3-glucoside when fermentation occurred at 30°C. The results showed that wheat bran and flour may contain hidden DON that may be enzymatically released during the breadmaking process when the fermentation temperature is close to 30°C.

  3. Sulfur bacteria in wastewater stabilization ponds periodically affected by the 'red-water' phenomenon.

    PubMed

    Belila, Abdelaziz; Abbas, Ben; Fazaa, Imed; Saidi, Neila; Snoussi, Mejdi; Hassen, Abdennaceur; Muyzer, Gerard

    2013-01-01

    Several wastewater stabilization ponds (WSP) in Tunisia suffer periodically from the 'red-water' phenomenon due to blooming of purple sulfur bacteria, indicating that sulfur cycle is one of the main element cycles in these ponds. In this study, we investigated the microbial diversity of the El Menzeh WSP and focused in particular on the different functional groups of sulfur bacteria. For this purpose, we used denaturing gradient gel electrophoresis of PCR-amplified fragments of the 16S rRNA gene and of different functional genes involved in microbial sulfur metabolism (dsrB, aprA, and pufM). Analyses of the 16S rRNA revealed a relatively high microbial diversity where Proteobacteria, Chlorobi, Bacteroidetes, and Cyanobacteria constitute the major bacterial groups. The dsrB and aprA gene analysis revealed the presence of deltaproteobacterial sulfate-reducing bacteria (i.e., Desulfobacter and Desulfobulbus), while the analysis of 16S rRNA, aprA, and pufM genes assigned the sulfur-oxidizing bacteria community to the photosynthetic representatives belonging to the Chlorobi (green sulfur bacteria) and the Proteobacteria (purple sulfur and non sulfur bacteria) phyla. These results point on the diversity of the metabolic processes within this wastewater plant and/or the availability of sulfate and diverse electron donors.

  4. Biochar affects carbon composition and stability in soil: a combined spectroscopy-microscopy study

    PubMed Central

    Hernandez-Soriano, Maria C.; Kerré, Bart; Kopittke, Peter M.; Horemans, Benjamin; Smolders, Erik

    2016-01-01

    The use of biochar can contribute to carbon (C) storage in soil. Upon addition of biochar, there is a spatial reorganization of C within soil particles, but the mechanisms remain unclear. Here, we used Fourier transformed infrared-microscopy and confocal laser scanning microscopy to examine this reorganization. A silty-loam soil was amended with three different organic residues and with the biochar produced from these residues and incubated for 237 d. Soil respiration was lower in biochar-amended soils than in residue-amended soils. Fluorescence analysis of the dissolved organic matter revealed that biochar application increased a humic-like fluorescent component, likely associated with biochar-C in solution. The combined spectroscopy-microscopy approach revealed the accumulation of aromatic-C in discrete spots in the solid-phase of microaggregates and its co-localization with clay minerals for soil amended with raw residue or biochar.The co-localization of aromatic-C:polysaccharides-C was consistently reduced upon biochar application. We conclude that reduced C metabolism is an important mechanism for C stabilization in biochar-amended soils. PMID:27113269

  5. Static Magnetic Field Attenuates Lipopolysaccharide-Induced Inflammation in Pulp Cells by Affecting Cell Membrane Stability

    PubMed Central

    Tsao, Jeng-Ting; Lee, Lin-Wen; Lin, Che-Tong

    2015-01-01

    One of the causes of dental pulpitis is lipopolysaccharide- (LPS-) induced inflammatory response. Following pulp tissue inflammation, odontoblasts, dental pulp cells (DPCs), and dental pulp stem cells (DPSCs) will activate and repair damaged tissue to maintain homeostasis. However, when LPS infection is too serious, dental repair is impossible and disease may progress to irreversible pulpitis. Therefore, the aim of this study was to examine whether static magnetic field (SMF) can attenuate inflammatory response of dental pulp cells challenged with LPS. In methodology, dental pulp cells were isolated from extracted teeth. The population of DPSCs in the cultured DPCs was identified by phenotypes and multilineage differentiation. The effects of 0.4 T SMF on DPCs were observed through MTT assay and fluorescent anisotropy assay. Our results showed that the SMF exposure had no effect on surface markers or multilineage differentiation capability. However, SMF exposure increases cell viability by 15%. In addition, SMF increased cell membrane rigidity which is directly related to higher fluorescent anisotropy. In the LPS-challenged condition, DPCs treated with SMF demonstrated a higher tolerance to LPS-induced inflammatory response when compared to untreated controls. According to these results, we suggest that 0.4 T SMF attenuates LPS-induced inflammatory response to DPCs by changing cell membrane stability. PMID:25884030

  6. Influenza A viruses suppress cyclooxygenase-2 expression by affecting its mRNA stability

    PubMed Central

    Dudek, Sabine Eva; Nitzsche, Katja; Ludwig, Stephan; Ehrhardt, Christina

    2016-01-01

    Infection with influenza A viruses (IAV) provokes activation of cellular defence mechanisms contributing to the innate immune and inflammatory response. In this process the cyclooxygenase-2 (COX-2) plays an important role in the induction of prostaglandin-dependent inflammation. While it has been reported that COX-2 is induced upon IAV infection, in the present study we observed a down-regulation at later stages of infection suggesting a tight regulation of COX-2 by IAV. Our data indicate the pattern-recognition receptor RIG-I as mediator of the initial IAV-induced COX-2 synthesis. Nonetheless, during on-going IAV replication substantial suppression of COX-2 mRNA and protein synthesis could be detected, accompanied by a decrease in mRNA half-life. Interestingly, COX-2 mRNA stability was not only imbalanced by IAV replication but also by stimulation of cells with viral RNA. Our results reveal tristetraprolin (TTP), which is known to bind COX-2 mRNA and promote its rapid degradation, as regulator of COX-2 expression in IAV infection. During IAV replication and viral RNA accumulation TTP mRNA synthesis was induced, resulting in reduced COX-2 levels. Accordingly, the down-regulation of TTP resulted in increased COX-2 protein expression after IAV infection. These findings indicate a novel IAV-regulated cellular mechanism, contributing to the repression of host defence and therefore facilitating viral replication. PMID:27265729

  7. Biochar affects carbon composition and stability in soil: a combined spectroscopy-microscopy study

    NASA Astrophysics Data System (ADS)

    Hernandez-Soriano, Maria C.; Kerré, Bart; Kopittke, Peter M.; Horemans, Benjamin; Smolders, Erik

    2016-04-01

    The use of biochar can contribute to carbon (C) storage in soil. Upon addition of biochar, there is a spatial reorganization of C within soil particles, but the mechanisms remain unclear. Here, we used Fourier transformed infrared-microscopy and confocal laser scanning microscopy to examine this reorganization. A silty-loam soil was amended with three different organic residues and with the biochar produced from these residues and incubated for 237 d. Soil respiration was lower in biochar-amended soils than in residue-amended soils. Fluorescence analysis of the dissolved organic matter revealed that biochar application increased a humic-like fluorescent component, likely associated with biochar-C in solution. The combined spectroscopy-microscopy approach revealed the accumulation of aromatic-C in discrete spots in the solid-phase of microaggregates and its co-localization with clay minerals for soil amended with raw residue or biochar.The co-localization of aromatic-C:polysaccharides-C was consistently reduced upon biochar application. We conclude that reduced C metabolism is an important mechanism for C stabilization in biochar-amended soils.

  8. Modifications of the C terminus Affect Functionality and Stability of Yeast Triacylglycerol Lipase Tgl3p*

    PubMed Central

    Koch, Barbara; Schmidt, Claudia; Ploier, Birgit; Daum, Günther

    2014-01-01

    Lipid droplets are specific organelles for the storage of triacylglycerols and steryl esters. They are surrounded by a phospholipid monolayer with a small but specific set of proteins embedded. Assembly and insertion of proteins into this surface membrane is an intriguing question of lipid droplet biology. To address this question we studied the topology of Tgl3p, the major triacylglycerol lipase of the yeast Saccharomyces cerevisiae, on lipid droplets. Employing the method of limited proteolysis of lipid droplet surface proteins, we found that the C terminus of Tgl3p faces the inside of the organelle, whereas the N terminus is exposed at the cytosolic side of lipid droplets. Detailed analysis of the C terminus revealed a stretch of seven amino acids that are critical for protein stability and functionality. The negative charge of two aspartate residues within this stretch is crucial for lipase activity of Tgl3p. A portion of Tgl3p, which is located to the endoplasmic reticulum, exhibits a different topology. In the phospholipid bilayer of the endoplasmic reticulum the C terminus faces the cytosol, which results in instability of the protein. Thus, the topology of Tgl3p is important for its function and strongly dependent on the membrane environment. PMID:24847060

  9. Residue Asn277 affects the stability and substrate specificity of the SMG1 lipase from Malassezia globosa.

    PubMed

    Lan, Dongming; Wang, Qian; Xu, Jinxin; Zhou, Pengfei; Yang, Bo; Wang, Yonghua

    2015-03-31

    Thermostability and substrate specificity are important characteristics of enzymes for industrial application, which can be improved by protein engineering. SMG1 lipase from Malassezia globosa is a mono- and diacylglycerol lipase (MDL) that shows activity toward mono- and diacylglycerols, but no activity toward triacylglycerols. SMG1 lipase is considered a potential biocatalyst applied in oil/fat modification and its crystal structure revealed that an interesting residue-Asn277 may contribute to stabilize loop 273-278 and the 3104 helix which are important to enzyme characterization. In this study, to explore its role in affecting the stability and catalytic activity, mutagenesis of N277 with Asp (D), Val (V), Leu (L) and Phe (F) was conducted. Circular dichroism (CD) spectral analysis and half-life measurement showed that the N277D mutant has better thermostability. The melting temperature and half-life of the N277D mutant were 56.6 °C and 187 min, respectively, while that was 54.6 °C and 121 min for SMG1 wild type (WT). Biochemical characterization of SMG1 mutants were carried out to test whether catalytic properties were affected by mutagenesis. N277D had similar enzymatic properties as SMG1 WT, but N277F showed a different substrate selectivity profile as compared to other SMG1 mutants. Analysis of the SMG1 3D model suggested that N277D formed a salt bridge via its negative charged carboxyl group with a positively charged guanidino group of R227, which might contribute to confer N277D higher temperature stability. These findings not only provide some clues to understand the molecular basis of the lipase structure/function relationship but also lay the framework for engineering suitable MDL lipases for industrial applications.

  10. The 3' untranslated region of human Cyclin-Dependent Kinase 5 Regulatory subunit 1 contains regulatory elements affecting transcript stability

    PubMed Central

    Moncini, Silvia; Bevilacqua, Annamaria; Venturin, Marco; Fallini, Claudia; Ratti, Antonia; Nicolin, Angelo; Riva, Paola

    2007-01-01

    Background CDK5R1 plays a central role in neuronal migration and differentiation during central nervous system development. CDK5R1 has been implicated in neurodegenerative disorders and proposed as a candidate gene for mental retardation. The remarkable size of CDK5R1 3'-untranslated region (3'-UTR) suggests a role in post-transcriptional regulation of CDK5R1 expression. Results The bioinformatic study shows a high conservation degree in mammals and predicts several AU-Rich Elements (AREs). The insertion of CDK5R1 3'-UTR into luciferase 3'-UTR causes a decreased luciferase activity in four transfected cell lines. We identified 3'-UTR subregions which tend to reduce the reporter gene expression, sometimes in a cell line-dependent manner. In most cases the quantitative analysis of luciferase mRNA suggests that CDK5R1 3'-UTR affects mRNA stability. A region, leading to a very strong mRNA destabilization, showed a significantly low half-life, indicating an accelerated mRNA degradation. The 3' end of the transcript, containing a class I ARE, specifically displays a stabilizing effect in neuroblastoma cell lines. We also observed the interaction of the stabilizing neuronal RNA-binding proteins ELAV with the CDK5R1 transcript in SH-SY5Y cells and identified three 3'-UTR sub-regions showing affinity for ELAV proteins. Conclusion Our findings evince the presence of both destabilizing and stabilizing regulatory elements in CDK5R1 3'-UTR and support the hypothesis that CDK5R1 gene expression is post-transcriptionally controlled in neurons by ELAV-mediated mechanisms. This is the first evidence of the involvement of 3'-UTR in the modulation of CDK5R1 expression. The fine tuning of CDK5R1 expression by 3'-UTR may have a role in central nervous system development and functioning, with potential implications in neurodegenerative and cognitive disorders. PMID:18053171

  11. PsbI affects the stability, function, and phosphorylation patterns of photosystem II assemblies in tobacco.

    PubMed

    Schwenkert, Serena; Umate, Pavan; Dal Bosco, Cristina; Volz, Stefanie; Mlçochová, Lada; Zoryan, Mikael; Eichacker, Lutz A; Ohad, Itzhak; Herrmann, Reinhold G; Meurer, Jörg

    2006-11-10

    Photosystem II (PSII) core complexes consist of CP47, CP43, D1, D2 proteins and of several low molecular weight integral membrane polypeptides, such as the chloroplast-encoded PsbE, PsbF, and PsbI proteins. To elucidate the function of PsbI in the photosynthetic process as well as in the biogenesis of PSII in higher plants, we generated homoplastomic knock-out plants by replacing most of the tobacco psbI gene with a spectinomycin resistance cartridge. Mutant plants are photoautotrophically viable under green house conditions but sensitive to high light irradiation. Antenna proteins of PSII accumulate to normal amounts, but levels of the PSII core complex are reduced by 50%. Bioenergetic and fluorescence studies uncovered that PsbI is required for the stability but not for the assembly of dimeric PSII and supercomplexes consisting of PSII and the outer antenna (PSII-LHCII). Thermoluminescence emission bands indicate that the presence of PsbI is required for assembly of a fully functional Q(A) binding site. We show that phosphorylation of the reaction center proteins D1 and D2 is light and redox-regulated in the wild type, but phosphorylation is abolished in the mutant, presumably due to structural alterations of PSII when PsbI is deficient. Unlike wild type, phosphorylation of LHCII is strongly increased in the dark due to accumulation of reduced plastoquinone, whereas even upon state II light phosphorylation is decreased in delta psbI. These data attest that phosphorylation of D1/D2, CP43, and LHCII is regulated differently.

  12. Factors affecting the stability and conformation of Locusta migratoria apolipophorin III.

    PubMed

    Weers, P M; Kay, C M; Oikawa, K; Wientzek, M; Van der Horst, D J; Ryan, R O

    1994-03-29

    Apolipophorin III (apoLp-III) from the migratory locust, Locusta migratoria, represents the only full-length apolipoprotein whose three-dimensional structure has been solved. In the present study, spectroscopic methods have been employed to investigate the effects of deglycosylation (via endoglycosidase F treatment) and complexation with lipid on the stability and conformation of this protein. Addition of isolated lipid-free apoLp-III to sonicated vesicles of dimyristoylphosphatidylcholine (DMPC) resulted in the formation of relatively uniform disklike complexes with an average Strokes diameter of 13.5 nm. Flotation equilibrium experiments conducted in the analytical ultracentrifuge revealed a particle molecular mass of 588 500 Da. Chemical cross-linking and compositional analysis of apoLp-III.DMPC complexes indicated five apoLp-III molecules per disk and an overall DMPC:apoLp-III molar ratio of 122:1. Circular dichroism (CD) spectra of apoLp-III samples suggested a loss of alpha-helical structure upon deglycosylation, while complexation with DMPC did not significantly alter the helix content (estimated to be > 75%). Fluorescence spectroscopy revealed that the apoLp-III tryptophan fluorescence emission maximum was blue-shifted from 347 to 332 and 321 nm upon deglycosylation and complexation with DMPC, respectively. In quenching experiments with native apoLp-III, tryptophan residues were shielded from the positively charged quencher, CsCl. Increased exposure to KI, CsCl, and acrylamide was observed upon deglycosylation, whereas complexation with DMPC yielded lower Ksv values for KI and acrylamide and an increased value for CsCl versus native lipid-free apoLp-III. In guanidine hydrochloride denaturation studies monitored by CD or fluorescence, native, lipid-free apoLp-III displayed a denaturation midpoint of 0.60 M, and delta GDH2O = 5.37 kcal/mol was calculated.(ABSTRACT TRUNCATED AT 250 WORDS)

  13. Arabian Slope Streaks

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-508, 9 October 2003

    Arabia Terra is a vast, heavily cratered region in the martian northern hemisphere. Much of Arabia Terra is thickly blanketed by dust. From time to time, on steep slopes, the dust will avalanche or slide downhill, creating a streak. The majority of slope streaks are darker than their surroundings, but not all of them are dark. In Arabia, it is common to find bright and dark slope streaks, and to find them together. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example, taken from a crater near 10.5oN, 318.4oW. Why some streaks are bright and others are dark is not yet known. This picture covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the left.

  14. Feeding dried distillers grains with solubles affects composition but not oxidative stability of milk.

    PubMed

    Testroet, E D; Li, G; Beitz, D C; Clark, S

    2015-05-01

    detected off-flavor scores were less than 1.5cm on a 15-cm line scale, indicating that the differences are not practically significant. Peroxide values support the findings by the sensory panel that both feeding DDGS at 10 and 25% and vitamin E and C fortification did not practically change the oxidative stability of milk. These results, taken together, indicate that feeding DDGS under our experimental conditions modified milk composition, but did not contribute to the development of off-flavors in milk.

  15. Deep soil compaction as a method of ground improvement and to stabilization of wastes and slopes with danger of liquefaction, determining the modulus of deformation and shear strength parameters of loose rock.

    PubMed

    Lersow, M

    2001-01-01

    For the stabilization of dumps with the construction of hidden dams and for building ground improvement, for instance for traffic lines over dumps, nearly all applied compaction methods have the aim to reduce the pore volume in the loose rock. With these methods, a homogenization of the compacted loose rock will be obtained too. The compaction methods of weight compaction by falling weight, compaction by vibration and compaction by blasting have been introduced, and their applications and efficiencies have been shown. For the estimation of the effective depth of the compaction and for a safe planning of the bearing layer, respectively, the necessary material parameters have to be determined for each deep compaction method. Proposals for the determination of these parameters have been made within this paper. In connection with the stabilization of flow-slide-prone dump slopes, as well as for the improvement of dump areas for the use as building ground, it is necessary to assess the deformation behavior and the bearing capacity. To assess the resulting building ground improvement, deformation indexes (assessment of the flow-prone layer) and strength indexes (assessment of the bearing capacity) have to be determined with soil mechanical tests. Förster and Lersow, [Patentschrift DE 197 17 988. Verfahren, auf der Grundlage last- und/oder weggesteuerter Plattendruckversuche auf der Bohrlochsohle, zur Ermittlung des Spannungs-Verformungs-Verhaltens und/oder von Deformationsmoduln und/oder von Festigkeitseigenschaften in verschiedenen Tiefen insbesondere von Lockergesteinen und von Deponiekörpern in situ; Förster W, Lersow M. Plattendruckversuch auf der Bohrlochsohle, Ermittlung des Spannungs-Verformungs-Verhaltens von Lockergestein und Deponiematerial Braunkohle--Surface Mining, 1998;50(4): 369-77; Lersow M. Verfahren zur Ermittlung von Scherfestigkeitsparametern von Lockergestein und Deponiematerial aus Plattendruckversuchen auf der Bohrlochsohle. Braunkohle

  16. Alkaline decontamination of sputum specimens adversely affects stability of mycobacterial mRNA.

    PubMed Central

    Desjardin, L E; Perkins, M D; Teixeira, L; Cave, M D; Eisenach, K D

    1996-01-01

    Reverse transcriptase PCR (RT-PCR) is an important tool for Mycobacterium tuberculosis research and diagnostics. A standard procedure using N-acetyl-L-cysteine (NALC) and NaOH has been widely adopted for digestion and decontamination of sputum specimens for mycobacterial culture. The objective of this study was to determine the compatibility of this method with the recovery of RNA for RT-PCR assays. Nineteen sputum specimens were collected from smear-positive, pretreatment tuberculosis patients. After homogenization with NALC and glass beads, specimens were further processed by the addition of either NaOH, as per the standard decontamination protocol, or phosphate buffer. RNA was prepared by using a modified guanidine-phenol extraction method developed specifically for sputum sediments. DNA was isolated from the same specimens. Reverse transcriptions of alpha antigen (85B protein) mRNA and 16S rRNA were performed together, and aliquots were removed for separate PCRs. In all specimens, the 85B mRNA target was greatly diminished by treatment with NaOH; however, the 16S rRNA target remained unaffected. Storing sputum specimens for 48 h at 4 degrees C before processing did not seem to affect the integrity or yield of RNA; however, some degradation occurred by 72 h. Data suggest that the NaOH-NALC method for processing sputum samples is not suitable for detecting mRNA targets in RT-PCR assays. PMID:8880495

  17. Slope evolution at the Calvert Cliffs, Maryland -- measuring the change from eroding bluffs to stable slopes

    USGS Publications Warehouse

    Herzog, Martha; Larsen, Curtis E.; McRae, Michele

    2002-01-01

    Despite a long history of geomorphic studies, it is difficult to ascertain the time required for slopes to change from near vertical exposures to relatively stable slopes due to inadequate age control. Actively eroding coastal bluffs along the western shore of the Chesapeake Bay provide a key for understanding the centennial-scale development of stable slopes from eroding bluff faces. The Calvert Cliffs are composed of sandy silts, silty sands, and clayey silts of Miocene-age. Active wave erosion at the bluff toes encourages rapid sloughing from bluff faces and maintains slope angles of 70-80 degrees and relatively constant bluff-retreat rates. Naturally stabilized slopes are preserved as a fossil bluff line inland from a prograding cuspate foreland at Cove Point. The foreland is migrating southward at a rate of ca. 1.5 m/yr. As it moves south, it progressively protects bluffs from wave action as new beaches are deposited at their toes. Wave erosion is reinitiated at the northern end of the complex as the landform passes. An incremental record of slope change is preserved along the fossil bluff line. 14C dating of swales between beach ridges shows the complex to span 1700 years of progressive migration history. We hypothesized that slopes would change from steep, eroding faces to low-angle slopes covered with vegetation and sought to document the rate of change. Our team measured slope angles at intervals along the fossil bluff line and dated profiles by interpolating 14C ages of adjacent beach ridges. There was no progressive decrease in slope with age. All slopes along the fossil bluff line were 30-40 degrees with a mean of 35 degrees. Constancy in slope angle suggests that steep, actively eroding bluffs were quickly changed to stable slopes by landslides and slumping once they were protected. Given the accuracy of our age control, we conclude that the time required to attain a stable slope under natural processes is less than one century. This indicates that

  18. Dynamics of aggregate stability and soil organic C distribution as affected by climatic aggressiveness: a mesocosm approach

    NASA Astrophysics Data System (ADS)

    Pellegrini, Sergio; Elio Agnelli, Alessandro; Costanza Andrenelli, Maria; Barbetti, Roberto; Castelli, Fabio; Costantini, Edoardo A. C.; Lagomarsino, Alessandra; Pasqui, Massimiliano; Tomozeiu, Rodica; Razzaghi, Somayyeh; Vignozzi, Nadia

    2014-05-01

    In the framework of a research project aimed at evaluating the adaptation scenarios of the Italian agriculture to the current climate change, a mesocosm experiment under controlled conditions was set up for studying the dynamics of soil aggregate stability and organic C in different size fractions. Three alluvial loamy soils (BOV - Typic Haplustalfs coarse-loamy; CAS - Typic Haplustalfs fine-loamy; MED - Typic Hapludalfs fine-loamy) along a climatic gradient (from dryer to moister pedoclimatic conditions) in the river Po valley (northern Italy), under crop rotation for animal husbandry from more than 40 years, were selected. The Ap horizons (0-30cm) were taken and placed in 9 climatic chambers under controlled temperature and rainfall. Each soil was subjected to three different climate scenarios in terms of erosivity index obtained by combining Modified Fournier and Bagnouls-Gaussen indexes: i) typical (TYP), the median year of each site related to the 1961-1990 reference period; ii) maximum aggressive year (MAX) observed in the same period, and iii) the simulated climate (SIM), obtained by projections of climate change precipitation and temperature for the period 2021-2050 as provided by the IPCC-A1B emission scenario. In the climatic chambers the year climate was reduced to six months. The soils were analyzed for particle size distribution, aggregate stability by wet and dry sieving, and organic C content at the beginning and at the end of the trial. The soils showed different behaviour in terms of aggregate stability and dynamics of organic C in the diverse size fractions. The soils significantly differed in terms of initial mean weight diameter (MWD) (CAS>MED>BOV). A general reduction of MWD in all sites was observed at the end of the experiment, with the increase of the smallest aggregate fractions (0.250-0.05 mm). In particular, BOV showed the maximum decrease of the aggregate stability and MED the lowest. C distribution in aggregate fractions significantly

  19. How can climate, soil, and monitoring schedule affect temporal stability of soil water contents?

    NASA Astrophysics Data System (ADS)

    Martinez, G.; Pachepsky, Y. A.; Vereecken, H.

    2012-12-01

    Temporal stability (TS) of soil water content (SWC) reflects the spatio-temporal organization of soil water. The TS SWC was originally recognized as a phenomenon that can be used to provide temporal average SWC of an area of interest from observations at a representative location(s). Currently application fields of TS SWC are numerous, e.g. up- and downscaling SWC, SWC monitoring and data assimilation, precision farming, and sensor network design and optimization. However, the factors that control the SWC organization and TS SWC are not completely understood. Among these factors are soil hydraulic properties that are considered as local controls, weather patterns, and the monitoring schedule. The objective of this work was to use modeling to assess the effect of these factors on the spatio-temporal patterns of SWC. We ran the HYDRUS6 code to simulate four years of SWC in 4-m long soil columns. The columns were assumed homogeneous, soil hydraulic conductivity was drawn from lognormal distributions. Sets of columns were generated separately for sandy loam and loamy soils, soil water retention was set to typical values for those soil textures. Simulations were carried out for four climates present at the continental US. The climate-specific weather patterns were obtained with the CLIGEN code using climate-specific weather observation locations that were humid subtropical from College Station (TX), humid continental from Indianapolis (IN), cold semiarid from Moscow (ID) and hot semiarid from Tucson (AZ). We evaluated the TS and representative location (RL) selections by comparing i) different climates; ii) for the same climates different years; iii) different time intervals between samplings; iv) one year duration surveys vs. one month summer campaigns; and v) different seasons of the same year. Spatial variability of the mean relative differences (MRD) differed among climates for both soils, as the probability of observing the same variance in the MRD was lower than

  20. Liming effects on cadmium stabilization in upland soil affected by gold mining activity.

    PubMed

    Hong, Chang Oh; Lee, Do Kyoung; Chung, Doug Young; Kim, Pil Joo

    2007-05-01

    To reduce cadmium (Cd) uptake of plants cultivated in heavy metal-contaminated soil, the best liming material was selected in the incubation test. The effect of the selected material was evaluated in the field. In the incubation experimentation, CaCO(3), Ca(OH)(2), CaSO(4).2H(2)O, and oyster shell meal were mixed with soil at rates corresponding to 0, 400, 800, 1600, 3200 mg Ca kg(-1). The limed soil was moistened to 70% of field moisture capacity, and incubated at 25 degrees C for 4 weeks. Ca(OH)(2) was found to be more efficient on reducing soil NH(4)OAc extractable Cd concentration, due to pH increase induced net negative charge. The selected Ca(OH)(2) was applied at rates 0, 2, 4, 8 Mg ha(-1) and then cultivated radish (Raphanus sativa L.) in the field. NH(4)OAc extractable Cd concentration of soil and plant Cd concentration decreased significantly with increasing Ca(OH)(2) rate, since alkaline-liming material markedly increased net negative charge of soil induced by pH increase, and decreased bioavailable Cd fractions (exchangeable + acidic and reducible Cd fraction) during radish cultivation. Cadmium uptake of radish could be reduced by about 50% by amending with about 5 Mg ha(-1) Ca(OH)(2) without adverse effect on radish yield and growth. The increase of net negative charge of soil by Ca(OH)(2) application may suppress Cd uptake and the competition between Ca(2+) and Cd(2+) may additionally affect the suppression of Cd uptake.

  1. Seismically induced rock slope failures resulting from topographic amplification of strong ground motions: The case of Pacoima Canyon, California

    USGS Publications Warehouse

    Sepulveda, S.A.; Murphy, W.; Jibson, R.W.; Petley, D.N.

    2005-01-01

    The 1994 Northridge earthquake (Mw = 6.7) triggered extensive rock slope failures in Pacoima Canyon, immediately north of Los Angeles, California. Pacoima Canyon is a narrow and steep canyon incised in gneissic and granitic rocks. Peak accelerations of nearly 1.6 g were recorded at a ridge that forms the left abutment of Pacoima Dam; peak accelerations at the bottom of the canyon were less than 0.5 g, suggesting the occurrence of topographic amplification. Topographic effects have been previously suggested to explain similarly high ground motions at the site during the 1971 (Mw = 6.7) San Fernando earthquake. Furthermore, high landslide concentrations observed in the area have been attributed to unusually strong ground motions rather than higher susceptibility to sliding compared with nearby zones. We conducted field investigations and slope stability back-analyses to confirm the impact of topographic amplification on the triggering of landslides during the 1994 earthquake. Our results suggest that the observed extensive rock sliding and falling would have not been possible under unamplified seismic conditions, which would have generated a significantly lower number of areas affected by landslides. In contrast, modelling slope stability using amplified ground shaking predicts slope failure distributions matching what occurred in 1994. This observation confirms a significant role for topographic amplification on the triggering of landslides at the site, and emphasises the need to select carefully the inputs for seismic slope stability analyses. ?? 2005 Elsevier B.V. All rights reserved.

  2. Cognitive vulnerability to depression during middle childhood: Stability and associations with maternal affective styles and parental depression.

    PubMed

    Hayden, Elizabeth P; Olino, Thomas M; Mackrell, Sarah V M; Jordan, Patricia L; Desjardins, Jasmine; Katsiroumbas, Patrice

    2013-11-01

    Theories of cognitive vulnerability to depression (CVD) imply that CVD is early-emerging and trait-like; however, little longitudinal work has tested this premise in middle childhood, or examined theoretically relevant predictors of child CVD. We examined test-retest correlations of self-referent encoding task performance and self-reported attributional styles and their associations with parental characteristics in 205 seven-year-olds. At baseline, child CVD was assessed, structured clinical interviews were conducted with parents, and ratings of observed maternal affective styles were made. Children's CVD was re-assessed approximately one and two years later. Both measures of children's CVD were prospectively and concurrently associated with children's depressive symptoms and showed modest stability. Multilevel modeling indicated that maternal criticism and paternal depression were related to children's CVD. Findings indicate that even early-emerging CVD is a valid marker of children's depression risk.

  3. Design of Rock Slope Reinforcement: An Himalayan Case Study

    NASA Astrophysics Data System (ADS)

    Tiwari, Gaurav; Latha, Gali Madhavi

    2016-06-01

    The stability analysis of the two abutment slopes of a railway bridge proposed at about 359 m above the ground level, crossing a river and connecting two hill faces in the Himalayas, India, is presented. The bridge is located in a zone of high seismic activity. The rock slopes are composed of a heavily jointed rock mass and the spacing, dip and dip direction of joint sets are varying at different locations. Geological mapping was carried out to characterize all discontinuities present along the slopes. Laboratory and field investigations were conducted to assess the geotechnical properties of the intact rock, rock mass and joint infill. Stability analyses of these rock slopes were carried out using numerical programmes. Loads from the foundations resting on the slopes and seismic accelerations estimated from site-specific ground response analysis were considered. The proposed slope profile with several berms between successive foundations was simulated in the numerical model. An equivalent continuum approach with Hoek and Brown failure criterion was initially used in a finite element model to assess the global stability of the slope abutments. In the second stage, finite element analysis of rock slopes with all joint sets with their orientations, spacing and properties explicitly incorporated into the numerical model was taken up using continuum with joints approach. It was observed that the continuum with joints approach was able to capture the local failures in some of the slope sections, which were verified using wedge failure analysis and stereographic projections. Based on the slope deformations and failure patterns observed from the numerical analyses, rock anchors were designed to achieve the target factors of safety against failure while keeping the deformations within the permissible limits. Detailed design of rock anchors and comparison of the stability of slopes with and without reinforcement are presented.

  4. The oxidation of methionine-54 of epoetinum alfa does not affect molecular structure or stability, but does decrease biological activity.

    PubMed

    Labrenz, Steven R; Calmann, Melissa A; Heavner, George A; Tolman, Glen

    2008-01-01

    Erythropoietin therapy is used to treat severe anemia in renal failure and chemotherapy patients. One of these therapies based on recombinant human erythropoietin is marketed under the trade name of EPREX and utilizes epoetinum alfa as the active pharmaceutical ingredient. The effect of oxidation of methionine-54 on the structure and stability of the erythropoietin molecule has not been directly tested. We have observed partial and full chemical oxidation of methionine-54 to methionine-54 sulfoxide, accomplished using tert-Butylhydroperoxide and hydrogen peroxide, respectively. A blue shift in the fluorescence center of spectral mass wavelength was observed as a linear response to the level of methionine sulfoxide in the epoetinum alfa molecule, presumably arising from a local change in the environment near tryptophan-51, as supported by potassium iodide quenching studies. Circular dichroism studies demonstrated no change in the folded structure of the molecule with methionine oxidation. The thermal unfolding profiles of partial and completely oxidized epoetinum alfa overlap, with a T(m) of 49.5 degrees C across all levels of methionine sulfoxide content. When the protein was tested for activity, a decrease in biological activity was observed, correlating with methionine sulfoxide levels. An allosteric effect between Met54, Trp51, and residues involved in receptor binding is proposed. These results indicate that methionine oxidation has no effect on the folded structure and global thermodynamic stability of the recombinant human erythropoietin molecule. Oxidation can affect potency, but only at levels significantly in excess of those seen in EPREX.

  5. Response mechanism of post-earthquake slopes under heavy rainfall

    NASA Astrophysics Data System (ADS)

    Qiu, Hong-zhi; Kong, Ji-ming; Wang, Ren-chao; Cui, Yun; Huang, Sen-wang

    2017-01-01

    This paper uses the catastrophic landslide that occurred in Zhongxing Town, Dujiangyan City, as an example to study the formation mechanism of landslides induced by heavy rainfall in the post-Wenchuan earthquake area. The deformation characteristics of a slope under seismic loading were investigated via a shaking table test. The results show that a large number of cracks formed in the slope due to the tensile and shear forces of the vibrations, and most of the cracks had angles of approximately 45° with respect to the horizontal. A series of flume tests were performed to show how the duration and intensity of rainfall influence the responses of the shaken and non-shaken slopes. Wetting fronts were recorded under different rainfall intensities, and the depth of rainfall infiltration was greater in the shaken slope than in the non-shaken slope because the former experienced a greater extreme rainfall intensity under the same early rainfall and rainfall duration conditions. At the beginning of the rainfall infiltration experiment, the pore water pressure in the slope was negative, and settling occurred at the top of the slope. With increasing rainfall, the pore water pressure changed from negative to positive, and cracks were observed on the back surface of the slope and the shear outlet of the landslide on the front of the slope. The shaken slope was more susceptible to crack formation than the non-shaken slope under the same rainfall conditions. A comparison of the responses of the shaken and non-shaken slopes under heavy rainfall revealed that cracks formed by earthquakes provided channels for infiltration. Soil particles in the cracks of slopes were washed away, and the pore water pressure increased rapidly, especially the transient pore water pressure in the slope caused by short-term concentrated rainfall which decreased rock strength and slope stability.

  6. Rapid eye movement sleep deprivation decreases long-term potentiation stability and affects some glutamatergic signaling proteins during hippocampal development.

    PubMed

    Lopez, J; Roffwarg, H P; Dreher, A; Bissette, G; Karolewicz, B; Shaffery, J P

    2008-04-22

    Development of the mammalian CNS requires formation and stabilization of neuronal circuits and synaptic connections. Sensory stimulation provided by the environment orchestrates neuronal circuit formation in the waking state. Endogenous sources of activation are also implicated in these processes. Accordingly we hypothesized that sleep, especially rapid eye movement sleep (REMS), the stage characterized by high neuronal activity that is more prominent in development than adulthood, provides endogenous stimulation, which, like sensory input, helps to stabilize and refine neuronal circuits during CNS development. Young (Y: postnatal day (PN) 16) and adolescent (A: PN44) rats were rapid eye movement sleep-deprived (REMSD) by gentle cage-shaking for only 4 h on 3 consecutive days (total 12 h). The effect of REMS deprivation in Y and A rats was tested 3-7 days after the last deprivation session (Y, PN21-25; A, PN49-53) and was compared with younger (immature, I, PN9-12) untreated, age-matched, treated and normal control groups. REMS deprivation negatively affected the stability of long-term potentiation (LTP) in Y but not A animals. LTP instability in Y-REMSD animals was similar to the instability in even the more immature, untreated animals. Utilizing immunoblots, we identified changes in molecular components of glutamatergic synapses known to participate in mechanisms of synaptic refinement and plasticity. Overall, N-methyl-d-aspartate receptor subunit 2B (NR2B), N-methyl-d-aspartate receptor subunit 2A, AMPA receptor subunit 1 (GluR1), postsynaptic density protein 95 (PSD-95), and calcium/calmodulin kinase II tended to be lower in Y REMSD animals (NR2B, GluR1 and PSD-95 were significantly lower) compared with controls, an effect not present in the A animals. Taken together, these data indicate that early-life REMS deprivation reduces stability of hippocampal neuronal circuits, possibly by hindering expression of mature glutamatergic synaptic components. The findings

  7. GIS-based seismic shaking slope vulnerability map of Sicily (Central Mediterranean)

    NASA Astrophysics Data System (ADS)

    Nigro, Fabrizio; Arisco, Giuseppe; Perricone, Marcella; Renda, Pietro; Favara, Rocco

    2010-05-01

    Earthquakes often represent very dangerouses natural events in terms of human life and economic losses and their damage effects are amplified by the synchronous occurrence of seismically-induced ground-shaking failures in wide regions around the seismogenic source. In fact, the shaking associated with big earthquakes triggers extensive landsliding, sometimes at distances of more than 100 km from the epicenter. The active tectonics and the geomorphic/morphodinamic pattern of the regions affected by earthquakes contribute to the slopes instability tendency. In fact, earthquake-induced groun-motion loading determines inertial forces activation within slopes that, combined with the intrinsic pre-existing static forces, reduces the slope stability towards its failure. Basically, under zero-shear stress reversals conditions, a catastrophic failure will take place if the earthquake-induced shear displacement exceeds the critical level of undrained shear strength to a value equal to the gravitational shear stress. However, seismic stability analyses carried out for various infinite slopes by using the existing Newmark-like methods reveal that estimated permanent displacements smaller than the critical value should also be regarded as dangerous for the post-earthquake slope safety, in terms of human activities use. Earthquake-induced (often high-speed) landslides are among the most destructive phenomena related to slopes failure during earthquakes. In fact, damage from earthquake-induced landslides (and other ground-failures), sometimes exceeds the buildings/infrastructures damage directly related to ground-shaking for fault breaking. For this matter, several hearthquakes-related slope failures methods have been developed, for the evaluation of the combined hazard types represented by seismically ground-motion landslides. The methodologies of analysis of the engineering seismic risk related to the slopes instability processes is often achieved through the evaluation of the

  8. Agricultural terraces and slope instability at Cinque Terre (NW Italy)

    NASA Astrophysics Data System (ADS)

    Brandolini, Pierluigi; Cevasco, Andrea

    2015-04-01

    Cinque Terre, located in the eastern Liguria, are one of the most representative examples of terraced coastal landscape within the Mediterranean region. They are the result of a century-old agricultural practice and constitute an outstanding example of human integration with the natural landscape. For this highly unusual man-made coastal landscape, the Cinque Terre have been recognized as a World Heritage Site by UNESCO since 1997 and became National Park in 1999. The complex network of retaining dry stone walls and drainage networks ensured through times the control of shallow water erosion and therefore, indirectly, favoured debris cover stability. The lack of maintenance of terracing due to farmer abandonment since the 1950s led to widespread slope erosion phenomena. The effects of such phenomena culminated during the 25 October 2011 storm rainfall event, when slope debris materials charged by streams gave rise to debris floods affecting both Monterosso and Vernazza villages. As the analysis of the relationships between geo-hydrological processes and land use in the Vernazza catchment highlighted, abandoned and not well maintained terraces were the most susceptible areas to shallow landsliding and erosion triggered by intense rainfall. As a consequence, the thousands of kilometres of dry stone walls retaining millions of cubic metres of debris cover at Cinque Terre currently constitute a potential menace for both villages, that are mainly located at the floor of deep cut valleys, and tourists. Given the increasing human pressure due to tourist activities, geo-hydrological risk mitigation measures are urgently needed. At the same time, restoration policies are necessary to preserve this extraordinary example of terraced coastal landscape. In this framework, the detailed knowledge of the response of terraced areas to intense rainfall in terms of slope instability is a topic issue in order to identify adequate land planning strategies as well as the areas where

  9. Standard Local Operating Procedures for Endangered Species (SLOPES) for Selected Nationwide Permit Activities Affecting Bull Trout in Western Montana and Northern Idaho. Endangered Species Act Section 7 Consultation: Biological Opinion

    DTIC Science & Technology

    2013-05-17

    57 Table 8. Nature of expected bull trout take and level of SLOPES activity for the action area within each core area...Replacement of existing stream crossings will be designed to promote natural sediment transport, allow maximum fluvial debris movement, and improve... natural movement of existing streambed material. Utility Line Activities: (NWP 12 type actions) Utility line construction or repair could involve

  10. "DNA Binding Region" of BRCA1 Affects Genetic Stability through modulating the Intra-S-Phase Checkpoint.

    PubMed

    Masuda, Takaaki; Xu, Xiaoling; Dimitriadis, Emilios K; Lahusen, Tyler; Deng, Chu-Xia

    2016-01-01

    The breast cancer associated gene 1 (BRCA1) contains 3 domains: an N-terminal RING domain with ubiquitin E3 ligase activity, C-terminal BRCT protein interaction domain and a central region. RING and BRCT domains are well characterized, yet the function of the central region remains unclear. In this study, we identified an essential DNA binding region (DBR: 421-701 amino acids) within the central region of human BRCA1, and found that BRCA1 brings DNA together and preferably binds to splayed-arm DNA in a sequence-independent manner. To investigate the biological role of the DBR, we generated mouse ES cells, which lack the DBR (ΔDBR) by using the TALEN method. The ΔDBR cells exhibited decreased survival as compared to the wild type (WT) cells treated with a PARP inhibitor, however they have an intact ability to conduct DNA repair mediated by homologous recombination (HR). The ΔDBR cells continued to incorporate more EdU in the presence of hydroxyurea (HU), which causes replication stress and exhibited reduced viability than the WT cells. Moreover, phosphorylation of CHK1, which regulates the intra-S phase checkpoint, was moderately decreased in ΔDBR cells. These data suggest that DNA binding by BRCA1 affects the stability of DNA replication folks, resulting in weakened intra-S-phase checkpoint control in the ΔDBR cells. The ΔDBR cells also exhibited an increased number of abnormal chromosome structures as compared with WT cells, indicating that the ΔDBR cells have increased genetic instability. Thus, we demonstrated that the DBR of BRCA1 modulates genetic stability through the intra-S-phase checkpoint activated by replication stress.

  11. Cross Talk between β1 and αV Integrins: β1 Affects β3 mRNA Stability

    PubMed Central

    Retta, Saverio Francesco; Cassarà, Georgia; D'Amato, Monica; Alessandro, Riccardo; Pellegrino, Maurizio; Degani, Simona; De Leo, Giacomo; Silengo, Lorenzo; Tarone, Guido

    2001-01-01

    There is increasing evidence that a fine-tuned integrin cross talk can generate a high degree of specificity in cell adhesion, suggesting that spatially and temporally coordinated expression and activation of integrins are more important for regulated cell adhesive functions than the intrinsic specificity of individual receptors. However, little is known concerning the molecular mechanisms of integrin cross talk. With the use of β1-null GD25 cells ectopically expressing the β1A integrin subunit, we provide evidence for the existence of a cross talk between β1 and αV integrins that affects the ratio of αVβ3 and αVβ5 integrin cell surface levels. In particular, we demonstrate that a down-regulation of αVβ3 and an up-regulation of αVβ5 occur as a consequence of β1A expression. Moreover, with the use of GD25 cells expressing the integrin isoforms β1B and β1D, as well as two β1 cytoplasmic domain deletion mutants lacking either the entire cytoplasmic domain (β1TR) or only its “variable” region (β1COM), we show that the effects of β1 over αV integrins take place irrespective of the type of β1 isoform, but require the presence of the “common” region of the β1 cytoplasmic domain. In an attempt to establish the regulatory mechanism(s) whereby β1 integrins exert their trans-acting functions, we have found that the down-regulation of αVβ3 is due to a decreased β3 subunit mRNA stability, whereas the up-regulation of αVβ5 is mainly due to translational or posttranslational events. These findings provide the first evidence for an integrin cross talk based on the regulation of mRNA stability. PMID:11598197

  12. “DNA Binding Region” of BRCA1 Affects Genetic Stability through modulating the Intra-S-Phase Checkpoint

    PubMed Central

    Masuda, Takaaki; Xu, Xiaoling; Dimitriadis, Emilios K.; Lahusen, Tyler; Deng, Chu-Xia

    2016-01-01

    The breast cancer associated gene 1 (BRCA1) contains 3 domains: an N-terminal RING domain with ubiquitin E3 ligase activity, C-terminal BRCT protein interaction domain and a central region. RING and BRCT domains are well characterized, yet the function of the central region remains unclear. In this study, we identified an essential DNA binding region (DBR: 421-701 amino acids) within the central region of human BRCA1, and found that BRCA1 brings DNA together and preferably binds to splayed-arm DNA in a sequence-independent manner. To investigate the biological role of the DBR, we generated mouse ES cells, which lack the DBR (ΔDBR) by using the TALEN method. The ΔDBR cells exhibited decreased survival as compared to the wild type (WT) cells treated with a PARP inhibitor, however they have an intact ability to conduct DNA repair mediated by homologous recombination (HR). The ΔDBR cells continued to incorporate more EdU in the presence of hydroxyurea (HU), which causes replication stress and exhibited reduced viability than the WT cells. Moreover, phosphorylation of CHK1, which regulates the intra-S phase checkpoint, was moderately decreased in ΔDBR cells. These data suggest that DNA binding by BRCA1 affects the stability of DNA replication folks, resulting in weakened intra-S-phase checkpoint control in the ΔDBR cells. The ΔDBR cells also exhibited an increased number of abnormal chromosome structures as compared with WT cells, indicating that the ΔDBR cells have increased genetic instability. Thus, we demonstrated that the DBR of BRCA1 modulates genetic stability through the intra-S-phase checkpoint activated by replication stress. PMID:26884712

  13. Tiltmeter Indicates Sense of Slope

    NASA Technical Reports Server (NTRS)

    Lonborg, J. O.

    1985-01-01

    Tiltmeter indicates sense and magnitude of slope used in locations where incline not visible to operator. Use of direct rather than alternating current greatly simplifies design of instrument capable of indicating sense of slope.

  14. Transformation of upland wash slope - a case study from the Lublin Upland (SE Poland)

    NASA Astrophysics Data System (ADS)

    Janicki, Grzegorz

    2014-06-01

    Slopes do not constitute independent geomorphological systems. Due to their relation and belonging to specific groups of relief macroforms, they are subject to the same development patterns in a long timescale (geological time) as the superior form in a specific morphogenetic zone. Therefore, they are usually polygenetic, and seldom, only within “young” forms, homogenous. The slope relief includes a record of their geological past, individual development stages, and processes shaping slopes. The record constitutes a response of the system to changing environmental conditions, and particularly a manifestation of their adjustment to tectonic, climatic or land cover changes (Davis 1899; Dylik 1969). In short periods of time (geomorphological time), slopes can be recognized as relatively autonomous (independent), natural environmental systems, distinguished by their own development patterns, different than those of e.g. river valleys or gullies. Their development is determined by local factors, e.g. lithology of the bedrock underlying slopes, or degree of their fragmentation. Those factors, related to the state of evolution of the environment, can be treated as independent in the discussed timescale. The second factor, indirectly related to “geology, is land cover and land use, determined in the Neoholocene by human activity. It seems that especially currently, the anthropogenic factor determines the condi tions and rate, as well as directions of relief development, at least for settled areas. In the modern times, in the intermediate climate conditions of temperate zone, forested slopes are distinguished by high stability and very low intensity of modern morphogenetic processes, where decalcification dominates (Maruszczak 1986; Starkel 1986; Rodzik et al. 2008). Slopes with no forest cover, and those occupied by agricultural fields behave differently. In areas subject to agricultural use, slope development conditions become similar to those occurring in the semi

  15. Beach slopes of Massachusetts

    USGS Publications Warehouse

    Doran, Kara S.; Long, Joesph W.; Birchler, Justin J.; Weber, Kathryn M.

    2016-01-01

    The National Assessment of Coastal Change Hazards project derives features of beach morphology from lidar elevation data for the purpose of understanding and predicting storm impacts to our nation's coastlines. This dataset defines mean beach slopes along the United States Northeast Atlantic Ocean for Massachusetts for data collected at various times between 2000 and 2013. For further information regarding data collection and/or processing methods refer to USGS Open-File Report 2015–1053 (http://pubs.usgs.gov/of/2015/1053/).

  16. Effects of grapevine root density and reinforcement on slopes prone to shallow slope instability

    NASA Astrophysics Data System (ADS)

    Meisina, Claudia; Bordoni, Massimiliano; Bischetti, Gianbattista; Vercesi, Alberto; Chiaradia, Enrico; Cislaghi, Alessio; Valentino, Roberto; Bittelli, Marco; Vergani, Chiara; Chersich, Silvia; Giuseppina Persichillo, Maria; Comolli, Roberto

    2016-04-01

    density and root strength have been combined in a physical model (Fiber Bundle Model), for the assessment of the trends of the root reinforcement in soil. The results of this study have contributed to identify root distribution behaviours, in different agricultural and environmental conditions, that have not been enough to guarantee slope stability or that can promote an increase of it. This can furnish important indications for a better identification of slopes more susceptible to slope instabilities and for improving land planning.

  17. Genetic stability of murine pluripotent and somatic hybrid cells may be affected by conditions of their cultivation.

    PubMed

    Ivanovna, Shramova Elena; Alekseevich, Larionov Oleg; Mikhailovich, Khodarovich Yurii; Vladimirovna, Zatsepina Olga

    2011-01-01

    Using mouse pluripotent teratocarcinoma PCC4azal cells and proliferating spleen lymphocytes we obtained a new type of hybrids, in which marker lymphocyte genes were suppressed, but expression the Oct-4 gene was not effected; the hybrid cells were able to differentiate to cardiomyocytes. In order to specify the environmental factors which may affect the genetic stability and other hybrid properties, we analyzed the total chromosome number and differentiation potencies of hybrids respectively to conditions of their cultivation. Particular attention was paid to the number and transcription activity of chromosomal nucleolus organizing regions (NORs), which harbor the most actively transcribed - ribosomal - genes. The results showed that the hybrids obtained are characterized by a relatively stable chromosome number which diminished less than in 5% during 27 passages. However, a long-term cultivation of hybrid cells in non-selective conditions resulted in preferential elimination of some NO- chromosomes, whereas the number of active NORs per cell was increased due to activation of latent NORs. On the contrary, in selective conditions, i.e. in the presence of hypoxantine, aminopterin and thymidine, the total number of NOR-bearing chromosomes was not changed, but a partial inactivation of remaining NORs was observed. The higher number of active NORs directly correlated with the capability of hybrid cells for differentiation to cardiomyocytes.

  18. The FlgT Protein Is Involved in Aeromonas hydrophila Polar Flagella Stability and Not Affects Anchorage of Lateral Flagella

    PubMed Central

    Merino, Susana; Tomás, Juan M.

    2016-01-01

    Aeromonas hydrophila sodium-driven polar flagellum has a complex stator-motor. Consist of two sets of redundant and non-exchangeable proteins (PomA/PomB and PomA2/PomB2), which are homologs to other sodium-conducting polar flagellum stator motors; and also two essential proteins (MotX and MotY), that they interact with one of those two redundant pairs of proteins and form the T-ring. In this work, we described an essential protein for polar flagellum stability and rotation which is orthologs to Vibrio spp. FlgT and it is encoded outside of the A. hydrophila polar flagellum regions. The flgT was present in all mesophilic Aeromonas strains tested and also in the non-motile Aeromonas salmonicida. The A. hydrophila ΔflgT mutant is able to assemble the polar flagellum but is more unstable and released into the culture supernatant from the cell upon completion assembly. Presence of FlgT in purified polar hook-basal bodies (HBB) of wild-type strain was confirmed by Western blotting and electron microscopy observations showed an outer ring of the T-ring (H-ring) which is not present in the ΔflgT mutant. Anchoring and motility of proton-driven lateral flagella was not affected in the ΔflgT mutant and specific antibodies did not detect FlgT in purified lateral HBB of wild type strain. PMID:27507965

  19. Does the temperature of beverages affect the surface roughness, hardness, and color stability of a composite resin?

    PubMed Central

    Tuncer, Duygu; Karaman, Emel; Firat, Esra

    2013-01-01

    Objective: To investigate the effect of beverages’ temperature on the surface roughness, hardness, and color stability of a composite resin. Materials and Methods: Fifty specimens of the Filtek Z250 composite (3M ESPE, Dental Products, St.Paul, MN, USA) were prepared and initial roughness, microhardness, and color were measured. Then the specimens were randomly divided into five groups of 10 specimens each: Coffee at 70°C, coffee at 37°C, cola at 10°C, cola at 37°C, and artificial saliva (control). After the samples were subjected to 15 min × 3 cycles per day of exposure to the solutions for 30 days, the final measurements were recorded. Results: After immersion in beverages, the artificial saliva group showed hardness values higher than those of the other groups (P < 0.001) and the microhardness values were significantly different from the initial values in all groups except for the control group. Both cola groups showed roughness values higher than the baseline values (P < 0.05), while the other groups showed values similar to the baseline measurements. When ΔE measurements were examined, the 70°C coffee group showed the highest color change among all the groups (P < 0.05). Conclusion: High-temperature solutions caused alterations in certain properties of composites, such as increased color change, although they did not affect the hardness or roughness of the composite resin material tested. PMID:24883021

  20. Model slope infiltration experiments for shallow landslides early warning

    NASA Astrophysics Data System (ADS)

    Damiano, E.; Greco, R.; Guida, A.; Olivares, L.; Picarelli, L.

    2009-04-01

    Occurrence of fast landslides has become more and more dangerous during the last decades, due to the increased density of settlements, industrial plants and infrastructures. Such problem is particularly worrying in Campania (Southern Italy), where the fast population growth led a diffuse building activity without planning: indeed, recent flowslides caused hundreds of victims and heavy damages to buildings, roads and other infrastructures. Large mountainous areas in Campania are mantled by loose pyroclastic granular soils up to a depth of a few meters from top soil surface. These soils have usually a grain size that falls in the domain of silty sands, including pumice interbeds (gravelly sands), with saturated hydraulic conductivities up to the order of 10-1 cm/min. Such deposits often cover steep slopes, which stability is guaranteed by the apparent cohesion due to suction under unsaturated conditions, that are the most common conditions for these slopes [Olivares and Picarelli, 2001]. Whereas rainfall infiltration causes soil to approach saturation, suction vanishes and slope failure may occur. Besides soil physical properties, landslide triggering is influenced by several factors, such as rainfall intensity, soil initial moisture and suction, slope inclination, boundary conditions. Whereas slope failure occurs with soil close to being saturated, landslide may develop in form of fast and destructive flowslide. Calibration of reliable mathematical models of such a complex phenomenon requires availability of experimental observations of the major variables of interest, such as soil moisture and suction, soil deformation and displacements, pore water pressure, during the entire process of infiltration until slope failure. Due to the sudden trigger and extremely rapid propagation of such type of landslides, such data sets are rarely available for natural slopes where flowslides occurred. As a consequence landslide risk assessment and early warning in Campania rely on

  1. A Hybrid FEM-ANN Approach for Slope Instability Prediction

    NASA Astrophysics Data System (ADS)

    Verma, A. K.; Singh, T. N.; Chauhan, Nikhil Kumar; Sarkar, K.

    2016-09-01

    Assessment of slope stability is one of the most critical aspects for the life of a slope. In any slope vulnerability appraisal, Factor Of Safety (FOS) is the widely accepted index to understand, how close or far a slope from the failure. In this work, an attempt has been made to simulate a road cut slope in a landslide prone area in Rudrapryag, Uttarakhand, India which lies near Himalayan geodynamic mountain belt. A combination of Finite Element Method (FEM) and Artificial Neural Network (ANN) has been adopted to predict FOS of the slope. In ANN, a three layer, feed- forward back-propagation neural network with one input layer and one hidden layer with three neurons and one output layer has been considered and trained using datasets generated from numerical analysis of the slope and validated with new set of field slope data. Mean absolute percentage error estimated as 1.04 with coefficient of correlation between the FOS of FEM and ANN as 0.973, which indicates that the system is very vigorous and fast to predict FOS for any slope.

  2. Frosty Polar Slope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    11 August 2004 Acquired just last week on 3 August 2004, this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dark, layered scarp in the martian north polar region. All of the light-toned surfaces in this image are covered by frost left over from the previous winter. On the scarp, about half of the surfaces once covered by frost are now exposed (as the frost has sublimed away), leaving a large number of bright patches. These patches of frost enhance the appearance of layering on the slopes. This image is located near 81.8oN, 84.4oW. The image covers an area 3 km (1.9 mi) wide, and is illuminated by sunlight from the lower left.

  3. Gullied Slopes on Mars

    NASA Astrophysics Data System (ADS)

    Martel, L. M. V.

    2003-08-01

    There are a lot of gullies on certain Martian slopes and just about as many ideas of how they formed. The proposed origins of gullies include seepage of groundwater or brines, outbursts of carbon dioxide, snowmelt, geothermal activity, or dry flows of windblown dust and silt. Research teams have been publishing their hypotheses since the gullies were first announced in 2000, and the discussions are still lively. For example, a quick search of the terms "Martian or Mars or gullies or seepage" on the NASA Astrophysics Data System delivered nearly 20 references to papers or abstracts published just in the past eight months. Gullies are such a hot topic, some researchers would argue, because they could indicate sources of liquid water at shallow depths. PSRD provides a rundown of the leading hypotheses to explain how Martian gullies form and how researchers use chemical data from Martian meteorites and knowledge of the Earth to support their points of view.

  4. Whole genome sequencing identifies a deletion in protein phosphatase 2A that affects its stability and localization in Chlamydomonas reinhardtii.

    PubMed

    Lin, Huawen; Miller, Michelle L; Granas, David M; Dutcher, Susan K

    2013-01-01

    Whole genome sequencing is a powerful tool in the discovery of single nucleotide polymorphisms (SNPs) and small insertions/deletions (indels) among mutant strains, which simplifies forward genetics approaches. However, identification of the causative mutation among a large number of non-causative SNPs in a mutant strain remains a big challenge. In the unicellular biflagellate green alga Chlamydomonas reinhardtii, we generated a SNP/indel library that contains over 2 million polymorphisms from four wild-type strains, one highly polymorphic strain that is frequently used in meiotic mapping, ten mutant strains that have flagellar assembly or motility defects, and one mutant strain, imp3, which has a mating defect. A comparison of polymorphisms in the imp3 strain and the other 15 strains allowed us to identify a deletion of the last three amino acids, Y313F314L315, in a protein phosphatase 2A catalytic subunit (PP2A3) in the imp3 strain. Introduction of a wild-type HA-tagged PP2A3 rescues the mutant phenotype, but mutant HA-PP2A3 at Y313 or L315 fail to rescue. Our immunoprecipitation results indicate that the Y313, L315, or YFLΔ mutations do not affect the binding of PP2A3 to the scaffold subunit, PP2A-2r. In contrast, the Y313, L315, or YFLΔ mutations affect both the stability and the localization of PP2A3. The PP2A3 protein is less abundant in these mutants and fails to accumulate in the basal body area as observed in transformants with either wild-type HA-PP2A3 or a HA-PP2A3 with a V310T change. The accumulation of HA-PP2A3 in the basal body region disappears in mated dikaryons, which suggests that the localization of PP2A3 may be essential to the mating process. Overall, our results demonstrate that the terminal YFL tail of PP2A3 is important in the regulation on Chlamydomonas mating.

  5. Measuring acoustic emissions in an avalanche slope

    NASA Astrophysics Data System (ADS)

    Reiweger, Ingrid; Schweizer, Jürg

    2014-05-01

    Measurements of acoustic emissions are a common technique for monitoring damage and predicting imminent failure of a material. Within natural hazards it has already been used to successfully predict the break-off of a hanging glacier. To explore the applicability of the acoustic emission (AE) technique for avalanche prediction, we installed two acoustic sensors (with 30 kHz and 60 kHz resonance frequency) in an avalanche prone slope at the Mittelgrat in the Parsenn ski area above Davos, Switzerland. The slope is north-east facing, frequently wind loaded, and approximately 35° steep. The AE signals - in particular the event energy and waiting time distributions - were compared with slope stability. The latter was determined by observing avalanche activity. The results of two winter's measurements yielded that the exponent β of the inverse cumulative distribution of event energy showed a significant drop (from a value of 3.5 to roughly 2.5) at very unstable conditions, i.e. on the three days during our measurement periods when spontaneous avalanches released on our study slope.

  6. Amphotericin B severely affects expression and activity of the endothelial constitutive nitric oxide synthase involving altered mRNA stability

    PubMed Central

    Suschek, Christoph Viktor; Bonmann, Eckhard; Kleinert, Hartmut; Wenzel, Michael; Mahotka, Csaba; Kolb, Hubert; Förstermann, Ulrich; Gerharz, Claus-Dieter; Kolb-Bachofen, Victoria

    2000-01-01

    The therapeutic use of the antifungal drug amphotericin B (AmB) is limited due to severe side effects like glomerular vasoconstriction and risk of renal failure during AmB administration. As nitric oxide (NO) has substantial functions in renal autoregulation, we have determined the effects of AmB on endothelial constitutive NO synthase (ecNOS) expression and activity in human and rat endothelial cell cultures.AmB used at concentrations of 0.6 to 1.25 μg ml−1 led to increases in ecNOS mRNA and protein expression as well as NO production. This was the result of an increased ecNOS mRNA half-life. In contrast, incubation of cells with higher albeit subtoxic concentrations of AmB (2.5–5.0 μg ml−1) resulted in a decrease or respectively in completely abolished ecNOS mRNA and protein expression with a strongly reduced or inhibited ecNOS activity, due to a decrease of ecNOS mRNA half-life. None of the AmB concentrations affected promoter activity as found with a reporter gene construct stably transfected into ECV304 cells.Thus, our experiments show a concentration-dependent biphasic effect of AmB on expression and activity of ecNOS, an effect best explained by AmB influencing ecNOS mRNA stability. In view of the known renal accumulation of this drug the results reported here could help to elucidate its renal toxicity. PMID:11015297

  7. Recent slope failures in the Dolomites (Northeastern Italian Alps) in a context of climate change

    NASA Astrophysics Data System (ADS)

    Chiarle, Marta; Paranunzio, Roberta; Laio, Francesco; Nigrelli, Guido; Guzzetti, Fausto

    2014-05-01

    Climate change in the Greater Alpine Region is seriously affecting permafrost distribution, with relevant consequences on slope stability. In the Italian Alps, the number of failures from rockwalls at high elevation markedly increased in the last 20-30 years: the consistent temperature increase, which warmed twice than the global average, may have seriously influenced slope stability, in terms of glaciers retreat and permafrost degradation. Moreover, the growing number of tourists and activities in alpine regions (in particular in the Dolomites) made these areas particularly critical in relation to natural hazards. In this light, an integrated short-term geomorphological and climatic analysis was performed, in order to better comprehend the impact of main climate elements (especially temperature and precipitation) on slope failures in high mountain areas. In this contribution, we focus on three recent slope failures occurred at high elevation sites in the Dolomites (Northeastern Italian Alps), declared a UNESCO World Heritage Site in August 2009. We describe here three important rock falls occurred in the autumn 2013: 1) the Sorapiss rock fall, on 30 September 2013; 2) the Monte Civetta rock fall, on 16 November 2013; 3) the Monte Antelao rock fall, on 22 November 2013. The Monte Civetta rock fall damaged some climbing routes, while the other two landslides did not cause any damage or injury. Despite the limited volume involved, these three events represent an important warning sign in the context of ongoing climate change. Geomorphological information about the rock fall sites were combined with the climatic data acquired from the meteorological stations surrounding the slope failure areas. A short-term climatic analysis was performed, with the aim of understanding the role of the main climatic elements in the triggering of natural instability events in this area and in the Alps in general.

  8. Soil erosion-vegetation interactions in Mediterranean-dry reclaimed mining slopes

    NASA Astrophysics Data System (ADS)

    Moreno de las Heras, Mariano; Merino-Martín, Luis; Espigares, Tíscar; Nicolau, José M.

    2014-05-01

    Mining reclamation in Mediterranean-dry environments represents a complex task. Reclaimed mining slopes are particularly vulnerable to the effects of accelerated soil erosion processes, especially when these processes lead to the formation of rill networks. On the other hand, encouraging early vegetation establishment is perceived as indispensable to reduce the risk of degradation in these man-made ecosystems. This study shows a synthesis of soil erosion-vegetation research conducted in reclaimed mining slopes at El Moral field site (Teruel coalfield, central-east Spain). Our results highlight the role of rill erosion processes in the development of reclaimed ecosystems. Runoff routing is conditioned by the development of rill networks, maximizing the loss of water resources at the slope scale by surface runoff and altering the spatial distribution of soil moisture. As a result, the availability of water resources for plant growth is drastically reduced, affecting vegetation development. Conversely, vegetation exerts a strong effect on soil erosion: erosion rates rapidly decrease with vegetation cover and no significant rill erosion is usually observed after a particular cover threshold is reached. These interactive two-way vegetation-soil erosion relationships are further studied using a novel modeling approach that focuses on stability analysis of water-limited reclaimed slopes. Our framework reproduces two main groups of trends along the temporal evolution of reclaimed slopes: successful trends, characterized by widespread vegetation development and the effective control of rill erosion processes; and gullying trends, characterized by the progressive loss of vegetation and a sharp logistic increase in erosion rates. This stability-analysis also facilitates the determination of threshold values for both vegetation cover and rill erosion that drive the long-term reclamation results, assisting the identification of critical situations that require specific human

  9. How do how internal and external processes affect the behaviors of coupled marsh mudflat systems; infill, stabilize, retreat, or drown?

    NASA Astrophysics Data System (ADS)

    Carr, J. A.; Mariotti, G.; Wiberg, P.; Fagherazzi, S.; McGlathery, K.

    2013-12-01

    an eventual lateral equilibrium are possible only with large allochthonous sediment supply. Once marshes expanded, marsh retreat can be prevented by a sediment supply smaller than the one that filled the basin. At the GCE, the Altamaha River allows for enhanced allochthonous supply directly to the salt marsh platform, reducing the importance of waves on the tidal flat. As a result, infilling or retreat become the prevalent behaviors. For the VCR, the presence of seagrass decreases near bed shear stresses and sediment flux to the salt marsh platform, however, seagrass also reduces the wave energy acting on the boundary of the marsh reducing boundary erosion. Results indicate that the reduction in wave power allows for seagrass to provide a strong stabilizing affect on the coupled salt marsh tidal flat system, but as external sediment supply increases and light conditions decline the system reverts to that of a bare tidal flat. Across all systems and with current rates of sea level rise, retreat is a more likely marsh loss modality than drowning.

  10. Geotechnical properties of Kentucky`s AML landslides and slope failure evaluation

    SciTech Connect

    Iannacchione, A.T.; Bhatt, S.K.; Sefton, J.

    1995-12-31

    A large body of geotechnical data, obtained from the U.S. Office of Surface Mining Reclamation and Enforcement (OSM) and the Kentucky Division of Abandoned Lands, is analyzed in this paper. The analysis includes causes of subsurface failures, phreatic levels, soil profiles, and soil composition data. Soil properties calculated from laboratory procedures and stability analysis techniques were also reviewed. Employing prudent engineering practices and parameters, seven failed slopes were subjected to back analysis for estimating realistic factors of safety. Important factors affecting landslides in eastern Kentucky are presented with appropriate examples.

  11. [Analysis of related factors of slope plant hyperspectral remote sensing].

    PubMed

    Sun, Wei-Qi; Zhao, Yun-Sheng; Tu, Lin-Ling

    2014-09-01

    In the present paper, the slope gradient, aspect, detection zenith angle and plant types were analyzed. In order to strengthen the theoretical discussion, the research was under laboratory condition, and modeled uniform slope for slope plant. Through experiments we found that these factors indeed have influence on plant hyperspectral remote sensing. When choosing slope gradient as the variate, the blade reflection first increases and then decreases as the slope gradient changes from 0° to 36°; When keeping other factors constant, and only detection zenith angle increasing from 0° to 60°, the spectral characteristic of slope plants do not change significantly in visible light band, but decreases gradually in near infrared band; With only slope aspect changing, when the dome meets the light direction, the blade reflectance gets maximum, and when the dome meets the backlit direction, the blade reflectance gets minimum, furthermore, setting the line of vertical intersection of incidence plane and the dome as an axis, the reflectance on the axis's both sides shows symmetric distribution; In addition, spectral curves of different plant types have a lot differences between each other, which means that the plant types also affect hyperspectral remote sensing results of slope plants. This research breaks through the limitations of the traditional vertical remote sensing data collection and uses the multi-angle and hyperspectral information to analyze spectral characteristics of slope plants. So this research has theoretical significance to the development of quantitative remote sensing, and has application value to the plant remote sensing monitoring.

  12. Amino Acid Substitutions That Affect Receptor Binding and Stability of the Hemagglutinin of Influenza A/H7N9 Virus

    PubMed Central

    Schrauwen, Eefje J. A.; Burke, David F.; Rimmelzwaan, Guus F.; Herfst, Sander; Fouchier, Ron A. M.

    2016-01-01

    Receptor-binding preference and stability of hemagglutinin have been implicated as crucial determinants of airborne transmission of influenza viruses. Here, amino acid substitutions previously identified to affect these traits were tested in the context of an A/H7N9 virus. Some combinations of substitutions, most notably G219S and K58I, resulted in relatively high affinity for α2,6-linked sialic acid receptor and acid and temperature stability. Thus, the hemagglutinin of the A/H7N9 virus may adopt traits associated with airborne transmission. PMID:26792744

  13. Integrating Near-Real Time Hydrologic-Response Monitoring and Modeling for Improved Assessments of Slope Stability Along the Coastal Bluffs of the Puget Sound Rail Corridor, Washington State

    NASA Astrophysics Data System (ADS)

    Mirus, B. B.; Baum, R. L.; Stark, B.; Smith, J. B.; Michel, A.

    2015-12-01

    Previous USGS research on landslide potential in hillside areas and coastal bluffs around Puget Sound, WA, has identified rainfall thresholds and antecedent moisture conditions that correlate with heightened probability of shallow landslides. However, physically based assessments of temporal and spatial variability in landslide potential require improved quantitative characterization of the hydrologic controls on landslide initiation in heterogeneous geologic materials. Here we present preliminary steps towards integrating monitoring of hydrologic response with physically based numerical modeling to inform the development of a landslide warning system for a railway corridor along the eastern shore of Puget Sound. We instrumented two sites along the steep coastal bluffs - one active landslide and one currently stable slope with the potential for failure - to monitor rainfall, soil-moisture, and pore-pressure dynamics in near-real time. We applied a distributed model of variably saturated subsurface flow for each site, with heterogeneous hydraulic-property distributions based on our detailed site characterization of the surficial colluvium and the underlying glacial-lacustrine deposits that form the bluffs. We calibrated the model with observed volumetric water content and matric potential time series, then used simulated pore pressures from the calibrated model to calculate the suction stress and the corresponding distribution of the factor of safety against landsliding with the infinite slope approximation. Although the utility of the model is limited by uncertainty in the deeper groundwater flow system, the continuous simulation of near-surface hydrologic response can help to quantify the temporal variations in the potential for shallow slope failures at the two sites. Thus the integration of near-real time monitoring and physically based modeling contributes a useful tool towards mitigating hazards along the Puget Sound railway corridor.

  14. Landslide boost from entrainment of erodible material along the slope

    NASA Astrophysics Data System (ADS)

    Farin, M.; Mangeney, A.; Roche, O.; Ionescu, I.; Hungr, O.

    2011-12-01

    . Entrainment begins to affect the flow at inclination angles exceeding a critical angle, almost equal to half of the repose angle. Triangular shaped frontal surges are observed at high inclination angles over both rigid or erodible beds. Erosion effects are smaller as the compaction of the erodible granular bed increases and larger as the initial height-to-length ratio and volume of the released mass increase. The avalanche excavates the erodible layer immediately at the flow front, behind which waves travelling downstream that help removing grains from the erodible bed are observed. When increasing the depth of the erodible bed, the excavation depth first increases and then stabilizes to a critical value, and then decreases. Finally, numerical simulations using a 3D visco-plastic model are performed to obtain insight into the physical processes at work during entrainment processes.

  15. Does the Implant Surgical Technique Affect the Primary and/or Secondary Stability of Dental Implants? A Systematic Review

    PubMed Central

    Shadid, Rola Muhammed; Sadaqah, Nasrin Rushdi; Othman, Sahar Abdo

    2014-01-01

    Background. A number of surgical techniques for implant site preparation have been advocated to enhance the implant of primary and secondary stability. However, there is insufficient scientific evidence to support the association between the surgical technique and implant stability. Purpose. This review aimed to investigate the influence of different surgical techniques including the undersized drilling, the osteotome, the piezosurgery, the flapless procedure, and the bone stimulation by low-level laser therapy on the primary and/or secondary stability of dental implants. Materials and methods. A search of PubMed, Cochrane Library, and grey literature was performed. The inclusion criteria comprised observational clinical studies and randomized controlled trials (RCTs) conducted in patients who received dental implants for rehabilitation, studies that evaluated the association between the surgical technique and the implant primary and/or secondary stability. The articles selected were carefully read and classified as low, moderate, and high methodological quality and data of interest were tabulated. Results. Eight clinical studies were included then they were classified as moderate or high methodological quality and control of bias. Conclusions. There is a weak evidence suggesting that any of previously mentioned surgical techniques could influence the primary and/or secondary implant stability. PMID:25126094

  16. Reactivity of disulfide bonds is markedly affected by structure and environment: implications for protein modification and stability

    PubMed Central

    Karimi, Maryam; Ignasiak, Marta T.; Chan, Bun; Croft, Anna K.; Radom, Leo; Schiesser, Carl H.; Pattison, David I.; Davies, Michael J.

    2016-01-01

    Disulfide bonds play a key role in stabilizing protein structures, with disruption strongly associated with loss of protein function and activity. Previous data have suggested that disulfides show only modest reactivity with oxidants. In the current study, we report kinetic data indicating that selected disulfides react extremely rapidly, with a variation of 104 in rate constants. Five-membered ring disulfides are particularly reactive compared with acyclic (linear) disulfides or six-membered rings. Particular disulfides in proteins also show enhanced reactivity. This variation occurs with multiple oxidants and is shown to arise from favorable electrostatic stabilization of the incipient positive charge on the sulfur reaction center by remote groups, or by the neighboring sulfur for conformations in which the orbitals are suitably aligned. Controlling these factors should allow the design of efficient scavengers and high-stability proteins. These data are consistent with selective oxidative damage to particular disulfides, including those in some proteins. PMID:27941824

  17. Reactivity of disulfide bonds is markedly affected by structure and environment: implications for protein modification and stability

    NASA Astrophysics Data System (ADS)

    Karimi, Maryam; Ignasiak, Marta T.; Chan, Bun; Croft, Anna K.; Radom, Leo; Schiesser, Carl H.; Pattison, David I.; Davies, Michael J.

    2016-12-01

    Disulfide bonds play a key role in stabilizing protein structures, with disruption strongly associated with loss of protein function and activity. Previous data have suggested that disulfides show only modest reactivity with oxidants. In the current study, we report kinetic data indicating that selected disulfides react extremely rapidly, with a variation of 104 in rate constants. Five-membered ring disulfides are particularly reactive compared with acyclic (linear) disulfides or six-membered rings. Particular disulfides in proteins also show enhanced reactivity. This variation occurs with multiple oxidants and is shown to arise from favorable electrostatic stabilization of the incipient positive charge on the sulfur reaction center by remote groups, or by the neighboring sulfur for conformations in which the orbitals are suitably aligned. Controlling these factors should allow the design of efficient scavengers and high-stability proteins. These data are consistent with selective oxidative damage to particular disulfides, including those in some proteins.

  18. Reactivity of disulfide bonds is markedly affected by structure and environment: implications for protein modification and stability.

    PubMed

    Karimi, Maryam; Ignasiak, Marta T; Chan, Bun; Croft, Anna K; Radom, Leo; Schiesser, Carl H; Pattison, David I; Davies, Michael J

    2016-12-12

    Disulfide bonds play a key role in stabilizing protein structures, with disruption strongly associated with loss of protein function and activity. Previous data have suggested that disulfides show only modest reactivity with oxidants. In the current study, we report kinetic data indicating that selected disulfides react extremely rapidly, with a variation of 10(4) in rate constants. Five-membered ring disulfides are particularly reactive compared with acyclic (linear) disulfides or six-membered rings. Particular disulfides in proteins also show enhanced reactivity. This variation occurs with multiple oxidants and is shown to arise from favorable electrostatic stabilization of the incipient positive charge on the sulfur reaction center by remote groups, or by the neighboring sulfur for conformations in which the orbitals are suitably aligned. Controlling these factors should allow the design of efficient scavengers and high-stability proteins. These data are consistent with selective oxidative damage to particular disulfides, including those in some proteins.

  19. Restricted Arm Swing Affects Gait Stability and Increased Walking Speed Alters Trunk Movements in Children with Cerebral Palsy

    PubMed Central

    Delabastita, Tijs; Desloovere, Kaat; Meyns, Pieter

    2016-01-01

    Observational research suggests that in children with cerebral palsy, the altered arm swing is linked to instability during walking. Therefore, the current study investigates whether children with cerebral palsy use their arms more than typically developing children, to enhance gait stability. Evidence also suggests an influence of walking speed on gait stability. Moreover, previous research highlighted a link between walking speed and arm swing. Hence, the experiment aimed to explore differences between typically developing children and children with cerebral palsy taking into account the combined influence of restricting arm swing and increasing walking speed on gait stability. Spatiotemporal gait characteristics, trunk movement parameters and margins of stability were obtained using three dimensional gait analysis to assess gait stability of 26 children with cerebral palsy and 24 typically developing children. Four walking conditions were evaluated: (i) free arm swing and preferred walking speed; (ii) restricted arm swing and preferred walking speed; (iii) free arm swing and high walking speed; and (iv) restricted arm swing and high walking speed. Double support time and trunk acceleration variability increased more when arm swing was restricted in children with bilateral cerebral palsy compared to typically developing children and children with unilateral cerebral palsy. Trunk sway velocity increased more when walking speed was increased in children with unilateral cerebral palsy compared to children with bilateral cerebral palsy and typically developing children and in children with bilateral cerebral palsy compared to typically developing children. Trunk sway velocity increased more when both arm swing was restricted and walking speed was increased in children with bilateral cerebral palsy compared to typically developing children. It is proposed that facilitating arm swing during gait rehabilitation can improve gait stability and decrease trunk movements in

  20. Restricted Arm Swing Affects Gait Stability and Increased Walking Speed Alters Trunk Movements in Children with Cerebral Palsy.

    PubMed

    Delabastita, Tijs; Desloovere, Kaat; Meyns, Pieter

    2016-01-01

    Observational research suggests that in children with cerebral palsy, the altered arm swing is linked to instability during walking. Therefore, the current study investigates whether children with cerebral palsy use their arms more than typically developing children, to enhance gait stability. Evidence also suggests an influence of walking speed on gait stability. Moreover, previous research highlighted a link between walking speed and arm swing. Hence, the experiment aimed to explore differences between typically developing children and children with cerebral palsy taking into account the combined influence of restricting arm swing and increasing walking speed on gait stability. Spatiotemporal gait characteristics, trunk movement parameters and margins of stability were obtained using three dimensional gait analysis to assess gait stability of 26 children with cerebral palsy and 24 typically developing children. Four walking conditions were evaluated: (i) free arm swing and preferred walking speed; (ii) restricted arm swing and preferred walking speed; (iii) free arm swing and high walking speed; and (iv) restricted arm swing and high walking speed. Double support time and trunk acceleration variability increased more when arm swing was restricted in children with bilateral cerebral palsy compared to typically developing children and children with unilateral cerebral palsy. Trunk sway velocity increased more when walking speed was increased in children with unilateral cerebral palsy compared to children with bilateral cerebral palsy and typically developing children and in children with bilateral cerebral palsy compared to typically developing children. Trunk sway velocity increased more when both arm swing was restricted and walking speed was increased in children with bilateral cerebral palsy compared to typically developing children. It is proposed that facilitating arm swing during gait rehabilitation can improve gait stability and decrease trunk movements in

  1. Experimental and molecular dynamics studies showed that CBP KIX mutation affects the stability of CBP:c-Myb complex.

    PubMed

    Odoux, Anne; Jindal, Darren; Tamas, Tamara C; Lim, Benjamin W H; Pollard, Drake; Xu, Wu

    2016-06-01

    The coactivators CBP (CREBBP) and its paralog p300 (EP300), two conserved multi-domain proteins in eukaryotic organisms, regulate gene expression in part by binding DNA-binding transcription factors. It was previously reported that the CBP/p300 KIX domain mutant (Y650A, A654Q, and Y658A) altered both c-Myb-dependent gene activation and repression, and that mice with these three point mutations had reduced numbers of platelets, B cells, T cells, and red blood cells. Here, our transient transfection assays demonstrated that mouse embryonic fibroblast cells containing the same mutations in the KIX domain and without a wild-type allele of either CBP or p300, showed decreased c-Myb-mediated transcription. Dr. Wright's group solved a 3-D structure of the mouse CBP:c-Myb complex using NMR. To take advantage of the experimental structure and function data and improved theoretical calculation methods, we performed MD simulations of CBP KIX, CBP KIX with the mutations, and c-Myb, as well as binding energy analysis for both the wild-type and mutant complexes. The binding between CBP and c-Myb is mainly mediated by a shallow hydrophobic groove in the center where the side-chain of Leu302 of c-Myb plays an essential role and two salt bridges at the two ends. We found that the KIX mutations slightly decreased stability of the CBP:c-Myb complex as demonstrated by higher binding energy calculated using either MM/PBSA or MM/GBSA methods. More specifically, the KIX mutations affected the two salt bridges between CBP and c-Myb (CBP-R646 and c-Myb-E306; CBP-E665 and c-Myb-R294). Our studies also revealed differing dynamics of the hydrogen bonds between CBP-R646 and c-Myb-E306 and between CBP-E665 and c-Myb-R294 caused by the CBP KIX mutations. In the wild-type CBP:c-Myb complex, both of the hydrogen bonds stayed relatively stable. In contrast, in the mutant CBP:c-Myb complex, hydrogen bonds between R646 and E306 showed an increasing trend followed by a decreasing trend, and hydrogen

  2. Factors affecting stability of z-ligustilide in the volatile oil of radix angelicae sinensis and ligusticum chuanxiong and its stability prediction.

    PubMed

    Cui, F; Feng, L; Hu, J

    2006-07-01

    The purpose of this investigation is to obtain a suitable vehicle for Z-ligustilide in the volatile oil of Radix Angelicae Sinensis and Ligusticum Chuanxiong in which it is stable enough for the application in pharmaceutics, to investigate its degradation laws, and to predict its shelf-life at 25 degrees C. Factors including temperature, light, pH value, co-solvents and antioxidants can all influence the stability of Z-ligustilide, thereinto antioxidants could markedly improve its stability in aqueous solution by almost 35%. The suitable vehicle for Z-ligustilide contains 1.5% tween-80, 0.3% Vitamin C, and 20% propylene glycol (PG). Furthermore, the degradation rates of Z-ligustilide were found to conform to a rate equation following Weibull probability distribution within a range of degradation ratio, and the equation could be expressed as follow: ln ln (1/1-alpha) = ln k + m ln t. Where alpha is degradation ratio; t is time; m and k are constants relating to the degradation rate. The degradation rate will get greater as the increasing of parameter k. According to the degradation law obtained from the equation, the drug shelf-life (10% of active ingredient degraded, T90) in this vehicle was predicted to be more than 1.77 years at 25 degrees C through Arrehenius equation and accelerating experiments. The present investigation was undertaken to propose a kinetic treatment that may be applicable to any type of degradation of the active ingredient of pharmaceutical formulation, and also could provide a good foundation for the new drug development of Z-ligustilide, especially for injection formulation.

  3. pH-sensitive residues in the p19 RNA silencing suppressor protein from carnation Italian ringspot virus affect siRNA binding stability

    PubMed Central

    Law, Sean M; Zhang, Bin W; Brooks, Charles L

    2013-01-01

    Tombusviruses, such as Carnation Italian ringspot virus (CIRV), encode a protein homodimer called p19 that is capable of suppressing RNA silencing in their infected hosts by binding to and sequestering short-interfering RNA (siRNA) away from the RNA silencing pathway. P19 binding stability has been shown to be sensitive to changes in pH but the specific amino acid residues involved have remained unclear. Using constant pH molecular dynamics simulations, we have identified key pH-dependent residues that affect CIRV p19–siRNA binding stability at various pH ranges based on calculated changes in the free energy contribution from each titratable residue. At high pH, the deprotonation of Lys60, Lys67, Lys71, and Cys134 has the largest effect on the binding stability. Similarly, deprotonation of several acidic residues (Asp9, Glu12, Asp20, Glu35, and/or Glu41) at low pH results in a decrease in binding stability. At neutral pH, residues Glu17 and His132 provide a small increase in the binding stability and we find that the optimal pH range for siRNA binding is between 7.0 and 10.0. Overall, our findings further inform recent experiments and are in excellent agreement with data on the pH-dependent binding profile. PMID:23450521

  4. pH-sensitive residues in the p19 RNA silencing suppressor protein from carnation Italian ringspot virus affect siRNA binding stability.

    PubMed

    Law, Sean M; Zhang, Bin W; Brooks, Charles L

    2013-05-01

    Tombusviruses, such as Carnation Italian ringspot virus (CIRV), encode a protein homodimer called p19 that is capable of suppressing RNA silencing in their infected hosts by binding to and sequestering short-interfering RNA (siRNA) away from the RNA silencing pathway. P19 binding stability has been shown to be sensitive to changes in pH but the specific amino acid residues involved have remained unclear. Using constant pH molecular dynamics simulations, we have identified key pH-dependent residues that affect CIRV p19-siRNA binding stability at various pH ranges based on calculated changes in the free energy contribution from each titratable residue. At high pH, the deprotonation of Lys60, Lys67, Lys71, and Cys134 has the largest effect on the binding stability. Similarly, deprotonation of several acidic residues (Asp9, Glu12, Asp20, Glu35, and/or Glu41) at low pH results in a decrease in binding stability. At neutral pH, residues Glu17 and His132 provide a small increase in the binding stability and we find that the optimal pH range for siRNA binding is between 7.0 and 10.0. Overall, our findings further inform recent experiments and are in excellent agreement with data on the pH-dependent binding profile.

  5. New Evidence That Nonlinear Source-Filter Coupling Affects Harmonic Intensity and fo Stability During Instances of Harmonics Crossing Formants.

    PubMed

    Maxfield, Lynn; Palaparthi, Anil; Titze, Ingo

    2017-03-01

    The traditional source-filter theory of voice production describes a linear relationship between the source (glottal flow pulse) and the filter (vocal tract). Such a linear relationship does not allow for nor explain how changes in the filter may impact the stability and regularity of the source. The objective of this experiment was to examine what effect unpredictable changes to vocal tract dimensions could have on fo stability and individual harmonic intensities in situations in which low frequency harmonics cross formants in a fundamental frequency glide. To determine these effects, eight human subjects (five male, three female) were recorded producing fo glides while their vocal tracts were artificially lengthened by a section of vinyl tubing inserted into the mouth. It was hypothesized that if the source and filter operated as a purely linear system, harmonic intensities would increase and decrease at nearly the same rates as they passed through a formant bandwidth, resulting in a relatively symmetric peak on an intensity-time contour. Additionally, fo stability should not be predictably perturbed by formant/harmonic crossings in a linear system. Acoustic analysis of these recordings, however, revealed that harmonic intensity peaks were asymmetric in 76% of cases, and that 85% of fo instabilities aligned with a crossing of one of the first four harmonics with the first three formants. These results provide further evidence that nonlinear dynamics in the source-filter relationship can impact fo stability as well as harmonic intensities as harmonics cross through formant bandwidths.

  6. Suspension stability and aggregation of multi-walled carbon nanotubes as affected by dissolved organic matters extracted from agricultural wastes.

    PubMed

    Li, Helian; Qiu, Yanhua; Wang, Xiaonuan; Liu, Wenhao; Chen, Guangcai; Ma, Yibing; Xing, Baoshan

    2016-03-01

    Dissolved organic matters (DOMs) extracted from wheat straw (SDOM) and cow manure (MDOM) were used to investigate their effects on the suspension stability and aggregation of multi-walled carbon nanotubes (MWCNTs). Two types of DOM can effectively disperse and stabilize the MWCNTs. At initial MWCNT concentration of 500 mg/L, suspended MWCNT concentration ranged from 8.0 to 17.9 mg/L as DOM were varied from 50 to 200 mg/L dissolved organic carbon (DOC). The critical coagulation concentration (CCC) values were estimated to be 41.4 mM NaCl and 5.3 mM CaCl2 in the absence of DOM. The presence of SDOM and MDOM significantly retarded the aggregation rate of MWCNTs. The CCC values increased to 120 mM NaCl and 14.8 mM CaCl2 at SDOM concentration of 20 mg/L DOC. Due to its higher aromaticity and molecular weight, MDOM showed higher ability to stabilize MWCNTs, with CCC values of 201 mM and 15.8 mM at 20 mg/L DOC. These findings revealed that DOMs originated from agricultural wastes will have great impact on the dispersion and stabilization of MWCNTs, thus their fate in the aquatic environment.

  7. Does Implant Design Affect Implant Primary Stability? A Resonance Frequency Analysis-Based Randomized Split-Mouth Clinical Trial.

    PubMed

    Gehrke, Sergio Alexandre; da Silva, Ulisses Tavares; Del Fabbro, Massimo

    2015-12-01

    The purpose of this study was to assess implant stability in relation to implant design (conical vs. semiconical and wide-pitch vs narrow-pitch) using resonance frequency analysis. Twenty patients with bilateral edentulous maxillary premolar region were selected. In one hemiarch, conical implants with wide pitch (group 1) were installed; in the other hemiarch, semiconical implants with narrow pitch were installed (group 2). The implant allocation was randomized. The implant stability quotient (ISQ) was measured by resonance frequency analysis immediately following implant placement to assess primary stability (time 1) and at 90 days after placement (time 2). In group 1, the mean and standard deviation ISQ for time 1 was 65.8 ± 6.22 (95% confidence interval [CI], 55 to 80), and for time 2, it was 68.0 ± 5.52 (95% CI, 57 to 77). In group 2, the mean and standard deviation ISQ was 63.6 ± 5.95 (95% CI, 52 to 78) for time 1 and 67.0 ± 5.71 (95% CI, 58 to 78) for time 2. The statistical analysis demonstrated significant difference in the ISQ values between groups at time 1 (P = .007) and no statistical difference at time 2 (P = .54). The greater primary stability of conical implants with wide pitch compared with semiconical implants with narrow pitch might suggest a preference for the former in case of the adoption of immediate or early loading protocols.

  8. Disruption of a hydrogen bond network in human versus spider monkey cytochrome c affects heme crevice stability.

    PubMed

    Goldes, Matthew E; Jeakins-Cooley, Margaret E; McClelland, Levi J; Mou, Tung-Chung; Bowler, Bruce E

    2016-05-01

    The hypothesis that the recent rapid evolution of primate cytochromes c, which primarily involves residues in the least stable Ω-loop (Ω-loop C, residues 40-57), stabilizes the heme crevice of cytochrome c relative to other mammals, is tested. To accomplish this goal, we have compared the properties of human and spider monkey cytochrome c and a set of four variants produced in the process of converting human cytochrome c into spider monkey cytochrome c. The global stability of all variants has been measured by guanidine hydrochloride denaturation. The stability of the heme crevice has been assessed with the alkaline conformational transition. Structural insight into the effects of the five amino acid substitutions needed to convert human cytochrome c into spider monkey cytochrome c is provided by a 1.15Å resolution structure of spider monkey cytochrome c. The global stability for all variants is near 9.0kcal/mol at 25°C and pH7, which is higher than that observed for other mammalian cytochromes c. The heme crevice stability is more sensitive to the substitutions required to produce spider monkey cytochrome c with decreases of up to 0.5 units in the apparent pKa of the alkaline conformational transition relative to human cytochrome c. The structure of spider monkey cytochrome c indicates that the Y46F substitution destabilizes the heme crevice by disrupting an extensive hydrogen bond network that connects three surface loops including Ω-loop D (residues 70-85), which contains the Met80 heme ligand.

  9. Rock slope instabilities in Norway: First systematic hazard and risk classification of 22 unstable rock slopes

    NASA Astrophysics Data System (ADS)

    Böhme, Martina; Hermanns, Reginald L.; Oppikofer, Thierry; Penna, Ivanna

    2016-04-01

    average displacement rates of up to 6 cm are measured with differential GNSS and InSAR. Cosmogenic nuclide dating suggests an acceleration of the present displacement compared to the average displacement since the initiation of the gravitational movement approximately 7000 years ago. Furthermore, there exists a pre-historic rock avalanche 3 km north along the same slope. These characteristics result in a very high hazard for the Gamanjunni unstable rock slope. The consequence analyses focus on the possibility of life loss only. For this the number of persons in the area that can be affected by either the rock slope failure itself and/or its secondary consequence of a displacement wave in case that a rock slope failure would hit a water body is estimated. For Gamanjunni the direct consequences are approximately 40 casualties, representing medium consequences. A total of 48 scenarios were finally analyzed for hazard, consequences and risk. The results are plotted in a risk matrix with 5 hazard and 5 consequence classes, leading to 4 risk classes. One unstable rock slope was classified as very high hazard, 9 scenarios as high hazard, 25 as medium hazard and 13 as low hazard, while none were classified as very low hazard. The consequence analyses for those scenarios resulted in 5 scenarios with very high consequences (>1000 potential casualties), 13 scenarios with high consequences (100-1000 casualties), 9 scenarios with medium consequences (10-100 casualties), 6 scenarios with low consequences (1-10 casualties) and 15 scenarios with very low consequences (0-1 casualties). This resulted in a high risk for 6 scenarios, medium to high risk for 16 scenarios, medium risk for 7 scenarios and low risk for 19 scenarios. These results allow determining which unstable rock slopes do not require further follow-up and on which further investigations and/or mitigation measures should be considered.

  10. Using IKONOS imagery for mapping instability factors and slope failures along a county road (Daunia, Italy)

    NASA Astrophysics Data System (ADS)

    Lamanna, C.; Casarano, D.; Wasowski, J.

    2009-04-01

    We report on the exploitation of high resolution optical imagery for the detection of slope conditions leading to instability and for mapping of active landslides along a road located in the Daunia Apennines (Southern Italy). The study area belongs to the municipal territory of Rocchetta Sant'Antonio and is known for recurrent landslide problems. We focus on 11 km long portion of SP99bis road, which has been damaged by many landslides and is currently closed to the traffic. This study is a part of an ongoing engineering geology investigation whose outcomes will be used to design future slope stabilization works. In order to obtain good quality data the IKONOS imagery was first orthorectified and pan-sharped. To overcome the lack of stereoscopic capability and to aid landslide identification, the imagery was draped over a detailed DEM (5 m grid). The image interpretation resulted in the recognition of 48 active landslides (some of small dimensions), which affect about 15% of the road length. Furthermore, thanks to the high resolution of the imagery it was possible to obtain very detailed information on water runoff in the areas upslope, downslope, as well as along the road track. Particular attention was paid to features indicative of the drainage conditions negative for the slope (and the road) stability, such as disordered surface drainage, water ponding, undrained depressions, anomalous wet areas. Poor drainage conditions (detected from satellite imagery) were found to coincide with 30 landslides. Further, in situ inspections conducted shortly after periods of intense rainfall confirmed that the hillslope areas in the vicinity the road landslides, as well as the road itself, are characterized by inadequate drainage. A comparison of field observations and remotely sensed data revealed that over 80% of the anomalous wet sites identified in situ was also detected from the satellite imagery. In conclusion, this case study demonstrates the practical applicability of

  11. Water Retention and Structure Stability in Smectitic or Kaolinitic Loam and Clay Soils Affected by Polyacrylamide Addition

    NASA Astrophysics Data System (ADS)

    Mamedov, Amirakh; Levy, Guy

    2015-04-01

    Studying the effects of polyacrylamide (PAM) on soil aggregate and structure stability is important in developing effective soil and water conservation practices and in sustaining soil and water quality. Five concentrations of an anionic PAM (0, 25, 50, 100 and 200 mg L-1) with a high molecular weight were tested on loam and clay soils having either a predominant smectitic or kaolinitic clay mineralogy. The effects of the PAM and of soil texture on soil water retention at near saturation and on aggregate and structure stability were investigated using the high energy moisture characteristic (HEMC) method. The S-shaped water retention curves obtained by the HEMC method were characterized by the modified van Genuchten (1980) model that provided: (i) the model parameters α and n, which represent the location of the inflection point and the steepness of the water retention curve, respectively; and (ii) the soil structure index, SI =VDP/MS, where VDP is the volume of drainable pores, an indicator of the quantity of water released by a soil over the range of applied suctions (0-5 J kg-1), and MS is the modal suction representing the most frequent pore sizes (> 60 μm). In general, the treatments tested (clay mineralogy, soil type and PAM concentration) resulted in: (i) a considerable modification of the shape of the water retention curves as indicated by the changes in the α and n values; and; (ii) substantial effects on the stability indices and other model parameters. The contribution of PAM concentration to soil structure stability depended on the clay mineralogy, being more effective in the smectitic soils than in the kaolinitic ones. Although kaolinitic soils are usually more stable than smectitic soils, when the latter were treated with PAM (25-200 mg L-1) the opposite trend was observed. In the loam soils, increasing the PAM concentration notably decreased the differences between values of the stability indices of the smectitic and kaolinitic samples. The

  12. Neurotransmitter Release Can Be Stabilized by a Mechanism That Prevents Voltage Changes Near the End of Action Potentials from Affecting Calcium Currents.

    PubMed

    Clarke, Stephen G; Scarnati, Matthew S; Paradiso, Kenneth G

    2016-11-09

    At chemical synapses, presynaptic action potentials (APs) activate voltage-gated calcium channels, allowing calcium to enter and trigger neurotransmitter release. The duration, peak amplitude, and shape of the AP falling phase alter calcium entry, which can affect neurotransmitter release significantly. In many neurons, APs do not immediately return to the resting potential, but instead exhibit a period of depolarization or hyperpolarization referred to as an afterpotential. We hypothesized that presynaptic afterpotentials should alter neurotransmitter release by affecting the electrical driving force for calcium entry and calcium channel gating. In support of this, presynaptic calcium entry is affected by afterpotentials after standard instant voltage jumps. Here, we used the mouse calyx of Held synapse, which allows simultaneous presynaptic and postsynaptic patch-clamp recording, to show that the postsynaptic response is affected significantly by presynaptic afterpotentials after voltage jumps. We therefore tested the effects of presynaptic afterpotentials using simultaneous presynaptic and postsynaptic recordings and AP waveforms or real APs. Surprisingly, presynaptic afterpotentials after AP stimuli did not alter calcium channel responses or neurotransmitter release appreciably. We show that the AP repolarization time course causes afterpotential-induced changes in calcium driving force and changes in calcium channel gating to effectively cancel each other out. This mechanism, in which electrical driving force is balanced by channel gating, prevents changes in calcium influx from occurring at the end of the AP and therefore acts to stabilize synaptic transmission. In addition, this mechanism can act to stabilize neurotransmitter release when the presynaptic resting potential changes.

  13. The influence of slope on Spartium junceum root system: morphological, anatomical and biomechanical adaptation.

    PubMed

    Lombardi, Fabio; Scippa, G S; Lasserre, B; Montagnoli, A; Tognetti, R; Marchetti, M; Chiatante, D

    2017-03-15

    Root systems have a pivotal role in plant anchorage and their mechanical interactions with the soil may contribute to soil reinforcement and stabilization of slide-prone slopes. In order to understand the responses of root system to mechanical stress induced by slope, samples of Spartium junceum L., growing in slope and in plane natural conditions, were compared in their morphology, biomechanical properties and anatomical features. Soils sampled in slope and plane revealed similar characteristics, with the exception of organic matter content and penetrometer resistance, both higher in slope. Slope significantly influenced root morphology and in particular the distribution of lateral roots along the soil depth. Indeed, first-order lateral roots of plants growing on slope condition showed an asymmetric distribution between up- and down-slope. Contrarily, this asymmetric distribution was not observed in plants growing in plane. The tensile strength was higher in lateral roots growing up-slope and in plane conditions than in those growing down-slope. Anatomical investigations revealed that, while roots grown up-slope had higher area covered by xylem fibers, the ratio of xylem and phloem fibers to root diameter did not differ among the three conditions, as also, no differences were found for xylem fiber cell wall thickness. Roots growing up-slope were the main contributors to anchorage properties, which included higher strength and higher number of fibers in the xylematic tissues. Results suggested that a combination of root-specific morphological, anatomical and biomechanical traits, determines anchorage functions in slope conditions.

  14. The shaping of continental slopes by internal tides.

    PubMed

    Cacchione, D A; Pratson, L F; Ogston, A S

    2002-04-26

    The angles of energy propagation of semidiurnal internal tides may determine the average gradient of continental slopes in ocean basins (approximately 2 to 4 degrees). Intensification of near-bottom water velocities and bottom shear stresses caused by reflection of semi-diurnal internal tides affects sedimentation patterns and bottom gradients, as indicated by recent studies of continental slopes off northern California and New Jersey. Estimates of bottom shear velocities caused by semi-diurnal internal tides are high enough to inhibit deposition of fine-grained sediment onto the slopes.

  15. Stability of Chloropyromorphite in Ryegrass Rhizosphere as Affected by Root-Secreted Low Molecular Weight Organic Acids

    PubMed Central

    Wei, Wei; Wang, Yu; Wang, Zheng; Han, Ruiming; Li, Shiyin; Wei, Zhenggui; Zhang, Yong

    2016-01-01

    Understanding the stability of chloropyromorphite (CPY) is of considerable benefit for improving risk assessment and remediation strategies in contaminated water and soil. The stability of CPY in the rhizosphere of phosphorus-deficient ryegrass was evaluated to elucidate the role of root-secreted low molecular weight organic acids (LMWOAs) on the dissolution of CPY. Results showed that CPY treatments significantly reduced the ryegrass biomass and rhizosphere pH. The presence of calcium nitrate extractable lead (Pb) and phosphorus (P) suggested that CPY in the rhizosphere could be bioavailable, because P and Pb uptake by ryegrass potentially provided a significant concentration gradient that would promote CPY dissolution. Pb accumulation and translocation in ryegrass was found to be significantly higher in P-sufficient conditions than in P-deficient conditions. CPY treatments significantly enhanced root exudation of LMWOAs irrigated with P-nutrient solution or P-free nutrient solution. Oxalic acid was the dominant species in root-secreted LMWOAs of ryegrass under P-free nutrient solution treatments, suggesting that root-secreted oxalic acid may be the driving force of root-induced dissolution of CPY. Hence, our work, provides clarifying hints on the role of LMWOAs in controlling the stability of CPY in the rhizosphere. PMID:27494023

  16. North Slope (Wahluke Slope) expedited response action cleanup plan

    SciTech Connect

    Not Available

    1994-02-01

    The purpose of this action is to mitigate any threat to public health and the environment from hazards on the North Slope and meet the expedited response action (ERA) objective of cleanup to a degree requiring no further action. The ERA may be the final remediation of the 100-I-3 Operable Unit. A No Action record of decision (ROD) may be issued after remediation completion. The US Department of Energy (DOE) currently owns or administers approximately 140 mi{sup 2} (about 90,000 acres) of land north and east of the Columbia River (referred to as the North Slope) that is part of the Hanford Site. The North Slope, also commonly known as the Wahluke Slope, was not used for plutonium production or support facilities; it was used for military air defense of the Hanford Site and vicinity. The North Slope contained seven antiaircraft gun emplacements and three Nike-Ajax missile positions. These military positions were vacated in 1960--1961 as the defense requirements at Hanford changed. They were demolished in 1974. Prior to government control in 1943, the North Slope was homesteaded. Since the initiation of this ERA in the summer of 1992, DOE signed the modified Hanford Federal Agreement and Consent Order (Tri-Party Agreement) with the Washington Department of Ecology (Ecology) and the US Environmental Protection Agency (EPA), in which a milestone was set to complete remediation activities and a draft closeout report by October 1994. Remediation activities will make the North Slope area available for future non-DOE uses. Thirty-nine sites have undergone limited characterization to determine if significant environmental hazards exist. This plan documents the results of that characterization and evaluates the potential remediation alternatives.

  17. The N-terminal tails of the H2A-H2B histones affect dimer structure and stability.

    PubMed

    Placek, Brandon J; Gloss, Lisa M

    2002-12-17

    The histone proteins of the core nucleosome are highly basic and form heterodimers in a "handshake motif." The N-terminal tails of the histones extend beyond the canonical histone fold of the hand-shake motif and are the sites of posttranslational modifications, including lysine acetylations and serine phosphorylations, which influence chromatin structure and activity as well as alter the charge state of the tails. However, it is not well understood if these modifications are signals for recruitment of other cellular factors or if the removal of net positive charge from the N-terminal tail plays a role in the overall structure of chromatin. To elucidate the effects of the N-terminal tails on the structure and stability of histones, the highly charged N-terminal tails were truncated from the H2A and H2B histones. Three mutant dimers were studied: DeltaN-H2A/WT H2B; WT H2A/DeltaN-H2B, and DeltaN-H2A/DeltaN-H2B. The CD spectra, stabilities to urea-denaturation, and the salt-dependent stabilization of the three truncated dimers were compared with those of the wild-type dimer. The data support four conclusions regarding the effects of the N-terminal tails of H2A and H2B: (1) Removal of the N-terminal tails of H2A and H2B enhance the helical structure of the mutant heterodimers. (2) Relative to the full-length WT heterodimer, the DeltaN-H2A/WT H2B dimer is destabilized, while the WT H2A/DeltaN-H2B and DeltaN-H2A/DeltaN-H2B dimers are slightly stabilized. (3) The truncated dimers exhibit decreased m values, relative to the WT dimer, supporting the hypothesis that the N-terminal tails in the isolated dimer adopt a collapsed structure. (4) Electrostatic repulsion in the N-terminal tails decreases the stability of the H2A-H2B dimer.

  18. The influence of somatosensory and muscular deficits on postural stabilization: Insights from an instrumented analysis of subjects affected by different types of Charcot-Marie-Tooth disease.

    PubMed

    Lencioni, Tiziana; Piscosquito, Giuseppe; Rabuffetti, Marco; Bovi, Gabriele; Calabrese, Daniela; Aiello, Alessia; Di Sipio, Enrica; Padua, Luca; Diverio, Manuela; Pareyson, Davide; Ferrarin, Maurizio

    2015-08-01

    Charcot-Marie-Tooth (CMT) disease is the most common hereditary neuromuscular disorder. CMT1 is primarily demyelinating, CMT2 is primarily axonal, and CMTX1 is characterized by both axonal and demyelinating abnormalities. We investigated the role of somatosensory and muscular deficits on quiet standing and postural stabilization in patients affected by different forms of CMT, comparing their performances with those of healthy subjects. Seventy-six CMT subjects (CMT1A, CMT2 and CMTX1) and 41 healthy controls were evaluated during a sit-to-stand transition and the subsequent quiet upright posture by means of a dynamometric platform. All CMT patients showed altered balance and postural stabilization compared to controls. Multivariate analysis showed that in CMT patients worsening of postural stabilization was related to vibration sense deficit and to dorsi-flexor's weakness, while quiet standing instability was related to the reduction of pinprick sensibility and to plantar-flexor's weakness. Our results show that specific sensory and muscular deficits play different roles in balance impairment of CMT patients, both during postural stabilization and in static posture. An accurate evaluation of residual sensory and muscular functions is therefore necessary to plan for the appropriate balance rehabilitation treatment for each patient, besides the CMT type.

  19. Effects of heel base size, walking speed, and slope angle on center of pressure trajectory and plantar pressure when wearing high-heeled shoes.

    PubMed

    Luximon, Yan; Cong, Yan; Luximon, Ameersing; Zhang, Ming

    2015-06-01

    High-heeled shoes are associated with instability and a high risk of fall, fracture, and ankle sprain. This study investigated the effects of heel base size (HBS) on walking stability under different walking speeds and slope angles. The trajectory of the center of pressure (COP), maximal peak pressure, pressure time integral, contact area, and perceived stability were analyzed. The results revealed that a small HBS increased the COP deviations, shifting the COP more medially at the beginning of the gait cycle. The slope angle mainly affected the COP in the anteroposterior direction. An increased slope angle shifted the COP posterior and caused greater pressure and a larger contact area in the midfoot and rearfoot regions, which can provide more support. Subjective measures on perceived stability were consistent with objective measures. The results suggested that high-heeled shoes with a small HBS did not provide stable plantar support, particularly on a small slope angle. The changes in the COP and pressure pattern caused by a small HBS might increase joint torque and muscle activity and induce lower limb problems.

  20. Reduced oxide sites and surface corrugation affecting the reactivity, thermal stability, and selectivity of supported Au-Pd bimetallic clusters on SiO2/Si(100).

    PubMed

    Gross, Elad; Sorek, Elishama; Murugadoss, Arumugam; Asscher, Micha

    2013-05-21

    The morphology and surface elemental composition of Au-Pd bimetallic nanoclusters are reported to be sensitive to and affected by reduced silicon defect sites and structural corrugation on SiO2/Si(100), generated by argon ion sputtering under ultrahigh vacuum (UHV) conditions. Metastable structures of the bimetallic clusters, where Au atoms are depleted from the top surface upon annealing, are stabilized by the interaction with the reduced silica sites, as indicated from CO temperature programmed desorption (TPD) titration measurements. Acetylene conversion to ethylene and benzene has been studied as a probe reaction, revealing the modification of selectivity and reactivity enhancement in addition to improved thermal stability on substrates rich in reduced-silica sites. These observations suggest that these unique sites play an important role in anchoring thermodynamically metastable conformations of supported Au-Pd bimetallic catalysts and dictate their high-temperature activity.

  1. The cellular energization state affects peripheral stalk stability of plant vacuolar H+-ATPase and impairs vacuolar acidification.

    PubMed

    Schnitzer, Daniel; Seidel, Thorsten; Sander, Tim; Golldack, Dortje; Dietz, Karl-Josef

    2011-05-01

    The plant vacuolar H(+)-ATPase takes part in acidifying compartments of the endomembrane system including the secretory pathway and the vacuoles. The structural variability of the V-ATPase complex as well as its presence in different compartments and tissues involves multiple isoforms of V-ATPase subunits. Furthermore, a versatile regulation is essential to allow for organelle- and tissue-specific fine tuning. In this study, results from V-ATPase complex disassembly with a chaotropic reagent, immunodetection and in vivo fluorescence resonance energy transfer (FRET) analyses point to a regulatory mechanism in plants, which depends on energization and involves the stability of the peripheral stalks as well. Lowering of cellular ATP by feeding 2-deoxyglucose resulted in structural alterations within the V-ATPase, as monitored by changes in FRET efficiency between subunits VHA-E and VHA-C. Potassium iodide-mediated disassembly revealed a reduced stability of V-ATPase after 2-deoxyglucose treatment of the cells, but neither the complete V(1)-sector nor VHA-C was released from the membrane in response to 2-deoxyglucose treatment, precluding a reversible dissociation mechanism like in yeast. These data suggest the existence of a regulatory mechanism of plant V-ATPase by modification of the peripheral stator structure that is linked to the cellular energization state. This mechanism is distinct from reversible dissociation as reported for the yeast V-ATPase, but might represent an evolutionary precursor of reversible dissociation.

  2. SUMF1 mutations affecting stability and activity of formylglycine generating enzyme predict clinical outcome in multiple sulfatase deficiency.

    PubMed

    Schlotawa, Lars; Ennemann, Eva Charlotte; Radhakrishnan, Karthikeyan; Schmidt, Bernhard; Chakrapani, Anupam; Christen, Hans-Jürgen; Moser, Hugo; Steinmann, Beat; Dierks, Thomas; Gärtner, Jutta

    2011-03-01

    Multiple Sulfatase Deficiency (MSD) is caused by mutations in the sulfatase-modifying factor 1 gene encoding the formylglycine-generating enzyme (FGE). FGE post translationally activates all newly synthesized sulfatases by generating the catalytic residue formylglycine. Impaired FGE function leads to reduced sulfatase activities. Patients display combined clinical symptoms of single sulfatase deficiencies. For ten MSD patients, we determined the clinical phenotype, FGE expression, localization and stability, as well as residual FGE and sulfatase activities. A neonatal, very severe clinical phenotype resulted from a combination of two nonsense mutations leading to almost fully abrogated FGE activity, highly unstable FGE protein and nearly undetectable sulfatase activities. A late infantile mild phenotype resulted from FGE G263V leading to unstable protein but high residual FGE activity. Other missense mutations resulted in a late infantile severe phenotype because of unstable protein with low residual FGE activity. Patients with identical mutations displayed comparable clinical phenotypes. These data confirm the hypothesis that the phenotypic outcome in MSD depends on both residual FGE activity as well as protein stability. Predicting the clinical course in case of molecularly characterized mutations seems feasible, which will be helpful for genetic counseling and developing therapeutic strategies aiming at enhancement of FGE.

  3. How dangerous are slope failures offshore western Thailand (Andaman Sea, Indian Ocean)?

    NASA Astrophysics Data System (ADS)

    Schwab, J.; Krastel, S.; Grün, M.; Gross, F.; Pananont, P.; Jintasaeranee, P.; Bunsomboonsakul, S.; Weinrebe, W.; Winkelmann, D.

    2012-12-01

    The Thai west coast is well known for being hit by tsunami waves triggered by earthquakes arising from the nearby Sunda Trench. However, so far little has been known about additional factors that may trigger tsunamis in the area, such as submarine landslides at the shelf slope area. In order to assess the stability of the slope and evaluate the tsunamigenic potential of submarine landslides off western Thailand, 2D seismic data from the top and the western slope of a bathymetric high (Mergui Ridge about 200 km off the Thai west coast) have been investigated. These data were the basis for mapping locations and approximate volumes of mass transport deposits (MTDs). In total, 17 mass transport deposits were found. The estimated minimum volumes of individual MTDs range between 0.3 cbkm and 14 cbkm. MTDs have been identified in three different settings: i) stacked MTDs within disturbed and faulted basin sediments at the transition of the Mergui Ridge to the adjacent East Andaman Basin, ii) MTDs within a pile of drift sediments at the basin-ridge transition, and iii) MTDs near the edge of/on top of Mergui Ridge in relatively shallow water depths (<1000m). Our data indicate that the Mergui Ridge-slope area seems to have been generally unstable. Slide events occurred repeatedly and slope failures may occur again in the future. We find that the most likely causes for slope instabilities are the presence of unstable drift sediments, excess pore pressure in the sediments, and active tectonics. Most MTDs are located in large water depths (> 1000 m) and/or comprise small volumes; hence it is very unlikely that they triggered significant tsunamis in the past. Moreover, the recurrence rates of failure events seem to be low. Some MTDs with tsunami potential, however, have been identified on top of Mergui Ridge in water depths below 1000 m. Mass-wasting events that may occur in the future at similar locations do have a tsunami potential if they comprise sufficient volumes

  4. Interior Slopes of Copernican Craters

    NASA Astrophysics Data System (ADS)

    Robinson, M. S.; Burns, K.; Stelling, R.; Speyerer, E.; Mahanti, P.

    2012-12-01

    The Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) routinely acquires high resolution (50 to 200 cm pixel scales) stereo pairs from adjacent orbits through spacecraft slews; parallax angles are typically >20°, and the local incidence angle between 40° and 65°. These observations are reduced to digital elevation models (DEM) using a combination of ISIS (USGS) and SOCET Set (BAE Systems). For this study DEMs originally sampled at 2 m scales were reduced (averaging technique) to 5 m scales to provide slopes calculated over 3x3 pixel boxes (15 m x 15 m). The upper 50% of interior walls of Copernican craters (2 to 20 km diameter) typically have average slopes of 36°, with slopes locally above 40° not uncommon (i.e. Fig 1: 2.3 km diam, 17.68°S, 144.41°E). Giordano Bruno (GB; 35.97N°, 102.86°E) is likely the youngest 20-km diameter class crater on the Moon. Its floor is dominated by impact forms (ponds and flows), and inner walls exhibit a series of coalesced flow lobes emanating from steep upper slopes. The lobes appear to be composed of dry granular material based on the observation of boulder trails superposed on many examples. The upper slopes average 36° or more, with some slopes above 40°. For much of GB, slopes exceed 30° all the way to the crater floor (especially in the SE). The high slopes imply angular grains, some level of cohesion, and/or higher angles of repose due to the Moon's relatively low gravity. Larmor Q (28.56°N, 176.33°E), another large Copernican crater, is elliptical in plan (23 x 18 km diameter), with an interior floor dominated by large slump blocks. Like GB its walls exhibit overlapping lobes (granular materials) emanating from interior wall slopes that range from 30° to 36°. Other Copernican craters exhibit similar steep slopes on interior walls: Moore F (23 km diam), Necho (30 km), and two unnamed craters (9 km,13.31°S, 257.55°E; 9 km, 15.72°, 177.39°E). Slopes of the central peaks of Tycho crater (0

  5. Deciphering the Dynamics of Non-Covalent Interactions Affecting Thermal Stability of a Protein: Molecular Dynamics Study on Point Mutant of Thermus thermophilus Isopropylmalate Dehydrogenase

    PubMed Central

    Sharma, Reetu; Sastry, G. Narahari

    2015-01-01

    Thermus thermophilius isopropylmalate dehydrogenase catalyzes oxidative decarboxylation and dehydrogenation of isopropylmalate. Substitution of leucine to alanine at position 172 enhances the thermal stability among the known point mutants. Exploring the dynamic properties of non-covalent interactions such as saltbridges, hydrogen bonds and hydrophobic interactions to explain thermal stability of a protein is interesting in its own right. In this study dynamic changes in the non-covalent interactions are studied to decipher the deterministic features of thermal stability of a protein considering a case study of a point mutant in Thermus thermophilus isopropylmalate dehydrogenase. A total of four molecular dynamic simulations of 0.2 μs were carried out on wild type and mutant’s functional dimers at 300 K and 337 K. Higher thermal stability of the mutant as compared to wild type is revealed by root mean square deviation, root mean square fluctuations and Cα-Cα distance with an increase in temperature from 300 K to 337 K. Most of the regions of wild type fluctuate higher than the corresponding regions of mutant with an increase in temperature. Cα-Cα distance analysis suggests that long distance networks are significantly affected in wild type as compared to the mutant. Short lived contacts are higher in wild type, while long lived contacts are lost at 337 K. The mutant forms less hydrogen bonds with water as compared to wild type at 337 K. In contrast to wild type, the mutant shows significant increase in unique saltbridges, hydrogen bonds and hydrophobic contacts at 337 K. The current study indicates that there is a strong inter-dependence of thermal stability on the way in which non-covalent interactions reorganize, and it is rewarding to explore this connection in single mutant studies. PMID:26657745

  6. Deciphering the Dynamics of Non-Covalent Interactions Affecting Thermal Stability of a Protein: Molecular Dynamics Study on Point Mutant of Thermus thermophilus Isopropylmalate Dehydrogenase.

    PubMed

    Sharma, Reetu; Sastry, G Narahari

    2015-01-01

    Thermus thermophilius isopropylmalate dehydrogenase catalyzes oxidative decarboxylation and dehydrogenation of isopropylmalate. Substitution of leucine to alanine at position 172 enhances the thermal stability among the known point mutants. Exploring the dynamic properties of non-covalent interactions such as saltbridges, hydrogen bonds and hydrophobic interactions to explain thermal stability of a protein is interesting in its own right. In this study dynamic changes in the non-covalent interactions are studied to decipher the deterministic features of thermal stability of a protein considering a case study of a point mutant in Thermus thermophilus isopropylmalate dehydrogenase. A total of four molecular dynamic simulations of 0.2 μs were carried out on wild type and mutant's functional dimers at 300 K and 337 K. Higher thermal stability of the mutant as compared to wild type is revealed by root mean square deviation, root mean square fluctuations and Cα-Cα distance with an increase in temperature from 300 K to 337 K. Most of the regions of wild type fluctuate higher than the corresponding regions of mutant with an increase in temperature. Cα-Cα distance analysis suggests that long distance networks are significantly affected in wild type as compared to the mutant. Short lived contacts are higher in wild type, while long lived contacts are lost at 337 K. The mutant forms less hydrogen bonds with water as compared to wild type at 337 K. In contrast to wild type, the mutant shows significant increase in unique saltbridges, hydrogen bonds and hydrophobic contacts at 337 K. The current study indicates that there is a strong inter-dependence of thermal stability on the way in which non-covalent interactions reorganize, and it is rewarding to explore this connection in single mutant studies.

  7. Pleistocene tectonic accretion of the continental slope off Washington

    USGS Publications Warehouse

    Silver, E.A.

    1972-01-01

    Interpretation of reflection profiles across the Washington continental margin suggests deformation of Cascadia basin strata against the continental slope. Individual reflecting horizons can be traced across the slope-basin boundary. The sense of offset along faults on the continental slope is predominantly, but not entirely, west side up. Two faults of small displacement are seen to be west-dipping reverse faults. Magnetic anomalies on the Juan de Fuca plate can be traced 40-100 km eastward under the slope, and structural interpretation combined with calculated rates of subduction suggests that approximately 50 km of the outer continental slope may have been formed in Pleistocene time. Rocks of Pleistocene age dredge from a ridge exposing acoustic "basement" on the slope, plus the results of deep-sea drilling off northern Oregon, are consistent with this interpretation. The question of whether or not subduction is occurring at present is unresolved because significant strain has not affected the upper 200 m of section in the Cascadia basin. However, deformation of the outer part of the slope has been episodic and may reflect episodic yield, deposition rate, subduction rate, or some combination of these factors. ?? 1972.

  8. Does the personal lift-assist device affect the local dynamic stability of the spine during lifting?

    PubMed

    Graham, Ryan B; Sadler, Erin M; Stevenson, Joan M

    2011-02-03

    The personal lift-assist device (PLAD) is an on-body ergonomic aid that reduces low back physical demands through the restorative moment of an external spring element, which possesses a mechanical advantage over the erector spinae. Although the PLAD has proven effective at reducing low back muscular demand, spinal moments, and localized muscular fatigue during laboratory and industrial tasks, the effects of the device on the neuromuscular control of spinal stability during lifting have yet to be assessed. Thirty healthy subjects (15M, 15F) performed repetitive lifting for three minutes, at a rate of 10 lifts per minute, with and without the PLAD. Maximum finite-time Lyapunov exponents, representing short-term (λ(max-s)) and long-term (λ(max-l)) divergence were calculated from the measured trunk kinematics to estimate the local dynamic stability of the lumbar spine. Using a mixed-design repeated-measures ANOVA, it was determined that wearing the PLAD did not significantly change λ(max-s) (μ(NP)=0.335, μ(P)=0.321, p=0.225), but did significantly reduce λ(max-l) (μ(NP)=0.0024, μ(P)=-0.0011, p=0.014, η(2)=0.197). There were no between-subject effects of sex, or significant interactions (p>0.720). The present results indicated that λ(max-s) was not statistically different between the device conditions, but that the PLAD significantly reduced λ(max-l) to a negative (stable) value. This shows that subjects' neuromuscular systems were able to respond to local perturbations more effectively when wearing the device, reflecting a more stable control of spinal movements. These findings are important when recommending the PLAD for long-term industrial or clinical use.

  9. LogN-logS slope determination in imaging X-ray astronomy

    NASA Technical Reports Server (NTRS)

    Maccacaro, Tommaso; Romaine, Suzanne; Schmitt, H. M. M.

    1987-01-01

    The problem of estimating the slope of the number-counts relations for the specific case of imaging X-ray surveys is briefly discussed. Results have been obtained from extensive simulations of Einstein Observatory imaging X-ray data. It is concluded that the bias which affects the X-ray number-counts slope determination is much smaller than that which affects the radio number-counts slope.

  10. Buoyant Turbulent Kinetic Energy Production in Steep-Slope Katabatic Flow

    NASA Astrophysics Data System (ADS)

    Oldroyd, Holly J.; Pardyjak, Eric R.; Higgins, Chad W.; Parlange, Marc B.

    2016-12-01

    We develop several critical concepts that should be considered when interpreting, modelling and designing future experiments for flows over sloping terrain. Vertical buoyancy fluxes in katabatic flows can be positive and a source of turbulent kinetic energy (TKE) despite the statically stable, thermal stratification that drives these flows. This phenomenon occurs when the ratio of along-slope to slope-normal kinematic heat fluxes is greater than the cotangent of the slope angle, suggesting a critical value of slope-angle steepness found in earlier studies. We provide field-data-based evidence that the along-slope heat flux may dominate the variables in this inequality, and therefore in generating buoyant TKE production or suppression over a steep slope. These data show the along-slope heat flux can be more variable and significantly larger in magnitude than the slope-normal component. The gradient Richardson number does not include the effects of the along-slope buoyancy; furthermore, none of the canonical stability parameters can properly reflect the TKE redistribution from turbulent transport divergence and the sink of TKE in cases of counter-gradient momentum fluxes, which we frequently observe near the peak of the katabatic jet. In such cases, canonical stability parameters inadequately represent the physical mechanisms associated with stability. These results have broad implications related to accurately modelling turbulence and surface exchanges over sloping terrain and illustrate the need to more thoroughly investigate the along-slope heat flux and its drivers, the meaning and definitions of stability, and the effects of non-local turbulent transport.

  11. Stability of psychological impairment: two year follow-up of former microelectronics workers' affective and personality disturbance.

    PubMed

    Bowler, R M; Mergler, D; Rauch, S S; Bowler, R P

    1992-01-01

    For the past twenty years women's complaints in the microelectronics industry have often been diagnosed as mass psychogenic illness, despite evidence of potential exposure to organic solvents, which have been associated with affect and mood changes. In the present study, the standard version of the Minnesota Multiphasic Personality Inventory (MMPI) was used to evaluate affective and personality disturbance among 63 former microelectronics workers (56 women and 7 men) over a two-year period of time. In both 1986 and 1988, the former workers obtained mean scale score elevations beyond two standard deviations above the normative sample (T = greater than 70) on the MMPI clinical scales of schizophrenia, hypochondriasis, psychasthenia, depression and hysteria. For most scales, 86-88 mean score differences did not attain the 0.05 significance level (two-tailed paired t-test) and no significant differences were observed for 86-88 comparison scale scores = greater than 70 (McNemar paired statistic). Although there were too few men to perform gender comparisons, men scored higher than women on 5 scales and all of the men had scores = greater than 70 on hypochondriasis, depression, hysteria, psychasthenia and schizophrenia. These findings reveal that these former microelectronics workers manifested affective and personality disturbances, consistent with organic solvent toxicity, which persisted over a two year period, indicating that they were not reactive, transient hysterical neurosis.

  12. Terrane daylight mapping on large dip-slope terrain based on high-resolution DTM and semi-automatic geoprocessing processes

    NASA Astrophysics Data System (ADS)

    Yeh, Chih-Hsiang; Lin, Ming-Lang; Chan, Yu-Chang; Chang, Kuo-Jen; Hsieh, Yu-Chung

    2015-04-01

    "Daylight" in slope engineering means a lineament appearing on the ground surface casued by a internal weak plane of a rock slope. The morphology of the daylight implies the free surface condition of the rock mass upper the weak plane, directly affecting the slope stability and safety. Traditionally, the reconnaissance of daylight employs field investigation and drillings in local dip slope area, but when mapping in large area, it would be subjected to vegetation cover and budget limitation to get a simply result not used for engineering applications. Therefore, the purpose of this study is to develop a rapid and reliable mapping program based on high-resolution DTM, and to generate a large-scale daylight map for large dip slope area. The methodology can be divided into two phases: the first is re-mapping terrane boundary lineaments using LiDAR data and 3D GIS mapping technology; the second is automatically mapping daylight tracks by trend surface analysis and python scripts based on above terrane boundary lineaments. This study takes the area of Keelung River north bank, which is mainly cuesta topography, for an example. Recently, in the area, the frequency of dip slope landslide occurrence becomes more higher because of human development. One major reason to cause the daylight appearing on downslope is the slope toe cutting or river incision. Hereby, according to the final results of the daylight map, we can assess where the potential landsides dip slops are, and further differentiate three different risks of dip slope from the daylight's morphology, expecting to provide more detail engineering and geological information for furture engineering site selection and the design and application of disaster prevention.

  13. Western Slope of Andes, Peru

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Along the western flank of the Andes, 400 km SE of Lima Peru, erosion has carved the mountain slopes into long, narrow serpentine ridges. The gently-sloping sediments have been turned into a plate of worms wiggling their way downhill to the ocean.

    The image was acquired September 28, 2004, covers an area of 38 x 31.6 km, and is located near 14.7 degrees south latitude, 74.5 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  14. Public transit bus ramp slopes measured in situ.

    PubMed

    Bertocci, Gina; Frost, Karen; Smalley, Craig

    2014-05-02

    Abstract Purpose: The slopes of fixed-route bus ramps deployed for wheeled mobility device (WhMD) users during boarding and alighting were assessed. Measured slopes were compared to the proposed Americans with Disabilities Act (ADA) maximum allowable ramp slope. Methods: A ramp-embedded inclinometer measured ramp slope during WhMD user boarding and alighting on a fixed-route transit bus. The extent of bus kneeling was determined for each ramp deployment. In-vehicle video surveillance cameras captured ramp deployment level (street versus sidewalk) and WhMD type. Results: Ramp slopes ranged from -4° to 15.5° with means of 4.3° during boarding (n = 406) and 4.2° during alighting (n = 405). Ramp slope was significantly greater when deployed to street level. During boarding, the proposed ADA maximum allowable ramp slope (9.5°) was exceeded in 66.7% of instances when the ramp was deployed to street level, and in 1.9% of instances when the ramp was deployed to sidewalk level. During alighting, the proposed ADA maximum allowable slope was exceeded in 56.8% of instances when the ramp was deployed to street level and in 1.4% of instances when the ramp was deployed to sidewalk level. Conclusions: Deployment level, built environment and extent of bus kneeling can affect slope of ramps ascended/descended by WhMD users when accessing transit buses. Implications for Rehabilitation Since public transportation services are critical for integration of wheeled mobility device (WhMD) users into the community and society, it is important that they, as well as their therapists, are aware of conditions that may be encountered when accessing transit buses. Knowledge of real world ramp slope conditions that may be encountered when accessing transit buses will allow therapists to better access capabilities of WhMD users in a controlled clinical setting. Real world ramp slope conditions can be recreated in a clinical setting to allow WhMD users to develop and practice necessary

  15. Progressive rock slope failure resulting from fluvial incision and far-field stress changes in alpine landscapes

    NASA Astrophysics Data System (ADS)

    Leith, K.; Moore, J. R.; Loew, S.; Krautblatter, M.

    2013-12-01

    Modifications to rock slope morphology are commonly associated with the destabilization of local rock masses where shear, normal, or tensile stress changes cause in situ stresses to exceed intact or rock mass failure envelopes. Such destabilization is most commonly attributed to ';debuttressing' causing a loss of support from adjacent bodies, or a reduction in effective rock mass strength as critical planes of weakness are ';undercut' by erosional processes. Lower magnitude stress changes which approach the brittle failure envelopes are often implicated in progressive rock slope failure, as local stress concentrations propagate existing fractures or weaken existing joints. We model the development of long-term in situ stresses within an alpine valley affected by ongoing tectonic and erosional processes. We allow for the mechanical effects of long-term bedrock strength limits, and analyze the magnitude of far-field stress changes associated with 100 m of fluvial incision at the axis of a 3000 m wide, 2500 m deep alpine valley. Our model configuration mirrors the erosional history of the Matter Valley (southern Swiss Alps) at the location of the 30 x 106 m3 Randa rock slope failure. We find that incision focuses stresses at the valley floor, reducing stress magnitudes throughout the remainder of the landscape. This effect is particularly strong near the valley shoulder, where decreases in shear stress are approximately half those of normal stresses. Although the magnitude of changes are relatively low (10's to 100's of kPa), we find incision may have had a negative impact on the stability of rock slopes over 1000 m from the valley axis, perhaps initiating progressive failure of the Randa rock slope. Such progressive failure is particularly important in alpine regions, as its initiation requires relatively minor morphological change, and the resulting strength degradation modulates temporal increases in rock slope sensitivity. Our proposition is supported by the

  16. Permeability models affecting nonlinear stability in the asymptotic suction boundary layer: the Forchheimer versus the Darcy model

    NASA Astrophysics Data System (ADS)

    Wedin, Håkan; Cherubini, Stefania

    2016-12-01

    The asymptotic suction boundary layer (ASBL) is used for studying two permeability models, namely the Darcy and the Forchheimer model, the latter being more physically correct according to the literature. The term that defines the two apart is a function of the non-Darcian wall permeability {\\hat{K}}2 and of the wall suction {\\hat{V}}0, whereas the Darcian wall permeability {\\hat{K}}1 is common to the two models. The underlying interest of the study lies in the field of transition to turbulence where focus is put on two-dimensional nonlinear traveling waves (TWs) and their three-dimensional linear stability. Following a previous study by Wedin et al (2015 Phys. Rev. E 92 013022), where only the Darcy model was considered, the present work aims at comparing the two models, assessing where in the parameter space they cease to produce the same results. For low values of {\\hat{K}}1 both models produce almost identical TW solutions. However, when both increasing the suction {\\hat{V}}0 to sufficiently high amplitudes (i.e. lowering the Reynolds number Re, based on the displacement thickness) and using large values of the wall porosity, differences are observed. In terms of the non-dimensional Darcian wall permeability parameter, a, strong differences in the overall shape of the bifurcation curves are observed for a≳ 0.70, with the emergence of a new family of solutions at Re lower than 100. For these large values of a, a Forchheimer number {{Fo}}\\max ≳ 0.5 is found, where Fo expresses the ratio between the kinetic and viscous forces acting on the porous wall. Moreover, the minimum Reynolds number, {{Re}}g, for which the Navier-Stokes equations allow for nonlinear solutions, decreases for increasing values of a. Fixing the streamwise wavenumber to α = 0.154, as used in the study by Wedin et al referenced above, we find that {{Re}}g is lowered from Re ≈ 3000 for zero permeability, to below 50 for a = 0.80 for both permeability models. Finally, the stability of

  17. ALS as a distal axonopathy: molecular mechanisms affecting neuromuscular junction stability in the presymptomatic stages of the disease

    PubMed Central

    Moloney, Elizabeth B.; de Winter, Fred; Verhaagen, Joost

    2014-01-01

    Amyotrophic Lateral Sclerosis (ALS) is being redefined as a distal axonopathy, in that many molecular changes influencing motor neuron degeneration occur at the neuromuscular junction (NMJ) at very early stages of the disease prior to symptom onset. A huge variety of genetic and environmental causes have been associated with ALS, and interestingly, although the cause of the disease can differ, both sporadic and familial forms of ALS show a remarkable similarity in terms of disease progression and clinical manifestation. The NMJ is a highly specialized synapse, allowing for controlled signaling between muscle and nerve necessary for skeletal muscle function. In this review we will evaluate the clinical, animal experimental and cellular/molecular evidence that supports the idea of ALS as a distal axonopathy. We will discuss the early molecular mechanisms that occur at the NMJ, which alter the functional abilities of the NMJ. Specifically, we focus on the role of axon guidance molecules on the stability of the cytoskeleton and how these molecules may directly influence the cells of the NMJ in a way that may initiate or facilitate the dismantling of the neuromuscular synapse in the presymptomatic stages of ALS. PMID:25177267

  18. Hepatitis B Virus Core Protein Phosphorylation Sites Affect Capsid Stability and Transient Exposure of the C-terminal Domain.

    PubMed

    Selzer, Lisa; Kant, Ravi; Wang, Joseph C-Y; Bothner, Brian; Zlotnick, Adam

    2015-11-20

    Hepatitis B virus core protein has 183 amino acids divided into an assembly domain and an arginine-rich C-terminal domain (CTD) that regulates essential functions including genome packaging, reverse transcription, and intracellular trafficking. Here, we investigated the CTD in empty hepatitis B virus (HBV) T=4 capsids. We examined wild-type core protein (Cp183-WT) and a mutant core protein (Cp183-EEE), in which three CTD serines are replaced with glutamate to mimic phosphorylated protein. We found that Cp183-WT capsids were less stable than Cp183-EEE capsids. When we tested CTD sensitivity to trypsin, we detected two different populations of CTDs differentiated by their rate of trypsin cleavage. Interestingly, CTDs from Cp183-EEE capsids exhibited a much slower rate of proteolytic cleavage when compared with CTDs of Cp183-WT capsids. Cryo-electron microscopy studies of trypsin-digested capsids show that CTDs at five-fold symmetry vertices are most protected. We hypothesize that electrostatic interactions between glutamates and arginines in Cp183-EEE, particularly at five-fold, increase capsid stability and reduce CTD exposure. Our studies show that quasi-equivalent CTDs exhibit different rates of exposure and thus might perform distinct functions during the hepatitis B virus lifecycle. Our results demonstrate a structural role for CTD phosphorylation and indicate crosstalk between CTDs within a capsid particle.

  19. A preliminary study of factors affecting the calibration stability of the iridium versus iridium-40 percent rhodium thermocouple

    NASA Technical Reports Server (NTRS)

    Ahmed, Shaffiq; Germain, Edward F.; Daryabeigi, Kamran; Alderfer, David W.; Wright, Robert E.

    1987-01-01

    An iridium versus iridium-40% rhodium thermocouple was studied. Problems associated with the use of this thermocouple for high temperature applications (up to 2000 C) were investigated. The metallurgical studies included X-ray, macroscopic, resistance, and metallographic studies. The thermocouples in the as-received condition from the manufacturer revealed large amounts of internal stress caused by cold working during manufacturing. The thermocouples also contained a large amount of inhomogeneities and segregations. No phase transformations were observed in the alloy up to 1100 C. It was found that annealing the thermocouple at 1800 C for two hours, and then at 1400 C for 2 to 3 hours yielded a fine grain structure, relieving some of the strains, and making the wire more ductile. It was also found that the above annealing procedure stabilized the thermal emf behavior of the thermocouple for application below 1800 C (an improvement from + or - 1% to + or - 0.02% within the range of the test parameters used).

  20. Storage Stability of Kinnow Fruit (Citrus reticulata) as Affected by CMC and Guar Gum-Based Silver Nanoparticle Coatings.

    PubMed

    Shah, Syed Wasim Ahmad; Jahangir, Muhammad; Qaisar, Muhammad; Khan, Sher Aslam; Mahmood, Talat; Saeed, Muhammad; Farid, Abid; Liaquat, Muhammad

    2015-12-18

    The influence of carboxy methyl cellulose (CMC) and guargum-based coatings containing silver nanoparticles was studied on the postharvest storage stability of the kinnow mandarin (Citrus reticulata cv. Blanco) for a period of 120 days (85%-90% relative humidity) at 4 °C and 10 °C. Physicochemical and microbiological qualities were monitored after every 15 days of storage. Overall results revealed an increase in total soluble solid (TSS), total sugars, reducing sugars and weight loss but this increase was comparatively less significant in coated fruits stored at 4 °C. Ascorbic acid, total phenolics, and antioxidant activity was significantly enhanced in coated fruits stored at 4 °C. Titratable acidity significantly decreased during storage except for coated kinnow stored at 4 °C. In control samples stored at 10 °C, high intensity of fruit rotting and no chilling injury was observed. Total aerobic psychrotrophic bacteria and yeast and molds were noticed in all treatments during storage but the growth was not significant in coated fruits at 4 °C. Kinnow fruit can be kept in good quality after coating for four months at 4 °C and for 2 months at 10 °C.

  1. A replacement of the active-site aspartic acid residue 293 in mouse cathepsin D affects its intracellular stability, processing and transport in HEK-293 cells.

    PubMed Central

    Partanen, Sanna; Storch, Stephan; Löffler, Hans-Gerhard; Hasilik, Andrej; Tyynelä, Jaana; Braulke, Thomas

    2003-01-01

    The substitution of an active-site aspartic acid residue by asparagine in the lysosomal protease cathepsin D (CTSD) results in a loss of enzyme activity and severe cerebrocortical atrophy in a novel form of neuronal ceroid lipofuscinosis in sheep [Tyynelä, Sohar, Sleat, Gin, Donnelly, Baumann, Haltia and Lobel (2000) EMBO J. 19, 2786-2792]. In the present study we have introduced the corresponding mutation by replacing aspartic acid residue 293 with asparagine (D293N) into the mouse CTSD cDNA to analyse its effect on synthesis, transport and stability in transfected HEK-293 cells. The complete inactivation of mutant D293N mouse CTSD was confirmed by a newly developed fluorimetric quantification system. Moreover, in the heterologous overexpression systems used, mutant D293N mouse CTSD was apparently unstable and proteolytically modified during early steps of the secretory pathway, resulting in a loss of mass by about 1 kDa. In the affected sheep, the endogenous mutant enzyme was stable but also showed the shift in its molecular mass. In HEK-293 cells, the transport of the mutant D293N mouse CTSD to the lysosome was delayed and associated with a low secretion rate compared with wild-type CTSD. These data suggest that the mutation may result in a conformational change which affects stability, processing and transport of the enzyme. PMID:12350228

  2. Deletion of a C-terminal intrinsically disordered region of WRINKLED1 affects its stability and enhances oil accumulation in Arabidopsis.

    PubMed

    Ma, Wei; Kong, Que; Grix, Michael; Mantyla, Jenny J; Yang, Yang; Benning, Christoph; Ohlrogge, John B

    2015-09-01

    WRINKLED1 (WRI1) is a key transcription factor governing plant oil biosynthesis. We characterized three intrinsically disordered regions (IDRs) in Arabidopsis WRI1, and found that one C-terminal IDR of AtWRI1 (IDR3) affects the stability of AtWRI1. Analysis by bimolecular fluorescence complementation and yeast-two-hybrid assays indicated that the IDR3 domain does not determine WRI1 stability by interacting with BTB/POZ-MATH proteins connecting AtWRI1 with CULLIN3-based E3 ligases. Analysis of the WRI1 sequence revealed that a putative PEST motif (proteolytic signal) is located at the C-terminal region of AtWRI1(IDR) (3). We also show that a 91 amino acid domain at the C-terminus of AtWRI1 without the PEST motif is sufficient for transactivation. We found that removal of the PEST motif or mutations in putative phosphorylation sites increased the stability of AtWRI1, and led to increased oil biosynthesis when these constructs were transiently expressed in tobacco leaves. Oil content was also increased in the seeds of stable transgenic wri1-1 plants expressing AtWRI1 with mutations in the IDR3-PEST motif. Taken together, our data suggest that intrinsic disorder of AtWRI1(IDR3) may facilitate exposure of the PEST motif to protein kinases. Thus, phosphorylation of the PEST motif in the AtWRI1(IDR) (3) domain may affect AtWRI1-mediated plant oil biosynthesis. The results obtained here suggest a means to increase accumulation of oils in plant tissues through WRI1 engineering.

  3. Exploring Slope with Stairs & Steps

    ERIC Educational Resources Information Center

    Smith, Toni M.; Seshaiyer, Padmanabhan; Peixoto, Nathalia; Suh, Jennifer M.; Bagshaw, Graham; Collins, Laurena K.

    2013-01-01

    As much as ever before, mathematics teachers are searching for ways to connect mathematics to real-life scenarios within STEM contexts. As students develop skill in proportional reasoning, they examine graphical representations of linear functions, learn to associate "slope" with "steepness" and rate of change, and develop…

  4. Experimentally increased temperature and hypoxia affect stability of social hierarchy and metabolism of the Amazonian cichlid Apistogramma agassizii.

    PubMed

    Kochhann, Daiani; Campos, Derek Felipe; Val, Adalberto Luis

    2015-12-01

    The primary goal of this study was to understand how changes in temperature and oxygen could influence social behaviour and aerobic metabolism of the Amazonian dwarf cichlid Apistogramma agassizii. Social hierarchies were established over a period of 96h by observing the social interactions, feeding behaviour and shelter use in groups of four males. In the experimental environment, temperature was increased to 29°C in the high-temperature treatment, and oxygen lowered to 1.0mg·L(-1)O2 in the hypoxia treatment. Fish were maintained at this condition for 96h. The control was maintained at 26°C and 6.6mg·L(-1)O2. After the experimental exposure, metabolism was measured as routine metabolic rate (RMR) and electron transport system (ETS) activity. There was a reduction in hierarchy stability at high-temperature. Aggression changed after environmental changes. Dominant and subdominant fish at high temperatures increased their biting, compared with control-dominant. In contrast, hypoxia-dominant fish decreased their aggressive acts compared with all other fish. Shelter use decreased in control and hypoxic dominant fish. Dominant fish from undisturbed environments eat more than their subordinates. There was a decrease of RMR in fish exposed to the hypoxic environment when compared with control or high-temperature fish, independent of social position. Control-dominant fish had higher RMR than their subordinates. ETS activity increased in fish exposed to high temperatures; however, there was no effect on social rank. Our study reinforces the importance of environmental changes for the maintenance of hierarchies and their characteristics and highlights that most of the changes occur in the dominant position.

  5. TSC2 N-terminal lysine acetylation status affects to its stability modulating mTORC1 signaling and autophagy.

    PubMed

    García-Aguilar, Ana; Guillén, Carlos; Nellist, Mark; Bartolomé, Alberto; Benito, Manuel

    2016-11-01

    There is a growing evidence of the role of protein acetylation in different processes controlling metabolism. Sirtuins (histone deacetylases nicotinamide adenine dinucleotide-dependent) activate autophagy playing a protective role in cell homeostasis. This study analyzes tuberous sclerosis complex (TSC2) lysine acetylation, in the regulation of mTORC1 signaling activation, autophagy and cell proliferation. Nicotinamide 5mM (a concentration commonly used to inhibit SIRT1), increased TSC2 acetylation in its N-terminal domain, and concomitantly with an augment in its ubiquitination protein status, leading to mTORC1 activation and cell proliferation. In contrast, resveratrol (RESV), an activator of sirtuins deacetylation activity, avoided TSC2 acetylation, inhibiting mTORC1 signaling and promoting autophagy. Moreover, TSC2 in its deacetylated state was prevented from ubiquitination. Using MEF Sirt1 +/+ and Sirt1 -/- cells or a SIRT1 inhibitor (EX527) in MIN6 cells, TSC2 was hyperacetylated and neither NAM nor RESV were capable to modulate mTORC1 signaling. Then, silencing Tsc2 in MIN6 or in MEF Tsc2-/- cells, the effects of SIRT1 modulation by NAM or RESV on mTORC1 signaling were abolished. We also observed that two TSC2 lysine mutants in its N-terminal domain, derived from TSC patients, differentially modulate mTORC1 signaling. TSC2 K599M variant presented a lower mTORC1 activity. However, with K106Q mutant, there was an activation of mTORC1 signaling at the basal state as well as in response to NAM. This study provides, for the first time, a relationship between TSC2 lysine acetylation status and its stability, representing a novel mechanism for regulating mTORC1 pathway.

  6. Evaluating factors affecting the permeability of emulsions used to stabilize radioactive contamination from a radiological dispersal device.

    PubMed

    Fox, Garey A; Medina, Victor F

    2005-05-15

    Present strategies for alleviating radioactive contamination from a radiological dispersal device (RDD) or dirty bomb involve either demolishing and removing radioactive surfaces or abandoning portions of the area near the release point. In both cases, it is imperative to eliminate or reduce migration of the radioisotopes until the cleanup is complete or until the radiation has decayed back to acceptable levels. This research investigated an alternative strategy of using emulsions to stabilize radioactive particulate contamination. Emergency response personnel would coat surfaces with emulsions consisting of asphalt or tall oil pitch to prevent migration of contamination. The site can then be evaluated and cleaned up as needed. In order for this approach to be effective, the treatment must eliminate migration of the radioactive agents in the terror device. Water application is an environmental condition that could promote migration into the external environment. This research investigated the potential for water, and correspondingly contaminant, migration through two emulsions consisting of Topein, a resinous byproduct during paper manufacture. Topein C is an asphaltic-based emulsion and Topein S is a tall oil pitch, nonionic emulsion. Experiments included water adsorption/ mobilization studies, filtration tests, and image analysis of photomicrographs from an environmental scanning electron microscope (ESEM) and a stereomicroscope. Both emulsions were effective at reducing water migration. Conductivity estimates were on the order of 10(-80) cm s(-1) for Topein C and 10(-7) cm s(-1) for Topein S. Water mobility depended on emulsion flocculation and coalescence time. Photomicrographs indicate that Topein S consisted of greater and more interconnected porosity. Dilute foams of isolated spherical gas cells formed when emulsions were applied to basic surfaces. Gas cells rose to the surface and ruptured, leaving void spaces that penetrated throughout the emulsion. These

  7. Landslide hazard assessment on the northern slopes of Fru\\vska Gora Mountain (Vojvodina, Serbia)

    NASA Astrophysics Data System (ADS)

    Mészáros, M.; Marković, S. B.; Mucsi, L.; Szatmári, J.; Pavić, D.

    2009-04-01

    Fru\\vska gora is a low (539 m) mountain surrounded by plains on the southern rim of the Pannonian Basin, situated between two large urban areas in Serbia and an important regional and local transport routes. The Danube flows along entire length of the northern and eastern side of the mountain (more than 80 km), permanently eroding the base of Quaternary sediments, causing slope instability. These mass movements often result in damages to railroad tracks, roads, infrastructure, and housing. Most of the northern slopes near Danube are affected by landslides, although many areas are considered temporarily stabilized after earlier movements. Uncontrolled building activities can be observed in some of these zones, increasing the risk of landslide reactivation. In this study we evaluate the potential mass movements hazard over a wider area of the mountain using the Stability Index Mapping (SINMAP)model. The model calibration was supported with terrain survey, high resolution aerial and stereo-satellite images interpretation. The primary input for the analysis is a Digital Elevation Model (DEM) obtained from a 1:25000 topographic map with previous landslide inventory and data describing local modifying factors such as geologic, vegetation, climatic, and soil cover data. As a result of the analysis, a map of landslide hazard zones was created, along with an updated landslide inventory of the Fru\\vska gora, providing overview of landslide risk distribution based on more objective methodology. The results of this large scale assessment highlight the locations of interest for planing smaller scale and more detailed examination.

  8. Shaking and Sliding: Timing, Magnitudes and Locations of Paleoearthquakes Revealed by Slope Instabilities in Lakes.

    NASA Astrophysics Data System (ADS)

    Strasser, M.; Anselmetti, F. S.; Bussmann, F.; Faeh, D.; Giardini, D.; Rick, B.; Stegmann, S.

    2006-12-01

    Quantitatively reconstructing the stability of submerged slopes that failed or resisted during earthquake shaking provides critical maximal and minimal seismic ground accelerations that affected the slopes at the time of failure. Furthermore, regional, temporal and spatial correlations of precisely-dated multiple subaquatic landslide deposits allow for reconstruction of chronology, magnitudes and epicenters of past earthquakes. Here we present results from two case studies assessing the stability of subaquatic slopes in Lake Lucerne (Central Switzerland) that failed during a historic (1601 AD) and during a prehistoric Late Holocene earthquake (~2250 cal yr. BP), respectively. The historically well-documented 1601 AD (M=6.2) earthquake triggered 13 synchronous subaquatic landslides in Lake Lucerne that generated a tsunami wave of up to 4 m height. The head areas of two landslides, one of 1601 AD and one of 2250 BP, were investigated using seismic subsurface imaging, in situ vane shear- and cone penetration testing, and sedimentological/petrophysical core analyses. Absolute in situ measured strength characteristics, implemented into numerical limit equilibrium slope stability models reveal that both slopes at the time were stable under static loading conditions with factors of safety between 1.5 and 2. An additional seismic acceleration of ~0.8 g and ~1.4 g for the historic and the prehistoric event, respectively, is required to trigger slope failure at the two studied sites. In order to reconstruct the magitudes and source locations of past earthquakes on a regional scale, the subsurface of Lake Zurich, which is at ~40 km distance from Lake Lucerne, was investigated. The goal was to find characteristic earthquake-triggered multiple landslide patterns that potentially could coincide with events recorded in Lake Lucerne. The results indicate that the historic 1601 AD event was not recorded in Lake Zurich (i.e. the earthquake was either not strong enough or to far away

  9. Seismic response of rock slopes: Numerical investigations on the role of internal structure

    NASA Astrophysics Data System (ADS)

    Arnold, L.; Applegate, K.; Gibson, M.; Wartman, J.; Adams, S.; Maclaughlin, M.; Smith, S.; Keefer, D. K.

    2013-12-01

    The stability of rock slopes is significantly influenced and often controlled by the internal structure of the slope created by such discontinuities as joints, shear zones, and faults. Under seismic conditions, these discontinuities influence both the resistance of a slope to failure and its response to dynamic loading. The dynamic response, which can be characterized by the slope's natural frequency and amplification of ground motion, governs the loading experienced by the slope in a seismic event and, therefore, influences the slope's stability. In support of the Network for Earthquake Engineering Simulation (NEES) project Seismically-Induced Rock Slope Failure: Mechanisms and Prediction (NEESROCK), we conducted a 2D numerical investigation using the discrete element method (DEM) coupled with simple discrete fracture networks (DFNs). The intact rock mass is simulated with a bonded assembly of discrete particles, commonly referred to as the bonded-particle model (BPM) for rock. Discontinuities in the BPM are formed by the insertion of smooth, unbonded contacts along specified planes. The influence of discontinuity spacing, orientation, and stiffness on slope natural frequency and amplification was investigated with the commercially available Particle Flow Code (PFC2D). Numerical results indicate that increased discontinuity spacing has a non-linear effect in decreasing the amplification and increasing the natural frequency of the slope. As discontinuity dip changes from sub-horizontal to sub-vertical, the slope's level of amplification increases while the natural frequency of the slope decreases. Increased joint stiffness decreases amplification and increases natural frequency. The results reveal that internal structure has a strong influence on rock slope dynamics that can significantly change the system's dynamic response and stability during seismic loading. Financial support for this research was provided by the United States National Science Foundation (NSF

  10. Mass movement slope streaks imaged by the Mars Orbiter Camera

    NASA Astrophysics Data System (ADS)

    Sullivan, Robert; Thomas, Peter; Veverka, Joseph; Malin, Michael; Edgett, Kenneth S.

    2001-10-01

    Narrow, fan-shaped dark streaks on steep Martian slopes were originally observed in Viking Orbiter images, but a definitive explanation was not possible because of resolution limitations. Pictures acquired by the Mars Orbiter Camera (MOC) aboard the Mars Global Surveyor (MGS) spacecraft show innumerable examples of dark slope streaks distributed widely, but not uniformly, across the brighter equatorial regions, as well as individual details of these features that were not visible in Viking Orbiter data. Dark slope streaks (as well as much rarer bright slope streaks) represent one of the most widespread and easily recognized styles of mass movement currently affecting the Martian surface. New dark streaks have formed since Viking and even during the MGS mission, confirming earlier suppositions that higher contrast dark streaks are younger, and fade (brighten) with time. The darkest slope streaks represent ~10% contrast with surrounding slope materials. No small outcrops supplying dark material (or bright material, for bright streaks) have been found at streak apexes. Digitate downslope ends indicate slope streak formation involves a ground-hugging flow subject to deflection by minor topographic obstacles. The model we favor explains most dark slope streaks as scars from dust avalanches following oversteepening of air fall deposits. This process is analogous to terrestrial avalanches of oversteepened dry, loose snow which produce shallow avalanche scars with similar morphologies. Low angles of internal friction typically 10-30¡ for terrestrial loess and clay materials suggest that mass movement of (low-cohesion) Martian dusty air fall is possible on a wide range of gradients. Martian gravity, presumed low density of the air fall deposits, and thin (unresolved by MOC) failed layer depths imply extremely low cohesive strength at time of failure, consistent with expectations for an air fall deposit of dust particles. As speed increases during a dust avalanche, a

  11. The British Geological Survey's 'Slope Dynamics' Project

    NASA Astrophysics Data System (ADS)

    Hobbs, Peter; Foster, Claire; Pearson, Stephen; Jones, Lee; Pennington, Catherine; Jenkins, Gareth; Gibson, Andrew; Cooper, Anthony; Freeborough, Katherine

    2010-05-01

    The aim of the British Geological Survey (BGS)'s ‘Slope Dynamics' project is to provide observational data to slope stability modelling and zoning based on factors of safety obtained from a combination of geotechnical, geomorphological and oceanographic models. The project has been monitoring since 2001 the progress of terrestrial and coastal landslides within 'soft rock' formations in the UK. Recently, field observatories have been set up to allow a variety of methods, some traditional and others novel, to be applied to actively unstable natural slopes in order to achieve a thorough understanding of the substrata, the mass movement processes within them and their relationship to the environment and environmental change. Monitoring has been carried out at six or twelve monthly intervals at test sites on the east coast of England (Holderness and Norfolk) and at Hollin Hill in North Yorkshire. A key part of the project makes use of innovative terrestrial LiDAR methods to produce repeated accurate 3-D models of the ground surface, which then enable ‘change models' of landslide movements to be determined. This work was started in 2001 and is continuing. The BGS currently has two Riegl terrestrial laser scanners: the long-range LPM-i800HA and the very-long-range LPM-2K; the former being equipped with a digital camera. The multiple scans are positioned in the national grid co-ordinate system using high resolution dGPS. Together, these allow accurate observations to be made in remote and exposed locations without the need for potentially dangerous direct access to the steeper more unstable slopes. The coastal test sites, which have exhibited recession rates of between 2m and 9m per year, allow rapid changes to be monitored. Inland active landslides are less common but more suited to instrumentation and long-term monitoring. Results to date have revealed the relationships between landslide style and geology, and also the patterns and time scales of characteristic

  12. Locking and unlocking of running wheel affects circadian period stability differently in three inbred strains of rats.

    PubMed

    Kohler, M; Wollnik, F

    1998-08-01

    Running-wheel access has been shown to shorten the circadian period length (tau) of various mammalian species. Due to the close correlation between tau and the level of activity, running wheel-induced changes of the activity level are thought to be responsible for the observed changes in tau. In the present study, the influence of the running wheel on tau and the activity level was examined in three inbred strains of rats (ACI, BH, LEW). Four animals of each strain had free access to their running wheels, while the wheels of the other 4 animals of each strain were mechanically locked. These conditions were changed twice, so that each animal encountered both kinds of changes, that is, from a locked to an unlocked running wheel and vice versa. During the whole study, overall activity was measured by infrared detectors. Running-wheel access resulted in a significant increase of overall activity in strains LEW and ACI. However, significant changes of tau were observed only in LEW rats. These rats showed a significant shortening of tau after the second change of the housing conditions regardless of whether the wheel was locked or unlocked. Consequently, no causal relationship was found between changes of tau and running wheel-induced changes of overall activity. Instead, the results suggest that subtle environmental influences like locking or unlocking the running wheel affect tau in a strain-dependent manner, whereas changes in the activity level are neither necessary nor sufficient to induce changes of tau.

  13. Factors affecting individual foraging specialization and temporal diet stability across the range of a large “generalist” apex predator

    USGS Publications Warehouse

    Rosenblatt, Adam E.; Nifong, James C.; Heithaus, Michael R.; Mazzotti, Frank J.; Cherkiss, Michael S.; Jeffery, Brian M.; Elsey, Ruth M.; Decker, Rachel A.; Silliman, Brian R.; Guillette, Louis J.; Lowers, Russell H.; Larson, Justin C.

    2015-01-01

    Individual niche specialization (INS) is increasingly recognized as an important component of ecological and evolutionary dynamics. However, most studies that have investigated INS have focused on the effects of niche width and inter- and intraspecific competition on INS in small-bodied species for short time periods, with less attention paid to INS in large-bodied reptilian predators and the effects of available prey types on INS. We investigated the prevalence, causes, and consequences of INS in foraging behaviors across different populations of American alligators (Alligator mississippiensis), the dominant aquatic apex predator across the southeast US, using stomach contents and stable isotopes. Gut contents revealed that, over the short term, although alligator populations occupied wide ranges of the INS spectrum, general patterns were apparent. Alligator populations inhabiting lakes exhibited lower INS than coastal populations, likely driven by variation in habitat type and available prey types. Stable isotopes revealed that over longer time spans alligators exhibited remarkably consistent use of variable mixtures of carbon pools (e.g., marine and freshwater food webs). We conclude that INS in large-bodied reptilian predator populations is likely affected by variation in available prey types and habitat heterogeneity, and that INS should be incorporated into management strategies to efficiently meet intended goals. Also, ecological models, which typically do not consider behavioral variability, should include INS to increase model realism and applicability.

  14. Low operational stability of enzymes in dry organic solvents: changes in the active site might affect catalysis.

    PubMed

    Bansal, Vibha; Delgado, Yamixa; Legault, Marc; Barletta, Gabriel

    2012-02-14

    The potential of enzyme catalysis in organic solvents for synthetic applications has been overshadowed by the fact that their catalytic properties are affected by organic solvents. In addition, it has recently been shown that an enzyme's initial activity diminishes considerably after prolonged exposure to organic media. Studies geared towards understanding this last drawback have yielded unclear results. In the present work we decided to use electron paramagnetic resonance spectroscopy (EPR) to study the motion of an active site spin label (a nitroxide free radical) during 96 h of exposure of the serine protease subtilisin Carlsberg to four different organic solvents. Our EPR data shows a typical two component spectra that was quantified by the ratio of the anisotropic and isotropic signals. The isotropic component, associated with a mobile nitroxide free radical, increases during prolonged exposure to all solvents used in the study. The maximum increase (of 43%) was observed in 1,4-dioxane. Based on these and previous studies we suggest that prolonged exposure of the enzyme to these solvents provokes a cascade of events that could induce substrates to adopt different binding conformations. This is the first EPR study of the motion of an active-site spin label during prolonged exposure of an enzyme to organic solvents ever reported.

  15. Centrifugal Modelling of Soil Structures. Part I. Centrifugal Modelling of Slope Failures.

    DTIC Science & Technology

    1979-03-01

    centrifugal loading in multiples of earth’s gravitational acceleration Nd number of equipotential drops in a flow net Nf number of flow channels in a... straight line from point A to point B. It is valid for laminar flow , where v - discharge velocity, k - coefficient of permeability, i - hydraulic gradient...number) Soil mechanics, embankmen’: stability, sloPe Stability, centrifuge modelling, clay slopes, mine waste slltpes, sea clay, landslides, flow slides

  16. Multiple slope failures shaped the lower continental slope offshore NW Svalbard in the Fram Strait

    NASA Astrophysics Data System (ADS)

    Osti, Giacomo; Mienert, Jürgen; Forwick, Matthias; Sverre Laberg, Jan

    2016-04-01

    Bathymetry data show that the lower slope (between 1300 m and 3000 m water depth) of the NW-Svalbard passive margin has been affected by multiple slope failure events. The single events differ in terms of extension, volume of mobilized sediments, morphology of the slide scar, run-out distance and age. As for several mega-scale and minor Arctic slides, the trigger mechanism is still speculative and may include high sedimentation rates, dissociation of gas hydrates, excess pore pressure, or earthquakes caused by isostatic rebound. In this study, we discuss the potential trigger mechanisms that have led to the multiple slope failure events within what we suggest to be named the Fram Strait Slide Complex. The slide complex lies in proximity to the tectonically active Spitsbergen Fracture Zone where earthquakes events, occurrences of potential weak layers in the sediment column, low sedimentation rates, and extended gas hydrate-bearing sediments may all have contributed to the causes leading to multiple slope failures. Preliminary results obtained from 14C dating on N. pachyderma sin. from sediment cores from the Spitsbergen Fracture Zone slides (SFZS 1 and 2), coupled with sub-bottom profiler data (frequency 9 to 15 KHz) show that the two shallowest glide planes within one of the observed slide scars failed ~100,000 and ~115,000 yr BP. Whilst SFZS 1 affected an area of 750 km2 mobilizing a total sediment volume of 40 km3, SFZS 2 moved an area of 230 km2 with a sediment volume of 4.5 km3.

  17. Slope Failure Prediction and Early Warning Awareness Education for Reducing Landslides Casualty in Malaysia

    NASA Astrophysics Data System (ADS)

    Koay, S. P.; Tay, L. T.; Fukuoka, H.; Koyama, T.; Sakai, N.; Jamaludin, S. B.; Lateh, H.

    2015-12-01

    Northeast monsoon causes heavy rain in east coast of Peninsular Malaysia from November to March, every year. During this monsoon period, besides the happening of flood along east coast, landslides also causes millions of Malaysian Ringgit economical losses. Hence, it is essential to study the prediction of slope failure to prevent the casualty of landslides happening. In our study, we introduce prediction method of the accumulated rainfall affecting the stability of the slope. If the curve, in the graph, which is presented by rainfall intensity versus accumulated rainfall, crosses over the critical line, the condition of the slope is considered in high risk where the data are calculated and sent from rain gauge in the site via internet. If the possibility of slope failure is going high, the alert message will be sent out to the authorities for decision making on road block or setting the warning light at the road side. Besides road block and warning light, we propose to disseminate short message, to pre-registered mobile phone user, to notify the public for easing the traffic jam and avoiding unnecessary public panic. Prediction is not enough to prevent the casualty. Early warning awareness of the public is very important to reduce the casualty of landslides happening. IT technology does not only play a main role in disseminating information, early warning awareness education, by using IT technology, should be conducted, in schools, to give early warning awareness on natural hazard since childhood. Knowing the pass history on landslides occurrence will gain experience on the landslides happening. Landslides historical events with coordinate information are stored in database. The public can browse these historical events via internet. By referring to such historical landslides events, the public may know where did landslides happen before and the possibility of slope failure occurrence again is considered high. Simulation of rainfall induced slope failure mechanism

  18. Slope orientation assessment for open-pit mines, using GIS-based algorithms

    NASA Astrophysics Data System (ADS)

    Grenon, Martin; Laflamme, Amélie-Julie

    2011-09-01

    Standard stability analysis in geomechanical rock slope engineering for open-pit mines relies on a simplified representation of slope geometry, which does not take full advantage of available topographical data in the early design stages of a mining project; consequently, this may lead to nonoptimal slope design. The primary objective of this paper is to present a methodology that allows for the rigorous determination of interramp and bench face slope orientations on a digital elevation model (DEM) of a designed open pit. Common GIS slope algorithms were tested to assess slope orientations on the DEM of the Meadowbank mining project's Portage pit. Planar regression algorithms based on principal component analysis provided the best results at both the interramp and the bench face levels. The optimal sampling window for interramp was 21×21 cells, while a 9×9-cell window was best at the bench level. Subsequent slope stability analysis relying on those assessed slope orientations would provide a more realistic geometry for potential slope instabilities in the design pit. The presented methodology is flexible, and can be adapted depending on a given mine's block sizes and pit geometry.

  19. Characterization of Unstable Rock Slopes Through Passive Seismic Measurements

    NASA Astrophysics Data System (ADS)

    Kleinbrod, U.; Burjanek, J.; Fäh, D.

    2014-12-01

    Catastrophic rock slope failures have high social impact, causing significant damage to infrastructure and many casualties throughout the world each year. Both detection and characterization of rock instabilities are therefore of key importance. An analysis of ambient vibrations of unstable rock slopes might be a new alternative to the already existing methods, e.g. geotechnical displacement measurements. Systematic measurements have been performed recently in Switzerland to study the seismic response of potential rockslides concerning a broad class of slope failure mechanisms and material conditions. Small aperture seismic arrays were deployed at sites of interest for a short period of time (several hours) in order to record ambient vibrations. Each measurement setup included a reference station, which was installed on a stable part close to the instability. Recorded ground motion is highly directional in the unstable parts of the rock slope, and significantly amplified with respect to stable areas. These effects are strongest at certain frequencies, which were identified as eigenfrequencies of the unstable rock mass. In most cases the directions of maximum amplification are perpendicular to open cracks and in good agreement with the deformation directions obtained by geodetic measurements. Such unique signatures might improve our understanding of slope structure and stability. Thus we link observed vibration characteristics with available results of detailed geological characterization. This is supported by numerical modeling of seismic wave propagation in fractured media with complex topography.For example, a potential relation between eigenfrequencies and unstable rock mass volume is investigated.

  20. Gravity-induced stresses in finite slopes

    USGS Publications Warehouse

    Savage, W.Z.

    1994-01-01

    An exact solution for gravity-induced stresses in finite elastic slopes is presented. This solution, which is applied for gravity-induced stresses in 15, 30, 45 and 90?? finite slopes, has application in pit-slope design, compares favorably with published finite element results for this problem and satisfies the conditions that shear and normal stresses vanish on the ground surface. The solution predicts that horizontal stresses are compressive along the top of the slopes (zero in the case of the 90?? slope) and tensile away from the bottom of the slopes, effects which are caused by downward movement and near-surface horizontal extension in front of the slope in response to gravity loading caused by the additional material associated with the finite slope. ?? 1994.

  1. Overland flow resistances on varying slope gradients and partitioning on grassed slopes under simulated rainfall

    NASA Astrophysics Data System (ADS)

    Pan, Chengzhong; Ma, Lan; Wainwright, John; Shangguan, Zhouping

    2016-04-01

    It is still unclear how slope steepness (S) and revegetation affect resistance (f) to overland flow. A series of experiments on runoff hydraulics was conducted on granular surfaces (bare soil and sandpaper) and grassed surfaces, including grass plots (GP), GP with litter (GL), and GP without leaves (GS) under simulated rainfall and inflow (30slopes ranging from 2.6% to 50%. The results show that the observed f based on a small-size runoff plot under rainfall conditions tends to be overestimated due to the increase in flow rate, or Re (Reynolds number), with downward cross sections and a good f-Re relation (f = KRe-1). There exists a good f-Re relation for granular surfaces and a good f-Fr relation (Fr, Froude number) for grass plots. A greater f occurred at the gentle and steep slopes for the granular surfaces, while f decreased with increasing slopes for the grass treatments. The different f-S relations suggest that f is not a simple function of S. When Re≈1000, the sowing rye grass with level lines increased f by approximately 100 times and decreased bed shear stress to approximately 5%. The contribution of grass leaves, stems, litter, and grain surface to total resistance in the grass plots were averagely 52%, 32%, 16%, and 1%. The greater resistance from leaves may result from the leaves lying at the plot surface impacted by raindrop impact. These results are beneficial to understand the dynamics of runoff and erosion on hillslopes impacted by vegetation restoration.

  2. Slope protection for artificial island

    SciTech Connect

    Czerniak, M.T.; Collins, J.I.; Shak, A.T.

    1981-08-01

    The technology under development to protect artificial-island production platforms from Arctic sea and ice damage involves three major considerations: (1) sea conditions during the ice-free season, (2) ice conditions during winter, and (3) construction constraints imposed by material availability, transportation problems, and length of the construction season. So far, researchers have evaluated 15 different slope-protection systems on the basis of reliability, construction-cost, and maintenance-cost factors, choosing 8 candidates for wave and ice model testing. The cases of interest involve exploration and production islands in shallow and deeper water applications.

  3. Beach Slopes of New Jersey

    USGS Publications Warehouse

    Doran, Kara; Long, Joseph W.; Birchler, Justin; Morgan, Karen L. M.

    2016-01-01

    The National Assessment of Coastal Change Hazards project derives features of beach morphology from lidar elevation data for the purpose of understanding and predicting storm impacts to our nation's coastlines. This dataset defines mean beach slopes along the United States Northeast Atlantic Ocean for New Jersey for data collected at various times between 2007 and 2014. For further information regarding data collection and/or processing methods refer to USGS Open-File Report 2015–1053 (http://pubs.usgs.gov/of/2015/1053/).

  4. Karstic slope "breathing": morpho-structural influence and hazard implications

    NASA Astrophysics Data System (ADS)

    Devoti, Roberto; Falcucci, Emanuela; Gori, Stefano; Eliana Poli, Maria; Zanferrari, Adriano; Braitenberg, Carla; Fabris, Paolo; Grillo, Barbara; Zuliani, David

    2016-04-01

    The study refers to the active slope deformation detected by GPS and tiltmeter stations in the Cansiglio karstic plateau located in the western Carnic Prealps (NE Italy). The observed transient deformation clearly correlates with the rainfall, so that the southernmost border of the Plateau reacts instantly to heavy rains displaying a "back and forth" deformation up to a few centimeters wide, with different time constants, demonstrating a response to different catchment volumes. We carried out a field survey along the southern Cansiglio slope, to achieve structural characterization of the relief and to verify the possible relation between structural features and the peculiar geomorphological setting dominated by widespread karstic features. The Cansiglio plateau develops on the frontal ramp anticline of the Cansiglio thrust, an about ENE-WSW trending, SSE-verging, low angle thrust, belonging to the Neogene-Quaternary front of the eastern Southern Alps. The Cansiglio thrust outcrops at the base of the Cansiglio plateau, where it overlaps the Mesozoic carbonates on the Miocene-Quaternary terrigenous succession. All along its length cataclastic limestone largely outcrop. The Cansiglio thrust is bordered by two transfer zones probably inherited from the Mesozoic paleogeography: the Caneva fault in the west and the Col Longone fault in the east. The carbonatic massif is also characterized by a series of about northward steeply dipping reverse minor faults and a set of subvertical joints parallel to the axes of the Cansiglio anticline. Other NNW-SSE and NNE-SSW conjugate faults and fractures perpendicular to the Cansiglio southern slope are also identified. This structural setting affect pervasively the whole slope and may determine centimetre- to metre-scale rock prisms. Interestingly, along the topmost portion of the slope, some dolines and swallow holes show an incipient coalescence, that trends parallel to the massif front and to the deformation zones related to the

  5. Interesting insights into instability of slopes and rock fall in the morphodynamic Himalayan terrane

    NASA Astrophysics Data System (ADS)

    Singh, T. N.; Vishal, V.; Pradhan, S. P.

    2015-12-01

    Himalayan mountain ranges are tectonically and seismically very active and experience many disastrous events with time due to slope failure. Frequent failures of rock cut slopes cause obstruction in traffic and often lead to fatalities. In recent years, the number of tragedies has increased when associated with regional phenomena such at the Kedarnath tragedy of 2013 and the Gorkha earthquake of 2015. The influence of such phenomena on the stability of slopes along important national highways and key settlement areas only raise the risk to lives and property. We conducted a multi-approach investigation for some key slopes along the National Highway 58 in Uttarakhand Himalaya, India. A very detailed field work was conducted to identify the unstable slopes and those with some history of failure. The pertinent geomechanical characteristics of the representative rock samples were determined in the laboratory. Based on the structural data, kinematic analysis was carried out. Finally the slopes were simulated using FDM based simulator, Flac/Slope for analysing the health of the slopes and Rockfall 4.0 to investigate the phenomenon of rockfall along the Highway. It was found that few slopes were weak due to the inherent weak rock materials while few slopes made up of high strength rocks were effectively weak due to prone-to-failure orientation of the joints. Quantification of bounce-height of rock blocks during fall, their energy, velocity and displacement along the slope was also done. Using 3-D simulations, few critically-stable slopes that appear to be stable, were identified. Little ground movement could be capable of triggering a large scale failure in the area. Slopes in the studied region are under threat to failure and need immediate proper planning using the suggested remedial measures.

  6. Transverse bed slope effects in an annular flume

    NASA Astrophysics Data System (ADS)

    Baar, Anne; Kleinhans, Maarten; de Smit, Jaco; Uijttewaal, Wim

    2016-04-01

    Large scale morphology, in particular bar dimensions and bifurcation dynamics, are greatly affected by the deflection of sediment transport on transverse bed slopes due to gravity and by helical flows. However, existing transverse bed slope predictors are based on a small set of experiments with a minor range of flow conditions and sediment sizes, and do not account for the presence of bedforms. In morphological modelling the deflection angle is therefore often calibrated on measured morphology. Our objective is to experimentally quantify the transverse slope effect for a large range of near-bed flow conditions and sediment sizes (0.17 - 4 mm) to test existing predictors, in order to improve morphological modelling of rivers and estuaries. We have conducted about 400 experiments in an annular flume, which functions as an infinitely long bended flume and therefore avoids boundary effects. Flow is generated by rotating the lid of the flume, while the intensity of the helical flow can be decreased by counterrotating the bottom of the flume. The equilibrium transverse slope that develops during the experiments is a balance between the transverse bed slope effect and the bed shear stress caused by the helical flow. We obtained sediment mobilities from no motion to sheet flow, ranging across bedload and suspended load. Resulting equilibrium transverse slopes show a clear trend with varying sediment mobilities and helical flow intensities that deviate from typical power relations with Shields number. As an end member we found transversely horizontal beds by counterrotation that partially cancelled the helical flow near the bed, which allows us to quantify helical flow. The large range in sediment mobilities caused different bed states from ripples and dunes to sheet flow that affect near-bed flow, which cause novel nonlinear relations between transverse slope and Shields number. In conclusion, our results show for a wide range of conditions and sediments that transverse

  7. North Atlantic slope and canyon study. Volume 2. Final report

    SciTech Connect

    Butman, B.

    1986-12-01

    A field program to investigate the currents and sediment transport along the outershelf and upper slope along the southern flank of Georges Bank was conducted between 1980 and 1984. A major part of the field experiment was conducted in Lydonia Canyon, a large submarine canyon which cuts northward about 20 km into the continental shelf from the shelfbreak. A smaller experiment was conducted in Oceanographer Canyon to compare the currents in these two major canyons. Long-term current observations were made at 20 locations in or adjacent to Lydonia Canyon, and at 9 stations on the continental slope. Detailed semi-synoptic hydrographic observations were made on 9 cruises. The currents associated with Gulf Stream warm core rings (WCR's) strongly affect the flow along the outer shelf and upper slope; eastward currents in excess of 75cm/s were associated with WCR's.

  8. Climate, soil texture, and soil types affect the contributions of fine-fraction-stabilized carbon to total soil organic carbon in different land uses across China.

    PubMed

    Cai, Andong; Feng, Wenting; Zhang, Wenju; Xu, Minggang

    2016-05-01

    Mineral-associated organic carbon (MOC), that is stabilized by fine soil particles (i.e., silt plus clay, <53 μm), is important for soil organic carbon (SOC) persistence and sequestration, due to its large contribution to total SOC (TSOC) and long turnover time. Our objectives were to investigate how climate, soil type, soil texture, and agricultural managements affect MOC contributions to TSOC in China. We created a dataset from 103 published papers, including 1106 data points pairing MOC and TSOC across three major land use types: cropland, grassland, and forest. Overall, the MOC/TSOC ratio ranged from 0.27 to 0.80 and varied significantly among soil groups in cropland, grassland, and forest. Croplands and forest exhibited significantly higher median MOC/TSOC ratios than in grassland. Moreover, forest and grassland soils in temperate regions had higher MOC/TSOC ratios than in subtropical regions. Furthermore, the MOC/TSOC ratio was much higher in ultisol, compared with the other soil types. Both the MOC content and MOC/TSOC ratio were positively correlated with the amount of fine fraction (silt plus clay) in soil, highlighting the importance of soil texture in stabilizing organic carbon across various climate zones. In cropland, different fertilization practices and land uses (e.g., upland, paddy, and upland-paddy rotation) significantly altered MOC/TSOC ratios, but not in cropping systems (e.g., mono- and double-cropping) characterized by climatic differences. This study demonstrates that the MOC/TSOC ratio is mainly driven by soil texture, soil types, and related climate and land uses, and thus the variations in MOC/TSOC ratios should be taken into account when quantitatively estimating soil C sequestration potential of silt plus clay particles on a large scale.

  9. A hazard and risk classification system for catastrophic rock slope failures in Norway

    NASA Astrophysics Data System (ADS)

    Hermanns, R.; Oppikofer, T.; Anda, E.; Blikra, L. H.; Böhme, M.; Bunkholt, H.; Dahle, H.; Devoli, G.; Eikenæs, O.; Fischer, L.; Harbitz, C. B.; Jaboyedoff, M.; Loew, S.; Yugsi Molina, F. X.

    2012-04-01

    outburst floods. It became obvious that large rock slope failures cannot be evaluated on a slope scale with frequency analyses of historical and prehistorical events only, as multiple rockslides have occurred within one century on a single slope that prior to the recent failures had been inactive for several thousand years. In addition, a systematic analysis on temporal distribution indicates that rockslide activity following deglaciation after the Last Glacial Maximum has been much higher than throughout the Holocene. Therefore the classification system has to be based primarily on the geological conditions on the deforming slope and on the deformation rates and only to a lesser weight on a frequency analyses. Our hazard classification therefore is primarily based on several criteria: 1) Development of the back-scarp, 2) development of the lateral release surfaces, 3) development of the potential basal sliding surface, 4) morphologic expression of the basal sliding surface, 5) kinematic feasibility tests for different displacement mechanisms, 6) landslide displacement rates, 7) change of displacement rates (acceleration), 8) increase of rockfall activity on the unstable rock slope, 9) Presence post-glacial events of similar size along the affected slope and its vicinity. For each of these criteria several conditions are possible to choose from (e.g. different velocity classes for the displacement rate criterion). A score is assigned to each condition and the sum of all scores gives the total susceptibility score. Since many of these observations are somewhat uncertain, the classification system is organized in a decision tree where probabilities can be assigned to each condition. All possibilities in the decision tree are computed and the individual probabilities giving the same total score are summed. Basic statistics show the minimum and maximum total scores of a scenario, as well as the mean and modal value. The final output is a cumulative frequency distribution of

  10. Item Strength Influences Source Confidence and Alters Source Memory zROC Slopes

    ERIC Educational Resources Information Center

    Starns, Jeffrey J.; Ksander, John C.

    2016-01-01

    Increasing the number of study trials creates a crossover pattern in source memory zROC slopes; that is, the slope is either below or above 1 depending on which source receives stronger learning. This pattern can be produced if additional learning affects memory processes such as the relative contribution of recollection and familiarity to source…

  11. An Examination of Slope Stability Computation Procedures for Sudden Drawdown.

    DTIC Science & Technology

    1987-09-01

    materials the 41 41 .i following LaPlace equation is the governing equation which must be solved: a2 h a2h -2 0 2.26 ax ay Cedergren (1948) appears to have...a direction perpendicular to the phreatic surface (obtained from the new flow net), Cedergren estimated the amount of water which would have flowed... Cedergren , but employed the finite element, rather than graphical (flow net) procedures to solve the LaPlace equation (Eq. 2.26). Although procedures

  12. Spectral slope and Kolmogorov constant of MHD turbulence.

    PubMed

    Beresnyak, A

    2011-02-18

    The spectral slope of strong MHD turbulence has recently been a matter of controversy. While the Goldreich-Sridhar model predicts a -5/3 slope, shallower slopes have been observed in numerics. We argue that earlier numerics were affected by driving due to a diffuse locality of energy transfer. Our highest-resolution simulation (3072(2)×1024) exhibited the asymptotic -5/3 scaling. We also discover that the dynamic alignment, proposed in models with -3/2 slope, saturates and cannot modify the asymptotic, high Reynolds number slope. From the observed -5/3 scaling we measure the Kolmogorov constant C(KA)=3.27±0.07 for Alfvénic turbulence and C(K)=4.2±0.2 for full MHD turbulence, which is higher than the hydrodynamic value of 1.64. This larger C(K) indicates inefficient energy transfer in MHD turbulence, which is in agreement with diffuse locality.

  13. A model for predicting embankment slope failures in clay-rich soils; A Louisiana example

    NASA Astrophysics Data System (ADS)

    Burns, S. F.

    2015-12-01

    A model for predicting embankment slope failures in clay-rich soils; A Louisiana example It is well known that smectite-rich soils significantly reduce the stability of slopes. The question is how much smectite in the soil causes slope failures. A study of over 100 sites in north and south Louisiana, USA, compared slopes that failed during a major El Nino winter (heavy rainfall) in 1982-1983 to similar slopes that did not fail. Soils in the slopes were tested for per cent clay, liquid limits, plasticity indices and semi-quantitative clay mineralogy. Slopes with the High Risk for failure (85-90% chance of failure in 8-15 years after construction) contained soils with a liquid limit > 54%, a plasticity index over 29%, and clay contents > 47%. Slopes with an Intermediate Risk (55-50% chance of failure in 8-15 years) contained soils with a liquid limit between 36-54%, plasticity index between 16-19%, and clay content between 32-47%. Slopes with a Low Risk chance of failure (< 5% chance of failure in 8-15 years after construction) contained soils with a liquid limit < 36%, a plasticity index < 16%, and a clay content < 32%. These data show that if one is constructing embankments and one wants to prevent slope failure of the 3:1 slopes, check the above soil characteristics before construction. If the soils fall into the Low Risk classification, construct the embankment normally. If the soils fall into the High Risk classification, one will need to use lime stabilization or heat treatments to prevent failures. Soils in the Intermediate Risk class will have to be evaluated on a case by case basis.

  14. Effects of basin bottom slope on jet hydrodynamics and river mouth bar formation

    NASA Astrophysics Data System (ADS)

    Jiménez-Robles, A. M.; Ortega-Sánchez, M.; Losada, M. A.

    2016-06-01

    River mouth bars are strategic morphological units primarily responsible for the development of entire deltaic systems. This paper addresses the role of receiving basin slope in the hydrodynamics of an exiting sediment-laden turbulent jet and in resulting mouth bar morphodynamics. We use Delft3D, a coupled hydrodynamic and morphodynamic numerical model, along with a theoretical formulation to reproduce the physics of the problem, characterized by a fluvially dominated inlet free of waves and tides. We propose an updated theoretical model with a slope-dependent entrainment coefficient, showing that the rate at which ambient fluid is incorporated into a jet increases with higher basin slopes. Transient results reveal that the magnitude of a basin slope can alter the stability of a jet, favoring the formation of an unstable meandering jet. While a stable jet gives rise to "middle-ground" bars accompanied by diverging channels, a "lunate" mouth bar results from unstable jets. Additional morphodynamic simulations demonstrate that the time required for mouth bar stagnation in its final position increases linearly with the basin slope. In contrast, the distance at which the mouth bar eventually forms decreases until reaching an asymptotic value for slopes higher than 2%. Moreover, the basin slope highly influences sedimentary processes responsible for bar formation: for milder slopes, progradation processes prevail, while in steeper basins aggradation is more relevant. Finally, the minimum relative water depth over a bar crest that forces the flow to bifurcate around a fully developed bar decreases with the basin slope.

  15. Parameters affecting the stability of the digestate from a two-stage anaerobic process treating the organic fraction of municipal solid waste.

    PubMed

    Trzcinski, Antoine P; Stuckey, David C

    2011-07-01

    This paper focused on the factors affecting the respiration rate of the digestate taken from a continuous anaerobic two-stage process treating the organic fraction of municipal solid waste (OFMSW). The process involved a hydrolytic reactor (HR) that produced a leachate fed to a submerged anaerobic membrane bioreactor (SAMBR). It was found that a volatile solids (VS) removal in the range 40-75% and an operating temperature in the HR between 21 and 35 °C resulted in digestates with similar respiration rates, with all digestates requiring 17 days of aeration before satisfying the British Standard Institution stability threshold of 16 mg CO(2) g VS(-1) day(-1). Sanitization of the digestate at 65 °C for 7 days allowed a mature digestate to be obtained. At 4 g VS L(-1) d(-1) and Solid Retention Times (SRT) greater than 70 days, all the digestates emitted CO(2) at a rate lower than 25 mg CO(2) g VS(-1) d(-1) after 3 days of aeration, while at SRT lower than 20 days all the digestates displayed a respiration rate greater than 25 mg CO(2) g VS(-1) d(-1). The compliance criteria for Class I digestate set by the European Commission (EC) and British Standard Institution (BSI) could not be met because of nickel and chromium contamination, which was probably due to attrition of the stainless steel stirrer in the HR.

  16. Langley Full-scale-tunnel Investigation of the Factors Affecting the Static Lateral-stability Characteristics of a Typical Fighter-type Airplane

    NASA Technical Reports Server (NTRS)

    Lange, Roy H

    1947-01-01

    The factors that affect the rate of change of rolling moment with yaw of a typical fighter-type airplane were investigated in the Langley full-scale tunnel on a typical fighter-type airplane.Eight representative flight conditions were investigated in detail. The separate effects of propeller operation, of the wing-fuselage combination, and of the vertical tail to the effective dihedral of the airplane in each condition were determined. The results of the tests showed that for the airplane with the propeller removed, the wing-fuselage combination had positive dihedral effect which increased considerably with increasing angle of attack for all conditions. Flap deflection decreased the dihedral effect of the wing-fuselage combination slightly as compared with that with the flaps retracted. Flap deflection resulted in negative dihedral effect due to the vertical tail. Propeller operation decreased the lateral stability parameter of the airplane for all the conditions investigated with larger decreases being measured for the flaps deflected conditions.

  17. The genetic background affects composition, oxidative stability and quality traits of Iberian dry-cured hams: purebred Iberian versus reciprocal Iberian × Duroc crossbred pigs.

    PubMed

    Fuentes, Verónica; Ventanas, Sonia; Ventanas, Jesús; Estévez, Mario

    2014-02-01

    This study examined the physico-chemical characteristics, oxidative stability and sensory properties of Iberian cry-cured hams as affected by the genetic background of the pigs: purebred Iberian (PBI) pigs vs reciprocal cross-bred Iberian × Duroc pigs (IB × D pigs: Iberian dams × Duroc sires; D × IB pigs: Duroc dams × Iberian sires). Samples from PBI pigs contained significantly higher amounts of IMF, monounsaturated fatty acids, heme pigments and iron than those from crossbred pigs. The extent of lipid and protein oxidation was significantly larger in dry-cured hams of crossbred pigs than in those from PBI pigs. Dry-cured hams from PBI pigs were defined by positive sensory properties (i.e. redness, brightness and juiciness) while hams from crossbred pigs were ascribed to negative ones (i.e. hardness, bitterness and sourness). Hams from PBI pigs displayed a superior quality than those from crossbred pigs. The position of the dam or the sire in reciprocal Iberian × Duroc crosses had no effect on the quality of Iberian hams.

  18. Geomorphological control on variably saturated hillslope hydrology and slope instability

    USGS Publications Warehouse

    Giuseppe, Formetta; Simoni, Silvia; Godt, Jonathan W.; Lu, Ning; Rigon, Riccardo

    2016-01-01

    In steep topography, the processes governing variably saturated subsurface hydrologic response and the interparticle stresses leading to shallow landslide initiation are physically linked. However, these processes are usually analyzed separately. Here, we take a combined approach, simultaneously analyzing the influence of topography on both hillslope hydrology and the effective stress fields within the hillslope itself. Clearly, runoff and saturated groundwater flow are dominated by gravity and, ultimately, by topography. Less clear is how landscape morphology influences flows in the vadose zone, where transient fluxes are usually taken to be vertical. We aim to assess and quantify the impact of topography on both saturated and unsaturated hillslope hydrology and its effects on shallow slope stability. Three real hillslope morphologies (concave, convex, and planar) are analyzed using a 3-D, physically based, distributed model coupled with a module for computation of the probability of failure, based on the infinite slope assumption. The results of the analyses, which included parameter uncertainty analysis of the results themselves, show that convex and planar slopes are more stable than concave slopes. Specifically, under the same initial, boundary, and infiltration conditions, the percentage of unstable areas ranges from 1.3% for the planar hillslope, 21% for convex, to a maximum value of 33% for the concave morphology. The results are supported by a sensitivity analysis carried out to examine the effect of initial conditions and rainfall intensity.

  19. Large slope instabilities in Northern Chile and Southern Peru

    NASA Astrophysics Data System (ADS)

    Crosta, Giovanni B.; Hermanns, Reginald L.; Valbuzzi, Elena; Frattini, Paolo; Valagussa, Andrea

    2014-05-01

    Deep canyon incision into Tertiary paleosurfaces and large slope instabilities along the canyon flanks characterize the landscape of western slope of the Andes of northern Chile and South Peru. This area belongs to the Coastal Escarpment and Precordillera and is formed by coarse-grained clastic and volcanoclastic formations. The area is characterized by intense seismicity and long-term hyperaridity (Atacama Desert). Landslides along the canyon flanks affect volumes generally up to 1 km3 and locally evolved in large rock avalanches. We prepared a landslide inventory covering an area of about 30,000 km2, extending from Iquique (Chile) to the South and Tacna (Peru) to the North. A total of 606 landslides have been mapped in the area by use of satellite images and direct field surveys, prevalently including large phenomena. The landslides range from 1 10-3 km2 to 464 km2 (Lluta landslide). The total landslide area, inclusive of the landslide scarp and of the deposit, amounts to about 2,130 km2 (about 7% of the area). The mega landslides can be classified as large block slides that can evolve in large rock avalanches (e.g. Minimini landslide). Their initiation seems to be strongly associated to the presence of secondary faults and large fractures transversal to the slope. These landslides show evidence suggesting a re-incision by the main canyon network. This seems particularly true for the Lluta collapse where the main 'landslide' mass is masked or deleted by the successive erosion. Other landslides have been mapped along the Coastal Escarpment and some of the major tectonic escarpments with an E-W trend. We examined area-frequency distributions of landslides by developing logarithmically binned, non-cumulative size frequency distributions that report frequency density as a function of landslide planar area A. The size frequency distribution presents a strong undersampling for smaller landslides, due to the extremely old age of the inventory. For landslides larger than

  20. The stability and the hydrological behavior of biological soil crusts is significantly affected by the complex nature of their polysaccharidic matrix

    NASA Astrophysics Data System (ADS)

    De Philippis, Roberto

    2015-04-01

    colloidal fraction of the EPSs, which is more dispersed in the soil, is more easily degradable by the microflora residing in the crusts, while the EPS fraction tightly bound to the soil particles, which is characterized by a high molecular weight, plays a key role in giving a structural stability to the BSCs and in affecting the hydrological behavior of the soil covered by the crusts.

  1. Negative P-T slopes characterize phase change processes: Case of the Ge1Sb2Te4 phase change alloy

    NASA Astrophysics Data System (ADS)

    Kalkan, B.; Sen, S.; Aitken, B. G.; Raju, S. V.; Clark, S. M.

    2011-07-01

    The crystalline, liquid and amorphous phase stabilities and transformations of the Ge1Sb2Te4 (GST124) alloy are investigated as a function of pressure and temperature using synchrotron diffraction experiments in a diamond anvil cell. The results indicate that the solid-state amorphization of the cubic GST124 phase under high pressure may correspond to a metastable extension of the stability field of the GST124 liquid along a hexagonal crystal-liquid phase boundary with a negative P-T slope. The internal pressures generated during phase change are shown to be too small to affect phase stability. However, they may be important in understanding reliability issues related to thermomechanical stress development in phase change random access memory structures.

  2. Unsteady Katabatic Winds on Mountain Slopes

    NASA Astrophysics Data System (ADS)

    Fernando, H. J. S.; Princevac, M.; Hunt, J. C. R.

    2003-04-01

    UNSTEADY KATABATIC WINDS ON MOUNTAIN SLOPES H.J.S. Fernando (1), M. Princevac (1) and J.C.R. Hunt (2) (1) Arizona State University, Tempe, (2) University College, London j.fernando@asu.edu Theoretical and field studies were carried out on velocity and temperature fields of an unsteady nighttime atmospheric boundary layer on sloping surfaces. Field data were collected during the Vertical Transport and Mixing Experiment (VTMX) conducted in the Salt Lake basin, Utah. Nighttime data from two slope sites, with measurements taken using six tethersonde systems and three sonic anemometers placed at a various representative locations along the slope, were used in the analysis. This analysis concerned simple katabatic flows as well as the interaction between (evening) down-slope flows on lower (elevation) gentle slopes and those originating at adjoining higher (elevation) steep mountain slopes. Katabatic winds that form on the steep slope overrun those on the lower slope, thus dominating the micrometeorology at the bottom of the valley. Yet, the flow and temperature on higher slopes are independent of those in the lower valley, given that katabatic flows on steeper slopes are generally supercritical and do not transmit flow information upstream. By employing assumptions on the flow structure and using parameterizations for pertinent processes, an expression was derived for the layer-averaged katabatic flow velocity. Using energy arguments to calculate the growth rate of the katabatic-layer thickness, a new expression for the flow depth was derived. Extensive comparisons between theoretical results and field observations were made, allowing cross-fertilization between theoretical developments, eduction of flow physics and interpretation of field data. Unsteady effects pertinent to katabatic flows were also considered, following Fleagle’s approach, and it is shown theoretically and using observations that the down-slope flow pulsates with a period inversely proportional to

  3. Percent Agricultural Land Cover on Steep Slopes

    EPA Pesticide Factsheets

    Clearing land for agriculture tends to increase soil erosion. The amount of erosion is related to the steepness of the slope, farming methods used and soil type. High amounts of agriculture on steep slopes can increase the amount of soil erosion leading to increased sediment in surface water. Agricultural land cover on steep slopes (AGSL) is the percent of agriculture on slopes greater than or equal to 9%. More information about these resources, including the variables used in this study, may be found here: https://edg.epa.gov/data/Public/ORD/NERL/ReVA/ReVA_Data.zip.

  4. Water related triggering mechanisms of shallow landslides: Numerical modelling of hydraulic flows in slopes verified with field experiments

    NASA Astrophysics Data System (ADS)

    Broennimann, C.; Tacher, L.

    2009-04-01

    To assess hill slope stability and landslide triggering mechanisms, it is essential to understand the hydrogeological regime in slopes. In this work finite element models are elaborated and field experiments are carried out to study particularly shallow landslides with thickness of a few meters. The basis hypothesis of the presented research assumes that even for shallow landslides the hydrogeological role of the substratum, mostly bedrock, is determinant for the slopes behaviour, either it is draining or feeding the overlaying unstable mass. The investigated area of about 1 square kilometre is situated next to the villages Buchberg and Rüdlingen (canton Schaffhausen, Switzerland) at the border of the river Rhine. The lithology in this region is characterized mainly by horizontally layered sandstones intersected by marls from the upper seawater and the lower freshwater molasse, overlaid by soil and weathered bedrock of about 1 to 4 m thickness, both classified as silty sands. With a slope inclination of locally up to 40° the area is rather steep and characterized by continuous regressive erosion processes. During heavy rainfall events, such as the one from May 2002, shallow landslides occurred in the area affecting afforested soils as well as woodless areas. Geological field observations, infiltration and tracer tests show a fairly complicated hydrogeological character of the region. Along the slope, in the first few meters of depth, no groundwater table was found. However, seasonally controlled sources can be observed in-between outcropping bedrock. Within the sandstone, vertical faults in decametre scale oriented parallel to the Rhine that most likely opened during decompression due to the cutting of the river affect locally the hydrogeological regime by draining the slope. This implies a high grade of heterogeneity in the water flows in a local scale. Based on these conceptual hydrological and geological models, a numerical flow model was obtained using finite

  5. Limited proteolysis differentially modulates the stability and subcellular localization of domains of RPGRIP1 that are distinctly affected by mutations in Leber's congenital amaurosis.

    PubMed

    Lu, Xinrong; Guruju, Mallikarjuna; Oswald, John; Ferreira, Paulo A

    2005-05-15

    The retinitis pigmentosa GTPase regulator (RPGR) protein interacts with the retinitis pigmentosa GTPase regulator interacting protein-1 (RPGRIP1). Genetic lesions in the cognate genes lead to distinct and severe human retinal dystrophies. The biological role of these proteins in retinal function and pathogenesis of retinal diseases is elusive. Here, we present the first physiological assay of the role of RPGRIP1 and mutations therein. We found that the monoallelic and homozygous mutations, DeltaE1279 and D1114G, in the RPGR-interacting domain (RID) of RPGRIP1, enhance and abolish, respectively, its interaction in vivo with RPGR without affecting the stability of RID. In contrast to RID(WT) and RID(D1114G), chemical genetics shows that the interaction of RID(DeltaE1279) with RPGR is resistant to various stress treatments such as osmotic, pH and heat-shock stimuli. Hence, RID(D1114G) and RID(DeltaE1279) constitute loss- and gain-of-function mutations. Moreover, we find that the isoforms, bRPGRIP1 and bRPGRIP1b, undergo limited proteolysis constitutively in vivo in the cytoplasm compartment. This leads to the relocation and accumulation of a small and stable N-terminal domain of approximately 7 kDa to the nucleus, whereas the cytosolic C-terminal domain of RPGRIP1 is degraded and short-lived. The RID(D1114G) and RID(DeltaE1279) mutations exhibit strong cis-acting and antagonistic biological effects on the nuclear relocation, subcellular distribution and proteolytic cleavage of RPGRIP1 and/or domains thereof. These data support distinct and spatiotemporal subcellular-specific roles to RPGRIP1. A novel RPGRIP1-mediated nucleocytoplasmic crosstalk and transport pathway regulated by RID, and hence by RPGR, emerges with implications in the molecular pathogenesis of retinopathies, and a model to other diseases.

  6. Parameters affecting the stability of the digestate from a two-stage anaerobic process treating the organic fraction of municipal solid waste

    SciTech Connect

    Trzcinski, Antoine P.; Stuckey, David C.

    2011-07-15

    This paper focused on the factors affecting the respiration rate of the digestate taken from a continuous anaerobic two-stage process treating the organic fraction of municipal solid waste (OFMSW). The process involved a hydrolytic reactor (HR) that produced a leachate fed to a submerged anaerobic membrane bioreactor (SAMBR). It was found that a volatile solids (VS) removal in the range 40-75% and an operating temperature in the HR between 21 and 35 {sup o}C resulted in digestates with similar respiration rates, with all digestates requiring 17 days of aeration before satisfying the British Standard Institution stability threshold of 16 mg CO{sub 2} g VS{sup -1} day{sup -1}. Sanitization of the digestate at 65 {sup o}C for 7 days allowed a mature digestate to be obtained. At 4 g VS L{sup -1} d{sup -1} and Solid Retention Times (SRT) greater than 70 days, all the digestates emitted CO{sub 2} at a rate lower than 25 mg CO{sub 2} g VS{sup -1} d{sup -1} after 3 days of aeration, while at SRT lower than 20 days all the digestates displayed a respiration rate greater than 25 mg CO{sub 2} g VS{sup -1} d{sup -1}. The compliance criteria for Class I digestate set by the European Commission (EC) and British Standard Institution (BSI) could not be met because of nickel and chromium contamination, which was probably due to attrition of the stainless steel stirrer in the HR.

  7. What is the slope of the U.S. continental slope?

    SciTech Connect

    Pratson, L.F.; Haxby, W.F.

    1996-01-01

    Extensive high-resolution, multibeam bathymetry of five U. S. continental margins provides new, detailed information about the angle of continental slopes in different sedimentary and tectonic settings. The steepest continental slope examined is the passive-carbonate west Florida slope (4.4{degree} regional slope and 12.0{degree} mean local slope). The steepest of the four clastic continental slopes is the passive New Jersy-Maryland slope (2.5{degree} and 7.6{degree}). Less steep, at both regional and local scales, are the more rugged, tectonically active and probably unstable salt-tectonized louisiana slope (0.5{degree} and 2.9{degree}), strike-slip California slope (1.8{degree} and 5.2{degree}) and convergent oregon slope (2.0{degree} and 5.2{degree}). Frequency grids of local slope magnitude vs. depth and dip direction for the two passive continental slopes reflect present-day morphology predominantly being shaped by lithology (West Florida), sedimentation (New Jersey-Maryland), and downslope-directed erosion(New Jersey-Maryland, west Florida). The grids for the three tectonically acctive continental slopes reflect morphology partly (California) to predominantly (Louisiana, Oregon) being shaped by tectonics. 15 refs., 2 figs.

  8. Modelling long term damage in rock slopes and impact of deglaciation

    NASA Astrophysics Data System (ADS)

    Amitrano, D.; Lacroix, P.

    2014-12-01

    Long-term observations of large active rockslides show accelerating deformation over many thousands of years since the last deglaciation. The effect of deglaciation on slope stability is however poorly understood due to (1) limited long-term observations and (2) a complex interaction between glacier retreat and hydrogeological, mechanical, and morphological processes. To assess the sensitivity of rockslide dynamics to these different processes, a model of progressive damage through intact rock mass is developed in this study, based on the finite element method. This model uses time-to-failure laws based on rock laboratory creep experiments. It is able to reproduce progressive damage localization along shear bands associated with strain rate acceleration as observed during tertiary creep. The model reproduces the different phases of deformation associated with morphologies typical of large rockslides. This model is thus suitable for simulating the dynamics of large rockslides and the transition from initiation to rapid sliding. The sensitivity of rockslide kinematics and morphology to different mechanical properties is analyzed. This analysis shows that the time evolution of the rockslide can be inferred with the knowledge of only one time parameter, independent of the knowledge of the mechanical properties of the rock mass. This parameter is here chosen as the time when the summit slope displacement has reached 10 m, a parameter that can be estimated with cosmogenic dating. The model is then used to study the effects of deglaciation on the valley flank stability and the formation of large rockslides. This study shows that the deglaciation velocity can affect the morphology of the rockslide, with the shear band of the rockslide emerging at higher elevation as the velocity decreases.We also show that the response to the deglaciation can last several thousands of years after the glacier retreat.

  9. Influence of cartilage and menisci on the sagittal slope of the tibial plateaus.

    PubMed

    Cinotti, Gianluca; Sessa, Pasquale; Ragusa, Giovanni; Ripani, Francesca Romana; Postacchini, Roberto; Masciangelo, Raffaele; Giannicola, Giuseppe

    2013-10-01

    We analyzed the magnetic resonance studies of the knee in 80 subjects, 45 men and 35 women with a mean age of 38.9 years, who showed no pathological condition of the joint. Using an imaging visualization software, the sagittal longitudinal axis of the tibia was identified. The angle between this axis and a line tangent to the bone profile of the tibial plateau (bone slope) and to the superior border of the menisci (meniscal slope) were calculated. Thickness of anterior and posterior portion of menisci and underlying cartilage were also measured. The bone slope averaged 8° and 7.7° on the medial and lateral sides, respectively. The mean meniscal slope was 4.1° and 3.3° on the medial and lateral sides, respectively, with a significant difference compared with the bone slope. Menisci and underlying cartilage were significantly thicker in their posterior than their anterior portion (7.6 and 5.2 mm, respectively, in the medial compartment; 8.6 and 5.2 mm, respectively, in the lateral compartment). The presence of cartilage and menisci implies a significant decrease in the posterior tibial slope. In the lateral compartment, the greater the bone slope, the larger the difference between bone and meniscal slope, which means that a marked posterior tilt of the lateral tibial plateau is decreased by the cartilage and meniscus. These findings should be taken into account in planning surgical procedures which affect the slope of the articular tibial surface.

  10. Regional landslide-hazard evaluation using landslide slopes, Western Wasatch County, Utah

    USGS Publications Warehouse

    Hylland, M.D.; Lowe, Mark

    1997-01-01

    Landsliding has historically been one of the most damaging geologic hazards in western Wasatch County, Utah. Accordingly, we mapped and analyzed landslides (slumps and debris slides) in the area to provide an empirical basis for regional landslide-hazard evaluation. The 336 landslides in the 250-sq-mi (650-km2) area involve 20 geologic units, including Mississippian- to Quaternary-aged rock and unconsolidated deposits. Landsliding in western Wasatch County is characterized by a strong correlation between geologic material and landslide-slope inclination. From a simple statistical analysis of overall slope inclinations of late Holocene landslides, we determined "critical" slope inclinations above which late Holocene landsliding has typically occurred and used these as the primary basis for defining relative landslide hazard. The critical slopes vary for individual geologic units and range from 15 to 50 percent (9??-27??). The critical slope values and landslide locations were used in conjunction with geologic and slope maps to construct qualitative landslide-susceptibility maps for use by county planners. The maps delineate areas of low, moderate, and high relative hazard and indicate where studies should be completed prior to development to evaluate site-specific slope-stability conditions. Critical slopes as determined in this study provide a consistent empirical reference that is useful for evaluating relative landslide hazard and guiding land-use-planning decisions in large, geologically complex areas.

  11. Recent sedimentation on the new jersey slope and rise.

    PubMed

    Stanley, D J; Nelsen, T A; Stuckenrath, R

    1984-10-12

    Radiocarbon dating and sedimentological studies of closely spaced cores indicate movement during the Holocene of sediments on the New Jersey continental slope and upper rise between Wilmington and Lindenkohl canyons. The uneven time-stratigraphic thickness of the late Quaternary sediment sections between cores and the nonuniform deposition rate at any given core site and among core sites show that the sediment blanket in canyon and intercanyon areas has been affected by downslope, gravity-driven pocesses during the Holocene to the present. The reduced rate of deposition on the slope and upper rise between the late Pleistocene and the present is largely due to decreased off-shelf transport in response to the eustatic rise in sea level. Very old radiocarbon dates at core tops result from emplacement of older reworked materials from upslope or from truncation of sections by mass wasting processes exposing older material at the sea floor. These processes also account for an irregular sequence of dated sections within cores and stratigraphic irregularities of the surficial cover from core to core. Marked variability in deposition rates on the slope and upper rise is largely a function of topographic configuration, proximity and accessibility to sediment source, and transport processes seaward of the shelf break. Moreover, higher accumulation rates on the upper rise are attributed primarily to slope bypassing. Bypassing, prevalent during the late Pleistocene, has continued periodically to the present.

  12. Rockfall risk assessment for a road along the coastal rocky slope of Maratea (Basilicata Region, Italy)

    NASA Astrophysics Data System (ADS)

    Pellicani, R.; Spilotro, G.; Colangelo, G.; Petraglia, A.; Pizzo, V.

    2012-04-01

    The rockfall risk has been evaluated for the Tirrena Inferiore State Road SS18 between 220+600 and 243+670 Kilometers in the coastal area of Maratea (Basilicata, Italy) through a specific multilayer technique. These results are particularly significant as validated in field through the occurrence of rockfall events after the study. The study part of "Tirrena Inferiore" SS18 road is often affected by rockfalls, which periodically (coinciding with abundant rainfalls, earthquakes and temperature lowering) cause large amount of damage and traffic interruptions. In order to assess the rockfall risk and define the countermeasure needed to mitigate the risk, an integrated index-based and physically-based approach was implemented. The roadway is subject to slopes with steep rocky vertical or sub-vertical faces affected by different systems of discontinuities, that show a widespread fracturing. The superficial parts of slopes are characterized by gaping fracturing, often karstified. Several historical rockfall events were recognized in the area and numerous geomechanical analyses, finalized to the stability analysis of rock walls, were carried out. The localization of the potentially unstable areas and the quantification of relative rockfall risk were evaluated through three successive phases of analysis. First, a map based on SMR (Slope Mass Rating) Index of Romana (1985) was produced, through a spatial analysis of both geomechanical parameters, such as the RMR Index of Bieniawski, and the distribution of the discontinuities. This approach therefore allowed the estimation of the potentially unstable zones and their classification on the basis of the resulting stability degree. Subsequently, an analysis of the rockfall trajectories in correspondence to the most unstable zones of slope was carried out by using ROTOMAP, a 3-dimensional rock-fall simulation software. The input data for computing the rockfall trajectories are the following: (1) digital terrain model (DTM), (2

  13. 27 CFR 9.192 - Wahluke Slope.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Wahluke Slope. 9.192... Wahluke Slope. (a) Name. The name of the viticultural area described in this section is “Wahluke Slope”. For purposes of part 4 of this chapter, “Wahluke Slope” and “Wahluke” are terms of...

  14. 27 CFR 9.192 - Wahluke Slope.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Wahluke Slope. 9.192... Wahluke Slope. (a) Name. The name of the viticultural area described in this section is “Wahluke Slope”. For purposes of part 4 of this chapter, “Wahluke Slope” and “Wahluke” are terms of...

  15. The Slope Test: Applications in Formative Evaluation.

    ERIC Educational Resources Information Center

    Baggaley, Jon; Brauer, Aaron-Henry

    1989-01-01

    Discusses problems with formative evaluation of educational materials and examines the slope test when used in a pretest/posttest multiple group (PPMG) design to adjust posttest scores treatment interaction studies. An example is given of the utility of the slope test and analysis of covariance procedure using an educational film about AIDS. (five…

  16. Local and regional slope instability inferred from sea-floor morphology at accretive and erosive convergent margins: case studies of the offshore Hikurangi and Peru fore-arcs

    NASA Astrophysics Data System (ADS)

    Kukowski, N.; Greinert, J.; Hoth, S.; Henrys, S.

    2009-04-01

    The mechanics of a forearc, a wedge-shaped part of the overriding plate between the trench and the volcanic arc, are elegantly and in a straightforward way described in terms of the critical taper concept. Based on the Mohr-Coulomb failure criterion and applying an elasto-plastic rheology, it describes the state (sub-critical, stable, super-critical) of any point of the wedge as a function of its geometry (slope and dip), basal and internal friction as well as basal and internal fluid pressure parameter. Subduction erosion or the subduction of seamounts and other lower plate topographic features such as basement ridges lead to temporarily increasing surface slope and therefore may facilitate mechanical instability. Here we study the causes of local and regional failure at the central Hikurangi wedge offshore New Zealand's North Island and along the Peruvian margin. The geometry of both margins is well known from seismic studies and swath bathymetry coverage and therefore allows to quantify local slope gradients and other curvature attributes. New high-resolution swath bathymetry data show a complex seafloor morphology from the Rock Garden area, offshore Hikurangi Margin, that coincides with the subduction of a seamount presently located beneath the summit of Rock Garden. Another ridge-shaped lower plate feature is initially colliding with Rock Garden, forming a re-entrant at is seaward flank. The slopes of the accretionary ridges are steeper than 10∘ and often more than 20∘ regionally. Slumping mostly occurs on the trench-ward slopes, with individual failures up to several km2. Critical taper analysis shows that much of the seaward slopes probably are outside the stability field and therefore subject to failure. The most prominent feature of seafloor maps is the trench-ward flank of Rock Garden with a height of 1800 to 2000 m and an average slope of more than 10∘. Extensional faults arranged in two sub-circular arcs indicate that Rock Garden may be on the

  17. [Effects of slope gradient on slope runoff and sediment yield under different single rainfall conditions].

    PubMed

    He, Ji-Jun; Cai, Qiang-Guo; Liu, Song-Bo

    2012-05-01

    Based on the field observation data of runoff and sediment yield produced by single rainfall events in runoff plots, this paper analyzed the variation patterns of runoff and sediment yield on the slopes with different gradients under different single rainfall conditions. The differences in the rainfall conditions had little effects on the variation patterns of slope runoff with the gradient. Under the conditions of six different rainfall events in the study area, the variation patterns of slope runoff with the gradient were basically the same, i. e., the runoff increased with increasing gradient, but the increment of the runoff decreased slightly with increasing gradient, which was mainly determined by the infiltration flux of atmospheric precipitation. Rainfall condition played an important role on the slope sediment yield. Generally, there existed a critical slope gradient for slope erosion, but the critical gradient was not a fixed value, which varied with rainfall condition. The critical slope gradient for slope erosion increased with increasing slope gradient. When the critical slope gradient was greater, the variation of slope sediment yield with slope gradient always became larger.

  18. A slippery directional slope: Individual differences in using slope as a directional cue.

    PubMed

    Weisberg, Steven M; Newcombe, Nora S

    2014-05-01

    Navigators rely on many different types of cues to build representations of large-scale spaces. Sloped terrain is an important cue that has received recent attention in comparative and human spatial research. However, the studies to date have been unable to determine how directional slope information leads to more accurate spatial representations. Moreover, whereas some studies have shown that the inclusion of slope cues improves performance on spatial tasks across participants (Kelly, 2011; Restat, Steck, Mochnatzki, & Mallot, 2004), other research has suggested individual differences in the benefits of slope cues (Chai & Jacobs, 2010; Nardi, Newcombe, & Shipley, 2011). We sought to clarify the role of sloped terrain in improving the representation of large-scale environments. In Experiment 1, participants learned the layout of buildings in one of two desktop virtual environments: either a directionally sloped terrain or a completely flat one. Participants in the sloped environment outperformed those in the flat environment. However, participants used slope information as an additional cue, rather than as a preferred reference direction. In Experiment 2, the two virtual environments were again either flat or sloped, but we increased the complexity of the relations between the slope and the path. In this experiment, better performance in the sloped environment was only seen for participants with good self-reported senses of direction. Taken together, the studies show that slope provides useful information for building environmental representations in simple cases, but that individual differences emerge in more complex situations. We suggest that good and bad navigators use different navigational strategies.

  19. Liquid marbles stabilized by charged polymer latexes: how does the drying of the latex particles affect the properties of liquid marbles?

    PubMed

    Sun, Guanqing; Sheng, Yifeng; Wu, Jie; Ma, Guanghui; Ngai, To

    2014-10-28

    The coating of solid particles on the surface of liquid in air makes liquid marbles a promising approach in the transportation of a small amount of liquid. The stabilization of liquid marbles by polymeric latex particles imparts extra triggers such as pH and temperature, leading to the remote manipulation of droplets for many potential applications. Because the functionalized polymeric latexes can exist either as colloidally stable latex or as flocculated latex in a dispersion, the drying of latex dispersions under different conditions may play a significant role in the stabilization of subsequent liquid marbles. This article presents the investigation of liquid marbles stabilized by poly(styrene-co-methacrylic acid) (PS-co-MAA) particles drying under varied conditions. Protonation of the particles before freeze drying makes the particles excellent liquid marble stabilizers, but it is hard to stabilize liquid marbles for particles dried in their deprotonated states. The static properties of liquid marbles with increasing concentrations of protonating reagent revealed that the liquid marbles are gradually undermined by protonating the stabilizers. Furthermore, the liquid marbles stabilized by different particles showed distinct behaviors in separation and merging manipulated by tweezers. This study shows that the initial state of the particles should be carefully taken into account in formulating liquid marbles.

  20. The effects of oppositely sloping boundaries with Ekman dissipation in a nonlinear baroclinic system

    NASA Technical Reports Server (NTRS)

    Weng, H.-Y.

    1990-01-01

    The present analytical and numerical examination of the effect of the slope Delta with dissipation delta on baroclinic flows in linear and nonlinear systems uses a modified Eady channel model with oppositely sloping top and bottom Ekman layers, and truncates the spectral wave solution up to six components. Comparisons are made wherever possible with results from beta-plane dissipative systems. In the linear system, the combined effect of Delta and delta strongly stabilizes long waves. In a nonlinear system without wave-wave interaction, Delta stabilizes the flow even for small delta and reduces the domain of vacillation while enlarging the domain of single-wave steady state.

  1. The two-component system CpxR/A represses the expression of Salmonella virulence genes by affecting the stability of the transcriptional regulator HilD

    PubMed Central

    De la Cruz, Miguel A.; Pérez-Morales, Deyanira; Palacios, Irene J.; Fernández-Mora, Marcos; Calva, Edmundo; Bustamante, Víctor H.

    2015-01-01

    Salmonella enterica can cause intestinal or systemic infections in humans and animals mainly by the presence of pathogenicity islands SPI-1 and SPI-2, containing 39 and 44 genes, respectively. The AraC-like regulator HilD positively controls the expression of the SPI-1 genes, as well as many other Salmonella virulence genes including those located in SPI-2. A previous report indicates that the two-component system CpxR/A regulates the SPI-1 genes: the absence of the sensor kinase CpxA, but not the absence of its cognate response regulator CpxR, reduces their expression. The presence and absence of cell envelope stress activates kinase and phosphatase activities of CpxA, respectively, which in turn controls the level of phosphorylated CpxR (CpxR-P). In this work, we further define the mechanism for the CpxR/A-mediated regulation of SPI-1 genes. The negative effect exerted by the absence of CpxA on the expression of SPI-1 genes was counteracted by the absence of CpxR or by the absence of the two enzymes, AckA and Pta, which render acetyl-phosphate that phosphorylates CpxR. Furthermore, overexpression of the lipoprotein NlpE, which activates CpxA kinase activity on CpxR, or overexpression of CpxR, repressed the expression of SPI-1 genes. Thus, our results provide several lines of evidence strongly supporting that the absence of CpxA leads to the phosphorylation of CpxR via the AckA/Pta enzymes, which represses both the SPI-1 and SPI-2 genes. Additionally, we show that in the absence of the Lon protease, which degrades HilD, the CpxR-P-mediated repression of the SPI-1 genes is mostly lost; moreover, we demonstrate that CpxR-P negatively affects the stability of HilD and thus decreases the expression of HilD-target genes, such as hilD itself and hilA, located in SPI-1. Our data further expand the insight on the different regulatory pathways for gene expression involving CpxR/A and on the complex regulatory network governing virulence in Salmonella. PMID:26300871

  2. Spatial Variability of Snowpack Fracture Propagation Propensity at the Slope Scale

    NASA Astrophysics Data System (ADS)

    Hoyer, I.; Hendrikx, J.; Birkeland, K.; Irvine, K. M.

    2013-12-01

    Understanding the spatial variability of fracture propagation is very important for avalanche forecasting, assessing the representativeness of point stability tests, and for working towards a fuller understanding of avalanche processes. There has been a significant amount of prior research examining the spatial variability of snow stability at the slope scale. However, most earlier research focused on measurements associated with fracture initiation. As both fracture initiation and propagation are necessary ingredients for an avalanche, an investigation of the spatial variability of fracture propagation is important to an understanding of spatial snow stability. The small body of previous work examining the spatial variability of fracture propagation has shown inconsistent results, with early studies related to testing the Extended Column Test (ECT) showing very homogenous results, while later studies showed more heterogeneous results. The ECT is used in this study to measure the fracture propagation potential of the snowpack for a range of weak layer types. On each slope we conducted 28 ECTs in a structured grid with a 30m by 30m extent. The slopes sampled were wind sheltered clearings, below treeline, with uniform slope and aspect, across southwest Montana. We tested slopes with a variety of weak layers (surface hoar, depth hoar, new snow, and near surface facets), a variety of slab characteristics (slab harness, slab depth), and varying levels of forecasted stability. Our data shows that on many slopes there is considerable spatial variability in fracture propagation potential. There was often significant variability in fracture propagation even without substantial variation in snowpack structure. Weak layer type was found not to be a controlling factor in the level of spatial variability; for any given weak layer type some slopes had very variable fracture propagation while others had quite homogenous results.

  3. Alaskan North Slope petroleum systems

    USGS Publications Warehouse

    Magoon, L.B.; Lillis, P.G.; Bird, K.J.; Lampe, C.; Peters, K.E.

    2003-01-01

    Six North Slope petroleum systems are identified, described, and mapped using oil-to-oil and oil-to-source rock correlations, pods of active source rock, and overburden rock packages. To map these systems, we assumed that: a) petroleum source rocks contain 3.2 wt. % organic carbon (TOC); b) immature oil-prone source rocks have hydrogen indices (HI) >300 (mg HC/gm TOC); c) the top and bottom of the petroleum (oil plus gas) window occur at vitrinite reflectance values of 0.6 and 1.0% Ro, respectively; and d) most hydrocarbons are expelled within the petroleum window. The six petroleum systems we have identified and mapped are: a) a southern system involving the Kuna-Lisburne source rock unit that was active during the Late Jurassic and Early Cretaceous; b) two western systems involving source rock in the Kingak-Blankenship, and GRZ-lower Torok source rock units that were active during the Albian; and c) three eastern systems involving the Shublik-Otuk, Hue Shale and Canning source rock units that were active during the Cenozoic. The GRZ-lower Torok in the west is correlative with the Hue Shale to the east. Four overburden rock packages controlled the time of expulsion and gross geometry of migration paths: a) a southern package of Early Cretaceous and older rocks structurally-thickened by early Brooks Range thrusting; b) a western package of Early Cretaceous rocks that filled the western part of the foreland basin; c) an eastern package of Late Cretaceous and Paleogene rocks that filled the eastern part of the foreland basin; and d) an offshore deltaic package of Neogene rocks deposited by the Colville, Canning, and Mackenzie rivers. This petroleum system poster is part of a series of Northern Alaska posters on modeling. The poster in this session by Saltus and Bird present gridded maps for the greater Northern Alaskan onshore and offshore that are used in the 3D modeling poster by Lampe and others. Posters on source rock units are by Keller and Bird as well as

  4. Far-field stress changes and progressive rock slope instability resulting from fluvial incision at the axis of a major Alpine valley

    NASA Astrophysics Data System (ADS)

    Leith, Kerry; Moore, Jeffrey R.; Loew, Simon; Krautblatter, Michael

    2014-05-01

    Geomorphic processes alter both the form and near-surface structure of alpine rock slopes. These processes drive progressive changes in the magnitude of shear, normal, and tensile stresses, and where in situ stresses exceed intact or rock mass failure envelopes, can lead to local rock mass destabilization. Such destabilization is most commonly attributed to 'debuttressing' causing a loss of support from adjacent bodies, or a reduction in effective rock mass strength as critical planes of weakness are 'undercut' by erosional processes. Where stress changes are lower in magnitude, progressive rock slope failure is often attributed to a shift in near-critical stresses toward the brittle failure envelope, allowing local stress concentrations to propagate existing fractures or weaken existing joints. We model the development of long-term in situ stresses within an alpine valley affected by ongoing tectonic and erosional processes. We allow for the mechanical effects of long-term bedrock strength limits, and analyze the magnitude of far-field stress changes associated with 100 m of fluvial incision at the axis of a 3000 m wide, 2500 m deep alpine valley. Our model configuration mirrors the erosional history of the Matter Valley (southern Swiss Alps) at the location of the 30 x 106 m3 Randa rock slope failure. We find that incision focuses stresses at the valley floor, reducing stress magnitudes throughout the remainder of the landscape. This effect is particularly strong near the valley shoulder, where decreases in shear stress are approximately half those of normal stresses. Although the magnitude of changes are relatively low (10's to 100's of kPa), we find incision may have had a negative impact on the stability of rock slopes over 1000 m from the valley axis, perhaps initiating progressive failure of the Randa rock slope. This proposition is supported by the presence of glacial striations within large tension cracks above the Randa rock slope failure. These formed

  5. Recent slope mobilizations in the Storegga Slide area

    NASA Astrophysics Data System (ADS)

    Berndt, C.; Crutchley, G.; Karstens, J.; Dumke, I.; Duennbier, K.

    2012-12-01

    With ~3500 km3 of mobilized material the Storegga Slide off mid-Norway is one of the largest known sub-marine slope failures. It occurred approximately 8150 years ago and there is strong evidence suggesting that the slide caused a large tsunami that propagated through the North Atlantic and affected the coasts of Norway, Iceland and the U.K. In the Nyegga area along the northern side wall of the slide numerous shallow faults exist. These faults detach within the top 100 m below the sea floor at various stratigraphic levels below, at, and above the main slide plain of the Storegga Slide. Previous studies proposed that these faults are evidence for partial slope movements during the Storegga Slide event indicating that the adjacent slopes were deformed due to the stress variations caused by the Storegga Slide. New high-resolution Parasound data that we have collected in May 2012 onboard RV Meteor show offsets of reflectors that are buried less than 3 m below the sea floor. Assuming that the sedimentation rates derived from a near-by Marion Dufresne sediment core, can be extrapolated to the study area, these reflector offsets suggest that the faults are younger than the Storegga Slide. Given a several million year-long history of repeated slope failures in the area it is important to obtain more precise dates for the activity of the faults in order to assess if these faults can be used as an indicator for future slope failures in the area or if they are the result of small-scale adjustments of the head wall topography in the wake of the Storegga Slide.

  6. Significance of the actual nonlinear slope geometry for catastrophic failure in submarine landslides.

    PubMed

    Puzrin, Alexander M; Gray, Thomas E; Hill, Andrew J

    2015-03-08

    A simple approach to slope stability analysis of naturally occurring, mild nonlinear slopes is proposed through extension of shear band propagation (SBP) theory. An initial weak zone appears in the steepest part of the slope where the combined action of gravity and seismic loads overcomes the degraded peak shear resistance of the soil. If the length of this steepest part is larger than the critical length, the shear band will propagate into the quasi-stable parts of the slope, where the gravitational and seismically induced shear stresses are smaller than the peak but larger than the residual shear strength of the soil. Growth of a shear band is strongly dependent on the shape of the slope, seismic parameters and the strength of soil and less dependent on the slope inclination and the sensitivity of clay. For the slope surface with faster changing inclination, the criterion is more sensitive to the changes of the parameters. Accounting for the actual nonlinear slope geometry eliminates the main challenge of the SBP approach-determination of the length of the initial weak zone, because the slope geometry can be readily obtained from submarine site investigations. It also helps to identify conditions for the early arrest of the shear band, before failure in the sliding layer or a change in loading or excess pore water pressures occurs. The difference in the size of a landslide predicted by limiting equilibrium and SBP approaches can reach orders of magnitude, potentially providing an explanation for the immense dimensions of many observed submarine landslides that may be caused by local factors acting over a limited portion of the slope.

  7. Ecohydrological Implications of Contrasting Slope and Aspect in Complex Terrain

    NASA Astrophysics Data System (ADS)

    Seyfried, M. S.; Link, T. E.; Klos, P. Z.; Patton, N. R.; Lohse, K. A.

    2014-12-01

    Understanding how complex terrain affects ecohydrological processes is increasingly important as we attempt to understand how water and carbon fluxes are integrated across relatively large domains. Spatial variations of incoming solar radiation are well understood and quantified, but the understanding their impacts on ecohydrologic processes is primarily qualitative. We provide detailed, extensive data quantifying the effects of contrasting slope/aspect on the soil physical environment and document the implications of those differences on ecohydrological processes. The study site, Johnston Draw, is located in the Reynolds Creek Experimental Watershed and CZO in southwest Idaho, USA (43° latitude). Johnston Draw flows over granitic bedrock nearly due east, resulting in steep (25 to 40°) side slopes oriented north-south. At the study elevation (1600 m) approximately 50% of the annual precipitation is snow. We measured meteorological variables, snow depth, soil water (SW) and temperature (ST) at three paired locations for two years. Each soil pair consisted of depth profiles from 5 cm to bedrock measured hourly which were supplemented with periodic extensive measurements. Hourly photographs were taken at two of the pairs for one year. Streamflow is monitored at the Johnston Draw outlet and precipitation was measured at stations at the topographic bottom and top of the watershed. Geophysical data were collected in a transect across both slopes. The ST was warmer all year on the south-facing slope, with a mean annual difference of 5°C. This ST difference is effectively equivalent to a 1000 m elevation difference in Reynolds Creek. Despite clear differences in evaporative demand and the timing of spring "green up", the timing of summer SW decline is similar on both slopes. Deeper soil on north-facing slopes resulted in more plant available water and a longer growing season, which is reflected in the vegetation. Geophysical data indicate much deeper weathering on the

  8. SLOPE PROFILOMETRY OF GRAZING INCIDENCE OPTICS.

    SciTech Connect

    TAKACS,P.Z.

    2003-01-14

    Profiling instruments are well-suited to the measurement of grazing incidence optics, such as those found in synchrotron radiation beam lines. Slope measuring profilers, based upon the principle of the pencil beam interferometer, have proven to be especially useful in measuring the figure and slope errors on cylindrical aspheres. The Long Trace Profiler, in various configurations, is the most widely used of this class of profiler. Current performance provides slope measurement accuracy at the microradian level and height measurements accurate to 25 nm over 1 meter trace lengths.

  9. [Community structure of soil fauna in Eucalyptus grandis plantations at different slope locations].

    PubMed

    Zhao, Yu; Zhong, Yu; Zhang, Jian; Yang, Wan-qin

    2010-09-01

    To understand the effects of slope location on the community structure of soil fauna in Eucalyptus grandis plantation, an investigation was made on the soil fauna in 3 E. grandis plantations at different slope locations in the hilly area of Sichuan Province from January to October 2009. A total of 39,2762 individuals were observed, belonging to 146 groups, 7 phyla, 16 classes, and 31 orders. The community composition, trophic group, diversity, and seasonal dynamics of soil fauna in the plantations all varied with slope. The abundance of macro-fauna, xeric meso- and micro-fauna, saprophagous macro-fauna, and omnivorous xeric meso- and micro-fauna increased with the decrease of slope, indicating that soil fauna had sensitive responses to the soil environmental factors affected by slope. Significant differences in the diversity of soil saprophagous macro-fauna and hygrophilous meso- and micro-fauna were observed at different slope locations, suggesting that these two faunal groups could be used as the indicators of the habitat heterogeneity of E. grandis plantations at different slope. Overall, slope location had definite effects on the community structure and distribution of soil fauna in the E. grandis plantations, but the effects were not statistically significant.

  10. Slope restoration for a 100-year old canal

    SciTech Connect

    Skaggs, R.L.; Lewis, S.W.; Liebersbach, D.C.

    1995-12-31

    Turlock Irrigation District (TID) is located in the northern portion of the fertile San Joaquin Valley of California. TID`s primary water supply is conveyed from the 100-year-old LaGrange Diversion Dam via their historic Upper Main Canal. The original canal was constructed by excavating into slate bedrock for the uphill (cut) bank, and constructing unmortared rock walls and rock fill for the downhill (fill) embankment; the excavation was then lined with concrete. Soil fill raises of the downhill embankment over the last 30 years have reduced the slope stability to unacceptable levels in the steepest embankment areas. In March of 1994, two surficial slides prompted investigation of the long term embankment stability in the Warehouse Slide Area. Based on results of analysis for various stabilization scenarios, TID chose a stabilization method which included: (1) excavation of an access bench below the existing canal, (2) installation of steel pipe piles through the existing rock fill and into the bedrock, (3) construction of a mechanically stabilized earth (MSE) retaining wall and (4) construction of a soil-cement canal roadway pavement. The design was chosen by the owner because of cost competitiveness compared to other design alternatives and because the construction sequence allowed uninterrupted use of the canal. By using local river cobble for the MSE wall facing material, TID met the desired 50-year design life of the repair while maintaining the area`s historic visual features.

  11. 30 CFR 77.1911 - Ventilation of slopes and shafts.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Ventilation of slopes and shafts. 77.1911... COAL MINES Slope and Shaft Sinking § 77.1911 Ventilation of slopes and shafts. (a) All slopes and... be examined before each shift and the quantity of air in the slope or shaft measured daily by...

  12. 30 CFR 77.1911 - Ventilation of slopes and shafts.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Ventilation of slopes and shafts. 77.1911... COAL MINES Slope and Shaft Sinking § 77.1911 Ventilation of slopes and shafts. (a) All slopes and... be examined before each shift and the quantity of air in the slope or shaft measured daily by...

  13. Slope activity in Gale crater, Mars

    USGS Publications Warehouse

    Dundas, Colin M.; McEwen, Alfred S.

    2015-01-01

    High-resolution repeat imaging of Aeolis Mons, the central mound in Gale crater, reveals active slope processes within tens of kilometers of the Curiosity rover. At one location near the base of northeastern Aeolis Mons, dozens of transient narrow lineae were observed, resembling features (Recurring Slope Lineae) that are potentially due to liquid water. However, the lineae faded and have not recurred in subsequent Mars years. Other small-scale slope activity is common, but has different spatial and temporal characteristics. We have not identified confirmed RSL, which Rummel et al. (Rummel, J.D. et al. [2014]. Astrobiology 14, 887–968) recommended be treated as potential special regions for planetary protection. Repeat images acquired as Curiosity approaches the base of Aeolis Mons could detect changes due to active slope processes, which could enable the rover to examine recently exposed material.

  14. The critical slope for orographic rain

    NASA Astrophysics Data System (ADS)

    Breidenthal, Robert; Zagar, Nedjeljka

    2013-11-01

    Krishnamurti has shown that orographic rain depends on the slope of the windward terrain rather than just the total elevation gain. A simple physical model is proposed to account for the effect of slope. Based on the inhibiting effect of vortex (rotational) acceleration on entrainment, a critical slope angle is derived. If the rate of orographic lifting is sufficiently large, the enhanced buoyancy from latent heat release increases the acceleration parameter. As a consequence, the entrainment rate of under-saturated air is reduced. The critical slope corresponds to the situation where the rate of condensation in a rising adiabatic parcel just equals the rate of evaporation due to the entrainment of under-saturated air. The model is also applied to the trigger conditions for towering cumulus in general.

  15. The critical slope angle for orographic rain

    NASA Astrophysics Data System (ADS)

    Breidenthal, R. E.; Zagar, N.

    2013-12-01

    Krishnamurti has shown that orographic rain depends on the slope of the windward terrain rather than just the total elevation gain. A simple physical model is proposed to account for the effect of slope. Based on the inhibiting effect of vortex (rotational) acceleration on entrainment, a critical slope angle is derived. If the rate of orographic lifting is sufficiently large, the enhanced buoyancy from latent heat release increases the acceleration parameter. As a consequence, the entrainment rate of under-saturated air is reduced. The critical slope corresponds to the situation where the rate of condensation in a rising adiabatic parcel just equals the rate of evaporation due to the entrainment of under-saturated air. The model is also applied to the trigger conditions for towering cumulus in general.

  16. Topographic measurements of slope streaks on Mars

    NASA Astrophysics Data System (ADS)

    Brusnikin, Eugene S.; Kreslavsky, Mikhail A.; Zubarev, Anatoly E.; Patratiy, Vyacheslav D.; Krasilnikov, Sergey S.; Head, James W.; Karachevtseva, Irina P.

    2016-11-01

    Slope streaks are enigmatic, actively forming albedo features occurring on slopes in high-albedo, low-thermal-inertia, dust-rich equatorial regions on Mars. They are a specifically martian phenomenon with no direct analogs on the Earth. Their morphology suggests that the streaks are initiated at their upslope tips and propagate down to their termini; however, the physical mechanism of their formation is uncertain. We performed a large series of measurements of slopes associated with slope streaks using stereo pairs of high-resolution orbital images obtained by HiRISE camera and generated several digital elevation models for selected streaks. We found that: (1) slopes at the upslope streak tips range widely, however, there is a strong indication that streaks can be initiated only on slopes steeper than ∼20°; (2) slopes of the streak termini show an even wider range, with some streaks terminating at slopes as steep as their tips, while others propagate all the way down to horizontal surfaces; (3) the streaks can propagate stably for long (many hundreds of meters) distances and can turn, following the topographic gradient on ∼10°-15° slopes; (4) no uphill propagation of streaks is detected over baselines of tens of meters; (5) the slope streaks often propagate over 1-2 m high obstacles and can climb 1-2 m uphill over short (meters) distances. We used these findings to assess the viability of two classes of hypotheses about slope streak formation mechanisms proposed earlier: 1) "dry", some kind of run-away avalanche-like dry granular flow, and 2) "wet", some kind of run-away propagation of a front of percolating brines in the shallow subsurface. No specific observation unambiguously proves or rejects either of the two mechanisms. Several of our findings are readily explained by the "dry" mechanism and cannot be easily explained with any kind of "wet" mechanism, while other findings are closely consistent with the "wet" mechanism and are difficult to reconcile

  17. Recurring Slope Lineae on Mars: Atmospheric Origin?

    NASA Astrophysics Data System (ADS)

    McEwen, AS; Chojnacki, M.; Dundas, C.; Ojha, L.; Masse, M.; Schaefer, E.; Leung, C.

    2015-10-01

    Recurring Slope Lineae (RSL) are seasonal flows or seeps on warm Martian slopes. Observed gradual or incremental growth, fading, and yearly recurrence can be explained by seasonal seeps of water, which is probably salty. The origin of the water is not understood, but several observations indicate a key role for atmospheric processes. If sufficient deliquescent salts are present at these locations, the water could be entirely of atmospheric origin.

  18. Slope instability caused by small variations in hydraulic conductivity

    USGS Publications Warehouse

    Reid, M.E.

    1997-01-01

    Variations in hydraulic conductivity can greatly modify hillslope ground-water flow fields, effective-stress fields, and slope stability. In materials with uniform texture, hydraulic conductivities can vary over one to two orders of magnitude, yet small variations can be difficult to determine. The destabilizing effects caused by small (one order of magnitude or less) hydraulic conductivity variations using ground-water flow modeling, finite-element deformation analysis, and limit-equilibrium analysis are examined here. Low hydraulic conductivity materials that impede downslope ground-water flow can create unstable areas with locally elevated pore-water pressures. The destabilizing effects of small hydraulic heterogeneities can be as great as those induced by typical variations in the frictional strength (approximately 4??-8??) of texturally similar materials. Common "worst-case" assumptions about ground-water flow, such as a completely saturated "hydrostatic" pore-pressure distribution, do not account for locally elevated pore-water pressures and may not provide a conservative slope stability analysis. In site characterization, special attention should be paid to any materials that might impede downslope ground-water flow and create unstable regions.

  19. Geotechnical properties of cemented sands in steep slopes

    USGS Publications Warehouse

    Collins, B.D.; Sitar, N.

    2009-01-01

    An investigation into the geotechnical properties specific to assessing the stability of weakly and moderately cemented sand cliffs is presented. A case study from eroding coastal cliffs located in central California provides both the data and impetus for this study. Herein, weakly cemented sand is defined as having an unconfined compressive strength (UCS) of less than 100 kPa, and moderately cemented sand is defined as having UCS between 100 and 400 kPa. Testing shows that both materials fail in a brittle fashion and can be modeled effectively using linear Mohr-Coulomb strength parameters, although for weakly cemented sands, curvature of the failure envelope is more evident with decreasing friction and increasing cohesion at higher confinement. Triaxial tests performed to simulate the evolving stress state of an eroding cliff, using a reduction in confinement-type stress path, result in an order of magnitude decrease in strain at failure and a more brittle response. Tests aimed at examining the influence of wetting on steep slopes show that a 60% decrease in UCS, a 50% drop in cohesion, and 80% decrease in the tensile strength occurs in moderately cemented sand upon introduction to water. In weakly cemented sands, all compressive, cohesive, and tensile strength is lost upon wetting and saturation. The results indicate that particular attention must be given to the relative level of cementation, the effects of groundwater or surficial seepage, and the small-scale strain response when performing geotechnical slope stability analyses on these materials. ?? 2009 ASCE.

  20. Up by upwest: Is slope like north?

    PubMed

    Weisberg, Steven M; Nardi, Daniele; Newcombe, Nora S; Shipley, Thomas F

    2014-10-01

    Terrain slope can be used to encode the location of a goal. However, this directional information may be encoded using a conceptual north (i.e., invariantly with respect to the environment), or in an observer-relative fashion (i.e., varying depending on the direction one faces when learning the goal). This study examines which representation is used, whether the sensory modality in which slope is encoded (visual, kinaesthetic, or both) influences representations, and whether use of slope varies for men and women. In a square room, with a sloped floor explicitly pointed out as the only useful cue, participants encoded the corner in which a goal was hidden. Without direct sensory access to slope cues, participants used a dial to point to the goal. For each trial, the goal was hidden uphill or downhill, and the participants were informed whether they faced uphill or downhill when pointing. In support of observer-relative representations, participants pointed more accurately and quickly when facing concordantly with the hiding position. There was no effect of sensory modality, providing support for functional equivalence. Sex did not interact with the findings on modality or reference frame, but spatial measures correlated with success on the slope task differently for each sex.

  1. Slope Estimation in Noisy Piecewise Linear Functions✩

    PubMed Central

    Ingle, Atul; Bucklew, James; Sethares, William; Varghese, Tomy

    2014-01-01

    This paper discusses the development of a slope estimation algorithm called MAPSlope for piecewise linear data that is corrupted by Gaussian noise. The number and locations of slope change points (also known as breakpoints) are assumed to be unknown a priori though it is assumed that the possible range of slope values lies within known bounds. A stochastic hidden Markov model that is general enough to encompass real world sources of piecewise linear data is used to model the transitions between slope values and the problem of slope estimation is addressed using a Bayesian maximum a posteriori approach. The set of possible slope values is discretized, enabling the design of a dynamic programming algorithm for posterior density maximization. Numerical simulations are used to justify choice of a reasonable number of quantization levels and also to analyze mean squared error performance of the proposed algorithm. An alternating maximization algorithm is proposed for estimation of unknown model parameters and a convergence result for the method is provided. Finally, results using data from political science, finance and medical imaging applications are presented to demonstrate the practical utility of this procedure. PMID:25419020

  2. Influence of pore pressure on the successive failures of intact slopes

    NASA Astrophysics Data System (ADS)

    Voulgari, Chrysoula; Utili, Stefano

    2016-04-01

    The presence of water can significantly change the stability of a slope and as a result the evolution of a slope in time. In this paper the influence of pore water pressure on the morphological evolution of natural cliffs subject to progressive retreat is investigated. The upper bound theorem of limit analysis is employed to evaluate the stability number and the failure mechanism of successive failures of uniform c, φ slopes with the presence of water. This model extends the existing analytical framework on the evolution of slopes subjected to weathering by accounting for the presence of water. Pore-water pressure is considered in the model by using the coefficient ru, a description of the pore-water pressure distribution that is approximate, but is commonly used in slope stability analyses. To account for the influence of the pore pressure, the work of pore-water pressure on the deformation of the soil along the failure surface had to be included in the model leading to modified analytical expressions of the energy balance equation (the balance between external work and dissipated energy) and as a consequence, of the function whose minimum provides the solution in terms of failure mechanisms and associated values of soil strength. With this model it is possible to relate the evolution of natural slopes with the presence of water by a sequence of rotational sliding block failures to the degradation of material strength properties. Computations were carried out for a wide range of parameters (friction angle φ and initial slope inclination β) and a set of normalized solutions is presented for different values of ru coefficient.

  3. Interaction of octahedral ruthenium(II) polypyridyl complex [Ru(bpy)2(PIP)](2+) with poly(U)·poly(A)*poly(U) triplex: Increasing third-strand stabilization of the triplex without affecting the stability of the duplex.

    PubMed

    Zhu, Zhiyuan; Peng, Mengna; Zhang, Jingwen; Tan, Lifeng

    2017-04-01

    Triple-helical RNA are of interest because of possible biological roles as well as the potential therapeutic uses of these structures, while the stability of triplexes is usually weaker than that of the Watson-Crick base pairing duplex strand due to the electrostatic repulsion between three polyanionic strands. Therefore, how to increase the stability of the specific sequences of triplexes are of importance. In this paper the binding of a Ru(II) complex, [Ru(bpy)2(PIP)](2+) (bpy=2.2'-bipyridine, PIP=2-phenyl-1H-imidazo[4,5-f]- [1,10]-phenanthroline), with poly(U)·poly(A)*poly(U) triplex has been investigated by spectrophotometry, spectrofluorometry, viscosimetry and circular dichroism. The results suggest that [Ru(bpy)2(PIP)](2+) as a metallointercalator can stabilize poly(U)·poly(A)*poly(U) triplex (where · denotes the Watson-Crick base pairing and * denotes the Hoogsteen base pairing),while it stabilizes third-strand with no obvious effect on the duplex of poly(U)·poly(A), reflecting the binding of this complex with the triplex is favored by the Hoogsteen paired poly(U) third strand to a great extent.

  4. Surface slope probabilities from the spectra of weak radar echoes - Application to Mars

    NASA Technical Reports Server (NTRS)

    Lipa, B.; Tyler, G. L.

    1976-01-01

    A method is described for stabilizing the inversion of the power spectra of comparatively weak radar echoes from Mars. It is noted that such stabilization is necessary for echoes with S/N power-spectral densities of order unity as well as for those with broad spectral distributions. The method is applied to the Martian surface, using two data sets obtained with radars of approximately 12.5-cm wavelength. The resulting slope probabilities are interpreted in terms of diffuse and quasi-specular scatter, and values of rms slope are calculated. The results for a sample of Martian locations clearly indicate extreme variations in the local nature of the surface and yield evidence for an apparent planetwide distribution of roughness that may be due to extreme slopes, surface or subsurface rock populations, or a combination of these.

  5. Elliptically Bent X-ray Mirrors with Active Temperature Stabilization

    SciTech Connect

    Yuan, Sheng; Church, Matthew; Yashchuk, Valeriy V.; Goldberg, Kenneth A.; Celestre, Rich; McKinney, Wayne R.; Kirschman, Jonathan; Morrison, Greg; Noll, Tino; Warwick, Tony; Padmore, Howard A.

    2010-01-31

    We present details of design of elliptically bent Kirkpatrick-Baez mirrors developed and successfully used at the Advanced Light Source for submicron focusing. A distinctive feature of the mirror design is an active temperature stabilization based on a Peltier element attached directly to the mirror body. The design and materials have been carefully optimized to provide high heat conductance between the mirror body and substrate. We describe the experimental procedures used when assembling and precisely shaping the mirrors, with special attention paid to laboratory testing of the mirror-temperature stabilization. For this purpose, the temperature dependence of the surface slope profile of a specially fabricated test mirror placed inside a temperature-controlled container was measured. We demonstrate that with active mirror-temperature stabilization, a change of the surrounding temperature by more than 3K does not noticeably affect the mirror figure. Without temperature stabilization, the surface slope changes by approximately 1.5 ?mu rad rms (primarily defocus) under the same conditions.

  6. Interplay between down-slope and along-slope sedimentary processes during the late Quaternary along the Capo Vaticano margin (southern Tyrrhenian Sea, Italy)

    NASA Astrophysics Data System (ADS)

    Martorelli, Eleonora; Bosman, Alessandro; Casalbore, Daniele; Falcini, Federico

    2016-04-01

    Late Quaternary along-slope and down-slope sedimentary processes and structures in the upper slope-shelf sector of the Calabro-Tyrrhenian continental margin off Capo Vaticano have been investigated using very high-resolution single-channel seismic profiles and multibeam bathymetric data. The results show that a competition among along-slope bottom currents-vs down-slope mass-wasting mostly contributed in shaping the seafloor and controlling deposition of sedimentary units during the Late Quaternary. Along-slope processes mostly formed elongated drifts located on the upper continental slope and outer shelf, between -90 and -300 m. The contourite deposits and associated erosive elements indicate the presence of a northwestward geostrophic flow that can be related to the modified-LIW issued by the Messina Strait. According to the proposed stratigraphic reconstruction it is likely that the activity of bottom-currents off Capo Vaticano was intensified around the LGM period and during the post-glacial sea-level rise, whereas they were less intense during the Holocene. Gravity-driven down-slope processes formed mass-transport deposits and turbidite systems with erosive channels, locally indenting the present-day shelf. Several slide events affected the upper 10-20 m of the stratigraphic record, dismantling considerable volume of contourite sediment. High-resolution seismic profiles indicate that failure processes appear to be dominated by translational sliding with glide plains mainly developed within contourite deposits. The most striking feature is the Capo Vaticano slide complex, which displays a large spatial coverage (area of about 18 km2) and is composed by several intersecting slide scars and overlapping deposits; these characteristics are peculiar for the Tyrrhenian continental margins, where slide events developed in open-slope areas are usually less complex and smaller in size. The presence of high-amplitude reflectors within contourite deposits (representing

  7. INFILTRATION ON MOUNTAIN SLOPES: A COMPARISON OF THREE ENVIRONMENTS. (R825157)

    EPA Science Inventory

    Water is well established as a major driver of the geomorphic change that eventually reduces mountains to lower relief landscapes. Nonetheless, within the altitudinal limits of continuous vegetation in humid climates, water is also an essential factor in slope stability. In th...

  8. The effect of shearing rate and slope angle on the simple shear response of marine clays

    NASA Astrophysics Data System (ADS)

    Biscontin, G.; Rutherford, C.

    2010-12-01

    The response of submarine slopes to seismic or storm loading has become an important element in the risk assessment for offshore structures and local tsunami hazard. Evaluation of submarine slope stability requires characterization of soil behavior and relies on the selection of appropriate parameter values. Although the traditional simple shear device has been used to investigate cyclic loading effects on marine clay, it does not allow for complex loading conditions which often contribute to the failure on submarine slopes. Understanding the interaction between the initial shear stress, the slope angle, and the multi-directional shaking due to earthquakes or storm loading is an important aspect to understanding the failure mechanisms of submarine slope failures. The initial static driving force on the slope is combined with the dynamic loading by storms and earthquakes to create complex loading paths. Therefore, the ability to apply complex stress or strain paths is important to fully study the shear response of marine clays on submarine slopes. A new multi-directional simple shear device developed at Texas A&M University allows loading along three independent axes, two perpendicular horizontal directions to allow any stress or strain paths in the horizontal plane, and a third in the vertical direction. This device is used to investigate the response of Gulf of Mexico marine deposits to different loading conditions. To study the effect of slope angle on the shear response of the soil, samples are subjected to a shear stress during consolidation, Kα consolidation. One-dimensional monotonic and cyclic shearing of Ko consolidated specimens is used to simulate level ground conditions, whereas sloping surfaces were simulated using Kα consolidation for both monotonic and cyclic tests. The effects of shearing rate on the soil response are investigated using strain controlled tests at varying frequencies.

  9. Examining the influence of vegetation on slope hydrology in Hong Kong using the capacitive resistivity technique

    NASA Astrophysics Data System (ADS)

    Niu, Qifei; Zhao, Kairan; Wang, Yu-Hsing; Wu, Yuxin

    2016-06-01

    Vegetation essentially has both beneficial and detrimental hydrological effects on slope stability, and the balance between these effects changes throughout the year. For engineers considering vegetation as an ecotechnological solution to slope instability, it is therefore necessary to understand how the net hydrological effect varies with local weather conditions. In this