Distribution by Scientific Domains

Kinds of Slope

  • allometric slope
  • average slope
  • bed slope
  • channel slope
  • common slope
  • constant slope
  • continental slope
  • different slope
  • eastern slope
  • gentle slope
  • hill slope
  • initial slope
  • lee slope
  • lower slope
  • mean slope
  • negative slope
  • north slope
  • northern slope
  • positive slope
  • regression slope
  • response slope
  • rr slope
  • slippery slope
  • south-facing slope
  • southern slope
  • spectral slope
  • steep slope
  • steeper slope
  • talus slope
  • turbulence slope
  • upper slope
  • vertical slope
  • windward slope

  • Terms modified by Slope

  • slope angle
  • slope aspect
  • slope close
  • slope conductance
  • slope deposit
  • slope efficiency
  • slope failure
  • slope gradient
  • slope length
  • slope parameter
  • slope position
  • slope process
  • slope region
  • slope stability
  • slope stability analysis
  • slope zone

  • Selected Abstracts


    ADDICTION, Issue 7 2007
    No abstract is available for this article. [source]

    Regional analysis of bedrock stream long profiles: evaluation of Hack's SL form, and formulation and assessment of an alternative (the DS form)

    Geoff Goldrick
    Abstract The equilibrium form of the fluvial long profile has been used to elucidate a wide range of aspects of landscape history including tectonic activity in tectonic collision zones, and in continental margin and other intraplate settings, as well as other base-level changes such as due to sealevel fluctuations. The Hack SL form of the long profile, which describes a straight line on a log,normal plot of elevation (normal) versus distance (logarithmic), is the equilibrium long profile form that has been most widely used in such studies; slope,area analysis has also been used in recent years. We show that the SL form is a special case of a more general form of the equilibrium long profile (here called the DS form) that can be derived from the power relationship between stream discharge and downstream distance, and the dependence of stream incision on stream power. The DS form provides a better fit than the SL form to river long profiles in an intraplate setting in southeastern Australia experiencing low rates of denudation and mild surface uplift. We conclude that, if an a priori form of the long profile is to be used for investigations of regional landscape history, the DS form is preferable. In particular, the DS form in principle enables equilibrium steepening due to an increase in channel substrate lithological resistance (parallel shift in the DS plot) to be distinguished from disequilibrium steepening due to long profile rejuvenation (disordered outliers on the DS plot). Slope,area analysis and the slope,distance (DS) approach outlined here are complementary approaches, reflecting the close relationship between downstream distance and downstream catchment area. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Distribution and growth of benthic macroinvertebrates among different patch types of the littoral zones of two arctic lakes

    FRESHWATER BIOLOGY, Issue 12 2006
    Summary 1. To evaluate the effect of habitat patch heterogeneity on abundance and growth of macroinvertebrates in arctic lakes, macroinvertebrate abundance, individual biomass, and potential food resources were studied in three patch types in two arctic lakes on the Alaskan North Slope near the Toolik Lake Field Station. An experiment was conducted to determine which sediment patch type supported higher growth rates for Chironomus sp., a commonly occurring macroinvertebrate. 2. Potential organic matter (OM) resources were significantly higher in both rock and macrophyte patches than in open-mud patches. Total macroinvertebrate densities in both lakes were highest in rock patches, intermediate in macrophytes and lowest in open-mud. The open-mud patches also had lower species richness compared with other patch types. Additionally, individual biomass for one clam species and two chironomid species was significantly greater in rock patches than in open-mud. 3. In a laboratory experiment, Chironomus showed two to three times greater mass increase in sediments from macrophyte and rock patches than from open-mud patches. Rock and macrophyte experimental sediments had at least 1.5 × the percentage OM as open-mud sediments. 4. Chlorophyll a appeared to be the best predictor for invertebrate abundances across all patch types measured, whereas OM content appeared to be the variable most closely associated with Chironomus growth. 5. Our results combined with previous studies show that the relationships between macroinvertebrate community structure, individual growth, and habitat heterogeneity are complex, reflecting the interaction of multiple resources, and biotic interactions, such as the presence or absence of a selective vertebrate predator (lake trout, Salvelinus namaycush). [source]

    Evaluating interactions between soil drainage and seedling performance in a restoration of Pinus sylvestris woodland, Scotland

    GLOBAL ECOLOGY, Issue 2 2001
    M. D. Crowell
    Abstract 1,This paper evaluates the role of soil drainage in tree seedling performance at a site being restored from Calluna vulgaris moorland to Pinus sylvestris woodland, in Glen Affric, Scotland. The investigation focuses on the relationships between height of planted seedlings, type of ground vegetation and drainage conditions. 2,Slope, aspect, and soil depth were assessed as potential surrogates for direct measures of soil drainage, all of which were derived from digital terrain data. 3,Six variables related to drainage were recorded at 58 seedling locations and used in a factor analysis to understand links between soil moisture conditions, topographic variables and soil depth characteristics. 4,Factor analysis generated two factors that accounted for 70.5% of the variance in the correlation matrix of these variables: Factor 1 correlated strongly with variables that controlled peat accumulation and Factor 2 correlated strongly with topographic controls upon drainage patterns. 5,These two factors explained a significant amount of the variance in height of the Pinus seedlings planted at these locations. Significant differences were found between the factor scores associated with different types of ground vegetation, as well as between the seedling heights observed at locations with different vegetation types. 6,Multiple regressions were developed that indicated that slope, aspect, and soil depth were significant as independent variables in models where soil moisture content and aerobic soil depth were the dependent variables. [source]

    Original article: Apparent thermal diffusivity estimation for the heat transfer modelling of pork loin under air/steam cooking treatments

    Massimiliano Rinaldi
    Summary Apparent thermal diffusivity linear functions vs. product temperature were estimated for pork cooked under two different treatments (forced convection, FC and forced convection/steam combined, FC/S) at 100, 110, 120 and 140 °C by means of experimental time,temperature data and a developed finite-difference algorithm. Slope and intercept of each function were employed to calculate apparent thermal diffusivity at 40, 55 and 70 °C. Generally, FC/S treatments gave significantly higher apparent thermal diffusivities in comparison with FC conditions. Apparent thermal diffusivities were used to develop a model for cooking time and final core temperature prediction on the basis of oven setting. The model was validated by means of additional cooking tests performed at different temperatures of those employed for model development. Root mean square error values lower than 3.8 °C were obtained comparing predicted and experimental temperature profiles. Percentage errors lower than 3.1% and 3.5% were, respectively, obtained for cooking times and final core temperatures. [source]

    Phylogeography of the northern hogsucker, Hypentelium nigricans (Teleostei: Cypriniformes): genetic evidence for the existence of the ancient Teays River

    Peter B. Berendzen
    Abstract Aim, To assess the roles of dispersal and vicariance in shaping the present distribution and diversity within Hypentelium nigricans, the northern hogsucker (Teleostei: Cypriniformes). Location, Eastern United States. Methods, Parsimony analyses, Bayesian analyses, pairwise genetic divergence and mismatch plots are used to examine patterns of genetic variation across H. nigricans. Results, Species relationships within the genus Hypentelium were consistent with previous hypotheses. However, relationships between haplotypes within H. nigricans revealed two deeply divergent groups, a clade containing haplotypes from the New and Roanoke rivers (Atlantic Slope) plus Interior Highlands and upper Mississippi River and a clade containing haplotypes from the Eastern Highlands, previously glaciated regions of the Ohio and Wabash rivers, and the Amite and Homochitto rivers of south-western Mississippi. Main conclusions, The phylogenetic history of Hypentelium was shaped by old vicariant events associated with erosion of the Blue Ridge and separation of the Mobile and Mississippi river basins. Within H. nigricans two clades existed prior to the Pleistocene; a widespread clade in the pre-glacial Teays-Mississippi River system and a clade in Cumberland and Tennessee rivers. Pleistocene events fragmented the Teays-Mississippi fauna. Following the retreat of the glaciers H. nigricans dispersed northward into previously glaciated regions. These patterns are replicated in other clades of fishes and are consistent with some of the predictions of Mayden's (Systematic Zoology, 37, 329, 1988) pre-Pleistocene vicariance hypothesis. [source]

    Electrical Restitution and Ventricular Fibrillation: Negotiating a Slippery Slope



    Yunpeng Wang
    In this paper we derive kinetic parameters for the generation of gaseous hydrocarbons (C1-5) and methane (C1) from closed-system laboratory pyrolysis of selected samples of marine kerogen and oil from the SW Tarim Basin. The activation energy distributions for the generation of both C1-5 (Ea = 59-72kcal, A = 1.0×1014 s,1) and C1 (Ea = 61-78kcal, A = 6.06×1014 s,1) hydrocarbons from the marine oil are narrower than those for the generation of these hydrocarbons from marine kerogen (Ea = 50-74kcal, A = 1.0×1014 s,1 for C1-5; and Ea = 48-72kcal, A=3.9×1013 s,1 for C1, respectively). Using these kinetic parameters, both the yields and timings of C1-5 and C1 hydrocarbons generated from Cambrian source rocks and from in-reservoir cracking of oil in Ordovician strata were predicted for selected wells along a north-south profile in the SW of the basin. Thermodynamic conditions for the cracking of oil and kerogen were modelled within the context of the geological framework. It is suggested that marine kerogen began to crack at temperatures of around 120°C (or 0.8 %Ro) and entered the gas window at 138°C (or 1.05 %Ro); whereas the marine oil began to crack at about 140 °C (or 1.1 %Ro) and entered the gas window at 158 °C (or 1.6%Ro). The main geological controls identified for gas accumulations in the Bachu Arch (Southwest Depression, SW Tarim Basin) include the remaining gas potential following Caledonian uplift; oil trapping and preservation in basal Ordovician strata; the extent of breaching of Ordovician reservoirs; and whether reservoir burial depths are sufficiently deep for oil cracking to have occurred. In the Maigaiti Slope and Southwest Depression, the timing of gas generation was later than that in the Bachu Arch, with much higher yields and generation rates, and hence better prospects for gas exploration. It appears from the gas generation kinetics that the primary source for the gases in the Hetianhe gasfield was the Southwest Depression. [source]

    Thermal expansion of organic crystals and precision of calculated crystal density: A survey of Cambridge Crystal Database

    Changquan Calvin Sun
    Abstract True density is a physical property of both fundamental and practical importance to the study of pharmaceutical powders. True density may be calculated from crystal structure. However, precision of such calculated density is not well understood. Furthermore, thermal expansion properties of organic crystals have rarely been characterized. A survey of Cambridge Crystal Database is conducted to assess (1) precision of calculated crystal density from crystal structure; (2) thermal expansion properties of organic crystals. It is shown that calculated crystal density exhibits, on average, a relative standard deviation (RSD) of ,0.4%. It is found that crystal density generally increases linearly with decreasing temperature provided no phase change occurs. Slope of the line, termed thermal density gradient, of organic crystals ranges between 0.04 and 1.74 mg,cm,3,K,1 with an average of ,0.2 mg,cm,3,K,1. It is shown that majority polymorph pairs exhibit significantly different thermal expansion behavior and their density,temperature lines can cross. This likely contributes to the less than perfect prediction of relative stability of polymorphs at ambient temperature using the density rule. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 1043,1052, 2007 [source]

    Use of Synthetic Aperture Radar for Selecting Alaskan Lakes for Winter Water Use,

    D.M. White
    Abstract:, Water resources are limited in many areas of the North Slope, Alaska, particularly during winter. Water is used by the oil industry for ice road construction and maintenance, drilling and facility operations, and potable water supplies. The coastal plain between Teshekpuk Lake, in the National Petroleum Reserve-Alaska (NPR-A) and the Colville River has numerous shallow lakes, but further south in the northern foothills of the Brooks Range, and east to the Canning River, lakes are fewer. While many oil and gas lease sales have been conducted, or are proposed, access to the leases may be limited because of the lack of available water for ice road construction. Ice roads are the main means by which exploration is conducted in the Arctic, putting a stress on freshwater bodies that do not freeze to the lakebed in winter. Lakes that do not freeze to the lakebed also serve as overwintering habitat for fish. The purpose of this paper is to report on the potential distribution of water bodies that may provide overwinter water in selected areas from Teshekpuk Lake to the Canning River. The project used synthetic aperture radar (SAR) imagery to search for the presence of water in lakes in March 2006. In the Kuparuk and Canning SAR images, 52 and 61% of lakes were frozen to their beds by March 2006, accounting for 49 and 57% of the lake area in these study regions. Conversely, only 2% of the lakes in the Teshekpuk region were frozen to the bottom by March 2006. Unfrozen water was more available because of deeper and more numerous lakes in the Teshekpuk Lake region (west) than in the Canning River area (east). While only specific SAR tiles were analyzed herein, the method will be a useful tool for land managers who seek to evaluate the potential for ice road construction across the Arctic. [source]

    Importance of soils, topography and geographic distance in structuring central Amazonian tree communities

    Stephanie A. Bohlman
    Abstract Question: What is the relative contribution of geographic distance, soil and topographic variables in determining the community floristic patterns and individual tree species abundances in the nutrient-poor soils of central Amazonia? Location: Central Amazonia near Manaus, Brazil. Methods: Our analysis was based on data for 1105 tree species (, 10 cm dbh) within 40 1-ha plots over a ca. 1000-km2 area. Slope and 26 soil-surface parameters were measured for each plot. A main soil-fertility gradient (encompassing soil texture, cation content, nitrogen and carbon) and five other uncorrelated soil and topographic variables were used as potential predictors of plant-community composition. Mantel tests and multiple regressions on distance matrices were used to detect relationships at the community level, and ordinary least square (OLS) and conditional autoregressive (CAR) models were used to detect relationships for individual species abundances. Results: Floristic similarity declined rapidly with distance over small spatial scales (0,5 km), but remained constant (ca. 44%) over distances of 5 to 30 km, which indicates lower beta diversity than in western Amazonian forests. Distance explained 1/3 to 1/2 more variance in floristics measures than environmental variables. Community composition was most strongly related to the main soil-fertility gradient and C:N ratio. The main fertility gradient and pH had the greatest impact of species abundances. About 30% of individual tree species were significantly related to one or more soil/topographic parameters. Conclusions: Geographic distance and the main fertility gradient are the best predictors of community floristic composition, but other soil variables, particularly C:N ratio, pH, and slope, have strong relationships with a significant portion of the tree community. [source]


    PALAEONTOLOGY, Issue 4 2009
    Abstract:, Late Quaternary sediments from Ocean Drilling Program (ODP) Hole 1055B, Carolina Slope, western North Atlantic (32°47.041, N, 76°17.179, W; 1798 m water depth) were examined for deep-sea ostracod taxonomy. A total of 13 933 specimens were picked from 207 samples and c. 120 species were identified. Among them, 87 species were included and illustrated in this paper. Twenty-eight new species are described. The new species are: Ambocythere sturgio, Argilloecia abba, Argilloecia caju, Argilloecia keigwini, Argilloecia robinwhatleyi, Aversovalva carolinensis, Bythoceratina willemvandenboldi, Bythocythere eugeneschornikovi, Chejudocythere tenuis, Cytheropteron aielloi, Cytheropteron demenocali, Cytheropteron didieae, Cytheropteron richarddinglei, Cytheropteron fugu, Cytheropteron guerneti, Cytheropteron richardbensoni, Eucytherura hazeli, Eucytherura mayressi, Eucytherura namericana, Eucytherura spinicorona, Posacythere hunti, Paracytherois bondi, Pedicythere atroposopetasi, Pedicythere kennettopetasi, Pedicythere klothopetasi, Pedicythere lachesisopetasi, Ruggieriella mcmanusi and Xestoleberis oppoae. Taxonomic revisions of several common species were made to reduce taxonomic uncertainty in the literature. This study provides a robust taxonomic baseline for application to palaeoceanographical reconstruction and biodiversity analyses in the deep and intermediate-depth environments of the North Atlantic Ocean. [source]

    Relationship between sound pressure and reaction rate in sonochemical reaction

    Yasuhiko Takuma
    Abstract Relationship between sound pressure in a sonochemical reactor and degradation rate of organic compounds, p -chlorophenol and p -nitrophenol, was investigated. Reaction rates were analyzed as first-order reaction. As a result, linear relationship was shown for each compound. Slope indicating the first reaction rate constant was remarkably affected by the position of the reaction flask. The sound pressure profile was measured and the relationship between the averaged pressure in a flask and the rate constant was shown. The relation was found to be remarkably different between the two. The threshold values were observed as 67kPa for p -chlorophenol and 22kPa for p -nitrophenol, respectively. From these results, it was shown that nature of compounds affects the dependency on sound pressure. On a étudié la relation entre les vitesses de dégradation des composés organiques, le p-chlorophénol et le p-nitrophénol, et la pression acoustique dans une réaction sonochimique. Les premières constantes de vitesse de réaction se sont avérées fortement influencée par la position de la cellule de réaction dans notre installation. Le profil de pression acoustique dans l'installation a été mesuré et la relation entre la pression moyennée dans la cellule et la constante de vitesse a été déterminée. On a trouvé que la relation était significativement différente entre les deux composés et que les valeurs seuils étaient de 100,kPa pour le p-chlorophénol. On a montré également que la nature des composés avait une influence sur leur dépendance à la pression acoustique. [source]

    Modelling and economic analysis of gas production from hydrates by depressurization method

    Santanu Khataniar
    Abstract Gas production from a hydrate reservoir involves decomposition of the solid hydrate. An analytical model is developed to predict reservoir performance for gas production by the depressurization method from a hydrate reservoir containing associated free gas. The model is developed by combining the intrinsic kinetics of hydrate decomposition, which is of interest to chemical engineers, with gas inflow performance relationship and material balance equations. An economic analysis model is also developed and incorporated with the reservoir performance model. These models are used in a case study of gas production from a hydrate reservoir in the Alaskan North Slope. The results show that gas transportation cost is the main factor controlling feasibility of commercial gas production. The hydrate zone contributes significantly to overall reservoir performance by arresting pressure decline and maintaining gas production rate. La production de gaz à partir d'un réservoir d'hydrates fait intervenir la décomposition d'hydrates solides. On a mis au point un modèle analytique afin de prédire la performance du réservoir pour la production de gaz par la méthode de la dépressurisation à partir d'un réservoir d'hydrates contenant un gaz libre associé. Dans ce modèle, on combine les cinétiques intrinsèques de la décomposition des hydrates, ce qui est intéressant pour les ingénieurs chimistes, avec la relation de performance du débit de gaz et les équations de bilans de matière. Un modèle d'analyse économique a également été élaboré et incorporé au modèle de performance du réservoir. Ces modèles sont utilisés dans une étude de cas sur la production de gaz à partir d'un réservoir d'hydrates du North Slope d'Alaska. Les résultats montrent que le couCt du transport de gaz est le principal facteur qui conditionne la faisabilité de la production commerciale de gaz. La région des hydrates contribue considérablement à la performance globale du réservoir en stoppant la chute de pression et en maintenant la vitesse de production de gaz. [source]

    Beat-to-Beat QT Dynamics in Healthy Subjects

    Berit T. Jensen M.D.
    Background: Measures of QT dynamics express repolarization abnormalities that carry prognostic information, but the reproducibility of beat-to-beat QT dynamics has never been established. The QT interval is prolonged at night, but how the circadian rhythm and heart rate influence the dynamic QT measurements is still unsettled. The aims of the present study were: (1) to describe the reproducibility of beat-to-beat QT dynamics with respect to intrasubject, between-subject, and between-observer variability and (2) to describe the normal range, circadian variation, and heart rate dependence of QT dynamics. Methods: Ambulatory Holter recordings were performed three times on 20 healthy volunteers and were analyzed by two experienced cardiologists. Slope and intercept of the QT/RR regression, the variability of QT and R-R intervals expressed as the standard deviation, and the relation between QT and RR variability expressed as a variability ratio were measured among other QT dynamics. Results: The reproducibility of all QT dynamics was good. All QT dynamics showed circadian variation when calculated on an hourly basis. The day/night variation in slope could be explained by the differences in heart rate, whereas the day/night variation in intercept was heart rate independent. Conclusion: The present study shows that reliable automatic QT measurements could be performed, encouraging further evaluation of the clinical value of QT dynamics in risk stratification of cardiac patients. [source]

    Baroreflex Sensitivity of an Arterial Wall During Rotary Blood Pump Assistance

    ARTIFICIAL ORGANS, Issue 9 2009
    Tomoyuki Yambe
    Abstract It is well known that the baroreflex system is one of the most important indicators of the pathophysiology in hypertensive patients. We can check the sensitivity of the baroreflex by observing heart rate (HR) responses; however, there is no simple diagnostic method to measure the arterial behavior in the baroreflex system. Presently, we report the development of a method and associated hardware that enables the diagnosis of baroreflex sensitivity by measuring the responses of both the heart and the artery. In this system, the measurements are obtained by monitoring an electrocardiogram and a pulse wave recorded from the radial artery or fingertip. The arterial responses were measured in terms of the pulse wave velocity (PWV) calculated from the pulse wave transmission time (PTT) from the heart to the artery. In this system, the HR change corresponding to the blood pressure change in time series sequence was observed. Slope of the changes in blood pressure and HR indicated the sensitivity of the baroreflex system of the heart. This system could also measure the sensitivity of the baroreflex system of an artery. Changes in the PWV in response to the blood pressure changes were observed. Significant correlation was observed in the time sequence between blood pressure change and PWV change after calculating the delay time by cross-correlation. The slope of these parameter changes was easily obtained and it demonstrated the sensitivity of the baroreflex system of an artery. We evaluated this method in animal experiments using rotary blood pump (RBP) with undulation pump ventricular assist device, and PTT elongation was observed in response to increased blood pressure with RBP assistance. Furthermore, when tested clinically, decreased sensitivity of the baroreflex system in hypertensive patients was observed. This system may be useful when we consider the ideal treatment and follow-up of patients with hypertension. [source]

    Origin of the Silurian Crude Oils and Reservoir Formation Characteristics in the Tazhong Uplift

    YANG Haijun
    Abstract: The Silurian stratum in the Tazhong uplift is an important horizon for exploration because it preserves some features of the hydrocarbons produced from multi-stage tectonic evolution. For this reason, the study of the origin of the Silurian oils and their formation characteristics constitutes a major part in revealing the mechanisms for the composite hydrocarbon accumulation zone in the Tazhong area. Geochemical investigations indicate that the physical properties of the Silurian oils in Tazhong vary with belts and blocks, i.e., heavy oils are distributed in the TZ47,15 well-block in the North Slope while normal and light oils in the No. I fault belt and the TZ16 well-block, which means that the oil properties are controlled by structural patterns. Most biomarkers in the Silurian oils are similar to that of the Mid-Upper Ordovician source rocks, suggesting a good genetic relationship. However, the compound specific isotope of n -alkanes in the oils and the chemical components of the hydrocarbons in fluid inclusions indicate that these oils are mixed oils derived from both the Mid-Upper Ordovician and the Cambrian,Lower Ordovician source rocks. Most Silurian oils have a record of secondary alterations like earlier biodegradation, including the occurrence of "UCM" humps in the total ion current (TIC) chromatogram of saturated and aromatic hydrocarbons and 25-norhopane in saturated hydrocarbons of the crude oils, and regular changes in the abundances of light and heavy components from the structural low to the structural high. The fact that the Silurian oils are enriched in chain alkanes, e.g., n -alkanes and 25-norhopane, suggests that they were mixed oils of the earlier degraded oils with the later normal oils. It is suggested that the Silurian oils experienced at least three episodes of petroleum charging according to the composition and distribution as well as the maturity of reservoir crude oils and the oils in fluid inclusions. The migration and accumulation models of these oils in the TZ47,15 well-blocks, the No. I fault belt and the TZ16 well-block are different from but related to each other. The investigation of the origin of the mixed oils and the hydrocarbon migration and accumulation mechanisms in different charging periods is of great significance to petroleum exploration in this area. [source]

    Thermal Characteristics of the Embankment with Crushed Rock Side Slope to Mitigate Thaw Settlement Hazards of the Qinghai-Tibet Railway

    Guoyu LI
    Abstract: Permafrost (perennially frozen ground) appears widely in the Golmud-Lhasa section of the Qinghai-Tibet railway and is characterized by high ground temperature (,,1°C) and massive ground ice. Under the scenarios of global warming and human activity, the permafrost under the railway will gradually thaw and the massive ground ice will slowly melt, resulting in some thaw settlement hazards, which mainly include longitudinal and lateral cracks, and slope failure. The crushed rock layer has a thermal semiconductor effect under the periodic fluctuation of natural air. It can be used to lower the temperature of the underlying permafrost along the Qinghai-Tibet railway, and mitigate the thaw settlement hazards of the subgrade. In the present paper, the daily and annual changes in the thermal characteristics of the embankment with crushed rock side slope (ECRSS) were quantitatively simulated using the numerical method to study the cooling effect of the crushed rock layer and its mitigative ability. The results showed that the ECRSS absorbed some heat in the daytime in summer, but part of it was released at night, which accounted for approximately 20% of that absorbed. Within a year, it removed more heat from the railway subgrade in winter than that absorbed in summer. It can store approximately 20% of the "cold" energy in subgrade. Therefore, ECRSS is a better measure to mitigate thaw settlement hazards to the railway. [source]

    Comparison of the Typical Metallogenic Systems in the North Slope of the Tongbai-East Qinling Mountains and its Geologic Implications

    Jing ZHANG
    Abstract: The Tongbai-East Qinling Mountains, an important part of the Central orogenic belt, is one of the most important metallogenic belts in China and contains lots of orogenic-type and VMS-type (Volcanogenic Massive Sulfide type) metallogenic systems. The Dahe and Shuidongling VMS-type Cu-Zn deposits, located in the Erlangping Group in Tongbai and East Qinling Mountains, respectively, show similar geological and geochemical features. The Huoshenmiao Formation in the East Qinling region and the Liushanyan Formation in the Tongbai region are spilite-keratophyre sequences occurring in the western and eastern sides of the Nanyang Basin, respectively, and are interpreted to be equivalent to each other. The orogenic-type Au-Ag deposits can be subdivided into two styles; namely, fault- or structure-controlled (e.g. Yindonggou) and stratabound (e.g. Poshan). The Poshan and Yindongpo orogenic-type Au-Ag deposits, whose ore bodies are strictly hosted in carbonaceous strata in the Tongbai Mountains, show obvious stratabound characteristics. Their ore-fluids are enriched in K+ and SO2,4 and are regarded as K+ -SO2,4 types. The Pb-isotope ratios of sulfides of the ores are extremely uniform and significantly different from those of the tectonostratigraphic terranes of the Qinling orogens except for the ore-hosting strata of the Waitoushan Formation. The Yindonggou and Xuyaogou orogenic Au-Ag deposits in the East Qinling Mountains, whose ore bodies are hosted in the faults cutting the hosting strata or granite body, show fault-controlled characteristics. Their ore-fluids belong to the Na+ -Cl, type. The Pb-isotope ratios of sulfides of ores are similar to those of the northern Qinling orogenic belt. The Waitoushan Formation, dominated by carbonaceous sericite-rich schists and only occurring in Tongbai region, should be detached from the Erlangping Group, which occurs both in the western and eastern sides of the Nanyang Basin. Future ore exploration in the Tongbai-East Qinling Mountains should focus on fault-controlled Au-Ag lodes. [source]

    Deep-water Fan Systems and Petroleum Resources on the Northern Slope of the South China Sea

    PANG Xiong
    Abstract, The shallow shelf delta/strand arenaceous-pelitic deposit region in the north of the Pearl River mouth basin, sitting on the northern continental shelf of the South China Sea, has already become an important oil production base in China. Recent researched has revealed that a great deal of deep-water fans of great petroleum potentiality exist on the Baiyun deep-water slope below the big paleo Pearl River and its large delta. Based on a mass of exploration wells and 2-D seismic data of the shallow shelf region, a interpretation of sequence stratigraphy confirmed the existence of deep-water fans. The cyclic falling of sea level, abundant detrital matter from the paleo Pearl River and the persistent geothermal subsidence in the Baiyun sag are the three prerequisites for the formation and development of deep-water fans. There are many in common between the deep-water shelf depositional system of the northern South China Sea and the exploration hotspots region on the two banks of the Atlantic. For example, both are located on passive continent margins, and persistent secular thermal subsidence and large paleo rivers have supplied abundant material sources and organic matter. More recently, the discovery of the big gas pool on the northern slope of the Baiyun sag confirms that the Lower Tertiary lacustrine facies in the Baiyun sag has a great potentiality of source rocks. The fans overlying the Lower Tertiary source rocks should become the main exploration areas for oil and gas resources. [source]

    Relation between flow, surface-layer armoring and sediment transport in gravel-bed rivers

    John Pitlick
    Abstract This study investigates trends in bed surface and substrate grain sizes in relation to reach-scale hydraulics using data from more than 100 gravel-bed stream reaches in Colorado and Utah. Collocated measurements of surface and substrate sediment, bankfull channel geometry and channel slope are used to examine relations between reach-average shear stress and bed sediment grain size. Slopes at the study sites range from 0·0003 to 0·07; bankfull depths range from 0·2 to 5 m and bankfull widths range from 2 to 200 m. The data show that there is much less variation in the median grain size of the substrate, D50s, than there is in the median grain size of the surface, D50; the ratio of D50 to D50s thus decreases from about four in headwater reaches with high shear stress to less than two in downstream reaches with low shear stress. Similar trends are observed in an independent data set obtained from measurements in gravel-bed streams in Idaho. A conceptual quantitative model is developed on the basis of these observations to track differences in bed load transport through an idealized stream system. The results of the transport model suggest that downstream trends in total bed load flux may vary appreciably, depending on the assumed relation between surface and substrate grain sizes. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Elimination Mechanisms in the Aminolysis of Sulfamate Esters of the Type NH2SO2OC6H4X , Models of Enzyme Inhibitors

    William J. Spillane
    Abstract The kinetics of the reaction of 4-nitrophenyl sulfamate NH2SO2OC6H4NO2 -4 (1a) in acetonitrile (ACN) with a series of pyridines (pKa range ca. 8 units) and alicyclic amines (pKa range ca. 3.6 units) has been studied in the presence of excess amine at various temperatures. The compounds 1a,1f are important as model substrates for the medicinally important sulfamate esters 667-coumate and emate and analogues. Pseudo-first-order rate constants (kobsd.) have been obtained mainly by the release of 4-nitrophenol/4-nitrophenoxide. Slopes of plots of kobsd. vs. [amine] gave second-order rate constants (k2), and Brönsted plots were biphasic for the aminolysis (with alicyclic amines) with an initial slope ,1 = 0.53 and a subsequent slope ,2 = 0.19. The change in slope occurs near the first pKa of 1a (17.9) in ACN. Leaving-group effects were probed by using the same series of phenyl sulfamates, i.e. 1a,f and the alicyclic amines N -formylpiperazine and pyrrolidine. The reactions were considered to be dissociative in nature involving E2- and E1cB- type mechanisms with the phenyl sulfamate anion 2 being involved in pyridine and in the weaker alicyclic amines (,1 segment) and a phenyl sulfamate dianion 3 being involved with the stronger alicyclic bases (,2 segment). The calculation of Leffler indices (,) for bond-forming (base···H+) and bond-breaking (S,OAr) steps allows fuller interpretation of the mechanisms occurring, which are seen as having the N -sulfonylamines, HN=SO2 and ,N=SO2 on the reaction pathways leading to products. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Rural Youth Migration Trends in Australia: an Overview of Recent Trends and Two Inland Case Studies

    Abstract Much of what has been written on the topic of Australian rural youth migration trends and processes has often proceeded from data-free, or data-poor grounds. In this context, this paper analyses recent trends in youth (15 to 24 years of age) migration for a temporally-consistent set of Statistical Divisions (SDs) in inland rural Australia, and for local government areas within the Northern Tablelands and Slopes and Ranges of northern New South Wales and the Western Australian Central Wheatbelt. The paper finds that rates of youth loss from rural regions have increased over the past twenty years. Yet the patterns, processes, causes and impacts of rural youth migration are distributed in a spatially-uneven fashion. Some remote areas are receiving net migration gains while booming ,sea change' coastal regions have experienced heavy losses. While the ,flight to the bright city lights' syndrome is evident, relatively high proportions of young people in the Northern SD of NSW move within their immediate region. Nevertheless, some common understandings concerning youth mobility were also confirmed. Gender differentials in migration propensity between women and men are evident even at quite local scales. Young people are also more likely to search out capital cities than the rest of the population. Most inland areas still continue to experience heavy losses of local youth. A more precise understanding of rural youth migration trends is an important stepping stone in the establishment of a reinvigorated research effort into young rural people's perspectives of their changing life chances in their home communities. [source]

    Transient storage and downstream solute transport in nested stream reaches affected by beaver dams

    Li Jin
    Abstract Transient storage constitutes a key element in the hydrologic cycle of watersheds. Both in-channel slow moving water (dead zones) and hyporheic zones can contribute to transient storage, which retains water and solutes, increases residence time and influences solute transport in streams. Beaver dams and other in-stream obstructions throughout low-order streams attenuate streamflow and provide dead zone storage in pools. In this article, we report the results of four tracer tests in nested stream reaches in Cherry Creek (Wyoming, USA) covering ,2·5 km of stream length to explore how the degree of beaver dam obstructions and their impoundments influence water transient storage and downstream solute transport in low-order streams in the Rocky Mountain region of the American West. Travel-time parameters for the tracer tests increased linearly with beaver dam number (N) and pond size (V). Linear regression of the travel time to the peak concentration (Tp), the leading (Tl) and tailing edge (Tt) of the dye cloud and the duration of the dye cloud (Td) versus N and V were all significant (R2 = 0·99). Slopes of the linear regressions of Tt versus N and V, were three times larger than those for Tl, suggesting that longer residence times may be caused, in part, by transient storage in the stream system. One-dimensional transport with inflow and storage (OTIS) modelled cross-sectional area of transient storage zone (As) and dispersion coefficients (D) increased linearly with N and V and reach length. Two transient storage metrics, Fmean and , also showed a general increase with N and V, although the relationship was not as strong. This suggests that in-channel dead zones associated with beaver dams provide opportunities for generating transient water storage. The linear relationship between dispersion coefficient and reach length suggests the dispersion process might be analogous to the hydrodynamic dispersion in groundwater settings. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Forest plant species richness in small, fragmented mixed deciduous forest patches: the role of area, time and dispersal limitation

    Hans Jacquemyn
    Aim The research aimed to investigate how plant species richness of small, fragmented forest patches changes over time. Also interactions between time and area were studied in relation to species richness. Finally, the relative importance of plant dispersal limitation on the process of species accumulation was examined by investigating how species were distributed within a regional landscape. Location Mixed deciduous forest patches in central Belgium. Methods The land use history of a region of 80 km2 was reconstructed using nine historical maps dating from 1775 to 1991. Within a central area of 42 km2, 241 forest patches were surveyed for presence/absence of 203 species predominantly occurring in forests. Aggregation of species within this region was estimated using a Monte Carlo simulation. Spatial and temporal patterns of species richness were investigated by both regression and analysis of variance (ANOVA). Results Fifty-one of 103 species showed significant spatial aggregation patterns, suggesting severe dispersal limitation. Species richness significantly increased with age. However, the effects of time on species richness could not be separated from area and area and time clearly interacted. Slopes of regression equations for species number on area and patch age were shown to be significantly interrelated. Main conclusions Area and time cannot be treated independently as predictors of plant species richness. Dispersal proved to be important in structuring local forest plant community composition, contrary to most other studies that have investigated local forest plant community structure. The processes of forest succession and species accumulation are controlled by both local and regional processes. More studies focusing on the regional factors determining local community composition are needed in order to fully understand the process of forest plant community assembly. [source]

    The evolution of rewards: seed dispersal, seed size and elaiosome size

    JOURNAL OF ECOLOGY, Issue 3 2006
    Summary 1We examine the relationship between the reward offered to ants to disperse seeds (elaiosome size) and seed size, and the possible mechanisms that may generate this relationship in Australian plant species. 2We used seed and elaiosome sizes from our own data set containing 87 Acacia species, supplemented with 22 species from a previously published data set, and 98 ,Other species' from 51 genera in 25 families, also from published data. 3The relationship between ln(elaiosome size) and ln(seed size) was determined using standard major axis (SMA) regression for both data sets. For the Other data set we also determined the relationship among species independent of the differences between genera, among genera independent of the differences between families, among genera and among families. We used SMA to test for differences in slopes between groups. 4We found a significant common slope amongst all subsets of the larger data set. The estimated common slope and the 95% confidence interval for the relationship between ln(elaiosome size) and ln(seed size) across all data sets fell above one (1.24, 95%CI = 1.17,1.32), suggesting positive allometry. Slopes were also significantly positive and strikingly similar between the Acacia species data set and the Other species data sets. Similar positive allometry was shown in the ,other' species data set among genera and families, and among species independent of genus means (,species effects'). 5Significant and consistent relationships between taxonomic levels, independent of relationships at other levels, along with significant relationships at the species level, and similarity of slopes, suggest independent convergence towards an underlying functional relationship that has persisted over long evolutionary periods. Our results therefore suggest that ants have been agents of selection on seed traits. 6Such a functional relationship might result from a trade-off in ant foraging behaviour between the benefit of the reward (elaiosome) and the cost of the dispersal (determined by seed size). Slopes > 1 would then suggest that ants need more than proportionally larger rewards to remove larger seeds. [source]

    Acidification of sandy grasslands , consequences for plant diversity

    Pål Axel Olsson
    Abstract Questions: (1) Does soil acidification in calcareous sandy grasslands lead to loss of plant diversity? (2) What is the relationship between the soil content of lime and the plant availability of mineral nitrogen (N) and phosphorus (P) in sandy grasslands? Location: Sandy glaciofluvial deposits in south-eastern Sweden covered by xeric sand calcareous grasslands (EU habitat directive 6120). Methods: Soil and vegetation were investigated in most of the xeric sand calcareous grasslands in the Scania region (136 sample plots distributed over four or five major areas and about 25 different sites). Environmental variables were recorded at each plot, and soil samples were analysed for exchangeable P and N, as well as limestone content and pH. Data were analysed with regression analysis and canonical correspondence analysis. Results: Plant species richness was highest on weakly acid to slightly alkaline soil; a number of nationally red-listed species showed a similar pattern. Plant species diversity and number of red-listed species increased with slope. Where the topsoil had been acidified, limestone was rarely present above a depth of 30 cm. The presence of limestone restricts the availability of soil P, placing a major constraint on primary productivity in sandy soils. Conclusions: Acidification of sandy grasslands leads to reduced abundance of desirable species, although the overall effect is rather weak between pH 5 and pH 9. Slopes are important for high diversity in sandy grasslands. Calcareous soils cannot be restored through shallow ploughing, but deep perturbation could increase the limestone content of the topsoil and favour of target species. [source]

    Effect of age on anterior chamber angle configuration in Asians determined by anterior segment optical coherence tomography; clinic-based study

    Mi Hyun Cheon
    Acta Ophthalmol. 2010: 88: e205,e210 Abstract. Purpose:, To evaluate the distribution of anterior chamber angle (ACA) parameters and to assess association of these parameters with age in Asian subjects. Methods:, Four hundred and thirty-nine consecutive Korean subjects aged from 30 to 89 were enrolled from a university clinic. All participants were scanned using anterior segment optical coherence tomography (AS-OCT, Visante, version 2.0). We measured ACA parameters such as anterior chamber depth (ACD), angle opening distance at 500 and 750 ,m (AOD500,750), angle recess area at 500 and 750 ,m (ARA500,750), trabecular iris space area at 500 and 750 ,m (TISA500,750), and determined age-related changes in these parameters with use of a linear mixed effect model that adjusted for gender, axial length, intraocular pressure, and keratometry data. Slopes of ACA parameters as a function of age were determined. For various AS-OCT parameters, the normalized slope was calculated by dividing the slope by the mean value. Results:, All analysed ACA parameters decreased with age in both nasal and temporal quadrants. Axial length and keratometry data were significant covariates for ACA changes. The slopes of ACD were ,0.02396 mm/year, AOD500, ARA500, and TISA500 measured at the temporal angle were ,0.00634 mm/year, ,0.0019 mm2/year, and ,0.00177 mm2/year, respectively. There was no age-dependent difference in central corneal thickness (p value; 0.4597) Based on the normalized slopes, the AOD showed the steepest slope at both temporal and nasal sectors. Conclusion:, All ACA parameters assessed by AS-OCT, which accounted for other ocular biometric parameters, showed significant negative slopes with increasing age. These results should be considered when assessing changes in the anterior chamber over time. [source]

    Is Functional Capacity Related to Left Atrial Contractile Function in Nonobstructive Hypertrophic Cardiomyopathy?

    Yukitaka Shizukuda MD
    The mechanisms underlying reduced exercise capacity in patients with nonobstructive hypertrophic cardiomyopathy (NHCM) could include perturbations of ventricular relaxation, diastolic compliance, or compensatory atrial systolic function. We hypothesized that a loss of atrial contractility in NHCM patients leads to reduced functional capacity. To test this hypothesis, we compared resting noninvasive left atrial ejection phase indices in 49 consecutive patients with NHCM (ages 36±10 years; 41% female) and normal left ventricular ejection fraction (mean, 68%±8%) with objective metabolic exercise parameters. Left atrial active emptying fraction, ejection force, and kinetic energy failed to predict exercise capacity. Only left atrial total and active emptying volumes correlated weakly with minute volume/CO2 production slope (r=0.31 and r=0.33; p<0.05 for both). Furthermore, when subjects were stratified by New York Heart Association symptomatology, exercise parameters,but not atrial contractility,differed between groups. These data, obtained at rest, fail to suggest that NHCM-related heart failure symptoms are due to an atrial myopathy. [source]

    Application of High Current and Current Zero Simulations of High-Voltage Circuit Breakers

    C. M. Franck
    Abstract This paper reports on the use of computational fluid dynamic (CFD) simulations to predict the interruption behaviour of high-voltage circuit breakers (HV-CB) using the self-blast principle. Two different levels of accuracy of the arc model are proven to be sufficiently accurate for simulating the high-current phase and the period around current zero (CZ). For the high-current phase, a simplified equivalent model of the arc is implemented to predict the pressure build-up, and even more important to accurately trace the hot gas from the arcing zone into the exhausts and the heating volume. A detailed analysis of the gas mixing in the heating volume for different arcing times and current amplitudes showed the optimum geometrical design of the heating volume. For the CZ phase, a more detailed arc model is needed including the effects of ohmic heating, radiative energy transfer, and turbulent cooling fully resolved in space and time. The validation with experiments was done and shows good agreement which justifies the use of the implemented model. With it, scaling laws varying only one parameter at a time (pressure and applied current slope) were derived and confirm previously found empirical laws. This is of particular interest, as it is very difficult to derive such scaling laws from experiments where the scatter is always very large and where it is impossible to vary only one parameter at a time. The influence of the most important geometrical parameters of the nozzle on the interruption performance is shown. In addition to previous experimental indications of this, the simulation reveals that turbulent cooling on the arc edge is the main reason for the difference in interruption performance. Moreover, the exact spatio-temporal build-up of arc resistance and with it the detailed understanding of the arc interruption process is possible and shown here for the first time. These simulations enable us to predict HV-CB performance and to minimise the number of development tests and are routinely used in new development projects. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]