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Ground Level (ground + level)
Selected AbstractsSettling the kings' lands: aprisio in Catalonia in perspectiveEARLY MEDIEVAL EUROPE, Issue 3 2010Jonathan Jarrett Important aspects of social history can sometimes be lost in legalisms. A long debate, recently continued in EME, has studied the right of aprisio claimed by those who took over wasteland on the frontier of the future Catalonia. This paper argues that previous treatments of the term have conflated many separate factors and misunderstood what aprisio actually was in practice. When studied at ground level it seems that, despite the role given to immigrant settlers by historians, landholders by aprisio need not have been newcomers, but locals using new rules for otherwise normal land clearances. [source] Dating young geomorphic surfaces using age of colonizing Douglas fir in southwestern Washington and northwestern Oregon, USA,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2007Thomas C. Pierson Abstract Dating of dynamic, young (<500 years) geomorphic landforms, particularly volcanofluvial features, requires higher precision than is possible with radiocarbon dating. Minimum ages of recently created landforms have long been obtained from tree-ring ages of the oldest trees growing on new surfaces. But to estimate the year of landform creation requires that two time corrections be added to tree ages obtained from increment cores: (1) the time interval between stabilization of the new landform surface and germination of the sampled trees (germination lag time or GLT); and (2) the interval between seedling germination and growth to sampling height, if the trees are not cored at ground level. The sum of these two time intervals is the colonization time gap (CTG). Such time corrections have been needed for more precise dating of terraces and floodplains in lowland river valleys in the Cascade Range, where significant eruption-induced lateral shifting and vertical aggradation of channels can occur over years to decades, and where timing of such geomorphic changes can be critical to emergency planning. Earliest colonizing Douglas fir (Pseudotsuga menziesii) were sampled for tree-ring dating at eight sites on lowland (<750 m a.s.l.), recently formed surfaces of known age near three Cascade volcanoes , Mount Rainier, Mount St. Helens and Mount Hood , in southwestern Washington and northwestern Oregon. Increment cores or stem sections were taken at breast height and, where possible, at ground level from the largest, oldest-looking trees at each study site. At least ten trees were sampled at each site unless the total of early colonizers was less. Results indicate that a correction of four years should be used for GLT and 10 years for CTG if the single largest (and presumed oldest) Douglas fir growing on a surface of unknown age is sampled. This approach would have a potential error of up to 20 years. Error can be reduced by sampling the five largest Douglas fir instead of the single largest. A GLT correction of 5 years should be added to the mean ring-count age of the five largest trees growing on the surface being dated, if the trees are cored at ground level. This correction would have an approximate error of ±5 years. If the trees are cored at about 1·4 m above the ground surface (breast height), a CTG correction of 11 years should be added to the mean age of the five sampled trees (with an error of about ±7 years). Published in 2006 by John Wiley & Sons, Ltd. [source] Aeolian dust dynamics in agricultural land areas in Lower Saxony, GermanyEARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2001Dirk Goossens Abstract The dynamics of fine aeolian dust emitted from agricultural land was investigated over 15 months near Grönheim, Lower Saxony, Germany. The following aspects were studied: airborne dust concentration, the ratio of mineral versus organic dust, the vertical distribution of the particles in the atmosphere, horizontal and vertically integrated horizontal dust flux, vertical dust flux, dust deposition at ground level, grain-size distribution of the mineral dust component, and vertical distribution of organic matter in the dust. Standard meteorological parameters (wind speed and direction, precipitation) were measured as well. Dust activity in Grönheim is high in spring (March,May) and autumn (October,November) and low to very low during the rest of the year. There is a strong relationship between the periods of tillage and the intensity of dust activity. Also, there is high dust activity during wind erosion events. For the year 1999, dust emission due to tillage was 6·6 times higher than dust emission due to wind erosion. A dust transport of 15·8 ton km,1 a,1 was calculated for the first 10 m of the atmosphere in 1999. Total dust transport (in the entire mixing layer) was estimated between 16 and 20 ton km,1 a,1. About 25,30 per cent of this dust is mineral dust, emitted from the fields during tillage or during wind erosion events. In spring and autumn there is a strong vertical stratification in the airborne sediment, with much (coarse) dust in the lower air layers and significantly less (and finer) dust at higher altitudes. In summer and winter, when there is no local dust production, there is no stratification: equal amounts of dust are transported at all heights. The stratification in spring and autumn is exclusively caused by the mineral part of the dust. The organic particles are much better mixed in the atmosphere because of their lower density. Copyright © 2001 John Wiley & Sons, Ltd. [source] Torsional response of symmetric buildings to incoherent and phase-delayed earthquake ground motionEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2003Ernesto Heredia-Zavoni Abstract This paper studies the effect of coherency loss and wave passage on the seismic torsional response of three-dimensional, multi-storey, multi-span, symmetric, linear elastic buildings. A model calibrated against statistical analyses of ground motion records in Mexico City is used for the coherency function. The structural response is assessed in terms of shear forces in structural elements. Incoherence and wave passage effects are found to be significant only for columns in the ground level of stiff systems. The increase of column shears in the ground level is much higher for soft than for firm soil conditions. For the torsionally stiff systems considered, it is found that incoherent and phase-delayed ground motions do not induce a significant rotational response of the structure. The use of a code eccentricity to account for torsion due to ground motion spatial variation is assessed. On firm soil, the use of a base shear along with an accidental eccentricity results in highly overestimated shear forces; however, for soft soil conditions, code formulations may result in underestimated shear forces. Copyright © 2003 John Wiley & Sons, Ltd. [source] Soil,pile,structure interaction under SH wave excitationEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2003K. K. Koo Abstract A continuum model for the interaction analysis of a fully coupled soil,pile,structure system under seismic excitation is presented in this paper. Only horizontal shaking induced by harmonic SH waves is considered so that the soil,pile,structure system is under anti-plane deformation. The soil mass, pile and superstructure were all considered as elastic with hysteretic damping, while geometrically both pile and structures were simplified as a beam model. Buildings of various heights in Hong Kong designed to resist wind load were analysed using the present model. It was discovered that the acceleration of the piled-structures at ground level can, in general, be larger than that of a free-field shaking of the soil site, depending on the excitation frequency. For typical piled-structures in Hong Kong, the amplification factor of shaking at the ground level does not show simple trends with the number of storeys of the superstructure, the thickness and the stiffness of soil, and the stiffness of the superstructure if number of storeys is fixed. The effect of pile stiffness on the amplification factor of shaking is, however, insignificant. Thus, simply increasing the pile size or the superstructure stiffness does not necessarily improve the seismic resistance of the soil,pile,structure system; on the contrary, it may lead to excessive amplification of shaking for the whole system. Copyright © 2003 John Wiley & Sons, Ltd. [source] Food or sex; pollinator,prey conflict in carnivorous plantsECOLOGY LETTERS, Issue 6 2001B. Anderson Carnivorous plants potentially trap their own pollinators and it has been argued that considerable spatial separation of flowers and traps has evolved to protect pollinators. We investigated flower-trap separation of Drosera and Utricularia. Short Drosera had a greater element of floral,trap separation than tall Drosera. Such a relationship is unexpected for plants whose peduncles were evolved to protect their pollinators. Utricularia can not trap pollinators but this genus still produces exceptionally long peduncles. We propose that flower-trap separation evolved because carnivorous plants are often short and need to project their flowers well above ground level to make them more attractive to pollinators. [source] Enhancing the P trapping of pasture filter strips: successes and pitfalls in the use of water supply residue and polyacrylamideEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2008M. R. Redding Summary In intensive pastoral systems the landscape at ground level is clad in dense, filtering vegetation , yet phosphorus losses in overland flow do occur, and pollution of surface waters is a serious consequence. The use of pre-applied polyacrylamide (PAM) or chitosan to trap particulate phosphorus (PP) and P-sorbing potable water treatment alum residue (PWTR) to enhance vegetative filtering effects is examined here using field and laboratory overland flow simulation (flows from 0.43 to 0.34 litres s,1 (m width),1) and analysis. Fitted equations suggest that up to 40% of dissolved reactive P applied (0.75 mg P litre,1) in overland flow could be captured in a flow length of 2.1 m (1 kg PWTR m,2). Unfortunately, drying decreased PWTR effectiveness, though little of the P captured was readily desorbed. This effect did not appear to be the result of gibbsite formation. Compared with the other treatments, there was a strong treatment effect of pre-applied PAM on the change in PP losses (P < 0.001) over time, though evidence suggests the PAM effect declined during a 44 minute flow period. We showed that the investigated two-pronged approach to the enhancement of the effectiveness of P trapping by pasture had limitations. Laboratory sheet-flow simulations suggest that a field-stable P sorber with sorption characteristics similar to those of the un-dried PWTR could be an effective retention enhancer for dissolved P. Pre-applied PAM can have an effect on particulate-P trapping but was rapidly dissolved and removed by flow. [source] Mitigation of the produced voltages in AC overhead power-lines/pipelines parallelism during power frequency and lightning conditionsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2005I. A. Metwally Abstract This paper presents a theoretical simulation for a pipeline running in parallel to AC overhead power lines using the ,CONCEPT II' package. This package is based on the method of moment combined with a transmission-line model. A 1,km long, 132,kV, three-phase, double-circuit transmission line, and a 2,km long, 40,cm diameter, 1,m high above-ground pipeline are modelled. Extra shielding wires (ESW) under the phase conductors are investigated. Produced voltages in the pipeline are computed under steady-state power frequency (50,Hz) as well as under direct and indirect lightning strikes to the power line. Different current waveforms are simulated to cover the whole range of those of the anticipated lightning. Under lightning strikes, the voltages across line insulators are computed, too. The results reveal that the ESW give many advantages; namely, (1) reducing the power-frequency electric and magnetic fields at the ground level to meet the regularity limits, (2) improving the shielding effectiveness during lightning strikes by reducing the insulator voltages, (3) mitigating the induced voltages in any metallic structure near the power lines, e.g., pipelines, and (4) using them as optical ground wires for telecommunication purposes, where the probability of lightning strikes to such ESW is much lower than that for the normally used grounding wire(s) at the tower top. Copyright © 2005 John Wiley & Sons, Ltd. [source] Design approach for the hybrid underground station at Union Suare/Market Street in San Francisco.GEOMECHANICS AND TUNNELLING, Issue 4 2009Entwurfskonzept für eine hybride U-Bahnstation Union Square/Market Street in San Francisco Abstract The new Central Subway extension through downtown San Francisco consists of three underground stations and 2.7 km TBMdriven twin tunnel. This paper provides a description of the preliminary analyses and design of the ground support and final lining for the Union Square\Market Street Station (UMS) along Stockton Street. This station will serve the Union Square Shopping District and connect to the BART Powell Street Station. Due to shortage of space above ground and to minimize surface disruption, the UMS station design requires a complex hybrid method consisting of a 20 m deep braced cut-and-cover box with a mined enlargement bulb below it with a height of 9.3 m and a width of 17.8 m. The majority of the UMS station will be excavated in saturated alluvial deposits. Undifferentiated old bay deposits will be encountered in the invert, underlain by dense marine sands. The groundwater varies from 5 to 10 m below ground level, so uplift of the combined bulb/box structure has to be taken into account. The Finite Element (FE) analysis of the UMS station cavern reflects the separate construction phases of the station platform box and the bulb to account for soil-structure interaction and load-sharing effects. FE analyses are used to estimate support requirements including ground improvement and to predict surface settlements. Die Erweiterung der Central Subway durch die Innenstadt von San Francisco beinhaltet drei Stationsbauwerke und 2,7 km maschinell vorgetriebene Doppelröhrentunnel. In diesem Artikel erfolgt eine Beschreibung der Voruntersuchungen und Vorbemessung der Stützmaßnahmen sowie der Innenschale der Union Square\Market Street Station (UMS) im Verlauf der Stockton Street. Diese Station soll dem Union Square Shopping Distrikt dienen und zur BART Powell Street Station verbinden. Aufgrund der beengten Platzverhältnisse und zur Minimierung der Beeinträchtigung der Oberfläche ist ein "hybrides" Konzept der UMS-Station erforderlich. Dieses besteht aus einer 20 m tiefen ausgesteiften Baugrube (Box) und einer darunterliegenden bergmännisch hergestellten Kaverne (Bulb) mit 9,3 m Höhe und 17,8 m Breite. Der Großteil der UMS-Station befindet sich in gesättigten alluvialen Ablagerungen. Undifferenziert werden alte Bucht-Ablagerungen und dichte marine Sande in der Sohle vorgefunden. Der Grundwasserspiegel variiert in einer Teufe zwischen 5 bis 10 m unter der Oberfläche, aus diesem Grund ist der Auftrieb des kombinierten Bauwerks bestehend aus Bulb und Box zu berücksichtigen. In Finite Element (FE) Berechnungen der UMS-Station werden die einzelnen Bauphasen des Stationsbauwerks, sowohl von Box als auch Bulb, modelliert, um die Wechselwirkungen von Baugrund-Bauwerk und die jeweiligen Lastumlagerungen zu berücksichtigen. Mittels FE-Berechnungen werden schließlich die notwendigen Stützmaßnahmen , diese beinhalten auch Bodenverbesserungsmaßnahmen , und die Oberflächensetzungen festgelegt. [source] Empirical models of UV total radiation and cloud effect studyINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2010David Mateos Villán Abstract Several empirical models of hourly ultraviolet total radiation (UVT) have been proposed in this study. Measurements of UVT radiation, 290,385 nm, have been recorded at ground level from February 2001 to June 2008 in Valladolid, Spain (latitude 41°40,N, longitude 4°50,W and 840 m a.s.l.). The empirical models have emerged due to the lack of some radiometric variables in measuring stations. Hence, good forecasts of them can be obtained from usual measures in these stations. Therefore, some advantages of the empirical models are that they allow the estimation of past missing data in the database and the forecast of future ultraviolet solar availability. In this study, reported models in the bibliography have been assessed and recalibrated. New expressions have been proposed that allow obtaining hourly values of ultraviolet radiation from global radiation measures and parameters as clearness index and relative optical air mass. The accuracy of these models has been assessed through the following statistical indices: mean bias, mean-absolute bias and root-mean-square errors whose values are close to zero, below 7% and below 10%, respectively. Two new clear sky models have been used to evaluate two new parameters: ultraviolet and global cloud modification factors, which can help to understand the role of the clouds on solar radiation. The ultraviolet cloud modification factor depends on cloudiness in such a way that its value under overcast skies is half of the cloudless skies one. Exponential and potential fits are the best relationships between both cloud factors. Finally, these parameters have been used to build new UV empirical models which show low values of the statistical indices mentioned above. Copyright © 2009 Royal Meteorological Society [source] UV and global solar radiation in ,ód,, Central PolandINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2010Agnieszka Podstawczy Abstract With the overall aim of quantifying urban atmospheric effects on different parts of the solar spectrum, a multi year analysis of data collected at ,ód, was undertaken. UV (290,400 nm) and global solar radiation measured by means of a Kipp and Zonen CUV3 radiometer and a Kipp and Zonen CM11 pyranometer in the center of ,ód, between 1997 and 2001 are analysed. The mean annual sum of global and UV solar radiation equaled 3710.8 MJ m,2 and 154.1 MJ m,2, respectively. The minimum monthly total of solar energy occurred in December (48.7 M Jm,2,global; 2.1 MJ m,2,UV); however, the maximum monthly total occurred atypically in May (620.9 MJ m,2,global; 25.3 MJ m,2,UV). UV clearness index (Kuv) is approximately half of the clearness index of the global solar radiation, indicating greater attenuation of that part of the spectrum (Kuv 0.14 in December to 0.26 in May). A linear regression model was fitted to the daily values of UV and global (g) solar irradiation (Duv = a + Dgb). The slope coefficient b and the coefficient of determination equal 0.039 and 0.98, respectively. Cloudiness exerts an important control on the solar radiation flux at the ground level and for the relation between UV and global solar radiation. The convective clouds caused an increase of global and UV solar irradiance by about 10,20% compared to clear days, the enhancement resulting from reflections. On clear days, UV comprises 3.3,4% of global solar irradiance (10-min values) on average, while during cloudy weather it increases to 8%. The results presented have implications for understanding the radiative transfer of UV and global solar radiation in the atmosphere over an urban area and the influence of clouds on transmission of solar radiation flux. Copyright © 2009 Royal Meteorological Society [source] Magnetic field of high-phase order and compact transmission linesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2002Hanafy M. IsmailArticle first published online: 14 DEC 200 Abstract Research has been conducted in high phase order (HPO) power transmission wherein 6 or 12 phases are used to transmit power in less physical space and with reduced environmental effects than conventional designs. In this paper, existing 3-phase double circuit transmission lines (TL) are reconfigured to 6-phase systems for the purpose of calculating and comparing the magnetic field of both systems. The magnetic field of several single-phase configurations; flat, vertical, delta and inverted-delta with the same degree of compaction is calculated and analysed at 1m height above the ground level. The magnetic field of the inverted-delta arrangement, which showed the lowest field profile, is compared with the magnetic field of 6- and 12-phase TLs having the same degree of line compaction and current loading conditions. The three systems are analysed when their lowest conductors had the same clearance to ground in one case and when their highest conductor positions were matched in another case. A comparison between 12-, 6- and 3-phase double circuit TLs having the same degree of compaction, the same phase voltage, the same clearance to ground and the same current per conductor is made to demonstrate if HPO lines reduce fields or not. The 6- and 12-phase lines are raised while keeping their conductors within the space, which would be taken by the conductors of the double circuit line. In this case, the highest conductor positions of the two systems are matched and the magnetic field is recomputed to conclude the results. The vector magnetic field potential concept, as extended to HPO transmission lines, together with a flexible developed computer program are used to calculate and present the magnetic flux density components profiles around the mentioned systems. Copyright © 2002 John Wiley & Sons, Ltd. [source] A model for optimisation of water management in rice polders in Thailand,IRRIGATION AND DRAINAGE, Issue 5 2005Preecha Wandee modèle mathématique; polders de riz; polder système de gestion de l'eau; optimisation Abstract This paper presents a mathematical model for the determination of optimal values for the main components of water management systems in rice polders in Thailand. The aim of the water management system in a rice area is to create good growing conditions for the crops. Under the hydrological conditions of Thailand the average rainfall during the rainy season is more than enough for growing rice or other crops. However, during the dry season there is a very small amount of rainfall. Thus the farmers are confronted with two quite different conditions and water management has to deal with irrigation and drainage issues. The main components of the water management system in a rice polder are the water level in the canals, the percentage of open surface water, discharge capacity from the field and discharge capacity of the pumping station or sluice. A model has been developed that takes into account damage due to flooding and drought as well as construction and maintenance cost for irrigation and drainage systems based on the hydrological conditions. Optimising of such a water management system means determining the main components in such a way that the equivalent annual costs are minimal. A case study has been done for a rice polder in Suphanburi province. It was found that the polder water level for rice under rainfed conditions could be kept above ground level to minimise loss of water from the rice field, whereas under irrigated conditions the polder water level has to be kept below ground level to get good drainage conditions. Copyright © 2005 John Wiley & Sons, Ltd. Cet article présente un modèle mathématique pour l'optimisation des composants principaux du système de gestion de l'eau dans des polders de riz en Thaïlande. Le but du système de gestion de l'eau dans un secteur de riz est de créer de bonnes conditions de croissance pour les récoltes. Dans la situation hydrologique de la Thaïlande les précipitations moyennes pendant la saison des pluies sont plus que suffisantes pour cultiver du riz croissant ou d'autres récoltes. Cependant, durant la saison sèche il y a très peu de précipitations. Ainsi les fermiers sont confrontés à deux conditions tout à fait différentes. Par conséquent la gestion de l'eau doit prendre en compte des problèmes d'irrigation et de drainage. Les composants principaux du système de gestion de l'eau dans un polder de riz sont le niveau d'eau dans les canaux, le pourcentage de l'eau ouverte, la capacité de décharge du champ et capacité de décharge de la station de pompage ou d'écluse. On a développé un modèle qui tient compte des dommages dus à l'inondation et à la sécheresse aussi bien que du coût de construction et d'entretien pour l'irrigation et à la canalisation basée sur les conditions hydrologiques. La linéarisation d'un tel système de gestion de l'eau implique de déterminer les composants principaux de telle manière que le système entier ait le coût équivalent annuel minimum. Une étude de cas a été faite pour un polder de riz dans la province de Suphanburi. On a constaté que le niveau d'eau du polder pour le riz irrigué à l'eau de pluie pouvait être gardé au-dessus du niveau du sol pour réduire au minimum la perte d' eau de la rizière, tandis que dans des conditions irriguées le niveau d'eau de polder doit être gardé au-dessous du niveau du sol pour obtenir de bonnes conditions de drainage. Copyright © 2005 John Wiley & Sons, Ltd. [source] Hardened foliated fault gouge from the Nojima Fault zone at Hirabayashi: Evidence for earthquake lightning accompanying the 1995 Kobe earthquake?ISLAND ARC, Issue 3-4 2001Yuji Enomoto Abstract Two anomalous features were found in the Nojima Fault zone at Hirabayashi in Awaji Island, south-west Japan: (i) hard foliated gouge between weathered granitic fault breccia and weakly consolidated mudstone of the Osaka Group; and (ii) mudstone near the gouge showing anomalous magnetization behavior. Roots of herbaceous vegetation near the foliated gouge were extraordinarily charred. In order to understand the nature of the gouge, shallow drillings were made to a depth of 3,14 m across the fault zone. Various physicochemical measurements of the gouge at depths and charred roots of herbaceous vegetation were conducted. The main results were: (i) Using electron spin resonance (ESR) analysis, the carbon radical peak (g = 2.006) of the charred roots was found to be 25 times larger than that of the non-charred roots of the same vegetation taken near the fault, indicating that the charred roots were subjected to baking; (ii) the hard foliated gouge clearly showed a lamellar structure consisting alternately of gray and black layers; (iii) the black layers in most of the foliated gouge showed flow structures almost parallel to the fault, but the gray layers rarely showed flow patterns; (iv) natural remanent magnetization (NRM) of the foliated gouge was 430 times greater than that of the granitic fault breccia and approximately 70 times greater than that of the mudstone; (v) the NRM intensity of the mudstone near the fault was highest near the ground level and decreased as the depth increased, although the magnetic susceptibility of the mudstone was almost constant and independent of depth; (vi) the high-coe civity magnetization component vectors of both the mudstone and the foliated gouge in a Schmidt equal-area projection was quite different from that of the present direction of the Earth's field; and (vii) using a magnetic force microscope, intense magnetic force lines were found in the black parts of the foliated gouge. It is suggested that these anomalies were possibly caused by earthquake lightning that accompanied the 1995 Kobe earthquake. In a spark plasma sintering test, which was conducted to simulate the possibility of earthquake lightning-induced sintering of the gouge, weakly altered gouge was successfully sintered within 10 s. The hardness of sintered sample was comparable to that of the hard foliated gouge. [source] Influence of hypobaric hypoxia on bispectral index and spectral entropy in volunteersACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 7 2009T. IKEDA Background: Hypoxia has been shown to change electroencephalogram parameters including frequency and amplitude, and may thus change bispectral index (BIS) and spectral entropy values. If hypoxia per se changes BIS and spectral entropy values, BIS and spectral entropy values may not correctly reflect the depth of anaesthesia during hypoxia. The aim of this study was to examine the changes in BIS and spectral entropy values during hypobaric hypoxia in volunteers. Methods: The study was conducted in a high-altitude chamber with 11 volunteers. After the subjects breathed 100% oxygen for 15 min at the ground level, the simulated altitude increased gradually to the 7620 m (25,000 ft) level while the subjects continued to breathe oxygen. Then, the subjects discontinued to breath oxygen and breathed room air at the 7620 m level for up to 5 min until they requested to stop hypoxic exposure. Oxygen saturation (SpO2), heart rate, 95% spectral edge frequency (SEF), BIS, response entropy (RE), and state entropy (SE) of spectral entropy were recorded throughout the study period. Results: Of the 11 subjects, seven subjects who underwent hypoxic exposure for 4 min were analysed. SpO2 decreased to 69% at the 7620 m level without oxygen. However, SEF, BIS, RE, and SE before and during hypoxic exposure were almost identical. Conclusion: These data suggest that hypoxia of oxygen saturation around 70% does not have a strong effect on BIS and spectral entropy. [source] Short-term survival and long-term mortality of Acacia drepanolobium after a controlled burnAFRICAN JOURNAL OF ECOLOGY, Issue 3 2008B. D. Okello Abstract We investigated the short- and long-term effects of a controlled burn in Acacia drepanolobium woodland in Laikipia, Kenya in 1998. Fire temperatures averaged 250°C at ground level, with a maximum of over 500°C, but were rarely >100°C at 1.5 m above the ground or more. Nine months after the fire, virtually all A. drepanolobium trees had survived the fire. Some smaller trees were burnt to ground level, but most were only ,top-killed' and had coppiced. Taller trees suffered less damage than smaller trees. However, a 2003 satellite image suggested a dramatic reduction in A. drepanolobium canopy cover at the site. A survey of the site in 2006 revealed that the density of larger A. drepanolobium trees was nearly three times greater in adjacent control areas than in the old burn, with a lesser reduction in the density of smaller trees. These data suggest that short-term measures of postburn survivorship may be deceptive, and that an additional source of tree mortality (perhaps elephants) was concentrated on trees in burned areas, even many months after the burn, with long-term consequences for tree and ecosystem dynamics. Résumé Nous avons étudié les effets à court et à long terme d'un feu contrôlé dans la forêt àAcacia drepanolobium située à Laikipia, au Kenya, en 1998. La température du feu avoisinait les 250°C au niveau du sol, avec un maximum de 500°C, mais elle dépassait rarement les 100°C à 1,5 mètre au-dessus du sol et plus haut. Neuf mois après le feu, pratiquement tous les Acacia drepanolobium avaient survécu. Certains des arbres plus petits avaient brûlé jusqu'au ras du sol, mais chez la plupart, seule la partie aérienne avait brûlé et ils avaient fait des repousses. Les arbres plus grands avaient subi moins de dommages. Pourtant, une image satellite prise en 2003 a suggéré une réduction spectaculaire de la canopée d'A. drepanolobiumà cet endroit. Une étude du site réalisée en 2006 a révélé que la densité des plus grands A. drepanolobiumétait près de trois fois plus forte dans les zones de contrôle adjacentes que sur le site brûlé, où la densité des plus petits arbres était moins réduite. Ces données suggèrent que les mesures de la survie postincendie faites à court terme peuvent être trompeuses, et qu'une source supplémentaire de mortalité des arbres (peut-être des éléphants) s'est concentrée sur les arbres des zones brûlées, même plusieurs mois plus tard, avec des conséquences à long terme pour les arbres et la dynamique de l'écosystème. [source] Effects of ground cover (straw and compost) on the abundance of natural enemies and soil macro invertebrates in vineyardsAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2007Linda J. Thomson Abstract 1,Herbicides are commonly applied under grapevines in Australia to remove weeds and thereby to avoid water loss through transpiration. 2,Interest in sustainability promotes a reduction in chemical inputs, including herbicides, leading to trials with surface mulches to suppress weeds. 3,Surface mulches may also influence the abundance of a range of invertebrates. Potentially, an increase in natural enemies will contribute to pest control and encourage a reduction in pesticide application. 4,We used three trapping methods and direct soil sampling to assess invertebrates at ground level, in the canopy and in the soil to determine the influence of mulch on natural enemies, potential pests and soil macroinvertebrates, including earthworms. 5,Collections sorted to family demonstrated that the addition of straw or compost mulches increased natural enemies collected with pitfall traps and soil organisms. However, there was no clear indication of the overall superiority of either mulch. 6,Abundance of ground beetles, parasitoid Hymenoptera and spiders collected with pitfall traps were increased by the addition of mulches. In the canopy, predatory and parasitic Diptera and predatory Hemiptera increased after mulching. 7,Earthworms collected by hand sorting soil increased with straw mulching. 8,No influence on pests was detected. Although Lepidoptera and Sigmurethra, collected in pitfall traps, increased with straw mulching, neither included pest species. 9,The results are discussed with reference to the potential economic impact of mulches. [source] Mechanisms blocking Pinus sylvestris colonization of Mediterranean mountain meadowsJOURNAL OF VEGETATION SCIENCE, Issue 5 2002Jorge Castro Tutin et al. (1964,1980) Abstract. In southern Mediterranean Pinus sylvestris forests there are grassy meadows that resist invasion of trees despite the proximity to seed sources. In this study, we investigate the mechanisms blocking colonization by Pinus sylvestris of the meadows. Two experiments were conducted in which seeds were sown either at 1 cm depth or on the surface to simulate dispersal, and three treatments of vegetation removal were applied: Disturbed (where the herbaceous layer was eliminated, exposing the mineral soil), Clipped (vegetation cut at ground level) and Control (no disturbance of the herbaceous layer). In addition, the effect of seed predators was controlled by using wire cages in the case of the surface sown experiment. When seeds were sown at 1 cm depth, seedling emergence was not reduced by the herbaceous layer. In contrast, when seeds were surface sown and predators were excluded, the rate of emergence was low in the Control treatment, intermediate in Clipped and high in Disturbed. Seedling emergence was, however, minimal when predators were not excluded, irrespective of the disturbance level. Seedling survival and growth after three years of study were similar among treatments. The results show that the seed predation and the physical barrier created by the herbaceous layer are the two mechanisms blocking the encroachment of Pinus sylvestris onto these Mediterranean mountain meadows, limiting the regeneration and potential expansion of the forest. [source] Evaluation of biological and chemical insecticide mixture against Aedes aegypti larvae and adults by thermal fogging in SingaporeMEDICAL AND VETERINARY ENTOMOLOGY, Issue 3 2001Y. K. Chung Abstract. To improve the operational efficiency of dengue vector control in Singapore, larvicide and adulticide were applied together by thermal fog generator (Agrofog® AF40). The mixture consisted of Bacillus thuringiensis var. israelensis (Vectobac® 12 AS) as biological larvicide at 1.5 L/ha and pirimiphos-methyl (Actellic® 50 EC) as adulticide at 100 g ai/ha, diluted 10-fold with water. Aerosol of this mixture was evaluated against the mosquito Aedes aegypti (L.) (Diptera: Culicidae) in bioassays using cages of 10 adult females exposed at heights of 0.3,2.4 m and distances of 3,12 m from the hand-held generator. Cups containing 200 mL water were treated at ground level by exposure to the aerosol application at the same distances from the generator. Subsequent larval bioassays on days 1, 7, 14, 21 and 28 post-spray involved exposing 20 larvae/cup for 48 h. Droplets had VMD 57 µm and female mosquitoes were killed by 2 s exposure to the aerosol at 3 m. We obtained 92,100% mortality of the adult mosquitoes and 100% control of larvae at 3 m distance, but only 10,13% mortality at 12 m from the fogger. In treated cups, larvae showed high mortality (92%) when exposed for 48 h even 1 month post-treatment. Results demonstrate the practical advantage of using this mixture of Vectobac® 12AS and Actellic® 50 EC for simultaneous control of Aedes adults and larvae, with prolonged larvicidal efficacy in treated containers. [source] Flow and pollution transport during Wagerup 2006: a case studyMETEOROLOGICAL APPLICATIONS, Issue 3 2010Charles Retallack Abstract As part of a broader field campaign dubbed Wagerup 2006, a case study was carried out to determine the overnight pollution transport mechanisms and flow characteristics near Wagerup, Western Australia. The ambient conditions were characterized by stable stratification with little synoptic influence in the lower boundary layer. An elevated jet intrusion originating on a nearby escarpment slope was found to induce sufficient mixing causing elevated pollution plumes to reach ground level. Onset of mixing was accurately predicted by non-linear critical Richardson number estimates obtained in previous laboratory work. The increase in ground level temperatures brought about by shear induced mixing later prompted a sea-breeze like gravity current that was completely blocked by the escarpment and as a result pollutants were trapped against the escarpment slope. A notable side effect of the topographic blocking was the subsequent steady 360° rotation of ground level winds within an area of influence described by the Rossby deformation radius. Copyright © 2009 Royal Meteorological Society [source] Sky view factor analysis , implications for urban air temperature differencesMETEOROLOGICAL APPLICATIONS, Issue 3 2004Marie K. Svensson This study identifies the use of the sky view factor (SVF) in urban climate studies. In addition, it relates air temperature differences to the SVF and examines these differences with respect to the height at which fish-eye photographs are taken for the calculation of the SVF. The study focuses on night-time air temperature patterns within the urban canopy using data collected during clear, calm nights from sixteen permanent stations and from car measurements. Fish-eye photographs taken at two levels (2 m above ground and at ground level) are compared and shown to be statistically different. The results of the study performed in Göteborg, Sweden, indicate a fairly strong relationship between air temperature and SVF. The permanent stations used indicate that it is better to use fish-eye photographs taken at ground level. The relationship is determined by means of regression analysis. The SVF variation in urban areas and the importance of SVF in relation to other central parameters such as thermal admittance are also discussed. Copyright © 2004 Royal Meteorological Society [source] A simple device for the evaluation of the UV radiation indexMETEOROLOGICAL APPLICATIONS, Issue 2 2003Giuseppe Rocco Casale The solar ultraviolet radiation (UV) flux density at the earth's surface depends on the incoming solar energy and the transmission properties of the atmosphere. UV radiation is strongly absorbed by ozone in the spectral range 200,310 nm, while the attenuation is increasingly weaker at longer wavelengths. Following the discovery of the Antarctic ozone hole in 1985, the risk of a possible UV increase at ground level, due to the observed stratospheric ozone depletion, has heightened the interest within the scientific community given the potentially harmful effects on terrestrial and aquatic ecosystems. Spectroradiometers, broad-band meters and dosimeters may be used for measurements of solar UV. In addition, radiation transfer models can be used to quantify UV irradiances at various times and locations, provided that the extraterrestrial solar radiation and the state of the atmosphere are known. Information about UV radiation at the earth's surface is given by the ultraviolet index ,UVI', which is defined as the effective integrated irradiance (280,400 nm) weighted by the erythemal action spectrum. The UV Index is widely used by many international weather services as an indicator of UV levels at the earth's surface providing public awareness of the effects of prolonged exposure to the sun's rays. The aim of this paper is to present a device capable of estimating the UV Index. This device is a compact disc, used as a sundial, and is based on modelled UV irradiances derived from the STAR radiative transfer model (System for Transfer of Atmospheric Radiation). The device was tested in an urban setting under clear sky conditions. Copyright © 2003 Royal Meteorological Society [source] Conidial dispersal by Alternaria brassicicola on Chinese cabbage (Brassica pekinensis) in the field and under simulated conditionsPLANT PATHOLOGY, Issue 5 2003L. Y. Chen This study investigated conidial dispersal in the field, and effects of simulated wind and rain on the dispersal of A. brassicicola on Chinese cabbage (Brassica pekinensis). Spores were sampled using a Burkard volumetric spore sampler and rotorod samplers in a Chinese cabbage crop. Disease incidence in the field was well fitted by a Gompertz curve with an adjusted r2 of >0·99. Conidia of A. brassicicola were trapped in the field throughout the growing season. Peaks of high spore concentrations were usually associated with dry days, shortly after rain, high temperature or high wind speed. Diurnal periodicity of spore dispersal showed a peak of conidia trapped around 10·00 h. The number of conidia trapped at a height of 25 cm above ground level was greater than that at 50, 75 and 100 cm. Conidial dispersal was also studied under simulated conditions in a wind tunnel and a rain simulator. Generalized linear models were used to model these data. The number of conidia caught increased significantly at higher wind speeds and at higher rain intensities. Under simulated wind conditions, the number of conidia dispersed from source plants with wet leaves was only 22% of that for plants with dry leaves. Linear relationships were found between the number of conidia caught and the degree of infection of trap plants. [source] Effects of a Severe Frost on Riparian Rainforest Restoration in the Australian Wet Tropics: Foliage Retention by Species and the Role of Forest ShelterRESTORATION ECOLOGY, Issue 4 2010Timothy J. Curran Restoration of ecological communities that can withstand future climate and land use changes requires information on species responses to various natural disturbances. Frost is an important disturbance that regulates plant species distributions, and although rare in tropical rainforest, it can occur in upland areas, especially where deforestation has occurred. We report the impacts of a severe frost that occurred in June and July 2007 on the Atherton Tablelands, Queensland, Australia and caused extensive damage to riparian restoration plots of upland rainforest species. We estimated proportion foliage retention to (1) compare impacts across 45 species; (2) examine the influence of plant height on frost effects; and (3) determine if plantings under shelterbelts of mature trees received less damage. Species exhibited different levels of foliage retention. Species that were particularly frost resistant included those from riparian habitats and a conifer. Some heavily impacted species are deciduous and may survive frost by shedding leaves; this warrants further investigation. Plant canopy height above ground level was only weakly correlated to foliage retention. Sheltered plants were much less damaged than unsheltered conspecifics, suggesting a useful way to mitigate frost impacts. These principles should help guide the development of resilient ecological communities in frost-prone areas. [source] Digital Surface Development of Large Cylindrical and Conical Structures With a Single-Image TechniqueTHE PHOTOGRAMMETRIC RECORD, Issue 97 2001Iliana Theodoropoulou Normally, regular surfaces of architectural or archaeological interest can be accurately mapped with single-image techniques. Whenever possible, such surfaces are developed digitally, or they are presented as suitable cartographic projections. This paper describes the raster development of two large towers, one conical and one cylindrical, with heights of 19m and 12 m, and diameters of approximately 10m and 8m, respectively. The towers, dating from circa 300 BC, are situated on Greek islands and are accessible only on foot. The first tower was imaged from its surrounding hills with several lenses, including powerful telephoto lenses. The other tower was recorded from up to 9m above ground level by means of a modified fishing rod carrying a lightweight 35mm camera. All the non-metric photographs, taken at a negative scale of approximately 1:350 which allowed an overall accuracy of 3 cm to 4 cm to be achieved, were developed digitally and then mosaicked. The raster products are described and discussed. [source] Numerical simulation of meso-gamma scale features of föhn at ground level in the Rhine valleyTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 608 2005G. Jaubert Abstract This paper examines the impact of a mesoscale analysis (2.5 km grid distance) on the simulation of the meso-gamma scale aspects of föhn in the Rhine Valley. The föhn event, documented during IOP15 (5 November 1999) of the Mesoscale Alpine Programme, was standard in terms of intensity and was characterized by an important temporal variability. Many instruments operating in the Rhine valley target area are used to validate the simulation, in particular the airborne nadir-pointing lidar LEANDRE 2 (flown over the lower Rhine valley) as well as a wind profiler and a radio accoustic sounding system collocated in Rankweil, Austria. The large observational dataset acquired during the IOP allowed documentation of the entire föhn life cycle. For most of the IOP, a cold pool remained near the ground in the lower northern part of the valley. The non-hydrostatic model Meso-NH, used in a grid-nesting configuration with two nested models and initialized with a mesoscale analysis, allowed us to simulate realistically the location and depth of the cold pool. The relationship between the föhn intensity and the large-scale environment is also examined. The flow regime is a ,flow around' the Alps. The variability of this flow at the western tip of the Alps could explain some of the temporal changes observed at low level in the Rhine valley. Copyright © 2005 Royal Meteorological Society [source] Density currents in shear flows: Effects of rigid lid and cold-pool internal circulation, and application to squall line dynamicsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 579 2002Ming Xue Abstract Idealized density current models that contain a rigid lid, developed in previous studies, are evaluated. It is shown, through numerical experiments, that a realistic stable layer placed at the level of the rigid lid acts very much like a rigid lid, in confining the environmental flow to the levels below and in controlling the behaviour of density currents that propagate in the flow. When this stable layer is replaced by a neutrally stable layer, the behaviour of the density current is very different. These results support the hypothesis that in the atmosphere, the tropopause or a tropospheric inversion layer acts much like a rigid lid in the idealized density current models, and the solutions of these models are applicable to organized quasi-two-dimensional convective systems such as squall lines in the atmosphere. The effects of cold-pool internal circulations on density current behaviour are also examined. When a single circulation is present initially inside the cold pool, the direction of circulation that gives rise to a smaller shear across the density interface leads to a smoother interface and a much more steady density current head. Large-amplitude eddies develop along the interface when the direction of circulation is reversed. When two layers of shear are initially present inside the cold pool, the flow pattern inside the cold pool tends to be dominated by the circulation of the lower layer. In this case, the behaviour of the density interface and density current head depends on more than just the initial cross-interface shear. The overall flow pattern in the density current, in which the cold-pool circulation contains rearward flows at the ground level, bears a close similarity to that found in mature squall line systems, as shown by comparisons with a simulated squall line. When the cold pool in a squall line is defined in terms of the equivalent potential temperature, the solutions of idealized density currents in sheared flows become more readily applicable to squall lines. Copyright © 2002 Royal Meteorological Society. [source] Pressures within air-filled tracheal cuffs at altitude , an in vivo studyANAESTHESIA, Issue 3 2004J. Henning Summary Aeromedical transport of mechanically ventilated critically ill patients is now a frequent occurrence. However, the performance of the air filled tracheal tube cuff at altitude has not been studied in vivo. We measured the tracheal cuff pressures at ground level and at 3000 ft, in 10 intubated patients. With air providing the seal in the cuff the mean rise in cuff pressure was 23 cmH2O, which took the pressures above the critical perfusion pressure of the tracheal mucosa. This could lead to tracheal injury. [source] Response to cutting of Larrea divaricata and L. cuneifolia in ArgentinaAPPLIED VEGETATION SCIENCE, Issue 1 2002E. Martinez Carretero Abstract. The response of Larrea divaricata and L. cuneifolia to cutting stems 0,20 cm above the ground was studied in the arid piedmont area west of Mendoza, Argentina. The species occur at different elevations and in vegetation zones: L. cuneifolia < 1250 m; L. divaricata between 1250 and 2500 m. Four treatments with 10 replicates were analysed in randomly chosen plants: cut at ground level with lopping shears; cut at ground level with a pick; cut at 10 cm with lopping shears; and cut at 20 cm with lopping shears. The initial and final height, volume, and dry matter (above- and below-ground) were determined. The relation between volume and initial and final dry matter and height was analysed through a factorial MANOVA (p < 0,05), and the functional relation between volume, dry matter and height was estimated by adjusting a regression model. In both species, maximum recovery was reached when cut with shears, and predicted recovery (turnover) was 17-18 yr. In the two last treatments height was a useful predictor of dry matter. L. divaricata -dominated plots have a lower biomass, growth rate, and allocation to stems and root than L. cuneifolia -dominated plots. Regrowth following clipping on an area of 3,10 ha, is sufficient to support the annual needs (cooking and heating) of one family. [source] The Tree Canopy as BlueprintARCHITECTURAL DESIGN, Issue 3 2010Mitchell Schwarzer Abstract As the opportunities for new territories become more limited, the only way is up. Mitchell Schwarzer explores the dizzying heights of the ,last biotic frontier' of arboreal architecture with its high platforms, walkways and canopy craft. Challenging in construction and engineering terms, the tree canopy also requires engaging with a different atmospheric and climatic range to those conditions encountered at ground level. 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