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Construction Activity (construction + activity)

Distribution by Scientific Domains

Engineering	33%

Selected Abstracts

Soil Nitrogen Pools Associated with Revegetation of Disturbed Sites in the Lake Tahoe Area

RESTORATION ECOLOGY, Issue 2 2002
V. P. Claassen
Abstract Thin, poorly developed soils in the high elevation, summer-dry environment near Lake Tahoe, California are easily disturbed by anthropogenic impacts. Subsoils and parent materials that are exposed by vegetation removal and topsoil erosion or by burial during construction activities are difficult to revegetate and may continue to erode for decades after disturbance. The resulting sediment loads contribute to decreased water quality in local watersheds and to the loss of clarity in Lake Tahoe. Field observations suggest that soil disturbance often results in depletion of soil nitrogen (N) reserves and that the remaining substrates may be unable to provide adequate N for revegetation. To quantify the levels of soil N that are associated with higher levels of percent plant cover on previously disturbed soils in the Lake Tahoe area, a basin-wide survey and a second paired site study were conducted. Results indicate that extractable ammonium and nitrate levels correlate poorly with percent vegetative cover, whereas the correlations of anaerobically mineralizable N and total N are stronger and account for nearly 50% of the variability in plant cover data. Sites with plant cover measuring greater than 40% are associated with total soil N levels of about 1,200 kg N/ha and anaerobic mineralizable N levels of about 26 kg N/ha. Despite high concentrations of N in the surface soils, a large fraction of the N in the 0- to 50-cm profile occurs below 30 cm, when measured on a landscape basis. [source]

Q- und R-Matten aus Kunststoff für Bewehrungsaufgaben in der Geotechnik

BAUTECHNIK, Issue 9 2004
Georg Heerten Dr.-Ing.
Wachsende Güterströme und Warenverkehre im Zentrum eines wachsenden Europas und zunehmender Warenaustausch als Folge der Globalisierung der Weltwirtschaft stellen erhebliche Anforderungen an den Erhalt und Ausbau leistungsfähiger Infrastruktursysteme (Straße, Schiene, Wasserstraße). Nachhaltigkeitskonzepte bei der Bautätigkeit und Finanzierungsprobleme der öffentlichen Auftraggeber sind aktuelle Randbedingungen, denen mit Geokunststoff-Bauweisen optimal Rechnung getragen werden kann. Es können neben den technischen auch die ökonomischen und ökologischen Vorteile , Baukosten sparen, Baustoffressourcen schonen , parallel genutzt werden. Eine Stützwand als "Bewehrte-Erde-Konstruktion" kann ganz erheblich kostengünstiger als eine Stahlbeton-Stützmauer hergestellt werden. Die Ertüchtigung von wenig tragfähigen Böden mit flächig angeordneten Bewehrungslagen und/oder pfahlartigen geokunststoffummantelten Bodensäulen vermeidet umfangreichen Bodenaustausch, spart Kosten, verhindert umfangreichen Transport von Bodenmassen mit LKWs. Hierdurch werden knappe Baustoffressourcen wie Sand und Kies geschont sowie eine z. T. erhebliche Entlastung örtlicher Verkehrswege bewirkt. Q and R mats made of synthetics for reinforcement functions in the field of geotechnics. An increasing flow of goods in a growing central Europe, resulting from the globalisation of the world economy, makes high demands on the maintenance and development of an efficient infrastructure (road, railway, waterway). Sustainability concepts for the construction activities and funding problems of the contracting authorities are current boundary conditions which can be accommodated optimally with geosynthetic construction methods. At the same time, besides the technical advantages, the economical and ecological advantages can be used too , saving of construction costs and taking care of building materials resources. A retaining wall as "Reinforced-Earth-Structure" can be constructed at much lower cost than a retaining wall made of reinforced concrete. The improvement of subsoils with low bearing capacity, by using reinforcing layers in the area and/or soil columns similar to piles wrapped with geosynthetics, avoids a considerable exchange of soil, saves costs and avoids substantial soil transports by trucks. Thus, care is taken on rare building materials resources like sand and gravel and the traffic routes are partly released to a high extent. [source]

Toward a Trust-Based Construction Management

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2010
Annie Guerriero
Moreover, the uncertainty linked to the environment of the construction activity makes way for the notion of trust. The coordinator can make use of multiple tools/views for accomplishing his mission. This research work suggests analyzing data coming from these different views to consolidate trust indicators informing the coordinator about "trust in the correct progression of the construction activity." The approach suggested in this article distinguishes between four aspects of the activity determining the global trust level: task progress, actor's performance, documents required to perform the task, and building elements resulting from the task. The proposal suggests introducing these trust indicators in a dashboard, included in a multiview interface, thus allowing the coordinator to identify the tasks with a low trust level and to understand the nature of dysfunctions. A prototype has been developed and integrated in a service-based IT infrastructure. Results of an experiment stage are finally discussed to validate the approach. [source]

CONSTRUCTION COSTS AND THE SUPPLY OF HOUSING STRUCTURE,

JOURNAL OF REGIONAL SCIENCE, Issue 4 2006
Joseph Gyourko
ABSTRACT Construction costs account for the bulk of the price of new houses in most markets, but their study has been relatively neglected. We document that there are economically large differences in construction costs across U.S. housing markets. We also estimate a very elastic supply for physical structure; hence, differences in construction activity across markets do not explain the variation in costs. Supply shifters that collectively do account for differences in building costs include the extent of unionization within the construction sector, local wages, local topography in terms of the presence of high hills and mountains, and the local regulatory environment. [source]

ECONOMIC FUNDAMENTALS IN LOCAL HOUSING MARKETS: EVIDENCE FROM U.S. METROPOLITAN REGIONS

JOURNAL OF REGIONAL SCIENCE, Issue 3 2006
Min Hwang
ABSTRACT This paper investigates the effects of national and regional economic conditions on outcomes in the single-family housing market: housing prices, vacancies, and residential construction activity. Our three-equation model confirms the importance of changes in regional economic conditions, income, and employment on local housing markets. The results also provide the first detailed evidence on the importance of vacancies in the owner-occupied housing market on housing prices and supplier activities. The results also document the importance of variations in materials, labor and capital costs, and regulation in affecting new supply. Simulation exercises, using standard impulse response models, document the lags in market responses to exogenous shocks and the variations arising from differences in local parameters. The results also suggest the importance of local regulation in affecting the pattern of market responses to regional income shocks. [source]

Paradoxical early glucocorticoid induction of stem cell factor (SCF) expression in inflammatory conditions

BRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2004
Carla Alexandra Da Silva
Stem cell factor (SCF) is a major growth factor for mast cells, promoting their differentiation and chemotaxis. Its expression is regulated by glucocorticoids in inflammatory conditions, showing an early increased protein expression, before the expected anti-inflammatory decrease (Da Silva et al., Br. J. Pharmacol. 2002:135,1634). We here evaluated the early kinetic of SCF expression regulated by interleukin (IL)-1,, budesonide and the combination of both in human lung fibroblasts in culture. Budesonide potentiated the IL-1, -enhanced expression of SCF mRNA (+103%) and protein (+98%) very shortly after treatment (at 30 min and 1 h, respectively). A gentle downregulation followed. This potentiating effect of budesonide was related to increased SCF mRNA stability and SCF gene transcription. Deletion of a ,B-like site that we identified in the first intron of the SCF gene, in a luciferase reporter system, abolished the potentiation by budesonide, as well as the effect of IL-1, alone, as compared to the wild-type construction activity. All budesonide-induced effects were glucocorticoid-receptor dependent, since they were reproduced by dexamethasone and blocked by RU486. IL-1,+budesonide did not affect the relative expression of the soluble and membrane-bound forms of SCF. In conclusion, our results clearly show that glucocorticoids act very early to adversely increase the expression of SCF mRNA and protein in the inflammatory conditions created by IL-1,, and that this effect involves increased mRNA stability and increased gene expression through activation of the NF- ,B-like responsive element. British Journal of Pharmacology (2004) 141, 75,84. doi:10.1038/sj.bjp.0705598 [source]