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Active Sources (active + source)

Distribution by Scientific Domains

Earth and Environmental Science	44%
Engineering	22%

Distribution within Earth and Environmental Science

Environmental Management, Policy & Planning	50%

Selected Abstracts

When is a minority a minority?

EUROPEAN JOURNAL OF SOCIAL PSYCHOLOGY, Issue 4 2002
Active versus passive minority advocacy, social influence
Some conceptions of minority influence have stressed the impact of the mere existence of an unpopular, deviant position. Others (e.g. Moscovici, 1980) have emphasized the active opposition of a committed minority to a powerful majority. An active advocate is defined as one that is aware of the level of support for his/her position, expresses his/her position openly, and whose outcomes may depend on others' agreement/disagreement. In the present study, the potential moderating role of an advocates' active/passive status on opinion change was examined. When the issue was highly relevant to the target of influence, all that mattered was the quality of the source's arguments (i.e. majority, minority, active source,=,passive source). When the issue was not highly relevant to the target, though, active and passive sources had different impact: (1) active sources prompted attention to argument quality (for minorities) and heuristic compliance (for majorities); (2) passive sources prompted insensitivity to both the popularity of the position and to the quality of the source's arguments. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Inflammatory cytokine production by immunological and foreign body multinucleated giant cells

IMMUNOLOGY, Issue 3 2000
R. Hernandez-Pando
Summary Multinucleated giant cells (MGC) are a common feature of granulomas. The mechanism of their formation has been studied extensively, but their function has not been completely characterized. A new method for the in vivo production of MGC was developed involving subcutaneous injection of microscopic nitrocellulose particles with adsorbed mycobacterial antigens into the footpads of sensitized BALB/c mice (immune [I]-MGC), or by nitrocellulose administration to non-sensitized mice (foreign body [FB]-MGC). The development of granulomas with a highly enriched MGC population was observed 2 weeks after the nitrocellulose injection. MGC were larger with a greater number of nuclei in I-MGC than in FB-MGC. From days 7,28 after nitrocellulose administration, the production of interleukin-1, (IL-1,) and tumour necrosis factor-, (TNF-,) was demonstrated in both MGC types by in situ reverse transcription,polymerase chain reaction (RT,PCR) and immunohistochemistry. After 2 months, the MGC had ceased production of IL-1, and TNF-,, but the expression of transforming growth factor-, (TGF-,) was very high, occurring together with extensive fibrosis. These results suggest that MGC are an active source of inflammatory cytokines, which can contribute to the initiation, maintenance and down-regulation of granulomatous inflammation induced by immunological and inert substances. [source]

An X-band microstrip oscillator integrated with frequency-selecting patch antenna

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2009
D. H. Lee
Abstract A simple design for microstrip oscillator consisting of an active source and an output patch antenna is presented. The active source is designed to possess negative-resistance over broad bandwidth but not to oscillate without the output patch antenna. Two different source circuits that are potentially unstable over full C-band and X-band are fabricated. Six different-size patch antennas are then connected with each source circuit to demonstrate the oscillation frequency control. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1963,1966, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24481 [source]

When is a minority a minority?

Required source distribution for interferometry of waves and diffusive fields

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2009
Yuanzhong Fan
SUMMARY The Green's function that describes wave propagation between two receivers can be reconstructed by cross-correlation provided that the receivers are surrounded by sources on a closed surface. This technique is referred to as ,interferometry' in exploration seismology. The same technique for Green's function extraction can be applied to the solution of the diffusion equation if there are sources throughout in the volume. In practice, we have only a finite number of active sources. The issues of the required source distribution is investigated, as is the feasibility of reconstructing the Green's function of the diffusion equation using a limited number of sources within a finite volume. We study these questions for homogeneous and heterogeneous media for wave propagation and homogeneous media for diffusion using numerical simulations. These simulations show that for the used model, the angular distribution of sources is critical in wave problems in homogeneous media. In heterogeneous media, the position and size of the heterogeneous area with respect to the sources determine the required source distribution. For diffusion, the sensitivity to the sources decays from the midpoint between the two receivers. The required width of the source distribution decreases with frequency, with the result that the required source distribution for early- and late-time reconstruction is different. The derived source distribution criterion for diffusion suggests that the cross-correlation-based interferometry is difficult to apply in field condition. [source]

Distance separated simultaneous sweeping, for fast, clean, vibroseis acquisition

GEOPHYSICAL PROSPECTING, Issue 1 2010
Jack Bouska
ABSTRACT Distance separated simultaneous sweeping DS3 is a new vibroseis technique that produces independent records, uncontaminated by simultaneous source interference, for a range of offsets and depths that span all target zones of interest. Use of DS3 on a recent seismic survey in Oman, resulted in a peak acquisition rate of 1024 records per hour. This survey employed 15 vibrators, with a distance separation of 12 km between simultaneous active sources, recorded by 8000 active channels across 22 live lines in an 18.5 km × 11 km receiver patch. Broad distribution of simultaneous sources, across an adequately sized recording patch, effectively partitions the sensors so that each trace records only one of the simultaneous sources. With proper source separation, on a scale similar to twice the maximum usable source receiver offset, wavefield overlap occurs below the zone of interest. This yields records that are indistinguishable from non-simultaneous source data, within temporal and spatial limits. This DS3 technique may be implemented using a wide variety of acquisition geometries, optimally with spatially large recording patches that enable appropriate source separation distances. DS3 improves acquisition efficiency without data quality degradation, eliminating the requirement for special data processing or noise attenuation. [source]

Equivalent circuit representation for integral formulations of electromagnetic problems

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1 2002
H. Baudrand
The purpose of this study is to investigate the resources offered by electromagnetic equivalent circuits as a tool for the systematic derivation of integral equations and also, to propose consistent models for active sources. Copyright © 2002 John Wiley & Sons, Ltd. [source]

The management lessons learned from sediment remediation in the Detroit River , western Lake Erie watershed

LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 3-4 2004
John H. Hartig
Abstract During the 1970s,1990s, considerable emphasis was placed on minimizing the inputs of polychlorinated biphenyls (PCBs) from active sources. In addition, between 1993 and 2001, , $US130 × 106 was spent for sediment remediation within the western Lake Erie , Detroit River basin. In general, although PCB contamination of the Detroit River and Lake Erie declined significantly between the 1970s and mid-1990s, it has remained fairly stable over the past 10 years. Control of PCBs and other contaminants at their source remains a primary imperative for action. Remediation of contaminated sediments is growing in importance, however, as greater levels of source control are achieved. From a sediment management perspective, it is estimated that between 1993 and 2001 a substantially higher mass of PCBs (over two orders of magnitude higher) was removed as a result of contaminated sediment remediation, as compared to navigational dredging of shipping channels. In addition, there is a strong and compelling rationale for moving expeditiously to remediate severely contaminated sediment while it is still relatively contained in a small geographical area. The cost of not acting in a timely manner might be to exacerbate environmental problems including increased deformities and reproductive problems in wildlife, delayed ecosystem recovery and increased costs, or even preclusion of future sediment remediation. Based on discussions at a United States of America,Canada workshop held in 2002, key management advice includes continued emphasis to be placed on remediating contaminated sediment hot spots (including evaluating the effectiveness of projects), integrated monitoring efforts to be focused on beneficial use restoration and a high priority to be placed on sustaining and building upon modelling efforts, in order to be able to accurately predict and evaluate ecosystem responses to remedial and preventive actions. [source]

Evaluation of natural attenuation at a 1,4-dioxane-contaminated site

REMEDIATION, Issue 1 2008
Dora Sheau-Yun Chiang
1,4-Dioxane entered the environment as a result of historic leaks and spills in the production area at an industrial facility in the southeastern coastal plain. The areal extent of the 1,4-dioxane plume is several hundred acres and is largely contained on the site. Land use adjacent to the plant property is primarily undeveloped (wetlands or woods) or industrial, with a small area of mixed land use (commercial/residential) to the southwest and north. The surficial aquifer is a relatively simple hydrogeologic system with well-defined boundaries and is comprised of a 50- to 70-foot-thick deposit of alluvial/fluvial sand and gravel that overlies an aquitard in excess of 100 feet thick. A groundwater flow model, developed and calibrated using field-measured data, was used for the fate-and-transport modeling of 1,4-dioxane. The flow-and-transport model, combined with the evaluation of other site geochemical data, was used to support the selection of monitored natural attenuation (MNA) as the proposed groundwater remedy for the site. Since the active sources of contamination have been removed and the modeling/field data demonstrated that the plume was stable and not expanding, the proposed MNA approach was accepted and approved by the regulatory agency for implementation in 2004. Subsequent accumulated data confirm that concentrations in the 1,4-dioxane plume are declining as predicted by the fate-and-transport modeling. © 2008 Wiley Periodicals, Inc. [source]