9,283 research outputs found
How Much Is Your Advertising Agency Worth To You?
The subject of advertising remuneration has always been a controversial subject despite the advertising industry coexisting with other industries for over a century. Both clients and agencies have different views on the subject depending on their objectives. Business needs however, have compelled both, to call a truce to these altercations, since both cannot exist without the other, especially the agencies. This paper examines the various options of remuneration prevalent in the industry, how these have evolved as time has elapsed and how clients and agencies have adapted to it over time. It critically examines the motivations and conflicts arising in the evolvement of a suitable remuneration system and the means of resolution available to both parties for amicable settlement
Nuclear magnetic resonance probes for the Kondo scenario for the 0.7 feature in semiconductor quantum point contact devices
We propose a probe based on nuclear relaxation and Knight shift measurements
for the Kondo scenario for the "0.7 feature" in semiconductor quantum point
contact (QPC) devices. We show that the presence of a bound electron in the QPC
would lead to a much higher rate of nuclear relaxation compared to nuclear
relaxation through exchange of spin with conduction electrons. Furthermore, we
show that the temperature dependence of this nuclear relaxation is very
non-monotonic as opposed to the linear-T relaxation from coupling with
conduction electrons. We present a qualitative analysis for the additional
relaxation due to nuclear spin diffusion (NSD) and study the extent to which
NSD affects the range of validity of our method. The conclusion is that nuclear
relaxation, in combination with Knight shift measurements, can be used to
verify whether the 0.7 feature is indeed due to the presence of a bound
electron in the QPC.Comment: Published version. Appears in a Special Section on the 0.7 Feature
and Interactions in One-Dimensional Systems. 16 page
SPATIO-TEMPORAL VARIABILITY IN GROUNDWATER DISCHARGE AND CONTAMINANT FLUXES ALONG A CHANNELIZED STREAM IN WESTERN KENTUCKY
Spatio-temporal variability in groundwater discharge and contaminant fluxes along a channelized stream in western Kentucky
Surface and groundwater discharges and contaminant fluxes can vary with time and space depending upon the hydrogeological processes and geological setting of the area of interest. This study examined a ~300-m-long, channelized reach of a first-order perennial stream, Little Bayou Creek, in the Coastal Plain of far western Kentucky during the period October 2010–February 2012. Along the study reach, springs discharge groundwater contaminated by the chlorinated organic compound trichloroethene (TCE) and radionuclide technetium-99 (99Tc) released as a result of past activities at the U.S. Department of Energy’s Paducah Gaseous Diffusion Plant. The study addressed variability in groundwater discharge patterns and contaminant concentrations at various timescales (seasonal, annual, and decadal) and the extent to which the discharge sites are spatially persistent. Understanding patterns of groundwater discharge along a stream can be important for assessing the fate and transport of aqueous contaminants.
Groundwater discharge was estimated during baseflow conditions using different mass-balance approaches, including velocity-area and dye-dilution gauging. Discharge fluctuated seasonally but typically increased downstream, indicating the entire study reach to be gaining throughout the year. Discharge rates of individual springs also fluctuated seasonally. Tracer test data were utilized to model flow and transient storage along the reach using the USGS software OTIS-P. Cross-sectional area determined from OTIS-P was similar to that measured by velocity-area gauging. Reach area-normalized discharge fluxes were comparable to values determined by Darcy’s law calculations from a pair of monitoring wells at the downstream end of the study reach. Temperature data acquired from probing along grids in winter and summer, from fiber-optic sensing along the reach in autumn, and from data-loggers and manual measurements in springs were used to delineate focused discharge locations. Comparison of temperature-probing results with prior studies indicated that locations of some springs persisted over a decade, whereas other springs emerged and disappeared. Because the stream is located in unlithified sediments, discharge rates of springs appear to fluctuate with soil piping and collapse along joints in fractured clay. Contaminant concentrations in springs decreased downstream along the reach and were lower than observed during September 1999 – May 2001. The continued occurrence of dissolved oxygen and the absence of TCE daughter products in springs suggest that the decrease in TCE concentrations resulted from the installation of upgradient extraction wells, rather than from intrinsic reductive degradation.
KEYWORDS: Contaminant fluxes, trichloroethene, technetium-99, baseflow, temperature probing
USE OF SURFACE GEOPHYSICAL TECHNIQUES TO LOCATE A KARST CONDUIT IN THE CANE RUN - ROYAL SPRING BASIN, KENTUCKY
Groundwater flow in karst terrains is difficult to map because it can be concentrated through conduits that do not necessarily coincide with the surface features. We applied electrical resistivity (ER) and self-potential (SP) techniques at three sites to locate an inferred trunk conduit feeding a major spring in the Inner Bluegrass region of Kentucky. Royal Spring is the primary water supply for the city of Georgetown; the upper part of its basin coincides with the Cane Run watershed. ER and SP profiles were perpendicular to the inferred trunk conduit orientation. ER profiles (972 m total length) were measured using a dipole–dipole electrode configuration with 2- to 3-m spacing. SP measurements were taken along those ER lines and an additional test profile (230 m) using one stationary reference electrode and another roving electrode at a fixed interval.
The low resistivity of water in the conduit, as compared to the high background resistivity of limestone bedrock, is the ER exploration target. A negative SP anomaly corresponds to a low ER anomaly for most of the profiles, but a few are not comparable. Five of seven SP profiles measured over a period of several months were found to be reproducible. Although the overall trends of the final SP profiles for different dates were similar, the SP magnitudes varied with the amount of precipitation and the average soil temperature. The low-resistivity anomalies in the 2D inverted sections and corresponding negative SP anomalies could be water-filled conduits, although mud-filled voids encountered during drilling suggest that these may be tributary conduits rather than the trunk conduit
Investigation of ion induced bending mechanism for nanostructures
Ion induced bending is a promising controlled technique for manipulating nanoscale structures. However, the underlying mechanism of the process is not well understood. In this letter, we report a detailed study of the bending mechanism of Si nanowires (NWs) under Ga+ irradiation. The microstructural changes in the NW due to ion beam irradiation are studied and molecular dynamics simulations are used to explore the ion–NW interaction processes. The simulation results are compared with the microstructural studies of the NW. The investigations inform a generic understanding of the bending process in crystalline materials, which we suggest to be feasible as a versatile manipulation and integration technique in nanotechnology
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