Home About us Contact
|
Home About us Contact | ||
|
|
||
Concentration Patterns (concentration + pattern)
Selected AbstractsWater uptake and nutrient concentrations under a floodplain oak savanna during a non-flood period, lower Cedar River, Iowa,HYDROLOGICAL PROCESSES, Issue 21 2009Keith E. Schilling Abstract Floodplains during non-flood periods are less well documented than when flooding occurs, but non-flood periods offer opportunities to investigate vegetation controls on water and nutrient cycling. In this study, we characterized water uptake and nutrient concentration patterns from 2005 to 2007 under an oak savanna located on the floodplain of the Cedar River in Muscatine County, Iowa. The water table ranged from 0·5 to 2·5 m below ground surface and fluctuated in response to stream stage, plant water demand and rainfall inputs. Applying the White method to diurnal water table fluctuations, daily ET from groundwater averaged more than 3·5 mm/day in June and July and approximately 2 mm/day in May and August. Total annual ET averaged 404 mm for a growing season from mid-May to mid-October. Savanna groundwater concentrations of nitrate-N, ammonium-N, and phosphate-P were very low (mean <0·18, <0·14, <0·08 mg/l, respectively), whereas DOC concentrations were high (7·1 mg/l). Low concentrations of N and P were in contrast to high nutrient concentrations in the nearby Cedar River, where N and P averaged 7·5 mg/l and 0·13, respectively. In regions dominated by intensive agriculture, study results document valuable ecosystem services for native floodplain ecosystems in reducing watershed-scale nutrient losses and providing an oasis for biological complexity. Improved understanding of the environmental conditions of regionally significant habitats, including major controls on water table elevations and water quality, offers promise for better management aimed at preserving the ecology of these important habitats. Copyright © 2009 John Wiley & Sons, Ltd. [source] Local forcing of a nonlinear surface reaction: CO oxidation on Pt(100)AICHE JOURNAL, Issue 1 2009Daniel Bilbao Abstract A novel spatiotemporal perturbation method for nonlinear surface reactions is reported, thus allowing the creation of new spatially localized structures. Forcing was achieved by dosing reactant gases through a capillary positioned near the catalyst surface, providing control over the local surface coverage and reaction rate. The emergence of localized concentration patterns and oscillations in an otherwise stable system is attributed to a local modification of the catalytic properties of the surface due to external forcing. Based on the spatial orientation, the temporal and thermal stability of the modified surface, as well as the affinity of CO toward the perturbed surface, subsurface O is proposed as a possible source of the observed localized patterning and surface memory effect. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Deposition and taphonomy of earthworm granules in relation to their interpretative potential in Quaternary stratigraphy,JOURNAL OF QUATERNARY SCIENCE, Issue 2 2007M. G. Canti Calcium carbonate granules up to 2.5,mm in size are commonly found in Quaternary soils and sediments but have only rarely been used for any form of interpretation. Growing interest in recent years has focused on the concentration patterns in stratigraphy containing buried land surfaces, and the possibility of dating the granules. Making sense of either of these approaches requires a basic understanding of granule types, together with their modes of accumulation and destruction in stratigraphy. Details of the formation, morphology, deposition and post-depositional changes are discussed along with the necessary ecological and pedological information on earthworm behaviour and effects, then summarised into a framework for interpretations. Copyright © 2006 John Wiley & Sons, Ltd. [source] THE IMPORTANCE OF THE ,BEST RELATIVE FIT FACTOR' WHEN EVALUATING ELEMENTAL CONCENTRATION DATA OF POTTERY DEMONSTRATED WITH MYCENAEAN SHERDS FROM SINDA, CYPRUSARCHAEOMETRY, Issue 2 2007H. MOMMSEN Neutron activation analysis of pottery was established at Bonn in 1983 and has since become one of the primary archaeometry-based analytical techniques at the facility. A brief history of the laboratory and a discussion of the best relative fit procedure for pottery is provided. When comparing concentration data for pottery, a best relative fit should always be considered. This mathematical procedure generally results in ,sharper' concentration patterns and improves the separability of chemically not very different compositional groups. This is demonstrated for a set of 30 Late Cypriot (Myc. IIIC1) pottery samples from Sinda, Cyprus, which allow formation of a good reference pattern for this site. Applying factors in the range of 0.82,1.43, a number of samples from Egypt and Palestine can be assigned with high probability to a Cypriot origin. [source] Surface Electromigration Patterns in a Confined Adsorbed Metal Film: Ga on GaNCHEMPHYSCHEM, Issue 12 2002Alexei Barinov Dr. Abstract The mass transport of gallium adatoms in a confined gallium bilayer on GaN(0001) is studied with photoelectron spectromicroscopy with the goal to identify the diffusing species and their lateral distribution during directional surface electromigration and/or "random" thermal diffusion. It has been found that only the gallium atoms from the second layer undergo biased diffusion involving formation of three-dimensional islands. The development of different gallium concentration patterns is described by means of a general model, considering the presence of vacancies and trapping centres for the diffusing atoms. [source] | |||||||||||||