Wind signatures in the X-ray emission-line profiles of the late-O supergiant ζ Orionis

X-ray line-profile analysis has proved to be the most direct diagnostic of the kinematics and spatial distribution of the very hot plasma around O stars. The Doppler-broadened line profiles provide information about the velocity distribution of the hot plasma, while the wavelength-dependent attenuation across a line profile provides information about the absorption to the hot plasma, thus providing a strong constraint on its physical location. In this paper, we apply several analysis techniques to the emission lines in the Chandra High Energy Transmission Grating Spectrometer (HETGS) spectrum of the late-O supergiant ζ Ori (O9.7 Ib), including the fitting of a simple line-profile model. We show that there is distinct evidence for blueshifts and profile asymmetry, as well as broadening in the X-ray emission lines of ζ Ori. These are the observational hallmarks of a wind-shock X-ray source, and the results for ζ Ori are very similar to those for the earlier O star, ζ Pup, which we have previously shown to be well fit by the same wind-shock line-profile model. The more subtle effects on the line-profile morphologies in ζ Ori, as compared to ζ Pup, are consistent with the somewhat lower density wind in this later O supergiant. In both stars, the wind optical depths required to explain the mildly asymmetric X-ray line profiles imply reductions in the effective opacity of nearly an order of magnitude, which may be explained by some combination of mass-loss rate reduction and large-scale clumping, with its associated porosity-based effects on radiation transfer. In the context of the recent reanalysis of the helium-like line intensity ratios in both ζ Ori and ζ Pup, and also in light of recent work questioning the published mass-loss rates in OB stars, these new results indicate that the X-ray emission from ζ Ori can be understood within the framework of the standard wind-shock scenario for hot stars.     

Winter chemical leaching from deciduous tree branches as a function of branch inclination angle in central Massachusetts

Leaching is an important process in the biogeochemical cycling of nutrients from above‐ground vegetative surfaces to the forest floor. Little is known about winter leaching from deciduous tree species and the influence of branch inclination angle on leachate chemistry. Using a set of field‐based isolated branches harvested from mature crowns of Betula lenta, Carya glabra and Quercus rubra, we tested the null hypothesis that during winter neither branch inclination angle nor branch species would have a detectable influence on differences in leachate chemistry and the quantity of intercepted precipitation from the branch surface. Leachate concentrations were significantly greater from branches inclined at 20° than 5° or 38°. Absolute nutrient inputs were also greatest for branches inclined at 20°. The significantly enriched branchflow and greater total nutrient input from branches inclined at 20° were attributed to increased residence time of intercepted precipitation with the branch surface, the lower probability of branch drip than branches inclined at 5°, and only minimal differences in branchflow quantity compared with branches inclined at 38°. Branchflow was more enriched from all three branch angles during precipitation events of longer duration and lower intensity than shorter, intense events. The leachate quantities of K⁺ and Ca²⁺ differ significantly among species. Carya glabra and Quercus rubra leached more K⁺ than Betula lenta. All three species leached significantly different amounts of Ca²⁺, with Quercus rubra leaching the most and Carya glabra the least. The adaptive geometry of deciduous canopy trees should be considered in relation to the interception of precipitation and aqueous leaching during winter when the canopy is leafless. Copyright © 2002 John Wiley & Sons, Ltd.     

Geoelectrical inversion and evaluation of lithology based on optimized Adaptive Neuro Fuzzy Inference System (ANFIS)

Soft computing tools play a vital role in fixing certain non-linear problems related to the earth. More specifically, digging out the mysteries of subsurface of the earth, the nonlinearity can be converging to assemble an approximate solution which resembles the real characteristics of the earth. Adaptive Neuro Fuzzy Inference System (ANFIS) tool is one of the best soft computing tools to estimate the complex data analysis. ANFIS was applied to estimate the subsurface parameters of earth using the Vertical Electrical Sounding (VES) data. Classifying the lithology based on the resistivity values by ANFIS is employed here in this paper. As the resistivity of each formation varies in range of values, ANFIS tool thus approximates the subsurface features based on effective training. In this study, ANFIS performance was checked with training data, and successively it has been tested with the field data. Optimized ANFIS algorithm provides the necessary tool for predicting the non-linear subsurface features. The best training performance of this soft computing tool efficiently predicts the subsurface lithology. Also the interpreted results show the true resistivity and thickness of the subsurface layers of the earth. The proposed technique was represented in Graphical User Interface (GUI), and the lithological variables are predicted in texture format and linguistic variables.     

Coastal margin evolution and postulated “basin‐shipyard” area at ancient Locri‐Epizephiri,Calabria, Italy

Environmental settings on the Ionian coastal plain and inner shelf seaward of Locri‐Epizephiri in Calabria, Italy, differed markedly before, during, and following settlement by the Greeks. Sediment core analyses and geophysical surveys in this study support recent archaeological findings and the hypothesis that the margin may once have served as a harbor and/or shipyard. The subsurface Holocene stratigraphy records that (1) the shoreline advanced to a maximum landward position before Greek settlement, then regressed offshore to what is now the inner shelf before once again migrating landward. These marked coastal shifts were triggered primarily by land uplift and probable subsidence offshore along this structurally active Calabrian Arc segment. Associated with this are: (2) a sediment fining‐upward sequence in Greek–Roman time that indicates only partial protection of the coastal area, and (3) possible presence of subsurface structures seaward of the city wall in a sector now positioned ∼200 m offshore. © 2010 Wiley Periodicals, Inc.     

Comparisons of wetland and drainage lake influences on stream dissolved carbon concentrations and yields in a north temperate lake-rich region

Processes occurring at various scales interact to influence the export of organic carbon from watersheds to freshwater ecosystems and eventually the ocean. The goal of this study was to determine if and how differences in wetland extent and presence of lakes influenced dissolved organic carbon (DOC) concentrations and yields in streams. We monitored stream flow, DOC and dissolved inorganic carbon concentrations periodically for 2 years at four sites with forested watersheds, four sites with wetland watersheds, and four sites with wetland watersheds that also contained in-network lakes. As expected, the presence of wetlands resulted in higher DOC concentrations and yields, but the impact of lakes was less clear on the magnitude of DOC concentrations and yields. With respect to temporal dynamics, we found positive relationships between stream flow and DOC concentration (median r² = 0.89) in streams without upstream lakes. The relationships for forested sites are among the strongest reported in the literature, and suggest a clear shift in hydrologic flowpath from intersecting mineral soils at low flow, to organic soils at high flow. In streams with upstream lakes, the relationship between flow and concentration was non-significant for three of four sites unless time lags with flow were applied to the concentration data, after which the relationship was similar to the non-lake streams (median r² = 0.95). These findings suggest that lakes buffering temporal patterns in streams by hydrologically delaying pulses of carbon, but provide little support that in-line lakes have a net effect on carbon exports in this region.     

EVALUATION OF THE ASSUMPTION OF WATERTIGHT BEDROCK UNDERLYING AN EXPERIMENTAL WATERSHED

The long-term studies of water and chemical budgets in the Hubbard Brook watershed, White Mountains, New Hampshire, have assumed that the underlying bedrock is watertight and that all of the liquid water discharged from the experimental subcatchment areas was measured using stream gauging instrumentation. This paper reviews the evidence used by past workers to support this assumption. In a reanalysis of the reported relationship between precipitation inputs and stream outputs of chloride, the mean annual groundwater discharge beneath the stream gauging stations was computed to be at least 5–10% of the mean annual precipitation. Groundwater discharge of this quantity would change both the evapotranspiration and the rock-weathering rates reported for the Hubbard Brook watershed. On-site hydrogeological field tests are recommended in all watersheds that are assumed to be underlain by watertight bedrock. [Key words: forested ecosystems, groundwater hydrology, bedrock fractures, water budgets, evapotranspiration, chemical budgets, rock weathering.]     

PREDICTING ABOVE-GROUND NET PRIMARY PRODUCTIVITY OF TROPICAL RAINFORESTS FROM EVAPOTRANSPIRATION DATA

The relationship between above-ground net primary productivity (ANPP) and actual evapotranspiration (AE) has been previously shown by Rosenzweig (1968) to be significant for a variety of mainly temperate terrestrial ecosystems. Our study of ANPP and AE data from the humid tropics showed that AE remains a useful predictor of ANPP in tropical rainforest environments. However, we also noted that 80% of the tropical rainforest data points were depressed below Rosenzweig's original regression line. We attribute these lower-than-predicted ANPP values to transpiration losses and rainfall interception losses that do not result in a corresponding production of biomass.     

CALCIUM,MAGNESIUM AND POTASSIUM USE EFFICIENCY OF TROPICAL RAINFORESTS

A useful index of nutrient use efficiency (NUE) is the relationship between litterfall mass and the quantity of a nutrient returned to the ground by litterfall and by aqueous leaching from aboveground vegetative surfaces. Using previously published data, Ca, Mg and K use by tropical rainforests in widely separated geographic localities were considered in relation to the availability of these nutrient elements in the soil. Significant inverse relationships were found between Ca use efficiency and soil Ca availability (P < 0.001), and between Mg use efficiency and soil Mg availability (P < 0.01). The relationship was not found to be statistically significant for K (P > 0.1). The predicted inverse relationship between tropical rainforest NUE and soil fertility is evidently not consistent for all nutrient elements.