Heating the Solar Atmosphere by the Self-Enhanced Thermal Waves Caused by the Dynamo Processes

We discuss a possible mechanism for heating the solar atmosphere by the ensemble of thermal waves, generated by the photospheric dynamo and propagating upwards with increasing magnitudes. These waves are self-sustained and amplified due to the specific dependence of the efficiency of heat release by Ohmic dissipation on the ratio of the collisional to gyro- frequencies, which in its turn is determined by the temperature profile formed in the wave. In the case of sufficiently strong driving, such a mechanism can increase the plasma temperature by a few times, i.e. it may be responsible for heating the chromosphere and the base of the transition region.Comment: v2: A number of minor corrections and additional explanations. AASTeX, 5 pages, 2 EPS figures, submitted to The Astrophysical Journa

A model of solid-solution interactions in acid organic soils, based on the complexation properties of humic substances

CHAOS (Complexation by Humic Acids in Organic Soils) is a quantitative chemical model of organic soils that incorporates complexation by the functional groups of humic substances and non-specific ion-exchange reactions. The two types of interaction are linked by the net humic charge, Z, which depends on the extents of proton and metal complexation, and which in turn determines ionic concentrations in the diffuse part of the electrical double layer, by a Donnan equilibrium. CHAOS was found to account satisfactorily for the results of acid-base titration experiments (pH range 3–5) with soil samples, giving reasonable simultaneous predictions of solution pH and concentration of A13+. Predictive calculations with CHAOS suggest that organic soils acidified by acid rain would respond on a time-scale of years-to-decades to reductions in rain acidity. An associated effect might be an increase in the concentration of dissolved organic matter in the soil solution

Using LISREL to analyze genetic and environmental covariance structure

Describes a method in which the linear structural relationships (LISREL) computer program is used for the genetic analysis of covariance structure. The method is illustrated with simulated and published twin data, including an analysis of twin data by N. G. Martin et al (1981) on psychomotor performance during alcohol intoxication

Log‐linear modelling of pairwise interobserver agreement on a categorical scale

This article uses log‐linear models to describe pairwise agreement among several raters who classify a sample on a subjective categorical scale. The models describe agreement structure simultaneously for second‐order marginal tables of a multidimensional cross‐classification of ratings. Practical difficulties arise in fitting the models, because models refer to pairwise marginal tables of a very large and sparse table. A standard analysis that treats the marginal tables as independent yields consistent estimates of model parameters, but not of the covariance matrix of the estimates. We estimate the covariance matrix using the jackknife. We apply the models to describe agreement between evaluations made by seven pathologists of carcinoma in situ of the uterine cervix, using a five‐level ordinal scale. Previous analyses showed differences among the pathologists in their pairwise levels of agreement, but we observe near homogeneity in the dependence structure of their ratings.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98788/1/4780110109_ftp.pd

Comparison of root absorption, translocation and tolerance of arsenic in the hyperaccumulator Pteris vittata and the nonhyperaccumulator Pteris tremula

Several fern species can hyperaccumulate arsenic, although the mechanisms are not fully understood. Here we investigate the roles of root absorption, translocation and tolerance in As hyperaccumulation by comparing the hyperaccumulator Pteris vittata and the nonhyperaccumulator Pteris tremula. The two species were grown in a pot experiment with 0-500 mg As kg(-1) added as arsenate, and in a short-term (8 h) uptake experiment with 5 pm arsenate under phosphorus-sufficient conditions. In the pot experiment, P. vittata accumulated up to 2500 mg As kg(-1) frond d. wt and suffered no phytotoxicity. P. tremula accumulated < 100 mg As kg(-1) frond d. wt and suffered severe phytotoxicity with additions of ! 25 mg As kg-1. In the short-term uptake experiment, P. vittata had a 2.2-fold higher rate of arsenate uptake than P. tremula, and distributed more As taken up to the fronds (76%) than did P. tremula (9%). Our results show that enhanced root uptake, efficient root-to-shoot translocation, and a much elevated tolerance through internal detoxification all contribute to As hyperaccumulation in P. vittata