An estimate of energy dissipation due to soil-moisture hysteresis

Processes of infiltration, transport and outflow in unsaturated soil necessarily involve the dissipation of energy through various processes. Accounting for these energetic processes can contribute to modelling hydrological and ecological systems. The well-documented hysteretic relationship between matric potential and moisture content in soil suggests that one such mechanism of energy dissipation is associated with the cycling between wetting and drying processes. Working from a time-series of soil moisture content data (taken in the south-west of Ireland), and making rather straightforward assumptions regarding the hysteretic relationship mentioned, the average rate of energy dissipation was found to be O(10−5)

Radio Triggered Star Formation in Cooling Flows

The giant galaxies located at the centers of cluster cooling flows are frequently sites of vigorous star formation. In some instances, star formation appears to have been triggered by the galaxy's radio source. The colors and spectral indices of the young populations are generally consistent with short duration bursts or continuous star formation for durations much less than 1 Gyr, which is less than the presumed ages of cooling flows. The star formation properties are inconsistent with fueling by a continuously accreting cooling flow, although the prevalence of star formation is consistent with repeated bursts and periodic refueling. Star formation may be fueled, in some cases, by cold material stripped from neighboring cluster galaxies

The Ethics of Ambiguity in Quintilian

In a list of twelve stylistic and grammatical errors of oratory, the fourth-century grammarian Donatus includes the fault of amphibolia, a transliteration of a Greek word that Donatus further defines as an ambiguitas dictionis. This understanding of ambiguitas dictionis as a flaw in composition is unique neither to the texts of late antiquity nor to technical grammatical treatises, and one can find ample cautioning against it in pedagogical texts both before and after Donatus. In his first-century Institutio Oratoria, for instance, Quintilian similarly cautions against writing ambiguous language and encourages his students to compose lucid and straightforward Latin, particularly in regard to syntax

Evening Methane Emission Pulses from a Boreal Wetland Correspond to Convective Mixing in Hollows

Spatial and temporal heterogeneity of methane flux from boreal wetlands makes prediction and up-scaling challenging, both within and among wetland systems. Drivers of methane production and emissions are also highly variable, making empirical model development difficult and leading to uncertainty in methane emissions estimates from wetlands. Previous studies have examined this problem using point-scale (static chamber method) and ecosystem-scale (flux tower methods) measurements, but few studies have investigated whether different processes are observed at these scales. We analyzed methane emissions from a boreal fen, measured by both techniques, using data from the Boreal Ecosystem-Atmosphere Study. We sought to identify driving processes associated with methane emissions at two scales and explain diurnal patterns in emissions measured by the tower. The mean methane emission rates from flux chambers were greater than the daytime, daily mean rates measured by the tower, but the nighttime, daily mean emissions from the tower were often an order of magnitude greater than emissions recorded during the daytime. Thus, daytime measurements from either the tower or chambers would lead to a biased estimate of total methane emissions from the wetland. We found that the timing of nighttime emission events was coincident with the cooling and convective mixing within hollows, which occurred regularly during the growing season. We propose that diurnal thermal stratification in shallow pools traps methane by limiting turbulent transport. This methane stored during daytime heating is later released during evening cooling due to convective turbulent mixing