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

Cylindric skew Schur functions

Cylindric skew Schur functions, which are a generalisation of skew Schur functions, arise naturally in the study of P-partitions. Also, recent work of A. Postnikov shows they have a strong connection with a problem of considerable current interest: that of finding a combinatorial proof of the non-negativity of the 3-point Gromov-Witten invariants. After explaining these motivations, we study cylindric skew Schur functions from the point of view of Schur-positivity. Using a result of I. Gessel and C. Krattenthaler, we generalise a formula of A. Bertram, I. Ciocan-Fontanine and W. Fulton, thus giving an expansion of an arbitrary cylindric skew Schur function in terms of skew Schur functions. While we show that no non-trivial cylindric skew Schur functions are Schur-positive, we conjecture that this can be reconciled using the new concept of cylindric Schur-positivity.Comment: 32 pages, 14 figures. Minor expository improvements. Version to appear in Advances in Mathematic

EL-labelings, Supersolvability and 0-Hecke Algebra Actions on Posets

We show that a finite graded lattice of rank n is supersolvable if and only if it has an EL-labeling where the labels along any maximal chain form a permutation. We call such a labeling an S_n EL-labeling and we consider finite graded posets of rank n with unique top and bottom elements that have an S_n EL-labeling. We describe a type A 0-Hecke algebra action on the maximal chains of such posets. This action is local and gives a representation of these Hecke algebras whose character has characteristic that is closely related to Ehrenborg's flag quasi-symmetric function. We ask what other classes of posets have such an action and in particular we show that finite graded lattices of rank n have such an action if and only if they have an S_n EL-labeling.Comment: 18 pages, 8 figures. Added JCTA reference and included some minor corrections suggested by refere

Locating a blockage in the cerebral vascular network

Ischemic strokes make up 70-80% of strokes, and are characterised by blockages of arteries carrying blood to the brain. This problem involves the identification of blockages using a species distribution derived from an MRI scan of the brain. Blood flow in the brain may be described using a network of branching vessels which are the sources for porous media-type flow in the capillary bed. The topologically intricate nature of the branching blood vessels hinder most attempts at simplifying the problem, and the report concludes that a longer-term modelling process would be required in order to provide therapeutically useful conclusions. Some recommendations for the direction such future work could take are also included

disAbility in Farm Households

[Excerpt] Recent information from the Census 2002 and a national survey conducted by the Teagasc National Farm Survey, indicates that disability affects a significant number of farm household members. Government through current and proposed legislation is in the process of developing both policy and practice to ensure that people with disability enjoy equality and full participation in society. Teagasc in the delivery of its services wishes to ensure that persons with disability are accommodated to the fullest possible extent. Teagasc plan to continue to investigate what services and supports are required by farm families related to disability. This booklet aims to inform the farming community about disability issues and to indicate how Teagasc services could be of assistance to farm households with a disabled member

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)