On separability finiteness conditions in semigroups

Funding: The first author is grateful to EPSRC for financial support. The second author is grateful to the School of Mathematics and Statistics of the University of St Andrews for financial support.Taking residual finiteness as a starting point, we consider three related finiteness properties: weak subsemigroup separability, strong subsemigroup separability and complete separability. We investigate whether each of these properties is inherited by Schützenberger groups. The main result of this paper states that for a finitely generated commutative semigroup S, these three separability conditions coincide and are equivalent to every H -class of S being finite. We also provide examples to show that these properties in general differ for commutative semigroups and finitely generated semigroups. For a semigroup with finitely many H -classes, we investigate whether it has one of these properties if and only if all its Schützenberger groups have the property.Publisher PDFPeer reviewe

Shorebird and Passerine Abundance and Habitat Use at a High Arctic Breeding Site: Creswell Bay, Nunavut

Shorebirds and passerines were surveyed at Creswell Bay, Somerset Island, in the High Arctic Ecozone (Canadian Arctic Islands) during the breeding season (June and July, 1995–97) and in August 1995 (post-breeding). The study area, situated on the north and south sides of Creswell Bay, consisted of sedge marsh and sedge wetland in the lowest areas, with shrub tundra dominated by Dryas spp. or Cassiope spp. and sparse herbaceous tundra over more upland areas. Surveys were carried out on 400 x 400 m plots distributed among the vegetation types according to their relative amounts within the study areas (34 plots in 1995; 33 plus 56 new plots in 1997). Eleven shorebird and three passerine species were observed during the surveys. Densities of breeding shorebirds were similar in 1995 and 1997 (37.3 and 33.1 birds/km2), while in 1996 a late spring with heavy snow cover resulted in reduced numbers of birds and no breeding. Shorebirds and passerines were much more numerous in sedge marsh and sedge wetland. White-rumped sandpiper (Calidris fuscicollis) and red phalarope (Phalaropus fulicarius) were the most abundant shorebirds breeding at Creswell Bay, and Lapland longspur (Calcarius lapponicus) was the most abundant breeding passerine. White-rumped sandpiper and sanderling (Calidris alba) were the most numerous species present after the breeding period. American golden-plover (Pluvialis dominica), red phalarope, and white-rumped sandpiper showed significant habitat preferences. An estimated 10 341 (± 6596; 95% CI) shorebirds were on the north area in 1995 and 14 840 (± 10 744) on both areas in 1997. The estimated maximum numbers over both years of white-rumped sandpiper (6769 ± 3725) and buff-breasted sandpiper (Tryngites subruficollis) (908 ± 1169) at Creswell Bay were more than 1% of the species’ estimated national populations (1.5% and 5.1%, respectively). This abundance, along with the relatively high species diversity at this high-latitude site, warrants its continued status as a Canadian Wildlife Service “key habitat site,” and every possible effort should be made to ensure its long-term protection.Les oiseaux de rivage et les passereaux ont fait l’objet d’une étude menée à la baie Creswell, dans l’île Somerset située dans l’écozone de l’Extrême-Arctique (archipel Arctique canadien) durant la saison de nidification (juin et juillet, 1995–97) et en août 1995 (période post-reproductrice). La zone d’étude, située sur les rivages nord et sud de la baie Creswell, consistait en des cariçaies de terrains marécageux et humides dans les terres les plus basses, avec une toundra arbustive dominée par Dryas spp. ou Cassiope spp. et une toundra herbacée clairsemée dans les terres plus hautes. L’étude a été effectuée sur des parcelles carrées de 400 m de côté réparties dans les divers types de végétation selon l’importance relative de ces derniers dans les zones d’étude (34 parcelles en 1995; 33 parcelles plus 56 nouvelles en 1997). On a observé 11 espèces d’oiseaux de rivage et trois espèces de passereaux durant l’étude. Les densités des oiseaux de rivage qui nidifiaient étaient semblables en 1995 et en 1997 (37,3 et 33,1 oiseaux/km2), alors qu’en 1996, un printemps tardif accompagné d’un important couvert nival a fait que le nombre des oiseaux a diminué et qu’aucun nid n’a été construit. Les oiseaux de rivage et les passereaux étaient beaucoup plus nombreux dans les cariçaies de terrains marécageux et humides. Le bécasseau à croupion blanc (Calidris fuscicollis) et le phalarope à bec large (Phalaropus fulicarius) étaient les oiseaux les plus nombreux à nidifier à la baie Creswell, et le bruant lapon (Calcarius lapponicus) était le passereau nidificateur le plus abondant. Le bécasseau à croupion blanc et le bécasseau sanderling (Calidris alba) étaient les espèces les plus nombreuses présentes après la période de nidification. Le pluvier bronzé (Pluvialis dominica), le phalarope à bec large et le bécasseau à croupion blanc affichaient une nette préférence quant à leur habitat. On a estimé à 10 341 (± 6596; intervalle de confiance à 95 %) le nombre des oiseaux de rivage présents sur la côte septentrionale en 1995, et à 14 840 (± 10 744) celui des oiseaux de rivage présents sur les côtes nord et sud en 1997. Au cours des deux années, le nombre maximal estimé pour le bécasseau à croupion blanc (6769 ± 3725) et celui pour le bécasseau roussâtre (Tryngites subruficollis) (908 ± 1169) à la baie Creswell représentaient plus de 1 % des populations nationales estimées de ces espèces (1,5 % et 5,1 % respectivement). Cette abondance, jointe à une diversité relativement forte des espèces dans cette région de haute latitude, justifie le maintien de son statut de «site d’habitat clé» du Service canadien de la faune, et toutes les mesures devraient être prises pour en garantir la protection à long terme

Trends in traffic casualties in South Australia, 1981-2003

There has been a reduction in traffic fatalities in South Australia between 1981 and 2003, but this has not been accompanied by a fall in the total number of traffic casualties, and even the number of fatalities has declined very little since about 1992. This report throws light on these and related observations. The main data source is TARS, the database of crashes reported to the police; in addition, some use is made of statistics of death registration and of casualties hospitalised. Among the findings are the following. (a) Although the number of fatalities has not fallen much since about 1992, this has been a result of a continued decline in fatality rate and an increase in vehicle kilometres. (b) The increase in total casualties over the period 1992-2000 was largely confined to the minor categories of injury. (c) An increase in minor rear-end crashes was part of this, but not all of it. (d) In the metropolitan area of Adelaide, hospital-admitted casualties have been falling faster than fatalities over the period 1981-2003. (The evidence is less clear for country areas.) (e) There are numerous other features of the data that are not fully understood. In some cases, a more elaborate tabulation of subcategory numbers might resolve the issue, but in other cases, it is difficult to imagine doing so with mass accident data.T.P. Hutchinson, R.W.G Anderson, A.J. McLean and C.N. Kloede

Sobering assessment of Scotland’s NHS

No abstract available

Rhythm makes the world go round:an MEG-TMS study on the role of right TPJ theta oscillations in embodied perspective taking

While some aspects of social processing are shared between humans and other species, some aspects are not. The former seems to apply to merely tracking another's visual perspective in the world (i.e., what a conspecific can or cannot perceive), while the latter applies to perspective taking in form of mentally “embodying” another's viewpoint. Our previous behavioural research had indicated that only perspective taking, but not tracking, relies on simulating a body schema rotation into another's viewpoint. In the current study we employed Magnetoencephalography (MEG) and revealed that this mechanism of mental body schema rotation is primarily linked to theta oscillations in a wider brain network of body-schema, somatosensory and motor-related areas, with the right posterior temporo-parietal junction (pTPJ) at its core. The latter was reflected by a convergence of theta oscillatory power in right pTPJ obtained by overlapping the separately localised effects of rotation demands (angular disparity effect), cognitive embodiment (posture congruence effect), and basic body schema involvement (posture relevance effect) during perspective taking in contrast to perspective tracking. In a subsequent experiment we interfered with right pTPJ processing using dual pulse Transcranial Magnetic Stimulation (dpTMS) and observed a significant reduction of embodied processing. We conclude that right TPJ is the crucial network hub for transforming the embodied self into another's viewpoint, body and/or mind, thus, substantiating how conflicting representations between self and other may be resolved and potentially highlighting the embodied origins of high-level social cognition in general

The Importance of Background in the Detection and Identification of Gas Plumes Using Emissive Infrared Hyperspectral Sensing

Using a Fourier transform infrared field spectrometer, spectral infrared radiance measurements were made of several generated gas plumes against both a uniform sky and terrestrial background. Background temperature, spectral complexity, and physical homogeneity each influenced the success of emissive infrared spectral sensing technology in detecting and identifying the presence of a gas plume and its component constituents. As expected, high temperature contrast and uniform backgrounds provided the best conditions for detectability and diagnostic identification. This report will summarize some of SITAC’s findings concerning plume detectability, including the importance of plume cooling, plumes in emission and absorption, the effects of optical thickness, and the effects of condensing plumes on gas detection