On faint companions in the close environment of star-forming dwarf galaxies. Possible external star formation triggers ?

We have searched for companion galaxies in the close environment of 98 star-forming dwarf galaxies (SFDGs) from field and low density environments, using the NASA Extragalactic Database. Most of the companions are dwarf galaxies which due to observational selection effects were previously disregarded in environmental studies of SFDGs. A subsample at low redshift, cz<2000 km/s, was chosen to partially eliminate the observational bias against distant dwarf companions. We find companion candidates for approximately 30% of the objects within a projected linear separation s_p<100 kpc and a redshift difference (Delta cz)<500 km/s. The limited completeness of the available data sets, together with the non-negligible frequency of HI clouds in the vicinity of SFDGs indicated by recent radio surveys, suggest that a considerably larger fraction of these galaxies may be accompanied by low-mass systems. This casts doubt on the hypothesis that the majority of them can be considered truly isolated. The velocity differences between companion candidates and sample SFDGs amount typically to (Delta cz)<250 km/s, and show a rising distribution towards lower (Delta cz). This is similarly found for dwarf satellites of spiral galaxies, suggesting a physical association between the companion candidates and the sample SFDGs. SFDGs with a close companion do not show significant differences in their Hbeta equivalent widths and B-V colours as compared to isolated ones. However, the available data do not allow us to rule out that interactions with close dwarf companions can influence the star formation activity in SFDGs.Comment: 9 pages, 5 figures, to appear in A&A; also available at http://www.uni-sw.gwdg.de/~knoeske/PUB_LIST/sfdg_comps.ps.g

The even darker side of the eastern gray squirrel (Sciurus carolinensis): a review of global introductions, invasion biology, and pest management strategies

Huynh, H.M., Bertolino, S., Lurz, P.W.W., Koprowski, J.L., Williams, G.R., Thompson, C.W., McAlpine, D.F

Inter-specific aggression generates ant mosaics in canopies of primary tropical rainforest

The ant mosaic is a concept of the non-random spatial distribution of individual ant species in trees built upon the assumption of interspecific behavioural associations. However, colony identity and environmental variance may also play a role in species distribution. Here we assess the presence of ant mosaics in a primary forest ecosystem and whether they are structured by species' aggressive behaviours or by habitat filtering. We sampled arboreal ants from vertically stratified baits exposed in 225 canopy trees in a 9-ha plot of primary lowland forest in Papua New Guinea, the largest forest area surveyed to detect ant mosaics. We performed behavioural tests on conspecific ants from adjacent trees to determine the territories of individual colonies. We explored the environmental effects on the ant communities using information on the plot vegetation structure and topography. Furthermore, we created a novel statistical method to test for the community non-random spatial structure across the plot via spatial randomisation of individual colony territories. Finally, we linked spatial segregation among the four most common species to experimentally assessed rates of interspecies aggression. The ant communities comprised 57 species of highly variable abundance and vertical stratification. Ant community composition was spatially dependent, but it was not affected by tree species composition or canopy connectivity. Only local elevation had a significant but rather small effect. Individual colony territories ranged from one tree to 0.7 ha. Species were significantly over-dispersed, with their territory overlap significantly reduced. The level of aggression between pairs of the four most common species was positively correlated with their spatial segregation. Our study demonstrates the presence of ant mosaics in tropical pristine forest, which are maintained by interspecific aggression rather than habitat filtering, with vegetation structure having a rather small and indirect effect, probably linked to microclimate variability.publishedVersio

Multifunctional Devices and Logic Gates With Undoped Silicon Nanowires

We report on the electronic transport properties of multiple-gate devices fabricated from undoped silicon nanowires. Understanding and control of the relevant transport mechanisms was achieved by means of local electrostatic gating and temperature dependent measurements. The roles of the source/drain contacts and of the silicon channel could be independently evaluated and tuned. Wrap gates surrounding the silicide-silicon contact interfaces were proved to be effective in inducing a full suppression of the contact Schottky barriers, thereby enabling carrier injection down to liquid-helium temperature. By independently tuning the effective Schottky barrier heights, a variety of reconfigurable device functionalities could be obtained. In particular, the same nanowire device could be configured to work as a Schottky barrier transistor, a Schottky diode or a p-n diode with tunable polarities. This versatility was eventually exploited to realize a NAND logic gate with gain well above one.Comment: 6 pages, 5 figure

Joule-assisted silicidation for short-channel silicon nanowire devices

We report on a technique enabling electrical control of the contact silicidation process in silicon nanowire devices. Undoped silicon nanowires were contacted by pairs of nickel electrodes and each contact was selectively silicided by means of the Joule effect. By a realtime monitoring of the nanowire electrical resistance during the contact silicidation process we were able to fabricate nickel-silicide/silicon/nickel- silicide devices with controlled silicon channel length down to 8 nm.Comment: 6 pages, 4 figure

Impact of Redshift Information on Cosmological Applications with Next-Generation Radio Surveys

In this paper, we explore how the forthcoming generation of large-scale radio continuum surveys, with the inclusion of some degree of redshift information, can constrain cosmological parameters. By cross-matching these radio surveys with shallow optical to near-infrared surveys, we can essentially separate the source distribution into a low- and a high-redshift sample, thus providing a constraint on the evolution of cosmological parameters such as those related to dark energy. We examine two radio surveys, the Evolutionary Map of the Universe (EMU) and the Westerbork Observations of the Deep APERTIF Northern sky (WODAN). A crucial advantage is their combined potential to provide a deep, full-sky survey. The surveys used for the cross-identifications are SkyMapper and SDSS, for the southern and northern skies, respectively. We concentrate on the galaxy clustering angular power spectrum as our benchmark observable, and find that the possibility of including such low redshift information yields major improvements in the determination of cosmological parameters. With this approach, and provided a good knowledge of the galaxy bias evolution, we are able to put strict constraints on the dark energy parameters, i.e. w_0=-0.9+/-0.041 and w_a=-0.24+/-0.13, with type Ia supernovae and CMB priors (with a one-parameter bias in this case); this corresponds to a Figure of Merit (FoM) > 600, which is twice better than what is obtained by using only the cross-identified sources and greater than four time better than the case without any redshift information at all.Comment: 12 pages, 6 figures, 6 tables; accepted for publication in MNRA

Transgressing the moral economy: Wheelerism and management of the nationalised coal industry in Scotland

This article illuminates the links between managerial style and political economy in post-1945 Britain, and explores the origins of the 1984–1985 miners' strike, by examining in longer historical context the abrasive attitudes and policies of Albert Wheeler, Scottish Area Director of the National Coal Board (NCB). Wheeler built on an earlier emphasis on production and economic criteria, and his micro-management reflected pre-existing centralising tendencies in the industries. But he was innovative in one crucial aspect, transgressing the moral economy of the Scottish coalfield, which emphasised the value of economic security and changes by joint industrial agreement

Towards the fabrication of phosphorus qubits for a silicon quantum computer

The quest to build a quantum computer has been inspired by the recognition of the formidable computational power such a device could offer. In particular silicon-based proposals, using the nuclear or electron spin of dopants as qubits, are attractive due to the long spin relaxation times involved, their scalability, and the ease of integration with existing silicon technology. Fabrication of such devices however requires atomic scale manipulation - an immense technological challenge. We demonstrate that it is possible to fabricate an atomically-precise linear array of single phosphorus bearing molecules on a silicon surface with the required dimensions for the fabrication of a silicon-based quantum computer. We also discuss strategies for the encapsulation of these phosphorus atoms by subsequent silicon crystal growth.Comment: To Appear in Phys. Rev. B Rapid Comm. 5 pages, 5 color figure

Diabetic Retinopathy: more patients, less laser. A longitudinal population-based study in Tayside, Scotland

WSTĘP. Celem badania było porównanie występowania retinopatii cukrzycowej i makulopatii wymagających leczenia laseroterapią z kontrolą czynników ryzyka w populacji chorych na cukrzycę mieszkających w Tayside, w Szkocji w latach 2001-2006. MATERIAŁ I METODY. Analizie poddano zabieg laseroterapii siatkówki, przesiewowe badania dna oka oraz okresowe badania monitorujące przebieg cukrzycy wykonywane w latach 2001-2006. Końcowym, głównym kryterium oceny była liczba pacjentów, u których wykonano pierwszą lub kolejną laseroterapię z powodu retinopatii cukrzycowej lub makulopatii. W czasie badania analizowano również średnie stężenie HbA1c, wartość ciśnienia tętniczego oraz liczbę wykonanych przesiewowych badań dna oka. WYNIKI. W ciągu 6 lat liczba chorych na cukrzycę w Tayside zwiększyła się z 9694 do 15 207 (wzrost o 57%). Liczba pacjentów wymagających laseroterapii zmniejszyła się z 222 do 138, a liczba laseroterapii wykonywanych po raz pierwszy zmniejszyła się ze 100 (1,03% w populacji chorych na cukrzycę) do 56 (0,37%). Liczba chorych na cukrzycę typu 2 leczonych z powodu makulopatii zmniejszyła się ze 180 do 103 w latach 2001&#8211;2006 (spadek o 43%; p = = 0,03). Średnie stężenie HbA1c zmniejszyło się zarówno w populacji osób z cukrzycą typu 1, jak i typu 2 (p < 0,01); u chorych na cukrzycę typu 2 obserwowano zmniejszenie średnich wartości ciśnienia tętniczego (p < 0,01). Liczba pacjentów uczestniczących w corocznym przesiewowym fotograficznym badaniu dna oka zwiększyła się z 3012 do 11 932. WNIOSKI. W ciągu 6 lat obserwacji częstość laseroterapii przeprowadzonych z powodu makulopatii cukrzycowej wśród chorych na cukrzycę typu 2 zamieszkujących Tayside zmniejszyła się, mimo zwiększonej częstości występowania cukrzycy i wykonywania badań przesiewowych. Autorzy niniejszej pracy uważają, że wcześniejsza identyfikacja cukrzycy typu 2 i ulepszona kontrola czynników ryzyka wpłynęły na zmniejszenie częstości występowania makulopatii wymagającej wykonania laseroterapii.INTRODUCTION. We aim to correlate the incidence of diabetic retinopathy and maculopathy requiring laser treatment with the control of risk factors in the diabetic population of Tayside, Scotland, for the years 2001-2006. MATERIALS AND METHODS. Retinal laser treatment, retinal screening, and diabetes care databases were linked for calendar years 2001-2006. Primary end points were the numbers of patients undergoing first or any laser treatment for diabetic retinopathy or maculopathy. Mean HbA1c and blood pressure and retinal screening rates were followed over the study period. RESULTS. Over 6 years, the number of patients with diabetes in Tayside increased from 9694 to 15 207 (57% increase). The number of patients receiving laser treatment decreased from 222 to 138 and first laser treatments decreased from 100 (1.03% of diabetic population) to 56 (0.37%). The number of patients with type 2 diabetes treated for maculopathy decreased from 180 in 2001 to 103 in 2006 (43% reduction; p = 0.03). Mean HbA1c decreased for type 1 and type 2 diabetic populations (p < 0.01) and a reduction in blood pressure was observed in type 2 diabetic patients (p < 0.01). The number of patients attending annual digital photographic retinopathy screening increased from 3012 to 11 932. CONCLUSIONS. Laser treatment for diabetic maculopathy in type 2 diabetic patients has decreased in Tayside over a six-year period, despite an increased prevalence of diabetes and increased screening effort. We propose that earlier identification of type 2 diabetes and improved risk factor control has reduced the incidence of maculopathy severe enough to require laser treatment

Tuning of Human Modulation Filters Is Carrier-Frequency Dependent

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