Reconstructing vectorised photographic images

We address the problem of representing captured images in the continuous mathematical space more usually associated with certain forms of drawn ('vector') images. Such an image is resolution-independent so can be used as a master for varying resolution-specific formats. We briefly describe the main features of a vectorising codec for photographic images, whose significance is that drawing programs can access images and image components as first-class vector objects. This paper focuses on the problem of rendering from the isochromic contour form of a vectorised image and demonstrates a new fill algorithm which could also be used in drawing generally. The fill method is described in terms of level set diffusion equations for clarity. Finally we show that image warping is both simplified and enhanced in this form and that we can demonstrate real histogram equalisation with genuinely rectangular histograms

Baryon polarization in low-energy unpolarized meson-baryon scattering

We compute the polarization of the final-state baryon, in its rest frame, in low-energy meson--baryon scattering with unpolarized initial state, in Unitarized BChPT. Free parameters are determined by fitting total and differential cross-section data (and spin-asymmetry or polarization data if available) for $pK^-$, $pK^+$ and $p\pi^+$ scattering. We also compare our results with those of leading-order BChPT

The role of amateurs in the growth of bat conservation and research in South Africa

During the 1980s and 1990s, Britain experienced an unprecedented increase in scientific and public interest in bat conservation, culminating in 90 ‘bat groups’ by 1992. In South Africa, bats are poorly protected or unprotected, and most of the country's 54 species are poorly known. With the formation of bat interest groups in Kwa- Zulu-Natal and Gauteng in 1994 and 1995, the British ‘bat group’ conservation model was applied in a South African context. The primary aim of South African bat groups has been to promote bats, bat research and bat conservation through public participation and education, and the training of amateur ‘bat workers’ by scientists. I evaluate the success of this approach, based on activities of the Durban Bat Interest Group (DBIG) over four years (1994–1997 inclusive), and on estimates of media impact available for 1994–1996 inclusive. The number of public activities increased by between 14% and 44% per year. Some 12 million South Africans have been exposed to a positive message about bats. A database containing 316 bat roost visit records from 239 individual bat roosts (mostly in buildings) has been compiled. Two species of bats were recorded for the first time in South Africa. Conservation efforts have focussed on a roof-dwelling species restricted to the Durban area, the large- eared free-tailed bat (Otomops martiensseni); this species and one other, the short-eared trident bat, Cloeotis perciuali, have recently been protected in terms of provincial legislation.Keywords: Chiroptera, bats, conservation, amateurs, roost database, public awarenes

Echolocation calls of twenty southern African bat species

Echolocation data and sonograms are reported for twenty southern African bat species from 13 localities, recorded with the Pettersson D980 time-expansion bat detector. Data for eight species have not previously been reported. For seven species, two or more individuals were analysed in a range of situations, including handheld, tethered and free-flying (in a room and in different natural habitats). Sonograms, and seven echolocation call parameters agreed, with a few exceptions, with published data for individual species. Although intraspecific variation in echolocation call structure was documented, species tended to have recognisable ‘vocal signatures’, particularly when dominant frequency and harmonic structure were considered. The latter variables are readily retrieved by time expansion detectors, but not by frequency division or heterodyne detectors. Although generally they should be interpreted with caution, recordings from room-flown (five species) and hand-held (six species) bats obtained during this study matched, reasonably closely, additional recordings and observations of naturally flying individuals of the same species, using time expansion and heterodyne bat detectors. In four species, recordings obtained from a known species flying in a room or hand-held enabled the accurate, a posteriori species identification of unknown call sequences obtained during subsequent general recordings from bat feeding areas

Paying attention to meaning

Several paradigms show that responses to one event compromise responses to a second event for around 500 ms. Such effects are generally attributed to attentional capacity limitations associated with processing information in the first event. In a task in which targets could be distinguished only by their meaning, we varied the semantic relationship between distractors and targets following at different lags. Semantic relatedness alone produced a classic attentional blink. We conclude by discussing how attention theory might best accommodate these new effects

Implementation of Four Real-Time Software Defined Receivers and a Space-Time Decoder using Xilinx Virtex 2 Pro Field Programmable Gate Array

This paper describes the concept, architecture, development and demonstration of a real time, high performance, software defined 4-receiver system and a space time decoder to be implemented on a Xilinx Virtex 2 Pro Field Programmable Gate Array. It is designed and developed for research into receiver diversity and multiple input and multiple output (MIMO)wireless systems. Each receiver has a Freescale DSP56321 digital signal processor (DSP) to run synchronization, channel state estimation and equalization algorithms. The system is software defined to allow for flexibility in the choice of receiver demodulation formats, output data rates and space-time decoding schemes. Hardware, firmware and software aspects of the receiver and space time decoder system to meet design requirements are discussed

Acceptor–donor–acceptor small molecules based on derivatives of 3,4-ethylenedioxythiophene for solution processed organic solar cells

Three simple semiconducting acceptor–donor–acceptor (A–D–A) small molecules based on an electron-rich (3,4-ethylenedioxythiophene) EDOT central core have been synthesised (DIN-2TE, DRH-2TE, DECA-2TE) and characterised. Organic photovoltaic (OPV) devices incorporating these materials have been prepared and evaluated. The physical properties of the molecules were characterised by TGA, DSC, UV/vis spectroscopy and cyclic voltammetry. The optical HOMO–LUMO energy gaps of the molecules in the solid state were in the range 1.57–1.82 eV, and in solution 1.88–2.04 eV. Electrochemical HOMO–LUMO energy gaps determined by cyclic voltammetry were found to be in the range 1.97–2.31 eV. The addition of 1% 1,8-diiodooctane (DIO) to photoactive blends of the A–D–A molecules and PC71BM more than doubled the power conversion efficiency (PCE) in the case of DRH-2TE:PC71BM devices to 1.36%

Distribution patterns of terrestrial mammals in KwaZulu-Natal

Distribution patterns, plotted by eighth-degree squares (7.5' x 7.5'), of the 162 mammal species recorded in the province of KwaZulu-Natal, South Africa were examined in relation to the combined factors of vegetation type, climate, and altitude (= bioregions); and in relation to protected areas within the nine bioregions. Highest species richness was recorded in the warmest most heterogeneous (vegetation) bioregions, and lowest in a cool montane region. Species richness was intermediate in relatively homogeneous, predominantly grassland bioregions. Mammalian biodiversity in KwaZulu-Natal is concentrated in the savanna regions in the north-east of the province, although further species-rich areas are found in the north-west and south-west for carnivores, and in the central region for many of the smaller mammals (Insectívora, Chiroptera, Rodentia). Analysis of taxonomic resemblances between bioregions distinguished taxonomically distinct ‘savanna’ and ‘grassland’ groups. Taxonomic resemblances between bioregions were generally lowest in bats (i.e. greatest bioregion specificity) and highest in carnivores (i.e. lowest specificity). In total, 92% of the mammal species occur in one or more protected areas. The percentages of species within protected areas in each of the bioregions are generally high (68-100%). In four of the bioregions the amount of land occupied by protected areas is adequate (6-96%) and protected areas are large, but in the other five bioregions the opposite holds (< 2% protected) and populations within them may not be viable