Urban-like night illumination reduces melatonin release in European blackbirds (Turdus merula): implications of city life for biological time-keeping of songbirds

<p>Introduction: Artificial light-at-night is known to affect a broad array of behaviours and physiological processes. In urbanized bird species, light-at-night advances important biological rhythms such as daily cycles of activity/rest and timing of reproduction, but our knowledge of the underlying physiological mechanisms is limited. Given its role as chronobiological signal, melatonin is a strong candidate for mediating the effects of light-at-night.</p> <p>Results: We exposed urban and rural European blackbirds (Turdus merula) to two light treatments equal in photoperiod but with different light intensities at night. The control group was exposed to 0.0001 lux (almost darkness), while the experimental group was exposed to 0.3 lux at night, simulating conditions recorded previously on free-living urban blackbirds. We obtained diel profiles of plasma melatonin for all birds in summer (July) and winter (January), while simultaneously recording locomotor activity. Daily patterns of melatonin concentrations were clearly affected by light-at-night in both seasons. In winter, melatonin concentrations of light-at-night birds were lower in the early and late night than in those of birds kept in darkness. In summer, melatonin concentrations of the light-at-night birds were lower through all night compared to birds kept in darkness. Locomotor activity in light-at-night birds was overall higher than in control individuals, both during the day and at night, and it increased sharply before dawn. In winter, the amount of activity before dawn in the light-at-night group correlated with changes in melatonin from midnight to late night: the greater the decrease in melatonin, the greater the amount of pre-dawn activity. Urban and rural birds responded similarly to light-at-night with respect to melatonin, but differed in their behaviour, with rural birds showing more locomotor activity than urban counterparts.</p> <p>Conclusions: This study points to reduced melatonin release at night as a potential physiological mechanism underlying the advanced onset of morning activity of urbanized birds. Based on the pattern of melatonin secretion, we suggest that birds responded to light-at-night as if they were exposed to a longer day than birds kept under dark nights.</p&gt

Optical Resonances in Reflectivity near Crystal Modes with Spatial Dispersion

We study the effect of spatial dispersion of crystal modes on optical properties such as the reflectivity $R$. As an example for isotropic media, we investigate the simplest model for phonons in ionic crystals and compare with previous results for highly anisotropic plasmons, which are now understood from a more general point of view. As a consequence of the wave vector dependence of the dielectric function small changes in the lineshape are predicted. Beyond that, if the frequency of minimal $R$ is near a pole of the dispersionless dielectric function, the relative amplitude of dips in $R$ with normal and anomalous dispersion differ significantly, if dissipation and disorder are low.Comment: 4 pages, 7 eps figures, minor change

When the sun never sets: diverse activity rhythms under continuous daylight in free-living arctic-breeding birds

Circadian clocks are centrally involved in the regulation of daily behavioural and physiological processes. These clocks are synchronized to the 24-hour day by external cues (Zeitgeber), the most important of which is the light-dark cycle. In polar environments, however, the strength of the Zeitgeber is greatly reduced around the summer and winter solstices (continuous daylight or continuous darkness). How animals time their behaviour under such conditions has rarely been studied in the wild. Using a radio-telemetry-based system, we investigated daily activity rhythms under continuous daylight in Barrow, Alaska, throughout the breeding season in four bird species that differ in mating system and parental behaviour. We find substantial diversity in daily activity rhythms depending on species, sex and breeding stage. Individuals exhibited either robust, entrained 24-hour activity cycles, were continuously active (arrhythmic), or showed “free-running” activity cycles. In semipalmated sandpipers, a shorebird with biparental incubation, we show that the free-running rhythm is synchronized between pair mates. The diversity of diel time-keeping under continuous daylight emphasizes the plasticity of the circadian system and the importance of the social and life-history context. Our results support the idea that circadian behaviour can be adaptively modified to enable species-specific time-keeping under polar conditions

Black economic empowerment in the South African mining industry : a case study of Exxaro Limited

The original publication is available at http://reference.sabinet.co.za/sa_epublication/busmanThis paper explores some of the key challenges and opportunities in the implementation of the broad-based black economic empowerment (BBBEE) deal of Kumba Resources, which subsequently led to the formation of Exxaro Limited, a large black-owned mining conglomerate in South Africa. Qualitative data were collected through in-depth interviews with a sample of 11 leaders involved directly in the deal. The data were content-analysed and the findings suggested that BEE transactions faced numerous challenges, including finding sustainable funding, securing suitable investors, merging various cultures, dealing with fronting and leadership, and planning management and leadership succession. The study concluded that the deal led successfully to both the equitable transfer of ownership and management and to the control of financial and economic resources to a wider base of the black population. However, several malpractices were identified which may have impeded the process of achieving the intended outcomes. The article provides recommendations, indicates limitations and proposes a way forward.Publishers' versio

Biosensing with T-ray spectroscopy

Copyright © 2007 SPIE - The International Society for Optical Engineering Copyright 2007 Society of Photo-Optical Instrumentation Engineers. This paper was published in Biophotonics 2007: Optics in Life Science, edited by Jürgen Popp, Gert von Bally, Proc. of SPIE-OSA Biomedical Optics, SPIE Vol. 6633, 66331D and is made available as an electronic reprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.In the recent years, it has been shown that terahertz (or T-ray) spectroscopy is a versatile tool for biosensing and safety applications. This is due to the fact that the THz-spectra of many biomolecules show very characteristic, distinct spectroscopic features. Furthermore, most non-metallic packaging materials are nearly transparent in this frequency range (0.1-6 THz, 3 cm-1-200 cm-1), so that it is possible to non-invasively identify even sealed substances like pharmaceuticals, illicit drugs or explosives by their spectroscopic signatures. This opens a significant potential for a wide range of applications from quality control of pharmaceutical substances via safety applications through to biomedical applications. The individual spectroscopic features below approximately 5 THz that spurred the increased world wide interest in T-ray spectroscopy are mainly due to intermolecular rather than intramolecular vibrations in the polycrystalline samples. The spectra of more complex biomolecules, like proteins and nucleotides, typically show less or even no sharp features, due to the lack of long-range intermolecular order. Furthermore, due to the typically significantly smaller sample amount, the signal to noise ratio is strongly increased. Water shows a strong absorption in this frequency range, which all together makes real biomedical applications of T-ray spectroscopy rather difficult. Yet, by combining a careful sample preparation, novel experimental techniques and an advanced signal processing of the experimental data we can still clearly distinguish between even complex biomolecules and therefore demonstrate the potential the technique holds for biomedical applications. © 2007 SPIE-OSA.Bernd M. Fischer, Hanspeter Helm and Derek Abbot

Obtenção e caracterização de farinha de endosperma e de casca de pinhão para fins alimentícios.

Editores técnicos: Marcílio José Thomazini, Elenice Fritzsons, Patrícia Raquel Silva, Guilherme Schnell e Schuhli, Denise Jeton Cardoso, Luziane Franciscon. EVINCI. Resumos

Scare Tactics: Evaluating Problem Decompositions Using Failure Scenarios

Our interest is in the design of multi-agent problem-solving systems, which we refer to as composite systems. We have proposed an approach to composite system design by decomposition of problem statements. An automated assistant called Critter provides a library of reusable design transformations which allow a human analyst to search the space of decompositions for a problem. In this paper we describe a method for evaluating and critiquing problem decompositions generated by this search process. The method uses knowledge stored in the form of failure decompositions attached to design transformations. We suggest the benefits of our critiquing method by showing how it could re-derive steps of a published development example. We then identify several open issues for the method