Ultraviolet Vision May Enhance the Ability of Reindeer to Discriminate Plants in Snow

In reindeer/caribou (Rangifer tarandus), the lens and cornea of the eye transmit ultraviolet (UV) light, and the retinae respond to it electro-physiologically. Here we tie this finding to the unusual visual environment experienced by these animals and propose that their sensitivity to UV light enhances vision at the low luminance characteristic of the polar winter. For such visual enhancement to occur, it is essential that functional components of the environment, such as forage plants, be visually salient under natural UV luminance. However, it is not self-evident that this is the case. Although organic material generally absorbs UV radiation, powerful scattering of UV light by snow crystals may reduce the contrast with the background. We therefore recorded UV images of vegetation in situ on snow-covered pasture under natural winter (March) luminance in northern Norway. For each vegetation scene, we made three monochrome digital images, at 350 – 390 nm (UV-Only), 400 – 750 nm (No-UV), and 350 – 750 nm (control), respectively. Plants at the snow surface appeared in high achromatic contrast against snow in UV-Only images. The contrast was substantially greater in the UV-Only images than in corresponding images in which UV was blocked. We conclude that plants are visually salient under natural UV luminance at wavelengths to which Rangifer are sensitive. This sensitivity is likely to improve the animals’ ability to discriminate forage in snow, particularly at low but relatively UV-enriched twilight luminance.Le cristallin et la cornée de l’oeil du caribou (aussi connu sous le nom de renne) (Rangifer tarandus) transmettent une lumière ultraviolette (UV), à laquelle la rétine envoie une réponse électrophysiologique. Ici, nous faisons le lien entre cette observation et l’environnement visuel inhabituel de ces animaux, puis nous proposons que leur sensibilité à la lumière UV enrichit leur vision dans la faible luminance de l’hiver polaire. Pour que cet enrichissement ait lieu, il est essentiel que les composantes fonctionnelles de l’environnement, comme les plantes fourragères, soient visuellement saillantes sous la luminance UV naturelle. Il ne va cependant pas de soi que c’est le cas. Bien que la matière organique absorbe généralement le rayonnement ultraviolet, la diffusion puissante de la lumière UV découlant de la présence des cristaux de neige peut avoir pour effet de réduire le contraste avec l’arrière-plan. Par conséquent, nous avons enregistré des images ultraviolettes de la végétation in situ dans des pâturages couverts de neige sous la luminance naturelle de l’hiver (en mars), dans le nord de la Norvège. Pour chacune des scènes de végétation, nous avons fait trois images monochromes numériques, soit 350 à 390 nm (UV seulement), 400 à 750 nm (sans UV) et 350 à 750 nm (contrôlé), respectivement. Les plantes à la surface de la neige apparaissaient en fort contraste achromatique contre la neige dans le cas des images en UV seulement. Le contraste était beaucoup plus grand dans les images en UV seulement que dans les images correspondantes pour lesquelles l’UV était bloqué. Nous concluons que les plantes sont visuellement saillantes sous la luminance UV naturelle aux longueurs d’onde auxquelles le Rangifer est sensible. Cette sensibilité est susceptible d’améliorer l’aptitude de cet animal à distinguer le fourrage dans la neige, particulièrement en situation de faible luminance relativement enrichie en UV, au crépuscule

Further delineation of the critical region for Noonan syndrome on the long arm of chromosome 12

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Pyridyl-thiazole multidentate ligands: metal-specific recognition of a combination of ligands from a mixture

Comparison of the crystal structures of the dinuclear double helicates [M2(L1)2][ClO4]4 (M = Ni, Zn; L1 is a potentially hexadentate ligand containing a py–th–py–py–th–py sequence, where ‘py’ denotes pyridyl and ‘th’ denotes thiazolyl) illustrates how L1 can show two different coordination modes: in [Zn2(L1)2][ClO4]4 the ligands L1 are bisbidentate chelates (via the terminal py–th fragments, with the central bipyridyl unit not coordinated) such that the metal ions are four-coordinate, whereas in [Ni2(L1)2][ClO4]4 the ligand coordinates in a more usual bis-terdentate manner such that the metal ions are six-coordinate. Reaction of Ni(), Cu() or Zn() salts with a 1 : 1 mixture of the potentially hexadentate ligands L1 and L2 (where L2 contains a phen–th–th–phen sequence, ‘phen’ denoting a 1,10- phenanthroline unit) afforded in each case a mixture of helical complexes [M2(L1)2]4, [M2(L1)(L2)]4 and [M2(L2)2]4 in different proportions according to the preferences of the different metal ions for different coordination numbers, and the actual denticity of the ligand. For example the mixed-ligand complex [M2(L1)(L2)]4 was formed to the same extent (ca. 50%) for M = Ni and M = Cu, but hardly at all for M = Zn, indicating that self–self ligand recognition operates during assembly of L1 and L2 with Zn() such that the homoleptic complexes [Zn2(L1)2]4 and [Zn2(L2)2]4 are favoured more than simple statistical considerations would suggest

Biochar application does not improve the soil hydrological function of a sandy soil

Biochar application to soil is currently being widely posited as a means to improve soil quality and thereby increase crop yield. Next to beneficial effects on soil nutrient availability and retention, biochar is assumed to improve soil water retention. However, evidence for such an effect in the primary literature remains elusive. Therefore, we studied the effect of biochar on soil hydrological characteristics in two separate field experiments on a sandy soil in The Netherlands. In Experiment I, biochar produced through slowpyrolysis of herbaceous feedstock at two temperatures (400 °C and 600 °C) was applied to soil at a rate of 10 t ha-1. In Experiment II, the 400 °C biochar was applied at rates of 1, 5, 20 and 50 t ha-1. Soils were analysed for soil water retention, aggregate stability and other soil physical parameters after three growing seasons and one growing season for Experiment I and Experiment II, respectively.Wecharacterised the pore structure of the biochar using X-ray computed micro-tomography (XRT) and hydrophobicity using contact angle measurements.We found no significant effects of biochar application on soilwater retention in either experiment. Aggregate stability was also not significantly affected, nor was field saturated hydraulic conductivity. XRT analysis of the biochars showed that they were highly porous, with 48% and 57% porosity for the 400 °C and 600 °C biochar respectively. More than 99% of internal pores of the biochar particles were connected to the surface, suggesting a potential role for biochars in improving soil water retention. However, the biochars were highly hydrophobic. We postulate that this strong hydrophobicity prevented water from infiltrating into the biochar particles, prohibiting an effect on soil water retention. Our results suggest that, in addition to characterising pore space, biochars should be analysed for hydrophobicity when assessing their potential for improving soil physical properties

Further delineation of the critical region for Noonan syndrome on the long arm of chromosome 12

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