Ambient UV irradiation induces a blue pigment in Xanthoparmelia stenophylla

2006 ◽  
Vol 38 (3) ◽  
pp. 285-289 ◽  
Author(s):  
Maria McEvoy ◽  
Knut Asbjørn Solhaug ◽  
Yngvar Gauslaa
Keyword(s):  
Environmental Factors ◽  
Experimental Studies ◽  
Usnic Acid ◽  
Temporal Variations ◽  
Blue Pigment ◽  
Relative Importance ◽  
Xanthoria Parietina ◽  
Taxonomic Studies ◽  
Fungal Pigments ◽  
Foliose Lichen

Lichens are colourful organisms owing to numerous combinations of algal and fungal pigments (as reviewed by Rikkinen 1995). Colour is often used in taxonomic studies to aid species identification but it is sometimes over-used as a characteristic to discriminate related genera such as, Xanthoparmelia and Neofuscelia (Poelt & Leuckert 1993). However, colour variations within species can be significant (Solhaug et al. 2003) because of spatial (Gauslaa & Solhaug 2001; Gauslaa & Ustvedt 2003) and temporal variations (Gauslaa & McEvoy 2005) in environmental factors. There are few experimental studies on lichen colours so far; as a result we do not know the relative importance of genetic versus environmental factors. Our study aimed to assess the effect of ultraviolet radiation (UVR) on the colour of the widespread foliose lichen Xanthoparmelia stenophylla (Ach.) Ahti & D. Hawksw. (until recently known as X. somloensis (Gyeln.) Hale, see Ahti & Hawksworth 2005). Usnic acid is responsible for the yellowish appearance of its upper cortex, but other colour variations are also mentioned in taxonomic literature (Brodo et al. 2001). More specifically, we wanted to discover if UVR and the photosynthate ribitol supplied by the photobiont would cause changes in pigmentation in a Xanthoparmelia species. These factors have been shown to induce and stimulate the synthesis of the orange parietin in Xanthoria parietina (Solhaug & Gauslaa 2004; Solhaug et al. 2003).

scholarly journals Predicting How Crack Tip Residual Stresses Influence Brittle Fracture

2002 ◽  
Author(s):  
Saeid Hadidimoud ◽  
Ali Mirzaee-Sisan ◽  
Chris E. Truman ◽  
David J. Smith
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Experimental Studies ◽  
Crack Tip ◽  
Distribution Model ◽  
Relative Importance ◽  
Local Approach ◽  
Weibull Parameters ◽  
Experimental Scatter ◽  
Crack Tip Blunting

A probability distribution model, based on the local approach to fracture, has been developed and used for estimating cleavage fracture following prior loading (or warm pre-stressing) in two ferritic steels. Although there are many experimental studies it is not clear from these studies whether the generation of local residual stress and/or crack tip blunting as a result of prior loading contribute to the enhancement in toughness. We first identify the Weibull parameters required to match the experimental scatter in lower shelf toughness of the candidate steels. Second we use these parameters in finite element simulations of prior loading on the upper shelf followed by unloading and cooling to lower shelf temperatures to determine the probability of failure. The predictions are consistent with experimental scatter in toughness following WPS and provide a means of determining the relative importance of the crack tip residual stresses and crack tip blunting. We demonstrate that for our steels the crack tip residual stress is the pivotal feature in improving the fracture toughness following WPS. The paper finally discusses these results in the context of the non-uniqueness and the sensitivity of the Weibull parameters.

scholarly journals MODERN CONCEPTION AS TO THE FUNCTIONAL MORPHOLOGY OF THE OLFACTORY SYSTEM AND ITS CHANGES UNDER THE INFLUENCE OF SOME EXOGENOUS POLLUTANTS

2019 ◽  
Vol 23 (3-4) ◽  
pp. 37-40
Author(s):  
A.D. Shkodina ◽  
R.M. Hrinko ◽  
I.I. Starchenko
Keyword(s):  
Environmental Factors ◽  
Olfactory Epithelium ◽  
Functional Organization ◽  
Morphological Changes ◽  
Human Life ◽  
Experimental Studies ◽  
Experimental Models ◽  
Functional Changes ◽  
Olfactory Analyzer ◽  
Long Time

The interaction between a body and an environment provides the main aspects of human life. The study of the functional structure of the olfactory analyzer plays an important role both in clinical and in experimental studies, but the question of its features in humans needs detailed research. The paper presents the modern data of the structural and functional organization of the olfactory analyzer. Particular attention is paid to the structural organization of olfactory bulbs as most complicated and least studied component of the olfactory analyzer. The morphological and functional changes of the olfactory analyzer are developing in some diseases and in action of adverse environmental factors are described while the accentuation is placed on the differences of the mechanism in the pathogenesis of damage to the olfactory analyzer, depending on the nature of the influence of pathogenic factors. In this way as the result of short-term intense effects of the pollutant, irreversible atrophic changes are primarily affected to the olfactory epithelium, thus, to some extent, preventing the spread of the toxin to other analyzer structures. Conversely, a long-term exposure to low doses usually retains the functional activity of the olfactory epithelium, while harmful substances penetrate the central unit of the olfactory analyzer. In such cases, the olfactory dysfunction can be diagnosed after a long time after the start of the cohort with certain pollutants. Currently, studies of the influence of exogenous toxins on various parts of the olfactory analyzer on animal experimental models are quite active. At the same time, the issue of functional and morphological changes in various structural components of the human olfactory analyzer under the influence of negative environmental factors remains poorly understood and requires further morphological and biochemical studies, in order to be able to further develop effective therapeutic and prophylactic means.

scholarly journals Treeline advance - driving processes and adverse factors

2007 ◽  
Vol 1 ◽  
pp. 1-33 ◽  
Author(s):  
Friedrich Karl Holtmeier ◽  
Gabriele E. Broll
Keyword(s):  
Experimental Studies ◽  
Temporal Variations ◽  
Considerable Effect ◽  
Future Climate Change ◽  
Anthropogenic Factors ◽  
Site Conditions ◽  
Mature Trees ◽  
Climatic Regions ◽  
Functional Relationships ◽  
Animal Populations

The general trend of climatically-driven treeline advance is modified by regional, local and temporal variations. Treelines will not advance in a closed front parallel to the shift of any isotherm to higher elevations and more northern latitudes. The effects of varying topography on site conditions and the after-effects of historical disturbances by natural and anthropogenic factors may override the effects of slightly higher average temperatures. Moreover, the varying treeline-forming species respond in different ways to a changing climate. Forest advance upwards and northwards primarily depends on successful regeneration and survival of young growth rather than on increasing growth rates of mature trees. Every assessment of treeline response to future climate change must consider the effects of local site conditions and feedbacks of increasing tree population in modulating the climatically-driven change. Treeline-shift will influence regional and local climates, pedogenesis, plant communities, animal populations and biodiversity as well as having a considerable effect on economic changes in primary production. A better understanding of the functional relationships between the many treeline-relevant factors and treeline dynamics can be achieved only by extensive research at different scales within different climatic regions supported by as many as possible experimental studies in the field together with laboratory and remote sensing techniques.

City Children’s Nature Knowledge and Contact: It Is Not Just About Biodiversity Provision

2017 ◽  
Vol 50 (10) ◽  
pp. 1145-1171 ◽  
Author(s):  
Claire Freeman ◽  
Aviva Stein ◽  
Kathryn Hand ◽  
Yolanda van Heezik
Keyword(s):  
New Zealand ◽  
Environmental Factors ◽  
Ethnic Group ◽  
Social Factors ◽  
Green Spaces ◽  
Social Connections ◽  
Relative Importance ◽  
Linear Modeling ◽  
Generalized Linear Modeling ◽  
Nature Contact

Much attention has been directed at the perceived decline in city children’s contact with nature. We used a child-centric approach to assess neighborhood nature knowledge in 187 children aged 9 to 11 years, from different socioeconomic and ethnic groups in three New Zealand cities. We evaluated the relative importance of social (independence, gender, social connections, deprivation, age) and environmental factors (biodiversity) in explaining variation in knowledge at a scale relevant to each child’s independent movements. Our biodiversity evaluation reflected the natural dimensions of the habitats where children interacted with nature. Generalized linear modeling identified ethnicity as having the strongest association with nature knowledge. Within each ethnic group, social factors were most important (independence, social connections, deprivation) except for Pākehā/NZ European children, where local biodiversity was most important. Enhancing biodiversity values of private green spaces (yards) would be effective in facilitating opportunities to experience nature, which is fundamental to supporting nature contact.

scholarly journals Phytochemical Investigation of the Australian Lichens Ramalina glaucescens and Xanthoria parietina

2009 ◽  
Vol 4 (7) ◽  
pp. 1934578X0900400 ◽  
Author(s):  
Daniel A. Dias ◽  
Sylvia Urban
Keyword(s):  
Antibacterial Properties ◽  
Usnic Acid ◽  
2D Nmr ◽  
Antibacterial Activities ◽  
2D Nmr Spectroscopy ◽  
Full Characterization ◽  
Phytochemical Investigation ◽  
Xanthoria Parietina ◽  
Shift Assignment

Phytochemical investigation of the Australian lichen, Ramalina glaucescens resulted in the isolation of a new halogenated depside, 5-chlorosekikaic acid 5, together with (+)-usnic acid 1, sekikaic acid 2, atranorin 6 and parietin 7, the latter of which was isolated from the associated (co-occurring) lichen, X. parietina. Compound 5 is suspected to be an artifact of the isolation procedure. All structures were assigned using spectroscopic methods and mass spectrometry. In addition to the full characterization of 5, this report represents the first application of 2D NMR spectroscopy to complete the unequivocal chemical shift assignment for compounds 2 and 7. Compounds 1-2 and 5-7 all displayed varying degrees of antitumor activity (ranging from an IC50 of 15 μM to >44 μM) with compounds 1, 2 and 5 also displaying antibacterial properties. Of these, (+)-usnic acid 1 displayed the most significant antitumor and antibacterial activities.

Experimental Studies of the Surface Forces on Micro Gap Plates with Different Bumps

2009 ◽  
Vol 60-61 ◽  
pp. 130-134
Author(s):  
Xue Jin Shen ◽  
Wei Jun Qi
Keyword(s):  
Experimental Studies ◽  
Surface Force ◽  
Surface Forces ◽  
Flexible Beam ◽  
Relative Importance ◽  
Drive Voltage ◽  
Microelectromechanical Devices ◽  
Micromechanical Structures ◽  
Micro Structures ◽  
Adhesion Condition

An experimental analysis of the influence of the bumps on the surface forces in micro gap plates is presented. Because of extremely small sizes of micromechanical structures in MEMS, surface forces between micromechanical components may become significant to influence behaviors of microelectromechanical devices. The bumps are important in micro structures as they change the adhesion condition of the plates, and will influence the surface forces in micro gap plates greatly. To identify relative importance of surface forces with bumps, the experimental instrument which consists of the V-shaped electrothermal microactuator, the suspended plate and the flexible beam is designed. The displacements of the suspended plate with different bumps are measured by experiments, and the surface forces are got by calculation. By analysis, it could be found that the surface force increases with the increasing drive voltage and the increasing normal voltage, and the surface force gets the minimum when the number of the bumps is 9.

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