Stomatal responses to humidity, soil moisture and other factors that influence plant water status are critical drivers of photosynthesis, productivity, water yield, ecohydrology and climate forcing, ...yet we still lack a thorough mechanistic understanding of these responses. Here I review historical and recent advances in stomatal water relations. Clear evidence now implicates a metabolically mediated response to leaf water status (‘hydroactive feedback’) in stomatal responses to evaporative demand and soil drought, possibly involving abscisic acid production in leaves. Other hypothetical mechanisms involving vapor and heat transport within leaves may contribute to humidity, light and temperature responses, but require further theoretical clarification and experimental validation. Variation and dynamics in hydraulic conductance, particularly within leaves, may contribute to water status responses. Continuing research to fully resolve mechanisms of stomatal responses to water status should focus on several areas: validating and quantifying the mechanism of leaf-based hydroactive feedback, identifying where in leaves water status is actively sensed, clarifying the role of leaf vapor and energy transport in humidity and temperature responses, and verifying foundational but minimally replicated results of stomatal hydromechanics across species. Clarity on these matters promises to deliver modelers with a tractable and reliable mechanistic model of stomatal responses to water status.
The diffusion of the Internet is reaching a level between 80% and 90% in Western societies. Yet, while the digital divide is closing for young cohorts, it is still an issue when comparing various ...generations. This study focuses specifically on the so-called ‘grey divide’, a divide among seniors of age 65+ years. Based on a representative survey in Switzerland (N = 1105), it is found that Internet use is strongly skewed in this age group leading to a partial exclusion of the old seniors (70+). Logistic regression shows that gender differences in usage disappear if controlled for education, income, technical interest, pre-retirement computer use and marital status. Furthermore, the social context appears to have a manifold influence on Internet use. Encouragement by family and friends is a strong predictor for Internet use, and private learning settings are preferred over professional courses. Implications for digital inequality initiatives and further research are discussed.
Hyaluronan and versican are extracellular matrix (ECM) components that are enriched in the provisional matrices that form during the early stages of development and disease. These two molecules ...interact to create pericellular “coats” and “open space” that facilitate cell sorting, proliferation, migration, and survival. Such complexes also impact the recruitment of leukocytes during development and in the early stages of disease. Once thought to be inert components of the ECM that help hold cells together, it is now quite clear that they play important roles in controlling cell phenotype, shaping tissue response to injury and maintaining tissue homeostasis. Conversion of hyaluronan-/versican-enriched provisional matrix to collagen-rich matrix is a “hallmark” of tissue fibrosis. Targeting the hyaluronan and versican content of provisional matrices in a variety of diseases including, cardiovascular disease and cancer, is becoming an attractive strategy for intervention.
•Versican and hyaluronan are enriched in provisional matrices.•Provisional matrices occur in development and early stages of disease pathogenesis.•Versican/hyaluronan complexes facilitate cell proliferation and migration.•Versican/hyaluronan interacts with immune and inflammatory cells.•Inhibition of versican and/or hyaluronan accumulation alters disease progression.
The content of proteoglycans (PGs) is low in the extracellular matrix (ECM) of vascular tissue, but increases dramatically in all phases of vascular disease. Early studies demonstrated that ...glycosaminoglycans (GAGs) including chondroitin sulfate (CS), dermatan sulfate (DS), keratan sulfate (KS) and heparan sulfate (HS) accumulate in vascular lesions in both humans and in animal models in areas of the vasculature that are susceptible to disease initiation (such as at branch points) and are frequently coincident with lipid deposits. Later studies showed the GAGs were covalently attached to specific types of core proteins that accumulate in vascular lesions. These molecules include versican (CSPG), biglycan and decorin (DS/CSPGs), lumican and fibromodulin (KSPGs) and perlecan (HSPG), although other types of PGs are present, but in lesser quantities. While the overall molecular design of these macromolecules is similar, there is tremendous structural diversity among the different PG families creating multiple forms that have selective roles in critical events that form the basis of vascular disease. PGs interact with a variety of different molecules involved in disease pathogenesis. For example, PGs bind and trap serum components that accumulate in vascular lesions such as lipoproteins, amyloid, calcium, and clotting factors. PGs interact with other ECM components and regulate, in part, ECM assembly and turnover. PGs interact with cells within the lesion and alter the phenotypes of both resident cells and cells that invade the lesion from the circulation. A number of therapeutic strategies have been developed to target specific PGs involved in key pathways that promote vascular disease. This review will provide a historical perspective of this field of research and then highlight some of the evidence that defines the involvement of PGs and their roles in the pathogenesis of vascular disease.
•Proteoglycans increase dramatically in the extracellular matrix of blood vessels in vascular disease.•Proteoglycans interact with a large number of components in vascular disease and impact their atherogenecity.•Proteoglycans interact with lipids to cause their accumulation in vascular disease.•Targeting specific proteoglycans in animal models of vascular disease can interfere with vascular lesion development.•Proteoglycans interact with vascular cells and alter their pathogenic phenotype.
Water movement from the xylem to stomata is poorly understood. There is still no consensus about whether apoplastic or symplastic pathways are more important, and recent work suggests vapour ...diffusion may also play a role. The objective of this study was to estimate the proportions of hydraulic conductance outside the bundle sheath contributed by apoplastic, symplastic and gas phase pathways, using a novel analytical framework based on measurable anatomical and biophysical parameters. The calculations presented here suggest that apoplastic pathways provide the majority of conductance outside the bundle sheath under most conditions, whereas symplastic pathways contribute only a small proportion. The contributions of apoplastic and gas phase pathways vary depending on several critical but poorly known or highly variable parameters namely, the effective Poiseuille radius for apoplastic bulk flow, the thickness of cell walls and vertical temperature gradients within the leaf. The gas phase conductance should increase strongly as the leaf centre becomes warmer than the epidermis – providing up to 44% of vertical water transport for a temperature gradient of 0.2 K. These results may help to explain how leaf water transport is influenced by light absorption, temperature and differences in leaf anatomy among species.
This paper reviews the literature on moisture barrier properties of polymer/clay and polymer/graphene-based nanocomposites. The various models proposed to predict the effects of nanofillers in ...reducing water vapour permeability through polymers are outlined. These models are based on a range of different factors such as; tortuosity, geometry, platelet stacking, orientation, polymer chain confinement and plasticization. Published experimental studies of water vapour permeability in both polymer/clay and polymer/graphene nanocomposites are then reviewed. The extent to which the models are validated by the results of these studies is discussed, together with the degree to which the potential for water barrier improvement in polymer nanocomposites has been realised.
•Description of models predicting water permeability of polymer nanocomposites.•Introduction to polymer/clay and polymer/graphene nanocomposites.•Review of published studies on water barrier properties of polymer nanocomposites.•Discussion of validation of models.•Moisture barrier applications for polymer/clay and polymer/graphene nanocomposites.
Landesque Capital Håkansson, N. Thomas; Widgren, Mats
2014, 20160616, 2016-06-16, Letnik:
5
eBook, Book
This book is the first comprehensive, global treatment of landesque capital, a widespread concept used to understand anthropogenic landscapes that serve important economic, social, and ritual ...purposes. Spanning the disciplines of anthropology, human ecology, geography, archaeology, and history, chapters combine theoretical rigor with in-depth empirical studies of major landscape modifications from ancient to contemporary times. They assess not only degradation but also the social, political, and economic institutions and contexts that make sustainability possible. Offering tightly edited, original contributions from leading scholars, this book will have a lasting influence on the study long-term human-environment relations in the human and natural sciences.
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