As part of an immune response to foreign pathogens, histamine is produced by basophils and by mast cells found in nearby connective tissues. Histamine increases the permeability of the capillaries to white blood cells and some proteins, to allow them to engage pathogens in the infected tissues.
Where vegetation is sparse, temperature is hot. (Image: NASA) An urban heat island (UHI) is a metropolitan area which is significantly warmer than its surroundings. According to the EPA, many U.S. cities have air temperatures up to 10Â°F (5.6Â°C) warmer than the surrounding natural land cover.
it is well known that urban areas are generally warmer than nearby rural areas often referred to as the urban heat island effect urbanization has long been regarded as a potential serious contamination of the global climate signal e g landsberg 1956even for small settlements in arctic environments the temperature effect has been shown to be considerable hinkel et al 2003he main cause of the urban heat island effect is land surface changes with roads and buildings taking up an increasing part of the total area changing the overall reflectance albedo of the area