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As humans ventured into the twentieth century, the industrialized countries were confronted with the scourge of rickets. Although solariums were becoming common in the early 1900s and phototherapy was gaining popularity as a result of the awarding of a Nobel Prize to Finsen in 1903, it wasn't until 1921 when Hess and Unger demonstrated that rickets could be cured by exposure to sunlight that the healthful benefit of sun exposure appreciated. In 1941, Apperly (Cancer Research; 1: 191-195, 1941) noted that the occasional increased risk of skin cancer was associated with a decreased risk of many other more common and serious cancers. The alarming increase in the number of cases of skin cancer, especially melanoma, has caused great concern about the negative role of sunlight in health. The Sixth International Arnold Rikli Symposium on the Biologic Effects of Light was held in Boston, Massachusetts from June 16th - 18th, 2001. The goal of this Symposium was to focus on the very popular practice of tanning either by sunlight or by artificial light sources and the overall impact this practice has on health and disease. The program was organized by members of the Scientific Advisory Committee and my co-chair emeritus, Professor Ernst G. Jung. The Program Committee organized an outstanding state-of-the-art program that was enthusiastically received by the participants.
It is remarkable how much we take for granted the tremendous energy and vitality that the sun provides earth's inhabitants. As we enter the new millennium, it is worthwhile to review how our ancestors perceived the biologic effects of sunlight, and how science and medicine have advanced our knowledge about the biologic effects of light. At the turn of the century, a multitude of investigators explored the use of sunlight and artificial radiation for treating a multitude of diseases. These explorations gave rise to photodynamic therapy, phototherapy, and chemophototherapy. However, enthusiasm for using sunlight and artificial radiation to treat disease was dampened with the birth of pharmacology. It was the goal of the Fifth International Arnold Rikli Symposium on the Biologic Effects of Light, held in Basel, Switzerland, on November 1-3, 1998, to review the history of phototherapy and have some of the world's leading experts on the biologic effects of light provide new perspectives on the positive and negative effects of light. The general topics included a broad range of biologic effects of sunlight, artificial ultraviolet radiation and electromagnetic radiation. Special sessions on radiation and vitamin D and bone health, photoimmunology, biopositive effects of UV radiation, effects of electromagnetic currents and fields, and ocular and non-ocular regulation of circadian rhythms and melatonin, should be of particular interest to readers of Biologic Effects of Light.
"Form," writes the author, "is developed by means of light and shade; without these every object would appear flat." Originally published in the mid-nineteenth century, this classic approach to three-dimensional drawing was the first book to provide art students with instructions for correctly illustrating perspective outlines of various objects.
1.1 Overview We are living in a decade recently declared as the "Decade of the Brain". Neuroscientists may soon manage to work out a functional map of the brain, thanks to technologies that open windows on the mind. With the average human brain consisting of 15 billion neurons, roughly equal to the number of stars in our milky way, each receiving signals through as many as 10,000 synapses, it is quite a view. "The brain is the last and greatest biological frontier", says James Weston codiscoverer of DNA, considered to be the most complex piece of biological machinery on earth. After many years of research by neuroanatomists and neurophysÂ iologists, the overall organization of the brain is well understood, but many of its detailed neural mechanisms remain to be decoded. In order to understand the functioning of the brain, neurobiologists have taken a bottom-up approach of studying the stimulus-response characteristics of single neurons and networks of neurons, while psyÂ chologists have taken a top-down approach of studying brain funcÂ tions from the cognitive and behavioral level. While these two apÂ proaches are gradually converging, it is generally accepted that it may take another fifty years before we achieve a solid microscopic, intermediate, and macroscopic understanding of brain.
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