Chronic low back pain may be caused by many different sources. It may start from diseases, injuries or stresses to many different structures including bones, muscles, ligaments, joints, nerves or the spinal cord. The affected structure will send a signal through nerve endings, up the spinal cord and into the brain where it registers as pain. Many different theories try to explain chronic pain. The exact mechanism is not completely understood. In general, it is believed that the nerve pathways that carry the pain signals from the nerve endings through the spinal cord and to the brain may become sensitized. Sensitization of these pathways may increase the perceived pain out of proportion to the source of the pain. Stimuli that ordinarily are not perceived as painful, such as light touch, can be amplified or changed by these sensitized pathways and experienced as pain. Sometimes, even after the original injury or disease process has healed, sensitized pathways continue to send signals to the brain. These signals feel just as real as and sometimes worse than the pain caused by the original injury or disease process.
The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information. The impact factor of a journal is evaluated by dividing the number of current year citations to the source items published in that journal during the previous two years.
Last date updated on June, 2014