Health Physics: The science concerned with problems of radiation protection relevant to reducing or preventing radiation exposure, and the effects of ionizing radiation on humans and their environment.Physics: The study of those aspects of energy and matter in terms of elementary principles and laws. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Nuclear Physics: The study of the characteristics, behavior, and internal structures of the atomic nucleus and its interactions with other nuclei. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Physical Phenomena: The entities of matter and energy, and the processes, principles, properties, and relationships describing their nature and interactions.Health Status: The level of health of the individual, group, or population as subjectively assessed by the individual or by more objective measures.Public Health: Branch of medicine concerned with the prevention and control of disease and disability, and the promotion of physical and mental health of the population on the international, national, state, or municipal level.Delivery of Health Care: The concept concerned with all aspects of providing and distributing health services to a patient population.Health Policy: Decisions, usually developed by government policymakers, for determining present and future objectives pertaining to the health care system.Health Surveys: A systematic collection of factual data pertaining to health and disease in a human population within a given geographic area.Health Care Reform: Innovation and improvement of the health care system by reappraisal, amendment of services, and removal of faults and abuses in providing and distributing health services to patients. It includes a re-alignment of health services and health insurance to maximum demographic elements (the unemployed, indigent, uninsured, elderly, inner cities, rural areas) with reference to coverage, hospitalization, pricing and cost containment, insurers' and employers' costs, pre-existing medical conditions, prescribed drugs, equipment, and services.Health Promotion: Encouraging consumer behaviors most likely to optimize health potentials (physical and psychosocial) through health information, preventive programs, and access to medical care.Mental Health: The state wherein the person is well adjusted.