Silicon Dioxide: Transparent, tasteless crystals found in nature as agate, amethyst, chalcedony, cristobalite, flint, sand, QUARTZ, and tridymite. The compound is insoluble in water or acids except hydrofluoric acid.Silicon: A trace element that constitutes about 27.6% of the earth's crust in the form of SILICON DIOXIDE. It does not occur free in nature. Silicon has the atomic symbol Si, atomic number 14, and atomic weight [28.084; 28.086].Hafnium: Hafnium. A metal element of atomic number 72 and atomic weight 178.49, symbol Hf. (From Dorland, 28th ed)Dielectric Spectroscopy: A technique of measuring the dielectric properties of materials, which vary over a range of frequencies depending on the physical properties of the material. The technique involves measuring, over a range of frequencies, ELECTRICAL IMPEDANCE and phase shift of an electric field as it passes through the material.Nanomedicine: The branch of medicine concerned with the application of NANOTECHNOLOGY to the prevention and treatment of disease. It involves the monitoring, repair, construction, and control of human biological systems at the molecular level, using engineered nanodevices and NANOSTRUCTURES. (From Freitas Jr., Nanomedicine, vol 1, 1999).Silicon Compounds: Inorganic compounds that contain silicon as an integral part of the molecule.Nanoparticles: Nanometer-sized particles that are nanoscale in three dimensions. They include nanocrystaline materials; NANOCAPSULES; METAL NANOPARTICLES; DENDRIMERS, and QUANTUM DOTS. The uses of nanoparticles include DRUG DELIVERY SYSTEMS and cancer targeting and imaging.Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.Carbon Compounds, Inorganic: Inorganic compounds that contain carbon as an integral part of the molecule but are not derived from hydrocarbons.Nitrogen Dioxide: Nitrogen oxide (NO2). A highly poisonous gas. Exposure produces inflammation of lungs that may only cause slight pain or pass unnoticed, but resulting edema several days later may cause death. (From Merck, 11th ed) It is a major atmospheric pollutant that is able to absorb UV light that does not reach the earth's surface.Nanowires: Nanometer-scale wires made of materials that conduct electricity. They can be coated with molecules such as antibodies that will bind to proteins and other substances.Sulfur Dioxide: A highly toxic, colorless, nonflammable gas. It is used as a pharmaceutical aid and antioxidant. It is also an environmental air pollutant.Semiconductors: Materials that have a limited and usually variable electrical conductivity. They are particularly useful for the production of solid-state electronic devices.Organosilicon Compounds: Organic compounds that contain silicon as an integral part of the molecule.Nanotechnology: The development and use of techniques to study physical phenomena and construct structures in the nanoscale size range or smaller.