Spin polarized density functional theory has been used to investigate the structural stability and electronic properties of extrinsic and intrinsic defects in boron nitride nanotubes. Carbon substitutional defects under nitrogen rich and boron-rich growth conditions have the lowest heats of formation compared to boron and nitrogen antisites. Creating a defect reduces the band gap of the nanotub...

We report the application of our dc SQUID (superconducting quantum interference device) spectrometer [C. Connor, J. Chang, and A. Pines, Rev. Sci. Instrum. 61, 1059( 1990)] to nuclear quadrupole resonance (NQR) studies of aluminum-27, and boron-II in crystalline and glassy solids. Our results give eqQ /h = 2.38 MHz and 1] = 0.0 for a-A120 3 at 4.2 K. For the natural mineral petalite (LiAISi4 01...

Near edge x-ray absorption fine structure (NEXAFS) spectra at the boron K-edge were measured for aqueous boric acid, borate, and polyborate ions, using liquid microjet technology, and compared with simulated spectra calculated from first principles density functional theory in the excited electron and core hole (XCH) approximation. Thermal motion in both hydrated and isolated molecules was inco...

Solid-state neutron detectors based only on boron-rich semiconductors are of interest for their potential to provide the highest thermal neutron detection efficiencies of any solid-state neutron detectors. A simple physical model, recently shown to generate thermal neutron capture product spectra that agree quantitatively with full-physics GEANT4 simulation, is used to compare the capture produ...

In the preceding papers (7, 8) of this series we presented the effects of certain mineral deficiency on the organic constituents of tobacco plants. Changes in the organic composition were associated with the development of typical symptoms resulting from an abnormal supply of a specific mineral. Mineral deficiency symptoms, in general, appear initially in a localized area and are very mild. The...

The trace mineral boron is a micronutrient with diverse and vitally important roles in metabolism that render it necessary for plant, animal, and human health, and as recent research suggests, possibly for the evolution of life on Earth. As the current article shows, boron has been proven to be an important trace mineral because it (1) is essential for the growth and maintenance of bone; (2) gr...