• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 531
  • 168
  • 91
  • 62
  • 31
  • 16
  • 12
  • 10
  • 10
  • 8
  • 6
  • 6
  • 6
  • 6
  • 6
  • Tagged with
  • 1197
  • 193
  • 154
  • 124
  • 103
  • 99
  • 99
  • 99
  • 89
  • 88
  • 79
  • 71
  • 69
  • 68
  • 65
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
341

THE USE OF BORON-DOPED DIAMOND FILM ELECTRODES FOR THE OXIDATIVE DEGRADATION OF PERFLUOROOCTANE SULFONATE AND TRICHLOROETHYLENE

Carter, Kimberly Ellen January 2009 (has links)
The current treatment of water contaminated with organic compounds includes adsorption, air stripping, and advanced oxidation processes. These methods large quantities of water and require excessive energy and time. A novel treatment process of concentrating and then electrochemically oxidizing compound would be a more feasible practice. This research investigated the oxidative destruction of perfluorooctane sulfonate (PFOS), perfluorobutane sulfonate (PFBS) and trichloroethene (TCE) at boron-doped diamond film electrodes and the adsorption of PFOS and PFBS on granular activated carbon and ion exchange resins.Experiments measuring oxidation rates of PFOS and PFBS were performed over a range in current densities and temperatures using a rotating disk electrode (RDE) reactor and a parallel plate flow-through reactor. Oxidation of PFOS was rapid and yielded sulfate, fluoride, carbon dioxide and trace levels of trifluoroacetic acid. Oxidation of PFBS was slower than that of PFOS. A comparison of the experimentally measured apparent activation energy with those calculated using Density Functional Theory (DFT) studies indicated that the most likely rate-limiting step for PFOS and PFBS oxidation was direct electron transfer. The costs for treating PFOS and PFBS solutions were compared and showed that PFOS is cheaper to degrade than PFBS.Screening studies were performed to find a viable adsorbent or ion exchange resin for concentrating PFOS or PFBS. Granular activated carbon F400 (GAC-F400) and an ion exchange resin, Amberlite IRA-458, were the best methods for adsorbing PFOS. Ionic strength experiments showed that the solubility of the compounds affected the adsorption onto solid phases. Regeneration experiments were carried out to determine the best method of recovering these compounds from the adsorbents; however, the compounds could not be effectively removed from the adsorbents using standard techniques.The electrochemical oxidation of trichloroethene (TCE) at boron-doped diamond film electrodes was studied to determine if this would be a viable degradation method for chlorinated solvents. Flow-through experiments were performed and showed TCE oxidation to be very rapid. Comparing the data from the DFT studies and the experimentally calculated apparent activation energies the mechanism for TCE oxidation was determined to be controlled by both direct electron transfer and oxidation via hydroxyl radicals.
342

Theoretical Routes for c-BN Thin Film Growth

Karlsson, Johan January 2013 (has links)
Cubic boron nitride (c-BN) has been in focus for several years due to its interesting properties. The possibility for large area chemical vapor deposition (CVD) is a requirement for the realization of these different properties in various applications. Unfortunately, there are at present severe problems in the CVD growth of c-BN. The purpose with this research project has been to theoretically investigate, using density functional theory (DFT) calculations, the possibility for a layer-by-layer CVD growth of c-BN.  The results, in addition with experimental work by Zhang et al.57,  indicate that plasma-enhanced atomic layer deposition (PEALD), using a BF3-H2-NH3-F2 pulse cycle and a diamond substrate, is a promising method for deposition of c-BN films. The gaseous species will decompose in the plasma and form BFx, H, NHx, and F species (x = 0, 1, 2, 3). The H and F radicals will uphold the cubic structure by completely hydrogenate, or fluorinate, the growing surface. Surface radical sites will appear during the growth process as a result of atomic H, or F, abstraction reactions. However, introduction of energy (e.g., ionic bombardment) is probably necessary to promote removal of H from the surface. The addition of NHx growth species (x = 0, 1, 2) to the B radical sites, and BFx growth species (x = 0, 1, 2) to N radical sites, will then result in a continuous growth of c-BN.
343

Synthesis and Thermodynamic Investigation of Boron Allotropes

Cerqueira, Anthony 26 August 2011 (has links)
The focus of the present research is to find the relative thermodynamic stability of ?-boron and ?-boron via heat capacity measurements. Efforts to synthesize ?-boron through the application of vapour-liquid-solid theory resulted in the discovery of a new chemical vapour deposition approach. The heat capacities of both synthesized ?-boron and commercial (99.5%) ?-boron were determined using relaxation calorimetry over the temperature range 0.2 K to 400 K. These data, in combination with literature information, allowed the calculation of the Gibbs energy of the ?-boron to ?-boron transition from 0 K to 1985 K. It was found that the transition from ?-boron to ?-boron was thermodynamically favourable at all temperatures up to 1985 K with a value of ?Gt(T = 300 K) = -10 kJ mol-1 ± 1 kJ mol-1 and ?Gt(T = 1985 K) = -15 kJ mol-1 ± 1 kJ mol-1.
344

An accelerator-based epithermal photoneutron source for boron neutron capture therapy

Mitchell, Hannah Elizabeth 05 1900 (has links)
No description available.
345

Cell cycle affects accumulation of β-D-5-o-Carboranyl-2'-Deoxyuridine(D-CDU) in human glioma cell line

Moore, Casey Benjamin 12 1900 (has links)
No description available.
346

Neutron spectrum measurement for Boron Neutron Capture Therapy

Hefne, Jameel 08 1900 (has links)
No description available.
347

Development of a boron neutron capture enhanced fast neutron therapy beam

Sweezy, Jeremy Ed 05 1900 (has links)
No description available.
348

Perfluorovinyl complexes of PT(II) ; Bridge substitution in B5H9 ; The crystal structure of ((C2H5)2NBS)2 / I. Perfluorovinyl complexes of PT(II) ; II. Bridge substitution in B5H9 ; III. The crystal structure of ((C2H5)2NBS)2

Rivett, Garry Arthur 07 April 2014 (has links)
Graduate / 0485
349

Perfluorovinyl complexes of PT(II) ; Bridge substitution in B5H9 ; The crystal structure of ((C2H5)2NBS)2 / I. Perfluorovinyl complexes of PT(II) ; II. Bridge substitution in B5H9 ; III. The crystal structure of ((C2H5)2NBS)2

Rivett, Garry Arthur 07 April 2014 (has links)
Graduate / 0485
350

Structure and Properties of Nanomaterials: From Inorganic Boron Nitride Nanotubes to the Calcareous Biomineralized Tubes of H. dianthus

Tanur, Adrienne Elizabeth 07 January 2013 (has links)
Several nanomaterials systems, both inorganic and organic in nature, have been extensively investigated by a number of characterization techniques including atomic force microscopy (AFM), electron microscopy, Fourier transform infrared spectroscopy (FTIR), and energy dispersive x-ray spectroscopy (EDX). The first system consists of boron nitride nanotubes (BNNTs) synthesized via two different methods. The first method, silica-assisted catalytic chemical vapour deposition (SA-CVD), produced boron nitride nanotubes with different morphologies depending on the synthesis temperature. The second method, growth vapour trapping chemical vapour deposition (GVT-CVD), produced multiwall boron nitride nanotubes (MWBNNTs). The bending modulus of individual MWBNNTs was determined using an AFM three-point bending technique, and was found to be diameter-dependent due to the presence of shear effects. The second type of nanomaterial investigated is the biomineralized calcareous shell of the serpulid Hydroides dianthus. This material was found to be an inorganic-organic composite material composed of two different morphologies of CaCO3, collagen, and carboxylated and sulphated polysaccharides. The organic components were demonstrated to mediate the mineralization of CaCO3 in vitro. The final system studied is the proteinaceous cement of the barnacle Amphibalanus amphitrite. The secondary structure of the protein components was investigated via FTIR, revealing the presence of β-sheet conformation, and nanoscale rod-shaped structures within the cement were identified as β-sheet containing amyloid fibrils via chemical staining. These rod-shaped structures exhibited a stiffer nature compared with other structures in the adhesive, as measured by AFM nanoindentation.

Page generated in 0.0424 seconds