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The objective of this study is the preparation of a tetracycline-boron-10 derivative which is stable under biological conditions. The boron-10 should then provide a concentration of material capable of accepting thermal neutrons, thus producing localized high-energy alpha radiation. The fact that the tetracyclines are not retained by normal tissue should remove the danger of destruction of this tissue.

The effect of boron deficiency was studied in tomato plants grown hydroponically. Morphological studies showed that boron deficiency in the root system caused a cessation of root elongation, browning and thickening of root tips, the formation of branch roots close to the apex and decrease in the overall size of the root. The pyrimidine biosynthetic pathway remained intact and functional under boron limitation. The sugar nucleotide, uridine diphosphate glucose, was diminished in boron deficient medium and its level was restored to that of born sufficiency when uracil, cytosine, uridine, cytidine or orotic acid was provided.

B4C is an important engineering ceramic used in a number of different applications. One of the promising applications of B4C is in the nuclear industry. B4C has a high neutron absorption cross-section (600 barns) and that is why it can absorb neutrons without forming long lived radio nuclides. As a result, B4C is extensively used as control rods, shielding material and as neutron detectors in nuclear reactors. During the reactor’s operation, the B4C undergoes severe neutron radiation and defects, such as vacancies and helium bubbles, are generated in the structure. These defects are responsible for the degradation of mechanical performance of B4C and can make this material unsuitable for further exploitation. Therefore, both crystal structure and mechanical properties of B4C were studied before and after radiation, as well as for the case when irradiated by neutrons B4C samples has been annealed in order to heal the defects introduced by the radiation. Fully dense B4C ceramics were produced by hot pressing at 2100ºC, 30MPa, and 45 minutes dwell time. 120 small bars of 2×2.5×25mm were machined according to the MOR bar standard. 40 bars after machining were tested as they were, 80 bars were irradiated with neutrons in neutron source for 3.5 months. 40 out of the 80 irradiated bars were annealed at 400ºC for 1 hour with an attempt to heal the defects possibly introduced by the irradiation. iv 4-point bending strength, SEVNB fracture toughness, and Vickers hardness have been measured on as received B4C, B4C after radiation, and B4C after radiation and annealing. The Weibull parameters were determined for each set of the conditions. The fracture surfaces of the B4C samples before and after radiation as well as after radiation and annealing have also been analyzed using SEM. X-ray diffractometer was used to collect diffraction pattern of the B4C, and Raman spectrometer was used to evaluate the vibrational response of B4C. Thus the effect of neutron radiation and annealing on the mechanical performance and structure of B4C has been analyzed.

This is Part B of the Thesis. Here is the Link to Part A: http://hdl.handle.net/11375/17844 / <p> This report deals with the effects of various parameters on the resistance and the temperature coefficient of resistance (or the T.C.) of tin dioxide films doped with antimony and boron. The films were produced on cylindrical ceramic substrates by the hydrolysis of SnCl4 and SbCls in the presence of HCl and H3BO3. The T.C. was measured over the range of 25 to 150°C and averaged.</p> <p> Under normal conditions, the films were produced at 950°C with an antimony concentration of 0.457 molar % and a boron concentration of 2.73 molar %. Varying this firing temperature (from 800-1100°C) was found to have no effect on the resistance but increased the T.C. by 2 to 3 ppm/°C per degree change. Varying the antimony content from 0 to about 1 molar % was found to have little effect on resistance. The effect on T.C. was to increase it at lower Sb levels and then to decrease the T.C. as the level increased.</p> <p> Varying the boron content (0 to 4.46 molar %) was also found to have little effect on resistance. A decrease in T.C. with boron content was noted when only the boron was varied, but an increase in T.C. was found when HCl and H2O volumes were varied with the boron. The introduction of additional air into the system was found to have no effect.</p> <p> Film thicknesses were varied by controlling the chemical flowrates. Thinner films were found to have dramatically higher resistances and reduced T.C. values. It was observed that below a certain flowrate resistive failure occurred in the films. It was found in this study that within the statistical distribution of film values, those samples with above average resistance had below average T.C. values and vice-versa. Annealing in vacuum at 500°C was found to produce samples of reduced resistance and increased T.C. while the opposite was found with air annealed samples. Quickly cooled samples were found to be more stable.</p> / Thesis / Master of Engineering (MEngr)

<p> Nuclear magnetic resonance spectroscopy has been used to study donor-acceptor complexes of boron trifluoride with ketones, water, and methanol. Various NMR techniques have been applied which, in certain favourable cases, have yielded information on the stoichiometry, structure, relative stabilities, and reactions of the complexes in solution. A new method is proposed for the detection of BF3 complexes having low formation constants.</p> <p> The magnitude and sign of the B-F coupling constant in the tetra-fluoroborate anion have been found to be dependent on the solvent. This solvent dependence is interpreted in terms of solvation and association of the ion in solution.</p> <p> 19F spectra of 10BF3 over a range of temperatures agree well with line shapes calculated, using Pople's expressions, for coupling of fluorine-19 with boron-10 (I=3) which is undergoing partial quadrupole relaxation.</p> / Thesis / Doctor of Philosophy (PhD)

<p> Separated minerals From 18 different rock samples were available. These came From various locations in the Grenville province. OF these samples, there were 44 minerals which had at least one coexisting mineral phase. These were all analysed For boron by thermal neutron irradiation using the Prompt Gamma Neutron Activation Analysis at McMaster University Nuclear Reactor. There was a preferential boron partition determined For the samples originating From an igneous source, and a numerical value of 0.7 was determined for k-Feldspar/Biotite. There was no Preferential boron partition among the coexisting phases that originated From a metamorphic source. Sphene and Fluorite contained much less boron than other minerals that coexisted with them. </p> / Thesis / Bachelor of Science (BSc)

Thesis advisor: Amir H. Hoveyda / The possibility of accessing altered frameworks wherein the spatial relationship between several organic fragments can be controlled can notably impact drug discovery and development. In this context, we introduce a strategy that can be used for programmable and divergent synthesis of a diverse and otherwise difficult-to-prepare set of cyclic amines and bridged bicyclic enamines wherein up to four exit vectors can be altered accordingly. Central to the approach is a catalytic multicomponent reaction that merges a nitrile, a trisubstituted allenylboronate and a silyl hydride, delivering multifunctional 1,4-aminoboronates that contain a versatile and stereochemically defined trisubstituted alkenyl boronate. We show that the products can be modified to afford an assortment of complex, drug-like, polycyclic amines. What is more, a new cyclization strategy, involving the triflic anhydride-mediated reaction of a trisubstituted alkene and a nearby amide, was developed for synthesis of the corresponding bridged bicyclic scaffolds. These resulting bridged enamines and various derivatives are evocative of the 1-azabicyclo[3.2.1]octane core, found in a variety of bioactive alkaloids. / Thesis (PhD) — Boston College, 2023. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Silicon Carbide devices are proving to be most promising for high power and high-temperature application in recent times. Efficient and accurate characterization of the device characteristics is key to the fabrication of high quality devices and reproduction of the quality of the devices fabricated. Capacitance-Voltage profiling is one of the most commonly used techniques to measure the doping profiles of semiconductors. However, interpretation of C-V profiling in the presence of traps in the material becomes complicated. Various complications arising from compensation between donors and acceptors, partial ionization of dopants and presence of deep level impurities could yield anomalous measured profile. Silicon Carbide being a wide bandgap semiconductor, many impurities commonly found such as Boron and Aluminum are not completely ionized at Room temperature. This leads to complications in calculating doping profiles when the trap levels are deeper. Other complications arising due to series resistance effect and diode edge effect may also affect the measured profile. Accounting for these complications may be difficult by mere observation of the measured profile. Simulation can be an excellent tool to extract parameters of interest from experimental results that are influenced by non-ideal effects. Fitting of the experimentally obtained data with simulated profile using specific models may be a useful technique to quantitatively account for the deviations from the actual profiles.