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Including peanut (Arachis hypogaea L.) in crop rotations is common for eastern Virginia and the Carolinas, as it thrives in the long growing season and sandy soils. Boron (B) is widely deficient, and is more prone to leeching in sandy soils. Applied B has difficulty reaching growing points as B has reduced phloem mobility in peanuts. Current B fertilization recommendations are based on only three studies from the early 70s. Many changes have been made in cultivar breeding since then. This research examines if recommended B application rates and times are still necessary for optimal yield, plant health and seed quality for current cultivars. Two experiments in seven fields compared four total amounts of B applied (0, 0.3, 0.6, and 1.1 kg ha-1), and application time (planting; beginning peg, R2; full seed, R6; planting and R2; planting and R6), and runner and Virginia market types, newer and obsolete cultivars, with or without B fertilization. Leaf B was elevated only directly after fertilization (p=0.004, p<0.001), and in relation to total B applied (p<0.001), but seed B content was unaffected. Yield was not impacted by B rate or application time. Yield was higher (p=0.012) for newer cultivars when B fertilized, but no different than obsolete cultivars with B. Seed from obsolete cultivars had higher (p=0.010) B, no difference between market types or B fertilization. Germination of all seed was 97%. Based on this research, it is not necessary to apply B for optimal yield, plant health and seed quality for current cultivars. / Master of Science in Life Sciences

Cubic boron nitride (cBN) thin films offer attractive mechanical and electrical properties. The synthesis of cBN films have been deposited using both physical and chemical vapor deposition methods, which generate internal residual, stresses that result in delamination of the film from substrates. Boron nitride films were deposited using electron beam evaporation without bias voltage and nitrogen bombardment (to reduce stresses) were characterize using FTIR, XRD, SEM, EDS, TEM, and AFM techniques. In addition, a pin-on-disk tribological test was used to measure coefficient of friction. Results indicated that samples deposited at 400°C contained higher cubic phase of BN compared to those films deposited at room temperature. A BN film containing cubic phase deposited at 400°C for 2 hours showed 0.1 friction coefficient.

This thesis undertakes the development, characterization and optimization of boron diffusion for silicon solar cells. Heavy diffusions (sheet resistance < 40 Ohm/square) to form a back surface field, and light diffusions (sheet resistance > 100 Ohm/square) to form oxide-passivated emitters were developed. Test structures and solar cells were fabricated to assess uniformity, lifetime and recombination effects due to the light and heavy boron diffusions. It was found that the growth of a thin ~200 ??, thermal oxide, during stabilization ??? immediately prior to the boron diffusion - was required to maintain high lifetime and reduce surface recombination (reducing the emitter saturation current density) for all boron diffusions. The heavy boron diffusion process was incorporated into the single side buried contact solar cell processing sequence. The solar cells fabricated had both boron diffused and Al/Si alloyed P+ regions for comparison. This research conclusively showed that boron diffused solar cells had significantly higher open circuit voltage compared to Al/Si alloyed devices. Fabrication of n-type solar cells, and their subsequent characterization by overlayed secondary electron image and the electron beam induced current map showed that the Al/Si alloy varied in depth from 5 to 25 micrometers deep. Methodology and characterization for light, oxide-passivated boron diffusions are also presented. This study yielded boron diffused emitters (sheet resistance > 100 Ohm/square) with low emitter saturation current. It was observed that this was possible only when the thermal oxidation after the boron diffusion was minimal, less than 1,000 ??. This was due to the segregation effect of boron with oxide, decreasing the surface concentration that in turn decreased the electric field repulsion of electrons from the surface. Device modelling of n-type solar cells is presented where the parameters of the modelling include the results of the light, oxide-passivated boron diffusions. This modelling shows n-type-base material with light oxide-passivated boron diffusion has higher potential conversion efficiency than forming a solar cell from phosphorous diffused p-type material.

This thesis describes studies into the genetic control of tolerance of wheat to high concentrations of boron ( B ). Initially, experiments were conducted to determine selection criteria for distinguishing between tolerant and sensitive genotypes for both glasshouse and field grown wheat. Responses of plants to high concentrations of B, under glasshouse conditions, included reduced vigour, delayed development, expression of symptoms of toxicity and reduced grain and total dry matter yields. Significant differences between tolerant and sensitive genotypes resulted for all parameters, however the greatest discrimination for tolerance to B, between genotypes, resulted during vegetative growth. Tolerant genotypes accumulated less B than the more sensitive genotypes for both glasshouse and field experiments. The concentration of boron in shoots was a highly heritable character and B concentrations in shoots were significantly correlated between high boron conditions in a glasshouse and the field. The concentration of B in grain was highly correlated with the concentration in shoots for field grown wheat, but this relationship did not occur for wheat grown in pots and the anomalous result was related to the artifical growth conditions. Grain is an appropriate tissue for analysis to determine the B accumulation, and therefore tolerance, for field grown wheat. The tolerance to B for wheat varieties of historical importance in Australia was investigated. Many of the historically dominant varieties are tolerant to B and all tolerant Australian varieties are interrelated. The initial tolerant varieties were Federation and Currawa and members of the derived family include Ghurka, Quadrat, Insignia, Heron, Olympic, Halberd, Spear and Dagger. The distribution of Insignia, Heron and Halberd followed a similar pattern in South Australia and the regions where these varieties were most widely cultivated corresponds to the regions where the highest concentrations of B have been measured in barley grain samples. Thus, there is correlative evidence that the high concentration of B occurring in the subsoils has been a major selective force in South Australian wheat production. Tolerance to high concentrations of boron is inherited as an additive character, however expression of tolerance varies from being a dominant to a partially dominant character depending upon the concentration of applied boron. Major gene control of tolerance to boron was identified from the segregation patterns of F2 and F3 generations derived from parents of contrasting tolerance to boron. The parents used represented five levels of tolerance to boron and the difference between successive levels of tolerance was under the control of single genes. Three independent single gene differences were identified. Transgressive segregation resulted between two tolerant lines, Halberd and G61450, and this suggests they have contrasting genes controlling the uptake of boron. A genetic model comprising four independent loci, designated Borl, Bor2, Bor3 and Bor4 was proposed for the five lines. The five lines and their proposed genotypes were : Kenya Farmer ( very sensitive ) borl bor2 bor3 bor4, ( W1 * MMC ) ( sensitive ) borl bor2 Bor3 bor4, Warigal ( moderately sensitive ) borl Bor2 Bor3 bor4, Halberd ( moderately tolerant ) Borl Bor2 Bor3 bor4 and G61450 ( very tolerant ) bor1 Bor2 Bor3 Bor4. As tolerance to high concentrations of B is under the control of major genes, incorporation of tolerance into sensitive but otherwise adapted local varieties should be readily achieved through backcrossing. The chromosomal location of genes controlling tolerance to B was undertaken by the use of intervarietal substitution lines, monosomic analysis and interspecific addition lines. Chromosome 4A of the Chinese Spring - Kenya Farmer substitution lines had a significant effect upon tolerance to boron and the 4A substitution line was more sensitive than Chinese Spring. Results for monosomic analysis were inconclusive, however chromosomes identified as the more probable locations of genes controlling tolerance to boron included 4A and 7D for analysis of the F3 ' s of ( Chinese Spring monosomics * G61450 ) and chromosomes 7B, 3A and 2B for reciprocal monosomic analysis between Chinese Spring and Federation. The Chinese Spring x Ag. elongatum amphiploid was more tolerant than Chinese Spring and the chromosome 7E addition line was also more tolerant than Chinese Spring. The results of three separate comparisons therefore implicate the chromosomes of homoeologous group seven in the control of tolerance to boron. Random F4 and F5 lines derived from the tolerant Halberd and sensitive I ( W1 * MMC ) were tested under naturally occurring high B conditions in the field. Chemical analysis of shoots and grain by inductively coupled plasma spectrometry found uptake of B to be independent of nine other elements. The correlation between tolerance to B, as measured by B uptake, and yield among lines of this population was tested at six sites to identify conditions where tolerance to B resulted in a yield advantage. A significant correlation between tolerance to B and yield resulted only at sites where high boron concentrations of grain resulted. Genetic variation for concentrations of several other elements in shoots and grain also occurred within this population and significant correlations between the efficiency of nutrient uptake and grain yield resulted for Mn at Two Wells and Minnipa while genotypes with low Na accumulation produced significantly higher yields than genotypes with high Na uptake at Rudall. Genetic variation in response to soil elements, other than B, may explain the variable performance of varieties, between environments, and this is an area which warrants further investigation. / Thesis (Ph.D.)--Department of Agronomy, 1990.

Bibliography: leaves 132-159. Boron efficiency in oilseed rape (Brassica napua L. and B. juncea L.) was investigated in a wide range of genotypes. Using a solution culture screening of 10 day old seedlings, root length best described shoot growth response, and was used to characterise a total of 65 genotypes. Varieties and breeders lines tolerant of B-deficient growing conditions were identified, and the screening process validated through field trials. B responses in plants sampled at the 'green bud' stage indicated that vegetative growth is important in B efficiency. Studies were conducted to investigate the mechanism of B efficiency in oilseed rape. Results suggest no association between B efficiency and the capacity to acidify the root rhizosphere, or an increased translocation of B from root to shoot. Boron retranslocation was also studied as a mechanism of B efficiency.

This thesis undertakes the development, characterization and optimization of boron diffusion for silicon solar cells. Heavy diffusions (sheet resistance < 40 Ohm/square) to form a back surface field, and light diffusions (sheet resistance > 100 Ohm/square) to form oxide-passivated emitters were developed. Test structures and solar cells were fabricated to assess uniformity, lifetime and recombination effects due to the light and heavy boron diffusions. It was found that the growth of a thin ~200 ??, thermal oxide, during stabilization ??? immediately prior to the boron diffusion - was required to maintain high lifetime and reduce surface recombination (reducing the emitter saturation current density) for all boron diffusions. The heavy boron diffusion process was incorporated into the single side buried contact solar cell processing sequence. The solar cells fabricated had both boron diffused and Al/Si alloyed P+ regions for comparison. This research conclusively showed that boron diffused solar cells had significantly higher open circuit voltage compared to Al/Si alloyed devices. Fabrication of n-type solar cells, and their subsequent characterization by overlayed secondary electron image and the electron beam induced current map showed that the Al/Si alloy varied in depth from 5 to 25 micrometers deep. Methodology and characterization for light, oxide-passivated boron diffusions are also presented. This study yielded boron diffused emitters (sheet resistance > 100 Ohm/square) with low emitter saturation current. It was observed that this was possible only when the thermal oxidation after the boron diffusion was minimal, less than 1,000 ??. This was due to the segregation effect of boron with oxide, decreasing the surface concentration that in turn decreased the electric field repulsion of electrons from the surface. Device modelling of n-type solar cells is presented where the parameters of the modelling include the results of the light, oxide-passivated boron diffusions. This modelling shows n-type-base material with light oxide-passivated boron diffusion has higher potential conversion efficiency than forming a solar cell from phosphorous diffused p-type material.

Bibliography: leaves 132-159. / xv, 159 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Boron efficiency in oilseed rape (Brassica napua L. and B. juncea L.) was investigated in a wide range of genotypes. Using a solution culture screening of 10 day old seedlings, root length best described shoot growth response, and was used to characterise a total of 65 genotypes. Varieties and breeders lines tolerant of B-deficient growing conditions were identified, and the screening process validated through field trials. B responses in plants sampled at the 'green bud' stage indicated that vegetative growth is important in B efficiency. Studies were conducted to investigate the mechanism of B efficiency in oilseed rape. Results suggest no association between B efficiency and the capacity to acidify the root rhizosphere, or an increased translocation of B from root to shoot. Boron retranslocation was also studied as a mechanism of B efficiency. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1999?

Bibliography: leaves 132-159. / xv, 159 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Boron efficiency in oilseed rape (Brassica napua L. and B. juncea L.) was investigated in a wide range of genotypes. Using a solution culture screening of 10 day old seedlings, root length best described shoot growth response, and was used to characterise a total of 65 genotypes. Varieties and breeders lines tolerant of B-deficient growing conditions were identified, and the screening process validated through field trials. B responses in plants sampled at the 'green bud' stage indicated that vegetative growth is important in B efficiency. Studies were conducted to investigate the mechanism of B efficiency in oilseed rape. Results suggest no association between B efficiency and the capacity to acidify the root rhizosphere, or an increased translocation of B from root to shoot. Boron retranslocation was also studied as a mechanism of B efficiency. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1999?