No description available.

Call number: LD2668 .T4 1956 G46 / Master of Science

Call number: LD2668 .T4 1961 V39

This diploma thesis deals with creation of reduction core problem mainly in fired roofing tiles. With those is the emphasis on the impermeability and frost resistance. Black reduction core is reducing frost resistance but depends on firing temperature. At 1060 °C the reduction in frost resistance is not as unfavorable as at 900 °C. This thesis includes overview of research conducted on reduction core topic. There is enough literature focusing on frost resistance, experimental part is focused mainly on the impact of reduction core on impermeability and compares two types of production mixtures used in Czech Republic (calcium-containing type from Hranice and non-calcium type from Stod). It includes comparison of mixtures with fluidized fly ash and dust from grinding masonry elements. It opens discussion if those mixtures can be used for reduction core elimination.

No description available.

No description available.

Frost can be detrimental to canola (Brassica napus L.) production. Depending on the severity, the entire field can be killed. Having frost tolerance in canola would benefit growers by allowing them to plant early, utilize early season moisture, and avoid high heat during flowering. However, frost tolerance in canola has not been well studied. A protocol was developed that determined 14 day old seedlings should be acclimated at 4°C for 7 days before being exposed to overnight frost (-4°C) in a small freezing chamber. However, when a larger chamber was used for freezing, the protocol was optimized to -8°C instead. A greenhouse study was conducted on a diverse collection of 231 genotypes and genome-wide association scan (GWAS) was conducted to identify potential genes that were related to frost tolerance or abiotic stress tolerance. Thirty-eight significant single nucleotide polymorphism (SNP) markers were selected based on 10,000 bootstraps and 0.1 percent tail of the empirical distribution. The markers were located on chromosomes A01, A02, A03, A04, A07, A08, A09, A10, C03, C05, C06, C07, and C09. Stepwise regression highlighted a QTL located on chromosomes A02. Another GWAS was done on 147 canola germplasm lines phenotyped under natural conditions. Thirty-eight significant SNPs identified from this study were located on chromosomes A05, A07, A09, C01, C02, C03, C04, C05, C06, C07, and C09. Stepwise regression identified a QTL located on chromosome C04. A protocol was developed to measure the freezing induced electrolyte leakage from leaves of rapeseed/canola. A total of 157 germplasm lines were evaluated for freezing induced (-12°C for 2 h) electrolyte leakage. Thirty-six significant SNPs located on chromosomes A01, A02, A03, A04, A05, A06, A07, A08, A09, A10, C01, C02, C04, C05, C06, C07, and C09 were identified. Stepwise regression identified 10 QTL located on chromosomes A01, A02, A04, A06, A07, C02, C05, C07, C09, and one that could not be assigned. All GWAS studies identified potential genes of interest that were related to frost tolerance, abiotic stress, and transcription factors. / Northern Canola Growers Association

Graduation date: 1991

Graduation date: 1992

Cold-acclimation-specific (CAS) gene expression was examined by screening a cDNA library prepared from poly(A)$ sp+$ RNA of cold-acclimated seedlings of a freezing-tolerant variety of alfalfa (Medicago falcata cv Anik). Three distinct CAS cDNA clones, pSM784, pSM2201, and pSM2358 were isolated. The genes corresponding to all three clones are coordinately induced by cold. Expression of these genes is not triggered by other stress treatments such as heat shock, water stress, wounding, or treatment with exogenous ABA. A positive correlation was observed between the level of expression of each gene and the degree of freezing tolerance of four alfalfa cultivars. / A full-length cDNA clone for the most abundantly-expressed gene, cas18 was isolated and sequenced. The deduced polypeptide, CAS18, is relatively small (167 amino acids), is highly hydrophillic, rich in glycine and threonine, and contains two distinctive repeat elements. It exhibits homology with members of the LEA/RAB/Dehydrin gene family--proteins which accumulate in response to water stress or abscisic acid (ABA). The cas18 cDNA hybridizes to three transcripts of 1.6, 1.4 and 1.0 kb in cold acclimated seedlings and cell cultures. The clone described here, Acs784, corresponds to the 1.0 kb transcript. / Expression of this gene is 30-fold greater in cold-acclimated cells than in nonacclimated cells after one week of low temperature treatment. Return to room temperature (deacclimation) results in the rapid disappearance of the three transcripts within just 5 hours. Studies of nuclear "run-on" transcription and transcript stability show that low temperature regulates the expression of cas18 at both the transcriptional and post-transcriptional levels.