Seed loss in canola (Brassica napus, Brassica rapa and Brassica juncea) leads to considerable loss of revenue and dispersal of canola seeds into the soil seedbank. Once canola seeds enter the soil seedbank a portion can become secondarily dormant and persist for many years creating volunteer weed problems in following crops. Reducing canola seed loss and seedbank persistence can be an important strategy to reduce the incidence of volunteer weeds. The primary hypothesis of this research was that canola seedbank addition and dormancy induction in the seed are affected by genotype and harvest method. To test this hypothesis, three studies were conducted with the following objectives: i) to determine canola seedbank addition from windrowing and direct-harvesting operations on commercial farms in western Canada, ii) to determine agronomic- and harvest-related factors that may increase seed loss in canola, iii) to determine the effect of stage of crop maturity at harvest on potential to develop seed dormancy in canola, iv) to evaluate canola genotypes and harvest methods to reduce canola seedbank addition. A total of 66 canola fields were surveyed across Saskatchewan in 2010 and 2011. Shattered seeds from these fields were sampled within 3 weeks of harvest by using a vacuum cleaner. Agronomic- and harvest-related data were collected for each field using questionnaires. In a separate small plot study the effects of harvest methods (windrowing and direct-harvesting) and pod sealant products (Pod-Stik® and Pod Ceal DC®) on seed loss in five canola genotypes (InVigor5440, RR45H26, InVigor5020, RR4362, and CL8571) were evaluated in 2010 and 2011. In both years, 6 harvest samples were collected weekly from InVigor5440 and InVigor5020 genotypes starting at early stage of crop maturity until harvest to assess the effect of seed maturity on dormancy induction. On commercial farms, the average seedbank addition was 5,821 viable seeds m-2, which was equivalent to 7.3% of the total seed yield. There was no difference in the reported yield and seedbank addition between windrowed and direct-harvested canola on commercial farms. But in the small plot study, windrowing resulted in higher seedbank addition. Higher seedbank addition was observed when the yield of canola was higher and when producers had a larger area seeded to canola. The observed seedbank addition was also higher in Roundup Ready genotypes and when a conventional combine harvester was used to harvest canola. Little primary dormancy and low potential to secondary dormancy induction was observed in InVigor5440 and InVigor5020 seeds at an early stage of crop maturity. But at full maturity seeds of both genotypes had no primary dormancy but showed high potential for secondary dormancy induction. This indicates that windrowing the evaluated genotypes at early stage of crop maturity lowered the potential for secondary dormancy induction. There were appreciable differences in seedbank addition among the evaluated canola genotypes but pod sealant products did not affect seed yield and seed shatter in canola. The results of this study suggest that canola seedbank addition can be minimized by growing genotypes having reduced seed loss and with the adoption of direct-harvesting operations.

Activated cyclopropanes have been extensively used in synthetic chemistry as precursors for cycloaddition reactions. The rationale behind this is their ability to undergo ring-opening when activated by a Lewis acid, this can be enhanced further by the presence of a carbocation stabilising group like electron-rich aromatics. The stabilised dipole formed after ring opening can be trapped with suitable electrophiles such as imines and aldehydes via a [3+2] cycloaddition reaction. This results in the synthesis of pyrrolidines and tetrahydrofurans in excellent yields but moderate diastereoselectivity. Similarly, 6-membered heterocycles can be formed via a [3+3] cycloaddition reaction of activated cyclopropanes with nitrones. Now to extend the scope of the methodology, a [3+3] dipolar cycloaddition has been developed using activated 2,3 disubstituted cyclopropane diesters to access a range of highly functionalised oxazines in moderate to good yields (50-75%) and with reasonable diastereoselectivity. The use of activated symmetrical disubstituted cyclopropanes afforded the desired oxazines in a regio- and diastereocontrolled manner, while the use of unsymmetrical cyclopropanes significantly reduced the diastereoselectivity of the reaction. The stereochemistry outcome of the reaction developed was determined by nOe analyses and X-ray diffraction structures could be recorded in some examples. A new methodology has also been developed to gain access to novel N-heterocyclic- and phenol- substituted cyclopropanes in one step from the corresponding cyclopropene via a conjugated addition.

A variety of optically active macrocyclic crown ethers that serve as "host" systems that are capable of differentiating between enantiomeric "guest" molecules during host-guest complexation have been prepared via incorporation of chiral elements into the crown ring skeleton. The ability of these crown ethers to recognize the enantiomers of guest salts, i.e., (+) a-methyl benzylamine and to transport them enantioselectively in W-tube transport experiments were studied. The ability of these crown ethers to perform as chiral catalysts in an enantioselective Michael addition was studied. The extent of asymmetric induction, expressed in terms of the enantiomeric excess (%ee), was monitored by measuring the optical rotation of the product and comparing to the literature value.

Målet med arbetet är att få förståelse för hur elever och lärare resonerar om och arbetar med problemlösning inom addition och subtraktion med hjälp av laborativa material. Undersökningen genomfördes i två stycken klasser i årskurs 3 med 43 elever och 3 lärare. Genom intervju och observation klargörs aspekter kring inom problemlösning inom ovan nämnda matematiska område. Resultaten i studien har analyserats utifrån begrepp inom variationsteorin. Utifrån insamlad empiri har vi kunnat dra slutsatsen att förkunskaper, varierad undervisning, reflektion samt kommunikation mellan lärare och elever är viktigt att vidta inom matematikundervisningen för ett utvecklat lärande.

Syftet med studien var att analysera matematikappar gällande addition och talområdet 0-20. Studiens frågeställningar besvarades utifrån Bernsteins teori. Centrala begrepp för teorin är klassifikation och inramning och de här verkade som analysverktyg. Studien syftade även till att se vilka kopplingar till Lgr11 som apparna kunde göra och vad det fanns för valmöjligheter i apparna. De delar som undersöktes utifrån Lgr11 var det centrala innehållet och syftets sammanfattning. Valmöjligheterna som undersöktes var om det fanns möjlighet till samarbete, individanpassade uppgifter, olika sorters uppgifter och om det gick att välja talområdet 0-20. Arbetet är en kvalitativ studie där analyserna genomfördes med innehållsanalyser i form av intervjufrågor till apparna. De appar som har analyserats är Nomp, King of math junior och Tiokompisar. I resultatet framkom det att alla tre appar hade någon koppling till Lgr11. Resultatet visade även på vikten av att ha ett genomtänkt syfte med appanvändandet i undervisningen. Nomp är en app som är användbar om läraren vill individanpassa uppgifter till varje elev. Appen Tiokompisar är användbar om läraren vill ha uppgifter där eleverna kan samarbeta eller spela tillsammans. King of math junior är användbar i undervisningen för den tidiga inlärningen och om läraren vill att en elev ska arbeta med ett visst talområde. Således är apparna användabara för olika saker vilket gör det betydande att läraren behöver veta vad hen vill att eleverna ska träna på för att kunna välja en passande app.

De senaste PISA-undersökningarna visar på en nedåtgående trend hos svenska elever inom matematik, läsförståelse och naturvetenskap. Syftet med litteraturstudien är att undersöka lärarens undervisning beträffande addition och subtraktion under de första skolåren. Detta ämne är viktigt att lyfta eftersom läroplanen betonar att undervisningen ska gynna elevens fortsatta lärande och kunskapsutveckling (Skolverket, 2011). Datainsamlingen skedde genom artikelsökning i databaserna ERIC och Unisearch. Resultatet visar på viken av användning av variation i undervisningsformer. Klassrumsdiskussion, vägledande frågor och arbete med laborativt material framhävs som positiva aspekter för elevens utveckling inom matematiken under de första skolåren. Resultatet visar även på en skillnad i lärarens undervisning i olika länder. I litteraturstudiens diskussion framhävs forskarnas delade meningar om vilka arbetsformer och undervisningsverktyg som medför en positiv effekt för elevernas matematiska utveckling.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Thesis advisor: Amir H. Hoveyda / Chapter 1. The development of chiral monodentate N-heterocyclic carbenes (NHCs) is presented. Structurally varied twenty-eight new chiral imidazolinim salts, NHC precursors, were synthesized and characterized. Chapter 2. The first example of Cu-catalyzed enantioselective conjugate additions of alkyl- and arylzinc reagents to unactivated cyclic enones is presented. Transformations are promoted in the presence of 2.5-15 mol % of a readily available chiral NHC-based Cu complex, affording the desired products bearing all-carbon quaternary stereogenic centers in 67-98% yield and in up to 97% ee. Catalytic enantioselective reactions can be carried out on a benchtop, with undistilled solvent and commercially available (not further purified) Cu salts. Chapter 3. A new class of enantioselective conjugate addition (ECA) reactions that involve aryl- or alkenylsilylfluoride reagents and are catalyzed by chiral non-C2-symmetric Cu-based NHC complexes are presented. Transformations have been designed based on the principle that a catalytically active chiral NHC-Cu-aryl or NHC-Cu-alkenyl complex can be accessed from reaction of a Cu-halide precursor with in situ-generated aryl- or alkenyl-tetrafluorosilicate. Reactions proceed in the presence of 1.5 equivalents of the aryl- or alkenylsilane reagents and 1.5 equivalents of tris(dimethylamino)sulfonium difluorotrimethylsilicate. Desired products are isolated in 63-97% yield and 73.5:26.5-98.5:1.5 enantiomeric ratio (47%-97% ee). Chapter 4. An efficient Cu-catalyzed protocol for enantioselective addition of a dimethylphenylsilanyl group to a wide range of cyclic and acyclic unsaturated ketones, esters, acrylonitriles and dienones is presented. Reactions are performed in the presence of 1-5 mol % of commercially available and inexpensive CuCl, a readily accessible monodentate imidazolinium salt as well as commercially available (dimethylphenylsilyl)pinacolatoboron. Cu-catalyzed 1,4- and 1,6-conjugate additions afford the enantiomerically enriched silanes in 72%-98% yield and 90:10->99:1 enantiomeric ratio (er) with up to >25:1 of Z:E selectivity. Chapter 5. A Cu-catalyzed method for enantioselective boronate conjugate additions to trisubstituted alkenes of acyclic a,b-unsaturated carboxylic esters, ketones, and thioesters is presented. All transformations are promoted by 5 mol % of a chiral monodentate NHC-Cu complex, derived from a readily available C1-symmetric imidazolinium salt, and in the presence of commercially available bis(pinacolato)diboron. Reactions are efficient (typically, 60% to >98% yield after purification) and deliver the desired boryl carbonyls in up to >98:2 enantiomer ratio (er). In addition, metal-free, nucleophilic activation of a B-B bond has been exploited in the development of a highly efficient method for conjugate additions of commercially available bis(pinacolato)diboron to cyclic or acyclic a,b-unsaturated carbonyls. Reactions are readily catalyzed by 2.5-10 mol % of a simple NHC. A variety of cyclic and acyclic unsaturated ketones and esters can serve as substrates. Transformations deliver boryl carbonyls bearing tertiary as well as quaternary B-substituted carbons in up to >98% yield. / Thesis (PhD) — Boston College, 2010. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

A research report submitted to the Faculty of Science, in partial fulfilment of the requirements for the degree of Master of Science, University of the Witwatersrand. Johannesburg, October 2016. / This research study makes an attempt at intervening in the Grade6learners’ use of models and strategies in solving addition and subtraction word problems based on Realistic Mathematics Education (RME) theory. RME theory advocates for the provision of understandable contexts that learners can relate with to support them in developing models and strategies, with specific reference to the empty number line model in assisting learners to develop an understanding of the structure of number and to work flexibly in solving addition and subtraction word problems. It is in understanding the models and strategies learners are using that we can begin to understand how the learners need to be supported in order to operate at the appropriate mathematics levels for their grade. Participants in this research study, forty boys and girls doing grade six, all with a weaker mathematical background, wrote the same tests in the form of pre test, post test and the delayed post test. After writing the pre test, the learners attended a series of six intervention lessons before writing the post tests. The intervention lessons encouraged learner engagement with word problems and the development of models as representations of problem situations and strategies which represent learner’s manipulation of models in an RME-advocated approach. Learner responses were analysed aiming at the identification of models and strategies they employed, as well as the correctness and success in solving the problems. The analysis found out that mainly there have been some improvements in the repeat sittings from predominantly using the column model with a lot of incorrect answers to using the empty number line with more correct answers. I would therefore encourage the maximum participation of teamwork amongst teachers for identifying and using efficient models and strategies in order to promote performance levels in mathematics through developing an understanding of the structure of number and working flexibly in solving addition and subtraction word problems. / LG2017