Cannabis use is illegal according to swedish drugpolicy. Self-reported data shows that cannabis is the most common drug used by adolescents in Sweden. Among results from previous studies several findings indicate a strong correlation between cannabis use during adolscence and failure in school, poor parental ties and criminal behaviour. This study used a school-based sample of adolescents in Stockholm. The main focus of this study was to examine if social factors linked to Hirschi's social bonding theory affect if adolescents used cannabis. Results from a logistic regression analysis partly supported Hirschi's theory. The results suggested that cigarettesmoking and alcohol intoxication are the two strongest factors which affect if adolescents use cannabis. Findings also indicated that young cannabis users tend to have friends who use illegal drugs. / Att bruka cannabis är illegalt enligt svensk narkotikapolitik. Självrapporterad data visar att cannabis är det mest vanliga narkotikaklassade preparatet som används bland ungdomar i Sverige. Av tidigare studier indikerar resultat att det finns ett samband mellan cannabisbruk i ungdomen och misslyckand i skolan, svag anknytning till föräldrar och brottsligt beteende. Denna studie använde ett skolbaserat urval av ungdomar i Stockholms stad. Huvudfokus i studien var att undersöka om faktorer, kopplade till Hirschis sociala bandteori, påverkar om ungdomar använder cannabis. Resultat från en logistisk regressionsanalys gav delvis stöd åt Hirschis teori. Resultaten indikerar att rökning av tobak och berusningsdrickande är de faktorer som mest påverkar att ungdomar använder cannabis. Resultaten indikerar också på att unga som använt cannabis tenderar att ha vänner som använder illegala narkotiska preparat.

Teaching of chemistry at secondary school level is not always carried out in the most effective way and this is often because teachers do not realise the difficulties experienced by pupils while studying a conceptually challenging topic. The development of a teaching strategy to assist teachers is thus of value. The research questions:  Do focussed intervention questions followed by rapid feedback to pupils foster sound concept formation in chemical bonding?  Is this new teaching method more effective than traditional methods? In this study I have examined the effect of a novel teaching method (referred to as the Targeted Intervention Questioning process) on concept formation during the study of chemical bonding. This study involves action research in secondary school classrooms. The findings from the study are being used to further inform current teaching practice. The teaching method is a set of focused intervention questions administered at relevant stages during the teaching of the topic. Pupils answer these questions with the help of their learning material and are given rapid feedback with an evaluation of their answers. This questioning process is designed to focus pupils’ attention on the relevant concepts and the feedback is to inform pupils of their progress in mastering the topic. The effectiveness of the method was measured using a concept development test. The learning gain in a test group was compared to that of a control group in a quasi-experimental study. This research involves action research as findings will inform practice and practice will change in line with the research findings. Data gathering to ascertain the effectiveness of the teaching method will be through quantitative methods in a quasi-experimental setup. The sample size was approximately 80 learners, divided into the four classes. All teachers use the methods and techniques that they normally use. The learning gain was determined through the use of a concept development test developed by the author (referred to as the Conceptual Test tool). This test tool contained a set of 25 conceptual questions, either requiring selection of a correct answer from a multiple choice selection or requiring a free response answer. The testing tool was piloted using a group of Grade 11 pupils in 2010. The test was then refined and used to measure the effectiveness of the intervention questioning process in 2011. A second run of the intervention process was carried out in 2012 using a slightly modified testing tool. The result of the test group was compared to that of the control group. A Correlation analysis and a Rasch analysis determined the validity of the testing tool. Results from both runs of the intervention process show that the test group has a statistically significant greater learning gain (LG) over the control group. Analysis of answers given by pupils to the intervention questions provided insight into the learning process that was happening. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Science, Mathematics and Technology Education / unrestricted

Donor–acceptor complexes have been known for over a century and enjoy a long list of applications in chemistry. In this thesis, the dative interaction between phosphorus and its two heavier congeners, arsenic and antimony, are explored. Utilising peri-substitution atoms can be forced in close proximity to one another, resulting in a repulsive (nonbonding) interaction or an attractive (bonding) interaction. Hence, peri-substitution can be used to support traditionally ephemeral species. A range of phosphorus, arsenic and antimony containing peri-substituted compounds were synthesised and characterised using multi-nuclear NMR, mass spectrometry, elemental microanalysis and single crystal X-ray diffraction. The reduction of a peri-substituted dichloroarsine, led to the formation of a primary arsine, which underwent spontaneous elimination of hydrogen gas forming the first structurally characterised cyclic arsanylidene–σ⁴–phosphorane, the formation of which is essentially thermoneutral. With no sterically demanding groups shielding the arsenic atom, the reactivity and spectroscopic characteristics of this compound were explored through reactions with selected metal complexes. Reaction of the arsanylidene–phosphorane with a limited amount of oxygen reveals arsinidene–like reactivity via the formation of cycloarsines, supporting the formulation that the bonding can be described as a Lewis base–stabilised arsinidene R₃P→AsR. A series of phosphine–stibine and phosphine–stiborane peri-substituted acenaphthenes containing all permutations of pentavalent groups –SbCl[sub]nPh[sub](4-n) as well as trivalent groups –SbCl₂, –Sb(R)Cl, and –SbPh₂ (R = Ph, Mes), were synthesised and characterised by multi-nuclear NMR, MS, microanalysis and X-ray crystallography. The bonding in these species was studied by DFT computational methods. The P–Sb dative interactions range from strongly bonding to nonbonding as the Lewis acidity of the Sb acceptor is decreased. Unexpectedly, the phosphine–stiborane complexes represent the first examples of σ⁴P→σ⁶Sb structural motif. A study of unsymmetrical bis(phosphino)acenaphthenes showed the presence of a 3c–4e interaction, supported by the short P∙∙∙P distances and the large J[sub](PP) through-space couplings. Severely strained bis(sulfides) of the unsymmetrical phosphines experience pronounced displacements of the exocyclic peri-atoms. The resulting nonbonded intramolecular P∙∙∙P distances (ca. 4.05 Å) are among the largest ever reported peri-separations, independent of the heteroatoms involved. In addition, three metal complexes with square planar, tetrahedral and octahedral geometry are reported. In all three cases, the acenaphthene backbone is distorted to a greater extent than in the free bis(phosphine) but notably less than in the bis(sulfides).

This thesis deals with the impact of hydrogen bonding on the properties of phenols. The possibility for tyrosine to form hydrogen bonds to other amino acids has been found to be important for its function as an electron transfer mediator in a number of important redox enzymes. This study has focused on modeling the function of tyrosine in Photosystem II, a crucial enzyme in the photosynthetic pathway of green plants. Hydrogen bonds between phenol and amines in both inter- and intramolecular systems have been studied with quantum chemical calculations and also in some solid-state structures involving phenol and imidazole. Different phenols linked to amines have been synthesized and their possibilities of forming intra- and intermolecular hydrogen bonds have been studied as well as the thermodynamics and kinetics of the generation of phenoxyl radicals via oxidation reactions. Since carboxylates may in principle act as hydrogen bond acceptors in a manner similar to imidazole, proton coupled electron transfer has also been studied for a few phenols intramolecularly hydrogen bonded to carboxylates with the aim to elucidate the mechanism for oxidation. Electron transfer in a new linked phenol—ruthenium(II)trisbipyridine complex was studied as well. The knowledge is important for the ultimate goal of the project, which is to transform solar energy into a fuel by an artificial mimic of the natural photosynthetic apparatus

Fluorescent proteins (FPs) are extremely valuable biochemical markers which have found a wide range of applications in cellular and molecular biology research. The monomeric variants of red fluorescent proteins (RFPs), known as mFruits, have been especially valuable for in vivo applications in mammalian cell imaging. Fluorescent proteins consist of a chromophore caged in the beta-barrel protein scaffold. The photophysical properties of an FP is determined by its chromophore structure and its interactions with the protein barrel. Application of hydrostatic pressure on FPs results in the modification of the chromophore environment which allows a systematic study of the role of the protein-chromophore interactions on photophysical properties of FPs. Using Molecular Dynamics (MD) computer simulations, I investigated the pressure induced structural changes in the monomeric variants mCherry, mStrawberry, and Citrine. The results explain the molecular basis for experimentally observed pressure responses among FP variants. It is found that the barrel flexibility, hydrogen bonding interactions and chromophore planarity of the FPs can be correlated to their contrasting photophysical properties at vaious pressures. I also investigated the oxygen diffusion pathways in mOrange and mOrange2 which exhibit marked differences in oxygen sensitivities as well as photostability. Such computational identifications of structural changes and oxygen diffusion pathways are important in guiding mutagenesis efforts to design fluorescent proteins with improved photophysical properties.

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Purpose: This thesis investigated whether perceived parental care and overprotection predicted accuracy of face emotion recognition in psychiatrically healthy youth. The study also examined whether child gender and having a parent with a history of anxiety moderated the relationship between parental bonding and facial emotion recognition, and whether behavioural inhibition mediated this relationship. Methods: The sample comprised 176 males and females aged 7-18 years. Participants completed the Parental Bonding Instrument, Childhood Self-Report of Inhibition, and the Ekman emotion recognition task. Results: Child gender and parental history of anxiety moderated the relationship between perceived parenting style and affect recognition. In boys, overprotection by father predicted deficits in recognizing fearful faces; in children with parental anxiety, low paternal care predicted deficits in recognizing angry faces; and in boys with parental anxiety, negative maternal bonding predicted deficits in recognizing expressions of surprise. Also, maternal overprotection predicted intensity of subjective anxiety while viewing expressions of surprise and happiness for all offspring, and behaviour inhibition mediated these relationships. Implications: The present study provides preliminary evidence that parental bonding interacts with risk group and gender in predicting accuracy of facial affect recognition in healthy youth. Further research is needed to confirm these findings and determine whether the interaction between gender, risk group and deficits in social cognition increase risk for developing pathological anxiety.

A computational chemistry analysis combined with a crystallographic database study of the bonding in late transition metal N-heterocyclic carbene (NHC) complexes is reported. The results illustrate a metal-carbon bond for these complexes, approximately 4% shorter than that of a M-C single bond found in metal alkyl complexes. As a consequence of this result, two hypotheses are investigated. The first hypothesis explores the possibility of multiple-bond character in the metal-carbon linkage of the NHC complex, and the second, considers the change in the hybridization of the carbenoid carbon to incorporate more p character. The latter hypothesis is supported by the results. Analysis of these complexes using the natural bond orbital method evinces NHC ligands possessing trans influence.

Density functional (ca, BLYP, BPW91, B3LYP and B3PW91), MP2 and CCSD(T) methods in combination with LANL2DZ or cc-pVxZ-PP (where x=D(double), T(triple) Q(quadruple), and 5(quintuple)) basis sets have been employed in computing electronic transition energies of zinc and cadmium monomers. CCSD(T)/aug-cc-pV5Z-PP combination finds values that are 150 cm-1 from the experimental value for the zinc monomer and 240 cm-1 remove from the cadmium monomer excitation experimental value. These method/basis set combinations are also used to find spectroscopic values (re, De, we, wexe, Be , and Te) that rival experimental values for dimers and excimers. Examples of this can be seen with the CCSD(T)/aug-cc-pV5Z-PP combination phosphorescent emission results. The values found are within 120 cm-1 of the zinc emission energy and 290 cm-1 of the cadmium emission energy. While this combination rigorously models spectroscopic constants for monomers, dimers, and excimers, it does not efficiently model these constants for larger clusters with available modern computational resources. It is important to show spectroscopic trends (bonding, phosphorescent excitation and emissions) as clusters increase as the monomer and dimer emission energies do not model solid state metallophilic interactions and phosphorescence. The MP2/LANL2DZ combinations show qualitative cooperative bonding trends in group oligomers and extended excimers as size increases and shape change. Changes in excitation and emission energies are also shown as a function of size and shape of the clusters.

Marijuana is the most prevalent illicit drug used in the world and among Turkish juveniles. Although studies have examined marijuana use among Turkish juveniles, none has tested Hirschi's social bonding theory, one of the most frequently tested and applied criminological theories in the United States and other Western and developed countries. This study investigated the empirical validity and generalizability of Hirschi's theory to juveniles' marijuana use in Turkey, a non-Western and developing country. Data on 2,740 Turkish tenth grade students from the 2006 Youth in Europe survey were used. Results from binary logistic regression analyses were generally consistent with the propositions of Hirschi's theory and the findings of previous empirical studies. Regarding the attachment component of the theory, Turkish juveniles who lived in two-parent families and those who were closely monitored by their parents were less likely to have tried marijuana. In addition, teens who were strongly attached to their school and religion were also less likely to have used the drug. As for the commitment component, language grade was negatively associated with marijuana use. None of the involvement items had significant effects on marijuana use in the predicted direction. Participation in club sports had a positive effect on marijuana use. Belief items, such as acceptance of societal norms, values, and rules, had the predicted inhibiting effects on teens' marijuana use. Of the six sociodemographic/controls included in the analyses, only gender had a significant effect; male students were more likely to have tried marijuana than the female peers. Policy implications of the results for adolescents, parents, and schools are discussed.