This thesis presents the study of films derived from the reduction of aryldiazonium salts at gold surfaces. The properties of bare polycrystalline surfaces were investigated via the observation of the electrochemical oxidation and reduction of the gold. Films derived from diazonium salts were electrochemically grafted to the gold surface. The structure and stability of these interfaces was examined through the use of redox probes, gold oxide electrochemistry and water contact angle measurements. The spontaneous reduction of aryldiazonium salts at gold surfaces was investigated and the possible applications it presented towards printing and patterning of the gold surface with films were explained. Polycrystalline gold surfaces were prepared and subjected to various treatments, to observe the behaviour of gold oxide formation and reduction at the surface. Various effects on the surface structure were observed after treatment in solvents and electrolyte solutions. The surface structure of the gold atoms frequently changed due to the high mobilities of the gold atoms, and it is difficult to achieve a reproducibly stable surface. The electrochemical modification of gold surfaces via the reduction of aryldiazonium salts was investigated. Surfaces were modified with methylphenyl and carboxyphenyl films and exposed to various treatments. Monitoring the gold oxide reduction changes enabled the surface coverage of modifier directly attached to the surface to be calculated. The films appear to be stable, loosely packed and porous. The films are flexible in nature; redox probe responses showed reversible changes after repeated sonication in solvents of differing polarities and hydrophilicities. Contact angle measurements further support the notion of films that can reorganise in response to their environment. The spontaneous reduction of aryldiazonium salts at gold surfaces was observed. Film coverage was significantly lower at the spontaneously grafted surface than for films grafted electrochemically. Gold surfaces were successfully modified via microcontact printing, and surface coverages similar to the spontaneously grafted film were achieved. Microcontact printing was also used to pattern surfaces with films derived from diazonium salts. Feature sizes down to 100 µm were successfully achieved.

Thesis (M. Ed.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 64-69).

Thesis (M. Ed.)--University of Hong Kong, 1993.

Thesis (M.Ed.)--University of Hong Kong, 1993. / Also available in print.

Thesis (M.Ed.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 64-69). Also available in print.

The present study consisted of two experiments. The purpose of Experiment 1 was to develop a questionnaire (Parent-Child Scale) that could be used to effectively measure parents’ disciplining attitudes, their feelings about their disciplining practices, and their feelings toward their children.

No description available.

Intervention for students' antisocial behaviour is a challenging issue for teachers in secondary schools. Even though Government has implemented intervention measures in secondary schools to assist teachers in interveni.ng in curbing antisocial behaviour by students, the problems of student misconduct still prevail. The purpose of this study was to investigate intervention measures employed to curb antisocial bebaviour by students in a secondary school in Lobatse Botswana. The researcher was interested in the types of intervention measures employed by teachers in the school and the effectiveness of those implemented by Government, which are the pastoral care and the guidance and counseling programmes. The researcher was interested in assessing the impact of these intervention measures in assisting teachers to curb antisocial behaviour by the students. To accomplish this aim seven teachers were purposively sampled as they were the relevant people affected by the area of study. The research was conducted in the form of a case study. It was based on the qualitative approach in research. Multi methods of collecting data, such as interviews, document analysis and observation were used in order to ensure validity and reliability. Based on the respc.nses from the empirical research, as well as personal observation, the results of the study revealed that, teachers mainly apply punitive measures to curb antisocial behaviour by students. The intervention measures of pastoral care and guidance and counseling experience challenges in implementing their interventions, teachers seem to rely more on the pastoral programme than on guidance and counseling to. assist in issues of student's problem behaviour. Teachers indicated dissatisfaction with the input by the guidance and counseling programme. They complained about the inactiveness of the guidance department in assisting them to curb students' antisocial behaviour. The research recommends that, the guidance and counseling programmes be upgraded. Teachers require in-service training on the application of intervention measures that are more positive and have a long term impact on students' behaviour. Teachers need to withdraw from implementing punitive measures like punishment, to curb students' antisocial behaviour. Intervention measures such as punishment have been seen to have a negative impact on the students as punitive measures may cause the students to become rebellious and stubborn. Positive intervention measures have a lasting impact on students' characters and behaviour. Positive interventions help to instill character traits such as responsibility and accountability in students'. So teachers need to adhere to such intervention measures when curbing students' antisocial behaviour. / Thesis (M.Ed) North-West University, Mafikeng Campus, 2012

Dans le contexte de la production d’éthanol cellulosique, la cellulose doit être hydrolysée par voie chimique ou enzymatique. Dans ce procédé d’hydrolyse, la partie cristalline de la cellulose est plus difficilement fragmentable, ce qui entraîne des coûts supplémentaires dues au temps de traitement plus élevé ou à la quantité supplémentaire de produits chimiques nécessaires. Dans l’optique de réduire les coûts de l’hydrolyse tout en recherchant une voie pour valoriser la cellulose cristalline, l’idée de fabriquer des composites polymères/cellulose est attrayante. L’objectif du présent travail a donc été de valider si la cellulose microcristalline tirée d’un processus d’hydrolyse acide pourrait mener à de nouveaux matériaux composites à valeur ajoutée. Un obstacle anticipé dans le projet a été la faible adhésion de la cellulose, hydrophile et polaire, aux polymères généralement beaucoup moins polaires. Le développement de composites performants et l’atteinte de teneurs élevés en cellulose microcristalline a donc inclus, sur le plan chimique, l’objectif de comparer divers traitements de surface de la cellulose qui permettrait de pallier aux défis anticipés. La méthodologie utilisée dans ce projet a consisté à développer et optimiser un protocole de modification chimique sur de la cellulose microcristalline commerciale à l’échelle laboratoire. Les celluloses modifiées ont été soumises à une caractérisation par analyse de l’angle de contact pour caractériser l’hydrophobicité des fibres, par spectrométrie photoélectronique X pour l’analyse de la composition chimique des fibres, par granulométrie laser pour mesurer la longueur des différentes fibres et microscopie optique pour l’observation de la longueur des fibres. Toutes les techniques ont été utilisées afin de comparer les propriétés des celluloses modifiées à celles de la cellulose de référence. La cellulose de référence et les celluloses modifiées chimiquement ont ensuite été mélangées à des concentrations de 0 à 50% avec du polyéthylène de basse densité à l’état fondu en utilisant un mélangeur interne de type Brabender®. Les composites ont été caractérisés par microscopie électronique à balayage pour analyser la morphologie de mélange sur les surfaces de rupture et l’homogénéité du mélange, par des analyses rhéologiques afin d’obtenir la viscosité en fonction du cisaillement et par des essais de traction afin de déterminer leur Module de Young, leur résistance à la traction et leur élongation à la rupture. Ces caractéristiques permettent de prévoir la performance des composites dans des applications structurales.

No description available.