The purpose of the current dissertation is to explore the contribution of development-oriented farmer groups to the diffusion of innovations in rural communities of Kenya and Ethiopia, to identify the key factors that determine the effectiveness of diffusion, and to derive recommendations that aim at better utilizing the potential of groups for rural extension work. A profound review of four theoretical frameworks served to derive a multiple-pathway model of innovation diffusion that amalgamates major concepts of the social network and functional group theory. By accommodating multiplex social relationships and by facilitating analyses at multiple levels the model alleviates major conceptual shortcomings of previous research. The research employs a multiple case study design. Four peasant communities have been investigated that are largely comparable in respect with bio-physical conditions. The case studies aim to cover the maximum diversity with regard to the role of farmer groups in the prevailing extension approach, as well as the mode of group organization. Data collection tools comprise reconnaissance surveys, standardized household interviews (N=841), qualitative key informant and in-depth interviews, participant observation, and the review of secondary sources. Group and non-group social networks constitute the units of analysis. Inferential statistical analyses mainly used multivariate linear regression techniques. The findings illustrate that farmers, through their group and non-group networks and under group-oriented and individual extension alike, exchange information, knowledge, social pressures and other forms of influence that shape their individual adoption decisions. Yet, innovations tend to disseminate more effectively in farmer groups vis-à-vis non-group networks, and the groups tend to be more effective when addressed by extension agents. Lack of access to extension services represents a crucial limitation to innovation adoption in the study villages. Yet, increased extension intensity has proved to foster innovation diffusion only in situations of group extension, whereas intensified individual extension services do not considerably increase horizontal farmer-to-farmer knowledge exchange. The research reveals that the advantage of farmer groups can be attributed to their dimorphic character combining the bridging and bonding effects of ‘weak’ and ‘strong’ ties. By facilitating the emergence of cohesive relationships among the group members and by simultaneously enhancing the members’ exposure to external information sources group-oriented extension work considerably contributes to foster the diffusion of innovations among farmers. Intermediate absolute levels of group homogeneity best facilitate the diffusion of innovations among the group members. The findings suggest that increased group activity can overcome diffusion barriers that arise from too heterogeneous or too homogeneous configurations alike. Member commitment is the group climate dimension most consistently related to diffusion effectiveness in farmer groups. The results suggest that group-oriented extension services can alleviate obstructions of the diffusion process that result from less favorable group climate. Thus, this research work proposes that the effectiveness of innovation diffusion among farmers is under the managerial control of the extension agencies in group-oriented extension approaches through at least one of the following mechanisms: (a) promoting the emergence of cohesive member relationships, which in turn foster effective innovation spread; (b) stimulating the activity of farmer groups, which in turn compensates for less effective diffusion under unfavorable group composition; and (c) compensating for diffusion barriers that result from a less favorable group climate. Recommendations refer to the improvement of extension practice and directions for future research.

Made available in DSpace on 2014-06-11T19:26:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-01-27Bitstream added on 2014-06-13T20:47:35Z : No. of bitstreams: 1 gomes_nm_me_sjrp.pdf: 689280 bytes, checksum: e326708cb7096ea2640f86118ab525a2 (MD5) / Neste trabalho apresentamos um estudo da sequência espectral associada à uma filtração (finita) de um complexo de cadeias de módulos sobre um anel arbitrário R. Em especial, destacamos as sequências espectrais de Lyndon-Hochschild-Serre e de Cartan-Leray, e algumas aplicações na teoria de homologia. / In this work we present a study of the spectral sequence associated to the filltration (finite) of a chain complex of modules on an arbitrary ring R. In special, we emphasize the spectral sequences of Lyndon-Hochschild-Serre and Cartan-Leray and some applications in the homology theory.

Orientador: Ermínia de Lourdes Campello Fanti / Banca: Luiz Queiroz Pegher / Banca: João Peres Vieira / Resumo: Neste trabalho apresentamos um estudo da sequência espectral associada à uma filtração (finita) de um complexo de cadeias de módulos sobre um anel arbitrário R. Em especial, destacamos as sequências espectrais de Lyndon-Hochschild-Serre e de Cartan-Leray, e algumas aplicações na teoria de homologia. / Abstract: In this work we present a study of the spectral sequence associated to the filltration (finite) of a chain complex of modules on an arbitrary ring R. In special, we emphasize the spectral sequences of Lyndon-Hochschild-Serre and Cartan-Leray and some applications in the homology theory. / Mestre

The purpose of the current dissertation is to explore the contribution of development-oriented farmer groups to the diffusion of innovations in rural communities of Kenya and Ethiopia, to identify the key factors that determine the effectiveness of diffusion, and to derive recommendations that aim at better utilizing the potential of groups for rural extension work. A profound review of four theoretical frameworks served to derive a multiple-pathway model of innovation diffusion that amalgamates major concepts of the social network and functional group theory. By accommodating multiplex social relationships and by facilitating analyses at multiple levels the model alleviates major conceptual shortcomings of previous research. The research employs a multiple case study design. Four peasant communities have been investigated that are largely comparable in respect with bio-physical conditions. The case studies aim to cover the maximum diversity with regard to the role of farmer groups in the prevailing extension approach, as well as the mode of group organization. Data collection tools comprise reconnaissance surveys, standardized household interviews (N=841), qualitative key informant and in-depth interviews, participant observation, and the review of secondary sources. Group and non-group social networks constitute the units of analysis. Inferential statistical analyses mainly used multivariate linear regression techniques. The findings illustrate that farmers, through their group and non-group networks and under group-oriented and individual extension alike, exchange information, knowledge, social pressures and other forms of influence that shape their individual adoption decisions. Yet, innovations tend to disseminate more effectively in farmer groups vis-à-vis non-group networks, and the groups tend to be more effective when addressed by extension agents. Lack of access to extension services represents a crucial limitation to innovation adoption in the study villages. Yet, increased extension intensity has proved to foster innovation diffusion only in situations of group extension, whereas intensified individual extension services do not considerably increase horizontal farmer-to-farmer knowledge exchange. The research reveals that the advantage of farmer groups can be attributed to their dimorphic character combining the bridging and bonding effects of ‘weak’ and ‘strong’ ties. By facilitating the emergence of cohesive relationships among the group members and by simultaneously enhancing the members’ exposure to external information sources group-oriented extension work considerably contributes to foster the diffusion of innovations among farmers. Intermediate absolute levels of group homogeneity best facilitate the diffusion of innovations among the group members. The findings suggest that increased group activity can overcome diffusion barriers that arise from too heterogeneous or too homogeneous configurations alike. Member commitment is the group climate dimension most consistently related to diffusion effectiveness in farmer groups. The results suggest that group-oriented extension services can alleviate obstructions of the diffusion process that result from less favorable group climate. Thus, this research work proposes that the effectiveness of innovation diffusion among farmers is under the managerial control of the extension agencies in group-oriented extension approaches through at least one of the following mechanisms: (a) promoting the emergence of cohesive member relationships, which in turn foster effective innovation spread; (b) stimulating the activity of farmer groups, which in turn compensates for less effective diffusion under unfavorable group composition; and (c) compensating for diffusion barriers that result from a less favorable group climate. Recommendations refer to the improvement of extension practice and directions for future research.

Let C be the class of finite nilpotent, solvable, symmetric, simple or semi-simple groups and n be a positive integer. We discuss the following question on group laws: What is the length of the shortest non-trivial law holding for all finite groups from the class C of order less than or equal to n?:Introduction 0 Essentials from group theory 1 The two main tools 1.1 The commutator lemma 1.2 The extension lemma 2 Nilpotent and solvable groups 2.1 Definitions and basic properties 2.2 Short non-trivial words in the derived series of F_2 2.3 Short non-trivial words in the lower central series of F_2 2.4 Laws for finite nilpotent groups 2.5 Laws for finite solvable groups 3 Semi-simple groups 3.1 Definitions and basic facts 3.2 Laws for the symmetric group S_n 3.3 Laws for simple groups 3.4 Laws for finite linear groups 3.5 Returning to semi-simple groups 4 The final conclusion Index Bibliography / Sei C die Klasse der endlichen nilpotenten, auflösbaren, symmetrischen oder halbeinfachen Gruppen und n eine positive ganze Zahl. We diskutieren die folgende Frage über Gruppengesetze: Was ist die Länge des kürzesten nicht-trivialen Gesetzes, das für alle endlichen Gruppen der Klasse C gilt, welche die Ordnung höchstens n haben?:Introduction 0 Essentials from group theory 1 The two main tools 1.1 The commutator lemma 1.2 The extension lemma 2 Nilpotent and solvable groups 2.1 Definitions and basic properties 2.2 Short non-trivial words in the derived series of F_2 2.3 Short non-trivial words in the lower central series of F_2 2.4 Laws for finite nilpotent groups 2.5 Laws for finite solvable groups 3 Semi-simple groups 3.1 Definitions and basic facts 3.2 Laws for the symmetric group S_n 3.3 Laws for simple groups 3.4 Laws for finite linear groups 3.5 Returning to semi-simple groups 4 The final conclusion Index Bibliography