This study explored mindfulness in eight self–injuring psychiatric adolescents. A concurrent triangulation mixed–method design was used. In–depth semi–structured clinical interviews and clinical records constituted the qualitative data, while quantitative data was gathered using the Five–Facet Mindfulness Questionnaire (FFMQ). Thematic analysis was used to generate themes and subthemes for both selfinjury and mindfulness. Findings regarding self–injury were in line with the literature. In terms of mindfulness, two groups emerged: one sometimes acting mindfully and the other often acting mindfully. Both similarities and differences were found between the groups. Similarities in self–injuring behaviour can be explained by their similar scores on Observe and Nonreact, while the differences can be explained by the differences in their scores on Describe, Act with Awareness and Nonjudge. Those who sometimes act mindfully tend to be more self–critical, report more severe and lethal self–injuring episodes and more often use self–injury for self–punishment. Although those who often act mindfully self–injure more often, they show more selfcompassion and report less severe injuries and less lethal methods. Future research should explore the usefulness of mindfulness–based interventions, especially teaching Nonjudge and Nonreact skills, to not only increase mindfulness, but to decrease selfinjuring behaviour. Seeing that this is an exploratory study on a small sample, the results presented here should be considered to be preliminary until replicated with a larger clinical sample. / Thesis (M.A. (Clinical Psychology))--North-West University, Potchefstroom Campus, 2011.

XAVIER, Alinson Santos. Geração de Facetas para Politopos de Conjuntos Independentes. 2011. 141 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências, Departamento de Computação, Fortaleza-CE, 2011. / Submitted by guaracy araujo (guaraa3355@gmail.com) on 2016-05-23T19:04:42Z No. of bitstreams: 1 2011_dis_asxavier.pdf: 1098827 bytes, checksum: b69a55ab904901d692a7afbf26cfbb04 (MD5) / Approved for entry into archive by guaracy araujo (guaraa3355@gmail.com) on 2016-05-23T19:10:07Z (GMT) No. of bitstreams: 1 2011_dis_asxavier.pdf: 1098827 bytes, checksum: b69a55ab904901d692a7afbf26cfbb04 (MD5) / Made available in DSpace on 2016-05-23T19:10:07Z (GMT). No. of bitstreams: 1 2011_dis_asxavier.pdf: 1098827 bytes, checksum: b69a55ab904901d692a7afbf26cfbb04 (MD5) Previous issue date: 2011 / A stable set of a graph is a set of pairwise non-adjacent vertices. The maximum stable set problem is to find a stable set of maximum cardinality in a given graph. The maximum induced k-partite subgraph problem is to find k stable sets such that their union has maximum cardinality. Besides having applications in various fields, including computer vision, molecular biology and VLSI circuit design, these problems also model other important combinatorial problems, such as set packing and vertex coloring. In the present work, we study the facial structure of the polytopes associated with both problems. First, we describe a new facet generating procedure for the stable set polytope, which unifies and subsumes several previous procedures. Besides generating many well-known facet inducing inequalities, this procedure can also generate new facet-inducing inequalities which have not been previously described. Then, we study the maximum induced k-partite polytope formulated by asymmetric representatives. We describe its simplest facets, show that some of its facets arise from vertex induced subgraphs, and identify two classes of subgraphs which generate facets of the polytope. To reach these main results, we study the affine equivalence between polyhedra, and also develop a new facet generating procedure for general polyhedra which subsumes the many versions of the lifting of variables. / Um conjunto independente de um grafo é um subconjunto de vértices que não contém nenhum par de vértices vizinhos. O problema do maior conjunto independente consiste em encontrar um conjunto independente de cardinalidade máxima. O problema do maior subgrafo induzido k-partido consiste em encontrar k conjuntos independentes cuja união tenha cardinalidade máxima. Além de possuírem aplicação em diversas áreas, como visão computacional, biologia molecular e projeto de circuitos integrados, estes problemas também modelam outros problemas de otimização combinatória, como empacotamento de conjuntos e coloração de vértices. Neste trabalho, estudamos os politopos associados aos dois problemas. Primeiro, descrevemos um novo procedimento de geração de facetas para o politopo de conjuntos independentes, que unifica e generaliza diversos procedimentos anteriores. Além de gerar várias classes de desigualdades indutoras de facetas já conhecidas, este procedimento também gera novas desigualdades que ainda não foram descritas na literatura. Em seguida, estudamos o politopo do subgrafo induzido k-partido associado à formulação por representantes de cor. Identificamos suas facetas mais simples, mostramos que facetas podem ser geradas a partir de subgrafos induzidos, e descrevemos duas classes de subgrafos que geram facetas deste politopo. Para obter os principais resultados desta dissertação, fazemos um estudo da relação de afim-isomorfismo entre poliedros, e desenvolvemos um novo procedimento de conversão de faces em facetas que generaliza as diversas versões do procedimento de levantamento de variáveis.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-08-26T15:37:10Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese NormandoJQViana_Biblioteca Central_UFPE (0).pdf certa.pdf: 2847669 bytes, checksum: 035b1ec1bda1217eaae08822bf17ca9e (MD5) / Made available in DSpace on 2016-08-26T15:37:10Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese NormandoJQViana_Biblioteca Central_UFPE (0).pdf certa.pdf: 2847669 bytes, checksum: 035b1ec1bda1217eaae08822bf17ca9e (MD5) Previous issue date: 2016-02-29 / CNPq / Vem de longa data o interesse da ciência psicológica pela busca do autoconhecimento (James, 1890/1983). Neste contexto, os estudos oriundos do campo da autoconsciência, em especial com o advento da Teoria OSA (Duval & Wicklund, 1972), uma das primeiras teorias a considerar as discrepâncias entre o self e os padrões (Duval & Silva, 2001), têm reunido esforços no intuito de superar tamanha lacuna. Neste contexto, entusiasmado pela compreensão do self, em especial em sua vertente simbólica, bem como no instanciamento dos processos autoavaliativos por este operados, tramados à identificação da natureza dos padrões de atratividade e a forma como estes têm sido fenomenologicamente consciencizados no fluxo da experiência interna dos sujeitos, o presente estudo de tese objetiva identificar o que são os padrões de autoatratividade, qual sua dinâmica representacional no seio da experiência interna e o enlaçamento no processo autoavaliativo dos processos de atratividade autopercebida, autofocalização (autoconsciência situacional e disposicional), autoestima, bem estar (satisfação com a vida e felicidade), humor depressivo e religiosidade. Para o estudo em questão, foi recrutada uma amostra mista composta por 657 participantes (563 brasileiros e 94 portugueses), adolescentes, jovens, adultos e idosos, de ambos os sexos e orientações sexuais homossexual e heterossexual, residentes na Região Metropolitana do Recife e na cidade de Lisboa, Portugal. Os procedimentos relativos à coleta ocorreram em três etapas: a primeira com objetivo de levantar emicamente, por intermédio de procedimentos multimétodos, o campo semântico de autoatratividade (Estudo 1 – Qualitativo); a segunda, com base nos achados da etapa anterior, corresponde ao processo de elaboração e validação da Escala de Autoatratividade - EAA junto à pesquisa desta com o conjunto de instrumentos utilizados (Escala de Apreciação Corporal (EAC); Escala de Autoconsciência Situacional (EAS); Escala de Autoconsciência Disposicional (EAD); Escala de Autoestima de Rosenberg; Escala de Satisfação com a Vida; Escala de Felicidade Subjetiva; Escala CES-D (Rastreamento de depressão); Escala de Religiosidade Global (ERG) e Escala de religiosidade de item único, bem como o roteiro de entrevista Fenomenológico-Cognitiva dos Estados Autoconscientes – EFEA), a fim de permitir a identificação da multidimensionalidade da maquinaria psíquica atrelada ao construto atratividade dentre a amostra recrutada (Estudo 2 – Ex-post-facto) e a terceira etapa refere-se ao aprofundamento dos achados da etapa que a antecede, por intermédio da apresentação do gradiente fenomenal dos padrões de atratividade com base na identificação dos modos como estes são representados no fluxo da experiência dos participantes durante estado autoconsciente relacionado a autoatratividade (Estudo 3 – Fenomenal). A hipótese geral que dá sustentação ao estudo em questão considera que quanto mais autoconscientes e de modo reflexivo as pessoas são maior seria a capacidade que estas têm de minorar as influências que os padrões de atratividade exercem sobre os processos autoavaliativos, ocasionando prejuízos ao funcionamento psicológico saudável, além de que, os padrões, caso emerjam à consciência, no seio da experiência interna, se realizarão cognitivamente em elementos variados de natureza representacional, em especial na forma da fala interna e visualização interna. De modo específico, dentre o conjunto de hipóteses que dá sustenção ao referido estudo, destaca-se aquela que chama atenção ao papel moderador da religiosidade no possível impacto deletério que os padrões de atratividade ocasionam à vida das pessoas, haja vista, a importância e centralidade de tal dimensão para subjetividade humana. O modelo de análise de dados adotado no presente estudo de tese prezou, no tocante ao material quantitativo, pela investigação da dimensionalidade das escalas por via da metodologia das facetas (Guttman, 1968), com base nas Análises Multidimensionais não-métricas do tipo SSA (Similarity Structure Analysis, ver Guttman, 1968; Roazzi, 1995). Por sua vez, o material qualitativo foi submetido à análise de conteúdo (Estudo 1, Bardin, 1970) e a metodologia fenomenológica padrão (Estudo 2, Cott & Rock, 2008). Os principais achados do presente estudo de tese apontam que os padrões de autoatratividade e sua fenomenologia são representados cognitivamente na consciência por intermédio dos elementos da fala interna e das visualizações internas, associadas aos elementos do sentimento, bem como a consciência sensória. Não se encontrou, todavia, ocorrência de pensamento não simbolizado na análise fenomenal operada. A estrutura de tal padrão se organiza a partir de duas dimensões, uma física e outra não física, representadas pelos fatores: sensualidade, moralidade, apresentação pessoal, afetividade, inteligência, bom humor e asseio. Tais fatores quando correlacionados entre si, e junto as demais medidas utilizadas, apontam a presença de correlações estatisticamente significantes, em especial, no tocante às variáveis: Orientação sexual, no âmbito geral, os heterossexuais encontram-se mais próximos de um campo de afeto positivo, e os homossexuais nas cercanias do afeto negativo; Idade, os mais jovens, também situados num campo do afeto negativo, passando por um campo intermediário, onde há a presença de jovens adultos, findando com os participantes com idades entre 36 e 76 anos, cravados num campo de afeto positivo; Religiosidade, igualmente caracterizada por uma disposição polar, nas cercanias desta variável, os que se dizem religiosos, os heterossexuais e os adultos e idosos, e distanciando-se da religiosidade, localizados em plano antagônico, os que relatam não professar nenhuma fé, os adolescentes de 14 a 20 anos e os jovens homossexuais; e Nacionalidade, os portugueses mais próximos de um padrão de atratividade com base em princípios morais e os brasileiros simpáticos às variáveis sociodemográficas de natureza religiosa, inferindo que estas exercem influência sobre o instanciamento dos processos autofocalizadores, correlações estas cujos significados são corroborados pelos achados oriundos do estudo fenomenal. Tal estudo representa um esforço em dar visibilidade a uma temática pouco investigada na ciência psicológica, a natureza dos padrões de correção e o impacto destes nos processos autofocalizadores, em diálogo com uma perspectiva de mente dual, que contempla aspectos psicológicos e fenomenais da subjetividade e cognição humanas, a fim de contribuir com uma compreensão mais profunda sobre os aspectos cognitivos cruciais relacionados ao instanciamento de modos mais adaptados e, consequentemente, menos comprometedores da existência significativa e feliz. / The interest of the psychological science in the search for self-knowledge has come a long way (James, 1890/1983). In this context, studies from the self-awareness field, especially with the advent of the OSA Theory (Duval & Wicklund, 1972), one of the first to consider the discrepancies between the self and the patterns (Duval & Silva, 2001), have gathered efforts in order to overcome such gap. Within this framework, keen on understanding the self, especially in its symbolic aspect as well as in the instantiation of the self-assessment processes it operates, hatched in the identification of the nature of attractiveness patterns and how they have phenomenologically been made aware in the flow of the subjects‟ inner experience, this study aims to identify self-attractiveness patterns, their representational dynamics within the inner experience and the intertwining of the self-perceived attractiveness processes, of self-focusing (situational and dispositional self-awareness), self-esteem and well-being (life satisfaction and happiness), depressive mood and religiosity in the self-assessment process. For this study, a mixed sample of 657 participants (563 Brazilian and 94 Portuguese) was recruited, among whom were teenagers, adults and elderly people of both sexes, as well as homo and heterosexual orientations, living in the metropolitan area of Recife and in Lisbon, Portugal. The collecting-related procedures were carried out in three steps: the first one, to emically raise, through multimethod procedures, the semantic field of self-attractiveness (Study 1 - Qualitative); the second, based on the findings from the previous step, corresponds to the process of development and validation of the Self-attractiveness Scale – SAS, along with its survey with the set of instruments used (Body Assessment Scale - BAS); Situational Self-Awareness Scale (SSAE); Dispositional Self-Awareness Scale (DSAS); Rosenberg Self-Esteem Scale; Life Satisfaction Scale; Subjective Happiness Scale; CES-D Scale (Depression Tracking); Global Religiosity Scale (GRS) and Single-item Religiosity Scale, as well as the Self-Aware States Phenomenological-Cognitive interview script – SASPG), to enable the identification of the multidimensionality of the psychic machinery linked to the attractiveness construct within the recruited sample (Study 2 - Ex-post-facto). The third stage refers to deepening the findings of the previous one through the presentation of the phenomenal gradient of attractiveness patterns based on the identification of the ways they are represented in the flow of the participants‟ experience during the self-aware state related to self-attractiveness (Study 3 - Phenomenal). The general hypothesis that supports the present study considers that the more self-aware and reflective people are, the greater the capacity they have to reduce the influence attractiveness patterns have on self-assessment processes, which bring harm to healthy psychological functioning. Moreover, those patterns, should they emerge to awareness within the inner experience, will cognitively take place in a range of elements of representational nature, especially in the form of inner speech and inner visualization. In particular, among the set of assumptions that support this study, there is one that draws attention to the moderating role of religiosity in the possible deleterious impact attractiveness patterns cause to people's lives, given the importance and centrality of such dimension to human subjectivity. With regard to the quantitative material, the data analysis model adopted in this thesis study valued the investigation of the scale dimensionality by means of the facet methodology (Guttman, 1968), based on the non-metric SSA (Similarity Structure Analysis, see Guttman, 1968; Roazzi, 1995) type Multidimensional Analysis. In turn, the qualitative material was submitted to content analysis (Study 1, Bardin, 1970) and to the pattern phenomenological methodology (Study 2, Cott & Rock, 2008). The main findings of the present study indicate the self-attractiveness patterns and their phenomenology to be represented cognitively in the awareness by means of the inner speech and inner visualization elements, associated with both feelings and sensory awareness. There was no occurrence of non-symbolized thought in the carried out phenomenal analysis, though. The structure of such a pattern is set considering two dimensions, physical and non-physical, represented by the following factors: sensuality, morality, personal presentation, affection, intelligence, good humor and neatness. Such factors, when correlated and with the use of other measures, suggest the presence of statistically significant correlations, especially regarding the variables: Sexual orientation, in general, heterosexuals are closer to a positive affection ground, while homosexuals, around negative affection; Age, the youngest also being in a negative affection ground, passing to a middle ground where young adults are present, ending with between 36 and 76 year-old participants, nailed to a positive affection ground; Religiosity, also characterized by a polar layout around this variable, those who claim to be religious, the heterosexual, the adults and the elderly, as opposed to those distant from religiosity, located in an antagonistic plan, who report not to profess any faith, 14 to 20 year-old adolescents and young homosexuals; and Nationality, with the Portuguese closer to an attractiveness pattern based on moral principles, whilst the Brazilians sympathize with the sociodemographic variables of a religious nature, inferring that they influence the instancing of self-focusing processes, correlations whose meanings are corroborated by findings of the phenomenal study. This study represents an effort to give visibility to a little investigated topic in the psychological science, the nature of correction patterns and their impact on the self-focusing processes, dialoguing with a dual mind perspective, which includes psychological and phenomenal aspects of human subjectivity and cognition in order to contribute to a deeper understanding of the crucial cognitive aspects related to the instancing of more adapted and consequently less compromising forms of a meaningful and happy existence.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Um conjunto independente de um grafo à um subconjunto de vÃrtices que nÃo contÃm nenhum par de vÃrtices vizinhos. O problema do maior conjunto independente consiste em encontrar um conjunto independente de cardinalidade mÃxima. O problema do maior subgrafo induzido k-partido consiste em encontrar k conjuntos independentes cuja uniÃo tenha cardinalidade mÃxima. AlÃm de possuÃrem aplicaÃÃo em diversas Ãreas, como visÃo computacional, biologia molecular e projeto de circuitos integrados, estes problemas tambÃm modelam outros problemas de otimizaÃÃo combinatÃria, como empacotamento de conjuntos e coloraÃÃo de vÃrtices. Neste trabalho, estudamos os politopos associados aos dois problemas. Primeiro, descrevemos um novo procedimento de geraÃÃo de facetas para o politopo de conjuntos independentes, que unifica e generaliza diversos procedimentos anteriores. AlÃm de gerar vÃrias classes de desigualdades indutoras de facetas jà conhecidas, este procedimento tambÃm gera novas desigualdades que ainda nÃo foram descritas na literatura. Em seguida, estudamos o politopo do subgrafo induzido k-partido associado à formulaÃÃo por representantes de cor. Identificamos suas facetas mais simples, mostramos que facetas podem ser geradas a partir de subgrafos induzidos, e descrevemos duas classes de subgrafos que geram facetas deste politopo. Para obter os principais resultados desta dissertaÃÃo, fazemos um estudo da relaÃÃo de afim-isomorfismo entre poliedros, e desenvolvemos um novo procedimento de conversÃo de faces em facetas que generaliza as diversas versÃes do procedimento de levantamento de variÃveis. / A stable set of a graph is a set of pairwise non-adjacent vertices. The maximum stable set problem is to find a stable set of maximum cardinality in a given graph. The maximum induced k-partite subgraph problem is to find k stable sets such that their union has maximum cardinality. Besides having applications in various fields, including computer vision, molecular biology and VLSI circuit design, these problems also model other important combinatorial problems, such as set packing and vertex coloring. In the present work, we study the facial structure of the polytopes associated with both problems. First, we describe a new facet generating procedure for the stable set polytope, which unifies and subsumes several previous procedures. Besides generating many well-known facet inducing inequalities, this procedure can also generate new facet-inducing inequalities which have not been previously described. Then, we study the maximum induced k-partite polytope formulated by asymmetric representatives. We describe its simplest facets, show that some of its facets arise from vertex induced subgraphs, and identify two classes of subgraphs which generate facets of the polytope. To reach these main results, we study the affine equivalence between polyhedra, and also develop a new facet generating procedure for general polyhedra which subsumes the many versions of the lifting of variables.

No description available.

Syftet med denna studie var att undersöka de individuella skillnaderna i hur personlighet påverkar identitetsutvecklingen. ”Honesty-humility (H), Emotionality (E), Extraversion (X), Agreeableness versus Anger (A), Conscientiousness (C) och Openess to Experience (O)” förkortas till HEXACO och används för att definiera personlighet. ”Dimensions of Identity Development Scale” förkortas till DIDS och används för att definiera identitetsutveckling. Studien har samlat data genom fysiska enkäter från 261 svenska högskolestudenter i åldrarna 19-45. Enkäten bestod av färdigställda empiriska instrument för personlighet och identitetsutveckling. Personlighetsdomänerna som testades var ärlighet-ödmjukhet, extraversion, känslosamhet, målmedvetenhet, välvillighet och öppenhet. Identitetsfacetterna som testades var åtagande, identifiering med ställningstagande, utforskande på bredden, utforskande på djupet och grubblande utforskande. Studiens frågeställningar var hur HEXACO påverkar DIDS och hur denna studies resultat kommer att skilja sig från den tidigare forskningens resultat. Resultatet visade exempelvis att hög grad av ärlighet-ödmjukhet påverkar utforskandet negativt, vilket indikerar att personer som tenderar att undvika att manipulera andra och är ointresserade av lyx i mindre grad är utforskande i sin identitetsutveckling. I jämförelsen med den tidigare forskningen har denna studies resultat funnit alternativa personlighets påverkan på identitetsutvecklingen som tidigare forskning inte uppvisar. Exempelvis att hög grad av målmedvetenhet påverkar grubblande utforskande negativt, vilket indikerar att målmedvetna personer har en bra grund för en reflekterade självuppmärksamhet i sitt utforskande av identitetsutveckling. / The purpose of this study was to analyze how individual differences in personality affects identity development. Honesty-humility (H), Emotionality (E), Extraversion (X), Agreeableness versus Anger (A), Conscientiousness (C) och Openess to Experience (O) is short for HEXACO, and it is used to define personality. Dimension of Identity Development Scale is short for DIDS, and it is used to define identity development. This study has gathered data by collecting questionnaires from 261 Swedish college students in the ages of 19-45. The questionnaire that was used consisted of established definitions for personality and identity development. The personality domains that were analyzed were Honesty-humility, Emotionality, Extraversion, Agreeableness versus Anger, Conscientiousness, and Openess to Experience. The identity facets that was analyzed were Commitment making, Exploration in breadth, Ruminative exploration, Identification with commitment, and Exploration in depth. The questions posed by this study were how HEXACO will affect DIDS, and how the results will compare to previous research. The results showed, for example, that high a degree of Honesty-humility affects exploration negatively. This indicates that people who tend to avoid manipulating others and is not interested in luxuries is less explorative in his or her identity development. In comparing with results with previous research, this study has found new ways in which personality can affect identity development. One example is that a high degree of Conscientiousness affects Ruminative exploration negatively, which indicates that Conscientious people have a good basis for a reflective self to emerge in his or her identity development exploration.

No description available.

No description available.

This study focused on multilingualism as the primary linguistic cognitive objective of investigation. An integrative approach focused on second language linguistics in order to acquire a background in the cognitive foundations of language and research methodology and theoretical models for the study of phenomena, such as language planning in multicultural societies and language and ethnic diversity. To design cognitive reading methods, a literature survey was conducted regarding the latest developments in the theories pertaining to cognitive formulas of the second language learner. A quantitative experimental study was conducted, data gathered was scrutinised and a cognitive reading programme was experimentally administered to twenty primary school learners. The responses were coded, the data captured and statistically computed. Conclusions indicated that cognitive reading materials were practical, valid and reliable. Cognitive formulas hold the potential of contributing to the understanding of cognitive reading development in second language proficiency in the Foundation Phase of schooling. / Teacher Education / M. Ed. (Didactics)

Thema dieser Arbeit ist die Synthese von GaAs Nanodrähten mittels Molekularstrahlepitaxie. Dabei wird das Wachstum mittels Au- und jenes mittels selbst-induziertem VLS-Mechanismus verglichen. Die Au-induzierte Methode ist als vielseitiger Ansatz für die Herstellung von Nanodrähten bekannt. Darüberhinaus wird seit Neuerem der selbst-induzierte Mechanismus untersucht, bei dem Galliumtropfen die Rolle des Goldes übernehmen, um eine etwaige Verunreinigung mit Au von vornherein auszuschliessen. Mit beiden Wachstumsmethoden erzielen wir GaAs Nanodrähte mit großem Aspektverhältnis und epitaktischer Beziehung zum Si(111) Substrat. Während des Au-induzierten Wachstums entsteht eine parasitäre Schicht zwischen den Drähten, die mittels des selbst-induzierten Mechanismus vermieden werden. Alle GaAs Drähte sind vollständig relaxiert. Die durch die Gitterfehlanpassung (4,1\% zwischen GaAs und Si) verursachte Verspannung wird durch Versetzungen an der Grenzfläche abgebaut. Selbst-induzierte Drähten zeigen ausschließlich unpolare Seitenfacetten, während verschiedene polare Facetten für Au-induzierte Nanodrähte beschrieben werden. Mittels VLS-Nukleationstheorie könnne wir den Einfluss des Tropfenmaterials auf die Stabilität der verschiedenen Seitenfacetten erklären. Optoelektronische Anwendungen benötigen lange Minoritätsladungsträgerlebensdauern bei Raumtemperatur. Daher wurden mit (Al,Ga)As Hüllen ummantelte GaAs Nanodrähte mittels zeitaufgelöster PL vermessen. Das Ergebnis sind 2,5 ns für die selbst-induzierten aber nur 9 ps für die Au-induzierten Nanodrähte. Durch temperaturabhängige PL Messungen kann eine charakteristische Aktivierungsenergie von 77 meV nachgewiesen werden, die nur in den Au-induzierten Nanodrähten vorliegt. Dies suggeriert, dass sich Au aus den Tröpfchen in die GaAs Nanodrähte einbaut und dort als tiefes, nichtstrahlendes Rekombinationszentrum fungiert. / In this work the synthesis of GaAs nanowires by molecular beam epitaxy (MBE) using the vapour-liquid-solid (VLS) mechanism is investigated. A comparison between Au- and self-assisted VLS growth is at the centre of this thesis. While the Au-assisted method is established as a versatile tool for nanowire growth, the recently developed self-assisted variation results from the exchange of Au by Ga droplets and thus eliminates any possibility of Au incorporation. By both methods, we achieve nanowires with epitaxial alignment to the Si(111) substrates. Caused by differences during nanowire nucleation, a parasitic planar layer grows between the nanowires by the Au-assisted method, but can be avoided by the self-assisted method. Au-assisted nanowires grow predominantly in the metastable wurtzite crystal structure, while their self-assisted counterparts have the zincblende structure. All GaAs nanowires are fully relaxed and the strain arising from the lattice mismatch between GaAs and Si of 4.1\% is accommodated by misfit dislocations at the interface. Self-assisted GaAs nanowires are generally found to have vertical and non-polar side facets, while tilted and polar nanofacets were described for Au-assisted GaAs nanowires. We employ VLS nucleation theory to understand the effect of the droplet material on the lateral facets. Optoelectronic applications require long minority carrier lifetimes at room temperature. We fabricate GaAs/(Al,Ga)As core-shell nanowires and analyse them by transient photoluminescence (PL) spectroscopy. The results are 2.5 ns for the self-assisted nanowires as well as 9 ps for the Au-assisted nanowires. By temperature-dependent PL measurements we find a characteristic activation energy of 77 meV that is present only in the Au-assisted nanowires. We conclude that most likely Au is incorporated from the droplets into the GaAs nanowires and acts as a deep, non-radiative recombination centre.