Made available in DSpace on 2016-01-26T12:51:31Z (GMT). No. of bitstreams: 1 marcialigoncalvesfonsecasilva_tese.pdf: 2713411 bytes, checksum: 0a80a6f7e55d27a62b6f8efd161d2ec7 (MD5) Previous issue date: 2011-12-07 / The prematurity with their comorbidities can result in a long period of mechanical ventilation in the intensive care unit. A method for the diagnostic assessment of organic maturity would be useful for this population. The heart rate variability (HRV), as an indicator of homeostasis, presents this profile. Objective: The purpose of this research was to assess the HRV in neonates intubated in the neonatal intensive care unit (ICU) of Hospital de Base before extubation. Casuistic and Method: A total of 44 neonates, 16(36.4%) males and 28(63.6%) females, in neonatal ICU at Hospital de Base (HB) of São José do Rio Preto were prospectively studied. HRV was evaluated in time, frequency and chaos by recording of electrocardiographic times series with the aid of a Polar RS800. The results obtained in this study group (RNP2) were compared with samples previously studied of preterm neonates of neonatal ICU of Curitiba (RNP1) and term neonates of HB (RNT). Results: There was no significant difference among clinical findings of neonates with and without of extubation failure. The results of 47 records of HRV revealed in time a significant difference among the groups RNT x RNP1 for mean RR intervals (MeanRR) (p < 0.0001), RMSSD (p < 0.0001), and PNN50 (p = 0.0012); SD1 e SD2 (p < 0,0001) and SD1/SD2 rate (p = 0,0448); RNT x RNP2 for MeanRR (p < 0.0001) and RMSSD (p = 0.0034); SD1 (p = 0,0036) e SD2 (p = 0,0002) among RNP1 x RNP2 for MeanRR (p = 0.0016) and SD1/SD2 rate (p = 0,0443). In the frequency, significant differences were found among RNT x RNP1 for LF ms2, HF ms2, total ms2 (p < 0.0001 in all these measurements), LF/HF ratio (p = 0.0031); RNT x RNP2 for LF ms2 (p < 0.0001), HF ms2 (p = 0.0048), total ms2 (p < 0.0001), and among RNP1 x RNP2 for LF/HF ratio (p < 0.0017). In chaos, there was significant difference among RNT x RNP1 for mean line length (Lmean), recurrence rate (RecRate), Shannon's entropy (p < 0.0001 in all these measurements), and determinism rate (DET) (p = 0.004); RNP1 x RNP2 the difference was significant for Lmean (p = 0.0188), RecRate (p = 0.029), DET (p = 0.0472), and Shannon's entropy (p = 0.0205). Conclusions: In time, frequency, and chaos, HRV was not considered as predictive value to extubation failure, but in intubated neonates this methodology present potential of clinical application. Neonates with good clinical conditions and greater development of autonomic nervous system show largest HRV, mainly in the chaos domain, indicating greater homeostatic balance similar to the pattern of term neonates. / A prematuridade com suas comorbidades pode resultar em permanência dos recém-nascidos (RN) em ventilação mecânica na UTI. Um método de avaliação diagnóstica da maturidade orgânica seria de grande utilidade para essa população. A variabilidade da frequência cardíaca (VFC) por ser um indicador da homeostase encaixa-se nesse perfil. Objetivo: O objetivo deste estudo foi avaliar a VFC em RN prematuros intubados na UTI Neonatal do Hospital de Base (HB) antes da extubação. Casuística e Método: Foram estudados prospectivamente 44 RN prematuros, sendo 16 (36,4%) do sexo masculino, internados na Unidade de Terapia Intensiva (UTI) Neonatal do HB de São José do Rio Preto. A metodologia consistiu na avaliação da VFC nos domínios do tempo, frequência e caos, utilizando-se registro das séries temporais eletrocardiográficas com auxílio do equipamento Polar RS800. Os resultados obtidos nesse grupo de estudo (RNP2) foram comparados a amostras previamente estudadas de RN prematuros da UTI Neonatal de Curitiba (RNP1) e RN de termo do HB (RNT). Resultados: Na comparação entre achados clínicos de RN com e sem falha de extubação e também com relação aos índices de variabilidade da frequência cardíaca não houve diferença significativa. Os resultados obtidos de 47 registros da VFC mostraram no domínio do tempo diferença significativa entre RNT x RNP1 para intervalos RR médios (MeanRR) (p < 0,0001), RMSSD (p < 0,0001) e PNN50 (p = 0,0012) e SD1 e SD2 (p < 0,0001) e relação SD1/SD2 (p = 0,0448); entre RNT x RNP2 para MeanRR (p < 0,0001) e RMSSD (p = 0,0034); SD1 (p = 0,0036) e SD2 (p = 0,0002) entre RNP1 x RNP2 para MeanRR (p = 0,0016) e relação SD1/SD2 (p = 0,0443). No domínio da frequência diferenças significativas foram obtidas entre RNT x RNP1 para LF ms2, HF ms2, total ms2 (p < 0,0001 em todas essas medidas), relação LF/HF (p = 0,0031) entre RNT x RNP2 para LF ms2 (p < 0,0001), HF ms2 (p = 0,0048), total ms2 (p < 0,0001), e entre RNP1 x RNP2 para relação LF/HF (p < 0,0017). No domínio do caos houve diferença significativa entre RNT x RNP1 para comprimento médio da linha diagonal (Lmean), taxa de recorrência (RecRate), entropia de Shannon, (p < 0,0001 em todas essas medidas) e taxa de determinismo (DET) (p = 0,004); entre RNP1 x RNP2 a diferença foi significativa para Lmean (p = 0,0188), RecRate (p = 0,029), DET (p = 0,0472) e entropia de Shannon (p = 0,0205). Conclusões: A VFC nos domínios do tempo, frequência e caos não se caracterizou como preditivo de falha de extubação, mas em prematuros intubados é uma metodologia com potencial de aplicação clínica e diagnóstica. Prematuros, quando estabilizados e com maior desenvolvimento do sistema nervoso autônomo, apresentam melhor VFC, principalmente no domínio do caos, mostrando maior equilíbrio homeostático se aproximando do padrão do RN de termo.

Made available in DSpace on 2016-01-26T12:51:35Z (GMT). No. of bitstreams: 1 fabioaugustoselig_dissert.pdf: 852758 bytes, checksum: 966b17099569a3dd4e20f70a9e415ad8 (MD5) Previous issue date: 2010-08-06 / The role of Autonomic Nervous System and its components sympathic and parassympathic in the regulation of the interaction between different parts of human body has been exhaustibly discussed in scientific literature. These studies demonstrated the applicability of the Chaos Theory in different situations, diseases and ages. Objective: Apply the concepts of nonlinear dynamics and Chaos Theory to evaluate premature newborns (PT), analyzing their heart rate variability (HRV) and comparing them with healthy term newborns (TN). Methods: By using a Polar Advanced S810, 59 PT born with different gestational ages had their HRV obtained and analyzed in time (SDNN, RMSSD, SD1/SD2), frequency (VLF, LF, HF and LF/HF) and chaos domain (TAU, Lyapunov Exponent, Entropy and Hurst Exponent) variables. The premature were compared to 78 healthy term newborns. The comparison were made applying Kruskal-Wallis statistic method and their graphic demonstration made by using Box-plots. Results: All time, frequency and chaos domain variables demonstrated statistic difference comparing term and preterm newborns except Hurst Exponent. Conclusion: Preterm newborn follow the rules of chaos theory and have more linear behavior when compared with term newborn. / : Vários trabalhos publicados nos últimos anos demonstram a importância do Sistema Nervoso Autônomo por meio dos componentes Simpático e Parassimpático na gerência da interação entre as diferentes partes do todo, fornecendo padrão caótico ao organismo humano. Estes estudos aplicaram a Teoria do Caos em diferentes situações, doenças e faixas etárias. Objetivo: Aplicar os conhecimentos da Teoria do Caos e da dinâmica não-linear na avaliação de recém-natos prematuros (PT), analisando sua Variabilidade da Frequência Cardíaca (VFC) e comparando-os com recém-natos de termo (RNT) saudáveis. Casuística e Método: 59 recém-natos prematuros com diferentes idades gestacionais tiveram seus batimentos cardíacos captados com auxílio do equipamento Polar Advanced S810 e sua VFC obtida pelo registro dos intervalos RR. A VFC foi analisada nos Domínios do Tempo (SDNN, RMSSD, SD1/SD2), da Frequência (VLF, LF, HF e a relação LF/HF) e do Caos (TAU e sua normalização [TAU(n]], Expoente de Lyapunov, Entropia e o expoente de Hurst). Os recém-natos prematuros foram comparados com um grupo de 78 recém-natos de termo saudáveis e sem intercorrências perinatais. O teste estatístico utilizado para comparação entre os grupos foi o teste não-paramétrico de Kruskal-Wallis com comparações múltiplas e sua demonstração gráfica feita com auxílio do gráfico tipo Box-plots. Resultados: Detectou-se diferença estatisticamente significativa entre os grupos para todas as variáveis estudadas (nos domínios do tempo, da frequência e do caos) sendo única exceção o Expoente de Hurst. Conclusão: Recém-natos prematuros obedecem às regras da Teoria do Caos e tendem a ter comportamento menos complexo, ou seja, mais linear, quando comparados com recém-natos de termo.

Made available in DSpace on 2016-01-26T12:51:53Z (GMT). No. of bitstreams: 1 paulorogeriocorrea_tese.pdf: 1233217 bytes, checksum: 4e4b574f24af12fb3446f5336ad9af00 (MD5) Previous issue date: 2006-12-01 / Heart Rate Variability (HRV) is the most frequently used non-invasive diagnostic method for evaluating the heart autonomic control. Taking into consideration that the autonomous nervous system modulates, in an important way, the cardiovascular function, any alteration in the autonomous cardiovascular function constitutes cause and/or coadjuvant condition for numerous diseases. Recent studies have shown that through the heart frequency variability, by evaluating it within time, frequency and chaos domain, the human organisms, generally speaking, show a behavior of nonlinear complex systems, thus following the laws of Chaos Theory. The HRV analysis, by other nonlinear dynamic methods in the myocardial revascularization surgery pre-operation period, could predict more morbidity in the post-operation period, for example, lung infections. Objective: Evaluate the heart rate variability (HRV) behavior in the chaos domain (nonlinear dynamic) in the preoperative period of surgical myocardial revascularization and its relationship to lung infections occurrences in postoperative stay. Casuistic and Method: 72 non-selected patients were studied (age range from 58.4±10.2 years old) with coronary artery disease and having elective surgery indication for myocardial revascularization. In order to quantify the HRV in the chaos domain, the Detrended Fluctuation Analysis (DFA total) variables, their short-term (&#945;1) and long-term (&#945;2) correlations, Approximate Entropy (-ApEn), Lyapunov Exponent (LE), self-correlation (Tau), Normalized Tau (nT) and Hurst Exponent (HE) were measured in temporal series of 1.000 RR intervals of electrocardiogram recorded on the day before the operation, with Polar S810i equipment. Results: The cut-off levels were determined with help from ROC curve being for DFA total, &#945;1, &#945;2, Approximate Entropy, Lyapunov Exponent, Tau, Normalized Tau and Hurst Exponent, respectively: &#61619;1.036917, &#61619; 0.727273, &#61619; 0.906397, &#61603; 0.480176, &#61603; 0.832, &#61603; 28.23143, &#61619;11.312504, &#61603; and 0.210447. In the Chaos Domain, the DFA total, Normalized Tau , Approximate Entropy and Lyapunov Exponent in the pre-operation period, were associated with the lung infection occurrences in the postoperative period with P =0.0309, P=0.0232, P= 0.0307 and P= 0.0006, respectively. In conclusion, the nonlinear dynamic methods, in their respective cut-off levels, allowed differentiating the cases that evolved into lung infection in the postoperative period of surgical myocardial revascularization. / A Variabilidade da freqüência cardíaca (HRV Heart Rate Variability ) é o método diagnóstico não invasivo mais freqüentemente usado na avaliação do controle autonômico do coração. Considerando que o sistema nervoso autônomo modula, de maneira importante, a função cardiovascular, as alterações na função autonômica cardiovascular constituem causa e/ou condição coadjuvante de numerosas doenças. Estudos recentes têm mostrado que pela análise da variabilidade da freqüência cardíaca, avaliando-a nos domínios do tempo, da freqüência e do caos, os organismos humanos, de forma geral, comportam-se como sistemas complexos não-lineares, obedecendo-se, assim, às leis da Teoria do Caos. A análise da HRV por outros métodos de dinâmica não linear no período pré-operatório da cirurgia de revascularização do miocárdio poderia ser preditora de maior morbidade no pós-operatório, como por exemplo, infecções pulmonares. Objetivo: Avaliar o comportamento da variabilidade da freqüência cardíaca (HRV) no domínio do caos (dinâmica não-linear) no período pré-operatório da cirurgia de revascularização do miocárdio e sua relação com a ocorrência de infecções pulmonares no período pós-operatório hospitalar. Casuística e Método: Foram estudados 72 pacientes não-selecionados (média de idade de 58,4±10,2 anos) com doença arterial coronária e indicação eletiva de cirurgia de revascularização do miocárdio. Para quantificar a dinâmica da HRV no domínio do caos foram medidas as variáveis, Análise das Flutuações Depuradas de Tendências (DFA total), seus componentes de curto (&#945;1) e longo (&#945;2) prazos, Entropia Aproximada (-ApEn), Expoente de Lyapunov (LE), Autocorrelação (Tau), Tau normalizado e Expoente de Hurst (HE) em séries temporais de 1.000 intervalos RR do eletrocardiograma captados na véspera da operação, com equipamento Polar S810i. Resultados: Os respectivos valores de corte determinados com auxílio da curva ROC foram para: DFA total, &#945;1, &#945;2, Entropia aproximada, Expoente de Lyapunov, Tau, Tau normalizado e HE respectivamente: &#61619;1, 036917, &#61619; 0, 727273, &#61619; 0, 906397, &#61603; 0, 480176, &#61603; 0, 832, &#61603; 28, 23143, &#61619;11, 312504, &#61603; 0,210447. No domínio do caos, a DFA total, Tau normalizado, Entropia Aproximada e Expoente Lyapunov no período pré-operatório, se associaram com a ocorrência de infecções pulmonares no pós-operatório de revascularização do miocárdio com P =0, 0309, P=0, 0232, P= 0,0307 e P= 0,0006 respectivamente. Em conclusão, os métodos de dinâmica não-linear, nos seus respectivos níveis de corte, permitiram diferenciar os casos que evoluíram com infecção pulmonar no período pós-operatório de cirurgia de revascularização do miocárdio.

<p>In today’s world, exposure to other cultures has become a symbol of increasing globalization processes. Many people leave their home area to embark on a voyage of discovery and learning that affects their original cultural identity.</p><p>This study explores the life experience of independent transcultural sojourners, i.e. people who freely decide to relocate to different cultural contexts after their formative years. The inquiry covers three major themes of their intercultural experience: Multicultural identity, processes of intercultural adaptation, and change and transformation ensuing from multiple intercultural relocations. The aim of this study is to show the effects of multiple intercultural experiences on the identity of transcultural sojourners, and how they dealt with relevant emerging processes of intercultural adaptation.</p><p>Following a format suggested by Seidman (1996), five respondents were asked to recount and reflect on their transcultural experience in three separate, asynchronous interviews that covered three dimensions of their intercultural experience: past, present, and reflections. The ensuing text comprised about 16,000 words and was analyzed using both a narrative and a thematic approach using a mixed typology of categories and sub-themes made up of indigenous typology stemming from relevant scholarly literature and researcher-constructed typology suggested by the researcher and the respondents.</p><p>The analysis indicates that personal factors like mindfulness, motivation, resourcefulness, and intercultural awareness strongly influence processes of Intercultural communication competence and Multicultural identity development. Contextual factors are also relevant, as they include issues of avowed and ascribed identity. The analysis also shows no specific, generalizable link between the presence of intercultural stimuli in the original cultural milieus and the decision to relocate across cultural boundaries. Furthermore, it points to a strong relation between Piagetian constructivist learning theories and the development of ICC competence. The study also indicates that independent transcultural sojourners are in a position to negotiate the level of their integration and marginality, which in turn affects the spectrum of their Intercultural communication competence.</p><p>Finally, this study indicates the limited applicability of traditional functionalist approaches to understanding and conceptualizing processes of intercultural adaptation and multicultural identity building. It also suggests the need for a shift towards a dialogical perspective informed by systems-thinking and Chaos theory.</p> / The author would like to acknowledge the inspiration and passion for intercultural issues provided over the years by the Intercultural Insights on-line community.Seattle, summer 2010.

In today’s world, exposure to other cultures has become a symbol of increasing globalization processes. Many people leave their home area to embark on a voyage of discovery and learning that affects their original cultural identity. This study explores the life experience of independent transcultural sojourners, i.e. people who freely decide to relocate to different cultural contexts after their formative years. The inquiry covers three major themes of their intercultural experience: Multicultural identity, processes of intercultural adaptation, and change and transformation ensuing from multiple intercultural relocations. The aim of this study is to show the effects of multiple intercultural experiences on the identity of transcultural sojourners, and how they dealt with relevant emerging processes of intercultural adaptation. Following a format suggested by Seidman (1996), five respondents were asked to recount and reflect on their transcultural experience in three separate, asynchronous interviews that covered three dimensions of their intercultural experience: past, present, and reflections. The ensuing text comprised about 16,000 words and was analyzed using both a narrative and a thematic approach using a mixed typology of categories and sub-themes made up of indigenous typology stemming from relevant scholarly literature and researcher-constructed typology suggested by the researcher and the respondents. The analysis indicates that personal factors like mindfulness, motivation, resourcefulness, and intercultural awareness strongly influence processes of Intercultural communication competence and Multicultural identity development. Contextual factors are also relevant, as they include issues of avowed and ascribed identity. The analysis also shows no specific, generalizable link between the presence of intercultural stimuli in the original cultural milieus and the decision to relocate across cultural boundaries. Furthermore, it points to a strong relation between Piagetian constructivist learning theories and the development of ICC competence. The study also indicates that independent transcultural sojourners are in a position to negotiate the level of their integration and marginality, which in turn affects the spectrum of their Intercultural communication competence. Finally, this study indicates the limited applicability of traditional functionalist approaches to understanding and conceptualizing processes of intercultural adaptation and multicultural identity building. It also suggests the need for a shift towards a dialogical perspective informed by systems-thinking and Chaos theory. / The author would like to acknowledge the inspiration and passion for intercultural issues provided over the years by the Intercultural Insights on-line community.Seattle, summer 2010.

En esta Tesis se aborda la estimación óptima de señales caóticas generadas por mapas unidimensionales y contaminadas por ruido aditivo blanco Gaussiano, desde el punto de vista de los dos marcos de inferencia estadística más extendidos: máxima verosimilitud (ML) y Bayesiano. Debido al elevado coste computacional de estos estimadores, se proponen asimismo diversos estimadores subóptimos, aunque computacionalmente eficientes, con un rendimiento similar al de los óptimos. Adicionalmente se analiza el problema de la estimación de los parámetros de un mapa caótico explotando la relación conocida entre muestras consecutivas de la secuencia caótica. Por último, se considera la aplicación de los estimadores anteriores al diseño de receptores para dos esquemas de comunicaciones caóticas diferentes: conmutación caótica y codificación simbólica o caótica. / This Thesis studies the optimal estimation of chaoticsignals generated iterating unidimensional maps and contaminated by additive white Gaussian noise, from the point of view of the two most common frameworks in statistical inference: maximum likelihood (ML) and Bayesian. Due to the high computational cost of optimum estimators, several suboptimal but computationally efficient estimators are proposed, which attain a similar performance as the optimum ones. Additionally, the estimation of the parameters of a chaotic map is analyzed, exploiting the known relation between consecutive samples of the chaotic sequence. Finally, we consider the application of the estimators developed in the design of receivers for two different schemes of chaotic communications: chaotic switching and symbolic or chaotic coding.

The purpose of this study is to explore the nature of dynamic relationships within families, and indicating how the decision to divorce may result from a family's difficulty in adjusting to new changes and stressors. Thus, divorce results in the redefinition of a nuclear system. This study made use of social constructionism as its epistemological framework. By means of in-depth one-on-one interviews, the researcher was able to hear the narratives of all six participants. Hermeneutics was used to analyze the data. The participants' stories were reencountered through the researcher's own frame of reference in which common themes of the divorce process were co-constructed. These themes were later elaborated on and a comparative analysis was undertaken to link them to the available literature. The information gained from the study could contribute to existing research on the impact of divorce, family reorganization following a divorce, and offer a new perspective in understanding family systems. / Clinical Psychology / M.A. (Clinical Psychology)

The purpose of this ethnographic study is to explore the following: 1. The counsellors’ experience of the process of career counselling provided to students at a distance learning institution 2. My own experiences of doing counselling with Unisa students. 3. How Holland’s career theory, the social cognitive career theory and the chaos theory of careers could shape the process of career counselling. The themes that emanated from the stories of six counsellors indicate that they view counselling as a continuous process wherein it is necessary to strike a balance through blended counselling between the needs of individuals versus helping the multitude of anonymous students. In order to facilitate counselling effectively, counsellors need resources and in order to develop these resources they use a diversity of career theories which act as a frame of reference. Attention is given to the development of career counsellors’ identity and self-confidence and how this impacts on the counsellors’ growth. The recommendations of this study hold the promise of contributing to the counselling process at the DCCD. / Psychology / D.Litt.et Phil. (Psychology)

The study examines cognitive rationality as to()l for problemsolving within the context of a movement from determinism and monolithic universal Reason towards indeterminism and plurality. It is contended that theories of literature do not provide an adequate conceptual framework, and therefore, extensive use is made of pluralist fallibilism (Popper, Helmut Spinner) and chaos theory. The philosophy of Friedrich Nietzsche is viewed as a decisive influence in the shift towards plurality and scepticism. In chapter 2, Conan Doyle's Sherlock Holmes stories, a novel by Agatha Christie and Gaston Leroux's Le mystere de Ia chambre jaune are discussed as examples of optimistic rationalism. Chapter 3 indicates that Eco's II nome della rosa emphasizes the conjectural nature of truth and objective knowledge, underpinned by a 'soft' rationalism which amounts to monopolistic pluralism. Chapter 4 analyses the defeat of cognitive rationality by the complex interaction of a multiplicity of independent causal series. The detectives' relationship with the feminine exemplifies the interpenetration of rationality and the instinctual, while the mystery of the feminine is a metaphor for impenetrable complexity. Chapter 5 shows that hypotheses concerning random complex systems remain inconclusive. However, as the trajectory of a complex system can be regulated, so reason can be viewed as the underlying regulative pattern (strange attractorl for an infinite proliferation of hypotheses. Thus, despite .shifting conceptions of rationality and order, all the detectives in the study accept objective truth as regulative principle and are involved in a search for objective knowledge / Afrikaans and Theory of Literature / D.Litt. et Phil. (Theory of literature)

Cette thèse analyse les enjeux du développement économique liés aux dynamiques des cours des matières premières en général et ceux du coton en particulier. Traditionnellement, les travaux s’inscrivant dans une optique de long terme questionnent la pertinence des spécialisations primaires des PMA. À moyen terme l’intérêt porte davantage sur l’instabilité dont les conséquences sont d’autant plus importantes que la dépendance des pays à l’exportation de tels produits est forte. Les enjeux s’articulent alors autour des modalités de régulation des marchés, du choix d'outils (publics ou marchands) pour la gestion des incertitudes, le tout dépendant de l’appréhension de l’instabilité comme un phénomène endogène ou exogène. Dans un contexte nouveau marqué par l’affirmation d’oligopoles de firmes, la segmentation du processus productif mondial, et la financiarisation des marchés de matières premières, nous proposons un cadre analytique permettant d’aborder différemment ces problématiques. Nos travaux montrent d’abord comment les approches du type chaînes globales de valeur peuvent être mobilisées pour mieux orienter les stratégies commerciales / industrielles des PMA. S’appuyant sur la notion de rationalité limitée dans le cadre de modèles de comportements hétérogènes, ils prouvent ensuite l’existence d’une forte composante endogène dans l’instabilité et par là même, l'inefficacité des seuls outils marchands. Au final, pour les pays africains producteurs de coton, il apparait qu’il reste possible de mettre ce produit au service d’une stratégie globale de développement. Cela passe par le recours à des mécanismes hybrides de gestion de l’instabilité, combiné au renforcement des dynamiques de coopération transfrontalières en vue d’une structuration de chaînes régionales de valeur. / This thesis analyzes the economic development issues related to the medium and long-term dynamics of commodities prices in general and cotton prices in particular. Studies on the long-term perspective traditionally question the relevance of primary specializations of LDCs. In the medium term, the interest is relates to price instability for which the consequences are all the more important as countries’ dependency on the exports of such products becomes stronger. The stakes then revolve around market regulation modalities, and the choice of risk management tools (e.g. public or private interventions). These depend on the apprehension of price fluctuations as a phenomenon arising from endogenous or exogenous market factors. In a new economical context influenced by the growing importance of oligopolistic firms, a segmentation of the productive process and the financialization of commodity markets, we address differently these issues through a new analytical framework. The proposed analysis first shows how approaches such as the ones related to global value chains are more adapted to tackle industrial/commercial policies in commodity dependent LDCs. Second, in a context of heterogeneous behavioral models, we rely on the concept of bounded rationality to show the presence of a strong endogenous component in instability. Thus, it proves the inefficiency of private interventions to counter instability. Considering these findings in the case of African cotton producers, we conclude that it remains possible to incorporate the commodity in a global development strategy. But this involves the use of hybrid-type mechanisms (public-private) for managing uncertainty, combined with a reinforcement of cross-border cooperation dynamics in order to structure regional value chains.