Yehia Badr

Resumen Diversos datos epidemiológicos muestran que el síndrome de apneas-hipopneas del sueño (SAHS) se relaciona independientemente con el desarrollo de resistencia a la insulina e intolerancia a la glucosa. Además, y pese a la existencia de notables limitaciones metodológicas, algunos estudios refieren una elevada prevalencia de \{SAHS\} en pacientes con diabetes tipo 2 (DM2). Un reciente metaanálisis muestra que el \{SAHS\} moderado-grave se asocia a un mayor riesgo de \{DM2\} (riesgo relativo = 1,63 [1,09-2,45]), en relación con la ausencia de apneas-hipopneas. La existencia de alteraciones comunes de diversas vías patogénicas le proporciona plausibilidad biológica a esta relación. La hipoxia intermitente y la fragmentación del sueño, originadas por la sucesión de episodios de apneas-hipopneas, inducen diversos trastornos intermedios, como la activación del sistema nervioso simpático, el estrés oxidativo, la inflamación sistémica, alteraciones en las hormonas reguladoras del apetito y activación del eje hipotálamo-hipófiso-suprarrenal, que favorecen el desarrollo de resistencia a la insulina, así como su progresión a intolerancia a la glucosa y, en última instancia, a DM2. La coexistencia del \{SAHS\} parece agravar la evolución de la DM2, al empeorar el control glucémico y potenciar el efecto de la aterosclerosis en el desarrollo de complicaciones macrovasculares. Además, el \{SAHS\} podría asociarse al desarrollo de complicaciones microvasculares, particularmente la retinopatía, nefropatía o neuropatía diabéticas. Aunque todavía escasos, algunos datos sugieren que la \{DM2\} también podría empeorar la evolución del SAHS, al favorecer la colapsabilidad de la vía aérea superior y potenciar la aparición de apneas-hipopneas centrales. Abstract Epidemiological data suggest that sleep apnea-hypopnea syndrome (SAHS) is independently associated with the development of insulin resistance and glucose intolerance. Moreover, despite significant methodological limitations, some studies report a high prevalence of \{SAHS\} in patients with type 2 diabetes mellitus (DM2). A recent meta-analysis shows that moderate-severe \{SAHS\} is associated with an increased risk of \{DM2\} (relative risk = 1.63 [1.09 to 2.45]), compared to the absence of apneas and hypopneas. Common alterations in various pathogenic pathways add biological plausibility to this relationship. Intermittent hypoxia and sleep fragmentation, caused by successive apnea-hypopnea episodes, induce several intermediate disorders, such as activation of the sympathetic nervous system, oxidative stress, systemic inflammation, alterations in appetite-regulating hormones and activation of the hypothalamic-pituitary-adrenal axis which, in turn, favor the development of insulin resistance, its progression to glucose intolerance and, ultimately, to DM2. Concomitant \{SAHS\} seems to increase \{DM2\} severity, since it worsens glycemic control and enhances the effects of atherosclerosis on the development of macrovascular complications. Furthermore, \{SAHS\} may be associated with the development of microvascular complications: retinopathy, nephropathy or diabetic neuropathy in particular. Data are still scant, but it seems that \{DM2\} may also worsen \{SAHS\} progression, by increasing the collapsibility of the upper airway and the development of central apneas and hypopneas.

Abstract This paper presents a review of the optimization techniques and strategies applied to wind turbine performance optimization. The topic is addressed by identifying the most significant objectives, targets and issues, as well as the optimization formulations, schemes and models available in the published literature. The current energy demand combined with depletion of fossil-fuel reserves and stricter environmental regulations have led to the development of alternative renewable energy solutions like wind energy. The current 2030 United States target is to have at least 20% of the \{US\} energy supply by onshore and offshore wind farms. To meet these demands, wind energy costs have to be able to compete with traditional fossil fuel sources. Hence, it is essential and vital that wind turbine designers and manufactures search the optimal solution that fits the objectives under a set of design constraints. Throughout the last 30 years, the objective function has evolved from the earlier maximized metric of the power coefficient to the maximization of the annual energy production. Common alternatives such as blade mass minimization and maximization of the rotor thrust and torque have been examined. However, the main objective has been focused on the minimization of the cost of energy in order for wind energy to become more competitive and economically attractive. The purpose of this paper is to review previous work that undertakes the performance optimization of horizontal wind turbines by highlighting the main aspects when tackling the wind turbine optimization problem such as: objective functions, design constraints, tools and models and optimization algorithms. In addition, in a conclusion of the review, a discussion and argument about the challenges, issues and future developments are identified.