Synthesis and Thermal Characterization of Polyurethanes Obtained from Cottonseed and Corn Oil-Based Polyols

The use of vegetable oils to replace fossil feedstock has become an area of opportunity and a priority for study in the field of polymer science. Vegetable oils are considered as renewable resources with high potential, low cost and full availability. The aim of this study is the synthesis of biobased polyols from cottonseed oil (Gossypium barbadanse) and corn oil (Zea mays) as feedstock. Their synthesis was successfully performed, as can be concluded from the determination of their hydroxyl index as well as the structural and thermal characterization carried out in this work. Polyurethanes from biobased polyols were synthesized with two different isocyanates (HDI and MDI) and variable polyol/isocyanate ratio and they were further characterized by infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy, concluding that cottonseed and corn oils could be considered as valid alternatives for the synthesis of biobased polymeric materials.The authors thank the Spanish Ministry of Economy and Competitiveness (MAT2014-59242-C2-2-R) and CONACYT-Mexico (No.CB06825 and doctoral scholarship No.234299/212279) for their financial support

SELECCIÓN DE ÁNGULOS DE CONMUTACIÓN PARA UN INVERSOR MULTINIVEL EN CASCADA USANDO UN ALGORITMO DE BÚSQUEDA ALEATORIA (SWITCHING ANGLES SELECTION FOR A CASCADED MULTILEVEL INVERTER USING A RANDOM SEARCH ALGORITHM)

Resumen Un inversor de cascada trifásico H-Bridge de varios niveles en condiciones de fallo de un solo interruptor puede funcionar como un inversor asimétrico aplicando un cambio en la estrategia de modulación para mejorar su rendimiento. Este documento presenta el Algoritmo de Búsqueda Aleatoria aplicado a la modulación de Eliminación Selectiva de Armónicos para Inversores de Cascada Multinivel Asimétricos. El algoritmo propuesto tiene por objeto encontrar una solución óptima a un conjunto de ecuaciones trascendentales, que garantizan la eliminación de armónicos no deseados y el control de la magnitud de la componente fundamental de la tensión generada por el inversor. Además, el algoritmo propuesto se comparó con el algoritmo de optimización de enjambre de partículas y la estrategia tradicional de eliminación selectiva de armónicos. Los resultados comparativos obtenidos mostraron que la técnica de modulación que usa la técnica Algoritmo de Búsqueda Aleatoria es la más adecuada para el inversor multinivel trifásico de siete niveles (caso de estudio). Palabras Clave: Algoritmo de búsqueda aleatoria, Eliminación selectiva de armónicos, Estrategia de tolerancia a fallos, Inversor de modulación de ancho de pulso, Inversor multinivel. Abstract A three-phase H-Bridge multi-level cascade inverter under Single-Switch Fault Condition can operate as an asymmetrical inverter by applying a change in the modulation strategy to improve its performance. This paper presents the Random Search Algorithm applied to the modulation of Selective Harmonic Elimination for Asymmetric Cascade Multilevel Inverters. The proposed algorithm aims to find an optimal solution to a set of transcendental equations, which guarantee the elimination of undesired harmonics and controlling the magnitude of the fundamental component of the voltage generated by the inverter. In addition, the proposed algorithm was compared with the Particle Swarm Optimization algorithm and the traditional selective harmonic elimination strategy. The comparative results obtained showed that the modulation technique using the Random Search Algorithm technique is the most suitable for the seven-level three-phase multilevel inverter (case study). Keywords: Fault Tolerant Strategy, Pulse Width Modulation inverter, Random Search Algorithm, Selective Harmonic Elimination, Multilevel inverter

Expression of voltage-gated Ca2+ channels, Insp3Rs, and RyRs in the immature mouse ovary

Abstract Background The postnatal mammalian ovary undergoes a series of changes to ensure the maturation of sufficient follicles to support ovulation and fecundation over the reproductive life. It is well known that intracellular [Ca2+]i signals are necessary for ovulation, fertilization, and egg activation. However, we lack detailed knowledge of the molecular identity, cellular distribution, and functional role of Ca2+ channels expressed during folliculogenesis. In the neonatal period, ovarian maturation is controlled by protein growth factors released from the oocyte and granulosa cells. Conversely, during the early infantile period, maturation becomes gonadotropin-dependent and is controlled by granulosa and theca cells. The significance of intracellular Ca2+ signaling in folliculogenesis is supported by the observation that mice lacking the expression of Ca2+/calmodulin-dependent kinase IV in granulosa cells suffer abnormal follicular development and impaired fertility. Results Using immunofluorescence in frozen ovarian sections and confocal microscopy, we assessed the expression of high-voltage activated Ca2+ channel alpha subunits and InsP3 and ryanodine receptors in the postnatal period from 3 to 16 days. During the neonatal stage, oocytes from primordial and primary follicles show high expression of various Ca2+-selective channels, with granulosa and stroma cells expressing significantly less. These channels are likely involved in supporting Ca2+-dependent secretion of peptide growth factors. In contrast, during the early and late infantile periods, Ca2+ channel expression in the oocyte diminishes, increasing significantly in the granulosa and particularly in immature theca cells surrounding secondary follicles. Conclusions The developmental switch of Ca2+ channel expression from the oocytes to the perifollicular cells likely reflects the vanishing role of the oocytes once granulosa and theca cells take control of folliculogenesis in response to gonadotropins acting on their receptors

Interstage Pressures of a Multistage Compressor with Intercooling

This paper considers the criterion of minimum compression work to derive an expression for the interstage pressure of a multistage compressor with intercooling that includes the gas properties, pressure drops in the intercoolers, different suction gas temperatures, and isentropic efficiencies in each compression stage. The analytical expression for the interstage pressures is applied to estimate the number of compression stages and to evaluate its applicability in order to estimate interstage pressures in the operation of multistage compressors, which can be especially useful when their measurements are not available

Decentralized neural identifier and control for nonlinear systems based on extended Kalman filter

Neurogenesis continues at least in two regions of the mammalian adult brain, the subventricular zone (SVZ) and the subgranular zone in hippocampal dentate gyrus. Neurogenesis in these regions is subjected to physiological regulation and can be modified by pharmacological and pathological events. Here we report the induction of neurogenesis in the SVZ and the differentiation after nigrostriatal pathway lesion along with transcranial magnetic field stimulation (TMFS) in adult rats. Significant numbers of proliferating cells demonstrated by bromodeoxyuridine-positive reaction colocalized with the neuronal marker NeuN were detected bilaterally in the SVZ, and several of these cells also expressed tyrosine hydroxylase. Transplanted chromaffin cells into lesioned animals also induced bilateral appearance of subependymal cells. These results show for the first time that unilateral lesion, transplant, and/or TMFS induce neurogenesis in the SVZ of rats and also that TMFS prevents the motor alterations induced by the lesion. " 2004 Wiley-Liss, Inc.",,,,,,"10.1002/jnr.20235",,,"http://hdl.handle.net/20.500.12104/43087","http://www.scopus.com/inward/record.url?eid=2-s2.0-4644305290&partnerID=40&md5=f28807c5133684dfb45e32719fa2bfab",,,,,,"1",,"Journal of Neuroscience Research",,"1

Neurogenesis in the subventricular zone following transcranial magnetic field stimulation and nigrostriatal lesions

Neurogenesis continues at least in two regions of the mammalian adult brain, the subventricular zone (SVZ) and the subgranular zone in hippocampal dentate gyrus. Neurogenesis in these regions is subjected to physiological regulation and can be modified by pharmacological and pathological events. Here we report the induction of neurogenesis in the SVZ and the differentiation after nigrostriatal pathway lesion along with transcranial magnetic field stimulation (TMFS) in adult rats. Significant numbers of proliferating cells demonstrated by bromodeoxyuridine-positive reaction colocalized with the neuronal marker NeuN were detected bilaterally in the SVZ, and several of these cells also expressed tyrosine hydroxylase. Transplanted chromaffin cells into lesioned animals also induced bilateral appearance of subependymal cells. These results show for the first time that unilateral lesion, transplant, and/or TMFS induce neurogenesis in the SVZ of rats and also that TMFS prevents the motor alterations induced by the lesion. © 2004 Wiley-Liss, Inc

OBTAINING COTTON SEED OIL EPOXIDIZED USING AN WEAK ACID

In this study, parameters which influence the chemical modification under mild conditions using a weak organic acid, fatty acids of unsaturated oil, cottonseed to produce epoxidized oil, which is a useful precursor in obtaining resins epoxy industrial importance, were evaluated. We studied the following reaction parameters: concentration of acetic acid, hydrogen peroxide, catalyst and solvent, as well as temperature, agitation rate and reaction time. The results showed that the agitation and temperature are the parameters which influence the modification of unsaturated fatty acids. Studied conditions allowed obtaining up to 70% relative conversion of oxygen-oxirane from cottonseed oil

Development of the hypersecretory phenotype in the population of adrenal chromaffin cells from prehypertensive SHRs

The hypersecretory phenotype of adrenal chromaffin cells (CCs) from early spontaneously hypertensive rats (SHRs) mainly results from enhanced Ca2+-induced Ca2+-release (CICR). A key question is if these abnormalities can be traced to the prehypertensive stage. Spontaneous and stimulus-induced catecholamine exocytosis, intracellular Ca2+ signals, and dense-core granule size and density were examined in CCs from prehypertensive and hypertensive SHRs and compared with age-matched Wistar-Kyoto rats (WKY). During the prehypertensive stage, the depolarization-elicited catecholamine exocytosis was ~ 2.9-fold greater in SHR than in WKY CCs. Interestingly, in half of CCs the exocytosis was indistinguishable from WKY CCs, while it was between 3- and sixfold larger in the other half. Likewise, caffeine-induced exocytosis was ~ twofold larger in prehypertensive SHR. Accordingly, depolarization and caffeine application elicited [Ca2+]i rises ~ 1.5-fold larger in prehypertensive SHR than in WKY CCs. Ryanodine reduced the depolarization-induced secretion in prehypertensive SHR by 57%, compared to 14% in WKY CCs, suggesting a greater contribution of intracellular Ca2+ release to exocytosis. In SHR CCs, the mean spike amplitude and charge per spike were significantly larger than in WKY CCs, regardless of age and stimulus type. This difference in granule content could explain in part the enhanced exocytosis in SHR CCs. However, electron microscopy did not reveal significant differences in granule size between SHRs and WKY rats’ adrenal medulla. Nonetheless, preSHR and hypSHR display 63% and 82% more granules than WKY, which could explain in part the enhanced catecholamine secretion. The mechanism responsible for the heterogeneous population of prehypertensive SHR CCs and the bias towards secreting more medium and large granules remains unexplained.This study is financially supported by Grants 315803 (Laboratorio Nacional de Canalopatías) from Consejo Nacional de Ciencia y Tecnología (CONACYT), México, and PAPIIT AG200119 from Dirección General de Asuntos del Personal Académico (DGAPA-UNAM) and by a grant of Ministerio de Ciencia e Innovación (Project PID2020-114824GB-I00 to LMG).Peer reviewe