Repositorio IPICYT
Not a member yet
1534 research outputs found
Sort by
Evaluación de biocompatibilidad de nanotubos de carbono con fibroblastos de ratón NIH-3T3
Get PDF"Los nanotubos de carbono son cilindros huecos de grafeno cuyas dimensiones son de nanoescala. Dadas sus peculiares características químicas, físicas, eléctricas y térmicas se han buscado sus posibles aplicaciones en la industria y biomedicina. En este último campo, las investigaciones de respuesta celular a nanotubos de carbono puros (MWCNT) o funcionalizados han sido extensas y a la vez inconsistentes y contradictorias. Se ha propuesto que los nanotubos dopados con nitrógenos (CNx) presentan mejor biocompatibilidad celular que los puros o funcionalizados. En esta investigación se evaluó el efecto de MWCNT y CNx sobre fibroblastos de ratón usando distintas concentraciones de los nanomateriales y diferentes ensayos de exposición. Los resultados obtenidos mostraron que los CNx se dispersan mejor que los MWCNT en medio de cultivo, agua destilada y etanol. También se encontró que la respuesta celular depende de la concentración de nanotubos y del ensayo de exposición, siendo los CNx los que mayor biocompatibilidad tienen con los fibroblastos. En general, los resultados muestran que los CNx son menos tóxicos que los MWCNT.""Carbon nanotubes (CNTs) are graphitic sheets grown as hollow cylinders with diameters on the order of only few nanometers (2 to 200 nm) and the lengths ranging from hundred of nanometers to micrometers. Due to their unique chemical, physical, electrical and thermal properties there has been much interest to find applications in industrial and biomedical fields. In the latter field, researches of cellular response to either non-functionalized or functionalized multi-walled carbon nanotubes (MWCNT) have been extensive. The chemical doping with nitrogen of CNTs (CNx) has been suggested to have positive effects on cellular biocompatibility than MWCNT. In this study, we evaluated the effects of MWCNT and CNx on mouse fibroblast cells (NIH-3T3) using different concentrations and exposed assays. Results showed that CNx was better dispersed than MWCNT in culture medium, ethanol and water. We found that cell toxicity is concentration dependent and the exposed assay influences on biocompatibility of CNTs. In general, our results suggested that CNx are less toxic than MWCNT.
Effects of burial depth on seed germination and seedling emergence of Mexican oaks: a glasshouse experiment
Get PDF"Despite the interest in restoring oak forests in Mexico, very little is known about their regeneration ecology. We assessed the influence of acorn burial depth on seed germination and seedling emergence for eight Mexican oak species (Q. affinis, Q. castanea, Q. coccolobiolia, Q. laeta, Q. mexicana, Q. polymorpha, Q. tinkhamii and Q. viminea). We performed a glasshouse experiment in which acorns were buried at five soil depths (0, 2, 4, 6 and 8 cm). After four months, acorn germination and seedling emergence were recorded. Buried acorns showed higher germination and seedling emergence than unburied ones, but burial depth also influenced these responses. The optimum burial depth for seedling emergence of each species was 2, 4, 6 and 8 cm depth for four species (Q. castanea, Q. mexicana, Q. tinkhamii, and Q. viminea); 2 and 4 cm for Q. laeta; as well as 2, 4 and 8 cm for Q. coccolobifolia.
Neuronal receptors involved in the inflammatory process
Get PDFTesis (Doctorado en Ciencias en Biología Molecular)"Este estudio examinó si los productos celulares bacterianos que podrían tener acceso al intersticio intestinal podrían activar las neuronas nociceptivas colonicas de ganglios de la raíz dorsal (GRD) de ratón utilizando técnicas moleculares y de registro electrofisiológico. Las neuronas con proyecciones colonicas fueron identificadas usando el marcador retrogrado azul rápido; y la expresión de RNAm del receptor tipo Toll (TLR) 1, 2, 3, 4, 5, 6 y 9, las proteínas adaptadoras MD1 y MD2 y MYD88 fueron observados en neuronas marcadas con azul rápido capturadas por láser. 1 μg/ml de LPS grado ultrapuro incrementó el transcrito de TNF-α y IL-1β y estimuló la secreción de de TNF-α de neuronas disociadas de GRD. Por otra parte, el lisado de E. coliincrementó significativamente la actividad basal de los nervios aferentes mesentéricos y en ratones con un tratamiento crónico DSS. Estos datos demuestran que los productos celulares bacterianos pueden activar directamente las neuronas de GRD colónicas llevando a la producción de citocinas inflamatorias e incrementando su excitabilidad. El LPS grado estándar pudiera también tener acciones independientes de la señalización de TLR.""This study examined whether bacterial cell products that might gain access to the intestinal interstitium could activate mouse colonic nociceptive dorsal root ganglion (DRG) neurons using molecular and electrophysiological recording techniques. Colonic projecting neurons were identified by using the retrograde tracer fast blue and Toll-like receptor (TLR) 1, 2, 3, 4, 5, 6, 9, adapter proteins Md-1 and Md-2, and MYD88 mRNA expression was observed in laser-captured fast blue-labeled neurons. Ultrapure LPS 1 g/ml phosphorylated p65 NF-κB subunits increased transcript for TNF- and IL-1 and stimulated secretion of TNF- from acutely dissociated DRG neurons. Moreover, lysate also activated afferent discharge from colonic mesenteric nerves, and this was significantly increased in chronic dextran sulfate sodium salt mice. These data demonstrate that bacterial cell products can directly activate colonic DRG neurons leading to production of inflammatory cytokines by neurons and increased excitability. Standard-grade LPS may also have actions independent of TLR signaling.
On the emergence of chaos in dynamical networks
Get PDF"We investigate how changes of specific topological features result on transitions among different bounded behaviours in dynamical networks. In particular, we focus on networks with identical dynamical systems, synchronised to a common equilibrium point, then a transition into chaotic behaviour is observed as the number of nodes and the strength of their coupling changes. We analyse the network's transverse Lyapunov exponents (tLes) to derive conditions for the emergence of bounded complex behaviour on different basic network models. We find that, for networks with a given number of nodes, chaotic behaviour emerges when the coupling strength is within a specific bounded interval; this interval is reduced as the number of nodes increases. Furthermore, the endpoints the emergence interval depend on the coupling structure of network. We also find that networks with homogeneous connectivity, such as regular lattices and small-world networks are more conducive to the emergence of chaos than networks with heterogeneous connectivity like scale-free and star-connected graphs. Our results are illustrated with numerical simulations of the chaotic benchmark Lorenz systems, and to underline their potential applicability to real-world systems, our results are used to establish conditions for the chaotic activation of a network of electrically coupled pancreatic β-cell models.
Computing the Conway polynomial of several closures of oriented 3-braids
Get PDF"This paper deals with polynomial invariants of a class of oriented 3-string tangles and the knots (or links) obtained by applying six different closures. In Cabrera-Ibarra (2004) [1], expressions were given to compute the Conway polynomials of four different closures of the composition of two such 3-string tangles. By using the expressions and results from that reference, and using an algorithm developed on the basis of Gillerʼs calculations for 3-string tangles, we provide new results concerning six closures of 3-braids. Surprisingly, for 3-braids two of the closures turn out to be affine functions of the four previously defined. Among the contributions in this paper one finds computational tools to obtain the Conway polynomial of closures of 3-braids in terms of continuous fractions and their expansions. An interesting feature is that our calculations yield explicit, nonrecursive formulas in the case of 3-braids, thereby considerably lowering the time required to compute them. As a byproduct, explicit expressions are also given to obtain both numerators and denominators of continuous fractions in a nonrecursive way.
Note on Hawking-Unruh effects in graphene
Get PDF"Beltrami-shaped graphene sheets have been recently proposed as analogs of curved spacetimes with Hawking-Unruh e?ects detected through typi-cal condensed matter measurements involving scanning tunneling micro-scopes and spectroscopy. However, such deformed sheets, if ever fabri-cated, will contain large strain-induced pseudomagnetic ?elds with im-portant guiding e?ects on the motion of the electrons in the conduction band. Besides, possible surface polariton and plasmon modes are known to be important players in the radiative heat transfer which takes place in the natural near-?eld nanoscale experimental conditions. Therefore, we suggest that the latter class of experiments could shed light on phenomena related to the black hole membrane paradigm instead
Fermentation of lactose and its constituent sugars by Escherichia coli WDHL: impact on hydrogen production
Get PDF"Fermentations of lactose, glucose and galactose using Escherichia coli WDHL, a hydrogen over producer strain, were performed. With glucose as substrate pyruvate was mainly routed to the lactate pathway, resulting in hydrogen production and yield of 1037 mL and 0.30 mol H2/mol of glucose, respectively. When galactose was the substrate, the pyruvate formate lyase pathway was the main route for pyruvate and a fermentation yield of 1.12 mol H2/mol of galactose and a hydrogen production of 2080 mL were obtained. The fermentation of lactose or glucose plus galactose showed a similar yield of 1.02 mol H2/mol of hexose consumed. This work clearly demonstrated that the kinetics of hydrogen and metabolites production as well as the hydrogen yield were affected by the type of sugar used as substrate as reflected by the deviations from the metabolic hydrogen-production pathway.
Exponential stability of integral delay systems with a class of analytic kernels
Get PDF"The exponential stability of a class of integral delay systems with analytic kernels is investigated by using the Lyapunov-Krasovskii functional approach. Sufficient delay-dependent stability conditions and exponential estimates for the solutions are derived. Special attention is paid to the particular cases of polynomial and exponential kernels.
Simple method to synthesize functionalized carbon nanotubes employing cobalt nitrate and acetone by using spray pyrolysis deposition technique
Get PDF"Recently alcohols and ketones have been employed to sensitize CNT by CVD. A study has shown the importance of the chemical nature of those carbon precursors on the characteristics of the CNT (carbon nanotubes) obtained. In the present work we show the influence of the catalyst employed on the synthesis of functionalized multiwall carbon nanotubes (MWCNTs) utilizing acetone as carbon source and cobalt nitrate Co(NO3)2 as catalyst.
Análisis de una familia de osciladores con múltiples enroscados
No full text""En este trabajo se analizan series de tiempo con dinámica caótica provenientes de un sistema de comunicación. El análisis se realiza con la transformada ondoleta ortogonal, la cual nos proporciona información sobre la distribución de energía en los diferentes niveles ondoleta de las series de tiempo. Ademas, se establece la región útil en función de la amplitud y frecuencia de la señal de información a ser transmitida.""In this paper we analyze time series with chaotic dynamics from a communication system. The analysis is performed with the orthogonal wavelet transform, which gives us information about of energy distribution in the different wavelet levels from the time series. Furthermore, It is established the useful region as a function of the amplitude and frequency values of the information signal to be transmitted.