Incidencia socioeconómica de las políticas cambiarias en el comercio con Venezuela: Maicao

El Comercio Fronterizo en el distrito de Maicao, es para sus pobladores (Comerciantes) el generador de la dinámica económica. Importancia que asume dado la gran influencia que ejerce este sobre el monto de capital invertido, los ingresos, y la creación de empleo en el municipio. Los factores que han condicionado a Maicao, a depender del comercio fronterizo son netamente estructurales, los cuales se pusieron de manifiesto con la devaluación del bolívar. La crisis de 1.983 mostró como la dinámica economice de Maicao se fundamenta en la actividad mercantil, que hasta entonces dependió de la demanda venezolana, principalmente. La crisis coyuntural que vivió Maicao a partir de 1.983, es un fenómeno que la economía de frontera siempre tendrá que enfrentar, puesto que se presenta en esas regiones colindantes entre los países, políticas económicas diferentes, que en el momento de tomar por ejemplo una medida cambiarla por parte de algunos de los dos países se afecta la economía del otro; es el caso de Maicao, en 1.903. Este hecho le da al distrito una connotada inestabilidad y vulnerabilidad en su economía. Peor aún, si se sabe que el sector terciario (Comercio Fronterizo) genera el mayor número de personas ocupadas como se anotó anteriormente. La importancia que ha tomado el subsector comercio a lo largo de su historia obedece a la ausencia de un sector (Agropecuario o Industrial) capaz de engendrar o contribuir con el empleo y los ingresos de los pobladores del distrito y que les permita de esta forma, crearles mejores condiciones socio-económicas; en otro lugar, hacer que su “modus vivendi" no esté determinado por las condiciones favorables o desfavorables del comercio con Venezuela. El Comercio de Maicao, hasta 1.983 estuvo en su mayoría sujeto a la demanda que por sus productos realizaban los venezolanos, dándole esta situación al distrito y a nuestro país una salida de mercancía, no solamente colombiana sino también extranjera, y por ende obtención de divisas por concepto de exportaciones. La medida cambiaria (devaluación del bolívar) que asumió el gobierno venezolano, creo a partir de 1.983 en el distrito de Maicao, un cambio sustancial en su actividad principal (el Comercio); cambio que se patentizó en la reducción de las ventas de mercancías nacionales; quiebra y desaparición de muchos almacenes. con esto, un incremento de desocupados y contribución al desempleo estructural del municipio; haciendo más crítico el flagelo de inseguridad de los maicaeros. Tras de esto se ha presentado un aumento en la oferta de productos venezolanos por el incremento del poder adquisitivo de nuestra moneda (Peso) que ha afectado los ingresos de algunos comerciantes. Los subsectores del Comercio de Maicao, se han caracterizado, por ofrecer un gran volumen de productos y mercancías extranjeras; en los últimos tres años consolidándose más este monto ofrecido con la penetración al mercado de Maicao de los productos venezolanos. Los comerciantes bien Instalados, presentan los mayores volúmenes de venta diarios y con esto los más altos ingresos; además poseen los almacenes con mayor capital invertido, esto con respecto a los comerciantes estacionarios. Los comerciantes en mención (Bien Instalados) son los que generan la dinámica económica dentro del subsector comercio, puesto que es el que mayor influencia sobre el empleo y. los ingresos presentan, dentro del sector terciario. También se puede anotar que los Comerciantes Bien Instalados, 173 en su mayoría venden y compran mercancía al por mayor. Los Comerciantes Estacionarios estén caracterizados por vender al detal y aprovisionar sus puestos de ventas de productos y mercancías compradas directamente a los Comerciantes mayoristas Bien Instalados. En la relación comercial anterior son frecuentes las compras a crédito por parte del Comerciante Estacionario, aunque con plazos irrisorios. El peso es la moneda más utilizada, en las transacciones, y después de 1.983 su uso se ha asentado. El dólar ha sido una moneda poco empleada en las transacciones por los Comerciantes estacionarios. Hoy día su uso es remitido a la relación comercial que entablan los Comerciantes Mayoristas de Maicao con demás comerciantes del extranjero. Las entrevistas realizadas muestran que la crisis atestó en forma directa e indirecta a las diferentes. instituciones oficiales de Maicao, que dicho sea de paso aportaron poco para menguar los efectos de la devaluación del bolívar sobre los Comerciantes de Maicao

Resonant Magnetic Field Sensors Based On MEMS Technology

Microelectromechanical systems (MEMS) technology allows the integration of magnetic field sensors with electronic components, which presents important advantages such as small size, light weight, minimum power consumption, low cost, better sensitivity and high resolution. We present a discussion and review of resonant magnetic field sensors based on MEMS technology. In practice, these sensors exploit the Lorentz force in order to detect external magnetic fields through the displacement of resonant structures, which are measured with optical, capacitive, and piezoresistive sensing techniques. From these, the optical sensing presents immunity to electromagnetic interference (EMI) and reduces the read-out electronic complexity. Moreover, piezoresistive sensing requires an easy fabrication process as well as a standard packaging. A description of the operation mechanisms, advantages and drawbacks of each sensor is considered. MEMS magnetic field sensors are a potential alternative for numerous applications, including the automotive industry, military, medical, telecommunications, oceanographic, spatial, and environment science. In addition, future markets will need the development of several sensors on a single chip for measuring different parameters such as the magnetic field, pressure, temperature and acceleration

Stochastic Resonance in the Motor System: Effects of Noise on the Monosynaptic Reflex Pathway of the Cat Spinal Cord

10 pages, 4 figures.-- PMID: 17428901 [PubMed].In sensory systems the presence of a particular non-zero level of noise may significantly enhance the ability of an individual to detect weak sensory stimuli through a phenomenon known as stochastic resonance (SR). The aim of this study was to demonstrate if such phenomenon is also exhibited by the motor system; in particular, in the Ia-motoneuron synapse of the cat spinal cord. Monosynaptic reflexes elicited by periodic electrical stimulation to the medial gastrocnemius nerve were recorded in the L7 ventral root (or in single motoneurons) of decerebrated cats. Random stretches (mechanical noise) were applied to the lateral gastrocnemius plus soleus muscle by means of a closed-loop mechanical stimulator-transducer. In all cats we observed the SR phenomenon. The amplitude of the monosynaptic reflexes (or number of action potentials recorded in the motoneurons) evoked by the weak electrical stimuli applied to the medial gastrocnemius nerve were an inverted U-like function of the mechanical noise applied to the lateral gastrocnemius plus soleus muscle. A significant maximum value in the amplitude of the monosynaptic responses was reached with a particular noise amplitude value. Numerical simulations on a model of the monosynaptic reflex pathway qualitatively reproduce this stochastic resonance behavior. We conclude that the monosynaptic reflex response elicited by Ia afferents is optimized by the noisy stretching of a synergistic muscle. Our study provides the first direct demonstration that the motor system, and not only the sensory systems, exhibits the SR phenomenon.We thank the Spanish Ministerio de Ciencia y Tecnología and Feder support under project FIS2004-00953 and European Commission through project Global Approach to Brain Activity 043309. T. Pérez acknowledges support from the Govern Balear and L. Martínez from CONACyT México fellowship.This work was supported by Project J36062-N Consejo Nacional de Ciencia y Tecnología México and Programa Integral de Fortalecimiento Institucional, Vicerrectoría de Investigación, Benemérita Universidad Autónoma de Puebla México to E. Manjarrez.Peer reviewe

OA: Ansiedad, ¿Qué es y cómo afrontarla?

La ansiedad es una reacción normal de nuestro organismo ante las demandas del ambiente. Sin embargo, hay factores que pueden convertir la ansiedad en un problema. Por ello, es importante conocer los factores de riesgo, las manifestaciones físicas, psicológicas, emocionales y conductuales de la ansiedad, y técnicas para poder sobrellevarla de una mejor manera.https://ecampus.cetys.mx/cursos/ansiedad/story.htm

An Intersegmental Neuronal Architecture for Spinal Wave Propagation under Deletions

10 pages, 7 figures, 2 tables.Recent studies have established and characterized the propagation of traveling electrical waves along the cat spinal cord during scratching, but the neuronal architecture that allows for the persistence of such waves even during periods of absence of bursts of motoneuron activity (deletions) is still unclear. Here we address this problem both theoretically and experimentally. Specifically, we monitored during long lasting periods of time the global electrical activity of spinal neurons during scratching. We found clear deletions of unaltered cycle in extensor activity without associated deletions of the traveling spinal wave. Furthermore, we also found deletions with a perturbed cycle associated with a concomitant absence of the traveling spinal wave. Numerical simulations of an asymmetric two-layer model of a central-pattern generator distributed longitudinally along the spinal cord qualitatively reproduce the sinusoidal traveling waves, and are able to replicate both classes of deletions. We believe these findings shed light into the longitudinal organization of the central-pattern generator networks in the spinal cord.This work was supported by the following grants: Consejo Nacional de Ciencia y Tecnología (CONACyT) under project F1-62610 (E.M.), Vicerrectoria de Investigación y Estudios de Posgrado-Benemérita Universidad Autónoma de Puebla (VIEP-BUAP-00070) (E.M.), and Programa Integral de Fortalecimiento Institucional under projects 2008– 2009 (E.M.), Mexico; Spanish Ministerio de Educación y Ciencia and Feder under projects FIS2007-60327 (C.M., T.P.) and FIS2006-11452 (J.G.O.); and the European Community under Global Approach to Brain Activity FP6-NEST-043309 project (C.M., J.G.O.). T.P. acknowledges support from Govern Balear. J.A.T. and C.A.C. acknowledge support from CONACyT Mexico.Peer reviewe

Modeling zero-lag synchronization of dorsal horn neurons during the traveling of electrical waves in the cat spinal cord

The first electrophysiological evidence of the phenomenon of traveling electrical waves produced by populations of interneurons within the spinal cord was reported by our interdisciplinary research group. Two interesting observations derive from this study: first, the negative spontaneous cord dorsum potentials (CDPs) that are superimposed on the propagating sinusoidal electrical waves are not correlated with any scratching phase; second, these CDPs do not propagate along the lumbosacral spinal segments, but they appear almost simultaneously at different spinal segments. The aim of this study was to provide experimental data and a mathematical model to explain the simultaneous occurrence of traveling waves and the zero¿lag synchronization of some CDPs.This work was supported by the following grants: FIS2007‐60327 (FISICOS) and FIS2012‐30634 (Intense@cosyp) from MICINN (Spain) and FEDER, Grups Competitius, Comunitat Autónoma de les Illes Balears, Spain, PIFI‐VIEP‐CONACyT‐153583, and Cátedra Moshinsky (E. M.), México.Peer Reviewe

Ghost resonance in a pool of heterogeneous neurons

7 pages.-- Final full-text version of the paper available at: http://dx.doi.org/10.1016/j.biosystems.2006.04.014.We numerically study the subharmonic response of a heterogeneous pool of neurons to a pair of independent inputs. The neurons are stimulated with periodic pulse trains of frequencies f1 = 2 Hz and f2 = 3 Hz, and with inharmonic pulses whose frequencies f1 and f2 are equally shifted an amount Δf. When both inputs are subthreshold, we find that the neurons respond at a frequency equal to f2−f1 in the harmonic situation (Δf = 0), that increases linearly with Δf in the inharmonic case. Thus the neurons detect a frequency not present in the input; this effect is termed "ghost resonance". When one of the inputs is slightly suprathreshold the ghost resonance persists, but responses related with the frequency of the suprathreshold input also emerge. This behavior must be taken into account in experimental studies of signal integration and coincidence detection by neuronal pools.Financial support has been provided by Ministerio de Educación y Ciencia (Spain) and FEDER through projects BFM2003-07850 and FIS2004-00953, and ORDEN by the Generalitat de Catalunya. P.B. is a member of "Carrera de Conicet", Argentina, and was supported by a fellowship C-RED of the Generalitat de Catalunya

Ghost resonance in a pool of heterogeneous neurons

7 pages.-- Final full-text version of the paper available at: http://dx.doi.org/10.1016/j.biosystems.2006.04.014.We numerically study the subharmonic response of a heterogeneous pool of neurons to a pair of independent inputs. The neurons are stimulated with periodic pulse trains of frequencies f1 = 2 Hz and f2 = 3 Hz, and with inharmonic pulses whose frequencies f1 and f2 are equally shifted an amount Δf. When both inputs are subthreshold, we find that the neurons respond at a frequency equal to f2−f1 in the harmonic situation (Δf = 0), that increases linearly with Δf in the inharmonic case. Thus the neurons detect a frequency not present in the input; this effect is termed "ghost resonance". When one of the inputs is slightly suprathreshold the ghost resonance persists, but responses related with the frequency of the suprathreshold input also emerge. This behavior must be taken into account in experimental studies of signal integration and coincidence detection by neuronal pools.Financial support has been provided by Ministerio de Educación y Ciencia (Spain) and FEDER through projects BFM2003-07850 and FIS2004-00953, and ORDEN by the Generalitat de Catalunya. P.B. is a member of "Carrera de Conicet", Argentina, and was supported by a fellowship C-RED of the Generalitat de Catalunya

Phantom reflexes: Muscle contractions at a frequency not physically present in the input stimuli

Final full-text version of the paper available at: http://dx.doi.org/10.1016/j.biosystems.2006.10.002.In the motor system, the periodic stimulation of one Ia-afferent input produces reflex muscle contractions at the input frequency. However, we observed that when two Ia monosynaptic reflex-afferent inputs are involved the periodic muscle contractions may occur at a frequency physically not present in the afferent inputs even when these inputs are sub-threshold. How can the muscles respond with such phantom reflex contractions at a frequency physically absent in the sub-threshold Ia-afferent input stimuli? Here we provide an explanation for this phenomenon in the cat spinal cord, that we termed “ghost motor response”. We recorded monosynaptic reflexes in the L7 ventral root, intracellular potentials in the motoneurons, and the associated muscular contractions elicited by stimulation of the lateral and medial gastrocnemius nerves. By stimulating with periodic pulses of sub-threshold intensities and distinct frequencies of 2 and 3 Hz the lateral and medial gastrocnemius nerves, respectively, we observed monosynaptic responses and phantom reflex muscle contractions occurring at the fundamental frequency (1 Hz), which was absent in the input stimuli. Thus we observed a reflex ghost motor response at a frequency not physically present in the inputs. We additionally studied the inharmonic case for sub-threshold stimuli and observed muscular contractions occurring at much lower frequencies, which were also conspicuously absent in the inputs. This is the first experimental evidence of a phantom reflex response in the nervous system. The observed behavior was modeled by numerical simulations of a pool of neurons subjected to two different input pulses.This work was partly supported by the following grants: CONACyT J36062-N (E.M), Fondo-Ricardo J. Zevada (A.F) and FOMES-BUAP, México; MEC (Spain) and Feder projects BFM2003-07850 and FIS2004-00953, and Generalitat de Catalunya

Absence of Neuroplastic Changes in the Bilateral H-Reflex Amplitude following Spinal Manipulation with Activator IV

Background and Objectives: Chiropractic spinal manipulation is an alternative medical procedure for treating various spinal dysfunctions. Great interest exists in investigating its neuroplastic effects on the central nervous system. Previous studies have found contradictory results in relation to the neuroplastic changes in the H-reflex amplitude as a response to manual spinal manipulation. The discrepancies could be partly due to differences in the unilateral nature of these recordings and/or the variable force exerted in manual techniques applied by distinct chiropractors. Concerning the latter point, the variability in the performance of manual interventions may bias the determination of the significance of changes in H-reflex responses derived from spinal manipulation. To investigate such responses, a chiropractic device can be used to provide more precise and reproducible results. The current contribution aimed to examine whether spinal manipulation with an Activator IV instrument generates neuroplastic effects on the bilateral H-reflex amplitude in dancers and non-dancers. Materials and Methods: A radiograph verified spinal dysfunction in both groups of participants. Since there were significant differences between groups in the mean Hmax values of the H-reflex amplitude before spinal intervention, an assessment was made of the possible dependence of the effects of spinal manipulation with Activator IV on the basal conditions. Results: Ten sessions of spinal manipulation with Activator IV did not cause statistically significant changes in the bilateral H-reflex amplitude (measured as the Hmax/Mmax ratio) in either group. Furthermore, no significant difference was detected in the effects of spinal manipulation between groups, despite their distinct basal H-reflex amplitude. Conclusions: Regarding the therapeutic benefits of a chiropractic adjustment, herein carried out with Activator IV, the present findings suggest that the mechanism of action is not on the monosynaptic H-reflex pathway. Further research is needed to understand the mechanisms involved