Modelado circuital multimodal de un resonador pasobanda reconfigurable

In this work, we present a simple uniplanar bandpass resonator that can be used for the development of reconfigurable uniplanar filters. The multimodal behaviour of the coplanar waveguide is taken into account for the design of the resonator. We show that a simple multimodal model can be used to represent the proposed structure. Experimental measurements validate the accuracy of the proposed model.Postprint (published version

Unidirectional Neuronal Cell growth and Differentiation on Aligned Polyhydroxyalkanoate Blend Microfibres with Varying Diameters

Polyhydroxyalkanoates (PHAs) are a family of prokaryotic-derived biodegradable and biocompatible natural polymers known to exhibit neuroregenerative properties. In this work, poly(3-hydroxybutyrate), P(3HB) and poly(3-hydroxyoctanoate), P(3HO), have been combined to form blend fibres for directional guidance of neuronal cell growth and differentiation. A 25:75 P(3HO)/P(3HB) blend (PHA blend) was used for the manufacturing of electrospun fibres as resorbable scaffolds to be used as internal guidance lumen structures in nerve conduits. The biocompatibility of these fibres was studied using neuronal and Schwann cells. Highly aligned and uniform fibres with varying diameters were fabricated by controlling electrospinning parameters. The resulting fibre diameters were 2.4 ± 0.3 µm, 3.7 ± 0.3 µm and 13.5 ± 2.3 µm for small, medium and large diameter fibres respectively. The cell response to these electrospun fibres was investigated with respect to growth and differentiation. Cell migration observed on the electrospun fibres showed topographical guidance in accordance with the direction of the fibres. The correlation between fibre diameter and neuronal growth under two conditions; individually and in co-culture with Schwann cells was evaluated. Results obtained from both assays revealed that all PHA blend fibre groups were able to support growth and guide aligned distribution of neuronal cells and there was a direct correlation between the fibre diameter and neuronal growth and differentiation. This work has led to the development of a family of unique biodegradable and highly biocompatible 3D substrates capable of guiding and facilitating the growth, proliferation and differentiation of neuronal cells as internal structures within nerve conduits

Site Fidelity and Residency of Tursiops truncatus off the Aragua Coast, Venezuela-First Records of Long Residency

This study represents the first comprehensive analysis of the residency patterns of a coastal population of bottlenose dolphin off the coast of Aragua, Venezuela, over a multi-year period. Using photo-identification, the most recent study (2019-2020) identified 56 individuals with the time between encounters from one to 344 days between the first and last sighting. Site Fidelity (SF) and Residence (RES) indices were calculated and Agglomerative Hierarchical Clustering (AHC) modeling was performed, with three patterns of residence obtained: resident (25%), semiresident (17.86%) and transient (57.14%). These results were contrasted with remodeled data from a previous study (2006-2007), showing similar patterns: resident (24.44%), semi-resident (28.89%) and transient (46.67%). Importantly, two individuals were found to have been resident over the extended period. A breeding female sighted for the first time in 2004 and again in 2020 (16 years) and the other from 2005 to 2020 (15 years). This region is an important area for marine mammals, known to support a resident reproductive population over many years, as well seabirds, sea turtles, whale sharks and fishermen. We recommend that consideration be given to designating the waters as a Marine Protected Area to safeguard the existing population and provide benefit to the surrounding marine environment

Nerve tissue engineering using blends of poly(3-hydroxyalkanoates) for peripheral nerve regeneration

The only types of polyhydroxyalkanoates (PHAs) that have been explored for use in nerve regeneration are poly(3‐hydroxybutyrate), P(3HB), and poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (P(3HB‐co‐3HHx)). However, nerve regeneration induced by these PHAs is inferior to that of autologous nerve grafting. The aim of this work was to study novel PHA blends as resorbable biomaterials for the manufacture of nerve guidance conduits. PHA blend films with varying ratios of poly(3‐hydroxyoctanoate)/poly(3‐hydroxybutyrate) (P(3HO)/P(3HB)) were produced using the solvent‐casting method. Neat films of P(3HO) and P(3HB), along with 25:75, 50:50, and 75:25 blend films of P(3HO)/P(3HB), were characterized with respect to chemical, material, and biological properties. On surface analysis, the blends exhibited higher values of roughness compared with the neat films. The differential scanning calorimetry characterization of the blends confirmed that P(3HO) and P(3HB) formed immiscible blends. FTIR and XRD analysis of the blends showed a decrease in crystallinity along with an increase of the proportion of P(3HO) . However, an increase in the stiffness of the blends was observed when the proportion of P(3HB) increased. Although all of the blends were biocompatible with NG108‐15 neuronal cells, the 25:75 P(3HO)/P(3HB) blend showed significantly better support for growth and differentiation of these cells. The mechanical properties of PHA blends correspond to the reported properties of peripheral nerves. Therefore, they could serve as base material for the manufacture of nerve guidance conduits

Preclinical study of peripheral nerve regeneration using nerve guidance conduits based on polyhydroxyalkanaotes

Nerve guidance conduits (NGCs) are used as an alternative to the “gold standard” nerve autografting, preventing the need for surgical intervention required to harvest autologous nerves. However, the regeneration outcomes achieved with the current NGCs are only comparable with autografting when the gap is short (less than 10 mm). In the present study, we have developed NGCs made from a blend of Polyhydroxyalkanoates, a family of natural resorbable polymers. Hollow NGCs made from a 75:25 Poly(3‐hydroxyoctanoate)/Poly(3‐hydroxybutyrate) blend (PHA‐NGCs) were manufactured using dip‐moulding. These PHA‐NGCs showed appropriate flexibility for peripheral nerve regeneration. In vitro cell studies performed using RT4‐D6P2T rat Schwann cell line confirmed that the material is capable of sustaining cell proliferation and adhesion. PHA‐NGCs were then implanted in vivo to repair 10 mm gaps of the median nerve of female Wistar rats for 12 weeks. Functional evaluation of the regenerated nerve using the grasping test showed that PHA‐NGCs displayed similar motor recovery as the autograft, starting from week 7. Additionally, nerve cross‐sectional area, density and number of myelinated cells, as well as axon diameter, fibre diameter, myelin thickness and g‐ratio obtained using the PHA‐NGCs were found comparable to an autograft. This preclinical data confirmed that the PHA‐NGCs are indeed highly promising candidates for peripheral nerve regeneration

Vesicular-arbuscular mycorrhizal, dark septate endophytes and root anatomy in Fragaria ananassa var. Camino Real (Rosaceae) in the province of Tucumán, Argentina

En la provincia de Tucumán el cultivo de frutilla ocupa una superficie de 350 hectáreas. El mismo es invernal, con cosechas periódicas de fines de mayo a noviembre inclusive. Para evitar esta discontinuidad de producción, se incorporan al espectro de variedades precoces (Fortuna y Festival), variedades tardías, entre ellas Camino Real. Los objetivos de este trabajo fueron estudiar las micorrizas vesículo-arbusculares, los endófitos septados oscuros y caracterizar la anatomía radical en Fragaria ananassa var. Camino Real en cultivo comercial en la provincia de Tucumán. El muestreo fue realizado en el INTA-EEA Famaillá, Tucumán, Argentina. Se recolectaron los sistemas radicales correspondientes a un total de 20 individuos; los que fueron tratados con técnicas convencionales. Los sistemas radicales de la variedad Camino Real presentan las células del parénquima cortical colonizadas por micorrizas vesículo-arbusculares con dos tipos morfológicos simultáneos: Arum y Paris, siendo la morfología Arum la de mayor frecuencia. Además, el tejido cortical presenta endófitos septados oscuros. La anatomía radical de la estructura primaria presenta una histología típica con estelas de tipo diarca a tetrarca. Mientras que la estructura secundaria de la raíz muestra diferentes estadios de crecimiento, con restos de epidermis y parénquima cortical adheridos a la polidermis en formación. Se describen por primera vez, para Argentina, las micorrizas vesículoarbusculares, los endófitos septados oscuros y la anatomía radical en Fragaria ananassa var. Camino Real.In the province of Tucumán strawberry cultivation occupies an area of 350 hectares. It is a winter crop, with periodic harvests since late May to November inclusive. To avoid this discontinuity of production, a late variety (Camino Real) was added to the spectrum of early varieties (Fortuna and Festival). This paper aims to evaluate the vesicular-arbuscular mycorrhiza, dark septate endophytes and characterize the radical anatomy in Fragaria ananassa variety Camino Real in the province of Tucumán. The sampling was carried out at INTA-EEA Famaillá, Tucumán, Argentina. The radicals systems corresponding to 20 individuals were collected and treated with conventional techniques. The root systems of the variety Camino Real, show cortical parenchyma cells colonized by vesicular-arbuscular mycorrhizae which have two simultaneous morphological types: Arum and Paris. The Arum morphology is the most frequent. In addition, the cortical tissue has dark septate endophytes. The radical anatomy of the primary structure presents a typical histology with diarca to tetrarch stela, while the secondary root structure show different stages of growth with traces of epidermis and cortical parenchyma attached to the polidermis in development. The vesicular-arbuscular mycorrhizae, dark septate endophytes and radical anatomy of Fragaria ananassa var. ‘Camino Real’ were described for the first time for ArgentinaFil: Lizarraga, Sofía Valentina. Fundación Miguel Lillo; ArgentinaFil: Ruiz, A. I.. Fundación Miguel Lillo; ArgentinaFil: Salazar, Sergio Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Diaz Ricci, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Albornoz, Patricia Liliana. Fundación Miguel Lillo; Argentin

RF-MEMS switches for a full control of the propagating modes in uniplanar microwave circuits and their application to reconfigurable multimodal microwave filters

This is a copy of the author 's final draft version of an article published in the journal Microsystem technologies. The final publication is available at Springer via http://dx.doi.org/10.1007/s00542-017-3379-8In this paper, new RF-MEMS switch configurations are proposed to enable control of the propagating (even and odd) modes in multimodal CPW transmission structures. Specifically, a switchable air bridge (a switchable short-circuit for the CPW odd mode) and switchable asymmetric shunt impedances (for transferring energy between modes) are studied and implemented using bridge-type and cantilever-type ohmic-contact switches, respectively. The switchable air bridge is based in a novel double ohmic-contact bridge-type structure. Optimized-shape suspension configurations, namely folded-beam or diagonal-beam for bridge-type switches, and straight-shaped or semicircular-shaped for cantilever-type switches, are used to obtain robust structures against fabrication-stress gradients. The switches are modelled using a coupled-field 3D finite-element mechanical analysis showing a low to moderate pull-in voltage. The fabricated switches are experimentally characterized using S-parameter and DC measurements. The measured pull-in voltages agree well with the simulated values. From S-parameter measurements, an electrical model with a very good agreement for both switch states (ON and OFF) has been obtained. The model is used in the design of reconfigurable CPW multimodal microwave filters.Peer ReviewedPostprint (author's final draft