Search

Carbon nanotubes oxidation has attracted the interest of researchers, because in addition to eliminating impurities, it increases the dispersion of aggregates creating new interac­tions between materials. In this work, carbon nanotubes (CNT) were treated using two dif­ferent oxidation methods to determine the effects of each treatment on the surface area of the material. The following methods were used: the traditional chemical treatment (using strong acids) and a treatment supported by microwaves. Results showed that both treat­ments reduced the surface area (traditional CNT < microwaves CNT < non-treated CNT). By using microwaves, oxidation time was shortened, greater concentration of carboxylic func­tional groups was obtained and damage to the structure diminished, resulting in oxidized nanotubes with improved structural characteristics. La oxidación de los nanotubos de carbono, ha generado gran interés porque además de eliminar impurezas, aumenta el grado de dispersión de los agregados y logra nuevas in­teracciones entre los materiales. En este trabajo, nanotubos de carbono (NTC) fueron tra­tados con diferentes métodos de oxidación para conocer la modificación superficial que cada tratamiento efectúa en la estructura del material. Los métodos contrastados fueron el tratamiento químico tradicional (mediante ácidos fuertes) y el tratamiento asistido por microondas. Los resultados mostraron que ambos tratamientos disminuyen el área super­ficial (NTC tradicional < NTC microondas < NTC sin tratamiento). Utilizando microondas, se redujo el tiempo de oxidación, se obtuvo una mayor concentración de grupos funcionales carboxílicos y se disminuyó el daño en la estructura con lo que se obtienen nanotubos oxi­dados con mejores características estructurales.

The aim of this work is to evaluate and compare the radiographic results and complications of the surgical treatment of adolescents with idiopathic scoliosis greater than 75 degrees, using a double approach (DA) or an isolated posterior approach with hybrid instruments (posterior hybrid [PH]), or with «all-pedicle screws» (posterior screws [PS]).A retrospective review was performed on 69 patients with idiopathic scoliosis greater than 75°, with a follow-up of more than 2 years, to analyze the flexibility of the curves, the correction obtained, and the complications depending on the type of surgery. The Kruskal-Wallis test for non-parametric variables was used for the statistical analysis.There were no statistically significant differences between the 3 patient groups in the pre-surgical Cobb angle values (DA=89°, PH=83°, PS=83°), in the immediate post-surgical (DA=34°, PH=33°, PS=30°), nor at the end of follow-up (DA=36°, PH=36°, PS=33°) (P.05). The percentage correction (DA=60%, PH=57%, PS=60%) was similar between groups (P.05). The percentage of complications associated with the procedure was 20.8% in DA, 10% in PH and 20% in PS. Two patients in the PS group showed changes, with no neurological lesions, in the spinal cord monitoring, and one patient in the same group suffered a delayed and transient incomplete lesion.No significant differences were observed in the correction of severe idiopathic scoliosis between patients operated using the double or isolated posterior approach, regardless of the type of instrumentation used.

To create an experimental structural scoliosis model in mice to evaluate the efficacy of shape-memory metals to gradually correct the deformity over time.Experimental scoliosis was generated in 3 week-old mice by means of a suture between the left scapula and pelvis for 8 weeks. They were then randomised into two groups: a control group, in which the suture was cut, and another, in those that also had a Nitinol straight memory-wire implant fixed to the column. Serial X-rays were performed to determine the efficacy of the Nitinol in the correction of the scoliosis. In a second time, the histological changes at apical vertical body level and the adjacent discs were evaluated pre- and post-correction.A mean 81.5° kyphoscoliosis was gradually induced. In the control group, after cutting the suture, an initial reduction in the deformity was observed, but later it remained stable throughout the time (54° at two weeks). In the Nitinol group, a gradual reduction was observed in the scoliosis angle value, to a mean of 8.7° at two weeks. The curvature of the apical vertebral body and adjacent discs were partially corrected after two weeks of correcting the deformity.This scoliosis model has demonstrated the efficacy of a straight Nitinol wire fixed to the spinal column in the gradual correction of kyphoscoliosis and in the changes in its adjacent structures.

La oxidación de los nanotubos de carbono, ha generado gran interés porque además de eliminar impurezas, aumenta el grado de dispersión de los agregados y logra nuevas in­teracciones entre los materiales. En este trabajo, nanotubos de carbono (NTC) fueron tra­tados con diferentes métodos de oxidación para conocer la modificación superficial que cada tratamiento efectúa en la estructura del material. Los métodos contrastados fueron el tratamiento químico tradicional (mediante ácidos fuertes) y el tratamiento asistido por microondas. Los resultados mostraron que ambos tratamientos disminuyen el área super­ficial (NTC tradicional < NTC microondas < NTC sin tratamiento). Utilizando microondas, se redujo el tiempo de oxidación, se obtuvo una mayor concentración de grupos funcionales carboxílicos y se disminuyó el daño en la estructura con lo que se obtienen nanotubos oxi­dados con mejores características estructurales.

To determine the efficacy of growing rods in the treatment of early onset scoliosis.A total of 32 patients were treated using fusion techniques that included double growing rods and Vertical Expandable Prosthetic Titanium Ribs (VEPTR), in our Early Onset Scoliosis Centre between 2004 and 2011. After analysing the clinical histories and x-rays, 20 patients were included due to meeting the inclusion criteria. All patients had previously received conservative treatment with cranial traction and a series of plasters/corsets. The deformity was analysed before and after the initial surgery, and in successive tightenings, using the x-rays of the coronal and sagittal planes by means of the Cobb angle, as well as the longitudinal and coronal growth of the thorax, and the growth of the spinal column. A series of 188 x-rays of 53 patients with cystic fibrosis were studied in order to perform a comparative analysis with the patients with early-onset scoliosis.There was significant improvement in the angle (Cobb and kyphosis) and linear parameters (T1-S1 distance, T1-T12 distance, and coronal width of the thorax) after the initial surgery, but the successive tightenings had a minimal beneficial effect, losing effectiveness over a period of time. The patients with early-onset scoliosis showed a lower growth of the thorax compared to the patients with cystic fibrosis.Treatment of early-onset scoliosis with expandable devices is mainly beneficial with the initial procedure and the first tightenings, but shows a loss of efficacy over a period time.

In this paper, the influence of bypasses in heat exchanger networks on theoretical control properties and closed-loop behavior was investigated. According to theoretical control properties obtained using the singular value decomposition technique, the presence of bypasses increases flexibility of the heat exchanger network. This result was corroborated using closed-loop dynamic simulations using a proportional integral controller and a proportional integral controller with dynamic estimation of uncertainties. The heat exchanger network including bypasses outperformed the dynamic behavior of the heat exchanger network without bypasses. Moreover, closed-loop dynamic responses were improved significantly using controllers with dynamic estimation of uncertainties.