Isoperimetric Regions on a Weighted 2-Dimensional Lattice

We investigate isoperimetric regions in the 1st quadrant of the 2- dimensional lattice, where each point is weighted by the sum of its coordinates. We analyze the isoperimetric properties of six types of regions located in the first quadrant of the Cartesia

La contribución de los sirios al crecimiento económico kurdo

Ahora mismo se dan en la región kurda de Irak las circunstancias para que se lleve a cabo satisfactoriamente un programa de integración laboral para los refugiados, de manera que contribuyan con la economía local

Hearing outcome following ?-knife treatment of vestibular schwannomas: A series of 33 cases

Due to the progress in neuro-imaging vestibular schwannomas (benign tumors rooting from Scwann cells of vestibular nerve) witness an increase in incidence in the last decade. Despite the advances in operating techniques and intraoperative technologies used surgery still presents a rate of morbidity and mortality. Gamma-Knife became a therapeutic alternative for selected cases of vestibular schwannomas. However, the results of gamma-knife radiosurgery showed an influence on the audiograms of the patientstreated with this technique. The goal of our study is to assess the measure in which gamma-knife treatment influences the neuro-otologic behavior of these tumors. We study a series of the 33 consecutive cases which completed a 24 months follow-up after gamma-knife treatment. We use a neuroimagistic and neuro-otologic protocol aproved by our institution.24 patients didn’t show a deterioration of the audiogram. Among these 11 report an unmodified hearing function, while 11 describe an improvement in hearing (we excluded the cases with complete hearing loss. We manage to show that strictly following the patient selection criteria for gamma-knife treatment, radiosurgery is a safe treatment option for the patients with small to medium-sized vestibular scwannomas

Imaging of vestibular schwannomas following ?-knife treatment: A series of 79 cases

Gamma-Knife became an established therapeutic alternative for selected cases of vestibular schwannomas (benign tumors rooting from Scwann cells of vestibular nerve). However, the long term results and effects on the tumor and surrounding brain are still a matter of research. We analyze the imagistic findings in the patients with vestibular scwannomas treated with gamma-knife radiosurgery in the Gamma-Knife Department, Hygeia Hospital, Athens. We performed radiosurgery on 79 cases of vestibular scwannomas. 23 of them were first operated with incomplete resection and had gamma-knife performed on residual tumor. Of all cases, one patient died 4 years after the treatment, while 4 cases didn’t comply with the follow-up protocol and were excluded from the study. The other cases underwent a follow-up protocol with MRI sudies at 6, 12, 18, and 24 months following the gamma-knife session. We looked at the tumoral volume, and the evolution of the tumor in relationship with the iradiation dise and isodose curve. Our results confirm the landmark results of Karolinska an Pittsburg studies. We show that small gamma-knife doses are suitable for a satisfactory control of tumoral volume. Stereotactic MRI imaging and multiple doses programs are the main factors contributing to these results

Curing Pressure Influence of Out-of-Autoclave Processing on Structural Composites for Commercial Aviation

Autoclaving is a process that ensures the highest quality of carbon fiber reinforced polymer (CFRP) composite structures used in aviation. During the autoclave process, consolidation of prepreg laminas through simultaneous elevated pressure and temperature results in a uniform high-end material system. This work focuses on analyzing in a fundamental way the applications of pressure and temperature separately during prepreg consolidation. A controlled pressure vessel (press-clave) has been designed that applies pressure during the curing process while the temperature is being applied locally by heat blankets. This vessel gives the ability to design manufacturing processes with different pressures while applying temperature at desired regions of the composite. The pressure role on the curing extent and its effect on the interlayer region are also tested in order to evaluate the consolidation of prepregs to a completely uniform material. Such studies may also be used to provide insight into the morphology of interlayer reinforcement concepts, which are widely used in the featherweight composites. Specimens manufactured by press-clave, which separates pressure from heat, are analytically tested and compared to autoclaved specimens in order to demonstrate the suitability of the press-clave to manufacture high-quality composites with excessively reduced cost

Electrical conductivity and Raman imaging of double wall carbon nanotubes in a polymer matrix

Raman spectroscopy is used to access the dispersion state of DWNTs in a PEEK polymer matrix. The interaction of the outer tube with the matrix can be determined from the line shape of the Raman G band. This allows us to distinguish regions where the nanotubes are well dispersed and regions where the nanotubes are agglomerated. The percolation threshold of the electrical conductivity of the double wall carbon nanotubes (DWNTs)/PEEK nanocomposites is found to be at 0.2–0.3 wt.%. We find a maximum electrical conductivity of 3 x 10-2 S/cm at 2 wt.% loading. We detect nanotube weight concentrations as low as 0.16 wt.% by Raman spectroscopy using a yellow excitation wavelength. We compare the Raman images with transmission electron microscopy images and electrical conductivity measurements. A statistical method is used to find a quantitative measure of the DWNTs dispersion in the polymer matrix from the Raman images