Terahertz epsilon-near-zero graded-index lens

An epsilon-near-zero graded-index converging lens with planar faces is proposed and analyzed. Each perfectly-electric conducting (PEC) waveguide comprising the lens operates slightly above its cut-off frequency and has the same length but different cross-sectional dimensions. This allows controlling individually the propagation constant and the normalized characteristic impedance of each waveguide for the desired phase front at the lens output while Fresnel reflection losses are minimized. A complete theoretical analysis based on the waveguide theory and Fermat’s principle is provided. This is complemented with numerical simulation results of two-dimensional and three-dimensional lenses, made of PEC and aluminum, respectively, and working in the terahertz regime, which show good agreement with the analytical work.Effort sponsored by Spanish Government under contracts Consolider “Engineering Metamaterials” CSD2008-00066 and TEC2011-28664-C02-01. P.R.-U. is sponsored by the Government of Navarra under funding program “Formación de tecnólogos” 055/01/11. M.N.- C. is supported by the Imperial College Junior Research Fellowship. M. B. acknowledges funding by the Spanish Government under the research contract program Ramon y Cajal RYC-2011-08221. N.E. acknowledges the support from the US Office of Naval Research (ONR) Multidisciplinary University Research Initiatives (MURI) grant number N00014-10-1- 0942

Comparison of different constitutive models to characterize the viscoelastic properties of human abdominal adipose tissue. A pilot study

Knowing the mechanical properties of human adipose tissue is key to simulate surgeries such as liposuction, mammoplasty and many plastic surgeries in which the subcutaneous fat is present. One of the most important surgeries, for its incidence, is the breast reconstruction surgery that follows a mastectomy. In this case, achieving a deformed shape similar to the healthy breast is crucial. The reconstruction is most commonly made using autologous tissue, taken from the patient's abdomen. The amount of autologous tissue and its mechanical properties have a strong influence on the shape of the reconstructed breast. In this work, the viscoelastic mechanical properties of the human adipose tissue have been studied. Uniaxial compression stress relaxation tests were performed in adipose tissue specimens extracted from the human abdomen. Two different viscoelastic models were used to fit to the experimental tests: a quasi-linear viscoelastic (QLV) model and an internal variables viscoelastic (IVV) model; each one with four different hyperelastic strain energy density functions to characterise the elastic response: a 5-terms polynomial function, a first order Ogden function, an isotropic Gasser-Ogden-Holzapfel function and a combination of a neoHookean and an exponential function. The IVV model with the Ogden function was the best combination to fit the experimental tests. The viscoelastic properties are not important in the simulation of the static deformed shape of the breast, but they are needed in a relaxation test performed under finite strain rate, particularly, to derive the long-term behaviour (as time tends to infinity), needed to estimate the static deformed shape of the breast. The so obtained stiffness was compared with previous results given in the literature for adipose tissue of different regions, which exhibited a wide dispersion.Ministerio de Economía y Competitividad DPI2011-2808

Self-assessed Contrast-Maximizing Adaptive Region Growing

In the context of an experimental virtual-reality surgical planning software platform, we propose a fully self-assessed adaptive region growing segmentation algorithm. Our method successfully delineates main tissues relevant to head and neck reconstructive surgery, such as skin, fat, muscle/organs, and bone. We rely on a standardized and self-assessed region-based approach to deal with a great variety of imaging conditions with minimal user intervention, as only a single-seed selection stage is required. The detection of the optimal parameters is managed internally using a measure of the varying contrast of the growing regions. Validation based on synthetic images, as well as truly-delineated real CT volumes, is provided for the reader’s evaluation

Fast parameter-free region growing segmentation with application to surgical planning

In this paper, we propose a self-assessed adaptive region growing segmentation algorithm. In the context of an experimental virtual-reality surgical planning software platform, our method successfully delineates main tissues relevant for reconstructive surgery, such as fat, muscle, and bone. We rely on a self-tuning approach to deal with a great variety of imaging conditions requiring limited user intervention (one seed). The detection of the optimal parameters is managed internally using a measure of the varying contrast of the growing region, and the stopping criterion is adapted to the noise level in the dataset thanks to the sampling strategy used for the assessment function. Sampling is referred to the statistics of a neighborhood around the seed(s), so that the sampling period becomes greater when images are noisier, resulting in the acquisition of a lower frequency version of the contrast function. Validation is provided for synthetic images, as well as real CT datasets. For the CT test images, validation is referred to manual delineations for 10 cases and to subjective assessment for another 35. High values of sensitivity and specificity, as well as Dice’s coefficient and Jaccard’s index on one hand, and satisfactory subjective evaluation on the other hand, prove the robustness of our contrast-based measure, even suggesting suitability for calibration of other region-based segmentation algorithms

Comparison of the viscoelastic properties of human abdominal and breast adipose tissue and its incidence on breast reconstruction surgery. A pilot study

Background: Breast cancer is the leading malignant tumor in women in the world. Reconstruction after mastectomy plays a key role in the physical and psychological recuperation, being the abdominal skin and adipose tissue the best current option for the DIEP surgery. The aim of the surgery is to obtain a reconstructed breast which looks and behaves naturally. Therefore, it would be useful to characterize the mechanical behaviour of the adipose tissue in the abdomen and breast to compare their mechanical properties, also investigating possible regional differences. Methods: Experimental tests have been carried out in breast and abdominal adipose tissue samples, obtaining their viscoelastic properties. The specimens have been subjected to uniaxial compression relaxation tests and a mechanical behaviour model has been fitted to the experimental curves. Afterwards, statistical analyses have been used to detect differences between different individuals' abdominal fat tissue and finally between different areas of the same individual's breast and abdominal adipose tissue. Findings: Several conclusions could be extracted from the results: 1) inter-individual differences may exist in the abdominal adipose tissue; 2) the breast fat could be regarded as a unique tissue from the mechanical point of view; 3) significant differences were detected between the superficial breast and all the locations of the abdomen, except for the superficial lateral one and 4) the mechanical properties of the abdominal adipose tissue seem to change with the depth. These conclusions can be of great value for DIEP surgeries and other surgeries in which the adipose tissue is involved.Ministerio de Economía y Competitividad DPI2011-2808

Color analysis of the reconstructed complex nipple-areola after a mastectomy

In this paper a colour analysis of the reconstructed NAC (nipple-areola complex) after a mastectomy is performed. First, a colour segmentation algorithm based on the Live Wire method is proposed to separate the NAC from the rest of skin. And then the colour differences between the healthy and the reconstructed NAC are measured using colour-difference formulas recommended in CIE: CIELAB, CIE94 and CIEDE2000. The application domain is analyzing how the NAC is modified after applying a new reconstructed technique of areola-nipple complex, grafted after its cryopreservation. The analysis has been performed for 20 images, and good segmentation results have been obtained and quantitative colour difference in accordance with perceptual colour difference has been obtained

Evolución de los factores de riesgo cardiovascular a los 15 años de seguimiento de una cohorte de jóvenes sanos

Se trata de una análisis longitudinal de cohortes, llevada cabo con una muestra de valores estudiada hace 15 años, cuando contaban con una media de edad de 19,84 años. En la actualidad se ha realizado una nueva encuesta transversal, siendo la media actual de los sujetos de 35,48. Los parámetros analizados son: antropométricos, de presión arterial, hábito tabáquico y parámetros lipídicos. Tras llevar a cabo el análisis estadístico, se ha observado un incremento cuantitativo del hábito tabáquico con el paso del tiempo y un empeoramiento en las variables lipídicas. El incremento del peso y el índice de masa corporal de los sujetos estudiados durante estos 15 años, ha sido superior al esperado, habiendo condicionado, en gran parte, el deterioro lipídico. Se ha realizado la estimación del riesgo coronario de la cohorte estudiada, basándonos en la ecuación de riesgo de Framingham, calculando una probabilidad de riesgo de 11,83 % para la edad de 60 años

Traduccions Theodor W. Adorno: Notas musicales (Graeculus)

Abstract not availabl