Pressure screening in the interior of primary shells in double-wall carbon nanotubes

The pressure response of double-wall carbon nanotubes has been investigated by means of Raman spectroscopy up to 10 GPa. The intensity of the radial breathing modes of the outer tubes decreases rapidly but remain observable up to 9 GPa, exhibiting a behavior similar (but less pronounced) to that of single-wall carbon nanotubes, which undergo a shape distortion at higher pressures. In addition, the tangential band of the external tubes broadens and decreases in amplitude. The corresponding Raman features of the internal tubes appear to be considerably less sensitive to pressure. All findings lead to the conclusion that the outer tubes act as a protection shield for the inner tubes whereas the latter increase the structural stability of the outer tubes upon pressure application.Comment: PDF with 15 pages, 3 figures, 1 table; submitted to Physical Review

Landscape planning to achieve sustainability : the Iztacci�huatl-Popocate�petl region, Mexico, case study

The overall goal of this thesis is to investigate the applicability of a landscape planning methodology that is founded on an ecosystem-based approach and focused on the delineation of ecologically sensitive areas. Its design is concerned with an ecosystem-based management approach as part of a broader landscape planning process that is intended to achieve environmental sustainability objectives; the key idea is that an ecosystem/landscape scale may well be the most important for the attainment of sustainability. Considering this, this research supports the idea that the employment of a network of watershed-ecosystem units provides an appropriate framework for planning towards sustainability at the landscape scale. In addition, the design of this methodology also gives room to solve theoretical and practical problems. The main theoretical problem is related to the generation of overall schemes that are consistent with holistic-multidimensional viewpoints about patterns and processes in landscapes. On the other hand, two practical problems are also confronted: the need to employ ecological principles and spatial concepts in landscape planning and the development of strategies to define and delineate areas of interest to planners. In this research this point is focused on the delineation of ecologically sensitive areas. In order to test the application of the planning methodology to a real-life context, the Iztaccihuatl-Popocatepetl volcanoes National Park region of Mexico was selected. This region is recognised as a typical example of a fragile mountain region. The major contributions of the thesis are related to theoretical and practical issues in an ecosystem-based management approach. In practical terms, results derived from the practical case study provide important inputs (database, diagnosis and proposals) to improve the planning process of the Iztaccihuatl-Popocatepetl region. Also, this methodological approach can be useful to solve the problems linked to fragile mountain ecosystems. It is concluded that ecosystem-based management is taking shape as an ecologically well-founded potential landscape planning approach, capable of playing the role of creating more sustainable regional systems and of searching for enduring multifunctional landscapes for the future

Las gotas lípidicas nucleares constituyen un nuevo dominio nuclear

Teniendo en cuenta que los lípidos neutros nucleares pueden representar pooles alternativos de ácidos grasos y lípidos de señalización celular, el objetivo de este trabajo fue dilucidar un modelo de organización de estos lípidos neutro

Evolutionary algorithm for content-based image search

Content-based image retrieval systems attempt to provide a means of searching for images in large repositories without using any information other than that contained in the image itself, usually in the form of low-level descriptors. Since these descriptors do not accurately represent the semantics of the image, evaluating the perceptual similarity between two images based only on them is not a trivial task. This paper describes an effective method for image recovery based on evolutionary computing techniques. The results are compared with those obtained by the classical approach of the movement of the query point and the rescheduling of the axes and by a technique based on self-organizing maps, showing a remarkably higher performance in the repositories

Electron-phonon renormalization of the absorption edge of the cuprous halides

Compared to most tetrahedral semiconductors, the temperature dependence of the absorption edges of the cuprous halides (CuCl, CuBr, CuI) is very small. CuCl and CuBr show a small increase of the gap $E_0$ with increasing temperature, with a change in the slope of $E_0$ vs. $T$ at around 150 K: above this temperature, the variation of $E_0$ with $T$ becomes even smaller. This unusual behavior has been clarified for CuCl by measurements of the low temperature gap vs. the isotopic masses of both constituents, yielding an anomalous negative shift with increasing copper mass. Here we report the isotope effects of Cu and Br on the gap of CuBr, and that of Cu on the gap of CuI. The measured isotope effects allow us to understand the corresponding temperature dependences, which we also report, to our knowledge for the first time, in the case of CuI. These results enable us to develop a more quantitative understanding of the phenomena mentioned for the three halides, and to interpret other anomalies reported for the temperature dependence of the absorption gap in copper and silver chalcogenides; similarities to the behavior observed for the copper chalcopyrites are also pointed out.Comment: 14 pages, 5 figures, submitted to Phys. Rev.

Estudio de las poblaciones de gotas lipídicas en el insecto vector de la enfermedad de chagas : (Triatoma infestans)

El objetivo del trabajo fue dilucidar las funciones, metabolismo y estructura de las poblaciones de gotas lipídicas en el insecto Triatoma infestans (vinchuca); el insecto es el principal vector del parásito Tripanozoma cruzi, agente causal de la enfermedad de chagas en Argentina y continente americano.Fil: Girotti, Juan R.. Consejo Nacional de Investigaciones Científicas y TécnicasFil: Borús, Delfina L.. Consejo Nacional de Investigaciones Científicas y TécnicasFil: Scelsio, Natalia S.. Consejo Nacional de Investigaciones Científicas y TécnicasFil: Favale, Nicolás O.. Consejo Nacional de Investigaciones Científicas y TécnicasFil: Ves Losada, Ana. Consejo Nacional de Investigaciones Científicas y Técnica

Radioluminescence, thermoluminescence and dosimetric properties of ZnO ceramics

Two types of ZnO ceramics were fabricated and characterized by XRD, SEM methods. The radioluminescence spectra were measured within the 300–550 K range. The defect luminescence band peaking at ~2.35 eV is the dominant one in radioluminescence spectra in both of the fabricated ceramics. The thermostimulated luminescence (TSL) glow-curves were measured after X-ray irradiation at 300 K. It was concluded that the complex overlapping peak within the 320–450 K temperature range consists of two components (~360–375 K and 400–420 K). The ratio of component intensities differs in both ceramics. The positions of high temperature TSL components (480–520 K) also differ in both samples; therefore not only sintering conditions but also the properties of the initial powder are very important for characteristics of TSL. A linear dependence of peak intensity on irradiation dose was observed up to ~3 kGy for ceramic 1 and up to 9 kGy for ceramic 2. © 2017 Elsevier Ltd and Techna Group S.r.l