Analysis of the main drivers of CO2 emissions changes in Colombia (1990e2012) and its political implications

In this study, an Index Decomposition Analysis-Logarithmic Mean Divisia Index (IDA-LMDI) model was developed to find the drivers behind the changes in CO2 emissions between 1990 and 2012 in Colombia. The results facilitate the assessment of the impact in Colombia of the main measures regarding the mitigation of CO2 emissions. Likewise, it allows us to analyze whether the recent measures implemented by the Colombian authorities to mitigate emissions are moving in the right direction. To carry out the decomposition analysis, six effects were taken into consideration: carbonization, the substitution of fossil fuels, the penetration of renewable energy, energy intensity, wealth and population. The effects of income and population appear as drivers of emissions for the period analyzed. A stylized analysis allows richer conclusions to be extracted regarding a battery of recommendations for emission mitigation policies that are compatible with economic growth in Colombi

CD44-high neural crest stem-like cells are associated with tumour aggressiveness and poor survival in neuroblastoma tumours

BACKGROUND: Neuroblastoma is a paediatric tumour originated from sympathoadrenal precursors and characterized by its heterogeneity and poor outcome in advanced stages. Intra-tumoral cellular heterogeneity has emerged as an important feature in neuroblastoma, with a potential major impact on tumour aggressiveness and response to therapy. CD44 is an adhesion protein involved in tumour progression, metastasis and stemness in different cancers; however, there has been controversies about the significance of CD44 expression in neuroblastoma and its relationship with tumour progression. METHODS: We have performed transcriptomic analysis on patient tumour samples studying the outcome of patients with high CD44 expression. Adhesion, invasion and proliferation assays were performed in sorted CD44high neuroblastoma cells. Tumoursphere cultures have been used to enrich in undifferentiated stem-like cells and to asses self-renewal and differentiation potential. We have finally performed in vivo tumorigenic assays on cell line-derived or Patient-derived xenografts. FINDINGS: We show that high CD44 expression is associated with low survival in high-grade human neuroblastoma, independently of MYCN amplification. CD44 is expressed in a cell population with neural crest stem-like features, and with the capacity to generate multipotent, undifferentiated tumourspheres in culture. These cells are more invasive and proliferative in vitro. CD44 positive cells obtained from tumours are more tumorigenic and metastatic, giving rise to aggressive neuroblastic tumours at high frequency upon transplantation. INTERPRETATION: We describe an unexpected intra-tumoural heterogeneity within cellular entities expressing CD44 in neuroblastoma, and propose that CD44 has a role in neural crest stem-like undifferentiated cells, which can contribute to tumorigenesis and malignancy in this type of cancer. FUNDING: Research supported by grants from the "Asociación Española contra el Cáncer" (AECC), the Spanish Ministry of Science and Innovation SAF program (SAF2016-80412-P), and the European Research Council (ERC Starting Grant to RP).Spanish Ministry of Science and Innovation SAF program (SAF2016-80412-P

Non-Markovian polymer reaction kinetics

Describing the kinetics of polymer reactions, such as the formation of loops and hairpins in nucleic acids or polypeptides, is complicated by the structural dynamics of their chains. Although both intramolecular reactions, such as cyclization, and intermolecular reactions have been studied extensively, both experimentally and theoretically, there is to date no exact explicit analytical treatment of transport-limited polymer reaction kinetics, even in the case of the simplest (Rouse) model of monomers connected by linear springs. We introduce a new analytical approach to calculate the mean reaction time of polymer reactions that encompasses the non-Markovian dynamics of monomer motion. This requires that the conformational statistics of the polymer at the very instant of reaction be determined, which provides, as a by-product, new information on the reaction path. We show that the typical reactive conformation of the polymer is more extended than the equilibrium conformation, which leads to reaction times significantly shorter than predicted by the existing classical Markovian theory.Comment: Main text (7 pages, 5 figures) + Supplemantary Information (13 pages, 2 figures

Theory and design of Inx_{x}Ga1−x_{1-x}As1−y_{1-y}Biy_{y} mid-infrared semiconductor lasers: type-I quantum wells for emission beyond 3 μ\mum on InP substrates

We present a theoretical analysis and optimisation of the properties and performance of mid-infrared semiconductor lasers based on the dilute bismide alloy In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$, grown on conventional (001) InP substrates. The ability to independently vary the epitaxial strain and emission wavelength in this quaternary alloy provides significant scope for band structure engineering. Our calculations demonstrate that structures based on compressively strained In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$ quantum wells (QWs) can readily achieve emission wavelengths in the 3 -- 5 $\mu$m range, and that these QWs have large type-I band offsets. As such, these structures have the potential to overcome a number of limitations commonly associated with this application-rich but technologically challenging wavelength range. By considering structures having (i) fixed QW thickness and variable strain, and (ii) fixed strain and variable QW thickness, we quantify key trends in the properties and performance as functions of the alloy composition, structural properties, and emission wavelength, and on this basis identify routes towards the realisation of optimised devices for practical applications. Our analysis suggests that simple laser structures -- incorporating In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$ QWs and unstrained ternary In$_{0.53}$Ga$_{0.47}$As barriers -- which are compatible with established epitaxial growth, provide a route to realising InP-based mid-infrared diode lasers.Comment: Submitted versio

Room temperature upconversion electroluminescence from a mid-infrared In(AsN) tunneling diode

Light emitting diodes (LEDs) in the mid-infrared (MIR) spectral range require material systems with tailored optical absorption and emission at wavelengths lambda > 2 mu m. Here, we report on MIR LEDs based on In(AsN)/(InAl)As resonant tunneling diodes (RTDs). The N-atoms lead to the formation of localized deep levels in the In(AsN) quantum well (QW) layer of the RTD. This has two main effects on the electroluminescence (EL) emission. By electrical injection of carriers into the N-related levels, EL emission is achieved at wavelengths significantly larger than for the QW emission (lambda similar to 3 mu m), extending the output of the diode to lambda similar to 5 mu m. Furthermore, for applied voltages well below the flatband condition of the diode, EL emission is observed at energies much larger than those supplied by the applied voltage and/or thermal energy, with an energy gain Delta E>0.2eV at room temperature. We attribute this upconversion luminescence to an Auger-like recombination process

Influencia del uso de WhatsApp y correo electrónico en la competencia digital en el área de comunicación

The technological advance of mobile devices has significantly changed the way students communicate and interact. The purpose of this research is to analyse the level of digital competence in the area of communication of Spanish schoolchildren aged 12-16 years and to determine whether the use of WhatsApp and email influence this competence. A quantitative methodology was used, working with a sample of 807 students and a problem-solving test was used for data collection. The results show that the use of these communicative tools does not improve students' level of competence.El avance tecnológico de los dispositivos móviles ha cambiado significativamente la manera en que los estudiantes se comunican e interactúan. Se presenta una investigación cuya finalidad es analizar el nivel de competencia digital, en el área de comunicación, que tienen escolares españoles de 12-16 años, y determinar si el uso de WhatsApp y correo electrónico influyen en él. Se empleó una metodología cuantitativa, se trabajó con una muestra de 807 estudiantes y se utilizó una prueba de resolución de problemas para la recogida de datos. Los resultados evidencian que el uso de estas herramientas comunicativas no mejora el nivel competencial