High-Mobility Toolkit for Quantum Dot Films

Semiconductor colloidal quantum dots (CQDs) are being increasingly exploited in electronics, optoelectronics, and solar energy harvesting, using a variety of different architectures, mostly based on ordered 2D or 3D arrays of these nanostructures. A crucial issue for optimizing the performance of such devices is the ability to predict and tune the transport properties of these assemblies. In this work we provide general guidelines to precisely that effect, indicating specific materials, crystal structures, lattice arrangements, surface stoichiometries, and morphologies that favor high electron mobilities in these systems and, conversely, materials that will exhibit low mobilities if nanostructured. At the same time our results evidence a surprising independence of the film’s transport properties from those of the bulk material from which the dots are made, highlighting the crucial role of theoretical modeling to guide device design

Efficient, non-stochastic, Monte-Carlo-like-accurate method for the calculation of the temperature-dependent mobility in nanocrystal films

We present a new non-stochastic framework for the calculation of the temperature dependence of the mobility in nanocrystal films, that enables speed-ups of several orders of magnitude compared to conventional Monte Carlo approaches, while maintaining a similar accuracy. Our model identifies a new contribution to the reduction of the mobility with increasing temperature in these systems (conventionally attributed to interactions with phonons), that alone is sufficient to explain the observed experimental trend up to room temperature. Comparison of our results with the theoretical predictions of the hopping model and the observed temperature dependence of recent field-effect mobility measurements in nanocrystal films, provides the means to discriminate between band-like and hopping transport and a definitive answer to whether the former has been achieved in quantum dot films

NOA36 Protein Contains a Highly Conserved Nucleolar Localization Signal Capable of Directing Functional Proteins to the Nucleolus, in Mammalian Cells

NOA36/ZNF330 is an evolutionarily well-preserved protein present in the nucleolus and mitochondria of mammalian cells. We have previously reported that the pro-apoptotic activity of this protein is mediated by a characteristic cysteine-rich domain. We now demonstrate that the nucleolar localization of NOA36 is due to a highly-conserved nucleolar localization signal (NoLS) present in residues 1–33. This NoLS is a sequence containing three clusters of two or three basic amino acids. We fused the amino terminal of NOA36 to eGFP in order to characterize this putative NoLS. We show that a cluster of three lysine residues at positions 3 to 5 within this sequence is critical for the nucleolar localization. We also demonstrate that the sequence as found in human is capable of directing eGFP to the nucleolus in several mammal, fish and insect cells. Moreover, this NoLS is capable of specifically directing the cytosolic yeast enzyme polyphosphatase to the target of the nucleolus of HeLa cells, wherein its enzymatic activity was detected. This NoLS could therefore serve as a very useful tool as a nucleolar marker and for directing particular proteins to the nucleolus in distant animal species

New strategies for colloidal-quantum-dot-based intermediate-band solar cells

The intermediate-band solar cell (IBSC) concept promises to increase the efficiency limit in a single-junction solar cell through the absorption of below-bandgap-energy photons. Despite their operating principle having been proposed over 20 years ago, IBSCs have not delivered on this promise yet, and the devices fabricated so far, mainly based on embedded epitaxial quantum dots, have instead operated with lower efficiency than conventional solar cells. A new paradigm, based on the exploitation as the intermediate band of the intragap states naturally occurring in the density functional theory description of colloidal (i.e., chemically synthesized) quantum dots, was suggested recently. Here, we revisit this intriguing concept unveiling its shortcomings and propose two alternative schemes: in the first, the localized electron surface trap states, ubiquitously found in commonly synthesized colloidal quantum dots, are used as intermediate bands in strongly coupled films made of small InAs nanocrystals and, in the second scheme, the intermediate band is provided by the conduction-band-minimum-derived miniband in films of larger InAs nanocrystals. Both schemes yield estimated limiting IBSC efficiencies exceeding Shockley-Queisser’s limit for a single absorber

Institucionalización de la educación secundaria obligatoria. Evaluación del proceso de implantación en Andalucía. Un estudio de caso.

El propósito general de esta la investigación que presentamos es evaluar el proceso de implantación del segundo ciclo de la Educación Secundaria Obligatoria en Andalucía atendiendo a las condiciones de inicio y desarrollo de la institucionalización de los nuevos planteamientos curriculares y la apropiación de los factores de cambio que realiza el profesorado de Institutos de Educación Secundaria de Andalucía. Todo este proceso se ejemplifica con un estudio de caso.Grupo de Investigación FORCE (Formación Centrada en la Escuela) Universidad de Granad

Band-like electron transport in 2D quantum dot periodic lattices: the effect of realistic size distributions

Electron mobility in nanocrystal films has been a controversial topic in the last few years. Theoretical and experimental studies evidencing carrier transport by hopping or showing band-like features have been reported in the past. A relevant factor to analyze transport results is the progressive improvement in quantum dot superlattice fabrication, leading to better regimented structures for which band-like transport would be more relevant. This work presents an efficient model to compute temperature-dependent band-like electronic mobilities in 2D quantum dot arrays when a realistic quantum dot size distribution is considered. Comparisons with experimental results are used to estimate these size distributions, in good agreement with data of the samples

Contribution of the Microbial Communities Detected on an Oil Painting on Canvas to Its Biodeterioration

In this study, we investigated the microbial community (bacteria and fungi) colonising an oil painting on canvas, which showed visible signs of biodeterioration. A combined strategy, comprising culture-dependent and -independent techniques, was selected. The results derived from the two techniques were disparate. Most of the isolated bacterial strains belonged to related species of the phylum Firmicutes, as Bacillus sp. and Paenisporosarcina sp., whereas the majority of the non-cultivable members of the bacterial community were shown to be related to species of the phylum Proteobacteria, as Stenotrophomonas sp. Fungal communities also showed discrepancies: the isolated fungal strains belonged to different genera of the order Eurotiales, as Penicillium and Eurotium, and the non-cultivable belonged to species of the order Pleosporales and Saccharomycetales. The cultivable microorganisms, which exhibited enzymatic activities related to the deterioration processes, were selected to evaluate their biodeteriorative potential on canvas paintings; namely Arthrobacter sp. as the representative bacterium and Penicillium sp. as the representative fungus. With this aim, a sample taken from the painting studied in this work was examined to determine the stratigraphic sequence of its cross-section. From this information, “mock paintings,” simulating the structure of the original painting, were prepared, inoculated with the selected bacterial and fungal strains, and subsequently examined by micro-Fourier Transform Infrared spectroscopy, in order to determine their potential susceptibility to microbial degradation. The FTIR-spectra revealed that neither Arthrobacter sp. nor Penicillium sp. alone, were able to induce chemical changes on the various materials used to prepare “mock paintings.” Only when inoculated together, could a synergistic effect on the FTIR-spectra be observed, in the form of a variation in band position on the spectrum.The FTIR analyses performed in this study were financed by the Junta de Andalucía (RNM-325 group). The molecular analyses performed in this study were financed by the Austrian Science Fund (FWF) project ‘Hertha-Firnberg T137’ and the Spanish Ministry of Science and Innovation (Project CTQ2008-06727-C03-03). G. Piñar also thanks the “Elise-Richter V194-B20” projects

Desigualdad en educación y desarrollo profesional de los docentes que trabajan con alumnos, centros y zonas en riesgo de sufrir procesos de exclusión

Celebrado en Granada los días 25, 26 y 27 de septiembre de 2003.Hablar de formación del profesor en contextos de desigualdad –dado que ésta profesionalización es un proceso continuo a lo largo de toda su trayectoria profesional–, supone invariablemente hablar de un modelo de profesor, de interacción didáctica, de educación... De partida, nos plateábamos que existía un modelo de profesor, de socialización en la zona y de desarrollo profesional en estas circunstancias muy particulares. Por lo que parece relevante comprender cómo sienten los profesores el ejercicio de su profesión en estos contextos, cómo varían sus necesidades y orientaciones vitales y qué opinan ellos como fundamental para ajustarse a y transformar la realidad en la que trabajan; pero también contextualizar y atemperar sus opiniones y relatos de experiencia con las de otros agentes de la comunidad

Bladder cancer index: cross-cultural adaptation into Spanish and psychometric evaluation

BACKGROUND: The Bladder Cancer Index (BCI) is so far the only instrument applicable across all bladder cancer patients, independent of tumor infiltration or treatment applied. We developed a Spanish version of the BCI, and assessed its acceptability and metric properties. METHODS: For the adaptation into Spanish we used the forward and back-translation method, expert panels, and cognitive debriefing patient interviews. For the assessment of metric properties we used data from 197 bladder cancer patients from a multi-center prospective study. The Spanish BCI and the SF-36 Health Survey were self-administered before and 12 months after treatment. Reliability was estimated by Cronbach's alpha. Construct validity was assessed through the multi-trait multi-method matrix. The magnitude of change was quantified by effect sizes to assess responsiveness. RESULTS: Reliability coefficients ranged 0.75-0.97. The validity analysis confirmed moderate associations between the BCI function and bother subscales for urinary (r = 0.61) and bowel (r = 0.53) domains; conceptual independence among all BCI domains (r ≤ 0.3); and low correlation coefficients with the SF-36 scores, ranging 0.14-0.48. Among patients reporting global improvement at follow-up, pre-post treatment changes were statistically significant for the urinary domain and urinary bother subscale, with effect sizes of 0.38 and 0.53. CONCLUSIONS: The Spanish BCI is well accepted, reliable, valid, responsive, and similar in performance compared to the original instrument. These findings support its use, both in Spanish and international studies, as a valuable and comprehensive tool for assessing quality of life across a wide range of bladder cancer patients

Consequences of a large-scale fragmentation experiment for Neotropical bats : disentangling the relative importance of local and landscape-scale effects

Context Habitat loss, fragmentation and degradation are widespread drivers of biodiversity decline. Understanding how habitat quality interacts with landscape context, and how they jointly affect species in human-modified landscapes, is of great importance for informing conservation and management. Objectives We used a whole-ecosystem manipulation experiment in the Brazilian Amazon to investigate the relative roles of local and landscape attributes in affecting bat assemblages at an interior-edge-matrix disturbance gradient. Methods We surveyed bats in 39 sites, comprising continuous forest (CF), fragments, forest edges and intervening secondary regrowth. For each site, we assessed vegetation structure (local-scale variable) and, for five focal scales, quantified habitat amount and four landscape configuration metrics. Results Smaller fragments, edges and regrowth sites had fewer species and higher levels of dominance than CF. Regardless of the landscape scale analysed, species richness and evenness were mostly related to the amount of forest cover. Vegetation structure and configurational metrics were important predictors of abundance, whereby the magnitude and direction of response to configurational metrics were scale-dependent. Responses were ensemble-specific with local-scale vegetation structure being more important for frugivorous than for gleaning animalivorous bats. Conclusions Our study indicates that scale-sensitive measures of landscape structure are needed for a more comprehensive understanding of the effects of fragmentation on tropical biota. Although forest fragments and regrowth habitats can be of conservation significance for tropical bats our results further emphasize that primary forest is of irreplaceable value, underlining that their conservation can only be achieved by the preservation of large expanses of pristine habitat