Photochemical solution processing of films of metastable phases for flexible devices: the beta-Bi2O3 polymorph

The potential of UV-light for the photochemical synthesis and stabilization of non-equilibrium crystalline phases in thin films is demonstrated for the beta-Bi2O3 polymorph. The pure beta-Bi2O3 phase is thermodynamically stable at high temperature (450-667 degrees C), which limits its applications in devices. Here, a tailored UV-absorbing bismuth(III)-N-methyldiethanolamine complex is selected as an ideal precursor for this phase, in order to induce under UV-light the formation of a -Bi-O-Bi- continuous network in the deposited layers and the further conversion into the beta-Bi2O3 polymorph at a temperature as low as 250 degrees C. The stabilization of the beta-Bi2O3 films is confirmed by their conductivity behavior and a thorough characterization of their crystal structure. This is also supported by their remarkable photocatalytic activity. Besides, this processing method has allowed us for the first time the preparation of beta-Bi2O3 films on flexible plastic substrates, which opens new opportunities for using these materials in potential applications not available until now (e.g., flexible photocatalytic reactors, self-cleaning surfaces or wearable antimicrobial fabrics). Therefore, photochemical solution deposition (PCSD) demonstrates to be not only an efficient approach for the low temperature processing of oxide films, but also an excellent alternative for the stabilization of metastable phases

Mapping subnational HIV mortality in six Latin American countries with incomplete vital registration systems

BackgroundHuman immunodeficiency virus (HIV) remains a public health priority in Latin America. While the burden of HIV is historically concentrated in urban areas and high-risk groups, subnational estimates that cover multiple countries and years are missing. This paucity is partially due to incomplete vital registration (VR) systems and statistical challenges related to estimating mortality rates in areas with low numbers of HIV deaths. In this analysis, we address this gap and provide novel estimates of the HIV mortality rate and the number of HIV deaths by age group, sex, and municipality in Brazil, Colombia, Costa Rica, Ecuador, Guatemala, and Mexico.MethodsWe performed an ecological study using VR data ranging from 2000 to 2017, dependent on individual country data availability. We modeled HIV mortality using a Bayesian spatially explicit mixed-effects regression model that incorporates prior information on VR completeness. We calibrated our results to the Global Burden of Disease Study 2017.ResultsAll countries displayed over a 40-fold difference in HIV mortality between municipalities with the highest and lowest age-standardized HIV mortality rate in the last year of study for men, and over a 20-fold difference for women. Despite decreases in national HIV mortality in all countries-apart from Ecuador-across the period of study, we found broad variation in relative changes in HIV mortality at the municipality level and increasing relative inequality over time in all countries. In all six countries included in this analysis, 50% or more HIV deaths were concentrated in fewer than 10% of municipalities in the latest year of study. In addition, national age patterns reflected shifts in mortality to older age groups-the median age group among decedents ranged from 30 to 45years of age at the municipality level in Brazil, Colombia, and Mexico in 2017.ConclusionsOur subnational estimates of HIV mortality revealed significant spatial variation and diverging local trends in HIV mortality over time and by age. This analysis provides a framework for incorporating data and uncertainty from incomplete VR systems and can help guide more geographically precise public health intervention to support HIV-related care and reduce HIV-related deaths.Peer reviewe

Reading tea leaves worldwide: decoupled drivers of initial litter decomposition mass-loss rate and stabilisation

The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large-scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass-loss rates and stabilization factors of plant-derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy-to-degrade components accumulate during early-stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass-loss rates and stabilization, notably in colder locations. Using TBI improved mass-loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early-stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models

Mapping subnational HIV mortality in six Latin American countries with incomplete vital registration systems

Background: Human immunodeficiency virus (HIV) remains a public health priority in Latin America. While the burden of HIV is historically concentrated in urban areas and high-risk groups, subnational estimates that cover multiple countries and years are missing. This paucity is partially due to incomplete vital registration (VR) systems and statistical challenges related to estimating mortality rates in areas with low numbers of HIV deaths. In this analysis, we address this gap and provide novel estimates of the HIV mortality rate and the number of HIV deaths by age group, sex, and municipality in Brazil, Colombia, Costa Rica, Ecuador, Guatemala, and Mexico. Methods: We performed an ecological study using VR data ranging from 2000 to 2017, dependent on individual country data availability. We modeled HIV mortality using a Bayesian spatially explicit mixed-effects regression model that incorporates prior information on VR completeness. We calibrated our results to the Global Burden of Disease Study 2017. Results: All countries displayed over a 40-fold difference in HIV mortality between municipalities with the highest and lowest age-standardized HIV mortality rate in the last year of study for men, and over a 20-fold difference for women. Despite decreases in national HIV mortality in all countries�apart from Ecuador�across the period of study, we found broad variation in relative changes in HIV mortality at the municipality level and increasing relative inequality over time in all countries. In all six countries included in this analysis, 50 or more HIV deaths were concentrated in fewer than 10 of municipalities in the latest year of study. In addition, national age patterns reflected shifts in mortality to older age groups�the median age group among decedents ranged from 30 to 45 years of age at the municipality level in Brazil, Colombia, and Mexico in 2017. Conclusions: Our subnational estimates of HIV mortality revealed significant spatial variation and diverging local trends in HIV mortality over time and by age. This analysis provides a framework for incorporating data and uncertainty from incomplete VR systems and can help guide more geographically precise public health intervention to support HIV-related care and reduce HIV-related deaths

Mapping subnational HIV mortality in six Latin American countries with incomplete vital registration systems

Background Human immunodeficiency virus (HIV) remains a public health priority in Latin America. While the burden of HIV is historically concentrated in urban areas and high-risk groups, subnational estimates that cover multiple countries and years are missing. This paucity is partially due to incomplete vital registration (VR) systems and statistical challenges related to estimating mortality rates in areas with low numbers of HIV deaths. In this analysis, we address this gap and provide novel estimates of the HIV mortality rate and the number of HIV deaths by age group, sex, and municipality in Brazil, Colombia, Costa Rica, Ecuador, Guatemala, and Mexico. Methods We performed an ecological study using VR data ranging from 2000 to 2017, dependent on individual country data availability. We modeled HIV mortality using a Bayesian spatially explicit mixed-effects regression model that incorporates prior information on VR completeness. We calibrated our results to the Global Burden of Disease Study 2017. Results All countries displayed over a 40-fold difference in HIV mortality between municipalities with the highest and lowest age-standardized HIV mortality rate in the last year of study for men, and over a 20-fold difference for women. Despite decreases in national HIV mortality in all countries—apart from Ecuador—across the period of study, we found broad variation in relative changes in HIV mortality at the municipality level and increasing relative inequality over time in all countries. In all six countries included in this analysis, 50% or more HIV deaths were concentrated in fewer than 10% of municipalities in the latest year of study. In addition, national age patterns reflected shifts in mortality to older age groups—the median age group among decedents ranged from 30 to 45 years of age at the municipality level in Brazil, Colombia, and Mexico in 2017. Conclusions Our subnational estimates of HIV mortality revealed significant spatial variation and diverging local trends in HIV mortality over time and by age. This analysis provides a framework for incorporating data and uncertainty from incomplete VR systems and can help guide more geographically precise public health intervention to support HIV-related care and reduce HIV-related deaths

Láminas delgadas de (Bi0.5Na0.5)1-xBaxTiO3 en torno a la frontera de fase morfotrópica preparadas por métodos de depósito químico y fotoquímico de disoluciones

Esta tesis doctoral demuestra que el depósito químico de disoluciones (Chemical Solution Deposition, CSD) es una técnica viable para la preparación de láminas delgadas sin plomo de (Bi0.5Na0.5)1-xBaxTiO3 (BNBT), con un control preciso de su composición y estructura cristalina. Un estudio de estos materiales llevado a cabo con técnicas avanzadas de caracterización composicional y estructural ha permitido situar la frontera de fase morfotrópica (Morphotropic Phase Boundary, MPB) de estas láminas, así como establecer un perfil estructural y composicional de las mismas. Por otro lado, se ha desarrollado una nueva ruta sintética en disolución para materiales basados en bismuto, basada en reacciones fotoquímicas inducidas por luz UV, que ha permitido reducir notablemente la temperatura de procesado de las láminas delgadas de BNBT

Effects of soil compaction and light on growth of Quercus pyrenaica Willd. (Fagaceae) seedlings

Soil compaction and light availability influence plant growth via different mechanisms. In general, soil compaction has a direct effect on roots, whereas light affects leaves and stems. Although plants in nature are exposed to variable levels of soil compaction and light, no study on the potential mutual interactions of these limiting factors in woody plants has to the authors' knowledge been reported to date. The aim of this work was therefore to elucidate the effects of soil compaction and light availability on growth and biomass allocation in the deciduous oak Quercus pyrenaica. To this end, a study was conducted at two light levels (viz. 3% and 100% of incident light, designated as low-light and high-light, respectively) under a wide range of soil compaction (0.02-3 MPa as penetration resistance) in a greenhouse. Total biomass was found to be positively affected by both light and soil compaction. There was marginally significant interaction between the effects of the two factors on total biomass, which was positively affected by soil compaction only under high-light conditions. Soil compaction had a strong, negative effect on the length of the main root; thus, at maximum soil compaction, such a length was roughly one-half that observed at lower compaction levels. Also, the specific root length of main root (root length to root mass ratio) was reduced by roughly one-half in highly compacted soils. These results suggest that an unfavourable combination of soil compaction and light availability may have severely adverse effects on woody plant performance in drought periods since plants with short roots can hardly access water at deep soil levels. The strength of this effect may be modulated by light availability

Láminas delgadas de (Bi0.5Na0.5)1-xBaxTiO3 en torno a la frontera de fase morfotrópica preparadas por métodos de depósito químico y fotoquímico de disoluciones

Esta tesis doctoral demuestra que el depósito químico de disoluciones (Chemical Solution Deposition, CSD) es una técnica viable para la preparación de láminas delgadas sin plomo de (Bi0.5Na0.5)1-xBaxTiO3 (BNBT), con un control preciso de su composición y estructura cristalina. Un estudio de estos materiales llevado a cabo con técnicas avanzadas de caracterización composicional y estructural ha permitido situar la frontera de fase morfotrópica (Morphotropic Phase Boundary, MPB) de estas láminas, así como establecer un perfil estructural y composicional de las mismas. Por otro lado, se ha desarrollado una nueva ruta sintética en disolución para materiales basados en bismuto, basada en reacciones fotoquímicas inducidas por luz UV, que ha permitido reducir notablemente la temperatura de procesado de las láminas delgadas de BNBT

A UV-absorber bismuth(III)-N-methyldiethanolamine complex as a low-temperature precursor for bismuth-based oxide thin films

Novel synthetic methods in solution that reduce the formation temperature of bismuth-based electronic oxides are essential for their successful integration with substrates of low thermal stability within microand flexible-electronic devices. This has become crucial for these oxides, since they appear as promising low-toxic functional materials alternative to other electronic oxides containing heavy metals. However, this is a challenge, since the crystallization of bismuth oxides occurs at high temperatures. To overcome these problems, we synthesize here a UV-absorber charge transfer metal complex in solution between the Bi(III) ion and an alkanolamine, N-methyldiethanolamine (Bi(III)–mdea). We take advantage of the photoreactivity of this complex to prepare bismuth-based oxide thin films at low temperature, which cannot be achieved by traditional thermal processing methods. Room temperature stable oxide thin films of the high-temperature d-Bi2O3 phase are prepared from these solutions by UV-irradiation and annealing at 350 C. The efficiency of this synthetic strategy is additionally proven for the low temperature preparation of thin films of much more complex bismuth based functional oxides: the multiferroic bismuth ferrite, BiFeO3, and the relaxor-ferroelectric perovskite of bismuth, sodium and barium titanate, (Bi0.5Na0.5)0.945Ba0.055TiO3

A UV-absorber bismuth(III)-N-methyldiethanolamine complex as a low-temperature precursor for bismuth-based oxide thin films

Novel synthetic methods in solution that reduce the formation temperature of bismuth-based electronic oxides are essential for their successful integration with substrates of low thermal stability within microand flexible-electronic devices. This has become crucial for these oxides, since they appear as promising low-toxic functional materials alternative to other electronic oxides containing heavy metals. However, this is a challenge, since the crystallization of bismuth oxides occurs at high temperatures. To overcome these problems, we synthesize here a UV-absorber charge transfer metal complex in solution between the Bi(III) ion and an alkanolamine, N-methyldiethanolamine (Bi(III)–mdea). We take advantage of the photoreactivity of this complex to prepare bismuth-based oxide thin films at low temperature, which cannot be achieved by traditional thermal processing methods. Room temperature stable oxide thin films of the high-temperature d-Bi2O3 phase are prepared from these solutions by UV-irradiation and annealing at 350 C. The efficiency of this synthetic strategy is additionally proven for the low temperature preparation of thin films of much more complex bismuth based functional oxides: the multiferroic bismuth ferrite, BiFeO3, and the relaxor-ferroelectric perovskite of bismuth, sodium and barium titanate, (Bi0.5Na0.5)0.945Ba0.055TiO3