Search

LA VORAGINE/TIERRA DE PROMISION JOSE EUSTASIO RIVERA 432pp. Penguin Clasicos. Paperback, COL$42,000. Jose Eustasio Rivera's La voragine (The Vortex, 1924) is the most influential Colombian novel before Gabriel Garcia Marquez. [...]

EXPLOSION IN A CATHEDRAL ALEJO CARPENTIER Translated by Adrian Nathan West 368pp. Penguin Classics. Paperback, 14 [pounds sterling]. El Siglo de las luces (1962)--a foundational text of the Latin American [...]

The instability exhibited by perovskite solar cells when exposed to the environment under illumination is one of the major obstacles for the entry of perovskite technology in the photovoltaic market. In this work, we use the external quantum efficiency (EQE) technique to study the photoinduced degradation of two types of solar cells having CH3NH3PbI3 as an absorber layer: one deposited by spin coating with an n-i-p architecture and the other deposited by evaporation with an inverted p-i-n structure. We also study the effect of different encapsulants to protect the cells against atmospheric agents. We find that EQE provides information regarding the areas of the cell most susceptible to degradation, in addition to providing an estimate of the optical gap and the Urbach energy of the absorbent material. We confirm that the combined action of illumination and the environment markedly accelerate the degradation, which is reflected in the deterioration of all the parameters of the cell. The rear part of the cell is the first region to suffer the light-induced degradation. On the other hand, the cells deposited by evaporation and with a good encapsulation process are highly stable since after 30 h of exposure just a small spectral change is noticed in the red/infrared region of the EQE spectrum. [ABSTRACT FROM AUTHOR]

Computer tomography image quality control assessment take part of Cuban national legislation, which could be difficult to accomplish for many reasons. This work is part of the set-up verifications of "in house tool" (EvaCT) designed to calculate parameters of quality control of CT images (CCCT) in various manufacturer's phantoms, "at distance". For this, the behavior of the established parameters was studied in 17 studies of the stablished CCCT routine with the Mediso PET/SPECT/CT Anyscan Trio equipment, comparing the results using manufacture´s reference values, and/ or the international recommended parameter´s tolerances. The results of the system were compared numerically with those obtained by the manufacturer, for each available related parameter, in the corresponding protocol, and did not show significant differences (p≥0.05). In general, the system showed a satisfactory behavior, taking as reference the values and tolerances of the manufacturer, CECMED and IAEA. The correlation between quality descriptors established with different methodologies was analyzed. The tool showed correspondence with the manufacturer's results, making available a greater number of parameters and more operational conditions to be evaluated. The mean values ±SD characterize these parameters in the equipment and its phantom, and can be used for periodic, independent and remote CCCT verification. [ABSTRACT FROM AUTHOR]

Comprehensive monitoring of NO 2 exceedances is imperative for protecting human health, especially in urban areas with traffic. However, an accurate spatial characterization of the exceedances is challenging due to the typically low density of air quality monitoring stations and the inherent uncertainties in urban air quality models. We study how observational data from different sources and timescales can be combined with a dispersion air quality model to obtain bias-corrected NO 2 hourly maps at the street scale. We present a kriging-based data fusion workflow that merges dispersion model output with continuous hourly observations and uses a machine-learning-based land use regression (LUR) model constrained with past short intensive passive dosimeter campaign measurements. While the hourly observations allow the bias adjustment of the temporal variability in the dispersion model, the microscale LUR model adds information on the NO 2 spatial patterns. Our method includes an uncertainty calculation based on the estimated error variance of the universal kriging technique, which is subsequently used to produce urban maps of probability of exceeding the 200 µgm-3 hourly and the 40 µgm-3 annual NO 2 average limits. We assess the statistical performance of this approach in the city of Barcelona for the year 2019. Our results show that simply merging the monitoring stations with the model output already significantly increases the correlation coefficient (r) by +29 % and decreases the root mean square error (RMSE) by -32 %. When adding the time-invariant microscale LUR model in the data fusion workflow, the improvement is even more remarkable, with +46 % and -48 % for the r and RMSE, respectively. Our work highlights the usefulness of high-resolution spatial information in data fusion methods to better estimate exceedances at the street scale. [ABSTRACT FROM AUTHOR]

Organo–inorganic halide perovskites continue to generate enormous interest for their potential use in various optoelectronic devices. Among the different fabrication methods, vacuum thermal deposition allows uniform films over large areas, providing good material quality without using organic solvents. However, the influence of the substrate on the properties of the material deposited by vacuum processing is a point that deserves further investigation. Herein, time‐dependent photoconductivity measurements are used to investigate the dynamics of charge carriers under illumination in planar films of CH3NH3PbI3. The samples are deposited by thermal sublimation on different substrates: PbI2, TaTm, C60, and glass. Experimentally, it is shown that the substrate has a profound effect on perovskite behavior and that photoconductivity is sensitive enough to probe these behaviors. Furthermore, a model based on Shockley–Read–Hall statistics is proposed, explaining the different photoconductivity responses by changing only the relative values of the different capture coefficients and the position of the Fermi level. It is argued that the substrate changes the stoichiometry of the evaporated material, affecting the transient photoconductivity response. [ABSTRACT FROM AUTHOR]

Copyright of Espirales Revista Multidisciplinaria de Investigación is the property of Grupo Compas and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Comprehensive monitoring of NO2 exceedances is imperative for protecting human health, especially in trafficked urban areas. However, accurate spatial characterization of exceedances is challenging due to the typically low density of air quality monitoring stations and the inherent uncertainties of urban air quality models. We study how observational data from different sources and time scales can be combined with a dispersion air quality model to obtain bias-corrected NO2 hourly maps at the street scale. We present a kriging-based data-fusion workflow that merges a dispersion model output with continuous hourly observations, and uses a machine-learning-based Land Use Regression (LUR) model constrained with past short intensive passive dosimeter campaigns observations. While the hourly observations allow to bias-adjust the temporal variability of the dispersion model, the microscale-LUR model adds information on the NO2 spatial patterns. Our method includes uncertainty calculation based on the estimated error variance of the Universal Kriging technique, which is subsequently used to produce urban maps of probability of exceeding the 200 µg / m 3 hourly and the 40 µg / m 3 NO2 annual average limits. We assess the statistical performance of this approach in the city of Barcelona for the year 2019. Our results show that simply merging the monitoring stations with the model output already significantly increases the correlation coefficient (r) by +29 % and decreases the Root Mean Square Error (RMSE) by -32 %. When adding the time-invariant LUR model in the data-fusion workflow, the improvement is even more remarkable: +46 % and -48 % for the r and RMSE, respectively. Our work highlights the usefulness of high-resolution spatial information in data-fusion methods to estimate exceedances at the street scale better. [ABSTRACT FROM AUTHOR]

The gene products of the rbsRA CBD (rbs) operon of C. glutamicum (cg1410-cg1414) encode a ribose-specific ATP-binding cassette (ABC) transport system and its corresponding regulatory protein (RbsR). Deletion of the structural genes rbsACBD prohibited ribose uptake. Deletion of the regulatory gene rbsR resulted in an increased mRNA level of the whole operon. Analysis of the promoter region of the rbs operon by electrophoretic mobility shift assays identified a catabolite-responsive element (cre)-like sequence as the RbsR-binding site. Additional RbsR-binding sites were identified in front of the recently characterized uriR operon (uriR-rbsKl-uriT-uriH) and the ribokinase gene rbsK2. In vitro, the repressor RbsR bound to its targets in the absence of an effector. A probable negative effector of RbsR in vivo is ribose 5-phosphate or a derivative thereof, since in a ribokinase (rbsK1 rbsK2) double mutant, no derepression of the rbs operon in the presence of ribose was observed. Analysis of the ribose stimulon in the C. glutamicum wild-type revealed transcriptional induction of the uriR and rbs operons as well as of the rbsK2 gene. The inconsistency between the existence of functional RbsR-binding sites upstream of the ribokinase genes, their transcriptional induction during growth on ribose, and the missing induction in the rbsR mutant suggested the involvement of a second transcriptional regulator. Simultaneous deletion of the regulatory genes rbsR and uriR finally demonstrated a transcriptional co-control of the rbs and uriR operons and the rbsK2 gene by both regulators, RbsR and UriR, which were furthermore shown to recognize the same cognate DNA sequences in the operators of their target genes.

KILO Life and death inside the secret world of the cocaine cartels TOBY MUSE 320pp. Ebury. 16.99 [pounds sterling]. In 2016, the Colombian state signed a historic peace treaty with [...]

Deep‐sea sediments record palaeoenvironmental and oceanographic changes over time through variations in their magnetochemical and sedimentological properties. This study presents the Late Quaternary sedimentary reconstruction of three sediment cores extracted from a source‐to‐sink sedimentary system located in a high marginal platform of the north‐west Iberian Margin. The aim of this reconstruction is to explore the palaeoclimatic, palaeoproductivity and diagenetic changes over the last 172 cal ka bp attending to geochemical, magnetic and sedimentological variations. The record is comprised of four sedimentary units consisting of pelagic, hemipelagic and detrital facies, the latter associated with ice‐rafted debris events at Heinrich Stadials. These findings allowed the reconstruction of the lithostratigraphy attending to climatic changes, covering the last eleven Heinrich Stadials. These units and facies successions are controlled by the superposition of the Milankovitch and Dansgaard–Oeschger cycles. Low sedimentation rates have been reported, especially during cold periods. Palaeoproductivity was assessed using total organic carbon and calcium carbonate content, together with biogenic barium (Babio) and organic phosphorus (Porg), both calculated via total digestion analysis using standard calculations. Mass accumulation rates for total organic carbon, Babio and Porg were calculated. Furthermore, a sequential extraction was performed to explore the different phases of the barium within sediments: biogenic barite (Babar), barium associated with iron and manganese oxides (Baox) and Ba associated with aluminosilicates (Badet). Results display a limitation in the use of the biogenic barium and phosphorus and mass accumulation rates, suggesting detrital Ba (Badetr) contribution during Heinrich Stadials, which could mask the calculations. In contrast, only calcium carbonate fluctuates attending to glacial/interglacial cycles. Regarding some diagenetic proxies (i.e. Mn, Mn/Fe and Mn/Ti), they reveal oxidation fronts of different generations, suggesting that the early diagenesis has not reached steady‐state, because the redoxcline fluctuates. This fact suggests an erosional activity that causes the continuous oxygenation of the sediment and non‐steady‐state conditions. [ABSTRACT FROM AUTHOR]

Metal halide perovskite solar cells (PSCs) are of interest for high altitude and space applications due to their lightweight and versatile form factor. However, their resilience toward the particle spectrum encountered in space is still of concern. For space cells, the effect of these particles is condensed into an equivalent 1 MeV electron fluence. The effect of high doses of 1 MeV e‐beam radiation up to an accumulated fluence to 1016 e− cm−2 on methylammonium lead iodide perovskite thin films and solar cells is probed. By using substrate and encapsulation materials that are stable under the high energy e‐beam radiation, its net effect on the perovskite film and solar cells can be studied. The quartz substrate‐based PSCs are stable under the high doses of 1 MeV e‐beam irradiation. Time‐resolved microwave conductivity analysis on pristine and irradiated films indicates that there is a small reduction in the charge carrier diffusion length upon irradiation. Nevertheless, this diffusion length remains larger than the perovskite film thickness used in the solar cells, even for the highest accumulated fluence of 1016 e− cm−2. This demonstrates that PSCs are promising candidates for space applications. [ABSTRACT FROM AUTHOR]

Abstract Background Corynebacterium glutamicum is a high-GC Gram-positive soil bacterium of great biotechnological importance for the production of amino acids. To facilitate the rational design of sulphur amino acid-producing strains, the pathway for assimilatory sulphate reduction providing the necessary reduced sulfur moieties has to be known. Although this pathway has been well studied in Gram-negative bacteria like Escherichia coli and low-GC Gram-positives like Bacillus subtilis, little is known for the Actinomycetales and other high-GC Gram-positive bacteria. Results The genome sequence of C. glutamicum was searched for genes involved in the assimilatory reduction of inorganic sulphur compounds. A cluster of eight candidate genes could be identified by combining sequence similarity searches with a subsequent synteny analysis between C. glutamicum and the closely related C. efficiens. Using mutational analysis, seven of the eight candidate genes, namely cysZ, cysY, cysN, cysD, cysH, cysX, and cysI, were demonstrated to be involved in the reduction of inorganic sulphur compounds. For three of the up to now unknown genes possible functions could be proposed: CysZ is likely to be the sulphate permease, while CysX and CysY are possibly involved in electron transfer and cofactor biosynthesis, respectively. Finally, the candidate gene designated fpr2 influences sulphur utilisation only weakly and might be involved in electron transport for the reduction of sulphite. Real-time RT-PCR experiments revealed that cysIXHDNYZ form an operon and that transcription of the extended cluster fpr2 cysIXHDNYZ is strongly influenced by the availability of inorganic sulphur, as well as L-cysteine. Mapping of the fpr2 and cysIXHDNYZ promoters using RACE-PCR indicated that both promoters overlap with binding-sites of the transcriptional repressor McbR, suggesting an involvement of McbR in the observed regulation. Comparative genomics revealed that large parts of the extended cluster are conserved in 11 of 17 completely sequenced members of the Actinomycetales. Conclusion The set of C. glutamicum genes involved in assimilatory sulphate reduction was identified and four novel genes involved in this pathway were found. The high degree of conservation of this cluster among the Actinomycetales supports the hypothesis that a different metabolic pathway for the reduction of inorganic sulphur compounds than that known from the well-studied model organisms E. coli and B. subtilis is used by members of this order, providing the basis for further biochemical studies.

Herein, the dehydration of a hydrogen molybdenum bronze (HYMoO3), converting it to molybdenum oxide (MoOX), is explored toward the development of perovskite solar cells (PSCs) for the first time. H0.11MoO3 bronze is synthesized, characterized, and deposited on indium tin oxide (ITO) under different concentrations and annealing conditions for in situ conversion into MoOX with appropriate oxygen vacancies. Vacuum‐deposited PSCs are fabricated using the as‐produced MoOX hole injection layers, achieving a power conversion efficiency of 17.3% (average) for the optimal device. The latter has its stability and reproducibility tested, proving the robustness and affordability of the developed hole transport layer in PSCs. [ABSTRACT FROM AUTHOR]

Efficient perovskite devices consist of a perovskite film sandwiched between charge selective layers, in order to avoid non-radiative recombination. A common metal oxide used as a p-type or hole transport layer is molybdenum oxide. MoO3 is of particular interest for its very large work function, which allows it to be used both as an interfacial charge transfer material and a dopant for organic semiconductors. However, high quality and high work function MoO3 is typically thermally evaporated in a vacuum. An alternative solution-processable high work function material is phosphomolybdic acid (PMA), which is stable, commercially available and environmentally friendly. In this Communication, we show the first application of PMA in efficient vacuum processed perovskite devices. We found that the direct growth of perovskite films onto PMA leads to strong charge carrier recombination, hindering the solar cell photovoltage. Using an energetically suitable selective transport layer placed between PMA and the perovskite film, solar cells with efficiency ＞13% as well as LEDs with promising quantum efficiency can be obtained. [ABSTRACT FROM AUTHOR]

Efficient monolithic perovskite/perovskite tandem solar cells are fabricated using two perovskite absorbers with complementary bandgaps. By employing doped organic semiconductors, an efficient and selective extraction of the charge carriers is ensured. This study demonstrates perovskite/perovskite tandem cells delivering a maximum efficiency of 18%, highlighting the potential of vacuum‐deposited multilayer structures in overcoming the efficiency of single‐junction perovskite devices. [ABSTRACT FROM AUTHOR]

In this work we study the band gap variation and properties of the perovskite compound Cs0.15FA0.85Pb(BrxI1−x)3 as a function of the halide composition, with the aim of developing an efficient complementary absorber for MAPbI3 in all-perovskite tandem devices. We have found the perovskite stoichiometry Cs0.15FA0.85Pb(Br0.7I0.3)3 to be a promising candidate, thanks to its band gap of approximately 2 eV. Single junction devices using this perovskite absorber lead to a maximum PCE of 11.5%, among the highest reported for solar cells using perovskites with a band gap wider than 1.8 eV. [ABSTRACT FROM AUTHOR]

The problem of forecasting the behavior of a complex dynamical system through analysis of observational time-series data becomes difficult when the system expresses chaotic behavior and the measurements are sparse, in both space and/or time. Despite the fact that this situation is quite typical across many fields, including numerical weather prediction, the issue of whether the available observations are "sufficient" for generating successful forecasts is still not well understood. An analysis by Whartenby et al. (2013) found that in the context of the nonlinear shallow water equations on a β plane, standard nudging techniques require observing approximately 70% of the full set of state variables. Here we examine the same system using a method introduced by Rey et al. (2014a), which generalizes standard nudging methods to utilize time delayed measurements. We show that in certain circumstances, it provides a sizable reduction in the number of observations required to construct accurate estimates and high-quality predictions. In particular, we find that this estimate of 70% can be reduced to about 33% using time delays, and even further if Lagrangian drifter locations are also used as measurements. [ABSTRACT FROM AUTHOR]