Orientational transitions in a nematic confined by competing surfaces

The effect of confinement on the orientational structure of a nematic liquid crystal model has been investigated by using a version of density-functional theory (DFT). We have focused on the case of a nematic confined by opposing flat surfaces, in slab geometry (slit pore), which favor planar molecular alignment (parallel to the surface) and homeotropic alignment (perpendicular to the surface), respectively. The spatial dependence of the tilt angle of the director with respect to the surface normal has been studied, as well as the tensorial order parameter describing the molecular order around the director. For a pore of given width, we find that, for weak surface fields, the alignment of the nematic director is perpendicular to the surface in a region next to the surface favoring homeotropic alignment, and parallel along the rest of the pore, with a interface separating these regions (S phase). For strong surface fields, the director is distorted uniformly, the tilt angle exhibiting a linear dependence with the distance normal to the surface (L phase). Our calculations reveal the existence of a first-order transition between the two director configurations, which is driven by changes in the surface field strength, and also by changes in the pore width. In the latter case the transition occurs, for a given surface field, between the S phase for narrow pores and the L phase for wider pores. A link between the L-S transition and the anchoring transition observed for the semi-infinite case is proposed. We also provide calculations with a phenomenological approach that yields the same main result that DFT in the scale length where this is valid.Comment: submitted to PR

Seasonal niche of planktonic prokaryotes inhabiting surface waters of the upwelling region off NW Iberia

Prokaryotes play an important role in biogeochemical cycling in marine ecosystems, but little is known about their diversity and composition, and it’s even less understood how they may contribute to the ecological functioning of highly variable coastal areas affected by upwelling. Between May 2016 and May 2018, we carried out 26 one-day samplings in the temperate northwestern Iberian upwelling system to investigate the temporal patterns of variability for prokaryotic abundance, diversity and community composition by combining flow cytometry and 16S RNA high- throughput sequencing. A marked seasonality was found for prokaryotic abundance, peaking during summer upwelling and relaxation season (≈May to September), when extracellular release of organic matter from phytoplanktonic blooms is a significant process, and decreasing in downwelling events (≈October to April). Those downwelling conditions, characterized by deeper mixed layers and a homogeneous water column, favored a higher abundance of the archaeal groups, Marine Group II (Euryarchaeota) and Nitrosopelagicus (Thaumarchaeota), as well as of Marinimicrobia bacterium (SAR406 clade) and the group Bacteria_Others. By contrast, upwelling and relaxation conditions characterized by enhanced vertical stratification and hydrographic variability, included a community generally less diverse with core-phylotypes (occurring > 75% of the samples) proliferating, i.e. Flavobacteriaceae (Bacteroidetes), Chloroplast (Cyanobacteria) and Amylibacter (Proteobacteria). Overall, the environmental conditions explained 60% (R2=0.60, AIC=125.64) of the prokaryotic community composition, being temperature, inorganic nutrients, chlorophyll and particulate organic nitrogen the variables that best explained the variation in the prokaryotic community composition (r=0.40). Additional efforts are currently underway on a fine-tuning composition assessment (oligotypes composition from particular core-phylotypes) to study if this variability along the temporal environmental gradient could be associated with the differentiation of ecotypes (oligotype ́s seasonality within particular phylotypes). Overall, the present study provides new insights into the barely explored seasonal niche partitioning of surface prokaryotic community driven by hydrodynamic forcing in an upwelling system, which may support further investigations on the role of bacterioplankton in the biogeochemistry of these ecosystems

Seasonal niche of planktonic prokaryotes inhabiting surface waters of the upwelling region off NW Iberia

Oral communicationProkaryotes play an important role in biogeochemical cycling in marine ecosystems, but little is known about their diversity and composition, and it’s even less understood how they may contribute to the ecological functioning of highly variable coastal areas affected by upwelling. Between May 2016 and May 2018, we carried out 26 one-day samplings in the temperate northwestern Iberian upwelling system to investigate the temporal patterns of variability for prokaryotic abundance, diversity and community composition by combining flow cytometry and 16S RNA high- throughput sequencing. A marked seasonality was found for prokaryotic abundance, peaking during summer upwelling and relaxation season (≈May to September), when extracellular release of organic matter from phytoplanktonic blooms is a significant process, and decreasing in downwelling events (≈October to April). Those downwelling conditions, characterized by deeper mixed layers and a homogeneous water column, favored a higher abundance of the archaeal groups, Marine Group II (Euryarchaeota) and Nitrosopelagicus (Thaumarchaeota), as well as of Marinimicrobia bacterium (SAR406 clade) and the group Bacteria_Others. By contrast, upwelling and relaxation conditions characterized by enhanced vertical stratification and hydrographic variability, included a community generally less diverse with core-phylotypes (occurring > 75% of the samples) proliferating, i.e. Flavobacteriaceae (Bacteroidetes), Chloroplast (

Bacterial community composition and optical signature of DOM shape empirical leucine-to-carbon conversion factors in north-eastern Atlantic waters (0-4000 m)

Oral communicationMicrobial heterotrophic activity is a major process regulating the flux of dissolved organic matter (DOM) in the ocean. DOM quantity and quality strongly influence its microbial utilization and fate in the ocean. In order to broaden the vertical resolution of leucine-to-carbon conversion factors (CFs), needed for converting substrate incorporation into biomass production by heterotrophic bacteria, nine dilution experiments were performed in the north Atlantic. We found a very consistent depth-stratification in empirical CFs values from epipelagic to bathypelagic waters (3.95 ± 0.05 to 0.90 ± 0.51 kg C mol Leu-1). Our results demonstrated that the customarily used CF of 1.55 kg C mol Leu-1 in oceanic waters leads to an underestimation of prokaryotic heterotrophic production in epi- and mesopelagic waters, while it causes a severe overestimation in bathypelagic waters. Pearson correlations showed that CFs were related not only to hydrographic variables but also to specific phylogenetic groups and DOM quality and quantity indicators. Furthermore, a multiple linear regression model predicting CFs from relatively simple hydrographic and optical spectroscopic measurements is provided. Taken together, our results suggest that differences in CFs throughout the water column might be mostly associated to the quality of DOM affecting the response of particular phylogenetic groups.ASL

Molecular characterization of dissolved organic matter linked to microbial (Bacteria and Archaea) diversity in the main water masses of the Eastern North Atlantic Ocean

The microbe-dissolved organic matter (DOM) interactions include microbial uptake and DOM reworking and release, affecting the composition of the heterogeneous DOM pool. In turns, this distinct DOM composition can select for microbial assemblages. We investigated the diversity of microbial (both Bacteria and Archaea) communities (combining Illumina tag sequencing of 16S rRNA gen -amplicon sequencing variants, ASVs- and metagenomics) and the chemodiversity of dissolved organic molecules (extracted by solid phase extraction and analyzed by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, FT-ICR-MS) in the Eastern North Atlantic Ocean off the Galician coast (43oN, 9o-15oW). Sampling ranged from 100 m to 5000 m, thereby encompassing a wide variety of water masses with contrasting origins and different aging. Applying diversity ecological metrics to both organic compounds and ASVs, we found that microbial diversity and richness were negatively correlated with DOM concentration and chemo-diversity. Besides, our results demonstrated the link between this trend and water mass aging, which enhances biosphere taxonomic diversity but reduces molecular variety. DOM diversity, decreasing along the water mass aging gradient, would likely reflect the persistence of the most refractory molecules, generated as by- product of the DOM degradation by microbes. In two PCoAs based on the metagenomic data, combined PCoA axis 1 and PCoA axis 2, explained the 80% and 20% of the microbial gene ́s structural variability among water masses. The oldest water masses, originated at high latitudes, such as NADW and LDW, were associated to higher abundance of genes involved in metabolism of aromatic compound. Intermediate waters such as ENACWst were related to sulphur/iron/phosphorous metabolism related genes. Surface waters were linked to genes involved in photosynthesis, autotrophy and cell division. Taken together, the observed increase of DOM homogenization along water mass aging was associated to differences in the functional diversity of microbial communities

Manganese Defective Clustering: Influence on the Spectroscopic Features of Ceria-Based Nanomaterials

The influence of manganese modification on the spectroscopic features of manganese-doped CeO2 systems synthesized by the microwave-assisted hydrothermal route and their correlation with the presence of O defective structures were verified, focusing on their interaction with poisonous atmospheres. Raman and electron paramagnetic resonance studies confirmed the presence of defective clusters formed by dipoles and/or quadrupoles. The number of paramagnetic species was found to be inversely proportional to the doping concentration, resulting in an increase in the Mn2+ signal, likely due to the reduction of Mn3+ species after the interaction with CO. X-ray photoelectron spectroscopy data showed the pure system with 33% of its cerium species in the Ce3+ configuration, with an abrupt decrease to 19%, after the first modification with Mn, suggesting that 14% of the Ce3+ species are donating one electron to the Mn2+ ions, thus becoming nonparamagnetic Ce4+ species. On the contrary, 58% of the manganese species remain in the Mn2+ configuration with five unpaired electrons, corroborating the paramagnetic feature of the samples seen in the electron paramagnetic resonance study

Evaluation of the GEXCAT software in the design and correction of multiple choice exams: preliminary data

Resúmenes IV Congreso VetDoc de Docencia Veterinaria, León 2017 (6-7 de Julio)[ES] El sistema de evaluación continua propuesto por el Plan Bolonia supone un incremento de la carga de trabajo del profesor universitario (Pagani y González, 2002). Los exámenes tipo test son una opción, sobre todo en el caso de asignaturas con un elevado número de créditos. Permiten una pronta corrección y se puede aumentar el número de evaluaciones, mejorando los resultados de los alumnos, lo que aumenta su motivación (Escolano et al., 2014). Para que los alumnos no se copien convienen preparar varios modelos de exámenes, aunque esto complica la corrección, facilitando el error humano. Para evitar tal situación se han creado programas informáticos. El programa privativo de Gestión de Exámenes y Corrección Automática de Tests, GEXCAT (Innocan, 2017), es una herramienta que ayuda en la preparación y corrección de exámenes tipo test, con la ventaja de utilizar hojas DINA4 y un escáner básico. Permite generar exámenes de tipo test tanto en formato electrónico como en papel. Barajando tanto las preguntas como las respuestas puede llegar a generar hasta nueve modelos de examen. Además, las preguntas pueden ser clasificadas por nivel de dificultad. El programa proporciona las correcciones casi instantáneamente, pudiendo exportar las calificaciones en formato Excel, enviar los resultados a los alumnos vía email y gestionar eficazmente las evaluaciones continuas

Superficial radiotherapy as haemostatic treatment in breast cancer

Poster Session [EP-1661] Purpose or Objective Breast cancer is a common pathology in which o = 25% in tumor size and absence of bleeding was observed. Conclusion Surface radiotherapy is a treatment modality that should be taken into account in patients with breast cancer who present bleeding as a consequence of local tumor growth, given that this is a treatment comfortable for the patient, non invasive and increases the quality of patient’s life