Gravity-induced Wannier-Stark ladder in an optical lattice

We discuss the dynamics of ultracold atoms in an optical potential accelerated by gravity. The positions and widths of the Wannier-Stark ladder of resonances are obtained as metastable states. The metastable Wannier-Bloch states oscillate in a single band with the Bloch period. The width of the resonance gives the rate transition to the continuum.Comment: 5 pages + 8 eps figures, submitted to Phys. Rev.

Aerosol direct radiative effects of a transatlantic biomass burning plume over Granada, Spain

This work presents the assessment of the aerosol direct radiative effects for a special episode of transatlantic transport of a biomass burning plume, performed over Granada, south-eastern Iberian Peninsula, on 20th August 2007. The knowledge of aerosol radiative impact requires an accurate determination of their optical and microphysical properties, which are obtained here using ground-based remote sensing instrumentation by means of a combination of lidar and sun-photometer. Our data highlight the presence of a multilayered structure with a well-defined planetary boundary layer and biomass-particles in elevated layers, extending up to 9 km asl, at the south-eastern part of the Iberian Peninsula. The aerosol direct shortwave radiative effects, evaluated from simulations with SBDART code, show that the biomass burning plume increases the heating rate up to 0.5 K/day in spite of the small contribution of these particles to the total aerosol optical depth (10-20%). In addition, our results indicate that the biomass burning plume strengths the negative radiative forcing about -5 down to -8 W/m2 at the surface, between noon and evening. At the TOA, radiative forcing appeared slightly positive but very close to zero at noon, and negative in the evening with a decrease of 1.5 W/m2 caused by the presence of the biomass burning plume.Postprint (published version

RNA-seq and Tn-seq reveal fitness determinants of vancomycin-resistant Enterococcus faecium during growth in human serum

BACKGROUND: The Gram-positive bacterium Enterococcus faecium is a commensal of the human gastrointestinal tract and a frequent cause of bloodstream infections in hospitalized patients. The mechanisms by which E. faecium can survive and grow in blood during an infection have not yet been characterized. Here, we identify genes that contribute to growth of E. faecium in human serum through transcriptome profiling (RNA-seq) and a high-throughput transposon mutant library sequencing approach (Tn-seq). RESULTS: We first sequenced the genome of E. faecium E745, a vancomycin-resistant clinical isolate, using a combination of short- and long read sequencing, revealing a 2,765,010 nt chromosome and 6 plasmids, with sizes ranging between 9.3 kbp and 223.7 kbp. We then compared the transcriptome of E. faecium E745 during exponential growth in rich medium and in human serum by RNA-seq. This analysis revealed that 27.8% of genes on the E. faecium E745 genome were differentially expressed in these two conditions. A gene cluster with a role in purine biosynthesis was among the most upregulated genes in E. faecium E745 upon growth in serum. The E. faecium E745 transposon mutant library was then used to identify genes that were specifically required for growth of E. faecium in serum. Genes involved in de novo nucleotide biosynthesis (including pyrK_2, pyrF, purD, purH) and a gene encoding a phosphotransferase system subunit (manY_2) were thus identified to be contributing to E. faecium growth in human serum. Transposon mutants in pyrK_2, pyrF, purD, purH and manY_2 were isolated from the library and their impaired growth in human serum was confirmed. In addition, the pyrK_2 and manY_2 mutants were tested for their virulence in an intravenous zebrafish infection model and exhibited significantly attenuated virulence compared to E. faecium E745. CONCLUSIONS: Genes involved in carbohydrate metabolism and nucleotide biosynthesis of E. faecium are essential for growth in human serum and contribute to the pathogenesis of this organism. These genes may serve as targets for the development of novel anti-infectives for the treatment of E. faecium bloodstream infections

Dietary Fat Patterns and Outcomes in Acute Pancreatitis in Spain

Background/Objective: Evidence from basic and clinical studies suggests that unsaturated fatty acids (UFAs) might be relevant mediators of the development of complications in acute pancreatitis (AP). Objective: The aim of this study was to analyze outcomes in patients with AP from regions in Spain with different patterns of dietary fat intake. Materials and Methods: A retrospective analysis was performed with data from 1,655 patients with AP from a Spanish prospective cohort study and regional nutritional data from a Spanish cross-sectional study. Nutritional data considered in the study concern the total lipid consumption, detailing total saturated fatty acids, UFAs and monounsaturated fatty acids (MUFAs) consumption derived from regional data and not from the patient prospective cohort. Two multivariable analysis models were used: (1) a model with the Charlson comorbidity index, sex, alcoholic etiology, and recurrent AP; (2) a model that included these variables plus obesity. Results: In multivariable analysis, patients from regions with high UFA intake had a significantly increased frequency of local complications, persistent organ failure (POF), mortality, and moderate-to-severe disease in the model without obesity and a higher frequency of POF in the model with obesity. Patients from regions with high MUFA intake had significantly more local complications and moderate-to-severe disease; this significance remained for moderate-to-severe disease when obesity was added to the model. Conclusions: Differences in dietary fat patterns could be associated with different outcomes in AP, and dietary fat patterns may be a pre-morbid factor that determines the severity of AP. UFAs, and particulary MUFAs, may influence the pathogenesis of the severity of AP

Validation of a method for cylindrospermopsin determination in vegetables: Application to real samples such as lettuce (lactuca sativa l.)

Reports on the occurrence of the cyanobacterial toxin cylindrospermopsin (CYN) have increased worldwide because of CYN toxic effects in humans and animals. If contaminated waters are used for plant irrigation, these could represent a possible CYN exposure route for humans. For the first time, a method employing solid phase extraction and quantification by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) of CYN was optimized in vegetables matrices such as lettuce (Lactuca sativa). The validated method showed a linear range, from 5 to 500 ng CYN g−1 of fresh weight (f.w.), and detection and quantitation limits (LOD and LOQ) of 0.22 and 0.42 ng CYN g−1 f.w., respectively. The mean recoveries ranged between 85 and 104%, and the intermediate precision from 12.7 to 14.7%. The method showed to be robust for the three different variables tested. Moreover, it was successfully applied to quantify CYN in edible lettuce leaves exposed to CYN-contaminated water (10 µg L−1), showing that the tolerable daily intake (TDI) in the case of CYN could be exceeded in elderly high consumers. The validated method showed good results in terms of sensitivity, precision, accuracy, and robustness for CYN determination in leaf vegetables such as lettuce. More studies are needed in order to prevent the risks associated with the consumption of CYN-contaminated vegetables. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.Acknowledgments: The authors would like to acknowledge the Ministerio de Economía y Competitividad of Spain (AGL2015-64558-R, MINECO/FEDER, UE) for its financial support and the FCT Project UID/Multi/04423/2013. The authors also gratefully acknowledge the Spanish Ministerio de Economia y Competitividad for the grant FPI (BES-2016-078773) awarded to Leticia Díez-Quijada Jiménez. A. Campos work was supported by a postdoctoral grant (SFRH/BPD/103683/2014) from FCT

Resonant Raman-active localized vibrational modes in AlyGa{1-y}NxAs{1-x} alloys: Experiment and firstprinciples calculations

The localized vibrational modes associated with substitutional aluminium and nitrogen atoms in AlyGa1−yNxAs1−x have been studied within first-principles density functional theory using a supercell approach. Localized vibrational modes related to N-AlmGa4−m (1≤m≥4) complexes have been identified, which reveal the formation of N-Al4 units well above random abundance, in qualitative agreement with a large calculated value (391 meV) of the Al-N bond formation energy. We determine the resonant Raman-active modes from the selection rule obtained by calculating the electron-phonon coupling strength and optical transition matrix elements and compare them with resonant Raman spectroscopy measurements. The localized modes from Raman scattering measurements with frequencies around 325, 385, 400, 450, 500, and 540 cm−1 are found to be in good agreement with the calculated modes (326, 364, 384, 410, 456, 507, and 556 cm−1). The modes are classified as follows: the two modes at 326 and 556 cm−1 belong to the N-AlGa3 configuration; there are three modes which belong to N-Al2Ga2 with frequencies at 326, 364, and 507 cm−1; the N-Al3Ga configuration gives rise to modes whose frequencies are 384 and 456 cm−1; and the mode at a frequency of 410 cm−1 belongs to the N-Al4 complex. The comparison of line intensities from samples before and after rapid thermal annealing allows us to experimentally distinguish vibrational modes associated with different clusters, in agreement with the theoretical assignments

Resonant Raman study of local vibrational modes in AlGaAsN layers

We report on resonant inelastic light scattering in dilute AlGaAsN films. Intense narrow peaks associated to N-related local vibration modes (LVM) have been observed around 325, 385, 400, 450, 500 and 540 cm−1. Their frequencies are compared to density functional theory supercell calculations of AlnGa4−nN complexes (n=1−4). We find clear indications of the formation of Al4N complexes. The values of the extended phonon frequencies reveal changes in the N distribution depending on the growth conditions. The LVM spectra are resonant in the energy range from 1.75 to 1.79 eV, which corresponds to an N-related electronic transition. Our results confirm the preferential bonding of N to Al in AlGaAsN

Potential use of chemoprotectants against the toxic effects of cyanotoxins: A review

Cyanobacterial toxins, particularly microcystins (MCs) and cylindrospermopsin (CYN), are responsible for toxic effects in humans and wildlife. In order to counteract or prevent their toxicity, various strategies have been followed, such as the potential application of chemoprotectants. A review of the main substances evaluated for this aim, as well as the doses and their influence on cyanotoxin-induced toxicity, has been performed. A search of the literature shows that research on MCs is much more abundant than research on CYN. Among chemoprotectants, antioxidant compounds are the most extensively studied, probably because it is well known that oxidative stress is one of the toxic mechanisms common to both toxins. In this group, vitamin E seems to have the strongest protectant effect for both cyanotoxins. Transport inhibitors have also been studied in the case of MCs, as CYN cellular uptake is not yet fully elucidated. Further research is needed because systematic studies are lacking. Moreover, more realistic exposure scenarios, including cyanotoxin mixtures and the concomitant use of chemoprotectants, should be considered. © 2017 by the authors. Licensee MDPI, Basel, Switzerland.This work was supported by the the Ministerio de Economía y Competitividad of Spain (AGL2015-64558-R, MINECO/FEDER, UE), by the FCT Project—UID/Multi/04423/2013, and by the Structured Program of R&D&I INNOVMAR—Innovation and Sustainability in the Management and Exploitation of Marine Resources (reference NORTE-01-0145-FEDER-000035, Research Line NOVELMAR), funded by the Northern Regional Operational Program (NORTE2020) through the European Regional Development Fund (ERDF). Alexandre Campos work is supported by a post-doctoral grant (SFRH/BPD/103683/2014) from Foundation for Science and Technology (FCT, Lisbon, Portugal)

Monitoring of the Eyjafjalla volcanic plume at four lidar stations over the Iberian Peninsula: 6 to 8 May 2010

Lidar measurements were performed in the framework of the EARLINET and SPALINET networks during the eruption of Eyjafjalla volcano (Iceland) since 14 April 2010. The profiles of the aerosol optical properties, namely backscatter and extinction coefficients, lidar ratio and Angström exponent, show the presence of volcanic aerosol layers over all SPALINET stations since 5 May. The volcanic particles were monitored both within the planetary boundary layer and in decoupled layers up to 8 km agl over the Iberian Peninsula. This is the first time that the spatial and temporal distributions of volcanic aerosols have been studied with active remote sensing techniques over the Iberian Peninsula.Postprint (published version

New Method for Simultaneous Determination of Microcystins and Cylindrospermopsin in Vegetable Matrices by SPE-UPLC-MS/MS

Cyanotoxins are a large group of noxious metabolites with different chemical structure and mechanisms of action, with a worldwide distribution, producing effects in animals, humans, and crop plants. When cyanotoxin-contaminated waters are used for the irrigation of edible vegetables, humans can be in contact with these toxins through the food chain. In this work, a method for the simultaneous detection of Microcystin-LR (MC-LR), Microcystin-RR (MC-RR), Microcystin-YR (MC-YR), and Cylindrospermopsin (CYN) in lettuce has been optimized and validated, using a dual solid phase extraction (SPE) system for toxin extraction and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for analysis. Results showed linear ranges (5⁻50 ng g-1 f.w.), low values for limit of detection (LOD) (0.06⁻0.42 ng g-1 f.w.), and limit of quantification (LOQ) (0.16⁻0.91 ng g-1 f.w.), acceptable recoveries (41⁻93%), and %RSDIP values for the four toxins. The method proved to be robust for the three variables tested. Finally, it was successfully applied to detect these cyanotoxins in edible vegetables exposed to cyanobacterial extracts under laboratory conditions, and it could be useful for monitoring these toxins in edible vegetables for better exposure estimation in terms of risk assessment.Funding: This research was funded by the SPANISH MINISTERIO DE ECONOMÍA Y COMPETITIVIDAD (AGL2015-64558-R, MINECO/FEDER, UE); by the FPI grant number BES-2016-078773 awarded to Leticia Díez-Quijada Jiménez; by the FCT project UID/Multi/04423/2013, and the post-doctoral grant (SFRH/BPD/103683/2014) from FCT awarded to Alexandre Campos. Acknowledgments: Spanish Ministerio de Economía y Competitividad for the project AGL2015-64558-R, MINECO/FEDER, UE, and for the grant FPI (BES-2016-078773) awarded to Leticia Díez-Quijada Jiménez. CIIMAR members acknowledge FCT project UID/Multi/04423/2013 and the post-doctoral grant (SFRH/BPD/103683/2014) from FCT awarded to Alexandre Campos