Fernando Moreno

Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the Sun

Critical measurements for understanding accretion and the dust/gas ratio in the solar nebula, where planets were forming 4.5 billion years ago, are being obtained by the GIADA (Grain Impact Analyser and Dust Accumulator) experiment on the European Space Agency’s Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko. Between 3.6 and 3.4 astronomical units inbound, GIADA and OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) detected 35 outflowing grains of mass 10−10 to 10−7 kilograms, and 48 grains of mass 10−5 to 10−2 kilograms, respectively. Combined with gas data from the MIRO (Microwave Instrument for the Rosetta Orbiter) and ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instruments, we find a dust/gas mass ratio of 4 ± 2 averaged over the sunlit nucleus surface. A cloud of larger grains also encircles the nucleus in bound orbits from the previous perihelion. The largest orbiting clumps are meter-sized, confirming the dust/gas ratio of 3 inferred at perihelion from models of dust comae and trails.

Scattering matrix of large Saharan dust particles: Experiments and computations

We present measurements of the complete scattering matrix as a function of the scattering angle of a sample of Sahara sand particles collected from a dune in Libya. The measurements were performed at a wavelength of 632.8 nm in the scattering angle range from 4° to 174°. To facilitate the use of the experimental data for multiple-scattering calculations with polarization included, we present a synthetic scattering matrix based on the measurements and defined in the full angle range from 0° to 180°. The Libyan sample consists of large particles distributed over a narrow size distribution which makes it an interesting test case for the Ray Optics Approximation (ROA) that provides accurate results for particles with curvature radii much larger than the wavelength. Numerical simulations using the ROA are compared with the experimental data. Moreover, the traditional ROA was modified with ad hoc simple schemes of Lambertian surface elements and internal screens to study the effects of small-scale surface roughness and internal structures, respectively. Model particle shapes used in the simulations are based on a shape analysis of our sample. The traditional ray optics approximation does not reproduce the experimental data although a significant improvement is obtained if unrealistically spiky particle shapes are used. When the Lambertian schemes are applied the agreement with the experimental data improves. Still, to get a good agreement with the experimental data we need unrealistic spiky particles together with the inclusion of external Lambertian reflections. This seems to indicate that a more refined treatment is needed to reproduce the scattering effects of the small-scale surface roughness of the Libyan sand particles.

Quasi-random narrow-band model fits to near-infrared low-temperature laboratory methane spectra and derived exponential-sum absorption coefficients

Near-infrared 10-cm−1 resolution spectra of methane obtained at various temperatures, pressures, and abundances are fit to a quasi-random narrow-band model. Exponential-sum absorption coefficients for three temperatures (112 K, 188 K, and 295 K), and 20 pressures from 0.0001 to 5.6 bars, applicable to the cold environments of the major planets, are then derived from the band model for the 230 wavelengths measured from 1.6 to 2.5 μm. Root-mean-square deviations between the laboratory and the exponential-sum synthetic transmissions are reported for the best fitting 50 wavelengths. Deviations relevant to broadband, 1% spectral resolution observations such as planned to be acquired by Galileo/Near Infrared Mapping Spectrometer (NIMS)and Cassini/Visual and Infrared Mapping Spectrometer are also presented. The validity of exponential-sum coefficients derived from broadband (10 cm−1) transmission data is demonstrated via direct comparison with line-by-line calculations. The complete atlas of coefficients is available from the Planetary Data System-Planetary Atmospheres Discipline Node.

Impact of postharvest methyl jasmonate treatment on the volatile composition and flavonol content of strawberries

BACKGROUND Although strawberry aroma is very complex, certain compounds have been described as main contributors, i.e. furanones, aldehydes, alcohols, sulfur compounds and particularly methyl and ethyl esters. In addition, strawberries possess potent antioxidant activity because of their high content of phenolic compounds. Among them, flavonols are highlighted as important antioxidant compounds in strawberry. The objective of this study was to assess the effect of methyl jasmonate (MJ) on the composition of the major contributors to aroma and on the content of certain flavonols in strawberry fruits. RESULTS The levels of all studied volatile compounds were significantly affected by MJ treatment, though the individual effect differed according to the specific compound considered. Most of them increased significantly (P < 0.05), except methyl butanoate, which always showed higher levels in untreated strawberries. In contrast to aroma compounds, the change in the concentration of flavonols (i.e. myricetin, quercetin and kaempferol) was not significant in MJ-treated strawberries. Considering the health-promoting activity of these compounds, further investigations on the experimental conditions related to the treatment are required to control flavonol bioformation by means of MJ. CONCLUSION The exogenous application of MJ vapour to strawberry enhances, in general, the production of the most relevant aroma-active compounds. On the contrary, MJ treatment does not appear to influence the levels of myricetin, quercetin and kaempferol. Thus postharvest MJ treatment is proposed as an approach to obtain improved strawberry fruits in terms of sensory quality and health-promoting properties.

Evaluation of pesticide residue contents in fruit juice by solid-phase microextraction and multidimensional gas chromatography coupled with mass spectrometry

A new method based on the use of SPME followed by the MDGC-MS analysis was developed to determine pesticides in fruit juice. Different pesticide mixture standards (i.e. Mix 101, 13 and 164) were initially analyzed to optimize the separation conditions. To evaluate the advantages of the two-dimensional system over monodimensional GC, a comparative study on relative standard deviations, detection limits and correlation coefficients was carried out. As a result, selective transfers of some pesticides from the first to the second dimension were at times essential to avoid overlapping. The selected separation conditions from the study with standards were applied to fruit juices spiked with some pesticide standards. The results found in this work prove that the employment of a multidimensional analysis technique permits to avoid false positives obtained frequently on monodimensional techniques as a consequence of interferences of the analytes with matrix components.

Bayesian deconvolution with prior knowledge of object location : applications to ground-based planetary images

A Bayesian method to deconvolve images when the location of the objects in the image is known in advance is presented. This knowledge of location is incorporated into the prior model via a labeling process. An iterative method is proposed to find the maximum a posteriori estimator of the image. The method was tested on both synthetic images and ground-based CCD images of Saturn with very encouraging results

Development of a method based on on-line reversed phase liquid chromatography and gas chromatography coupled by means of an adsorption-desorption interface for the analysis of selected chiral volatile compounds in methyl jasmonate treated strawberries

A method based on the use of the through oven transfer adsorption-desorption (TOTAD) interface in on-line coupling between reversed phase liquid chromatography and gas chromatography (RPLC-GC) for the determination of chiral volatile compounds was developed. In particular, the method was applied to the study of the influence of methyl jasmonate (MJ) treatment on the production and enantiomeric composition of selected aroma compounds in strawberry. The compounds studied were ethyl 2-methylbutanoate, linalool and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (i.e. furaneol), which were examined on days 3, 6 and 9 after treatment. The method developed resulted in relative standard deviations (RSDs) of 21.6%, 8.1% and 9.8% and limits of detection (LD) of 0.04, 0.07 and 0.02mg/l for ethyl 2-methylbutanoate, linalool and furaneol, respectively. The application of the RPLC-TOTAD-GC method allowed higher levels of ethyl 2-methylbutanoate, linalool and furaneol to be detected, particularly after 9 days of treatment. Besides, MJ demonstrated to affect the enantiomeric distribution of ethyl 2-methylbutanoate. On the contrary, the enantiomeric composition of linalool and furaneol kept constant in both control and MJ-treated strawberries throughout the study. These results are discussed.

Models of the SL‐9 collision‐generated hazes

From subarcsec-seeing infrared images and spectra in the K and H bands, we present reflectivities and limb-darkening results for two of the hazy regions generated during the SL-9 collision. These highly reflective impact areas at infrared methane wavelengths have been studied in terms of multiple scattering radiative models. The results for both the H and D/G impact remnants show that a considerable amount of particles have been injected in Jovian stratospheric levels from ∼1 mbar to the upper level of the assumed Jovian tropospheric NH3 ice haze (at ∼350 mbar). Our models suggest a concentration of small particles, with mean radius of 0.15 µm for a real refractive index of 1.7. The imaginary refractive indices are in the range 1 × 10−4 to 1 × 10−3. For the H impact region, absorption at 2.0 µm is enhanced compared to unperturbed regions at the same scattering geometry. This enhancement is not observed in the older D/G complex.

Pseudomonas pseudoalcaligenes CECT5344, a cyanide‑degrading bacterium with by‑product (polyhydroxyalkanoates) formation capacity

BackgroundCyanide is one of the most toxic chemicals produced by anthropogenic activities like mining and jewelry industries, which generate wastewater residues with high concentrations of this compound. Pseudomonas pseudoalcaligenes CECT5344 is a model microorganism to be used in detoxification of industrial wastewaters containing not only free cyanide (CN−) but also cyano-derivatives, such as cyanate, nitriles and metal-cyanide complexes. Previous in silico analyses suggested the existence of genes putatively involved in metabolism of short chain length (scl-) and medium chain length (mcl-) polyhydroxyalkanoates (PHAs) located in three different clusters in the genome of this bacterium. PHAs are polyesters considered as an alternative of petroleum-based plastics. Strategies to optimize the bioremediation process in terms of reducing the cost of the production medium are required.ResultsIn this work, a biological treatment of the jewelry industry cyanide-rich wastewater coupled to PHAs production as by-product has been considered. The functionality of the pha genes from P. pseudoalcaligenes CECT5344 has been demonstrated. Mutant strains defective in each proposed PHA synthases coding genes (Mpha−, deleted in putative mcl-PHA synthases; Spha−, deleted in the putative scl-PHA synthase) were generated. The accumulation and monomer composition of scl- or mcl-PHAs in wild type and mutant strains were confirmed by gas chromatography-mass spectrometry (GC–MS). The production of PHAs as by-product while degrading cyanide from the jewelry industry wastewater was analyzed in batch reactor in each strain. The wild type and the mutant strains grew at similar rates when using octanoate as the carbon source and cyanide as the sole nitrogen source. When cyanide was depleted from the medium, both scl-PHAs and mcl-PHAs were detected in the wild-type strain, whereas scl-PHAs or mcl-PHAs were accumulated in Mpha− and Spha−, respectively. The scl-PHAs were identified as homopolymers of 3-hydroxybutyrate and the mcl-PHAs were composed of 3-hydroxyoctanoate and 3-hydroxyhexanoate monomers.ConclusionsThese results demonstrated, as proof of concept, that talented strains such as P. pseudoalcaligenes might be applied in bioremediation of industrial residues containing cyanide, while concomitantly generate by-products like polyhydroxyalkanoates. A customized optimization of the target bioremediation process is required to gain benefits of this type of approaches.

Phenylalanine ammonia-lyase, flavanone 3β-hydroxylase and flavonol synthase enzyme activity by a new in vitro assay method in berry fruits.

An HPLC method for the determination of phenylalanine ammonia-lyase, flavanone 3β-hydroxylase and flavonol synthase enzyme activity is proposed. This method is based on the determination of the compounds produced and consumed on the enzymatic reaction in just one chromatographic analysis. Optimisation of the method considered kinetic studies to establish the incubation time to perform the assay. The method here described proved to be an interesting approach to measure the activities of the three enzymes simultaneously increasing the rapidity, selectivity and sensitivity over other exiting methods. The enzyme activity method developed was applied to strawberry, raspberry, blackberry, redcurrant and blackcurrant fruits.