Ultrastructure of the onset of chilling injury in cucumber fruit

The onset of the symptoms of disorders provoked by low temperature storage or chilling injury (CI) in pickling cucumber fruit (Cucumis sativus L. cv. 'Trópico' and in the cv. 'Perichán 121') and associated rot were monitored by cryoscanning electron microscopy. Fruit were stored at 4°C for different times (4 to 12 d) and samples were transferred to 20°C every 2-3 d (cv. Trópico). In a second experiment, fruit cv. 'Perichán 121' were stored at 6°C. Macroscopic CI symptoms included small-flattened areas with sunken but externally sound tissue. Later, the damage was manifested as pitting and decay due to the presence of necrotrophic fungi (Pleospora herbarum, Alternaria sp.) on the surface of the broken areas, and Botrytis cinerea in cv. 'Perichán 121'. The period of induction of CI becoming apparent lasted about 4 d at 4oC followed by a phase of slow increase of around 4-5 d prior to an exponential increase in CI. Micro fractures of 45-250 μm length developed in CI tissue around the stomata of 20 μm Ø. The first response to chilling was the sinking of stomata accompanied by 10 μm Ø fractures with collapse of hypodermal cells. These small fractures expanded into a sink of around 40 μm Ø and more than 50 μm depth. Refrigerated tissue had visibly collapsed in 4-6 d, starting with a small brown area indicating collapse of parenchymatous cells, followed by sinking and collapse of epidermal cells, particularly around the micro fractures. The pitted tissue showed flattening of the cell walls, plasmalemma and middle lamella region, with severity increasing with increasing depth in the parenchymatous tissue. Translucent water soaked areas were also located depth in the mesocarp tissue with similar cell damages

Quality of two table grape guard cultivars treated with single or dual-phase release SO2 generators

Berries of seeded table grapes (cultivars Napoleón and Aledo) were trimmed in commercial packing houses, inoculated with Botrytis cinerea, packed with single and dual-phase release SO2 pads, and stored for up to four months at 0 ºC and 85±5 % relative humidity. Control grapes with or without inoculation, but without SO2 pads, were stored for up to 2 months. Botrytis cinerea rot (grey mould) limited the shelf-life of Aledo grapes to one month, while a two month shelf-life was established for Napoleón grapes, which suffered from berry splitting, Cladosporium herbarum and Botrytis cinerea rots. Yeasts of the Candida genera and secondary fungi were also identified in fruit suffering sour rot after 2 months at 0oC. No differences in grey mould development in the treatments without SO2 pads with or without inoculation. The native grey mould of these grapes was purified and included as the B. cinerea strain 20248 in the Spanish Type Culture Collection. Storage time, but not SO2 pads, slightly affected fruit quality. During the first month at 0oC, total soluble solids decreased by 1oBrix in 'Áledo' and berry hardness temporarily increased by around 30% in both cultivars. The pads provoked an SO2 taste acceptable for consumption, which was slightly higher in Napoleón than in Aledo grapes. The dual-phase release SO2 pads showed better performance for the long-term storage of grapes than single-release pads (both as regards berry sensory attributes and stem appearance, with lower stem browning). The dual-phase release SO2 pads extended the shelf-life of grapes by around 1 month, depending on the cultivar. Napoleón grapes showed a better potential for longterm storage than Aledo grapes due to thicker and more compact epidermis, thicker cell walls, and different epidermal microstructure including the transition cells between epidermis and the parenchyma

Anomalous circular polarization profiles in the He I 1083.0 nm multiplet from solar spicules

We report Stokes vector observations of solar spicules and a prominence in the He I 1083 nm multiplet carried out with the Tenerife Infrared Polarimeter. The observations show linear polarization profiles that are produced by scattering processes in the presence of a magnetic field. After a careful data reduction, we demonstrate the existence of extremely asymmetric Stokes V profiles in the spicular material that we are able to model with two magnetic components along the line of sight, and under the presence of atomic orientation in the energy levels that give rise to the multiplet. We discuss some possible scenarios that can generate the atomic orientation in spicules. We stress the importance of spectropolarimetric observations across the limb to distinguish such signals from observational artifacts.Comment: accepted for publication in Ap

Predictive models based on RSM and ANN for roughness and wettability achieved by laser texturing of S275 carbon steel alloy

Laser texturing is increasingly gaining attention in the field of metal alloys due to its ability to improve surface properties, particularly in steel alloys. However, the input parameters of the technology must be carefully controlled to achieve the desired surface roughness. Roughness is critical to the activation of the surface before further bonding operations, and it is often assessed using several parameters such as Ra, Rt, Rz, and Rv. This surface activation affects the properties of the metal alloy in terms of wettability, which has been evaluated by the deposition of ethylene glycol droplets through a contact angle. This allowed a direct relationship to be established between the final roughness, the wettability of the surface and the texturing parameters of the alloy. This raises the interest of being able to predict the behaviour in terms of roughness and wettability for future applications in improving the behaviour of metallic alloys. In this research, a comparative analysis between Response Surface Models (RSM) and predictive models based on Artificial Neural Networks (ANN) has been conducted. The model based on neural networks was able to predict all the output variables with a fit greater than 90%., improving that obtained by RSM. The model obtained by ANN allows a greater adaptability to the variation of results obtained, reaching deviations close to 0.2 μm. The influence of input parameters, in particular power and scanning speed, on the achieved roughness and surface wettability has been figured out by contact angle measurements. This increases its surface activation in terms of wettability. Superhydrophilic surfaces were achieved by setting the power to 20 W and scanning speed to ten mm/s. In contrast, a power of 5 W and a scanning speed of 100 mm/s reduced the roughness values.Funding for open access charge: Universidad de Málaga / CBU

A Petal of the Sunflower: Photometry of the Stellar Tidal Stream in the Halo of Messier 63 (NGC 5055)

We present surface photometry of a very faint, giant arc feature in the halo of the nearby spiral galaxy NGC 5055 (M63) that is consistent with being a part of a stellar stream resulting from the disruption of a dwarf satellite galaxy. This faint feature was first detected in early photographic studies by van der Kruit (1979); more recently by Mart\'inez-Delgado et al. (2010) and as presented in this work, the loop has been realized to be the result of a recent minor merger through evidence obtained by deep images taken with a telescope of only 0.16 m aperture. The stellar stream is confirmed in additional images taken with the 0.5 m of the BlackBird Remote Observatory and the 0.8 m of the McDonald Observatory. This low surface brightness structure around the disk of the galaxy extends ~29 kpc from its center, with a projected width of 3.3 kpc. The stream's morphology is consistent with that of the visible part of a "great-circle" stellar stream originating from the accretion of a ~10^8 M_sun dwarf satellite in the last few Gyr. The progenitor satellite's current position and fate are not conclusive from our data. The color of the stream's stars is consistent with Local Group dwarfs and is similar to the outer regions of M63's disk and stellar halo. We detect other low surface brightness "plumes"; some of these may be extended spiral features related to the galaxy's complex spiral structure and others may be tidal debris associated with the disruption of the galaxy's outer stellar disk as a result of the accretion event. We differentiate between features related to the tidal stream and faint, blue features in the outskirts of the galaxy's disk previously detected by the GALEX satellite. With its highly warped HI gaseous disk (~20 deg), M63 represents one of several examples of an isolated spiral galaxy with a warped disk showing strong evidence of an ongoing minor merger.Comment: 16 pages, 10 figures, 3 tables, Accepted for publication in The Astronomical Journa

Estimating the longitudinal magnetic field in the chromosphere of quiet-Sun magnetic concentrations

Details of the magnetic field in the quiet Sun chromosphere are key to our understanding of essential aspects of the solar atmosphere. We aim to determine the longitudinal magnetic field component (B_lon) of quiet Sun regions depending on their size. We estimated B_lon by applying the weak-field approximation (WFA) to high-spatial-resolution Ca II 854.2 nm data taken with the Swedish 1m Solar Telescope. Specifically, we analyzed the estimates inferred for different spectral ranges using the data at the original cadence and temporally integrated signals. The longitudinal magnetic field in each considered plasma structure correlates with its size. Using a spectral range restricted to the line core leads to chromospheric longitudinal fields varying from 50 G at the edges to 150-500 G at the center of the structure. These values increase as the spectral range widens due to the photospheric contribution. However, the difference between this contribution and the chromospheric one is not uniform for all structures. Small and medium-sized concentrations show a steeper height gradient in B_lon compared to their chromospheric values, so estimates for wider ranges are less trustworthy. Signal addition does not alleviate this situation as the height gradients in B_lon are consistent with time. Finally, despite the amplified noise levels that deconvolving processes may cause, data restored with the destretching technique show similar results, though are affected by smearing. We obtained B_lon estimates similar to those previously found, except for large concentrations and wide spectral ranges. In addition, we report a correlation between the height variation of B_lon compared to the chromospheric estimates and the concentration size. This correlation affects the difference between the photospheric and chromospheric magnetic flux values and the reliability of the estimates for wider spectral ranges.Comment: 14 pages, 14 figures. Accepted for publication in Astronomy & Astrophysics; abstract has been abridge

Wave propagation and shock formation in different magnetic structures

Velocity oscillations "measured" simultaneously at the photosphere and the chromosphere -from time series of spectropolarimetric data in the 10830 A region- of different solar magnetic features allow us to study the properties of wave propagation as a function of the magnetic flux of the structure (i.e. two different-sized sunspots, a tiny pore and a facular region). While photospheric oscillations have similar characteristics everywhere, oscillations measured at chromospheric heights show different amplitudes, frequencies and stages of shock development depending on the observed magnetic feature. The analysis of the power and the phase spectra, together with simple theoretical modeling, lead to a series of results concerning wave propagation within the range of heights of this study. We find that, while the atmospheric cut-off frequency and the propagation properties of the different oscillating modes depend on the magnetic feature, in all the cases the power that reaches the high chromosphere above the atmospheric cut-off comes directly from the photosphere by means of linear vertical wave propagation rather than from non-linear interaction of modes.Comment: Accepted for publication in The Astrophysical Journal. 29 pages, 9 figures, 12pt, preprin

The stellar atmosphere simulation code Bifrost

Context: Numerical simulations of stellar convection and photospheres have been developed to the point where detailed shapes of observed spectral lines can be explained. Stellar atmospheres are very complex, and very different physical regimes are present in the convection zone, photosphere, chromosphere, transition region and corona. To understand the details of the atmosphere it is necessary to simulate the whole atmosphere since the different layers interact strongly. These physical regimes are very diverse and it takes a highly efficient massively parallel numerical code to solve the associated equations. Aims: The design, implementation and validation of the massively parallel numerical code Bifrost for simulating stellar atmospheres from the convection zone to the corona. Methods: The code is subjected to a number of validation tests, among them the Sod shock tube test, the Orzag-Tang colliding shock test, boundary condition tests and tests of how the code treats magnetic field advection, chromospheric radiation, radiative transfer in an isothermal scattering atmosphere, hydrogen ionization and thermal conduction. Results: Bifrost completes the tests with good results and shows near linear efficiency scaling to thousands of computing cores

Balancing porosity and mechanical properties of titanium samples to favor cellular growth against bacteria

Two main problems limit the success of titanium implants: bacterial infection, which restricts their osseointegration capacity; and the stiffness mismatch between the implant and the host cortical bone, which promotes bone resorption and risk of fracture. Porosity incorporation may reduce this difference in stiffness but compromise biomechanical behavior. In this work, the relationship between the microstructure (content, size, and shape of pores) and the antibacterial and cellular behavior of samples fabricated by the space-holder technique (50 vol % NH4HCO3 and three ranges of particle sizes) is established. Results are discussed in terms of the best biomechanical properties and biofunctional activity balance (cell biocompatibility and antibacterial behavior). All substrates achieved suitable cell biocompatibility of premioblast and osteoblast in adhesion and proliferation processes. It is worth to highlighting that samples fabricated with the 100–200 μm space-holder present better mechanical behavior—in terms of stiffness, microhardness, and yield strength—which make them a very suitable material to replace cortical bone tissues. Those results exposed the relationship between the surface properties and the race of bacteria and mammalian cells for the surface with the aim to promote cellular growth over bacteria.University of Seville (Spain) VI Plan Propio de Investigación y Transferencia—US 2018, I.3A