On the scaling of the damping time for resonantly damped oscillations in coronal loops

There is not as yet full agreement on the mechanism that causes the rapid damping of the oscillations observed by TRACE in coronal loops. It has been suggested that the variation of the observed values of the damping time as function of the corresponding observed values of the period contains information on the possible damping mechanism. The aim of this Letter is to show that, for resonant absorption, this is definitely not the case unless detailed a priori information on the individual loops is available

The resonant damping of fast magnetohydrodynamic oscillations in a system of two coronal slabs

Observations of transversal coronal loop oscillations very often show the excitation and damping of oscillations in groups of coronal loops rather than in individual and isolated structures. We present results on the oscillatory properties (periods, damping rates, and spatial distribution of perturbations) for resonantly damped oscillations in a system of two inhomogeneous coronal slabs and compare them to the properties found in single slab loop models. A system of two identical coronal loops is modeled, in Cartesian geometry, as being composed by two density enhancements. The linear magnetohydrodynamic (MHD) wave equations for oblique propagation of waves are solved and the damping of the different solutions, due to the transversal inhomogeneity of the density profile, is computed. The physics of the obtained results is analyzed by an examination of the perturbed physical variables. We find that, due to the interaction between the loops, the normal modes of oscillation present in a single slab split into symmetric and antisymmetric oscillations when a system of two identical slabs is considered. The frequencies of these solutions may differ from the single slab results when the distance between the loops is of the order of a few slab widths. Oblique propagation of waves weakens this interaction, since solutions become more confined to the edges of the slabs. The damping is strong for surface-like oscillations, while sausage body-like solutions are unaffected. For some solutions, and small slab separations, the damping in a system of two loops differs substantially from the damping of a single loop.Comment: 25 pages, 9 figure

Densidad y área de los canales resiníferos de "Pinus pinaster" ante tratamientos de fertilización, y su relación con la defensa ante "Hylobius abietis"

6 páginas, 3 tablas -- Actas de la I Reunión sobre Sanidad Forestal celebrada en Palencia el 24 y 25 de septiembre de 2007.Las coníferas poseen una estructura de canales resiníferos que actúa como defensa contra el ataque de insectos y patógenos. Varios autores han observado que un aumento en la disponibilidad de nutrientes puede alterar el reparto de energía en las plantas, en detrimento de los sistemas defensivos. El presente estudio tiene como objetivo determinar el efecto de la fertilización de establecimiento sobre el desarrollo del sistema de canales resiníferos en Pinus pinaster. Mediante histología en brinzales de 3 savias sometidos a dos ensayos familia x fertilización se cuantificó la densidad y el área de los canales resiníferos del floema y del xilema tanto en el tallo principal como en ramas laterales en dos ensayos familia x fertilización. Se observó un efecto significativo de la fertilización en el desarrollo de los canales resiníferos del floema (p<0,05), con valores de 0,45 y 0,36 canales.mm-2 para brinzales no fertilizados y sí fertilizados, respectivamente. Este efecto no se observó en las variables del xilema. La densidad de canales resiníferos en el xilema fue significativamente diferente entre las dos parcelas estudiadas, siendo mayor en la atacada por el curculiónido Hylobius abietis. Por último, la relación tallo-rama de las variables cuantificadas no fue lo suficientemente consistente como para utilizar los canales en ramas de P. pinaster como indicadores de los canales en el tronco principal.Este trabajo se ha realizado bajo financiación del proyecto INIA-RTA05-173.Peer reviewe

Innovative passive and active countermeasures for near side crash safety

This research presents six simultaneous innovative occupant near side lateral impact protection concepts including a dynamic door, high-volume side airbag, a large external airbag that covers doors, sill and B-pillar of the struck vehicle and other concepts for increasing the distance between the occupant and the door panel (active armrest, inflatable door beam and moving seat). All systems are based on pre crash detection of the impact and are activated as soon as 80ms before the impact. This paper details the task of integrating these systems into a vehicle using FE models, sled tests, and full scale crash tests. Sled test dummy responses were compared with and without the countermeasures.Postprint (published version

Evaluation of a crop rotation with biological inhibition potential to avoid N2O emissions in comparison with synthetic nitrification inhibition

Agriculture has increased the release of reactive nitrogen to the environment due to crops' low nitrogen-use efficiency (NUE) after the application of nitrogen-fertilisers. Practices like the use of stabilized-fertilisers with nitrification inhibitors such as DMPP (3,4-dimethylpyrazole phosphate) have been adopted to reduce nitrogen losses. Otherwise, cover crops can be used in crop-rotation-strategies to reduce soil nitrogen pollution and benefit the following culture. Sorghum (Sorghum bicolor) could be a good candidate as it is drought tolerant and its culture can reduce nitrogen losses derived from nitrification because it exudates biological nitrification inhibitors (BNIs). This work aimed to evaluate the effect of fallow-wheat and sorghum cover crop-wheat rotations on N2O emissions and the grain yield of winter wheat crop. In addition, the suitability of DMPP addition was also analyzed. The use of sorghum as a cover crop might not be a suitable option to mitigate nitrogen losses in the subsequent crop. Although sorghum–wheat rotation was able to reduce 22% the abundance of amoA, it presented an increment of 77% in cumulative N2O emissions compared to fallow–wheat rotation, which was probably related to a greater abundance of heterotrophic-denitrification genes. On the other hand, the application of DMPP avoided the growth of ammonia-oxidizing bacteria and maintained the N2O emissions at the levels of unfertilized-soils in both rotations. As a conclusion, the use of DMPP would be recommendable regardless of the rotation since it maintains NH4+ in the soil for longer and mitigates the impact of the crop residues on nitrogen soil dynamics.This work was supported by the Spanish Government (RTI2018-094623-B-C21 and C22 MCIU/AEI/FEDER, UE) and the Basque Government (IT-932-16). Dr. Adrián Bozal-Leorri held a grant from the Basque Government (PRE-2020-2-0142). Dr. Mario Corrochano-Monsalve held a grant from the Ministry of Economy and Business of the Spanish Government (BES-2016-076725)

Biological and synthetic approaches to inhibiting nitrification in non‑tilled Mediterranean soils

[EN] Background: The increasing demand for food production has led to a tenfold increase in nitrogen (N) fertilizer use since the Green Revolution. Nowadays, agricultural soils have been turned into high-nitrifying environments that increase N pollution. To decrease N losses, synthetic nitrification inhibitors (SNIs) such as 3,4-dimethylpyrazole phosphate (DMPP) have been developed. However, SNIs are not widely adopted by farmers due to their biologically limited stability and soil mobility. On the other hand, allelopathic substances from root exudates from crops such as sorghum are known for their activity as biological nitrification inhibitors (BNIs). These substances are released directly into the rhizosphere. Nevertheless, BNI exudation could be modified or even suppressed if crop development is affected. In this work, we compare the performance of biological (sorghum crop) and synthetic (DMPP) nitrification inhibitors in field conditions. Results: Sorghum crop BNIs and DMPP prevented an increase in the abundance of ammonia-oxidizing bacteria (AOB) without affecting the total bacterial abundance. Both nitrification inhibitors maintained similar soil NH4+ content, but at 30 days post-fertilization (DPF), the sorghumBNIs resulted in higher soil NO3- content than DMPP. Even so, these inhibitors managed to reduce 64% and 96%, respectively, of the NO3--N/NH4+-N ratio compared to the control treatment. Similar to soil mineral N, there were no differences in leaf delta N-15 values between the two nitrification inhibitors, yet at 30 DPF, delta N-15 values from sorghum BNI were more positive than those of DMPP. N2O emissions from DMPP-treated soil were low throughout the experiment. Nevertheless, while sorghum BNIs also maintained low N2O emissions, they were associated with a substantial N2O emission peak at 3 DPF that lasted until 7 DPF. Conclusions: Our results indicate that while sorghum root exudates can reduce nitrification in field soil, even at the same efficiency as DMPP for a certain amount of time, they are not able to prevent the N pollution derived from N fertilization as DMPP does during the entire experiment. Graphic AbstractThis project was funded by the Spanish Government (RTI2018-094623-B-C22 MCIU/AEI/FEDER, UE) and by the Basque Government (IT-932-16). Adrian Bozal-Leorri holds a Grant from the Basque Government (PRE-2020-2-0142). Mario Corrochano-Monsalve holds a Grant from the Ministry of Economy and Business of the Spanish Government (BES-2016-076725)

Nuevas obtenciones de plantas libres de virus de materiales frutales autóctonos de Murcia

En un trabajo previo se obtuvieron plantas libres de virus de 13 clones de melocotonero infectados por "apple chlorotic leaf spot virus" (ACLSV), mediante la técnica del microinjerto de ápices caulinares in vitro, En el presente trabajo, la aplicación del microinjerto ha permitido obtener plantas libres de virus de los siguientes materiales autóctonos de Murcia: - Diez nuevos clones de melocotonero infectados por ACLSV. - Un clon de melocotonero y un clon de híbrido melocotonero x almendro infectados por "prunus necrotic ring spot virus" (PNRSV). - Tres clones de melocotonero infectados simultáneamente por PNRSV y ACLSV, más otro clon infectado por PNRSV, ACLSV y "prune dwarf virus" (PDV). Se han obtenido también plantas libres de ACLSV de 5 clones de ciruelo Pollizo, mediante injerto en verano sobre patrones sanos, aprovechando la irregular distribución de este virus en dicha época del año

Damping mechanisms for oscillations in solar prominences

Small amplitude oscillations are a commonly observed feature in prominences/filaments. These oscillations appear to be of local nature, are associated to the fine structure of prominence plasmas, and simultaneous flows and counterflows are also present. The existing observational evidence reveals that small amplitude oscillations, after excited, are damped in short spatial and temporal scales by some as yet not well determined physical mechanism(s). Commonly, these oscillations have been interpreted in terms of linear magnetohydrodynamic (MHD) waves, and this paper reviews the theoretical damping mechanisms that have been recently put forward in order to explain the observed attenuation scales. These mechanisms include thermal effects, through non-adiabatic processes, mass flows, resonant damping in non-uniform media, and partial ionization effects. The relevance of each mechanism is assessed by comparing the spatial and time scales produced by each of them with those obtained from observations. Also, the application of the latest theoretical results to perform prominence seismology is discussed, aiming to determine physical parameters in prominence plasmas that are difficult to measure by direct means.Comment: 36 pages, 16 figures, Space Science Reviews (accepted