S-locus diversity of sweet cherry varieties from Galicia, North Western Spain (abstract)

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Serendipitous discovery of the long-sought AGN in Arp 299-A

Context: The dusty nuclear regions of luminous infra-red galaxies (LIRGs) are heated by either an intense burst of massive star formation, an active galactic nucleus (AGN), or a combination of both. Disentangling the contribution of each of those putative dust-heating agents is a challenging task, and direct imaging of the innermost few pc can only be accomplished at radio wavelengths, using very high-angular resolution observations. Aims: We observed the nucleus A of the interacting starburst galaxy Arp 299, using very long baseline interferometry (VLBI) radio observations at 1.7 and 5.0 GHz. Our aim was to characterize the compact sources in the innermost few pc region of Arp 299-A, as well as to detect recently exploded core-collapse supernovae. Methods: We used the European VLBI Network (EVN) to image the 1.7 and 5.0 GHz compact radio emission of the parsec-scale structure in the nucleus of Arp 299-A with milliarcsecond resolution. Results: Our EVN observations show that one of the compact VLBI sources, A1, previously detected at 5.0 GHz, has a flat spectrum between 1.7 and 5.0 GHz and is the brightest source at both frequencies. Our 1.7 GHz EVN image shows also diffuse, low-surface brightness emission extending westwards from A1 and displays a prominent core-jet structure. Conclusions: The morphology, radio luminosity, spectral index and ratio of radio-to-X-ray emission of the A1-A5 region is consistent with a low-luminosity AGN (LLAGN), and rules out the possibility that it is a chain of young radio supernovae (RSNe) and supernova remnants (SNRs). We therefore conclude that A1-A5 is the long-sought AGN in Arp 299-A. This finding may suggest that both starburst and AGN are frequently associated phenomena in mergers.Comment: Accepted for publication in Letters to Astronomy and Astrophysics on 12 August 2010. 4 pages, 1 figur

S-locus diversity of sweet cherry varieties from Galicia, North Western Spain

1 Pag.In this work, a group of local sweet cherry varieties from Galicia have been initially investigated to study the diversity at the S-locus and to establish their genetic cross-compatibility.Peer reviewe

DC and RF Performance of AlGaN/GaN HEMTs on SiC at High Temperatures

GaN-based transistors have demonstrated to be the most promising candidates for applications with high power and high frequency requirements, and working in harsh environments. They take advantage of some interesting properties of nitrides such as their thermal stability or high electron velocity, together with a high sheet carrier density (~1013 cm-2) provided by AlGaN/GaN heterostructures thanks to the favorable band offsets and internal piezoelectric fields. In above applications, transistors may work in small signal amplifiers under high ambient temperatures, or in power amplifiers where channel temperatures may increase significantly. Thus, high temperature (HT) operation and related reliability issues have become important research topics in GaN electronics. Although some works have been recently published about DC characterization of HEMTs at HT [1-5], there are few papers studying their behaviour at RF [4,5]. This work aims to understand the small signal performance of AlGaN/GaN HEMTs on SiC at HT, using DC and RF measurements combined with proper modeling and small signal parameters extraction

The nuclear starburst in Arp 299-A: From the 5.0 GHz VLBI radio light-curves to its core-collapse supernova rate

The nuclear region of the Luminous Infra-red Galaxy Arp 299-A hosts a recent ($\simeq 10$ Myr), intense burst of massive star formation which is expected to lead to numerous core-collapse supernovae (CCSNe). Previous VLBI observations, carried out with the EVN at 5.0 GHz and with the VLBA at 2.3 and 8.4 GHz, resulted in the detection of a large number of compact, bright, non-thermal sources in a region \lsim150 pc in size. We aim at establishing the nature of all non-thermal, compact components in Arp 299-A, as well as estimating its core-collapse supernova rate. We use multi-epoch European VLBI Network (EVN) observations taken at 5.0 GHz to image with milliarcsecond resolution the compact radio sources in the nuclear region of Arp 299-A. We also use one single-epoch 5.0 GHz Multi-Element Radio Linked Interferometer Network (MERLIN) observation to image the extended emission in which the compact radio sources --traced by our EVN observations-- are embedded. Twenty-six compact sources are detected, 8 of them are new objects not previously detected. The properties of all detected objects are consistent with them being a mixed population of CCSNe and SNRs. We find clear evidence for at least two new CCSNe, implying a lower limit to the CCSN rate of \nu_{\rm SN}\gsim0.80 SN/yr indicating that the bulk of the current star formation in Arp 299-A is taking place in the innermost $\sim 150$ pc. Our MERLIN observations trace a region of diffuse, extended emission which is co-spatial to the region where all compact sources are found. From this diffuse, non-thermal radio emission we obtain an independent estimate for the core-collapse supernova rate, which is in the range $\nu_{\rm SN}=0.40$ - 0.65 SN/yr, roughly in agreement with previous estimates and our direct estimate of the CCSN rate from the compact radio emission.Comment: 13 pages, 5 figures, accepted for publication on Astronomy & Astrophysic

The nature of supernovae 2010O and 2010P in Arp 299 - II. Radio emission

We report radio observations of two stripped-envelope supernovae (SNe), 2010O and 2010P, which exploded within a few days of each other in the luminous infrared galaxy Arp 299. Whilst SN 2010O remains undetected at radio frequencies, SN 2010P was detected (with an astrometric accuracy better than 1 milli arcsec in position) in its optically thin phase in epochs ranging from ~1 to ~3yr after its explosion date, indicating a very slow radio evolution and a strong interaction of the SN ejecta with the circumstellar medium. Our late-time radio observations toward SN 2010P probe the dense circumstellar envelope of this SN, and imply a mass-loss rate (Msun/yr) to wind velocity (in units of 10 km/s) ratio of (3.0-5.1)E-05, with a 5 GHz peak luminosity of ~1.2E+27 erg/s/Hz on day ~464 after explosion. This is consistent with a Type IIb classification for SN 2010P, making it the most distant and most slowly evolving Type IIb radio SN detected to date.Comment: 14 pages, 8 tables and 7 figures. Accepted for publication in MNRA

Vibroacoustic effects of resonant sonic crystals in sound absorption

[EN] A resonant sonic crystal made of solid elastic clamped beams is experimentally analysed in this work. The sonic crystal studied in this work has three characteristics: (i) a low filling fraction, (ii) a high frequency Band Gap and (iii) resonant scatterers. Due to the properties (i) and (ii), the sonic crystal behaves as an equivalent fluid with acoustic properties very closed to ones of the air. This means that the crystal is almost impedance matched, being the crystal transparent to the incident waves. However, the resonant elements have a resonance frequency in the range analysed in this work, introducing an absorption peak due to the resonances produced by the vibroacoustic coupling. The two microphone transfer function method is used to measure the (complex) impedance and then to evaluate experimentally the absorption coefficient of the 2D SC made of a set of parallel solid beams in the low frequency regime.Authors ackowledge the support of the European Space Agency under the 441-2015 Co-Sponsored PhD "Acoustic Noise Reduction Methods for the Launch Pad"Herrero-Durá, I.; Picó Vila, R.; Sánchez Morcillo, VJ.; García-Raffi, LM.; Romero García, V. (2016). Vibroacoustic effects of resonant sonic crystals in sound absorption. Universidade do Porto. 1-7. http://hdl.handle.net/10251/181082S1

Sound absorption and diffusion by 2D arrays of Helmholtz resonators

[EN] We report a theoretical and experimental study of an array of Helmholtz resonators optimized to achieve both efficient sound absorption and diffusion. The analysis starts with a simplified 1D model where the plane wave approximation is used to design an array of resonators showing perfect absorption for a targeted range of frequencies. The absorption is optimized by tuning the geometry of the resonators, i.e., by tuning the viscothermal losses of each element. Experiments with the 1D array were performed in an impedance tube. The designed system is extended to 2D by periodically replicating the 1D array. The 2D system has been numerically modeled and experimentally tested in an anechoic chamber. It preserves the absorption properties of the 1D system and introduces efficient diffusion at higher frequencies due to the joint effect of resonances and multiple scattering inside the discrete 2D structure. The combined effect of sound absorption at low frequencies and sound diffusion at higher frequencies, may play a relevant role in the design of noise reduction systems for different applications.This research was funded by the European Space Agency under the Networking/Partnering Initiative (NPI) contract number 441-2015. In memoriam to Julián Santiago-Prowald, Senior Advisor for the Structures, Mechanisms and Materials Division of ESA, a great man that always gave us his tireless support. AC acknowledges financial support from Generalitat Valenciana through the grant APOSTD/2018/229. VRG acknowledges the financial support from RFI Le Mans Acoustique (Région Pays de la Loire) in the framework of the project HYPERMETA funded under the program Étoiles Montantes of the Région Pays de la Loire. Authors acknowledge the support of the European Space Agency under contract 441-2015 Co- Sponsored PhD ¿Acoustic Reduction Methods for the Launch Pad¿ and project TRP ESA AO/1-9479/18/NL/LvH ¿Launch Sound Level Reduction¿. This article is based upon work from COST Action DENORMS CA15125, supported by COST (European Cooperation in Science and Technology).Herrero-Durá, I.; Cebrecos, A.; Picó Vila, R.; Romero-García, V.; García-Raffi, LM.; Sánchez Morcillo, VJ. (2020). Sound absorption and diffusion by 2D arrays of Helmholtz resonators. Applied Sciences. 10(5):1-15. https://doi.org/10.3390/app10051690S115105Sigalas, M. M., & Economou, E. N. (1992). Elastic and acoustic wave band structure. Journal of Sound and Vibration, 158(2), 377-382. doi:10.1016/0022-460x(92)90059-7Matlack, K. H., Bauhofer, A., Krödel, S., Palermo, A., & Daraio, C. (2016). Composite 3D-printed metastructures for low-frequency and broadband vibration absorption. 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