About the existence of warm H-rich pulsating white dwarfs

Context. The possible existence of warm (Teff ∼ 19 000 K) pulsating DA white dwarf (WD) stars, hotter than ZZ Ceti stars, was predicted in theoretical studies more than 30 yr ago. These studies reported the occurrence of g-mode pulsational instabilities due to the κ mechanism acting in the partial ionization zone of He below the H envelope in models of DA WDs with very thin H envelopes (MH/M⋆ ≲ 10-10). However, to date, no pulsating warm DA WD has been discovered, despite the varied theoretical and observational evidence suggesting that a fraction of WDs should be formed with a range of very low H content. Aims: We re-examine the pulsational predictions for such WDs on the basis of new full evolutionary sequences. We analyze all the warm DAs observed by the TESS satellite up to Sector 9 in order to search for the possible pulsational signal. Methods: We computed WD evolutionary sequences of masses 0.58 and 0.80 M☉ with H content in the range -14.5 ≲ log(MH/M⋆)≲ - 10, appropriate for the study of pulsational instability of warm DA WDs. Initial models were extracted from progenitors that were evolved through very late thermal pulses on the early cooling branch. We use LPCODE stellar code into which we have incorporated a new full-implicit treatment of time-dependent element diffusion to precisely model the H-He transition zone in evolving WD models with very low H content. The nonadiabatic pulsations of our warm DA WD models were computed in the effective temperature range of 30 000 - 10 000 K, focusing on ℓ = 1 g modes with periods in the range 50 - 1500 s. Results: We find that traces of H surviving the very late thermal pulse float to the surface, eventually forming thin, growing pure H envelopes and rather extended H-He transition zones. We find that such extended transition zones inhibit the excitation of g modes due to partial ionization of He below the H envelope. Only in the cases where the H-He transition is assumed much more abrupt than predicted by diffusion do models exhibit pulsational instability. In this case, instabilities are found only in WD models with H envelopes in the range of -14.5 ≲ log(MH/M⋆)≲ - 10 and at effective temperatures higher than those typical for ZZ Ceti stars, in agreement with previous studies. None of the 36 warm DAs observed so far by TESS satellite are found to pulsate. Conclusions: Our study suggests that the nondetection of pulsating warm DAs, if WDs with very thin H envelopes do exist, could be attributed to the presence of a smooth and extended H-He transition zone. This could be considered as indirect proof that element diffusion indeed operates in the interior of WDs.Fil: Althaus, Leandro Gabriel. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Corsico, Alejandro Hugo. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Uzundag, Murat. Universidad de Valparaíso; ChileFil: Vucković, Maja. Universidad de Valparaíso; ChileFil: Baran, Andrzej S.. Obserwatorium na Suhorze; PoloniaFil: Bell, Keaton J.. University of Whashington; Estados UnidosFil: Camisassa, María Eugenia. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Calcaferro, Leila Magdalena. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: de Gerónimo, Francisco César. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Kepler, Souza Oliveira. Universidade Federal do Rio Grande do Sul; BrasilFil: Silvotti, Roberto. Osservatorio Astrofisico Di Torino; Itali

Outlook for inverse design in nanophotonics

Recent advancements in computational inverse design have begun to reshape the landscape of structures and techniques available to nanophotonics. Here, we outline a cross section of key developments at the intersection of these two fields: moving from a recap of foundational results to motivation of emerging applications in nonlinear, topological, near-field and on-chip optics.Comment: 13 pages, 6 figure

The Effects of Flunixin Meglumine and L-NAME on the Carrageenan-induced Hyperalgesia in Rats

Flunixin meglumine (FM) is a potent non-steroidal anti-inflammatory drug used in veterinary clinical practice. Hyperalgesia was induced by mtraplantar (i.pl.) administration of carrageenan (500 mu g) into the rat hind paw. Electronic von Frey apparatus was used to determine paw withdrawal threshold in grams (g). Both, FM (0.095-0.12 mg/kg: s.c.) and N-G-nitro-L-arginine methyl ester (L-NAME 2.5 and 5 mg/kg; i.p.), given 2.5 h after i.pl. injection of carrageenan produced significant dose-dependent antinociceptive effects. When FM (0.095 mg/kg) and subeffective dose of L-NAME (7.5 mg/kg) were co-administered, the anti-nociceptive effect was significantly increased M comparison with the effect of FM alone. L-arginme (10 mg/kg: i.p.) itself did not produce significant effect on carrageenan-induced hyperalgesia, but significantly inhibited the anti-nociceptive effects of both FM and FM + L-NAME combination. The inhibition of production of nitric oxide might be involved in the mechanism of the anti-hyperalgesic effect of FM in a model of carrageenan-induced hyperalgesia in rats

The effects of flunixin meglumine and l-name on the carrageenan-induced hyperalgesia in rats

Flunixin meglumine (FM) is a potent non-steroidal anti-inflammatory drug used in veterinary clinical practice. Hyperalgesia was induced by mtraplantar (i.pl.) administration of carrageenan (500 mu g) into the rat hind paw. Electronic von Frey apparatus was used to determine paw withdrawal threshold in grams (g). Both, FM (0.095-0.12 mg/kg: s.c.) and N-G-nitro-L-arginine methyl ester (L-NAME 2.5 and 5 mg/kg; i.p.), given 2.5 h after i.pl. injection of carrageenan produced significant dose-dependent antinociceptive effects. When FM (0.095 mg/kg) and subeffective dose of L-NAME (7.5 mg/kg) were co-administered, the anti-nociceptive effect was significantly increased M comparison with the effect of FM alone. L-arginme (10 mg/kg: i.p.) itself did not produce significant effect on carrageenan-induced hyperalgesia, but significantly inhibited the anti-nociceptive effects of both FM and FM + L-NAME combination. The inhibition of production of nitric oxide might be involved in the mechanism of the anti-hyperalgesic effect of FM in a model of carrageenan-induced hyperalgesia in rats

Peripheral antinociception by carbamazepine in an inflammatory mechanical hyperalgesia model in the rat: a new target for carbamazepine?

This study investigated whether carbamazepine could produce local peripheral antinociception in a rat model of inflammatory mechanical hyperalgesia, and whether adenosine receptors are involved. Carbamazepine (100-1000 nmol/paw) coadministrated with a proinflammatory compound, concanavalin A, into the hind paw caused a significant dose- and time-dependent anti-hyperalgesia. Coadministration of caffeine (250 - 1000 nmol/paw), a nonselective adenosine-receptor antagonist, as well as DPCPX (10-30 nmol/paw), a selective adenosine A(1)-receptor antagonist, with carbamazepine, significantly depressed its anti-hyperalgesic effect. Drugs injected into the contralateral hind paw did not produce significant effects. These results suggest that carbamazepine produces local peripheral anti-hyperalgesia via peripheral adenosine A(1) receptors