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| 2. |
- Das, Ankan, et al.
(författare)
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Exploring the Possibility of Identifying Hydride and Hydroxyl Cations of Noble Gas Species in the Crab Nebula Filament
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 902:2
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Tidskriftsartikel (refereegranskat)abstract
- The first identification of the argonium ion (ArH+) toward the Crab Nebula supernova remnant was proclaimed by Herschel in the submillimeter and far-infrared domains. Very recently, the discovery of the hydro-helium cation (HeH+) in the planetary nebula (NGC 7027) by SOFIA has been reported. The elemental abundance of neon is much higher than that of argon. However, the presence of neonium ions (NeH+) is yet to be confirmed in space. Though the hydroxyl radicals (-OH) are very abundant in both neutral and cationic forms, hydroxyl cations of such noble gases (i.e., ArOH+, NeOH+, and HeOH+) are yet to be identified in space. Here, we employ a spectral synthesis code to examine the chemical evolution of the hydride and hydroxyl cations of the various isotopes of Ar, Ne, and He in the Crab Nebula filament and calculate their line emissivity and intrinsic line surface brightness. We successfully explain the observed surface brightness of two transitions of ArH+ (617 and 1234 GHz), one transition of OH+ (971 GHz), and one transition of H2 (2.12 μm). We also explain the observed surface brightness ratios between various molecular and atomic transitions. We find that our model reproduces the overall observed features when a hydrogen number density of ∼(104-106) cm-3 and a cosmic-ray ionization rate per H2 of ∼(10-11-10-10) s-1 are chosen. We discuss the possibility of detecting some hydride and hydroxyl cations in the Crab and diffuse cloud environment. Some transitions of these molecules are highlighted for future astronomical detection.
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| 3. |
- Dey, Dipanjan, et al.
(författare)
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An assessment of TropFlux and NCEP air-sea fluxes on ROMS simulations over the Bay of Bengal region
- 2017
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Ingår i: Dynamics of atmospheres and oceans (Print). - : Elsevier BV. - 0377-0265 .- 1872-6879. ; 80, s. 47-61
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Tidskriftsartikel (refereegranskat)abstract
- This study presents an assessment of the TropFlux and the National Centers for Environmental Prediction (NCEP) reanalysis air-sea fluxes in simulating the surface and subsurface oceanic parameters over the Bay of Bengal (BoB) region during 2002-2014 using the Regional Ocean Modelling System (ROMS). The assessment has been made by comparing the simulated fields with in-situ and satellite observations. The simulated surface and subsurface temperatures in the TropFlux forced experiment (TropFlux-E) show better agreement with the Research Moored Array for African-Asian-Australian Monsoon Analysis (RAMA) and Argo observations than the NCEP forced experiment (NCEP-E). The BoB domain averaged sea surface temperature (SST) simulated in the NCEP-E is consistently cooler than the satellite SST, with a root mean square error (RMSE) of 0.79 C. Moreover, NCEP-E shows a limitation in simulating the observed seasonal cycle of the SST due to substantial underestimation of the pre-monsoon SST peak. These limitations are mostly due to the lower values of the NCEP net hedt flux. The seasonal and interannual variations of SST in the TropFlux-E are better comparable to the observations with correlations and skills more than 0.80 and 0.90 respectively. However, SST is overestimated during summer monsoon periods mainly due to higher net heat flux. The superiority of TropFlux forcing over the NCEP reanalysis can also.be seen when simulating the interannual variabilities of the magnitude and vertical extent of Wyrtki jets at two equatorial RAMA buoy locations. The jet is weaker in the NCEP-E relative to the TropFlux-E and observations. The simulated sea surface height anomalies (SSHA) from both the experiments are able to capture the regions of positive and negative SSHA with respect to satellite-derived altimeter data with better performance in the TropFlux-E. The speed of the westward propagating Rossby wave along 18 N in the TropFlux-E is found to be about 4.7 cm/s, which is close to the theoretical phase speed of Rossby waves.
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| 4. |
- Nieuwenhuis, Bart P. S., et al.
(författare)
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On the asymmetry of mating in natural populations of the mushroom fungus Schizophyllum commune
- 2013
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Ingår i: Fungal Genetics and Biology. - : Elsevier BV. - 1087-1845 .- 1096-0937. ; 56, s. 25-32
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Tidskriftsartikel (refereegranskat)abstract
- Before a mycelium of a mushroom-forming basidiomycete develops mushrooms, the monokaryotic mycelium needs to become fertilized. Although the mechanistic details of mating in mushrooms have been studied thoroughly in laboratory research, very little is known on mating patterns in nature. In this study, we performed fine-scale analyses of three populations of Schizophyllum commune from their natural substrate (i.e. dead beech branches). From the three branches, 24, 12, and 24 fruiting bodies were isolated and for each mushroom, the origins of its nuclei and cytoplasm were reconstructed using DNA markers. Nuclear genotypes were determined using sequencing data and mating types, and mitochondrial haplotypes using SNP markers. From these combined data we reconstructed colonization and mating patterns of the mycelia. On each branch, we found multiple dikaryons (3, 3, and 8, respectively); in two instances one nuclear haplotype was shared between two dikaryons and in two other cases a nuclear haplotype was shared between three dikaryons. Each dikaryon always had a single mitochondrial haplotype. These findings indicate that mating usually is not symmetrical and that a monokaryon is most likely fertilized by a small monokaryon, a spore or a dikaryon. Sharing of nuclear haplotype between different dikaryons resulted either from multiple fertilizations of a single monokaryon, if the dikaryons had identical mitochondrial haplotypes, or, if the dikaryons had different mitochondria] haplotypes, most likely from secondary matings between a monokaryon and a dikaryon (Buller phenomenon). We conclude that mating in S. commune between same-sized monokaryons with reciprocal migration, as generally described in textbooks, is rare in nature. We discuss the implications of non-symmetric mating for basidiomycete evolution.
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