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Danehkar, A., M. S. Oey i W. J. Gray. "Numerical Modeling of Galactic Superwinds with Time-evolving Stellar Feedback". Proceedings of the International Astronomical Union 17, S370 (sierpień 2021): 217–22. http://dx.doi.org/10.1017/s1743921323000066.
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AbstractMass-loss and radiation feedback from evolving massive stars produce galactic-scale superwinds, sometimes surrounded by pressure-driven bubbles. Using the time-dependent stellar population typically seen in star-forming regions, we conduct hydrodynamic simulations of a starburst-driven superwind model coupled with radiative efficiency rates to investigate the formation of radiative cooling superwinds and bubbles. Our numerical simulations depict the parameter space where radiative cooling superwinds with or without bubbles occur. Moreover, we employ the physical properties and time-dependent ionization states to predict emission line profiles under the assumption of collisional ionization and non-equilibrium ionization caused by wind thermal feedback in addition to photoionization created by the radiation background. We see the dependence of non-equilibrium ionization structures on the time-evolving ionizing source, leading to a deviation from collisional ionization in radiative cooling wind regions over time.
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Dwarkadas, Vikram V. "On the Evolution of, and Hot Gas in, Wind-Blown Bubbles around Massive Stars - Wind Bubbles Are Not Energy-Conserving". Galaxies 11, nr 3 (19.06.2023): 78. http://dx.doi.org/10.3390/galaxies11030078.
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The structure and evolution of wind-blown bubbles (WBBs) around massive stars has primarilybeen investigated using an energy-conserving model of wind-blown bubbles. While this model is useful in explaining the general properties of the evolution, several problems remain, including inconsistencies between observed wind luminosities and those derived using this formulation. Major difficulties include the low X-ray temperature and X-ray luminosity, compared to the model. In this paper, we re-examine the evolution, dynamics, and kinematics of WBBs around massive stars, using published ionization gasdynamic simulations of wind-blown bubbles. We show that WBBs can cool efficiently due to the presence of various instabilities and turbulence within the bubble. The expansion of WBBs is more consistent with a momentum-conserving solution, rather than an energy-conserving solution. This compares well with the dynamics and kinematics of observed wind bubbles. Despite the cooling of the bubble, the shocked wind temperature is not reduced to the observed values. We argue that the X-ray emission arise mainly from clumps and filaments within the hot shocked wind region, with temperatures just above 106 K. The remainder of the plasma can contribute to a lesser extent.
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Soria, R., M. W. Pakull, C. Motch, J. C. A. Miller-Jones, A. D. Schwope, R. T. Urquhart i M. S. Ryan. "The ultraluminous X-ray source bubble in NGC 5585". Monthly Notices of the Royal Astronomical Society 501, nr 2 (9.12.2020): 1644–62. http://dx.doi.org/10.1093/mnras/staa3784.
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ABSTRACT Some ultraluminous X-ray sources (ULXs) are surrounded by collisionally ionized bubbles, larger and more energetic than supernova remnants: they are evidence of the powerful outflows associated with super-Eddington X-ray sources. We illustrate the most recent addition to this class: a huge (350 pc × 220 pc in diameter) bubble around a ULX in NGC 5585. We modelled the X-ray properties of the ULX (a broadened-disc source with LX ≈ 2–4 × 1039 erg s−1) from Chandra and XMM–Newton, and identified its likely optical counterpart in Hubble Space Telescope images. We used the Large Binocular Telescope to study the optical emission from the ionized bubble. We show that the line emission spectrum is indicative of collisional ionization. We refine the method for inferring the shock velocity from the width of the optical lines. We derive an average shock velocity ≈125 km s−1, which corresponds to a dynamical age of ∼600 000 yr for the bubble, and an average mechanical power Pw ∼ 1040 erg s−1; thus, the mechanical power is a few times higher than the current photon luminosity. With Very Large Array observations, we discovered and resolved a powerful radio bubble with the same size as the optical bubble, and a 1.4-GHz luminosity ∼1035 erg s−1, at the upper end of the luminosity range for this type of source. We explain why ULX bubbles tend to become more radio luminous as they expand while radio supernova remnants tend to fade.
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Xu, Yidong, Bin Yue i Xuelei Chen. "The Neutral Islands during the Late Epoch of Reionization". Proceedings of the International Astronomical Union 12, S333 (październik 2017): 64–67. http://dx.doi.org/10.1017/s174392131701153x.
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AbstractThe large-scale structure of the ionization field during the epoch of reionization (EoR) can be modeled by the excursion set theory. While the growth of ionized regions during the early stage are described by the “bubble model”, the shrinking process of neutral regions after the percolation of the ionized region calls for an “island model”. An excursion set based analytical model and a semi-numerical code (islandFAST) have been developed. The ionizing background and the bubbles inside the islands are also included in the treatment. With two kinds of absorbers of ionizing photons, i.e. the large-scale under-dense neutral islands and the small-scale over-dense clumps, the ionizing background are self-consistently evolved in the model.
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Bolotnova, R. Kh. "Wide-range equations of state for organic liquids". Proceedings of the Mavlyutov Institute of Mechanics 5 (2007): 113–20. http://dx.doi.org/10.21662/uim2007.1.011.
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The method of construction the wide-range equations of state for organic liquids, describing the gas and liquid phases including dissociation and ionization which occurs during an intense collapse of steam bubbles and accompanied by ultra-high pressures and temperatures, is proposed.
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Yasui, Kyuichi. "Multibubble Sonoluminescence from a Theoretical Perspective". Molecules 26, nr 15 (30.07.2021): 4624. http://dx.doi.org/10.3390/molecules26154624.
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In the present review, complexity in multibubble sonoluminescence (MBSL) is discussed. At relatively low ultrasonic frequency, a cavitation bubble is filled mostly with water vapor at relatively high acoustic amplitude which results in OH-line emission by chemiluminescence as well as emissions from weakly ionized plasma formed inside a bubble at the end of the violent bubble collapse. At relatively high ultrasonic frequency or at relatively low acoustic amplitude at relatively low ultrasonic frequency, a cavitation bubble is mostly filled with noncondensable gases such as air or argon at the end of the bubble collapse, which results in relatively high bubble temperature and light emissions from plasma formed inside a bubble. Ionization potential lowering for atoms and molecules occurs due to the extremely high density inside a bubble at the end of the violent bubble collapse, which is one of the main reasons for the plasma formation inside a bubble in addition to the high bubble temperature due to quasi-adiabatic compression of a bubble, where “quasi” means that appreciable thermal conduction takes place between the heated interior of a bubble and the surrounding liquid. Due to bubble–bubble interaction, liquid droplets enter bubbles at the bubble collapse, which results in sodium-line emission.
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Medling, Anne M., Lisa J. Kewley, Daniela Calzetti, George C. Privon, Kirsten Larson, Jeffrey A. Rich, Lee Armus i in. "Tracing the Ionization Structure of the Shocked Filaments of NGC 6240". Astrophysical Journal 923, nr 2 (1.12.2021): 160. http://dx.doi.org/10.3847/1538-4357/ac2ebb.
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Abstract We study the ionization and excitation structure of the interstellar medium in the late-stage gas-rich galaxy merger NGC 6240 using a suite of emission-line maps at ∼25 pc resolution from the Hubble Space Telescope, Keck/NIRC2 with Adaptive Optics, and the Atacama Large Millimeter/submillimeter Array (ALMA). NGC 6240 hosts a superwind driven by intense star formation and/or one or both of two active nuclei; the outflows produce bubbles and filaments seen in shock tracers from warm molecular gas (H2 2.12 μm) to optical ionized gas ([O iii], [N ii], [S ii], and [O i]) and hot plasma (Fe XXV). In the most distinct bubble, we see a clear shock front traced by high [O iii]/Hβ and [O iii]/[O i]. Cool molecular gas (CO(2−1)) is only present near the base of the bubble, toward the nuclei launching the outflow. We interpret the lack of molecular gas outside the bubble to mean that the shock front is not responsible for dissociating molecular gas, and conclude that the molecular clouds are partly shielded and either entrained briefly in the outflow, or left undisturbed while the hot wind flows around them. Elsewhere in the galaxy, shock-excited H2 extends at least ∼4 kpc from the nuclei, tracing molecular gas even warmer than that between the nuclei, where the two galaxies’ interstellar media are colliding. A ridgeline of high [O iii]/Hβ emission along the eastern arm aligns with the southern nucleus’ stellar disk minor axis; optical integral field spectroscopy from WiFeS suggests this highly ionized gas is centered at systemic velocity and likely photoionized by direct line of sight to the southern active galactic nucleus.
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Dwarkadas, Vikram V. "Ionization-Gasdynamic Simulations of Wind-Blown Nebulae around Massive Stars". Galaxies 10, nr 1 (17.02.2022): 37. http://dx.doi.org/10.3390/galaxies10010037.
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Using a code that employs a self-consistent method for computing the effects of photo-ionization on circumstellar gas dynamics, we model the formation of wind-driven nebulae around massive stars. We take into account changes in stellar properties and mass-loss over the star’s evolution. Our simulations show how various properties, such as the density and ionization fraction, change throughout the evolution of the star. The multi-dimensional simulations reveal the presence of strong ionization front instabilities in the main-sequence phase, similar to those seen in galactic ionization fronts. Hydrodynamic instabilities at the interfaces lead to the formation of filaments and clumps that are continually being stripped off and mixed with the low density interior. Even though the winds start out as completely radial, the spherical symmetry is quickly destroyed, and the shocked wind region is manifestly asymmetrical. The simulations demonstrate that it is important to include the effects of the photoionizing photons from the star, and simulations that do not include this may fail to reproduce the observed density profile and ionization structure of wind-blown bubbles around massive stars.
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Gorce, Adélie, i Jonathan R. Pritchard. "Studying the morphology of reionization with the triangle correlation function of phases". Monthly Notices of the Royal Astronomical Society 489, nr 1 (9.08.2019): 1321–37. http://dx.doi.org/10.1093/mnras/stz2195.
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ABSTRACT We present a new statistical tool, called the triangle correlation function (TCF), inspired by the earlier work of Obreschkow et al. It is derived from the three-point correlation function and aims to probe the characteristic scale of ionized regions during the epoch of reionization from 21cm interferometric observations. Unlike most works, which focus on power spectrum, i.e. amplitude information, our statistic is based on the information we can extract from the phases of the Fourier transform of the ionization field. In this perspective, it may benefit from the well-known interferometric concept of closure phases. We find that this statistical estimator performs very well on simple ionization fields. For example, with well-defined fully ionized discs, there is a peaking scale, which we can relate to the radius of the ionized bubbles. We explore the robustness of the TCF when observational effects such as angular resolution and noise are considered. We also get interesting results on fields generated by more elaborate simulations such as 21CMFAST. Although the variety of sources and ionized morphologies in the early stages of the process make its interpretation more challenging, the nature of the signal can tell us about the stage of reionization. Finally, and in contrast to other bubble size distribution algorithms, we show that the TCF can resolve two different characteristic scales in a given map.
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Sönksen, Carsten P., Peter Roepstorff, Per-Olof Markgren, U. Helena Danielson, Markku D. Hämäläinen i Östen Jansson. "Capture and Analysis of Low Molecular Weight Ligands by Surface Plasmon Resonance Combined with Mass Spectrometry". European Journal of Mass Spectrometry 7, nr 4-5 (sierpień 2001): 385–91. http://dx.doi.org/10.1255/ejms.448.
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The combination of biomolecular interaction analysis (BIA)by surface plasmon resonance (SPR)and nano-electrospray ionization ion trap mass spectrometry (nanoESI-Ion Trap MS)as well as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS)is demonstrated for the binding of low molecular weight inhibitors (∼ 600 Da) to HIV-1 protease. Inhibitors were captured on sensor chips of a manual or an automated SPR biosensor, to which HIV-1 protease was immobilized. Compounds and buffer components that bound unspecifically to the sensor surface were removed and the inhibitors were eluted in a minimal volume (3 μL), between air bubbles, in order to prevent dispersion of analyte into buffer eluent. Molecular weights were subsequently determined by mass spectrometry, structural information was obtained by MALDI-ToF post-source decay as well as by electrospray ionization tandem mass spectrometry (MS/MS)analysis. Furthermore, competition experiments, using a mixture of different ligands, demonstrated that the peak intensities in the MALDI-ToF spectrum could be used for relative quantification of the amount of the different ligands bound to the immobilized target. Methodology for automated capture and elution of analytes was developed and evaluated.
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Tulasi Ram, S., P. V. S. Rama Rao, D. S. V. V. D. Prasad, K. Niranjan, A. Raja Babu, R. Sridharan i C. V. Devasia. "The combined effects of electrojet strength and the geomagnetic activity (<I>K<sub>p</sub></I>-index) on the post sunset height rise of the F-layer and its role in the generation of ESF during high and low solar activity periods". Annales Geophysicae 25, nr 9 (2.10.2007): 2007–17. http://dx.doi.org/10.5194/angeo-25-2007-2007.
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Abstract. Several investigations have been carried out to identify the factors that are responsible for the day-to-day variability in the occurrence of equatorial spread-F (ESF). But the precise forecasting of ESF on a day-to-day basis is still far from reality. The nonlinear development and the sustenance of ESF/plasma bubbles is decided by the background ionospheric conditions, such as the base height of the F-layer (h'F), the electron density gradient (dN/dz), maximum ionization density (Nmax), geomagnetic activity and the neutral dynamics. There is increasing evidence in the literature during the recent past that shows a well developed Equatorial Ionization Anomaly (EIA) during the afternoon hours contributes significantly to the initiation of ESF during the post-sunset hours. Also, there exists a good correlation between the Equatorial Ionization Anomaly (EIA) and the Integrated Equatorial ElectroJet (IEEJ) strength, as the driving force for both is the same, namely, the zonal electric field at the equator. In this paper, we present a linear relationship that exists between the daytime integrated equatorial electrojet (IEEJ) strength and the maximum elevated height of the F-layer during post-sunset hours (denoted as peak h'F). An inverse relationship that exists between the 6-h average Kp-index prior to the local sunset and the peak h'F of the F-layer is also presented. A systematic study on the combined effects of the IEEJ and the average Kp-index on the post-sunset, peak height of the F-layer (peak h'F), which controls the development of ESF/plasma bubbles, is carried out using the ionosonde data from an equatorial station, Trivandrum (8.47° N, 76.91° E, dip.lat. 0.5° N), an off-equatorial station, SHAR (13.6° N, 79.8° E, dip.lat. 10.8° N) and VHF scintillations (244 MHz) observed over a nearby low-latitude station, Waltair (17.7° N, 83.3° E, dip.lat. 20° N). From this study, it has been found that the threshold base height of the F-layer at the equator for the development of plasma bubbles is reduced from 405 km to 317 km as the solar activity decreases from March 2001 (mean Rz=113.5) to March 2005 (mean Rz=24.5). This decrease in threshold height with the decreasing solar activity is explained on the basis of changes in the local linear growth rate of the collisional Rayleigh-Taylor instability, due to the variability of various terms such as inverse density gradient scale length (L−1), ion-neutral collision frequency (νin) and recombination rate (R) with the changes in the solar activity.
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Liu, J. Y., P. K. Rajesh, I. T. Lee i T. C. Chow. "Airglow observations over the equatorial ionization anomaly zone in Taiwan". Annales Geophysicae 29, nr 5 (5.05.2011): 749–57. http://dx.doi.org/10.5194/angeo-29-749-2011.
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Abstract. Airglow imaging at mid-latitude stations often show intensity modulations associated with medium scale travelling ionospheric disturbances (MSTID), while those carried out near the equatorial regions reveal depletions caused by equatorial plasma bubbles (EPB). Two all sky cameras are used to observe plasma depletions in the 630.0 nm emission over the equatorial ionization anomaly (EIA) region, Taiwan (23° N, 121° E; 13.5° N Magnetic) during 1998–2002 and 2006–2007. The results show EPB and MSTID depletions in different solar activity conditions. Several new features of the EPB depletions such as bifurcation, secondary structure on the walls, westward tilt, etc., are discussed in this paper. Evidence of tilted depletions with secondary structures developing on the eastern wall that later evolve to appear as bifurcations, are presented for the first time. Moreover, detail investigations are carried out using International Reference Ionosphere (IRI) model as well as the electron density from Ionosonde and Global Positioning System (GPS) Occultation Experiment (GOX) onboard FORMOSAT-3/COSMIC satellite, to understand the conditions that favor the propagation of MSTID to the latitude of Taiwan.
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Kil, H., M. DeMajistre, L. J. Paxton i Y. Zhang. "<i>F</i>-region Pedersen conductivity deduced using the TIMED/GUVI limb retrievals". Annales Geophysicae 24, nr 5 (3.07.2006): 1311–16. http://dx.doi.org/10.5194/angeo-24-1311-2006.
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Abstract. As a proxy of the Rayleigh-Taylor instability growth rate for equatorial plasma bubbles, we investigate the flux-tube integrated F-region Pedersen conductivity (ΣPF) using the electron density profiles (EDPs) provided by the Global Ultraviolet Imager (GUVI) on board the Thermosphere Ionosphere and Mesosphere Energetics and Dynamics (TIMED) satellite. The investigation is conducted using the EDPs obtained in the Atlantic sector at 19:00-22:00 LT during 4–17 August and 6-16 December 2002. The seasonal difference of the strength and location of the equatorial ionization anomalies (EIAs) induces a significant difference in the deduced ΣPF. Much stronger EIAs are created at higher altitudes and latitudes in December rather than in August. At 19:00–20:00 LT, the peak value of the ΣPF has 23 mhos at 1100 km apex height during 14–16 December and 18mhos at 600 km during 15–17 August. The ΣPF decreases as local time progresses. Therefore, ΣPF provides a preferred condition for the growth of bubbles to higher altitudes at 19:00-20:00 LT than at later hours, in December rather than in August in the Atlantic sector.
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Xu, Jin-Long, Ye Xu, Chuan-Peng Zhang, Xiao-Lan Liu, Naiping Yu, Chang-Chun Ning i Bing-Gang Ju. "Gas kinematics and star formation in the filamentary molecular cloud G47.06+0.26". Astronomy & Astrophysics 609 (styczeń 2018): A43. http://dx.doi.org/10.1051/0004-6361/201629189.
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Aims. We performed a multi-wavelength study toward the filamentary cloud G47.06+0.26 to investigate the gas kinematics and star formation. Methods. We present the 12CO (J = 1−0), 13CO (J = 1−0) and C18O (J = 1−0) observations of G47.06+0.26 obtained with the Purple Mountain Observation (PMO) 13.7 m radio telescope to investigate the detailed kinematics of the filament. Radio continuum and infrared archival data were obtained from the NRAO VLA Sky Survey (NVSS), the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey, and the Multi-band Imaging Photometer Survey of the Galaxy (MIPSGAL). To trace massive clumps and extract young stellar objects in G47.06+0.26, we used the BGPS catalog v2.0 and the GLIMPSE I catalog, respectively. Results. The 12CO (J = 1−0) and 13CO (J = 1−0) emission of G47.06+0.26 appear to show a filamentary structure. The filament extends about 45′ (58.1 pc) along the east-west direction. The mean width is about 6.8 pc, as traced by the 13CO (J = 1−0) emission. G47.06+0.26 has a linear mass density of ~361.5 M⊙pc-1. The external pressure (due to neighboring bubbles and H II regions) may help preventing the filament from dispersing under the effects of turbulence. From the velocity-field map, we discern a velocity gradient perpendicular to G47.06+0.26. From the Bolocam Galactic Plane Survey (BGPS) catalog, we found nine BGPS sources in G47.06+0.26, that appear to these sources have sufficient mass to form massive stars. We obtained that the clump formation efficiency (CFE) is ~18% in the filament. Four infrared bubbles were found to be located in, and adjacent to, G47.06+0.26. Particularly, infrared bubble N98 shows a cometary structure. CO molecular gas adjacent to N98 also shows a very intense emission. H II regions associated with infrared bubbles can inject the energy to surrounding gas. We calculated the kinetic energy, ionization energy, and thermal energy of two H II regions in G47.06+0.26. From the GLIMPSE I catalog, we selected some Class I sources with an age of ~105 yr, which are clustered along the filament. The feedback from the H II regions may cause the formation of a new generation of stars in filament G47.06+0.26.
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Venkatesan, Aparna, i Andrew Benson. "X-rays and hard ultraviolet radiation from the first galaxies: ionization bubbles and 21-cm observations". Monthly Notices of the Royal Astronomical Society 417, nr 3 (12.09.2011): 2264–75. http://dx.doi.org/10.1111/j.1365-2966.2011.19407.x.
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Li, Guozhu, Baiqi Ning, Libo Liu, Biqiang Zhao, Xinan Yue, S. Y. Su i Sarita Venkatraman. "Correlative study of plasma bubbles, evening equatorial ionization anomaly, and equatorial prereversalE×Bdrifts at solar maximum". Radio Science 43, nr 4 (sierpień 2008): n/a. http://dx.doi.org/10.1029/2007rs003760.
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Wiens, R. H., B. M. Ledvina, P. M. Kintner, M. Afewerki i Z. Mulugheta. "Equatorial plasma bubbles in the ionosphere over Eritrea: occurrence and drift speed". Annales Geophysicae 24, nr 5 (3.07.2006): 1443–53. http://dx.doi.org/10.5194/angeo-24-1443-2006.
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Abstract. An all-sky imager was installed in Asmara, Eritrea (15.4° N, 38.9° E, 7° N dip) and used to monitor the OI 630-nm nightglow. Nine months of data were studied between September 2001 and May 2002, a time including the recent maximum in the solar activity cycle. Equatorial plasma bubbles (EPBs) were recorded on 63% of nights with adequate viewing conditions. The station location within view of the equatorial ionization anomaly and with a magnetic declination near zero makes it an excellent test case for comparison with satellite studies of the seasonal variation of EPBs with longitude. The imager was accompanied by two Cornell GPS scintillation monitors, and the amplitude scintillation data are compared to the all-sky data. GPS scintillations indicate the beginning of EPBs, but die out sooner in the post-midnight period than the larger scale EPBs. Both phenomena exhibit clear occurrence maxima around the equinoxes. Ionospheric zonal drift speeds have been deduced from EPB and GPS scintillation pattern movement. Average near-midnight EPB drift speeds are between 100 and 120 m/s most months, with the GPS scintillation speeds being about the same. A winter drift speed maximum is evident in both EPB and GPS scintillation monthly means.
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Mookerjea, Bhaswati. "Star Formation Triggered by the Expanding Bubble S111". Astrophysical Journal 926, nr 1 (1.02.2022): 4. http://dx.doi.org/10.3847/1538-4357/ac4258.
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Abstract This paper investigates the impact of radiative and mechanical feedback from O-type stars on their parent molecular clouds and the triggering of formation of a future generation of stars. We study the infrared bubble S111 created by the embedded massive stellar cluster G316.80–0.05. A significant fraction of gas in shells created due to the compression of the ambient medium by expanding bubbles is photodissociated by the stellar radiation. The kinematics of the shells are thus best studied using spectroscopic observations of singly ionized carbon, the most dominant species. We have used velocity-resolved maps of the 2P3/2 → 2P1/2 transition of [C ii] at 158 μm, the J = 2–1 transition of 13CO and C18O, and the J = 1–0 transition of HCO+ to study the rim of the bubble S111 that partly coincides with the southern part of the infrared dark ridge G316.75. The [C ii] spectra conclusively show evidence of a shell expanding with a moderate velocity of ∼7 km s−1, which amounts to a kinetic energy that is ∼0.5–40 times the thermal energy of the H ii region. The pressure causing the expansion of the H ii region arises mainly from hydrogen ionization and dust-processed radiation. Among the far-infrared sources located in compressed shells, we find the core G316.7799–0.0942 to show broad spectral features consistent with outflow activity and conclude that it is a site of active star formation. Based on the age of the H ii region we conclude that this expanding H ii region is responsible for triggering the current star formation activity in the region.
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Decataldo, D., A. Lupi, A. Ferrara, A. Pallottini i M. Fumagalli. "Shaping the structure of a GMC with radiation and winds". Monthly Notices of the Royal Astronomical Society 497, nr 4 (11.08.2020): 4718–32. http://dx.doi.org/10.1093/mnras/staa2326.
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ABSTRACT We study the effect of stellar feedback (photodissociation/ionization, radiation pressure, and winds) on the evolution of a Giant Molecular Cloud (GMC), by means of a 3D radiative transfer, hydrosimulation implementing a complex chemical network featuring H2 formation and destruction. We track the formation of individual stars with mass $M\gt 1\, {\rm M}_{\odot }$ with a stochastic recipe. Each star emits radiation according to its spectrum, sampled with 10 photon bins from near-infrared to extreme ultraviolet bands; winds are implemented by energy injection in the neighbouring cells. We run a simulation of a GMC with mass $M=10^5\, {\rm M}_{\odot }$, following the evolution of different gas phases. Thanks to the simultaneous inclusion of different stellar feedback mechanisms, we identify two stages in the cloud evolution: (1) radiation and winds carve ionized, low-density bubbles around massive stars, while FUV radiation dissociates most H2 in the cloud, apart from dense, self-shielded clumps; (2) rapid star formation (SFR$\simeq 0.1\, {\rm M}_{\odot }\, {\rm yr}^{-1}$) consumes molecular gas in the dense clumps, so that UV radiation escapes and ionizes the remaining $\mathrm{H\,{\small I}}$ gas in the GMC. H2 is exhausted in 1.6 Myr, yielding a final star formation efficiency of 36 per cent. The average intensity of FUV and ionizing fields increases almost steadily with time; by the end of the simulation (t = 2.5 Myr) we find 〈G0〉 ≃ 103 (in Habing units), and a ionization parameter 〈Uion〉 ≃ 102, respectively. The ionization field has also a more patchy distribution than the FUV one within the GMC. Throughout the evolution, the escape fraction of ionizing photons from the cloud is fion, esc ≲ 0.03.
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Jiang, N., i J. Silcox. "Electron Irradiation Damage in Multi-Component Glasses". Microscopy and Microanalysis 6, S2 (sierpień 2000): 390–91. http://dx.doi.org/10.1017/s1431927600034449.
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Understanding electron beam induced damage in glasses, especially in multi-component glasses, is very important, since the interaction of electron probes with glass is a very common approach to determine glass composition and structure. For example, the decay of characteristic X-ray and Auger electron intensities, using electron beams as probes, of alkalis in glasses have been known for years. In addition, both phase separation and formation of gas bubbles in the glasses have also been reported. Many irradiation effects are strongly dependent on the structure, bonding and composition of matter. In general, three types of mechanisms, knock-on damage, ionization and field-induced migration have been introduced to describe the damage induced by electron irradiation. Here, we demonstrate electron irradiation induced phase decomposition in a multi-component oxide glass, and introduce a modified model to interpret the damage process.
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Park, Jaeheung, Stephen B. Mende, Richard W. Eastes i Harald U. Frey. "Climatology of Equatorial Plasma Bubbles in Ionospheric Connection Explorer/Far-UltraViolet (ICON/FUV) Limb Images". Journal of Astronomy and Space Sciences 39, nr 3 (wrzesień 2022): 87–98. http://dx.doi.org/10.5140/jass.2022.39.3.87.
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The Far-UltraViolet (FUV) imager onboard the Ionospheric Connection Explorer (ICON) spacecraft provides two-dimensional limb images of oxygen airglow in the nightside low-latitude ionosphere that are used to determine the oxygen ion density. As yet, no FUV limb imager has been used for climatological analyses of Equatorial Plasma Bubbles (EPBs). To examine the potential of ICON/FUV for this purpose, we statistically investigate small-scale (~180 km) fluctuations of oxygen ion density in its limb images. The seasonal-longitudinal variations of the fluctuation level reasonably conform to the EPB statistics in existing literature. To further validate the ICON/FUV data quality, we also inspect climatology of the ambient (unfiltered) nightside oxygen ion density. The ambient density exhibits (1) the well-known zonal wavenumber-4 signatures in the Equatorial Ionization Anomaly (EIA) and (2) off-equatorial enhancement above the Caribbean, both of which agree with previous studies. Merits of ICON/FUV observations over other conventional data sets are discussed in this paper. Furthermore, we suggest possible directions of future work, e.g., synergy between ICON/FUV and the Global-scale Observations of the Limb and Disk (GOLD) mission.
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Lee, C. C., F. D. Chu, W. S. Chen, J. Y. Liu, S. Y. Su, Y. A. Liou i S. B. Yu. "Spread F, GPS phase fluctuations, and plasma bubbles near the crest of equatorial ionization anomaly during solar maximum". Journal of Geophysical Research: Space Physics 114, A8 (sierpień 2009): n/a. http://dx.doi.org/10.1029/2009ja014195.
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Eyal, Y., R. Evron i Y. Cohen. "Defect Structure of Ion-Irradiated Amorphous SiO2". Journal of Applied Crystallography 30, nr 5 (1.10.1997): 618–22. http://dx.doi.org/10.1107/s0021889897001325.
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Uniformly enhanced small-angle X-ray scattering intensities of amorphous SiO2, measured following irradiation with 320 keV H+ and He+ beams, are shown to be correlated, irrespective of the incident ion, with the O and Si cumulative displacement yields. Damage by both beams originated primarily from nuclear stopping but, under H+-ion irradiation, contributions from ionization processes were significant as well. At low beam fluences, the irradiated structure is compatible with the presence of stable radiation-induced interstitial-like O and Si atoms and complementary O and Si vacancy-like sites. There is no evidence for recovery near room temperature of the modified structure to the pre-irradiated state or for formation of colloidal-size scattering centers, such as gas bubbles or voids. Thus, ion-irradiation-induced changes in physical and chemical properties of silica seem to be due to the effect of the preserved primary atomic displacement damage.
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Dahmer-Hahn, L. G., R. Riffel, T. V. Ricci, J. E. Steiner, T. Storchi-Bergmann, R. A. Riffel, R. B. Menezes i in. "A panchromatic spatially resolved study of the inner 500 pc of NGC 1052 – II. Gas excitation and kinematics". Monthly Notices of the Royal Astronomical Society 489, nr 4 (5.09.2019): 5653–68. http://dx.doi.org/10.1093/mnras/stz2453.
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ABSTRACT We map the optical and near-infrared (NIR) emission-line flux distributions and kinematics of the inner 320 × 535 pc2 of the elliptical galaxy NGC 1052. The integral field spectra were obtained with the Gemini Telescope using the GMOS-IFU and NIFS instruments, with angular resolutions of 0.88 and 0.1 arcsec in the optical and NIR, respectively. We detect five kinematic components: (1) and (2) two spatially unresolved components: a broad-line region visible in H α, with a full width at half-maximum (FWHM) of ∼3200 km s−1, and an intermediate broad component seen in the [O iii] λλ4959,5007 doublet; (3) an extended intermediate-width component with 280 km s−1 < FWHM < 450 km s−1 and centroid velocities up to 400 km s−1, which dominates the flux in our data, attributed either to a bipolar outflow related to the jets, rotation in an eccentric disc or to a combination of a disc and large-scale gas bubbles; (4) and (5) two narrow (FWHM < 150 km s−1) components, one visible in [O iii], and another visible in the other emission lines, extending beyond the field of view of our data, which is attributed to large-scale shocks. Our results suggest that the ionization within the observed field of view cannot be explained by a single mechanism, with photoionization being the dominant mechanism in the nucleus with a combination of shocks and photoionization responsible for the extended ionization.
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Pakull, Manfred W. "High-exitation nebulae around Magellanic Wolf-Rayet stars". Proceedings of the International Astronomical Union 4, S256 (lipiec 2008): 437–42. http://dx.doi.org/10.1017/s1743921308028834.
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AbstractThe SMC harbours a class of hot nitrogen-sequence Wolf-Rayet stars (WNE) that display only relatively weak broad Heiiλ4686 emission indicative of their low mass-loss rates and which are therefore hard to detect. However, such stars are possible emitters of strong He+Lyman continua which in turn could ionize observable Heiiiregions, i.e. highly excited Hiiregions emitting nebular Heiiλ4686 emission. We here report the discovery of a second Heiiiregion in the SMC within OB association NGC 249 within which the weak-lined WN star SMC WR10 is embedded. SMC WR10 is of special importance since it is a single star showing the presence of atmospheric hydrogen. While analysing the spectrum in the framework of two popular, independent WR atmosphere models we found strongly discrepant predictions (by 1 dex) of the He+continuum for the same input parameters. A second interesting aspect of the work reported here concerns the beautiful MCELS images which clearly reveal a class of strongly Oiiiλ5007 emitting (blue-coded) nebulae. Not unexpectedly, most of the “blue” nebulae are known Wolf-Rayet bubbles, but new bubbles around a few WRs are also detected. Moreover, we report the existence of blue nebulae without associated known WRs and discuss the possibility that they reveal weak-wind WR stars with very faint stellar Heiiλ4686 emission. Alternatively, such nebulae might hint at the hitherto missing population of relatively low-mass, hot He stars predicted by massive binary evolution calculations. Such a binary system is probably responsible for the ionization of the unique Heiiλ4686-emitting nebula N 44C.
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Roberts-Borsani, Guido, Tommaso Treu, Charlotte Mason, Richard S. Ellis, Nicolas Laporte, Thomas Schmidt, Marusa Bradac, Adriano Fontana, Takahiro Morishita i Paola Santini. "Nature and Nurture? Comparing Lyα Detections in UV-bright and Fainter [O iii]+Hβ Emitters at z ∼ 8 with Keck/MOSFIRE". Astrophysical Journal 948, nr 1 (1.05.2023): 54. http://dx.doi.org/10.3847/1538-4357/acc798.
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Abstract The 100% detection rate of Lyα emission in a sample of four luminous z ∼ 8 galaxies with red Spitzer/IRAC colors suggests objects with unusual ionizing capabilities that created early ionized bubbles in a neutral era. Whether such bubbles reflect enhanced ionizing properties (nature) or an overdense environment (nurture), however, remains unclear. Here we aim to distinguish between these hypotheses via a search for Lyα emission in five fainter galaxies drawn from the CANDELS-GOODS fields using a similar IRAC excess and UV magnitudes that should reflect reduced clustering effects. Using Keck/MOSFIRE we tentatively detect >4σ line emission in only two targets at redshifts z Lyα = 7.1081 and 7.9622 with rest-frame EWs of 16–17 Å, ∼1.5× weaker compared to their brighter counterparts. Thus, we find a reduced rate for Lyα emission of 0.40 − 0.25 + 0.30 compared to 1.00 − 0.44 + 0.00 for more luminous examples. The lower rate agrees with predictions from simulations of a mostly neutral intergalactic medium and an intrinsic EW0,Lyα distribution for z ∼ 6 galaxies. However, even with an extreme EW0,Lyα model, it is challenging to match the detection rate for the luminous objects. Spectral energy distribution fitting of our fainter sample indicates young and star-forming systems, albeit with less extreme star formation rates and ionization parameters compared to their luminous counterparts. The enhanced Lyα rate in luminous galaxies is thus likely a byproduct of both extreme ionizing properties as well as environmental effects. Further studies with JWST may be required to resolve the physical nature of this puzzling population.
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Tremblin, P., E. Audit, V. Minier, W. Schmidt i N. Schneider. "Formation of structures around HII regions: ionization feedback from massive stars". Proceedings of the International Astronomical Union 10, H16 (sierpień 2012): 590. http://dx.doi.org/10.1017/s1743921314012307.
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AbstractWe present a new model for the formation of dense clumps and pillars around HII regions based on shocks curvature at the interface between a HII region and a molecular cloud. UV radiation leads to the formation of an ionization front and of a shock ahead. The gas is compressed between them forming a dense shell at the interface. This shell may be curved due to initial interface or density modulation caused by the turbulence of the molecular cloud. Low curvature leads to instabilities in the shell that form dense clumps while sufficiently curved shells collapse on itself to form pillars. When turbulence is high compared to the ionized-gas pressure, bubbles of cold gas have sufficient kinetic energy to penetrate into the HII region and detach themselves from the parent cloud, forming cometary globules.Using computational simulations, we show that these new models are extremely efficient to form dense clumps and stable and growing elongated structures, pillars, in which star formation might occur (see Tremblin et al.2012a). The inclusion of turbulence in the model shows its importance in the formation of cometary globules (see Tremblin et al.2012b). Globally, the density enhancement in the simulations is of one or two orders of magnitude higher than the density enhancement of the classical “collect and collapse“ scenario. The code used for the simulation is the HERACLES code, that comprises hydrodynamics with various equation of state, radiative transfer, gravity, cooling and heating.Our recent observations with Herschel (see Schneider et al.2012a) and SOFIA (see Schneider et al.2012b) and additional Spitzer data archives revealed many more of these structures in regions where OB stars have already formed such as the Rosette Nebula, Cygnus X, M16 and Vela, suggesting that the UV radiation from massive stars plays an important role in their formation. We present a first comparison between the simulations described above and recent observations of these regions.
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Wang, Weicong, Yunxia Zhou, Bowen Liu, Hisham Essawy, Zhiyan Liu, Shuduan Deng, Xiaojian Zhou i Jun Zhang. "Tannin-Epoxidized Soybean Oil as Bio-Based Resin for Fabrication of Grinding Wheel". Polymers 14, nr 24 (11.12.2022): 5423. http://dx.doi.org/10.3390/polym14245423.
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Formaldehyde-free epoxidized soybean oil-based resin has been prepared under acidic conditions by co-condensation of the epoxidized soybean oil and condensed tannin originating from agricultural and forestry sources as the main raw materials, whereas 1,6-hexanediamine was employed as a cross-linking agent. Fourier transform infrared spectroscopy (FTIR) and electrospray ionization (ESI) corroborated that tannin and epoxidized soybean oil underwent crosslinking under acidic conditions supported by hexamethylenediamine. A bio-based grinding wheel was fabricated by formulation of the developed resin with wood powder as source of grinding particles. The appearance, hardness, compressive strength and wear resistance of the resulting grinding wheel were studied. The results have shown that the grinding wheel possesses a smooth surface with no bubbles or cracks, and its hardness and wear resistance were greater than that of a phenolic resin-based grinding wheel. Interestingly, the grinding wheel incorporates more than 90% of its raw materials as biomass renewable materials; thus, it is generally considered non-toxic. In addition, the future feasibility of this approach to replace some petrochemical resins that are frequently used in the fabrication of grinding wheels is considered.
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Mukherjee, G. K. "Mapping of the Simultaneous Movement of the Equatorial Ionization Anomaly (EIA) and Ionospheric Plasma Bubbles Through All-sky Imaging of OI630nm Emission". Terrestrial, Atmospheric and Oceanic Sciences 13, nr 1 (2002): 053. http://dx.doi.org/10.3319/tao.2002.13.1.53(a).
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Yusef-Zadeh, F., i M. Wardle. "Cosmic-ray-driven outflow from the Galactic Centre and the origin of magnetized radio filaments". Monthly Notices of the Royal Astronomical Society: Letters 490, nr 1 (13.09.2019): L1—L5. http://dx.doi.org/10.1093/mnrasl/slz134.
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Abstract Radio, X-ray, and infrared observations of the inner few hundred parsecs of the Galactic Centre have highlighted two characteristics of the interstellar medium. The cosmic-ray ionization rate derived from molecular ions such as H$^+_3$ is at least two to three orders of magnitude higher than in the Galactic disc. The other is bipolar X-ray and radio emission away from the Galactic plane. These features are consistent with a scenario in which high cosmic-ray pressure drives large-scale winds away from the Galactic plane. The interaction of such a wind with stellar wind bubbles may explain the energetic non-thermal radio filaments found throughout the Galactic Centre. Some of the implications of this scenario is the removal of gas driven by outflowing winds, acting as a feedback to reduce the star formation rate in the central molecular zone (CMZ), and the distortion of azimuthal magnetic field lines in the CMZ to vertical direction away from the plane. The combined effects of the wind and the vertical magnetic field can explain why most magnetized filaments run perpendicular to the galactic plane. This proposed picture suggests our Milky Way nucleus has recently experienced starburst or black hole activity, as recent radio and X-ray observations indicate.
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Li, Qiang, Yanbo Zhu, Kun Fang i Jisi Fang. "Statistical Study of the Seasonal Variations in TEC Depletion and the ROTI during 2013–2019 over Hong Kong". Sensors 20, nr 21 (30.10.2020): 6200. http://dx.doi.org/10.3390/s20216200.
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Equatorial plasma bubbles (EPBs) can cause large total electron content (TEC) gradient magnitudes and significant density irregularities. In this paper, depletions and irregularities due to EPBs are identified by using the Global Positioning System (GPS)-TEC time series extracted from nine Global Navigation Satellite System (GNSS) stations over Hong Kong near the equatorial ionization anomaly (EIA) crest region from 2013 to 2019. The correlation analyses between the daily variation in the rate of TEC change index (ROTI) and that of the EPB occurrence rate, depth, and duration are presented. The monthly EPB occurrence rate, depth, duration, and ROTI show strong seasonal variations, with maxima during equinoctial seasons, especially during the moderate-to-high solar activity years of 2013–2016. Furthermore, two seasonal asymmetries can be clearly seen for these parameters from 2013 to 2016. The EPB occurrences rate, depth, and duration vary annually with the solar radio flux at 10.7 cm (F10.7) index. The correlation analyses of the EPB occurrence rate, depth, and duration are found to be much more strongly correlated with the F10.7 index on an annual basis than on a monthly basis. The correlation analysis of monthly variations shows the impacts of solar activity on EPB occurrence, depth, and duration are seasonally dependent, which is significantly greater in the equinoctial seasons and summer than in winter.
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Bik, A., G. Östlin, V. Menacho, A. Adamo, M. Hayes, J. Melinder i P. Amram. "The super star cluster driven feedback in ESO338-IG04 and Haro 11". Proceedings of the International Astronomical Union 12, S316 (sierpień 2015): 44–49. http://dx.doi.org/10.1017/s1743921316007031.
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AbstractThe stellar content of young massive star clusters emit large amounts of Lyman continuum photons and inject momentum into the inter stellar medium (ISM) by the strong stellar winds of the most massive stars in the cluster. When the most massive stars explode as supernovae, large amounts of mechanical energy are injected in the ISM. A detailed study of the ISM around these massive cluster provides insights on the effect of cluster feedback.We present high quality integral field spectroscopy taken with VLT/MUSE of two starburst galaxies: ESO 338-IG04 and Haro 11. Both galaxies contain a significant number of super star clusters. The MUSE data provide us with an unprecedented view of the state and kinematics of the ionized gas in the galaxy allowing us to study the effect of stellar feedback on small and large spatial scales. We present our recent results on studying the ISM state of these two galaxies. The data of both galaxies show that the mechanical and ionization feedback of the super star clusters in the galaxy modify the state and kinematics of the ISM substancially by creating highly ionized bubbles around the cluster, making the central part of the galaxy highly ionized. This shows that the HII regions around the individual clusters are density bounded, allowing the ionizing photons to escape and ionize the ISM further out.
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YUAN, LI, i PING HE. "INFLUENCE OF SONOCHEMISTRY ON SINGLE-BUBBLE SONOLUMINESCENCE". Modern Physics Letters B 19, nr 28n29 (20.12.2005): 1711–14. http://dx.doi.org/10.1142/s0217984905010281.
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Spherical oscillation of an acoustically levitated gas bubble in water was simulated numerically to elucidate the phenomenon of single-bubble sonoluminescence (SBSL). A refined hydro-chemical model was used, which took into account the processes of water vapor evaporation and condensation, mass diffusion, and chemical reactions. The numerical results show significant water vapor dissociations but rather low degrees of ionizations. A widely accepted weakly ionized gas model is then used to compute the light emission. Contrary to earlier predictions without chemical reactions, the present calculated light spectra are generally too small and the pulses are too short to fit to recent experimental results within stable SBSL range. To solve this contradiction, the electrostatic interactions of the ionized gases are included, which is shown to lower the ionization potentials of gas species in the bubble significantly.
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Thampi, S. V., T. K. Pant, S. Ravindran, C. V. Devasia i R. Sridharan. "Simulation studies on the tomographic reconstruction of the equatorial and low-latitude ionosphere in the context of the Indian tomography experiment: CRABEX". Annales Geophysicae 22, nr 10 (3.11.2004): 3445–60. http://dx.doi.org/10.5194/angeo-22-3445-2004.
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Abstract. Equatorial ionosphere poses a challenge to any algorithm that is used for tomographic reconstruction because of the phenomena like the Equatorial Ionization Anomaly (EIA) and Equatorial Spread F (ESF). Any tomographic reconstruction of ionospheric density distributions in the equatorial region is not acceptable if it does not image these phenomena, which exhibit large spatial and temporal variability, to a reasonable accuracy. The accuracy of the reconstructed image generally depends on many factors, such as the satellite-receiver configuration, the ray path modelling, grid intersections and finally, the reconstruction algorithm. The present simulation study is performed to examine these in the context of the operational Coherent Radio Beacon Experiment (CRABEX) network just commenced in India. The feasibility of using this network for the studies of the equatorial and low-latitude ionosphere over Indian longitudes has been investigated through simulations. The electron density distributions that are characteristic of EIA and ESF are fed into various simulations and the reconstructed tomograms are investigated in terms of their reproducing capabilities. It is seen that, with the present receiver chain existing from 8.5° N to 34° N, it would be possible to obtain accurate images of EIA and the plasma bubbles. The Singular Value Decomposition (SVD) algorithm has been used for the inversion procedure in this study. As is known, by the very nature of ionospheric tomography experiments, the received data contain various kinds of errors, like the measurement and discretization errors. The sensitivity of the inversion algorithm, SVD in the present case, to these errors has also been investigated and quantified.
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Moini, Mehdi, Ping Cao i Allen J. Bard. "Hydroquinone as a Buffer Additive for Suppression of Bubbles Formed by Electrochemical Oxidation of the CE Buffer at the Outlet Electrode in Capillary Electrophoresis/Electrospray Ionization-Mass Spectrometry". Analytical Chemistry 71, nr 8 (kwiecień 1999): 1658–61. http://dx.doi.org/10.1021/ac9811266.
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Böhringer, Hans. "Equilibrium Ionization and Non-Equilibrium Ionization Plasma Models". International Astronomical Union Colloquium 166 (1997): 341–52. http://dx.doi.org/10.1017/s0252921100071232.
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AbstractThis paper provides a brief review on ionization and radiation models of an optically thin, hot plasma and their application to the interpretation of observations of the Local Bubble. The basic structure and atomic physics ingredients of the models are outlined. Some general characteristic results of ionization equilibrium and non-equilibrium calculations are shown. Recent progress in plasma model codes is reviewed. The interpretation of the observations of absorption lines and emission spectra from the Local Bubble is discussed in the framework of ionization equilibrium and non-equilibrium ionization models with particular reference to the fast adiabatic cooling model of Breitschwerdt and Schmutzler.
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Vankadara, Ram Kumar, Sampad Kumar Panda, Christine Amory-Mazaudier, Rolland Fleury, Venkata Ratnam Devanaboyina, Tarun Kumar Pant, Punyawi Jamjareegulgarn, Mohd Anul Haq, Daniel Okoh i Gopi Krishna Seemala. "Signatures of Equatorial Plasma Bubbles and Ionospheric Scintillations from Magnetometer and GNSS Observations in the Indian Longitudes during the Space Weather Events of Early September 2017". Remote Sensing 14, nr 3 (29.01.2022): 652. http://dx.doi.org/10.3390/rs14030652.
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Scintillation due to ionospheric plasma irregularities remains a challenging task for the space science community as it can severely threaten the dynamic systems relying on space-based navigation services. In the present paper, we probe the ionospheric current and plasma irregularity characteristics from a latitudinal arrangement of magnetometers and Global Navigation Satellite System (GNSS) stations from the equator to the far low latitude location over the Indian longitudes, during the severe space weather events of 6–10 September 2017 that are associated with the strongest and consecutive solar flares in the 24th solar cycle. The night-time influence of partial ring current signatures in ASYH and the daytime influence of the disturbances in the ionospheric E region electric currents (Diono) are highlighted during the event. The total electron content (TEC) from the latitudinal GNSS observables indicate a perturbed equatorial ionization anomaly (EIA) condition on 7 September, due to a sequence of M-class solar flares and associated prompt penetration electric fields (PPEFs), whereas the suppressed EIA on 8 September with an inverted equatorial electrojet (EEJ) suggests the driving disturbance dynamo electric current (Ddyn) corresponding to disturbance dynamo electric fields (DDEFs) penetration in the E region and additional contributions from the plausible storm-time compositional changes (O/N2) in the F-region. The concurrent analysis of the Diono and EEJ strengths help in identifying the pre-reversal effect (PRE) condition to seed the development of equatorial plasma bubbles (EPBs) during the local evening sector on the storm day. The severity of ionospheric irregularities at different latitudes is revealed from the occurrence rate of the rate of change of TEC index (ROTI) variations. Further, the investigations of the hourly maximum absolute error (MAE) and root mean square error (RMSE) of ROTI from the reference quiet days’ levels and the timestamps of ROTI peak magnitudes substantiate the severity, latitudinal time lag in the peak of irregularity, and poleward expansion of EPBs and associated scintillations. The key findings from this study strengthen the understanding of evolution and the drifting characteristics of plasma irregularities over the Indian low latitudes.
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Jennings, W. D., C. A. Watkinson i F. B. Abdalla. "Analysing the Epoch of Reionization with three-point correlation functions and machine learning techniques". Monthly Notices of the Royal Astronomical Society 498, nr 3 (29.08.2020): 4518–32. http://dx.doi.org/10.1093/mnras/staa2598.
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ABSTRACT Three-point and high-order clustering statistics of the high-redshift 21 cm signal contain valuable information about the Epoch of Reionization (EoR). We present 3PCF-fast, an optimized code for estimating the three-point correlation function (3PCF) of 3D pixelized data such as the outputs from numerical and seminumerical simulations. After testing 3PCF-fast on data with known analytical 3PCF, we use machine learning techniques to recover the mean bubble size and global ionization fraction from correlations in the outputs of the publicly available 21cmfast code. We assume that foregrounds have been perfectly removed and negligible instrumental noise. Using ionization fraction data, our best multilayer perceptron (MLP) model recovers the mean bubble size with a median prediction error of around $10 {{\ \rm per\ cent}}$, or from the 21 cm differential brightness temperature with median prediction error of around $14 {{\ \rm per\ cent}}$. A further two MLP models recover the global ionization fraction with median prediction errors of around $4 {{\ \rm per\ cent}}$ (using ionization fraction data) or around $16 {{\ \rm per\ cent}}$ (using brightness temperature). Our results indicate that clustering in both the ionization fraction field and the brightness temperature field encode useful information about the progress of the EoR in a complementary way to other summary statistics. Using clustering would be particularly useful in regimes where high signal-to-noise ratio prevents direct measurement of bubble size statistics. We compare the quality of MLP models using the power spectrum, and find that using the 3PCF outperforms the power spectrum at predicting both global ionization fraction and mean bubble size.
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Franklin, Cole. "Impacts of Ionization Potentials and Megasonic Dispersion". Solid State Phenomena 145-146 (styczeń 2009): 19–22. http://dx.doi.org/10.4028/www.scientific.net/ssp.145-146.19.
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It has been shown that megasonics can accelerate strip processes such as doped and plasma treated photoresist [1]. However, applied megasonic energy can also damage sensitive semiconductor devices. It was shown that adding a solvent such as IPA or lowering the temperature helps to control cavitation in semi-aqueous fluids [2]. Sonochemical reactions have been observed in various industries, however, there are no published observations in semiconductor cleaning. Ions may form in megasonic driven bubble collapse impacted by the characteristics of a gas or liquid that enters the bubble from the bulk liquid. Lower ionization potential gases or liquids may form ions earlier in the bubble collapse, so as to use up some of the total available energy through sonochemical reactions and possibly reducing the cavitations implosive energy. Here, tests are conducted to vary the liquid and gas type based on ionization potential to look into the impact this would have on cleaning and damage. It is shown that lower ionization or liquid additives lower the device damage.
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Slavin, Jonathan D. "The Evaporation of Nearby Clouds and the Soft X-ray Background". International Astronomical Union Colloquium 166 (1997): 169–72. http://dx.doi.org/10.1017/s0252921100070925.
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AbstractIn recent years the nature of the low density clouds within the Local Bubble has been increasingly well characterized. These clouds, including the one which surrounds the solar system, are embedded in the hot gas and therefore should be evaporating via thermal conduction. If several evaporation fronts exist within the Local Bubble, the emissivity and spectrum of the hot gas is significantly different from a single temperature, equilibrium ionization plasma. We explore models in which the the temperature, density and ionization in the hot gas are influenced by cloud evaporation and compare the results with the observed Soft X-ray Background.
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Dupin, Olivier, i Cécile Gry. "Diffuse Ionized Gas in the β CMa Tunnel". International Astronomical Union Colloquium 166 (1997): 173–76. http://dx.doi.org/10.1017/s0252921100070937.
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AbstractWe present HST observations of the interstellar medium toward the star β CMa known to be located in a low density extension of the Local Bubble. Most of the matter in the sight-line is ionized and clumped in two main components. One of them, as well as one of the components detected toward ϵ CMa, is mostly ionized and only slightly depleted. Their ionization ratios are compatible with collisional ionization at T~25 000 K. These clouds could have been ionized by shocks related to the Local Bubble creation and also responsible of some dust grain sputtering.
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Slavin, Jonathan D., i Priscilla C. Frisch. "The Influence of the Local Bubble on the Ionization of the Local Interstellar Cloud". International Astronomical Union Colloquium 166 (1997): 305–8. http://dx.doi.org/10.1017/s0252921100071165.
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AbstractThe ionization of the the Local Interstellar Cloud (LIC) is quite unusual compared with most warm (T ~ 104 K) interstellar gas. Hydrogen and helium are both partially ionized with helium surprisingly more ionized than hydrogen. Directly observed ionization sources including nearby stellar EUV sources and the diffuse emission of the Soft X-ray Background (SXRB), do not provide enough ionization and heating to account for both the ionization state and temperature of the LIC. We propose that an evaporative boundary between the LIC and the hot gas of the Local Bubble can provide the necessary ionizing radiation. Results of detailed models of the emission from the interface are presented and shown to be adequate to explain the observations.
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Frisch, Priscilla C. "The Local Bubble, Local Fluff, and Heliosphere". International Astronomical Union Colloquium 166 (1997): 269–78. http://dx.doi.org/10.1017/s0252921100071104.
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AbstractThe properties of the Local Bubble, Local Fluff complex of nearby interstellar clouds, and the heliosphere are mutually constrained by data and theory. Observations and models of the diffuse radiation field, interstellar ionization, pickup ion and anomalous cosmic-ray populations, and interstellar dust link the physics of these regions. The differences between the one-asymmetric-superbubble and twosuperbubble views of the Local Bubble are discussed.
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de Avillez, M. A., i D. Breitschwerdt. "Non-equilibrium ionization modeling of the Local Bubble". Astronomy & Astrophysics 539 (20.02.2012): L1. http://dx.doi.org/10.1051/0004-6361/201117172.
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Ho, C. Y., L. Yuan, M. C. Chu, P. T. Leung i W. Wei. "Ionization and photon emission in single-bubble sonoluminescence". Europhysics Letters (EPL) 56, nr 6 (grudzień 2001): 891–97. http://dx.doi.org/10.1209/epl/i2001-00603-9.
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KOU, Wei, Hua ZHANG, Chingin KONSTANTIN i Huan-Wen CHEN. "Charged Bubble Extractive Ionization Mass Spectrometry for Protein Analysis". Chinese Journal of Analytical Chemistry 45, nr 12 (grudzień 2017): 1937–43. http://dx.doi.org/10.1016/s1872-2040(17)61060-0.
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Stepanov, Sergey V., Vsevolod M. Byakov, Dmitrii S. Zvezhinskiy, Gilles Duplâtre, Roman R. Nurmukhametov i Petr S. Stepanov. "Positronium in a Liquid Phase: Formation, Bubble State and Chemical Reactions". Advances in Physical Chemistry 2012 (21.08.2012): 1–17. http://dx.doi.org/10.1155/2012/431962.
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The present approach describes the e+ fate since its injection into a liquid until its annihilation. Several stages of the e+ evolution are discussed: (1) energy deposition and track structure of fast positrons: ionization slowing down, number of ion-electron pairs, typical sizes, thermalization, electrostatic interaction between e+ and the constituents of its blob, and effect of local heating; (2) positronium formation in condensed media: the Ore model, quasifree Ps state, intratrack mechanism of Ps formation; (3) fast intratrack diffusion-controlled reactions: Ps oxidation and ortho-paraconversion by radiolytic products, reaction rate constants, and interpretation of the PAL spectra in water at different temperatures; (4) Ps bubble models. Inner structure of positronium (wave function, energy contributions, relationship between the pick-off annihilation rate and the bubble radius).
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Guo, Jing, Jianfeng Wu, Hua Feng, Zheng Cai, Ping Zhou, Changxing Zhou, Shiwu Zhang i in. "Bubble in the Whale: Identifying the Optical Counterparts and Extended Nebula for the Ultraluminous X-Ray Sources in NGC 4631". Astrophysical Journal 946, nr 2 (31.03.2023): 72. http://dx.doi.org/10.3847/1538-4357/acaddd.
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Abstract We present a deep optical imaging campaign on the starburst galaxy NGC 4631 with CFHT/MegaCam. By supplementing the HST/ACS and Chandra/ACIS archival data, we search for the optical counterpart candidates of the five brightest X-ray sources in this galaxy, four of which are identified as ultraluminous X-ray sources (ULXs). The stellar environments of the X-ray sources are analyzed using the extinction-corrected color–magnitude diagrams and the isochrone models. We discover a highly asymmetric bubble nebula around X4 that exhibits different morphology in the Hα and [O iii] images. The [O iii]/Hα ratio map shows that the Hα-bright bubble may be formed mainly via the shock ionization by the one-sided jet/outflow, while the more compact [O iii] structure is photoionized by the ULX. We constrain the bubble expansion velocity and interstellar medium density with the MAPPINGS V code and hence estimate the mechanical power injected into the bubble as P w ∼ 5 × 1040 erg s−1 and the corresponding bubble age as ∼7 × 105 yr. Relativistic jets are needed to provide such a level of mechanical power with a mass-loss rate of ∼10−7 M ⊙ yr−1. Besides the accretion, the black hole spin is likely an additional energy source for the super-Eddington jet power.
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Buckalew, Brent, Reginald J. Dufour, Parviz Ghavamian, Patrick Hartigan, Don K. Walter, Jeff J. Hester i Paul A. Scowen. "HST-STIS spectroscopy of the Bubble Nebula, NGC 7635". Symposium - International Astronomical Union 193 (1999): 336–37. http://dx.doi.org/10.1017/s0074180900205615.
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We report the results of long-slit spectroscopy of the wind-blown bubble and photo-evaporating knots around the O6.5IIIf star BD+60°2522 made with the HST-Space Telescope Imaging Spectrograph. The Of star is the primary ionizing source for the H II region NGC 7635, located in the Perseus Arm. The spectra were taken through a 0″.2 x 52″ slit with low and medium resolution gratings covering the wavelength range 2900-6870 Å. Observations with two slit orientations were made; one across the line of embedded knots to the west of the Of star and the second running from the Of star across the bubble to the NE.The 2D-STIS spectra permit us to subtract the surrounding H II region's diffuse emission from that of the knots and the bubble, and to study the spatial variations in various emission lines in these features to a resolution of ∼ 0″.2, an order of magnitude improvement over the best ground-based spectra of this object in the literature. We present high spatial-resolution emission-line and line-ratio profiles across the bubble and knots, and compare them with the predicted variations from photo-ionization, photo-evaporation, and wind-shock models. We also present an analysis of temperatures, densities, and abundances in the features from higher S/N spectra extracted over selected lengths of the slit.
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Ji, Xihan, i Renbin Yan. "Correlation between the gas-phase metallicity and ionization parameter in extragalactic H II regions". Astronomy & Astrophysics 659 (marzec 2022): A112. http://dx.doi.org/10.1051/0004-6361/202142312.
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The variations of the metallicity and ionization parameter in H II regions are usually thought to be the dominant factors that produce the variations we see in the observed emission line spectra. There is an increasing amount of evidence that these two quantities are physically correlated, although the exact form of this correlation is debatable in the literature. Simulated emission line spectra from photoionized clouds provide important clues about the physical conditions of H II regions and are frequently used for deriving metallicities and ionization parameters. Through a systematic investigation on the assumptions and methodology used in applying photoionization models, we find that the derived correlation has a strong dependence on the choice of model parameters. On the one hand, models that give consistent predictions over multiple emission-line ratios yield a positive correlation between the metallicity and ionization parameter for the general population of H II regions or star-forming galaxies. On the other hand, models that are inconsistent with the data locus in high-dimensional line ratio space yield discrepant correlations when different subsets of line ratios are used in the derivation. The correlation between the metallicity and ionization parameter has a secondary dependence on the surface density of the star formation rate (SFR), with the higher SFR regions showing a higher ionization parameter but weaker correlations. The existence of the positive correlation contradicts the analytical wind-driven bubble model for H II regions. We explore assumptions in both dynamical models and photoionization models, and conclude that there is a potential bias associated with the geometry. However, this is still insufficient to explain the correlation. Mechanisms that suppress the dynamical influence of stellar winds in realistic H II regions might be the key to solving this puzzle, though more sophisticated combinations of dynamical models and photoionization models to test are required.