Artykuły w czasopismach na temat „Black Star (Picture agency)”
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Smith, C. Zoe. "Black Star Picture Agency: Life's European Connection". Journalism History 13, nr 1 (marzec 1986): 19–25. http://dx.doi.org/10.1080/00947679.1986.12066618.
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Chen, Amanda C., Christina Xiang Fu i David C. Grabowski. "Claims-Based vs Agency-Reported Patient Outcomes Among Home Health Agencies, 2013-2019". JAMA Network Open 7, nr 4 (10.04.2024): e245692. http://dx.doi.org/10.1001/jamanetworkopen.2024.5692.
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ImportanceGiven the growth of home health agency (HHA) care, it is important to understand whether quality reporting programs, such as star ratings, are associated with improved patient outcomes.ObjectiveTo assess the immediate and long-term association of the introduction of HHA star ratings with patient-level quality outcomes, comparing claims-based and agency-reported measures.Design, Setting, and ParticipantsThis cross-sectional study used Medicare HHA claims and agency-reported assessments to identify sequential patient episodes (ie, spells) among US adults with traditional Medicare who received HHA care (2013-2019). An interrupted time series (ITS) model was used to measure changes in trends and levels before and after the introduction of star ratings. Statistical analysis was performed from November 2022 to September 2023.ExposureThe exposure was the introduction of HHA star ratings. The postexposure period was set as starting January 1, 2016, to account for the period when both star ratings (quality of patient care and patient satisfaction rating) were publicly reported.Main Outcomes and MeasuresThe main outcomes included claims-based hospitalization measures (both during the patient spell and 30 days after HHA discharge) and agency-reported functional measures, such as improvement in ambulation, bathing, and bed transferring. There was also a measure to capture timely initiation of care among post–acute care HHA users, defined as HHA care initiated within 2 days of inpatient discharge.ResultsThis study identified 22 958 847 patient spells to compare annual changes over time; 9 750 689 patient spells were included during the pre–star ratings period from January 1, 2013, to December 31, 2015 (6 067 113 [62.2%] female; 1 100 145 [11.3%] Black, 512 487 [5.3%] Hispanic, 7 845 197 [80.5%] White; 2 656 124 [27.2%] dual eligible; mean [SD] patient spell duration, 70.9 [124.9] days; mean [SD] age, 77.4 [12.0] years); 13 208 158 patient spells were included during the post–star ratings period from January 1, 2016, to December 31, 2019 (8 104 69 [61.4%] female; 1 385 180 [10.5%] Black, 675 536 [5.1%] Hispanic, 10 664 239 [80.7%] White; 3 318 113 [25.1%] dual eligible; mean [SD] patient spell duration, 65.3 [96.2] days; mean [SD] age, 77.7 [11.6] years). Results from the ITS models found that the introduction of star ratings was associated with an acceleration in the mean [SE] hospitalization rate during the spell (0.39% [0.05%] per year) alongside functional improvements in ambulation (2.40% [0.29%] per year), bed transferring (3.95% [0.48%] per year) and bathing (2.34% [0.19%] per year) (P < .001). This occurred alongside a 1.21% (0.12%) per year reduction in timely initiation of care (P < .001).Conclusions and RelevanceThis cross-sectional study found an observed improvement in agency-reported functional measures, which contrasted with slower increases in more objective measures such as hospitalization rates and declines in timely initiation of care. These findings suggest a complex picture of HHA quality of care after the introduction of star ratings.
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Duckworth, Melanie. "Agency and Multispecies Communities in Picture Books". Environmental Humanities 14, nr 1 (1.03.2022): 162–81. http://dx.doi.org/10.1215/22011919-9481495.
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Abstract This article discusses two children’s picture books, The Snail and the Whale (2003), written by Julia Donaldson and illustrated by Axel Scheffler, and The Secret of Black Rock (2017) by Joe Todd-Stanton, as vibrant and fantastic engagements with multispecies worlds. Drawing on new materialism and multispecies studies, the article argues that these two picture books exemplify the possibilities inherent in children’s literature of imaging encounters with multispecies communities and apprehending the dynamic agencies of the material world. With reference to the real marine animals and environments alluded to by the books, it addresses the limitations and opportunities of anthropomorphism, and the significance of the concept of agency in the environmental humanities and children’s literature studies. It argues that the gleeful rhymes of The Snail and the Whale and the awe-inspiring illustrations of The Secret of Black Rock are not mere entertainment but serious and playful explorations of connections between bodies and language, stories and communities, children and adults, human and non-human animals, rocks and fish, and agency and the more-than-human world.
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Hurley, Kevin. "Cosmic Gamma-Ray Bursts: The Big Picture". International Astronomical Union Colloquium 192 (2005): 433–39. http://dx.doi.org/10.1017/s0252921100009519.
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SummaryA “typical” GRB occurs in a star-forming region of a galaxy at a redshift z~1. In currently popular models, it is caused by the collapse of a massive star which has exhausted its nuclear fuel supply. The star collapses to a black hole threaded by a strong magnetic field, and possibly fed by an accretion torus. Through a variety of processes, electrons are accelerated and gamma-rays, X-rays, optical light, and radio emission ensue, with durations from seconds to years. In this talk, I will review the general observational properties of bursts, their afterglows and host galaxies, and some of the open questions about them.
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Biermann, Peter L. "Star and Black Hole Formation at High Redshift". Universe 8, nr 3 (25.02.2022): 146. http://dx.doi.org/10.3390/universe8030146.
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Evidence for dark matter (DM) was originally discovered in 1933 by Zwicky (Zwicky 1933, 1937), and has defied all explanations since then. The original discovery was based on the motions of galaxies in clusters of galaxies. The MicroWave Back Ground (MWBG) observations by the Planck mission and other satellites give definitive numbers. Galaxy correlations give results down to small galaxies, which match theoretical expectations. Here we focus on a few interesting aspects, that may allow to determine the nature of dark matter: (1) Ultra Faint Dwarf (UFD) galaxies, that represent the oldest galaxies known. UFDs are almost devoid of baryonic matter. (2) Calculations show that there can be super-sonic flow of baryonic matter. It follows that there are ubiquitous shockwaves; commonly oblique they generate vorticity. (3) Early virialized clumps, mini-halos, have a density that is consistent with the density implied by Super Massive Black Holes (SMBHs) today, if we assume that SMBHs grow by merging, akin to the Press & Schechter (1974) picture for galaxies. This implies that the oldest SMBHs observed today give powerful constraints on the very early phases.
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Chen, Chien-Ting J., i Ryan C. Hickox. "A correlation between star formation rate and average black hole accretion rate in star forming galaxies". Proceedings of the International Astronomical Union 9, S304 (październik 2013): 302–6. http://dx.doi.org/10.1017/s1743921314004128.
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AbstractWe present the results of recent studies on the co-evolution of galaxies and the supermassive black holes (SMBHs) using Herschel far-infrared and Chandra X-ray observations in the Boötes survey region. For a sample of star-forming (SF) galaxies, we find a strong correlation between galactic star formation rate and the average SMBH accretion rate in SF galaxies. Recent studies have shown that star formation and AGN accretion are only weakly correlated for individual AGN, but this may be due to the short variability timescale of AGN relative to star formation. Averaging over the full AGN population yields a strong linear correlation between accretion and star formation, consistent with a simple picture in which the growth of SMBHs and their host galaxies are closely linked over galaxy evolution time scales.
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Neumayer, Nadine, i C. Jakob Walcher. "Are Nuclear Star Clusters the Precursors of Massive Black Holes?" Advances in Astronomy 2012 (2012): 1–13. http://dx.doi.org/10.1155/2012/709038.
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We present new upper limits for black hole masses in extremely late type spiral galaxies. We confirm that this class of galaxies has black holes with masses less than 106M⊙, if any. We also derive new upper limits for nuclear star cluster masses in massive galaxies with previously determined black hole masses. We use the newly derived upper limits and a literature compilation to study the low mass end of the global-to-nucleus relations. We find the following. (1) TheMBH-σrelation cannot flatten at low masses, but may steepen. (2) TheMBH-Mbulgerelation may well flatten in contrast. (3) TheMBH-Sersicnrelation is able to account for the large scatter in black hole masses in low-mass disk galaxies. Outliers in theMBH-Sersicnrelation seem to be dwarf elliptical galaxies. When plottingMBHversusMNCwe find three different regimes: (a) nuclear cluster dominated nuclei, (b) a transition region, and (c) black hole-dominated nuclei. This is consistent with the picture, in which black holes form inside nuclear clusters with a very low-mass fraction. They subsequently grow much faster than the nuclear cluster, destroying it when the ratioMBH/MNCgrows above 100. Nuclear star clusters may thus be the precursors of massive black holes in galaxy nuclei.
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Ishida, Manabu, Kazuyuki Morio i Yoshihiro Ueda. "Possibility of a White Dwarf as the Accreting Compact Star in CI Cam (XTE J0421+560)". International Astronomical Union Colloquium 194 (2004): 104–5. http://dx.doi.org/10.1017/s025292110015208x.
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AbstractAlthough CI Cam, which showed an outburst in April 1998, has been regarded as a soft X-ray transient (SXT) harboring a, black hole, it has some characteristics that can hardly be reconciled with the SXT picture. In this paper, we propose a white dwarf as the central accreting star in CI Cam.
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Schödel, Rainer, i A. Eckart. "The (quite dark) stellar cluster around the supermassive black hole Sagittarius A* at the center of the Milky Way". Proceedings of the International Astronomical Union 3, S245 (lipiec 2007): 207–10. http://dx.doi.org/10.1017/s1743921308017663.
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AbstractHigh-resolution seeing limited and adaptive optics near-infrared imaging observations of the stellar cluster within about one parsec of the massive black hole Sagittarius A* allow us to obtain a detailed picture of the structure of the nuclear star cluster of the Milky Way. We find that the stellar number counts and the diffuse light of the unresolved stellar population can be described very well by a stellar density function in the form of a broken-power law. This agrees well with theoretical predictions on the structure of a dynamically relaxed star cluster around a massive black hole. However, the cusp slope is found to be too shallow, which may be related to mixing of different stellar populations and continuous star formation, phenomena that are not taken into account by current theory. Mass densities larger than 107 solar masses per pc3 are reached within 0.1 pc of the central black hole. Intriguingly, up to several tens of percent of the total cluster mass in the central parsec may be in the form of dark stellar remnants.
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Irrgang, A., S. Geier, S. Kreuzer, I. Pelisoli i U. Heber. "A stripped helium star in the potential black hole binary LB-1". Astronomy & Astrophysics 633 (styczeń 2020): L5. http://dx.doi.org/10.1051/0004-6361/201937343.
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Context. The recently claimed discovery of a massive (MBH = 68−13+11 M⊙) black hole in the Galactic solar neighborhood has led to controversial discussions because it severely challenges our current view of stellar evolution. Aims. A crucial aspect for the determination of the mass of the unseen black hole is the precise nature of its visible companion, the B-type star LS V+22 25. Because stars of different mass can exhibit B-type spectra during the course of their evolution, it is essential to obtain a comprehensive picture of the star to unravel its nature and, thus, its mass. Methods. To this end, we study the spectral energy distribution of LS V+22 25 and perform a quantitative spectroscopic analysis that includes the determination of chemical abundances for He, C, N, O, Ne, Mg, Al, Si, S, Ar, and Fe. Results. Our analysis clearly shows that LS V+22 25 is not an ordinary main sequence B-type star. The derived abundance pattern exhibits heavy imprints of the CNO bi-cycle of hydrogen burning, that is, He and N are strongly enriched at the expense of C and O. Moreover, the elements Mg, Al, Si, S, Ar, and Fe are systematically underabundant when compared to normal main-sequence B-type stars. We suggest that LS V+22 25 is a stripped helium star and discuss two possible formation scenarios. Combining our photometric and spectroscopic results with the Gaia parallax, we infer a stellar mass of 1.1 ± 0.5 M⊙. Based on the binary system’s mass function, this yields a minimum mass of 2–3 M⊙ for the compact companion, which implies that it may not necessarily be a black hole but a massive neutron- or main sequence star. Conclusions. The star LS V+22 25 has become famous for possibly having a very massive black hole companion. However, a closer look reveals that the star itself is a very intriguing object. Further investigations are necessary for complete characterization of this object.
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PARENTANI, R., i R. BROUT. "PHYSICAL INTERPRETATION OF BLACK HOLE EVAPORATION AS A VACUUM INSTABILITY". International Journal of Modern Physics D 01, nr 01 (styczeń 1992): 169–91. http://dx.doi.org/10.1142/s0218271892000082.
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Using tunneling concepts which account for particle production in the cases of an accelerated detector and a static electric Field in Minkowski space, the more elusive case of black hole evaporation is analyzed in terms of a detailed tunneling mechanism. For the case of the incipient black hole (collapsing star) Hawking’s “heuristic” picture in terms of pair creation, wherein one member crosses the horizon to fall into the singularity as the other is emitted to infinity, is established. The inception of tunneling is due to the motion of the star’s surface, but its completion concerns traversal of the horizon, thereby reconciling varying schools of thought concerning this problem.
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Gitti, Myriam, Fabrizio Brighenti i Brian R. McNamara. "Evidence for AGN Feedback in Galaxy Clusters and Groups". Advances in Astronomy 2012 (2012): 1–24. http://dx.doi.org/10.1155/2012/950641.
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The current generation of flagship X-ray missions,ChandraandXMM-Newton, has changed our understanding of the so-called “cool-core” galaxy clusters and groups. Instead of the initial idea that the thermal gas is cooling and flowing toward the center, the new picture envisages a complex dynamical evolution of the intracluster medium (ICM) regulated by the radiative cooling and the nongravitational heating from the active galactic nucleus (AGN). Understanding the physics of the hot gas and its interplay with the relativistic plasma ejected by the AGN is key for understanding the growth and evolution of galaxies and their central black holes, the history of star formation, and the formation of large-scale structures. It has thus become clear that the feedback from the central black hole must be taken into account in any model of galaxy evolution. In this paper, we draw a qualitative picture of the current knowledge of the effects of the AGN feedback on the ICM by summarizing the recent results in this field.
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Coe, M. J., R. H. D. Corbet, K. E. McGowan, V. A. McBride, M. P. E. Schurch, L. J. Townsend, J. L. Galache, I. Negueruela i D. Buckley. "Optical properties of High-Mass X-ray Binaries (HMXBs) in the Small Magellanic Cloud". Proceedings of the International Astronomical Union 4, S256 (lipiec 2008): 367–72. http://dx.doi.org/10.1017/s174392130802872x.
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AbstractThe SMC represents an exciting opportunity to observe the direct results of tidal interactions on star birth. One of the best indicators of recent star birth activity is the presence of significant numbers of High-Mass X-ray Binaries (HMXBs) — and the SMC has them in abundance! We present results from nearly 10 years of monitoring these systems plus a wealth of other ground-based optical data. Together they permit us to build a picture of a galaxy with a mass of only a few percent of the Milky Way but with a more extensive HMXB population. However, as often happens, new discoveries lead to some challenging puzzles — where are the other X-ray binaries (e.g., black hole systems) in the SMC? And why do virtually all the SMC HMXBs have Be star companions? The evidence arising from these extensive optical observations for this apparently unusual stellar evolution are discussed.
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Patrick, Stephanie. "Life Is But a Story: Female pleasure and agency in Beyoncé’s autobiographical film". Journal of Fandom Studies 8, nr 3 (1.09.2020): 251–63. http://dx.doi.org/10.1386/jfs_00022_1.
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While the rise of new media has led to a blurring of stars’ public personae and private, intimate lives, the musician, in particular, has long been expected to share their private, authentic self through their music. This is certainly the case with superstar Beyoncé, whose 2016 solo album Lemonade was widely received as a revealing portrait of her marriage to hip hop mogul Jay-Z. Yet Beyoncé has long been playing with the public‐private divide as a key part of her star persona. Her decision to limit media interviews has allowed her to maintain unprecedented control of her star image; an image that is now corralled through the texts that she herself circulates via her music, videos and other media. One such notable, yet under-examined text is her 2013 autobiographical film Life Is But a Dream. Both the narrative and the production of the film serve to teach audiences how to read the rest of Beyoncé’s cultural work; as work that is fully controlled by her and intended for women. This pedagogical film disrupts common readings of her image and performances as being in the service of a male gaze, thus opening up new pleasures and potentials for female fans more broadly and Black female fans more specifically. Life Is But a Dream is thus a central, rather than a periphery text in Beyoncé’s star image, complementing and complicating the work she produces across other media formats.
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Kormendy, John. "Supermassive black holes: Coevolution (or not) of black holes and host galaxies". Proceedings of the International Astronomical Union 8, S295 (sierpień 2012): 241–56. http://dx.doi.org/10.1017/s174392131300495x.
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AbstractSupermassive black holes (BHs) have been found in 75 galaxies by observing spatially resolved dynamics. The Hubble Space Telescope (HST) revolutionized BH work by advancing the subject from its ‘proof of concept’ phase into quantitative studies of BH demographics. Most influential was the discovery of a tight correlation between BH masses M• and the velocity dispersions σ of stars in the host galaxy bulge components at radii where the stars mostly feel each other and not the BH. Together with correlations between M• and bulge luminosity, with the ‘missing light’ that defines galaxy cores, and with numbers of globular clusters, this has led to the conclusion that BHs and bulges coevolve by regulating each other's growth. This simple picture with one set of correlations for all galaxies dominated BH work in the past decade.New results are now replacing the above, simple story with a richer and more plausible picture in which BHs correlate differently with different kinds of galaxy components. BHs with masses of 105—106M⊙ live in some bulgeless galaxies. So classical (merger-built) bulges are not necessary equipment for BH formation. On the other hand, while they live in galaxy disks, BHs do not correlate with galaxy disks or with disk-grown pseudobulges. They also have no special correlation with dark matter halos beyond the fact that halo gravity controls galaxy formation. This leads to the suggestion that there are two modes of BH feeding, (1) local, secular and episodic feeding of small BHs in largely bulgeless galaxies that involves too little energy feedback to drive BH–host-galaxy coevolution and (2) global feeding in major galaxy mergers that rapidly grows giant BHs in short-duration events whose energy feedback does affect galaxy formation. After these quasar-like phases, maintenance-mode BH feedback into hot, X-ray-emitting gas continues to have a primarily negative effect in preventing late-time star formation when cold gas or gas-rich galaxies get accreted. Finally, the highest-mass galaxies inherit coevolution effects from smaller galaxies; the tightness of their BH correlations is caused mainly by averaging during dissipationless major mergers.
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Ramachandran, V., W. R. Hamann, L. M. Oskinova, J. S. Gallagher, R. Hainich, T. Shenar, A. A. C. Sander, H. Todt i L. Fulmer. "Testing massive star evolution, star formation history, and feedback at low metallicity". Astronomy & Astrophysics 625 (maj 2019): A104. http://dx.doi.org/10.1051/0004-6361/201935365.
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Stars that start their lives with spectral types O and early B are the progenitors of core-collapse supernovae, long gamma-ray bursts, neutron stars, and black holes. These massive stars are the primary sources of stellar feedback in star-forming galaxies. At low metallicities, the properties of massive stars and their evolution are not yet fully explored. Here we report a spectroscopic study of 320 massive stars of spectral types O (23 stars) and B (297 stars) in the Wing of the Small Magellanic Cloud (SMC). The spectra, which we obtained with the ESO Very Large Telescope, were analyzed using state-of-the-art stellar atmosphere models, and the stellar parameters were determined. We find that the stellar winds of our sample stars are generally much weaker than theoretically expected. The stellar rotation rates show broad, tentatively bimodal distributions. The upper Hertzsprung–Russell diagram (HRD) is well populated by the stars of our sample from a specific field in the SMC Wing. A few very luminous O stars are found close to the main sequence, while all other, slightly evolved stars obey a strict luminosity limit. Considering additional massive stars in evolved stages, with published parameters and located all over the SMC, essentially confirms this picture. The comparison with single-star evolutionary tracks suggests a dichotomy in the fate of massive stars in the SMC. Only stars with an initial mass below ∼30 M⊙ seem to evolve from the main sequence to the cool side of the HRD to become a red supergiant and to explode as type II-P supernova. In contrast, stars with initially more than ∼30 M⊙ appear to stay always hot and might evolve quasi chemically homogeneously, finally collapsing to relatively massive black holes. However, we find no indication that chemical mixing is correlated with rapid rotation. We measured the key parameters of stellar feedback and established the links between the rates of star formation and supernovae. Our study demonstrates that in metal-poor environments stellar feedback is dominated by core-collapse supernovae in combination with winds and ionizing radiation supplied by a few of the most massive stars. We found indications of the stochastic mode of massive star formation, where the resulting stellar population is fully capable of producing large-scale structures such as the supergiant shell SMC-SGS 1 in the Wing. The low level of feedback in metal-poor stellar populations allows star formation episodes to persist over long timescales.
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Rosswog, Stephan. "The multi-messenger picture of compact binary mergers". International Journal of Modern Physics D 24, nr 05 (18.03.2015): 1530012. http://dx.doi.org/10.1142/s0218271815300128.
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In the last decade, enormous progress has been achieved in the understanding of the various facets of coalescing double neutron star and neutron black hole binary systems. One hopes that the mergers of such compact binaries can be routinely detected with the advanced versions of the ground-based gravitational wave detector facilities, maybe as early as in 2016. From the theoretical side, there has also been mounting evidence that compact binary mergers could be major sources of heavy elements and these ideas have gained recent observational support from the detection of an event that has been interpreted as a "macronova", an electromagnetic transient powered by freshly produced, radioactively decaying heavy elements. In addition, compact binaries are the most plausible triggers of short gamma-ray bursts (sGRBs) and the last decade has witnessed the first detection of a sGRB afterglow and subsequent observations have delivered a wealth of information on the environments in which such bursts occur. To date, compact binary mergers can naturally explain most — though not all — of the observed sGRB properties. This paper reviews major recent developments in various areas related to compact binary mergers.
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Linial, Itai, i Brian D. Metzger. "EMRI + TDE = QPE: Periodic X-Ray Flares from Star–Disk Collisions in Galactic Nuclei". Astrophysical Journal 957, nr 1 (25.10.2023): 34. http://dx.doi.org/10.3847/1538-4357/acf65b.
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Abstract Roughly half of the quasiperiodic eruption (QPE) sources in galactic nuclei exhibit a remarkably regular alternating “long-short” pattern of recurrence times between consecutive flares. We show that a main-sequence star (brought into the nucleus as an extreme mass-ratio inspiral; EMRI) that passes twice per orbit through the accretion disk of the supermassive black hole (SMBH) on a mildly eccentric inclined orbit, each time shocking and ejecting optically thick gas clouds above and below the midplane, naturally reproduces observed properties of QPE flares. Inefficient photon production in the ejecta renders the QPE emission much harder than the blackbody temperature, enabling the flares to stick out from the softer quiescent disk spectrum. Destruction of the star via mass ablation limits the QPE lifetime to decades, precluding a long-lived AGN as the gaseous disk. By contrast, a tidal disruption event (TDE) naturally provides a transient gaseous disk on the requisite radial scale, with a rate exceeding the EMRI inward migration rate, suggesting that many TDEs should host a QPE. This picture is consistent with the X-ray TDE observed several years prior to the QPE appearance from GSN 069. Remarkably, a second TDE-like flare was observed from this event, starting immediately after detectable QPE activity ceased; this event could plausibly result from the (partial or complete) destruction of the QPE-generating star triggered by runaway mass loss, though other explanations cannot be excluded. Our model can also be applied to black hole–disk collisions, such as those invoked in the context of the candidate SMBH binary OJ 287.
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Sciurba, Katie. "Depicting Hate: Picture Books and the Realities of White Supremacist Crime and Violence". Teachers College Record: The Voice of Scholarship in Education 122, nr 8 (sierpień 2020): 1–44. http://dx.doi.org/10.1177/016146812012200813.
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Background/Context Since the 2016 presidential election, hate-based speech, crime, and violence have been on the rise in the United States, (re)creating a need for adults to engage children in dialogue related to white supremacy as it exists today, instead of framing it as a problem that ended with the civil rights movement. Following an incident of racist vandalism at her home, the author of this article (a White mother) conducted a search for picture books that could serve as vehicles to discuss race-based hate and whiteness with children like her young Black son. Purpose/Objective/Research Question/Focus of Study This study draws upon Critical Race Theory, Critical Whiteness Studies, and Critical Multicultural Analysis to explore the emancipatory possibilities of literacy education. Given that children's literature has the potential to engage young readers in transactions that promote critical literacy, this study focuses on the following research questions: 1) To what extent do picture books set in a post-civil-rights era United States address explicit and physical acts of white supremacy or hate directed against Black people's bodies, families, or properties? 2) How might such picture books aid parents, educators, and other adults in their attempts to raise children's awareness about white supremacy/hate? Research Design The first part of this article, which documents the author's search for children's picture books about explicit and physical acts of white supremacy/hate, utilizes first person narrative. The second part of this article consists of a multimodal content analysis of five texts, all meeting the following criteria: 1) written and illustrated in picture book format, 2) include child characters, 3) set in the United States, 4) set in a post-civil-rights era, 5) include an incident of white supremacist crime or violence (a physical act directed toward a person or property), 6) depict/address an incident directed against a Black individual or group. Conclusions/Recommendations Findings of this study point to the need for more picture books that challenge whiteness in its overt and covert forms, particularly in contemporary contexts, in order to provide children with opportunities to engage critically with current issues that have emerged in this heightened era of white supremacy and hate-based crime and violence. The picture books that do address white supremacy, in its current manifestation, tend to include stories about White police killing and shooting Black individuals and the protests that follow such incidents. Yet these stories, as well as one about an incident in which a group of White gang members physically attack two Black children (Ntozake Shange's Whitewash), are not equal in their level of explicitness about what occurs, their identifications of the White perpetrators involved in what happens, or their demonstrations of how the incidents are rooted in white supremacy. Accordingly, educators and other adults will often need to fill in significant “truth gaps” in order to raise children's social consciousness related to whiteness and racism. One of the primary recommendations presented in this piece is to accompany these picture books and picture books like them with discussion questions related to the stories that are and are not told in the texts, as well as to facilitate conversation with children related to power and agency as exhibited by the Black characters. Most important, educators and other adults should remain cognizant of the fact that, while books like the ones in this examination may help to address traumas and help facilitate testimony related to race-based hate, children should have opportunities to construct and express their own understandings of textual relevance on this topic.
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Davies, Richard. "Imminent understanding of the structure of nearby AGN from IFUs". Proceedings of the International Astronomical Union 9, S304 (październik 2013): 252. http://dx.doi.org/10.1017/s1743921314003986.
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AbstractIntegral field spectroscopy provides us with immensely rich datasets about spatially resolved distributions and kinematics of emission and absorption lines. In this contribution I will describe some of the key insights that have been made about AGN using optical, near infrared, and far infrared IFUs. These encompass gas inflow and outflow mechanisms, and the relations between star formation, the torus, and accretion onto the black hole. Progress so far has largely relied on archetypal and small sets of objects. In the future, a more statistically robust approach will be required. I will end by discussing a number of issues that can easily confuse an emerging picture, and need to be borne in mind for such surveys.
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Cenko, S. Bradley. "Observational Progress in Identifying and Characterizing Tidal Disruption Flares". Proceedings of the International Astronomical Union 12, S324 (wrzesień 2016): 93–98. http://dx.doi.org/10.1017/s1743921317001764.
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AbstractI present an overview of observational efforts across the electromagnetic spectrum to identify and study tidal disruption flares (TDFs), when a star wanders too close to a super-massive black hole and is torn apart by tidal forces. In particular I will focus on four unexpected surprises that challenge the most basic analytic picture of these events: 1) large inferred radii for the optical/UV-emitting material; 2) the ubiquity of outflows, detected at radio, X-ray, and UV wavelengths, ranging from speeds of 100 km/s to near the speed of light; 3) the peculiar atomic abundances observed in the UV and optical spectra of these objects; and, 4) the preference for these events to occur in post-starburst galaxies.
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AHLUWALIA, D. V. "ON QUANTUM NATURE OF BLACK-HOLE SPACETIME: A POSSIBLE NEW SOURCE OF INTENSE RADIATION". International Journal of Modern Physics D 08, nr 05 (październik 1999): 651–57. http://dx.doi.org/10.1142/s0218271899000456.
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Atoms and the planets acquire their stability from the quantum mechanical incompatibility of the position and momentum measurements. This incompatibility is expressed by the fundamental commutator [x, px]=iℏ, or equivalently, via the Heisenberg's uncertainty principle Δx Δ px~ℏ. A further stability-related phenomenon where the quantum realm plays a dramatic role is the collapse of certain stars into white dwarfs and neutron stars. Here, an intervention of the Pauli exclusion principle, via the fermionic degenerate pressure, stops the gravitational collapse. However, by the neutron-star stage the standard quantum realm runs dry. One is left with the problematic collapse of a black hole. This essay is devoted to a concrete argument on why the black-hole spacetime itself should exhibit a quantum nature. The proposed quantum aspect of spacetime is shown to prevent the general-relativistic dictated problematic collapse. The quantum nature of black-hole spacetime is deciphered from a recent result on the universal equal-area spacing [Formula: see text] for black holes. In one interpretation of the emergent picture, an astrophysical black hole can fluctuate to [Formula: see text] time its classical size, and thus allow radiation and matter to escape to the outside observers. These fluctuations I conjecture provide a new source, perhaps beyond Hawking radiation, of intense radiation from astrophysical black holes and may be the primary source of observed radiation from those galactic cores what carry black hole(s). The presented interpretation may be used as a criterion to choose black holes from black hole candidates.
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Cappelluti, Nico, Günther Hasinger i Priyamvada Natarajan. "Exploring the High-redshift PBH-ΛCDM Universe: Early Black Hole Seeding, the First Stars and Cosmic Radiation Backgrounds". Astrophysical Journal 926, nr 2 (1.02.2022): 205. http://dx.doi.org/10.3847/1538-4357/ac332d.
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Abstract We explore the observational implications of a model in which primordial black holes (PBHs) with a broad birth mass function ranging in mass from a fraction of a solar mass to ∼106 M ⊙, consistent with current observational limits, constitute the dark matter (DM) component in the universe. The formation and evolution of dark matter and baryonic matter in this PBH-Λ cold dark matter (ΛCDM) universe are presented. In this picture, PBH-DM mini-halos collapse earlier than in standard ΛCDM, baryons cool to form stars at z ∼ 15–20, and growing PBHs at these early epochs start to accrete through Bondi capture. The volume emissivity of these sources peaks at z ∼ 20 and rapidly fades at lower redshifts. As a consequence, PBH DM could also provide a channel to make early black hole seeds and naturally account for the origin of an underlying DM halo–host galaxy and central black hole connection that manifests as the M bh–σ correlation. To estimate the luminosity function and contribution to integrated emission power spectrum from these high-redshift PBH-DM halos, we develop a halo occupation distribution model. In addition to tracing the star formation and reionization history, it permits us to evaluate the cosmic infrared and X-ray backgrounds. We find that accretion onto PBHs/active galactic nuclei successfully accounts for the detected backgrounds and their cross-correlation, with the inclusion of an additional IR stellar emission component. Detection of the deep IR source count distribution by the James Webb Space Telescope could reveal the existence of this population of high-redshift star-forming and accreting PBH DM.
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Swihart, Samuel J., Jay Strader, Laura Chomiuk, Elias Aydi, Kirill V. Sokolovsky, Paul S. Ray i Matthew Kerr. "A New Flaring Black Widow Candidate and Demographics of Black Widow Millisecond Pulsars in the Galactic Field". Astrophysical Journal 941, nr 2 (1.12.2022): 199. http://dx.doi.org/10.3847/1538-4357/aca2ac.
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Abstract We present the discovery of a new optical/X-ray source likely associated with the Fermi γ-ray source 4FGL J1408.6–2917. Its high-amplitude periodic optical variability, large spectroscopic radial-velocity semiamplitude, evidence for optical emission lines and flaring, and X-ray properties together imply the source is probably a new black widow millisecond pulsar binary. We compile the properties of the 41 confirmed and suspected field black widows, finding a median secondary mass of 0.027 ± 0.003 M ⊙. Considered jointly with the more massive redback millisecond pulsar binaries, we find that the “spider” companion mass distribution remains strongly bimodal, with essentially zero systems having companion masses of between ∼0.07 and 0.1 M ⊙. X-ray emission from black widows is typically softer and less luminous than in redbacks, consistent with less efficient particle acceleration in the intrabinary shock in black widows, excepting a few systems that appear to have more efficient “redback-like” shocks. Together black widows and redbacks dominate the census of the fastest spinning field millisecond pulsars in binaries with known companion types, making up ≳80% of systems with P spin < 2 ms. Similar to redbacks, the neutron star masses in black widows appear on average significantly larger than the canonical 1.4 M ⊙, and many of the highest-mass neutron stars claimed to date are black widows with M NS ≳ 2.1 M ⊙. Both of these observations are consistent with an evolutionary picture where spider millisecond pulsars emerge from short orbital period progenitors that had a lengthy period of mass transfer initiated while the companion was on the main sequence, leading to fast spins and high masses.
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Tsujimoto, Takuji. "Evidence of outflow from the Galactic bulge imprinted in stellar elemental abundances". Proceedings of the International Astronomical Union 3, S245 (lipiec 2007): 369–70. http://dx.doi.org/10.1017/s1743921308018164.
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AbstractWe explore the elemental abundance features of metal-rich disk stars, highlighting the comparisons made with those of the recently revealed Galactic bulge stars. A similarity between two of the comparisons leads to a new theoretical picture of the bulge-disk connection in the Galaxy, where a supermassive black hole resides at the center. We postulate that a metal-rich outflow, triggered by feedback from a black hole, was generated and quenched the star formation, which had lasted several billion years in the bulge. The expelled gas cooled down in the Galactic halo without escaping from the gravitational potential of the Galaxy. The gas gradually started to accrete to the disk around five billion years ago, corresponding to the time of sun's birth, and replaced a low-metallicity halo gas that had been accreting over nearly ten billion years. The metal-rich infalling gas, whose elemental abundance reflects that of metal-rich bulge stars, mixed with the interstellar gas already present in the disk. Stars formed from the mixture compose the metal-rich stellar disk.
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Höflich, P., D. Baade, A. Khokhlov, L. Wang i J. C. Wheeler. "The Supernova/GRB Connection". International Astronomical Union Colloquium 192 (2005): 403–10. http://dx.doi.org/10.1017/s0252921100009477.
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SummaryWe discuss the possible connection between supernova explosions (SN) and gamma-ray bursters (GRB) from the perspective of our current understanding of SN physics. Core collapse supernovae (SN) are the final stages of stellar evolution in massive stars during which the central region collapses, forms a neutron star (NS) or black hole, and the outer layers are ejected. Recent explosion scenarios assumed that the ejection is due to energy deposition by neutrinos into the envelope but detailed models do not produce powerful explosions. There is new and mounting evidence for an asphericity and, in particular, for axial symmetry in several supernovae which may be hard to reconcile within the spherical picture. The 3-D signatures are a key to understand core collapse supernovae and the GRB/SN connection. In this paper we study the effects and observational consequences of asymmetric explosions.
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Heckman, Timothy M., i Philip N. Best. "A Global Inventory of Feedback". Galaxies 11, nr 1 (24.01.2023): 21. http://dx.doi.org/10.3390/galaxies11010021.
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Feedback from both supermassive black holes and massive stars plays a fundamental role in the evolution of galaxies and the inter-galactic medium. In this paper, we use available data to estimate the total amount of kinetic energy and momentum created per co-moving volume element over the history of the universe from three sources: massive stars and supernovae, radiation pressure and winds driven by supermassive black holes, and radio jets driven by supermassive black holes. Kinetic energy and momentum injection from jets peaks at z ≈ 1, while the other two sources peak at z ≈ 2. Massive stars are the dominant global source of momentum injection. For supermassive black holes, we find that the amount of kinetic energy from jets is about an order-of-magnitude larger than that from winds. We also find that the amount of kinetic energy created by massive stars is about 2.5 εstar times that carried by jets (where εstar is the fraction of injected energy not lost to radiative cooling). We discuss the implications of these results for the evolution of galaxies and IGM. Because the ratio of the black hole mass to galaxy mass is a steeply increasing function of mass, we show that the relative importance of black hole feedback to stellar feedback likewise increases with mass. We show that there is a trend in the present-day universe which, in the simplest picture, is consistent with galaxies that have been dominated by black hole feedback being generally quenched, while galaxies that have been dominated by stellar feedback are star-forming. We also note that the amount of kinetic energy carried by jets and winds appears to be sufficient to explain the properties of hot gas in massive halos (>1013 Mʘ).
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Axelsson, Magnus, i Alexandra Veledina. "Accretion geometry of the black hole binary MAXI J1820+070 probed by frequency-resolved spectroscopy". Monthly Notices of the Royal Astronomical Society 507, nr 2 (4.08.2021): 2744–54. http://dx.doi.org/10.1093/mnras/stab2191.
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ABSTRACT The geometry of the inner accretion flow in the hard and hard-intermediate states of X-ray binaries remains controversial. Using Neutron star Interior Composition Explorer observations of the black hole X-ray binary MAXI J1820+070 during the rising phase of its 2018 outburst, we study the evolution of the timing properties, in particular the characteristic variability frequencies of the prominent iron K α line. Using frequency-resolved spectroscopy, which is robust against uncertainties in the line profile modelling, we find that reflection occurs at large distances from the Comptonizing region in the bright hard state. During the hard-to-soft transition, the variability properties suggest that the reflector moves closer to the X-ray source. In parallel, the peak of the iron line shifts from 6.5 to ∼7 keV, becoming consistent with that expected of from a highly inclined disc extending close to the black hole. We additionally find significant changes in the dependence of the root-mean-square (rms) variability on both energy and Fourier frequency as the source softens. The evolution of the rms-energy dependence, the line profile, and the timing properties of the iron line as traced by the frequency-resolved spectroscopy all support the picture of a truncated disc/inner flow geometry.
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Andres, Katharina. "Fashion’s Final Frontier": The Correlation of Gender Roles and Fashion in Star Trek". Culture Unbound 5, nr 4 (12.12.2013): 639–49. http://dx.doi.org/10.3384/cu.2000.1525.135639.
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Since its creation in 1966, Star Trek has been a dominant part of popular culture and as thus served as the source for many cultural references. Star Trek’s creator Gene Roddenberry wanted to realize his vision of a utopia but at the same time, he used the futuristic setting of the show to comment on the present time, on ac-tual social and political circumstances. This means that each series can be regarded as a mirror image of the time in which it was created. The clothing of the characters in the different series is one part of that image. The uniforms of The Original Series show influences of the 1960s pop art movement as well as the mini-skirt trend that experienced its peak in that decade. In the course of almost 40 years, however, many things changed. In the 1990s, in Deep Space Nine and Voyager, a unisex uniform replaced the mini-dresses, with few exceptions; the colorful shirts gave way to ones that were mostly black. This trend continues into the new century. This essay interprets the evolution of the female officers’ uniforms from femi-nized dresses to androgynous clothing over the development of the series as a reflection of the change of gender roles in contemporary American society. The general functions of the female characters’ uniforms are the central object of its analysis while the few, but noteworthy exceptions to this pattern are given specific attention. Finally, one of the most intriguing lines of enquiry is, how the prequel series Enterprise, supposed to be set before The Original Series, but produced and aired from 2001 to 2005, fits in the picture.
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Figueroa, Jose, Yevgeniy Feyman, Daniel Blumenthal i Ashish Jha. "Do the stars align? Distribution of high-quality ratings of healthcare sectors across US markets". BMJ Quality & Safety 27, nr 4 (12.09.2017): 287–92. http://dx.doi.org/10.1136/bmjqs-2017-006801.
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BackgroundThe US government created five-star rating systems to evaluate hospital, nursing homes, home health agency and dialysis centre quality. The degree to which quality is a property of organisations versus geographical markets is unclear.ObjectivesTo determine whether high-quality healthcare service sectors are clustered within US healthcare markets.DesignUsing data from the Centers for Medicare and Medicaid Services’ Hospital, Dialysis, Nursing Home and Home Health Compare databases, we calculated the mean star ratings of four healthcare sectors in 304 US hospital referral regions (HRRs). For each sector, we ranked HRRs into terciles by mean star rating. Within each HRR, we assessed concordance of tercile rank across sectors using a multirater kappa. Using t-tests, we compared characteristics of HRRs with three to four top-ranked sectors, one to two top-ranked sectors and zero top-ranked sectors.ResultsSix HRRs (2.0% of HRRs) had four top-ranked healthcare sectors, 38 (12.5%) had three top-ranked health sectors, 71 (23.4%) had two top-ranked sectors, 111 (36.5%) had one top-ranked sector and 78 (25.7%) HRRs had no top-ranked sectors. A multirater kappa across all sectors showed poor to slight agreement (K=0.055). Compared with HRRs with zero top-ranked sectors, those with three to four top-ranked sectors had higher median incomes, fewer black residents, lower mortality rates and were less impoverished. Results were similar for HRRs with one to two top-ranked sectors.ConclusionsFew US healthcare markets exhibit high-quality performance across four distinct healthcare service sectors, suggesting that high-quality care in one sector may not be dependent on or improve care quality in other sectors. Policies that promote accountability for quality across sectors (eg, bundled payments and shared quality metrics) may be needed to systematically improve quality across sectors.
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Margalit, Ben, Adam S. Jermyn, Brian D. Metzger, Luke F. Roberts i Eliot Quataert. "Angular-momentum Transport in Proto-neutron Stars and the Fate of Neutron Star Merger Remnants". Astrophysical Journal 939, nr 1 (1.11.2022): 51. http://dx.doi.org/10.3847/1538-4357/ac8b01.
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Abstract Both the core collapse of rotating massive stars, and the coalescence of neutron star (NS) binaries result in the formation of a hot, differentially rotating NS remnant. The timescales over which differential rotation is removed by internal angular-momentum transport processes (viscosity) have key implications for the remnant’s long-term stability and the NS equation of state (EOS). Guided by a nonrotating model of a cooling proto-NS, we estimate the dominant sources of viscosity using an externally imposed angular-velocity profile Ω(r). Although the magneto-rotational instability provides the dominant source of effective viscosity at large radii, convection and/or the Tayler–Spruit dynamo dominate in the core of merger remnants where dΩ/dr ≥ 0. Furthermore, the viscous timescale in the remnant core is sufficiently short that solid-body rotation will be enforced faster than matter is accreted from rotationally supported outer layers. Guided by these results, we develop a toy model for how the merger remnant core grows in mass and angular momentum due to accretion. We find that merger remnants with sufficiently massive and slowly rotating initial cores may collapse to black holes via envelope accretion, even when the total remnant mass is less than the usually considered threshold ≈1.2 M TOV for forming a stable solid-body rotating NS remnant (where M TOV is the maximum nonrotating NS mass supported by the EOS). This qualitatively new picture of the post-merger remnant evolution and stability criterion has important implications for the expected electromagnetic counterparts from binary NS mergers and for multimessenger constraints on the NS EOS.
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Gottlieb, Ore, Brian D. Metzger, Eliot Quataert, Danat Issa, Tia Martineau, Francois Foucart, Matthew D. Duez, Lawrence E. Kidder, Harald P. Pfeiffer i Mark A. Scheel. "A Unified Picture of Short and Long Gamma-Ray Bursts from Compact Binary Mergers". Astrophysical Journal Letters 958, nr 2 (29.11.2023): L33. http://dx.doi.org/10.3847/2041-8213/ad096e.
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Abstract The recent detections of the ∼10 s long γ-ray bursts (GRBs) 211211A and 230307A followed by softer temporally extended emission (EE) and kilonovae point to a new GRB class. Using state-of-the-art first-principles simulations, we introduce a unifying theoretical framework that connects binary neutron star (BNS) and black hole–NS (BH–NS) merger populations with the fundamental physics governing compact binary GRBs (cbGRBs). For binaries with large total masses, M tot ≳ 2.8 M ⊙, the compact remnant created by the merger promptly collapses into a BH surrounded by an accretion disk. The duration of the pre-magnetically arrested disk (MAD) phase sets the duration of the roughly constant power cbGRB and could be influenced by the disk mass, M d . We show that massive disks (M d ≳ 0.1 M ⊙), which form for large binary mass ratios q ≳ 1.2 in BNS or q ≲ 3 in BH–NS mergers, inevitably produce 211211A-like long cbGRBs. Once the disk becomes MAD, the jet power drops with the mass accretion rate as M ̇ ∼ t − 2 , establishing the EE decay. Two scenarios are plausible for short cbGRBs. They can be powered by BHs with less massive disks, which form for other q values. Alternatively, for binaries with M tot ≲ 2.8 M ⊙, mergers should go through a hypermassive NS (HMNS) phase, as inferred for GW170817. Magnetized outflows from such HMNSs, which typically live for ≲1 s, offer an alternative progenitor for short cbGRBs. The first scenario is challenged by the bimodal GRB duration distribution and the fact that the Galactic BNS population peaks at sufficiently low masses that most mergers should go through an HMNS phase.
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Perley, Daniel A., Jesper Sollerman, Steve Schulze, Yuhan Yao, Christoffer Fremling, Avishay Gal-Yam, Anna Y. Q. Ho i in. "The Type Icn SN 2021csp: Implications for the Origins of the Fastest Supernovae and the Fates of Wolf–Rayet Stars". Astrophysical Journal 927, nr 2 (1.03.2022): 180. http://dx.doi.org/10.3847/1538-4357/ac478e.
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Abstract We present observations of SN 2021csp, the second example of a newly identified type of supernova (SN) hallmarked by strong, narrow, P Cygni carbon features at early times (Type Icn). The SN appears as a fast and luminous blue transient at early times, reaching a peak absolute magnitude of −20 within 3 days due to strong interaction between fast SN ejecta (v ≈ 30,000 km s−1) and a massive, dense, fast-moving C/O wind shed by the WC-like progenitor months before explosion. The narrow-line features disappear from the spectrum 10–20 days after explosion and are replaced by a blue continuum dominated by broad Fe features, reminiscent of Type Ibn and IIn supernovae and indicative of weaker interaction with more extended H/He-poor material. The transient then abruptly fades ∼60 days post-explosion when interaction ceases. Deep limits at later phases suggest minimal heavy-element nucleosynthesis, a low ejecta mass, or both, and imply an origin distinct from that of classical Type Ic SNe. We place SN 2021csp in context with other fast-evolving interacting transients, and discuss various progenitor scenarios: an ultrastripped progenitor star, a pulsational pair-instability eruption, or a jet-driven fallback SN from a Wolf–Rayet (W-R) star. The fallback scenario would naturally explain the similarity between these events and radio-loud fast transients, and suggests a picture in which most stars massive enough to undergo a W-R phase collapse directly to black holes at the end of their lives.
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Guetta, Dafne. "Multimessenger Probes of High-energy Sources". EPJ Web of Conferences 209 (2019): 01036. http://dx.doi.org/10.1051/epjconf/201920901036.
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Multimessenger observations may hold the key to learn about the most energetic sources in the universe. The recent construction of large scale observatories opened new possibilities in testing non thermal cosmic processes with alternative probes, such as high energy neutrinos and gravitational waves. We propose to combine information from gravitational wave detections, neutrino observations and electromagnetic signals to obtain a comprehensive picture of some of the most extreme cosmic processes. Gravitational waves are indicative of source dynamics, such as the formation, evolution and interaction of compact objects. These compact objects can play an important role in astrophysical particle acceleration, and are interesting candidates for neutrino and in general high-energy astroparticle studies. In particular we will concentrate on the most promising gravitational wave emitter sources: compact stellar remnants. The merger of binary black holes, binary neutron stars or black hole-neutron star binaries are abundant gravitational wave sources and will likely make up the majority of detections. However, stellar core collapse with rapidly rotating core may also be significant gravitational wave emitter, while slower rotating cores may be detectable only at closer distances. The joint detection of gravitational waves and neutrinos from these sources will probe the physics of the sources and will be a smoking gun of the presence of hadrons in these objects which is still an open question. Conversely, the non-detection of neutrinos or gravitational waves from these sources will be fundamental to constrain the hadronic content.
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Bekmurzaeva, F. Sh. "Mythosymbolic Component of the Animalistic Concept Horse (Loshad' / Kon') in the Russian Language Picture of the World". Bulletin of Kemerovo State University 22, nr 1 (31.03.2020): 216–25. http://dx.doi.org/10.21603/2078-8975-2020-22-1-216-225.
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The research featured concept "horse", which is one of the key archetypal concepts of the Russian culture. The present article focuses on the secondary symbolic constituents that form the structure of the concept. The research objective was to describe symbolic features in the structure of the concept. The material involved sources of the Russian national corpus, Russian folk tales, and other genres of the belles-lettres discourse representing diverse functional styles of the language. The study revealed the ambivalent nature of symbolic categorization of the animal concept in the Russian language through the prism of religious and mythological worldview. The ambivalent nature represented in the bilateral image is in its polar opposition. On the one hand, it is a solar symbol, a symbol of celestial source, and deity. On the other hand, it is chthonic and demonological. Thus, it implies the following symbolic signs: sun; sky; rain; earth; star; month; bird; fire; light; air; red; water; white; gold; another world; age; sea; mountains; death; Kelpie – a water spirit; immortality; black; centaur; Trojan horse; the magic; time of day; number; unity; fertility; spirituality; speed; inspiration, contemplation; loyalty; persistence; fearlessness; luck; chivalry, nobility; purity, and inaccessibility; lust, riot; secrecy, deceit; power; beauty; intelligence; wisdom; power; life force. Ambivalent features revealed on the basis of factual material are invariant, since their historical significance is also actualized in modern linguistic realities. In addition, for the most part they are positively oriented, which indicates the marking and significance of the horse in the consciousness and life of the Russian people.
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Fogasy, Judit, K. K. Knudsen, G. Drouart, C. D. P. Lagos i L. Fan. "SMM J04135+10277: a distant QSO–starburst system caught by ALMA". Monthly Notices of the Royal Astronomical Society 493, nr 3 (18.02.2020): 3744–56. http://dx.doi.org/10.1093/mnras/staa472.
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ABSTRACT The gas content of galaxies is a key factor for their growth, starting from star formation and black hole accretion to galaxy mergers. Thus, characterizing its properties through observations of tracers like the CO emission line is of big importance in order to understand the bigger picture of galaxy evolution. We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of dust continuum, CO(5–4) and CO(8–7) line emission in the quasar–star-forming companion system SMM J04135+10277 (z = 2.84). Earlier low-J CO studies of this system found a huge molecular gas reservoir associated with the companion galaxy, while the quasar appeared gas-poor. Our CO observations revealed that the host galaxy of the quasar is also gas-rich, with an estimated molecular gas mass of $\sim (0.7{\!-\!}2.3)\times 10^{10}\, \rm M_{\odot}$. The CO line profiles of the companion galaxy are very broad ($\sim 1000\, \rm km\, s^{-1}$), and show signs of rotation of a compact, massive system. In contrast to previous far-infrared observations, we resolve the continuum emission and detect both sources, with the companion galaxy dominating the dust continuum and the quasar having a $\sim 25{{\ \rm per\ cent}}$ contribution to the total dust emission. By fitting the infrared spectral energy distribution of the sources with mr-moose and empirical templates, the infrared luminosities of the quasar and the companion are in the range of $L_{\rm IR, QSO}\sim (2.1{\!-\!}9.6)\times 10^{12}\, \rm L_{\odot}$ and $L_{\rm IR, Comp.}\sim (2.4{\!-\!}24)\times 10^{12}\, \rm L_{\odot}$, while the estimated star formation rates are $\sim 210{\!-\!}960$ and $\sim 240{\!-\!}2400\, \rm M_{\odot }\, yr^{-1}$, respectively. Our results demonstrate that non-detection of low-J CO transition lines in similar sources does not necessarily imply the absence of massive molecular gas reservoir but that the excitation conditions favour the excitation of high-J transitions.
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Melchor, Denyz, Brenna Mockler, Smadar Naoz, Sanaea C. Rose i Enrico Ramirez-Ruiz. "Tidal Disruption Events from the Combined Effects of Two-body Relaxation and the Eccentric Kozai–Lidov Mechanism". Astrophysical Journal 960, nr 1 (20.12.2023): 39. http://dx.doi.org/10.3847/1538-4357/acfee0.
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Abstract Tidal disruption events (TDEs) take place when a star ventures too close to a supermassive black hole (SMBH) and becomes ruptured. One of the leading proposed physical mechanisms often invoked in the literature involves weak two-body interactions experienced by the population of stars within the host SMBH’s sphere of influence, commonly referred to as two-body relaxation. This process can alter the angular momentum of stars at large distances and place them into nearly radial orbits, thus driving them to disruption. On the other hand, gravitational perturbations from an SMBH companion via the eccentric Kozai–Lidov (EKL) mechanism have also been proposed as a promising stellar disruption channel. Here we demonstrate that the combination of EKL and two-body relaxation in SMBH binaries is imperative for building a comprehensive picture of the rates of TDEs. Here we explore how the density profile of the surrounding stellar distribution and the binary orbital parameters of an SMBH companion influence the rate of TDEs. We show that this combined channel naturally produces disruptions at a rate that is consistent with observations and also naturally forms repeated TDEs, where a bound star is partially disrupted over multiple orbits. Recent observations show stars being disrupted in short-period orbits, which is challenging to explain when these mechanisms are considered independently. However, the diffusive effect of two-body relaxation, combined with the secular nature of the eccentricity excitations from EKL, is found to drive stars on short eccentric orbits at a much higher rate. Finally, we predict that rTDEs are more likely to take place in the presence of a steep stellar density distribution.
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Obiora, L. Amede. "Neither Here nor There: Of the Female in American Legal Education". Law & Social Inquiry 21, nr 02 (1996): 355–432. http://dx.doi.org/10.1111/j.1747-4469.1996.tb00085.x.
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In this Critical Review Essay, Professor Obiora brings together work from many traditions to address the issue of how differences among students beyond gender–and, in particular, differences in terms of race–might affect legal education. After situating the question in terms of the literature on legal education generally (including standard critiques), she delves into work on gender–in law generally, in kgal education, in moral development and learning, in language use, and in education generally–to elucidate hypothesized differences between men and women that might affect differential experience in law school. She then moves on to make the picture more complex by drawing on work that indicates cross-cultural and class-based variation around conceptions of gender. Using research by sociolinguists on educational processes and work by historians and feminists of color on the intersection of gender, race, and class, Professor Obiora suggests specific ways in which women of color and working-class women might diverge from middle-class white women in their approach to kgal education. In particular, she notes: (1) different speech patterns and linguistic socialization lend different meaning to “voice,”“silence,” and “interruption” in classroom interactions; (2) the historical distinction between public and private spheres has been much more sharply drawn for upper-middle-class white women than it has been for black and working-class women; (3) the exclusion of black women from male “chivalry” and feminine idealization necessitated the development of agency; black women could not afford to be passive. Given these points of divergence, but also given convergences among the experiences of women, Obiora suggests a complex and contextually sensitive approach to the issue of gender in legal education, one that takes seriously the differences that exist among women. Because of the richness of the literature reviewed here, we include a Bibliography at the end of the article.
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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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i Bernadich, M. C., A. D. Schwope, K. Kovlakas, A. Zezas i I. Traulsen. "An expanded ultraluminous X-ray source catalogue". Astronomy & Astrophysics 659 (marzec 2022): A188. http://dx.doi.org/10.1051/0004-6361/202141560.
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Context. Ultraluminous X-ray sources (LX ≳ ×1039 erg s−1, ULXs) are excellent probes for extreme accretion physics, star formation history in galaxies, and intermediate-mass black holes searches. As the sample size of X-ray data from modern observatories such as XMM-Newton and Chandra increases, producing extensive catalogues of ULXs and studying their collective properties has become both a possibility and a priority. Aims. Our aim is to build a clean updated ULX catalogue based on one of the most recent XMM-Newton X-ray serendipitous survey data releases, 4XMM-DR9, and the most recent and exhaustive catalogue of nearby galaxies, HECATE. We performed a preliminary population study to test if the properties of the expanded XMM-Newton ULX population are consistent with previous findings. Methods. We performed positional cross-matches between XMM-Newton sources and HECATE objects to identify host galaxies, and we used distance and luminosity arguments to identify ULX candidates. We flagged interlopers by finding known counterparts in external catalogues and databases such as Gaia DR2, SSDS, Pan-STARRS1, the NASA/IPAC Extragalactic Database, and SIMBAD. Source, galaxy and variability parameters from 4XMM-DR9, HECATE, and 4XMM-DR9s were used to study the spectral, abundance, and variability properties of the ULX sample. Results. We identify 779 ULX candidates, 94 of which hold LX ≳ 5 × 1040 erg s−1. Spiral galaxies are more likely to host ULXs. For early spiral galaxies the number of ULX candidates per star-forming rate is consistent with previous studies, while a significant ULX population in elliptical and lenticular galaxies also exists. Candidates hosted by late-type galaxies tend to present harder spectra and to undergo more extreme inter-observation variability than those hosted by early-type galaxies. Approximately 30 candidates with LX > 1041 erg s−1 are also identified, constituting the most interesting candidates for intermediate-mass black hole searches. Conclusions. We have built the largest ULX catalogue to date. Our results on the spectral and abundance properties of ULXs confirm the findings made by previous studies based on XMM-Newton and Chandra data, while our population-scale study on variability properties is unprecedented. Our study, however, provides limited insight into the properties of the brightest ULX candidates due to the small sample size. The expected growth of X-ray catalogues and potential future follow-ups will aid in drawing a clearer picture.
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Papaderos, Polychronis, Iris Breda, Andrew Humphrey, Jean Michel Gomes, Bodo L. Ziegler i Cirino Pappalardo. "Inside-out star formation quenching and the need for a revision of bulge-disk decomposition concepts for spiral galaxies". Astronomy & Astrophysics 658 (luty 2022): A74. http://dx.doi.org/10.1051/0004-6361/202140641.
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Our knowledge about the photometric and structural properties of bulges in late-type galaxies (LTGs) is founded upon image decomposition into a Sérsic model for the central luminosity excess of the bulge and an exponential model for the more extended underlying disk. We argue that the standard practice of adopting an exponential model for the disk all the way to its center is inadequate because it implicitly neglects the fact of star formation (SF) quenching in the centers of LTGs. Extrapolating the fit to the observable star-forming zone of the disk (outside the bulge) inwardly overestimates the true surface brightness of the disk in its SF-quenched central zone (beneath the bulge). We refer to this effect as δio. Using predictions from evolutionary synthesis models and by applying to integral field spectroscopy data REMOVEYOUNG, a tool that allows the suppression of stellar populations younger than an adjustable age cutoff we estimate the δio in the centers of massive SF-quenched LTGs to be up to ∼2.5 (0.7) B (K) mag. The primary consequence of the neglect of δio in bulge-disk decomposition studies is the oversubtraction of the disk underneath the bulge, leading to a systematic underestimation of the true luminosity of the latter. Secondary biases impact the structural characterization (e.g., Sérsic exponent η and effective radius) and color gradients of bulges, and might include the erroneous classification of LTGs with a moderately faint bulge as bulgeless disks. Framed in the picture of galaxy downsizing and inside-out SF quenching, δio is expected to differentially impact galaxies across redshift and stellar mass ℳ⋆, thus leading to systematic and complex biases in the scatter and slope of various galaxy scaling relations. We conjecture that correction for the δio effect will lead to a down-bending of the bulge versus supermassive black hole relation for galaxies below log(ℳ⋆/M⊙) ∼ 10.7. A decreasing ℳ∙/ℳ⋆ ratio with decreasing ℳ⋆ would help to consistently explain the scarcity and weakness of accretion-powered nuclear activity in low-mass spiral galaxies. Finally, it is pointed out that a well-detectable δio (> 2 r mag) can emerge early on through inward migration of star-forming clumps from the disk in combination with a strong contrast of emission-line equivalent widths between the quenched protobulge and its star-forming periphery. Spatially resolved studies of δio with the James Webb Space Telescope, the Extremely Large Telescope, and Euclid could therefore offer key insights into the chronology and physical drivers of SF-quenching in the early phase of galaxy assembly.
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Tiutiunnyk, Anastasiia. "TRACKING THE DYNAMICS OF LECTURER RATING INDICATORS TO ENSURE THE QUALITY OF HIGHER EDUCATION". OPEN EDUCATIONAL E-ENVIRONMENT OF MODERN UNIVERSITY, nr 13 (2022): 141–52. http://dx.doi.org/10.28925/2414-0325.2022.1312.
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The importance of the role of the lecturer in ensuring the quality of higher education cannot be denied. The system of internal quality assurance provides for the availability of developed and published criteria, rules, and procedures for the evaluation of academic and research staff, as well as their annual review by European standards, the Law of Ukraine "On Higher Education", recommendations of the National Agency for Higher Education Quality Assurance. Borys Grinchenko Kyiv University has developed a lecturer rating system "E-portfolio", one of the components of the information and educational environment, to form the qualitative composition of the scientific and pedagogical staff. To analyze the activities of the academic staff and all departments of Grinchenko University, several types of reports were presented in the "E-portfolio" system, which can be built according to such criteria as the main activities, rating points, structural units, positions, academic rank, degree, etc. For several years, only built-in statistics were used to analyze the activities of lecturers and units, but there was a need to monitor more detailed dynamics of all indicators. Modern business intelligence tools were analyzed for the development of visualization. It was decided to use the Power BI business intelligence tool, which will allow you to have a complete picture of the lecturer's performance by all the necessary criteria. The article presents an analytical report of Power BI based on the "Star Scheme" model. Thanks to the created "Measures" and standard functions of pivot tables, it became possible to visualize the input rating data and create details and filters for more convenient viewing and data analysis. After completing all the settings of visualization and filters, the report was published using the Power BI report server tool in the public domain. The use of this tool allows the top managers of the university to have a holistic picture of the results in the performance of employees and departments, as well as to determine the priorities of activities, to make fair decisions when extending contracts, which fully and unconditionally contributes to ensuring the quality of higher education.
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Di Cintio, Pierfrancesco, Mario Pasquato, Alicia Simon-Petit i Suk-Jin Yoon. "Introducing a new multi-particle collision method for the evolution of dense stellar systems". Astronomy & Astrophysics 659 (28.02.2022): A19. http://dx.doi.org/10.1051/0004-6361/202140710.
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Context. In a previous paper we introduced a new method for simulating collisional gravitational N-body systems with linear time scaling on N, based on the multi-particle collision (MPC) approach. This allows us to easily simulate globular clusters with a realistic number of stellar particles (105 − 106) in a matter of hours on a typical workstation. Aims. We evolve star clusters containing up to 106 stars to core collapse and beyond. We quantify several aspects of core collapse over multiple realizations and different parameters while always resolving the cluster core with a realistic number of particles. Methods. We run a large set of N-body simulations with our new code MPCDSS. The cluster mass function is a pure power law with no stellar evolution, allowing us to clearly measure the effects of the mass spectrum on core collapse. Results. Leading up to core collapse, we find a power-law relation between the size of the core and the time left to core collapse. Our simulations thus confirm the theoretical self-similar contraction picture but with a dependence on the slope of the mass function. The time of core collapse has a non-monotonic dependence on the slope, which is well fitted by a parabola. This also holds for the depth of core collapse and for the dynamical friction timescale of heavy particles. Cluster density profiles at core collapse show a broken-power-law structure, suggesting that central cusps are a genuine feature of collapsed cores. The core bounces back after collapse, with visible fluctuations, and the inner density slope evolves to an asymptotic value. The presence of an intermediate-mass black hole inhibits core collapse, making it much shallower, irrespective of the mass-function slope. Conclusions. We confirm and expand on several predictions of star cluster evolution before, during, and after core collapse. Such predictions were based on theoretical calculations or small-size direct N-body simulations. Here we put them to the test in MPC simulations with a much larger number of particles, allowing us to resolve the collapsing core.
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Fernández-Ontiveros, Juan A., i Teo Muñoz-Darias. "X-ray binary accretion states in active galactic nuclei? Sensing the accretion disc of supermassive black holes with mid-infrared nebular lines". Monthly Notices of the Royal Astronomical Society 504, nr 4 (22.04.2021): 5726–40. http://dx.doi.org/10.1093/mnras/stab1108.
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ABSTRACT Accretion states, which are universally observed in stellar mass black holes in X-ray binaries, might be expected in active galactic nuclei (AGN). This is the case at low luminosities, when the jet–corona coupling dominates the energy output in both populations. Previous attempts to extend this framework to a wider AGN population have been extremely challenging due to heavy hydrogen absorption of the accretion disc continuum and starlight contamination from the host galaxies. We present the luminosity–excitation diagram (LED), based on the [O iv]25.9 μm and [Ne ii]12.8 μm mid-infrared nebular line fluxes. This tool enables to probe the accretion disc contribution to the ionizing continuum. When applied to a sample of 167 nearby AGN, the LED recovers the characteristic q-shaped morphology outlined by individual X-ray binaries during a typical accretion episode, allowing us to tentatively identify the main accretion states. The soft state would include broad-line Seyferts and about half of the Seyfert 2 population, showing highly excited gas and radio-quiet cores consistent with disc-dominated nuclei, in agreement with previous studies. The hard state mostly includes low-luminosity AGN ($\lesssim 10^{-3}\, \rm {L_{Edd}}$) characterized by low-excitation radio-loud nuclei and a negligible disc contribution. The remaining half of Seyfert 2 nuclei and the bright LINERs show low excitation at high accretion luminosities and could be identified with the bright hard and intermediate states. Their hosts show ongoing star formation in the central kiloparsecs. We discuss the above scenario, its potential links with the galaxy evolution picture, and the possible presence of accretion state transitions in AGN, as suggested by the growing population of changing-look quasars.
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P. Krüger, Louis. "Macro-environments of South Africa: time to stop the rot, deterioration, distrust and dysfunctionality". Problems and Perspectives in Management 16, nr 1 (23.03.2018): 361–80. http://dx.doi.org/10.21511/ppm.16(1).2018.35.
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Since the introduction of black economic empowerment (BEE) in South Africa by the African National Congress (ANC) in 2003, the impact of the legislation and its accompanying policies on the six major “PESTIS” (political, economic, social, technological, institutional and structural-physical) macro-environments in which businesses in the private sector and government in the public sector operate, has largely gone unnoticed or has been ignored. In an exploratory study using the “5 Star” research methodology, and with the aid of specially developed qualitative research adjudication matrix (QRAM), the impact of the ANC’s BEE policies on these macro-environments was investigated. Unfortunately, it appears that these policies have negatively affected South Africa’s political, economic, social/cultural and institutional macro-environments. Allegations of state capture and nefarious influences on government and ministerial appointments, poor economic performance and possible further credit downgrade to “junk” status by the international ratings agencies, increased prevalence of racism, hate speech and discrimination, and violation of the Constitution of South Africa and international treaties by the ANC government, paint a dismal picture. In addition, the coun¬try is facing unseen high levels of corruption, graft, fraud, looting, bribery, nepotism and self-enrichment in government, state-owned enterprises (SOEs) and businesses. BEE can be regarded as the ANC’s “Achilles heel” in South Africa, and the political party should rather abandon this policy in order to stop the rot, and further deterioration, distrust and decay in the country’s most important macro-environments.
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Grafton-Waters, S., G. Branduardi-Raymont, M. Mehdipour, M. J. Page, E. Behar, J. Kaastra, N. Arav i in. "Multi-wavelength campaign on NGC 7469". Astronomy & Astrophysics 633 (styczeń 2020): A62. http://dx.doi.org/10.1051/0004-6361/201935815.
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Aims. We aim to investigate and characterise the photoionised X-ray emission line regions within the Seyfert 1 galaxy NGC 7469. Methods. We applied the photoionisation model, PION, within the spectral fitting code SPEX to analyse the 640 ks reflection grating spectrometer spectrum of NGC 7469 gathered during an XMM-Newton observing campaign in 2015. Results. We find the emission line region in NGC 7469 to be multiphased, consisting of two narrow components with ionisation parameters of log ξ = 0.4 and 1.6. A third, broad emission component, with a broadening velocity of vb ∼ 1400 km s−1 and an outflow velocity of vout ∼ −4500 km s−1 is required to fit the residuals in the O VII triplet at around 22 Å. Assuming a volume filling factor of 0.1, the lower distance limits of the narrow emission line region components are estimated for the first time at 2.6 and 2.5 pc from the central black hole, whereas the broad component has an estimated lower bound distance between 0.004 and 0.03 pc, depending on the assumed plasma parameters. The collisionally ionised plasma from the star burst region in NGC 7469 has a plasma temperature of 0.32 keV and an outflow velocity of −280 km s−1, which is consistent with previous results in this campaign. In addition, we model the photoionised plasma of the warm absorber (WA) in NGC 7469 and find that it consists of three photoionised phases with different values of ξ, NH and vout. The upper bound distances of these WA components are 1.9, 0.3, and 0.6 pc, respectively, consistent with archival results. Conclusion. The environment of NGC 7469 is a complex mix of plasma winds absorbing and emitting X-rays. We find the picture painted by our results can be attributed to line emitting plasma located at distances ranging from near the black hole to the torus and beyond the ionised outflows.
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Nayazi, Mohd Mustafa. "Credit Cards: Types and Fiqhi Characterisation". مجلة إسرا الدولية للمالية الإسلامية 10, nr 1 (29.06.2019): 115–44. http://dx.doi.org/10.55188/ijifarabic.v10i1.259.
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Today's credit cards play a key role in facilitating new transactions, are to give the bank to the client a document includes a balance that can take money and pay the price is committed to repay in installments, Its first appearance was in 1914 when banks appeared in America, They have many types with different considerations in terms of advantages, The issuer and how to deal with it and others and others,The holding of cards in its sections and objectives is considered a new contract on Islamic jurisprudence Cannot be included in the overall picture under one contract, but is a complex contract of several decades Contracts in the relationship between their source and holder consist of three contracts: bail, lending, agency, In the relationship between the source and the merchant consists of two contracts: the guarantee and the agency, In the relationship between the cardholder and the merchant, the sale or lease is governed by the nature of the contract between them, As for its jurisprudential ruling, what the bank takes from the customer is a fee for the issuance and renewal of the card and when withdrawing the cash for his fees and administrative costs, this is permissible and nothing in it, Because it is in exchange for the apparent benefit of facilitating purchasing, cash and other services, but it is stipulated that this commission is reasonable for these services, If the condition of payment and payment is absolute or when the payment is delayed, that condition is invalid, so that this transaction is null and void because it is a Riba that is haraam, Alternative solutions for delay penalties are the debtor's eyesight if he is insolvent, the cancellation of membership, the withdrawal of the card, the recourse to the judiciary and the charging of the expenses of the dispute, Or the publication of the name of the client in a black list deterrent and Neglect and for the purchase of gold and silver powered if it is achieved by the immediate arrest is permissible, but if not achieved so it is not permissible to buy gold and silver.
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Sander, A. A. C., W. R. Hamann, H. Todt, R. Hainich, T. Shenar, V. Ramachandran i L. M. Oskinova. "The Galactic WC and WO stars". Astronomy & Astrophysics 621 (styczeń 2019): A92. http://dx.doi.org/10.1051/0004-6361/201833712.
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Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae. Their strong mass-loss furthermore provides challenges and constraints to the theory of radiatively driven winds. Thus, the determination of the WC star parameters is of major importance for several astrophysical fields. With Gaia DR2, for the first time parallaxes for a large sample of Galactic WC stars are available, removing major uncertainties inherent to earlier studies. In this work, we re-examine a previously studied sample of WC stars to derive key properties of the Galactic WC population. All quantities depending on the distance are updated, while the underlying spectral analyzes remain untouched. Contrasting earlier assumptions, our study yields that WC stars of the same subtype can significantly vary in absolute magnitude. With Gaia DR2, the picture of the Galactic WC population becomes more complex: We obtain luminosities ranging from logL/L⊙ = 4.9–6.0 with one outlier (WR 119) having logL/L⊙ = 4.7. This indicates that the WC stars are likely formed from a broader initial mass range than previously assumed. We obtain mass-loss rates ranging between log Ṁ = −5.1 and −4.1, with Ṁ ∝ L0.68 and a linear scaling of the modified wind momentum with luminosity. We discuss the implications for stellar evolution, including unsolved issues regarding the need of envelope inflation to address the WR radius problem, and the open questions in regard to the connection of WR stars with Gamma-ray bursts. WC and WO stars are progenitors of massive black holes, collapsing either silently or in a supernova that most-likely has to be preceded by a WO stage.
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C., Ezugu L., Philip S i Isaac J. I. "Tools and Equipment Utilization in Radio Television and Global System Mobile Servicing In Vocational Training Centres in Gombe State, Nigeria". Journal of Electronics,Computer Networking and Applied Mathematics, nr 31 (2.01.2023): 16–26. http://dx.doi.org/10.55529/jecnam.31.16.26.
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Determining the tools and equipment use in Radio Television and Global System Mobile Servicing at Vocational Centers in Gombe State, Nigeria, was the major goal of the study. The study used a descriptive survey research approach and was carried out in Gombe State, Nigeria. 55 respondents made up the study's population, including 42 teachers and 13 administrators (principals). There was no sampling because the population was of a manageable size, hence the entire population was employed for the study. A structured questionnaire called the "Tools and Equipment Utilization Questionnaire (TEUQ)" was the instrument used to gather the data. The instrument was evaluated by three professionals, and Cronbach Alpha yielded a reliability value of 0.72. The mean statistics were utilized to answer the research questions, and the null hypotheses were tested using a t-test with a 0.05 threshold of significance. Equipment in RTV and GSM servicing trade workshops at the Vocational Training Centers in Gombe State, including workstations, multimeters-digital, multimeters-analog, Booster meters, white lights, various phone panels, Tornados (soft wire boxes), television training modules, probe/logic pulsar, oscilloscopes, pattern generators, picture tube testers, isolation transformers, vector scopes, signal strength meters, black and white television, colored television, and TV. The study also showed that the tools used in the RTV and GSM servicing Trade workshop at the Vocational Training Centers in Gombe State, including (Set of flat Screwdrivers, (large, medium, and small), Asterics, a Set of Allen keys, Set of Star Screwdrivers, Set of Spanners and Soldering Iron) is sufficient. It was suggested that in order for the schools to succeed, the Gombe State Ministry of Education should supply them with the necessary training materials and apparatus. Additionally, the government has to provide all trainers with greater technical training so they can use new technology in the workshop.
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Kaasinen, Melanie, Bram Venemans, Kevin C. Harrington, Leindert A. Boogaard, Romain A. Meyer, Eduardo Bañados, Roberto Decarli i in. "The cold molecular gas in z ≳ 6 quasar host galaxies". Astronomy & Astrophysics 684 (29.03.2024): A33. http://dx.doi.org/10.1051/0004-6361/202348463.
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Context. Probing the molecular gas reservoirs of z ≳ 6 quasar (QSO) host galaxies is fundamental to understanding the coevolution of star formation and black hole growth in these extreme systems. Yet, there is still an inhomogeneous coverage of molecular gas tracers for z ≳ 6 QSO hosts. Aims. To measure the average excitation and mass of the molecular gas reservoirs in the brightest z > 6.5 QSO hosts, we combined new observations of CO(2–1) emission with existing observations of CO(6–5), CO(7–6), [C I] (2–1), [C II] 158 μm, and dust-continuum emission. Methods. We reduced and analysed observations of CO(2–1), taken with the Karl G. Jansky Very Large Array, in three z = 6.5 − 6.9 QSO hosts – the highest redshift observations of CO(2–1) to date. By combining these with the nine z = 5.7 − 6.4 QSO hosts for which CO(2–1) emission has already been observed, we studied the spread in molecular gas masses and CO excitation of z ≳ 6 QSOs. Results. Two of our three QSOs, P036+03 and J0305–3150, were not detected in CO(2–1), implying more highly excited CO than in the well-studied z = 6.4 QSO J1148+5251. However, we detected CO(2–1) emission at 5.1σ for our highest-redshift target, J2348–3054, yielding a molecular gas mass of (1.2 ± 0.2)×1010 M⊙, assuming αCO = 0.8 (K km s−1 pc2)−1 and r2, 1 = 1. This molecular gas mass is equivalent to the lower limit on the dynamical mass measured previously from resolved [C II] 158 μm observations, implying that there is little mass in stars or neutral gas within the [C II]-emitting region and that a low CO-to-H2 conversion factor is applicable. On average, these z ≳ 6 QSO hosts have far higher CO(6–5)-, CO(7–6)-, and [C II] 158 μm versus CO(2–1) line ratios than the local gas-rich and IR-luminous galaxies that host active galactic nuclei, but with a large range of values, implying some variation in their interstellar medium conditions. We derived a mean CO(6–5)-to-CO(1–0) line luminosity ratio of r6, 1 = 0.9 ± 0.2. Conclusions. Our new CO(2–1) observations show that even at 780 Myr after the Big Bang, QSO host galaxies can already have molecular gas masses of 1010 M⊙, consistent with a picture in which these z ≳ 6 QSOs reside in massive starbursts that are coevolving with the accreting supermassive black holes. Their high gas versus dynamical masses and extremely high line excitation imply the presence of extremely dense and warm molecular gas reservoirs illuminated by strong interstellar radiation fields.