One of the most distant galaxies GN-z11 was formed when the Universe was ≤ 400 Myr old, and it displays a burst-like star formation rate ∼25 M⊙ yr−1 with a metallicity Z ∼ 0.2 ± 0.1Z⊙. It resembles z = 2 − 3 galaxies (at “cosmic noon”) except for the fact that the measured reddening E(B − V) = 0.01 ± 0.01 indicates the presence of little or no dust. This marked absence of dust hints towards violent dynamical events that destroy or evacuate dust along with gas out of the galaxy on a relatively short time scale and make it transparent. We apply a 3D numerical model to infer possible physical characteristics of these events. We demonstrate that the energetics of the observed star formation rate is sufficient to tear apart the dusty veil on time scales of 20 − 25 Myr. This can explain the apparent lack of evolution of UV luminosity function of galaxies between and z ≥ 10 and z ∼ 7, by compensating for the lower galaxy masses at higher redshift by the absence of dust. We show, however, that this is a temporary phenomenon and soon after the last of the supernovae explosions have taken place, the expanding shell shrinks and obscures the galaxy on time scales of ≈5 − 8 Myr.
We consider the dynamics of and emission from growing superbubbles in a stratified interstellar gaseous disc driven by energy release from supernovae explosions in stellar clusters with masses = 10 5 − 1.6 × 10 6 ⊙ . Supernovae are spread randomly within a sphere of = 60 pc, and inject energy episodically with a specific rate 1/130 −1 ⊙ proportional to the star formation rate (SFR) in the cluster. Models are run for several values of SFR in the range 0.01 to 0.1 ⊙ yr −1 , with the corresponding average surface energy input rate ∼ 0.04 − 0.4 erg cm −2 s −1 . We find that the discrete energy injection by isolated SNe are more efficient in blowing superbubbles: asymptotically they reach heights of up to 3 to 16 kpc for = 10 5 − 1.6 × 10 5 ⊙ , correspondingly, and stay filled with a hot and dilute plasma for at least 30 Myr. During this time they emit X-ray, H and dust infrared emission. X-ray liminosities ∝ SFR 3/5 that we derive here are consistent with observations in star-forming galaxies. Even though dust particles of small sizes ≤ 0.03 m are sputtered in the interior of bubbles, larger grains still contribute considerably ensuring the bubble luminosity IR /SFR ∼ 5 × 10 7 ⊙ −1 ⊙ yr. It is shown that the origin of the North Polar Spur in the Milky Way can be connected with activity of a cluster with the stellar mass of ∼ 10 5 ⊙ and the SFR ∼ 0.1 ⊙ yr −1 some 25-30 Myr ago. Extended luminous haloes observed in edge-on galaxies (NGC 891 as an example) can be maintained by disc spread stellar clusters of smaller masses * < ∼ 10 5 ⊙ .
We consider the dynamics of and emission from growing superbubbles in a stratified interstellar gaseous disc driven by energy release from supernovae explosions in stellar clusters with masses Mcl = 105 − 1.6 × 106 M⊙. Supernovae are spread randomly within a sphere of rc = 60 pc, and inject energy episodically with a specific rate $1/130~M_\odot ^{-1}$ proportional to the star formation rate (SFR) in the cluster. Models are run for several values of SFR in the range 0.01 to 0.1 M⊙ yr−1, with the corresponding average surface energy input rate ∼0.04 − 0.4 erg cm−2 s−1. We find that the discrete energy injection by isolated SNe are more efficient in blowing superbubbles: asymptotically they reach heights of up to 3 to 16 kpc for Mcl = 105 − 1.6 × 105 M⊙, correspondingly, and stay filled with a hot and dilute plasma for at least 30 Myr. During this time they emit X-ray, Hα and dust infrared emission. X-ray liminosities LX∝SFR3/5 that we derive here are consistent with observations in star-forming galaxies. Even though dust particles of small sizes a ≤ 0.03 μm are sputtered in the interior of bubbles, larger grains still contribute considerably ensuring the bubble luminosity $L_{\rm IR}/{\rm SFR}\sim 5\times 10^7 L_\odot M_\odot ^{-1} ~{\rm yr}$. It is shown that the origin of the North Polar Spur in the Milky Way can be connected with activity of a cluster with the stellar mass of ∼105 M⊙ and the SFR ∼ 0.1 M⊙ yr−1 some 25–30 Myr ago. Extended luminous haloes observed in edge-on galaxies (NGC 891 as an example) can be maintained by disc spread stellar clusters of smaller masses $M_\ast {\,\,\lesssim \,\,}10^5~M_\odot$.
BACKGROUND: Diagnostics and treatment of syndesmotic ankle injuries in children is one of the important problems in pediatrics. The generally accepted examination algorithms and standards developed for adult patients do not apply to children. The ligamentous apparatus in children is much more elastic, and the tibiofibular space is smaller, which significantly complicates the diagnostic search. OBJECTIVE: This study aimed to create a diagnostic algorithm for examining middle and older children with ankle joint injuries. MATERIALS AND METHODS: To create a diagnostic algorithm, whether the ultrasonographic stress test of external foot rotation in adult practice is relevant for patients with closed growth zones was investigated. Two open cohorts of middle and older children were formed. The first cohort included children aged 1114 years with a closed growth zone of the distal tibia, and the second cohort included children aged 1517 years with a closed growth zone. The inclusion criteria were the absence of injuries of the studied ankle joint and the correspondence of the body mass index to the age norm. RESULTS: The variability of the tibiofibular space during the stress test of external foot rotation in children with a closing growth zone averages 3.035 mm and in children with a closed growth zone was 2.319 mm. Data indicate a high degree of elasticity of the anterior tibialperoneal ligament in children in contrast to adults in whom this structure is more rigid. In children experiencing pain, active muscle resistance makes the test of internal rotation ineffective, and excessive elasticity of the structure in the area of a healthy joint does not give a correct comparative result for the operator. CONCLUSION: The use of a test with internal rotation for diagnosing damage to the distal tibiofibular syndesmosis in children with closing and closed growth zones is limited, and the operator must rely on other ultrasound signs of damage to this structure.
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