A small and vigorous black hole in the early Universe.

Several theories have been proposed to describe the formation of black hole seeds in the early Universe and to explain the emergence of very massive black holes observed in the first thousand million years after the Big Bang1-3. Models consider different seeding and accretion scenarios4-7, which require the detection and characterization of black holes in the first few hundred million years after the Big Bang to be validated. Here we present an extensive analysis of the JWST-NIRSpec spectrum of GN-z11, an exceptionally luminous galaxy at z = 10.6, revealing the detection of the [NeIV]λ2423 and CII*λ1335 transitions (typical of active galactic nuclei), as well as semi-forbidden nebular lines tracing gas densities higher than 109 cm-3, typical of the broad line region of active galactic nuclei. These spectral features indicate that GN-z11 hosts an accreting black hole. The spectrum also reveals a deep and blueshifted CIVλ1549 absorption trough, tracing an outflow with velocity 800-1,000 km s-1, probably driven by the active galactic nucleus. Assuming local virial relations, we derive a black hole mass of log ( M BH / M ⊙ ) = 6.2 ± 0.3 , accreting at about five times the Eddington rate. These properties are consistent with both heavy seeds scenarios and scenarios considering intermediate and light seeds experiencing episodic super-Eddington phases. Our finding explains the high luminosity of GN-z11 and can also provide an explanation for its exceptionally high nitrogen abundance.

A recently quenched galaxy 700 million years after the Big Bang.

Local and low-redshift (z < 3) galaxies are known to broadly follow a bimodal distribution: actively star-forming galaxies with relatively stable star-formation rates and passive systems. These two populations are connected by galaxies in relatively slow transition. By contrast, theory predicts that star formation was stochastic at early cosmic times and in low-mass systems1-4. These galaxies transitioned rapidly between starburst episodes and phases of suppressed star formation, potentially even causing temporary quiescence-so-called mini-quenching events5,6. However, the regime of star-formation burstiness is observationally highly unconstrained. Directly observing mini-quenched galaxies in the primordial Universe is therefore of utmost importance to constrain models of galaxy formation and transformation7,8. Early quenched galaxies have been identified out to redshift z < 5 (refs. 9-12) and these are all found to be massive (M⋆ > 1010 M⊙) and relatively old. Here we report a (mini-)quenched galaxy at z = 7.3, when the Universe was only 700 Myr old. The JWST/NIRSpec spectrum is very blue (U-V = 0.16 ± 0.03 mag) but exhibits a Balmer break and no nebular emission lines. The galaxy experienced a short starburst followed by rapid quenching; its stellar mass (4-6 × 108 M⊙) falls in a range that is sensitive to various feedback mechanisms, which can result in perhaps only temporary quenching.

Carbonaceous dust grains seen in the first billion years of cosmic time.

Large dust reservoirs (up to approximately 108 M⊙) have been detected1-3 in galaxies out to redshift z ≃ 8, when the age of the Universe was only about 600 Myr. Generating substantial amounts of dust within such a short timescale has proven challenging for theories of dust formation4,5 and has prompted the revision of the modelling of potential sites of dust production6-8, such as the atmospheres of asymptotic giant branch stars in low-metallicity environments, supernova ejecta and the accelerated growth of grains in the interstellar medium. However, degeneracies between different evolutionary pathways remain when the total dust mass of galaxies is the only available observable. Here we report observations of the 2,175 Å dust attenuation feature, which is well known in the Milky Way and galaxies at z ≲ 3 (refs. 9-11), in the near-infrared spectra of galaxies up to z ≃ 7, corresponding to the first billion years of cosmic time. The relatively short timescale implied for the formation of carbonaceous grains giving rise to this feature12 suggests a rapid production process, possibly in Wolf-Rayet stars or supernova ejecta.

Comparative evaluation of intracanal cryotherapy and curcumin as a final irrigant in reducing post endodontic pain in primary teeth.

Aim: The aim of this study was to evaluate the intracanal effectiveness of cryotherapy, curcumin irrigant, and normal saline as a final irrigant in reducing postendodontic pain in primary teeth. Materials and Methods: A total of 120 teeth between the ages of 4 and 7 years requiring pulpectomy in primary teeth were included in the study. The teeth were randomly assigned to one of the three treatment groups: intracanal cryotherapy using 2.5°C cold saline, curcumin irrigant, or normal saline. Following completion of chemomechanical preparation, final irrigation with 2.5°C cold saline, curcumin irrigant, and normal saline solution at room temperature were employed in the groups. Participants were asked to rate the severity of their postoperative pain on the Visual Analog Scale before, immediate postoperative after wearing of local anesthetic effect, and 24 h after the procedure. The results were analyzed statistically. Results: The differences in reduction of postendodontic pain between the three irrigating regimens were statistically not significant. Cryotherapy utilizing 2.5°C cold saline or curcumin irrigant can be used instead of normal saline as a final irrigant in pulpectomy of primary teeth. Conclusions: Cryotherapy can be a straightforward, cost-effective, and nontoxic treatment option for the management of postendodontic pain. Curcumin irrigant with its anti-inflammatory properties is also a better alternative as a final irrigant for reducing postoperative pain in primary teeth.

An In vitro Assessment of Retention Force of ZrO2, Polyether Ether Ketone, and ZrO2-Polyether Ether Ketone Telescopic Attachment for Mandibular Overdentures.

Objectives: The objective of this study was to compare ZrO2, polyether ether ketone (PEEK), and ZrO2-PEEK telescopic attachments in terms of retention of overdenture. Methodology: Forty-five acrylic resin models of the lower arch were divided into 3 groups of 15 each. In Group I, primary and secondary crowns were constructed from all zirconia (ZrO2), whereas all PEEK was used for Group II and Group III was made up of ZrO2 PEEK. Results: The mean retention value in Group I was 14.12 ± 3.4 N, in Group II was 15.86 ± 5.1, and in Group III was 22.40 ± 10.3 N. The mean final initial retention value in Group I was 14.50 ± 6.1 N, in Group II was 14.97 ± 8.2, and in Group III was 17.21 ± 9.3 N. A significant difference was observed in intergroup comparison (P < 0.05). Conclusion: Zirconia resulted in maximum retention as compared to other telescopic crown materials.