Context. The tight empirical M − σ relation between the mass of a supermassive black hole (SMBH) and the velocity dispersion of the host galaxy bulge is often interpreted as the result of self-regulation via active galactic nucleus (AGN) feedback. This picture is motivated by analytical and semi-analytical models in which momentum-driven AGN winds can expel the gas once the SMBH reaches a critical mass. However, these models typically assume idealised conditions: smooth gas distributions, spherical symmetry, and very efficient cooling of the shocked AGN wind. It is unclear whether this paradigm is applicable under more realistic conditions. Aims. We checked whether AGN outflows can establish the M − σ relation in a multi-phase and turbulent galactic bulge subject to realistic radiative cooling while conserving the shocked AGN wind energy. Methods. We ran a suite of purpose-built hydrodynamical simulations of AGN outflows in turbulent gas shells, covering a wide range of constant AGN luminosities. We tracked the outflow evolution over the course of ≥1 Myr. We analysed the effect of AGN outflow on the cold dense gas and SMBH feeding, estimating the luminosity threshold for removing most of the cold gas from the central regions. Results. We find that AGNs with significantly sub-Eddington luminosities cannot suppress SMBH feeding, while luminosities exceeding ∼0.7 times Eddington clear out both the diffuse hot gas and the cold clumps, consistent with the momentum-driven outflow formalism. We also show that dense gas clusters are affected almost exclusively by the AGN wind momentum, while the shocked wind energy escapes through low-density channels and inflates large bubbles of diffuse gas. Conclusions. Active galactic nucleus wind-driven energy-conserving feedback in a turbulent multi-phase medium affects the dense gas only via the wind momentum. Thus, the momentum-driven outflow paradigm is applicable for explaining the M − σ relation even in realistic systems.
Fixed-bed electrode reactors represent a promising low-cost configuration for microbial electrochemical technologies, particularly bioremediation. To assess performance and guide development, it is essential to quantify the relevant electrode area. This is challenging for fixed-bed electrodes composed of coarse carbonaceous materials like graphite granules, granular activated carbon, or biochar, because gas adsorption/desorption coupled to Brunauer-Emmett-Teller (BET) theory likely overestimates microbially accessible areas. We compared four methods for determining the surface area of graphite granules: the copper underpotential deposition and cyclic voltammetry analysis, both providing electrochemical active surface area; BET measurement for total area; and profilometry combined with volumetry for topographic area. By cultivating Geobacter sulfurreducens biofilms on single graphite granules and smooth graphite plates, it was demonstrated that profilometry, combined with volumetry, yields the most realistic results (1.5 & times;10-3 +/- 3 & times;10-4 m2 g-1 or 1.11 +/- 0.33 cm2 per granule) for calculating current densities, while BET measurements (0.8 +/- 0.2 m2 g-1) caused significant overestimation. This was verified by helium ion microscopy of G. sulfurreducens biofilms on single graphite granules, demonstrating limited colonization of open pores (diameter 9.0 +/- 3.0 & micro;m) likely due to mass-transfer limitations. The results indicate that topographic surface area from profilometry is most suitable for quantifying the relevant electrode surface area in fixed-bed reactors.
Disformal couplings to fermions lead to a unique derivative coupling to the axial fermionic current, which contains higher derivatives in general. We derive general conditions on consistent disformal couplings by requiring the absence of higher time derivatives, as they typically lead to ghost degrees of freedom. For a two-scalar field disformal transformation, we show that the consistent disformal coupling must have a degenerate field space metric. This allows us to explore consistent, new two-scalar field modified gravity models. We show that the transformation of the Einstein-Hilbert action leads to two-field Horndeski or two-field DHOST theories. Our formalism also applies to disformal transformations with higher derivatives. We derive the consistent subclasses of disformal transformations that include second derivatives of a scalar field and first derivatives of a vector field that lead to generalized U-DHOST and degenerate beyond generalized Proca theories.
Laser direct writing (LDW) enables the spatially defined creation of room-temperature single-photon emitters (SPEs) in hexagonal boron nitride (hBN). However, the rapid characterization of written sites remains a bottleneck, and the available toolset for efficient screening is limited. Here, we demonstrate a streamlined LDW workflow utilizing single-shot pulses combined with a confocal screening technique that exploits the hBN E2g Stokes line to rapidly localize and map laser-modified regions without relying a priori on defect photoluminescence (PL). This approach enables the direct correlation of site morphology with PL hotspots, revealing that the emergence of single-photon emitters coincides with a threshold regime of minimal lattice modification. Micro-Raman spectral mapping further uncovers localized compressive strain surrounding these emission sites. We classify the generated defects into two families: narrowband “red” emitters (650–750 nm) with weak phonon sidebands (PSB), and 600–650 nm emitters with stronger vibronic coupling, both exhibiting linear polarization and high single-photon purity. These results establish a practical protocol for rapid prototyping, offering a valuable addition to the characterization toolkit for scalable quantum nanophotonics.
Abstract Seagrass meadows store sedimentary carbon and nitrogen and thus play an important role in climate change mitigation and nutrient retention globally. Here we reconstruct the impact of land-use and coastal land uplift on millennial–scale seagrass (Zostera marina) blue carbon and nitrogen accumulation in the Baltic Sea based on a multiproxy paleoreconstruction approach. We show that increased landscape clearance resulted in higher terrestrial runoff and increased accumulation of carbon and nitrogen, whereas land uplift led to hydrodynamically sheltered environments facilitating seagrass colonization, occurring 1700 and > 4000 years ago. The establishment of the seagrass meadows resulted in enhancement of the quality of carbon and nitrogen stocks with increased lignin contents. Seagrass establishment also likely supported export of organic matter to surrounding unvegetated areas and thereby contributed to carbon and nitrogen accumulation beyond habitat boundaries. The findings show that the long-term carbon and nitrogen accumulation rates and permanence are shaped by land cultivation and geomorphological changes and highlights the importance of seagrass conservation for maintaining thousands of years of sedimentary carbon and nitrogen storage.
