New York University Abu Dhabi

This work presents a comprehensive numerical investigation of flashback phenomena in premixed hydrogen-air flames, focusing on the influence of bulk slit velocity, equivalence ratio, and porous media integration on flame stability. A stable laminar flame was first established at the stoichiometric equivalence ratio (phi = 1.0), providing a baseline for subsequent parametric analyses. Systematic flashback studies were then conducted by varying the bulk slit velocity to determine the critical flashback velocity at which the flame propagates upstream into the burner. The analysis was extended to fuel-lean mixtures (phi = 0.5-0.9) to characterize the dependence of flashback limits on equivalence ratio and to highlight the sensitivity of hydrogen flame stability to mixture strength. The results show a decreasing flashback velocity threshold with leaner mixtures, consistent with reductions in laminar burning velocity, flame temperature, and heat release rate. To mitigate flashback, the effect of integrating porous media at the burner inlet was numerically examined. The porous insert modifies local velocity profiles and thermal gradients, enhancing flame anchoring and preventing upstream flame propagation. Detailed analyses of flow and temperature fields demonstrate that porous media stabilize the flame front by suppressing near-wall velocity deficits and promoting heat recirculation near the flame base. These findings provide practical insight into flashback control mechanisms and contribute to the design of safer and more reliable hydrogen combustion systems.

We report the multiwavelength properties of eROSITA Final Equatorial Depth Survey (eFEDS) J084222.9+001000 (hereafter ID830), a quasar at z = 3.4351, identified as the most X-ray luminous radio-loud quasar in the eFEDS field. ID830 shows a rest-frame 0.5-2 keV luminosity of log (L0.5-2kev/erg S-1)=46.20 +/- 0.12, with a steep X-ray photon index (Gamma = 2.43 +/- 0.21), and a significant radio counterpart detected with the Very Large Array FIRST 1.4 GHz and Very Large Array Sky Survey 3 GHz bands. The rest-frame UV to optical spectra from Sloan Digital Sky Survey and Subaru/MOIRCS J band show a dust-reddened quasar feature with A(V) = 0.39 +/- 0.08 mag, and the expected bolometric active galactic nuclei luminosity from the dust-extinction-corrected UV luminosity reaches L-bol,L-3000 & Aring; = (7.62 +/- 0.31) x 10(46) erg s(-1). We estimate a black hole mass of M-BH = (4.40 +/- 0.72) x 10(8) M-circle dot based on the Mg II lambda 2800 emission-line width, and Eddington ratios from the dust-extinction-corrected UV continuum luminosity and X-ray luminosity that reach lambda(Edd,UV) = 1.44 +/- 0.24 and lambda(Edd,X) = 12.8 +/- 3.9, respectively, both indicating super-Eddington accretion. ID830 shows a high ratio of UV to X-ray luminosities, alpha(OX) = -1.20 +/- 0.07 (or alpha(OX) = -1.42 +/- 0.07 after correcting for jet-linked X-ray excess), higher than quasars and little red dots in the super-Eddington phase with similar UV luminosities, with alpha(OX) < -1.8. Such a high alpha(OX) suggests the coexistence of a prominent radio jet and X-ray corona in this high-Eddington-accretion phase. We propose that ID830 may be in a transitional phase after an accretion burst, evolving from a super-Eddington to a sub-Eddington state, which could naturally describe the high alpha(OX).

Individuals often use minimal cues such as gait, face, gestures and voice to categorise others' sexual orientation, a process known as making gaydar judgments. However, it remains unclear whether these judgments change over time, particularly as a function of personal information sharing. In this study, we examined whether heterosexual and sexual minority men made accurate gaydar judgments and whether these judgments changed during the process of getting to know the person. Participants watched videos of men who self-identified as either gay or straight and judged their sexual orientation. They did so first after observing them walking into a room, reading a written text and describing a given image, and then again seeing and hearing them talk about their personal experiences. Next, participants rated the perceived masculinity of the targets based on their gait, gesture, and voice and indicated how informative different minimal cues were for their gaydar judgments. Results showed that accuracy was higher for straight than gay targets. However, in the phase where targets talked about personal information, participants were more likely to categorise the gay targets as such. These effects emerged regardless of the raters' sexual orientation. Gay targets were perceived as less masculine than straight targets and perceived masculinity based on gestures was particularly relevant for differentiating gay and straight targets. These findings highlight the dynamic nature of gaydar judgments, suggesting that, as individuals share more personal information, perceptions shift and masculinity plays a role in making such judgments.

Hydrogels are widely used in regenerative medicine due to their biocompatibility and tissue-like properties; however, many rely on non-renewable resources and exhibiting limited functionality. This study presents a sustainable hydrogel composite derived from agro-marine waste, addressing both environmental and biomedical challenges. The composite integrates nanocellulose (NCs) extracted from date fruit pomace with collagen methacryloyl (ColMA) obtained from fish skin. The extracted NCs exhibited an average length of 529 nm, diameter of 63 nm, and crystallinity index of 40.2%. Incorporating 6% NCs into ColMA significantly improved the hydrogel's mechanical strength, increasing the bulk and nano-elastic moduli to 31 and 24 kPa, respectively. The NC-ColMA hydrogels displayed excellent shear-thinning behavior, recovery ability, and UV crosslinking potential, alongside reduced pore size and swelling ratio with enhanced enzymatic and hydrolytic stability. Moreover, the hydrogels supported >95% hMSC viability, promoted proliferation, and upregulated chondrogenic markers (SOX-9, ACAN, ELN) without elevating pro-inflammatory cytokines, while modestly increasing TGF-beta 1 expression. The composite also demonstrated superior injectability and printability, enabling precise 3D bioprinting. Overall, this NC-ColMA hydrogel, with its tunable mechanical characteristics and biological compatibility, shows great potential for diverse medical applications while also contributing to waste reduction efforts in the date and fishing industries.

The relationship between single-crystal-to-single-crystal (SCSC) transformations in solid-state [2 + 2] photocycloaddition and light-induced motion of crystals, known as the photosalient effect, remains poorly understood. Here, we report a two-dimensional zinc(II) coordination polymer (1) that exhibits both reversible SCSC [2 + 2] photocycloaddition reactivity and macroscopic photomechanical motions (jumping, splitting, and other effects). 1 contains three crystallographically distinct olefin pairs, enabling stepwise [2 + 2] cycloaddition under ultraviolet light, and the reverse reaction proceeds by heating. Single-crystal X-ray diffraction was used to capture the intermediate states during stepwise photodimerization and thermal ring cleavage, revealing the preferred reactivity of the olefin pairs in the structure. This work provides an example of fully reversible, photosalient SCSC [2 + 2] photocycloaddition, demonstrating that macroscopic dynamics and precise molecular-scale transformations can coexist in dynamic crystals.