We examine a sample of ∼250 000 ‘locally brightest galaxies’ selected from the Sloan Digital Sky Survey to be central galaxies within their dark matter haloes. We stack the X-ray emission from these ...haloes, as a function of the stellar mass of the central galaxy, using data from the ROSAT All-Sky Survey. We detect emission across almost our entire sample, including emission which we attribute to hot gas around galaxies spanning a range of 1.2 dex in stellar mass (corresponding to nearly two orders of magnitude in halo mass) down to M
* = 1010.8 M⊙ (M
500 ≈ 1012.6 M⊙). Over this range, the X-ray luminosity can be fit by a power law, either of stellar mass or of halo mass. From this, we infer a single unified scaling relation between mass and L
X which applies for galaxies, groups, and clusters. This relation has a slope steeper than expected for self-similarity, showing the importance of non-gravitational heating. Assuming this non-gravitational heating is predominately due to AGN feedback, the lack of a break in the relation shows that AGN feedback is tightly self-regulated and fairly gentle, in agreement with the predictions of recent high-resolution simulations. Our relation is consistent with established measurements of the L
X–L
K
relation for elliptical galaxies as well as the L
X–M
500 relation for optically selected galaxy clusters. However, our L
X–M
500 relation has a normalization more than a factor of 2 below most previous relations based on X-ray-selected cluster samples. We argue that optical selection offers a less biased view of the L
X–M
500 relation for mass-selected clusters.
A highly selective C–H amination reaction under iron catalysis has been developed. This novel system, which employs an inexpensive, nontoxic FeIIIPc catalyst (typically used as an industrial ink ...additive), displays a strong preference for allylic C–H amination over aziridination and all other C–H bond types (i.e., allylic > benzylic > ethereal > 3° > 2° ≫ 1°). Moreover, in polyolefinic substrates, the site selectivity can be controlled by the electronic and steric character of the allylic C–H bond. Although this reaction is shown to proceed via a stepwise mechanism, the stereoretentive nature of C–H amination for 3° aliphatic C–H bonds suggests a very rapid radical rebound step.
To initiate infection, enveloped viruses must fuse with a cell membrane, a process mediated by a dedicated viral fusion protein. To date, these proteins group into three basic structural classes. ...Most require priming (via a protease) to prepare them to respond to a fusion‐triggering signal. Known fusion triggers include receptors, low pH and proteases (and combinations thereof). Here, we provide an update on viral fusion protein priming and triggering, with a focus on virus fusion in endosomes.
Ari Helenius launched the field of enveloped virus fusion in endosomes with a seminal paper in the Journal of Cell Biology in 1980. In the intervening years, a great deal has been learned about the structures and mechanisms of viral membrane fusion proteins as well as about the endosomes in which different enveloped viruses fuse and the endosomal cues that trigger fusion. We now recognize three classes of viral membrane fusion proteins based on structural criteria and four mechanisms of fusion triggering. After reviewing general features of viral membrane fusion proteins and viral fusion in endosomes, we delve into three characterized mechanisms for viral fusion triggering in endosomes: by low pH, by receptor binding plus low pH and by receptor binding plus the action of a protease. We end with a discussion of viruses that may employ novel endosomal fusion‐triggering mechanisms. A key take‐home message is that enveloped viruses that enter cells by fusing in endosomes traverse the endocytic pathway until they reach an endosome that has all of the environmental conditions (pH, proteases, ions, intracellular receptors and lipid composition) to (if needed) prime and (in all cases) trigger the fusion protein and to support membrane fusion.
We use a complete and uniform sample of almost half a million galaxies from the Sloan Digital Sky Survey to characterize the distribution of stellar mass in the low-redshift Universe. Galaxy ...abundances are well determined over almost four orders of magnitude in stellar mass and are reasonably but not perfectly fit by a Schechter function with characteristic stellar mass m*= 6.7 × 1010 M⊙ and with faint-end slope α=−1.155. For a standard cosmology and a standard stellar initial mass function, only 3.5 per cent of the baryons in the low-redshift Universe are locked up in stars. The projected autocorrelation function of stellar mass is robustly and precisely determined for rp < 30 h−1 Mpc. Over the range 10 h−1 kpc < rp < 10 h−1 Mpc, it is extremely well represented by a power law. The corresponding three-dimensional autocorrelation function is ξ*(r) = (r/6.1 h−1 Mpc)−1.84. Relative to the dark matter, the bias of the stellar mass distribution is approximately constant on large scales, but varies by a factor of 5 for rp < 1 h−1 Mpc. This behaviour is approximately but not perfectly reproduced by current models for galaxy formation in the concordance Λcold dark matter cosmology. Detailed comparison suggests that a fluctuation amplitude σ8∼ 0.8 is preferred to the somewhat larger value adopted in the Millennium Simulation models with which we compare our data. This comparison also suggests that observations of stellar mass autocorrelations as a function of redshift might provide a powerful test for the nature of Dark Energy.
Reactions that directly install nitrogen into C-H bonds of complex molecules are significant because of their potential to change the chemical and biological properties of a given compound. Although ...selective intramolecular C-H amination reactions are known, achieving high levels of reactivity while maintaining excellent site selectivity and functional-group tolerance remains a challenge for intermolecular C-H amination. Here, we report a manganese perchlorophthalocyanine catalyst MnIII(ClPc) for intermolecular benzylic C-H amination of bioactive molecules and natural products that proceeds with unprecedented levels of reactivity and site selectivity. In the presence of a Brønsted or Lewis acid, the MnIII(ClPc)-catalysed C-H amination demonstrates unique tolerance for tertiary amine, pyridine and benzimidazole functionalities. Mechanistic studies suggest that C-H amination likely proceeds through an electrophilic metallonitrene intermediate via a stepwise pathway where C-H cleavage is the rate-determining step of the reaction. Collectively, these mechanistic features contrast with previous base-metal-catalysed C-H aminations and provide new opportunities for tunable selectivities.
Transgender people in the United States experience widespread prejudice, discrimination, violence, and other forms of stigma.
This critical review aims to integrate the literature on stigma towards ...transgender people in the US.
This review demonstrates that transgender stigma limits opportunities and access to resources in a number of critical domains (e.g., employment, healthcare), persistently affecting the physical and mental health of transgender people. The applied social ecological model employed here elucidates that transgender stigma operates at multiple levels (i.e., individual, interpersonal, structural) to impact health. Stigma prevention and coping interventions hold promise for reducing stigma and its adverse health-related effects in transgender populations.
Additional research is needed to document the causal relationship between stigma and adverse health as well as the mediators and moderators of stigma in US transgender populations. Multi-level interventions to prevent stigma towards transgender people are warranted.
•Stigma contributes to widespread health inequities in US transgender communities.•We review the multiple levels at which stigma towards transgender people operates.•The stress mechanisms through which stigma contributes to health are discussed.•Intervention strategies to reduce transgender stigma are outlined at each level.•Multi-level interventions are needed to reduce transgender stigma in the US.
Understanding public perceptions of government responses to COVID-19 may foster improved public cooperation. Trust in government and population risk of exposure may influence public perception of the ...response. Other population-level characteristics, such as country socio-economic development, COVID-19 morbidity and mortality, and degree of democratic government, may influence perception.
We developed a novel ten-item instrument that asks respondents to rate key aspects of their government's response to the pandemic (COVID-SCORE). We examined whether the results varied by gender, age group, education level, and monthly income. We also examined the internal and external validity of the index using appropriate predefined variables. To test for dimensionality of the results, we used a principal component analysis (PCA) for the ten survey items. We found that Cronbach's alpha was 0.92 and that the first component of the PCA explained 60% of variance with the remaining factors having eigenvalues below 1, strongly indicating that the tool is both reliable and unidimensional. Based on responses from 13,426 people randomly selected from the general population in 19 countries, the mean national scores ranged from 35.76 (Ecuador) to 80.48 (China) out of a maximum of 100 points. Heterogeneity in responses was observed across age, gender, education and income with the greatest amount of heterogeneity observed between countries. National scores correlated with respondents' reported levels of trust in government and with country-level COVID-19 mortality rates.
The COVID-SCORE survey instrument demonstrated satisfactory validity. It may help governments more effectively engage constituents in current and future efforts to control COVID-19. Additional country-specific assessment should be undertaken to measure trends over time and the public perceptions of key aspects of government responses in other countries.
We present results from 13 cosmological simulations that explore the parameter space of the ‘Evolution and Assembly of GaLaxies and their Environments’ (EAGLE) simulation project. Four of the ...simulations follow the evolution of a periodic cube L = 50 cMpc on a side, and each employs a different subgrid model of the energetic feedback associated with star formation. The relevant parameters were adjusted so that the simulations each reproduce the observed galaxy
stellar mass function at z = 0.1. Three of the simulations fail to form disc galaxies as extended as observed, and we show analytically that this is a consequence of numerical radiative losses that reduce the efficiency of stellar feedback in high-density gas. Such losses are greatly reduced in the fourth simulation – the EAGLE reference model – by injecting more energy in higher density gas. This model produces galaxies with the observed size distribution, and also reproduces many galaxy scaling relations. In the remaining nine simulations, a single parameter or process of the reference model was varied at a time. We find that the properties of galaxies with stellar mass ≲ M
⋆ (the ‘knee’ of the galaxy stellar mass function) are largely governed by feedback associated with star formation, while those of more massive galaxies are also controlled by feedback from accretion on to their central black holes. Both processes must be efficient in order to reproduce the observed galaxy population. In general, simulations that have been calibrated to reproduce the low-redshift galaxy stellar mass function will still not form realistic galaxies, but the additional requirement that galaxy sizes be acceptable leads to agreement with a large range of observables.
We present a precise estimate of the bulk virial scaling relation of halos formed via hierarchical clustering in an ensemble of simulated cold dark matter cosmologies. The result is insensitive to ...cosmological parameters; the presence of a trace, dissipationless gas component; and numerical resolution down to a limit of similar to 1000 particles. The dark matter velocity dispersion scales with total mass log unk=log(1082.9 plus or minus 4.0 km s super(-1)) + (0.3361 plus or minus 0.0026)log h(z) unk/10 super(13)M unk, with h(z) being the dimensionless Hubble parameter. At fixed mass, the velocity dispersion likelihood is nearly lognormal, with scatter unk = 0.0426 plus or minus 0.015, except for a tail with higher dispersions containing 10% of the population that are merger transients. We combine this relation with the halo mass function in Lambda CDM models and show that a low normalization condition, unk( Omega m/0.3) super(0.35)=0.69, favored by recent WMAP and SDSS analysis requires that galaxy and gas-specific energies in rich clusters be 50% larger than that of the underlying dark matter. Such large energetic biases are in conflict with the current generation of direct simulations of cluster formation. A higher normalization, S sub(s) = 0.80, alleviates this tension and implies that the hot gas fraction within r sub(500) is (0.71 plus or minus 0.09) unk Omega sub(b)/ Omega sub(m), a value consistent with recent Sunyaev-Zel'dovlch observations.
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