In exponential population growth, variability in the timing of individual division events and environmental factors (including stochastic inoculation) compound to produce variable growth trajectories. In several stochastic models of exponential growth we show power-law relationships that relate variability in the time required to reach a threshold population size to growth rate and inoculum size. Population-growth experiments in E. coli and S. aureus with inoculum sizes ranging between 1 and 100 are consistent with these relationships. We quantify how noise accumulates over time, finding that it encodes-and can be used to deduce-information about the early growth rate of a population.

The structure of communities is influenced by many ecological and evolutionary processes, but the way these manifest in classic biodiversity patterns often remains unclear. Here we aim to distinguish the ecological footprint of selection-through competition or environmental filtering-from that of neutral processes that are invariant to species identity. We build on existing Massive Eco-evolutionary Synthesis Simulations (MESS), which uses information from three biodiversity axes-species abundances, genetic diversity, and trait variation-to distinguish between mechanistic processes. To correctly detect and characterise competition, we add a new and more realistic form of competition that explicitly compares the traits of each pair of individuals. Our results are qualitatively different to those of previous work in which competition is based on the distance of each individual's trait to the community mean. We find that our new form of competition is easier to identify in empirical data compared to the alternatives. This is especially true when trait data are available and used in the inference procedure. Our findings hint that signatures in empirical data previously attributed to neutrality may in fact be the result of pairwise-acting selective forces. We conclude that gathering more different types of data, together with more advanced mechanistic models and inference as done here, could be the key to unravelling the mechanisms of community assembly and question the relative roles of neutral and selective processes.

We report the All-Sky Automated Survey for SuperNovae discovery of the tidal disruption event (TDE) ASASSN-23bd (AT 2023clx) in NGC 3799, a LINER galaxy with no evidence of strong active galactic nucleus (AGN) activity over the past decade. With a redshift of z = 0.01107 and a peak ultraviolet (UV)/optical luminosity of (5.4 +/- 0.4) x 10(42) erg s(-1), ASASSN-23bd is the lowest-redshift and least-luminous TDE discovered to date. Spectroscopically, ASASSN-23bd shows H alpha and He i emission throughout its spectral time series, there are no coronal lines in its near-infrared spectrum, and the UV spectrum shows nitrogen lines without the strong carbon and magnesium lines typically seen for AGN. Fits to the rising ASAS-SN light curve show that ASASSN-23bd started to brighten on MJD 59988(-1)(+1), similar to 9 d before discovery, with a nearly linear rise in flux, peaking in the g band on MJD 60000(-3)(+3). Scaling relations and TDE light curve modelling find a black hole mass of similar to 10(6) M-circle dot, which is on the lower end of supermassive black hole masses. ASASSN-23bd is a dim X-ray source, with an upper limit of L0.3-10keV <1.0x 10(40)erg s(-1) from stacking all Swift observations prior to MJD 60061, but with soft (similar to 0.1 keV) thermal emission with a luminosity of L0.3-2keV similar to 4x 10(39) erg s(-1) in XMM-Newton observations on MJD 60095. The rapid (t < 15 d) light curve rise, low UV/optical luminosity, and a luminosity decline over 40 d of Delta L-40 approximate to -0.7 dex make ASASSN-23bd one of the dimmest TDEs to date and a member of the growing 'Low Luminosity and Fast' class of TDEs.

The recent inference of sulfur dioxide (SO2) in the atmosphere of the hot (approximately 1,100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations(1-3) suggests that photochemistry is a key process in high-temperature exoplanet atmospheres(4). This is because of the low (<1 ppb) abundance of SO2 under thermochemical equilibrium compared with that produced from the photochemistry of H2O and H2S (1-10 ppm)(4-9). However, the SO2 inference was made from a single, small molecular feature in the transmission spectrum of WASP-39b at 4.05 mu m and, therefore, the detection of other SO2 absorption bands at different wavelengths is needed to better constrain the SO2 abundance. Here we report the detection of SO2 spectral features at 7.7 and 8.5 mu m in the 5-12-mu m transmission spectrum of WASP-39b measured by the JWST Mid-Infrared Instrument (MIRI) Low Resolution Spectrometer (LRS)10. Our observations suggest an abundance of SO2 of 0.5-25 ppm (1 sigma range), consistent with previous findings(4). As well as SO2, we find broad water-vapour absorption features, as well as an unexplained decrease in the transit depth at wavelengths longer than 10 mu m. Fitting the spectrum with a grid of atmospheric forward models, we derive an atmospheric heavy-element content (metallicity) for WASP-39b of approximately 7.1-8.0 times solar and demonstrate that photochemistry shapes the spectra of WASP-39b across a broad wavelength range.

This paper presents a newly established sample of 103 unique galaxies or galaxy groups at 0.4 less than or similar to z less than or similar to 0.7 from the Cosmic Ultraviolet Baryon Survey (CUBS) for studying the warm-hot circumgalactic medium (CGM) probed by both O VI and Ne VIII absorption. The galaxies and associated neighbors are identified at <1 physical Mpc from the sightlines toward 15 CUBS QSOs at z(QSO) greater than or similar to 0.8. A total of 30 galaxies or galaxy groups exhibit associated O VI lambda lambda 1031, 1037 doublet absorption within a line-of-sight velocity interval of +/- 250 km s(-1), while the rest show no trace of O VI to a detection limit of log N-OVI/cm(-2) approximate to 13.7. Meanwhile, only five galaxies or galaxy groups exhibit the Ne VIII lambda lambda 770, 780 doublet absorption, down to a limiting column density of log N-NeVIII/cm(-2) approximate to 14.0. These O VI- and Ne VIII-bearing halos reside in different galaxy environments with stellar masses ranging from log M-star/M-circle dot approximate to 8 to approximate to 11.5. The warm-hot CGM around galaxies of different stellar masses and star formation rates exhibits different spatial profiles and kinematics. In particular, star-forming galaxies with log M-star/M-circle dot approximate to 9-11 show a significant concentration of metal-enriched warm-hot CGM within the virial radius, while massive quiescent galaxies exhibit flatter radial profiles of both column densities and covering fractions. In addition, the velocity dispersion of O VI absorption is broad with sigma(upsilon) > 40 km s(-1) for galaxies of log M-star/M-circle dot > 9 within the virial radius, suggesting a more dynamic warm-hot halo around these galaxies. Finally, the warm-hot CGM probed by O VI and Ne VIII is suggested to be the dominant phase in sub-L* galaxies with log M-star/M-circle dot approximate to 9-10 based on their high ionization fractions in the CGM.

The scarcity of rocks preserved from the first billion years (Gy) of Earth's history hinders our ability to study the nature of the earliest crust. Rare >4.0-Gy-old zircons confirm that felsic crust was present within 500 million years of Earth's formation. Given that most of that ancient crust has been destroyed, geochemical and isotopic tracers applied to rocks from the oldest sections of continents can be used to provide insights into the nature of the predecessor crust. Evidence from Earth's oldest rocks and minerals suggests multiple early mantle depletion episodes, possibly linked to the formation of an initial, dominantly mafic, crust. This early crust was the precursor to evolved rocks that now constitute considerable portions of Earth's oldest surviving crust.