Determination of the birth-mass function of neutron stars from observations
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Extreme shape coexistence observed in 70Co
The shape of the atomic nucleus is a property that underpins our understanding of nuclear systems, impacts the limits of nuclear existence, and enables probes of physics beyond the Standard Model. Nuclei can adopt a variety of shapes, including spheres, axially deformed spheroids, and pear shapes. In some regions of the nuclear chart where a spherical nucleus would naively be expected, deformed nuclear states can result from the collective action of constituent protons and neutrons. In a small subset of nuclei both spherical and deformed nuclear states have been experimentally observed, a phenomenon termed shape coexistence. We present spectroscopic evidence for the coexistence of Jπ = 1+ spherical and deformed states in 70Co, separated by less than 275 keV. This close degeneracy of levels with the same Jπ and different shapes demonstrates an extreme example of shape coexistence resulting from the interplay of independent particle motion and collective behavior in highly unstable nuclear systems and identifies the Co isotopes as a transition point between deformed ground states observed in the Cr isotopes and spherical configurations observed in the closed-shell Ni isotopes.
Intermediate-range solvent templating and counterion behaviour at charged carbon nanotube surfaces
The ordering of ions and solvent molecules around nanostructures is of profound fundamental importance, from understanding biological processes to the manipulation of nanomaterials to optimizing electrochemical devices. Classical models commonly used to describe these systems treat the solvent simplistically, an approach that endures, in part, due to the extreme difficulty of attaining experimental measurements that challenge this approximation. Here we perform total neutron scattering experiments on model systems—concentrated amide solutions of negatively charged carbon nanotubes and sodium counterions—and measure remarkably complex intermediate-range molecular solvent ordering. The charged surface orders the solvents up to ∼40 Å, even beyond its dense concentric solvation shells. Notably, the molecular orientation of solvent in direct contact with the nanotube surface itself is distinct, lying near-parallel and not interacting with desolvated sodium counterions. In contrast, beyond this layer the ordering of solvent is perpendicular to the surface. Our results underscore the critical importance of multibody interactions in solvated nanoscale systems and charged surfaces, highlighting competing ion/surface solvation effects.
Abundant water from primordial supernovae at cosmic dawn
Primordial (or population III) supernovae were the first nucleosynthetic engines in the Universe, and they forged the heavy elements required for the later formation of planets and life. Water, in particular, is thought to be crucial to the cosmic origins of life as we understand it, and recent models have shown that water can form in low-metallicity gas like that present at high redshifts. Here we present numerical simulations that show that the first water in the Universe formed in population III core-collapse and pair-instability supernovae at redshifts z ≈ 20. The primary sites of water production in these remnants are dense molecular cloud cores, which in some cases were enriched with primordial water to mass fractions that were only a factor of a few below those in the Solar System today. These dense, dusty cores are also probable candidates for protoplanetary disk formation. Besides revealing that a primary ingredient for life was already in place in the Universe 100–200 Myr after the Big Bang, our simulations show that water was probably a key constituent of the first galaxies.
Maternal weight during pregnancy and risk of childhood acute lymphoblastic leukemia in offspring
In addition to biological factors, maternal exposures during pregnancy can contribute to leukemogenesis in offspring. We conducted a population-based cohort study in Sweden to investigate the association between risk of acute lymphoblastic leukemia (ALL) in offspring and maternal anthropometrics during pregnancy. A total of 2,961,435 live-born singletons during 1983–2018 were followed from birth to ALL diagnosis, end of age 18, or end of 2018. 1388 children were diagnosed with ALL (55.6% boys). We observed an increased risk of ALL among daughters of overweight/obese mothers in early pregnancy [Body mass index (BMI) ≥ 25 kg/m2; Standardized incidence ratio (SIR) = 1.4, 95% CI: 1.2–1.6] compared with the risk in daughters of mothers with normal BMI. This association was not found in their sons (SIR = 1.0, 95% CI: 0.9–1.1). Similar results were found for the association between ALL and maternal BMI before delivery. We did not find an association between low or high gestational weight gain (GWG) and risk of ALL (both SIRs = 1.0) in male/female offspring. These suggest that maternal overweight/obesity are important risk factors for childhood ALL in daughters, whereas GWG is not associated with risk of ALL. Further research on this mother-daughter association may shed light on a possible sex hormone/chromosome-related etiology of ALL.
Real-time inference for binary neutron star mergers using machine learning
Mergers of binary neutron stars emit signals in both the gravitational-wave (GW) and electromagnetic spectra. Famously, the 2017 multi-messenger observation of GW170817 (refs. 1,2) led to scientific discoveries across cosmology3, nuclear physics4,5,6 and gravity7. Central to these results were the sky localization and distance obtained from the GW data, which, in the case of GW170817, helped to identify the associated electromagnetic transient, AT 2017gfo (ref. 8), 11 h after the GW signal. Fast analysis of GW data is critical for directing time-sensitive electromagnetic observations. However, owing to challenges arising from the length and complexity of signals, it is often necessary to make approximations that sacrifice accuracy. Here we present a machine-learning framework that performs complete binary neutron star inference in just 1 s without making any such approximations. Our approach enhances multi-messenger observations by providing: (1) accurate localization even before the merger; (2) improved localization precision by around 30% compared to approximate low-latency methods; and (3) detailed information on luminosity distance, inclination and masses, which can be used to prioritize expensive telescope time. Additionally, the flexibility and reduced cost of our method open new opportunities for equation-of-state studies. Finally, we demonstrate that our method scales to long signals, up to an hour in length, thus serving as a blueprint for data analysis for next-generation ground- and space-based detectors.
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