The millisecond pulsar mass distribution: Evidence for bimodality and constraints on the maximum neutron star mass

The mass function of neutron stars (NSs) contains information about the late evolution of massive stars, the supernova explosion mechanism, and the equation-of-state of cold, nuclear matter beyond the nuclear saturation density. A number of recent NS mass measurements in binary millisecond pulsar (MSP) systems increase the fraction of massive NSs (with $M > 1.8$ M$_{\odot}$) to $\sim 20\%$ of the observed population. In light of these results, we employ a Bayesian framework to revisit the MSP mass distribution. We find that a single Gaussian model does not sufficiently describe the observed population. We test alternative empirical models and infer that the MSP mass distribution is strongly asymmetric. The diversity in spin and orbital properties of high-mass NSs suggests that this is most likely not a result of the recycling process, but rather reflects differences in the NS birth masses. The asymmetry is best accounted for by a bimodal distribution with a low mass component centred at $1.393_{-0.029}^{+0.031}$ M$_{\odot}$ and dispersed by $0.064_{-0.025}^{+0.064}$ M$_{\odot}$, and a high-mass component with a mean of $1.807_{-0.132}^{+0.081}$ and a dispersion of $0.177_{-0.072}^{+0.115}$ M$_{\odot}$. We also establish a lower limit of $M_{max} \ge 2.018$ M$_{\odot}$ at 98% C.L. for the maximum NS mass, from the absence of a high-mass truncation in the observed masses. Using our inferred model, we find that the measurement of 350 MSP masses, expected after the conclusion of pulsar surveys with the Square-Kilometre Array, can result in a precise localization of a maximum mass up to 2.15 M$_{\odot}$, with a 5% accuracy. Finally, we identify possible massive NSs within the known pulsar population and discuss birth masses of MSPs.Comment: submitted to ApJ; 21 pages in aastex6 two-column format, 12 figures, 5 tables. Comments are welcom

Sexual Selection: Signals to Die for

SummarySexual signals are conspicuous and are typically assumed to be energetically costly, which keeps them honest. A recent study on fireflies has found that signal production is energetically cheap, but signalling remains expensive because of eavesdropping predators

Atmospheric rivers do not explain UK summer extreme rainfall

Extreme rainfall events continue to be one of the largest natural hazards in the UK. In winter, heavy precipitation and floods have been linked with intense moisture transport events associated with atmospheric rivers (ARs), yet no large-scale atmospheric precursors have been linked to summer flooding in the UK. This study investigates the link between ARs and extreme rainfall from two perspectives: 1) Given an extreme rainfall event, is there an associated AR? 2) Given an AR, is there an associated extreme rainfall event? We identify extreme rainfall events using the UK Met Office daily rain-gauge dataset and link these to ARs using two different horizontal resolution atmospheric datasets (ERA-Interim and 20th Century Re-analysis). The results show that less than 35% of winter ARs and less than 15% of summer ARs are associated with an extreme rainfall event. Consistent with previous studies, at least 50% of extreme winter rainfall events are associated with an AR. However, less than 20% of the identified summer extreme rainfall events are associated with an AR. The dependence of the water vapor transport intensity threshold used to define an AR on the years included in the study, and on the length of the season, is also examined. Including a longer period (1900-2012) compared to previous studies (1979-2005) reduces the water vapor transport intensity threshold used to define an AR

Neutral thioether and selenoether macrocyclic coordination to Group 1 cations (Li–Cs) – synthesis, spectroscopic and structural properties

The complexes [M(L)][BArF] (BArF = tetrakis{3,5-bis(trifluoromethyl)-phenyl}borate), L = [18]aneO4S2 (1,4,10,13-tetraoxa-7,16-dithiacyclooctadecane): M = Li–Cs; L = [18]aneO2S4 (1,10-dioxa-4,7,13,16-tetrathiacyclooctadecane): M = Li, Na, K; L = [18]aneO4Se2 (1,4,10,13-tetraoxa-7,16-diselenacyclooctadecane): M = Na, K, as well as [Na(18-crown-6)][BArF], are obtained in good yield as crystalline solids by reaction of M[BArF] with the appropriate macrocycle in dry CH2Cl2. X-ray crystallographic analyses of [Li([18]aneO4S2)][BArF] and [Li([18]aneO2S4)][BArF] show discrete distorted octahedral cations with hexadentate coordination to the macrocycle. The heavier alkali metal complexes all contain hexadentate coordination of the heterocrown, supplemented by M?F interactions via the anions, producing extended structures with higher coordination numbers; Na: CN = 7 or 8; K: CN = 8; Rb: CN = 9; Cs: CN = 8 or 10. Notably, all of the structures exhibit significant M–S/Se coordination. The crystal structures of the potassium and rubidium complexes show two distinct [M(heterocrown)]+ cations, one with M?F interactions to two mutually cis [BArF]? anions, and the other with mutually trans [BArF]? anions, giving 1D chain polymers. Solution multinuclear (1H, 13C, 7Li, 23Na, 133Cs) NMR data show that the macrocyclic coordination is retained in CH2Cl2 solution

Non-Interactive Zero-Knowledge from Non-Interactive Batch Arguments

Zero-knowledge and succinctness are two important properties that arise in the study of non-interactive arguments. Previously, Kitagawa et al. (TCC 2020) showed how to obtain a non-interactive zero-knowledge (NIZK) argument for NP from a succinct non-interactive argument (SNARG) for NP. In particular, their work demonstrates how to leverage the succinctness property from an argument system and transform it into a zero-knowledge property. In this work, we study a similar question of leveraging succinctness for zero-knowledge. Our starting point is a batch argument for NP, a primitive that allows a prover to convince a verifier of $T$ NP statements $x_1, \ldots, x_T$ with a proof whose size scales sublinearly with $T$. Unlike SNARGs for NP, batch arguments for NP can be built from group-based assumptions in both pairing and pairing-free groups and from lattice-based assumptions. The challenge with batch arguments is that the proof size is only amortized over the number of instances, but can still encode full information about the witness to a small number of instances. We show how to combine a batch argument for NP with a local pseudorandom generator (i.e., a pseudorandom generator where each output bit only depends on a small number of input bits) and a dual-mode commitment scheme to obtain a NIZK for NP. Our work provides a new generic approach of realizing zero-knowledge from succinctness and highlights a new connection between succinctness and zero-knowledge

Constraining the dense matter equation-of-state with radio pulsars

Radio pulsars provide some of the most important constraints for our understanding of matter at supranuclear densities. So far, these constraints are mostly given by precision mass measurements of neutron stars (NS). By combining single measurements of the two most massive pulsars, J0348$+$0432 and J0740$+$6620, the resulting lower limit of 1.98 $M_\odot$ (99% confidence) of the maximum NS mass, excludes a large number of equations of state (EOSs). Further EOS constraints, complementary to other methods, are likely to come from the measurement of the moment of inertia (MOI) of binary pulsars in relativistic orbits. The Double Pulsar, PSR J0737$-$3039A/B, is the most promising system for the first measurement of the MOI via pulsar timing. Reviewing this method, based in particular on the first MeerKAT observations of the Double Pulsar, we provide well-founded projections into the future by simulating timing observations with MeerKAT and the SKA. For the first time, we account for the spin-down mass loss in the analysis. Our results suggest that an MOI measurement with 11% accuracy (68% confidence) is possible by 2030. If by 2030 the EOS is sufficiently well known, however, we find that the Double Pulsar will allow for a 7% test of Lense-Thirring precession, or alternatively provide a $\sim3\sigma$-measurement of the next-to-leading order gravitational wave damping in GR. Finally, we demonstrate that potential new discoveries of double NS systems with orbital periods shorter than that of the Double Pulsar promise significant improvements in these measurements and the constraints on NS matter.Comment: 13 pages, 8 figures. Accepted by MNRA

Draft Genome Sequence of the Enteropathogenic Bacterium Campylobacter jejuni Strain cj255.

Published onlineJournal ArticleThe enteropathogen Campylobacter jejuni is a global health disaster, being one of the leading causes of bacterial gastroenteritis. Here, we present the draft genome sequence of C. jejuni strain cj255, isolated from a chicken source in Islamabad, Pakistan. The draft genome sequence will aid in epidemiological studies and quarantine of this broad-host-range pathogen.Higher Education Commission of Pakistan and British Counci

A Call to Action: A Blueprint for Academic Health Sciences in the Era of Mass Incarceration

Over 100 million Americans have criminal records, and the U.S. incarcerates seven times more citizens than most developed countries. The burden of incarceration disproportionately affects people of color and ethnic minorities, and those living in poverty. While 95% of incarcerated people return to society, recidivism rates are high with nearly 75% arrested again within five years of release. Criminal records impede access to employment and other social services such as shelter and health care. Justice-involved people have higher rates of substance, mental health, and some chronic medical disorders than the general population; furthermore, the incarcerated population is rapidly aging. Only a minority of academic health science centers are engaged in health services research, workforce training, or correctional health care. This commentary provides rationale and a blueprint for engagement of academic health science institutions to harness their capabilities to tackle one of the country\u27s most vexing public health crises

The three-dimensional structure of the biotin carboxylase-biotin carboxyl carrier protein complex of E. coli acetyl-CoA carboxylase

Acetyl-coenzyme A (acetyl-CoA) carboxylase is a biotin-dependent, multifunctional enzyme that catalyzes the regulated step in fatty acid synthesis. The Escherichia coli enzyme is composed of a homodimeric biotin carboxylase (BC), biotinylated biotin carboxyl carrier protein (BCCP), and an α2β2 heterotetrameric carboxyltransferase. This enzyme complex catalyzes two half-reactions to form malonyl-coenzyme A. BC and BCCP participate in the first half-reaction, whereas carboxyltransferase and BCCP are involved in the second. Three-dimensional structures have been reported for the individual subunits; however, the structural basis for how BCCP reacts with the carboxylase or transferase is unknown. Therefore, we report here the crystal structure of E. coli BCCP complexed with BC to a resolution of 2.49 Å. The protein-protein complex shows a unique quaternary structure and two distinct interfaces for each BCCP monomer. These BCCP binding sites are unique compared to phylogenetically related biotin-dependent carboxylases and therefore provide novel targets for developing antibiotics against bacterial acetyl-CoA carboxylase. © 2013 Elsevier Ltd

A Radio Pulsar/X-ray Binary Link

Radio pulsars with millisecond spin periods are thought to have been spun up by transfer of matter and angular momentum from a low-mass companion star during an X-ray-emitting phase. The spin periods of the neutron stars in several such low-mass X-ray binary (LMXB) systems have been shown to be in the millisecond regime, but no radio pulsations have been detected. Here we report on detection and follow-up observations of a nearby radio millisecond pulsar (MSP) in a circular binary orbit with an optically identified companion star. Optical observations indicate that an accretion disk was present in this system within the last decade. Our optical data show no evidence that one exists today, suggesting that the radio MSP has turned on after a recent LMXB phase.Comment: published in Scienc