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

Juvenile Probationers, Restitution Payments, and Empathy: An Evaluation of a Restorative Justice Based Program in Northeastern Pennsylvania

Restitution programs are widely used to hold offenders accountable for their actions while providing restoration to victims and community service. However, compliance with restitution requirements is a major problem, as reported by juvenile probation offices across the country. The Firewood Program was developed for juvenile probationers in a rural Pennsylvania county to improve the completion rate of restitution payments to victims and provide community service. This study examines the effectiveness of the restitution program, which was measured as an increase in the offender's level of empathy and shorter completion times of restitution payments.

The Cellular Metabolism and Effects of Gold Complexes

Leads to the cellular effects of the anti-arthritic gold complexes may come from the determination of their metabolism by target cells and, possibly, cells in the immediate environment of the target cells. Polymorphonuclear leukocytes (PMN) and mononuclear cells (monocytes and lymphocytes) are present in inflamed joints of patients with rheumatoid arthritis and these cells have been widely used in pharmacological studies on the gold complexes. It is suggested that the cellular effects of the gold complexes are mediated by the production of aurocyanide. According to this hypothesis, PMN metabolize small quantities of thiocyanate to cyanide which, in turn, converts gold complexes, such as aurothiomalate, to aurocyanide (dicyanogold(I)) which inhibits the functions of PMN and other cells. There is now considerable evidence for this hypothesis from in vitro studies but there is little in vivo work to back up the hypothesis. One of the few in vivo studies which tested the hypothesis involved the examination of the activity of aurothiomalate in the treatment of polyarthritis in Hooded Wistar rats. Activity of aurothiomalate is only shown in animals which received thiocyanate. Hydrogen cyanide is a constituent of cigarette smoke and the aurocyanide formed by the interaction with gold complexes and inhaled hydrogen cyanide rapidly diffuses into red blood cells. Because of the metabolism of hydrogen cyanide to thiocyanate in the liver, there are higher plasma levels of thiocyanate in smokers than in non-smokers. Smokers may have a greater incidence of side effects than non-smokers but there appears to be little difference in therapeutic response, possibly because there is sufficient thiocyanate in extracellular fluid, even in non-smokers, to support the conversion of gold complexes to aurocyanide. The relationship between the metabolism and effects of the orally active gold complex, auranofin are less clear. Auranofin itself is taken up by cells with the loss of the ligands bound to gold while its inhibitory activity against the oxidative burst of PMN decreases with increasing cell density. For example, the lucigenin-dependent chemiluminescence of 106 PMN/ml is 46 percent of control at 0.5 μM auranofin but only 2.2 percent in 2.105 PMN/ml in the presence of the same concentration of auranofin. A potentially active gold complex is a plasma component which is taken up by red blood cells

Inhibition of Poly(ADP-Ribose) polymerase enhances the toxicity of 131I-Metaiodobenzylguanidine/Topotecan combination therapy to cells and xenografts that express the noradrenaline transporter

Targeted radiotherapy using [131I]meta-iodobenzylguanidine ([131I]MIBG) has produced remissions in some neuroblastoma patients. We previously reported that combining [131I]MIBG with the topoisomerase I (Topo-I) inhibitor topotecan induced long-term DNA damage and supra-additive toxicity to NAT-expressing cells and xenografts. This combination treatment is undergoing clinical evaluation. This present study investigated the potential of PARP-1 inhibition, in vitro and in vivo, to further enhance [131I]MIBG/topotecan efficacy

Explicit teaching of models to enrich physical science learning

Good teaching inducts students into science as a human endeavour and demonstrates that scientific knowledge arises from a process of model construction, testing and review. The historical evolution of scientific knowledge is the development and refinement of models to explain scientific observations. The explicit use of models in teaching facilitates metacognitive engagement, which can lead to improved conceptual understanding (Kenyon et al., 2008). The Science curriculum in Victoria, Australia is modelled on the Australian national curriculum and begins with an explicit aim of students developing an understanding of “the nature of scientific inquiry and the ability to use a range of scientific inquiry methods.” Models are mentioned frequently in the more detailed curriculum statements. For example, the curriculum strand “Science as a human endeavour” includes the following statement: “Scientific understanding, including models and theories, are contestable and are refined over time through a process of review by the scientific community.” In this work we present examples of the representation of models in the secondary physical science curriculum and highlight opportunities for enriching the teaching of science through the explicit introduction of the history and nature of the model, with an emphasis on linking to metacognition (Avargil et al., 2017). REFERENCES Avargil, S., Lavi, R., & Dori, Y. (2017). Students’ Metacognition and Metacognitive Strategies in Science Education, in Y.J. Dori, Z.R. Mevarech, & D.R. Baker (ed.). Cognition, metacognition, and culture in STEM education: Learning, teaching and assessment, Springer International Publishing AG, 33-64. Kenyon, L., Schwarz, C. & Hug, B. (2008), The Benefits of Scientific Modeling. Science and Children, 46(2), 40-44

Addressing skills shortages in middle school physical science teaching

A key challenge in early secondary science education is that many teachers responsible for teaching key physical science concepts, such as forces, motion and electricity have little formal training in Physics (Carpendale & Hume, 2020). This leads to lack of teacher confidence and a reluctance to undertake practical work (Abrahams & Millar, 2008). The Victorian Physics Teachers’ Network is being supported by the Victorian Department of Education and Training Strategic Partnership Program to develop and present four intensive modules that cover the level 7 – 10 Victorian Physical Science curriculum content. Each module consists of six two-hour sessions. The four modules cover forces and motion, electricity, light and sound, and energy transfer and generation respectively. For each topic participants undertake a structured series of key practical activities that not only support the development of conceptual understanding in the given topic but are also directly transferable to the classroom. The first module, Forces and Motion, has been delivered in person to a group of sixteen teachers at a metropolitan school and will also be delivered face-to-face in rural and regional schools. The six workshops are constructed around engaging activities that explored the nature of force, force pairs and force diagrams and the connection between overall or net force and changes in motion and shape. Common misconceptions and alternative conceptions were addressed in each session. We will report on our learnings from the delivery of this initial module and present a summary of participant responses to the module. We will outline how the experience has informed our development and delivery of the next three modules. REFERENCES Abrahams, I., & Millar, R. (2008). Does Practical Work Really Work? A study of the effectiveness of practical work as a teaching and learning method in school science. International Journal of Science Education, 30(14), 1945-1969. https://doi.org/10.1080/09500690701749305   Carpendale, J., & Hume, A. (2020). Content Representations to Support Out-of-Field Physics Teachers. Physics Education, 55(6). https://doi.org/10.1088/1361-6552/abaf1

Electron Detachment in Low-Energy Collisions of H- and D- with He

Measurements and calculations have been made of elastic scattering and electron detachment in collisions of H− and D− with He at energies of 5-120 eV. The measurements show no other inelastic processes occurring in this energy range. The mechanism responsible for electron detachment is assumed to be the crossing of the H− bound state with the continuum of free states; the bound state is then assigned a complex energy. The measured elastic scattering differential cross section shows no structure except at Eθ∼200 eV deg, where there is a region of downward curvature in the graph of logσ vs θ. This is interpreted as the threshold angle for electron detachment, and it is directly related to the crossing point. By empirically fitting the experimental differential cross section, the general features of the complex potential were obtained. By using the resulting potentials, the total detachment cross section was calculated and compared to the experimental results of Bailey, May, and Muschlitz. Only fair agreement is found at low energies, and poor agreement at higher energies (\u3e100 eV). The theory predicts an isotope effect in the elastic differential cross section, and this effect provides a test of the theory. A careful series of experiments at 20 eV displayed the effect. A preliminary measurement of the electron energy spectrum was also made

Progress toward Miniature Space Weather Stations

Responding to a growing need to specify (nowcast) and predict (forecast) hazardous space weather events and their deleterious effects on space systems, the authors have developed a prototype suite of instruments that would serve as a key component of a miniature space weather station. Space environment data have been gathered over several solar cycles, and though these data assist space operators in predicting hazards to space systems based upon derived climatology, no true forecasting ability yet exists. (As an analogy, consider for example the difference between tropospheric weather reports based on data-driven forecast models versus a prediction based upon the average temperature for a given city on a given date over the last hundred years.) True space weather forecasting models require assimilation of space-based in situ data into physics-based models. Data collection of fundamental characteristics, such as plasma density and temperature, neutral wind and bulk ion velocity, and electric and magnetic field strengths is required at multiple grid points, similar to tropospheric weather stations that measure temperature, wind speed, humidity, etc. Recent breakthroughs in fabrication techniques have enabled the development of a suite of instruments that is comprised of 16 individual analyzers, each of which is capable of providing a unique measurement of a partially ionized space environment. The suite is designed to measure ion spectra differential in energy and angle, bulk ion velocities, bulk neutral velocities, and ion and neutral mass spectra. Preliminary functional testing has indicated the ability to resolve He, O, O2, and Ar; separation of O2 and N2 has proved elusive to date. In the prototype suite, the instrument assembly that houses the 16 analyzers is stacked to a conventional Printed Circuit Board (PCB) with anodes and circuit components and an electronics enclosure containing a high voltage power supply, amplifier Application Specific Integrated Circuits (ASICs), and a Rad Hard microcontroller. The suite configuration, including all aforementioned components, has a total volume of 7 cm ´ 7 cm ´ 4 cm = 196 cm3, a mass of 400 g, and a peak power requirement of 1.5 W (for neutral measurements). Challenges inherent to miniaturization of spacecraft capable of providing real utility are identified and addressed

Volcanic Stratigraphy and Age Model of the Kimama Deep Borehole (Project Hotspot): Evidence for 5.8 Million Years of Continuous Basalt Volcanism, Central Snake River Plain, Idaho

The Snake River Plain of central Idaho represents the world’s best example of a mantle hotspot track impinging upon continental crust and provides a record of bimodal volcanism extending over 12 Ma to the present. Project Hotspot recovered almost 2 km of continuous drill core from the Kimama borehole, located in central Idaho on the axial volcanic zone. The Kimama drill core represents the most complete record of mafic volcanism along the Yellowstone–Snake River Plain hotspot track. A total of 432 basalt flow units, representing 183 basalt flows, 78 basalt flow groups, and 34 super groups, along with 42 sediment interbeds are recognized using volcanic facies observations, stratigraphic relationships, borehole geophysical logs, and paleosecular variation in magnetostratigraphy. Rhyolite and other non-basaltic volcanic materials were not encountered in the drill core. Ages for six basalt lava flows were determined by 40Ar/39Ar using incremental heating experiments. Paleomagnetic inclination was measured on over 1200 samples collected at roughly 2-m-depth intervals, yielding mean values of paleosecular variation between ±50° to ±70° in Kimama flow groups, close to the expected 61° axial dipole average for the Kimama borehole location. Twenty-three magnetic reversals were identified and correlated to dated geomagnetic chrons and subchrons and compared with the 40Ar/39Ar radiometric ages. A linear fit to 40Ar/39Ar dates, geomagnetic chron and subchron boundaries, and volcanogenic zircon U-Pb ages defines a mean accumulation rate of ∼320 m/m.y. and extrapolates to a bottom hole age of 6.3 Ma. Average thicknesses of lithologic units increase from 2.7 m (sediment), 4 m (flow units), 10 m (flows), 23 m (flow groups), to 53 m (super groups). On average, one lava flow inundated the Kimama borehole location every 33 k.y. Intercalated sediments, ranging from 0.06 to 24.5 m thick, make up roughly 6% of the drill core and indicate lulls in local volcanic activity that may have lasted up to 77 k.y. Neutron and gamma-ray logs supplement observations from the drill cores: neutron logs document individual flow units through the contrast between massive flow interiors and more porous flow surfaces, and gamma-ray logs document the depth and thickness of sedimentary interbeds and high–K-Fe basalts. The 5.8 m.y. duration of basaltic volcanism in the Kimama drill core implies a steady rate of volcanism, indicating a relatively stable rate of mantle upflow along the lithosphere-mantle boundary in the wake of Yellowstone–Snake River Plain plume volcanism