Momentum flow in black-hole binaries. I. Post-Newtonian analysis of the inspiral and spin-induced bobbing

A brief overview is presented of a new Caltech/Cornell research program that is exploring the nonlinear dynamics of curved spacetime in binary black-hole collisions and mergers, and of an initial project in this program aimed at elucidating the flow of linear momentum in binary black holes (BBHs). The “gauge-dependence” (arbitrariness) in the localization of linear momentum in BBHs is discussed, along with the hope that the qualitative behavior of linear momentum will be gauge-independent. Harmonic coordinates are suggested as a possibly preferred foundation for fixing the gauge associated with linear momentum. For a BBH or other compact binary, the Landau-Lifshitz formalism is used to define the momenta of the binary’s individual bodies in terms of integrals over the bodies’ surfaces or interiors, and define the momentum of the gravitational field (spacetime curvature) outside the bodies as a volume integral over the field’s momentum density. These definitions will be used in subsequent papers that explore the internal nonlinear dynamics of BBHs via numerical relativity. This formalism is then used, in the 1.5 post-Newtonian approximation, to explore momentum flow between a binary’s bodies and its gravitational field during the binary’s orbital inspiral. Special attention is paid to momentum flow and conservation associated with synchronous spin-induced bobbing of the black holes, in the so-called “extreme-kick configuration” (where two identical black holes have their spins lying in their orbital plane and antialigned)

Gas Concentration Measurements in Underground Waste Storage Tanks

Currently over 100 underground tanks at the Hanford facility in eastern Washington state are being used to store high-level radioactive waste. With plans for a long-term nuclear-waste repository in Nevada in place (though not yet approved), one promising use for these underground storage tanks is as a temporary waystation for waste destined for the Nevada repository. However, without a reasonable understanding of the chemical reactions going on within the tanks, transporting waste in and out of the tanks has been deemed to be unsafe. One hazard associated with such storage mechanisms is explosion of flammable gases produced within the tank. Within many of the storage tanks is a sludge layer. This layer, which is a mixture of liquid and solids, contains most of the radioactive material. Radioactive decay and its associated heat can produce several flammable materials within this layer. Two components of particular concern are hydrogen (H2) and nitrous oxide (N2O), since they are highly volatile in the gaseous phase. Though the tanks have either forced or natural convection systems to vent these gases, the possibility of an explosion still exists. Measurements of these gases are taken in several ways. Continuous measurements are taken in the headspace, which is the layer between the tank ceiling and the liquid (supernatant) or sludge layer below. In tanks where a supernatant layer sits atop the sludge layer, there are often rollovers or gas release events (GREs), where a large chunk of sludge, after attaining a certain void fraction, becomes buoyant, rising through the supernatant and releasing its associated gas composition to the headspace. Such changes trigger a sensor, and thus measurements are also taken at that time. Lastly, a retained gas sample (RGS) can be taken from either the supernatant or sludge layer. Such a core sample is quite expensive, but can yield crucial data about the way gases are being produced in the sludge and convected through the supernatant. Unfortunately, the measurements from these three populations do not seem to match. In particular, the ratio r = [N2O]/[H2] varies from population to population. r also varies from tank to tank, but this can more readily be explained in terms of the waste composition of each tank. Since H2 is more volatile than N2O (and since there are more sources of oxygen in the headspace), lower values of r correspond to more hazardous situations. This variance in r is troubling, since we need to be able to explain why certain values of r are lower (and hence more dangerous) in certain areas of the tank. In this report we examine the data from three tanks. We first verify that the differences in r among populations is significant. We then postulate several mechanisms which could explain such a difference

The Vietnam-Era Veteran Enters College

During the past few years, new kinds of students have been entering our colleges and universities. No longer can the uppermiddle class white male, who moves smoothly from a college preparatory program in high school directly into college, be regarded as the typical student. Among the various groups of nontraditional students that make for greater heterogeneity within the college population are those from racial or ethnic minorities, those from lower socioeconomic backgrounds, those whose academic ability or high school preparation is relatively poor (as judged by conventional criteria) and those who are older than the average undergraduate. One subgroup of this last category consists of those whose college education was delayed or interrupted by military service during the Vietnam era, whether they actually served in Southeast Asia or not. It is generally recognized that such students may benefit from college at least as much as the typical student

“Fecal microbiome in epidemiologic studies” - Letter

We congratulate Sinha et al. on their recent report (1) comparing fecal sample collection methods for epidemiologic studies of the gut microbiome. These data contribute to the increasing body of literature describing robust methodological frameworks for specimen collection and processing (2, 3). However, their claim that fixation of stool using RNAlater® results in “considerable changes to the microbiome diversity” contrasts with previous findings (2, 3), including those from their earlier reports (4, 5). We have previously demonstrated that self-collected stool stabilized with RNAlater® or other fixatives yields high fidelity and reproducibility in compositional profiling of DNA and RNA from shotgun sequence data, compared to immediately-frozen specimens (3). Additionally, fixation offers several distinct advantages crucial for large-scale population-based studies: a straightforward self-collection procedure; sample stabilization without deep-freezing during shipping, receiving, and processing; and versatility for multiple molecular analyses. The authors’ finding that specimens preserved in RNAlater® had poor correlation with immediately frozen specimens (1) could be explained, for example, by improper fixation resulting from an excess of specimen relative to preservative volume (1–2 g:2.5 ml, compared to the manufacturer-recommended ratio of 1 g:5–10 ml; Thermo Fisher Scientific Inc., Waltham, MA)

The Effects of Different Types of Internal Controls on Self-Control

One reason companies implement internal controls is to reduce the likelihood of unethical behavior. Yet, ego depletion theory suggests that some controls may cause reductions in employees’ self-control, which could undermine the ability of controls to reduce unethical behavior. We examine whether various types of controls impact self-control and ethical judgments. Our results show that contrary to the ego depletion hypothesis, we find no significant relation between self-control and internal controls. Furthermore, we find that controls have no effect on ethical judgments or ethical ideology. Thus, our results suggest that internal controls do not differentially impact self-control and ethical decision-making

Shadow IT Use, Outcome Effects, and Subjective Performance Evaluation

Using shadow IT may be seen as either a form of organizational misbehavior or proactive and creative problem-solving. These perceptions have implications for the subjective evaluation of subordinate performance. In our experiment, participants choose whether to award a bonus to an employee when different IT systems are used across different outcome levels. We find that employees using shadow IT are less likely to receive the bonus in both high and low outcome conditions relative to employees using the normal IT system, suggesting that managers consider shadow IT usage an organizational misbehavior which casts a negative light on employee performance

Positive Interactions Promote Public Cooperation

The public goods game is the classic laboratory paradigm for studying collective action problems. Each participant chooses how much to contribute to a common pool that returns benefits to all participants equally. The ideal outcome occurs if everybody contributes the maximum amount, but the self-interested strategy is not to contribute anything. Most previous studies have found punishment to be more effective than reward for maintaining cooperation in public goods games. The typical design of these studies, however, represses future consequences for today’s actions. In an experimental setting, we compare public goods games followed by punishment, reward, or both in the setting of truly repeated games, in which player identities persist from round to round. We show that reward is as effective as punishment for maintaining public cooperation and leads to higher total earnings. Moreover, when both options are available, reward leads to increased contributions and payoff, whereas punishment has no effect on contributions and leads to lower payoff. We conclude that reward outperforms punishment in repeated public goods games and that human cooperation in such repeated settings is best supported by positive interactions with others.EconomicsMathematicsOrganismic and Evolutionary Biolog

The Path to an Ecosystem Approach for Forage Fish Management: A Case Study of Atlantic Menhaden

Atlantic menhaden (Brevoortia tyrannus) support the largest fishery by volume on the United States East Coast, while also playing an important role as a forage species. Managers’ and stakeholders’ increasing concerns about the impact of Atlantic menhaden harvest on ecosystem processes led to an evolution in the assessment and management of this species from a purely single-species approach to an ecosystem approach. The first coastwide stock assessment of Atlantic menhaden for management used a single-species virtual population analysis (VPA). Subsequent assessments used a forward projecting statistical catch-at-age framework that incorporated estimates of predation mortality from a multispecies VPA while analytical efforts continued toward the development of ecosystem models and explicit ecological reference points (ERPs) for Atlantic menhaden. As an interim step while ecosystem models were being developed, a series of ad hoc measures to preserve Atlantic menhaden biomass for predators were used by managers. In August 2020, the Atlantic States Marine Fisheries Commission formally adopted an ecological modeling framework as a tool to set reference points and harvest limits for the Atlantic menhaden that considers their role as a forage fish. This is the first example of a quantitative ecosystem approach to setting reference points on the United States Atlantic Coast and it represents a significant advance for forage fish management. This case study reviews the history of Atlantic menhaden stock assessments and management, outlines the progress on the current implementation of ERPs for this species, and highlights future research and management needs to improve and expand ecosystem-based fisheries management