Extreme Assumptions Research Articles

Cooperation in temporary partnerships

The literature on cooperation in infinitely repeated Prisoner's Dilemmas covers the extreme opposites of the matching spectrum: partners, a player's opponent never changes, and strangers, a player's opponent randomly changes in every period. Here, we extend the analysis to settings where the opponent changes, but not in every period. In these temporary partnerships, players can deter some deviations by directly sanctioning their partner. Hence, relaxing the extreme assumption of one-period matchings can support some cooperation also off equilibrium because a class of strategies emerges that are less extreme than the typical “grim” strategy. We establish conditions supporting full cooperation as a subgame perfect equilibrium under a social norm that complements direct sanctions with a cyclical community sanction. Though this strategy less effectively incentivizes cooperation, it more effectively incentivizes punishment after a deviation, hence, can be preferable to the grim strategy under certain conditions.

Interpretations of Generic Versus Comparative Statements About Groups: Similarities and Differences

We compare interpretations of two kinds of statements that are important for stereotype transmission: generics (e.g., “women are helpful”) and comparatives (e.g., “women are more helpful than men”). Participants ( N = 338) read and interpreted generic or comparative statements about positive and negative features of gender (Experiment A) and age groups (Experiment B). We found similarities and differences. Participants interpreted both generics and comparatives as conveying information not only about the target (women in the example) but also about the referent (men in the example), whether the statement explicitly mentioned the referent (in comparatives) or not (in generics). When statements said something positive (negative) about the target, they also communicated a rather negative (positive) view of the referent. Remarkably, although comparatives explicitly contrast groups while generics do not, generics implied bigger differences between the groups and provoked more extreme assumptions about the groups. We discuss implications for stereotype transmission.

Comparing PEMFC state-of-health characteristics obtained by Galvanostatic Charge Method with and without nitrogen flush

Onboard determination of state-of-health (SoH) parameters becomes increasingly important with tightened lifetime requirements for automotive polymer electrolyte membrane (PEM) fuel cell systems. One way to electrochemically characterize SoH parameters like active catalyst surface area (roughness factor, RF), double layer capacitance and membrane permeability is the nitrogen-flush-requiring Galvanostatic Charge Method (GCM). In this publication, a nitrogen-flush-free and thus, onboard-compatible adapted version of GCM (AGCM from Möller et al. (2023)), is directly compared to its original method, GCM. A 20-cell automotive shortstack was frequently characterized with both GCM and AGCM methods as well as standard Cyclic Voltammetry (CV) during a degradation test. Additionally, the evaluation model for AGCM was varied in two aspects: Firstly, modeling the hydrogen partial pressure difference (ΔpH2) responsible for hydrogen crossover and secondly, modeling hydrogen diffusion in the cathode volume with a 0-D transport model. The characterization results prove that all investigated model variations of AGCM can reproduce double layer capacitance results from GCM and CV, as well as the decreasing trend in roughness factor results. RF-values characterized by AGCM agree with either GCM or CV results, depending on the evaluation model. A thorough analysis revealed the neglected short circuit resistance in combination with the chosen modeling approach of ΔpH2 in AGCM as the reason. The two modeling approaches for ΔpH2 base on extreme assumptions about the homogeneity of hydrogen distribution in the anode volume. Neither of them could reproduce the membrane permeability of GCM. Instead, one overestimates, one underestimates it, indicating the truth to be in between the two extreme models. However, AGCM measurement conditions are identified as a lever to improve the AGCM permeability results and their robustness, even if the modeling approaches remain unchanged. Furthermore, this study showed that neglecting hydrogen diffusion in the cathode volume in the AGCM evaluation model leads to overestimation of the membrane permeability.

A component method approach for single-sided beam-to-column joints with CHS column and welded double-tee beam

This paper focuses on predicting the flexural stiffness and strength of beam-to-column joints with Circular-Hollow-Section (CHS) columns and externally welded double-tee beams using the Component Method approach. Currently, Eurocode 3 Part 1.8 lacks guidelines for assessing the stiffness of these joints, resulting in their practical modelling using extreme assumptions like pin or full restraint. Nevertheless, the literature demonstrates that these joints can exhibit semi-rigid behaviour due to the relatively high local deformability of the tube in the joint area. Another concern relates to the strength of these joints. In fact, recent studies have shown that Eurocode 3 Part 1.8 formula for predicting the yield resistance of these joints is over-conservative.Within this framework, the purpose of this study is to fill the current knowledge gaps (over-conservative strength prediction and lack of rules for determining the stiffness) by undertaking a thorough investigation involving numerical and analytical activities. Specifically, the research presents a component-based modelling approach for predicting stiffness and strength of CHS to double-tee beam connections.In this regard, the work presented in this paper has involved the selection of experimental tests from literature to validate a Finite Element (FE) model, specifically focusing on X- and T-joints and internal and external beam-to-column joints. The validated numerical models have been then employed to simulate the response under monotonic loading conditions of additional sets comprising forty T-joints and thirty external beam-to-column joints, respectively. The currently available formulations for predicting the resistance of T-joints were applied to the forty cases simulated, evaluating their accuracy. This allowed the individuation of the most accurate literature formula for the strength prediction of T-joints, showing that the recent proposal of Voth and Packer (2012) yields sufficiently accurate results. Instead, analytical formulations for predicting the stiffness of T-joints were properly derived in a closed-form solution and were validated against the results of the parametric study. Finally, drawing upon knowledge regarding the stiffness and strength of T-joints, the flexural response of external beam-to-columns connections was evaluated proposing a component model, whose accuracy was verified against the cases simulated in the parametric analysis.

Multisystemic inflammatory syndrome in children and the BNT162b2 vaccine: a nationwide cohort study.

This research demonstrates that vaccinating children and adolescents against COVID-19 has reduced the risk of MIS-C during the study period. • Most of the published literature regarding vaccine effectiveness is based on case-control studies, which are limited due to small sample sizes and the inability to fully estimate the risk of MIS-C among vaccinated and unvaccinated children and adolescents. • The known underestimation of COVID-19 diagnosis among children and adolescents is challenging, as they often have few to no symptoms. • Significant risk difference was found in favor of the vaccinated group, even after including extreme assumptions regarding the underdiagnosed COVID-19 rate. • During this nationwide study period, it was found that vaccinating children and adolescents reduced the risk of MIS-C and its complications.

A comparison of deflation methods for carbon footprint calculations using Japanese data

An embodied CO2 emissions intensity database estimated from input–output data at current prices is now available in Japan. This study compares two non-survey methods: The double-deflation (DD) method and an elaborated approach combining the DD method with the generalized RAS method to deflate an input–output table (IOT). We used these methods to estimate new datasets of embodied CO2 emission intensity data in Japan, utilizing Japan's IOTs for 2005, 2011, and 2015 at constant prices in 2015. Furthermore, we compare the estimated data of 367 commodity sectors for a specific year (2005 or 2011). The results reveal that the intensity for certain aggregated sector groups, such as non-ferrous metals and finance and insurance, exhibits higher uncertainty owing to the extreme price homogeneity assumption associated with the DD method. Consequently, we recommend that life-cycle-assessment practitioners use an open database when analyzing changes in the carbon footprint of products over time.

Conflict, Inertia, and Phillips Curve from a Sraffian Standpoint

ABSTRACT The recent post-Keynesian debate on conflict inflation revolves around plausible magnitudes of the parameters of the standard model. We assess this debate by examining the economic meaning of the ‘bargaining’ and ‘indexation’ parameters, and proposing a reinterpretation in which the bargaining power is reflected in the relative frequency of wage and price increases in a period. Inflation then depends on the size of the inconsistent distributive claims and the absolute frequency of wage and price increases. Distribution depends on the relative frequency of such increases. From the latter we derive the real wage and profit resistance parameters, which determine the structural degree of inflation inertia. By adding the employment rate as a determinant of the desired real wage, we get a conflict-augmented Phillips curve. We show how different assumptions on the real resistance parameters affect the shape of the Phillips curve and the distributive outcomes in different conflict inflation models. A NAIRU occurs only when there is both full real wage and real profit resistance. Conflict generates inflation (not acceleration) with less extreme assumptions. The old-type conflict-augmented Phillips curve, with income distribution depending on the relative frequency of wage and price adjustments, is the most plausible case.

BestCRM: An Exhaustive Search for Optimal Cis-Regulatory Modules in Promoters Accelerated by the Multidimensional Hash Function.

The concept of cis-regulatory modules located in gene promoters represents today's vision of the organization of gene transcriptional regulation. Such modules are a combination of two or more single, short DNA motifs. The bioinformatic identification of such modules belongs to so-called NP-hard problems with extreme computational complexity, and therefore, simplifications, assumptions, and heuristics are usually deployed to tackle the problem. In practice, this requires, first, many parameters to be set before the search, and second, it leads to the identification of locally optimal results. Here, a novel method is presented, aimed at identifying the cis-regulatory elements in gene promoters based on an exhaustive search of all the feasible modules' configurations. All required parameters are automatically estimated using positive and negative datasets. To be computationally efficient, the search is accelerated using a multidimensional hash function, allowing the search to complete in a few hours on a regular laptop (for example, a CPU Intel i7, 3.2 GH, 32 Gb RAM). Tests on an established benchmark and real data show better performance of BestCRM compared to the available methods according to several metrics like specificity, sensitivity, AUC, etc. A great practical advantage of the method is its minimum number of input parameters-apart from positive and negative promoters, only a desired level of module presence in promoters is required.

Long-period Radio Pulsars: Population Study in the Neutron Star and White Dwarf Rotating Dipole Scenarios

The nature of two recently discovered radio emitters with unusually long periods of 18 minutes (GLEAM-X J1627–52) and 21 minutes (GPM J1839–10) is highly debated. Their bright radio emission resembles that of radio magnetars, but their long periodicities and lack of detection at other wavelengths challenge the neutron star (NS) interpretation. In contrast, long rotational periods are common in white dwarfs (WDs) but, although predicted, dipolar radio emission from isolated magnetic WDs has never been unambiguously observed. In this work, we investigate these long-period objects as potential isolated NS or WD dipolar radio emitters and find that both scenarios pose significant challenges to our understanding of radio emission via pair production in dipolar magnetospheres. We also perform population-synthesis simulations based on dipolar spin-down in both pictures, assuming different initial-period distributions, masses, radii, beaming fractions, and magnetic field prescriptions, to assess their impact on the ultra-long pulsar population. In the NS scenario, we do not expect a large number of ultra-long-period pulsars under any physically motivated (or even extreme) assumptions for the period evolution. On the other hand, in the WD scenario, we can easily accommodate a large population of long-period radio emitters. However, no mechanism can easily explain the production of such bright coherent radio emission in either scenarios.

Improvement of Analytical Model for Oblique Cutting—Part I: Identification of Mechanical Characteristics of Machined Material

Analytical cutting models have recently become quite widespread due to the simplicity and rapidity of calculations as well as the stability of the solutions. This paper considers a procedure for determining the mechanical properties of machined material based on parameters for the analytical model of oblique cutting for a certain range of changes in cutting modes and inclination angles of the tool cutting edge. The model is based on the energy method of determining the main cutting process characteristics using the extreme assumptions of continuum mechanics. It is proposed to determine the parameters characterizing the mechanical properties of the processed material using the Johnson–Cook constitutive equation in two stages: preliminary determination of the constitutive equation parameters based on the results of mechanical compression specimen tests and experimental data of the oblique cutting process, and specifying the generalized values of the constitutive equation parameters using the inverse method through the finite element cutting model. The adequacy of the applied analytical cutting model is confirmed by comparing the kinetic characteristic values calculated using the analytical model of oblique cutting with the application of the specified parameters of the constitutive equation and the measured values of the kinetic characteristics. The deviation between the calculated and measured values of the cutting force components when changing the cutting depth (undeformed chip thickness) does not exceed 15%. The difference between the calculated and measured values of the cutting force components when the cutting speed is changed is about 20%.

Unemployment, Labor Mobility, and Climate Policy

We develop a computable general equilibrium model of the United States economy to study the unemployment effects of climate policy and the importance of cross-sectoral labor mobility. We consider two alternate extreme assumptions about labor mobility: either perfect mobility, as is assumed in much previous work, or perfect immobility. The effect of a $35 per ton carbon tax on aggregate unemployment is small and similar across the two labor mobility assumptions (0.2–0.3 percentage points). The effect on unemployment in fossil fuel sectors is much larger under the immobility assumption – a 30 percentage-point increase in the coal sector – suggesting that models omitting labor mobility frictions may greatly under-predict sectoral unemployment effects. Returning carbon tax revenue through labor tax cuts can dampen or even reverse negative impacts on unemployment, while command-and-control policies yield larger unemployment effects.

The importance of theory at the Information Systems Journal

The importance of theory at the <i>Information Systems Journal</i>

The importance of vaccinated individuals to population-level evolution of pathogens

Virus evolution shapes the epidemiological patterns of infectious disease, particularly via evasion of population immunity. At the individual level, host immunity itself may drive viral evolution towards antigenic escape. Using compartmental SIR-style models with imperfect vaccination, we allow the probability of immune escape to differ in vaccinated and unvaccinated hosts. As the relative contribution to selection in these different hosts varies, the overall effect of vaccination on the antigenic escape pressure at the population level changes.We find that this relative contribution to escape is important for understanding the effects of vaccination on the escape pressure and we draw out some fairly general patterns. If vaccinated hosts do not contribute much more than unvaccinated hosts to the escape pressure, then increasing vaccination always reduces the overall escape pressure. In contrast, if vaccinated hosts contribute significantly more than unvaccinated hosts to the population level escape pressure, then the escape pressure is maximised for intermediate vaccination levels. Past studies find only that the escape pressure is maximal for intermediate levels with fixed extreme assumptions about this relative contribution. Here we show that this result does not hold across the range of plausible assumptions for the relative contribution to escape from vaccinated and unvaccinated hosts.We also find that these results depend on the vaccine efficacy against transmission, particularly through the partial protection against infection. This work highlights the potential value of understanding better how the contribution to antigenic escape pressure depends on individual host immunity.

RELAP5/mod3.3 Analysis of Natural Circulation Cooldown with One Inactive Loop for Nuclear Power Plant Krško (NEK)

The paper presents the RELAP5/mod3.3 analysis of natural circulation cooldown with one inactive loop for Nuclear Power Plant Krško (NEK). The aim of the analysis is to determine the limiting cooldown rates during operator recovery actions to minimize the effect of flow stagnation in inactive loop. Since this is typical asymmetrical transient, the RELAP5/mod3.3 NEK model with split reactor vessel model was developed (models of the reactor vessel and core were axially divided in two parts) and used for this analysis. The several transients of cooldown, with one inactive loop, for different time after shutdown (different decay heat) were performed. The extreme conservative assumptions were applied for the analyses, i.e. the complete loss of feedwater (FW) and auxiliary feedwater (AF), including turbine driven (TD) AF pump, and the cooldown has started after the SG is completely dry (inactive). The analyses show that the cooldown rate shall be significantly reduced, and, based on the results the procedure ES-0.2 “Natural Circulation Cooldown” was modified.

Sensitivity analysis of failure correlation between structures, systems, and components on system risk

A seismic event caused an accident at the Fukushima Nuclear Power Plant, which further resulted in simultaneous accidents at several units. Consequently, this incident has aroused great interest in the safety of nuclear power plants worldwide. A reasonable safety evaluation of such an external event should appropriately consider the correlation between SSCs (structures, systems, and components) and the probability of failure. However, a probabilistic safety assessment in current nuclear industries is performed conservatively, assuming that the failure correlation between SSCs is independent or completely dependent. This is an extreme assumption; a reasonable risk can be calculated, or risk-based decision-making can be conducted only when the appropriate failure correlation between SSCs is considered. Thus, this study analyzed the effect of the failure correlation of SSCs on the safety of the system to realize rational safety assessment and decision-making. Consequently, the impact on the system differs according to the size of the failure probability of the SSCs and the AND and OR conditions.

A Sun-like star orbiting a black hole

ABSTRACT We report discovery of a bright, nearby ($G = 13.8;\, \, d = 480\, \rm pc$) Sun-like star orbiting a dark object. We identified the system as a black hole candidate via its astrometric orbital solution from the Gaia mission. Radial velocities validated and refined the Gaia solution, and spectroscopy ruled out significant light contributions from another star. Joint modelling of radial velocities and astrometry constrains the companion mass of $M_2 = 9.62\pm 0.18\, \mathrm{M}_{\odot }$. The spectroscopic orbit alone sets a minimum companion mass of $M_2\gt 5\, \mathrm{M}_{\odot }$; if the companion were a $5\, \mathrm{M}_{\odot }$ star, it would be 500 times more luminous than the entire system. These constraints are insensitive to the mass of the luminous star, which appears as a slowly rotating G dwarf ($T_{\rm eff}=5850\, \rm K$, log g = 4.5, $M=0.93\, \mathrm{M}_{\odot }$), with near-solar metallicity ($\rm [Fe/H] = -0.2$) and an unremarkable abundance pattern. We find no plausible astrophysical scenario that can explain the orbit and does not involve a black hole. The orbital period, Porb = 185.6 d, is longer than that of any known stellar-mass black hole binary. The system’s modest eccentricity (e = 0.45), high metallicity, and thin-disc Galactic orbit suggest that it was born in the Milky Way disc with at most a weak natal kick. How the system formed is uncertain. Common envelope evolution can only produce the system’s wide orbit under extreme and likely unphysical assumptions. Formation models involving triples or dynamical assembly in an open cluster may be more promising. This is the nearest known black hole by a factor of 3, and its discovery suggests the existence of a sizable population of dormant black holes in binaries. Future Gaia releases will likely facilitate the discovery of dozens more.

Testing the presence of a dormant black hole inside HR 6819

Context. HR 6819 was recently reported to be a triple system with a non-accreting black hole (BH). The inner binary system was defined as a B3 III type star (a 5 − 7 M⊙ star estimated to be at the end of its main sequence) and a dormant BH (&gt; 4.2 M⊙). The period of the inner binary was estimated to be ∼40 days with an eccentricity in the range 0.02 − 0.04. As the inner binary is not resolved, the third component may actually just be spatially coinciding with the inner binary. Aims. In this study we test whether the system’s inner binary can be reconstructed using the isolated binary evolution in the Galactic field or through the dynamical evolution within globular star clusters. Our goal is to understand the formation of the HR 6819 inner binary. Methods. To simulate the inner binary evolution we assumed that the influence of the third body on the inner binary is negligible. We created synthetic populations of BH-main sequence binaries for the Galactic disc and the Galactic globular clusters to compare to the reported parameters of the HR 6819 inner binary. We have adopted very optimistic input physics, in terms of common envelope evolution and BH formation, for the formation of binaries similar to the reported inner HR 6819 binary. Results. Despite our optimistic assumptions we cannot form systems like the inner HR 6819 binary in globular clusters. Even with our extreme assumptions, the formation of an HR 6819-like binary in the Galactic field population is not expected. Conclusions. We argue that if a dormant BH actually exists in the reported configuration inside HR 6819, its presence cannot easily be explained by our models based on isolated and dynamical binary evolution.

A Lower Bound on the Mass of Compact Objects from Dissipative Dark Matter

We study the fragmentation scale of dark gas formed in dissipative dark-matter halos and show that the simple atomic-dark-matter model consistent with all current observations can create low-mass fragments that can evolve into compact objects forbidden by stellar astrophysics. We model the collapse of the dark halo’s dense core by tracing the thermochemical evolution of a uniform-density volume element under two extreme assumptions for density evolution: hydrostatic equilibrium and pressure-free collapse. We then compute the opacity-limited minimum fragment mass from the minimum temperature achieved in these calculations. The results indicate that much of the parameter space is highly unstable to small-scale fragmentation.

Investigation on radial fuel relocation and its influence on heat split phenomenon of dual-cooled annular fuel element

Radial fuel relocation due to fuel fragmentation can significantly change the heat split, further affecting the thermal performance and safety of dual-cooled annular fuels. Considering the rarity of in-pile irradiation data for annular fuels, three different fuel relocation and its recovery models were developed based on modifications of relocation models for solid fuel rods or the mechanistic relocation simulation of pre-fragmented, interacting and deformable fuel fragments. The three relocation models were implanted into the fuel performance analysis code FROBA-ANNULAR, and thermo-mechanical simulation was carried out to investigate the influence of fuel relocation on gap size variation and heat split variation in an annular fuel. The results indicate that different relocation models lead to significant difference on the prediction of gap size and heat split. Relocation models developed through mechanistic simulation of pre-fragmented fragments seems to be more reasonable, compared with the other two models developed based on unreasonable and extreme assumptions. Mechanistic simulation results indicate that radial relocation of fragmented annular fuels can be bidirectional even at the initial burnup stages, resulting in the reduction of gap sizes of both internal and external fuel-cladding gaps. In addition, it was found that the gap size variation due to radial fuel relocation significantly changed the heat split and matching-rate between heat split and flow flux distribution, exerting an influence on fuel temperature and MDNBR.

Mitonuclear incompatibility as a hidden driver behind the genome ancestry of African admixed cattle

BackgroundAfrica is an important watershed in the genetic history of domestic cattle, as two lineages of modern cattle, Bos taurus and B. indicus, form distinct admixed cattle populations. Despite the predominant B. indicus nuclear ancestry of African admixed cattle, B. indicus mitochondria have not been found on the continent. This discrepancy between the mitochondrial and nuclear genomes has been previously hypothesized to be driven by male-biased introgression of Asian B. indicus into ancestral African B. taurus. Given that this hypothesis mandates extreme demographic assumptions relying on random genetic drift, we propose a novel hypothesis of selection induced by mitonuclear incompatibility and assess these hypotheses with regard to the current genomic status of African admixed cattle.ResultsBy analyzing 494 mitochondrial and 235 nuclear genome sequences, we first confirmed the genotype discrepancy between mitochondrial and nuclear genome in African admixed cattle: the absence of B. indicus mitochondria and the predominant B. indicus autosomal ancestry. We applied approximate Bayesian computation (ABC) to assess the posterior probabilities of two selection hypotheses given this observation. The results of ABC indicated that the model assuming both male-biased B. indicus introgression and selection induced by mitonuclear incompatibility explains the current genomic discrepancy most accurately. Subsequently, we identified selection signatures at autosomal loci interacting with mitochondria that are responsible for integrity of the cellular respiration system. By contrast with B. indicus-enriched genome ancestry of African admixed cattle, local ancestries at these selection signatures were enriched with B. taurus alleles, concurring with the key expectation of selection induced by mitonuclear incompatibility.ConclusionsOur findings support the current genome status of African admixed cattle as a potential outcome of male-biased B. indicus introgression, where mitonuclear incompatibility exerted selection pressure against B. indicus mitochondria. This study provides a novel perspective on African cattle demography and supports the role of mitonuclear incompatibility in the hybridization of mammalian species.