Subcritical Research Articles

Does a co‐opted director affect a firm's financial distress risk?

AbstractThis study examines the relationship between co‐opted directors (CODIR), measured as the fraction of directors appointed after the Chief Executive Officer (CEO) assumes office to board size, and firms' financial distress risk (FFDR). Understanding the relationship between CODIR and FFDR is imperative due to the significant impact of high risk‐taking on financial crises and the heightened expectations placed on board members for risk oversight. Despite growing research on corporate governance and FFDR, little attention has been paid to the role of CODIRs, presenting a significant gap in the literature. Using a US sample from 1996 to 2019, covering 13,486 firm‐year observations, we document that CODIR reduces FFDR, supporting the hypothesis that co‐opted directors have a lower financial distress risk‐taking propensity than their non‐co‐opted counterparts. We also find that a critical mass of at least three CODIRs and independent CODIRs reduces FFDR. Our results also document that CEO power in the form of CEO duality and CEO tenure, external monitoring in the form of the number of analysts following the firm, competition, and takeover susceptibility do not drive our main conclusions for co‐option and FFDR. Finally, the results show that CODIR reduces FFDR through liquidity channels. The findings remain robust to various definitions of co‐option and distress risk, and are consistent in both difference‐in‐differences analysis and propensity score matching.

Extrinsic and intrinsic drivers of natural killer cell clonality.

Clonal expansion of antigen-specific lymphocytes is the fundamental mechanism enabling potent adaptive immune responses and the generation of immune memory. Accompanied by pronounced epigenetic remodeling, the massive proliferation of individual cells generates a critical mass of effectors for the control of acute infections, as well as a pool of memory cells protecting against future pathogen encounters. Classically associated with the adaptive immune system, recent work has demonstrated that innate immune memory to human cytomegalovirus (CMV) infection is stably maintained as large clonal expansions of natural killer (NK) cells, raising questions on the mechanisms for clonal selection and expansion in the absence of re-arranged antigen receptors. Here, we discuss clonal NK cell memory in the context of the mechanisms underlying clonal competition of adaptive lymphocytes and propose alternative selection mechanisms that might decide on the clonal success of their innate counterparts. We propose that the integration of external cues with cell-intrinsic sources of heterogeneity, such as variegated receptor expression, transcriptional states, and somatic variants, compose a bottleneck for clonal selection, contributing to the large size of memory NK cell clones.

CFD modelling of flashing flows for nuclear safety analysis: possibilities and challenges

Abstract Because of its relevance for the safety analysis of pressurized water reactors (PWR), many research activities on flashing flows in pipes and nozzles arose from the mid of last century. Most of them have been focused on the critical mass flow rate and transient pressure or temperature fluctuations by means of experiments and system codes. Since the beginning of this century, owing to the increase in computer speed and capacity, computational fluid dynamics (CFD) is being used more and more in the investigation of flashing flows, which has the advantage of providing three-dimensional insights in the internal flow structure as well as its evolution. This work presents an overview of relevant flashing scenarios in the nuclear safety analysis, and focuses on the discussion about possibilities and challenges of using CFD modelling. It is shown that a two-fluid model with the thermal phase-change model is superior to a mixture model with pressure phase-change, relaxation and equilibrium models, respectively, in terms of interfacial mass transfer, however, efforts are still required to improve the interphase heat-transfer model. Furthermore, since flashing is accompanied with high void fraction and broad bubble size ranges, a poly-disperse two-fluid model is recommended, but the effect of phase change on bubble coalescence and breakup needs further research. In addition, during flashing the flow pattern may change from single phase to bubbly flow, churn flow, annular flow, and even mist flow. The rapid change of interfacial topology as well as its influence on the applicability of closure models remains a challenge.

Stimulated decay of collapsing axion stars and fast radio bursts

The radiation mechanism of fast radio bursts (FRBs) has been extensively studied but still remains elusive. In the search for dark matter candidates, the QCD axion and axionlike particles (ALPs) have emerged as prominent possibilities. These elusive particles can aggregate into dense structures called axion stars through Bose–Einstein condensation (BEC). Such axion stars could constitute a significant portion of the mysterious dark matter in the universe. When these axion stars grow beyond a critical mass, usually through processes like accretion or merging, they undergo a self-driven collapse. Traditionally, for spherically symmetric axion clumps, the interaction between axions and photons does not lead to parametric resonance, especially when the QCD axion-photon coupling is at standard levels. Nevertheless, our study indicates that even QCD axion stars with typical coupling values can trigger stimulated decay during their collapse, rather than producing relativistic axions through self-interactions. This process results in short radio bursts, with durations of around 0.1 s, and can be potentially observed using radio telescopes like FAST or SKA. Furthermore, we find that collapsing axion stars for ALPs with specific parameters may emit radio bursts lasting just milliseconds with a peak luminosity of 1.60×1042erg/s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1.60\ imes 10^{42}\\,\\mathrm{erg/s}$$\\end{document}, matching the characteristics of the observed non-repeating FRBs.

Understanding the role of head size and neck length in micromotion generation at the taper junction in total hip arthroplasty

Modular hip implants allow intra-operative adjustments for patient-specific customization and targeted replacement of damaged elements without full implant extraction. However, challenges arise from relative micromotions between components, potentially leading to implant failure due to cytotoxic metal debris. In this study magnitude and directions of micromotions at the taper junction were estimated, aiming to understand the effect of variations in head size and neck length. Starting from a reference configuration adhering to the 12/14 taper standard, six additional implant configurations were generated by varying the head size and/or neck length. A musculoskeletal multibody model of a prothesized lower limb was developed to estimate hip contact force and location during a normal walking task. Following the implant assembly, the multibody-derived loads were imposed as boundary conditions in a finite element analysis to compute the taper junction micromotions as the relative slip between the contacting surfaces. Results highlighted the L-size head as the most critical configuration, indicating a 2.81 μm relative slip at the mid-stance phase. The proposed approach enables the investigation of geometric variations in implants under accurate load conditions, providing valuable insights for designing less risky prostheses and informing clinical decision-making processes.

Critical mass phenomenon for a parabolic–elliptic multispecies chemotaxis system in a two‐dimensional disk

A parabolic–elliptic Keller–Segel model for multipopulations in a two‐dimensional unit ball will be considered in this paper. For the initial boundary value problem with mutually attractive populations, the global existence of bounded solutions has been proved through the logarithmic Hardy–Littlewood–Sobolev inequality for system when the initial masses satisfy the subcritical condition. Moreover, based on the moments technique, there exists a blow‐up solution when the initial masses satisfy the supercritical case. In a word, a critical mass phenomenon has been established in this multispecies chemotaxis system.

Pulsed Field Ablation and Neurocardiology: Inert to Efferents or Delayed Destruction?

The therapeutic use of irreversible electroporation in clinical cardiac laboratories, termed pulsed field ablation (PFA), is gaining pre-regulatory approval momentum among rhythm specialists for the mitigation of arrhythmogenic substrate without increased procedural risk. Though electroporation has been utilized in other branches of science and medicine for decades, apprehension regarding all the possible off-target complications of PFA have yet to be thoroughly identified and investigated. This brief review will summarize the preclinical and adult clinical data published to date on PFA's effects on the autonomic system that interplays closely with the cardiovascular system, termed the neurocardiovascular system. These data are contrasted with the findings of efferent destruction secondary to thermal cardiac ablation modalities, namely radiofrequency energy and liquid nitrogen-based cryoablation. In vitro neurocardiology findings, in vivo neurocardiology findings, and clinical neurocardiology findings to date nearly unanimously support the preservation of a critical mass of perineural structures and extracellular matrices to allow for long-term nervous regeneration in both cardiac and non-cardiac settings. Limited histopathologic data exist for neurocardiovascular outcomes post-PFA. Neuron damage is not only theoretically possible, but has been observed with irreversible electroporation, however regeneration is almost always concomitantly described.

Same Naira, More Possibilities! Assessing the Legal Status of the eNaira and Its Potential for Privacy and Inclusion

AbstractOn 25 October 2021, Nigeria became the second country in the world, and the first in Africa, to launch a central bank digital currency. Launched with the tag line “Same Naira. More possibilities”, the Central Bank of Nigeria publicized the eNaira as having the capability to deepen financial inclusion, reduce the cost of financial transactions and support a more efficient payment system. However, more than one year after its launch, its usage is yet to gain a critical mass. This article identifies the significant challenges that make the eNaira unacceptable and potentially ineffective. First, its status as legal tender is questionable; secondly, it undermines privacy, a critical component of physical cash. Thirdly, it is incapable of wide acceptance by individuals and entities across Nigeria. The article explains each of these challenges and proposes a roadmap to the eNaira's acceptance and effectiveness.

Do women in the boardroom influence foreign acquisitions' premium and outcomes? Evidence from China

AbstractThis paper examines whether gender diversity influences foreign merger and acquisition (M&A) premiums and outcomes in China. Consistent with agency and resource dependence theories, we find that female directors significantly reduce the acquisition premium paid for foreign targets. We show that the market responds positively in the short‐term (measured by cumulative abnormal returns) to the announcement of foreign acquisitions by firms with greater female representation in the boardroom. We further find significant evidence that acquirers' boards comprising more female directors experience value creation and better operating synergies (measured by buy‐and‐hold abnormal returns and changes in return on assets) in the long‐term following engagement in foreign M&A deals. Interestingly, after distinguishing between female independent and executive directors, we find that our previous finding on board gender diversity can be attributable to both the monitoring (independent directors) and supervisory (executive directors) roles played by female directors. We also find evidence accords with the argument of the critical mass of female directors' representation in the boardroom. Our results are robust after controlling for endogeneity issues using instrumental variables (IV), propensity score matching (PSM), Heckman, and firm fixed‐effects methods. Overall, our findings offer additional empirical support for the global concern by regulators for improving corporate governance practices by increasing female quotas in the boardroom.

Constraining mass transfer models with galactic neutron star–white dwarf binaries as gravitational wave sources

ABSTRACT Neutron star–white dwarf (NSWD) binaries are one of the most abundant sources of gravitational waves (GWs) in the Milky Way. These GW sources are the evolutionary products of primordial binaries that experienced many processes of binary interaction. We employ a binary population synthesis method to investigate the properties of Galactic NSWD binaries detectable by the Laser Interferometer Space Antenna (LISA). In this paper, only the NSWD systems with a COWD or ONeWD component are included. We consider various models related to mass-transfer efficiencies during primordial binary evolution, supernova explosion mechanisms at NS formation, common envelope ejection efficiencies, and critical WD masses that determine the stability of mass transfer between WDs and NSs. Based on our calculations, we estimate that tens to hundreds of LISA NSWD binaries exist in the Milky Way. We find that the detection of LISA NSWD binaries is able to provide profound insights into mass-transfer efficiencies during the evolution of primordial binaries and critical WD masses during mass transfer from a WD to an NS.

Blending access-based services and triadic frameworks: an empirical evaluation of Packaging-as-a-Service

PurposeRecently emerged Packaging-as-a-Service (PaaS) systems adopt aspects of access-based services and triadic frameworks, which have typically been treated as conceptually separate. The purpose of this paper is to investigate the implications of blending the two in what we call “access-based triadic systems,” by empirically evaluating intentions to adopt PaaS systems for takeaway food among restaurants and consumers.Design/methodology/approachWe derived relevant attributes of PaaS systems from a qualitative pre-study with restaurants and consumers. Next, we conducted two factorial survey experiments with restaurants (N = 176) and consumers (N = 245) in Germany to quantitatively test the effects of those system attributes on their adoption intentions.FindingsThis paper highlights that the role of access-based triadic system providers as both the owners of shared assets and the operators of a triadic system is associated with a novel set of challenges and opportunities: System providers need to attract a critical mass of business and end customers while balancing asset protection and system complexity. At the same time, asset ownership introduces opportunities for improved quality control and differentiation from competition.Originality/valueConceptually, this paper extends research on access-based services and triadic frameworks by describing an unexplored hybrid form of non-ownership consumption we call “access-based triadic systems.” Empirically, this paper addresses the need to account for the demands of two distinct target groups in triadic systems and demonstrates how factorial survey experiments can be leveraged in this field.

Does she belong here? Women in leadership positions and organizational performance in gendered institutions

AbstractGender diversity in leadership positions may not always bring desirable outcomes for an organization as diversity researchers have argued. Female leaders are less likely to contribute to effectiveness of their organization when it is male‐dominated and has strong masculine culture. We tested a nonlinear relationship between gender diversity at the top and organizational performance and the moderating effect of a female critical mass in an organization. Time‐series data were collected from state‐owned enterprises and quasi‐governmental organizations affiliated with the Korean government and were analyzed through fixed‐effects panel regressions. The results show that gender diversity on executive boards has an inverted U‐shaped relationship with organizational performance. The positive effect of gender diversity on executive boards on organizational performance increases up to a certain level, beyond which the diversity effect turns negative. Curvilinear relationships were found to be flatter in more gender‐balanced organizational settings, suggesting that the negative effect of gender diversity at the top is likely to increase to a lesser extent than in male‐skewed settings.

Towards reusable building blocks for agent-based modelling and theory development

Despite the increasing use of standards for documenting and testing agent-based models (ABMs) and sharing of open access code, most ABMs are still developed from scratch. This is not only inefficient, but also leads to ad hoc and often inconsistent implementations of the same theories in computational code and delays progress in the exploration of the functioning of complex social-ecological systems (SES). We argue that reusable building blocks (RBBs) known from professional software development can mitigate these issues. An RBB is a submodel that represents a particular mechanism or process that is relevant across many ABMs in an application domain, such as plant competition in vegetation models, or reinforcement learning in a behavioural model. RBBs need to be distinguished from modules, which represent entire subsystems and include more than one mechanism and process. While linking modules faces the same challenges as integrating different models in general, RBBs are “atomic” enough to be more easily re-used in different contexts. We describe and provide examples from different domains for how and why building blocks are used in software development, and the benefits of doing so for the ABM community and to individual modellers. We propose a template to guide the development and publication of RBBs and provide example RBBs that use this template. Most importantly, we propose and initiate a strategy for community-based development, sharing and use of RBBs. Individual modellers can have a much greater impact in their field with an RBB than with a single paper, while the community will benefit from increased coherence, facilitating the development of theory for both the behaviour of agents and the systems they form. We invite peers to upload and share their RBBs via our website - preferably referenced by a DOI (digital object identifier obtained e.g. via Zenodo). After a critical mass of candidate RBBs has accumulated, feedback and discussion can take place and both the template and the scope of the envisioned platform can be improved.

Cultural-linguistic diversity in Italy and Sweden? A sociomaterial analysis of policies for heritage language education

ABSTRACT In this paper, we critically discuss the impact of policy documents on the construction of national narratives on the provision of support for cultural-linguistic diversity in education systems in two European countries. The analysis focuses upon a selection of national policy documents that deal with the planning and provision of HLE since the 1990s. We take critical pedagogy and sociomateriality as theoretical lenses to investigate educational policies on HLE. Thus, this study critically traces the ways in which language ideologies are enmeshed with legislative, political and educational discourses by following an inductive and retroductive process, wherein key-concepts, themes and critical configurations of HLE are mapped, compared, re-assembled and discussed in terms of a complex system. The analysis shows that the (non-)provision of HLE shapes the educational space and the value references and world views that prevail and are (re)produced in it. Emerging deficit perspectives, linguistic assimilation and marginalisation processes limit the path towards more inclusive and equitable educational institutions and practices.

Evaluated Material Attractiveness of Plutonium Composition from Economic Simplified Boiling Water Reactor (ESBWR)

The potential for misuse of nuclear fuel has prompted many to make efforts to prevent a country from acquiring nuclear explosive devices (weapons). Weapon utility equated with nuclear material attractiveness when applied to protection and security. Material attractiveness evaluated using an equation first developed by Masaki Saito, namely ATTR. ESBWR is one of the reactors of the BWR reactor type that is still operating. The purpose of this study is to evaluate Material Attractiveness based on the composition of plutonium in the ESBWR reactor, during reactor operation and after reactor operation. The ATTR concept utilizes the plutonium isotope composition to evaluate the material attractiveness aspect. Parameters such as BCM, Rossi-alpha, and neutron prompt life become additional aspects in evaluating material attractiveness. In the research results, the ATTR value decreased from the beginning of reactor operation until the reactor stopped operating. At the beginning of the reactor operation, it was categorizing as a weapon-grade with an ATTR value of 0.19 and when the reactor stopped operating it was categorizing as an unusable grade with an ATTR value of 0.012. At the time of cooling time up to 1x106 (one million) cooling time, the ATTR value increases by 0.019 which was categorizing as an unusable grade. After a cooling time of 1x106 (one million) years up to 1x107 (ten million) years, the ATTR value was 0.001 which categorized as an exempt level. This states that the increasing burnup value will further reduce the ATTR value. Likewise with the Rossi-Alpha and Bare Critical Mass values. Conversely, it will decrease the value of neutron lifetime. The ATTR value after the reactor operates up to one hundred years of cooling time increases and then decreases significantly after 1x106 (one million) years due to the half-life of plutonium isotopes. Likewise, the Rossi-Alpha and Bare critical mass values. However, it is different with the neutron fast lifetime.

Dynamic mode characteristics of flow instabilities in a single-stage compressor under different throttling processes

To investigate the influence of throttling processes on dynamic characteristics of compressor stability, the rotating stall development of National Aeronautics and Space Administration Stage 35 was simulated with full-annulus Unsteady Reynolds-Averaged Navier–Stokes under different throttling processes. The numerical methods were verified. By combining Dynamic Mode Decomposition and flow field evolution research, the flow structures and dynamic characteristics of “critical mass flow” under different throttling processes were deeply studied; the flow mechanism of flow instabilities under different throttling processes was explored. It is found that the “critical mass flow” corresponds to the beginning of a rapid decrease in mass flow, mainly characterized by shock forward movement and a larger range of spillage flow. Around “critical mass flow,” if the throttle is still tightening, it presents stall pattern 2; otherwise, it presents stall pattern 1. During the pre-stall, both patterns are dominated by tip clearance vortex (TCV)-shock interference. Stall inception disturbance is generated from TCV-shock interference; pattern 1 presents a single disturbance, while pattern 2 presents multiple disturbances. Subsequently, the TCV-shock interference gradually weakens. The single stall disturbance of pattern 1 gradually develops and stabilizes. The multiple stall disturbances in pattern 2 undergo processes including fusion and disappearance, ultimately developing into a single stall cell. During the stable stall, the throttling processes have no significant impact on the speed of the stall cell, and the flow in the un-stalled region is basically consistent with the speedline. However, the tighter the throttle is, the larger the stalled region, and the weaker the flow capacity of the un-stalled region.

Ontogenetic changes in the mechanical stability of the main species of woody plants in the ecosystems of the city of Donetsk

The paper considers the issues of ontogenetic changes in the mechanical stability of 18 species of woody plants growing in the ecosystems of the industrial city of Donetsk: Acer campestre L., Acer negundo L., Acer platanoides L., Acer pseudoplatanus L., Acer saccharinum L., Aesculus hippocastanum L., Betula pendula Roth, Fraxinus excelsior L., Fraxinus lanceolata Borkh., Gleditsia triacanthos L., Populus simonii Carriere, Populus nigra L., Populus balsamifera L., Populus bolleana Lauche, Quercus robur L., Robinia pseudoacacia L., Tilia cordata Mill., Ulmus laevis Pall. It has been established that at the initial stages of the ontogenesis of woody plants, their biomechanics ensures survival through high flexibility. This is due to the low critical mass and load, which are easily achieved when static and dynamic factors act on the plant. Only a significant increase in linear dimensions makes it possible to maintain its own mass weighing several tons and above, as well as withstand the effects of adverse climatic factors. The studied ontogenetic dependences of the mechanical stability of the main species of woody plants in the ecosystems of the city of Donetsk should be used in landscaping the city.

Evolution of the Angular Momentum of Molecular Cloud Cores in Magnetized Molecular Filaments

The angular momentum of molecular cloud cores plays a key role in the star formation process. However, the evolution of the angular momentum of molecular cloud cores formed in magnetized molecular filaments is still unclear. In this paper, we perform 3D magnetohydrodynamics simulations to reveal the effect of the magnetic field on the evolution of the angular momentum of molecular cloud cores formed through filament fragmentation. As a result, we find that the angular momentum decreases by 30% and 50% at the mass scale of 1 M ⊙ in the case of weak and strong magnetic field, respectively. By analyzing the torques exerted on fluid elements, we identify the magnetic tension as the dominant process for angular momentum transfer for mass scales ≲3 M ⊙ for the strong magnetic field case. This critical mass scale can be understood semianalytically as the timescale of magnetic braking. We show that the anisotropy of the angular momentum transfer due to the presence of a strong magnetic field changes the resultant angular momentum of the core only by a factor of 2. We also find that the distribution of the angle between the rotation axis and the magnetic field does not show strong alignment even just before the first core formation. Our results also indicate that the variety of the angular momentum of the cores is inherited from the difference in the phase of the initial turbulent velocity field. The variety could contribute to the diversity in size and other properties of protoplanetary disks recently reported by observations.

Mastering geographically weighted regression: key considerations for building a robust model.

Geographically weighted regression (GWR) takes a prominent role in spatial regression analysis, providing a nuanced perspective on the intricate interplay of variables within geographical landscapes (Brunsdon et al., 1998). However, it is essential to have a strong rationale for employing GWR, either as an addition to, or a complementary analysis alongside, non-spatial (global) regression models (Kiani, Mamiya et al., 2023). Moreover, the proper selection of bandwidth, weighting function or kernel types, and variable choices constitute the most critical configurations in GWR analysis (Wheeler, 2021). [...].

A hybrid feature selection model for identifying groups of critical elements in aero‐engine assembly

AbstractAero‐engine assembly has a wide range of indicators, and finding critical assembly elements to guide assembly and troubleshooting is essential in improving the reliability and safety of aero‐engine. In order to identify critical elements in aero‐engine assembly components, this study aims to establish a two‐stage hybrid feature selection model, namely, FSBP approach, which integrated filter method and particle swarm algorithm with Bayesian optimization. Specifically, individual filter feature selection methods are compared to select a relatively effective method to reduce the data dimensions and ensure the quality of the initial subset. Then, the particle swarm algorithm combined with Bayesian optimization obtains a subset of features in the second stage that are more suitable for predictive models with more robust classification prediction capability. The algorithm is successfully applied to real aero‐engine assembly and trial test datasets, and the experimental results show that our proposed two‐stage hybrid feature selection model outperforms other benchmark methods.