Subcritical Research Articles

Advances in Oxygen Isotope Analysis of Phosphate by Electrospray Orbitrap Mass Spectrometry for Studying the Microbial Metabolism of Microorganisms.

Understanding the impact of human activities on the metabolic state of soil and aquatic environments is of paramount importance to implement measures for maintaining ecosystem services. Variations of natural abundance 18O/16O ratios in phosphate have been proposed as proxies for the holistic assessment of metabolic activity given the crucial importance of phosphoryl transfer reactions in fundamental biological processes. However, instrumental and procedural limitations inherent to oxygen isotope analysis in phosphate and organophosphorus compounds have so far limited the stable isotope-based evaluation of metabolic processes. Here, we discuss how recent developments in Orbitrap high resolution mass spectrometry enable measurements of 18O/16O ratios in phosphate and outline the critical mass spectrometry parameters for accurate and precise analysis. Subsequently, we evaluate the types of 18O kinetic isotope effects of phosphoryl transfer reactions and illustrate how novel analytical approaches will give rise to an improved understanding of 18O/16O ratio variations from biochemical processes affecting the microbial phosphorus metabolism.

Perspectives from students and teachers about the challenges of teaching and learning STEM subjects in Ghana

Ghana has recently renewed its commitment to build a strong Science, Technology, and Innovation (STI) base for improved socio-economic development. This commitment hinges on recognizing that the strength of the nation’s STI policy depends on the quality of pre-tertiary education and training in science and mathematics to produce a critical mass of young people well-prepared for Science, Technology, Engineering, and Mathematics (STEM) courses at the tertiary level. However, despite numerous interventions to improve upon STI, Ghana still performs poorly, along with other Sub-Sahara Africa (SSA) countries with common STI indicators in the Global Innovation Index. Using Ghana as a lens, this article highlights the challenges in STEM teaching and learning throughout the sub-region. The qualitative research approach was adopted to allow an in-depth exploration of participants’ perspectives. Six pre-tertiary schools (three Junior High Schools and three Senior High Schools) and the University of Ghana, Legon, were selected due to the availability of their students and teachers to participate in the interviews in Accra, the capital city. This article argues that, to develop the critical mass of human capital needed for sustainable development, there is a need to improve the performance of students in STEM subjects at the pre-tertiary level. In addition, performance improvement, which is linked to student interest in the study of STEM subjects, should increase the quality of students entering tertiary education institutions. These students will then be trained to meet the quality of human resources needed to run the STI system—a step toward achieving sustainable development this article recommends the redesign of STEM curriculum at the pre-tertiary level to align with tertiary STEM education as that in turn aligns with Ghana’s STI system.

Are Women Commissioners More Compassionate Spenders? Evidence From Florida County Governments

While the number of women in government has increased, prior research on whether enhancing women's political representation alters policy choices has produced inconclusive findings. This study asks if higher women's participation in electoral institutions at the local level is associated with a different spending profile. Using Peterson’s typology of developmental, redistributive, and allocational government programs, we argue that legislative bodies with more female members will spend more on redistributive programs than on developmental or allocational. Using data from Florida's 67 counties between 2005 and 2015, our analysis supports this theoretical expectation. In line with critical mass theory, women's representation in county commissions must reach a threshold of about 33% to sway budgetary decision-making toward more extensive redistribution. We also find that the traditional commission form of government intensifies the redistributive effect of women commissioners on county spending while having a home rule charter has no significant effect.

Progressive Collapse of Typical and Atypical Reinforced Concrete Framed Buildings

This paper investigates the progressive collapse potential of eight-story reinforced concrete framed buildings with several atypical structural configurations and compares results with a typical structural configuration. The alternative load path mechanism, the linear-static analysis procedure amplified by dynamic increase factors, and the demand capacity ratio criterion limits from the U.S. General Services Administration guideline were used to evaluate the vulnerability of the different atypical and typical framed structures. Variations in bay size, plan irregularity, and closely spaced columns were used to represent the atypical structural configurations. The extracted demand-capacity ratio (DCR) of the global structural response showed that the demand-capacity ratio for the longitudinal frame with short-span beams had a larger DCR than the transverse frame with longer beam spans with significant potential for progressive collapse. Furthermore, atypical building configurations with closely spaced columns failed by shear and showed the highest DCR limits. In addition to the global structural response, the local member end actions were also evaluated. The evaluation showed that the critical atypical frame configuration with closely spaced columns had a 91% and 127% maximum shear force and support bending moment value difference, respectively, when compared to a baseline typical frame configuration.

Explosive Cooperation in Social Dilemmas on Higher-Order Networks.

Understanding how cooperative behaviors can emerge from competitive interactions is an open problem in biology and social sciences. While interactions are usually modeled as pairwise networks, the units of many real-world systems can also interact in groups of three or more. Here, we introduce a general framework to extend pairwise games to higher-order networks. By studying social dilemmas on hypergraphs with a tunable structure, we find an explosive transition to cooperation triggered by a critical number of higher-order games. The associated bistable regime implies that an initial critical mass of cooperators is also required for the emergence of prosocial behavior. Our results show that higher-order interactions provide a novel explanation for the survival of cooperation.

Advancing nuclear science education through IRL Integration: A case experiment on criticality mass determination at the Kartini research reactor

Research reactors serve critical roles across multiple domains—from physics to medicine—while distinctly not being used for electrical power generation. The Kartini Research Reactor located in Indonesia exemplifies the integration of research reactors in education and scientific research, particularly highlighting its educational applications through the Internet Reactor Laboratory (IRL). Established in 1978 and operational since 1979, the Training Research and Isotope Production by General Atomic (TRIGA) Mark II reactor is instrumental in advancing nuclear science with facilities like the Lazy Suzan/Rotate Rack and Beam Port. The IRL significantly enhances its educational process, enabling remote access to reactor physics experiments, thus facilitating global university participation in nuclear engineering education. This capability allows for the real-time visualization of reactor operations and detailed presentation of operational data and experiment results, enriching the learning experience. This paper demonstrates the Kartini Reactor's educational utility through a case study investigating reactor criticality and determining the critical fuel mass under safe operational parameters. Employing telecommunication hardware and software, the study achieved reactor criticality by inserting 5 fuel elements, totaling 2524.57 g. The critical mass determination was further refined by plotting the inverse of counts against the total mass of U-235. This approach utilized both polynomial and linear trend lines to analyze the data. While the polynomial analysis provided upper and lower thresholds for critical mass, the linear regression offered a precise critical mass value of 2428.62 g, showcasing a deviation of only 4% from the experimental findings.

Effects of lubricant rheology and flow turbulence on the dynamic properties of hydrodynamic bearing

The present numerical investigation, which takes into account the coexisted consequence of the turbulence domain and non-Newtonian flow rheology, predicts the dynamic properties of a finite hydrodynamic bearing. Under the proper flow boundary conditions, the turbulence (linear) and non-Newtonian hypotheses have revised the Continuity and Navier–Stokes equation. The finite element approach is acclimated to calculate the clearance extent of the finite hydrodynamic bearing using the Galerkin approach and a sturdy iteration strategy. The cylindrical coordinate's versions of continuity and momentum equations are bestowed for the lubricant field of the finite hydrodynamic bearing, postulating the turbulence domain and non-Newtonian flow rheology. Dynamic properties of a finite hydrodynamic bearing have been enumerated using cross-coupled and direct lubricant-film bearing coefficients, whirl ratio and critical mass at various eccentricity ratios for different ranges of Reynolds numbers and different values of flow behavior index of the non-Newtonian rheological model. In comparison to perfect turbulence and non-Newtonian rheological status, the mixed regime demonstrated improved properties. The direct and cross-coupled lubricant-film bearing coefficients are improved by 12.28% and 20.85% respectively while critical mass is enhanced by 20.55% at selected values of Reynolds number and power-law index. The proposed severe fluid film domain improves the stability of finite hydrodynamic bearings significantly.

Global existence and aggregation of chemotaxis–fluid systems in dimension two

This paper investigates the coupled Patlak–Keller–Segel–Navier–Stokes (PKS–NS) system in two-dimensional bounded domains with a focus on global well-posedness and the formation of striking patterns, in which the boundary conditions are Neumann conditions for the cell density and the chemical concentration, and the Navier slip boundary condition with zero friction for the fluid velocity. We prove that the solution of the system exists globally in time in the case of subcritical mass. Concerning the critical mass case, we construct the boundary spot steady states rigorously via the inner-outer gluing method.While studying the global existence and the concentration phenomenon of the chemotaxis–fluid model, we develop the global W2,p theory for the 2D stationary Stokes system subject to Navier boundary conditions with zero friction and further establish semigroup estimates of the nonstationary counterpart by analyzing the Stokes eigenvalue problem.

Optimal fissile distribution in multiplying systems: Illustrative examples with Monte Carlo simulation and Pontryagin’s maximum principle

In multiplying systems, such as nuclear reactors and criticality experiments, it is desirable to place the fissile material in the optimal or ‘best’ way to reduce the critical mass of the system as well as to achieve uniform fuel burnup. This paper considers two methods, namely Pontryagin’s maximum principle (PMP) and Monte Carlo (MC) perturbation for estimating a minimum critical mass configuration. These methods are applied to an elementary multizone model of a pressurized water reactor (PWR) and a criticality experiment to estimate the minimum critical mass. It is found that while two-group diffusion theory with PMP predicts a minimum critical mass, more detailed MC simulations with MCNP5 show a consistent reduction in critical mass when fissile fuel is placed in inner zones. Such a distribution reduces the fissile material requirement but is undesirable due to the higher power peaking. MC simulations show that for a three-zone model of the KORI 1 PWR, a uniform fissile distribution gives criticality for 1.09 atomic percent (at.%) enrichment, whereas non-uniform fissile distribution (0.6, 1.6, 0.6 at.%) reduces the critical mass by 14%. The changes found from MC simulations were subsequently predicted from first- and second-order derivative sampling. It was found that substantial computational savings can be achieved for large-scale optimization problems. In the case of a criticality experiment, MC derivative sampling was also used to estimate optimal fissile distribution for minimizing the critical mass.

Beyond conventions: Unravelling perceived value's role in shaping digital-only banks' adoption

Advancements in FinTech and Industry 4.0 have made digital financial services more convenient and cost-effective, leading customers to expect them to be fun and offer higher perceived value. Therefore, this research investigates the determinants of digital-only banks' perceived value and its mediating role on the relationship between behavioural intention determinants and the intention to adopt digital-only banks. The data was collected through an online survey conducted among Klang Valley residents. Stratified random sampling was used to gather the data and structural equation modelling (SEM) was applied for the data analysis. The findings revealed that perceived value is a significant predictor of the intention to adopt digital-only banks. Furthermore, perceived convenience, economic efficiency, functional risk, trust, and environmental concern determined the perceived value of digital-only banks. However, security risk, critical mass, and number of services were non-significant predictors of perceived value. Notably, perceived value plays a significant mediating role between certain determinants and adoption intention. This research adds value by revealing multifaceted determinants of perceived value and incorporating environmental concern that highlights the significance of green perceived value in shaping adoption intention. Furthermore, it provides empirical results on a research gap related to digital-only banks' perceived value mediating effect on the intention to adopt these banks. Finally, the study can assist the practitioners of digital-only banks in attracting and retaining users in this modern competitive banking and financial market.

The Cumulative Effects of Marketized Care

Abstract Care is increasingly marketized. Previous marketing and consumer research has focused on specific tensions underlying marketized care provision and the ways in which consumers navigate them. In contrast, this conceptual article draws on interdisciplinary research on care to develop a cumulative understanding of marketized care, that is, based on those effects that build up over time when a critical mass of consumers routinely addresses care needs via markets. Defining marketized care as attending to the welfare needs of human and nonhuman others through the market, we identify four negative cumulative effects: individuating effects on consumer subjectivities, alienating effects on care relationships, responsibilizing effects on consumers as opposed to other institutional actors of care provision, and exploitative effects generated in global care and supply chains. We also outline four principles that can mitigate these effects: interdependent consumer autonomy, affective reconnections, proportionate responsibilization, and market reconfiguration. Our conceptualization moves the literature on marketized care forward by outlining its cumulative nature as well as offering potential solutions that are neither demonizing nor celebratory of markets. In doing so, we offer a series of generative insights for research on marketized care that contribute to addressing collective human and nonhuman flourishing.

Women on Board and ESG Performance: Insights from the Italian Utilities Sector

The purpose of this paper is to investigate the relationship between gender diversity and environmental, social and governance (ESG) performance in the Italian utilities sector. The study examines whether the presence of women on the board of directors (BoD) is related to ESG dimensions. We analyzed a sample of 482 utility companies for the period 2018-2022 and we developed an econometric model applying unbalanced panel regression data with firm fixed effects and controls per year. Within a multivariate regression model, the authors considered the ESG score provided by Refinitiv Eikon to test the research hypotheses. Findings show that the presence of women on board of directors improves ESG performance when a critical mass of female board members (at least three) is reached. A critical threshold of female directors also positively influences the scoring of environmental and social pillars. From a managerial perspective this study draws attention to BoD composition encouraging utility companies to define internal corporate governance mechanisms thoroughly. The overall findings support managers, policy makers and regulators on how to improve ESG performance through gender diversity on BoD. This paper offers an in-depth examination of the ESG practices of utility firms, and it attempts to bridge the gap in prior literature on the determinants of ESG performance in the Italian utilities sector. This study is the first that investigates the relationship between board gender diversity and ESG performance in such a context exploring how a critical mass of women on BoD affects ESG dimensions.

Critical Size of Silver Iodide Containing Glaciogenic Cloud Seeding Particles

AbstractCloud seeding is considered a practical but unproved method to enhance precipitation or suppress hail, due to insufficient knowledge of ice formation and evolution after seeding clouds with ice nucleating particles. This study investigates the size effects on the immersion freezing of aerosol produced from commercial silver iodide (AgI) containing flares at mixed‐phase cloud temperatures from 243 to 267 K. Flare‐generated aerosol exhibited comparable ice nucleation ability (INA) to pure AgI particles in the size range of 200 and 400 nm. Non‐AgI impurities reduced the INA of flare‐generated particles ≤90 nm, which is lower than pure AgI particles ≤40 nm. The critical mass ice‐active site density of the generated aerosols (critical‐nm) was derived, indicating the minimum mass of AgI particles required for efficient ice nucleation. The new parameterization to predict critical‐nm can serve as a reference to optimize the effectiveness of cloud‐seeding materials for practical use.

Origin of Melt Memory Effects in Poly(ethylene oxide): The Crucial Role of Entanglements.

The melt memory effect on crystallization is an intriguing phenomenon displayed by semicrystalline polymers, as opposed to low molar mass molecules. It concerns the effect of melt temperature on nucleation upon recrystallization. Typically, polymer crystals must be considerably superheated to erase the effect of previous morphology on the subsequent crystallization, avoiding an acceleration of the process. Despite being known for decades, its origin is still not fully understood. Investigating model poly(ethylene oxide) covering a wide range of molar mass, it is demonstrated that melt memory originates from topological constraints among the chains, i.e., entanglements, for PEO in which weak intermolecular interactions are present due to the ether groups. In fact, no memory is observed for samples below the critical molar mass for the formation of entanglements (about 1 kg mol-1). The increase in molar mass raises the number of entanglements and induces the formation of folded chains crystals, both factors leading to a topologically complex amorphous phase, enhancing the melt memory effect. The molecular origin of the melt memory effect in polymers with weak intermolecular interactions is thus ascribed to a slower isotropization in the melt of the chain segments originally contained in the crystals, due to the presence of entanglements among the chains. This study defines the distinction between small molecules and polymers from the point of view of melt memory.

Are women greener? Board gender diversity and corporate green technology innovation in China

This article investigates how board gender diversity impacts corporate green technology innovation, and whether regional gender contexts as well as corporate financial constraints moderate this relationship. Using a panel of 20,834 firm-year observations of China, the results indicate a statistically significant positive association between board gender diversity and corporate green technology innovation. Specifically, the study finds that boards with three or more female directors have a stronger positive effect on green technology innovation than boards with two or fewer female directors, in line with the critical mass theory. Besides, the result shows that the effect of female executive directors outweighs that of female independent directors. Further, the positive association between female directors and green technology innovation is found to be more pronounced in firms located in regions with higher levels of gender equality and higher proportions of women in politics, while financial constraints act to alleviate the extent of the positive relationship. Additionally, female directors play a potent role in reducing corporate carbon emissions, particularly for high-polluting firms and those located in regions with stricter environmental regulation. The key results remain unchanged after correcting for endogeneity concern. Overall, this study has substantial practical implications and provides valuable insights for managers and policymakers regarding the contribution of female leadership in enhancing corporate environmental performance.

Constructing a cut-off dam inside a water-filled circular tunnel with backfill grouting

This study employs laboratory model tests for backfill grouting and numerical analyses (coupled analysis of the discrete element method and computational fluid dynamics, DEM-CFD coupling analysis) to investigate the feasibility of constructing a cut-off dam inside a water-filled circular tunnel using the backfill grouting method from the ground surface. Several improved backfill methods were studied to enhance the effectiveness of the cut-off dam. These methods include: (a) adding an additional backfill grouting hole between the double-row cut-off dam and applying pressurized grouting; (b) adjusting the number of backfill grouting holes per row of the cut-off dam; (c) simultaneously grouting the double-row cut-off dams to minimize the formation of interface fissures and voids; (d) adjusting the grout hole spacing of the double-row cut-off dams to reduce the volume of backfill material. Additionally, pressurized mortar grouting is a critical mass to ensure the water tightness of the cut-off dam. The implementation of these backfilling arrangements improves the effectiveness and watertight of the cut-off dam, thereby reducing the construction time and cost. The findings of this study can serve as a reference for water-filled tunnels and subsequent rehabilitation works in the future.

Reproducible Benchmark for the SNAP 8 Experimental Reactor at Dry Conditions

This work provides fully reproducible benchmark models of the Systems for Nuclear Auxiliary Power (SNAP) 8 Experimental Reactor. Validation benchmarks of the criticality configuration experiments under dry conditions with no coolant are presented. In addition, relevant reactivity worth experiments, and measurement of power distributions are validated and presented here. Discrepancies between modeled and experimental results are at most 110 pcm for fuel and poison worths, and critical configurations that do not manipulate control elements are within 50 pcm. Larger discrepancies found in reflector element worth experiments are due to experimental methodology which was noted as being simplified due to limited calculational capabilities at the time, while discrepancy in the control element manipulated critical configuration is due the absence of structural components for modeling simplification. Power distributions closely follow what was observed in experiment with expected peaking in reflecting elements. All models are well documented with cited references describing and justifying assumptions, simplifications, and adjustments to reproduce the models with any nuclear safety codes; model inputs and outputs are stored in the snapReactors GitHub repository.

Forschungs-, Technologie- und Innovationspolitik muss die Entstehung kritischer Massen fördern

Abstract Economic research emphasises the role of increasing returns to scale and critical mass in research and technology development. This suggests that countries benefit from specialising in certain technologies and can thereby bundle available resources. Using the example of the Exzellenzstrategie and the Zukunftsstrategie, we argue that German RTI policy lacks strategic prioritisation. The lack of focus implies that Germany spreads its resources too thinly over many technological alternatives and therefore fails to create critical mass within each of them. The guiding principles for a German RTI policy should focus on creating critical mass through specialisation..

The application of the "inverse problem" method for constructing confining potentials that make N-soliton waveforms exact solutions in the Gross-Pitaevskii equation.

In this work, we discuss an application of the "inverse problem" method to find the external trapping potential, which has particular N trapped soliton-like solutions of the Gross-Pitaevskii equation (GPE) also known as the cubic nonlinear Schrödinger equation (NLSE). This inverse method assumes particular forms for the trapped soliton wave function, which then determines the (unique) external (confining) potential. The latter renders these assumed waveforms exact solutions of the GPE (NLSE) for both attractive (g<0) and repulsive (g>0) self-interactions. For both signs of g, we discuss the stability with respect to self-similar deformations and translations. For g<0, a critical mass Mc or equivalently the number of particles for instabilities to arise can often be found analytically. On the other hand, for the case with g>0 corresponding to repulsive self-interactions which is often discussed in the atomic physics realm of Bose-Einstein condensates, the bound solutions are found to be always stable. For g<0, we also determine the critical mass numerically by using linear stability or Bogoliubov-de Gennes analysis, and compare these results with our analytic estimates. Various analytic forms for the trapped N-soliton solutions in one, two, and three spatial dimensions are discussed, including sums of Gaussians or higher-order eigenfunctions of the harmonic oscillator Hamiltonian.

Expert‐in‐the‐loop design of integral nuclear data experiments

AbstractNuclear data are fundamental inputs to radiation transport codes used for reactor design and criticality safety. The design of experiments to reduce nuclear data uncertainty has been a challenge for many years, but advances in the sensitivity calculations of radiation transport codes within the last two decades have made optimal experimental design possible. The design of integral nuclear experiments poses numerous challenges not emphasized in classical optimal design, in particular, constrained design spaces (in both a statistical and engineering sense), severely under‐determined systems, and optimality uncertainty. We present a design pipeline to optimize critical experiments that uses constrained Bayesian optimization within an iterative expert‐in‐the‐loop framework. We show a successfully completed experiment campaign designed with this framework that involved two critical configurations and multiple measurements that targeted compensating errors in 239Pu nuclear data.