Search Results (16)

Between 1959 and 1962, Alvin Scodel, J. Sayer Minas, and colleagues conducted some of the earliest laboratory studies of strategic interaction using non-zero-sum games. Working at the margins of economics in the Journal of Conflict Resolution, they documented a striking pattern: subjects frequently chose options that reduced an opponent’s payoff by more than their own, even when mutual cooperation was both individually and collectively optimal. These results—especially the behavior observed in their so-called Game H4, a Harmony Game in which cooperation strictly dominated defection—anticipate a central insight of evolutionary game theory: what matters for adaptation is relative payoff, not absolute gain. This essay reinterprets the Scodel–Minas experiments through a Darwinian lens, arguing that they provide an early empirical challenge to Nash-equilibrium reasoning and to models that evaluate strategies solely in terms of absolute utility. By reconstructing the H4 payoff structure and embedding it within a simple evolutionary framework, I show how small levels of “competitive” behavior can destabilize cooperative equilibria that appear self-evident under standard assumptions. I then revisit three later “puzzles” in the evolution of cooperation—altruistic punishment, the fragility of “win–win” treaties, and rejections in ultimatum bargaining—to ask how differently they might have been framed had the Scodel–Minas findings been part of the canonical experimental literature. Rather than treating these phenomena as surprising anomalies, a historically informed, relative-payoff perspective suggests that they could have been recognized much earlier as natural expressions of an already documented pattern. Full article

This review systematizes data on the phase composition and key properties of compounds in the W–B system, including thermodynamic stability, crystal structure, and hardness. The current understanding of the binary W–B phase diagram and the stability of individual borides is discussed, alongside the influence of defects and non-stoichiometry on their properties. The main methods for synthesizing these materials and producing coatings based on them are summarized. Potential applications of tungsten borides are highlighted, particularly for high-temperature environments, cutting tools, and protective and functional coatings. Finally, key directions for future research are outlined, focusing on the refinement of phase equilibria, the scaling of production methods, and the development of W–B-based materials with tailored performance characteristics. Full article

We investigate the discrete energy behavior and long-time stability of a second-order Crank–Nicolson mixed finite element discretization for the shallow water equations with nonlinear bottom friction. The method combines a compatible ${\mathrm{BDM}}_1$–${\mathrm{DG}}_0$ spatial approximation with a skew-symmetric formulation of the advective terms and a midpoint treatment of dissipative source terms. At the fully discrete level, we derive a precise mechanical energy identity showing that the scheme is energy-consistent;the discrete energy satisfies a balance law consisting of a nonnegative frictional dissipation term and a higher-order midpoint defect of the order $\mathcal{O}(\Delta t^3)$. Although the method is not unconditionally energy-dissipative, we prove that strict Lyapunov decay holds under a mild CFL-type restriction on the time step. Furthermore, we establish uniform long-time boundedness of the discrete energy and asymptotic recovery of the continuous dissipation law as $\Delta t\to 0$. We also analyze the interaction between nonlinear solver tolerances and energy diagnostics, showing that the observed positive energy increments are controlled, non-accumulating, and intrinsic to the midpoint quadrature structure rather than solver artifacts. The scheme is proven to be precisely well balanced for lake-at-rest equilibria, including nonlinear bottom friction. Comprehensive numerical experiments confirm second-order temporal accuracy, robustness under friction, asymptotic monotonicity under time step refinement, and strict equilibrium preservation. The results provide a rigorous energy-diagnostic framework clarifying when Crank–Nicolson schemes are physically reliable despite the absence of unconditional discrete dissipation. Full article

The objective of this paper is to find new dynamic perspectives in a well-known two dimensional nonlinear system which is a modification of the phosphofructo kinase model by incorporating recycling of the product, $p$, into the substrate, $s$. Specifically, we investigate the affect of the negative cooperativity on the number of equilibria and their stability. Moreover, in the parameter space, we analyze analytically and numerically the number of periodic oscillations (solutions) and their stability using Lyapunov coefficients (in other words, quantities and focus values). Thus, we obtain that three different dynamical conditions (regimes) take place: (1) structurally unstable, (2) the existence of an unstable limit cycle with an external stable limit cycle, and (3) the existence of a stable limit cycle with an external unstable limit cycle. Moreover, for a zero rate of product synthesis (due to e.g., defective enzyme), we obtain that the modified system has a first integral. Full article

Perovskite-type proton conductors exist in two structural forms, ABO₃ and ${\mathrm{A}}_2{\mathrm{B}}^{\prime }{\mathrm{B}}^{″}{\mathrm{O}}_6$. In this study, novel A-site double-perovskite proton conductors (${\mathrm{A}}^{\prime }{\mathrm{A}}^{″}{\mathrm{B}}_2{\mathrm{O}}_6$) were proposed. Na_1+xLa_1-xZr₂O_6-δ (x = 0, 0.1, 0.2) perovskites were prepared by a solid-state reaction at 1200 °C. However, raising the sintering temperature to 1300 °C resulted in the Na to volatilize, converting the Na_1.1La_0.9Zr₂O_6-δ into La_0.9Zr₂O_6-δ. The conductivities of these materials in a humid atmosphere were tested using electrochemical impedance spectroscopy, and their carrier transport numbers were measured using the defect equilibria model and concentration cell method. Na_1.1La_0.9Zr₂O_6-δ and Na_1.2La_0.8Zr₂O_6-δ are predominantly proton conductors, with Na_1.1La_0.9Zr₂O_6-δ exhibiting the highest proton transport number of 0.52 at 800 °C. In contrast, NaLaZr₂O₆ is predominantly an electronic conductor, while La_0.9Zr₂O_6-δ functions as an oxide ion conductor. Due to their high protonic transport numbers, these Na_1+xLa_1-xZr₂O_6-δ A-site double-perovskite oxides present a promising avenue for the development of proton conductors. Full article

Background: Molar incisor hypomineralization (MIH) is a qualitative, demarcated enamel defect of hypomineralization affecting one to four first permanent molars, often with incisor involvement. Its etiology is complex. However, evidence suggests the influence of genetic factors, potentially including the single nucleotide polymorphisms (SNPs) rs2889956, rs4811117 and rs13058467, which were previously linked to MIH in a genome-wide association study of German children. The aim was to replicate analyses of possible associations between the SNPs and molar incisor hypomineralization in Polish children. Methods: The final study group consisted of 778 children aged 126–168 months old. Saliva samples were taken, and genomic DNA was extracted and genotyped using beadchip microarrays. Results: Among the 778 subjects, there were 68 (8.7%) subjects with MIH and 710 (91.3%) subjects without MIH. There were no significant differences in distributions in age, sex, or the frequency of caries in permanent dentition between the MIH and non-MIH groups. The rs2889956, rs4811117, and rs13058467 genotype distributions in the studied group conformed to the expected Hardy–Weinberg equilibria, and there were no significant differences in the distributions of their alleles or genotypes between the MIH and non-MIH groups. Conclusion: Our replication study did not confirm highly significant associations between the single nucleotide polymorphisms rs2889956, rs4811117, and rs13058467 with molar incisor hypomineralization in Polish children. Full article

The differential scanning calorimetry study showed that the double perovskite HoBaCo₂O_6-δ (HBC), depending on its oxygen content, undergoes three phase transitions in the temperature range 298–773 K. Their origin was tentatively explained using the relevant literature data. For the single-phase tetragonal HBC, the oxygen nonstoichiometry dependences on the oxygen partial pressure were investigated by thermogravimetric and flow reactor methods in the intermediate-temperature range of 573–773 K. The proposed defect structure of HBC was successfully verified using the obtained data on its oxygen nonstoichiometry combined with those reported earlier. As a result, the values of the thermodynamic parameters (${∆H}_i^{\circ }$, ${∆S}_i^{\circ }$) of the defect reactions proceeding in HBC were determined. The defect structure of HBC was shown to be similar to that of YBaCo₂O_6-δ (YBC) likely due to similar ionic radii of Ho³⁺ and Y³⁺. Full article

Materials (cement stone samples) in the CaO-K₂O-SO₃-H₂O system with the target phase compositions, including syngenite K₂Ca(SO₄)₂·H₂O and calcium sulfate dihydrate CaSO₄·2H₂O, were prepared from powder mixtures of calcium sulfate anhydrite CaSO₄, and/or calciolangbeinite K₂Ca₂(SO₄)₃, and potassium sulfate K₂SO₄ via hydration reactions at a water/powder ratio within an interval of 0.5–0.9. It was revealed that samples with contents of 25, 50, 75 and 100 mol% of syngenite K₂Ca(SO₄)₂·H₂O demonstrated a nonlinear dependence of their respective microstructures on their phase compositions. The microstructures of samples with phase compositions of 25 and 75 mol% of syngenite K₂Ca(SO₄)₂·H₂O consisted of pillar crystals. The microstructures of samples with phase compositions of 50 and 100 mol% of syngenite K₂Ca(SO₄)₂·H₂O consisted of plate crystals. An explanation of microstructure formation was set forth, taking into account equilibria of the dissolution–crystallization processes during cement stone formation. Materials obtained in the CaO-K₂O-SO₃-H₂O system consisting of biocompatible and resorbable (soluble in water) phases can be recommended for testing as potential substances for bone defect treatments. Full article

Cooperation is widely recognized to be fundamental for the well-balanced development of human societies. Several different approaches have been proposed to explain the emergence of cooperation in populations of individuals playing the Prisoner’s Dilemma game, characterized by two concurrent natural mechanisms: the temptation to defect and the fear to be betrayed by others. Few results are available for analyzing situations where only the temptation to defect (Chicken game) or the fear to be betrayed (Stag-Hunt game) is present. In this paper, we analyze the emergence of full and partial cooperation for these classes of games. We find the conditions for which these Nash equilibria are asymptotically stable, and we show that the partial one is also globally stable. Furthermore, in the Chicken and Stag-Hunt games, partial cooperation has been found to be more rewarding than the full one of the Prisoner’s Dilemma game. This result highlights the importance of such games for understanding and sustaining different levels of cooperation in social networks. Full article

In the much-studied Centipede Game, which resembles the Iterated Prisoners’ Dilemma, two players successively choose between (1) cooperating, by continuing play, or (2) defecting and terminating play. The subgame-perfect Nash equilibrium implies that play terminates on the first move, even though continuing play can benefit both players—but not if the rival defects immediately, which it has an incentive to do. We show that, without changing the structure of the game, interchanging the payoffs of the two players provides each with an incentive to cooperate whenever its turn comes up. The Nash equilibrium in the transformed Centipede Game, called the Reciprocity Game, is unique—unlike the Centipede Game, wherein there are several Nash equilibria. The Reciprocity Game can be implemented noncooperatively by adding, at the start of the Centipede Game, a move to exchange payoffs, which it is rational for the players to choose. What this interchange signifies, and its application to transforming an arms race into an arms-control treaty, are discussed. Full article

CeF₃ displays favorable scintillation properties, which have been utilized for decades in various solid-state systems. Its emission undergoes multi-component decays, which were interpreted by lattice defects and so-called intrinsic features herein. This study of the complex equilibria in connection with photophysical behavior of the cerium(III)-fluoride system in solution gave us the possibility to reveal the individual contribution of the [Ce^IIIF_x(H₂O)_9−x]^3−x species to the photoluminescence. Spectrophotometry and spectrofluorometry (also in time-resolved mode) were used, and combined with sophisticated evaluation methods regarding both the complex equilibria and the kinetics of the photoinduced processes. The individual photophysical parameters of the [Ce^IIIF_x(H₂O)_9−x]^3−x complexes were determined. For the kinetic evaluation, three methods of various simplifications were applied and compared. The results indicated that the rates of some excited-state equilibrium processes were comparable to those of the emission decay steps. Our results also contribute to the explanation of the multi-component emission decays in the CeF₃-containing scintillators, due to the various coordination environments of Ce³⁺, which can be affected by the excitation leading to the dissociation of the metal-ligand bonds. Full article

Water distribution in the deep Earth represents one of the most important topics in the field of geodynamics due to its large impact on the physical and chemical properties of the Earth’s mantle, such as electrical conductivity, seismic anisotropy, diffusion, and rheology. In this study, we synthesized hydrous forsterite at 1100 °C and up to 4 GPa with either a piston-cylinder or multianvil apparatus. As a starting material, we used synthetic forsterite, unbuffered by SiO₂, obtained by thermo-mechanical activation of talc and magnesium carbonate hydroxide. Hydration was carried out using liquid H₂O as hydrogen source. Samples were polycrystalline in an effort to distribute H₂O throughout the sample both rapidly and homogeneously. Using the Paterson calibration, we observed total water content concentrations ranging between 100 and 500 ppm wt H₂O. Multiple absorption bands are found in the frequency range between 3400 and 3650 cm⁻¹, identifying at least seven peaks in all samples. Vibrational bands were centered at 3476, 3535, 3550, 3566, 3578, 3605, and 3612 cm⁻¹, in good agreement with experimental studies conducted on both hydrous forsterite and single crystals of olivine. The stronger OH stretching peaks can be attributed to vibrational modes associated with the hydrogarnet defect ${4\mathrm{H}}_{\mathrm{Si}}^{\mathrm{x}}$ in which four protons occupy a vacant tetrahedral site. None of the OH bands observed are found at frequencies associated with hydrogen occupying vacant octahedral sites. High-temperature FTIR spectroscopy was used to evaluate the evolution of IR spectra as a function of temperature, up to 500 °C. The complete reversibility of peak absorption vs. temperature in the OH stretching region confirms that no water loss occurred during heating. We observe an overall a decrease in total absorption with increasing temperature, and a prominent decrease in the relative intensities of the higher frequency bands (>3600 cm⁻¹) with respect to lower frequency bands. We have assigned a series of equilibrium expressions based on the variation of relative peak areas with temperature and find that enthalpies of these processes range between 0.047–0.068 eV (4.5–6.5 kJ/mol), very low in comparison to activation energies observed for electrical conduction in hydrous olivine. Major changes in the vibrational spectrum are expected to be related to configurational changes of the same fully protonated hydrogarnet defect species. However, the complexity of the FTIR spectra may also be related to partially protonated defects, such as the associate defect ${3\mathrm{H}}_{\mathrm{Si}}^{\prime }$ + ${\mathrm{H}}_{\mathrm{i}}^{•}$ generated by a dissociation reaction of the hydrogarnet species. Full article

We study a model where agents face a continuum of two-player games and categorize them into a finite number of situations to make sense of their complex environment. Agents need not share the same categorization. Each agent can cooperate or defect, conditional on the perceived category. The games are fully ordered by the strength of the temptation to defect and break joint cooperation. In equilibrium agents share the same categorization, but achieve less cooperation than if they could perfectly discriminate games. All the equilibria are evolutionarily stable, but stochastic stability selects against cooperation. We model agents’ learning when they imitate successful players over similar games, but lack any information about the opponents’ categorizations. We show that imitation conditional on reaching an intermediate aspiration level leads to a shared categorization that achieves higher cooperation than under perfect discrimination. Full article

In the cell cycle, there are two checkpoint arrests that allow cells to repair damaged DNA in order to maintain genomic integrity. Many cancer cells have defective G1 checkpoint mechanisms, thus depending on the G2 checkpoint far more than normal cells. G2 checkpoint abrogation is therefore a promising concept to preferably damage cancerous cells over normal cells. The main factor influencing the decision to enter mitosis is a complex composed of Cdk1 and cyclin B. Cdk1/CycB is regulated by various feedback mechanisms, in particular inhibitory phosphorylations at Thr14 and Tyr15 of Cdk1. In fact, Cdk1/CycB activity is restricted by the balance between WEE family kinases and Cdc25 phosphatases. The WEE kinase family consists of three proteins: WEE1, PKMYT1, and the less important WEE1B. WEE1 exclusively mediates phosphorylation at Tyr15, whereas PKMYT1 is dual-specific for Tyr15 as well as Thr14. Inhibition by a small molecule inhibitor is therefore proposed to be a promising option since WEE kinases bind Cdk1, altering equilibria and thus affecting G2/M transition. Full article

Few studies on federalism analyze the role of courts as safeguards of the federal arrangement, and those that do tend to be too optimistic about what courts can do. This article analyzes the effect of judicial review on the interaction between the central and a regional government in a federation in order to understand the conditions under which courts may or may not enforce compliance with federalism. It argues that politicians of either level of government anticipate the likelihood of a judicial challenge and an eventual veto, and it finds distinct equilibria in the interaction between central and regional governments (imposition, auto-limitation, negotiation and litigation). Only under auto-limitation do courts effectively prevent transgressions to the federal arrangement. In all other scenarios, defection may take place despite the presence of courts. These findings show that as the court’s jurisprudence becomes more solid and defined, the chances for governments to successfully exceed their powers increase. Not only do transgressions take place despite the presence of the court, but because of it. Full article