The competition between metastable and equilibrium S (Al2CuMg) phase during the decomposition of AlCuMg alloys

Abstract The decomposition sequence of the supersaturated solid solution leading to the formation of the equilibrium S (Al2CuMg) phase in AlCuMg alloys has long been the subject of ambiguity and debate. Recent high-resolution synchrotron powder diffraction experiments have shown that the decomposition sequence does involve a metastable variant of the S phase (denoted S1), which has lattice parameters that are distinctly different to those of the equilibrium S phase (denoted S2). In this paper, the difference between these two phases is resolved using high-resolution synchrotron and neutron powder diffraction and atom probe tomography, and the transformation from S1 to S2 is characterised in detail by in situ synchrotron powder diffraction. The results of these experiments confirm that there are no significant differences between the crystal structures of S1 and S2, however, the powder diffraction and atom probe measurements both indicate that the S1 phase forms with a slight deficiency in Cu. The in situ isothermal aging experiments show that S1 forms rapidly, reaching its maximum concentration in only a few minutes at high temperatures, while complete conversion to the S2 phase can take thousands of hours at low temperature. The kinetics of S phase precipitation have been quantitatively analysed for the first time and it is shown that S1 phase forms with an average activation energy of 75 kJ/mol, which is much lower than the activation energy for Cu and Mg diffusion in an Al matrix (136 kJ/mol and 131 kJ/mol, respectively). The mechanism of the replacement of S1 with the equilibrium S2 phase is discussed.

Avoiding competition? Site use, diet and foraging behaviours in two similarly sized geese wintering in China

Competition may occur when two species with similar feeding ecologies exploit the same limited resources in time and space. In recent years, the Eastern Tundra Bean Goose Anser fabalis serrirostris and Greater White-fronted Goose Anser albifrons frontalis have increased in wintering numbers at Shengjin Lake, China. To examine the potential for coexistence and possible avoidance strategies, we studied (1) their habitat use, (2) foraging behaviours and (3) diets of birds foraging in mixed- and single-species flocks. Both species extensively exploited sedge meadows, where they showed considerable overlap in spatial distribution and diet. The percentage feeding time and diet of both species were unaffected by the presence of the other. Greater White-fronted Geese appeared diurnal sedge meadow specialists, almost never feeding in other habitats. Eastern Tundra Bean Geese were less selective, exploiting other habitats, which they increasingly exploited at night in mid-winter. The use of alternative habitats and night feeding may have avoided interspecific competition. While the specialised feeding ecology of Greater White-fronted Geese may make them particularly vulnerable to loss of sedge meadow habitat, Eastern Tundra Bean Geese may be able to adjust because of their use of alternative habitats and a less restricted diet.

State-owned enterprises, competition and product quality

We consider a general oligopoly model with consumer surplus moderated quantity competition among state-owned enterprises (SOEs), where the SOEs employ workers who are members of the state-owned worker union and produce differentiated products. We show that increasing the number of SOEs would lead to an outcome in which these enterprises choose a lower level of product quality and this, in turn, results in welfare losses for the society, depending on the degree of substitutability. Our findings are consistent with the evidence from China and uncovers important linkages that exist between worker union, product quality and competition, and that have mostly been ignored in the industrial organisation, trade and development literature.

Win at all costs or lose gracefully in high-stakes competition? Gender differences in professional tennis

This article examines line-call challenges by male and female professional tennis players in major tournaments around the world. In terms of utilization rates, we find that the genders behave similarly. Nevertheless, we do detect some intriguing gender differences in these challenges. First, male players’ challenges are more likely to be provoked by those of their opponents. More importantly, at tiebreaks, females are more likely to reverse an umpire’s unfavorable call, while males make relatively more unsuccessful challenges. Furthermore, we find that men are a lot more likely to make “embarrassing” line-call challenges at tiebreaks and offenses (i.e., when the shot lands at the opponent’s side of the tennis court) than women. These significant gender differences suggest that women particularly diverge from men at crucial junctures of the match such as tiebreaks. Differences in factors such as risk aversion, overconfidence, pride, shame, and strategic signalling behavior might help us to explain these gender-difference findings in line call challenges.

Competition between cluster fragmentation, C–C bond coupling and C–X bond activation in silver hexynyl cluster cations, [(C4H9CCAg)nAg]+. Size does matter!

Silver hexynyl cluster cations, [(C4H9CCAg)nAg]+, exhibit a rich unimolecular chemistry that is dependant on the cluster size, n (1–5), cluster fragmentation (for all n > 1); C–C bond coupling (n = 3 & 4); C–H bond activation with comcomitant silver hydride formation (n = 1 & 4); C–C bond activation (n = 1 & 4).