New insights into phase distribution, phase composition and disorder in Y2(Zr,Sn) 2O7 ceramics from NMR spectroscopy

A combination of 89Y and 119Sn NMR spectroscopy and DFT calculations are used to investigate phase evolution, local structure and disorder in Y2Zr2−xSnxO7 ceramics, where a phase change is predicted, from pyrochlore to defect fluorite, with increasing Zr content. The ability of NMR to effectively probe materials that exhibit positional and compositional disorder provides insight into the atomic-scale structure in both ordered and disordered phases and, by exploiting the quantitative nature of the technique, we are able to determine detailed information on the composition of the phase(s) present and the average coordination number (and next-nearest neighbour environment) of the cations. In contrast to previous studies, a more complex picture of the phase variation with composition emerges, with single-phase pyrochlore found only for the Sn end member, and a single defect fluorite phase only for x = 0 to 0.6. A broad two-phase region is observed, from x = 1.8 to 0.8, but the two phases present have very different composition, with a maximum of 13% Zr incorporated into the pyrochlore phase, whereas the composition of the defect fluorite phase varies throughout. Preferential ordering of the anion vacancies in the defect fluorite phase is observed, with Sn only ever found in a six-coordinate environment, while remaining vacancies are shown to be more likely to be associated with Zr than Y. Our findings are then discussed in the light of those from previous studies, many of which utilize diffraction-based approaches, where, in most cases, a single phase of fixed composition has been assumed for the refinement procedure. The significant and surprising differences encountered demonstrate the need for complementary approaches to be considered for a detailed and accurate picture of both the long- and short-range structure of a solid to be achieved

Looking inside the spiky bits : a critical review and conceptualisation of entrepreneurial ecosystems

The authors wish to thank the Organisational for Economic Cooperation and Development (OECD) for funding their original research on entrepreneurial ecosystems.The concept of entrepreneurial ecosystems has quickly established itself as one of the latest ‘fads’ in entrepreneurship research. At face value, this kind of systemic approach to entrepreneurship offers a new and distinctive path for scholars and policy makers to help understand and foster growth-oriented entrepreneurship. However, its lack of specification and conceptual limitations has undoubtedly hindered our understanding of these complex organisms. Indeed, the rapid adoption of the concept has tended to overlook the heterogeneous nature of ecosystems. This paper provides a critical review and conceptualisation of the ecosystems concept: it unpacks the dynamics of the concept; outlines its theoretical limitations; measurement approaches and use in policy-making. It sets out a preliminary taxonomy of different archetypal ecosystems. The paper concludes that entrepreneurial ecosystems are a highly variegated, multi-actor and multi-scalar phenomenon, requiring bespoke policy interventions.Publisher PDFPeer reviewe

Institutional distance and foreign subsidiary performance in emerging markets: moderating effects of ownership strategy and host-country experience

Institutional distance has been known to be an important driver of Multinational Enterprises’ strategies and performance in host countries. Based on a large panel dataset of 10562 firms operating in 17 emerging markets and spanning 80 home countries, we re-examine the relationship described by Gaur and Lu (2007) between regulatory institutional distance and subsidiary performance. We extend this research by (1) examining this relationship in the context of emerging markets, (2) examining the moderating effects of ownership strategy and host-country experience within the context of emerging markets and (3) accounting for a greater variety of institutions by including a large number of home and host countries. We find that institutional distance negatively affects subsidiary performance in emerging markets. Our findings also show that the negative effects of institutional distance on subsidiary performance are lesser for subsidiaries with partial ownership (than for subsidiaries with full ownership) and for subsidiaries with greater host-country experience. We discuss our findings with respect to Gaur and Lu’s model, which explores the relationships between these variables in a general context

Global Oceans

Global Oceans is one chapter from the State of the Climate in 2019 annual report and is avail-able from https://doi.org/10.1175/BAMS-D-20-0105.1. Compiled by NOAA’s National Centers for Environmental Information, State of the Climate in 2019 is based on contr1ibutions from scien-tists from around the world. It provides a detailed update on global climate indicators, notable weather events, and other data collected by environmental monitoring stations and instru-ments located on land, water, ice, and in space. The full report is available from https://doi.org /10.1175/2020BAMSStateoftheClimate.1

An Applied Investigation Of Rogers And Shoemakers Perceived Innovation Attribute Typology When Marketing To Elderly Consumers

Rogers and Shoemakers typology of innovation, which has long represented the bench mark for research on the relationship of perceive innovation characteristics to the diffusion process, may not be appropriate for most marketing innovations according to the theoretical and empirical evidence developed in this research. The appropriateness of the innovation typology was investigated across innovations classified on a continuous-discontinuous continuum. The results suggest their model is appropriate for discontinuous innovations, but that respondents evaluated the continuous innovation along dissimilar dimensions, which were also smaller in number. The results argued for marketing appeals based on the determinant perceptual dimensions of innovations. For discontinuous innovations, marketing efforts should primarily focus on addressing the relative advantage and observability of the innovation. Organizations marketing continuous innovations should focus on the economic and performance advantages and ease of use associated with the product

Arsenic mobilization and iron transformations during sulfidization of As(V)-bearing jarosite

Jarosite (KFe3(SO4) 2(OH)6) is an important host-phase for As in acid mine drainage (AMD) environments and coastal acid sulfate soils (CASS). In AMD and CASS wetlands, jarosite may encounter S(−II) produced by sulfate reducing bacteria. Here, we examine abiotic sulfidization of As(V)-bearing K-jarosite at pH 4.0, 5.0, 6.5 and 8.0. We quantify the mobilization and speciation of As and identify corresponding Fe mineral transformations. Sulfide-promoted dissolution of jarosite caused release of co-precipitated As and the majority of mobilized As was re-partitioned to a readily exchangeable surface complex (AsEx). In general, maximum As mobilization occurred in the highly sulfidized end-members of all treatments and was greatest at low pH, following the order pH 5.0≈4.0\u3e8.5\u3e 6.5. X-ray absorption spectroscopy revealed that most solid-phase As remained as oxygen-coordinated As(V) when pH values were \u3e5.0 — even during latter stages of sulfidization and the presence of ≥100 μM dissolved S(−II). In contrast at pH 4.0, As transitioned from oxygen-coordinated As(V) to a sulfur-coordinated orpiment-like phase. This transition coincided with a marked decrease in AsEx, attenuation of As(aq) and TEM-EDX spectra indicate concurrent formation of nano-scale zones variably enriched in As (~1–15%). Although discordant with geochemical modeling, the formation of an orpiment-like precipitate appears to be a primary control on As mobility during the late stages of complete jarosite sulfidization under acidic conditions (pH 4.0). Mackinawite was the main Fe-mineral end product in all pH treatments. However, at pH 8.0, jarosite rapidly (b1 h) transformed to a lepidocrocite intermediary. Although lepidocrocite efficiently adsorbed As(aq), the transformation process itself was incongruent with electron transfer to Fe(III). Further investigation is required to determine whether the electron donor triggering this transformation was direct via S(−II), or indirect via surface complexed Fe(II) and hence akin to the widely-known Fe(II)-catalyzed transformation of Fe(III) minerals. The results demonstrate that abiotic sulfidization of As(V)-co-precipitated jarosite can mobilize substantial As and that pH exerts a major control on the subsequent As solid-phase speciation, electron transfer kinetics and Fe mineralization pathways and products. The findings are particularly relevant to heterogeneous sediments in which As-bearing jarosite encounters dissolved sulfide under a range of pH conditions

The role of the geothermal heat flux in driving the abyssal ocean circulation

The results presented in this paper demonstrate that the geothermal heat flux (GHF) from the solid Earth into the ocean plays a non-negligible role in determining both abyssal stratification and circulation strength. Based upon an ocean data set, we show that the map of upward heat flux at the ocean floor is consistent (within a factor of 2) with the ocean floor age-dependent map of GHF. The observed buoyancy flux above the ocean floor is consistent with previous suggestions that the GHF acts to erode the abyssal stratification and thereby enhances the strength of the abyssal circulation. Idealized numerical simulations are performed using a zonally averaged single-basin model which enables us to address the GHF impact as a function of the depth dependence of diapycnal diffusivity. We show that ignoring this vertical variation leads to an under-prediction of the influence of the GHF on the abyssal circulation. Independent of the diffusivity profile, introduction of the GHF in the model leads to steepening of the Southern Ocean isopycnals and to strengthening of the eddy-induced circulation and the Antarctic bottom water cell. The enhanced circulation ventilates the GHF derived heating to shallow depths, primarily in the Southern Ocean.National Science Foundation (U.S.) (Grant OCE-1024198