The reaction of trans‐M(N2)2(dppe)2 (M=Mo, 1Mo, M=W, 1W) with B(C6F5)3 (2) provides the adducts (dppe)2M=N=N‐B(C6F5)3 (3) which can be regarded as M/B transition‐metal frustrated Lewis pair (TMFLP) ...templates activating dinitrogen. Easy borylation and silylation of the activated dinitrogen ligands in complexes 3 with a hydroborane and hydrosilane occur by splitting of the B−H and Si−H bonds between the N2 moiety and the perfluoroaryl borane. This reactivity of 3 is reminiscent of conventional frustrated Lewis pair chemistry and constitutes an unprecedented approach for the functionalization of dinitrogen.
Dinitrogen is one of the missing small‐molecule targets of the frustrated Lewis pair (FLP) chemistry. The use of a Group 6 metal (Mo or W)/boron comound allows activation of N2 that is reminiscent of conventional FLPs. This mode of activation allows its mild and easy borylation and silylation, under a mechanism in which coordinated N2 acts as the Lewis base component of an FLP.
The first example of a formal 1,3‐B−H bond addition across the M−N≡N unit of an end‐on dinitrogen complex has been achieved. The use of Piers’ borane HB(C6F5)2 was essential to observe this ...reactivity and it plays a triple role in this transformation: 1) electrophilic N2‐borylation agent, 2) Lewis acid in a frustrated Lewis pair‐type B−H bond activation, and 3) hydride shuttle to the metal center. This chemistry is supported by NMR spectroscopy and solid‐state characterization of products and intermediates. The combination of chelate effect and strong σ donation in the diphosphine ligand 1,2‐bis(diethylphosphino)ethane was mandatory to avoid phosphine dissociation that otherwise led to complexes where borylation of N2 occurred without hydride transfer.
And the B goes on. Application of frustrated Lewis pair (FLP)‐type reactions in dinitrogen coordination chemistry has led to the achievement of 1,3‐B−H bond addition across the M−N≡N unit of a N2 complex. A chelating, strongly σ‐donating phosphine ligand is necessary to observe the title reaction. The use of HB(C6F5)2 is essential as it plays a triple role: N2‐borylation agent, Lewis acid in a FLP‐type B−H bond activation, and hydride shuttle.
In an ineffective transfusion context, solid‐phase immunoassays using the Luminex platform for the detection and characterization of HLA antibodies are currently used to select HLA‐compatible ...platelet products. A new HLA antibody identification method, the HISTO SPOT® HLA AB test (BAG Health care GmbH, Lich, Germany), based on the detection of antibodies directed against a recombinant single antigen (SA) by colored spots detected by HISTO MATCH HLA AB module software, runs fully automated on the MR.SPOT®. The aim of this study was to compare the ability of the HISTO SPOT HLA AB and C1qScreen™ (C1q SAB) assays with that of the Labscreen single antigen class I (OL SAB) assay to detect anti‐HLA class I antibodies in 56 serum samples from 54 platelet refractory acute myeloid leukemia patients who received HLA mismatch platelet concentrates at a single oncohematology center. In total, 1414 class I specificities, 433 HLA‐A and 981 HLA‐B, were detected by the OL SAB test. The mean fluorescence intensity (MFI) was >5000 for 874 antigens and <5000 for 655 antigens. The HISTO SPOT® HLA AB and C1q SAB tests identified 85% and 79% of OL SA‐detected antigens with an MFI >5000, respectively, but did not identify 34% and 44% of OL SAB‐detected antigens, highlighting the lower sensitivity of these techniques. Interestingly, the donor‐specific antibodies (DSAs) identified by the HISTO SPOT® HLA AB and C1q SAB assays reacted against HLA mismatch platelet concentrates with the same specificity (86%) and positive predictive (77%) value as in the OL SAB test when the MFI threshold was >2000 for DSA detection. Although the HISTO SPOT® HLA AB test is less sensitive than the OL SAB test, this test could be used for the selection of HLA‐compatible platelet products.
ARDI Etienne, Michel; Du Toit, Derick R.; Pollard, Sharon
Ecology and society,
01/2011, Letnik:
16, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The outcomes of a series of tests of the ARDI (Actors, Resources, Dynamics, and Interactions) method in complex cases or conflict-ridden situations is presented. ARDI is part of a companion modeling ...approach that makes it possible to engage a broad spectrum of stakeholders in the design and development of land and water management plans. It is based on participatory workshops that set out to collaboratively imagine a future open, dynamic management system, capable of adaptation and anticipation, by gathering the various stakeholders in a partnership to examine conservation of the natural resources and promoting a sustainable development. Its originality lies in the co-construction of a “conceptual model” of the functioning of the territory, according to an overarching, negotiated development question. The approach is based on the collective articulation of the key elements of a context or territory by stakeholders such as managers, representatives, socio-professional technicians, nongovernmental organizations, experts, and scientists, and local policy makers. This sharing of representations is done by means of a series of collective workshops during which Actors, Resources, Dynamics, and Interactions constituting the profile of the territory are identified and clarified. This work of co-construction is conducted within a precise methodological framework that we present in a step-by-step format. The method is grounded in concrete experience gleened from tests conducted by the authors over the past five years. Finally, the requirement for specific skills as well as pitfalls to avoid when applying the method are discussed.
Protected areas (PAs) remain central to the conservation of biodiversity. Classical PAs were conceived as areas that would be set aside to maintain a natural state with minimal human influence. ...However, global environmental change and growing cross-scale anthropogenic influences mean that PAs can no longer be thought of as ecological islands that function independently of the broader social-ecological system in which they are located. For PAs to be resilient (and to contribute to broader social-ecological resilience), they must be able to adapt to changing social and ecological conditions over time in a way that supports the long-term persistence of populations, communities, and ecosystems of conservation concern. We extend Ostrom's social-ecological systems framework to consider the long-term persistence of PAs, as a form of land use embedded in social-ecological systems, with important cross-scale feedbacks. Most notably, we highlight the cross-scale influences and feedbacks on PAs that exist from the local to the global scale, contextualizing PAs within multi-scale social-ecological functional landscapes. Such functional landscapes are integral to understand and manage individual PAs for long-term sustainability. We illustrate our conceptual contribution with three case studies that highlight cross-scale feedbacks and social-ecological interactions in the functioning of PAs and in relation to regional resilience. Our analysis suggests that while ecological, economic, and social processes are often directly relevant to PAs at finer scales, at broader scales, the dominant processes that shape and alter PA resilience are primarily social and economic.
Purpose
The paper aims to address the organizational transformation of firms for value creation resulting from cloud computing (CC).
Design/methodology/approach
With reference to the theory of ...organizational fit, we modeled organizational transformation as a function of five aspects of CC practice: functionality, data management, roles and competences of information technology services, control and organizational culture. The output variable was tested against a set of input variables defined with reference to the technology–organization–environment (TOE) and technology acceptance model (TAM). Based on a sample of 487 companies in seven countries in Europe, Asia, and the United States, the authors distinguished two groups of firms: transformational and hyper transformational.
Findings
The results highlight the key factors that determine whether a firm falls into one of these two groups, and include perceived usefulness and perceived ease of use, complexity and compatibility of CC technology, and adequacy of resources. Top management support and government policy are found to only play a role for the transformational group while, surprisingly, vendor support had no impact for either group.
Originality/value
This research contributes to the literature on the role of digital transformation in value creation and on digitization of firms and organizational design, notably by considering the contribution of CC to the organizational dimension. To the best of the authors’ knowledge, this is the first study to make the link between TOE and TAM models and organizational fit theory, thereby going beyond the general approach to adoption found in information system research.
For a panel data linear regression model with both individual and time effects, empirical studies select the two-way random-effects (TWRE) estimator if the Hausman test based on the contrast between ...the two-way fixed-effects (TWFE) estimator and the TWRE estimator is not rejected. Alternatively, they select the TWFE estimator in cases where this Hausman test rejects the null hypothesis. Not all the regressors may be correlated with these individual and time effects. The one-way Hausman-Taylor model has been generalized to the two-way error component model and allow some but not all regressors to be correlated with these individual and time effects. This paper proposes a pretest estimator for this two-way error component panel data regression model based on two Hausman tests. The first Hausman test is based upon the contrast between the TWFE and the TWRE estimators. The second Hausman test is based on the contrast between the two-way Hausman and Taylor (TWHT) estimator and the TWFE estimator. The Monte Carlo results show that this pretest estimator is always second best in MSE performance compared to the efficient estimator, whether the model is random-effects, fixed-effects or Hausman and Taylor. This paper generalizes the one-way pretest estimator to the two-way error component model.
The direct synthesis of organocalcium compounds (heavy Grignard reagents) by the reduction of organyl halides with activated calcium powder succeeded in a straightforward manner for organic bromides ...and iodides that are bound at sp2‐hybridized carbon atoms. Extension of this strategy to alkyl halides was very limited, and only the reduction of trialkylsilylmethyl bromides and iodides with activated calcium allowed the isolation of the corresponding heavy Grignard reagents. Substitution of only one hydrogen atom of the methylene moiety by a phenyl or methyl group directed this reduction toward the Wurtz‐type coupling and the formation of calcium halide and the corresponding C−C coupling product. The stability of the methylcalcium and benzylcalcium derivatives in ethereal solvents suggests an unexpected reaction behavior of the intermediate organyl halide radical anions. Quantum chemical calculations verify a dependency between the ease of preparative access to organocalcium complexes and the C−I bond lengths of the organyl iodides. The bulkiness of the trialkylsilyl group is of minor importance. Chloromethyltrimethylsilane did not react with activated calcium; however, halogen‐exchange reactions allowed the isolation of Ca(CH2SiMe3)(thf)3(μ‐Cl)2. Furthermore, the metathetical approach of reacting Ca(CH2SiMe3)I(thf)4 with KN(SiMe3)2 and the addition of N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (pmdeta) allowed the isolation of heteroleptic CaCH2SiMe3{N(SiMe3)2}(pmdeta). In the reaction of this derivative with phenylsilane, the trimethylsilylmethyl group proved to be more reactive than the bis(trimethylsilyl)amido substituent.
Organocalcium complexes: The success of the direct synthesis of heavy Grignard reagents, that is, organocalcium iodides, strongly depends on the C−I bond length of the organyl iodide radical anion that forms after the initial single electron transfer (SET) reaction, yielding either R‐Ca‐I and/or Wurtz‐type C−C coupling products (see scheme).
This paper estimates a hedonic housing model based on flats sold in the city of Paris over the period 1990–2003. This is done using maximum likelihood estimation, taking into account the nested ...structure of the data. Paris is historically divided into 20 arrondissements, each divided into four quartiers (quarters), which in turn contain between 15 and 169 blocks (îlot, in French) per quartier. This is an unbalanced pseudo-panel data containing 156,896 transactions. Despite the richness of the data, many neighborhood characteristics are not observed, and we attempt to capture these neighborhood spillover effects using a spatial lag model. Using likelihood ratio tests, we find significant spatial lag effects as well as significant nested random error effects. The empirical results show that the hedonic housing estimates and the corresponding marginal effects are affected by taking into account the nested aspects of the Paris housing data as well as the spatial neighborhood effects.
Mental models are the cognitive representations of the world that frame how people interact with the world. Learning implies changing these mental models. The successful management of complex ...social-ecological systems requires the coordination of actions to achieve shared goals. The coordination of actions requires a level of shared understanding of the system or situation; a shared or common mental model. We first describe the elicitation and analysis of mental models of different stakeholder groups associated with water management in the Camargue Biosphere Reserve in the Rhône River delta on the French Mediterranean coast. We use cultural consensus analysis to explore the degree to which different groups shared mental models of the whole system, of stakeholders, of resources, of processes, and of interactions among these last three. The analysis of the elicited data from this group structure enabled us to tentatively explore the evidence for learning in the nonstatute Water Board; comprising important stakeholders related to the management of the central Rhône delta. The results indicate that learning does occur and results in richer mental models that are more likely to be shared among group members. However, the results also show lower than expected levels of agreement with these consensual mental models. Based on this result, we argue that a careful process and facilitation design can greatly enhance the functioning of the participatory process in the Water Board. We conclude that this methodology holds promise for eliciting and comparing mental models. It enriches group-model building and participatory approaches with a broader view of social learning and knowledge-sharing issues.
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