Enzyme kinetics for a two-step enzymic reaction with comparable initial enzyme-substrate ratios

We extend the validity of the quasi-steady state assumption for a model double intermediate enzyme-substrate reaction to include the case where the ratio of initial enzyme to substrate concentration is not necessarily small. Simple analytical solutions are obtained when the reaction rates and the initial substrate concentration satisfy a certain condition. These analytical solutions compare favourably with numerical solutions of the full system of differential equations describing the reaction. Experimental methods are suggested which might permit the application of the quasi-steady state assumption to reactions where it may not have been obviously applicable before

Crystal structures and magnetic order of La{0.5+delta}A{0.5-delta}Mn{0.5+epsilon}Ru{0.5-epsilon}O{3} (A= Ca, Sr, Ba): Possible orbital glass ferromagnetic state

The crystallographic and magnetic properties of La{0.5+delta}A{0.5-delta}Mn{0.5+epsilon}Ru{0.5-epsilon}O{3} (A= Ca, Sr, Ba) were investigated by means of neutron powder diffraction. All studied samples show the orthorhombic perovskite crystal structure, space group Pnma, with regular (Mn,Ru)O{6} octahedra and no chemical ordering of the Mn3+ and Ru4+ ions. Ferromagnetic spin structures were observed below Tc ~ 200-250 K, with an average ordered moment of ~ 1.8-2.0 Bohr magnetons per (Mn,Ru). The observation of long-range ferromagnetism and the absence of orbital ordering are rationalized in terms a strong Mn-Ru hybridization, which may freeze the orbital degree of freedom and broaden the eg valence band, leading to an orbital-glass state with carrier-mediated ferromagnetism

The cultural side of value creation

The question of how organizations create value has become a central question for understanding inter-firm competition and performance differentials. Much of the work on the topic emphasizes the importance of technological innovation for improving operational efficiency and/or product functionality . Accordingly, much of the work in the area has focused on understanding the development of technological capabilities and the dynamics of competition among different technologies. Whereas this line of research has contributed greatly to our understanding of value creation through technology performance improvement, it has also left unexplored the strategies for differentiating products on the basis of their cultural significance. Yet, research in a wide variety of disciplines ranging from anthropology, to cultural sociology, and consumer behavior shows that consumers value products not only for their functional and technical performance, but also for their cultural meanings. The infusion of products with cultural meanings enables consumers to use these products to make statements about their personal and social identity and status. It is therefore well understood that consumers derive value not only from what products do (functional value), but also from what they signify in a given social group (symbolic value). While strategy scholars recognize that product meanings are a source of differentiation and generate price premia (Porter, 1980), they also tend to view the activities that generate them – e.g. branding – as a part of the marketing strategy of the firm. More generally, strategy research has been criticized for its reluctance to delve into the demand side of value-creation. Rooted in disciplinary assumptions about atomistic consumers with idiosyncratic preferences, strategy researchers view demand as largely exogenous and ignore its cultural embeddedness in social conventions that define the cultural meanings of objects and shape consumption choices. As a result, they have given limited attention to the question of how firms can strategically manage the symbolic value of their products. In this paper we propose a cultural perspective on value creation that can direct strategic organization research toward the systematic investigation of how producers engage with the cultural meaning systems that supply frameworks for interpretation and valuation of goods. To guide research in this direction we first discuss how products acquire cultural significance and then outline three core implications of these ideas for the strategy and organization of firms. First, we discuss how recognizing the cultural significance of products shifts attention from technological innovation that alters product functionality to cultural innovation that alters their cultural significance. Second, we explain the need to develop distinct cultural resources that enable firms to identify and exploit opportunities for cultural innovation. Third, we draw attention to the need for cultural intent defined as developing an explicit strategy for utilizing cultural resources to achieve specific cultural positioning for the firm’s products

Toward a theory of repeat purchase drivers for consumer services

The marketing discipline’s knowledge about the drivers of service customers’ repeat purchase behavior is highly fragmented. This research attempts to overcome that fragmented state of knowledge by making major advances toward a theory of repeat purchase drivers for consumer services. Drawing on means–end theory, the authors develop a hierarchical classification scheme that organizes repeat purchase drivers into an integrative and comprehensive framework. They then identify drivers on the basis of 188 face-to-face laddering interviews in two countries (USA and Germany) and assess the drivers’ importance and interrelations through a national probability sample survey of 618 service customers. In addition to presenting an exhaustive and coherent set of hierarchical repeat-purchase drivers, the authors provide theoretical explanations for how and why drivers relate to one another and to repeat purchase behavior. This research also tests the boundary conditions of the proposed framework by accounting for different service types. In addition to its theoretical contribution, the framework provides companies with specific information about how to manage long-term customer relationships successfully

The role of leadership in salespeople’s price negotiation behavior

Salespeople assume a key role in defending firms’ price levels in price negotiations with customers. The degree to which salespeople defend prices should critically depend upon their leaders’ influence. However, the influence of leadership on salespeople’s price defense behavior is barely understood, conceptually or empirically. Therefore, building on social learning theory, the authors propose that salespeople might adopt their leaders’ price defense behavior given a transformational leadership style. Furthermore, drawing on the contingency leadership perspective, the authors argue that this adoption fundamentally depends on three variables deduced from the motivation–ability–opportunity (MAO) framework, that is, salespeople’s learning motivation, negotiation efficacy, and perceived customer lenience. Results of a multi-level model using data from 92 salespeople and 264 salesperson–customer interactions confirm these predictions. The first to explore contingencies of salespeople’s adoption of their transformational leaders’ price negotiation behaviors, this study extends marketing theory and provides actionable guidance to practitioners

Three-dimensional transport imaging for the spatially resolved determination of carrier diffusion length in bulk materials

The article of record as published may be found at http://dx.doi.org/10.1063/1.3698090A contact-free optical technique is developed to enable a spatially resolved measurement of minority carrier diffusion length and the associated mobility-lifetime (Î¼Ï ) product in bulk semiconductor materials. A scanning electron microscope is used in combination with an internal optical microscope and imaging charge-coupled device (CCD) to image the bulk luminescence from minority carrier recombination associated with one-dimensional excess carrier generation. Using a Greenâ s function to model steady-state minority carrier diffusion in a three-dimensional half space, non-linear least squares analysis is then applied to extract values of carrier diffusion length and surface recombination velocity. The approach enables measurement of spatial variations in the Î¼Ï product with a high degree of spatial resolution.This work was supported by the Academic Research Initiative (ARI) of DHS through Interagency Agreement HSHQDC-11-X-0015