Contractile stresses in cohesive cell layers on finite-thickness substrates

Using a minimal model of cells or cohesive cell layers as continuum active elastic media, we examine the effect of substrate thickness and stiffness on traction forces exerted by strongly adhering cells. We obtain a simple expression for the length scale controlling the spatial variation of stresses in terms of cell and substrate parameters that describes the crossover between the thin and thick substrate limits. Our model is an important step towards a unified theoretical description of the dependence of traction forces on cell or colony size, acto-myosin contractility, substrate depth and stiffness, and strength of focal adhesions, and makes experimentally testable predictions.Comment: 5 pages, 3 figure

a dynamic model of evolution

El estudio busca proveer evidencia empírica sobre cómo las sedes centrales configuran relaciones y organizan actividades con la red de filiales, así como los mecanismos para crear valor agregado mediante el uso de la estrategia de entrada de la “filial trampolín”. Mediante métodos cualitativos se exploran los determinantes, el desarrollo y la dinámica de la evolución de estas unidades en empresas multinacionales europeas, utilizando a España como filial trampolín para manejar sus operaciones en América Latina. El artículo amplía también la literatura internacional de negocios sobre sedes extra regionales y las ventajas del padrinazgo empresarial dentro de la empresa multinaciona

La influencia de las características y percepciones directivas en los nuevos modelos de internacionalización

En las economías desarrolladas y con el actual escenario competitivo, las pymes de los sectores industriales maduros están sometidas a una serie de fuerzas económicas que limitan su capacidad para subsistir. Factores como el endurecimiento de la competencia proveniente de los grandes productores asiáticos (China, India, Pakistán) y de los países de Europa del Este, el incremento espectacular del poder de negociación de los distribuidores o la desaparición del canal minorista y de los mercados referenciados en dólares (Camisón, 2001, Pla-Barber, et. al, 2007) han generado una alarmante disminución de empresas y empleos en estos sectores. Frente a este panorama poco alentador, existen soluciones que pueden favorecer las oportunas respuestas. Una de las estrategias que históricamente han utilizado las pymes para contrarrestar estas situaciones negativas ha sido la expansión internacional, sobre todo a través de la exportación en mercados cultural y geográficamente cercanos (Johanson y Vahlne, 1977). Sin embargo, se ha constatado en diferentes trabajos (Barker y Duhaime, 1997, Barker y Mone, 1998, Pearce y Robbins, 2008) que en estos sectores para hacer frente al nuevo entorno «globalizado e hipercompetitivo» son necesarias estrategias internacionales mucho más complejas que, en algunos casos, suponen plantearse la esencia misma de la empresa, aquello a lo que se dedica y, por tanto, son ajustes mucho más difíciles de implantar porque normalmente suponen cambios en los «límites» o «fronteras» de la empresa

Organisational learning capability, product innovation performance and export intensity

The hypothesis that managerial characteristics which facilitate the organisational learning process can provide firms with a basis for competitive advantage has received a great deal of attention. While there is evidence that organisational learning affects export intensity, we argue that intermediate variables, such as innovation, should be used in order to evaluate its impact in organisations. This study shows that firms with a higher organisational learning capability tend to be more innovative, and for this reason, they are more likely to export a higher share of their production. From a longitudinal perspective, we use structural equation modeling on a database from Italian and Spanish ceramic tile producers, worldwide leaders in terms of technology. The database combines primary and secondary data. The results support our theoretical conjectures. Findings improve our understanding of the antecedents of export intensity and are related to previous research

Bayesian Models for Spatially Explicit Interactions Between Neighbouring Plants

Interactions between neighbouring plants drive population and community dynamics in terrestrial ecosystems. Understanding these interactions is critical for both fundamental and applied ecology. Spatial approaches to model neighbour interactions are necessary, as interaction strength depends on the distance between neighbouring plants. Recent Bayesian advancements, including the Hamiltonian Monte Carlo algorithm, offer the flexibility and speed to fit models of spatially explicit neighbour interactions. We present a guide for parameterizing these models in the Stan programming language and demonstrate how Bayesian computation can assist ecological inference on plant–plant interactions. Modelling plant neighbour interactions presents several challenges for ecological modelling. First, nonlinear models for distance decay can be prone to identifiability problems, resulting in lack of model convergence. Second, the pairwise data structure of plant–plant interaction matrices often leads to large matrices that demand high computational power. Third, hierarchical structure in plant–plant interaction data is ubiquitous, including repeated measurements within field plots, species and individuals. Hierarchical terms (e.g. ‘random effects’) can result in model convergence problems caused by correlations between coefficients. We explore modelling solutions for these challenges with examples representing spatial data on plant demographic rates: growth, survival and recruitment. We show that ragged matrices reduce computational challenges inherent to pairwise matrices, resulting in higher efficiency across data types. We also demonstrate how metrics for model convergence, including divergent transitions and effective sample size, can help diagnose problems that result from complex nonlinear structures. Finally, we explore when to use different model structures for hierarchical terms, including centred and non-centred parameterizations. We provide reproducible examples written in Stan to enable ecologists to fit and troubleshoot a broad range of neighbourhood interaction models. Spatially explicit models are increasingly central to many ecological questions. Our work illustrates how novel Bayesian tools can provide flexibility, speed and diagnostic capacity for fitting plant neighbour models to large, complex datasets. The methods we demonstrate are applicable to any dataset that includes a response variable and locations of observations, from forest inventory plots to remotely sensed imagery. Further developments in statistical models for neighbour interactions are likely to improve our understanding of plant population and community ecology across systems and scales

Drought tolerance assessment of melon germplasm searching for adaptation to climate change

[EN] Shortage of irrigation water at critical melon growth stages can be the most important limiting factor in the future due to climate change, especially in the Mediterranean region. Apart from the improvement of irrigation systems and crop management, the development of drought tolerant cultivars by genetic breeding is the best solution to achieve stable yields. Screening germplasm collections is a prerequisite for that. A melon core collection was evaluated in the current work in two assays. Seven morphological traits were assessed at plantlet stage and compared under drought and standard conditions imposed. Significant differences for all traits were recorded among the sixty accessions evaluated. Clustering analysis also grouped the accessions according to their response to drought, detecting some landraces and wild types of interest, mainly of Indian and African origin, although the best behavior under drought was found in a flexuosus melon from Irak. Some Spanish inodorus landraces also showed better response than the average behavior of commercial types. The employment of this set of traits has allowed screening a large germplasm collection in an easy and non-expensive way, in one of the most sensitive developmental stages.The authors thank the Erasmus mundus team, WELCOME project, Third Cohort, for offering funds for the research and scholarship activities. Also, they thank the Conselleria d'Educació, Investigació, Cultura i Esport (Generalitat Valenciana) for funding the project Prometeo (2017/078).Elsayed, H.; Peiró Barber, RM.; Picó Sirvent, MB.; Esteras Gómez, C. (2019). Drought tolerance assessment of melon germplasm searching for adaptation to climate change. African Journal of Agricultural Research. 14(27):1180-1196. https://doi.org/10.5897/AJAR2018.13807S11801196142

Governance of global value chains after the Covid-19 pandemic: a new wave of regionalization?

The disruption of the trade and investment activities of multinational enterprises as a consequence of the Covid-19 pandemic has reinvigorated the debate on the configuration of global value chains (GVCs) as well as the risks and challenges associated with offshoring. This paper depicts how the pandemic might affect GVC configuration by driving a trend towards a more regional footprint in industries in which resilience and reliability are critical. Such a shift would create new opportunities for reshoring, and affect both the types of upgrading trajectories and the governance systems in value chains. The paper also draws from the intersection of the global-strategy and value-chain fields to propose potential topics and avenues for further research related to these trends

Configurational theory in traditional manufacturing industries: a new model of high-performing small and medium-sized enterprises

The goal of this study is to provide a model of high-performing small and medium-sized companies to address the new environmental challenges in traditional manufacturing industries. Adopting a configurational logic and following an inductive approach based on four high-performing firms, this paper provides new empirical evidence on how the steps followed by these firms are adjusted to the high-performance models prescribed by the literature. In doing so, it also offers a dynamic view of the interrelationships between the strategy and the new conditions of the environment. At a practitioner level, the paper illustrates which recipes are more appropriate to prescribe recommendations for a more robust model that reinforces competitiveness in these industries. This research suggests that competitive success in traditional manufacturing industries requires movement along five complementary and interlinked strategic-development axes: the use of cooperation agreements, the combination of local and international manufacturing, the greater control of the distribution channel, the sale of customized products, and an increasing concern for sustainability