931 research outputs found

    The Organizational Fitness Navigator: Creating and Measuring Organizational Fitness for Fast-Paced Transformation

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    In the fast-changing environment of today dynamic capabilities to manage organizational transformation are regarded as crucial for business survival and improved performance. Although dynamic organizational capabilities have been receiving intense scrutiny by researchers and practitioners in the past few years, relatively little attention has been directed towards creating a systemic model of dynamic capabilities, and how to effectively measure what the authors call organizational fitness capabilities. This paper builds on the concepts of organizational fitness and its profiling (OFP), and proposes the organizational fitness navigator (OFN) as a systemic model of dynamic organizational capabilities. Part of the OFP model is a systemic scorecard (SCC) as a measurement tool for organizational fitness - in contrast to the well-known balanced scorecard (BSC) - for improving business survival and performance in increasingly networked environments.dynamic capabilities, organizational fitness, organizational fitness profiling, organizational fitness navigator, systemic scorecard

    Effect of boundaries on grid cell patterns

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    Mammalian grid cells represent spatial locations in the brain via triangular firing patterns that tessellate the environment. They are regarded as the biological substrate for path integration and to provide an efficient code for space. However, grid cell patterns are strongly influenced by environmental manipulations, in particular, exhibiting local geometrical deformations and defects tied to the shape of the recording enclosure, challenging the view that grid cells constitute a universal code for space. We show that the observed responses to environmental manipulations arise as a natural result under the general framework of feedforward models with spatially unstructured feedback inhibition, which puts the development of triangular patterns in the context of a Turing pattern formation process over physical space. The model produces coherent neuronal populations with equal grid spacing, field size, and orientation

    Traveling Theta Waves and the Hippocampal Phase Code

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    Hippocampal place fields form a neuronal map of the spatial environment. In addition, the distance between two place field centers is proportional to the firing phase difference of two place cells with respect to the local theta rhythm. This consistency between spatial distance and theta phase is generally assumed to result from hippocampal phase precession: The firing phase of a place cell decreases with distance traveled in the place field. The rate of phase precession depends on place field width such that the phase range covered in a traversal of a place field is independent of field width. Width-dependent precession rates, however, generally disrupt the consistency between distance and phase differences. In this paper we provide a mathematical theory suggesting that this consistency can only be secured for different place field widths if phase precession starts at a width-dependent phase offset. These offsets are in accordance with the experimentally observed theta wave traveling from the dorsal to the ventral pole of the hippocampus. Furthermore the theory predicts that sequences of place cells with different widths should be ordered according to the end of the place field. The results also hold for considerably nonlinear phase precession profiles

    Regional metacommunities in two coastal systems: spatial structure and drivers of plant assemblages

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    Aim Biogeographical patterns in metacommunities are still poorly understood, and different processes are expected to occur in different habitats. We analysed the regional plant metacommunities of coastal habitats to test whether (1) the influence of space and climate differs between two habitats differentiated along the seashore–inland gradient, and (2) regional variation in species composition of these habitats can be ascribed to different metacommunity paradigms. Location The entire coast of the Iberian Peninsula, south-western Europe. Methods We collected data on the plant species composition of coastal sites on sand dunes across 3000 km of coastline. The sites were classified into two habitats corresponding to shifting and stable sand dunes, and divided into three distinct geographical regions: Cantabrian, Atlantic and Mediterranean. We assessed the geographical structure of the species composition using ordination, estimates of species turnover and spatial autocorrelation. We then used multivariate models and variation partitioning to test the influence of climatic and spatial effects. Analyses were conducted for the whole data set and the geographical subsets. Results Metacommunities from shifting and stable dunes showed similar spa- tial patterns, with the highest species turnover occurring in the Mediterranean region. Similarities between communities that were nearer each other (typically < 100 km) were weaker in shifting than in stable dunes, although the distance decay for sites that were further apart was similar in both habitats. Variation in species composition in shifting dunes was mainly explained by distance and climate, while in stable dunes the effect of climate was clearly dominant. The observed differences were relatively consistent across geographical regions. Main conclusions Distinct processes structure the metacommunities in two dune habitats differentiated along the seashore–inland gradient. Communities of shifting dunes seem to be structured by an interplay of neutral or patch-dynamic processes and to a lesser degree by species sorting. In contrast, communities of stable dunes are mainly governed by species sorting in response to climatic gradi- ents. These results highlight the importance of differentiating habitats according to local ecological factors when analysing regional patterns in metacommunities

    Starve to Sustain - An Ancient Syrian Landrace of Sorghum as Tool for Phosphorous Bio-Economy?

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    Phosphorus (P) is an essential macronutrient, playing a role in developmental and metabolic processes in plants. To understand the local and systemic responses of sorghum to inorganic phosphorus (Pi) starvation and the potential of straw and ash for reutilisation in agriculture, we compared two grain (Razinieh) and sweet (Della) sorghum varieties with respect to their morpho-physiological and molecular responses. We found that Pi starvation increased the elongation of primary roots, the formation of lateral roots, and the accumulation of anthocyanin. In Razinieh, lateral roots were promoted to a higher extent, correlated with a higher expression of SbPht1 phosphate transporters. Infrared spectra of straw from mature plants raised to maturity showed two prominent bands at 1371 and 2337 cm−1, which could be assigned to P-H(H2) stretching vibration in phosphine acid and phosphinothious acid, and their derivates, whose abundance correlated with phosphate uptake of the source plant and genotype (with a higher intensity in Razinieh). The ash generated from these straws stimulated the shoot elongation and root development of the rice seedlings, especially for the material derived from Razinieh raised under Pi starvation. In conclusion, sorghum growing on marginal lands has potential as a bio-economy alternative for mineral phosphorus recycling

    The shape of ecological networks

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    We study the statistics of ecosystems with a variable number of co-evolving species. The species interact in two ways: by prey-predator relationships and by direct competition with similar kinds. The interaction coefficients change slowly through successful adaptations and speciations. We treat them as quenched random variables. These interactions determine long-term topological features of the species network, which are found to agree with those of biological systems.Comment: 4 pages, 2 figure

    Ecological equivalence: a realistic assumption for niche theory as a testable alternative to neutral theory

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    Hubbell's 2001 neutral theory unifies biodiversity and biogeography by modelling steady-state distributions of species richness and abundances across spatio-temporal scales. Accurate predictions have issued from its core premise that all species have identical vital rates. Yet no ecologist believes that species are identical in reality. Here I explain this paradox in terms of the ecological equivalence that species must achieve at their coexistence equilibrium, defined by zero net fitness for all regardless of intrinsic differences between them. I show that the distinction of realised from intrinsic vital rates is crucial to evaluating community resilience. An analysis of competitive interactions reveals how zero-sum patterns of abundance emerge for species with contrasting life-history traits as for identical species. I develop a stochastic model to simulate community assembly from a random drift of invasions sustaining the dynamics of recruitment following deaths and extinctions. Species are allocated identical intrinsic vital rates for neutral dynamics, or random intrinsic vital rates and competitive abilities for niche dynamics either on a continuous scale or between dominant-fugitive extremes. Resulting communities have steady-state distributions of the same type for more or less extremely differentiated species as for identical species. All produce negatively skewed log-normal distributions of species abundance, zero-sum relationships of total abundance to area, and Arrhenius relationships of species to area. Intrinsically identical species nevertheless support fewer total individuals, because their densities impact as strongly on each other as on themselves. Truly neutral communities have measurably lower abundance/area and higher species/abundance ratios. Neutral scenarios can be parameterized as null hypotheses for testing competitive release, which is a sure signal of niche dynamics. Ignoring the true strength of interactions between and within species risks a substantial misrepresentation of community resilience to habitat los

    An Erythropoietin-Independent Mechanism of Erythrocytic Precursor Proliferation Underlies Hypoxia Tolerance in Sea Nomads

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    The Bajau Sea Nomads were recently demonstrated to have evolved larger spleens as an adaptation to millennia of a marine foraging lifestyle. The large-spleen phenotype appears to derive from increases in thyroid hormone (TH) production as a result of reduced expression of phosphodiesterase 10A (PDE10A), though the exact mechanism remains unknown. Through pharmacological inhibition of PDE10A using the selective inhibitor MP-10 in mice, we were able to mimic the Bajau adaptation and show that treated mice had significantly larger spleens than control animals. This difference appears connected to an excess of early stage erythrocytes and an apparent increase in red blood cell (RBC) precursor proliferation in response to increased TH. However, we determined that the stimulation of RBC production in the mouse model via TH is Erythropoietin (EPO)-independent, unlike in the altitude (chronic hypoxemia) response. We confirmed this using human GWAS data; although the Bajau PDE10A variants are significantly associated with increased TH levels and RBC count, they are not associated with EPO levels, nor are other strongly thyroid-associated SNPs. We therefore suggest that an EPO-independent mechanism of stimulating RBC precursor proliferation via TH upregulation underlies the increase in spleen size observed in Sea Nomad populations
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