3,176 research outputs found
The Experience of Improvising in Organizations: A Creative Process Perspective
In this paper, we explore how improvisation is experienced by people in organizations, conceptualizing improvisation as a creative process. We draw on a small number of scholarly accounts of the experience of improvising in organizations, and compare and contrast them with accounts from the performing arts. In both cases, improvising evokes simultaneous exhilaration and fear, as well as experiences of non-goal-directed action. In many organizational contexts, however, improvisation is normatively discouraged, which heightens the fearful aspect of the experience. This leads many workers to avoid improvising, using it as a method of last resort and even hiding its use. Thus, improvisation is seldom used in favorable circumstances nor practiced to the point of familiarity or expertise. We discuss the implications of these insights for research and practice of improvisation and creativity in organizations, and propose a research agenda for the experience of improvising in organizations
Modelling avalanches in martensites
Solids subject to continuous changes of temperature or mechanical load often
exhibit discontinuous avalanche-like responses. For instance, avalanche
dynamics have been observed during plastic deformation, fracture, domain
switching in ferroic materials or martensitic transformations. The statistical
analysis of avalanches reveals a very complex scenario with a distinctive lack
of characteristic scales. Much effort has been devoted in the last decades to
understand the origin and ubiquity of scale-free behaviour in solids and many
other systems. This chapter reviews some efforts to understand the
characteristics of avalanches in martensites through mathematical modelling.Comment: Chapter in the book "Avalanches in Functional Materials and
Geophysics", edited by E. K. H. Salje, A. Saxena, and A. Planes. The final
publication is available at Springer via
http://dx.doi.org/10.1007/978-3-319-45612-6_
Metal-insulator transition in vanadium dioxide nanobeams: probing sub-domain properties of strongly correlated materials
Many strongly correlated electronic materials, including high-temperature
superconductors, colossal magnetoresistance and metal-insulator-transition
(MIT) materials, are inhomogeneous on a microscopic scale as a result of domain
structure or compositional variations. An important potential advantage of
nanoscale samples is that they exhibit the homogeneous properties, which can
differ greatly from those of the bulk. We demonstrate this principle using
vanadium dioxide, which has domain structure associated with its dramatic MIT
at 68 degrees C. Our studies of single-domain vanadium dioxide nanobeams reveal
new aspects of this famous MIT, including supercooling of the metallic phase by
50 degrees C; an activation energy in the insulating phase consistent with the
optical gap; and a connection between the transition and the equilibrium
carrier density in the insulating phase. Our devices also provide a
nanomechanical method of determining the transition temperature, enable
measurements on individual metal-insulator interphase walls, and allow general
investigations of a phase transition in quasi-one-dimensional geometry.Comment: 9 pages, 3 figures, original submitted in June 200
Leaf Morphology, Taxonomy and Geometric Morphometrics: A Simplified Protocol for Beginners
Taxonomy relies greatly on morphology to discriminate groups. Computerized geometric morphometric methods for quantitative shape analysis measure, test and visualize differences in form in a highly effective, reproducible, accurate and statistically powerful way. Plant leaves are commonly used in taxonomic analyses and are particularly suitable to landmark based geometric morphometrics. However, botanists do not yet seem to have taken advantage of this set of methods in their studies as much as zoologists have done. Using free software and an example dataset from two geographical populations of sessile oak leaves, we describe in detailed but simple terms how to: a) compute size and shape variables using Procrustes methods; b) test measurement error and the main levels of variation (population and trees) using a hierachical design; c) estimate the accuracy of group discrimination; d) repeat this estimate after controlling for the effect of size differences on shape (i.e., allometry). Measurement error was completely negligible; individual variation in leaf morphology was large and differences between trees were generally bigger than within trees; differences between the two geographic populations were small in both size and shape; despite a weak allometric trend, controlling for the effect of size on shape slighly increased discrimination accuracy. Procrustes based methods for the analysis of landmarks were highly efficient in measuring the hierarchical structure of differences in leaves and in revealing very small-scale variation. In taxonomy and many other fields of botany and biology, the application of geometric morphometrics contributes to increase scientific rigour in the description of important aspects of the phenotypic dimension of biodiversity. Easy to follow but detailed step by step example studies can promote a more extensive use of these numerical methods, as they provide an introduction to the discipline which, for many biologists, is less intimidating than the often inaccessible specialistic literature
Incorporating prior knowledge improves detection of differences in bacterial growth rate
BACKGROUND: Robust statistical detection of differences in the bacterial growth rate can be challenging, particularly when dealing with small differences or noisy data. The Bayesian approach provides a consistent framework for inferring model parameters and comparing hypotheses. The method captures the full uncertainty of parameter values, whilst making effective use of prior knowledge about a given system to improve estimation. RESULTS: We demonstrated the application of Bayesian analysis to bacterial growth curve comparison. Following extensive testing of the method, the analysis was applied to the large dataset of bacterial responses which are freely available at the web-resource, ComBase. Detection was found to be improved by using prior knowledge from clusters of previously analysed experimental results at similar environmental conditions. A comparison was also made to a more traditional statistical testing method, the F-test, and Bayesian analysis was found to perform more conclusively and to be capable of attributing significance to more subtle differences in growth rate. CONCLUSIONS: We have demonstrated that by making use of existing experimental knowledge, it is possible to significantly improve detection of differences in bacterial growth rate
The smaller vesicomyid bivalves in the genus Isorropodon (Bivalvia, Vesicomyidae, Pliocardiinae) also harbour chemoautotrophic symbionts
Species of Isorropodon are vesicomyid bivalves for which little information is available regarding host phylogeny and bacterial symbioses. In this study we investigated the symbioses in three Isorropodon species from three cold seep areas: Isorropodon bigoti (Gulf of Guinea), Isorropodon megadesmus (Gulf of Cadiz) and Isorropodon perplexum (Eastern Mediterranean). Analysis of bacterial 16S ribosomal RNA gene sequences demonstrated that each vesicomyid species harbours a single symbiont phylotype, that symbionts from the three species cluster together, and that they are closely related to other known vesicomyid symbionts. These results are confirmed by other marker genes (encoding 23S rRNA and APS reductase) and by fluorescence in situ hybridization. Due to their extended depth range and transoceanic distribution Isorropodon species are interesting examples to further study evolutionary processes in bivalve hosts and their associated symbionts
Chemotherapy-Response Monitoring of Breast Cancer Patients Using Quantitative Ultrasound-Based Intra-Tumour Heterogeneities
© 2017 The Author(s). Anti-cancer therapies including chemotherapy aim to induce tumour cell death. Cell death introduces alterations in cell morphology and tissue micro-structures that cause measurable changes in tissue echogenicity. This study investigated the effectiveness of quantitative ultrasound (QUS) parametric imaging to characterize intra-tumour heterogeneity and monitor the pathological response of breast cancer to chemotherapy in a large cohort of patients (n = 100). Results demonstrated that QUS imaging can non-invasively monitor pathological response and outcome of breast cancer patients to chemotherapy early following treatment initiation. Specifically, QUS biomarkers quantifying spatial heterogeneities in size, concentration and spacing of acoustic scatterers could predict treatment responses of patients with cross-validated accuracies of 82 ± 0.7%, 86 ± 0.7% and 85 ± 0.9% and areas under the receiver operating characteristic (ROC) curve of 0.75 ± 0.1, 0.80 ± 0.1 and 0.89 ± 0.1 at 1, 4 and 8 weeks after the start of treatment, respectively. The patients classified as responders and non-responders using QUS biomarkers demonstrated significantly different survivals, in good agreement with clinical and pathological endpoints. The results form a basis for using early predictive information on survival-linked patient response to facilitate adapting standard anti-cancer treatments on an individual patient basis
Introduction to the functional RG and applications to gauge theories
These lectures contain an introduction to modern renormalization group (RG)
methods as well as functional RG approaches to gauge theories. In the first
lecture, the functional renormalization group is introduced with a focus on the
flow equation for the effective average action. The second lecture is devoted
to a discussion of flow equations and symmetries in general, and flow equations
and gauge symmetries in particular. The third lecture deals with the flow
equation in the background formalism which is particularly convenient for
analytical computations of truncated flows. The fourth lecture concentrates on
the transition from microscopic to macroscopic degrees of freedom; even though
this is discussed here in the language and the context of QCD, the developed
formalism is much more general and will be useful also for other systems.Comment: 60 pages, 14 figures, Lectures held at the 2006 ECT* School
"Renormalization Group and Effective Field Theory Approaches to Many-Body
Systems", Trento, Ital
AFLP analysis reveals high genetic diversity but low population structure in Coccidioides posadasiiisolates from Mexico and Argentina
BACKGROUND: Coccidioides immitis and C. posadasii cause coccidioidomycosis, a disease that is endemic to North and South America, but for Central America, the incidence of coccidioidomycosis has not been clearly established. Several studies suggest genetic variability in these fungi; however, little definitive information has been discovered about the variability of Coccidioides fungi in Mexico (MX) and Argentina (AR). Thus, the goals for this work were to study 32 Coccidioides spp. isolates from MX and AR, identify the species of these Coccidioides spp. isolates, analyse their phenotypic variability, examine their genetic variability and investigate the Coccidioides reproductive system and its level of genetic differentiation. METHODS: Coccidioides spp. isolates from MX and AR were taxonomically identified by phylogenetic inference analysis using partial sequences of the Ag2/PRA gene and their phenotypic characteristics analysed. The genetic variability, reproductive system and level of differentiation were estimated using AFLP markers. The level of genetic variability was assessed measuring the percentage of polymorphic loci, number of effective allele, expected heterocygosity and Index of Association (I(A)). The degree of genetic differentiation was determined by AMOVA. Genetic similarities among isolates were estimated using Jaccard index. The UPGMA was used to contsruct the corresponding dendrogram. Finally, a network of haplotypes was built to evaluate the genealogical relationships among AFLP haplotypes. RESULTS: All isolates of Coccidioides spp. from MX and AR were identified as C. posadasii. No phenotypic variability was observed among the C. posadasii isolates from MX and AR. Analyses of genetic diversity and population structure were conducted using AFLP markers. Different estimators of genetic variability indicated that the C. posadasii isolates from MX and AR had high genetic variability. Furthermore, AMOVA, dendrogram and haplotype network showed a small genetic differentiation among the C. posadasii populations analysed from MX and AR. Additionally, the I(A) calculated for the isolates suggested that the species has a recombinant reproductive system. CONCLUSIONS: No phenotypic variability was observed among the C. posadasii isolates from MX and AR. The high genetic variability observed in the isolates from MX and AR and the small genetic differentiation observed among the C. posadasii isolates analysed, suggest that this species could be distributed as a single genetic population in Latin America
Phase Structure and Compactness
In order to study the influence of compactness on low-energy properties, we
compare the phase structures of the compact and non-compact two-dimensional
multi-frequency sine-Gordon models. It is shown that the high-energy scaling of
the compact and non-compact models coincides, but their low-energy behaviors
differ. The critical frequency at which the sine-Gordon model
undergoes a topological phase transition is found to be unaffected by the
compactness of the field since it is determined by high-energy scaling laws.
However, the compact two-frequency sine-Gordon model has first and second order
phase transitions determined by the low-energy scaling: we show that these are
absent in the non-compact model.Comment: 21 pages, 5 figures, minor changes, final version, accepted for
publication in JHE
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