1,968 research outputs found

    Organisational Responses to Discontinuous Innovation: A Case Study Approach

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    Research that examines entrant-incumbent dynamics often points to the organisational limitations that constrain incumbents from successfully pursuing new technologies or fending off new entrants. Some incumbents are nevertheless able to successfully implement organisational structures and develop routines that overcome these institutional constraints. We provide a case-study analysis of how three firms - Motorola, IBM and Kodak - responded to discontinuous innovations and the associated structural and organisational limitations that are typical to incumbent organisations. Each firm was able to capture gains from new technologies and develop profitable products in emerging markets, although their abilities to sustain these gains varied due to subsequent organisational changes. Drawing from these case studies, we synthesise how firms can institute organisational strategies to continue to capture gains from disruptive innovations. A schema suggests that particular organisational strategies are comparatively optimal for corresponding points along an innovation lifecycle

    Dilated Floor Functions That Commute

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    We determine all pairs of real numbers (α,β)(\alpha, \beta) such that the dilated floor functions αx\lfloor \alpha x\rfloor and βx\lfloor \beta x\rfloor commute under composition, i.e., such that αβx=βαx\lfloor \alpha \lfloor \beta x\rfloor\rfloor = \lfloor \beta \lfloor \alpha x\rfloor\rfloor holds for all real xx.Comment: 6 pages, to appear in Amer. Math. Monthl

    Dilated floor functions having nonnegative commutator II. Negative dilations

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    This paper completes the classification of the set SS of all real parameter pairs (α,β)(\alpha,\beta) such that the dilated floor functions fα(x)=αxf_\alpha(x) = \lfloor{\alpha x}\rfloor, fβ(x)=βxf_\beta(x) = \lfloor{\beta x}\rfloor have a nonnegative commutator, i.e. [fα,fβ](x)=αβxβαx0 [ f_{\alpha}, f_{\beta}](x) = \lfloor{\alpha \lfloor{\beta x}\rfloor}\rfloor - \lfloor{\beta \lfloor{\alpha x}\rfloor}\rfloor \geq 0 for all real xx. This paper treats the case where both dilation parameters α,β\alpha, \beta are negative. This result is equivalent to classifying all positive α,β\alpha, \beta satisfying αβxβαx0 \lfloor{\alpha \lceil{\beta x}\rceil}\rfloor - \lfloor{\beta \lceil{\alpha x}\rceil}\rfloor \geq 0 for all real xx. The classification analysis is connected with the theory of Beatty sequences and with the Diophantine Frobenius problem in two generators.Comment: 18 pages, 8 figure

    Dissecting mechanisms of brain aging by studying the intrinsic excitability of neurons

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    Several studies using vertebrate and invertebrate animal models have shown aging associated changes in brain function. Importantly, changes in soma size, loss or regression of dendrites and dendritic spines and alterations in the expression of neurotransmitter receptors in specific neurons were described. Despite this understanding, how aging impacts intrinsic properties of individual neurons or circuits that govern a defined behavior is yet to be determined. Here we discuss current understanding of specific electrophysiological changes in individual neurons and circuits during aging

    Independent evaluation of a simple clinical prediction rule to identify right ventricular dysfunction in patients with shortness of breath

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    BACKGROUND: Many patients have unexplained persistent dyspnea after negative computed tomographic pulmonary angiography (CTPA). We hypothesized that many of these patients have isolated right ventricular (RV) dysfunction from treatable causes. We previously derived a clinical decision rule (CDR) for predicting RV dysfunction consisting of persistent dyspnea and normal CTPA, finding that 53% of CDR-positive patients had isolated RV dysfunction. Our goal is to validate this previously derived CDR by measuring the prevalence of RV dysfunction and outcomes in dyspneic emergency department patients. METHODS: A secondary analysis of a prospective observational multicenter study that enrolled patients presenting with suspected PE was performed. We included patients with persistent dyspnea, a nonsignificant CTPA, and formal echo performed. Right ventricular dysfunction was defined as RV hypokinesis and/or dilation with or without moderate to severe tricuspid regurgitation. RESULTS: A total of 7940 patients were enrolled. Two thousand six hundred sixteen patients were analyzed after excluding patients without persistent dyspnea and those with a significant finding on CTPA. One hundred ninety eight patients had echocardiography performed as standard care. Of those, 19% (95% confidence interval [CI], 14%-25%) and 33% (95% CI, 25%-42%) exhibited RV dysfunction and isolated RV dysfunction, respectively. Patients with isolated RV dysfunction or overload were more likely than those without RV dysfunction to have a return visit to the emergency department within 45 days for the same complaint (39% vs 18%; 95% CI of the difference, 4%-38%). CONCLUSION: This simple clinical prediction rule predicted a 33% prevalence of isolated RV dysfunction or overload. Patients with isolated RV dysfunction had higher recidivism rates and a trend toward worse outcomes

    Hyperactivity, impulsivity, and inattention in boys with cleft lip and palate: relationship to ventromedial prefrontal cortex morphology

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    The purpose of this study is to evaluate quantitative structural measures of the ventromedial prefrontal cortex (vmPFC) in boys with isolated clefts of the lip and/or palate (ICLP) relative to a comparison group and to associate measures of brain structure with quantitative measures of hyperactivity, impulsivity, and inattentiveness. A total of 50 boys with ICLP were compared to 60 healthy boys without clefts. Magnetic resonance imaging brain scans were used to evaluate vmPFC structure. Parents and teachers provided quantitative measures of hyperactivity, impulsivity, and inattentiveness using the Pediatric Behavior Scale. Boys with ICLP had significantly higher ratings of hyperactivity/impulsivity/inattention (HII) and significantly increased volume of the right vmPFC relative to the comparison group. There was a direct relationship between HII score and vmPFC volume in both the ICLP group and control group, but the relationship was in the opposite direction: in ICLP, the higher the vmPFC volume, the higher the HII score; for the comparison group, the lower the vmPFC volume, the greater the HII score. The vmPFC is a region of the brain that governs behaviors of hyperactivity, impulsivity and inattention (HII). In boys with ICLP, there are higher levels of HII compared to the controls and this is directly related to a significantly enlarged volume of the right vmPFC. Enlargement of this region of the brain is therefore considered to be pathological in the ICLP group and supports the notion that abnormal brain structure (from abnormal brain development) is the underlying etiology for the abnormal behaviors seen in this population

    Clinical features from the history and physical examination that predict the presence or absence of pulmonary embolism in symptomatic emergency department patients: results of a prospective, multi-center study

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    Study Objective—Prediction rules for pulmonary embolism (PE) employ variables explicitly shown to estimate the probability of PE. However, clinicians often use variables that have not been similarly validated, yet are implicitly believed to modify probability of PE. The objective of this study was to measure the predictive value of 13 implicit variables. Methods—Patients were enrolled in a prospective cohort study from 12 centers in the United States; all had an objective test for PE (D-dimer, CT angiography, or V/Q scan). Clinical features including 12 predefined previously validated (explicit) variables and 13 variables not part of existing prediction rules (implicit) were prospectively recorded at presentation. The primary outcome was VTE (venous thromboembolism: PE or deep venous thrombosis), diagnosed by imaging up to 45 days after enrollment. Variables with adjusted odds ratios from logistic regression with 95% confidence intervals not crossing unity were considered significant. Results—7,940 patients (7.2% VTE+) were enrolled. Mean age was 49±17 years and 67% were female. Eight of 13 implicit variables were significantly associated with VTE; those with an adjusted OR >1.5 included non-cancer related thrombophilia (1.99), pleuritic chest pain (1.53), and family history of VTE (1.51). Implicit variables that predicted no VTE outcome included: substernal chest pain, female gender, and smoking. Nine of 12 explicit variables predicted a positive outcome of VTE, including unilateral leg swelling, recent surgery, estrogen, hypoxemia and active malignancy. Conclusions—In symptomatic outpatients being considered for possible PE, non-cancer related thrombophilia, pleuritic chest pain, and family history of VTE increase probability of PE or DVT. Other variables that are part of existing pretest probability systems were validated as important predictors in this diverse sample of US Emergency department patients

    Long-term success for people living with HIV: A framework to guide practice

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    Objectives: In recent decades, the needs of people living with HIV have evolved as life expectancy has greatly improved. Now, a new definition of long-term success (LTS) is necessary to help address the multifaceted needs of all people living with HIV. Methods: We conducted a two-phase research programme to delineate the range of experiences of people living with HIV. The insights garnered from these research phases were explored in a series of expert-led workshops, which led to the development and refinement of the LTS framework. Results: The insights generated from the research phases identified a series of themes that form a part of LTS. These themes were subsequently incorporated into the LTS framework, which includes five outcome pillars: sustained undetectable viral load, minimal impact of treatment and clinical monitoring, optimized health-related quality of life, lifelong integration of healthcare, and freedom from stigma and discrimination. A series of supporting statements were also developed by the expert panel to help in the achievement of each of the LTS pillars. Conclusions: The LTS framework offers a comprehensive and person-centric approach that, if achieved, could help improve the long-term well-being of people living with HIV and support the LTS vision of 'every person living with HIV being able to live their best life'
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