20 research outputs found

    On the generalization of the GMS evolutionary model

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    We study a generalization of the evolution model proposed by Guiol, Machado and Schinazi (arXiv:0909.2108). In our model, at each moment of time a random number of species is either born or removed from the system; the species to be removed are those with the lower fitnesses, fitnesses being some numbers in [0,1][0,1]. We show that under some conditions, a set of species approaches (in some sense) a sample from a uniform distribution on [f,1][f,1] for some f[0,1)f\in [0,1), and that the total number of species forms a recurrent process in most other cases

    Benchmarked performance charts using principal components analysis to improve the effectiveness of feedback for audit data in HIV care

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    Abstract Background Feedback tools for clinical audit data that compare site-specific results to average performance over all sites can be useful for quality improvement. Proposed tools should be simple and clearly benchmark the site’s performance, so that a relevant action plan can be directly implemented to improve patient care services. We aimed to develop such a tool in order to feedback data to UK HIV clinics participating in the 2015 British HIV Association (BHIVA) audit assessing compliance with the 2011 guidelines for routine investigation and monitoring of adult HIV-1- infected individuals. Methods HIV clinic sites were asked to provide data on a random sample of 50–100 adult patients attending for HIV care during 2014 and/or 2015 by completing a self-audit spreadsheet. Outcomes audited included the proportion of patients with recorded resistance testing, viral load monitoring, adherence assessment, medications, hepatitis testing, vaccination management, risk assessments, and sexual health screening. For each outcome we benchmarked the proportion for a specific site against the average performance. We produced performance charts for each site using boxplots for the outcomes. We also used the mean and differences from the mean performance to produce a dashboard for each site. We used principal components analysis to group correlated outcomes and simplify the dashboard. Results The 106 sites included in the study provided information on a total of 7768 patients. Outcomes capturing monitoring of treatment of HIV-infection showed high performance across the sites, whereas testing for hepatitis, and risk assessment for cardiovascular disease and smoking, management of flu vaccination, sexual health screening, and cervical cytology for women were very variable across sites. The principal components analysis reduced the original 12 outcomes to four factors that represented HIV care, hepatitis testing, other screening tests, and resistance testing. These provided simplified measures of adherence to guidelines which were presented as a 4 bar dashboard of performance. Conclusion Our dashboard performance charts provide easily digestible visual summaries of locally relevant audit data that are benchmarked against the overall mean and can be used to improve feedback to HIV services. Feedback from clinicians indicated that they found these charts acceptable and useful

    Studying two different stochastic models : on the study of a random coloured tree and on the generalization of an evolutionary model

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    A simple method to estimate vegetation indices and crop canopy factors using field spectroscopy for solanum tuberosum during the whole phenological cycle

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    Field spectroscopy is a part of the remote sensing techniques and very important for studies in agriculture. A GER-1500 field spectro-radiometer was used in this study in order to retrieve the necessary spectrum data of the spring potatoes for estimating spectral vegetation indices (SVI's). A field campaign was undertaken from September to the end of November 2012 for the collection of spectro-radiometric measurements. The study area was in the Mandria Village in Paphos district in Cyprus. This paper demonstrates how crop canopy factors can be statistically related to remotely sensed data, namely vegetation indices. The paper is a part of an EU cofounded project regarding estimating crop water requirements using remote sensing techniques and informing the farmers through 3G smart telephony

    A simple method to estimate vegetation indices and crop canopy factors using field spectroscopy for solanum tuberosum during the whole phenological cycle

    No full text
    Field spectroscopy is a part of the remote sensing techniques and very important for studies in agriculture. A GER-1500 field spectro-radiometer was used in this study in order to retrieve the necessary spectrum data of the spring potatoes for estimating spectral vegetation indices (SVI's). A field campaign was undertaken from September to the end of November 2012 for the collection of spectro-radiometric measurements. The study area was in the Mandria Village in Paphos district in Cyprus. This paper demonstrates how crop canopy factors can be statistically related to remotely sensed data, namely vegetation indices. The paper is a part of an EU cofounded project regarding estimating crop water requirements using remote sensing techniques and informing the farmers through 3G smart telephony

    Application of SEBAL methodology for estimating and disseminating through 3rd generation mobile phones crop water requirements in Cyprus

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    Water allocation to crops has always been of great importance in agricultural process. In this context, and under the current conditions, where Cyprus is facing a severe drought from time to time, purpose of this study is basically to estimate the needed crop water requirements for supporting irrigation management and monitoring irrigation on a systematic basis for Cyprus using remote sensing techniques. The use of satellite images supported by ground measurements has provided quite accurate results. Intended purpose of this paper is to estimate the Evapotranspiration (ET) of specific crops which is the basis for irrigation scheduling and establish a procedure for monitoring and managing irrigation water over Cyprus, using remotely sensed data from Landsat TM/ ETM+ and a sound methodology used worldwide, the Surface Energy Balance Algorithm for Land (SEBAL). Finally Crop Water Requirements derived from the specific research are disseminated to crop producers through a network of 3rd generation mobile phones
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