1,720,968 research outputs found
Perceived neighbouhood quality and adult health status : new statistical advice useful to answer old questions?
No full textInterest in the quantitative effects of neighbourhood characteristics on adult health has recently increased . Particularly, investigations concern the statistical influence on health of several individual demographic and socioeconomic characteristics and of neighbourhood characteristics as perceived by respondents. We analyze these issues within an original conceptual framework and employing statistical models unusual in this context. We use data collected in the Los Angeles Family and Neighbourhood Survey (L.A.FANS) to model the number of hospital admissions occurred to each individual as a function of some individual and neighbourhood characteristics, the latter being related to the individual perceptions about the neighbourhood he lives in. We
employ generalized additive models with different istributional assumptions: Poisson,Negative Biomial and Z ro Inflated Poisson (ZIP). Such models allow us to estimate (through spline functions) potential non linear effects of the covariates on the response. Moreover, non standard representations are used to overcome difficulties in interpreting the results for ZIP models. It turns out that perceived neighbourhood characteristics, and in particular the perception of social cohesion, have a significant effect after controlling for individual characteristics relevant to hospital admissions frequency. From a modeling point of view ZIP and Negative binomial models prove to be superior to standard Poisson
model. We have confirmed the role of the neighbourhood where an individual lives in determining his health status. A strength of this analysis is that, due to the choice of the neighbourhood characteristics to be included in the model, the results do t depend of a particular definition of neighbourhood (which is traditionally based on
administrative boundaries), since each individual refers his perceptions to his personal definition of it
Modeling the relationship between perceived neighbourhood characteristics and adult hospitalization frequencies from a cross-sectional study
No full textInterest in the quantitative effects of neighbourhood characteristics on urban health has recently increased in social epidemiology. Such effects are mostly studied employing multilevel models based on some definition of the neighbourhood. We investigate the statistical relationship between health and the neighourhood quality as perceived by individuals, thus avoiding the need of choosing a specific definition of neighbourhood.
We use data from the Los Angeles Family and Neighbourhood Survey (L.A.FANS). We measure health status of an individual as the number of hospitalizations in the last two years. This number is related to individual carachteristics (including neighbourhood perceptions) through generalized additive models (GAM), focusing particularly on the Zero Inflated Poisson (ZIP), which is an unusual choice in this context.
We also overcome to some extent the difficulties in interpreting the results from a GAM with a ZIP distribution by simulating predicted values under varying assumptions in order to reveal the relationship of interest.
The analysis confirms that the quality of neighbourhood – as measured by perceptions of individuals – significantly relates to the health status of inhabitants – as measured by the number of hospitalizations
Retinal image synthesis through the least action principle
No full textEye fundus image analysis is a fundamental approach in medical diagnosis and follow-up ophthalmic diagnostics. Manual annotation by experts needs hard work, thus only a small set of annotated vessel structures is available. Examples such as DRIVE and STARE include small sets for training images of fundus image benchmarks. Moreover, there is no vessel structure annotation for a number of fundus image datasets. Synthetic images have been generated by using appropriate parameters for the modeling of vascular networks or by methods developing deep learning techniques and supported by performance hardware. Our methodology aims to produce high-resolution synthetic fundus images alternative to the increasing use of generative adversarial networks, to overcome the problems that arise in producing slightly modified versions of the same real images, to simulate pathologies and for the prediction of eye-related diseases. Our approach is based on the principle of the least action to place vessels on the simulated eye fundus
A visual framework to create photorealistic retinal vessels for diagnosis purposes
No full textThe methods developed in recent years for synthesising an ocular fundus can be been divided into two main categories. The first category of methods involves the development of an anatomical model of the eye, where artificial images are generated using appropriate parameters for modelling the vascular networks and fundus. The second type of method has been made possible by the development of deep learning techniques and improvements in the performance of hardware (especially graphics cards equipped with a large number of cores). The methodology proposed here to produce high-resolution synthetic fundus images is intended to be an alternative to the increasingly widespread use of generative adversarial networks to overcome the problems that arise in producing slightly modified versions of the same real images. This will allow the simulation of pathologies and the prediction of eye-related diseases. The proposed approach is based on the principle of least action and correctly places the vessels on the simulated eye fundus without using real morphometric information. An a posteriori analysis of the average characteristics such as the size, length, bifurcations, and endpoint positioning confirmed the substantial accuracy of the proposed approach compared to real data. A graphical user interface allows the user to make any changes in real time by controlling the positions of control points
Statistical issues in choosing indicators to evaluate healthy cities projects (not only a political task)
No full textWe develop statistical considerations about methodologies that, at least in our opinion, are suitable to synthesize appropriately the impact on health of urban populations of socio-economic and environmental conditions and local policies.
In particular, we focus attention on the so called Health Impact Assessment (HIA) proposed by the European working group “Promoting and Supporting Integrated Approaches for Health and Sustainable Development at the Local Level across Europe” PHASE (2003-2005) within the World Health Organization (WHO) - Healthy Cities Project (HCP) (http://www.euro.who.int/healthy-cities/).
Among open issues about HCP in general and HIA in particular, we focus on statistical tools allowing for the multidimensionality of the phenomenon, the heterogeneity of its various aspects and the complexity of local urban realities involved. This will be done considering simultaneously both conceptual framework and data, measures and statistical models, trying to give policymakers and citizens relevant information in a suitable form as the HCP – Phase IV “Healthy Cities and Urban Governance” needs
Modeling the relationship between perceived neighbourhood characteristics and adult hospitalization frequencies from a cross-sectional study
Full text linkInterest in the quantitative effects of neighbourhood characteristics on urban health has recently increased in social epidemiology.Such effects are mostly stydied employing multilevel models based on some definition of neighbourhood. We investigate the statistical relationship between health and the neighboururhood quality as perceived by individuals, thus avoiding the inconvenient of choosing a specific administrative definition. We use sampling data from the Los Angels Family and Neighb. Survey(L.A.FANS). We choose the number of hospitalizations in the last two years as health status and we have related this number to several individual characteristics through Generalized Additive Models(GAM),focusing on Zero Inflated Poisson(ZIP) , which are unusual choices in this context. We also overcome to some extent the difficulties in interpreting the results from a GAM with a ZIP distribution by simulating predicted values under varying assumptions in order to reveal the relationship of interest.The analyses confirm results already
published in the literature , suggesting also that new opportunities , from a statistical methods point of view, are available in this specific field of social epidemiology
Lower Limb Exoskeleton Control via Linear Quadratic Regulator and Disturbance Observer
No full textAchieving a more human-like trajectory of lower limb exoskeleton for locomotion assistance requires accurate trajectory tracking control. However, this task has challenges due to the nonlinearities and disturbances acting on the system, which is interacting with the wearer and the surroundings. In order to improve the control performance, a Linear Quadratic Regulator with integral action (LQRi) and Unknown Input Observer (UIO) to compensate for disturbances are introduced. The chosen control strategy is model-based, therefore an accurate model of the exoskeleton is derived. Experiments are conducted, and the testing results compared with the previous Proportional Derivative (PD) controller show a performance improvement throughout the gait cycle, which proves the proposed control to be effective and easily implementable for lower limb exoskeleton control
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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