Here we evaluated hospitalisation rates and associated risk factors of human immunodeficiency virus (HIV)-infected individuals who were followed up in an Italian reference hospital from 1998 to 2016. ...Incidence rates (IR) of hospitalisations were calculated for five study periods from 1998 to 2016. The random-effects Poisson regression model was used to assess risk factors for hospitalisation including demographic and clinical characteristics. To consider that more events may occur for the same subject, multiple failure-time data analysis was also performed for selected causes using the Cox proportional hazards model. We evaluated 2031 patients. During 13 173 person-years (py) of follow-up, 3356 hospital admissions were carried out for 756 patients (IR: 255 per 1000 py). IR decreased significantly over the study period, from 634 in 1998-2000 to 126 per 1000 py in 2013-2016. Major declines were detected for AIDS-defining events, non-HIV/AIDS-related infections and neurological diseases. Older age, female sex, longer HIV duration and HCV coinfection were associated with a higher hospitalisation risk, whereas higher CD4 nadir and antiretroviral therapy were associated with a reduced risk. Influence of advanced HIV disease markers declined over time. Hospitalisation rates decreased during the study period in most causes. The relative weight of hospitalisations for non-AIDS-related tumours, cardiovascular, respiratory and kidney diseases increased during the study period, whereas those for AIDS-defining events declined.
With the aim of characterising the different stress patterns in several egg types and evaluating the resistivity of the eggshell while impacting in free fall, experimental tests and computational ...simulations have been performed on eggs of the species Gallus gallus (domestic hen), Struthio camelus (ostrich), and Testudo sp. (tortoise). The different types of failure were determined for each taxa and stress distribution maps were recorded and correlated between experimental results and simulations using finite element analysis (FEA). For domestic hens, the numerical results obtained in both tests have highly correlation with the results obtained in previous works; for ostrich (S. camelus) and tortoise (Testudo sp.) eggshells, this new data represented a useful tool to understand in further works the failure mechanisms of the eggshells. More interestingly, the present study provides the first empirical and mathematic results that allow confident safety intervals to be established that relate to the laying process in the poultry industry.
•Understand the mechanical of eggshells are crucial for egg production.•Eggshell resistivity is evaluated using both empirical and computational tests.•Newly classification of failure helps to understand failure mechanisms.•For first time, ostrich and turtle eggshell mechanics are provided.•Results set relationships between impact velocity, substrate, and type of failure.
How do we understand and explain the apparent dichotomy between plasticity and robustness in the context of development? Can we identify these complex processes without resorting to 'either/or' ...solutions? Written by two leaders in the field, this is the first book to fully unravel the complexity of the subject, explaining that the epigenetic processes generating plasticity and robustness are in fact deeply intertwined. It identifies the different mechanisms that generate robustness and the various forms of plasticity, before considering the functional significance of the integrated mechanisms and how the component processes might have evolved. Finally, it highlights the ways in which epigenetic mechanisms could be instrumental in driving evolutionary change. Essential reading for biologists and psychologists interested in epigenetics and evolution, this book is also a valuable resource for biological anthropologists, sociobiologists, child psychologists and paediatricians.
Mathematicians and statisticians have made significant academic progress on the subject of distribution theory in the last two decades, and this area of study is becoming one of the main statistical ...tools for the analysis of lifetime (survival) data. In many ways, lifetime distributions are the common language of survival dialogue because the framework subsumes many statistical properties of interest, such as reliability, entropy and maximum likelihood. Recent Advances in Lifetime and Reliability Models provides a comprehensive account of models and methods for lifetime models. Building from primary definitions such as density and hazard rate functions, this book presents readers a broad framework on distribution theory in survival analysis. This framework covers classical methods - such as the exponentiated distribution method - as well as recent models explaining lifetime distributions, such as the beta family and compounding models. Additionally, a detailed discussion of mathematical and statistical properties of each family, such as mixture representations, asymptotes, types of moments, order statistics, quantile functions, generating functions and estimation is presented in the book. Key Features: - presents information about classical and modern lifetime methods - covers key properties of different models in detail - explores regression models for the beta generalized family of distributions - focuses information on both theoretical fundamentals and practical aspects of implementing different models - features examples relevant to business engineering and biomedical sciences Recent Advances in Lifetime and Reliability Models will equip students, researchers and working professionals with the information to make extensive use of observational data in a variety of fields to create inferential models that make sense of lifetime data.
This paper proposes a discrete-time linear parameter varying (LPV) unknown input observer (UIO) for the diagnosis of actuator faults and ice accretion in unmanned aerial vehicles (UAVs). The proposed ...approach, which is suited to an implementation on-board, exploits a complete 6-degrees of freedom (DOF) UAV model, which includes the coupled longitudinal/lateral dynamics and the impact of icing. The LPV formulation has the advantage of allowing the icing diagnosis scheme to be consistent with a wide range of operating conditions. The developed theory is supported by simulations illustrating the diagnosis of actuator faults and icing in a small UAV. The obtained results validate the effectiveness of the proposed approach.
Even in the absence of unmeasured confounding factors or model misspecification, standard methods for estimating the causal effect of time-varying treatments on survival are biased when (a) there ...exists a time-dependent risk factor for survival that also predicts subsequent treatment, and (b) past treatment history predicts subsequent risk factor level. In contrast, methods based on marginal structural models (MSMs) can provide consistent estimates of causal effects when unmeasured confounding and model misspecification are absent. MSMs are a new class of causal models whose parameters are estimated using a new class of estimators-inverse-probability-of-treatment weighted estimators. We use a marginal structural Cox proportional hazards model to estimate the joint effect of zidovudine (AZT) and prophylaxis therapy for Pneumocystis carinii pneumonia on the survival of HIV-positive men in the Multicenter AIDS Cohort Study, an observational study of homosexual men. We obtained an estimated causal mortality rate (hazard) ratio of .67 (conservative 95% confidence interval .46-.98) for AZT and of 1.14 (.79, 1.64) for prophylaxis therapy. These estimates will be consistent for the true causal rate ratios when the functional forms chosen for our models are correct and data have been obtained on all time-independent and time-dependent covariates that predict both subsequent treatment and mortality.
Abstract Purpose Longitudinal data linking area-level socioeconomic status (SES) to repeated acute coronary syndrome (ACS) events are limited. Using multiple failure-time data, we examined the ...association between neighborhood SES and ACS in a community-based cohort of myocardial infarction (MI) survivors. Methods Consecutive patients aged 65 years or younger discharged from eight hospitals in central Israel after first MI in 1992–1993 were followed through 2005. Recurrent MI and unstable angina pectoris (UAP) leading to hospitalization were recorded. Neighborhood SES was assessed through a composite census-derived index developed by the Israel Central Bureau of Statistics. Different variance-corrected proportional hazards models were used to account for multiple recurrent events: Andersen-Gill, Wei-Lin-Weissfeld (WLW), and Prentice-Williams-Peterson. Results During follow-up, 531 recurrent MIs and 1584 UAP episodes occurred among 1164 patients. Adjusting for known prognostic factors and individual SES using the Andersen-Gill model, higher estimated hazards were associated with poor neighborhood SES (hazard ratio, 1.55; 95% confidence interval CI, 1.13–2.14 for recurrent MI; and hazard ratio, 1.48; 95% CI, 1.22–1.79 for UAP; in the 5th vs. 95th percentiles). The WLW and Prentice-Williams-Peterson models yielded similar results. When the two outcomes were combined, the WLW-derived hazard ratio was 1.64 (95% CI, 1.39–1.93). Conclusions MI survivors living in a deprived neighborhood are at higher risk of repeated hospital admissions because of ACS. Secondary prevention initiatives should incorporate multilevel approaches to increase effectiveness and reduce geographic health disparities.
Reappraising Medfly Longevity Koenker, Roger; Geling, Olga
Journal of the American Statistical Association,
06/2001, Letnik:
96, Številka:
454
Journal Article
Recenzirano
Odprti dostop
In this article we explore the usefulness of a quantile regression formulation of reanalyzing a large experimental study that monitored age-specific mortality in a sample of roughly 1.2 million ...Mediterranean fruit flies. The quantile regression approach appears useful in refining several of the conclusions drawn from the original study including the apparent decline in mortality rates at advanced ages, and the gender crossover effect in survival functions for medflies.
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