Search results for "Hazard"

On statistical inference for the random set generated Cox process with set-marking.

2007

Cox point process is a process class for hierarchical modelling of systems of non-interacting points in ℝd under environmental heterogeneity which is modelled through a random intensity function. In this work a class of Cox processes is suggested where the random intensity is generated by a random closed set. Such heterogeneity appears for example in forestry where silvicultural treatments like harvesting and site-preparation create geometrical patterns for tree density variation in two different phases. In this paper the second order property, important both in data analysis and in the context of spatial sampling, is derived. The usefulness of the random set generated Cox process is highly…

On the relationship between the reversed hazard rate and elasticity

2012

Despite hazard and reversed hazard rates sharing a number of similar aspects, reversed hazard functions are far less frequently used. Understanding their meaning is not a simple task. The aim of this paper is to expand the usefulness of the reversed hazard function by relating it to other well-known concepts broadly used in economics: (linear or cumulative) rates of increase and elasticity. This will make it possible (i) to improve our understanding of the consequences of using a particular distribution and, in certain cases, (ii) to introduce our hypotheses and knowledge about the random process in a more meaningful and intuitive way, thus providing a means to achieving distributions that …

Comment on ‘Generating survival times to simulate Cox proportional hazards models with time-varying covariates’

2013

Segmented relationships to model erosion of regression effect in Cox regression

2010

In this article we propose a parsimonious parameterisation to model the so-called erosion of the covariate effect in the Cox model, namely a covariate effect approaching to zero as the follow-up time increases. The proposed parameterisation is based on the segmented relationship where proper constraints are set to accomodate for the erosion. Relevant hypothesis testing is discussed. The approach is illustrated on two historical datasets in the survival analysis literature, and some simulation studies are presented to show how the proposed framework leads to a test for a global effect with good power as compared with alternative procedures. Finally, possible generalisations are also present…

A comparison of semiparametric approaches to evaluate composite endpoints in heart failure trials

2021

In heart failure trials efficacy is usually proven by a composite endpoint including cardiovascular death (CVD) and recurrent heart failure hospitalisations (HFH), evaluated with time-to-first-event analysis based on a Cox model. As a considerable fraction of events is ignored that way, recurrent event[for full text, please go to the a.m. URL]

A segmented regression model for event history data: an application to the fertility patterns in Italy

2009

We propose a segmented discrete-time model for the analysis of event history data in demographic research. Through a unified regression framework, the model provides estimates of the effects of explanatory variables and jointly accommodates flexibly non-proportional differences via segmented relationships. The main appeal relies on ready availability of parameters, changepoints, and slopes, which may provide meaningful and intuitive information on the topic. Furthermore, specific linear constraints on the slopes may also be set to investigate particular patterns. We investigate the intervals between cohabitation and first childbirth and from first to second childbirth using individual data …

Comparison of Prognostic Signatures in Node-Negative Tamoxifen-Treated Breast Cancer Patients.

2009

Abstract Background: A number of molecular signatures have been published to aid breast cancer prognosis and therapy response prediction. A 76-gene signature has been developed in a node-negative patient cohort that did not receive systemic therapy.1 Another prognostic 97-gene signature measures predominantly proliferation-associated genes.2 Finally, a 21-gene signature has been developed for node-negative and estrogen receptor–positive breast cancer patients treated with tamoxifen in the adjuvant setting.3 Here we compare the prognostic performance of all three published algorithms in a cohort of 189 node-negative breast cancer patients treated with tamoxifen.Materials and Methods: Fresh-f…

Integration of SAR Data Into Monitoring of the 2014–2015 Holuhraun Eruption, Iceland: Contribution of the Icelandic Volcanoes Supersite and the Futur…

2018

We report how data from satellite and aerial synthetic aperture radar (SAR) observations were integrated into monitoring of the 2014–2015 Holuhraun eruption in the Bárðarbunga volcanic system, the largest effusive eruption in Iceland since the 1783–84 Laki eruption. A lava field formed in one of the most remote areas in Iceland, after the propagation of a ∼50 km-long dyke beneath the Vatnajökull ice cap, where the Bárðarbunga caldera is located. Due to the 6 month duration of the eruption, mainly in wintertime, daily monitoring was particularly challenging. During the eruption, the European volcanological project FutureVolc was ongoing, allowing collaboration of many European experts on vol…

Anaerobic Degradation of Environmentally Hazardous Aquatic Plant Pistia stratiotes and Soluble Cu(II) Detoxification by Methanogenic Granular Microbi…

2021

The aquatic plant Pistia stratiotes L. is environmentally hazardous and requires effective methods for its utilization. The harmfulness of these plants is determined by their excessive growth in water bodies and degradation of local aquatic ecosystems. Mechanical removal of these plants is widespread but requires fairly resource-intensive technology. However, these aquatic plants are polymer-containing substrates and have a great potential for conversion into bioenergy. The aim of the work was to determine the main patterns of Pistia stratiotes L. degradation via granular microbial preparation (GMP) to obtain biomethane gas while simultaneously detoxifying toxic copper compounds. The compos…

Efficacy of coronary revascularization in patients with acute chest pain managed in a chest pain unit.

2009

To investigate the safety of discharge of patients deemed at low risk of cardiac events after evaluation in a chest pain unit and to determine the prognostic effect of revascularization of patients deemed at high risk.The study population consisted of 1088 patients presenting at the emergency department from January 15, 2001, to September 1, 2006, with chest pain but without ischemia on electrocardiography or troponin elevation. Patients were managed by a chest pain unit protocol that included early exercise testing. Three groups of patients were distinguished: (1) those discharged after exercise testing (424 [39%]); (2) those in whom unstable angina was ruled out after in-hospital evaluati…