766 research outputs found
Estimation of parameters in linear structural relationships: Sensitivity to the choice of the ratio of error variances
Maximum likelihood estimation of parameters in linear structural relationships under normality assumptions requires knowledge of one or more of the model parameters if no replication is available. The most common assumption added to the model definition is that the ratio of the error variances of the response and predictor variates is known. The use of asymptotic formulae for variances and mean squared errors as a function of sample size and the assumed value for the error variance ratio is investigated
Cost-effective aperture arrays for SKA Phase 1: single or dual-band?
An important design decision for the first phase of the Square Kilometre
Array is whether the low frequency component (SKA1-low) should be implemented
as a single or dual-band aperture array; that is, using one or two antenna
element designs to observe the 70-450 MHz frequency band. This memo uses an
elementary parametric analysis to make a quantitative, first-order cost
comparison of representative implementations of a single and dual-band system,
chosen for comparable performance characteristics. A direct comparison of the
SKA1-low station costs reveals that those costs are similar, although the
uncertainties are high. The cost impact on the broader telescope system varies:
the deployment and site preparation costs are higher for the dual-band array,
but the digital signal processing costs are higher for the single-band array.
This parametric analysis also shows that a first stage of analogue tile
beamforming, as opposed to only station-level, all-digital beamforming, has the
potential to significantly reduce the cost of the SKA1-low stations. However,
tile beamforming can limit flexibility and performance, principally in terms of
reducing accessible field of view. We examine the cost impacts in the context
of scientific performance, for which the spacing and intra-station layout of
the antenna elements are important derived parameters. We discuss the
implications of the many possible intra-station signal transport and processing
architectures and consider areas where future work could improve the accuracy
of SKA1-low costing.Comment: 64 pages, 23 figures, submitted to the SKA Memo serie
Simultaneous perturbation gradient approximation based Metropolis adjusted Langevin Markov chain Monte Carlo for inference of ordinary differential equations
The role of affect regulation in the treatment of people who have committed sexual offences
Affect regulation problems have been found to play an important role in the onset of problematic behavior, such as sexual abuse. The role of emotion and maladaptive coping has become relevant in both research and treatment interventions. Forensic treatments have been strongly influenced by conceptualizations of affect regulation that emphasize the control of emotional experience and expression. For a long time, emotions were treated as less important than cognition. However, the view of emotion as an adaptive resource and meaning system is now emerging in the forensic literature. General psychotherapy research has shown that improved affect regulation and deeper experiencing is associated with better outcomes in psychotherapy. These findings, in combination with the role of emotions in behavioral and relational functioning, are leading to a shift in forensic treatment approaches. In this paper, we review the literature on affect regulation in treatment programs for individuals who have committed sexual offences. The implications of this work for forensic practice will be considered. Finally, Emotion-Focused Therapy will be presented as a promising therapeutic approach for forensic treatment programs to promote clients' emotional engagement and processing, and to improve treatment outcomes
A non-Markovian model for cell population growth: speed of convergence and central limit theorem
In De Gunst (1989) a stochastic model was developed for the growth of a batch culture of plant cells. In this paper the mathematical properties of the model are considered. We investigate the asymptotic behaviour of the population growth as predicted by the model when the initial cell number of population members tends to infinity. In particular it is shown that the total cell number, which is a non-Markovian counting process, converges almost surely, uniformly on the real line to a non-random function and the rate of convergence is established. Moreover, a central limit theorem is proved. Computer simulations illustrate the behaviour of the process. The model is graphically compared with experimental data
Wild Bootstrap for Counting Process-Based Statistics
The wild bootstrap is a popular resampling method in the context of
time-to-event data analyses. Previous works established the large sample
properties of it for applications to different estimators and test statistics.
It can be used to justify the accuracy of inference procedures such as
hypothesis tests or time-simultaneous confidence bands. This paper consists of
two parts: in Part~I, a general framework is developed in which the large
sample properties are established in a unified way by using martingale
structures. The framework includes most of the well-known non- and
semiparametric statistical methods in time-to-event analysis and parametric
approaches. In Part II, the Fine-Gray proportional sub-hazards model
exemplifies the theory for inference on cumulative incidence functions given
the covariates. The model falls within the framework if the data are
censoring-complete. A simulation study demonstrates the reliability of the
method and an application to a data set about hospital-acquired infections
illustrates the statistical procedure.Comment: 2 parts, 115 pages, 2 figures, 13 table
A network analysis of female sexual function: comparing symptom networks in women with decreased, increased, and stable sexual desire
Inference via Wild Bootstrap and Multiple Imputation under Fine-Gray Models with Incomplete Data
Fine-Gray models specify the subdistribution hazards for one out of multiple
competing risks to be proportional. The estimators of parameters and cumulative
incidence functions under Fine-Gray models have a simpler structure when data
are censoring-complete than when they are more generally incomplete. This paper
considers the case of incomplete data but it exploits the above-mentioned
simpler estimator structure for which there exists a wild bootstrap approach
for inferential purposes. The present idea is to link the methodology under
censoring-completeness with the more general right-censoring regime with the
help of multiple imputation. In a simulation study, this approach is compared
to the estimation procedure proposed in the original paper by Fine and Gray
when it is combined with a bootstrap approach. An application to a data set
about hospital-acquired infections illustrates the method.Comment: 32 pages, 2 figures, 1 tabl
Influence of functional rider and horse asymmetries on saddle force distribution during stance and in sitting trot
Asymmetric forces exerted on the horse's back during riding are assumed to have a negative effect on rider–horse interaction, athletic performance, and health of the horse. Visualized on a saddle pressure mat, they are initially blamed on a nonfitting saddle. The contribution of horse and rider to an asymmetric loading pattern, however, is not well understood. The aim of this study was to investigate the effects of horse and rider asymmetries during stance and in sitting trot on the force distribution on the horse's back using a saddle pressure mat and motion capture analysis simultaneously. Data of 80 horse-rider pairs (HRP) were collected and analyzed using linear (mixed) models to determine the influence of rider and horse variables on asymmetric force distribution. Results showed high variation between HRP. Both rider and horse variables revealed significant relationships to asymmetric saddle force distribution (P < .001). During sitting trot, the collapse of the rider in one hip increased the force on the contralateral side, and the tilt of the rider's upper body to one side led to more force on the same side of the pressure mat. Analyzing different subsets of data revealed that rider posture as well as horse movements and conformation can cause an asymmetric force distribution. Because neither horse nor rider movement can be assessed independently during riding, the interpretation of an asymmetric force distribution on the saddle pressure mat remains challenging, and all contributing factors (horse, rider, saddle) need to be considered
Healthcare access for refugees in Greece: Challenges and opportunities
The arrival of more than one million refugees and migrants in Europe in 2015, most of whom transited through Greece, has placed significant strains on local health systems and demonstrated the need for preparedness to meet the immediate and longer-term health needs of arrivals in EU countries. Population movements will continue to occur and the need for cost effective, appropriate provision of both primary and secondary health services to meet these needs is key. The Global Compact on Migration was ratified in 2018 and forms an overarching, international agreement to address safe, orderly and regular migration which benefits refugees and migrants as well as host communities; however, it did not give due emphasis to health. In this manuscript, we explore the evolution of the health response for refugees in Greece over the last three years, the challenges faced at different times of the response and the efforts to integrate refugees into Greece’s health system
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