Estimation in Semiparametric Quantile Factor Models

We propose an estimation methodology for a semiparametric quantile factor panel model. We provide tools for inference that are robust to the existence of moments and to the form of weak cross-sectional dependence in the idiosyncratic error term. We apply our method to daily stock return data

Estimation and Inference in Semiparametric Quantile Factor Models

We consider a semiparametric quantile factor panel model that allows observed stock-specific characteristics to affect stock returns in a nonlinear time-varying way, extending Connor, Hagmann, and Linton (2012) to the quantile restriction case. We propose a sieve-based estimation methodology that is easy to implement. We provide tools for inference that are robust to the existence of moments and to the form of weak cross-sectional dependence in the idiosyncratic error term. We apply our method to daily stock return data where we find significant evidence of nonlinearity in many of the characteristic exposure curves

Estimation and inference in semiparametric quantile factor models

We consider a semiparametric quantile factor panel model that allows observed stock-specific characteristics to affect stock returns in a nonlinear time-varying way, extending Connor, Hagmann,and Linton (2012) to the quantile restriction case. We propose a sieve-based estimation methodology that is easy to implement. We provide tools for inference that are robust to the existence of moments and to the form of weak cross-sectional dependence in the idiosyncratic error term. We apply our method to daily stock return data where we find significant evidence of nonlinearity in many of the characteristic exposure curves

Influences of clinical experience in the quantification of morphometric sarcopaenia: a cohort study

Objective: The measurement of total psoas muscle area (TPMA) on CT imaging is commonly made using either manual tracing or a semi-automated technique. We examined whether clinical experience influenced measurement of TPMA when utilising these two commonly used methods and describe the relationship between techniques. Methods: Pre-operative cross-sectional CT imaging of 114 consecutive patients undergoing elective endovascular aneurysm repair were analysed. Retrospective measurements of the TPMA were performed by four independent investigators with a range of clinical experience (medical student to specialist surgical registrar) using either technique. Intra- and inter-observer differences were assessed. Results: There was no significant intra- or inter-observer differences when measuring the TPMA. Clinical experience also did not influence TPMA measurements recorded. Significant differences were observed between techniques when measuring TPMA (mean −65.8, 239.3 SD, p = 0.004). Measurement differences between techniques were highly correlated and modelled using linear regression. Conclusion: Both manual tracing and semi-automated technique quantification methods of measuring TPMA are highly reproducible and independent of assessor bias and clinical experience. Advances in knowledge: Either of the commonly used techniques to measure TPMA may be reliably used by an individual with appropriate training. We describe a relationship to facilitate comparison between these methods by which sarcopaenia may be quantified in patients with routine CT imaging

Most Likely Transformations

We propose and study properties of maximum likelihood estimators in the class of conditional transformation models. Based on a suitable explicit parameterisation of the unconditional or conditional transformation function, we establish a cascade of increasingly complex transformation models that can be estimated, compared and analysed in the maximum likelihood framework. Models for the unconditional or conditional distribution function of any univariate response variable can be set-up and estimated in the same theoretical and computational framework simply by choosing an appropriate transformation function and parameterisation thereof. The ability to evaluate the distribution function directly allows us to estimate models based on the exact likelihood, especially in the presence of random censoring or truncation. For discrete and continuous responses, we establish the asymptotic normality of the proposed estimators. A reference software implementation of maximum likelihood-based estimation for conditional transformation models allowing the same flexibility as the theory developed here was employed to illustrate the wide range of possible applications.Comment: Accepted for publication by the Scandinavian Journal of Statistics 2017-06-1

Study protocol of cost-effectiveness and cost-utility of a biopsychosocial multidisciplinary intervention in the evolution of non-specific sub-acute low back pain in the working population: cluster randomised trial.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Background: Low back pain (LBP), with high incidence and prevalence rate, is one of the most common reasons to consult the health system and is responsible for a significant amount of sick leave, leading to high health and social costs. The objective of the study is to assess the cost-effectiveness and cost-utility analysis of a multidisciplinary biopsychosocial educational group intervention (MBEGI) of non-specific sub-acute LBP in comparison with the usual care in the working population recruited in primary healthcare centres. Methods/design: The study design is a cost-effectiveness and cost-utility analysis of a MBEGI in comparison with the usual care of non-specific sub-acute LBP.Measures on effectiveness and costs of both interventions will be obtained from a cluster randomised controlled clinical trial carried out in 38 Catalan primary health care centres, enrolling 932 patients between 18 and 65 years old with a diagnosis of non-specific sub-acute LBP. Effectiveness measures are: pharmaceutical treatments, work sick leave (% and duration in days), Roland Morris disability, McGill pain intensity, Fear Avoidance Beliefs (FAB) and Golberg Questionnaires. Utility measures will be calculated from the SF-12. The analysis will be performed from a social perspective. The temporal horizon is at 3 months (change to chronic LBP) and 12 months (evaluate the outcomes at long term. Assessment of outcomes will be blinded and will follow the intention-to-treat principle. Discussion: We hope to demonstrate the cost-effectiveness and cost-utility of MBEGI, see an improvement in the patients' quality of life, achieve a reduction in the duration of episodes and the chronicity of non-specific low back pain, and be able to report a decrease in the social costs. If the intervention is cost-effectiveness and cost-utility, it could be applied to Primary Health Care Centres. Trial registration: ISRCTN: ISRCTN5871969

The management of nanotechnology: analysis of technology linkages and the regional nanotechnology competencies

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordThis study maps the linkage of nanotechnologies and their clusters, identifies emerging and mature technologies and links to their application fields, and examines the profiles of the regional nanotechnology competencies. A model is proposed to assist with the analyses. The patent data were retrieved from the Thomson Innovation database, which were subsequently analysed with the Thomson Data Analyser. The results show technological linkages using the proposed linkage model, for example, the linkage between the cluster of nanotubes‐nanowires‐polymers and the cluster of nanowires‐semiconductors‐optical identifies a nanoelectronics domain. In the Techno‐Economic Network framework, the result shows that the United States maintains its position in the Science and Technology poles, revealing its strong competitiveness, while the nanotechnological competencies in Japan have lost strength significantly in recent years. Asian giants such as South Korea and China appear to be the most likely contenders for catching up with the United States. The theoretical contribution of this study is the theoretical framework that has been adapted and tested in this research. Practical contributions consist of descriptive and analytical findings based on actors' performances and the regions' competencies. The research offers a useful insight for academic and research practitioners on how an emerging field such as nanotechnology can be analysed, and a way forward for materialising science and technology policies in this field

Study protocol of effectiveness of a biopsychosocial multidisciplinary intervention in the evolution of non-speficic sub-acute low back pain in the working population : cluster randomised trial

Background: Non-specific low back pain is a common cause for consultation with the general practitioner, generating increased health and social costs. This study will analyse the effectiveness of a multidisciplinary intervention to reduce disability, severity of pain, anxiety and depression, to improve quality of life and to reduce the incidence of chronic low back pain in the working population with non-specific low back pain, compared to usual clinical care. Methods/Design: A Cluster randomised clinical trial will be conducted in 38 Primary Health Care Centres located in Barcelona, Spain and its surrounding areas. The centres are randomly allocated to the multidisciplinary intervention or to usual clinical care. Patients between 18 and 65 years old (n = 932; 466 per arm) and with a diagnostic of a non-specific sub-acute low back pain are included. Patients in the intervention group are receiving the recommendations of clinical practice guidelines, in addition to a biopsychosocial multidisciplinary intervention consisting of group educational sessions lasting a total of 10 hours. The main outcome is change in the score in the Roland Morris disability questionnaire at three months after onset of pain. Other outcomes are severity of pain, quality of life, duration of current non-specific low back pain episode, work sick leave and duration, Fear Avoidance Beliefs and Goldberg Questionnaires. Outcomes will be assessed at baseline, 3, 6 and 12 months. Analysis will be by intention to treat. The intervention effect will be assessed through the standard error of measurement and the effect-size. Responsiveness of each scale will be evaluated by standardised response mean and receiver-operating characteristic method. Recovery according to the patient will be used as an external criterion. A multilevel regression will be performed on repeated measures. The time until the current episode of low back pain takes to subside will be analysed by Cox regression. Discussion: We hope to provide evidence of the effectiveness of the proposed biopsychosocial multidisciplinary intervention in avoiding the chronification of low back pain, and to reduce the duration of non-specific low back pain episodes. If the intervention is effective, it could be applied to Primary Health Care Centres