Northumbria University

About: Northumbria University is a education organization based out in Newcastle upon Tyne, United Kingdom. It is known for research contribution in the topics: Context (language use) & Population. The organization has 5624 authors who have published 17423 publications receiving 381949 citations. The organization is also known as: University of Northumbria at Newcastle.

Effect of frailty on marginal regression estimates in survival analysis

Abstract: Unexplained heterogeneity in univariate survival data and association in multivariate survival can both be modelled by the inclusion of frailty effects. This paper investigates the consequences of ignoring frailty in analysis, fitting misspecified Cox proportional hazards models to the marginal distributions. Regression coefficients are biased towards 0 by an amount which depends in magnitude on the variability of the frailty terms and the form of frailty distribution. The bias is reduced when censoring is present. Fitted marginal survival curves can also differ substantially from the true marginals.

Innovation-Oriented Culture in the Public Sector: Do managerial autonomy and result control lead to innovation?

Abstract: This article examines the effect of specific new public management (NPM)-related characteristics to explain innovation-oriented culture within public sector organizations According to NPM doctrines, an enhanced managerial autonomy combined with result control will stimulate a more innovation-oriented culture in such organizations Using multi-country survey data of over 200 public sector agencies, we test for the influence of organizational autonomy, result control and their interactions, on innovation-oriented culture High levels of managerial autonomy and result control have independent and positive effects However, the interaction between high personnel management autonomy and high result control has a negative effect

Extraction of polycyclic aromatic hydrocarbons from highly contaminated soils using microwave energy

Abstract: Microwave energy, generated in a commercial microwave system designed for extraction of organic samples, has been used for the extraction of polycyclic aromatic hydrocarbons (PAHs) from highly contaminated land samples. Initial studies used a native soil and compared a 20 min microwave extraction with a 6 h conventional Soxhlet extraction (both using dichloromethane) with comparable results. The low concentration of PAHs found in the soil resulted in large relative standard deviation (sr) values for the individual PAHs (maximum of 60.9% for microwave extraction). A second soil, with higher PAH levels, was microwave extracted using both dichloromethane and different compositions of an acetone–hexane mixture and compared with Soxhlet extraction. The results indicate that microwave extraction using pure acetone is a more efficient procedure than other combinations studied. A repeatability study gave an sr value for the total PAHs extracted of 2.4%(n= 6). A central composite experimental design was used to elucidate optimum operating parameters but variations in temperature, extraction time and solvent volume were found to have little effect on recovery. The over-all sr for the design was 5.34% illustrating no statistical significance in recovery. A third, Laboratory of the Government Chemist, test soil was used which indicated that the soil matrix was the greatest factor affecting PAH recovery.