In Search of the Criterion Standard Test in Diagnostic Testing

Given a certain technology or procedure for diagnostic testing, different cutoff points produce different sensitivity and specificity rates. The cutoff point that generates highest sensitivity and specificity establishes the Criterion Standard Test (otherwise known as the Gold Standard Test). If, subject to good reason, a new testing technology or procedure emerges, the optimum cutoff point associated with it may generate higher sensitivity and specificity and thus a new improved Criterion Standard Test. Various cutoff selection methodologies have been proposed, all based on Euclidean geometry, involving the so-called Receiver Operating Characteristic (ROC) curve. Our purpose in this paper is to recommend a new selection methodology based on the P-Value associated with the well-known Pearson’s chi-squared test (χ2) – the conventional test utilized when testing for dependence between state of nature (disease present or not present) and evidence (test positive or negative measures). Using a hypothetical numerical example, we demonstrate that the cutoff point associated with the lowest P-Value of the Pearson’s chi-squared test is the one that maximizes sensitivity and specificity, or overall accuracy, thus establishing the Criterion Standard Test. Although the best geometric method (sums of squares) and the proposed method are equally effective in selecting the optimum cutoff point, only the proposed new procedure selects based on statistical significance. Additionally, we propose a simple theoretical benefits / costs linear setting to discuss the importance of net benefits associated with testing accuracy and reference harmful as well as beneficial testing cases found in various literature sources

Managerial Mindsets Toward Corporate Social Responsibility: The Case of Auto Industry in Iran

Despite a plethora of empirical evidence on the potential role of senior management in the success of corporate social responsibility (CSR) in Western-dominated organizational contexts, little attempt has been made to document the various managerial mindsets toward CSR in organizations in Muslim-dominated countries in the Middle East region. To address this existing lacuna of theoretical and empirical research in CSR management, this paper offers a qualitative case study of CSR in three manufacturing firms operating in Iran’s auto industry. Based on an inductive analysis of the qualitative data, three types of managerial mindset toward CSR are identified: conformist, self-seeker, and satisfier. While it is evident that these different mindsets of Iranian managers seek to serve managerial ends and short-term self-interests, they fall short of core values of Islamic ethics and CSR

Tar formation during eucalyptus gasification in a bubbling fluidized bed reactor : Effect of feedstock and reactor bed composition

Tar compounds are inevitably present in the raw producer gas from biomass gasification and currently represent the main barrier for the commercial breakthrough of gasification technologies. In the present work, tar concentration in the producer gas from direct gasification of distinct types of residual forest biomass from eucalyptus in a 5 kWth bubbling fluidized bed reactor was investigated. The influence of the feedstock chemical composition and gasifier operation time was evaluated. Average tar concentration values in the raw producer gas were between 1.5 and 13.3 g/Nm3, representing a tar production between 8.4 and 67.0 g tar/kg biomass db, which surpasses suggested tar concentration limits for various potential applications for the producer gas. Major average tar compounds present in the tar sampled from the raw producer gas were benzene (47.1 %wt), toluene (21.6 %wt), naphthalene (10 %wt) and indene (6.4 %wt). A significant decay of the tar concentration in the producer gas was observed with increasing gasifier operation time, namely up to 50% within 45 min of operation, indicating its dependency on inorganics (e.g., CaCO3, KCl, maximum 5.5 %wt) and solid carbon (maximum 22.7 %wt) accumulation in the reactor bed.</p

Iron-based catalyst (Fe2-xNixTiO5) for tar decomposition in biomass gasification

In this study, a novel Fe2-xNixTiO5 catalyst for potential applications in biomass gasification gas cleaning/ upgrading was investigated. The material was successfully synthesized through combined mechanical activation and microwave firing. Catalytic steam reforming was studied in a fixed bed tubular reactor, using a mixture of toluene and naphthalene as model tar compounds as well as downstream a fluidized bed gasifier. Fe2-xNixTiO5 catalyst showed high activity in converting the model compounds at temperatures higher than 700 degrees C. The catalyst exhibited a tar conversion of 78% at 800 degrees C when exposed to biomass-derived gas from a bubbling fluidized bed gasifier. Nevertheless, the catalytic activity declined with increased time on stream due to structural changes in iron active phases, caused by redox conditions of the producer gas. Furthermore, thermodynamic calculations suggest that sulfur chemisorption on the nickel surface, may also contribute to the catalyst deactivation.</p