Extended Model Analysis Research Articles

Responsible Sourcing Under Supplier-Auditor Collusion

Problem definition: Although they enjoy low costs in sourcing from emerging economies, global brands also face serious brand and reputation risks from their suppliers’ noncompliance with environmental and labor standards. Such a supplier problem can be viewed as a process quality problem concerning how products are sourced and produced. Academic/practical relevance: Addressing this problem is a key component of many global companies’ responsible sourcing programs. A common approach is to use an audit as an auxiliary supplier screening mechanism. However, in regions with lax law enforcement, an unethical, noncomplying supplier may attempt to bribe an unethical auditor to pass the audit. Such supplier-auditor collusion compromises the integrity of the audit and weakens its effectiveness. Methodology: In this paper, we develop a game-theoretical model to study the effect of supplier-auditor collusion on the buyer’s auditing and contracting strategy in responsible sourcing, as well as various driving factors that help reduce collusion. Results: We show that the buyer’s equilibrium contracting strategy is a shutout contract that takes three different forms, depending on the collusion risk level. We also define and analyze the screening errors and social efficiency loss caused by supplier-auditor collusion. By comparing the cost versus collusion elimination trade-off between a third-party audit and an in-house audit, we offer explanations for why many global brands fully rely on third-party audits and set higher process quality requirements for suppliers located in high-risk countries. The robustness of our insights is verified by two model extensions: one involving additional supplier audit cost and the other allowing for supplier process quality improvement before audit. Managerial implications: These model insights provide useful theoretical support and baseline guidance for the current supplier audit practices in responsible sourcing. Our extended model analysis further demonstrates the importance for global brands to lobby local governments to increase collusion penalties and to promote the ethical level of the third-party auditors located in high-risk countries.

Assessing the reproducibility of dynamic contrast enhanced magnetic resonance imaging in a murine model of breast cancer

Quantitative dynamic contrast enhanced magnetic resonance imaging estimates parameters related to tissue vascularity and volume fractions; additionally, semiquantitative parameters such as the initial area under the curve can be utilized to describe tissue behavior. The aim of this study was to establish the reproducibility of quantitative and semiquantitative analysis of dynamic contrast enhanced magnetic resonance imaging in a murine model of breast cancer. For each animal, a T1-weighted, gradient-echo sequence was used to acquire two sets of dynamic contrast enhanced magnetic resonance imaging data separated by 5 h. Data were acquired at both a 0.05 mm3 (128(2) , n=12) and a 0.2 mm3 (64(2), n=12) resolution, and analysis was performed using both the Tofts-Kety (to estimate Ktrans and ve) and extended Tofts-Kety (Ktrans, ve, and vp) models. Reproducibility analysis was performed for both the center slice and the total tumor volume for all parameters. For the total volume analysis, the repeatability index for Ktrans is 0.073 min(-1) in the standard model analysis and 0.075 min(-1) in the extended model analysis at the 128(2) acquisition. For the 64(2) acquisition, the values are 0.089 and 0.063 min(-1) for the standard and extended models, respectively. The repeatability index for initial area under the curve was 0.0039 and 0.0042 mM min for the 128(2) and 64(2) acquisitions, respectively.