Purpose:To examine the dependence of steady-state freeprecession (SSFP) -based myocardial blood-oxygen-leveldependent (BOLD) contrast on field strength using theoretical and experimental models. Materials and Methods:Numerical simulations using a two-pool exchange model and a surgically prepared dog model were used to assess the SSFP-based myocardial BOLD signal changes at 1.5T and 3.0T. Experimental studies were performed in eight canines with pharmacological vasodilation under various levels of left circumflex coronary artery stenosis. Experimentally obtained BOLD signal changes were correlated against microsphere-based true flow changes. Results:Theoretical results showed that, at 3.0T, relative to 1.5T, a threefold increase in oxygen sensitivity can be expected. Experimental studies in canines showed near similar results-a 2.5 Ϯ 0.2-fold increase in BOLD sensitivity at 3.0T relative to 1.5T (P Ͻ 0.05). Based on the scatter gram of BOLD data and microsphere data, it was found that the minimum regional flow difference that can be detected with SSFP-based myocardial BOLD imaging at 1.5T and 3.0T were 2.9 and 1.6, respectively (P Ͻ 0.05). Conclusion:This study demonstrated that SSFP-based myocardial BOLD sensitivity is substantially greater at 3.0T compared with 1.5T. The findings here suggest that SSFP-based myocardial BOLD imaging at 3.0T may have the necessary sensitivity to detect the clinically required minimum flow difference of 2.0.

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The concentration of micron-size particles in used oil is generally obtained by atomic emission spectrometry. These accurate results can be considered as the most important index for real-time reliability evaluation including failure prediction and residual life assessment of power-shift steering transmission in tracked vehicles. Stochastic process and especially Wiener process can be applied in processing the oil spectral data. In this article, 50 used oil samples in total were collected and analyzed in sequence which covered 250 motor hours. The eigenvalue and mean value of elemental concentration in those samples were also revealed by linear regression analysis. Then, the increasing trends and the first hitting times for indicating elements were solved by simulating stochastic differential equations, which were based on the positive drift Wiener process. Comparing to the existing conditional maintenance time, the first hitting time increased about 27 motor hours more (13.7%). The results show that the maintenance frequency can be decreased by a longer time and finally can increase the cost-effectiveness ratio of maintenance.

Pancreatic ductal adenocarcinoma (PDAC) is a particularly lethal form of cancer. In 2012, the incidence of PDAC was 43,920. Five-year survival for patients with PDAC is around 6%, regardless of staging, making PDAC one of the deadliest forms of cancer. One reason for this dismal prognosis is chemoresistance to the current first-line therapy, gemcitabine. There are multiple factors that contribute to the chemoresistance observed in pancreatic cancer. Among them, desmoplasia has been increasingly seen as a significant contributor to chemoresistance. To overcome desmoplastic chemoresistance, several novel methods of treatment have been developed. Electroporation is one such novel treatment. High electrical fields are applied to cells to create pores that increase cell permeability. It has been previously demonstrated that electroporation enhances the therapeutic efficacy of anticancer drugs in pancreatic tumor models. Nanoparticle-based drug delivery systems constitute a second novel method to overcome desmoplastic chemoresistance. Due to their intrinsic design advantages, nanoparticles have been shown to increase the effectiveness of chemotherapeutic agents, while further reducing or even eliminating side effects. To date, there have been no studies evaluating the cumulative effect of combining both nanoparticle and electroporation strategies to overcome chemoresistance in PDAC. Our preliminary studies assessed the in vitro and in vivo uptake of doxorubicin-loaded iron oxide nanoparticles as a function of electroporation voltage and timing of administration in pancreatic adenocarcinoma cells. Our studies demonstrated that addition of electroporation to administration of nanoparticles significantly increased the amount of intracellular iron oxide nanoparticle uptake by a PANC-1 cell line in an athymic nude mouse model of PDAC. Further, electroporation-assisted nanoparticle uptake could be significantly altered by changing the timing of application of electroporation.

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