This study evaluate intraoperative Magnetic Resonance Imaging (MRI) as predictor of tissue damage following cryoablation of porcine liver with and without concomitant hepatic vascular inflow occlusion.Inflow occlusion was used during freezing in 6 of 12 pigs included. The volumes of the procedural ice-balls were estimated from MR images. Immediately after thawing contrast (MnDPDP) enhanced MRI was performed to estimate the volume of the cryolesion. Four days after ablation MRI was repeated of the in-vivo and the ex-vivo liver. Photography was performed of the sliced liver specimens to estimate the volumes of the lesions. The intraoperative volume of the cryolesion as shown by contrast enhanced MRI corresponded well to the ice-ball volume for lesions made without vascular occlusion (difference 0.3 +/- 0.9 cm(3), p = 0.239). For lesions made during occlusion the volume of the intraoperative cryolesion was larger than the corresponding ice-ball (difference 7.5 +/- 3.3 cm(3), p = 0.003). The volume of the cryolesions as estimated from histopathology four days after freezing and contrast enhanced MRI immediately after freezing corresponded well for lesions made with (difference -2.6 +/- 4.5 cm(3), p = 0.110) and without vascular occlusion (difference -0.5 +/- 2.3 cm(3), p = 0.695).Intraoperative MnDPDP-enhanced MRI of the cryolesion is predictive of the tissue damage induced during cryoablation of porcine liver. The procedural ice-ball is not, if induced during inflow occlusion. 相似文献
The paper presents a bicriterion approach to solve the single-machine scheduling problem in which the job release dates can be compressed while incurring additional costs. The two criteria are the makespan and the compression cost. For the case of equal job processing times, an O(n4) algorithm is developed to construct integer Pareto optimal points. We discuss how the algorithm developed can be modified to construct an -approximation of noninteger Pareto optimal points. The complexity status of the problem with total weighted completion time criterion is also established. 相似文献
The problem of scheduling the production and delivery of a supplier to feed the production of F manufacturers is studied. The orders fulfilled by the supplier are delivered to the manufacturers in batches of the same size. The supplier's production line has to be set up whenever it switches from processing an order of one manufacturer to an order of another manufacturer. The objective is to minimize the total setup cost, subject to maintaining continuous production for all manufacturers. The problem is proved to be NP-hard. It is reduced to a single machine scheduling problem with deadlines and jobs belonging to F part types. An O(NlogF) algorithm, where N is the number of delivery batches, is presented to find a feasible schedule. A dynamic programming algorithm with O(NF/FF–2) running time is presented to find an optimal schedule. If F=2 and setup costs are unit, an O(N) time algorithm is derived. 相似文献
Albuterol (salbutamol) is a widely used medication in respiratory disease including asthma and chronic obstructive airways disease; however, like other beta2-agonists, it also exerts some extrapulmonary effects on muscle and fat. Surprisingly, there have been relatively few reports of albuterol tissue distribution, and the distribution of individual albuterol enantiomers into tissue has not been reported. The method presented here explores the use of an HPLC tandem mass spectrometry (LC–MS/MS) system (LTQ Orbitrap hybrid mass spectrometer) with deuterated standard and solid-phase extraction to determine low levels of albuterol enantiomers in tissue. The lower limit of quantification (LLOQ) was 0.156 ng g−1, with a precision RSD <15% for both enantiomers. The assay was linear over the calibration range of LLOQ-10.0 ng g−1 in muscle tissue (r2 > 0.98). The assay was successfully applied to pharmacokinetic studies in rats and mice. By utilizing a deuterated internal standard and LC–MS/MS detection, this assay can be used to measure albuterol enantiomers in muscle tissue. This assay has also identified that albuterol uptake appears to be stereoselective, and enantioselective assays are clearly warranted for myoanabolic studies involving administration of racemic-albuterol.
Surface-enhanced Raman scattering (SERS) spectroscopy and density functional theory (DFT) calculations were used to investigate the nature of the charge-transfer (CT) process between nitrothiophenol (NTP) isomers and the n-type semiconductor, TiO2. The Raman signals of p-NTP and m-NTP that were chemisorbed onto TiO2 were significantly enhanced with respect to their corresponding neat compounds. In particular, an enhancement factor (EF) of 102–103 was observed for both p-NTP and m-NTP, with m-NTP displaying a larger EF compared to p-NTP. The Raman signal of o-NTP on TiO2 was not detectable, owing to interference from fluorescence emissions. A molecule-to-TiO2 charge-transfer mechanism was responsible for the enhanced Raman signals observed in p-NTP and m-NTP. This transfer was due to a strong coupling between the adsorbate and the metal oxide, which led to an optically driven CT transition from the HOMO of NTP into the conduction band of TiO2. Based on the mesomeric effect, the NO2 group para to the thiol had a stronger electron-withdrawing ability than the NO2 group at the meta position. A less-efficient CT transition from p-NTP to TiO2 in the surface complex resulted in a weaker Raman-signal enhancement for p-NTP compared to m-NTP. The DFT calculation determined that the HOMO and the LUMO of NTP bound to TiO2 were located entirely on the adsorbate and the semiconductor, respectively, thereby supporting the experimental findings that a molecule-to-TiO2 mechanism was the driving force behind the observed SERS effect. 相似文献
In this paper a control strategy is formulated that minimizes the costs for a single chemical cleaning of a dead-end ultra filtration membrane. From the process model, the performance index and the constraints it can be derived that dynamic optimization will lead to a ‘maximum effort control problem’, in which the controls (cleaning flow and cleaning agent concentration) are either zero or maximum. The change from maximum to zero is called the switching point. This switching point depends on the overall cleaning time and the requested cleaning effectiveness. From the calculated optimal control strategy it follows that cleaning time can be significantly reduced, compared to conventional cleaning. 相似文献
The Pure Adaptive Search (PAS) algorithm for global optimization yields a sequence of points, each of which is uniformly distributed in the level set corresponding to its predecessor. This algorithm has the highly desirable property of solving a large class of global optimization problems using a number of iterations that increases at most linearly in the dimension of the problem. Unfortunately, PAS has remained of mostly theoretical interest due to the difficulty of generating, in each iteration, a point uniformly distributed in the improving feasible region. In this article, we derive a coupling equivalence between generating an approximately uniformly distributed point using Markov chain sampling, and generating an exactly uniformly distributed point with a certain probability. This result is used to characterize the complexity of a PAS-implementation as a function of (a) the number of iterations required by PAS to achieve a certain solution quality guarantee, and (b) the complexity of the sampling algorithm used. As an application, we use this equivalence to show that PAS, using the so-called Random ball walk Markov chain sampling method for generating nearly uniform points in a convex region, can be used to solve most convex programming problems in polynomial time. 相似文献