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Predicting ecological regime shift under climate change： New modelling techniques and potential of molecular-based approaches

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Current Zoology 2013年第3期59卷 403-417页

作者： richard stafford V. Anne SMITH Dirk HUSMEIER Thomas GRIMA Barbara-ann GUINN School of Applied Sciences Boumemouth University BH12 5BB UK School of Biology University of St Andrews St Andrews KY 16 9ST UK School of Mathematics and Statistics University of Glasgow G 12 8QW UK Department of Life Sciences University of Bedfordshire LU1 3JU UK

Ecological regime shift is the rapid transition from one stable community structure to another, often ecologically infe- rior, stable community. Such regime shifts are especially common in shallow marine communities, such as the transition of kelp forests to algal turfs that harbour far lower biodiversity. Stable regimes in communities are a result of balanced interactions be- tween species, and predicting new regimes therefore requires an evaluation of new species interactions, as well as the resilience of the ＇stable＇ position. While computational optimisation techniques can predict new potential regimes, predicting the most likely community state of the various options produced is currently educated guess work. In this study we integrate a stable regime op- timisation approach with a Bayesian network used to infer prior knowledge of the likely stress of climate change （or, in practice, any other disturbance） on each component species of a representative rocky shore community model. Combining the results, by calculating the product of the match between resilient computational predictions and the posterior probabilities of the Bayesian network, gives a refined set of model predictors, and demonstrates the use of the process in determining community changes, as might occur through processes such as climate change. To inform Bayesian priors, we conduct a review of molecular approaches applied to the analysis of the transcriptome of rocky shore organisms, and show how such an approach could be linked to meas- ureable stress variables in the field. Hence species-specific microarrays could be designed as biomarkers of in situ stress, and used to inform predictive modelling approaches such as those described here.

关键词： Regime shift Phase shift Altemative stable state Intertidal Food web Resilience

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An Investigation of the Required MR Bone Attenuation Correction for Quantitative Whole-Body PET/MR Imaging Using Clinical NaF PET/CT Studies

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2018年第3期7卷 273-295页

作者： Hua A. Ai Osama Mawlawi R. Jason stafford Jim Bankson Yiping Shao Michele Guindani richard E. Wendt III Department of Imaging Physics The University of Texas MD Anderson Cancer Center Houston USA Medical Physics Program The University of Texas Graduate School of Biomedical Sciences at Houston Houston USA Department of Radiation Oncology UT Southwest Medical Center Dallas USA Department of Biostatistics The University of Texas MD Anderson Cancer Center Houston USA Biostatistics Bioinformatics and Systems Biology Program The University of Texas Graduate School of Biomedical Sciences at Houston Houston USA

Tissue-classification-based attenuation correction strategies have been previously proposed to correct for bone attenuation in PET/MR imaging and simulated using computed tomography. However, the complication of voxel averaging uniquely associated with bone has not been considered explicitly in the past. This study investigated the effect of voxel averaging between bone and soft tissue in attenuation images and determined how accurately bone must be detected in MR images in order to perform acceptable attenuation correction of PET data by using CT-simulated attenuation correction. We found out that treating bone as soft tissue caused a mean quantification difference of -9.9% ± 5.5% in all 119 bone lesions. There were no significant differences between lesions in the pelvis and the vertebrae. The nominal difference in lesions in the ribs was significantly lower, likely due to the spatial misregistration between the emission and attenuation images. Interestingly, a non-monotonic relationship between the bone imaging ability and the absolute PET quantification accuracy was observed, with the minimal quantification difference achieved at a BVF around 40% for skull lesions (2.6% ± 2.1%), and 30% for non-skull lesions (1.4% ± 1.1%) and all lesions (1.5% ± 1.3%). This study established that a bone classification sensitivity of approximately 30% BVF is required in order for MR-based attenuation correction methods to achieve optimal quantification in whole-body PET/MR studies. For this purpose, higher bone imaging ability of MR may not be necessary.

关键词： PET/MR Attenuation Correction MR-Based Attenuation Correction

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