Comment on â Large area CMOS active pixel sensor xâ ray imager for digital breast tomosynthesis: Analysis, modeling, and characterizationâ [Med. Phys. 42, 6294â 6308 (2015)]

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134858/1/mp2487.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134858/2/mp2487_am.pd

REITERATIVE MINIMUM MEAN SQUARE ERROR ESTIMATOR FOR DIRECTION OF ARRIVAL ESTIMATION AND BIOMEDICAL FUNCTIONAL BRAIN IMAGING

Two novel approaches are developed for direction-of-arrival (DOA) estimation and functional brain imaging estimation, which are denoted as ReIterative Super-Resolution (RISR) and Source AFFine Image REconstruction (SAFFIRE), respectively. Both recursive approaches are based on a minimum mean-square error (MMSE) framework. The RISR estimator recursively determines an optimal filter bank by updating an estimate of the spatial power distribution at each successive stage. Unlike previous non-parametric covariance-based approaches, which require numerous time snapshots of data, RISR is a parametric approach thus enabling operation on as few as one time snapshot, thereby yielding very high temporal resolution and robustness to the deleterious effects of temporal correlation. RISR has been found to resolve distinct spatial sources several times better than that afforded by the nominal array resolution even under conditions of temporally correlated sources and spatially colored noise. The SAFFIRE algorithm localizes the underlying neural activity in the brain based on the response of a patient under sensory stimuli, such as an auditory tone. The estimator processes electroencephalography (EEG) or magnetoencephalography (MEG) data simulated for sensors outside the patient's head in a recursive manner converging closer to the true solution at each consecutive stage. The algorithm requires a minimal number of time samples to localize active neural sources, thereby enabling the observation of the neural activity as it progresses over time. SAFFIRE has been applied to simulated MEG data and has shown to achieve unprecedented spatial and temporal resolution. The estimation approach has also demonstrated the capability to precisely isolate the primary and secondary auditory cortex responses, a challenging problem in the brain MEG imaging community

The Plasticity of Functional Traits in the Dipterocarps of Borneo

Plasticity plays an important role in the adaptation of sessile organisms like plants to the environment. Plants have been shown to respond plastically in heterogeneous environments, with plants originating from more resource-diverse environments thought to display greater plasticity. There is also evidence that fast-growing species show greater plasticity, as acquisition of resources from resource flushes is greatly aided by faster adaptations. We tested these theories in a Bornean tropical rain forest among three soil specialization groups (clay specialists, sandy loam specialists, and generalists) using two treatments of soil (clay versus sandy loam) and two treatments of light (high versus low). Here, I address four research questions: (1) Do tree species with different soil specializations exhibit differences in the plasticity of functional traits and growth rates? (2) Does the magnitude of plasticity depend on the type of resource? (3) Do functional traits and growth rates vary in the magnitude of plasticity exhibited? (4) Is plasticity in functional traits correlated with plasticity in growth rates? Overall the results show that clay specialists and generalists are more plastic than their sandy loam counterparts. Second, on average plasticity due to light was greater than plasticity due to soil. Third, growth rates were generally more plastic than functional traits. And finally, the plasticity of functional traits and growth rates were positively correlated. These finding add important insights to the plastic response of long-lived tree species to the environment, where much remains to be explored. Adviser: Sabrina E. Russ

The Plasticity of Functional Traits in the Dipterocarps of Borneo

Plasticity plays an important role in the adaptation of sessile organisms like plants to the environment. Plants have been shown to respond plastically in heterogeneous environments, with plants originating from more resource-diverse environments thought to display greater plasticity. There is also evidence that fast-growing species show greater plasticity, as acquisition of resources from resource flushes is greatly aided by faster adaptations. We tested these theories in a Bornean tropical rain forest among three soil specialization groups (clay specialists, sandy loam specialists, and generalists) using two treatments of soil (clay versus sandy loam) and two treatments of light (high versus low). Here, I address four research questions: (1) Do tree species with different soil specializations exhibit differences in the plasticity of functional traits and growth rates? (2) Does the magnitude of plasticity depend on the type of resource? (3) Do functional traits and growth rates vary in the magnitude of plasticity exhibited? (4) Is plasticity in functional traits correlated with plasticity in growth rates? Overall the results show that clay specialists and generalists are more plastic than their sandy loam counterparts. Second, on average plasticity due to light was greater than plasticity due to soil. Third, growth rates were generally more plastic than functional traits. And finally, the plasticity of functional traits and growth rates were positively correlated. These finding add important insights to the plastic response of long-lived tree species to the environment, where much remains to be explored. Adviser: Sabrina E. Russ