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ItemImaging in "Healthy" Aging and Dementia: A Bigger Sandbox(Georgia Institute of Technology, 2018-03-28) Crosson, BruceA growing consensus in the field of dementia research is that Alzheimer’s disease (AD) starts long before, perhaps decades before, the manifestation of its cognitive phenotype. Further, recent research suggests that reduction in accumulation of abnormal proteins characteristic of AD does not change cognition in early AD. Hence, some investigators believe that intervention must take place before cognitive symptoms occur and prevention is becoming an emphasis. To foster development of prevention strategies, the dementia field is moving toward discovery of biomarkers that predict the emergence of AD in cognitively normal older adults and define the cascade of biological events leading to it. Magnetic resonance imaging and spectroscopy technologies are being applied in the search for cerebrovascular, biochemical, and structural biomarkers to predict AD. As a result of this biomarker search, some of the variance in aging-related biological and cognitive processes is being explained. The resulting rapid evolution of imaging and other biomarkers for AD may revolutionize cognitive aging research. This presentation will focus on promising neuroimaging biomarkers and their implications.
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ItemAnalytic Properties of Dispersion Relations and Spectra of Periodic Operators(Georgia Institute of Technology, 2016-10-11) Kuchment, PeterThe talk will survey some known results and unresolved problems concerning analytic properties of dispersion relations and their role in various spectral theory problems for periodic operators of mathematical physics, such as spectral structure, embedded impurity eigenvalues, Greens function asymptotics, Liouville theorems, etc.
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ItemQuantum Approximate Markov Chains and the Locality of Entanglement Spectrum(Georgia Institute of Technology, 2016-10-11) Brandão, FernandoIn this talk I will show that quantum many-body states satisfying an area law for entanglement have a local entanglement spectrum, i.e. the entanglement spectrum can be approximated by the spectrum of a local model acting on the boundary of the region. The result follows from a version of the Hammersley-Clifford Theorem (which states that classical Gibbs states are equivalent to Markov networks) for quantum approximate Markov chains. In particular I'll argue that those are in one-to-one correspondence to 1D quantum Gibbs states
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ItemMicrolocal Methods in Dynamical Systems(Georgia Institute of Technology, 2016-10-10) Zworski, MaciejMicrolocal analysis exploits mathematical manifestations of the classical/quantum (particle/wave) correspondence and has been a successful tool in spectral theory and partial differential equations. We can say that these last two fields lie on the quantum/wave side. Recently, microlocal methods have been applied to the study of classical dynamical problems, in particular of chaotic (Anosov) flows. I will illustrate this by proving that the order of vanishing of the dynamical zeta function at zero for negatively curved surfaces is given by the absolute value of the Euler characteristic (joint work with S Dyatlov).
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ItemA Class of Asymmetric Gapped Hamiltonians on Quantum Spin Chains and its Characterization(Georgia Institute of Technology, 2016-10-09) Ogata, Yoshiko
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ItemUniversality of Transport Coeffcients in the Haldane-Hubbard Model(Georgia Institute of Technology, 2016-10-08) Giuliani, Alessandro
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ItemEmergent Pfaffian Relations in Quasi-Planar Models(Georgia Institute of Technology, 2016-10-08) Aizenman, Michael
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ItemHoneycomb Schroedinger Operators in the Strong Binding Regime(Georgia Institute of Technology, 2016-09-09) Weinstein, Michael
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ItemRocker Profile Restores Leg Progression When Walking with Orthotic Ankle Constraint(Georgia Institute of Technology, 2013-04-19) Oludare, Simisola O.Rocker profiles are one of the most commonly prescribed therapeutic footwear modifications. Typically, they are used to allow lower limb forward progression when ankle and foot motion are restricted by mechanical constraint (i.e. lower limb orthosis) or clinical pathology (i.e. lower limb fracture). Although rocker profiles are commonly used, their design and performance have not been clearly described. To address this need, we studied the role of rocker profile footwear and its influence on lower limb forward progression when used in combination with an orthosis designed to constrain the ankle joint. We hypothesize that healthy subjects walking with unilateral ankle-foot orthosis footwear combination will elicit no difference in the shank forward progression compared to control (no ankle constraint) during stance phase (early, mid, late). The shank forward progression was quantified as the forward and vertical components of the acceleration. Analysis of constrained and unconstrained shank acceleration for three subjects revealed no difference during mid-stance, but showed differences during early and late stance. Although there are some differences in the shank acceleration when walking with and without ankle constraint, there is no notable gait deviation between the two conditions. This supports the notion that the rocker profile designed in our laboratory functions as a biomimetic ankle-foot complex that restores lower limb forward progression when the ankle is mechanically constrained by an orthosis.
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ItemUltrasound Analysis of Plantar Tissue Stiffness of Behavior Properties in the Midfoot(Georgia Institute of Technology, 2013-04-19) Kessler, Joshua ; Azzarelo, JosephFoot orthoses have been used for many years to treat various pathologies. While these orthoses can be effective, the mechanism of how plantar soft tissues and skeletal structures interface with the orthosis is not well understood. Studies have been conducted which examine tissue properties of the heel pad, including the use of ultrasound, but analysis of the midfoot is limited. This study aims to quantify displacement and stiffness of the plantar soft tissues of the midfoot under a known load through the use of ultrasonography in weight bearing and non- weight bearing conditions. Twenty -five subjects were recruited for the study ranging in age from 23-56 (Mean = 36.08) years old, consisting of 12 females and 13 males. Simple demographic information was recorded and a Foot Posture Index (FPI) examination was performed on all subjects. A force application apparatus was designed that utilizes a stepper-motor-driven linear actuator. The test set-up consisted of load cell mounted to the actuator which could drive an ultrasound transducer into the plantar surface of the midfoot to a maximum load of 40N. The results show plantar foot tissue stiffness exhibits a non-linear "toe" region at low force values, while increased force causes a shift to a linear stiffness profile. Midfoot plantar tissues are significantly stiffer in weight bearing conditions than in nonweight bearing conditions (p<0.05). Observations and measurements from ultrasound videos indicate that soft tissue between the skin and skeletal structure experiences greater change in compression in non-weight bearing. However, muscle tissue appears to have a greater change in deformation under non-weight bearing, while the connective tissue between skin and muscle display greater change in deformation under weight bearing conditions. The disparity in amount of deformation between tissues during different weight bearing conditions shows that stiffness properties in the foot are dynamic. The aim for future research is to develop a map of plantar soft tissue properties in all regions of the foot for clinical reference in selecting compatible orthotic interface materials.