Correlating the Energetics and Atomic Motions of the Metal-Insulator Transition of M1 Vanadium Dioxide

Materials that undergo reversible metal-insulator transitions are obvious candidates for new generations of devices. For such potential to be realised, the underlying microscopic mechanisms of such transitions must be fully determined. In this work we probe the correlation between the energy landscape and electronic structure of the metal-insulator transition of vanadium dioxide and the atomic motions occurring using first principles calculations and high resolution X-ray diffraction. Calculations find an energy barrier between the high and low temperature phases corresponding to contraction followed by expansion of the distances between vanadium atoms on neighbouring sub-lattices. X-ray diffraction reveals anisotropic strain broadening in the low temperature structure's crystal planes, however only for those with spacings affected by this compression/expansion. GW calculations reveal that traversing this barrier destabilises the bonding/anti-bonding splitting of the low temperature phase. This precise atomic description of the origin of the energy barrier separating the two structures will facilitate more precise control over the transition characteristics for new applications and devices.Comment: 11 Pages, 8 Figure

3D face and body reconstruction via volumetric regression networks

3D Face reconstruction is the process of estimating the full 3D geometry of a human's face from one or more images. Applications of 3D face reconstruction span many areas, from personalisation of video games and trying on accessories online, to measuring emotional arousal for psychological studies and in medicine, such as simulating the result of reconstructive surgery. Approaches to 3D face reconstruction generally depend on a 3D Morphable Model (3DMM) - a parametric model, where the shape, pose and expression can be adjusted using a small number of parameters. While methods based on such techniques can work well on frontal images, they often begin to fail on cases of large pose, difficult expression, occlusion, and bad lighting. Additionally, encoding detail in so few parameters is not possible. In this thesis, we propose a novel approach to the problem of 3D face reconstruction: Volumetric Regression Networks. Our non-parametric approach constrains the problem to the spatial domain using an end-to-end network which directly regresses the 3D geometry using a volumetric representation. This avoids the need for 3DMM generation, which involves finding correspondence between all vertices of all training samples, but also the fitting stage, which requires solving a difficult optimisation problem. We demonstrate that doing so can not only provide state-of-the-art results, but also be adapted to other deformable objects, such as the full human body

Restricted set classification: Who is there?

We consider a problem where a set X of N objects (instances) coming from c classes have to be classified simultaneously. A restriction is imposed on X in that the maximum possible number of objects from each class is known, hence we dubbed the problem who-is-there? We compare three approaches to this problem: (1) independent classification whereby each object is labelled in the class with the largest posterior probability; (2) a greedy approach which enforces the restriction; and (3) a theoretical approach which, in addition, maximises the likelihood of the label assignment, implemented through the Hungarian assignment algorithm. Our experimental study consists of two parts. The first part includes a custom-made chess data set where the pieces on the chess board must be recognised together from an image of the board. In the second part, we simulate the restricted set classification scenario using 96 datasets from a recently collated repository (University of Santiago de Compostela, USC). Our results show that the proposed approach (3) outperforms approaches (1) and (2).Spanish Ministry of Economy and Competitiveness through project TIN 2015-67534-

The thermal equation of state of (Mg, Fe)SiO3 bridgmanite (perovskite) and implications for lower mantle structures

The high‐pressure/high‐temperature equation of state (EOS) of synthetic 13% Fe‐bearing bridgmanite (Mg silicate perovskite) is measured using powder X‐ray diffraction in a laser‐heated diamond anvil cell with a quasi‐hydrostatic neon pressure medium. We compare these results, which are consistent with previous 300 K sound speed and compression studies, with a reanalysis of Fe‐free Mg end‐member data from Tange et al. (2012) to determine the effect of iron on bridgmanite’s thermoelastic properties. EOS parameters are incorporated into an ideal lattice mixing model to probe the behavior of bridgmanite at deep mantle conditions. With this model, a nearly pure bridgmanite mantle composition is shown to be inconsistent with density and compressibility profiles of the lower mantle. We also explore the buoyant stability of bridgmanite over a range of temperatures and compositions expected for Large Low‐Shear Velocity Provinces, concluding that bridgmanite‐dominated thermochemical piles are more likely to be passive dense layers externally supported by convection, rather than internally supported metastable domes. The metastable dome scenario is estimated to have a relative likelihood of only 4–7%, given the narrow range of compositions and temperatures consistent with seismic constraints. If buoyantly supported, such structures could not have remained stable with greater thermal contrast early in Earth’s history, ruling out formation scenarios involving a large concentration of heat producing elements.Key PointsHigh P‐T equation of state of 13% and 0% Fe bridgmanite (perovksite) is obtainedPure bridgmanite mantle is inconsistent with PREM at any Fe contentBuoyant stability of LLSVPs favors passive chemical piles over metastable domesPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141021/1/jgrb51327.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141021/2/jgrb51327_am.pd

Fulfilling Community Health Assessment Requirements: Lessons Learned From Facilitating State-Wide Community Health Forums

Background: A prerequisite for National Public Health Accreditation is completion of a Community Health Assessment (CHA) that presents an exhaustive profile of the population served by a particular public health agency. Methods: The Georgia Department of Public Health (GA DPH) contracted with the Center for Public Health Practice and Research at Georgia Southern University to facilitate five state-wide community health forums. Results: Evaluation of the forums yielded qualitative data illustrating current challenges faced by Georgians, as well as assets that could be leveraged to improve health status. Conclusion: Lessons learned from these state-wide community health forums can be applied to improve the overall process of gathering data for a comprehensive CHA throughout Georgia or other areas interested in pursuing public health agency accreditation

Fulfilling Community Health Assessment Requirements: Lessons Learned From Facilitating State-wide Community Health Forums

Background: A prerequisite for National Public Health Accreditation is completion of a Community Health Assessment (CHA) that presents an exhaustive profile of the population served by a particular public health agency. Methods: The Georgia Department of Public Health (GA DPH) contracted with the Center for Public Health Practice and Research at Georgia Southern University to facilitate five state-wide community health forums. Results: Evaluation of the forums yielded qualitative data illustrating current challenges faced by Georgians, as well as assets that could be leveraged to improve health status. Conclusion: Lessons learned from these state-wide community health forums can be applied to improve the overall process of gathering data for a comprehensive CHA throughout Georgia or other areas interested in pursuing public health agency accreditation

Relativistic three-particle scattering equations

We derive a set of relativistic three-particle scattering equations in the three-particle c.m. frame employing a relativistic three-particle propagator suggested long ago by Ahmadzadeh and Tjon in the c.m. frame of a two-particle subsystem. We make the coordinate transformation of this propagator from the c.m. frame of the two-particle subsystem to the three-particle c.m. frame. We also point out that some numerical applications of the Ahmadzadeh and Tjon propagator to the three-nucleon problem use unnecessary nonrelativistic approximations which do not simplify the computational task, but violate constraints of relativistic unitarity and/or covariance.Comment: 5pages, text and one ps figure (in revtex) include

SARS-CoV-2 viral RNA shedding for more than 87 days in an individual with an impaired CD8+ T cell response

Prolonged shedding of viral RNA occurs in some individuals following SARS-CoV-2 infection. We perform comprehensive immunologic evaluation of one individual with prolonged shedding. The case subject recovered from severe COVID-19 and tested positive for SARS-CoV-2 viral RNA repeatedly as many as 87 days after the first positive test, 97 days after symptom onset. The subject did not have any associated rise in anti-Spike protein antibody titers or plasma neutralization activity, arguing against re-infection. This index subject exhibited a profoundly diminished circulating CD8+ T cell population and correspondingly low SARS-CoV-2-specific CD8+ T cell responses when compared with a cohort of other recovering COVID-19 subjects. CD4+ T cell responses and neutralizing antibody responses developed as expected in this individual. Our results demonstrate that detectable viral RNA shedding in the upper airway can occur more than 3 months following infection in some individuals with COVID-19 and suggest that impaired CD8+ T cells may play a role in prolonged viral RNA shedding