Programmable and Modular DC-DC Converter

This project considers the design, implementation, and testing of an open-source dc-dc converter for microgrid prototyping. Unlike conventional dc-dc converters that are proprietary and require specialist knowledge, and are usually designed for a single function, the proposed dc-dc converter will comprise of a programmable MCU and a Raspberry Pi (RPi) interface to allow less-skilled consumers to monitor and modify a power converting system. We will develop an open-source library that contains voltage control, current control, maximum power point tracking, and battery charge control profiles. Each library will be easy to implement through a GUI on the Raspberry Pi and will be controlled using an Atmega328 located on the power conversion unit. C++ and the Arduino IDE will be used for testing and will retain functionality in the finished project for more knowledgeable customers to edit the pre-set profiles. Moreover, the Pi will need to communicate with multiple converters and monitor their set points in applications where more than one dc-dc converter is necessary. The supporting hardware around the microcontrollers is a dc-dc converter, while the connection with the RPi and any external hardware will be open-source and custom designed to accommodate multiple converters on a single system. As a result, the integration of our dc-dc converter will provide a way to easily set up a microgrid system without the use of proprietary voltage converting hardware

Spin dynamics in antiferromagnetic oxypnictides and fluoropnictides: LaMnAsO, LaMnSbO, and BaMnAsF

Inelastic neutron scattering (INS) from polycrystalline antiferromagnetic LaMnAsO, LaMnSbO, and BaMnAsF are analyzed using a J(1)-J(2)-J(c) Heisenberg model in the framework of the linear spin-wave theory. All three systems show clear evidence that the nearest- and next-nearest-neighbor interactions within the Mn square lattice layer (J(1) and J(2)) are both antiferromagnetic (AFM). However, for all compounds studied the competing interactions have a ratio of 2J(2)/J(1) \u3c 1, which favors the square lattice checkerboard AFM structure over the stripe AFM structure. The interplane coupling Jc in all three systems is on the order of similar to 3 x 10(-4)J(1), rendering the magnetic properties of these systems with quasi-two-dimensional character. The substitution of Sb for As significantly lowers the in-plane exchange coupling, which is also reflected in the decrease of the Neel temperature, T-N. Although BaMnAsF shares the same MnAs sheets as LaMnAsO, their J(1) and J(2) values are substantially different. Using density functional theory, we calculate exchange parameters J(ij) to rationalize the differences among these systems

Evolution of Magnetic Interactions in Sb-substituted MnBi2Te4

The Mn(Bi$_{1-x}$Sb$_x$)$_2$Te$_4$ series is purported to span from antiferromagnetic (AF) topological insulator at x = 0 to a trivial AF insulator at x = 1. Here we report on neutron diffraction and inelastic neutron scattering studies of the magnetic interactions across this series. All compounds measured possess ferromagnetic (FM) triangular layers and we find a crossover from AF to FM interlayer coupling near x = 1 for our samples. The large spin gap at x = 0 closes rapidly and the average FM exchange interactions within the triangular layer increase with Sb substitution. Similar to a previous study of MnBi$_2$Te$_4$, we find severe spectral broadening which increases dramatically across the compositional series. In addition to broadening, we observe an additional sharp magnetic excitation in MnSb$_2$Te$_4$ that may indicate the development of local magnetic modes based on recent reports of antisite disorder between Mn and Sb sublattices. The results suggest that both substitutional and antisite disorder contribute substantially to the magnetism in Mn(Bi$_{1-x}$Sb$_x$)$_2$Te$_4$.Comment: 10 pages, 6 figure

Baseline and longitudinal grey matter changes in newly diagnosed Parkinson\u27s disease: ICICLE-PD study

Mild cognitive impairment in Parkinson\u27s disease is associated with progression to dementia (Parkinson\u27s disease dementia) in a majority of patients. Determining structural imaging biomarkers associated with prodromal Parkinson\u27s disease dementia may allow for the earlier identification of those at risk, and allow for targeted disease modifying therapies. One hundred and five non-demented subjects with newly diagnosed idiopathic Parkinson\u27s disease and 37 healthy matched controls had serial 3 T structural magnetic resonance imaging scans with clinical and neuropsychological assessments at baseline, which were repeated after 18 months. The Movement Disorder Society Task Force criteria were used to classify the Parkinson\u27s disease subjects into Parkinson\u27s disease with mild cognitive impairment (n = 39) and Parkinson\u27s disease with no cognitive impairment (n = 66). Freesurfer image processing software was used to measure cortical thickness and subcortical volumes at baseline and follow-up. We compared regional percentage change of cortical thinning and subcortical atrophy over 18 months. At baseline, cases with Parkinson\u27s disease with mild cognitive impairment demonstrated widespread cortical thinning relative to controls and atrophy of the nucleus accumbens compared to both controls and subjects with Parkinson\u27s disease with no cognitive impairment. Regional cortical thickness at baseline was correlated with global cognition in the combined Parkinson\u27s disease cohort. Over 18 months, patients with Parkinson\u27s disease with mild cognitive impairment demonstrated more severe cortical thinning in frontal and temporo-parietal cortices, including hippocampal atrophy, relative to those with Parkinson\u27s disease and no cognitive impairment and healthy controls, whereas subjects with Parkinson\u27s disease and no cognitive impairment showed more severe frontal cortical thinning compared to healthy controls. At baseline, Parkinson\u27s disease with no cognitive impairment converters showed bilateral temporal cortex thinning relative to the Parkinson\u27s disease with no cognitive impairment stable subjects. Although loss of both cortical and subcortical volume occurs in non-demented Parkinson\u27s disease, our longitudinal analyses revealed that Parkinson\u27s disease with mild cognitive impairment shows more extensive atrophy and greater percentage of cortical thinning compared to Parkinson\u27s disease with no cognitive impairment. In particular, an extension of cortical thinning in the temporo-parietal regions in addition to frontal atrophy could be a biomarker in therapeutic studies of mild cognitive impairment in Parkinson\u27s disease for progression towards dementia