Electrochemical and Structural Analysis of Li-ion battery Materials by in-situ X-ray Absorption Spectroscopy.

Efficient inexpensive energy storage is essential for widespread adoption of alternatives to fossil fuels. Lithium-ion batteries are a promising technology for energy storage. This dissertation describes the electrochemical and local structural analysis of the Li-ion cathode/anode materials Li4Ti5O12, LiMn2O4, Li3V2(PO4)3, and Mg-doped Li3V2(PO4)3) using synchrotron-based X-ray Absorption Spectroscopy (XAS). For the well-known anode material Li4Ti5O12, XAS provides an explanation for the ‘‘Zero-strain’’ characteristic of the material; there is, as expected, an increase in Ti-O distance reduction but no change in Ti-Ti distance, consistent with the added lithium pulling the oxide anions closer together, allowing the Ti-O distance to expand, with negligible change in the lattice parameter. XAS showed that when the spinel LiMn2O4 cathode is annealed, there is a slight increase in the average Mn oxidation state. In-situ XAS studies of another cathode material, Li3V2(PO4)3, showed the presence of significant kinetic effects such that the measured electrochemical behavior does not represent the bulk vanadium. There are only two distinct vanadium species when the cathode is cycled between 3.0 and 4.5 V. However, when the potential exceed 4.5 V a third vanadium species is formed, consistent with the formation of V5+. The data suggest that a portion of the V5+ can migrate to empty Li sites, indicating a possible explanation for capacity loss at high potential. If a portion of the V is replaced with Mg giving Li3V(2-2/3x)Mgx(PO4)3, the electrochemical performance, cycling retention and stability increase up to X~0.30. In-situ XAS of Li3V(2-2/3x)Mgx(PO4)3, x=0.15, 0.30, and 0.45 was used to characterize the structural and electronic consequences of Mg doping. In general, the doped cathodes behave similarly to the undoped parent material, with oxidation of V3+ to V4+ over 3 – 4.5 V and for the oxidation to V5+ at higher potential. As in the undoped material, we see substantial migration of V5+ to Li sites, and find evidence, especially for x = 0.15, that this tetrahedral V can be reduced to V4+ without returning to the octahedral V site. The most important consequence of doping seems to be a decrease in the kinetic lag that is seen in the undoped material.PHDChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111390/1/soojeong_1.pd

Moral Distress of Neonatal Intensive Care Nurses in End-of-Life Care

https://scholarworks.seattleu.edu/fss-2019/1003/thumbnail.jp

A Study on the Transition of Power Dressing in Contemporary Fashion

The purpose of this study is to examine changes of power dressing from 1930s to present. I believe this study will help predict future changes of power dressing by reinterpreting trends in modern fashion based on history and investigating power dressing of women as a barometer of women\u27s social power

Slot-Mixup with Subsampling: A Simple Regularization for WSI Classification

Whole slide image (WSI) classification requires repetitive zoom-in and out for pathologists, as only small portions of the slide may be relevant to detecting cancer. Due to the lack of patch-level labels, multiple instance learning (MIL) is a common practice for training a WSI classifier. One of the challenges in MIL for WSIs is the weak supervision coming only from the slide-level labels, often resulting in severe overfitting. In response, researchers have considered adopting patch-level augmentation or applying mixup augmentation, but their applicability remains unverified. Our approach augments the training dataset by sampling a subset of patches in the WSI without significantly altering the underlying semantics of the original slides. Additionally, we introduce an efficient model (Slot-MIL) that organizes patches into a fixed number of slots, the abstract representation of patches, using an attention mechanism. We empirically demonstrate that the subsampling augmentation helps to make more informative slots by restricting the over-concentration of attention and to improve interpretability. Finally, we illustrate that combining our attention-based aggregation model with subsampling and mixup, which has shown limited compatibility in existing MIL methods, can enhance both generalization and calibration. Our proposed methods achieve the state-of-the-art performance across various benchmark datasets including class imbalance and distribution shifts

Evaluation of peristaltic micromixers for highly integrated microfluidic systems

Microfluidic devices based on the multilayer soft lithography allow accurate manipulation of liquids, handling reagents at the sub-nanoliter level, and performing multiple reactions in parallel processors by adapting micromixers. Here, we have experimentally evaluated and compared several designs of micromixers and operating conditions to find design guidelines for the micromixers. We tested circular, triangular, and rectangular mixing loops and measured mixing performance according to the position and the width of the valves that drive nanoliters of fluids in the micrometer scale mixing loop. We found that the rectangular mixer is best for the applications of highly integrated microfluidic platforms in terms of the mixing performance and the space utilization. This study provides an improved understanding of the flow behaviors inside micromixers and design guidelines for micromixers that are critical to build higher order fluidic systems for the complicated parallel bio/chemical processes on a chip

Improving the Expressiveness of Deep Learning Frameworks with Recursion

Recursive neural networks have widely been used by researchers to handle applications with recursively or hierarchically structured data. However, embedded control flow deep learning frameworks such as TensorFlow, Theano, Caffe2, and MXNet fail to efficiently represent and execute such neural networks, due to lack of support for recursion. In this paper, we add recursion to the programming model of existing frameworks by complementing their design with recursive execution of dataflow graphs as well as additional APIs for recursive definitions. Unlike iterative implementations, which can only understand the topological index of each node in recursive data structures, our recursive implementation is able to exploit the recursive relationships between nodes for efficient execution based on parallel computation. We present an implementation on TensorFlow and evaluation results with various recursive neural network models, showing that our recursive implementation not only conveys the recursive nature of recursive neural networks better than other implementations, but also uses given resources more effectively to reduce training and inference time.Comment: Appeared in EuroSys 2018. 13 pages, 11 figure

Empagliflozin Contributes to Polyuria via Regulation of Sodium Transporters and Water Channels in Diabetic Rat Kidneys

Besides lowering glucose, empagliflozin, a selective sodium-glucose cotransporter-2 (SGLT2) inhibitor, have been known to provide cardiovascular and renal protection due to effects on diuresis and natriuresis. However, the natriuretic effect of SGLT2 inhibitors has been reported to be transient, and long-term data related to diuretic change are sparse. This study was performed to assess the renal effects of a 12-week treatment with empagliflozin (3 mg/kg) in diabetic OLETF rats by comparing it with other antihyperglycemic agents including lixisenatide (10 μg/kg), a glucagon-like peptide receptor-1 agonist, and voglibose (0.6 mg/kg), an α-glucosidase inhibitor. At 12 weeks of treatment, empagliflozin-treated diabetic rats produced still high urine volume and glycosuria, and showed significantly higher electrolyte-free water clearance than lixisenatide or voglibose-treated diabetic rats without significant change of serum sodium level and fractional excretion of sodium. In empagliflozin-treated rats, renal expression of Na+-Cl- cotransporter was unaltered, and expressions of Na+/H+ exchanger isoform 3, Na+-K+-2Cl- cotransporter, and epithelial Na+ channel were decreased compared with control diabetic rats. Empagliflozin increased an expression of aquaporin (AQP)7 but did not affect AQP3 and AQP1 protein expressions in diabetic kidneys. Despite the increased expression in vasopressin V2 receptor, protein and mRNA levels of AQP2 in empagliflozin-treated diabetic kidneys were significantly decreased compared to control diabetic kidneys. In addition, empagliflozin resulted in the increased phosphorylation of AQP2 at S261 through the increased cyclin-dependent kinases 1 and 5 and protein phosphatase 2B. These results suggest that empagliflozin may contribute in part to polyuria via its regulation of sodium channels and AQP2 in diabetic kidneys

Kinematic oscillations of post-CME blobs detected by K-Cor on 2017 September 10

We investigate 20 post-coronal mass ejection (CME) blobs formed in the post-CME current sheet (CS) that were observed by K-Cor on 2017 September 10. By visual inspection of the trajectories and projected speed variations of each blob, we find that all blobs except one show irregular "zigzag" trajectories resembling transverse oscillatory motions along the CS, and have at least one oscillatory pattern in their instantaneous radial speeds. Their oscillation periods are ranging from 30 to 91 s and their speed amplitudes from 128 to 902 km s-1. Among 19 blobs, 10 blobs have experienced at least two cycles of radial speed oscillations with different speed amplitudes and periods, while 9 blobs undergo one oscillation cycle. To examine whether or not the apparent speed oscillations can be explained by vortex shedding, we estimate the quantitative parameter of vortex shedding, the Strouhal number, by using the observed lateral widths, linear speeds, and oscillation periods of the blobs. We then compare our estimates with theoretical and experimental results from MHD simulations and fluid dynamic experiments. We find that the observed Strouhal numbers range from 0.2 to 2.1, consistent with those (0.15-3.0) from fluid dynamic experiments of bluff spheres, while they are higher than those (0.15-0.25) from MHD simulations of cylindrical shapes. We thus find that blobs formed in a post-CME CS undergo kinematic oscillations caused by fluid dynamic vortex shedding. The vortex shedding is driven by the interaction of the outward-moving blob having a bluff spherical shape with the background plasma in the post-CME CS