Minimally-Invasive Lens-Free Computational Microendoscopy

Ultra-miniaturized imaging tools are vital for numerous biomedical applications. Such minimally-invasive imagers allow for navigation into hard-to-reach regions and, for example, observation of deep brain activity in freely moving animals with minimal ancillary tissue damage. Conventional solutions employ distal microlenses. However, as lenses become smaller and thus less invasive they develop greater optical aberrations, requiring bulkier compound designs with restricted field-of-view. In addition, tools capable of 3-dimensional volumetric imaging require components that physically scan the focal plane, which ultimately increases the distal complexity, footprint, and weight. Simply put, minimally-invasive imaging systems have limited information capacity due to their given cross-sectional area. This thesis explores minimally-invasive lens-free microendoscopy enabled by a successful integration of signal processing, optical hardware, and image reconstruction algorithms. Several computational microendoscopy architectures that simultaneously achieve miniaturization and high information content are presented. Leveraging the computational imaging techniques enables color-resolved imaging with wide field-of-view, and 3-dimensional volumetric reconstruction of an unknown scene using a single camera frame without any actuated parts, further advancing the performance versus invasiveness of microendoscopy

Switch for the Necroptotic Permeation Pore

The helical protein MLKL inserts into cell membranes and forms a permeation pore therein, resulting in cell death. In this issue of Structure, the article by Su and colleagues reports that helix 6 regulates the opening of the pore formed by preceding core helices

Reusable oxidation catalysis using metal-monocatecholato species in a robust metal-organic framework.

An isolated metal-monocatecholato moiety has been achieved in a highly robust metal-organic framework (MOF) by two fundamentally different postsynthetic strategies: postsynthetic deprotection (PSD) and postsynthetic exchange (PSE). Compared with PSD, PSE proved to be a more facile and efficient functionalization approach to access MOFs that could not be directly synthesized under solvothermal conditions. Metalation of the catechol functionality residing in the MOFs resulted in unprecedented Fe-monocatecholato and Cr-monocatecholato species, which were characterized by X-ray absorption spectroscopy, X-band electron paramagnetic resonance spectroscopy, and (57)Fe Mössbauer spectroscopy. The resulting materials are among the first examples of Zr(IV)-based UiO MOFs (UiO = University of Oslo) with coordinatively unsaturated active metal centers. Importantly, the Cr-metalated MOFs are active and efficient catalysts for the oxidation of alcohols to ketones using a wide range of substrates. Catalysis could be achieved with very low metal loadings (0.5-1 mol %). Unlike zeolite-supported, Cr-exchange oxidation catalysts, the MOF-based catalysts reported here are completely recyclable and reusable, which may make them attractive catalysts for 'green' chemistry processes

Rotational and Varus Instability in Chronic Lateral Ankle Instability: In Vivo 3D Biomechanical Analysis

We retrospectively evaluated the altered biomechanics of the talus in 15 adult patients (7 males, 8 females) with chronic lateral ankle instability when the ankle joint moved actively from full dorsiflexion to full plantarflexion under a non-weight bearing condition. CT images were taken for the unstable ankle and the contralateral normal (control) ankle. Three-dimensional surface models of both ankle joints were reconstructed from the CT data, and we used a computer simulation program to compare both ankle motions of inversion/eversion in the coronal plane, plantarflexion/dorsiflexion in the sagittal plane, and internal rotation/external rotation in the axial plane. This evaluation method provides in vivo, dynamic, and 3D results of ankle motion. In the ankles with chronic lateral instability and the controls, the average talar rotational movement of inversion (+)/eversion (−) was 19.0° and 15.5° and the internal rotation (+)/external rotation (−) was 30.4° and 20.7°, respectively. Paired t-tests revealed significant differences in the amount of inversion (+)/eversion (−) (p=0.012) and internal rotation (+)/external rotation (−) (p<0.001) between unstable and normal ankle joints. The difference of mean rotational movement in internal rotation (9.7°) was greater than that of inversion (3.5°). Rotational instability should be considered when evaluating chronic lateral ankle instability

Minimally-Invasive Lens-Free Computational Microendoscopy

Ultra-miniaturized imaging tools are vital for numerous biomedical applications. Such minimally-invasive imagers allow for navigation into hard-to-reach regions and, for example, observation of deep brain activity in freely moving animals with minimal ancillary tissue damage. Conventional solutions employ distal microlenses. However, as lenses become smaller and thus less invasive they develop greater optical aberrations, requiring bulkier compound designs with restricted field-of-view. In addition, tools capable of 3-dimensional volumetric imaging require components that physically scan the focal plane, which ultimately increases the distal complexity, footprint, and weight. Simply put, minimally-invasive imaging systems have limited information capacity due to their given cross-sectional area. This thesis explores minimally-invasive lens-free microendoscopy enabled by a successful integration of signal processing, optical hardware, and image reconstruction algorithms. Several computational microendoscopy architectures that simultaneously achieve miniaturization and high information content are presented. Leveraging the computational imaging techniques enables color-resolved imaging with wide field-of-view, and 3-dimensional volumetric reconstruction of an unknown scene using a single camera frame without any actuated parts, further advancing the performance versus invasiveness of microendoscopy

Relaxation Phenomena in Rechargeable Battery Electrode Materials Beyond Li Intercalation

An intercalation reaction is the most commonly utilized redox reaction scheme for commercial Li-ion batteries (LIBs) due to minimized crystal deformation during the redox reaction. However, to meet the growing demands for large-scale energy storage criteria, low cost and high energy density, other reaction schemes need to be explored. In order to fully utilize the new schemes, mechanistic understanding of the respective materials is crucial. A relaxation phenomenon facilitates the mechanistic understanding because it inspects both kinetic and thermodynamic products of the reaction. MIL-101(Fe), a MOF material is applied to study the relaxation phenomenon. MIL-101(Fe) demonstrates a unique rate dependent rechargeability. Through X-ray absorption spectroscopy and electronic state calculation, a kinetically stable product and thermodynamically stable product of MIL-101(Fe) are proposed. Kinetically, Fe3+ is reduced upon reduction, however, due to thermodynamic stability, the Fe2+ self oxidizes back to Fe3+ after relaxation. This work demonstrates relaxation phenomenon on the molecular level.Zn electrode is one of the conversion materials with high energy density, yet Zn electrode lacks rechargeability due to the zincate ion formation during oxidation reaction. The zincate ions dissolve into electrolyte making the Zn electrode not rechargeable. One of the ways to overcome this issue is incorporating Bi2O3 as a composite additive. We have added the Bi2O3 additive and identified a comprehensive role of the Bi2O3. Through electron microscopy coupled with energy dispersed X-ray spectroscopy and X-ray photoelectron spectroscopy, we have discovered that the ZnO and Bi2O3 form an intermediate phase that allows zincate ions to deposit and retain ZnO on the electrode surface. This work demonstrates relaxation phenomenon on the particle level. Understanding the relaxation phenomenon upon redox reactions distinguishes the kinetic and thermodynamic products. The findings in this dissertation provide more comprehensive methods to identify the energy storage mechanism. MnO2 is one of the low-cost, environmentally benign, and promising material for energy storage system. A preliminary Mn2+ deposition test suggested that Bi2O3 addition can adhere Mn2+. Based on the knowledge gained through relaxation characterization, a series of characterizations and methods to improve MnO2 aqueous energy storage system are proposed