Multiscale Electrochemomechanics Interaction and Degradation Analytics of Sn Electrodes for Sodium-Ion Batteries.

Sodium-ion batteries have emerged as a strong contender among the beyond lithium-ion chemistries due to elemental abundance and the low cost of sodium. Tin (Sn) is a promising alloying electrode with high capacity, redox reversibility, and earth abundance. Tin electrodes, however, undergo a series of intermediate reactions exhibiting multiple voltage plateaus upon sodiation/desodiation. Phase transformations related to incomplete sodiation in tin during cycling, in the presence of a frail solid electrolyte interphase layer, can quickly weaken the structural stability. The structural dynamics and reactivity of the electrode/electrolyte interface, being further dependent on the size and morphology of the active material particle in the presence of different electrolytes, dictate the electrode degradation and survivability during cycling. In this study, we paint a comprehensive picture of the underpinnings of the electrochemical and mechanics coupling and electrode/electrolyte interfacial interactions in alloying Sn electrodes. We elicit the fundamental role of electrode/electrolyte complexations in the Sn electrode structure-property-performance relationship based on multimodal analytics, including electrochemical, microscopy, and tomography analyses.

Environmental cell for in situ X-ray synchrotron micro-CT imaging with simultaneous acoustic measurements.

Synchrotron radiation provides the necessary spatial and temporal resolution for non-invasive operando studies of dynamic processes under complex environmental conditions. Here a new environmental cell for simultaneous in situ dynamic X-ray imaging and measuring acoustic properties of geological samples is presented. The primary purpose of this cell is to study gas-hydrate formation in porous geo-materials and its influence on their acoustic properties. The cell is designed for cylindrical samples of 9 mm in diameter, confining and pore pressures up to 12 MPa, and temperatures from -20°C to room temperature. The cell is portable and can be easily assembled and operated at different X-ray sources. This cell enables a wide range of experiments studying physical/chemical processes in the Earth subsurface that change the mechanical properties of rocks (geochemical reactions, phase transitions, etc.).

Microstructure and energy dispersive diffraction reconstruction of 3D patterns of crystallographic texture in a shark centrum.

Purpose: Tomography using diffracted x-rays produces reconstructions mapping quantities such as crystal lattice parameter(s), crystallite size, and crystallographic texture, information quite different from that obtained with absorption or phase contrast. Diffraction tomography is used to map an entire blue shark centrum with its double cone structure (corpora calcerea) and intermedialia (four wedges). Approach: Energy dispersive diffraction (EDD) and polychromatic synchrotron x-radiation at 6-BM-B, the Advanced Photon Source, were used. Different, properly oriented Bragg planes diffract different x-ray energies; these intensities are measured by one of ten energy-sensitive detectors. A pencil beam defines the irradiated volume, and a collimator before each energy-sensitive detector selects which portion of the irradiated column is sampled at any one time. Translating the specimen along X , Y , and Z axes produces a 3D map. Results: We report 3D maps of the integrated intensity of several bioapatite reflections from the mineralized cartilage centrum of a blue shark. The c axis reflection's integrated intensities and those of a reflection with no c axis component reveal that the cone wall's bioapatite is oriented with its c axes lateral, i.e., perpendicular to the backbone's axis, and that the wedges' bioapatite is oriented with its c axes axial. Absorption microcomputed tomography (laboratory and synchrotron) and x-ray excited x-ray fluorescence maps provide higher resolution views. Conclusion: The bioapatite in the cone walls and wedges is oriented to resist lateral and axial deflections, respectively. Mineralized tissue samples can be mapped in 3D with EDD tomography and subsequently studied by destructive methods.

Strategies for simultaneous strengthening and toughening via nanoscopic intracrystalline defects in a biogenic ceramic.

While many organisms synthesize robust skeletal composites consisting of spatially discrete organic and mineral (ceramic) phases, the intrinsic mechanical properties of the mineral phases are poorly understood. Using the shell of the marine bivalve Atrina rigida as a model system, and through a combination of multiscale structural and mechanical characterization in conjunction with theoretical and computational modeling, we uncover the underlying mechanical roles of a ubiquitous structural motif in biogenic calcite, their nanoscopic intracrystalline defects. These nanoscopic defects not only suppress the soft yielding of pure calcite through the classical precipitation strengthening mechanism, but also enhance energy dissipation through controlled nano- and micro-fracture, where the defects' size, geometry, orientation, and distribution facilitate and guide crack initialization and propagation. These nano- and micro-scale cracks are further confined by larger scale intercrystalline organic interfaces, enabling further improved damage tolerance.

Presynaptic CLC-3 determines quantal size of inhibitory transmission in the hippocampus.

The absence of the chloride channel CLC-3 in Clcn3(-/-) mice results in hippocampal degeneration with a distinct temporal-spatial sequence that resembles neuronal loss in temporal lobe epilepsy. We examined how the loss of CLC-3 might affect GABAergic synaptic transmission in the hippocampus. An electrophysiological study of synaptic function in hippocampal slices taken from Clcn3(-/-) mice before the onset of neurodegeneration revealed a substantial decrease in the amplitude and frequency of miniature inhibitory postsynaptic currents compared with those in wild-type slices. We found that CLC-3 colocalized with the vesicular GABA transporter VGAT in the CA1 region of the hippocampus. Acidification of inhibitory synaptic vesicles induced by Cl(-) showed a marked dependence on CLC-3 expression. The decrease in inhibitory transmission in Clcn3(-/-) mice suggests that the neurotransmitter loading of synaptic vesicles was reduced, which we attribute to defective vesicular acidification. Our observations extend the role of Cl(-) in inhibitory transmission from that of a postsynaptic permeant species to a presynaptic regulatory element.

Disease-causing mutations in the cystic fibrosis transmembrane conductance regulator determine the functional responses of alveolar macrophages.

Alveolar macrophages (AMs) play a major role in host defense against microbial infections in the lung. To perform this function, these cells must ingest and destroy pathogens, generally in phagosomes, as well as secrete a number of products that signal other immune cells to respond. Recently, we demonstrated that murine alveolar macrophages employ the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel as a determinant in lysosomal acidification (Di, A., Brown, M. E., Deriy, L. V., Li, C., Szeto, F. L., Chen, Y., Huang, P., Tong, J., Naren, A. P., Bindokas, V., Palfrey, H. C., and Nelson, D. J. (2006) Nat. Cell Biol. 8, 933-944). Lysosomes and phagosomes in murine cftr(-/-) AMs failed to acidify, and the cells were deficient in bacterial killing compared with wild type controls. Cystic fibrosis is caused by mutations in CFTR and is characterized by chronic lung infections. The information about relationships between the CFTR genotype and the disease phenotype is scarce both on the organismal and cellular level. The most common disease-causing mutation, DeltaF508, is found in 70% of patients with cystic fibrosis. The mutant protein fails to fold properly and is targeted for proteosomal degradation. G551D, the second most common mutation, causes loss of function of the protein at the plasma membrane. In this study, we have investigated the impact of CFTR DeltaF508 and G551D on a set of core intracellular functions, including organellar acidification, granule secretion, and microbicidal activity in the AM. Utilizing primary AMs from wild type, cftr(-/-), as well as mutant mice, we show a tight correlation between CFTR genotype and levels of lysosomal acidification, bacterial killing, and agonist-induced secretory responses, all of which would be expected to contribute to a significant impact on microbial clearance in the lung.