Manipulating the diffusion energy barrier at the lithium metal electrolyte interface for dendrite-free long-life batteries.

Constructing an artificial solid electrolyte interphase (SEI) on lithium metal electrodes is a promising approach to address the rampant growth of dangerous lithium morphologies (dendritic and dead Li0) and low Coulombic efficiency that plague development of lithium metal batteries, but how Li+ transport behavior in the SEI is coupled with mechanical properties remains unknown. We demonstrate here a facile and scalable solution-processed approach to form a Li3N-rich SEI with a phase-pure crystalline structure that minimizes the diffusion energy barrier of Li+ across the SEI. Compared with a polycrystalline Li3N SEI obtained from conventional practice, the phase-pure/single crystalline Li3N-rich SEI constitutes an interphase of high mechanical strength and low Li+ diffusion barrier. We elucidate the correlation among Li+ transference number, diffusion behavior, concentration gradient, and the stability of the lithium metal electrode by integrating phase field simulations with experiments. We demonstrate improved reversibility and charge/discharge cycling behaviors for both symmetric cells and full lithium-metal batteries constructed with this Li3N-rich SEI. These studies may cast new insight into the design and engineering of an ideal artificial SEI for stable and high-performance lithium metal batteries.

Anionic polymers amplify electrokinetic perfusion through extracellular matrices.

Electrical stimulation (ES) promotes healing of chronic epidermal wounds and delays degeneration of articular cartilage. Despite electrotherapeutic treatment of these non-excitable tissues, the mechanisms by which ES promotes repair are unknown. We hypothesize that a beneficial role of ES is dependent on electrokinetic perfusion in the extracellular space and that it mimics the effects of interstitial flow. In vivo, the extracellular space contains mixtures of extracellular proteins and negatively charged glycosaminoglycans and proteoglycans surrounding cells. While these anionic macromolecules promote water retention and increase mechanical support under compression, in the presence of ES they should also enhance electro-osmotic flow (EOF) to a greater extent than proteins alone. To test this hypothesis, we compare EOF rates between artificial matrices of gelatin (denatured collagen) with matrices of gelatin mixed with anionic polymers to mimic endogenous charged macromolecules. We report that addition of anionic polymers amplifies EOF and that a matrix comprised of 0.5% polyacrylate and 1.5% gelatin generates EOF with similar rates to those reported in cartilage. The enhanced EOF reduces mortality of cells at lower applied voltage compared to gelatin matrices alone. We also use modeling to describe the range of thermal changes that occur during these electrokinetic experiments and during electrokinetic perfusion of soft tissues. We conclude that the negative charge density of native extracellular matrices promotes electrokinetic perfusion during electrical therapies in soft tissues and may promote survival of artificial tissues and organs prior to vascularization and during transplantation.

Combination of mural thrombus and age improves the identification of all-cause mortality following branched endovascular repair.

BACKGROUND: In-hospital and 30-day mortality rates of endovascular repair of thoracoabdominal aortic aneurysms shows a significant improvement over open surgery, although we are not seeing a significant difference at 1 year. We assess the hypothesis that a greater mural thrombus ratio within the aorta could function as an indicator of postoperative mortality. METHODS: The mural thrombus ratio and preoperative comorbidities of 100 consecutive patients from a single center undergoing endo-debranching between 2012 and 2019 were evaluated. Logistic regression, survival analysis, and decision tree methods were used to examine each variable's association with death at 1 year. RESULTS: At the time of analysis, 73 subjects had 1-year outcomes and adequate imaging to assess the parameters. At 1 year, the overall survival for all subjects was 71.2% (21 died, 52 survived). For patients with a favorable mural thrombus ratio (n = 36), the overall 1-year survival was 86.1% (5 died, 31 survived). The subjects with an unfavorable mural thrombus ratio (n = 37), had an overall 1 year survival of 56.8% (16 died, and 21 survived). The only preoperative mortality factor that was statistically significant between the subjects with an unfavorable mural thrombus ratio was age of the patient. The survival for subjects 75 years and older with an unfavorable mural thrombus ratio was 90% (one died, nine survived) vs only 44.4% survival for subjects less than 75 years with an unfavorable mural thrombus ratio (15 died, 12 survived). CONCLUSIONS: This study examined whether a patient's mural thrombus ratio may be an indicator of 1-year survival. These findings suggest that the combination of a patient's aortic mural thrombus ratio and age can function as a preoperative indicator of their underlying cardiac reserve. Identifying patients with low cardiac reserve and fitness to handle the increased cardiac demands owing to the physiologic response to extensive aortic stent grafting before undergoing aortic repair may allow for modification of preoperative patient counseling and postoperative care guidelines to better treat this patient population.

Understanding the Impacts of AFEX™ Pretreatment and Densification on the Fast Pyrolysis of Corn Stover, Prairie Cord Grass, and Switchgrass.

Lignocellulosic feedstocks corn stover, prairie cord grass, and switchgrass were subjected to ammonia fiber expansion (AFEX™) pretreatment and densified using extrusion pelleting and ComPAKco densification technique. The effects of AFEX™ pretreatment and densification were studied on the fast pyrolysis product yields. Feedstocks were milled in a hammer mill using three different screen sizes (2, 4, and 8 mm) and were subjected to AFEX™ pretreatment. The untreated and AFEX™-pretreated feedstocks were moisture adjusted at three levels (5, 10, and 15 % wb) and were extruded using a lab-scale single screw extruder. The barrel temperature of the extruder was maintained at 75, 100, and 125 °C. Durability of the extruded pellets made from AFEX™-pretreated corn stover, prairie cord grass, and switchgrass varied from 94.5 to 99.2, 94.3 to 98.7, and 90.1 to 97.5 %, respectively. Results of the thermogravimetric analysis showed the decrease in the decomposition temperature of the all the feedstocks after AFEX™ pretreatment indicating the increase in thermal stability. Loose and densified feedstocks were subjected to fast pyrolysis in a lab-scale reactor, and the yields (bio-oil and bio-char) were measured. Bio-char obtained from the AFEX™-pretreated feedstocks exhibited increased bulk and particle density compared to the untreated feedstocks. The properties of the bio-oil were statistically similar for the untreated, AFEX™-pretreated, and AFEX™-pretreated densified feedstocks. Based on the bio-char and bio-oil yields, the AFEX™-pretreated feedstocks and the densified AFEX™-pretreated feedstocks (pellets and PAKs) exhibited similar behavior. Hence, it can be concluded that densifying the AFEX™-pretreated feedstocks could be a viable option in the biomass-processing depots to reduce the transportation costs and the logistical impediments without affecting the product yields.

Shear accumulation as a means for evaluating risk of thromboembolic events in novel endovascular stent graft designs.

OBJECTIVE: This study proposes to establish a simulation-based technique for evaluating shear accumulation in stent grafts and to use the technique to assess the performance of a novel branched stent graft system. METHODS: Computational fluid dynamics models, with transient boundary conditions, particle injection, and rigid walls, simplifying assumptions were developed and used to evaluate the shear accumulation in various stent graft configurations with a healthy aorta as comparison. RESULTS: Shear streamlines are presented for the various configurations. Shear accumulation was also calculated for each configuration. The number of particles with shear accumulations >3.5 Pa-s for each configuration was compared with the shear accumulation values of commercially available mechanical aortic valves from the literature. CONCLUSIONS: The stent graft configuration with the diaphragm does have particles with shear accumulation >3.5 Pa-s. However, the percentage of particles with shear accumulation above 3.5 Pa-s is less than the two commercially available mechanical aortic valves, and more surprisingly, is smaller than in the healthy aorta.

Examination of near-wall hemodynamic parameters in the renal bridging stent of various stent graft configurations for repairing visceral branched aortic aneurysms.

OBJECTIVE: This study examined the flow behavior of four stent graft configurations for endovascular repair of complex aneurysms of the descending aorta. METHODS: Computational fluid dynamics models with transient boundary conditions and rigid wall simplifying assumptions were developed and used with four distinct geometries to compare various near-wall hemodynamic parameters. RESULTS: Graphic plots for time-averaged wall shear stress, oscillating shear index, and relative residence time were presented and compared among the four stent graft configurations of interest. CONCLUSIONS: Abrupt 90° and 180° changes in stent geometry (particularly in the side branches) cause a high momentum change and thus increased flow separation and mixing, which has significant implications in blood flow characteristics near the wall. By comparison, longer bridging stents provide more gradual changes in momentum, thus allowing blood flow to develop before reaching the target vessel.