Analytically Pricing Credit Default Swaps under a Regime-Switching Model

In this paper, we consider the valuation of a CDS (credit default swap) contract when the reference asset is assumed to follow a regime-switching model with the volatility allowed to jump among different states. Our motivation originates from empirical evidence demonstrating the existence of regime-switching in real markets. The default probability is analytically derived first, based on which a closed-form formula for the CDS price is obtained so that it can be easily implemented for practical purposes. Finally, numerical experiments are carried out to show quantitatively some properties of the CDS price under the regime-switching model

INTERFACE DESIGN FOR ALL-SOLID-STATE LITHIUM METAL BATTERIES

Lithium-ion batteries (LIBs) have expanded their application from electronics to electric vehicles (EVs). To ease the safety concerns and the “range anxiety”, solid-state lithium batteries (SSLBs) become a more attractive choice. The replacement of flammable and toxic liquid electrolytes with solid-state electrolytes (SSEs) makes it a safer option. The utilization and compatibility of high specific capacity materials such as sulfur cathode and lithium-metal anode increase the cell energy density. However, SSLBs still face challenges towards practical application, which mainly from the solid-solid contact nature on the interfaces. On the anode side, lithium dendrite growth and high interface resistance both hindered the longevity of the cells. On the cathode side, low initial Coulombic efficiency (CE) and low capacity utilization of sulfur obstructed the realization of high loading cathodes.In this dissertation, I addressed both challenges of dendrite and contact on the anode side by adding strontium into lithium anodes. Different from all previous metal/metal oxide coating on garnet or Li alloy anodes that form lithiophilic interlayer, a lithiophilic/lithiophobic bifunctional layer is formed to reduce the interfacial resistance and to suppress the growth of lithium dendrite, which is confirmed by comprehensive material characterizations, electrochemical evaluations, and simulations. The optimum Li-Sr | garnet | Li-Sr symmetric cells achieve a high critical current density (CCD) of 1.3 mA/cm2 and can be cycled for 1,000 cycles under 0.5 mA/cm2 at room temperature, providing a new strategy for high-performance garnet SSLB. Furthermore, I (1) verified the importance of lithiophobic on dendrite suppression by discovering and successfully constructing the highest interface energy (γ, against lithium) material ever reported among all lithium compounds that can be formed on the electrolyte | anode interface; (2) revealed the impact of anode properties on the interface by enhancing the Li self-diffusivity by a co-doping method, achieved an outperformed critical loading of 4.1 mAh/cm2 at 1.0 mA∙cm-2 at room temperature. On the cathode side, I tackled both low CE and low capacity utilization issues by promoting both Li+ and e- transportation across the cathode | SSE interface, resulting in high capacity utilization of 96.5% and high capacity retention of 88.8% after 145 cycles at a high loading of 4.0 mAh cm-2 under room temperature in Li6PS5Cl based SSLB

Technical Issues of Vim–PSA Double-Target DBS for Essential Tremor

Background: Deep brain stimulation (DBS) is an effective surgical treatment for essential tremor (ET), with the ventral intermediate nucleus (Vim) and posterior subthalamic area (PSA) as the most common targets. The stimulation efficacy of ET with Vim–PSA double-target DBS has been reported. Herein, we aim to propose surgical techniques for Vim–PSA double-target DBS surgery. Methods: This study enrolled six patients with ET who underwent Vim–PSA double-target electrode implantation from October 2019 to May 2022. The targets were located and adjusted using coordinates and multimodality MRI images. A burr hole was accurately drilled in line with the electrode trajectory under the guidance of a stereotactic frame. Novel approaches were adopted during the electrode implantation process for pneumocephalus reduction, including “arachnoid piamater welding” and “water sealing”. Electrophysiological recording was used to identify the implantation sites of the electrodes. A 3D reconstruction model of electrodes and nuclei was established to facilitate programming. Results: The combination of coordinates and multimodality MRI images for target location and adjustment enabled the alignment of Vim and PSA. Postoperative CT scanning showed that the electrode was precisely implanted. Stereotactic guidance facilitated accurate burr hole drilling. “Arachnoid piamater welding” and “water sealing” were efficient in reducing pneumocephalus. Intraoperative electrophysiological verified the efficacy of Vim–PSA double-target DBS surgery. Conclusions: The methods for target location and adjustment, accurate drilling of the burr hole, reduction in pneumocephalus, and intraoperative electrophysiological verification are key issues in DBS surgery targeting both the Vim and PSA. This study may provide technical support for Vim–PSA DBS, especially for surgeons with less experience in functional neurosurgery

Formation of LiF-rich Cathode-Electrolyte Interphase by Electrolyte Reduction

The capacityof transitionmetal oxide cathodefor Li-ionbatteriescan be furtherenhancedby increas-ing the chargingpotential.However,these high voltagecathodessufferfrom fast capacitydecaybecausethelargevolumechangeof cathodebreaksthe activematerialsand cathode-electrolyteinterphase(CEI),resultingin electrolytepenetrationinto brokenactivematerialsand continuousside reactionsbetweencath-ode and electrolytes.Herein,a robustLiF-richCEI wasformedby potentiostaticreductionof fluorinatedelec-trolyteat a low potentialof 1.7 V. By takingLiCoO2asa modelcathode,we demonstratethat the LiF-richCEImaintainsthe structuralintegrityand suppresseselectro-lyte penetrationat a high cut-offpotentialof 4.6 V. TheLiCoO2with LiF-richCEI exhibiteda capacityof198 mAhghttps://doi.org/10.1002/anie.20220273

Clinical Quality Control of MRI Total Kidney Volume Measurements in Autosomal Dominant Polycystic Kidney Disease

Total kidney volume measured on MRI is an important biomarker for assessing the progression of autosomal dominant polycystic kidney disease and response to treatment. However, we have noticed that there can be substantial differences in the kidney volume measurements obtained from the various pulse sequences commonly included in an MRI exam. Here we examine kidney volume measurement variability among five commonly acquired MRI pulse sequences in abdominal MRI exams in 105 patients with ADPKD. Right and left kidney volumes were independently measured by three expert observers using model-assisted segmentation for axial T2, coronal T2, axial single-shot fast spin echo (SSFP), coronal SSFP, and axial 3D T1 images obtained on a single MRI from ADPKD patients. Outlier measurements were analyzed for data acquisition errors. Most of the outlier values (88%) were due to breathing during scanning causing slice misregistration with gaps or duplication of imaging slices (n = 35), slice misregistration from using multiple breath holds during acquisition (n = 25), composing of two overlapping acquisitions (n = 17), or kidneys not entirely within the field of view (n = 4). After excluding outlier measurements, the coefficient of variation among the five measurements decreased from 4.6% pre to 3.2%. Compared to the average of all sequences without errors, TKV measured on axial and coronal T2 weighted imaging were 1.2% and 1.8% greater, axial SSFP was 0.4% greater, coronal SSFP was 1.7% lower and axial T1 was 1.5% lower than the mean, indicating intrinsic measurement biases related to the different MRI contrast mechanisms. In conclusion, MRI data acquisition errors are common but can be identified using outlier analysis and excluded to improve organ volume measurement consistency. Bias toward larger volume measurements on T2 sequences and smaller volumes on axial T1 sequences can also be mitigated by averaging data from all error-free sequences acquired

Tuning Interface Lithiophobicity for Lithium Metal Solid-State Batteries

Solid-state lithium batteries (SSLBs) using garnet electrolytes potentially have a higher energy density and are safer than liquid organic electrolyte Li-ion batteries. However, SSLBs face challenges of Li dendrite and high interface resistance. In this work, we overcome both challenges by doping strontium (Sr) into lithium anodes. Different from all previous metal/metal oxide coating on garnet or Li alloy anodes that form lithiophilic interlayer, Li-Sr/SrO-doped Li2O are enriched on the interface forming a lithiophilic/lithiophobic bifunctional layer. The interlayer reduces the interfacial resistance and also suppresses lithium dendrite. The stability of the lithiophobic SrO-doped Li2O against Li prevents reducing the garnet and suppresses Li dendrite, which distinguishes it from all reported alloy electron-conducting interlayers. The optimized Li-Sr|garnet|Li-Sr symmetric cell achieves a critical current density of 1.3 mA/cm2 and can be cycled for 1,000 cycles under 0.5 mA/cm2 at room temperature. The bifunctional lithiophilic/lithiophobic interlayer provides a new strategy for high-performance garnet solid-state lithium batteries

Caging tin oxide in three-dimensional graphene networks for superior volumetric lithium storage

The excessive porous space in carbon anodes for lithium-ion batteries has to be utilized for high volumetric performance. Here the authors show an adaptable sulfur template strategy to yield graphene-caged noncarbon materials with a precisely controlled amount of void, enabling ultrahigh volumetric lithium storage

Enhancing Li\u3csup\u3e+\u3c/sup\u3e Transport in NMC811||Graphite Lithium-Ion Batteries at Low Temperatures by Using Low-Polarity-Solvent Electrolytes

LiNixCoyMnzO2 (x+y+z=1)||graphite lithium-ion battery (LIB) chemistry promises practical applications. However, its low-temperature (≤ −20 °C) performance is poor because the increased resistance encountered by Li+ transport in and across the bulk electrolytes and the electrolyte/electrode interphases induces capacity loss and battery failures. Though tremendous efforts have been made, there is still no effective way to reduce the charge transfer resistance (Rct) which dominates low-temperature LIBs performance. Herein, we propose a strategy of using low-polarity-solvent electrolytes which have weak interactions between the solvents and the Li+ to reduce Rct, achieving facile Li+ transport at sub-zero temperatures. The exemplary electrolyte enables LiNi0.8Mn0.1Co0.1O2||graphite cells to deliver a capacity of ≈113 mAh g−1 (98 % full-cell capacity) at 25 °C and to remain 82 % of their room-temperature capacity at −20 °C without lithium plating at 1/3C. They also retain 84 % of their capacity at −30 °C and 78 % of their capacity at −40 °C and show stable cycling at 50 °C