Unlocking Li superionic conductivity in face-centred cubic oxides via face-sharing configurations.

Oxides with a face-centred cubic (fcc) anion sublattice are generally not considered as solid-state electrolytes as the structural framework is thought to be unfavourable for lithium (Li) superionic conduction. Here we demonstrate Li superionic conductivity in fcc-type oxides in which face-sharing Li configurations have been created through cation over-stoichiometry in rocksalt-type lattices via excess Li. We find that the face-sharing Li configurations create a novel spinel with unconventional stoichiometry and raise the energy of Li, thereby promoting fast Li-ion conduction. The over-stoichiometric Li-In-Sn-O compound exhibits a total Li superionic conductivity of 3.38 × 10-4 S cm-1 at room temperature with a low migration barrier of 255 meV. Our work unlocks the potential of designing Li superionic conductors in a prototypical structural framework with vast chemical flexibility, providing fertile ground for discovering new solid-state electrolytes.

Novel Focused Ion Beam Liftouts for Spatial Characterization of Spherical Biominerals With Transmission Electron Microscopy.

Focused ion beam (FIB) is frequently used to prepare electron- and X-ray-beam-transparent thin sections of samples, called lamellae. Typically, lamellae are prepared from only a subregion of a sample. In this paper, we present a novel approach for FIB lamella preparation of microscopic samples, wherein the entire cross-section of the whole sample can be investigated. The approach was demonstrated using spherical, porous, and often hollow microprecipitates of biologically precipitated calcium carbonate. The microprecipitate morphology made these biogenic samples more fragile and challenging than materials commonly investigated using FIB lamellae. Our method enables the appropriate orientation of the lamellae required for further electron/X-ray analyses after attachment to the transmission electron microscopy (TEM) grid post and facilitates more secure adhesion onto the grid post. We present evidence of autofluorescence in bacterially precipitated vaterite using this lamella preparation method coupled with TEM selected area diffraction. This innovative approach allows studying biomineralization at the micro to nano scales, which can provide novel insights into bacterial responses to microenvironmental conditions.

Stacking Faults Assist Lithium-Ion Conduction in a Halide-Based Superionic Conductor.

In the pursuit of urgently needed, energy dense solid-state batteries for electric vehicle and portable electronics applications, halide solid electrolytes offer a promising path forward with exceptional compatibility against high-voltage oxide electrodes, tunable ionic conductivities, and facile processing. For this family of compounds, synthesis protocols strongly affect cation site disorder and modulate Li+ mobility. In this work, we reveal the presence of a high concentration of stacking faults in the superionic conductor Li3YCl6 and demonstrate a method of controlling its Li+ conductivity by tuning the defect concentration with synthesis and heat treatments at select temperatures. Leveraging complementary insights from variable temperature synchrotron X-ray diffraction, neutron diffraction, cryogenic transmission electron microscopy, solid-state nuclear magnetic resonance, density functional theory, and electrochemical impedance spectroscopy, we identify the nature of planar defects and the role of nonstoichiometry in lowering Li+ migration barriers and increasing Li site connectivity in mechanochemically synthesized Li3YCl6. We harness paramagnetic relaxation enhancement to enable 89Y solid-state NMR and directly contrast the Y cation site disorder resulting from different preparation methods, demonstrating a potent tool for other researchers studying Y-containing compositions. With heat treatments at temperatures as low as 333 K (60 °C), we decrease the concentration of planar defects, demonstrating a simple method for tuning the Li+ conductivity. Findings from this work are expected to be generalizable to other halide solid electrolyte candidates and provide an improved understanding of defect-enabled Li+ conduction in this class of Li-ion conductors.

Enhanced Electrochemical Performance of Disordered Rocksalt Cathodes Enabled by a Graphite Conductive Additive.

Cobalt-free cation-disordered rocksalt (DRX) cathodes are a promising class of materials for next-generation Li-ion batteries. Although they have high theoretical specific capacities (>300 mA h/g) and moderate operating voltages (∼3.5 V vs Li/Li+), DRX cathodes typically require a high carbon content (up to 30 wt %) to fully utilize the active material which has a detrimental impact on cell-level energy density. To assess pathways to reduce the electrode's carbon content, the present study investigates how the carbon's microstructure and loading (10-20 wt %) influence the performance of DRX cathodes with the nominal composition Li1.2Mn0.5Ti0.3O1.9F0.1. While electrodes prepared with conventional disordered carbon additives (C65 and ketjenblack) exhibit rapid capacity fade due to an unstable cathode/electrolyte interface, DRX cathodes containing 10 wt % graphite show superior cycling performance (e.g., reversible capacities ∼260 mA h/g with 85% capacity retention after 50 cycles) and rate capability (∼135 mA h/g at 1000 mA/g). A suite of characterization tools was employed to evaluate the performance differences among these composite electrodes. Overall, these results indicate that the superior performance of the graphite-based cathodes is largely attributed to the: (i) formation of a uniform graphitic coating on DRX particles which protects the surface from parasitic reactions at high states of charge and (ii) homogeneous dispersion of the active material and carbon throughout the composite cathode which provides a robust electronically conductive network that can withstand repeated charge-discharge cycles. Overall, this study provides key scientific insights on how the carbon microstructure and electrode processing influence the performance of DRX cathodes. Based on these results, exploration of alternative routes to apply graphitic coatings is recommended to further optimize the material performance.

Enhancing the Electrode Gravimetric Capacity of Li1.2Mn0.4Ti0.4O2 Cathode Using Interfacial Carbon Deposition and Carbon Nanotube-Mediated Electrical Percolation.

Mn-based cation-disordered rocksalt oxides (Mn-DRX) are emerging as promising cathode materials for next-generation Li-ion batteries due to their high specific capacities and cobalt- and nickel-free characteristic. However, to reach the usable capacity, solid-state synthesized Mn-DRX materials require activation via postsynthetic ball milling, typically incorporating more than 20 wt % conductive carbon that adversely reduces the electrode-level gravimetric capacity. To address this issue, we first deposit amorphous carbon on the surface of the Li1.2Mn0.4Ti0.4O2 (LMTO) particles to increase the electrical conductivity by 5 orders of magnitude. Although the cathode material gravimetric first charge capacity reaches 180 mAh/g, its highly irreversible behavior leads to a first discharge capacity of 70 mAh/g. Subsequently, to ensure a good electrical percolation network, the LMTO material is ball-milled with a multiwall carbon nanotube (CNT) to obtain a 78.7 wt % LMTO active material loading in the cathode electrode (LMTO-CNT). As a result, a 210 mAh/g cathode electrode gravimetric first charge and 165 mAh/g first discharge capacity values are obtained, compared to the respective capacity values of 222 and 155 mAh/g for the LMTO material ball-milled with 20 wt % SuperP C65 electrode (LMTO-SP). After 50 cycles, LMTO-CNT delivers a 121 mAh/g electrode gravimetric discharge capacity, largely outperforming the value of 44 mAh/g of LMTO-SP. Our study demonstrates that while ball milling is necessary to achieve a significant amount of capacity of LMTO, a careful selection of additives, such as CNT, effectively reduces the required carbon quantity to achieve a higher electrode gravimetric discharge capacity.

Surgical Procedure among Patients with Foreign Body Obstruction in Food Passage in a Tertiary Care Hospital: A Descriptive Cross-sectional Study.

INTRODUCTION: Foreign body is any object in a region it is not meant to be, where it can cause harm if immediate medical attention is not sought. Its removal by surgical procedure is one of the commonest surgeries done. The objective is to find out prevalence of the patients who underwent operation for foreign bodies obstruction in food passage in the Department of Otorhinolaryngology-Head and Neck Surgery in a tertiary care centre. METHODS: A descriptive cross-sectional study conducted among patients operated in the Department of Otorhinolaryngology and Head and Neck Surgery of a tertiary care center from August 2014 to May 2017. Ethical approval was received from the Institutional Review Committee of the Institute. Convenience sampling method was used. Statistical Package for the Social Sciences was used for analysis. Point estimate at 95% Confidence Interval was calculated along with frequency and proportion for binary data. RESULTS: Out of total 700 patients having operation in department, 115 (16.42%) (95% Confidence Interval = 13.67-19.16) had operation for foreign body obstruction in the food passage. Among 115 patients, 62 (53.90%) were males and 53 (46.10%) were females. Most common foreign bodies ingested in children was coin 17 (14.78%) and bone chips 40 (34.78%) in adults. Cricopharynx 90 (78.26%) is the commonest site for foreign body lodgement. CONCLUSIONS: Prevalence of the patients who underwent operation for foreign bodies obstruction in food passage in a tertiary care hospital is high. Their removal by rigid oesophagoscopy is one of the commonest surgical procedures done in tertiary care center.

Histopathology of Sinonasal and Nasopharyngeal Neoplastic Lesions in a Tertiary Care Center of Western Nepal: A Descriptive Cross-sectional Study.

INTRODUCTION: Sinonasal and nasopharyngeal regions harbor diverse clinical conditions including many non-neoplastic and neoplastic lesions presenting with nasal obstruction, facial pain and swelling, rhinorrhea, epistaxis, and other oral, ear, and orbital symptoms. Histopathology of excised lesions is the mainstay for the definitive diagnosis and management of neoplastic lesions. The aim of this study is to find out the prevalence of neoplastic lesions among sinonasal and nasopharyngeal masses. METHODS: This was a descriptive cross-sectional study conducted among sinonasal and nasopharyngeal masses in the Department of Pathology of a tertiary care center of western Nepal with primary data of 20 years from January 2001 to May 2020. Ethical approval was taken from the Institutional Review Committee. Convenience sampling method was used. Data management and statistical analysis were done using Statistical Package for Social Sciences. Point estimate at 95% Confidence Interval was calculated along with frequency and percentage. RESULTS: Out of 395 sinonasal and nasopharyngeal lesions, 134 (33.92%) (29.26-38.58 at 95% Confidence Interval) were neoplastic lesions. The malignant lesions were found to be 60 (44.77%). Inverted papilloma was the most common benign lesion comprising 28 (20.89%) of cases, and squamous cell carcinoma and nasopharyngeal carcinoma were the most common malignant lesions comprising 12 (8.95%) cases each. CONCLUSIONS: This study observed a variety of neoplastic lesions. The most common benign lesion was nasal polyp and squamous cell carcinoma and nasopharyngeal carcinoma were the most common malignant lesions.

Treatment of Acute Painful Thyroiditis with Low Dose Prednisolone: A Study on Patients from Western Nepal.

INTRODUCTION: Thyroiditis is a disorder that involves inflammation of the thyroid gland. Subacute thyroiditis is the most common cause of acute painful thyroiditis. It is thought to be a viral inflammatory disorder. Subacute thyroiditis has been treated with either nonsteroidal anti-inflammatory drugs (NSAIDs) or high dose corticosteroids. The response to steroids is more dramatic and quicker than the NSAIDs. Prednisolone is the most commonly used corticosteroid to treat subacute thyroiditis. The usual dose is one mg/kg/day tapered over six weeks although the basis for this dose has not been established yet by prospective studies. AIM: The current research was carried out to study if prednisolone in lower initial dose (20 mg/day tapered over four weeks) is effective in patients with acute painful thyroiditis. MATERIALS AND METHODS: This study was a prospective, cross sectional, observational study carried out at Pokhara, Nepal. All the patients presenting with anterior neck pain of less than 1 week with tender thyroid on palpation and ESR more than 30mm/h were included in the study. The patients were administered prednisolone in a starting dose of 20 mg/day tapered over four weeks. Data were collected, analysed and the results were interpreted. RESULTS: One hundred and twenty two patients of acute painful thyroiditis were included in our study. Age of the patients ranged from 19 years to 69 years with the mean age of 36.58 years. Female to Male ratio was 10:1. Mean ESR was 57.03 at the time of presentation. ESR decreased to 29.63 at two weeks and 17.03 mm per hour (normal) at 4 weeks after continuation of the drug. All the patients reported with severe pain in the anterior neck at the time of presentation. Pain was completely relieved in 115 patients (94%) at 2 weeks after starting the treatment and it was better than previous in seven patients. CONCLUSION: Twenty mg of prednisolone daily tapered over 4 weeks is an adequate treatment of subacute thyroiditis. However, dose can be drastically tapered after 2 weeks.