Explore the vast range of titles available.

As Li-ion batteries are increasingly being deployed in electric vehicles and grid-level energy storage, the demand for Li is growing rapidly. Extracting lithium from alternative aqueous sources such as geothermal brines plays an important role in meeting this demand. Electrochemical intercalation emerges as a promising Li extraction technology due to its ability to offer high selectivity for Li and its avoidance of harsh chemical regenerants. In this work, we design an economically feasible electrochemical process that achieves selective lithium extraction from Salton Sea geothermal brine and purification of lithium chloride using intercalation materials, and conversion to battery grade (>99.5% purity) lithium hydroxide by bipolar membrane electrodialysis. We conduct techno-economic assessments using a parametric model and estimated the levelized cost of LiOH•H 2 O as 4.6 USD/kg at an electrode lifespan of 0.5 years. The results demonstrate the potential of our technology for electro-driven, chemical-free lithium extraction from alternative sources. Extracting lithium from alternative aqueous sources becomes crucial in meeting increasing lithium demand. Here, authors design an economically feasible electrochemical process that achieves selective lithium extraction from geothermal brine and finally produce battery grade lithium hydroxide.

The carbon net negative conversion of bio-char, the low value byproduct of pyrolysis bio-oil production from biomass, to high value, very high purity, highly crystalline flake graphite agglomerates with rationally designed shape and size tailored for lithium-ion battery energy storage material is reported. The process is highly efficient, 0.41 g/Wh; the energy content of its co-product of the process, bio-oil, exceeds that needed to power the process. It is shown that the shape of the starting material is retained during the transformation, allowing the ultimate morphology of the graphite agglomerates to be engineered from relatively malleable biomass. In contrast to commercial graphite production, the process can be performed at small scale with low equipment costs, enabling individual research laboratories to produce Li-ion grade graphite with customizable shape, size and porosity for Si/graphite composite and other graphite involved anodes. The mechanism of the graphitization of bio-char, a “non-graphitizable” carbon, is explored, suggesting the molten metal catalyst is absorbed into the pore structure, transported through and transforming the largely immobile biochar. Finally, the transformation of biomass to rationally designed graphite morphologies with Li-ion anode performance that closely mimic commercial shaped graphite is demonstrated.

The theoretical energy density of Li-O 2 batteries is more than an order of magnitude larger than the current generation of Li-ion batteries. However, their practical performance is far less, in part due to their low true capacities, that is, capacity including the mass of the typically porous active material, electrolyte in the pores and the Li 2 O 2 discharge product. This is further limited by the particulate nature of the product, yielding a theoretical maximum packing density of 74%, impacting both gravimetric and volumetric capacities. Here we introduce carbon nanochains (CNCs), a material synthesized from biomass that is structurally similar to a commonly studied cathode material, multiwalled carbon nanotubes (MWCNTs). CNCs form densely packed agglomerates with mesoporosity that is similar to that of MWCNTs but far less microporosity, resulting in nearly twice the volumetric capacity and significantly larger true capacity despite obtaining essentially identical gravimetric capacity. Finally, while the initial discharge product is found to be toroidal Li 2 O 2 particles typical of Li-O 2 cathodes, it proceeds with the formation of thick films covering the surface of the cathode. This is, to our knowledge, the first report of thick film formation in Li-O 2 cells, overcoming the 74% density limit of particulate formation.

The conversion of biochar, the low value byproduct of pyrolysis bio-oil production from biomass multi-walled carbon nanotubes (MWCNTs) and carbon nanochains (CNCs), is reported. It is shown that biomass can be converted to long (>30 µm) carbon nanotubes with an anomalously deep (>280 nm) stacked-cup structure. A mechanism of the transformation that is consistent with previously reported graphitization of biochar, a “non-graphitizable” carbon, is proposed, suggesting the molten metal catalyst is absorbed into the biochar by capillary action, forming graphene walls as it percolates through pore structure. Graphite is formed when the diameter of the molten catalyst droplets is large (microns), while smaller droplets (submicron) form MWCNTs and still smaller (<100 nm) form CNCs. Branching in the biochar pore structure leads to subdivision of the catalyst droplets resulting in the progression from MWCNT to CNC formation. Very long MWCNTs (>50 µm) can be formed in the absence of CNCs by transforming lignite char rather than biochar, presumably due to the elimination of smaller branching pores during coalification. CNCs, in the absence of MWCNTs, can be formed in biochar by using low concentrations of catalyst nanoparticles formed by carbon thermal reduction of a metal salt during charring. The results presented suggest that developing methods to control the porosity of the char could yield the ability to rationally synthesize carbon nanotubes with control of length, breadth and wall thickness.

Graphene nanoshells (MGNS) were prepared from cellulose, a sustainable biopolymer. Different sizes/morphologies were obtained by simply changing the metal catalyst salt in the synthesis. The MGNS were shown to reversibly cycle Li-ions by an intercalation mechanism similar to graphite. The reversible capacity of each MGNS prepared from different metal salts correlates well to its degree of 3-D graphitic order. The small size of the MGNS allows for short Li diffusion distances and very rapid charging, obtaining a 20% charge in 36 s (100 C rate). The unique spherical structure provides stable cycling, losing only 3.8% capacity over 900 cycles, and eliminates exfoliation that occurs when cycling graphite in propylene carbonate (PC), an inexpensive, environmentally friendly electrolyte. This enables cycling in a PC-only solvent-based electrolyte, with stable cycling and high capacities at temperatures as low as −35 °C. At this very low temperature, 95% of the RT reversible capacity is retained, with only a modest charge potential increase due to the increase in viscosity of the solvent.

Introduction Viral load (VL) of 1000 copies/ml or greater is commonly used to define virologic failure (VF) in children and adolescents living with HIV (CALHIV) in low‐ and middle‐income countries (LMICs). However, evidence in adults suggests that low‐level viraemia (LLV) (VL 50–999 copies/ml) increases the risk of subsequent VF. There is limited research on LLV in CALHIV. Methods This study retrospectively reviewed VL data from Baylor College of Medicine Children's Foundation—Tanzania (sites in Mbeya and Mwanza) collected between January 2015 and December 2022. CALHIV (0−19 years) on antiretroviral therapy for ≥6 months with at least one VL <50 copies/ml plus ≥2 subsequent VLs were included. VF was defined as both VL ≥1000 and ≥200 copies/ml. Multivariable Cox regression models were used to assess the association between LLV and VF, reporting adjusted hazard ratios (aHR) with 95% confidence intervals (CI). Results Among 2618 CALHIV included in the outcome analysis (median age 13.2 years, 52.5% female), 81.9% were on first‐line dolutegravir‐based regimens and LLV was found in 40.5%. CALHIV with LLV had an increased risk of VF with aHRs of 1.63 (CI 1.38−1.91) (VL ≥1000 copies/ml) and 3.85 (3.33, 4.46) (VL ≥200 copies/ml). When stratifying by LLV (50−199, 200–399 and 400–999 copies/ml), all levels were associated with increased risk for VF (VL ≥1000 copies/ml) with aHRs of 1.39 (1.13, 1.69), 1.69 (1.33, 2.16) and 2.03 (1.63, 2.53). When VF was defined as VL ≥200 copies/ml, the corresponding aHRs were 1.41 (1.15, 1.72), 7.99 (6.68, 9.57) and 9.37 (7.85, 11.18). Conclusions LLV is associated with a greater risk of VF in CALHIV. The risk of VF increases with higher levels of LLV. This study provides further evidence for revising guidelines in LMICs that define VF as VL ≥1000 copies/ml.

To assess residual cervical intraepithelial neoplasia (CIN) 2/3 disease and clearance of high-risk (hr) human papillomavirus (HPV) infections at 6 months after cryotherapy among HIV-positive women. Follow-up study. 79 HIV-positive women received cryotherapy for CIN2/3 in Nairobi, Kenya, and underwent conventional cytology 6 months later. Biopsies were performed on high grade cytological lesions and hrHPV was assessed before (cervical cells and biopsy) and after cryotherapy (cells). At 6 months after cryotherapy CIN2/3 had been eliminated in 61 women (77.2%; 95% Confidence Interval, (CI): 66.4-85.9). 18 women (22.8%) had residual CIN2/3, and all these women had hrHPV at baseline. CD4 count and duration of combination antiretroviral therapy (cART) were not associated with residual CIN2/3. CIN3 instead of CIN2 was the only significant risk factor for residual disease (odds ratio, OR vs CIN2 = 4.3; 95% CI: 1.2-15.0) among hrHPV-positive women after adjustment for age and HPV16 infection. Persistence of hrHPV types previously detected in biopsies was found in 77.5% of women and was associated with residual CIN2/3 (OR = 8.1, 95% CI: 0.9-70). The sensitivity, specificity, and negative predictive value of hrHPV test in detecting residual CIN2/3 were 0.94, 0.36, and 0.96 respectively. Nearly one quarter of HIV-positive women had residual CIN2/3 disease at 6 months after cryotherapy, and the majority had persistent hrHPV. CD4 count and cART use were not associated with residual disease or hrHPV persistence. The value of hrHPV testing in the detection of residual CIN2/3 was hampered by a low specificity.

The work presented in this thesis explores the key design parameters of microphone sensing systems for beamforming, specifically for a stationary uniform rectangular array (URA) and a drone mounted uniform line array (ULA). It explains the development of a custom audio recorder using a Field Programmable Gate Array (FPGA) with Hard Processor System (HPS), using a unique distribution of Linux called NixOS. It details experiments conducted to characterize these systems in controlled environments like a wind tunnel and an anechoic chamber, as well as in the field for real-world testing. It also investigates methods for the autonomous detection of sound sources of interest, including drones and ground vehicles such as tanks and large diesel trucks. The novel detection method monitors the mean and standard deviation of the principal components from an audio spectrogram in real-time. The results of this analysis are presented and discussed, demonstrating how acoustics can enhance various sensing modalities and improve environmental awareness.

This paper explores how category membership features in talk where speakers address the issue of racial discrimination. In particular, it examines how category membership gets invoked to furnish speaker entitlement in the course of destabilizing and reworking the category-bound inferences that inform membership attribution. I begin with the analysis of two relatively short extracts of talk in which speakers invoke ethnic and racial group identity as a preliminary to an examination of the paradoxical uses for which category membership is made relevant, moving on to consider an extended episode of The 700 Club. In contrast to analytic approaches which seek to reveal the denial of racism in speaker claims that mitigate the pernicious implications of category attribution, I consider how category attribution serves as a speaker resource in efforts to identify and critique racism. This participant work is then considered in relation to ethnomethodology’s efforts to re-specify the foundational postulates that inform the investigation of social order production and the place that the examination of participant meaning-making has in the pursuit of that endeavor.