77 research outputs found
Theory of voltammetry in charged porous media
We couple the Leaky Membrane Model, which describes the diffusion and
electromigration of ions in a homogenized porous medium of fixed background
charge, with Butler-Volmer reaction kinetics for flat electrodes separated by
such a medium in a simple mathematical theory of voltammetry. The model is
illustrated for the prototypical case of copper electro-deposition/dissolution
in aqueous charged porous media. We first consider the steady state with three
different experimentally relevant boundary conditions and derive analytical or
semi-analytical expressions for concentration profiles, electric potential
profiles, current-voltage relations and overlimiting conductances. Next, we
perform nonlinear least squares fitting on experimental data, consider the
transient response for linear sweep voltammetry and demonstrate good agreement
of the model predictions with experimental data. The experimental datasets are
for copper electrodeposition from copper(II) sulfate solutions in a variety of
nanoporous media, such as anodic aluminum oxide, cellulose nitrate and
polyethylene battery separators, whose internal surfaces are functionalized
with positively and negatively charged polyelectrolyte polymers.Comment: 39 pages, 12 figures, 5 tables; clarified where other parameters are
taken from and fixed typo
Linear stability analysis of transient electrodeposition in charged porous media: suppression of dendritic growth by surface conduction
We study the linear stability of transient electrodeposition in a charged
random porous medium, whose pore surface charges can be of any sign, flanked by
a pair of planar metal electrodes. Discretization of the linear stability
problem results in a generalized eigenvalue problem for the dispersion relation
that is solved numerically, which agrees well with the analytical approximation
obtained from a boundary layer analysis valid at high wavenumbers. Under
galvanostatic conditions in which an overlimiting current is applied, in the
classical case of zero surface charges, the electric field at the cathode
diverges at Sand's time due to electrolyte depletion. The same phenomenon
happens for positive charges but earlier than Sand's time. However, negative
charges allow the system to sustain an overlimiting current via surface
conduction past Sand's time, keeping the electric field bounded. Therefore, at
Sand's time, negative charges greatly reduce surface instabilities and suppress
dendritic growth, while zero and positive charges magnify them. We compare
theoretical predictions for overall surface stabilization with published
experimental data for copper electrodeposition in cellulose nitrate membranes
and demonstrate good agreement between theory and experiment. We also apply the
stability analysis to how crystal grain size varies with duty cycle during
pulse electroplating.Comment: 55 pages, 12 figures, 2 table
Over-limiting Current and Control of Dendritic Growth by Surface Conduction in Nanopores
Understanding over-limiting current (faster than diffusion) is a
long-standing challenge in electrochemistry with applications in desalination
and energy storage. Known mechanisms involve either chemical or hydrodynamic
instabilities in unconfined electrolytes. Here, it is shown that over-limiting
current can be sustained by surface conduction in nano pores, without any such
instabilities, and used to control dendritic growth during electrodeposition.
Copper electrode posits are grown in anodized aluminum oxide membranes with
polyelectrolyte coatings to modify the surface charge. At low currents, uniform
electroplating occurs, unaffected by surface modification due to thin electric
double layers, but the morphology changes dramatically above the limiting
current. With negative surface charge, growth is enhanced along the nanopore
surfaces, forming surface dendrites and nanotubes behind a deionization shock.
With positive surface charge, dendrites avoid the surfaces and are either
guided along the nanopore centers or blocked from penetrating the membrane
Driving behavior-guided battery health monitoring for electric vehicles using machine learning
An accurate estimation of the state of health (SOH) of batteries is critical
to ensuring the safe and reliable operation of electric vehicles (EVs).
Feature-based machine learning methods have exhibited enormous potential for
rapidly and precisely monitoring battery health status. However, simultaneously
using various health indicators (HIs) may weaken estimation performance due to
feature redundancy. Furthermore, ignoring real-world driving behaviors can lead
to inaccurate estimation results as some features are rarely accessible in
practical scenarios. To address these issues, we proposed a feature-based
machine learning pipeline for reliable battery health monitoring, enabled by
evaluating the acquisition probability of features under real-world driving
conditions. We first summarized and analyzed various individual HIs with
mechanism-related interpretations, which provide insightful guidance on how
these features relate to battery degradation modes. Moreover, all features were
carefully evaluated and screened based on estimation accuracy and correlation
analysis on three public battery degradation datasets. Finally, the
scenario-based feature fusion and acquisition probability-based practicality
evaluation method construct a useful tool for feature extraction with
consideration of driving behaviors. This work highlights the importance of
balancing the performance and practicality of HIs during the development of
feature-based battery health monitoring algorithms
Prevalence of Potential Drug-Drug Interactions Involving Antiretroviral Drugs in a Large Kenyan Cohort
Background: Clinically significant drug-drug interactions (CSDIs) involving antiretrovirals are frequent and under-recognizedin developed countries, but data are lacking for developing countries.
Methodology and Principal Findings: To investigate the prevalence of CSDIs between antiretrovirals and coadministered drugs, we surveyed prescriptions dispensed in a large HIV clinic in Kenya. Of 1040 consecutive patients screened, 996 were eligible for inclusion. CSDIs were defined as ‘major’ (capable of causing severe or permanent damage, contraindicated, avoid or not recommended by the manufacturer, or requiring dose modification) ‘moderate’ (manufacturers advise caution, or
close monitoring, or capable of causing clinical deterioration). A total of 334 patients (33.5%) were at risk for a CSDI, potentially lowering antiretroviral drug concentrations in 120 (12%) patients. Major interactions most frequently involved rifampicin (12.4%, mostly with efavirenz) and azoles (2.7%) whereas moderate interactions were frequently azoles (13%), steroids (11%), and antimalarials (3%). Multivariable analyses suggested that patients at risk for CSDIs had lower CD4 counts (P = 0.006) and baseline weight (P = 0.023) and WHO Stage 3 or 4 disease (P#0.007). Risk for CSDIs was not associated with particular regimens, although only 116 (11.6%) patients were receiving WHO second line regimens.
Conclusions: One in three patients receiving antiretrovirals in our programme were at risk of CSDIs. Strategies need to be urgently developed to avoid important drug interactions, to identify early markers of toxicity and to manage unavoidable interactions safely in order to reduce risk of harm, and to maximize the effectiveness of mass antiretroviral deployment in Africa
Health diagnosis and recuperation of aged Li-ion batteries with data analytics and equivalent circuit modeling
Battery health assessment and recuperation play a crucial role in the
utilization of second-life Li-ion batteries. However, due to ambiguous aging
mechanisms and lack of correlations between the recovery effects and
operational states, it is challenging to accurately estimate battery health and
devise a clear strategy for cell rejuvenation. This paper presents aging and
reconditioning experiments of 62 commercial high-energy type lithium iron
phosphate (LFP) cells, which supplement existing datasets of high-power LFP
cells. The relatively large-scale data allow us to use machine learning models
to predict cycle life and identify important indicators of recoverable
capacity. Considering cell-to-cell inconsistencies, an average test error of
(mean absolute percentage error) for cycle life prediction
is achieved by gradient boosting regressor given information from the first 80
cycles. In addition, it is found that some of the recoverable lost capacity is
attributed to the lateral lithium non-uniformity within the electrodes. An
equivalent circuit model is built and experimentally validated to demonstrate
how such non-uniformity can be accumulated, and how it can give rise to
recoverable capacity loss. SHapley Additive exPlanations (SHAP) analysis also
reveals that battery operation history significantly affects the capacity
recovery.Comment: 20 pages, 5 figures, 1 tabl
"Knees" in lithium-ion battery aging trajectories
Lithium-ion batteries can last many years but sometimes exhibit rapid,
nonlinear degradation that severely limits battery lifetime. In this work, we
review prior work on "knees" in lithium-ion battery aging trajectories. We
first review definitions for knees and three classes of "internal state
trajectories" (termed snowball, hidden, and threshold trajectories) that can
cause a knee. We then discuss six knee "pathways", including lithium plating,
electrode saturation, resistance growth, electrolyte and additive depletion,
percolation-limited connectivity, and mechanical deformation -- some of which
have internal state trajectories with signals that are electrochemically
undetectable. We also identify key design and usage sensitivities for knees.
Finally, we discuss challenges and opportunities for knee modeling and
prediction. Our findings illustrate the complexity and subtlety of lithium-ion
battery degradation and can aid both academic and industrial efforts to improve
battery lifetime.Comment: Submitted to the Journal of the Electrochemical Societ
Microbial exposure during early human development primes fetal immune cells
Human fetal immune system begins to develop early during gestation, however factors responsible for fetal immune-priming remain elusive. We explored potential exposure to microbial agents in-utero and their contribution towards activation of memory T cells
in fetal tissues. We profiled microbes across fetal organs using 16S-rRNA
gene sequencing and detected low but consistent microbial signal in fetal gut, skin, placenta and lungs, in 2nd trimester of gestation. We identified several live bacterial strains including Staphylococcus and Lactobacillus in fetal tissues, which induced in vitro activation of memory T cells in fetal mesenteric lymph-node, supporting the role of microbial exposure in fetal immune-priming. Finally, using SEM and RNA-ISH, we visualised discrete localisation of bacteria-like structures and eubacterial-RNA within
14th week fetal gut lumen. These findings indicate selective presence of live-microbes in fetal organs during 2nd trimester of gestation and have broader implications towards establishment of immune competency and priming before birt
Multiple novel prostate cancer susceptibility signals identified by fine-mapping of known risk loci among Europeans
Genome-wide association studies (GWAS) have identified numerous common prostate cancer (PrCa) susceptibility loci. We have
fine-mapped 64 GWAS regions known at the conclusion of the iCOGS study using large-scale genotyping and imputation in
25 723 PrCa cases and 26 274 controls of European ancestry. We detected evidence for multiple independent signals at 16
regions, 12 of which contained additional newly identified significant associations. A single signal comprising a spectrum of
correlated variation was observed at 39 regions; 35 of which are now described by a novel more significantly associated lead SNP,
while the originally reported variant remained as the lead SNP only in 4 regions. We also confirmed two association signals in
Europeans that had been previously reported only in East-Asian GWAS. Based on statistical evidence and linkage disequilibrium
(LD) structure, we have curated and narrowed down the list of the most likely candidate causal variants for each region.
Functional annotation using data from ENCODE filtered for PrCa cell lines and eQTL analysis demonstrated significant
enrichment for overlap with bio-features within this set. By incorporating the novel risk variants identified here alongside the
refined data for existing association signals, we estimate that these loci now explain ∼38.9% of the familial relative risk of PrCa,
an 8.9% improvement over the previously reported GWAS tag SNPs. This suggests that a significant fraction of the heritability of
PrCa may have been hidden during the discovery phase of GWAS, in particular due to the presence of multiple independent
signals within the same regio
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