32 research outputs found
EC-FORC: A New Cyclic Voltammetry Based Method for Examining Phase Transitions and Predicting Equilibrium
We propose a new, cyclic-voltammetry based experimental technique that can
not only differentiate between discontinuous and continuous phase transitions
in an adsorbate layer, but also quite accurately recover equilibrium behavior
from dynamic analysis of systems with a continuous phase transition. The
Electrochemical first-order reversal curve (EC-FORC) diagram for a
discontinuous phase transition (nucleation and growth), such as occurs in
underpotential deposition, is characterized by a negative region, while such a
region does not exist for a continuous phase transition, such as occurs in the
electrosorption of Br on Ag(100). Moreover, for systems with a continuous phase
transition, the minima of the individual EC-FORCs trace the equilibrium curve,
even at very high scan rates. Since obtaining experimental data for the EC-FORC
method would require only a simple reprogramming of the potentiostat used in
conventional cyclic-voltammetry experiments, we believe that this method has
significant potential for easy, rapid, in-situ analysis of systems undergoing
electrochemical deposition.Comment: 8 pages, 4 figures, 211th ECS Meetin
Floridian high-voltage power-grid network partitioning and cluster optimization using simulated annealing
Many partitioning methods may be used to partition a network into smaller
clusters while minimizing the number of cuts needed. However, other
considerations must also be taken into account when a network represents a real
system such as a power grid. In this paper we use a simulated annealing Monte
Carlo (MC) method to optimize initial clusters on the Florida high-voltage
power-grid network that were formed by associating each load with its "closest"
generator. The clusters are optimized to maximize internal connectivity within
the individual clusters and minimize the power deficiency or surplus that
clusters may otherwise have.Comment: 9 pages, 3 figures, University of Georgia 24th Annual CSP Worksho
Spectral matrix methods for partitioning power grids: Applications to the Italian and Floridian high-voltage networks
Intentional islanding is used to limit cascading power failures by isolating
highly connected "islands" with local generating capacity. To efficiently
isolate an island, one should break as few power lines as possible. This is a
graph partitioning problem, and here we give preliminary results on islanding
of the Italian and Floridian high-voltage grids by spectral matrix methods.Comment: 4 pages, 2 figures
A new battery-charging method suggested by molecular dynamics simulations
Based on large-scale molecular dynamics simulations, we propose a new
charging method that should be capable of charging a Lithium-ion battery in a
fraction of the time needed when using traditional methods. This charging
method uses an additional applied oscillatory electric field. Our simulation
results show that this charging method offers a great reduction in the average
intercalation time for Li+ ions, which dominates the charging time. The
oscillating field not only increases the diffusion rate of Li+ ions in the
electrolyte but, more importantly, also enhances intercalation by lowering the
corresponding overall energy barrier.Comment: 11 pages, 5 figure
Effects of Lateral Diffusion on the Dynamics of Desorption
The adsorbate dynamics during simultaneous action of desorption and lateral
adsorbate diffusion is studied in a simple lattice-gas model by kinetic Monte
Carlo simulations. It is found that the action of the coverage-conserving
diffusion process during the course of the desorption has two distinct,
competing effects: a general acceleration of the desorption process, and a
coarsening of the adsorbate configuration through Ostwald ripening. The balance
between these two effects is governed by the structure of the adsorbate layer
at the beginning of the desorption process
Global prevalence and genotype distribution of hepatitis C virus infection in 2015 : A modelling study
Publisher Copyright: © 2017 Elsevier LtdBackground The 69th World Health Assembly approved the Global Health Sector Strategy to eliminate hepatitis C virus (HCV) infection by 2030, which can become a reality with the recent launch of direct acting antiviral therapies. Reliable disease burden estimates are required for national strategies. This analysis estimates the global prevalence of viraemic HCV at the end of 2015, an update ofâand expansion onâthe 2014 analysis, which reported 80 million (95% CI 64â103) viraemic infections in 2013. Methods We developed country-level disease burden models following a systematic review of HCV prevalence (number of studies, n=6754) and genotype (n=11â342) studies published after 2013. A Delphi process was used to gain country expert consensus and validate inputs. Published estimates alone were used for countries where expert panel meetings could not be scheduled. Global prevalence was estimated using regional averages for countries without data. Findings Models were built for 100 countries, 59 of which were approved by country experts, with the remaining 41 estimated using published data alone. The remaining countries had insufficient data to create a model. The global prevalence of viraemic HCV is estimated to be 1·0% (95% uncertainty interval 0·8â1·1) in 2015, corresponding to 71·1 million (62·5â79·4) viraemic infections. Genotypes 1 and 3 were the most common cause of infections (44% and 25%, respectively). Interpretation The global estimate of viraemic infections is lower than previous estimates, largely due to more recent (lower) prevalence estimates in Africa. Additionally, increased mortality due to liver-related causes and an ageing population may have contributed to a reduction in infections. Funding John C Martin Foundation.publishersversionPeer reviewe
Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study
PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19âfree surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19âfree surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19âfree surgical pathways. Patients who underwent surgery within COVID-19âfree surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19âfree surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity scoreâmatched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19âfree surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19âfree surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks
Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.
PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks
Variation in postoperative outcomes of patients with intracranial tumors: insights from a prospective international cohort study during the COVID-19 pandemic
Background:
This study assessed the international variation in surgical neuro-oncology practice and 30-day outcomes of patients who had surgery for an intracranial tumor during the COVID-19 pandemic.
Methods:
We prospectively included adults aged â„18 years who underwent surgery for a malignant or benign intracranial tumor across 55 international hospitals from 26 countries. Each participating hospital recorded cases for 3 consecutive months from the start of the pandemic. We categorized patientsâ location by World Bank income groups (high [HIC], upper-middle [UMIC], and low- and lower-middle [LLMIC]). Main outcomes were a change from routine management, SARS-CoV-2 infection, and 30-day mortality. We used a Bayesian multilevel logistic regression stratified by hospitals and adjusted for key confounders to estimate the association between income groups and mortality.
Results:
Among 1016 patients, the number of patients in each income group was 765 (75.3%) in HIC, 142 (14.0%) in UMIC, and 109 (10.7%) in LLMIC. The management of 200 (19.8%) patients changed from usual care, most commonly delayed surgery. Within 30 days after surgery, 14 (1.4%) patients had a COVID-19 diagnosis and 39 (3.8%) patients died. In the multivariable model, LLMIC was associated with increased mortality (odds ratio 2.83, 95% credible interval 1.37â5.74) compared to HIC.
Conclusions:
The first wave of the pandemic had a significant impact on surgical decision-making. While the incidence of SARS-CoV-2 infection within 30 days after surgery was low, there was a disparity in mortality between countries and this warrants further examination to identify any modifiable factors
Reply to "Remarks on the simulation of Cl electrosorption on Ag(1 0 0) reported in Electrochimica Acta 50 (2005) 5518"
We reply to the remarks by Lang and Horanyi [G.G. Lang, G. Horanyi, Electrochim. Acta (2006), doi: 10.1016/j.electacta.2006.07.009] on the meaning of the notion of "electrosorption valency" used by Abou Hamad et al. [I. Abou Hamad, S.J. Mitchell, Th. Wandlowski, P.A. Rikvold, G. Brown, Electrochim. Acta 50 (2005) 5518]. It is concluded that, contrary to the assertion of Lang and Horanyi, the magnitude of the current in the external circuit upon adsorption of an ion of charge ze with partial charge transfer is indeed given by an electrosorption valency gamma such that vertical bar ye vertical bar < vertical bar ze vertical bar. We believe the conclusion of Lang and Horanyi to the contrary is the result of an excessively severe charge-neutrality requirement. (c) 2006 Elsevier B.V. All rights reserved