Publications by authors named "Javier Parrondo"

10 Publications

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Quantifying the reduction in sexual transmission of HIV-1 among MSM by early initiation of ART: A mathematical model.

PLoS One 2020 20;15(7):e0236032. Epub 2020 Jul 20.

UCLA Center for Clinical AIDS Research & Education, Los Angeles, CA, United States of America.

Background: We analyzed the effect of time to initiation of antiretroviral therapy (ART) after diagnosis on the probability of HIV-1 transmission events (HIV-TE) in naïve HIV-1-infected men having sex with men (MSM).

Setting: Mathematical model.

Methods: We used discrete event simulation modeling to estimate the probability of HIV-TE in the first 8 weeks after ART initiation; we varied ART initiation from D0 to D28 after simulated "diagnosis". The model inputs used sexual behavior parameters from the MSM population of the START trial, and transmission rates per-sex act and HIV-1 RNA from recent meta-analyses. HIV-1 RNA decay curves were modeled from the databases of Single (efavirenz [EFV] v dolutegravir [DTG]), Spring-2 (raltegravir [RAL] v DTG), and Flamingo (darunavir/ritonavir [DRVr] v DTG) trials.

Results: We found that the number of HIV-TE per index patient in the first 8 weeks after ART initiation increased linearly for same-day ART to initiation on day 28. Small but statistically significant advantages of integrase strand transfer inhibitors (INSTI) over EFV and DRVr were found.

Conclusions: Rapid, if not same-day initiation of INSTI-based ART to newly diagnosed HIV-infected MSM has the potential for substantial public health benefits related to decreases in HIV-TE.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0236032PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7371210PMC
September 2020

Detection of Reactive Oxygen Species in Anion Exchange Membrane Fuel Cells using In Situ Fluorescence Spectroscopy.

ChemSusChem 2017 08 28;10(15):3056-3062. Epub 2017 Jun 28.

Center for Solar Energy and Energy Storage, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, One Brookings Dr., St. Louis, MO, 63130, USA.

The objectives of this study were: 1) to confirm superoxide anion radical (O ) formation, and 2) to monitor in real time the rate of O generation in an operating anion exchange membrane (AEM) fuel cell using in situ fluorescence spectroscopy. 1,3-Diphenlisobenzofuran (DPBF) was used as the fluorescent molecular probe owing to its selectivity and sensitivity toward O in alkaline media. The activation energy for the in situ generation of O during AEM fuel cell operation was estimated to be 18.3 kJ mol . The rate of in situ generation of O correlated well with the experimentally measured loss in AEM ion-exchange capacity and ionic conductivity attributable to oxidative degradation.
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http://dx.doi.org/10.1002/cssc.201700760DOI Listing
August 2017

Reactive oxygen species accelerate degradation of anion exchange membranes based on polyphenylene oxide in alkaline environments.

Phys Chem Chem Phys 2016 Jul;18(29):19705-12

Center for Electrochemical Science and Engineering, Department of Chemical and Biological Engineering, Illinois Institute of Technology, 10 W. 33rd St., Chicago, IL 60616, USA.

Anion exchange membranes (AEM) based on polyphenylene oxide (PPO) suffered quaternary-ammonium-cation-site degradation in alkaline environments. Surprisingly, the degradation rate was considerably faster in the presence of molecular oxygen. We postulated that the AEM cation-site catalyzes the reduction of dioxygen by hydroxide ions to yield the superoxide anion radical and the highly reactive hydroxyl free radical. We substantiated our hypothesis by using a phosphorous-containing spin trap (5-diisopropoxy-phosphoryl-5-methyl-1-pyrroline-N-oxide) to detect the adducts for both free radicals in situ using (31)P-NMR spectroscopy.
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http://dx.doi.org/10.1039/c6cp01978aDOI Listing
July 2016

[Cost-effectiveness analysis of Belimumab in patients with systemic lupus erythematosus in Spain].

Farm Hosp 2015 May 1;39(3):161-70. Epub 2015 May 1.

Departamento de Evaluación de Medicamentos, GSK España, Tres Cantos..

Objective: To estimate the cost-effectiveness of belimumab in patients with systemic lupus erythematosus (SLE) presenting positive biomarkers and active disease despite standard treatment (ST), from the Spanish social perspective.

Methods: A microsimulation model was used to estimate the cost-effectiveness of belimumab plus ST versus ST alone. A treatment duration of two years with a life-time horizon were considered. Efficacy data were obtained from belimumab clinical trials and the evolution of the disease was simulated from John Hopkins ´ patient cohort data in the United States. Utility data were obtained from literature review. Direct and indirect costs were calculated based on Spanish published data (€, 2014), applying a discount rate (DR) of 3% to both costs and effects. Results were expressed as incremental cost-effectiveness ratio (ICER) in terms of gained life years (LY) and quality of life adjusted life years (QALYs). Probabilistic (PSA) and deterministic sensitivity analyses (DR of 0% and 5%, 5-years treatment duration and excluding indirect costs) were performed to determine the robustness of the model.

Results: The incremental cost-effectiveness ratio (ICER) was 16,647€ per life year gained, with an incremental cost-utility ratio (ICUR) of 23,158€ per additional QALY gained. In 68% of the scenarios simulated in the PSA, belimumab was found to be a cost-effective alternative, considering a threshold of 30,000€/ QALY.

Conclusion: Belimumab can be regarded as a cost-effective alternative from the Spanish social perspective.
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http://dx.doi.org/10.7399/fh.2015.39.3.8814DOI Listing
May 2015

Platinum supported on titanium-ruthenium oxide is a remarkably stable electrocatayst for hydrogen fuel cell vehicles.

Proc Natl Acad Sci U S A 2014 Jan 23;111(1):45-50. Epub 2013 Dec 23.

Center for Electrochemical Science and Engineering, Department of Chemical and Biological Engineering, Illinois Institute of Technology, Chicago, IL 60616.

We report a unique and highly stable electrocatalyst-platinum (Pt) supported on titanium-ruthenium oxide (TRO)-for hydrogen fuel cell vehicles. The Pt/TRO electrocatalyst was exposed to stringent accelerated test protocols designed to induce degradation and failure mechanisms identical to those seen during extended normal operation of a fuel cell automobile-namely, support corrosion during vehicle startup and shutdown, and platinum dissolution during vehicle acceleration and deceleration. These experiments were performed both ex situ (on supports and catalysts deposited onto a glassy carbon rotating disk electrode) and in situ (in a membrane electrode assembly). The Pt/TRO was compared against a state-of-the-art benchmark catalyst-Pt supported on high surface-area carbon (Pt/HSAC). In ex situ tests, Pt/TRO lost only 18% of its initial oxygen reduction reaction mass activity and 3% of its oxygen reduction reaction-specific activity, whereas the corresponding losses for Pt/HSAC were 52% and 22%. In in situ-accelerated degradation tests performed on membrane electrode assemblies, the loss in cell voltage at 1 A · cm(-2) at 100% RH was a negligible 15 mV for Pt/TRO, whereas the loss was too high to permit operation at 1 A · cm(-2) for Pt/HSAC. We clearly show that electrocatalyst support corrosion induced during fuel cell startup and shutdown is a far more potent failure mode than platinum dissolution during fuel cell operation. Hence, we posit that the need for a highly stable support (such as TRO) is paramount. Finally, we demonstrate that the corrosion of carbon present in the gas diffusion layer of the fuel cell is only of minor concern.
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http://dx.doi.org/10.1073/pnas.1319663111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3890802PMC
January 2014

Estimation of electrode ionomer oxygen permeability and ionomer-phase oxygen transport resistance in polymer electrolyte fuel cells.

Phys Chem Chem Phys 2013 Sep;15(36):14994-5002

Center for Electrochemical Science and Engineering, Department of Chemical & Biological Engineering, Illinois Institute of Technology, Chicago, Illinois 60616, USA.

The oxygen permeability of perfluorinated and hydrocarbon polymer electrolyte membranes (PEMs; Nafion®, SPEEK and SPSU), which are used as electrolytes and electrode ionomers in polymer electrolyte fuel cells (PEFCs), was estimated using chronoamperometry using a modified fuel cell set-up. A thin, cylindrical microelectrode was embedded into the PEM and used as the working electrode. The PEM was sandwiched between 2 gas diffusion electrodes, one of which was catalyzed and served as the counter and pseudo-reference electrode. Independently, from fuel cell experiments, the oxygen transport resistance arising due to transport through the ionomer film covering the catalyst active sites was estimated at the limiting current and decoupled from the overall mass transport resistance. The in situ oxygen permeability measured at 80 °C and 75% RH of perfluorinated ionomers such as Nafion® (3.85 × 10(12) mol cm(-1) s(-1)) was observed to be an order of magnitude higher than that of hydrocarbon-based PEMs such as SPEEK (0.27 × 10(12) mol cm(-1) s(-1)) and SPSU (0.15 × 10(12) mol cm(-1) s(-1)). The obtained oxygen transport (through ionomer film) resistance values (Nafion® - 1.6 s cm(-1), SPEEK - 2.2 s cm(-1) and SPSU - 3.0 s cm(-1); at 80 °C and 75% RH) correlated well with the measured oxygen permeabilities in these ion-containing polymers.
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http://dx.doi.org/10.1039/c3cp51450aDOI Listing
September 2013

CeO2 surface oxygen vacancy concentration governs in situ free radical scavenging efficacy in polymer electrolytes.

ACS Appl Mater Interfaces 2012 Oct 25;4(10):5098-102. Epub 2012 Sep 25.

Center for Electrochemical Science and Engineering, Department of Chemical and Biological Engineering, Illinois Institute of Technology, 10 W, 33rd Street, Chicago, Illinois 60616, USA.

Nonstoichiometric CeO(2) and Ce(0.25)Zr(0.75)O(2) nanoparticles with varying surface concentrations of Ce(3+) were synthesized. Their surface Ce(3+) concentration was measured by XPS, and their surface oxygen vacancy concentrations and grain size were estimated using Raman spectroscopy. The surface oxygen vacancy concentration was found to correlate well with grain size and surface Ce(3+) concentration. When incorporated into a Nafion polymer electrolyte membrane (PEM), the added nonstoichiometric ceria nanoparticles effectively scavenged PEM-degradation-inducing free radical reactive oxygen species (ROS) formed during fuel cell operation. A 3-fold increase in the surface oxygen vacancy concentration resulted in an order of magnitude enhancement in the efficacy of free radical ROS scavenging by the nanoparticles. Overall, the macroscopic PEM degradation mitigation rate was lowered by up to 2 orders of magnitude using nonstoichiometric ceria nanoparticles with high surface oxygen vacancy concentrations.
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http://dx.doi.org/10.1021/am3016069DOI Listing
October 2012

Platinum supported on CeO2 effectively scavenges free radicals within the electrolyte of an operating fuel cell.

Chem Commun (Camb) 2011 Nov 26;47(41):11549-51. Epub 2011 Sep 26.

Department of Chemical and Biological Engineering, Illinois Institute of Technology, Chicago, IL 60616, USA.

CeO(2), Pt/CeO(2) and MnO(2) additives were found to lower the rate of free radical induced polymer electrolyte membrane degradation in an operating fuel cell by over one order of magnitude.
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http://dx.doi.org/10.1039/c1cc15155jDOI Listing
November 2011
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