| 1. |
- Ahlsson, Anders J., et al.
(författare)
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Postoperative atrial fibrillation is not correlated to C-reactive protein
- 2007
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Ingår i: Annals of Thoracic Surgery. - : Elsevier BV. - 0003-4975 .- 1552-6259. ; 83:4, s. 1332-1337
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The peak incidence of postoperative atrial fibrillation (AF) occurs around the second postoperative day, a time at which serum inflammatory markers are elevated. The aim of this study was to investigate differences between patients with and without postoperative AF with special regard to C-reactive protein (CRP) serum levels. METHODS: The study cohort included all heart surgery patients who had sinus rhythm preoperatively, survived postoperative day 3, and were operated on between July 1, 2004, and June 30, 2005 (n = 524). Any episode of AF during the first 7 postoperative days defined the patient as belonging to the postoperative AF group. Creatine kinase-myocardial band (CK-MB) was measured at postoperative day 1, and CRP was measured preoperatively and at postoperative day 3. Risk factors for postoperative AF were determined using bivariate and multivariate regression analysis. RESULTS: Of 524 patients, 182 had at least one episode of AF (34.7%). Preoperative and postoperative CRP concentrations did not differ between the groups (postoperative CRP 175.4 +/- 64.4 versus 175.3 +/- 60.1 mg/L respectively, p = 0.99). Atrial fibrillation patients were significantly older (p < 0.001) and had higher CK-MB levels (33.6 +/- 53.1 microg/L versus 22.5 +/- 26.7 microg/L, respectively, p = 0.009). The odds ratio for postoperative AF with postoperative CK-MB greater than 70 microg/L was 3.5 (confidence interval: 1.4 to 8.6). CONCLUSIONS: Postoperative AF has no correlation to the inflammatory marker CRP in heart surgery patients. Ischemic myocardial injury might predispose for postoperative AF.
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| 2. |
- Ajpi, Cesario, et al.
(författare)
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Crystal structure and Hirshfeld surface analysis of poly[tris-(μ4-benzene-1,4-di-carboxyl-ato)tetra-kis-(di-methyl-formamide)-trinickel(II)] : a two-dimensional coordination network.
- 2019
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Ingår i: Acta crystallographica. Section E, Crystallographic communications. - 2056-9890. ; 75:Pt 12, s. 1839-1843
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Tidskriftsartikel (refereegranskat)abstract
- The crystal structure of the title compound, [Ni3(C8H4O4)3(C3H7NO)4], is a two-dimensional coordination network formed by trinuclear linear Ni3(tp)3(DMF)4 units (tp = terephthalate = benzene-1,4-di-carboxyl-ate and DMF = di-methyl-formamide) displaying a characteristic coordination mode of acetate groups in polynuclear metal-organic compounds. Individual trinuclear units are connected through tp anions in a triangular network that forms layers. One of the DMF ligands points outwards and provides inter-actions with equivalent planes above and below, leaving the second ligand in a structural void much larger than the DMF mol-ecule, which shows positional disorder. Parallel planes are connected mainly through weak C-H⋯O, H⋯H and H⋯C inter-actions between DMF mol-ecules, as shown by Hirshfeld surface analysis.
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| 3. |
- Ajpi Condori, Cesario, et al.
(författare)
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Synthesis and Characterization of LiFePO4-PANI Hybrid Material as Cathode for Lithium-Ion Batteries
- 2020
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 13:12
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Tidskriftsartikel (refereegranskat)abstract
- This work focuses on the synthesis of LiFePO4-PANI hybrid materials and studies their electrochemical properties (capacity, cyclability and rate capability) for use in lithium ion batteries. PANI synthesis and optimization was carried out by chemical oxidation (self-assembly process), using ammonium persulfate (APS) and H3PO4, obtaining a material with a high degree of crystallinity. For the synthesis of the LiFePO4-PANI hybrid, a thermal treatment of LiFePO(4)particles was carried out in a furnace with polyaniline (PANI) and lithium acetate (AcOLi)-coated particles, using Ar/H(2)atmosphere. The pristine and synthetized powders were characterized by XRD, SEM, IR and TGA. The electrochemical characterizations were carried out by using CV, EIS and galvanostatic methods, obtaining a capacity of 95 mAhg(-1)for PANI, 120 mAhg(-1)for LiFePO(4)and 145 mAhg(-1)for LiFePO4-PANI, at a charge/discharge rate of 0.1 C. At a charge/discharge rate of 2 C, the capacities were 70 mAhg(-1)for LiFePO(4)and 100 mAhg(-1)for LiFePO4-PANI, showing that the PANI also had a favorable effect on the rate capability.
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| 4. |
- Ajpi Condori, Cesario, et al.
(författare)
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Synthesis and spectroscopic characterization of Fe3+-BDC metal organic framework as material for lithium ion batteries
- 2023
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Ingår i: Journal of Molecular Structure. - : Elsevier B.V.. - 0022-2860 .- 1872-8014. ; 1272
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Tidskriftsartikel (refereegranskat)abstract
- This work presents synthesis and spectroscopic characterization of a new metal-organic framework (MOF). The compound Fe-BDC-DMF was synthetized by the solvothermal method and prepared via a reaction between FeCl3.6H2O and benzene-1,4-dicarboxylic acid (H2BDC) or terephthalic acid using N,N-dimethylformamide (DMF) as solvent. The powder was characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR) analysis. The electrochemical properties were investigated in a typical lithium-ion battery electrolyte by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charging and discharging. The synthetized Fe-BDC-DMF metal-organic framework (MOF) contains a mixture of three phases, identified by PXRD as: MOF-235, and MIL-53(Fe) monoclinic with C2/c and P21/c space groups. The structure of the Fe-BDC is built up from Fe3+ ions, terephalates (BDC) bridges and in-situ-generated DMF ligands. The electrochemical measurements conducted in the potential range of 0.5–3.5 V vs. Li+/Li0 show the voltage profiles of Fe-BDC and a plateau capacity of around 175 mAh/g. © 2022 The Author(s)
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| 5. |
- Ajpi Condori, Cesario, et al.
(författare)
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Synthesis and spectroscopic characterization of NiII coordination network : Poly-[tris(µ4-Benzene-1,4-dicarboxylato)-tetrakis(µ1-dimethylformamide-κ1O)-trinickel(II)] as material for lithium ion batteries
- 2022
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Ingår i: Journal of Molecular Structure. - : Elsevier B.V.. - 0022-2860 .- 1872-8014. ; 1265
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Tidskriftsartikel (refereegranskat)abstract
- The compound Ni3(C8H4O4)3(C3H7NO)3, poly-[tris(µ4-Benzene-1,4-dicarboxylato)-tetrakis(µ1-dimethylformamide-κ1O)-trinickel(II)], was synthesized by the solvothermal method prepared via reaction between NiCl2•6H2O and terephthalic acid using N,N-dimethylformamide (DMF) as solvent. The structure was characterized by powder X-ray diffraction and infrared spectroscopy analyses. The electrochemical properties as a potential active material in lithium-ion batteries were characterized by electrochemical impedance spectroscopy and galvanostatic charge-discharge curves in a battery half-cell. The characterization results show that the coordination network contains one independent structure in the asymmetric unit. It is constructed from Ni2+ ions, terephthalate bridges and in-situ-generated DMF ligands, forming two similar two-dimensional (2D) layer structures. These similar 2D layers are in an alternating arrangement and are linked with each other by dense H—H interactions (45%) to generate a three-dimensional (3D) supramolecular framework with ordered and disordered DMF molecules. The electrochemical measurements, conducted in the potential range of 0.5–3.5 V vs Li/Li+, show that Ni3(C8H4O4)3(C3H7NO)4 has good electrochemical properties and can work as anode in lithium-ion batteries. The material presents an initial specific capacity of ∼420 mAh g−1, which drops during consecutive scans but stabilizes at ∼50 mAh g−1. However, due to the wide potential range there are indications of a gradual collapse of the structure. The electrochemical impedance spectroscopy shows an increase of charge transfer resistance from 24 to 1190 Ohms after cycling likely due to this collapse.
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| 6. |
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| 7. |
- Benavente Araoz, Fabian Andres, et al.
(författare)
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An Aging Study of NCA/Si-Graphite Lithium-Ion Cells for Off-Grid Photovoltaic Systems in Bolivia
- 2021
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Ingår i: Journal of the Electrochemical Society. - : IOP Publishing Ltd. - 0013-4651 .- 1945-7111. ; 168:10
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Tidskriftsartikel (refereegranskat)abstract
- Performance and aging of lithium-ion 18650 cylindrical cells containing NCA and Si-graphite composite electrodes are investigated during long-term low current rate (∼0.1C) cycling protocol resembling charge/discharge profile of off-grid photovoltaic battery system. The cells are cycled within 30% and 75% state-of-charge ranges (SOC) with low, middle and high cut-off voltages. Electrochemical impedance spectroscopy data of full cylindrical cells exhibit severe aging for cells that have been cycled at higher cut-off voltage of 4.2 V. Symmetric cell impedance from each electrode shows that aging of NCA is dominant over aging of Si-graphite. Using a Newman-based impedance model, the NCA symmetrical cells' impedance spectra are parameterized to evaluate the aging modes. The resulting parameterization confirms increased particles' surface film resistance due to possible electrolyte oxidation and tortuosity increase at high cut-off voltages. Cycling the cells with middle and low cut-off voltages causes few significant changes when compared to calendar-aged samples. This opens up the possibility to significantly increase battery lifetime for small photovoltaic battery systems in rural areas of Bolivia. © 2021 The Author(s).
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| 8. |
- Benavente Araoz, Fabian Andres, 1985-, et al.
(författare)
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Effect of Partial Cycling of NCA/Graphite Cylindrical Cells in Different SOC Intervals
- 2020
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Ingår i: Journal of the Electrochemical Society. - : Institute of Physics Publishing. - 0013-4651 .- 1945-7111. ; 167:4
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Tidskriftsartikel (refereegranskat)abstract
- A quasi-realistic aging test of NCA/graphite lithium-ion 18650 cylindrical cells is performed during a long-term low c-rate cycling and using a new protocol for testing and studying the aging. This to emulate a characteristic charge/discharge profile of off-grid PV-battery systems. The cells were partially cycled at four different cut-off voltages and two state of charge ranges (ΔSOC) for 1000 and 700 cycles over 24 months. Differential voltage analysis shows that a combination of loss of active material (LAM) and loss of lithium inventory (LLI) are the causes of capacity loss. Cells cycled with high cut-off voltages and wide ΔSOC (20% to 95%) were severely affected by material degradation and electrode shift. High cut-off voltage and narrow ΔSOC (65% to 95%) caused greater electrode degradation but negligible cell unbalance. Cell impedance is observed to increase in both cells. Cells cycled with middle to low cut-off voltages and narrow ΔSOC (35%-65% and 20% to 50%) had comparable degradation rates to calendar-aged cells. Cycling NCA/graphite cells with low c-rate and high cut-off voltages will degrade the electrode in the same way high c-rate would do. However, low c-rate at low and middle cut-off voltages greatly decrease cell degradation compared to similar conditions at middle to high c-rate, therefore increasing battery lifetime. © 2020 The Author(s).
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| 9. |
- Benavente Araoz, Fabian Andres, et al.
(författare)
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Experimental Investigation and Electrochemical Modeling of Aging Mechanisms on NCA and Si-graphite Electrodes Harvested from Off-grid PV Lithium-ion Cells
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Performance and aging of lithium-ion 18650 cylindrical cells containing NCA and Si-graphite composite electrodes are investigated during a long-term cycling process applying low current rates and different state of charge (SOC) ranges and cut-off voltages. Firstly, electrochemical impedance spectroscopy (EIS) is used to periodically extract impedance data from cylindrical cells. Secondly, NCA and Si-graphite electrode samples are reassembled into symmetrical cells to separate the impedance contribution from NCA and Si-graphite. Finally, using a physics-based impedance model, the symmetrical cells’ impedance spectra are parameterized to evaluate the aging modes. We introduce an additional pseudo-dimension to the model to distribute double layer capacitances on electrode-electrolyte interface, combined with a probability distribution function for total volumetric current, to fit the depressed semicircle in EIS spectra. The parameterization results show that high cut-off voltages cause increased particles’ surface film resistance of the NCA electrode and tortuosity increase in its structure. In Si-graphite electrodes, high cut-off voltages combined with wide ΔSOC range lead to increased surface film resistance attributed to the SEI layer and local limitations in solid lithium intercalation. Cycling the cells with middle and low cut-off voltages causes few significant changes when compared to calendar-aged samples. This opens up the possibility to significant increase of battery lifetime for applications such as small PV-battery systems.
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| 10. |
- Benavente Araoz, Fabian Andres, et al.
(författare)
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Photovoltaic/battery system sizing for rural electrification in Bolivia : Considering the suppressed demand effect
- 2019
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 235, s. 519-528
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Tidskriftsartikel (refereegranskat)abstract
- Rural electrification programs usually do not consider the impact that the increment of demand has on the reliability of off-grid photovoltaic (PV)/battery systems. Based on meteorological data and electricity consumption profiles from the highlands of Bolivian Altiplano, this paper presents a modelling and simulation framework for analysing the performance and reliability of such systems. Reliability, as loss of power supply probability (LPSP), and cost were calculated using simulated PV power output and battery state of charge profiles. The effect of increasing the suppressed demand (SD) by 20% and 50% was studied to determine how reliable and resilient the system designs are. Simulations were performed for three rural application scenarios: a household, a school, and a health centre. Results for the household and school scenarios indicate that, to overcome the SD effect, it is more cost-effective to increase the PV power rather than to increase the battery capacity. However, with an increased PV-size, the battery ageing rate would be higher since the cycles are performed at high state of charge (SOC). For the health centre application, on the other hand, an increase in battery capacity prevents the risk of electricity blackouts while increasing the energy reliability of the system. These results provide important insights for the application design of off-grid PV-battery systems in rural electrification projects, enabling a more efficient and reliable source of electricity.
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