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| 3. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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- Nguyen, Thanh N, et al.
(författare)
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Global Impact of the COVID-19 Pandemic on Stroke Volumes and Cerebrovascular Events: A 1-Year Follow-up.
- 2023
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Ingår i: Neurology. - 1526-632X. ; 100:4, s. e408-e421
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Tidskriftsartikel (refereegranskat)abstract
- Declines in stroke admission, IV thrombolysis (IVT), and mechanical thrombectomy volumes were reported during the first wave of the COVID-19 pandemic. There is a paucity of data on the longer-term effect of the pandemic on stroke volumes over the course of a year and through the second wave of the pandemic. We sought to measure the effect of the COVID-19 pandemic on the volumes of stroke admissions, intracranial hemorrhage (ICH), IVT, and mechanical thrombectomy over a 1-year period at the onset of the pandemic (March 1, 2020, to February 28, 2021) compared with the immediately preceding year (March 1, 2019, to February 29, 2020).We conducted a longitudinal retrospective study across 6 continents, 56 countries, and 275 stroke centers. We collected volume data for COVID-19 admissions and 4 stroke metrics: ischemic stroke admissions, ICH admissions, IVT treatments, and mechanical thrombectomy procedures. Diagnoses were identified by their ICD-10 codes or classifications in stroke databases.There were 148,895 stroke admissions in the 1 year immediately before compared with 138,453 admissions during the 1-year pandemic, representing a 7% decline (95% CI [95% CI 7.1-6.9]; p < 0.0001). ICH volumes declined from 29,585 to 28,156 (4.8% [5.1-4.6]; p < 0.0001) and IVT volume from 24,584 to 23,077 (6.1% [6.4-5.8]; p < 0.0001). Larger declines were observed at high-volume compared with low-volume centers (all p < 0.0001). There was no significant change in mechanical thrombectomy volumes (0.7% [0.6-0.9]; p = 0.49). Stroke was diagnosed in 1.3% [1.31-1.38] of 406,792 COVID-19 hospitalizations. SARS-CoV-2 infection was present in 2.9% ([2.82-2.97], 5,656/195,539) of all stroke hospitalizations.There was a global decline and shift to lower-volume centers of stroke admission volumes, ICH volumes, and IVT volumes during the 1st year of the COVID-19 pandemic compared with the prior year. Mechanical thrombectomy volumes were preserved. These results suggest preservation in the stroke care of higher severity of disease through the first pandemic year.This study is registered under NCT04934020.
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| 5. |
- Chang, Ribooga, et al.
(författare)
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Deciphering the existence of hexagonal sodium zirconate CO2 sorbent
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Sodium zirconate (sodium zirconium oxide; Na2ZrO3) is amongst the most investigated carbon dioxide (CO2) sorbent. Na2ZrO3 is renowned for its high capture capacity and cyclic stability. It can effectively capture CO2 at temperatures that are found in industrial processes such as the manufacture of steel or cement. Na2ZrO3 is reported to adopt monoclinic, hexagonal, and cubic structures since it was first discussed in the 1960s. Researchers relied on the differences in the relative intensities between two peaks (2θ ~ 16.2 and 38.7 °) in the powder X-ray diffraction (PXRD) pattern to determine the phase of this compound. It is also widely believed that the CO2 capture performance of Na2ZrO3 is related to the crystal structure, yet the crystal structure of hexagonal Na2ZrO3 has remained elusive. With the use of 3D electron diffraction (3D ED), X-ray photoelectron spectroscopy (XPS), and PXRD, we show that the hexagonal Na2ZrO3 does not exist. The so-called hexagonal Na2ZrO3 is Na2ZrO3 with three different types of disorder. Furthermore, the two PXRD peaks (2θ ~ 16.2 and 38.7 °) cannot be used to distinguish the different phases of Na2ZrO3, as the changes in the PXRD pattern are related to the extent of structure disorder. Finally, we also show that the CO2 capture properties of Na2ZrO3 are related to the Na+ site occupancy between different Na2ZrO3 samples, and not differences in crystal structures. The findings from our work shows that the current literature discussion on the structure of Na2ZrO3 is misleading. In order to further develop Na2ZrO3 as well as other mixed-metal oxides for applications, their structures, as well as any disorder, needs be understood using the methods shown in this study.
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| 6. |
- Chien, Yu-Chuan, et al.
(författare)
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Development of operando XRD coin cells for lithium-sulfur batteries
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Lithium-sulfur (Li-S) batteries has been regarded as one of the promising technology for the next generation of rechargeable batteries due to its high theoretical energy density (2600 Wh/kg [1]). Several works [2–7] on operando X-ray diffraction (XRD) of the Li-S system have been published; however, their experimental setups showed one or more of the following drawbacks. First, the amount of electrolyte was often not reported or would be considered too high for a common Li-S cell, which has been demonstrated to have a significant impact on the behavior of the system [8]. Another issue is the non-uniform stack pressure and electron conductivity of the operando cell setup, whose effects were found by both experiments and simulations [9].This work aims to tackle with the above-mentioned issues by modifying commercial coin cells and using X-ray transparent metal, beryllium, as the spacers. By doing so, the electron conductivity and stack pressure can be expected to be uniform throughout the electrodes. The amount of electrolyte can also be precisely controlled since no vacuum-sealing is required for coin cells. A preliminary diffraction pattern obtained with the cell setup can be seen in Fig. 1. With electrochemical properties similar to common Li-S cells, ‘online’ electrochemical characterization techniques, e.g. Intermittent Current Interruption (ICI) method for following cell resistance [10], will be applicable with operando XRD, revealing more information about this complex system.Figure 1 XRD patterns of alpha-S and electrode material in the modified coin cell.References[1] J. Tan, et al., Nanoscale (2017) 19001–19016.[2] J. Nelson, et al., J. Am. Chem. Soc. 134 (2012) 6337–6343.[3] N.A. Cañas, et al., J. Power Sources 226 (2013) 313–319.[4] S. Waluś, et al., Chem. Commun. 49 (2013) 7899.[5] M. a. Lowe, et al., RSC Adv. 4 (2014) 18347.[6] J. Kulisch, et al., Phys. Chem. Chem. Phys. 16 (2014) 18765–18771.[7] J. Conder, et al., Nat. Energy 2 (2017) 1–7.[8] M.J. Lacey, ChemElectroChem (2017) 1–9.[9] O.J. Borkiewicz, et al., J. Phys. Chem. Lett. 6 (2015) 2081–2085.[10] M.J. Lacey, et al., Chem. Commun. 51 (2015) 16502–16505.
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| 7. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Rapid determination of solid-state diffusion coefficients in Li-based batteries via intermittent current interruption method
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- The galvanostatic intermittent titration technique (GITT) is considered the go-to method for determining the Li+ diffusion coefficients in insertion electrode materials. However, GITT-based methods are either time-consuming, prone to analysis pitfalls or require sophisticated interpretation models. Here, we propose the intermittent current interruption (ICI) method as a reliable, accurate and faster alternative to GITT-based methods. Using Fick’s laws, we prove that the ICI method renders the same information as the GITT within a certain duration of time since the current interruption. Via experimental measurements, we also demonstrate that the results from ICI and GITT methods match where the assumption of semi-infinite diffusion applies. Moreover, the benefit of the non-disruptive ICI method to operando materials characterization is exhibited by correlating the continuously monitored diffusion coefficient of Li+ in a LiNi0.8Mn0.1Co0.1O2-based electrode to its structural changes captured by operando X-ray diffraction measurements.
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| 8. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Simultaneous Monitoring of Crystalline Active Materials and Resistance Evolution in Lithium-Sulfur Batteries
- 2020
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Ingår i: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 142:3, s. 1449-1456
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Tidskriftsartikel (refereegranskat)abstract
- Operando X-ray diffraction (XRD) is a valuable tool for studying secondary battery materials as it allows for the direct correlation of electrochemical behavior with structural changes of crystalline active materials. This is especially true for the lithium-sulfur chemistry, in which energy storage capability depends on the complex growth and dissolution kinetics of lithium sulfide (Li2S) and sulfur (S-8) during discharge and charge, respectively. In this work, we present a novel development of this method through combining operando XRD with simultaneous and continuous resistance measurement using an intermittent current interruption (ICI) method. We show that a coefficient of diffusion resistance, which reflects the transport properties in the sulfur/carbon composite electrode, can be determined from analysis of each current interruption. Its relationship to the established Warburg impedance model is validated theoretically and experimentally. We also demonstrate for an optimized electrode formulation and cell construction that the diffusion resistance increases sharply at the discharge end point, which is consistent with the blocking of pores in the carbon host matrix. The combination of XRD with ICI allows for a direct correlation of structural changes with not only electrochemical properties but also energy loss processes at a nonequilibrium state and, therefore, is a valuable technique for the study of a wide range of energy storage chemistries.
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| 9. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Understanding the Impact of Precipitation Kinetics on the Electrochemical Performance of Lithium–Sulfur Batteries by Operando X-ray Diffraction
- 2022
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:6, s. 2971-2979
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Tidskriftsartikel (refereegranskat)abstract
- The complex reaction mechanism of the lithium–sulfur battery system consists of re-petitive dissolution and precipitation of the sulfur-containing species in the positiveelectrode. In particular, the precipitation of lithium sulfide (Li2S) during discharge hasbeen considered a crucial factor for achieving a high degree of active material utiliza-tion. Here, the influence of electrolyte amount, electrode thickness, applied current andelectrolyte salt on the formation of Li2S is systematically investigated in a series ofoperando X-ray diffraction experiments. Through a combination of simultaneous dif-fraction and resistance measurements, the evolution of the intensity from Li2S is di-rectly correlated to the variation in internal resistance and transport properties insidethe positive electrode. The correlation indicates that at different stages, the Li2S precip-itation both facilitates and impedes the discharge process. The kinetic information ofLi2S formation offers mechanistic explanations for the strong impact of different elec-trochemical cell parameters on the performance and thus, directions for holistic optimi-zations to achieve high sulfur utilization.
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| 10. |
- Fritze, Stefan, et al.
(författare)
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Magnetron sputtering of carbon supersaturated tungsten films-A chemical approach to increase strength
- 2021
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 208
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Tidskriftsartikel (refereegranskat)abstract
- Tungsten (W)-based materials attract significant attention due to their superior mechanical properties. Here, we present a chemical approach based on the addition of carbon (C) for increased strength via the combination of three strengthening mechanisms in W thin films. W:C thin films with C concentrations up to-4 at.% were deposited by magnetron sputtering. All films exhibit a body-centred-cubic structure with strong texture and columnar growth behaviour. X-ray and electron diffraction measurements suggest the formation of supersaturated W:C solid solution phases. The addition of C reduced the average column width from-133 nm for W to-20 nm for the film containing-4 at.% C. The column refinement is explained by a mechanism where C acts as re-nucleation sites. The W film is-13 GPa hard, while the W:C films achieve a peak hardness of-24 GPa. The W:C films are-11 GPa harder than the W film, which is explained by a combination of grain refinement strengthening, solid solution strengthening and increased dislocation density. Additional micropillar compression tests showed that the flow stress increased upon C addition, from-3.8 to-8.3 GPa and no brittle fracture was observed.
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