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Radić D, Peterlechner M, Spangenberg K, Posselt M, Bracht H. Challenges of Electron Correlation Microscopy on Amorphous Silicon and Amorphous Germanium. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2023; 29:1579-1594. [PMID: 37632736 DOI: 10.1093/micmic/ozad090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 07/17/2023] [Accepted: 08/06/2023] [Indexed: 08/28/2023]
Abstract
Electron correlation microscopy experiments were conducted on amorphous germanium (a-Ge) and amorphous silicon (a-Si) with the goal to study self-diffusion. For this purpose, a series of tilted dark-field images were acquired during in situ heating of the samples in a transmission electron microscope. These experiments show that the measurements are greatly affected by artefacts. Contamination, crystallization, electron beam-induced sputtering, and macroscopic bending of the samples pose major obstacles to the measurements. Other, more subtle experimental artefacts could occur in addition to these which makes interpretations regarding the structural dynamics nearly impossible. The data were nonetheless evaluated to see if some useful information could be extracted. One such result is that the distribution of the characteristic times τKWW, which were obtained from stretched exponential fits to the intensity autocorrelation data, is spatially heterogeneous. This spatial heterogeneity is assumed to be caused by a potential nonergodicity of the materials, the artefacts or an inhomogeneous amorphous structure. Further data processing shows that the characteristic times τKWW are moreover temperature independent, especially for the a-Ge data. It is concluded that the structural rearrangements over time are primarily electron beam-driven and that diffusive dynamics are too slow to be measured at the chosen, experimentally accessible annealing temperatures.
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Affiliation(s)
- Dražen Radić
- Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, Münster, 48149 North Rhine-Westphalia, Germany
| | - Martin Peterlechner
- Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, Münster, 48149 North Rhine-Westphalia, Germany
| | - Katharina Spangenberg
- Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, Münster, 48149 North Rhine-Westphalia, Germany
| | - Matthias Posselt
- Ion Induced Nanostructures, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, Dresden, 01328 Saxony, Germany
| | - Hartmut Bracht
- Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, Münster, 48149 North Rhine-Westphalia, Germany
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The Analysis of WJ Distribution as an Extended Gaussian Function: Case Study. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12157773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The double exponential WJ distribution has been shown to competently describe extreme events and critical phenomena, while the Gaussian function has celebrated rich applications in many other fields. Here we present the analysis that the WJ distribution may be properly treated as an extended Gaussian function. Based on the Taylor expansion, we propose three methods to formulate the WJ distribution in the form of Gaussian functions, with Method I and Method III being accurate and self-consistent, and elaborate the relationship among the parameters of the functions. Moreover, we derive the parameter scaling formula of the WJ distribution to express a general Gaussian function, with the work illustrated by a classical case of extreme events and critical phenomena and application to topical medical image processing to prove the effectiveness of the WJ distribution rather than the Gaussian function. Our results sturdily advocate that the WJ distribution can elegantly represent a Gaussian function of arbitrary parameters, whereas the latter usually is not able to satisfactorily describe the former except for specific parameter sets. Thus, it is conclusive that the WJ distribution offers applicability in extreme events and critical phenomena as well as processes describable by the Gaussian function, namely, implying plausibly a unifying approach to the pertinent data processing of those quite distinct areas and establishing a link between relevant extreme value theories and Gaussian processes.
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Borelli AN, Young MW, Kirkpatrick BE, Jaeschke MW, Mellett S, Porter S, Blatchley MR, Rao VV, Sridhar BV, Anseth KS. Stress Relaxation and Composition of Hydrazone-Crosslinked Hybrid Biopolymer-Synthetic Hydrogels Determine Spreading and Secretory Properties of MSCs. Adv Healthc Mater 2022; 11:e2200393. [PMID: 35575970 DOI: 10.1002/adhm.202200393] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 04/11/2022] [Indexed: 12/12/2022]
Abstract
The extracellular matrix plays a critical role in mechanosensing and thereby influences the secretory properties of bone-marrow-derived mesenchymal stem/stromal cells (MSCs). As a result, interest has grown in the development of biomaterials with tunable properties for the expansion and delivery of MSCs that are used in cell-based therapies. Herein, stress-relaxing hydrogels are synthesized as hybrid networks containing both biopolymer and synthetic macromer components. Hyaluronic acid is functionalized with either aldehyde or hydrazide groups to form covalent adaptable hydrazone networks, which are stabilized by poly(ethylene glycol) functionalized with bicyclononyne and heterobifunctional small molecule crosslinkers containing azide and benzaldehyde moieties. Tuning the composition of these gels allows for controlled variation in the characteristic timescale for stress relaxation and the amount of stress relaxed. Over this compositional space, MSCs are observed to spread in formulations with higher degrees of adaptability, with aspect ratios of 1.60 ± 0.18, and YAP nuclear:cytoplasm ratios of 6.5 ± 1.3. Finally, a maximum MSC pericellular protein thickness of 1.45 ± 0.38 µm occurred in highly stress-relaxing gels, compared to 1.05 ± 0.25 µm in non-adaptable controls. Collectively, this study contributes a new understanding of the role of compositionally defined stress relaxation on MSCs mechanosensing and secretion.
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Affiliation(s)
- Alexandra N. Borelli
- Department of Chemical and Biological Engineering University of Colorado Boulder Boulder CO 80303 USA
- The BioFrontiers Institute University of Colorado Boulder Boulder CO 80303 USA
| | - Mark W. Young
- Department of Chemical and Biological Engineering University of Colorado Boulder Boulder CO 80303 USA
- The BioFrontiers Institute University of Colorado Boulder Boulder CO 80303 USA
| | - Bruce E. Kirkpatrick
- Department of Chemical and Biological Engineering University of Colorado Boulder Boulder CO 80303 USA
- The BioFrontiers Institute University of Colorado Boulder Boulder CO 80303 USA
- Medical Scientist Training Program University of Colorado Anschutz Medical Campus Aurora CO 80045 USA
| | - Matthew W. Jaeschke
- Department of Chemical and Biological Engineering University of Colorado Boulder Boulder CO 80303 USA
- The BioFrontiers Institute University of Colorado Boulder Boulder CO 80303 USA
| | - Sarah Mellett
- Department of Chemical and Biological Engineering University of Colorado Boulder Boulder CO 80303 USA
| | - Seth Porter
- Department of Chemical and Biological Engineering University of Colorado Boulder Boulder CO 80303 USA
| | - Michael R. Blatchley
- Department of Chemical and Biological Engineering University of Colorado Boulder Boulder CO 80303 USA
- The BioFrontiers Institute University of Colorado Boulder Boulder CO 80303 USA
| | - Varsha V. Rao
- Department of Chemical and Biological Engineering University of Colorado Boulder Boulder CO 80303 USA
- The BioFrontiers Institute University of Colorado Boulder Boulder CO 80303 USA
| | - Balaji V. Sridhar
- Department of Physical Medicine and Rehabilitation University of Colorado Aurora CO 80231 USA
| | - Kristi S. Anseth
- Department of Chemical and Biological Engineering University of Colorado Boulder Boulder CO 80303 USA
- The BioFrontiers Institute University of Colorado Boulder Boulder CO 80303 USA
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McKenzie I, Fujimoto D, Karner VL, Li R, MacFarlane WA, McFadden RML, Morris GD, Pearson MR, Raegen AN, Stachura M, Ticknor JO, Forrest JA. A β-NMR study of the depth, temperature, and molecular-weight dependence of secondary dynamics in polystyrene: Entropy–enthalpy compensation and dynamic gradients near the free surface. J Chem Phys 2022; 156:084903. [DOI: 10.1063/5.0081185] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigated the depth, temperature, and molecular-weight (MW) dependence of the γ-relaxation in polystyrene glasses using implanted 8Li+ and β-detected nuclear magnetic resonance. Measurements were performed on thin films with MW ranging from 1.1 to 641 kg/mol. The temperature dependence of the average 8Li spin–lattice relaxation time [Formula: see text] was measured near the free surface and in the bulk. Spin–lattice relaxation is caused by phenyl ring flips, which involve transitions between local minima over free-energy barriers with enthalpic and entropic contributions. We used transition state theory to model the temperature dependence of the γ-relaxation, and hence [Formula: see text]. There is no clear correlation of the average entropy of activation [Formula: see text] and enthalpy of activation [Formula: see text] with MW, but there is a clear correlation between [Formula: see text] and [Formula: see text], i.e., entropy–enthalpy compensation. This results in the average Gibbs energy of activation, [Formula: see text], being approximately independent of MW. Measurements of the temperature dependence of [Formula: see text] as a function of depth below the free surface indicate the inherent entropic barrier, i.e., the entropy of activation corresponding to [Formula: see text] = 0, has an exponential dependence on the distance from the free surface before reaching the bulk value. This results in [Formula: see text] near the free surface being lower than the bulk. Combining these observations results in a model where the average fluctuation rate of the γ-relaxation has a “double-exponential” depth dependence. This model can explain the depth dependence of [Formula: see text] in polystyrene films. The characteristic length of enhanced dynamics is ∼6 nm and approximately independent of MW near room temperature.
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Affiliation(s)
- Iain McKenzie
- TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Derek Fujimoto
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Victoria L. Karner
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Ruohong Li
- TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
| | - W. Andrew MacFarlane
- TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Ryan M. L. McFadden
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | | | - Matthew R. Pearson
- Department of Physics, University of Liverpool, Liverpool L69 7ZE, United Kingdom
| | - Adam N. Raegen
- TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | | | - John O. Ticknor
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - James A. Forrest
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
- Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada
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Araki T, Gomez-Solano JR, Maciołek A. Relaxation to steady states of a binary liquid mixture around an optically heated colloid. Phys Rev E 2022; 105:014123. [PMID: 35193287 DOI: 10.1103/physreve.105.014123] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
We study the relaxation dynamics of a binary liquid mixture near a light-absorbing Janus particle after switching on and off illumination using experiments and theoretical models. The dynamics is controlled by the temperature gradient formed around the heated particle. Our results show that the relaxation is asymmetric: The approach to a nonequilibrium steady state is much slower than the return to thermal equilibrium. Approaching a nonequilibrium steady state after a sudden temperature change is a two-step process that overshoots the response of spatial variance of the concentration field. The initial growth of concentration fluctuations after switching on illumination follows a power law in agreement with the hydrodynamic and purely diffusive model. The energy outflow from the system after switching off illumination is well described by a stretched exponential function of time with characteristic time proportional to the ratio of the energy stored in the steady state to the total energy flux in this state.
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Affiliation(s)
- Takeaki Araki
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Juan Ruben Gomez-Solano
- Instituto de Física, Universidad Nacional Autónoma de Mexico, Ciudad de Mexico, Código Postal 04510, Mexico
| | - Anna Maciołek
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, PL-01-224 Warsaw, Poland
- Max-Planck-Institut für Intelligente Systeme Stuttgart, Heisenbergstraße 3, D-70569 Stuttgart, Germany
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Vincze T, Micjan M, Nevrela J, Donoval M, Weis M. Photoresponse Dimensionality of Organic Field-Effect Transistor. MATERIALS 2021; 14:ma14237465. [PMID: 34885620 PMCID: PMC8659143 DOI: 10.3390/ma14237465] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 12/01/2021] [Accepted: 12/04/2021] [Indexed: 11/16/2022]
Abstract
Organic field-effect transistors have been envisioned for advanced photodetectors because the organic semiconductors provide unique absorption characteristics, low-cost fabrication, or compatibility with flexible substrates. However, the response time of organic phototransistors still does not reach the required application level. Here, we report the photoresponse of copper phthalocyanine phototransistor in a steady state and under pulsed illumination. The detailed analysis based on the random walk among a field of traps was used to evaluate the dimensionality of electron transport in a device.
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Malik A, Kashyap HK. Multiple evidences of dynamic heterogeneity in hydrophobic deep eutectic solvents. J Chem Phys 2021; 155:044502. [PMID: 34340384 DOI: 10.1063/5.0054699] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Hydrophobic deep eutectic solvents (HDESs) have gained immense popularity because of their promising applications in extraction processes. Herein, we employ atomistic molecular dynamics simulations to unveil the dynamics of DL-menthol (DLM) based HDESs with hexanoic (C6), octanoic (C8), and decanoic (C10) acids as hydrogen bond donors. The particular focus is on understanding the nature of dynamics with changing acid tail length. For all three HDESs, two modes of hydrogen bond relaxations are observed. We observe longer hydrogen bond lifetimes of the inter-molecular hydrogen bonding interactions between the carbonyl oxygen of the acid and hydroxyl oxygen of menthol with hydroxyl hydrogen of both acids and menthol. We infer strong hydrogen bonding between them compared to that between hydroxyl oxygen of acids and hydroxyl hydrogens of menthol and acids, marked by a faster decay rate and shorter hydrogen bond lifetime. The translational dynamics of the species in the HDES becomes slower with increasing tail length of the organic acid. Slightly enhanced caging is also observed for the HDES with a longer tail length of the acids. The evidence of dynamic heterogeneity in the displacements of the component molecules is observed in all the HDESs. From the values of the α-relaxation time scale, we observe that the molecular displacements become random in a shorter time scale for DLM-C6. The analysis of the self-van Hove function reveals that the overall distance covered by DLM and acid molecules in the respective HDES is more than what is expected from ideal diffusion. As marked by the shorter time scale associated with hole filling, the diffusion of the oxygen atom of menthol and the carbonyl oxygen of acid from one site to the other is fastest for hexanoic acid containing HDES.
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Affiliation(s)
- Akshay Malik
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Hemant K Kashyap
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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Nho HW, Park JH, Adhikari A, Kwon OH. Acid–base reaction of a cationic hydration probe in vicinity of anionic interface of AOT reverse micelles. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2020.115270] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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9
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Katsarou AF, Tsamopoulos AJ, Tsalikis DG, Mavrantzas VG. Dynamic Heterogeneity in Ring-Linear Polymer Blends. Polymers (Basel) 2020; 12:E752. [PMID: 32235530 PMCID: PMC7240694 DOI: 10.3390/polym12040752] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 03/15/2020] [Accepted: 03/18/2020] [Indexed: 11/16/2022] Open
Abstract
We present results from a direct statistical analysis of long molecular dynamics (MD) trajectories for the orientational relaxation of individual ring molecules in blends with equivalent linear chains. Our analysis reveals a very broad distribution of ring relaxation times whose width increases with increasing ring/linear molecular length and increasing concentration of the blend in linear chains. Dynamic heterogeneity is also observed in the pure ring melts but to a lesser extent. The enhanced degree of dynamic heterogeneity in the blends arises from the substantial increase in the intrinsic timescales of a large subpopulation of ring molecules due to their involvement in strong threading events with a certain population of the linear chains present in the blend. Our analysis suggests that the relaxation dynamics of the rings are controlled by the different states of their threading by linear chains. Unthreaded or singly-threaded rings exhibit terminal relaxation very similar to that in their own melt, but multiply-threaded rings relax much slower due to the long lifetimes of the corresponding topological interactions. By further analyzing the MD data for ring molecule terminal relaxation in terms of the sum of simple exponential functions we have been able to quantify the characteristic relaxation times of the corresponding mechanisms contributing to ring relaxation both in their pure melts and in the blends, and their relative importance. The extra contribution due to ring-linear threadings in the blends becomes immediately apparent through such an analysis.
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Affiliation(s)
- Anna F. Katsarou
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK;
| | - Alexandros J. Tsamopoulos
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA;
| | - Dimitrios G. Tsalikis
- Department of Chemical Engineering, University of Patras and FORTH-ICE/HT, GR 26504 Patras, Greece
| | - Vlasis G. Mavrantzas
- Department of Chemical Engineering, University of Patras and FORTH-ICE/HT, GR 26504 Patras, Greece
- Particle Technology Laboratory, Department of Mechanical and Process Engineering, ETH Zürich, CH-8092 Zürich, Switzerland
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Abstract
The time-dependent response of structural materials dominates our aging infrastructure's life expectancy and has important resilience implications. For calcium-silicate-hydrates, the glue of cement, nanoscale mechanisms underlying time-dependent phenomena are complex and remain poorly understood. This complexity originates in part from the inherent difficulty in studying nanoscale longtime phenomena in atomistic simulations. Herein, we propose a three-staged incremental stress-marching technique to overcome such limitations. The first stage unravels a stretched exponential relaxation, which is ubiquitous in glassy systems. When fully relaxed, the material behaves viscoelastically upon further loading, which is described by the standard solid model. By progressively increasing the interlayer water, the time-dependent response of calcium-silicate-hydrates exhibits a transition from viscoelastic to logarithmic creep. These findings bridge the gap between atomistic simulations and nanomechanical experimental measurements and pave the way for the design of reduced aging construction materials and other disordered systems such as metallic and oxide glasses.
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García-Peñas A, Gómez-Elvira JM, Lorenzo V, Pérez E, Cerrada ML. Influence of polymorphism and the new trigonal modification on the mechanical response of isotactic poly(propylene-co-1-pentene-co-1-hexene) terpolymers. Eur Polym J 2017. [DOI: 10.1016/j.eurpolymj.2017.10.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Medina JS, Arismendi-Arrieta DJ, Alemán JV, Prosmiti R. Developing time to frequency-domain descriptors for relaxation processes: Local trends. J Mol Liq 2017. [DOI: 10.1016/j.molliq.2017.08.034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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