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Mallem SPR, Puneetha P, Choi Y, Baek SM, Lee DY, Im KS, An SJ. Barrier Height, Ideality Factor and Role of Inhomogeneities at the AlGaN/GaN Interface in GaN Nanowire Wrap-Gate Transistor. Nanomaterials (Basel) 2023; 13:3159. [PMID: 38133056 PMCID: PMC10745394 DOI: 10.3390/nano13243159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/12/2023] [Accepted: 12/15/2023] [Indexed: 12/23/2023]
Abstract
It is essential to understand the barrier height, ideality factor, and role of inhomogeneities at the metal/semiconductor interfaces in nanowires for the development of next generation nanoscale devices. Here, we investigate the drain current (Ids)-gate voltage (Vgs) characteristics of GaN nanowire wrap-gate transistors (WGTs) for various gate potentials in the wide temperature range of 130-310 K. An anomalous reduction in the experimental barrier height and rise in the ideality factor with reducing the temperature have been perceived. It is noteworthy that the variations in barrier height and ideality factor are attributed to the spatial barrier inhomogeneities at the AlGaN/GaN interface in the GaN nanowire WGTs by assuming a double Gaussian distribution of barrier heights at 310-190 K (distribution 1) and 190-130 K (distribution 2). The standard deviation for distribution 2 is lower than that of distribution 1, which suggests that distribution 2 reflects more homogeneity at the AlGaN/GaN interface in the transistor's source/drain regions than distribution 1.
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Affiliation(s)
- Siva Pratap Reddy Mallem
- Advanced Material Research Center, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea;
| | - Peddathimula Puneetha
- Department of Robotics and Intelligent Machine Engineering, College of Mechanical and IT Engineering, Yeungnam University, Gyeongsan 38541, Republic of Korea; (P.P.); (D.-Y.L.)
| | - Yeojin Choi
- Department of Materials Science and Engineering, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea; (Y.C.); (S.M.B.)
| | - Seung Mun Baek
- Department of Materials Science and Engineering, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea; (Y.C.); (S.M.B.)
| | - Dong-Yeon Lee
- Department of Robotics and Intelligent Machine Engineering, College of Mechanical and IT Engineering, Yeungnam University, Gyeongsan 38541, Republic of Korea; (P.P.); (D.-Y.L.)
| | - Ki-Sik Im
- Department of Green Semiconductor System, Daegu Campus, Korea Polytechnics, Daegu 41765, Republic of Korea
| | - Sung Jin An
- Department of Materials Science and Engineering, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea; (Y.C.); (S.M.B.)
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2
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D’Astous A, Cereza G, Papp D, Gilbert KM, Stockmann JP, Alonso-Ortiz E, Cohen-Adad J. Shimming toolbox: An open-source software toolbox for B0 and B1 shimming in MRI. Magn Reson Med 2023; 89:1401-1417. [PMID: 36441743 PMCID: PMC9910837 DOI: 10.1002/mrm.29528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 10/21/2022] [Accepted: 10/25/2022] [Indexed: 11/29/2022]
Abstract
PURPOSE Introduce Shimming Toolbox ( https://shimming-toolbox.org), an open-source software package for prototyping new methods and performing static, dynamic, and real-time B0 shimming as well as B1 shimming experiments. METHODS Shimming Toolbox features various field mapping techniques, manual and automatic masking for the brain and spinal cord, B0 and B1 shimming capabilities accessible through a user-friendly graphical user interface. Validation of Shimming Toolbox was demonstrated in three scenarios: (i) B0 dynamic shimming in the brain at 7T using custom AC/DC coils, (ii) B0 real-time shimming in the spinal cord at 3T, and (iii) B1 static shimming in the spinal cord at 7T. RESULTS The B0 dynamic shimming of the brain at 7T took about 10 min to perform. It showed a 47% reduction in the standard deviation of the B0 field, associated with noticeable improvements in geometric distortions in EPI images. Real-time dynamic xyz-shimming in the spinal cord took about 5 min and showed a 30% reduction in the standard deviation of the signal distribution. B1 static shimming experiments in the spinal cord took about 10 min to perform and showed a 40% reduction in the coefficient of variation of the B1 field. CONCLUSION Shimming Toolbox provides an open-source platform where researchers can collaborate, prototype and conveniently test B0 and B1 shimming experiments. Future versions will include additional field map preprocessing techniques, optimization algorithms, and compatibility across multiple MRI manufacturers.
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Affiliation(s)
- Alexandre D’Astous
- NeuroPoly Lab, Institute of Biomedical Engineering,
Polytechnique Montréal, Montréal, QC, Canada
| | - Gaspard Cereza
- NeuroPoly Lab, Institute of Biomedical Engineering,
Polytechnique Montréal, Montréal, QC, Canada
| | - Daniel Papp
- NeuroPoly Lab, Institute of Biomedical Engineering,
Polytechnique Montréal, Montréal, QC, Canada
| | - Kyle M. Gilbert
- Centre for Functional and Metabolic Mapping, The
University of Western Ontario, London, Ontario, Canada
| | - Jason P. Stockmann
- Athinoula A. Martinos Center for Biomedical Imaging,
Massachusetts General Hospital, Charlestown, MA, United States
- Harvard Medical School, Boston, MA, United States
| | - Eva Alonso-Ortiz
- NeuroPoly Lab, Institute of Biomedical Engineering,
Polytechnique Montréal, Montréal, QC, Canada
| | - Julien Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering,
Polytechnique Montréal, Montréal, QC, Canada
- Functional Neuroimaging Unit, CRIUGM, Université de
Montréal, Montréal, QC, Canada
- Mila - Quebec AI Institute, Montréal, QC,
Canada
- Centre de recherche du CHU Sainte-Justine,
Université de Montréal, Montréal, QC, Canada
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3
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Poblador Rodriguez E, Moser P, Auno S, Eckstein K, Dymerska B, van der Kouwe A, Gruber S, Trattnig S, Bogner W. Real-time motion and retrospective coil sensitivity correction for CEST using volumetric navigators (vNavs) at 7T. Magn Reson Med 2021; 85:1909-1923. [PMID: 33165952 PMCID: PMC7839562 DOI: 10.1002/mrm.28555] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 09/22/2020] [Accepted: 09/22/2020] [Indexed: 12/12/2022]
Abstract
PURPOSE To explore the impact of temporal motion-induced coil sensitivity changes on CEST-MRI at 7T and its correction using interleaved volumetric EPI navigators, which are applied for real-time motion correction. METHODS Five healthy volunteers were scanned via CEST. A 4-fold correction pipeline allowed the mitigation of (1) motion, (2) motion-induced coil sensitivity variations, ΔB1- , (3) motion-induced static magnetic field inhomogeneities, ΔB0 , and (4) spatially varying transmit RF field fluctuations, ΔB1+ . Four CEST measurements were performed per session. For the first 2, motion correction was turned OFF and then ON in absence of voluntary motion, whereas in the other 2 controlled head rotations were performed. During post-processing ΔB1- was removed additionally for the motion-corrected cases, resulting in a total of 6 scenarios to be compared. In all cases, retrospective ∆B0 and - ΔB1+ corrections were performed to compute artifact-free magnetization transfer ratio maps with asymmetric analysis (MTRasym ). RESULTS Dynamic ΔB1- correction successfully mitigated signal deviations caused by head motion. In 2 frontal lobe regions of volunteer 4, induced relative signal errors of 10.9% and 3.9% were reduced to 1.1% and 1.0% after correction. In the right frontal lobe, the motion-corrected MTRasym contrast deviated 0.92%, 1.21%, and 2.97% relative to the static case for Δω = 1, 2, 3 ± 0.25 ppm. The additional application of ΔB1- correction reduced these deviations to 0.10%, 0.14%, and 0.42%. The fully corrected MTRasym values were highly consistent between measurements with and without intended head rotations. CONCLUSION Temporal ΔB1- cause significant CEST quantification bias. The presented correction pipeline including the proposed retrospective ΔB1- correction significantly reduced motion-related artifacts on CEST-MRI.
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Affiliation(s)
- Esau Poblador Rodriguez
- High Field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University Vienna, Vienna, Austria
| | - Philipp Moser
- High Field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University Vienna, Vienna, Austria
| | - Sami Auno
- Neuroscience Center, University of Helsinki, Helsinki, Finland
| | - Korbinian Eckstein
- High Field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University Vienna, Vienna, Austria
| | - Barbara Dymerska
- Medical Physics and Bioengineering, University College London, London, United Kingdom
| | - Andre van der Kouwe
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Stephan Gruber
- High Field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University Vienna, Vienna, Austria
| | - Siegfried Trattnig
- High Field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University Vienna, Vienna, Austria.,Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria
| | - Wolfgang Bogner
- High Field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University Vienna, Vienna, Austria
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Benedetti MH, Berrocal VJ, Narisetty NN. Identifying regions of inhomogeneities in spatial processes via an M-RA and mixture priors. Biometrics 2021; 78:798-811. [PMID: 33594698 DOI: 10.1111/biom.13446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 03/11/2019] [Accepted: 02/03/2021] [Indexed: 11/29/2022]
Abstract
Soils have been heralded as a hidden resource that can be leveraged to mitigate and address some of the major global environmental challenges. Specifically, the organic carbon stored in soils, called soil organic carbon (SOC), can, through proper soil management, help offset fuel emissions, increase food productivity, and improve water quality. As collecting data on SOC are costly and time-consuming, not much data on SOC are available, although understanding the spatial variability in SOC is of fundamental importance for effective soil management. In this manuscript, we propose a modeling framework that can be used to gain a better understanding of the dependence structure of a spatial process by identifying regions within a spatial domain where the process displays the same spatial correlation range. To achieve this goal, we propose a generalization of the multiresolution approximation (M-RA) modeling framework of Katzfuss originally introduced as a strategy to reduce the computational burden encountered when analyzing massive spatial datasets. To allow for the possibility that the correlation of a spatial process might be characterized by a different range in different subregions of a spatial domain, we provide the M-RA basis functions weights with a two-component mixture prior with one of the mixture components a shrinking prior. We call our approach the mixture M-RA. Application of the mixture M-RA model to both stationary and nonstationary data show that the mixture M-RA model can handle both types of data, can correctly establish the type of spatial dependence structure in the data (e.g., stationary versus not), and can identify regions of local stationarity.
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Affiliation(s)
- Marco H Benedetti
- Center for Injury Research and Policy, Nationwide Children's Hospital, Columbus, Ohio
| | | | - Naveen N Narisetty
- Department of Statistics, University of Illinois at Urbana-Champaign, Urbana-Champaign, Illinois
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5
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Savin A, Craus ML, Bruma A, Novy F, Malo S, Chlada M, Steigmann R, Vizureanu P, Harnois C, Turchenko V, Prevorovsky Z. Microstructural Analysis and Mechanical Properties of TiMo 20Zr 7Ta 15Si x Alloys as Biomaterials. Materials (Basel) 2020; 13:ma13214808. [PMID: 33126523 PMCID: PMC7663523 DOI: 10.3390/ma13214808] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 10/23/2020] [Accepted: 10/23/2020] [Indexed: 11/16/2022]
Abstract
TiMoZrTaSi alloys appertain to a new generation of metallic biomaterials, labeled high-entropy alloys, that assure both biocompatibility as well as improved mechanical properties required by further medical applications. This paper presents the use of nondestructive evaluation techniques for new type of alloys, TiMo20Zr7Ta15Six, with x = 0; 0.5; 0.75; 1.0, which were obtained by vacuum melting. In Ti alloys, the addition of Mo improves tensile creep strength, Si improves both the creep and oxidation properties, Zr leads to an α crystalline structure, which increases the mechanical strength and assures a good electrochemical behavior, and Ta is a β stabilizer sustaining the formation of solid β-phases and contributes to tensile strength improvement and Young modulus decreasing. The effects of Si content on the mechanical properties of the studied alloys and the effect of the addition of Ta and Zr under the presence of Si on the evolution of crystallographic structure was studied. The influence of composition on fracture behavior and strength was evaluated using X-ray diffraction, resonant ultrasound spectroscopy (RUS) analyses, SEM with energy dispersive X-ray spectroscopy, and acoustic emission (AE) within compression tests. The β-type TiMo20Zr7Ta15Six alloys had a good compression strength of over 800 MPa, lower Young modulus (69.11–89.03 GPa) and shear modulus (24.70–31.87 GPa), all offering advantages for use in medical applications.
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Affiliation(s)
- Adriana Savin
- Nondestructive Testing Department, National Institute for Research and Development for Technical Physics, 700050 Iasi, Romania;
- Correspondence: (A.S.); (M.L.C.); Tel.: +40-232-430680 (A.S.)
| | - Mihail Liviu Craus
- Nondestructive Testing Department, National Institute for Research and Development for Technical Physics, 700050 Iasi, Romania;
- Frank Laboratory for Neutron Physics, Joint Institute for Nuclear Research, Dubna 141980, Russia;
- Correspondence: (A.S.); (M.L.C.); Tel.: +40-232-430680 (A.S.)
| | - Alina Bruma
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA;
| | - František Novy
- Department of Materials Engineering, University of Zilina, 010 26 Zilina, Slovak Republic;
| | - Sylvie Malo
- Normandie Université, ENSICAEN, UNICAEN, CNRS, CRISMAT, 14000 Caen, France; (S.M.); (C.H.)
| | - Milan Chlada
- Institute of Thermomechanics, Academy of Sciences of the Czech Republic, 182 00 Prague, Czech Republic; (M.C.); (Z.P.)
| | - Rozina Steigmann
- Nondestructive Testing Department, National Institute for Research and Development for Technical Physics, 700050 Iasi, Romania;
| | - Petrica Vizureanu
- Faculty of Materials Science and Engineering, Technical University Gheorghe Asachi, 700050 Iasi, Romania;
| | - Christelle Harnois
- Normandie Université, ENSICAEN, UNICAEN, CNRS, CRISMAT, 14000 Caen, France; (S.M.); (C.H.)
| | - Vitalii Turchenko
- Frank Laboratory for Neutron Physics, Joint Institute for Nuclear Research, Dubna 141980, Russia;
| | - Zdenek Prevorovsky
- Institute of Thermomechanics, Academy of Sciences of the Czech Republic, 182 00 Prague, Czech Republic; (M.C.); (Z.P.)
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6
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Roberts NT, Hinshaw LA, Colgan TJ, Ii T, Hernando D, Reeder SB. B 0 and B 1 inhomogeneities in the liver at 1.5 T and 3.0 T. Magn Reson Med 2020; 85:2212-2220. [PMID: 33107109 DOI: 10.1002/mrm.28549] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 09/02/2020] [Accepted: 09/18/2020] [Indexed: 12/17/2022]
Abstract
PURPOSE The purpose of this work is to characterize the magnitude and variability of B0 and B1 inhomogeneities in the liver in large cohorts of patients at both 1.5 T and 3.0 T. METHODS Volumetric B0 and B1 maps were acquired over the liver of patients presenting for routine abdominal MRI. Regions of interest were drawn in the nine Couinaud segments of the liver, and the average value was recorded. Magnitude and variation of measured averages in each segment were reported across all patients. RESULTS A total of 316 B0 maps and 314 B1 maps, acquired at 1.5 T and 3.0 T on a variety of GE Healthcare MRI systems in 630 unique exams, were identified, analyzed, and, in the interest of reproducible research, de-identified and made public. Measured B0 inhomogeneities ranged (5th-95th percentiles) from -31.7 Hz to 164.0 Hz for 3.0 T (-14.5 Hz to 81.3 Hz at 1.5 T), while measured B1 inhomogeneities (ratio of actual over prescribed flip angle) ranged from 0.59 to 1.13 for 3.0 T (0.83 to 1.11 at 1.5 T). CONCLUSION This study provides robust characterization of B0 and B1 inhomogeneities in the liver to guide the development of imaging applications and protocols. Field strength, bore diameter, and sex were determined to be statistically significant effects for both B0 and B1 uniformity. Typical clinical liver imaging at 3.0 T should expect B0 inhomogeneities ranging from approximately -100 Hz to 250 Hz (-50 Hz to 150 Hz at 1.5 T) and B1 inhomogeneities ranging from approximately 0.4 to 1.3 (0.7 to 1.2 at 1.5 T).
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Affiliation(s)
- Nathan T Roberts
- Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Louis A Hinshaw
- Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Timothy J Colgan
- Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Takanori Ii
- Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Radiology, University of Yamanashi, Yamanashi, Japan
| | - Diego Hernando
- Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Scott B Reeder
- Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Emergency Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
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7
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Abstract
Cell migration and invasion is a key driving factor for providing essential cellular functions under physiological conditions or the malignant progression of tumors following downward the metastatic cascade. Although there has been plentiful of molecules identified to support the migration and invasion of cells, the mechanical aspects have not yet been explored in a combined and systematic manner. In addition, the cellular environment has been classically and frequently assumed to be homogeneous for reasons of simplicity. However, motility assays have led to various models for migration covering only some aspects and supporting factors that in some cases also include mechanical factors. Instead of specific models, in this review, a more or less holistic model for cell motility in 3D is envisioned covering all these different aspects with a special emphasis on the mechanical cues from a biophysical perspective. After introducing the mechanical aspects of cell migration and invasion and presenting the heterogeneity of extracellular matrices, the three distinct directions of cell motility focusing on the mechanical aspects are presented. These three different directions are as follows: firstly, the commonly used invasion tests using structural and structure-based mechanical environmental signals; secondly, the mechano-invasion assay, in which cells are studied by mechanical forces to migrate and invade; and thirdly, cell mechanics, including cytoskeletal and nuclear mechanics, to influence cell migration and invasion. Since the interaction between the cell and the microenvironment is bi-directional in these assays, these should be accounted in migration and invasion approaches focusing on the mechanical aspects. Beyond this, there is also the interaction between the cytoskeleton of the cell and its other compartments, such as the cell nucleus. In specific, a three-element approach is presented for addressing the effect of mechanics on cell migration and invasion by including the effect of the mechano-phenotype of the cytoskeleton, nucleus and the cell's microenvironment into the analysis. In precise terms, the combination of these three research approaches including experimental techniques seems to be promising for revealing bi-directional impacts of mechanical alterations of the cellular microenvironment on cells and internal mechanical fluctuations or changes of cells on the surroundings. Finally, different approaches are discussed and thereby a model for the broad impact of mechanics on cell migration and invasion is evolved.
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Affiliation(s)
- Claudia Tanja Mierke
- Faculty of Physics and Earth Science, Peter Debye Institute of Soft Matter Physics, Biological Physics Division, University of Leipzig, Leipzig, Germany
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8
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Paul K, Hartmann T, Posch C, Behrens D, Herwig C. Investigation of cell line specific responses to pH inhomogeneity and consequences for process design. Eng Life Sci 2020; 20:412-421. [PMID: 32944016 PMCID: PMC7481767 DOI: 10.1002/elsc.202000034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 06/15/2020] [Accepted: 06/25/2020] [Indexed: 12/13/2022] Open
Abstract
With increasing bioreactor volumes, the mixing time of the reactor increases as well, which creates an inhomogeneous environment for the cells. This can result in impaired process performance in large-scale production reactors. Particularly the addition of base through the reactor headspace can be problematic, since it creates an area, where cells are repeatedly exposed to an increased pH. The aim of this study is to simulate this large-scale phenomenon at lab-scale and investigate its impact. Two different cell lines were exposed to pH amplitudes of a maximal magnitude of 0.05 units (pH of 6.95). Both cell lines showed similar responses, like decreased viable cell counts, but unaffected lactate levels. However, cell line B showed an initially increased specific productivity in response to the introduced amplitudes, whereas cell line A showed a consistently lower specific productivity. Furthermore, the time point at which base addition is started influences the impact, which pH amplitudes have on process performance. When pH control was started earlier in the process, maximal viable cell counts decreased and the lactate metabolic shift was less pronounced. These results show that the potential negative impact of pH amplitudes can be minimized by strategic process design.
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Affiliation(s)
- Katrin Paul
- Institute of ChemicalEnvironmental and Bioscience EngineeringTU WienViennaAustria
- Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved BioprocessesTU WienViennaAustria
| | - Thomas Hartmann
- Institute of ChemicalEnvironmental and Bioscience EngineeringTU WienViennaAustria
- Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved BioprocessesTU WienViennaAustria
| | | | | | - Christoph Herwig
- Institute of ChemicalEnvironmental and Bioscience EngineeringTU WienViennaAustria
- Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved BioprocessesTU WienViennaAustria
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9
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Paul K, Böttinger K, Mitic BM, Scherfler G, Posch C, Behrens D, Huber CG, Herwig C. Development, characterization, and application of a 2-Compartment system to investigate the impact of pH inhomogeneities in large-scale CHO-based processes. Eng Life Sci 2020; 20:368-378. [PMID: 32774209 PMCID: PMC7401239 DOI: 10.1002/elsc.202000009] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/08/2020] [Accepted: 04/29/2020] [Indexed: 01/05/2023] Open
Abstract
Large-scale bioreactors for the production of monoclonal antibodies reach volumes of up to 25 000 L. With increasing bioreactor size, mixing is however affected negatively, resulting in the formation of gradients throughout the reactor. These gradients can adversely affect process performance at large scale. Since mammalian cells are sensitive to changes in pH, this study investigated the effects of pH gradients on process performance. A 2-Compartment System was established for this purpose to expose only a fraction of the cell population to pH excursions and thereby mimicking a large-scale bioreactor. Cells were exposed to repeated pH amplitudes of 0.4 units (pH 7.3), which resulted in decreased viable cell counts, as well as the inhibition of the lactate metabolic shift. These effects were furthermore accompanied by increased absolute lactate levels. Continuous assessment of molecular attributes of the expressed target protein revealed that subunit assembly or N-glycosylation patterns were only slightly influenced by the pH excursions. The exposure of more cells to the same pH amplitudes further impaired process performance, indicating this is an important factor, which influences the impact of pH inhomogeneity. This knowledge can aid in the design of pH control strategies to minimize the effects of pH inhomogeneity in large-scale bioreactors.
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Affiliation(s)
- Katrin Paul
- Institute of ChemicalEnvironmental and Bioscience EngineeringTU WienViennaAustria
- Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved BioprocessesTU WienViennaAustria
| | - Katharina Böttinger
- Department of BiosciencesBioanalytical Research LabsUniversity of SalzburgSalzburgAustria
- Christian Doppler Laboratory for Innovative Tools for Biosimilar CharacterizationUniversity of SalzburgSalzburgAustria
| | - Bernd M. Mitic
- Institute of ChemicalEnvironmental and Bioscience EngineeringTU WienViennaAustria
- Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved BioprocessesTU WienViennaAustria
| | - Georg Scherfler
- Institute of ChemicalEnvironmental and Bioscience EngineeringTU WienViennaAustria
- Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved BioprocessesTU WienViennaAustria
| | | | | | - Christian G. Huber
- Department of BiosciencesBioanalytical Research LabsUniversity of SalzburgSalzburgAustria
- Christian Doppler Laboratory for Innovative Tools for Biosimilar CharacterizationUniversity of SalzburgSalzburgAustria
| | - Christoph Herwig
- Institute of ChemicalEnvironmental and Bioscience EngineeringTU WienViennaAustria
- Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved BioprocessesTU WienViennaAustria
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10
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Abstract
The advent of thin-film electronics and the development of new materials, such as oxide semiconductors, bring great opportunities for new device designs and applications. A source-gated transistor (SGT) is created by combining two fundamental building blocks of electronics: a thin-film transistor and a Schottky diode. By developing a methodology to manipulate the source barrier profile, an extremely high gain of 29,000 is achieved, previously unthinkable with a single component. The SGT design overcomes several major bottlenecks to using oxide semiconductors in large-scale applications and broadens the range of channel materials beyond standard semiconductors. These advantages combined with an analytical theory confirmed by simulations and experiments demonstrate the potential of SGTs to be a fundamental component for thin-film electronics. Despite being a fundamental electronic component for over 70 years, it is still possible to develop different transistor designs, including the addition of a diode-like Schottky source electrode to thin-film transistors. The discovery of a dependence of the source barrier height on the semiconductor thickness and derivation of an analytical theory allow us to propose a design rule to achieve extremely high voltage gain, one of the most important figures of merit for a transistor. Using an oxide semiconductor, an intrinsic gain of 29,000 was obtained, which is orders of magnitude higher than a conventional Si transistor. These same devices demonstrate almost total immunity to negative bias illumination temperature stress, the foremost bottleneck to using oxide semiconductors in major applications, such as display drivers. Furthermore, devices fabricated with channel lengths down to 360 nm display no obvious short-channel effects, another critical factor for high-density integrated circuits and display applications. Finally, although the channel material of conventional transistors must be a semiconductor, by demonstrating a high-performance transistor with a semimetal-like indium tin oxide channel, the range and versatility of materials have been significantly broadened.
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11
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Luo Y, De Jesus LR, Andrews JL, Parija A, Fleer N, Robles DJ, Mukherjee PP, Banerjee S. Roadblocks in Cation Diffusion Pathways: Implications of Phase Boundaries for Li-Ion Diffusivity in an Intercalation Cathode Material. ACS Appl Mater Interfaces 2018; 10:30901-30911. [PMID: 30106560 DOI: 10.1021/acsami.8b10604] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Increasing intercalation of Li-ions brings about distortive structural transformations in several canonical intercalation hosts. Such phase transformations require the energy dissipative creation and motion of dislocations at the interface between the parent lattice and the nucleated Li-rich phase. Phase inhomogeneities within particles and across electrodes give rise to pronounced stress gradients, which can result in capacity fading. How such transformations alter Li-ion diffusivities remains much less explored. In this article, we use layered V2O5 as an intercalation host and examine the structural origins of the evolution of Li-ion diffusivities with phase progression upon electrochemical lithiation. Galvanostatic intermittent titration measurements show a greater than 4 orders of magnitude alteration of Li-ion diffusivity in V2O5 as a function of the extent of lithiation. Pronounced dips in Li-ion diffusivities are correlated with the presence of phase mixtures as determined by Raman spectroscopy and X-ray diffraction, whereas monophasic regimes correspond to the highest Li-ion diffusivity values measured within this range. First-principles density functional theory calculations confirm that the variations in Li-ion diffusivity do not stem from intrinsic differences in diffusion pathways across the different lithiated V2O5 phases, which despite differences in the local coordination environments of Li-ions show comparable migration barriers. Scanning transmission X-ray microscopy measurements indicate the stabilization of distinct domains reflecting the phase coexistence of multiple lithiated phases within individual actively intercalating particles. The results thus provide fundamental insight into the considerable ion transport penalties incurred as a result of phase boundaries formed within actively intercalating particles. The combination of electrochemical studies with ensemble structural characterization and single-particle X-ray imaging of phase boundaries demonstrates the profound impact of interfacial phenomena on macroscopic electrode properties.
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Affiliation(s)
- Yuting Luo
- Department of Chemistry, Department of Materials Science & Engineering , Texas A&M University , College Station , Texas 77843 , United States
| | - Luis R De Jesus
- Department of Chemistry, Department of Materials Science & Engineering , Texas A&M University , College Station , Texas 77843 , United States
| | - Justin L Andrews
- Department of Chemistry, Department of Materials Science & Engineering , Texas A&M University , College Station , Texas 77843 , United States
| | - Abhishek Parija
- Department of Chemistry, Department of Materials Science & Engineering , Texas A&M University , College Station , Texas 77843 , United States
| | - Nathan Fleer
- Department of Chemistry, Department of Materials Science & Engineering , Texas A&M University , College Station , Texas 77843 , United States
| | - Daniel Juarez Robles
- School of Mechanical Engineering , Purdue University , West Lafayette , Indiana 47907 , United States
| | - Partha P Mukherjee
- School of Mechanical Engineering , Purdue University , West Lafayette , Indiana 47907 , United States
| | - Sarbajit Banerjee
- Department of Chemistry, Department of Materials Science & Engineering , Texas A&M University , College Station , Texas 77843 , United States
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