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Jain N, Hao Y, Parekh U, Kaltenegger M, Pedrazo-Tardajos A, Lazzaroni R, Resel R, Geerts YH, Bals S, Van Aert S. Exploring the effects of graphene and temperature in reducing electron beam damage: A TEM and electron diffraction-based quantitative study on Lead Phthalocyanine (PbPc) crystals. Micron 2023; 169:103444. [PMID: 36965270 DOI: 10.1016/j.micron.2023.103444] [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: 01/06/2023] [Revised: 03/14/2023] [Accepted: 03/15/2023] [Indexed: 03/27/2023]
Abstract
High-resolution transmission electron microscopy (TEM) of organic crystals, such as Lead Phthalocyanine (PbPc), is very challenging since these materials are prone to electron beam damage leading to the breakdown of the crystal structure during investigation. Quantification of the damage is imperative to enable high-resolution imaging of PbPc crystals with minimum structural changes. In this work, we performed a detailed electron diffraction study to quantitatively measure degradation of PbPc crystals upon electron beam irradiation. Our study is based on the quantification of the fading intensity of the spots in the electron diffraction patterns. At various incident dose rates (e/Å2/s) and acceleration voltages, we experimentally extracted the decay rate (1/s), which directly correlates with the rate of beam damage. In this manner, a value for the critical dose (e/Å2) could be determined, which can be used as a measure to quantify beam damage. Using the same methodology, we explored the influence of cryogenic temperatures, graphene TEM substrates, and graphene encapsulation in prolonging the lifetime of the PbPc crystal structure during TEM investigation. The knowledge obtained by diffraction experiments is then translated to real space high-resolution TEM imaging of PbPc.
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Affiliation(s)
- Noopur Jain
- Electron Microscopy for Materials Science (EMAT) and NANOlab Center of Excellence, University of Antwerp, 2020 Antwerp, Belgium
| | - Yansong Hao
- Electron Microscopy for Materials Science (EMAT) and NANOlab Center of Excellence, University of Antwerp, 2020 Antwerp, Belgium; Laboratory for Chemistry of Novel Materials, Materials Research Institute, University of Mons, 7000 Mons, Belgium
| | - Urvi Parekh
- Electron Microscopy for Materials Science (EMAT) and NANOlab Center of Excellence, University of Antwerp, 2020 Antwerp, Belgium
| | - Martin Kaltenegger
- Institute of Solid State Physics, Graz University of Technology, 8010 Graz, Austria; Laboratory of Polymer Chemistry, Faculty of Science, Université Libre de Bruxelles (ULB), 1050 Brussels, Belgium
| | - Adrián Pedrazo-Tardajos
- Electron Microscopy for Materials Science (EMAT) and NANOlab Center of Excellence, University of Antwerp, 2020 Antwerp, Belgium
| | - Roberto Lazzaroni
- Laboratory for Chemistry of Novel Materials, Materials Research Institute, University of Mons, 7000 Mons, Belgium
| | - Roland Resel
- Institute of Solid State Physics, Graz University of Technology, 8010 Graz, Austria
| | - Yves Henri Geerts
- Laboratory of Polymer Chemistry, Faculty of Science, Université Libre de Bruxelles (ULB), 1050 Brussels, Belgium; International Solvay Institutes of Physics and Chemistry, 1050 Brussels, Belgium
| | - Sara Bals
- Electron Microscopy for Materials Science (EMAT) and NANOlab Center of Excellence, University of Antwerp, 2020 Antwerp, Belgium.
| | - Sandra Van Aert
- Electron Microscopy for Materials Science (EMAT) and NANOlab Center of Excellence, University of Antwerp, 2020 Antwerp, Belgium.
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Ghimire S, Rehhagen C, Fiedler S, Parekh U, Lesyuk R, Lochbrunner S, Klinke C. Synthesis, optoelectronic properties, and charge carrier dynamics of colloidal quasi-two-dimensional Cs 3Bi 2I 9 perovskite nanosheets. Nanoscale 2023; 15:2096-2105. [PMID: 36629319 DOI: 10.1039/d2nr06048e] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Non-toxicity and stability make two-dimensional (2D) bismuth halide perovskites better alternatives to lead-based ones for optoelectronic applications and catalysis. In this work, we synthesize sub-micron size colloidal quasi-2D Cs3Bi2I9 perovskite nanosheets and study their generation and relaxation of charge carriers. Steady-state absorption spectroscopy reveals an indirect bandgap of 2.07 eV, which is supported by the band structure calculated using density functional theory. The nanosheets show no detectable photoluminescence at room temperature at near bandgap excitation which is attributed to the indirect bandgap. However, cathodoluminescence spanning a broad range from 500 nm to 750 nm with an asymmetric and Stokes-shifted emission is observed, indicating the phonon- and trap-assisted recombination of charge carriers. We study the ultrafast charge carrier dynamics in Cs3Bi2I9 nanosheets using femtosecond transient absorption spectroscopy. The samples are excited with photon energies higher than their bandgap, and the results are interpreted in terms of hot carrier generation (<1 ps), thermalization with local phonons (∼1 ps), and cooling (>30 ps). Further, a relatively slow relaxation of excitons (≳3 ns) at the band edge suggests the formation of stable polarons which decay nonradiatively by releasing phonons.
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Affiliation(s)
- Sushant Ghimire
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18059 Rostock, Germany.
| | - Chris Rehhagen
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18059 Rostock, Germany.
| | - Saskia Fiedler
- Center for Nanophotonics, NWO-Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Urvi Parekh
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18059 Rostock, Germany.
| | - Rostyslav Lesyuk
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18059 Rostock, Germany.
- Pidstryhach Institute for Applied Problems of Mechanics and Mathematics of NAS of Ukraine, Naukowa str. 3b, 79060 Lviv & Department of Photonics, Lviv Polytechnic National University, Bandery str. 12, 79000 Lviv, Ukraine
| | - Stefan Lochbrunner
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18059 Rostock, Germany.
| | - Christian Klinke
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18059 Rostock, Germany.
- Department of Chemistry, Swansea University, Swansea SA2 8PP, UK
- Department "Life, Light & Matter", University of Rostock, Albert-Einstein-Str. 25, 18059 Rostock, Germany
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Maruta N, Trusov Y, Brenya E, Parekh U, Botella JR. Membrane-localized extra-large G proteins and Gbg of the heterotrimeric G proteins form functional complexes engaged in plant immunity in Arabidopsis. Plant Physiol 2015; 167:1004-16. [PMID: 25588736 PMCID: PMC4348786 DOI: 10.1104/pp.114.255703] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
In animals, heterotrimeric G proteins, comprising Ga, Gb, and Gg subunits, are molecular switches whose function tightly depends on Ga and Gbg interaction. Intriguingly, in Arabidopsis (Arabidopsis thaliana), multiple defense responses involve Gbg, but not Ga. We report here that the Gbg dimer directly partners with extra-large G proteins (XLGs) to mediate plant immunity. Arabidopsis mutants deficient in XLGs, Gb, and Gg are similarly compromised in several pathogen defense responses, including disease development and production of reactive oxygen species. Genetic analysis of double, triple, and quadruple mutants confirmed that XLGs and Gbg functionally interact in the same defense signaling pathways. In addition, mutations in XLG2 suppressed the seedling lethal and cell death phenotypes of BRASSINOSTEROID INSENSITIVE1-associated receptor kinase1-interacting receptor-like kinase1 mutants in an identical way as reported for Arabidopsis Gb-deficient mutants. Yeast (Saccharomyces cerevisiae) three-hybrid and bimolecular fluorescent complementation assays revealed that XLG2 physically interacts with all three possible Gbg dimers at the plasma membrane. Phylogenetic analysis indicated a close relationship between XLGs and plant Ga subunits, placing the divergence point at the dawn of land plant evolution. Based on these findings, we conclude that XLGs form functional complexes with Gbg dimers, although the mechanism of action of these complexes, including activation/deactivation, must be radically different form the one used by the canonical Ga subunit and are not likely to share the same receptors. Accordingly, XLGs expand the repertoire of heterotrimeric G proteins in plants and reveal a higher level of diversity in heterotrimeric G protein signaling.
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Hu Z, Parekh U, Maruta N, Trusov Y, Botella JR. Down-regulation of Fusarium oxysporum endogenous genes by Host-Delivered RNA interference enhances disease resistance. Front Chem 2015; 3:1. [PMID: 25654075 PMCID: PMC4299518 DOI: 10.3389/fchem.2015.00001] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [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: 11/14/2014] [Accepted: 01/01/2015] [Indexed: 01/17/2023] Open
Abstract
Fusarium oxysporum is a devastating pathogen causing extensive yield losses in a variety of crops and development of sustainable, environmentally friendly methods to improve crop resistance is crucial. We have used Host-Delivered RNA interference (HD-RNAi) technology to partially silence three different genes (FOW2, FRP1, and OPR) in the hemi-biotrophic fungus F. oxysporum f. sp. conglutinans. Expression of double stranded RNA (dsRNA) molecules targeting fungal pathogen genes was achieved in a number of transgenic Arabidopsis lines. F. oxysporum infecting the transgenic lines displayed substantially reduced mRNA levels on all three targeted genes, with an average of 75, 83, and 72% reduction for FOW2, FRP1, and OPR, respectively. The silencing of pathogen genes had a clear positive effect on the ability of the transgenic lines to fight infection. All transgenic lines displayed enhanced resistance to F. oxysporum with delayed disease symptom development, especially FRP1 and OPR lines. Survival rates after fungal infection were higher in the transgenic lines compared to control wild type plants which consistently showed survival rates of 10%, with FOW2 lines showing 25% survival; FRP1 lines 30-50% survival and OPR between 45 and 70% survival. The down-regulation effect was specific for the targeted genes without unintended effects in related genes. In addition to producing resistant crops, HD-RNAi can provide a useful tool to rapidly screen candidate fungal pathogenicity genes without the need to produce fungal knockout mutants.
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Affiliation(s)
- Zongli Hu
- Plant Genetic Engineering Laboratory, School of Agriculture and Food Sciences, University of QueenslandBrisbane, QLD, Australia
- Bioengineering College, Chongqing UniversityChongqing, China
| | - Urvi Parekh
- Plant Genetic Engineering Laboratory, School of Agriculture and Food Sciences, University of QueenslandBrisbane, QLD, Australia
| | - Natsumi Maruta
- Plant Genetic Engineering Laboratory, School of Agriculture and Food Sciences, University of QueenslandBrisbane, QLD, Australia
| | - Yuri Trusov
- Plant Genetic Engineering Laboratory, School of Agriculture and Food Sciences, University of QueenslandBrisbane, QLD, Australia
| | - Jose R. Botella
- Plant Genetic Engineering Laboratory, School of Agriculture and Food Sciences, University of QueenslandBrisbane, QLD, Australia
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Parekh U, Ashwin P, Thind G. Single injection peribulbar anaesthesia: total upper eyelid drop as an endpoint marker. Anaesthesia 2001; 56:501-2. [PMID: 11350366 DOI: 10.1046/j.1365-2044.2001.02047-28.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Abstract
Constipation is a common condition affecting millions of people throughout the world. The present study aimed to determine the effect of extra fluid intake, as recommended by many primary care physicians and gastroenterologists, on the actual stool output in normal healthy volunteers. We recruited 15 healthy volunteers (aged 23-46 years, mean 30.1) without any significant history of diarrhea or constipation to participate in our study. Nine subjects underwent extra intake of isotonic fluids (Gatorade), whereas the remainder received extra free water over their baseline. During period I (3 days), baseline diet and fluid intake were determined by a registered dietitian. During periods II and III (2 days each), the volunteers in each group increased their fluid intake by 1 and 2 l of isotonic (Gatorade) and hypotonic solution (water), respectively. Period IV (2 days) completed the study with the volunteers returning to their baseline fluid intake. Urine and stool outputs were measured in these volunteers. Additional increase in fluid intake (isotonic or free water) did not result in a significant change in stool output. However, there was a significant increase in urine output (P < 0.05). Despite common medical advice to consume extra fluid for constipation, our results indicate that extra fluid intake in normal healthy volunteers did not produce a significant increase in stool output.
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Affiliation(s)
- B D Chung
- Division of Gastroenterology, Hepatology, and Nutrition, University of Texas Medical School at Houston, 77030, USA
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Parekh U, Wacha DS. Triplet pregnancy in Lusaka. Med J Zambia 1982; 16:68-70. [PMID: 7186723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
A series of 8 triplet sets during the year 1980 at the University Teaching Hospital, Lusaka, has been analysed. The incidence was 1:2980 hospital deliveries. Age or parity of the mother did not appear to have any influence on foetal survival, in contrast to the birth weight and foetal presentation at the time of delivery. First triplet baby seemed to have a better chance of survival as compared to second and third triplet babies. There was prepondence of female babies. The corrected perinatal mortality was 273/1000 live births which is significantly high.
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Parekh U, Sathianathan I, Wacha DS. Spontaneous rupture of the liver during pregnancy. Med J Zambia 1982; 16:10-3. [PMID: 7170827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Spontaneous rupture of the liver, a rare but grave complication of pregnancy merits attention of an obstetrician. It is important to stress that proper antenatal care, prompt hospitalization with effective treatment at first alarming sign of preeclampsia and early induction of labour when medically indicated may prevent such a grave complication. The aim of this paper is to promote earlier diagnosis with massive fluid and blood replacement in order to decrease the mortality. It also forms the research bases for liver function tests in all those patients with essential hypertension or persistent toxaemia. The literature is reviewed briefly.
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Parekh U. Developmental studies on kwashiokor. Indian Pediatr 1975; 12:85. [PMID: 1158469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Dastur DK, Lalitha VS, Udani PM, Parekh U. The brain and meninges in tuberculous meningitis-gross pathology in 100 cases and pathogenesis. Neurol India 1970; 18:86-100. [PMID: 5459296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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