Publications
306 results found
Cooper S, Yue T, Miller P, et al., 2019, Tripodal N-centred phosphine ligands: Towards a novel donor set for <SUP>99m</SUP>Tc and <SUP>186/188</SUP>Re radiopharmaceutical formulation, Publisher: WILEY, Pages: S295-S296, ISSN: 0362-4803
Pensa E, Karpowicz R, Jabaoński A, et al., 2019, Gold-Induced Desulfurization in a Bis(ferrocenyl) Alkane Dithiol, Organometallics, ISSN: 0276-7333
© 2019 American Chemical Society. Thiol-modified ferrocenes on gold have been archetypical model systems for many fundamental charge transfer and other studies, since both thiol-gold and ferrocene redox chemistry are considered to be well-understood. Thus unexpectedly, we found that for a representative of a new class of flexibly linked bis-ferrocenyl compounds, namely, 1-10-bis(1-ferrocenyl)decane dithiol, surface immobilization on gold failed. Instead, in the presence of gold, molecular decomposition took place, resulting in sulfur-based adlayers and well-defined molecular elimination products, for which we provide spectroscopic evidence. Careful control experiments and comparison with related ferrocene compounds provide insight into the mechanism of the observed elimination reactions, as a combined effect of the molecular structure and the nature of the gold/sulfur bond. These findings, thus, have a broader impact on the design of molecular adlayers, for example, in the context of surface functionalization in sensing or the synthesis of gold nanoparticles.
Leber R, Wilson L, Robaschik P, et al., 2019, Vacuum deposition of biferrocene thin films: growth strategies for stability and tuneable magnetism, 257th National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Clough TJ, Jiang L, Wong K-L, et al., 2019, Ligand design strategies to increase stability of gadolinium-based magnetic resonance imaging contrast agents, NATURE COMMUNICATIONS, Vol: 10, ISSN: 2041-1723
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- Citations: 168
Leow CH, Braga M, Bush NL, et al., 2019, Contrast vs non-contrast enhanced microvascular imaging using acoustic sub-aperture processing (ASAP): in vivo demonstration, IEEE International Ultrasonics Symposium, IUS. 2018, Publisher: IEEE, ISSN: 1948-5719
Angiogenesis plays a vital role in the progression of cancer. Non-invasive imaging techniques capable of assessing the microenvironment are therefore of clinical interest. Although highly sensitive vascular mapping has been demonstrated using ultrafast Power Doppler (PD), the detectability of microvasculature from the background noise may be hindered by the low signal-to-noise ratio (SNR) in deeper region and without the use of contrast agents. We recently developed acoustic sub-aperture processing (ASAP) processing for super-contrast vasculature imaging. This technique relies on the spatial coherence of the backscattered echoes over different acquisitions to substantially reduce the noise floor compared to the power Doppler (PD) technique. In this study, we demonstrate the feasibility of applying ASAP processing for non-contrast enhanced microvascular imaging in preclinical condition, and compare it with contrast enhanced ASAP as well as ultrafast PD. Comparing to PD, ASAP exhibit SNR improvement up to 12 dB. Higher SNR and extra visibility of smaller vessel are also demonstrated in contrast enhanced images in comparison to the non-contrast images. In conclusion, we have demonstrated the feasibility of using ASAP in vivo for non-contrast microvascular imaging, and the added benefit of using contrast agents in microvascular imaging.
Hau Leow C, Bush NL, Stanziola A, et al., 2019, High-contrast 3D in vivo microvascular imaging using scanning 2D ultrasound and acoutic sub-aperture processing (ASAP), IEEE International Ultrasonics Symposium, IUS. 2018, Publisher: IEEE, ISSN: 1948-5719
Non-invasive techniques for microvascular environment assessment are invaluable for clinical diagnosis and treatment monitoring. We recently developed a super contrast processing to suppress noise background in ultrafast Power Doppler, known an acoustic sub-aperture processing (ASAP), and demonstrate using 2D contrast enhance ultrasound. However, 2D imaging is insufficient to represent the 3D complex vascular environment. We therefore extend our study to demonstrate the feasibility of our technique for volumetric imaging. A pseudo-3D imaging technique was developed and demonstrated using a research system and preclinical transducer. A mouse liver was scanned using 2D ultrafast ultrasound and a mechanical translation stage. Initial results not only demonstrated a substantial noise reduction in 2D vascular images using ASAP, but also a high contrast volumetric rendering of a mouse liver. Our technique is ready for clinical use to provide better evaluation of angiogenesis.
Jantan KA, McArdle J, Mognon L, et al., 2019, Heteromultimetallic compounds based on polyfunctional carboxylate linkers, New Journal of Chemistry, Vol: 43, Pages: 3199-3207, ISSN: 1144-0546
A series of homo- and hetero-nuclear, bi- and trimetallic compounds are accessible using polyfunctional linkers with carboxylic acid and alkynyl or pyridyl donor combinations. This versatile approach affords reaction at a specific donor site in each case, to accommodate both ruthenium(II) or osmium(II) units and also rhenium and gold centres. Due to the orientation of the nitrogen donors of the bipyridyl moiety in 2,2′-bipyridine-4,4′-dicarboxylic acid, the metal addition must be performed in a certain sequence due to steric considerations. One example was investigated crystallographically to add to the spectroscopic and analytical characterisation performed for all complexes. Photophysical investigations reveal the effect of incorporating second or third row transition metal centres. This approach was expanded through the use of a linker bearing both carboxylic acid and alkynyl functionalities, 1,1′-ethynylferrocene carboxylic acid. This allows initial coordination of the carboxylate donors to be followed by the formation of either an acetylide or a vinyl bridge to another metal, providing access to heterotrimetallic (FeRuOs and FeRuAu) compounds as well as a heteroheptametallic Fe3Ru2Au2 example. Preliminary electrochemical studies were performed on the latter compound.
Mann PB, McGregor IJ, Bourke S, et al., 2019, An atom efficient, single-source precursor route to plasmonic CuS nanocrystals, NANOSCALE ADVANCES, Vol: 1, Pages: 522-526, ISSN: 2516-0230
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- Citations: 15
Rains JGD, ODonnelly K, Oliver T, et al., 2019, Bicarbonate inhibition of carbonic anhydrase mimics hinders catalytic efficiency: Elucidating the mechanism and gaining insight toward improving speed and efficiency, ACS Catalysis, Vol: 9, Pages: 1353-1365, ISSN: 2155-5435
Carbonic anhydrase (CA) mimics are often studied with a focus on the hydration of CO2 for atmospheric carbon capture. Consequently, the reverse reaction (dehydration of HCO3–) has received minimal attention, so much so that the rate-limiting step of the dehydration reaction in CA mimics is currently unknown. The rate-limiting step of the hydration reaction is reported to be the bicarbonate-bound intermediate step, and thus is susceptible to product inhibition. It is not, however, clear if this inhibition is a consequence of an increase in the rate of the competing dehydration reaction or resulting from the strong affinity of bicarbonate to the mimic. To address this, insight into the dehydration reaction kinetics is needed. We therefore report the most comprehensive study of a CA mimic to date. The dehydration profile of the fastest small-molecule CA mimic, ZnL1S, was characterized, and consequently evidence for the rate-limiting step for the dehydration reaction was seen to be the bicarbonate-bound intermediate step, much like the hydration reaction. This experimental validation of the rate-limiting step was achieved through a variety of methods including NMR experiments and the effect of inhibitors, substrate concentration, and metal center on activity. With this understanding, an improvement in the favorability of the rate-limiting step was achieved, resulting in decreased bicarbonate inhibition. Thus, an increase in the mimic’s kcat for both reactions was observed, resulting in the largest rate constants of any small-molecule CA mimic reported to date (28 093 and 579 M–1 s–1 for hydration and dehydration, respectively). Enzyme-like kcat/km values were obtained for ZnL1S (5.9 × 105 M–1 s–1 for CO2 hydration), and notably there is only a difference of 2.5 orders of magnitude from the enzyme, the closest of any CA mimic reported in the literature. The results from this work can be applied to the development and improvement
Wilkinson L, Massey E, Yue T, et al., 2019, Cyanoferrocenes as redox-active metalloligands for coordination-driven self-assembly, Dalton Transactions, Vol: 48, Pages: 72-78, ISSN: 1477-9234
Ferrocene-based Lewis bases have found utility as metalloligands in a wide variety of applications. The coordination chemistry of cyanoferrocenes however, is underexplored. Herein, we describe a new synthetic protocol for the generation of cyanoferrocenes. The coordination chemistry of these metalloligands to [Cu(NCMe)4][PF6], [(PPh3)2Cu(NCMe)2][PF6] and [(dppf)Cu(NCMe)2][PF6] salts has been explored, providing crystallographic evidence of cluster and polymeric forms of 1,1′- and 1,2-dicyanoferrocene complexes. The stability of the complexes and ligand dissociation were found to be strongly solvent-dependent.
Zhang G, Harput S, Shah A, et al., 2019, Photoacoustic Super-Resolution Imaging using Laser Activation of Low-Boiling-Point Dye-Coated Nanodroplets in vitro and in vivo, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, Pages: 944-947, ISSN: 1948-5719
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- Citations: 1
Lahri R, Rahman M, Hernandez-Gil J, et al., 2019, Examination of zinc ferrites vs. iron oxides as contrast agents for microwave systems, 13th European Conference on Antennas and Propagation (EuCAP), Publisher: IEEE, ISSN: 2164-3342
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- Citations: 3
Smith A, Blower P, Southworth R, et al., 2018, Synthesis, gallium-68 radiolabelling and biological evaluation of a series of triarylphosphonium-functionalized DO3A chelators, Dalton Transactions, Vol: 47, Pages: 15448-15457, ISSN: 1477-9234
Radiolabelled lipophilic cations that accumulate in mitochondria according to the magnitude of the mitochondrial membrane potential can be used to report non-invasively on mitochondrial dysfunction in cardiovascular disease, cardiotoxicity, and cancer. While several such cations are already commercially available for SPECT imaging, PET offers greater promise in terms of sensitivity, resolution, and capacity for dynamic imaging and pharmacokinetic modelling. We have therefore synthesised a series of three triarylphosphonium-functionalised DO3A chelators for positron emitter gallium-68, with differing alkyl-functionalisation motifs to provide opportunities for tunable lipophilicity as a means of optimising their pharmacokinetics. To assess their capacity to report on mitochondrial membrane potential, we assessed their pharmacokinetic profiles in isolated tumour cells and isolated perfused rat hearts before and after mitochondrial depolarisation with the ionophore CCCP. All three compounds radiolabelled with over 97% RCY and exhibited log D values of between −3.12 and −1.81. In vitro assessment of the uptake of the radiotracers in cultured tumour cells showed a three-fold increase in uptake compared to unchelated [68Ga]Ga(III). However, each complex exhibited less than 1% retention in healthy hearts, which was not significantly diminished by mitochondrial depolarisation with CCCP. This preliminary work suggests that while this approach is promising, the lipophilicity of this class of tracers must be increased in order for them to be useful as cardiac or cancer imaging agents.
Li B, Famili M, Pensa E, et al., 2018, Cross-plane conductance through a graphene/molecular monolayer/Au sandwich, Nanoscale, Vol: 10, Pages: 19791-19798, ISSN: 2040-3364
The functionalities offered by single-molecule electrical junctions are yet to be translated into monolayer or few-layer molecular films, where making effective and reproducible electrical contact is one of the challenging bottlenecks. Here we take a significant step in this direction by demonstrating that excellent electrical contact can be made with a monolayer biphenyl-4,4′-dithiol (BPDT) molecular film, sandwiched between gold and graphene electrodes. This sandwich device structure is advantageous, because the current flows through the molecules to the gold substrate in a ‘cross-plane’ manner, perpendicular to the plane of graphene, yielding high-conductance devices. We elucidate the nature of the cross-plane graphene/molecule/Au transport using quantum transport calculations and introduce a simple analytical model, which captures generic features of the current–voltage characteristic. Asymmetry in junction properties results from the disparity in electrode electrical properties, the alignment of the BPDT HOMO–LUMO energy levels and the specific characteristics of the graphene electrode. The experimental observation of scalability of junction properties within the junction area, in combination with a theoretical description of the transmission probability of the thiol–graphene contact, demonstrates that between 10% and 100% of the molecules make contact with the electrodes, which is several orders of magnitude greater than that achieved to date in the literature.
Wilson LE, Jian X, White AJP, et al., 2018, Synthesis and characterisation of linear and towards cyclic diferrocenes with alkynyl spacers, Inorganics, Vol: 6, ISSN: 2304-6740
Ferrocenediyl systems offer a motif that incorporates multiple functionality and redox-active centers, enabling these units to be used as molecular scaffolds in linear and cyclic compounds. Herein, we discuss a new modular methodology for the synthesis and incorporation of ferrocenediyl motifs within extended conjugated systems. We have synthesized a family of compounds featuring ferrocenediyl-ethynyl units with various para-substituted aromatic linkages. Extended linear, open-chain species have been isolated and understanding towards the analogous cyclic compounds gained. The new compounds have been probed using NMR, mass spectrometry, cyclic voltammetry and X-ray crystallography to gain further understanding of their structural and electronic properties.
Apps SL, White AJP, Miller PW, et al., 2018, Synthesis and reactivity of an N-triphos Mo(0) dinitrogen complex, Dalton Transactions, Vol: 47, Pages: 11386-11396, ISSN: 1477-9234
The preparation and reactivity of a novel molybdenum dinitrogen complex supported by a nitrogen-centred tripodal phosphine ligand (N-triphos, N(CH2PPh2)3, NP3Ph) are reported. Reaction of N-triphos with [MoX3(THF)3] (X = Cl, Br, I) gave the Mo(III) complex [MoX3(κ2-NP3Ph)(THF)] (1), where bidentate N-triphos coordination was observed. Reduction of this complex in the presence of dppm (bis(diphenylphosphino)methane) gave the dinitrogen complex [Mo(N2)(dppm)(κ3-NP3Ph)] (2), which exhibits moderate dinitrogen activation. An additional hydride complex, [Mo(H)2(dppm)(κ3-NP3Ph)] (4), was produced either as a minor side product during the reduction step, or as a major product by direct hydrogenation of the dinitrogen complex 2. The reactivity of the dinitrogen complex 2 with a range of Lewis acids was also investigated. At low temperatures, protic or borane Lewis acids (H+, BBr3 and tris(pentafluorophenyl)borane (BCF)) were found to coordinate to the apical nitrogen atom of the N-triphos ligand, with no conclusive evidence of any functionalisation of the dinitrogen ligand. Alkali metal Lewis acid addition to 2 resulted in the unexpected rearrangement of the N-triphos ligand to form [Mo(dppm)(PMePh2)(PCP)][B(C6F5)4] (7), where PCP, [Ph2PCNHCH2PPh2] is the carbenic ligand formed upon rearrangement from the reaction of 2 with M[B(C6F5)4] (M = Li, Na or K). Single crystal X-ray diffraction of complexes 1, 2, 4 and 7 provided structural confirmation of the N-triphos molybdenum complexes described.
Evans RJ, Hernandez-Gil J, Mohri Z, et al., 2018, DEVELOPING NEW TARGETED MOLECULAR CONTRAST AGENTS FOR IMAGING INFLAMMATION OF VULNERABLE PLAQUES, Annual Meeting of the British-Atherosclerosis-Society (BAS), Publisher: OXFORD UNIV PRESS, Pages: S3-S4, ISSN: 0008-6363
Gawne P, Man F, Fonslet J, et al., 2018, Manganese-52: applications in cell radiolabelling and liposomal nanomedicine PET imaging using oxine (8-hydroxyquinoline) as an ionophore, DALTON TRANSACTIONS, Vol: 47, Pages: 9283-9293, ISSN: 1477-9226
Wang L, Long NJ, Li L, et al., 2018, Multi-functional bismuth-doped bioglasses: combining bioactivity and photothermal response for bone tumor treatment and tissue repair, LIGHT-SCIENCE & APPLICATIONS, Vol: 7, ISSN: 2047-7538
Zeng F, Wu Y, Li X, et al., 2018, Custom-made ceria nanoparticles show a neuroprotective effect by modulating phenotypic polarization of the microglia, Angewandte Chemie International Edition, Vol: 57, Pages: 5808-5812, ISSN: 1521-3757
The neuroprotective effect of ceria nanoparticles in the context of brain disorders has been explained by their antioxidant effect. However, the in-depth mechanism remains unknown. As resident immune cells in the brain, microglia exert a variety of functional reprogramming termed as polarization in response to stress stimuli. Herein, custom-made ceria nanoparticles were developed and found to scavenge multiple reactive oxygen species with extremely high efficiency. These nanoparticles drove microglial polarization from a pro-inflammatory phenotype to an anti-inflammatory phenotype under pathological conditions. Pretreatment of these nanoparticles changed the microglial function from detrimental to protective for the neuronal cells by blocking the pro-inflammatory signaling. This work not only helps to elucidate the mechanism of ceria-nanoparticle-mediated neuroprotection but also provides a new strategy to rebalance the immuno-environment by switching the equilibrium of the phenotypic activation of microglia.
Price TW, Firth G, Eling CJ, et al., 2018, A F-18 radiolabelled Zn(II) sensing fluorescent probe, CHEMICAL COMMUNICATIONS, Vol: 54, Pages: 3227-3230, ISSN: 1359-7345
Milan DC, Al-owaedi O, Bock S, et al., 2018, Insulated molecular wires: Inhibiting orthogonal contacts in metal complex, 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Bamber J, Shah A, Bush N, et al., 2018, Photoacoustic imaging and contrast agents in cancer research, Leeds Microbubble Symposium
Leow CH, Marta B, Stanziola A, et al., 2017, Multi-Frame Rate Plane Wave Contrast-Enhance Ultrasound Imaging for Tumour Vasculature Imaging and Perfusion Quantification, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
A multi-frame rate plane wave imaging strategy is developed to simultaneously image tumor vasculature and quantify tumor perfusion. Customised imaging sequences interleaving a short but high frame rate (HFR) plane wave imaging sequence with a long but low frame rate imaging (LFR) sequence were implemented using a programmable ultrasound research platform. The results from a spatio-temporal coherence processing technique of ours demonstrated a significant improvement in the SNR and vasculature contrast when compared with the existing ultrafast Power Doppler (PD) using the same data. Initial perfusion quantification using LFR imaging was also demonstrated. Mean time intensity curve and some parametric measures were generated. Combining both structural and functional perfusion imaging using the multiframe rate sequences, a better evaluation of the tumour angiogenesis can be assessed.
Morse SV, Pouliopoulos AN, Chan T, et al., 2017, Rapid short-pulse (RaSP) sequences improve the distribution of drug delivery to the brain in vivo, IEEE UFFC, Publisher: IEEE, ISSN: 1948-5719
Focused ultrasound and microbubbles have been shown to locally and noninvasively open the blood-brain barrier. Despite encouraging results in human patients, several performance and safety features, such as poor drug distribution, high drug accumulation along vessels and small sites of red blood cell extravasation, have been unavoidable. We have recently developed a new ultrasound sequence - rapid short-pulse (RaSP) sequence - designed to suppress these adverse features by promoting safer modes of cavitation activity throughout capillaries. In our RaSP sequences, low-pressure short ultrasonic pulses are emitted at kHz pulse repetition frequencies (PRF) and grouped into bursts. We have shown in vitro that RaSP sequences prolong microbubble lifetime and increase their mobility, enhancing the distribution of acoustic cavitation activity. Here we evaluate the ability of RaSP sequences to improve the in vivo performance and safety of ultrasound-mediated drug delivery to the brain.
Leow CH, Braga M, Hernandez-Gil J, et al., 2017, Multi-frame rate plane wave contrast-enhanced ultrasound imaging for tumour vascular imaging and perfusion quantification, IEEE International Ultrasonics Symposium, IUS, Publisher: IEEE, ISSN: 1948-5719
Angiogenesis and blood flow dynamics play an important role in the development of malignant tumours and their response to treatment. While contrast enhanced ultrasound (CEUS) imaging with microbubble contrast agents as a tool for imaging angiogenesis and flow dynamics has shown great potential [1], recent development of plane wave high frame-rate (HFR) CEUS has offered new opportunities in such applications. In this study, we demonstrate an interleaved multi-frame rate plane wave CEUS imaging to quantify perfusion and to image vascular structure with improved resolution and contrast.
Lin S, Shah A, Hernandez-Gil J, et al., 2017, Notice of Removal: Optically and acoustically triggerable sub-micron phase-change contrast agents for enhanced photoacoustic and ultrasound imaging, ISSN: 1948-5719
To explore the extravascular space, sub-micron phase-change droplets show widespread interest in medical imaging and therapy with various modalities, such as ultrasound and photoacoustic. Existing studies (Wilson 2012, Wei 2014) on such dual-modality contrast agents have demonstrated the generation of both optical and ultrasound contrast after optical activation. However these studies did not explore the option of acoustic activation. Furthermore, high boiling point perfluorocarbons were used in these studies. A low boiling point may be preferred, to minimise un-wanted bioeffects, especially when activating in deeper tissues. In this study, we demonstrate a versatile phase-change sub-micron contrast agent that can provide three modes of contrast enhancement: 1) photoacoustic imaging contrast, 2) ultrasound contrast with optical activation, and 3) ultrasound contrast with acoustic activation. This would add versatility of vaporisation triggering, offering new possibilities in dual mode imaging, molecular imaging and drug delivery.
Du S, Hernandez-Gil J, Dong H, et al., 2017, Design and validation of a new ratiometric intracellular pH imaging probe using lanthanide-doped upconverting nanoparticles, Dalton Transactions, Vol: 46, Pages: 13957-13965, ISSN: 1477-9234
pH homeostasis is strictly controlled at a subcellular level. A deregulation of the intra/extra/subcellular pH environment is associated with a number of diseases and as such, the monitoring of the pH state of cells and tissues is a valuable diagnostic tool. To date, only a few tools have been developed to measure the pH in living cells with the spatial resolution needed for intracellular imaging. Among the techniques available, only optical imaging offers enough resolution and biocompatibility to be proposed for subcellular pH monitoring. We present herein a ratiometric probe based on upconversion nanoparticles modified with a pH sensitive moiety for the quantitative imaging of pH at the subcellular level in living cells. This system provides the properties required for live cell quantitative imaging i.e. positive cellular uptake, biocompatibility, long wavelength excitation, sensitive response to pH within a biologically relevant range, and self-referenced signal.
Parker D, Long NJ, Faulkner S, 2017, Challenges for chemistry in molecular imaging, Philosophical Transactions of the Royal Society A. Mathematical, Physical and Engineering Sciences, Vol: 375, ISSN: 1364-503X
Leber R, Wilson LE, Robaschik P, et al., 2017, High Vacuum Deposition of Biferrocene Thin Films on Room Temperature Substrates, Chemistry of Materials, Vol: 29, Pages: 8663-8669, ISSN: 0897-4756
Metallocenes are a promising candidate for future spintronic devices due to their versatile and tunable magnetic properties. However, single metallocenes, e.g., ferrocene, sublimate below room temperature, and therefore the implementation for future applications is challenging. Here, a method to prepare biferrocene thin films using organic molecular beam deposition (OMBD) is presented, and the effect of substrate and deposition rate on the film structure and morphology as well as its chemical and magnetic properties is investigated. On Kapton and Si substrates, biferrocene interacts only weakly with the substrate, and distinct grains scattered over the surface are observed. By incorporating a 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) seeding layer and depositing biferrocene at high deposition rates of 1.0 Å s–1, it is possible to achieve a well-ordered densely packed film. With spintronic applications in mind, the magnetic properties of the thin films are characterized using superconducting quantum interference device (SQUID) magnetometry. Whereas initial SQUID measurements show weak ferromagnetic behavior up to room temperature due to oxidized molecule fragments, measurements of biferrocene on PTCDA capped with LiF show the diamagnetic behavior expected of biferrocene. Through the successful deposition of biferrocene thin films and the ability to control the spin state, these results demonstrate a first step toward metallocene-based spintronics.
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