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MANGANESE-BASED THIN FILM CATHODES FOR ADVANCED LITHIUM ION BATTERYZhimin Qi (8070293) 14 January 2021 (has links)
<p>Lithium ion batteries have been regarded as one of the most promising and intriguing
energy storage devices in modern society since 1990s. A lithium ion battery
contains three main components, cathode, anode, and electrolyte, and the
performance of battery depends on each component and the compatibility between
them. Electrolyte acts as a lithium ions conduction medium and two electrodes
contribute mainly to the electrochemical performance. Generally, cathode is the
limiting factor in terms of capacity and cell potential, which attracts significant
research interests in this field.Different
from conventional slurry thick film cathodes with additional electrochemically
inactive additives, binder-free thin film cathode has become a promising
candidate for advanced high-performance lithium ion batteries towards applications
such as all-solid-state battery, portable electronics, and microelectronics.
However, these electrodes generally require modifications to improve the
performance due to intrinsically slow kinetics of cathode materials. </p>
<p>In
this thesis work, pulsed laser deposition has been applied to design thin film
cathode electrodes with advanced nanostructures and improved electrochemical
performance. Both single-phase nanostructure designs and multi-phase
nanocomposite designs are explored. In terms of materials, the thesis focuses
on manganese based layered oxides because of their high electrochemical performance.
In Chapter 3 of the nanocomposite cathode work, well dispersed Au nanoparticles were introduced into highly
textured LiNi<sub>0.5</sub>Mn<sub>0.3</sub>Co<sub>0.2</sub>O<sub>2 </sub>(NMC532)
matrix to act as localized current collectors and decrease the charge transfer resistance.
To further develop this design, in Chapter 4, tilted Au pillars were incorporated
into Li<sub>2</sub>MnO<sub>3</sub> with more effective conductive Au
distribution using simple one-step oblique angle pulsed laser deposition. In
Chapter 5, the same methodology was also applied to grow 3D Li<sub>2</sub>MnO<sub>3</sub>
with tilted and isolated columnar morphology, which largely increase the lithium
ion intercalation and the resulted rate capability. Finally, in Chapter 6, direct
cathode integration of NMC532 was attempted on glass substrates for potential
industrial applications. </p>
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SHAPE-PRESERVING TRANSFORMATIONS OF BIO-ENABLED SILICA STRUCTURES FOR OPTICAL AND MECHANICAL APPLICATIONSSunghwan Hwang (9243854) 12 October 2021 (has links)
<p>Bio-inorganic structures have
been found to exhibit impressive optical and mechanical properties, such as control
of light and/or high fracture strength. Certain species of diatoms
(single-celled algae) form siliceous microshells (frustules) with organized structures
that affect the transmission of light or fracture strengths. It has been found
that <i>Coscinodiscus wailesii</i> diatoms
have frustules with a quasi-regular hexagonal pattern of pores, which act as
micro-lenses. In terms of mechanical strength, <i>Fragilariopsis kerguelensis</i> diatom SiO<sub>2</sub> frustules have
been observed to exhibit impressive compressive and tensile fracture stress
values. In this study, shape-preserving chemical conversion (using gas/solid
reactions) is used to transform biogenic structures (diatom frustules) into
high IR refractive index or ultrahigh specific strength materials. High-fidelity
MgO/Si, Mg<sub>2</sub>Si, Ca<sub>2</sub>Si, MgO/Ti, and Ti replicas are successfully
synthesized and characterized
by SEM, EDX, XRD, and TEM. Focal point imaging experiments are used to show that
focusing behavior of MgO/Si and Mg<sub>2</sub>Si replicas can be enhanced in
the IR range upon conversion into higher index replicas. Mechanical properties
of SiO<sub>2</sub> frustules, MgO/Ti replicas, and Ti replicas have been
measured by using in-situ and ex-situ indentation, which revealed that the
mechanical properties can be enhanced by the shape-preserved chemical
conversion of Bio-inorganic structures.</p><p><br></p>
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Designing Multifunctional Material Systems for Soft Robotic ComponentsRaymond Adam Bilodeau (8787839) 01 May 2020 (has links)
<p>By using flexible and stretchable materials in place of
fixed components, soft robots can materially adapt or change to their
environment, providing built-in safeties for robotic operation around humans or
fragile, delicate objects. And yet, building a robot out of only soft and
flexible materials can be a significant challenge depending on the tasks that
the robot needs to perform, for example if the robot were to need to exert higher
forces (even temporarily) or self-report its current state (as it deforms
unexpectedly around external objects). Thus, the appeal of multifunctional
materials for soft robots, wherein the materials used to build the body of the
robot also provide actuation, sensing, or even simply electrical connections,
all while maintaining the original vision of environmental adaptability or safe
interactions. Multifunctional material systems are explored throughout the body
of this dissertation in three ways: (1) Sensor integration into high strain
actuators for state estimation and closed-loop control. (2) Simplified control
of multifunctional material systems by enabling multiple functions through a
single input stimulus (<i>i.e.</i>, only requiring one source of input power).
(3) Presenting a solution for the open challenge of controlling both well
established and newly developed thermally-responsive soft robotic materials
through an on-body, high strain, uniform, Joule-heating energy source. Notably,
these explorations are not isolated from each other as, for example, work
towards creating a new material for thermal control also facilitated embedded
sensory feedback. The work presented in this dissertation paves a way forward
for multifunctional material integration, towards the end-goal of
full-functioning soft robots, as well as (more broadly) design methodologies
for other safety-forward or adaptability-forward technologies.</p>
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TUNABLE MULTIFUNCTIONALITIES ACHIEVED IN OXIDE-BASED NANOCOMPOSITE THIN FILMSXingyao Gao (8088647) 06 December 2019 (has links)
<p>Functional oxide-based thin films
have attracted much attention owing to their broad applications in modern
society. The multifunction tuning in oxide thin films is critical for obtaining
enhanced properties. In this dissertation, four new nanocomposite thin film
systems with highly textured growth have been fabricated by pulsed laser
deposition technique. The functionalities including ferromagnetism,
ferroelectricity, multiferroism, magnetoelectric coupling, low-field
magnetoresistance, transmittance, optical bandgap and dielectric constants have
been demonstrated. Besides, the tunability of the functionalities have been
studied via different approaches.</p>
<p>First, varies deposition
frequencies have been used in vertically aligned nanocomposite BaTiO<sub>3</sub>:YMnO<sub>3</sub>
(BTO:YMO) and BaTiO<sub>3</sub>:La<sub>0.7</sub>Sr<sub>0.3</sub>Mn<sub>3
</sub>(BTO:LSMO) thin films. In both systems, the strain coupling effect
between the phases are affected by the density of grain boundaries. Increasing
deposition frequency generates thinner columns in BTO:YMO thin films, which
enhances the anisotropic ferromagnetic response in the thin films. In contrast,
the columns in BTO:LSMO thin films become discontinuous as the deposition
frequency increases, leading to the diminished anisotropic ferromagnetic
response. Coupling with the ferroelectricity in BTO, the room temperature
multiferroic properties have been obtained in these two systems.</p>
<p> Second, the
impact of the film composition has been demonstrated in La<sub>0.7</sub>Ca<sub>0.3</sub>MnO<sub>3</sub>
(LCMO):CeO<sub>2 </sub>thin film system, which has an insulating CeO<sub>2 </sub>in
ferromagnetic conducting LCMO matrix structure. As the atomic percentage of the
CeO<sub>2 </sub>increases, enhanced low-field magnetoresistance and increased
metal-to-insulator transition temperature are observed. The thin films also
show enhanced anisotropic ferromagnetic response comparing with the pure LCMO
film.</p>
<p> Third, the
transition metal element in Bi<sub>3</sub>MoM<sub>T</sub>O<sub>9 </sub>(M<sub>T</sub>,
transition metals of Mn, Fe, Co and Ni) thin films have been varied. The thin
films have a multilayered structure with M<sub>T</sub>-rich pillar-like domains
embedded in Mo-rich matrix structure. The anisotropic magnetic easy axis and
optical properties have been demonstrated. By the element variation, the
optical bandgaps, dielectric constants as well as anisotropic ferromagnetic
properties have been achieved. </p>
<p> The studies
in this dissertation demonstrate several examples of tuning the
multifunctionalities in oxide-based nanocomposite thin films. These enhanced
properties can broaden the applications of functional oxides for advanced
nanoscale devices.</p><br>
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Acceptor Moieties With Extended Conjugation For Semiconducting PolymersXuyi Luo (12463584) 27 April 2022 (has links)
<p>New acceptor moieties with extended conjugation have been developed for further understanding of structure-property relationships in donor-acceptor type semiconducting polymers. These diketopyrrolopyrrole or isoindigo based conjugated polymers have been demonstrated as functional materials in organic field effect transistors, photoacoustic imaging and organic electrochemical transistors. With demonstrations of semiconducting molecular design, we hope to spark new research directions especially on deeper investigation of charge transport dependence on chemical structures, and new design strategies of acceptor moieties with extended conjugation could be applied for targeted applications.</p>
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Funkcionalni materijali na bazi elektrospinovanih nanovlakana / Functional materials based on electrospun nanofibersMiletić Aleksandra 01 November 2019 (has links)
<p>Funkcionalni materijali na osnovu elektrospinovanih nanovlakana nalaze sve veću primenu u raznim oblastima industrije: biomedicina, farmacija, senzori, filrtacija, ambalaža itd. Elektrospining tehnika je jedna od metoda za dobijanje materijala na osnovu nanovlakana iz polimernih rastvora korišćenjem visokog napona. Korišćenje elekrospining tehnike ima brojne prednosti u odnosu na konvencionalne tehnike, pre svega zbog lakoće inkorporacije aktivne komponente u polimernu matricu, a i specifične morfologije i 3D strukture, jer usled nanometarskih dimenzija, vlakna imaju veliki odnos specifične površine i zapremine i poroznosti, samim tim veliku kontaktnu površinu sa supstratima, reaktivnim agensima i mikroorganizmima. Zbog proizvodnje materijala na nanonivou, aktivna komponenta se fino dispergije u polimernoj matrici i time se obezbeđuje bolja aktivnost ovih materijala. Za razliku od konvencionalnih filmova, funkcionalni materijali na osnovu elektrospinovanih nanovlakana su aktivni po celoj zapremini. Cilj ove doktorske disertacije bio je optimizicija procesnih parametara elektrospininga i validacija aktivnosti funkcionalnih materijala za različite primene, što je postignuto pravilnim odabirom materijala i aktivnih komponenti, optimizacijom sastava materijala, karakterizacijom materijala adekvatnim metodama i validacijom aktivnosti materijala. Razvijeni su materijali za primenu u oblasti kozmetike, ambalaže, filtracije, senzora, stomatologije i provodnih materijala, čija je aktivnost verifikovana u laboratorijskim uslovima (TRL 4).</p> / <p>Functional materials based on electrospun nanofibers are increasingly used in various fields of industry: biomedicine, pharmacy, sensors, filtration, packaging, etc. Electrospining technique is one of the methods for obtaining nanofibers from polymer solutions using high voltage. The use of electrospinning technique has many advantages over conventional techniques, primarily because of the ease of incorporation of the active component into the polymer matrix, as well as the specific morphology and 3D structure, because due to the nanometer dimensions, the fibers have a large ratio of specific surface area to volume and porosity, and thus a high contact surface with substrates, reactive agents, and microorganisms. Due to the production of materials at the nanoscale, the active component is finely dispersed within the polymer matrix, thereby ensuring better activity of these materials. Unlike conventional films, functional materials based on electrospinned nanofibers are active throughout the volume. The aim of this PhD thesis was to optimize the electrospining process parameters and validate the activity of functional materials for various applications, which was achieved by proper selection of materials and active components, optimization of material composition, characterization of materials by appropriate methods and validation of material activity. Materials have been developed for use in the fields of cosmetics, packaging, filtration, sensors, dentistry and conductive materials, the activity of which has been verified under laboratory conditions (TRL 4).</p>
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Design and Optimization of TiO2 Nanomaterial-based Photoelectrochemical Biosensors / Photoelectrochemical BiosensingSakib, Sadman January 2023 (has links)
Recently, there has been a shift in the global healthcare paradigm, which is prioritizing a more patient-centric approach causing an increase in the demand for rapid and point-of-care (PoC) biomolecular detection. Electrochemical (EC) signal transduction has been used to great effect to meet some of this demand by constructing biosensors with high sensitivity and low limit-of-detection (LOD). However, signal generation in EC biosensors requires input bias potentials to activate electrochemical redox reactions. This means EC systems are inherently built-in with high background noise that limits the performance of biosensors. Biosensors with photoelectrochemical (PEC) signal transduction have recently shown great promise in being able to deliver biomolecular detection on par with, if not better than, EC biosensors. PEC biosensing directly improves upon EC signal transduction by combining EC signal readout with optical excitation as the bias input, and generally being able to achieve similar performance with simpler bioassay designs. In this scheme, the input and output of the signal transduction are decoupled from each other, significantly reducing background signal in biosensors to enhance their sensitivity. Despite being highly effective, PEC biosensors have yet to find commercial breakthrough as they have so far only shown quantitative analysis on a limited set of biomarkers and have not shown to be PoC-capable. In this thesis, we developed new strategies to improve PEC signal transduction so that it could be applied to build robust ultrasensitive PoC biosensors with high dynamic range, simple operation, and low LOD for detecting a wide variety of different disease biomarkers.
The most popular photoactive materials used in the fabrication of PEC biosensors are TiO2 nanomaterials on account of their availability, chemical stability, high catalytic efficiency, tunable morphology, and ideal band energy levels for driving useful EC reactions. However, unmodified TiO2 suffers from several drawbacks that limit its photocurrent generation efficiency, such as poor visible range absorbance due its wide bandgap and fast charge carrier recombination. Alongside the additional difficulty of biofunctionalization, PEC biosensors fabricated from TiO2 nanomaterials are limited in their bioanalytic performance. In order to make improvements on PEC biosensors, we modified the surface of TiO2 nanomaterials by chelating them with catecholate molecules. The surface modification with catecholates formed charge transfer complexes on TiO2, which resulted in enhanced photoexcitation due to enhanced electron injection attributable to intermolecular orbital excitations in the catecholate molecules. The catecholate ligands also added improved colloidal stability and additional functional groups that aided with biofunctionalization. This resulted in multifunctional TiO2 nanoparticles with improved photocurrent signal generation and enhanced visible range photoabsorption. We took this one step further by taking advantage of the high binding affinity of catecholates on TiO2 surfaces to create novel synthesis methods that created high surface area nanostructures. Photoelectrodes fabricated from these new TiO2 nanostructures had nanoporous morphology and were able to capture biomolecules more efficiently. Using our novel TiO2 nanomaterials, we fabricated signal-off biosensors that were able to detect DNA biomarkers and IL-6 protein (cancer and inflammatory biomarker) in urine with an LOD of 1.38 pM and 3.6 pg mL-1, respectively.
We further explored hybrid semiconductor structures by combining TiO2 nanomaterials with other materials such semiconductors with different bandgaps or plasmonic metal nanoparticles (NP). Using the aforementioned catechol-assisted synthesis techniques, we were able to produce different morphologies of TiO2 nanomaterials with distinct phases: anatase TiO2 nanorod assemblies and rutile TiO2 NP. The two different TiO2 nanomaterials have different bandgaps and can be used to form semiconductor heterostructures. By combining rutile TiO2 NPs with DNAzymes, a type of synthetic functional nucleic acid, we created a photoactive molecular switch that worked by making and breaking heterostructures between the two TiO2 nanomaterials. We used DNAzymes specific to E. coli bacteria to develop a highly sensitive signal-on bacterial detection platform that was able to detect E. coli in lake water samples with an LOD of 18 CFU mL-1. Using catecholate-assisted photoreduction synthesis, we developed an efficient and novel method for decorating TiO2 NP with silver (Ag) NP. The resultant nanomaterial featured TiO2 NP surfaces modified with Hematoxylin (HTX) dyes and covered with sub-nanometer sized silver NP. The band structure of TiO2/HTX/Ag NP hybrid material involved high energy electron generation through decay of surface plasmons in the Ag NP and then enhancing the photoelectron injection process between HTX and TiO2. This significantly enhances the photoexcitation and photoabsorbtion, resulting in the material with the highest photocurrent generation as presented in this thesis. By taking advantage of thiol-metal bonds, we used the TiO2/HTX/Ag NP material system in the fabrication of a highly sensitive signal-off microRNA (prostate cancer biomarker) sensor with an LOD of 172 fM in urine.
Special attention was paid to the design of PEC bioassays in this work so that they are miniaturized and easy to use, and thus suitable for PoC applications. Because PEC signal transduction generates ultrahigh signals compared to other transduction methods, it allows bioassay designs to remain simple without sacrificing performance. This allowed us to create bioassays with very few operational steps, that excel in reliability and ease-of-use. To further improve PoC capability, we explored multiplexing with the biosensor made from TiO2/HTX/Ag NP. Here we were able to demonstrate multiplexing with PEC signal transduction for the first time. Another major barrier to PEC biosensors becoming widespread is the requirement of large benchtop instrumentation such as potentiostats and light sources. To address this challenge, we designed a portable smartphone-interfacing potentiostat with a built-in LED light source to support PEC biosensing. This device, named the PECsense was as versatile as any commercial potentiostats, having features such as adjustable recording periods, variable illumination periods, automatic data processing and being able to record both anodic and cathodic photocurrents. The PECsense was demonstrated to be used successfully as a signal reader in a PEC DNA detection assay.
Ultimately, we designed several ultrasensitive PEC biosensors used for the detection of four different diagnostic biomarkers. Combined with the exploration of miniaturized design, multiplexing and portable signal-reading, our designed PEC biosensors were made PoC-capable. The work in this thesis presented innovations in areas of nanotechnology, material synthesis, solid-state physics, biotechnology and embedded systems for the advancement of biomolecular detection and PoC diagnostics. / Thesis / Doctor of Philosophy (PhD) / Biosensors show great promise for use in point-of-care diagnostics and health monitoring systems. Such deceives combine biorecongition with signal transduction for analyzing biologically relevant targets. Photoelectrochemical (PEC) mode of signal reading, particularly those based on TiO2 nanomaterials, have shown great promise in delivering point-of-care biosensors that have excellent diagnostic performance. In this thesis, our goal was to develope new techniques for creating low-cost, easy-to-use and ultrasensitive photoelectrochemical biosensors. To achieve this goal, our work here can broadly be split into three objectives. Firstly, we focused on developing new material synthesis methods to improve traditional TiO2 nanomaterials so they can be more useful in PEC biosensors. These methods involved combining TiO2 with organic molecules known as catecholates and metal nanoparticles. This work created material systems that are able to generate high signals and more easily interface with biomolecules for improving PEC biosensor sensitivity. For the second objective, we used our newly developed enhanced TiO2 nanomaterials as the foundation for designing various bioassays for the detection of a wide range of different biological targets such as DNA, RNA, proteins and bacteria. This served to demonstrate the robustness of PEC signal reading as a tool for various markers of diseases. Despite PEC biosensors being a powerful tool in healthcare, they have seen very little commercial breakthrough, which can primarily be attributed to needing bulky benchtop instruments and light sources for signal reading. For the last objective, we worked on designing a handheld smartphone-operated signal-reader for PEC biosensing with its own built-in light source.
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ORGANIC IONO-OPTOELECTRONICSKe Chen (17382961) 13 November 2023 (has links)
<p dir="ltr">Conjugated polymers are organic macromolecules that are characterized by a backbone chain of alternating double- and single-bonds. This alternating pattern results in delocalized π electronic systems, contributing to electronic conduction. In the solid state, conjugated polymers exhibit weak intermolecular interactions, rendering them soft nature in comparison to many of their inorganic counterparts, such as silicon, which consist of ‘hard' three-dimensional networks of rigid covalent bonds. In electrolyte, this weak intermolecular interaction creates free pathways for ion penetration and facilitates mixed ionic-electronic coupling. The ionic-electronic coupling of conjugated polymers impacts nearly all their properties, including light absorption, electronic conductivity, mechanical strength, etc.</p><p dir="ltr">Organic iono-optoelectronics represent a class of devices where the ionic-electronic coupling in conjugated polymers can be synergistically or independently controlled by light irradiation and electrical voltage, enabling multimode electronic and optical functionalities. This dissertation explores two types of organic iono-optoelectronic devices: electrochromic devices and artificial eyes. In electrochromic devices, the ionic-electronic coupling is dynamically modulated by electrical voltage, which induces optical changes of conjugated polymers for applications in information visualization, thermal management, camouflage, etc. Conversely, artificial eyes utilize optical stimulation to tailor the electronic-ionic coupling, with electrical potential changes serving as readout. This paradigm shift opens the door to the development of light-driven biomedical electronics and intelligent visual systems. In the development of electrochromic devices, we introduce two strategies that expand the color palette and enhance the optical control of electrochromic devices, promoting their potential use in display and camouflage. In the development of artificial eye development, we introduce an electrochemical transistor device with integrated functions of light perception, memorization, and recognition by leveraging photon-modulated ion-electronic coupling. This device demonstrates great potential for intelligent visual systems and promises future optoelectronic neural interfaces.</p>
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Selective Deposition of Conductive Inks Onto Rough Polymer Composites Using Drop-On-Demand Inkjet PrintingEric Jacob Williamson (17060409) 20 February 2024 (has links)
<p dir="ltr">Inkjet printing allows for rapid prototyping and design iteration that traditional printing methods do not. The use of inkjet printing for electronic devices has seen increased use in recent years owing to its high precision and ability to quickly test new devices. However, nearly all of this work has been done on smooth substrates with surface roughnesses on the nano scale. To further explore the capabilities of inkjet printing on rough surfaces, electrically conductive ink was printed onto a variety of solids-loaded polymer composite substrates using varied filler particle sizes with surface roughnesses on the micron scale. This work examines the necessary parameters required to print on these rough surfaces and characterizes the electrical properties of deposited ink. Electrical conductivity was demonstrated on surfaces across five distinct substrates using varied particle sizes. Further, two functional devices in the form of a heater and a strain gauge were printed and tested on these substrates. These devices showed comparable performance to commercially available devices. These findings offer improved ability to use inkjet technology on a variety of substrates and have implications in multiple fields. This demonstration of basic conductivity and advanced functionality shows the potential to continue development of complex devices and integrate them into new substrates. The optimization of printing algorithms on these rough surfaces also has significant potential to improve printability on rough surfaces and further expand capabilities.</p>
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Multi-functional PAN based composite fibersChien, An-Ting 07 January 2016 (has links)
Various nano-fillers can introduce specific functions into polymer and expand their application areas. Myriad properties, such as mechanical, electrical, thermal, or magnetic properties can be combined with original polymer characteristics, including flexible, light weight, and ease of use. These composites can be used to produce multi-functional fibers as the next generation textile or fabrics. In this research, Polyacrylonitrile (PAN) is adopted as the main polymer with different nano-fillers, such as carbon nanotube (CNT), iron oxide nanoparticle, and graphene oxide nanoribbon (GONR). Using gel-spinning technology, PAN-based composite fibers are fabricated in single- or bi-component fibers. Fibers are also characterized for their structure, morphology, mechanical properties, as well as for their electrical, thermal, or magnetic properties. For example, bi-component fibers with polymer sheath and polymer-CNT core as well as polymer-CNT sheath and polymer core are processed. With electrical and thermal conductivity introduced by CNT, such bi-components fibers can be applied for wearable electronics or for thermal management. Joule-heating effect owing to applied electrical current on single component PAN/CNT fibers is also investigated. With controllable electrical conductivity and fiber temperature, this active functional fiber can be applied for temperature regulation fibers or new carbon fiber manufacturing process. Another example is magnetic fiber with superparamagnetic iron oxide nano-particles. These novel magnetic fibers with high strength can be used for actuator, inductors, EMI shielding, or microwave absorption. GONR is also discussed and used to reinforce PAN-based fibers. Several theoretical models are considered to analyze the observed results.
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