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The emergence of coronavirus disease 2019 (COVID-19) has resulted in more than 300 million cases and 5 million deaths worldwide and innumerable economic losses. COVID-19 is acknowledged to transmit via air, but whether it is capable of transmitting via contaminated surfaces, also known as fomites, remains controversial. The overarching goal of this study was to investigate the presence and stability of SARS-CoV-2, the virus that causes COVID-19, on indoor surfaces and masks, and to provide insight into the possibility of fomite transmission. Since most transmission occurs indoors where humans spent 90% of their time, we first focused on quantifying the contamination level of SARS-CoV-2, including both viral RNA and viable virus, on commonly touched surfaces and in the heating, ventilation, and air cleaning (HVAC) systems in two university dormitories. Although we found up to 104 gene copies per ~10×10 cm2 on surfaces, we did not detect any viable virus, suggesting that the possibility of transmission via indoor surfaces is low. As universal masking has been recommended as an effective practice to prevent transmission of SARS-CoV-2, we shifted our focus to masks, both their effectiveness at filtering the virus from the air and their potential to serve as fomites. We evaluated the effectiveness of 11 face coverings for material filtration efficiency, inward protection efficiency on a manikin, and outward protection efficiency on a manikin. Masks made of filter materials, such as vacuum cleaner bag and HVAC filters, achieved a high material filtration efficiency whereas common textiles like cotton and acrylic usually showed the worst performance. The material filtration efficiency was generally positively correlated with either inward or outward protection effectiveness, but stiffer materials were an exception to this relationship as they did not fit as closely to the manikin's face and thus leaked substantially. Subsequently, we analyzed the survival of aerosolized SARS-CoV-2 in saliva on masks. Results suggested that the virus lost infectivity within one hour on an N95 respirator, surgical mask, polyester mask, and two types of cotton masks but not on a nylon/spandex mask. This study also highlighted the importance of applying virus in aerosols of realistic sizes when analyzing the stability of SARS-CoV-2 on surfaces. / Doctor of Philosophy / The emergence of coronavirus disease 2019 (COVID-19) has resulted in more than 300 million cases and 5 million deaths worldwide and innumerable economic losses. Researchers are debating if COVID-19 can transmit via surfaces contaminated with SARS-CoV-2, the virus that causes the disease. The goal of this study was to investigate whether SARS-CoV-2 is present and remains viable on indoor surfaces and masks, and to provide insight into the possibility of transmission via contaminated surfaces. Since most transmission occurs indoors where humans spent 90% of their time, we first focused on quantifying number of SARS-CoV-2 on commonly touched surfaces and in the heating, ventilation, and air cleaning (HVAC) systems in two university dormitories. Although we found a high concentration of SARS-CoV-2 genes on surfaces, we did not detect any viable virus, suggesting that the possibility of transmission via indoor surfaces is low. As universal masking has been recommended as an effective practice to prevent transmission of SARS-CoV-2, we shifted our focus to masks. We evaluated the effectiveness of 11 face coverings regarding their ability to trap viruses, protect wearers from inhaling viruses, and prevent infected individuals from expelling viruses into the surrounding air. Masks made of filter materials, such as a vacuum cleaner bag and HVAC filter, trapped the most viruses whereas common textiles like cotton and acrylic usually performed worst. It is also crucial that masks fit closely to the wearer's face to achieve better protection. Subsequently, we analyzed the ability of SARS-CoV-2 in aerosols, microscopic particles such as those exhaled by an infected person, to survive on different types of masks. Results suggested that the virus died within one hour on a majority of the masks. This study also highlighted the importance of applying aerosols of realistic sizes instead of large droplets when analyzing the survival of SARS-CoV-2 on surfaces.

Vat photopolymerization's (VP) use in large-scale industrial manufacturing is limited due to poor scalability, and limited catalogue of engineering polymers. The challenges in scalability stem from an inherent process paradox: the feature resolution, part size, and manufacturing throughput cannot be maximized simultaneously in standard VP platforms. In addition, VP's inability to process viscous and high-molecular weight engineering polymers limits the VP materials catalogue. To address these limitations, the research presented in this work was conducted in two stages: (1) Development and modeling of new VP platforms to address the scalability and viscosity challenges, and (2) Investigating the influence of using the new processes on the cured polymer network structure and mechanical properties. First, a scanning mask projection vat photopolymerization (S-MPVP) system was developed to address the scalability limitations in VP systems. The process paradox was resolved by scanning the mask projection device across the resin surface while simultaneously projecting the layer as a movie. Using actual projected pixel irradiance distribution, a process model was developed to capture the interaction between projected pixels and the resin, and predict the resulting cure profile with an error of 2.9%. The S-MPVP model was then extended for processing heterogeneous UV scattering resins (i.e. UV curable polymer colloids). Using computer vision, the scattering of incident UV radiation on the resin surface was successfully captured and used to predict scattering-compensated printing parameters (bitmap pattern, exposure time , scanning speed). The developed reverse-curing model was used to successfully fabricate complex features using photocurable SBR latex with XY errors < 1.3%. To address the low manufacturing throughput of VP systems, a recoat-less, volumetric curing VP system that fabricates parts by continuously irradiating the resin surface with a movie composed of different gray-scaled bitmap images ( Free-surface movie mask projection (FreeMMaP)) was developed. The effect of cumulative exposure on the cure profile (X,Y,Z dimensions) was investigated and used to develop an iterative gray-scaling algorithm that generated a combination of gray-scaled bitmap images and exposure times that result in accurate volumetric curing (errors in XY plane and Z axis < 5% and 3% respectively). Results of this work demonstrate that the elimination of the recoating process increased manufacturing speed by 8.05 times and enabled high-resolution fabrication with highly viscous resins or soft gels. Then, highly viscous resins were made processible in VP systems by using elevated processing temperatures to lower resin viscosity. New characterization techniques were developed to determine the threshold printing temperature and time that prevented the onset of thermally-induced polymerization. The effect of printing temperature on curing, cured polymer structure, cured polymer mechanical properties, and printable aspect ratio was also investigated using diacrylate and dimethacrylate resins. Results of this investigation revealed increasing printing temperature resulted in improvements in crosslink density, tensile strength, and printability. However, presence of hydroxl groups on the resin backbone caused deterioration of crosslink density, mechanical properties, and curing properties at elevated printing temperatures. Finally, the lack of a systematic, constraint based approach to resin design was bridged by using the results of earlier process-structure-property explorations to create an intuitive framework for resin screening and design. Key screening parameters (such as UV absorptivity, plateau storage modulus) and design parameters (such as photoinitiator concentration, polymer concentration, UV blocker concentration) were identified and the methods to optimize them to meet the desired printability metrics were demonstrated using case studies. Most work in vat photopolymerization either deal with materials development or process development and modeling. This dissertation is placed at the intersection of process development and materials development, thus giving it an unique perspective for exploring the inter-dependency of machine and material. The process models, machines and techniques used in this work to make a material printable will serve as a guide for chemists and engineers working on the next generation of vat photopolymerization machines and materials. / Doctor of Philosophy / Vat Photopolymerization (VP) is a polymer-based additive manufacturing platform that uses UV light to cure a photo-sensitive polymer into the desired shape. While parts fabricated via VP exhibit excellent surface finish and high-feature resolution, their use for commercial manufacturing is limited because of its poor scalability for large-scale manufacturing and limited selection of engineering materials. This work focuses on the development of new VP platforms, process models and the investigation of the process-structure-property relationships to mitigate these limitations and enable fabrication of performance polymers. The first section of the dissertation presents the development of two new VP platforms to address the limitations in scalability. The Scanning Mask Projection Vat Photopolymerization (S-MPVP)) was developed to fabricate large area parts with high-resolution features and the Free-surface movie mask projection (FreeMMaP) VP platform was developed to enable high-speed, recoat-less, volumetric fabrication of 3D objects. Computer-vision based models were developed to investigate the influence of these new processes on the resultant cure shape and dimensional accuracy. Process models that can: (1) predict the cure profile for given input printing parameters (error < 3%), (2) predict the printing parameters (exposure time, bitmap gray-scaling) required for accurate part fabrication in homogeneous and UV scattering resins, and (3) generate gray-scaled bitmap images that can induce volumetric curing inside the resin (dimensional accuracy of 97% Z axis, 95% XY axis), were designed and demonstrated successfully. In the second portion of this work, the use of high-temperature VP to enable processing of high-viscosity resins and expansion of materials catalogue is presented. New methods to characterize the resin's thermal stability are developed. Techniques to determine the printing temperature and time that will prevent the occurrence of thermally-induced polymerization are demonstrated. Parts were fabricated at different printing temperatures and the influence of printing temperature on the resultant mechanical properties and polymer network structure was studied. Results of this work indicate that elevated printing temperature can be used to alter the final mechanical properties of the printed part and improve the printability of the high-resolution, slender features. Finally, the results of the process-structure-property investigations conducted in this work were used to guide the development of a resin design framework that highlights the parameters, metrics, and methods required to (1) identify printable resin formulations, and (2) tune printable formulations for optimal photocuring. Elements of this framework were then combined into an intuitive flowchart to serve as a design tool for chemists and engineers.

The goal of this work was to design and build a mask projection microstereolithography (MPμSL) 3D printing system to characterize, process, and quantify the performance of novel photopolymers. MPμSL is an Additive Manufacturing process that uses DLP technology to digitally pattern UV light and selectively cure entire layers of photopolymer resin and fabricate a three dimensional part. For the MPμSL system designed in this body of work, a process was defined to introduce novel photopolymers and characterize their performance. The characterization process first determines the curing characteristics of the photopolymer, namely the Critical Exposure (Ec) and Depth of Penetration (Dp). Performance of the photopolymer is identified via the fabrication of a benchmark test part, designed to determine the minimum feature size, XY plane accuracy, Z-axis minimum feature size, and Z-axis accuracy of each photopolymer with the system. The first characterized photopolymer was poly (propylene glycol) diacrylate, which was used to benchmark the designed MPμSL system. This included the achievable XY resolution (212 micrometers), minimum layer thickness (20 micrometers), vertical build rate (360 layers/hr), and maximum build volume (6x8x36mm3). This system benchmarking process revealed two areas of underperformance when compared to systems of similar design, which lead to the development of the first two research questions: (i) 'How does minimum feature size vary with exposure energy?' and (ii) 'How does Z-axis accuracy vary with increasing Tinuvin 400 concentration in the prepolymer?' The experiment for research question (i) revealed that achievable feature size decreases by 67% with a 420% increase in exposure energy. Introducing 0.25wt% of the photo-inhibitor Tinuvin 400 demonstrated depth of penetration reduction from 398.5 micrometers to 119.7 micrometers. This corresponds to a decrease in Z-axis error from 119% (no Tinuvin 400) to 9% Z-axis error (0.25% Tinuvin 400). Two novel photopolymers were introduced to the system and characterized. Research question (iii) asks 'What are the curing characteristics of Pluronic L-31 how does it perform in the MPμSL system?' while Research Question 4 similarly queries 'What are the curing characteristics of Phosphonium Ionic Liquid and how does it perform in the MPμSL system?' The Pluronic L-31 with 2wt% photo-initiator had an Ec of 17.2 mJ/cm2 and a Dp of 288.8 micrometers, with a minimum feature size of 57.3 ± 5.7 micrometers, with XY plane error of 6% and a Z-axis error of 83%. Phosphonium Ionic Liquid was mixed in various concentrations into two base polymers, Butyl Diacrylate (0% PIL and 10% PIL) and Poly Ethylene Dimethacrylate (5% PIL, 15% PIL, 25% PIL). Introducing PIL into either base polymer caused the Ec to increase in all samples, while there is no significant trend between increasing concentrations of IL in either PEGDMA or BDA and depth of penetration. Any trends previously identified between penetration depth and Z accuracy do not seem to extend from one resin to another. This means that overall, among all resins, depth of penetration is not an accurate way to predict the Z axis accuracy of a part. Furthermore, increasing concentrations of PIL caused increasing % error in both XY plane and Z-axis accuracy . / Master of Science

Since approximately the dawn of the new millennium, neural networks and other machine learning algorithms have become increasingly capable of adeptly performing difficult, dull, and dangerous work conventionally carried out by humans in times of old. As these algorithms become steadily more commonplace in everyday consumer and industry applications, the consideration of how they may be implemented on constrained hardware systems such as smartphones and Internet-of-Things (IoT) peripheral devices in a time- and power- efficient manner while also understanding the scenarios in which they fail is of increasing importance. This work investigates implementations of convolutional neural networks specifically in the context of image inference tasks. Three areas are analyzed: (1) a time- and power-efficient face recognition framework, (2) the development of a COVID-19-related mask classification system suitable for deployment on low-cost, low-power devices, and (3) an investigation into the implementation of spiking neural networks on mobile hardware and their conversion from traditional neural network architectures. / Master of Science / The subject of machine learning and its associated jargon have become ubiquitous in the past decade as industries seek to develop automated tools and applications and researchers continue to develop new methods for artificial intelligence and improve upon existing ones. Neural networks are a type of machine learning algorithm that can make predictions in complex situations based on input data with human-like (or better) accuracy. Real-time, low-power, and low-cost systems using these algorithms are increasingly used in consumer and industry applications, often improving the efficiency of completing mundane and hazardous tasks traditionally performed by humans. The focus of this work is (1) to explore when and why neural networks may make incorrect decisions in the domain of image-based prediction tasks, (2) the demonstration of a low-power, low-cost machine learning use case using a mask recognition system intended to be suitable for deployment in support of COVID-19-related mask regulations, and (3) the investigation of how neural networks may be implemented on resource-limited technology in an efficient manner using an emerging form of computing.

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Bakgrund Vid ett prehospitalt hjärtstopp krävs utöver hjärt- och lungräddning med bröstkompressioner och defibrillering med hjärtstartare, även avancerad luftvägshantering för att skapa en fri luftväg vilket ambulanssjuksköterskan ansvarar för. Det finns en mängd olika luftvägshjälpmedel som ambulanssjuksköterskan kan använda sig av. För en del sjuksköterskor inom ambulanssjukvården kan en viss osäkerhet kring användningen av luftvägshjälpmedel finnas då de kan sakna rätt kompetens, utbildning eller ej fått tillräcklig träning i användandet för att utföra det på ett patientsäkert sätt.   Syfte Syftet med denna studie var att jämföra prehospitala luftvägshjälpmedel vid hjärtstopp utanför sjukhus i förhållande till överlevnad.   Metod Studien är en litteraturöversikt med kvantitativ ansats. Studien genomfördes genom en systematisk sökning av vetenskapliga artiklar vilka har jämfört olika luftvägshjälpmedel vid prehospitala hjärtstopp. Databaser som PubMed och CINAHL har främst använts. De utvalda artiklarna har kvalitetsgranskat.   Resultat Två huvudfynd framkom där mask- och blåsa var korrelerad till högre prevalens av överlevnad och där endotracheal intubering var korrelerad till högre prevalens att uppnå återkomst av spontan cirkulation.   Slutsats Av de inkluderade artiklarna visar resultatet på att mask- och blåsa är bästa alternativet för överlevnad och att endotracheal intubering är bästa alternativet för att uppnå återkomst av spontan cirkulation under ett prehospitalt hjärtstopp. Dock bör slutsatsen tas med försiktighet då resultaten kan skilja sig och bero på en mängd olika faktorer som skiljer sig åt i de olika studierna. / Background In addition to cardiac and pulmonary rescue with chest compressions and defibrillation with defibrillator, pre-hospital cardiac arrest also requires advanced airway management to create a clear airway for which the ambulance nurse is responsible. There are a variety of respiratory aids that the ambulance nurse can use. For some nurses in ambulance care, there may be some uncertainty about the use of respiratory aids as they may lack the right skills, education or have not received sufficient training in the use of it to perform it in a patient-safe manner.   Aim The purpose of this study was to compare prehospital airway aids in cardiac arrest outside of hospital in relation to survival.   Method The study is a literature review with a quantitative approach. The study was conducted through a systematic search of scientific articles comparing different respiratory aids at prehospital cardiac arrest. Databases such as PubMed and CINAHL have mainly been used. The selected articles have been quality checked.   Results Two main findings emerged where bag valve mask was correlated to higher prevalence to survival and where endotracheal intubation was correlated to higher prevalence to achieve return of spontaneous circulation.    Conclusion Of the included articles, the results indicate that bag valve mask is the best option for survival and that endotracheal intubation is the best option for achieving return of spontaneous circulation during a prehospital cardiac arrest. However, the conclusion should be taken with caution as the results may differ and depend on a variety of factors that differ in the different studies.

Anlässlich eines richterlichen Gutachtenauftrages zur Frage, ob das Tragen von Mund-Nase-Schutzmasken zu einer Verfälschung des Atemalkoholmesswertes zuungunsten des Angeklagten führen kann, erfolgte unter Pandemiebedingungen eine experimentelle Testreihe an 6 gesunden Proband*innen (4 Männer, 2 Frauen), die risikoarmen Freizeitalkoholkonsum betrieben. Pro Untersuchungstag wurde jeweils ein Maskentyp (Op.-Maske, Textilmaske, FFP2-Maske) untersucht. Nach Aufnahme einer individuell berechneten Menge Alkohol und einer 30-minütigen Resorptionsphase erfolgten in halbstündigen Abständen 6 aufeinanderfolgende Atemalkoholmessungen, wobei zwischen den Messungen jeweils im Wechsel eine der Masken oder keine Maske getragen wurde. Anschließend wurden Wertepaare für Zeiträume mit und ohne Maske gebildet und die stündlichen Atemalkoholabbauraten berechnet. Im Ergebnis unterschieden sich die Atemalkoholabbauraten mit und ohne Masken nicht voneinander. Fehlermeldungen durch das Atemalkoholmessgerät, die auf das vorherige Tragen einer Maske zurückzuführen sind, traten nicht auf.

The important roles of fluid dynamics in immersion lithography (IL) and step-and-flash imprint lithography (S FIL) are analyzed experimentally and theoretically. In IL there are many challenges with managing a fluid droplet between the lens and the wafer, including preventing separation of the fluid droplet from the lens and deposition of small droplets behind the lens. Fluid management is also critical in S FIL because the imprint fluid creates capillary and lubrication forces, both of which are primarily responsible for the dynamics of the template and fluid motion. The fluid flow and shape of the wafer determine how uniform the gap height between the wafer and the template is, and they affect the resistance during the alignment phase. IL was investigated as a methodology to improve laser lithography for making photomasks. The fluid flow in IL was investigated by building a test apparatus to simulate the motion of the fluid droplet during microlithographic production, and using this apparatus to conduct experiments on various immersion fluids and wafer topcoats to determine what instabilities would occur. A theoretical model was used to predict the fluid separation instabilities. Finite element simulations were also used to model the fluid droplet, and these simulations accurately predict the fluid instabilities and quantitatively agreed with the model and experiments. It is shown that the process is viable: capillary forces are sufficient to keep the fluid droplet stable, heating effects due to the laser are negligible, and other concerns such as evaporation and dissolution are manageable. Euler beam theory and the lubrication equation were used to model the bending of an S FIL template and the flow of the fluid between the template and a non-flat wafer. The template filling time, conformance of the template to the wafer, and the alignment phase are investigated with an analytical model and finite element simulations. Analysis and simulations show that uniformity of the residual film thickness and ease of proper alignment depend greatly on the planarity of the wafer, the properties of the template, and the surface tension of the fluid. / text

Title of this master thesis is “But what are you doing? Working with young people in difficult life situations focusing on the life stories.” Through practical knowledge theory, I will try to find ways to depict knowledge that cannot be fully explained in models or methods. I want to highlight what my career is about. I'm not a social worker, I'm not a therapist, a bit of an behaviourist, but without an exam. I do this by showing how I work with the individual's life stories, helping young people in vulnerable life situations to gain an understanding of their skills, abilities and interests. I have a narrative starting point in my work. By this I mean that through my conversations with young adults and their networks, are interested in how people use and relate to their life stories. I have also given some examples of how I use fictional stories like as a mask, to help the individual reflect on their own life situation. Through conversations with young adults and professional partners I have tried to show how I work for the individual to own his own process. / Genom praktisk kunskapsteori försöker jag finna vägar att gestalta den kunskap som inte fullständigt kan förklaras i modeller eller metoder. Jag vill belysa vad min yrkesroll går ut på. Jag är inte socionom, jag är inte terapeut, lite beteendevetare, men utan examen. Jag gör detta genom att visa hur jag arbetar med individens livsberättelser, hjälper unga i utsatta livssituationer att få syn på sina färdigheter, förmågor och intressen. Jag har i mitt arbete en narrativ utgångspunkt. Med det menar jag att genom mina samtal med unga och deras nätverk är intresserad av hur människor använder och förhåller sig till sina livsberättelser. Jag har också givit några exempel på hur jag använder fiktiva berättelser som mask, för att hjälpa individen att reflektera kring den egna livssituationen. Genom samtal med unga vuxna och professionella samverkansparter har jag försökt visa hur jag arbetar för att individen ska äga sin egen process.