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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Multi-Frequency Processing for Lumen Enhancement with Wideband Intravascular Ultrasound

Carrillo, Rory A 01 September 2010 (has links)
The application of high frequency ultrasound is the key to higher resolution intravascular ultrasound (IVUS) images. The need to further improve the IVUS spatial resolution may drive the transducer center frequency even higher than the current 40 MHz range. However, increasing the center frequency may be challenging as it leads to stronger scattering echoes from blood. The high level of blood scattering echoes may obscure the arterial lumen and make image interpretation difficult. Blood backscatter levels increase with transmission center frequency at a much greater rate compared to arterial tissue. These different frequency dependencies provide a potential method to distinguish blood from tissues by means of multi-frequency processing techniques. To obtain a good blood-tissue contrast with sufficient signal-to-noise ratio, a system with a wider bandwidth is highly desirable. The method described in this paper is based on the ratio of the received signal power between the high (60 MHz) and low (25 MHz) frequency ranges from a novel 40 MHz wideband IVUS catheter. In this paper we will present our in vitro experiment work on porcine blood and a tissue-mimicking arterial wall. Results of multi-frequency processing indicate that blood, at higher frequencies, has a greater backscatter power that is 8X greater than arterial tissue, suggesting this technique will provide a greater contrast between the blood-wall lumen boundary for coronary imaging.
12

Augustinian themes in Lumen Gentium, 8

Robertson, Charles Douglas 23 October 2008
Pope Benedict XVI, since his election to the papacy, has urged Catholic clergy and theologians to interpret the documents of the second Vatican Council using a "hermeneutic of continuity." This thesis seeks to answer whether such a hermeneutic is possible by focusing on one aspect of the Dogmatic Constitution on the Church, Lumen Gentium. The methodology here employed is a critical analysis of one of the major patristic sources of Lumen Gentiums teaching, St. Augustine of Hippo. In claiming St. Augustines support for its doctrine, Lumen Gentium also offers an interpretation of his thought. For Lumen Gentiums teaching to be plausible, we must be able to conclude that Augustines teaching is essentially identical to it. In that connection, Lumen Gentiums claim that the Church is both a spiritual and visible reality forces us to consider a controverted topic in Augustinian studies: can Augustines city of God be identified with the hierarchical Church? In order to resolve that question, we will examine both the historical and eschatological aspects of the Church in Augustines thought, with some reference (treated in an appendix) to the compatibility between his theory of predestination and his ecclesiology. Further, what the Council meant when it said that the Church of Christ subsists in the Catholic Church, and whether this change in terminology, along with its implications in the field of ecumenism, can be reconciled with St. Augustines ecclesiology must be determined with a view to establishing the continuity between pre and post conciliar Catholic ecclesiology. St. Augustine developed his understanding of the nature of the Church in the early years of his ecclesiastical career through his polemical battles with the Donatist schismatics, and so the history of that schism is related in an appendix.
13

Augustinian themes in Lumen Gentium, 8

Robertson, Charles Douglas 23 October 2008 (has links)
Pope Benedict XVI, since his election to the papacy, has urged Catholic clergy and theologians to interpret the documents of the second Vatican Council using a "hermeneutic of continuity." This thesis seeks to answer whether such a hermeneutic is possible by focusing on one aspect of the Dogmatic Constitution on the Church, Lumen Gentium. The methodology here employed is a critical analysis of one of the major patristic sources of Lumen Gentiums teaching, St. Augustine of Hippo. In claiming St. Augustines support for its doctrine, Lumen Gentium also offers an interpretation of his thought. For Lumen Gentiums teaching to be plausible, we must be able to conclude that Augustines teaching is essentially identical to it. In that connection, Lumen Gentiums claim that the Church is both a spiritual and visible reality forces us to consider a controverted topic in Augustinian studies: can Augustines city of God be identified with the hierarchical Church? In order to resolve that question, we will examine both the historical and eschatological aspects of the Church in Augustines thought, with some reference (treated in an appendix) to the compatibility between his theory of predestination and his ecclesiology. Further, what the Council meant when it said that the Church of Christ subsists in the Catholic Church, and whether this change in terminology, along with its implications in the field of ecumenism, can be reconciled with St. Augustines ecclesiology must be determined with a view to establishing the continuity between pre and post conciliar Catholic ecclesiology. St. Augustine developed his understanding of the nature of the Church in the early years of his ecclesiastical career through his polemical battles with the Donatist schismatics, and so the history of that schism is related in an appendix.
14

Hollow fiber sorbents for post-combustion CO₂ capture

Lively, Ryan P. 18 January 2011 (has links)
As concerns mount about the rise in atmospheric CO₂ concentrations, many different routes to reduce CO₂ emissions have been proposed. Of these, post-combustion CO₂ capture from coal-fired power stations is often the most controversial, as the CO₂ capture system will remove generating capacity from the grid whereas many of the other solutions involve increasing the generating capacity of the grid with low CO₂-emission plants. Despite this, coal-fired power stations represent a major point source for CO₂ emissions, and if a consensus is reached on the need to reduce CO₂ emissions, a low-cost method for capturing and storing the CO₂ released by these power plants needs to be developed. The overarching goal of this research is to design and develop a novel hollow fiber sorbent system for post-combustion CO₂ capture. To achieve this goal, three objectives were developed to guide this research: i) develop a conceptual framework for hollow fiber sorbents that focuses on the energetic requirements of the system, ii) demonstrate that hollow fiber sorbents can be created, and a defect-free lumen layer can be made, iii) perform proof-of-concept CO₂ sorption experiments to confirm the validity of this approach to CO₂ capture. Each of these objectives is addressed in the body of this dissertation. Work on the first objective showed that fiber sorbents can combine the energetic advantages of a physi-/chemi-sorption process utilizing a solid sorbent while mitigating the process deficiencies associated with using solid sorbents in a typical packed bed. All CO₂ capture technologies--including fiber sorbents--were shown to be highly parasitic to a host power plant in the absence of effective heat integration. Fiber sorbents have the unique advantage that heat integration is enabled most effectively by the hollow fiber morphology: the CO₂-sorbing fibers can behave as "adsorbing heat exchangers." A dry-jet, wet-quench based hollow fiber spinning process was utilized to spin fibers that were 75wt% solid sorbent (zeolite 13X) and 25wt% support polymer (cellulose acetate). The spinning process was consistent and repeatable, allowing for production of large quantities of fibers. The fibers were successfully post-treated with an emulsion-based polymer (polyvinylidene chloride) to create a defect-free lumen side coating that was an excellent barrier to both water and gas permeation. A film study was conducted to elucidate the dominant factors in the formation of a defect-free film, and these factors were used for the creation of defect-free lumen layers. The work discussed in this thesis shows that the second objective of this work was definitively achieved. For the third objective, sorption experiments conducted on the fiber sorbents indicated that the fiber sorbents CO₂ uptake is simply a weighted average of the support material CO₂ uptake and the solid sorbent uptake. Furthermore, kinetic experiments indicate that CO₂ access to the sorbents is not occluded noticeably by the polymer matrix. Using the fiber sorbents in a simulated rapid thermal swing adsorption cycle provided evidence for the fiber sorbents ability to capture the sorption enthalpy released by the CO₂-13X interaction. Finally, a slightly more-pure CO₂ product was able to be generated from the fiber sorbents via a thermal swing/inert purge process.
15

Proteomic analysis of Arabidopsis thaliana

Granlund, Irene January 2008 (has links)
A complete proteome analysis of the chloroplast stroma, using 2D-PAGE, from spinach and Arabidopsis was performed. To improve the identification of proteins a computer program named SPECLUST was used. In SPECLUST, peak masses that are similar in many spots cluster together because they originate from the same protein with different locations on the gel. Within this program peaks in a cluster can be investigated in detail by peaks-in-common, and the unidentified masses that differ between spots in a cluster could be caused by protein modifications, which was analysed further by MS/MS. The thylakoid is an internal membrane system in the chloroplast where protein complexes involved in photosynthesis are housed. Enclosed in the thylakoid membrane is the chloroplast lumen, with a proteome estimated to contain 80-200 different proteins. Because the chloroplast lumen is close to the photosynthesis machinery in the plant, one can expect that the lumen proteome will change depending on if the plant is dark or light adapted. DIGE analysis of lumen proteins found that 15 lumen proteins show increased relative abundance in light-adapted plants. In addition co-expression analysis of lumen protein genes suggests that the lumen protein genes are uniformly transcriptionally regulated, not only by light but in a general manner. Plastocyanin is one of the proteins involved in the electron transfer in photosynthesis. Two homologous plastocyanin isoforms are encoded by the genes PETE1 and PETE2 in the nuclear genome of Arabidopsis, where PETE2 is the more abundant isoform. Knockout mutants of each of the plastocyanin isoforms shows that a 90% reduction of plastocyanin levels affects rates of photosynthesis and growth only slightly. A corresponding over-expression of plastocyanin in each of the two knockout mutants results in essentially wild-type photosynthetic performance. Reduced plastocyanin levels make the plant sensitive to Cu stress and therefore plastocyanin plays a major role as a Cu sink. A by-product of photosynthesis is hydrogen peroxide, which may be harmful for the plant. The discovery that an abundant protein found in the chloroplast lumen, TL29, shared sequence homology to Ascorbate Peroxidase (APX) was therefore of interest. We have evidence that TL29 is not an APX protein; it lacks the heme-binding active site and shows no activity. TL29 is located in the grana region and is electrostaticaly attached to the thylakoid membrane. It has four isoforms, with different pIs, both in the native and denatured form. It has no interaction with ascorbate, when compared to raAPX1. TL29 has two cysteine residues and one of them seems to have redox-regulated function, proposing that it may interact with other proteins close to PSII.
16

Effekt och Lumen mätning av LED lampor

Östling, Johan January 2018 (has links)
I denna rapport undersökts effect förbrukning och uppmätt antal Lumen för en rad olika LED-lampor, reslutatet jämförs sedan med specifikationerna för respektive lampa. Slutsatsen är att även fast det är problematiskt att mäta antalet Lumen från en lampa, så går det att uppvisa liknande resultat som förpackningen påvisar. Effektförbruknings mätningar har mindre felkällor vilket ger ett noggrannare resultat.
17

Estudo de desempenho de ferramenta computacional no cálculo da luz natural em edificações para a cidade de Juiz de Fora

São José, Juliana Amaral de 02 June 2015 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-26T12:43:06Z No. of bitstreams: 1 julianaamaraldesaojose.pdf: 7938285 bytes, checksum: d9d0facf478a36117953b78e547880e2 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-26T13:17:13Z (GMT) No. of bitstreams: 1 julianaamaraldesaojose.pdf: 7938285 bytes, checksum: d9d0facf478a36117953b78e547880e2 (MD5) / Made available in DSpace on 2017-05-26T13:17:13Z (GMT). No. of bitstreams: 1 julianaamaraldesaojose.pdf: 7938285 bytes, checksum: d9d0facf478a36117953b78e547880e2 (MD5) Previous issue date: 2015-06-02 / FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais / A demanda crescente do mercado da construção civil por edificações que possuam baixo consumo energético exige, a cada dia, respostas rápidas e soluções de projeto eficientes. O uso de software na elaboração do projeto aperfeiçoa cada vez mais este processo. O objetivo dessa pesquisa foi conhecer a melhor aplicabilidade e usabilidade do software AutodeskR EcotectTM Analysis no processo de projeto, em relação à contribuição da luz natural no ambiente construído. O referido software se apresenta como uma alternativa para auxiliar a análise de conforto durante as primeiras etapas da elaboração do projeto. Para sua análise, foram cruzados os resultados de simulações computacionais e resultados obtidos através de medições feitas no local de estudo. A contribuição após a aferição de resultados deste trabalho, está na demonstração da adequação e usabilidade de softwares de simulação na otimização do processo de projeto. Assim, este estudo nos mostra a melhor aplicabilidade do software no que diz respeito à influência da iluminação natural na concepção arquitetônica. Este processo de usabilidade e desempenho do software pode proporcionar o desenvolvimento de novas metodologias de trabalho para o processo projetual. / The increasing market of low energy building constructions demand new efficiency projects and quickly solutions. The AutodeskR EcotectTM Analysis software allows the evaluation of comfort during the early stages of project design. The aim of this research was to evaluate the software performance on the architectural project concerning the daylighting. A sequence of methodological analyses were performed to compare results from computational simulation and collected data from the study site. According to the results is possible to prove the suitability and usability of the software in the project optimization. This work shows the optimization of the software concerning the effect of daylighting on the architectonic conception. The performance and adequacy of the software leads to the development of new strategies for the design process.
18

Energy savings and maintenance optimization of energy-efficient lighting retrofit projects incorporating lumen degradation

Ikuzwe, Alice January 2020 (has links)
The lighting retrofit method is adopted as one of the solutions to reduce lighting energy consumption and improve lighting quality in existing buildings. Lighting controls and energy-efficient light sources are used to achieve the goals of the lighting retrofit. Nowadays, Light-Emitting Diodes (LEDs) are replacing traditional lighting technology owing to their high efficiency and longevity. One of the advantages of LEDs is the controllability function, which allows users to set the light level according to their preferences. This saves more energy and satisfies users’ lighting needs. However, over time, the performance of lighting retrofit projects deteriorates subject to failure of the retrofitted lights. Therefore, to maintain the performance of lighting retrofit projects, maintenance must be planned and performed. The impacts of the users’ lighting level requirements on LEDs’ life characteristics and lighting system performance are investigated by using lighting controls. Light and occupancy sensors adjust artificial light to the light level required by users and detect the presence of users in the zones, respectively. Light sensors measure the average illuminance in the zones. The measured illuminance is compared to the users’ set illuminance; if the measured illuminance is higher than the users’ set illuminance, lamps are dimmed to meet users’ lighting preference, when the measured illuminance is less than the users’ set illuminance, lamps in the zone are replaced by new ones. The dimming level in each zone at each sampling interval is used to estimate the operating junction temperature, thereafter the degradation rate and luminous flux are calculated. Light levels at workspace are modelled using the lumen method. This model helps to quantify energy savings and predict when lamps will fail to deliver the required light levels. In existing studies, users’ lighting level requirements are neglected when investigating the lifetime of the lighting system; however, users’ profile and driving schemes affect the operating conditions of a lighting system. From the simulation results, it is noted that lumen output degradation increases when the user’s set illuminance is above the illuminance required under normal operating conditions and decreases when the user’s set illuminance is below the illuminance required under normal operating conditions. Increased lumen output degradation shortens the lifetime of LEDs and reduces energy savings, while decreased lumen output degradation extends the lifetime and increases energy savings. Generally, lighting retrofit projects contain a large lighting population; investigating when each lamp will fail can be time-consuming and costly. In this research, a mathematical model is formulated to model LEDs’ failure by analysing the statistical properties of the lumen degradation rates. Based on the statistical properties of the degradation rates, the cumulative probability of failure distribution and the survival function are modelled. The formulated survival function is incorporated into the lighting maintenance optimization problem to balance energy savings and maintenance costs. A case study carried out shows that, in 10 years, the optimal lighting maintenance plan would save up to 59% of lighting energy consumption with acceptable maintenance costs. It is found that the proposed maintenance plan is more cost-effective than full maintenance. It is concluded that lumen degradation failure should be considered when investigating the performance of lighting retrofit projects, as this may not only affect energy savings but also reduce the level of illumination, which can cause visual discomfort. The initial investment costs of LEDs are still a barrier to the implementation of LED lighting systems in residential buildings. Energy-efficiency projects often face hurdles to access capital investments because decision-makers and funders do not have enough information about operational savings the project can provide and specific financial requirements applied to efficiency investment. In this research, an optimization model is formulated to give decision-makers and funders detailed information about the performance and operational savings that a LED lighting retrofit project can offer and its economic viability. The lumen degradation failure model developed is used to monitor and estimate the energy savings, and the optimal maintenance plan is scheduled to replace failed lamps. In the existing studies, the economic analysis of the lighting retrofit projects is assessed based on lighting population decay due to burnout failure while in this research economic analysis is assessed by considering the lumen degradation failure. The case study results show that the substitution of halogen light bulbs with LED light bulbs could save up to 291.4 GWh of energy consumption, and reduce 273:92 103 tons of CO2 emissions over 10-year period. The optimization model formulated is effective to help the decision-makers and funders to quantify the savings and assess the economic viability of the LED lighting retroïnˇA˛t project. This optimization model can help the decision-makers and funders to make an informed decision. / Thesis (PhD (Electrical Engineering))--University of Pretoria, 2020. / Electrical, Electronic and Computer Engineering / PhD (Electrical Engineering) / Unrestricted
19

Head-to-head comparison between endoscopic ultrasound guided lumen apposing metal stent and plastic stents for the treatment of pancreatic fluid collections: A systematic review and meta-analysis

Guzmán-Calderón, Edson, Chacaltana, Alfonso, Díaz, Ramiro, Li, Bruno, Martinez-Moreno, Belen, Aparicio, José Ramón 01 February 2022 (has links)
Background/Aims: Peripancreatic fluid collections (PFCs) result from acute or chronic pancreatic inflammation that suffers a rupture of its ducts. Currently, there exists three options for drainage or debridement of pancreatic pseudocysts and walled-off necrosis (WON). The traditional procedure is drainage by placing double pigtail plastic stents (DPPS); lumen-apposing metal stent (LAMS) has a biflanged design with a wide lumen that avoids occlusion with necrotic tissue, which is more common with DPPS and reduces the possibility of migration. We performed a systematic review and meta-analyses head-to-head, including only studies that compare the two main techniques to drainage of PFCs: LAMS vs DPPS. Methods: We conducted a systematic review in different databases, such as PubMed, OVID, Medline, and Cochrane Databases. This meta-analysis considers studies published from 2014 to 2020, including only studies that compare the two main techniques to drainage of PFCs: LAMS vs DPPS. Results: Thirteen studies were included in the meta-analyses. Only one of all studies was a randomized controlled trial. These studies comprise 1584 patients; 68.2% were male, and 31.8% were female. Six hundred sixty-three patients (41.9%) were treated with LAMS, and 921 (58.1%) were treated with DPPS. Six studies included only WON in their analysis, two included only pancreatic pseudocysts, and five studies included both pancreatic pseudocysts and WON. The technical success was similar in patients treated with LAMS and DPPS (97.6% vs 97.5%, respectively, P =.986, RR = 1.00 [95% CI 0.93-1.08]). The clinical success was similar in both groups (LAMS: 90.1% vs DPPS: 84.2%, P =.139, RR = 1.063 [95% CI 0.98-1.15]). Patients treated with LAMS had a lower complication rate than the DPPS groups, with a significant statistical difference (LAMS: 16.0% vs DPPS: 20.2%, P =.009, RR = 0.746 [95% CI 0.60-0.93]). Bleeding was the most common complication in the LAMS group (33 patients, [5.0%]), whereas infection was the most common complication in the DPPS group (56 patients, [6.1%]). The LAMS migration rate was lower than in the DPPS (0.9% vs 2.2%, respectively, P =.05). The mortality rate was similar in both groups, 0.6% in the LAMS group (four patients) and 0.4% in the DPPS group (four patients; P =.640). Conclusion: The PFCs drainage is an indication when persistent symptoms or PFCs-related complications exist. EUS guided drainage with LAMS has similar technical and clinical success to DPPS drainage for the management of PFCs. The technical and clinical success rates are high in both groups. However, LAMS drainage has a lower adverse events rate than DPPS drainage. More randomized controlled trials are needed to confirm the real advantage of LAMS drainage over DPPS drainage. / Revisión por pares
20

Analyse der Funktion von Kuzbanian und Uncoordinated 5 während der Herzzelldeterminierung und Herzlumenbildung von Drosophila melanogaster

Albrecht, Stefanie 24 January 2011 (has links)
Die Kardiogenese kann speziesübergreifend in eine distinkte Abfolge von dynamischen Entwicklungsphasen unterteilt werden. In frühen Stadien der Vertebraten-Herzentwicklung wie auch bei Drosophila melanogaster beginnt die Organogenese des Herzens mit der Selektion und Spezifizierung der Herzvorläuferzellen aus bilateral angelegtem, mesodermalem Gewebe. Anschließend resultiert die Differenzierung der determinierten Herzvorläuferzellen in bilateralen Reihen spezifischer Herzzellgruppen. Die Herzzellen migrieren in dorsale Richtung aufeinander zu und assemblieren zu einem Herzrohr. Diese dynamischen Prozesse unterliegen einem komplexen Netzwerk an hoch konservierten Regulationsmechanismen. In der vorliegenden Dissertation konnte gezeigt werden, dass die Metalloprotease Kuzbanian/ADAM10 eine Rolle während der Kardiogenese von Drosophila spielt, in dem sie die Selektion der Herzzellvorläufer aus dem kardialen Mesoderm steuert. Durch die unterbleibende Prozessierung des Notch-Rezeptors in kuzbanian Mutanten wird eine Überzahl an Herzvorläuferzellen determiniert. Weiterhin ist die Notch-abhängige asymmetrische Zellteilung in kuzbanian Mutanten fehlreguliert. Die perikardialen Herzzelllinien verschieben sich zu Gunsten der kardialen Herzzellen und resultieren in einer Hyperplasie der Kardiomyozyten. Eine weitere Phase der Kardiogenese in Drosophila ist die korrekte Ausbildung des Herzrohres und die damit einhergehenden Herzlumenbildung. Durch das Herzlumen kann die Hämolymphe durch das Herzrohr in den Körper des Tieres gepumpt werden. Die Bildung des Lumens bedingt eine stereotype Zellformänderung der Kardiomyozyten. Diese Modulierung der Zellform resultiert in halbmondförmigen Kardiomyozyten, die dorsal und ventral miteinander in Kontakt treten und so einen zentralen, luminalen Bereich umschließen – das Herzlumen. Das Rezeptor/Liganden-Paar Uncoordinated 5 (Unc5) und NetrinB ist für die korrekte Ausbildung der luminalen Kardiomyozytenseite notwendig. Es konnte gezeigt werden, dass ein Fehlen von Unc5 oder NetrinB die Kardiomyozyten in einer runden Zellform verbleiben lässt. Die Kardiomyozyten lagern sich entlang ihrer gesamten Kontaktfläche aneinander ohne dass ein Lumen entsteht. Lebendbeobachtungen an unc5 Mutanten zeigten, dass das Fehlen des Herzlumens zu einem kompletten Verlust des Hämolymphstroms führt.

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