Synthesis of biphasic Al/Al2O3 nanostructures under microgravity and laser structuring on Al/Al2O3 surfaces for selective cell guidance

The first part of this thesis is dealing with gravity effect on the synthesis of biphasic core/shell Al/Al2O3 composites. By chemical vapor deposition of the precursor [tBuOAlH2]2 at 400°C, only spherical nanoparticles were observed on the substrate surface. The formation of nanowires was observed at 600°C. It is a good agreement with our previous results on earth condition and there is no gravity impact on the chemical reaction. At increased gravity levels, the nanoparticles formed large clusters and the nanowires showed bundle formation while the nanowires at microgravity have predominantly linear structures. It is proposed that the chaotic nature of nanowires and cluster formation of nanoparticles were caused by a dominance of gravity over the thermal creep. In the second part the use of Al/Al2O3 nanowire layers for bio applications is considered. Contact cell guidance and alignment were studied to understand how cells recognize and respond to certain surface patterns. Linear micro channels were created on Al/Al2O3 layer by direct laser writing and laser interference patterning. Although surface topography was altered, the surface chemistry was always identical (Al2O3) due to the unique core/shell nature of Al/Al2O3 nanowires. Human osteoblast, normal human dermal fibroblast and neuronal cells were cultured and investigated. The results indicate that different cell types show diverse responses to the topography independent from the surface chemistry of the material.Der erste Teil dieser Dissertation behandelt die Wirkung der Schwerkraft auf die Herstellung biphasischer Kern-Hülle Al/Al2O3 Verbundwerkstoffen. Bei der chemischen Gasphasenabscheidung des Präkursor [tBuOAlH2]2 wurden bei 400° C nur sphärische Nanopartikel auf der Substratoberfläche beobachtet. Bei 600° C wurde die Bildung von Nanodrähten beobachtet. Dies bestätigt unsere früheren Ergebnisse. Bei erhöhter Schwerkraft bildeten die Nanopartikel große Cluster und die Nanodrähte formten Bündel. In Schwerelosigkeit wiesen die Nanodrähte meist lineare Strukturen auf. Eine mögliche Erklärung für das chaotische Verhalten der Nanodrähte und das Formen der Cluster könnte eine Dominanz der Schwerkraft gegenüber dem thermischen Kriechen sein. Der zweite Teil behandelt die Verwendung der Al/Al2O3- Nanodrähte als Beschichtungen für Bioanwendungen. Das gerichtete Wachstum von Zellen wurde untersucht um zu verstehen wie Zellen verschiedene Strukturen erkennen und darauf reagieren. Dazu wurden Kanäle auf den Beschichtungen durch direktes Laserschreiben und Laserinterferenzstrukturieren erzeugt. Dabei wurde nur die Topografie verändert. Die Oberflächenchemie (Al2O3) blieb durch den einzigartigen Kern-Hülle Charakter der Beschichtung immer identisch. Menschliche Osteoblast-, Fibroblast- und Nervenzellen wurden kultiviert und untersucht. Die Ergebnisse zeigen, dass bei gleichbleibender Oberflächenchemie die Zellantwort verschiedener Zelltypen unterschiedlich von der Topografie abhängig ist

Experimentally validated heat exchanger refrigerant charge model and optimization of refrigerant charge for a heat pump

Refrigerant charge affects the efficiency, capacity, and reliability of a heat pump, and incorrect charge can lead to increased energy consumption and decreased performance as well as potential damage to the system. Furthermore, refrigerant charge has an environmental impact, with high Global Warming Potential (GWP) refrigerants contributing to climate change. The HVAC&R society is adopting low-GWP refrigerants to alleviate the concern. For these reasons, accurate prediction of refrigerant charge is vital in designing heat pumps, particularly for low-GWP refrigerants; this charge prediction is done by charge models.Meanwhile, existing charge models are limited in their charge prediction accuracy due to uncertainty in void-fraction models the charge models rely on for charge prediction. Experimental charge validation data can improve the accuracy of the charge model, but such data for low-GWP refrigerant charge is rare in the open literature.The goal of this study is to address the issue by improving the accuracy of charge prediction; that is done by creating a high-accuracy charge model that is verified by experimental charge validation data. To gather this experimental charge data, a novel charge measurement method and charge measurement facility for measuring charge is created, resulting in high-fidelity experimental charge data for heat exchangers across various operating conditions of heat pumps. This database includes multiple refrigerants, including low-GWP refrigerants, R1234yf and R468C, and additional R410A as a reference. Employing this experimental data, a high-accuracy charge model is developed and validated, which is used to optimize the charge and cooling capacity of a heat pump simultaneously on a developed multi-objective optimization framework

CFD Case Study: Heat Exchanger Inlet Air Velocity Distribution for Ducted Tests in a Psychrometric Chamber (ASHRAE RP-1785)

This paper presents the airside analysis of coil duct configurations using Computational Fluid Dynamics (CFD) to determine which configuration best mitigates airside maldistribution for ASHRAE RP-1785. RP-1785 has a global objective of providing accurate refrigerant charge and oil retention data for residential coils, collected in a controlled experiment. The final test matrix of the study includes several representative residential indoor and outdoor coils to be tested at various refrigerant and airside inlet conditions. The coil performance, charge, and oil retention behavior is strongly influenced by the airflow; therefore the uniform airflow distribution to coils is critical to RP-1785 to maintain a well-controlled experiment. Analysis of four 3D CFD cases are presented with the largest coil of the initial test matrix (105.6 in (268.2 cm) length, 40 in (101.6 cm) height, 5 in (12.7 cm) depth) installed in the Oklahoma State University psychrometric chambers. The simulation domain was extended to include the airflow characteristics within the psychrometric chamber to determine the effect of the asymmetric air inlet boundary condition. The analysis concluded the three significant factors affecting the airflow uniformity: the distance between the duct and wall, the distance between the duct and chamber floor, and the upward incoming airflow area of the floor. The CFD study results are used to inform the design of the duct to be used for coil testing in RP-1785 and the final duct design is presented

Guidewire insertion into the vertebral vein during right internal jugular vein central venous catheterization -A rare case report-

Background Internal jugular veins are the most frequently accessed site for central venous catheterization in patient management, whereas complications involving vertebral veins are a rare occurrence. Case A 73-year-old male suspected to have a urothelial carcinoma was scheduled for elective left nephroureterectomy. During central venous catheterization using the anatomic landmark technique to target the internal jugular vein, a guidewire is inadvertently inserted into the suspected vertebral vein. Following the correction of the catheterization, a radiologist reviewed the preoperative enhanced computed tomography and confirmed that the initially punctured vessel was the vertebral vein. On the third day after surgery, the central venous catheter was removed, and the patient did not exhibit any complications, such as bleeding, swelling, and neurological symptoms. Conclusions The use of ultrasonography during central venous catheterization is recommended to evaluate the anatomy of the puncture site and prevent misinsertion of the catheter, which can lead to several complications

Recombinant phage coated 1D Al2O3 nanostructures for controlling the adhesion and proliferation of endothelial cells

A novel synthesis of a nanostructured cell adhesive surface is investigated for future stent developments. One-dimensional (1D) Al2O3 nanostructures were prepared by chemical vapor deposition of a single source precursor. Afterwards, recombinant filamentous bacteriophages which display a short binding motif with a cell adhesive peptide (RGD) on p3 and p8 proteins were immobilized on these 1D Al2O3 nanostructures by a simple dip-coating process to study the cellular response of human endothelial EA hy.926. While the cell density decreased on as-deposited 1D Al2O3 nanostructures, we observed enhanced cell proliferation and cell-cell interaction on recombinant phage overcoated 1D Al2O3 nanostructures. The recombinant phage overcoating also supports an isotropic cell spreading rather than elongated cell morphology as we observed on as-deposited Al2O3 1D nanostructures

Synthesis of biphasic Al/Al2O3 nanostructures under microgravity and laser structuring on Al/Al2O3 surfaces for selective cell guidance

The first part of this thesis is dealing with gravity effect on the synthesis of biphasic core/shell Al/Al2O3 composites. By chemical vapor deposition of the precursor [tBuOAlH2]2 at 400°C, only spherical nanoparticles were observed on the substrate surface. The formation of nanowires was observed at 600°C. It is a good agreement with our previous results on earth condition and there is no gravity impact on the chemical reaction. At increased gravity levels, the nanoparticles formed large clusters and the nanowires showed bundle formation while the nanowires at microgravity have predominantly linear structures. It is proposed that the chaotic nature of nanowires and cluster formation of nanoparticles were caused by a dominance of gravity over the thermal creep. In the second part the use of Al/Al2O3 nanowire layers for bio applications is considered. Contact cell guidance and alignment were studied to understand how cells recognize and respond to certain surface patterns. Linear micro channels were created on Al/Al2O3 layer by direct laser writing and laser interference patterning. Although surface topography was altered, the surface chemistry was always identical (Al2O3) due to the unique core/shell nature of Al/Al2O3 nanowires. Human osteoblast, normal human dermal fibroblast and neuronal cells were cultured and investigated. The results indicate that different cell types show diverse responses to the topography independent from the surface chemistry of the material

Synthese von zweiphasigen Al/Al2O3 Nanostrukturen unter Mikrogravitation und Laser-Strukturierung auf Al/Al2O3 Oberflächen für die selektive Zellführung

The first part of this thesis is dealing with gravity effect on the synthesis of biphasic core/shell Al/Al2O3 composites. By chemical vapor deposition of the precursor [tBuOAlH2]2 at 400°C, only spherical nanoparticles were observed on the substrate surface. The formation of nanowires was observed at 600°C. It is a good agreement with our previous results on earth condition and there is no gravity impact on the chemical reaction. At increased gravity levels, the nanoparticles formed large clusters and the nanowires showed bundle formation while the nanowires at microgravity have predominantly linear structures. It is proposed that the chaotic nature of nanowires and cluster formation of nanoparticles were caused by a dominance of gravity over the thermal creep. In the second part the use of Al/Al2O3 nanowire layers for bio applications is considered. Contact cell guidance and alignment were studied to understand how cells recognize and respond to certain surface patterns. Linear micro channels were created on Al/Al2O3 layer by direct laser writing and laser interference patterning. Although surface topography was altered, the surface chemistry was always identical (Al2O3) due to the unique core/shell nature of Al/Al2O3 nanowires. Human osteoblast, normal human dermal fibroblast and neuronal cells were cultured and investigated. The results indicate that different cell types show diverse responses to the topography independent from the surface chemistry of the material.Der erste Teil dieser Dissertation behandelt die Wirkung der Schwerkraft auf die Herstellung biphasischer Kern-Hülle Al/Al2O3 Verbundwerkstoffen. Bei der chemischen Gasphasenabscheidung des Präkursor [tBuOAlH2]2 wurden bei 400° C nur sphärische Nanopartikel auf der Substratoberfläche beobachtet. Bei 600° C wurde die Bildung von Nanodrähten beobachtet. Dies bestätigt unsere früheren Ergebnisse. Bei erhöhter Schwerkraft bildeten die Nanopartikel große Cluster und die Nanodrähte formten Bündel. In Schwerelosigkeit wiesen die Nanodrähte meist lineare Strukturen auf. Eine mögliche Erklärung für das chaotische Verhalten der Nanodrähte und das Formen der Cluster könnte eine Dominanz der Schwerkraft gegenüber dem thermischen Kriechen sein. Der zweite Teil behandelt die Verwendung der Al/Al2O3- Nanodrähte als Beschichtungen für Bioanwendungen. Das gerichtete Wachstum von Zellen wurde untersucht um zu verstehen wie Zellen verschiedene Strukturen erkennen und darauf reagieren. Dazu wurden Kanäle auf den Beschichtungen durch direktes Laserschreiben und Laserinterferenzstrukturieren erzeugt. Dabei wurde nur die Topografie verändert. Die Oberflächenchemie (Al2O3) blieb durch den einzigartigen Kern-Hülle Charakter der Beschichtung immer identisch. Menschliche Osteoblast-, Fibroblast- und Nervenzellen wurden kultiviert und untersucht. Die Ergebnisse zeigen, dass bei gleichbleibender Oberflächenchemie die Zellantwort verschiedener Zelltypen unterschiedlich von der Topografie abhängig ist

Placental Abruption with Subamniotic Hemorrhage: A Case Report

Background: Subamniotic hemorrhage is a rare lesion with abnormal ultrasonographic findings that is caused by placental abruption. We report the case of a patient with placental abruption who presented with antepartum bleeding in whom the ultrasound findings of subamniotic hemorrhage were detected. This resulted in early diagnosis, leading to a favorable clinical outcome in this patient. Case: A primigravid 35-year-old woman visited the emergency room due to vaginal bleeding at 36 + 4 weeks of gestation. Ultrasound examination revealed a subamniotic hemorrhage that had not been evident on previous antenatal ultrasonography. An emergent cesarean section was performed, and the diagnosis of placental abruption was confirmed. The patient and baby were discharged after an uneventful course in the hospital. Conclusions: Detection of subamniotic hemorrhage by ultrasound helped in achieving an early diagnosis that resulted in prompt intervention against acute placental abruption and ensured favorable clinical outcomes. A thorough ultrasound examination of the placenta should be performed when managing patients with antepartum bleeding

Micro-/nanostructured alumina as model surface to study topography effects on cell-surface interactions

[no abstract available