No description available.

Multiple-mouse MRI (MMMRI) accelerates biomedical research by imaging multiple mice simultaneously. To date, MMMRI has been explored in three ways: shielded transmit-receive coils, shielded transmits coil with separate unshielded receive coils; and finally shielded transmit-receive coils with independent gradient coils. However alternative transmit coil configurations and possible benefits of eliminating shielding have not yet been explored. The goal of this thesis is to test possible radiofrequency configurations with and without shielding for the purpose of improving image quality for MMMRI. Results demonstrate that using an unshielded transmit-receive coil array provided a 20% improvement over an identical shielded coil. A new unshielded 7-coil MMMRI array is presented, minimizing the ghosting between image overlap using mutual inductance minimization and a sensitivity encoding (SENSE) reconstruction. The final array provided high resolution images (90µm) of up to seven live mice simultaneously with appropriate signal-to-noise for automated analysis.

Multiple-mouse MRI (MMMRI) accelerates biomedical research by imaging multiple mice simultaneously. To date, MMMRI has been explored in three ways: shielded transmit-receive coils, shielded transmits coil with separate unshielded receive coils; and finally shielded transmit-receive coils with independent gradient coils. However alternative transmit coil configurations and possible benefits of eliminating shielding have not yet been explored. The goal of this thesis is to test possible radiofrequency configurations with and without shielding for the purpose of improving image quality for MMMRI. Results demonstrate that using an unshielded transmit-receive coil array provided a 20% improvement over an identical shielded coil. A new unshielded 7-coil MMMRI array is presented, minimizing the ghosting between image overlap using mutual inductance minimization and a sensitivity encoding (SENSE) reconstruction. The final array provided high resolution images (90µm) of up to seven live mice simultaneously with appropriate signal-to-noise for automated analysis.

No description available.

Universiẗat, Diss., 2005--Würzburg.

Techn. Hochsch., Diss., 2004--Aachen.

Research on angiogenesis has been focused on developing anti-angiogenic therapies to target endothelial cell-specific signalling pathways, as a mean to limit tumour outgrowth and metastasis. One of the main targets is the endothelial cell-specific Tie2 receptor and its ligands, the angiopoietins, which controls the later stages of angiogenesis. Although the angiopoietin/Tie2 signalling pathways have been well characterized, the molecular mechanism by which the ligands regulate Tie2 activity remains unclear. To address this question, we determined whether the activation mechanism of Tie2 is induced by dimerisation alone, or whether subsequent relative rotation of the kinase domain is required. Here we employed a coiled-coiled based protein engineering approach to identify the relative orientations of the kinase domains that are optimal for Tie2 activation. By replacing the extracellular domain of Tie2 with the dimeric parallel coiled-coil motif Put3cc, we generated ligand-independent homodimers of the kinase domains Put3cc-Tie2 I-VII that have distinct orientations. We show that dimerisation is sufficient to induce Tie2 activation and downstream activation of Akt, and that varying the interface of the kinase domain in Tie2 dimers can increase its catalytic efficiency. In addition we examined for the presence of potential dimerisation within the transmembrane and intracellular domain of Tie2. We show that the KD and potentially the TM contain dimerisation motifs that stabilise Tie2 in the inactive and active conformations. In addition, we show that deletion of the potential coiled-coil motif in the JM does not disrupt dimerisation but decreases the catalytic efficiency of Tie2. Finally, we propose that the activation mechanism of Tie2 may be similar to the previously described asymmetric dimer formation of EGFR and FGFR receptors.

Master of Science / Department of Mechanical and Nuclear Engineering / Donald L. Fenton / Today air cooled chillers are often used in industrial applications where chilled water is pumped through processes or laboratory equipment. Industrial chillers are used for the controlled cooling of products, mechanisms and factory machinery in a wide range of industries. However, there is limited information on condenser coil design for a simulated model that uses R407c in a process chiller system with a focus on the finned tube condenser design. Therefore, a simulation tool that evaluates the performance of a condenser design, e.g. frontal area, cost, and overall system efficiency would be very useful. An optimization calculator for the air cooled fin-tube condenser design was developed. This calculator allows a user to specifically select the condenser geometric design parameters including the overall condenser length and height, number of rows, number of circuits, row and tube spacing, fin thickness, fin density, tube inner and outer diameters, and the quantity and power of the fan motors. This study applied the calculator finding an optimum condenser design for various frontal areas and cost constraints. The calculator developed is appropriate for engineering designers for use in the process chiller industry.

No description available.

Magnetic nerve stimulation is a non-invasive method of exciting a neural tissue which can be achieved by exposing the body to a transient magnetic field. This field is generated by passing a high current through a coil over a short period of time. By positioning this coil in a specific orientation over the targeted nerve, the time variation of the magnetic field will create an electric field in the conductive milieu of the body. Induced currents will result from that electric field. If those currents reach a certain amplitude within a specific time period this will cause a neural depolarization. This depolarization will enable us to test and examine the excited nerve which will provide us with the necessary data for an effective treatment. In my thesis I will analyse the benefits of magnetic nerve stimulation with the objective of designing a coil that provides a focussed magnetic field. This field will excite the targeted nerve with minimal or to no excitation to the surrounding nerves. This means that we can effectively apply or measure the excitation of the targeted nerve without involving the surrounding nerves. It is my intention to bring this application to a practical platform where a simple circuit with lower power requirements can be used. This will enable some patients requiring physiotherapy to safely administer magnetic nerve stimulation to themselves without the help of a therapist. / Thesis / Master of Engineering (ME)