Neurulation is critical for the proper development of the central nervous system during embryogenesis. This process requires coordinated morphogenetic movements driven by localized cell movements. The key morphogenetic process responsible for lengthening the neural plate is convergent extension. During convergent extension medially oriented cell polarity, protrusive activity, and motility are thought to generate forces through cell intercalation resulting in stiffer elongating tissues. My research determines that forces that help shape the neural plate arise from morphogenetic movements in the neural tissue and determines PCP signaling regulates tissue stiffness in the neural ectoderm. We have established an experimental system sensitive enough to evaluate the stiffness of Xenopus neural tissue. Stiffness is measured by gluing two fine wires onto neural explants from an early gastrula stage Xenopus laevis embryo. The wires stretch the tissue at a constant strain rate using a real-time image-based feedback system and stiffness is determined by measuring the deflection of one wire. Measurements obtained from control embryos prior to neurulation estimate tissue stiffness at approximately 12.7 ± 0.53 mN/m in both mediolateral and anteroposterior directions. Stiffness measurements double in early neurula embryos (P < 0.05). Mediolateral stiffness, 24.9 ±6.2 mN/m, is significantly greater than anteroposterior stiffness, 21.4 ±5.3 mN/m (P < 0.05). These trends are strengthened in normalized data to reduce clutch-to-clutch variation. Expressions of dominant-negative Wnt11, Fz7, and Dsh constructs successfully disrupt neurulation by interfering with the PCP pathway. Changes in stiffness of the neural plate were measured and show reduced stiffness at early neurula stage in both mediolateral and anteroposterior directions suggesting mechanical forces are generated within the neural plate.

Neurulation is critical for the proper development of the central nervous system during embryogenesis. This process requires coordinated morphogenetic movements driven by localized cell movements. The key morphogenetic process responsible for lengthening the neural plate is convergent extension. During convergent extension medially oriented cell polarity, protrusive activity, and motility are thought to generate forces through cell intercalation resulting in stiffer elongating tissues. My research determines that forces that help shape the neural plate arise from morphogenetic movements in the neural tissue and determines PCP signaling regulates tissue stiffness in the neural ectoderm. We have established an experimental system sensitive enough to evaluate the stiffness of Xenopus neural tissue. Stiffness is measured by gluing two fine wires onto neural explants from an early gastrula stage Xenopus laevis embryo. The wires stretch the tissue at a constant strain rate using a real-time image-based feedback system and stiffness is determined by measuring the deflection of one wire. Measurements obtained from control embryos prior to neurulation estimate tissue stiffness at approximately 12.7 ± 0.53 mN/m in both mediolateral and anteroposterior directions. Stiffness measurements double in early neurula embryos (P < 0.05). Mediolateral stiffness, 24.9 ±6.2 mN/m, is significantly greater than anteroposterior stiffness, 21.4 ±5.3 mN/m (P < 0.05). These trends are strengthened in normalized data to reduce clutch-to-clutch variation. Expressions of dominant-negative Wnt11, Fz7, and Dsh constructs successfully disrupt neurulation by interfering with the PCP pathway. Changes in stiffness of the neural plate were measured and show reduced stiffness at early neurula stage in both mediolateral and anteroposterior directions suggesting mechanical forces are generated within the neural plate.

We discuss the twist map, with a special interest in its use for the finite Frenkel–Kontorova model. We explain the meaning of the tensile force in some proposed models. We demonstrate that the application of the twist map for the finite FK model is not correct, because the procedure ignores the necessary boundary conditions.

Bridges often use pile foundations behind MSE walls to help resist lateral loading from seismic and thermal expansion and contraction loads. Overdesign of pile spacing and sizes occur owing to a lack of design code guidance for piles behind an MSE wall. However, space constraints necessitate the installation of piles near the wall. Full scale lateral load tests were conducted on piles behind an MSE wall. This study involves the testing of four HP12X74 H-piles and four HSS12X12X5/16 square piles. The H-piles were tested with ribbed strip soil reinforcement at a wall height of 15 feet, and the square piles were tested with welded wire reinforcement at a wall height of 20 feet. The H-piles were spaced from the back face of the MSE wall at pile diameters 4.5, 3.2, 2.5, and 2.2. The square piles were spaced at pile diameters 5.7, 4.2, 3.1, and 2.1. Testing was based on a displacement control method where load increments were applied every 0.25 inches up to three inches of pile deflection. It was concluded that piles placed closer than 3.9 pile diameters have a reduction in their lateral resistance. P-multipliers were back-calculated in LPILE from the load-deflection curves obtained from the tests. The p-multipliers were found to be 1.0, 0.85, 0.60, and 0.73 for the H-piles spaced at 4.5, 3.2, 2.5, and 2.2 pile diameters, respectively. The p-multipliers for the square piles were found to be 1.0, 0.77, 0.63, and 0.57 for piles spaced at 5.7, 4.2, 3.1, and 2.1 pile diameters, respectively. An equation was developed to estimate p-multipliers versus pile distance behind the wall. These p-multipliers account for reduced soil resistance, and decrease linearly with distance for piles placed closer than 3.9 pile diameters. Measurements were also taken of the force induced in the soil reinforcement. A statistical analysis was performed to develop an equation that could predict the maximum induced reinforcement load. The main parameters that went into this equation were the lateral pile load, transverse distance from the reinforcement to the pile center normalized by the pile diameter, spacing from the pile center to the wall normalized by the pile diameter, vertical stress, and reinforcement length to height ratio where the height included the equivalent height of the surcharge. The multiple regression equations account for 76% of the variation in observed tensile force for the ribbed strip reinforcement, and 77% of the variation for the welded wire reinforcement. The tensile force was found to increase in the reinforcement as the pile spacing decreased, transverse spacing from the pile decreased, and as the lateral load increased.

Die Arbeit beschäftigt sich mit der Untersuchung der Beanspruchungen von Staurollenketten. Zunächst wurde in den Grundlagen der Aufbau von unterschiedlichen Staurollenkettenarten dargestellt, die Eigenschaften miteinander verglichen und kategorisiert. Aufbauend auf dem anschließend geschaffenen Verständnis der wirkenden Reibpaarungen bzw. -arten wurden FEM-Analysen durchgeführt, um dadurch auftretende Spannungen zu detektieren und das thermische Verhalten der unterschiedlichen Werkstoffpaarungen zu ermitteln. Innerhalb der praktischen Versuche der Arbeit kam es zur Ermittlung der Bruch- und Dauerfestigkeiten nach ISO15654 [DIN04]. Zur Untersuchung der Eigenschaften der Ketten unter praxisnahen Randbedingungen wurde ein Versuchsstand konzipiert, welcher die Ermittlung von Kennwerten zwei unterschiedlicher Kettengrößen unter härtesten Bedingungen ermöglicht. Durch diesen Versuchsstand wurden die Staukraft, die Kettenzugkraft durch das Drehmoment am Antrieb, die Kettengeschwindigkeit, die Kettenlängung und das Temperaturverhalten dauerhaft überwacht. Im letzten Kapitel der Arbeit wurde eine Überwachungsstation für unterschiedliche Baugrößen von Staurollenketten entwickelt und die Funktionsweise durch Versuche nachgewiesen. / This dissertation is dealing with the investigation of the load behaviour of accumulation roller chains. Initially, the structures of different types of accumulation roller chains are described, properties are compared and categorised. Based on the created understanding of acting tribological pairing and friction mechanisms, FEM analysis have been performed to evaluate occurring stresses and determine the thermal behaviour of the various material combinations. Within the testing procedures, breaking strength and fatigue strength have been investigated in accordance with DIN ISO 15654 [cf. DIN04]. A test bench has been developed for practically relevant testing of the chains, where determination of characteristic values can be done under hard testing conditions for two different chain types. The test bench ensures measurement and survey of accumulation forces, tensile chain forces (by torque moment at drive), chain speed, chain elongation and chain temperature during whole testing time. The last chapter of the dissertation deals with the development of a 'control and monitoring unit' for accumulation roller chains with various dimensions including proof of function by trials.

Die Arbeit beschäftigt sich mit der Untersuchung der Beanspruchungen von Staurollenketten. Zunächst wurde in den Grundlagen der Aufbau von unterschiedlichen Staurollenkettenarten dargestellt, die Eigenschaften miteinander verglichen und kategorisiert. Aufbauend auf dem anschließend geschaffenen Verständnis der wirkenden Reibpaarungen bzw. -arten wurden FEM-Analysen durchgeführt, um dadurch auftretende Spannungen zu detektieren und das thermische Verhalten der unterschiedlichen Werkstoffpaarungen zu ermitteln. Innerhalb der praktischen Versuche der Arbeit kam es zur Ermittlung der Bruch- und Dauerfestigkeiten nach ISO15654 [DIN04]. Zur Untersuchung der Eigenschaften der Ketten unter praxisnahen Randbedingungen wurde ein Versuchsstand konzipiert, welcher die Ermittlung von Kennwerten zwei unterschiedlicher Kettengrößen unter härtesten Bedingungen ermöglicht. Durch diesen Versuchsstand wurden die Staukraft, die Kettenzugkraft durch das Drehmoment am Antrieb, die Kettengeschwindigkeit, die Kettenlängung und das Temperaturverhalten dauerhaft überwacht. Im letzten Kapitel der Arbeit wurde eine Überwachungsstation für unterschiedliche Baugrößen von Staurollenketten entwickelt und die Funktionsweise durch Versuche nachgewiesen. / This dissertation is dealing with the investigation of the load behaviour of accumulation roller chains. Initially, the structures of different types of accumulation roller chains are described, properties are compared and categorised. Based on the created understanding of acting tribological pairing and friction mechanisms, FEM analysis have been performed to evaluate occurring stresses and determine the thermal behaviour of the various material combinations. Within the testing procedures, breaking strength and fatigue strength have been investigated in accordance with DIN ISO 15654 [cf. DIN04]. A test bench has been developed for practically relevant testing of the chains, where determination of characteristic values can be done under hard testing conditions for two different chain types. The test bench ensures measurement and survey of accumulation forces, tensile chain forces (by torque moment at drive), chain speed, chain elongation and chain temperature during whole testing time. The last chapter of the dissertation deals with the development of a 'control and monitoring unit' for accumulation roller chains with various dimensions including proof of function by trials.