Auburn University Graduate School

An ex vivo biomechanical study of equine neonatal rib fracture repair by different fixation methods

2026-08-27T00:00:00Z

An ex vivo biomechanical study of equine neonatal rib fracture repair by different fixation methods Newell, Kayla Introduction: Rib fractures result in significant morbidity and mortality of equine neonates. Various methods to repair these fractures have been described but biomechanical testing in immature equine neonatal bone has not been performed. The study objective was to compare strength, stiffness, and mode of failure for four different methods of equine neonatal rib fracture repair. Methods: Equine neonatal cadavers (< 2 weeks of age) without history of dystocia or thoracic trauma present were used for this study. Ribs three through six on both left and right side were randomly allocated to one of four repair groups: nylon cable tie (NCT), modified reconstruction plate (MRP), string of pearls plate (SOP), or rib clip (RC). Intact ribs were first fractured under three-point bending to induce a simple, transverse fracture. The fracture was then reduced and repaired according to the assigned repair group. Repaired ribs were then tested to failure under single-cycle, four-point bending. Strength (maximum force, Fmax, and force at failure, Ffail) and mode of failure were recorded. Stiffness (N/mm2) was calculated. Data were analyzed using linear mixed models Results: In intact ribs, no significant differences in Fmax (P=0.46), Ffail (P=0.35), or stiffness (P=0.90) were observed between groups. Among repair groups, Fmax, Ffail, and stiffness differed significantly (P<0.0001). NCT repairs had significantly lower Fmax and Ffail than MRP and SOP, while MRP and SOP had greater stiffness compared to NCT and RC. NCT and RC groups failed at the original fracture site, whereas MRP and SOP failed mostly due to screw pullout. Conclusion: Rigid fixation with MRP or SOP provides stronger fracture repair than NCT or RC when equine neonatal ribs are tested under single-cycle load to failure. Further investigation of both rigid and non-rigid repair methods with cyclic loading is warranted.

Laboratory and Computational Evaluation of Mast Arm Foundations Under Torsion and Lateral Loading

2026-08-27T00:00:00Z

Laboratory and Computational Evaluation of Mast Arm Foundations Under Torsion and Lateral Loading Rojas Esparza, Olga Lucia Drilled shaft foundations are commonly used to support traffic signal mast arm structures because of their ability to resist large lateral, overturning, and torsional loads. Although current design procedures generally evaluate lateral and torsional loading independently, field observations and previous research indicate that these loading modes may interact, particularly under extreme wind events. This study investigates the behavior of drilled shaft foundations subjected to pure torsional, pure lateral, and combined lateral-torsional loading through a comprehensive program of full-scale testing and numerical modeling. Seven full-scale load tests were performed on two 36-in-diameter drilled shafts constructed within a controlled geotechnical chamber at Auburn University. The testing program included pure torsional loading, pure lateral loading, combined lateral-torsional loading, and sequential loading cases in two distinct phases. In Phase I, shafts were constructed in place through excavation and concrete placement. In Phase II, the shafts were exhumed, reinstalled, and surrounded by recompacted sand to evaluate the influence of construction method and shaft-soil interface conditions. Load, displacement, rotation, and strain measurements were collected throughout the testing program. The experimental results showed that torsional and lateral behavior are strongly influenced by loading sequence and shaft installation conditions. Pure torsional tests in both phases yielded similar ultimate torsional capacities of approximately 145-148 kip-ft; however, the recompacted Phase II configuration exhibited substantially higher initial torsional stiffness. Combined lateral-torsional loading reduced the mobilized torsional stiffness and altered the progression of resistance mobilization, requiring larger rotations to achieve the same torque levels observed under pure torsion. Sequential loading tests indicated that prior torsional loading reduced lateral stiffness and delayed the mobilization of resistance, although differences in ultimate lateral capacity were less pronounced. Numerical models were developed using FB-MultiPier and back-calculated against the measured load-displacement and torque-rotation responses. The best-fit estimation demonstrated that stiffness-related parameters, particularly shear modulus and horizontal subgrade reaction, were highly sensitive to construction effects, loading history, and stress path. Strength-related parameters, including unit weight, friction angle, and torsional shear resistance, exhibited comparatively smaller adjustments. The results demonstrate that conventional uncoupled design approaches do not adequately represent the behavior of drilled shafts under realistic loading conditions and highlight the need to consider construction effects, shaft-soil interface conditions, and load interactions in foundation design for mast arm structures.

Prenatal Cannabinoid Exposure: Persistent Sex-Dependent Alterations in Hippocampal Inhibitory Signaling and Neurobehavioral Function

2026-08-21T00:00:00Z

Prenatal Cannabinoid Exposure: Persistent Sex-Dependent Alterations in Hippocampal Inhibitory Signaling and Neurobehavioral Function Wiley, Miles Prenatal cannabinoid exposure (PCE) has increased despite concerns that it may produce lasting effects on brain development and behavior. Delta-9-tetrahydrocannabinol (THC), the primary psychoactive substance of cannabis, crosses the placental barrier and activates cannabinoid receptor type 1 (CB₁R), a key regulator of endocannabinoid signaling during neurodevelopment. Because the endocannabinoid system contributes to the maturation of hippocampal circuits that support learning and memory, PCE may disrupt hippocampal function; however, the underlying mechanisms remain unclear. This dissertation used two prenatal THC exposure models to characterize the developmental, behavioral, molecular, anatomical, and physiological consequences of PCE. In a translational vapor inhalation model, toxicokinetic analyses confirmed systemic THC exposure and neonatal transfer. PCE altered maternal and offspring developmental measures and produced sex-dependent behavioral abnormalities during adolescence, including increased anxiety-like behavior and marginal impairment of recognition memory. These effects were accompanied by sex-dependent changes in hippocampal GABAergic-associated protein expression and CB₁R-associated inhibitory circuitry. A second study used a subcutaneous THC exposure model to determine whether these molecular and anatomical alterations were associated with persistent changes in hippocampal physiology. Following confirmation of THC formulation stability, developmental outcomes, synaptosomal protein expression, and extracellular field recordings were evaluated. PCE increased vesicular glutamate transporter 1 expression in both sexes and produced sex-specific alterations in proteins associated with inhibitory signaling. PCE did not alter basal excitatory synaptic transmission in the absence of gabazine (GBZ), a competitive gamma-aminobutyric acid type A receptor (GABAAR) antagonist. However, partial GABAAR blockade revealed sex-dependent alterations in presynaptic recruitment and short-term plasticity. PCE also reduced long-term potentiation maintenance in both sexes and enhanced long-term depression in males. GBZ modified synaptic depression but did not attenuate the long-term potentiation deficit in THC-exposed offspring. Together, these findings demonstrate that PCE produces persistent, sex-dependent developmental, behavioral, molecular, anatomical, and physiological alterations that extend into adolescence. Across two exposure paradigms, PCE altered hippocampal excitatory and inhibitory signaling, as well as GABAergic regulation of glutamatergic transmission. These findings indicate that PCE-induced hippocampal dysfunction is not explained solely by excessive inhibitory transmission but instead involves disrupted coordination between glutamatergic and GABAergic signaling and impaired synaptic plasticity.

Evaluating the Safety Performance of Centerline Rumble Strips in Alabama

2026-08-19T00:00:00Z

Evaluating the Safety Performance of Centerline Rumble Strips in Alabama Villegas, Michelle Catheryn While research regarding the safety performance of centerline rumble strips (CLRS) has been studied nationally, no research has been conducted for Alabama. As such, the goal of this research is to assess the safety performance of CLRS in Alabama by executing the simple before-after and comparison group methodologies. The simple before-after analysis experienced reductions of -17.4%, -40.8%, and -45.1%, for total crashes, correctable, and correctable fatal and injury (FI) crashes, respectively. The comparison group analysis produced CMFs of 0.94, 0.62, and 0.61 for total crashes, correctable, and correctable FI crashes, respectively. Finally, changes in distribution for primary contributing circumstance and manner of crash were assessed for correctable and correctable FI crashes to evaluate CLRS efficacy across a variety of primary contributing circumstances and distribution of manner of crash commonly associated with crossover crashes. This research affirms the safety performance of CLRS and can support widespread implementation in Alabama.