Hexagonal close packed (hcp) crystal structures, such as magnesium and titanium, provide formidable strength in relation to density. Current interests in reducing CO2 emissions, hold magnesium as a contender to lightweight passenger vehicles. Although significant decreases in mass could be achieved through magnesium, poor formability and energy absorption capacity limit the possibility for cost-effective production. This Master’s thesis aims to observe the microstructure and micro texture evolution induced by twinning using interrupted electron backscattered diffraction (EBSD) characterization in order to determine potential mechanisms causing early failure of magnesium alloys. This study revealed {10-11} contraction twins at stress levels contrary to the basic hypothesis of the Schmid effect revealing the importance of non-Schmid effects in damage. Furthermore, it was observed that crack nucleation occurs in magnesium alloys, due mainly to interaction between twins and microstructure defects and form inside contraction twins, causing cleavage-like terraces in the fracture surface.

Contraction flow of viscoelastic fluids has been a benchmark problem in non-Newtonian fluid mechanics because it mimics flows occurring in a number of industrial applications. It is also of considerable interest to academia to gain fundamental understanding of factors that affect the evolution of vortices and a complete understanding of the dynamics for a simple polymeric fluid has not been achieved. In this two part study we investigate the effect of pre deformation of a Boger fluid in a contraction geometry and the flow of surfactants in a parallel contraction geometry. Entry flow of a polymeric fluid results in the formation of upstream vortices,the presence of recirculation zones may lead to a nonuniform residence time and hence inferior quality products. In this work we study the effect of pre-stretching dilute flexible chain polymers by placing a cylinder in front of a contraction in a microfluidic device.This deformation applied to the polymer is remembered before it completely relaxes, this memory effect changes the rheological properties during the fading period of the deformation history. Applying pre-deformation gives rise to new type of vortex evolution that is different from the standard contraction case. Semi-dilute surfactant solutions that exhibit shear thickening nature can be potentially used in enhanced oil recovery to increase the sweep efficiency. Two parallel microfluidic contractions of different cross sectional area are used to investigate the rheological effect on the mass flux of the two channels. Shear thickening micellar solutions were found to increase the mass flux through the small channel compared to a newtonian fluid. This effect was observed only for a small range of flow rates. As flow rates increased inlet instabilities were observed that evolved into a chaotic behavior upon further increase in the net flow rate.

Padel involves repetitive and high-velocity upper limb movements, which can be associated with overuse injuries. There is a lack of evidence regarding injury prevention in padel and a necessity of developing and evaluating ways to monitor workload. The objective of this study was to use a new mobile measurement method (Delsys Trigno Light System) to evaluate muscle activation and movement of the forearm during padel. The percentage of MVC (%MVC) of Mm. Extensor carpi radialis (ECR) longus et brevis and M. flexor carpi radialis (FCR), angular velocities of the wrist and co-contraction between ECR and FCR were measured and analyzed. The main results showed a relatively low general muscle activation; 1.42 (0.44 – 2.33) %MVC of FCR and 8.02 (4.23 – 12.62) %MVC of ECR, with significantly greater muscle activation of the ECR than the FCR (p<0.001), high angular wrist velocities; 17.0 (13.2 – 34.6) °/s, and a weak positive correlation for co-contraction with peak values of FCR > 0.15 V and concurrent ECR, Spearman’s r = 0.326, p<0.001 and peak values of ECR > 0,15 V and concurrent FCR, Spearman’s r = 0.181, p<0.001. This study indicates that this mobile measurement method may be used to evaluate biomechanical workload on the forearm during padel play and may serve as an injury preventive tool.

Indiana University-Purdue University Indianapolis (IUPUI) / Asthma, a chronic inflammatory disease of the airways, affects nearly 25 million Americans. The vast majority of these patients suffer from exercise-induced bronchoconstriction (EIB), a complication of asthma. Although traditionally treated pharmacologically, nutritional strategies provide a promising alternative for managing EIB as the prevalence of asthma may be due in part to changes in diet. Our objective was to determine the effects of novel nutritional strategies on hyperpnea-induced bronchoconstriction (HIB) in asthmatic individuals. HIB uses rapid breathing to identify EIB in a research or clinical setting. Fish oil, a combination of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docsahexaenoic acid (DHA), has been shown to be effective in suppressing EIB. However, its use in combination with other nutritional supplements, the optimal fish oil formula, and its effect on smooth muscle contractility have not been fully explored. An in vivo study (study 1) was conducted in individuals with both asthma and HIB to determine whether a combination of fish oil and vitamin C was more effective than either one alone in alleviating HIB. Pulmonary function was significantly improved with both fish oil and the combination treatment but not with vitamin C alone. In study 2, individuals with both asthma and HIB were supplemented with DHA alone since the optimal formula for fish oil has yet to be ascertained; previous in vitro studies have suggested DHA may be the more potent omega-3 fatty acid in fish oil. However, no significant changes in pulmonary function or airway inflammation were seen with DHA supplementation. For study 3, canine airway smooth muscle tissue was treated with fish oil to determine the in vitro effect of fish oil on smooth muscle contractility. Acute treatment with fish oil relaxed smooth muscle strips that had been contracted with 5-hydroxytryptamine. These minor relaxations in smooth muscle tension with fish oil may represent significant changes at the level of the smaller airways. These studies have confirmed that fish oil represents a viable treatment modality for asthmatic individuals with EIB and suggest that fish oil may influence airway smooth muscle contractility.

Indiana University-Purdue University Indianapolis (IUPUI) / Voltage-gated sodium channels (VGSCs) are dynamic membrane spanning proteins which mediate the rapid influx of Na+ during the upstroke of the action potential (AP). In addition to the large inward Na+ currents responsible for the upstroke of the AP, some VGSC isoforms produce smaller, subthreshold Na+ currents, which can influence the excitable properties of neurons. An example of such a subthreshold current is resurgent Na+ current (INaR). These unusual currents are active during repolarization of the membrane potential, where the channel is normally refractory to activity. INaR exhibit slow gating kinetics and unusual voltage-dependence derived from a novel mechanism of channel inactivation which allows the channel to recover through an open configuration resulting in membrane depolarization early in the falling phase of the AP, ultra-fast re-priming of channels, and multiple AP spikes. Although originally identified in fast spiking central nervous system (CNS) neurons, INaR has recently been observed in a subpopulation of peripheral dorsal root ganglion (DRG) neurons. Because INaR is believed to contribute to spontaneous and high frequency firing of APs, I have hypothesized that increased INaR may contribute to ectopic AP firing associated with inherited and acquired disorders of excitability. Specifically, this dissertation explores the mechanisms which underlie the electrogenesis of INaR in DRG neurons and determines whether the biophysical properties of these unique currents were altered by mutations that cause inherited muscle and neuronal channelopathies or in an experimental model of nerve injury. The results demonstrate that (1) multiple Na+ channel isoforms are capable of producing INaR in DRG neurons, including NaV1.3, NaV1.6, and NaV1.7, (2) inherited muscle and neuronal channelopathIy mutations that slow the rate of channel inactivation increase INaR amplitude, (3) temperature sensitive INaR produced by select skeletal muscle channelopthy mutations may contribute to the triggering of cold-induced myotonia, and (4) INaR amplitude and distribution is significantly increased two weeks post contusive spinal cord injury (SCI). Taken together, results from this dissertation provide foundational knowledge of the properties and mechanism of INaR in DRG neurons and indicates that increased INaR likely contributes to the enhanced membrane excitability associated with multiple inherited and acquired disorders of excitability.

An approach to a new class of compounds known as bridgehead dienone is described. The route is based on a tandem contraction-expansion event in which the contraction triggers the expansion. The two steps involved are a palladium-catalyzed Favorskii contraction and a cis-divinyl cyclopropanone rearrangement. Progress towards these goals is reported.

Placebo treatments have long been used to study the psychological effects of expectancy and conditioning on an inert intervention. Interestingly, open-label placebo treatments (i.e., directly telling subjects they are receiving an inactive intervention) have recently shown promise in minimizing pain in clinical patient populations. We utilized a repeated measures design to examine the acute effects of placebo, open-label placebo, and control treatments on muscle strength and voluntary activation (Experiment #1), as well as neuromuscular fatigue (Experiment #2). Twenty-one untrained males (n=11) and females (n=10) visited the laboratory on three occasions to receive each treatment in a randomized, counter-balanced manner. All visits involved a pretest, 15-minute intervention period, and posttest. In Experiment #1, knee extensor maximal voluntary isometric contraction (MVIC) peak torque and percent voluntary activation were evaluated. In Experiment #2, subjects performed 20, six-second MVICs while surface electromyographic signals were detected from the vastus lateralis. Subjective assessments of energy and perceived exertion were also examined. In Experiment #1, no differences among interventions were demonstrated for peak torque or voluntary activation, but a main effect revealed that energy levels increased following each treatment (p = .016, η2 = .257). Experiment #2 demonstrated that placebo and open-label placebo treatments had no influence on neuromuscular fatigue, but there were main effects for declines in absolute (p = .001, η2 = .675) and normalized peak torque (p = .001, η2 = .765), electromyographic mean frequency (p = .001, η2 = .565), neuromuscular efficiency (p = .001, η2 = .585), and energy levels (p = .006, η2 = .317). Collectively, placebo and open-label placebo treatments had minimal influence on strength, voluntary activation, and fatigue resistance in untrained subjects. We speculate that our subject population and study design intricacies that are unique to placebo trials may explain our findings.

Given the surmounting disagreement amongst researchers in the area of liquid flow behavior at the microscale for the past thirty years, this work presents a fundamental approach to analyzing the pressure losses experienced by the laminar flow of water (Re = 7 to Re = 130) through both rectangular straight duct microchannels (of widths ranging from 50 to 130 micrometers), and microchannels with sudden expansions and contractions (with area ratios ranging from 0.4 to 1.0) all with a constant depth of 104 micrometers. The simplified Bernoulli equations for uniform, steady, incompressible, internal duct flow were used to compare flow through these microchannels to macroscale theory predictions for pressure drop. One major advantage of the channel design (and subsequent experimental set-up) was that pressure measurements could be taken locally, directly before and after the test section of interest, instead of globally which requires extensive corrections to the pressure measurements before an accurate result can be obtained. Bernoulli's equation adjusted for major head loses (using Darcy friction factors) and minor head losses (using appropriate K values) was found to predict the flow behavior within the calculated theoretical uncertainty (~12%) for all 150+ microchannels tested, except for sizes that pushed the aspect ratio limits of the manufacturing process capabilities (microchannels fabricated via soft lithography using PDMS). The analysis produced conclusive evidence that liquid flow through microchannels at these relative channel sizes and Reynolds numbers follow macroscale predictions without experiencing any of the reported anomalies expressed in other microfluidics research. This work also perfected the delicate technique required to pierce through the PDMS material and into the microchannel inlets, exit and pressure ports without damaging the microchannel. Finally, two verified explanations for why prior researchers have obtained poor agreement between macroscale theory predictions and tests at the microscale were due to the presence of bubbles in the microchannel test section (producing higher than expected pressure drops), and the occurrence of localized separation between the PDMS slabs and thus, the microchannel itself (producing lower than expected pressure drops).

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