Sol-gel synthesis and densification of aluminoborosilicate powders. Part 2: Densification

Aluminoborosilicate (ABS) powders, high in alumina content, were synthesized by the sol-gel process utilizing four different methods of synthesis. The effect of these methods on the densification behavior of ABS powder compacts was studied. Five regions of shrinkage in the temperature range 25-1184 C were identified. In these regions, the greatest shrinkage occurred between the gel-to-glass transition temperature (T sub g approximately equal to 835 C) and the crystallization transformation temperature (T sub t approximately equal 900 C). The dominant mechanism of densification in this range was found to be viscous sintering. ABS powders were amorphous to x-rays up to T sub t at which a multiphasic structure crystallized. No 2Al2O3.B2O3 was found in these powders as predicted in the phase diagram. Above T sub t, densification was the result of competing mechanisms including grain growth and boria fluxed viscous sintering. Apparent activation energies for densification in each region varied according to the method of synthesis

The Effects of Energy Beverages in Counteracting the Symptoms of Mild Hypoxia at Legal General Aviation Altitudes

The purpose of this thesis was to conduct preliminary research, in the form of a pilot study, concerning the natural effects of hypoxia compared to the effects of hypoxia experienced after the consumption of an energy beverage. The study evaluated the effects of hypoxia on FAA certificated pilots at a simulated legal general aviation altitude, utilizing the normobaric High Altitude Lab (HAL) located at Embry Riddle Aeronautical University, Daytona Beach, Florida. The researcher tested 11 subjects, who completed three simulated flight tasks within the HAL using the Frasca International Mentor Advanced Aviation Training Device (AATD). The flight tasks were completed after consuming Red Bull® , Monster® , or a placebo beverage. The researcher derived three test variables from core outputs of the AATD: lateral deviations from the glide slope, vertical deviations from the localizer, and airspeed deviations from the target speed of 100 knots. A repeated-measures ANOVA was carried out to determine effects of the beverages on the test variables. While results were non-significant, the researcher concluded that further research should be conducted with a larger sample

Investigating the effect that disease-linked PLCγ2 variants have on enzymatic activity and exploring PLCγ2’s role within microglia cell function

Phospholipase C-gamma 2 (PLCγ2) is highly expressed in immune cells, such as microglia. PLCγ2 hydrolyses phosphatidylinositol 4,5-bisphosphate into inositol trisphosphate (IP3) and diacylglycerol. Variants of PLCγ2 have been described in several diseases, such as late onset Alzheimer’s disease (LOAD), inflammatory bowel disease, as well as rare immune disorders, suggesting a key role for this enzyme in the regulation of immune cell function. To characterise the enzymatic activity of disease-linked PLCγ2 variants, an assay measuring inositol monophosphate (IP1), a downstream metabolite of IP3, was adapted and optimised. The S707Y, Δ845-848 and M1141K PLCγ2 variants, linked to a complex immune disorder, have strong hypermorphic activity, whereas the PLCγ2 V1103I variant shows a mild increase in PLC activity. In the context of LOAD, microglia have been implicated as key mediators of disease pathophysiology. However, the role of PLCγ2 within microglia is still not fully understood. To address this issue, the hypermorphic PLCγ2 S707Y disease linked-variant was introduced into human inducible pluripotent stem cells (hiPSCs) to explore the role that strong gain-of-function PLCγ2 variants have within hiPSC-derived microglia. Based on the IP1 measurements, PLCγ2 S707Y hiPSC-derived microglia exhibited hypermorphic enzymatic activity under both basal and stimulated conditions, which in turn resulted in increased calcium flux. However, when challenged with apoptotic neuronal cells, a reduction in phagocytosis was observed. Additionally, secretion of IL-1β, IL-8 and TNF-α was shown to be elevated in basal conditions. However, when challenged with lipopolysaccharide, PLCγ2 S707Y hiPSC-derived microglia exhibited a reduction in IL-10, IL-6 and TNF-α secretion, likely due to decreased NF-κB activation and translocation. RNA sequencing of the PLCγ2 S707Y hiPSC-derived microglia revealed a downregulation of genes related to innate immunity and response. Therefore, this thesis demonstrates that despite the increase in PLCγ2 enzymatic activity, the PLCγ2 S707Y hiPSC-derived microglia display a loss of function for key microglial processes

INFO2009 - Team 'DROP TABLE groups;

Edshare for INFO2009 coursework 2 - Team 'DROP TABLE groups

Influence of inverse dynamics methods on the calculation of inter-segmental moments in vertical jumping and weightlifting

<p>Abstract</p> <p>Background</p> <p>A vast number of biomechanical studies have employed inverse dynamics methods to calculate inter-segmental moments during movement. Although all inverse dynamics methods are rooted in classical mechanics and thus theoretically the same, there exist a number of distinct computational methods. Recent research has demonstrated a key influence of the dynamics computation of the inverse dynamics method on the calculated moments, despite the theoretical equivalence of the methods. The purpose of this study was therefore to explore the influence of the choice of inverse dynamics on the calculation of inter-segmental moments.</p> <p>Methods</p> <p>An inverse dynamics analysis was performed to analyse vertical jumping and weightlifting movements using two distinct methods. The first method was the traditional inverse dynamics approach, in this study characterized as the 3 step method, where inter-segmental moments were calculated in the local coordinate system of each segment, thus requiring multiple coordinate system transformations. The second method (the 1 step method) was the recently proposed approach based on wrench notation that allows all calculations to be performed in the global coordinate system. In order to best compare the effect of the inverse dynamics computation a number of the key assumptions and methods were harmonized, in particular unit quaternions were used to parameterize rotation in both methods in order to standardize the kinematics.</p> <p>Results</p> <p>Mean peak inter-segmental moments calculated by the two methods were found to agree to 2 decimal places in all cases and were not significantly different (p > 0.05). Equally the normalized dispersions of the two methods were small.</p> <p>Conclusions</p> <p>In contrast to previously documented research the difference between the two methods was found to be negligible. This study demonstrates that the 1 and 3 step method are computationally equivalent and can thus be used interchangeably in musculoskeletal modelling technology. It is important that future work clarifies the influence of the other inverse dynamics methods on the calculation of inter-segmental moments. Equally future work is needed to explore the sensitivity of kinematics computations to the choice of rotation parameterization.</p

Lower-extremity musculoskeletal geometry affects the calculation of patellofemoral forces in vertical jumping and weightlifting

The calculation of the patellofemoral joint contact force using three-dimensional (3D) modelling techniques requires a description of the musculoskeletal geometry of the lower limb. In this study, the influence of the complexity of the muscle model was studied by considering two different muscle models, the Delp and Horsman models. Both models were used to calculate the patellofemoral force during standing, vertical jumping, and Olympic-style weightlifting. The patellofemoral forces predicted by the Horsman model were markedly lower than those predicted by the Delp model in all activities and represented more realistic values when compared with previous work. This was found to be a result of a lower level of redundancy in the Delp model, which forced a higher level of muscular activation in order to allow a viable solution. The higher level of complexity in the Horsman model resulted in a greater degree of redundancy and consequently lower activation and patellofemoral forces. The results of this work demonstrate that a well-posed muscle model must have an adequate degree of complexity to create a sufficient independence, variability, and number of moment arms in order to ensure adequate redundancy of the force-sharing problem such that muscle forces are not overstated. (Author's abstract

The development of a segment-based musculoskeletal model of the lower limb: Introducing FreeBody

Traditional approaches to the biomechanical analysis of movement are joint-based; that is the mechanics of the body are described in terms of the forces and moments acting at the joints, and that muscular forces are considered to create moments about the joints. We have recently shown that segment-based approaches, where the mechanics of the body are described by considering the effect of the muscle, ligament and joint contact forces on the segments themselves, can also prove insightful. We have also previously described a simultaneous, optimization-based, musculoskeletal model of the lower limb. However, this prior model incorporates both joint- and segment-based assumptions. The purpose of this study was therefore to develop an entirely segment-based model of the lower limb and to compare its performance to our previous work. The segment-based model was used to estimate the muscle forces found during vertical jumping, which were in turn compared with the muscular activations that have been found in vertical jumping, by using a Geers’ metric to quantify the magnitude and phase errors. The segment-based model was shown to have a similar ability to estimate muscle forces as a model based upon our previous work. In the future, we will evaluate the ability of the segment-based model to be used to provide results with clinical relevance, and compare its performance to joint-based approaches. The segment-based model described in this article is publicly available as a GUIbasedMATLAB _ application and in the original source code (at www.msksoftware.org.uk)

An Optimization-Based Simultaneous Approach to the Determination of Muscular, Ligamentous, and Joint Contact Forces Provides Insight into Musculoligamentous Interaction

Typical inverse dynamics approaches to the calculation of muscle, ligament, and joint contact forces are based on a step-wise solution of the equations of motion. This approach is therefore limited in its ability to provide insight as to the muscular, ligamentous, and articular interactions that create joint stability. In this study, a new musculoskeletal model of the lower limb is described, in which the equations of motion describing the force and moment equilibrium at the joints of the lower limb are solved simultaneously using optimization techniques. The new model was employed to analyze vertical jumping using a variety of different optimization cost functions and the results were compared to more traditional approaches. The new model was able to find a solution with lower muscular force upper bounds due to the ability of the ligaments to contribute to moment equilibrium at the ankle and knee joints. Equally, the new model produced lower joint contact forces than traditional approaches for cases which also included a consideration as to ligament or joint contact forces within the cost function. This study demonstrates the possibility of solving the inverse dynamic equations of motion simultaneously using contemporary technology, and further suggests that this might be important due to the complementary function of the muscles and ligaments in creating joint stability

Rapid-sequence MRI for long-term surveillance for paraganglioma and phaeochromocytoma in patients with succinate dehydrogenase (SDHx) mutations

INTRODUCTION: Patients with SDHx mutations need long-term radiological surveillance for the development of paragangliomas and phaeochromocytomas, but no longitudinal data exist. We assessed the performance of rapid-sequence non-contrast magnetic resonance imaging (MRI) in the long-term monitoring of patients with SDHx mutations. METHODS: Retrospective study between 2005-2015 at a University Hospital and regional endocrine genetics referral center. Clinical and imaging data of forty-seven patients with SDHx mutations [SDHB (36), SDHC (6), SDHD (5)] who had surveillance for detection of paragangliomas by rapid-sequence non-contrast MRI (base of skull to pubic symphysis) were collected. RESULTS: Twelve index cases (9 SDHB, 1 SDHC, 2 SDHD) and 35 mutation-positive relatives were monitored for a mean of 6.4 years (range 3.1 to 10.0 years). Mean age at the end of the study: SDHB 46.9+/-17.6 years; SDHC 42.3+/-24.4 years; SDHD 54.9 +/- 10.6 years. Excluding imaging at initial diagnosis of index cases forty-three patients underwent 116 rapid-sequence MRI scans: 83 scans were negative and 31 scans were positive for a sPGL/HNPGL in 13 patients. Most patients had multiple scans [n=number of patients (number of rapid-sequence MRI scans during screening)]; n=9 (2), n=20 (3), n=6 (4), n=1 (6). Nine patients (3 index) were diagnosed with new paragangliomas during surveillance and non-operated tumour size was monitored in 9 patients. There were two false positive scans (1.6%). Scans were repeated every 27 +/- 9 months. CONCLUSIONS: Biannual rapid-sequence non-contrast MRI is effective to monitor patients with SDHx mutations for detection of new tumours and monitoring of known tumours