Microfluidic devices and biological lasers for biophotonic applications

The increasing collaboration between physicists and biologists in recent years has led to a series of breakthroughs enabled, in part, by the use of lasers in biological experiments. Once such recent development is the biological laser where a living cell containing a fluorescent protein or dye acts as a laser gain medium. This thesis presents work designed to develop the idea of the living laser leading to their implementation as a research tool. This work has consisted of two main areas of research; microfluidics and biological lasers. The use of microfluidics enables the miniaturisation of many existing types of biological diagnostics. In this thesis devises are demonstrated for use in temperature sensing and flow cytometry. These were fabricated through the use of Ultrafast Laser Inscription (ULI) and selective chemical etching. As part of this work we have also investigated the integration of silver nanoparticles into microfluidic devices, using photo-reduction, for the enhancement of Raman sensing. Several types of living laser have been fabricated containing different fluorescent dyes and Enhanced Green Fluorescent Protein (eGFP). Lifetime extension has been achieved using vitamin C and work has been conducted towards demonstrating calcium sensing inside cells. As an alternative to the dyes used in these experiments we have also investigated the use of upconverting nanoparticles

The Vegetation of Great Smoky Mountains National Park: Past, Present, and Future

This research investigates the vegetation of Great Smoky Mountains National Park (GRSM) using three different techniques: 1) analysis of vegetation data collected circa 1930, 2) remote sensing of current (1984) vegetation using Landsat Thematic Mapper (TM) satellite imagery, and 3) the integration of gradient analysis with forest succession modeling. Analysis of the 1930\u27s data revealed that Castanea dentata was the dominant species in the GRSM at that time, even with the introduction of the chestnut blight to the park in 1926. Classification of the 1930\u27s plot data identified 16 unique vegetation types ranging from the low elevation, xeric Pinus rigida type to the high elevation, mesic Abies fraseri type. Ordination of the data indicated that species are responding to a complex moisture - elevation gradient. Unsupervised classification of the satellite data was able to identify 14 vegetation types. The classification process used all seven TM bands and had an overall classification accuracy of 83%. The types identified were Spruce - Fir, Northern Hardwood, Cove Hardwood, Mesic Oak, Mixed Mesic Hardwood, Tulip Poplar, Xeric Oak, Pine - Oak, Heath Bald, Grassy Bald, Grape Thicket, Treeless, and Water. The Cove Hardwood type was the most prominent type and occupied 33% of the park\u27s area. The integration of gradient analysis with a forest succession model yielded a model that was capable of replicating vegetation types throughout the entire GRSM landscape. The model was used to provide insights into the dynamics of Castanea dentata prior to the chestnut blight and patterns of replacement of Castanea dentata, and its effect on biomass after the blight, took place via multiple pathways depending on site conditions. This research emphasizes the vegetation of GRSM as a whole rather than as a study of specific types or locations. It provides insights into vegetation dynamics in the context of both space and time

Piezoelectric-based apparatus for strain tuning

We report the design and construction of piezoelectric-based apparatus for applying continuously tuneable compressive and tensile strains to test samples. It can be used across a wide temperature range, including cryogenic temperatures. The achievable strain is large, so far up to 0.23% at cryogenic temperatures. The apparatus is compact and compatible with a wide variety of experimental probes. In addition, we present a method for mounting high-aspect-ratio samples in order to achieve high strain homogeneity.Comment: 8 pages, 8 figure

RCAN1 regulates vesicle recycling and quantal release kinetics via effects on calcineurin activity

Author version made available in accordance with the publisher's policy.We have previously shown that Regulator of Calcineurin 1 (RCAN1) regulates multiple stages of vesicle exocytosis. However, the mechanisms by which RCAN1 affects secretory vesicle exocytosis and quantal release kinetics remain unknown. Here we use carbon fiber amperometry to detect exocytosis from chromaffin cells and identify these underlying mechanisms. We observe reduced exocytosis with repeated stimulations in chromaffin cells overexpressing RCAN1 (RCAN1ox), but not in wild type (WT) cells, indicating a negative effect of RCAN1 on vesicle recycling and endocytosis. Acute exposure to calcineurin inhibitors, cyclosporine A and FK-506, replicates this effect in WT cells but has no additional effect in RCAN1ox cells. When we chronically expose WT cells to cyclosporine A and FK-506 we find that catecholamine release per vesicle and pre-spike foot (PSF) signal parameters are decreased, similar to that in RCAN1ox cells. Inhibiting calcineurin activity in RCAN1ox cells has no additional effect on the amount of catecholamine release per vesicle but further reduces PSF signal parameters. Electron microscopy studies indicate these changes are not due to altered vesicle number or distribution in RCAN1ox cells but reduced vesicle release may be cause by decreased vesicle and dense core size in RCAN1ox cells. Thus, our results indicate that RCAN1 may negatively affects vesicle recycling and quantal release kinetics via the inhibition of calcineurin activity

Epidemiology of Traumatic Posterior Hip Instability in the National Football League

BACKGROUND There is a paucity of literature regarding injury incidence, mechanism, and return to play in National Football League (NFL) players who have sustained traumatic posterior hip instability. PURPOSE To describe the incidence of traumatic posterior hip instability and the rate of return to play in NFL players across 18 seasons. STUDY DESIGN Descriptive epidemiology study. METHODS We retrospectively assessed all traumatic posterior hip dislocations/subluxations that occurred during football-related activities in the NFL seasons from 2000 through 2017. Player demographics and injury data (injury mechanism, season of injury, treatment, days missed, and return to play time) were collected from all 32 NFL teams prospectively through a leaguewide electronic health record system. Descriptive statistics are presented. RESULTS Across the 18 NFL seasons, 16 posterior hip instability injuries in 14 players were reported, with a maximum incidence of 4 (25%) in 2013. Posterior hip instability was predominantly sustained by offensive players (64.3%), with tight ends being the most affected (31.3%). Half of the injuries occurred during the regular season, 43.8% in the preseason, and 6.2% in the offseason. Of all injuries, 37.5% were noncontact, while 56.3% involved contact (direct or indirect), and 6.2% were of unknown mechanism. Among noncontact injuries, 66.7% occurred during cutting and change of direction while sprinting. The time of return to full participation was documented for 11 of the 16 reported injuries (68.8%); among them, the mean time loss was 136.7 ± 83.8 days-143.3 ± 99.6 days if the player underwent surgery (n = 4) and 116.7 ± 76.2 days missed by players without surgery (n = 6)-the treatment modality was unknown in 1 player. CONCLUSION Although the incidence of traumatic posterior hip instability during the study period was low, all injured athletes missed time from football activities and competitions. Injuries that required surgery led to more missed time than those that did not. Ongoing research to understand risk factors and mechanisms of this injury, in conjunction with improvements to prevention and rehabilitation protocols, is necessary to ensure the safety of professional American football players

Social technologies for online learning: theoretical and contextual issues

Three exemplars are presented of social technologies deployed in educational contexts: wikis; a photo-sharing environment; and a social bookmarking tool. Students were found to engage with the technologies selectively, sometimes rejecting them, in the light of their prior conceptions of education. Some students (a minority in all the studies) were unsympathetic to the educational philosophy underpinning the technology’s adoption. The paper demonstrates, through an examination of in-context use, the importance of socio-cultural factors in relation to education, and the non-deterministic nature of educational technology. The academic study of technology has increasingly called into question the deterministic views which are so pervasive in popular discourse and among policy makers. Instead, socio-cultural factors play a crucial role in shaping and defining technology and educational technology is no exception, as the examples in the paper show. The paper concludes by drawing out some implications of the examples for the use of social technologies in education

The effect of distance on reaction time in aiming movements

Target distance affects movement duration in aiming tasks but its effect on reaction time (RT) is poorly documented. RT is a function of both preparation and initiation. Experiment 1 pre-cued movement (allowing advanced preparation) and found no influence of distance on RT. Thus, target distance does not affect initiation time. Experiment 2 removed pre-cue information and found that preparing a movement of increased distance lengthens RT. Experiment 3 explored movements to targets of cued size at non-cued distances and found size altered peak speed and movement duration but RT was influenced by distance alone. Thus, amplitude influences preparation time (for reasons other than altered duration) but not initiation time. We hypothesise that the RT distance effect might be due to the increased number of possible trajectories associated with further targets: a hypothesis that can be tested in future experiments