Growth, calcification and photosynthesis in the coccolithophorid chrysotila carterae

The mass culture of microalgae for the commercial production of a) low value commodities such as biofuel and food and b) high value products such as polyunsaturated fatty acids, carotenoids, and nano-scaffolds is becoming increasingly attractive. Coccolithophorid algae have been investigated as potential candidates for both low and high value products. This thesis provides data on the specific nutrient and growth requirements in the coccolithophorid, Chrysotila carterae (previously Pleurochrysis carterae). Via the use of oxygen evolution techniques and PAM fluorometry, it is shown that C. carterae is just as susceptible to photoinhibition as some other microalgae with photoinhibition occurring at around 1100-1500 μmol photon m2 s-1. C. carterae also has the ability to recover from short periods of acidification, with recovery from pH 5 when there was no organic carbon assimilation to pH 9 after 20 minutes, Carbon assimilation increased from almost 0, to 3.01 pg CORG cell-1 h-1 . This microalga has a fundamental requirement for selenium, with specific growth rates falling from a μmax of 0.6 d-1, with selenium to 0.1 d-1 in selenium-limited culture. Selenium is also required for coccolith production. In Se-limited culture coccolith production was almost reduced by half, from 70 x105 coccoliths mL-1 to 3.8 x 105 coccoliths mL-1. Diurnal studies of organic and inorganic carbon assimilation showed that C. carterae CCMP647 synthesises coccoliths during the day, and then extrudes them onto the cell surface during the last hours of the dark cycle. Investigations into the effect of various nitrogen sources indicated that with unregulated pH, nitrate achieved the greatest cell density and stable growth: The maximum cell densities reached were nitrate (66.61 x 104 ± 8.2 x 103 cells mL-1) > urea (34.0 x 104 ± 6.2 x 103 cells mL-1) = ammonium (36.08 x 104 ± 4.2 x 103 cells mL-1). Nitrate had the greatest effect on the culture medium ΔpH, (NO3- (0.134 ± 0.003) > urea (0.111 ± 0.003) > NH4+ (0.043 ± 0.001) and urea increased the growth rate of C. carterae by 150 % from 0.17 0.002 d-1 on NO3- to 0.44 ± 0.001 d-1 on urea. However, coccolith production increased with NO3- (73.81± 3.51 ng CaCO3 cell-1> NH4+ 55.18 ± 0.61 ng CaCO3 cell-1 > urea at 12.88 1.62 ng CaCO3 cell-1. Organic carbon (CORG) assimilation using NO3- far exceeded that on NH4+ and urea (CORG assimilated with NO3- = 7 x103 pg CORG cell-1 h-1 vs Urea at 6 x103 pg CORG cell-1 h-1 and NH4+ 5 x103 pg CORG cell-1 h-1 . Inorganic carbon assimilation (CINORG) was also elevated with NO3- producing 3 x103 pg CINORG cell-1 h-1 vs urea at 2 x103 pg CINORG cell-1 h-1 and NH4+ at 2 x103 pg CINORG cell-1 h-1. Thus, nitrate provides long term, stable growth with the highest cell overall cell density under unregulated pH. Under elevated medium pH, urea and ammonium had the highest rate of carbon assimilation far in excess of NO3- for both CORG (Urea 44921.73 ± 2191.08 pg CORG cell-1 h-1 > NH4+ 22006.22 ± 640.39 pg CORG cell-1 h-1 > NO3- 773.59 ± 14.8 pg CORG cell-1 h-1) and CINORG, Urea 773.59 ± 14.8 pg CINORG cell-1 h-1 NO3- 569.44 ± 31.4 pg CINORG cell-1 h-1. Although carbon assimilation rates were elevated under urea and NH4+ at higher pH levels, NO3- at pH 8 had the highest Calcifaction to photosynthsdis ratio (C:P) ratio of 0.158, while closely followed by urea at pH 9 (C:P = 0.150). With enhanced carbon assimilation at pH levels exceeding the pKa of CO2 in the medium pH indicated that this species must be using HCO3- as a carbon source, as cell growth and calcification were elevated at pH levels at which there is a greatly reduced level of CO2 in the medium which is typically in air equilibrated water approximately 10 μmol L-1

How much do U.S. corporations know (and care) about bilateral investmenttreaties? Some hints from new survey evidence

New evidence shows that top U.S. corporations are surprisingly unfamiliar with -- and/or lack confidence in -- bilateral investment treaties that are designed to benefit their investments in other countries. To understand whether or not such treaties "work," it is necessary to find out how and why they do, or do not, form part of firms' investment decision-making

Making Sense of Learning in VR

The goal of this qualitative study was to answer the question: How do educators make sense of learning in virtual reality? This study utilized multimedia learning theory and cognitive load theory to explore how educators understand virtual reality in education. Pre- and postinterviews as well as a VR experience were conducted with 13 educators from higher education institutions. The data was transcribed, coded, and developed into themes that created the data chapters. The findings from this research study revealed that educators identified two themes for extended reality in education. First, the design of virtual reality experiences for students was an important element the educators discussed when creating the types of experiences. Second, the educators discussed the importance of presence in virtual reality for students to feel immersed in the virtual spaces which eliminated distractions. The educators discussed how emotions increase presence which creates deeper connections to the content. The educator’s discussions of design and presence called attention to the importance of extended reality in education. The results of this study give insight into the understanding the educators have for using extended reality in the classroom. This study focuses attention on how educators discussed design and presence as it relates to student’s learning in extended reality. The shift that the educators in this dissertation study had in teaching and research after their first introduction to extended reality was also discussed in this dissertation. Their outlook for the future of extended reality in education is full of promise

Deadly Drones? Why FAA Regulations Miss the Mark on Drone Safety

A rapidly growing commercial drone industry has prompted the introduction of numerous regulations governing American airspace. Congress has tasked the Federal Aviation Administration (FAA) with “developing plans for the use of the navigable airspace to ensure the safety of aircraft and the efficient use” of American skies. While well-intended, the FAA has departed from Congressional will by imposing an excessive regulatory regime that threatens to stifle drone technology and innovation. In fact, many FAA regulations fail to address the very problem they seek to fix, namely the safety of our airspace. The unfortunate result is that myriad scientific and pragmatic applications of cuttingedge drone technology have been stalled or thwarted entirely inside the United States, forcing innovation efforts to move abroad. FAA regulations must be dramatically scaled back and reformed to reflect the countless benefits and comparatively minimal risks associated with drone technology. The current rules cover innocuous use cases, are too restrictive even when addressing cases where regulation makes sense, and fail to permit efficient technical approaches to reaching regulatory objectives. The nonsensical rule requiring any person over the age of thirteen to register her recreational “Christmas toy” drone is an excessive response to public safety concerns, especially as far more prominent threats to public safety, even guns, have no similar registration requirements. More pragmatically, the line-of-sight regulations that prevent pilots from using vision-enhancing devices such as first-person view technology needlessly restrict the commercial applications of drones, including long-distance package delivery. Finally, while the FAA and other regulatory bodies currently control the spaces in which drones can be legally flown, drone manufacturers are far better equipped to accomplish this goal themselves by incorporating geofencing technology (which directly prevents drones from flying into restricted areas like airports). In sum, American laws and regulations governing the flight of commercial drones are overly restrictive, unnecessarily stifle valuable innovation, and must be revised to ensure that the true potential of drone technology can be realized

Sulphur-isotope compositions of pig tissues from a controlled feeding study

Sulphur-isotope determinations are becoming increasingly useful for palaeodietary reconstruction, but knowledge of isotopic discrimination between diet and various tissues remains inadequate. In this study, we explore the sensitivity of δ34Stissue values to changes in δ34Sdiet values, sulphur isotopic discrimination between diet and consumer, and the potential impact of terrestrial vs. marine protein consumption on these discrimination offsets. We present new δ34S values of bone collagen, muscle, liver, hair, milk and faeces from ten mature sows, ten piglets and fifteen adolescent pigs from a controlled feeding study. The δ34Stissue values were found to co-vary with the δ34Sdiet values, the δ34Stissue – δ34Sdiet isotopic offsets (Δ34Stissue-diet) are small but consistent, and dietary protein source does not systematically alter the Δ34Stissue-diet isotopic discrimination. The outcomes of this study are of particular relevance to questions that are difficult to resolve using carbon and nitrogen stable isotopes alone, and will also be useful in regions where terrestrial, freshwater, and marine resources could have all potentially contributed to human diet