This thesis investigates breastfeeding and weaning patterns in an Iron Age (7th – 4th century BCE) sample of subadults (n=12) and adults (n=9) buried at the sites of Botromagno, Parco San Stefano and Padreterno in southern Italy. Stable isotope analysis of both human tooth dentine and bone collagen for each subadult, and tooth dentine for adults, was undertaken to create early-life feeding histories. The dentine serial sections were used to determine the onset and completion of weaning for each individual, as well as distinguish general trends in early feeding practices at these Iron Age sites. Results indicate that the average onset of weaning in subadults occurred at 8 ± 3.4 months and weaning was completed by 4 years of age at the latest for all individuals; however, the patterns of breastfeeding and weaning were variable in this sample. This study also explores variation in early childhood diet between survivors and non-survivors (i.e., < 4 years of age). Non-survivors were weaned more rapidly than survivors – possibly contributing to their earlier death – and some non-survivors demonstrated elevated δ15N values that may have been a result of physiological stress. It is, however, difficult to distinguish signals of breastfeeding versus stress in young children who were still likely consuming breast milk. Finally, differences in isotope data between dentine serial sampling and bulk-bone sampling of rib and femoral collagen from the same individuals were investigated. The results show that the combined use of dentine and bone data contribute to more nuanced interpretations of weaning. Further, rib samples represent diet closer to the time of death than femoral samples, as faster bone turnover rate in ribs allow for the incorporation of more recent dietary changes. / Thesis / Master of Arts (MA)

Hydroclimate evolution in the northern Caribbean region has been investigated by several studies, but they offer contradicting results and none of them cover a full glacial-interglacial transition to examine orbital climate forcing. Here we present refined U-Th dating and oxygen isotope (δ18O) data from a stalagmite named Katún collected from Rio Secreto cave in the Yucatan Peninsula that discontinuously spans the time interval between 198 thousand years (kyr) before present (BP) to 320 kyr BP. Stalagmite δ18O is interpreted to reflect precipitation amount variability as established by previous studies from this cave. On orbital timescales, we identified marine isotope stages (MIS) 7, 8, and 9 in the Katún stalagmite δ18O record. The average stalagmite δ18O value during MIS 7 and 9 interglacial intervals is ~-4.5‰, suggesting wetter conditions than the glacial MIS 8 with an average δ18O value of ~-3‰. The stalagmite δ18O record exhibits higher amplitude δ18O and thus precipitation variability, and an increase in the frequency and intensity of drought events during the drier glacial interval. The record suggests a strong link between atmospheric greenhouse gases, CO2 andCH4, and precipitation variability in the Caribbean, which affects hydroclimate via changes in tropical Atlantic sea surface and air temperature. We propose that changes in North Atlantic high latitude climate are connected to regional hydroclimate, as evidenced by concurrent Caribbean precipitation and atmospheric methane variability, similar to Greenland D-O events. The broader implication of this study is that human activities may alter the fundamental relationship between Caribbean hydroclimate and greenhouse gases, which have likely sustained tropical wetlands and modulated methane production for millennia.

An accurate understanding of global patterns through geologic time depends upon multi-scale analyses of spatial variation within narrow temporal intervals. This work investigates geochemical and paleoecological patterns in modern brachiopod faunas which may serve as analogues for ancient brachiopod assemblages. The paleoclimatic utility of delta18O in the phosphatic phase of lingulid brachiopod shells requires valve secretion in equilibrium with seawater, an assumption tested (and rejected) when analyzed at scales ranging from millimeters to kilometers. By contrast, biological encrustation of the brachiopod fauna of the Southeast Brazilian Bight shows strong sensitivity to microenvironmental conditions such as host identity, shape, and size, and may prove useful for studies of ancient planktonic productivity. Comparison of encrustation patterns on naturally occurring brachiopods and bivalves collected from the same sites, and occupying the same size range, demonstrates that the results of encrustation studies on modern bivalves cannot be directly applied to ancient brachiopods. However, careful comparisons may reveal patterns of epibiont selectivity and the impact of changes in the relative abundance of host shells through geologic time. Finally, neither epibiont abundance nor diversity increase with host age as indicated by dated brachiopod shells from the past 1000 years. These results suggest that the temporal resolution of epibiont assemblages matches their spatial resolution, and strengthen evidence for competition among encrusting taxa. By documenting geochemical and paleoecological variation within shells and across a continental shelf, this work demonstrates the importance of understanding spatial variation across all scales before interpreting trends through time. / Ph. D.

Multi-robot systems have recently witnessed a swell in interest in the past few years because of their various applications such as agricultural autonomy, medical robotics, industrial and commercial automation and, search and rescue. In this thesis, we particularly investigate the behavior of multi-robot systems with respect to stable topology control in asymmetric interaction settings. From theoretical perspective, we first classify stable topologies, and identify the conditions under which we can determine whether a topology is stable or not. Then, we design a limited fields-of-view (FOV) controller for robots that use sensors like cameras for coordination which induce asymmetric robot to robot interactions. Finally, we conduct a rigorous theoretical analysis to qualitatively determine which interactions are suitable for stable directed topology control of multi-robot systems with asymmetric interactions. In this regard, we solve an optimal topology selection problem to determine the topology with the best interactions based on a suitable metric that represents the quality of interaction. Further, we solve this optimal problem distributively and validate the distributed optimization formulation with extensive simulations.  For experimental purposes, we developed a portable multi-robot testbed which enables us to conduct multi-robot topology control experiments in both indoor and outdoor settings and validate our theoretical findings. Therefore, the contribution of this thesis is two fold: i) We provide rigorous theoretical analysis of  stable coordination of multi-robot systems with directed graphs, demonstrating the graph structures that induce stability for a broad class of coordination objectives; ii) We develop a testbed that enables validating multi-robot topology control in both indoor and outdoor settings. / Doctor of Philosophy / In this thesis, we address the problem of collaborative tasks in a multi-robot system where we investigate how interactions within members of the multi-robot system can induce instability. We conduct rigorous theoretical analysis and identify when the system will be unstable and hence classify interactions that will lead to stable multi-robot coordination. Our theoretical analysis tries to emulate realistic interactions in a multi-robot system such as limited interactions (blind spots) that exist when on-board cameras are used to detect and track other robots in the vicinity. So we study how these limited interactions induce instability in the multi-robot system. To verify our theoretical analysis experimentally,  we developed a portable multi-robot testbed that enables us to test our theory on stable coordination of multi-robot system with a team of Unmanned Aerial Vehicles (UAVs) in both indoor and outdoor settings. With this feature of the testbed we are able to investigate the difference in the multi-robot system behavior when tested in controlled indoor environments versus an uncontrolled outdoor environment. Ultimately, the motivation behind this thesis is to emulate realistic conditions for multi-robot cooperation and investigate suitable conditions for them to work in a stable and safe manner. Therefore, our contribution is twofold ; i) We provide rigorous theoretical analysis that enables stable coordination of multi-robot systems with limited interactions induced by sensor capabilities such as cameras; ii) We developed a testbed that enables testing of our theoretical contribution with a team of real robots in realistic environmental conditions.

Concern over rising atmospheric CO2 due to fossil fuel combustion has intensified research into carbon-neutral energy and fuel production. Therefore, bioenergy production has expanded during the last decade, increasing demand for forest-based bioenergy feedstocks. Millions of acres of privately and industrially owned pine plantations exist across the southeastern US, representing a vast area of land that could be utilized to produce bioenergy without significant land-use change or diversion of agricultural resources from food production. Furthermore, loblolly pine (Pinus taeda L.) plantations offer the unique opportunity to utilize space between rows of planted trees to grow an herbaceous bioenergy crop, such as switchgrass (Panicum virgatum L.). This novel forest management regime has the potential to provide positive environmental and economic services, but hinges in part on impacts to soil carbon (C) and nitrogen (N) cycling, availability of belowground resources, and potential negative impacts of competition between pine and switchgrass on plant productivity. Three specific objectives were addressed in this study: 1) compare different bioenergy management regimes in regards to temporal dynamics of N cycling and availability following forest establishment (see Chapter 2); 2) determine the impact of loblolly pine and switchgrass intercropping on microbial N cycling processes (see Chapter 3); and 3) evaluate chemical and physical mechanisms of soil organic matter (SOM) stabilization and test their sensitivity to pine-switchgrass intercropping (see Chapter 4). The study site was located in the Lower Coastal Plain physiographic province in Lenoir County, North Carolina, USA (35-12'59'' N; 077-26'13'' W). Soils were mapped as Pantego (fine‐loamy, siliceous, semiactive, thermic Umbric Paleaquults) or Rains (fine‐loamy, siliceous, semiactive, thermic Typic Paleaquults) soil series, both of which are very poorly drained. However, previous site management in the late 1960’s and early 1970’s included installation of ditches to lower the water table and reduce saturation at the soil surface. Additionally, bedding of soil in rows was used to raise root systems of planted loblolly pine seedlings above the water table, increase soil aeration, and reduce competition. Space between bedded rows of pine trees was referred to as the interbed. Results from Chapter 2 showed that switchgrass significantly reduced interbed soil NH4 + and NO3 - concentrations by 39% and 60%, respectively, over the course of the timeframe (30 months) of this study. Surprisingly, in beds of the pine-switchgrass treatment significant increases in NO3 - concentration were measured from July - December 2011. From Chapter 3, gross N mineralization rates ranged from 0.18 - 4.7 µg N g -1 soil d-1 , while gross nitrification rates ranged from 0.02 - 0.47 µg N g-1 soil d-1 . At the 0-5 cm depth in switchgrass interbeds, gross N mineralization was reduced from April to November potentially reflecting microbial C limitations due to reduced soil C concentrations. At the 0-5 cm depth in beds of the pine-switchgrass treatment, gross N mineralization rates were elevated by 1.29 µg N iii g -1 soil d-1 in November and 1.02 µg N g-1 soil d-1 in February on average corresponding to a 305% and 193% increase, respectively. From Chapter 4, total C content in beds and interbeds ranged from 15 to 88 Mg C ha-1 and was reduced by 27% in beds of the pine-switchgrass treatment. Average C concentration for aggregate fractions was significantly lower in beds of the pine-switchgrass treatment at 0-5, 15- 30, and 30-45 cm depths, amounting to ~23%, ~28%, and ~34% reduction, respectively. Values of δ 13C for the >2000 µm aggregate size fraction at the 0-5 cm depth were diluted, corresponding to estimates of 13 - 25% of the >2000 µm C pool comprised of new pine-derived C. For SOM fractionated by density, elevated C concentrations were found in the occluded light fractions in both beds and interbeds of the pine-switchgrass treatment. Enriched δ13C in occluded light fractions led to estimates of 2.5 - 12.5% of this C fraction comprised of new switchgrass-derived C. In the free light fraction, new pine-derived C accounted for 15% and 9% of C at the 5-15 and 15-30 cm depth, respectively. Three overarching conclusions were generated from my research: 1) switchgrass grown between loblolly pine trees effectively utilized excess soil NH4 + and NO3 - when N availability was high following harvesting of a mature plantation proceeded by establishment of a second rotation of loblolly pine (see Chapter 2); 2) gross N mineralization rates were reduced under switchgrass during the growing season when soil C availability was low, but were elevated under switchgrass and adjacent loblolly pines when switchgrass was dormant and C availability was likely higher (see Chapter 3); and 3) SOM stabilized by physical or chemical mechanisms responded differently to pine-switchgrass intercropping, with losses in aggregate-stabilized C and gains in occluded, mineral-stabilized C. Furthermore, losses of aggregate C was associated with a significant reduction in total soil C in beds of the pine-switchgrass treatment. Results from 13C mass balance suggested incorporation of switchgrass-derived C into occluded light fractions of beds and interbeds. Finally, incorporation of new pine-derived C into the >2000 µm aggregate size fraction and free light fraction indicate pine inputs of particulate organic matter into these SOM fractions in beds of the pine-switchgrass treatment (see Chapter 4). I hypothesize that loblolly pines have increased root growth in beds in response to competition with switchgrass for N in the interbed, thereby alleviating seasonal microbial C limitations and stimulating microbial N cycling processes and increasing plant-available N. Overall, this research suggests that soil C and N cycling in pine plantations is altered by intercropping of pine and switchgrass. Through a mechanistic understanding of how C and N are cycled in forests and the impact of various forest management regimes on soil C and N cycling, effective management strategies can be implemented to utilize forests for intensive biomass production while limiting loss of soil C and N, and in some cases even enhancing soil C and N retention. Future research initiatives should seek to unravel the complex belowground interactions between roots of different plant species and soil microbial communities competing for limiting resources. Understanding how these interactions drive soil C storage, N cycling and availability, and forest productivity will ultimately improve resource utilization in these managed ecosystems as well as our basic understanding of how natural and managed ecosystems function. / Ph. D.

Nitrogen is the most frequently limiting nutrient in southern pine plantations.  Previous studies found that only 10 to 25% of applied urea fertilizer N is taken up by trees.  Enhanced efficiency fertilizers could increase tree uptake efficiency by controlling the release of N and/or stabilize N.  Three enhanced efficiency fertilizers were selected as a representation of fertilizers that could be used in forestry: 1) NBPT treated urea (NBPT urea), 2) polymer coated urea (PC urea), and 3) monoammonium phosphate coated NBPT treated urea (MC NBPT urea). Urea, MC NBPT urea, and NBPT urea fertilizer treatments showed an extractable NH4+ spike 14 days after fertilization while the polymer coated urea showed a spike in NH4+ 49 days after fertilization. Total ecosystem recovery of fertilizer in each treatment was; MC NBPT urea, 51.29 g N; NBPT urea, 48.87 g N; urea, 45.09 g N; and PC urea, 31.30 g N which represents 78.7%, 74.7%, 72.1%, and 47.6% respectively of the total N applied.  For the MC NBPT urea, NBPT urea, and PC urea treatments the largest sinks for N were the forest floor and mineral soil.  The largest sink for fertilizer applied N in the urea treatment was in the tree.  The 2011 foliage cohort was the largest sinks for fertilizer N recovered by the tree.  N volatilization was around 20% for all fertilizer treatments except polymer coated fertilizer, which was 1.1%.  Urea preformed the same as the soluble enhanced efficiency fertilizers and better than the PC urea fertilizer.  The results emphasize the importance of climatic conditions on fertilizer release and effectiveness. / Master of Science

Yes / Objectives: This study presents isotopic information for incremental dentine collagen and bone bulk collagen from individuals from the Canary Islands (Tenerife and Gran Canaria) to explore dietary differences during childhood life. Materials and Methods: Eight individuals have been studied, which comprises 122 δ15N and δ13C incremental dentine measurements and eight bulk bone collagen analyses. A baseline of potentially consumed food sources has been developed for comparative purposes. A FRUITS model of probable contributions of each food source towards the diet of each individual has been developed. All samples but one belongs to the later period of indigenous occupation of the archipelago. Results: The dentine collagen data are presented in correlated δ13C and δ15N plots per individual, showing the isotopic changes throughout time. δ15N values for each individual tend to be variable whereas δ13C data are generally more stable with a range of +9.1 to +14‰ for δ15N and –17.4 to –20.8‰ for δ13C. Conclusion: The isotopic analysis allows for the reconstruction of 8 dietary profiles, which allow us to estimate the different dietary protein sources. The FRUITS model shows different percentages of the primary food sources for each individual. Where both δ13C and δ15N are elevated, this could be indicative of a higher marine contribution to the diet. There appear to be two main dietary profiles identifiable in the dataset and these may be related to changes in status or place of residence. Short-term variations in δ13C and δ15N and opposing co-variance of isotopic values can be indicative of nutritional stress, although metabolic changes during growth are also considered. / PhD grant from Universidad de La Laguna—Fundación La Caixa (“Contratos Predoctorales para la formación de doctores ULL-2015”), MINECO (Ministerio de Economía y Competitividad) project “Guanches y europeos en Las Cañadas del Teide, Ocupación, Producción y Comunicación” (HAR2015-68323-P), “Erasmus+ Scholarship” given by the University of La Laguna, ERC Starting Grant project IsoCAN (grant 851733, European Comission) and the projects RTI2018-101923-J-I00 and RYC2019-028346 (Ministerio de Ciencia e Innovación)

No / Four recently discovered frozen child mummies from two of the highest peaks in the south central Andes now yield tantalizing evidence of the preparatory stages leading to Inca ritual killing as represented by the unique capacocha rite. Our interdisciplinary study examined hair from the mummies to obtain detailed genetic and diachronic isotopic information. This approach has allowed us to reconstruct aspects of individual identity and diet, make inferences concerning social background, and gain insight on the hitherto unknown processes by which victims were selected, elevated in social status, prepared for a high-altitude pilgrimage, and killed. Such direct information amplifies, yet also partly contrasts with, Spanish historical accounts.

No / Bone collagen carbon and nitrogen stable isotope ratios were obtained from three La Tène period inhumation cemeteries in the Czech Republic (Kutná Hora-Karlov, Radovesice I and Radovesice II) and 16 Hallstatt period inhumations in northern Austria. Results indicate that during the La Tène period in Bohemia, overall diet was based on animal protein and plant foods following the C3 photosynthetic pathway, although ¿13C values for two individuals from Kutná Hora-Karlov indicate at least some contribution from C4 plant foods, most likely millet. At Kutná Hora-Karlov, more positive ¿15N values for male individuals buried with items of iron weaponry indicate the existence of a differential dietary system within the male population based on individual ¿warrior¿ status. A comparison with data from a number of Hallstatt period inhumations in northern Austria and a previously published study of a Hallstatt period site in Slovenia [Murray, M.L., Schoeninger, M.J., 1988. Diet, status, and complex social structure in Iron Age Central Europe: Some contributions from bone chemistry. In: Gibson, D.B., Geselowitz, M.N. (Eds.), Tribe and Polity in Late Prehistoric Europe: Demography, Production and Exchange in the Evolution of Complex Social Systems. Plenum Press, New York, pp. 155¿176] enables an examination of the spread of millet as a major dietary component. This data will be of use to studies of diet in prehistoric Europe and provides evidence for dietary divisions relating to social stratification during the La Tène B¿C, a period often seen as less complex than the preceding Hallstatt period.

No / This paper introduces stable light isotope analysis as a method of investigating the homogeneity and heterogeneity of communities inhabiting areas of the East Alpine region during the Late Bronze Age and Early Iron Age. It will present a short review on the use of carbon and nitrogen light isotope values, and discuss how they provide insight into the diet and health of past populations. A pilot study of results obtained from the bone collagen of 14 individuals, from 6 sites located in modern-day Slovenia and northern Croatia, will also be presented. This small dataset provides an example of the values that will be collected throughout the ENTRANS Project, and how they can be used as a tool to investigate the lives of people in the past. / HERA joint research programme