Scientific Analysis and Conservation of Waterlogged Woods Excavated from Suyoeng-ri Site, Hwaseong, Korea

Five waterlogged wood artefacts were excavated from Suyeong-ri site in Hwaseong, South Korea. The aim of the present study was to identify the species and estimate the date of manufacture and the manufacturing method of these artefacts. The study also aimed to conserve the original shapes of waterlogged wood artefacts by using the vacuum freeze drying method. The two large waterlogged woods were identified as Ulmus spp. and Morus spp., whereas one of the three small waterlogged woods was identified as Abies spp. and the other two as hard pine. Radiocarbon dating using wiggle match dated the manufacturing of these wooden artefacts between BCE 8520-8490 or BCE 8470-8290 in the Neolithic age, and a similar period was also confirmed for seed excavated from a place close to the location where the waterlogged wood artefacts were excavated. The surface of waterlogged wood artefacts had several traces of manufacturing processes - traces of tearing and chopping - were observed. Based on these observations, it was confirmed that stone adz was used to make these wooden artefacts. Thereafter, the waterlogged wood samples were conserved by immersing them into PEG#4,000 of concentration in water from 10% to 40% at room temperature(15~25℃) and subjecting them to vacuum freeze drying. However, the internal moisture was not completely removed in some thick parts of waterlogged woods by applying the general schedule such as raising the shelf temperature as the surface temperature rises. Therefore, additional study is required using the schedule-method for vacuum freeze drying of large waterlogged wood.

Transitions in Charpy Energy and Splitting for X80 Pipe Steel

Using data obtained for a recent production 48-inch diameter X80 PSL2 pipe, the transition in fracture behavior between fully brittle and fully ductile modes was examined to assess any effects of transverse splits or delaminations. The additional surface area formed at the splits can increase and decrease the Charpy energy by expending energy to form more fracture surface and reduce constraint on the propagating crack as it extends through the unnotched Charpy ligament. Fitting of full Charpy energy transition curves for the tested material with standard hyperbolic tangent functions does not represent the behavior well. An important transition is noted in the behavior between splitting that initiates at the initial notch tip and splitting that occurs further down in the ligament. Spitting across the notch tip increases Charpy energy by releasing constraint on crack initiation behavior at the machined notch and occurs at temperatures just above the lower shelf temperature where brittle fracture dominates. The splitting behavior can also be correlated to effects on fracture toughness in the same orientation for CTOD specimens in the base material and for correlated effects on CTOD behavior in the weld heat affected zone when the crack advance is in the through thickness direction.

Diagnosing the variability in temperature and velocity in the Middle Atlantic Bight

Observations of hydrographic and dynamical properties on the Middle Atlantic Bight shelf document strong variability at time scales spanning events that last a few days to century long trends. This thesis studies individual processes which impact shelf temperature and velocity structure, and quantifies the mean velocity conditions at the shelf break. Chapter 2 uses model output to study the dynamics that lead to the breakdown of summertime thermal stratification, and how the processes which reduce stratification vary from year to year. In summer, the atmosphere heats the surface of the ocean, leading to strong thermal stratification with warm water overlying cool water. During fall, strong storm events with downwelling-favorable winds are found to be the primary process by which stratification is reduced. The timing of these events and the associated destratification varies from year to year. In Chapter 3, the velocity structure of the New Jersey shelf break is examine, with a focus on the Shelfbreak Jet. Using 25 years of velocity measurements, mean velocity sections of the Shelfbreak Jet are created in both Eulerian and stream coordinate frameworks. The jet exhibits strong seasonal variability, with maximum velocities observed in spring and minimum velocities in summer. Evidence is found that Warm Core Rings, originating from the Gulf Stream and passing through the Slope Sea adjacent to the New Jersey shelf, tend to shift the Shelfbreak Jet onshore of its mean position or entirely shutdown the Shelfbreak Jet’s flow. At interannual timescales, variability in the Shelfbreak Jet velocity is correlated with the temperature on the New Jersey Shelf, with temperature lagging by about 2 months. Chapter 4 focuses on the impact of Warm Core Rings on the velocity and temperature structure on the New Jersey shelf. Warm Core Rings that have higher azimuthal velocities and whose cores approach closer to the shelf are found to exert greater influence on the shelf’s along-shelf velocities, with the fastest and closest rings reversing the direction of flow at the shelf break. Warm Core Rings are also observed to exert long-lasting impacts on the shelf temperature, with faster rings cooling the shelf and slower rings warming the shelf. Seasonal changes in thermal stratification strongly affect how rings alter the shelf temperature. Rings in summer tend to cool the shelf, and rings throughout the rest of the year generally warm the shelf.

Impact of cultivation strategy, freeze-drying process, and storage conditions on survival, membrane integrity, and inactivation kinetics of Bifidobacterium longum

Bifidobacterium longum, one of the main microorganisms in the human gut, is used as an adjunct to lactic acid starter cultures or sold as a probiotic product. Therefore, Bifidobacterium longum cell suspensions get freeze-dried with protective additives to prevent activity losses. To date, investigations covering growth and inactivation kinetics of Bifidobacterium longum during the whole process (cultivation, drying, and storage) have been lacking. In this study, the effect of cultivation conditions and shelf temperature as well as the influence of protectants (maltodextrin, glucitol, trehalose) at various concentrations on cell survival during freeze-drying was assessed. Drying was followed by a storage at + 4 °C and + 20 °C for 70 days to evaluate inactivation kinetics. The impact of the different factors was assessed by measuring surival rate and residual moisture content at various points of time over the whole process. In parallel cell membrane integrity and glass transition were determined to reveal inactivation effects. Cultivation strategy had a strong influence on survival with a huge potential for process improvement. A pH of 6.0 at the growth optimum of the strain provides better conditions regarding cell survival after drying than free acidification (non-regulated pH conditions). During the drying step, membrane leakage due to the removal of water is the main reason for the inactivation in this process step. In this study, the highest survival of 49% was obtained with cells dried at + 35 °C shelf temperature with an addition of maltodextrin (75% bacterial dry matter, w/w). The results show that Bifidobacterium longum cells are mostly inactivated during drying, whereas storage conditions at + 4 °C with an addition of 75% BDM maltodextrin relative to bacterial dry mass prevent cell loss completely.