Temporary Concrete Traffic Barriers (TCTBs) are essential in order to protect the traveling public and highway construction crews from accidents due to driver misfortune or negligence. In order for TCTBs to be installed, however, they must be successfully crash tested. Barrier height and drainage open space are key characteristics that influence this crash test rating. This is because an increase in height will insure that a vehicle will not over-top the barrier and a decrease in drainage open space will result in greater barrier mass, which will in turn resist larger impact forces. The factors that increase the crash worthiness of a barrier, however, lead to poor hydraulic performance. This then becomes a concern if barriers are placed in areas where they may adversely impact the local floodplain elevation. The objective of this research is the development of a hydraulic rating curve that describes the relationship between upstream energy head and the flow rate passing the barrier. To accomplish this objective, a three parameter model with three unknown coefficient terms was utilized. The model was then fit to experimentally obtained data, and a rating curve was developed. In addition, the effects of downstream submergence and clogging of the drainage opening, with respect to the rating curve, was also analyzed. Finally, a method for using this information in the hydraulic modeling software HEC-RAS was developed. / text

This work develops some simple models to study risky corporate debt using first passage-time approach. Analytical valuation expression derived from different models as functions of firm’s values and the short-term interest rate with time-dependent parameters governing the dynamics of the firm values and interest rate. We develop some numerical approximation of the analytical valuation, which is given implicitly through Voltera integral equation related to the density of the first-passage- time that a firm reaches some specified default barrier. For some appropriate default barrier arising from financial considerations we obtain a closed-form solution, which is more flexible for numerical calculation.

Currently, there is a growing body of research characterizing the blood-brain barrier (BBB) under normal physiological conditions; however, little is known about BBB regulation under pathophysiological conditions, such as inflammatory pain. This dissertation elucidates peripheral inflammatory pain effects on the BBB both functionally in terms of permeability and structurally via tight junction (TJ) protein expression and regulation.Inflammation was produced by subcutaneous injection of formalin, lambda-carrageenan, or complete Freund's adjuvant (CFA) into the right hind paw of rats. In situ perfusion and Western blot analyses were performed to assess BBB integrity after inflammatory insult. In situ brain perfusion determined that peripheral inflammation significantly increased the uptake of a membrane impermeant marker, sucrose into the cerebral hemispheres in all inflammatory models. Subsequently, a 0-168h time course study of lambda-carrageenan-induced inflammatory pain elicited a biphasic increase in BBB permeability of sucrose with the first phase occurring from 1-6h and the second phase occuring at 48h. Lambda-carrageenan-induced inflammatory pain also increased brain uptake of a commonly used analgesic, codeine at the same time-points. This is the first known observation that peripheral inflammation results in greater analgesic drug uptake to the brain. This uptake also correlated with its antinociceptive profile over a 168h time course. This suggests the presence of inflammatory pain may be an important consideration in therapeutic drug dosing, potential adverse effects and/or neurotoxicity.Western blot analyses showed altered TJ protein expression during peripheral inflammation. Occludin significantly decreased in the lambda-carrageenan- and CFA-treated groups. ZO-1 expression was significantly increased in all pain models. Claudin-1 protein expression was present at the BBB and remained unchanged during inflammation. Actin expression was significantly increased in the lambda-carrageenan- and CFA-treated groups. Over a 72h time period with lambda-carrageenan-induced inflammatory pain, altered TJ protein expression of occludin and ZO-1 correlated with permeability changes in BBB function. This is the first report of peripheral inflammation inducing alterations in TJs and increasing permeability of the BBB. This dissertation demonstrates that changes in the structure of TJs leading to alterations in the BBB may have important clinical ramifications concerning central nervous system homeostasis and therapeutic drug delivery.

No description available.

<p>Microtubules often adopt non-centrosomal arrays in differentiated tissues, where they are important for providing structure to the cell and maintaining polarity. Although the formation and organization of centrosomal arrays has been well-characterized, little is known about how microtubules form non-centrosomal arrays.</p><p>In the mouse epidermis, centrosomes in differentiated cells lose their microtubule-anchoring ability through the loss of proteins from the centrosome. Instead, microtubules are organized around the cell cortex. The cell-cell adhesion protein desmoplakin is required for this organization. Our model is that desmoplakin recruits microtubule-anchoring proteins like ninein to the desmosome, where they subsequently recruit and organize microtubules.</p><p>To test this model, we confirmed that the microtubule-binding proteins Lis1, Ndel1, and CLIP170 are recruited by desmoplakin to the cell cortex. Furthermore, by creating an epidermis-specific conditional Lis1 knockout mouse, I found that Lis1 is required for cortical microtubule organization. Surprisingly, however, Lis1 is also required for desmosome stability. This work reveals essential desmosome-associated components that control cortical microtubule organization and unexpected roles for centrosomal proteins in epidermal function.</p><p>Although Lis1 is required for microtubule organization, it is not sufficient. I created a culture-based system to determine what other factors may be required for cortical organization for microtubules. My work reveals that stabilization of the microtubules is sufficient to induce their cortical organization. Functionally, cortical microtubules are important for increasing the mechanical integrity of cell sheets by engaging adherens junctions. In turn, tight junction activity is increased. Therefore, I propose that cortical microtubules in the epidermis are important in forming a robust barrier by cooperatively strengthening each cell-cell junction.</p><p>To determine whether desmosomes play similar roles in simple epithelia as stratified epithelia, I examined intestinal epithelial-specific conditional desmoplakin conditional knockout mice. Unexpectedly, I found that desmoplakin is not required for cell-cell adhesion and tissue integrity in the small intestine. Furthermore, it does not organize intermediate filaments. Desmoplakin is required, however, for proper microvillus architecture. </p><p>Overall, my studies highlight novel tissue-specific roles for desmosomes, in particular desmoplakin, in organizing and integrating different cytoskeletal networks. How desmoplakin's function is regulated in each tissue will be a new interesting area of research.</p> / Dissertation

Pulmonary endothelial cell (EC) barrier dysfunction and recovery is critical to the pathophysiology of acute respiratory distress syndrome. Cytoskeletal and subsequent cell membrane dynamics play a key mechanistic role in determination of EC barrier integrity. Here, we characterizAQe the actin related protein 2/3 (Arp 2/3) complex, a regulator of peripheral branched actin polymerization, in human pulmonary EC barrier function through studies of transendothelial electrical resistance (TER), intercellular gap formation, peripheral cytoskeletal structures and lamellipodia. Compared to control, Arp 2/3 inhibition with the small molecule inhibitor CK-666 results in a reduction of baseline barrier function (1,241 +/- 53 vs 988 +/- 64 ohm; p < 0.01), S1P-induced barrier enhancement and delayed recovery of barrier function after thrombin (143 +/- 14 vs 93 +/- 6 min; p < 0.01). Functional changes of Arp 2/3 inhibition on barrier integrity are associated temporally with increased intercellular gap area at baseline (0.456 +/- 0.02 vs 0.299 +/- 0.02; p < 0.05) and thirty minutes after thrombin (0.885 +/- 0.03 vs 0.754 +/- 0.03; p < 0.05). Immunofluorescent microscopy reveals reduced lamellipodia formation after S1P and during thrombin recovery in Arp 2/3 inhibited cells. Individual lamellipodia demonstrate reduced depth following Arp 2/3 inhibition vs vehicle at baseline (1.83 +/- 0.41 vs 2.55 +/- 0.46 mm; p < 0.05) and thirty minutes after S1P treatment (1.53 +/- 0.37 vs 2.09 +/- 0.36 mm; p < 0.05). These results establish a critical role for Arp 2/3 activity in determination of pulmonary endothelial barrier function and recovery through formation of EC lamellipodia and closure of intercellular gaps.

Multiscale (analytical and computational) models have been developed based on a thermodynamic variational principle (TVP) to model sintering and eventual mudcracking in thermal barrier coatings (TBCs) made using the electron beam physical vapour deposition (EB-PVD) process. It is assumed that the sintering occurs by interfacial diffusion at local contacts between columns and driven by changes in interface free energy and elastic stored energy of the coating. The models link diffusional processes at the scale of contacting feathery columns with the macroscopic deformation and sintering response. In service, the columns can come into contact and sinter together. As sintering progresses there is a build up of strain energy in the system which reduces the driving force for sintering and leads to either complete or incomplete sintering of the TBC depending on the magnitude of effective modulus (E) of the coating. By seeding the coating with initial imperfections, different types of behaviour are observed depending on the value of E and the spacing between imperfections. For compliant coatings, the response is insensitive to the presence of imperfections and the coating fully sinters. At higher values of E, strain energy is released by the development of intercolumnar cracks in the coating, which can propagate to the interface with the TGO (thermally grown oxide), deflect into the interface and propagate, leading to spallation of regions of the coating and loss of thermal protection. It is observed that cracks develop at initial imperfections in the structure. The greater the spacing between imperfections the faster the development of cracks at these locations. If a TBC contains a distribution of imperfections there is progressive formation of cracks, with the average spacing decreasing with time, after an initial incubation period. The crack density eventually saturates to a constant value, which depends on the mechanical properties of the TBC. Initially, a crack spacing, CS, in the range 1.5H ≤ CS ≤ 3H has been predicted based on trapezoidal contact models. Here H is the thickness of the coating. Crack spacing predicted using this model is consistent in the lower range of experimentally observed crack spacing. However, axisymmetric contact models predict a crack spacing, CS, in the range 4H ≤ CS ≤ 8H, which is in good agreement with experimentally observed crack spacing range 3H ≤ CS ≤ 10H reported in the literature. Compared to the trapezoidal contact models, axisymmetric contact models more accurately predict the sintering response.

Species composition, temperature, soil nutrients, and leaf area index (LAI) were recorded across three encroaching Morella cerifera thicket edges and three free- standing shrubs on Hog Island, Virginia to characterize the effect of shrub thickets on the plant community and microclimate. Electron transport rate (ETR) was taken on shrub leaves to determine if microclimate benefits M. cerifera physiology. Species richness was lowest inside shrub thickets. Soil water content and LAI were higher in shrub thickets compared to grassland. Soil organic matter, N, and C were higher inside shrub thickets. Summer and fall maximum temperatures were more moderate in shrub thickets and at free-standing shrubs. Fall and winter minimum temperatures were higher inside shrub thickets. ETR was higher at the free-standing shrubs compared to the thicket edge. Morella cerifera impacts microclimate characteristics and species composition immediately upon encroachment. Improved shrub physiology was neither supported nor rejected by the research presented here.

M.Sc. / The KaNyaka barrier island system consists of the vegetated KaNyaka and Portuguese Islands, and various partially exposed sandbars. It is situated in south-easternmost Mozambique where it forms a barrier between Maputo Bay in the west and the Indian Ocean in the east. It forms part of the northern most limit of the Maputaland Group, which consists of Pliocene to Holocene sediments. The island system is an example of a compound barrier island since it comprises a stacked succession of several ancient shoreline marine and aeolian sedimentary rock units and sediments, along with various active sedimentary environments. This thesis describe the general geology of the island system, the petrography of the various rock and sedimentary units and provide information on provenance of sediment based on detrital zircon age populations. It also provides several new 14C age dates of shell fossils and calcified rhizoliths. KaNyaka Island consists of two high north-south trending dune cordons along its eastern and western shores, with a low-lying dune-covered area in between. The Western dune cordon consists of aeolian calcareous quartz arenite of the Ridjene Formation unconformably overlain by calcified aeolian dunes of the Alto Pocuane Formation in turn overlain by the unlithified red dunes of the Barreira Vermelha Formation. The core of the Eastern dune cordon consists of the calcareous quartz arenite of the Cabo Inhaca Formation comprised of stacked calcified aeolian dunes, the marine and tidal deposits of the Ponta Mazondue and Ponta Torres formations form the eastern and south-western flanks of the Eastern dune cordon. The formations are overlain by unlithified red to orange sands of the Changana Formation and partially lithified light grey to yellow sands of the Muamuluago Formation. The area between these two dune cordons is covered by low-lying aeolian dunes of the Alto Chumine Formation, ancient sandbar and beach deposits of the Chunhe Formation and both modern and paleo-intertidal flat deposits. Modern sedimentary environments include high-energy beaches, intertidal flats, sand spits, sandbars and aeolian dunes. The presence of aeolian deposits extending below the present sea-level, and marine deposits up to 3m above it, indicates that the KaNyaka barrier island system records a long history of sea-level change. 14C dating of marine and freshwater shell fossils and a rhizolith collected from several of the formations on the KaNyaka barrier island system assist in defining the history of the island with reference to sea-level fluctuations. Results from two freshwater shell fossils in the aeolian Alto Pocuane and Cabo Inhaca Formations indicate that they were deposited and subsequently calcified 47 000 and 30 000 years ago respectively, at times when the sea-level was 40 - 60 m lower than at present. The red sand of the Barreira Vermelha and Changana formation overlying these calcified dunes are suggested to have formed when climate was drier and sea-level even lower, during the Last Glacial Maximum (LGM) around 17 000 years ago. 14C ages on formations overlying the red sand deposits all postdate the Last Glacial Maximum and record sediment deposition of the past 7 000 years when the sea-level was either rather similar or somewhat higher than the present. Detrital zircon age populations, determined by laser ablation inductively coupled mass spectrometry (LA-ICP-MS), indicate that the majority of the sediment building the barrier island system was derived from the Grenvillian (~1100 Ma) and the Pan-African (~500 Ma) orogenic belts situated along the eastern side of Africa. Sediment was probably transported from exposed rock successions of these belts by large rivers like the Zambezi in the north and the Tugela in the south. The sediment was then dispersed along the coast by the south flowing Agulhas Current and northward directed long-shore current. Rivers feeding into Maputo Bay, like the Phongola, Umbeluzi and Incomati, draining the Kaapvaal Craton and Karoo Supergroup provided very little sediment to the barrier island system.

The mechanism of Holocene barrier formation aids in determining island geomorphologic responses to modifying climatic processes of the surrounding environment. The geometry and composition of local antecedent topography plays a role in barrier formation by providing an elevated base, nucleus for sedimentation and local sediment supply. Investigation of barriers' subsurface geology provides insight into island formation and evolution. High-resolution shallow seismic data acquired in the island's nearshore zone and interior canals, correlated with existing drillcore data, reveal that Cat Island, MS is situated over an Oxygen Isotope Stage 3 Phase 3 paleochannel located between two topographic high-grounds of the Pleistocene surface. Beach ridge strandplain sets on Cat Island provide additional evidence supporting the island's formation over a relict depocenter. A new, 4-stage model for Cat Island development and evolution incorporating the influence of pre-existing topographic high-grounds and abundant local sediment supply provided by a backfilling fluvial channel is presented here.