Inlet stability and case histories, Part II

Inlets which require frequent channel dredging due to gradual shoaling, exhibit migration, or shoal up during storms, are in general unstable and pose a problem to the engineer. This problem of inlet stability is a complex one, because of the rather large number of variables that go into defining stability. The reference here is to inlets on sandy coasts only, because the absence of sand or similar sedimentary material the problem does not arise. Shell is also found in varying proportions with sand. Some of this is. new, whereas in some areas it is ancient reworked material whose size distribution is close to that of the sand with which it is associated. (PDF has 24 pages.

Part I. Hydraulics of tidal inlets: simple analytic models for the engineer

Inlets are common coastal features around the world. Essentially an inlet connects a lagoon, a bay or an estuary to the ocean (or sea), and the flow through the inlet channel is primarily induced by the tidal rise and fall of water level in the ocean. When speaking of the hydraulics of an inlet, one is interested mainly in determining the flow through the inlet and the tidal variation in the bay, given the following: (1) Inlet geometry (2) Bay geometry (3) Bottom sediment characteristics in the inlet (4) Fresh water inflow into the bay (and out through the inlet) (5) Ocean tide characteristics A combination of all these factors can produce a rather complex situation. (PDF contains 34 pages.

Algorithms for generation of path-methods in object-oriented databases

A path-method is a mechanism in object-oriented databases (OODBs) to retrieve or to update information relevant to one class that is not stored with that class but with some other class. A path-method is a method which traverses from one class through a chain of connections between classes to access information at another class. However, it is a difficult task for a user to write path-methods, because it might require comprehensive knowledge of many classes of the conceptual schema, while a typical user has often incomplete or even inconsistent knowledge of the schema. This dissertation proposes an approach to the generation of path-methods in an OODB to solve this problem. We have developed the Path-Method Generator (P MG) system, which generates path-methods according to a naive user\u27s requests. PMG is based on access weights which reflect the relative frequency of the connections and precomputed access relevance between every pair of classes of the OODB computed from access weights of the connections. We present specific rules for access weight assignment, efficient algorithms to compute access relevance in a single OODB, and a variety of traversal algorithms based on access weights and precomputed access relevance. Experiments with a university environment OODB and a sample of path-methods identify some of these algorithms as very successful in generating most of the desired path-methods. Thus, the PMG system is an efficient tool for aiding the user with the difficult task of querying and updating a large OODB. The path-method generation in an interoperable multi object-oriented database (IM-OODB) is even more difficult than for a single OODB, since a user has to be familiar with several OODBs. We use a hierarchical approach for deriving efficient online algorithms for the computation of access relevance in an IM-OODB, based on precomputed access relevance for each autonomous OODB. In an IM-OODB the access relevance is used as guide in generating path-methods between the classes of different OODBs

Sediment storage at tidal inlets

Accumulation of sediment around tidal inlets has become a matter of renewed interest mainly for three reasons. The first of these is the need to estimate the shoal volumes, particularly in the ebb shoal, as a potential source of sediment for beach nourishment. The second reason is the need to assess the role of the inlet in influencing the rate of erosion of downdrift shoreline, as a result of interruption or deflection of the littoral drift. Finally, an evaluation of inlet sediment accumulation is essential to account for the long term sedimentary budget of shorelines interrupted by inlets

aGAL ANTIGEN AND RUTINOSE GLYCOSIDES AS MODEL COMPOUNDS FOR THE DESIGN OF CLASSICAL AND CONFORMATIONAL GLYCOMIMETICS

αGal or Galili epitope (αGal(1→3)βGal(1→4)GlcNAc) is a natural trisaccharide associated with cell-surface glycoproteins of certain mammalian and non-mammalian cells. The saccharide is not expressed by humans and anti-αGal antibodies account for ~1% of the total circulating antibodies in sera as a result of our constant exposition to the antigen from food and intestinal flora. Our interest in αGal relies on its involvement in a variety of pathologies including red meat allergy, hyperacute xenotransplant rejection, and parasitic and bacterial infections. In particular, we have an interest in developing structurally simple glycomimetics for engaging in high-affinity binding αGal-recognizing receptors such as the human anti-αGal IgG antibody and the Clostridium difficile toxins TcdA and TcdB in order to develop αGal based vaccine adjuvants and novel anti-infective therapies respectively. This communication presents our progress towards the synthesis of fluorinated αGal analogues as glycomimetics for their further applications to these goals. Apart from the role of carbohydrates in immune response, energy storage and as structural building blocks they are also involved in various other biological activities and many processes including cell-cell communication, immune response, fertilization, protein recycling, infection, among many others. The success of protein-carbohydrate interactions is conditioned to the fulfillment of conformational requirements imposed by the recognition site in the protein over the, inherently flexible, carbohydrate ligand. Hence, the study of the conformational preferences of saccharides is fundamental for the understanding of protein-carbohydrate interactions. In the second half of this thesis, we describe the results of the conformational study of rutinose (αRha(1→6)βGlcOR) glycosides. In particular, we centered our study on how the nature of the aglycone substituent can modulate the conformational equilibria around the interglycosidic linkage. Given the inherent flexibility of the (1→6) linkage, the hydrophobic nature of the rhamnose moiety, and the simplicity of the NMR spectra, rutinose constitutes a convenient model saccharide for performing these studies. The spectroscopic evidence gathered suggest the existence of an effect that could be used in the rational design of conformational mimetics of bioactive carbohydrates

Management of Renal Failure and Ascites in Patients with Cirrhosis

Ascites and renal dysfunction in cirrhosis occur when the liver disease is decompensated and signify the presence of advanced liver failure. However, the precipitating causes should be looked for and treated. Although liver transplantation is the treatment of choice in patients with advanced liver failure, mild to moderate ascites can be treated effectively with medical management. Similarly, renal failure in cirrhotics is reversible if the precipitating causes can be treated effectively and by use of combination of vasoconstrictors and albumin. Transjugular intrahepatic portosystemic shunts also offer an effective therapy for refractory ascites and HRS. Such treatments may offer effective bridge to liver transplantation, by improving short and medium term survivals. Here, we shall discuss all the options available for the management of these complications of cirrhosis

Laboratory experiments on cohesive soil bed fluidization by water waves

Part I. Relationships between the rate of bed fluidization and the rate of wave energy dissipation, by Jingzhi Feng and Ashish J. Mehta and Part II. In-situ rheometry for determining the dynamic response of bed, by David J.A. Williams and P. Rhodri Williams. A series of preliminary laboratory flume experiments were carried out to examine the time-dependent behavior of a cohesive soil bed subjected to progressive, monochromatic waves. The bed was an aqueous, 50/50 (by weight) mixture of a kaolinite and an attapulgite placed in a plexiglass trench. The nominal bed thickness was 16 cm with density ranging from 1170 to 1380 kg/m 3, and water above was 16 to 20 cm deep. Waves of design height ranging from 2 to 8 cm and a nominal frequency of 1 Hz were run for durations up to 2970 min. Part I of this report describes experiments meant to examine the rate at which the bed became fluidized, and its relation to the rate of wave energy dissipation. Part II gives results on in-situ rheometry used to track the associated changes in bed rigidity. Temporal and spatial changes of the effective stress were measured during the course of wave action, and from these changes the bed fluidization rate was calculated. A wave-mud interaction model developed in a companion study was employed to calculate the rate of wave energy dissipation. The dependence of the rate of fluidization on the rate of energy dissipation was then explored. Fluidization, which seemingly proceeded down from the bed surface, occurred as a result of the loss of structural integrity of the soil matrix through a buildup of the excess pore pressure and the associated loss of effective stress. The rate of fluidization was typically greater at the beginning of wave action and apparently approached zero with time. This trend coincided with the approach of the rate of energy dissipation to a constant value. In general it was also observed that, for a given wave frequency, the larger the wave height the faster the rate of fluidization and thicker the fluid mud layer formed. On the other hand, increasing the time of bed consolidation prior to wave action decreased the fluidization rate due to greater bed rigidity. Upon cessation of wave action structural recovery followed. Dynamic rigidity was measured by specially designed, in situ shearometers placed in the bed at appropriate elevations to determine the time-dependence of the storage and loss moduli, G' and G", of the viscoelastic clay mixture under 1 Hz waves. As the inter-particle bonds of the space-filling, bed material matrix weakened, the shear propagation velocity decreased measurably. Consequently, G' decreased and G" increased as a transition from dynamically more elastic to more viscous response occurred. These preliminary experiments have demonstrated the validity of the particular rheometric technique used, and the critical need for synchronous, in-situ measurements of pore pressures and moduli characterizing bed rheology in studies on mud fluidization. This study was supported by WES contract DACW39-90-K-0010. (This document contains 151 pages.

Fine sediment erodibility in Lake Okeechobee, Florida

The critical need to predict the turbidity in water due to fine-grained sediment suspension under wave action over mud deposits for sedimentation and erosion studies, as well as sorbed contaminant transport, is well known. Since fall velocities of fine sediment particles are very small, they can be easily transported by hydrodynamic flows such as waves and currents. The presence of these particles in the water column affects accoustic transmission, heat absorption and depth of the eutrophic zone (Luettich et al., 1989). Because these sediments also have a strong affinity for sorbing nutrients and toxic chemicals, sediments which have been deposited on the bottom may function as a source of contaminants to the water column if they are disturbed by eroding forces resulting, for instance, from wave action. An outstanding example of a water body for these problems is Lake Okeechobee, the largest shallow lake in Florida. This lake shows typical signs of artificial eutrophication mainly due to increased phosphorus loading associated with the surrounding region. Resuspension of sediment at the bottom of Lake Okeechobee composed of fine-grained material has been examined. A sediment transport model was used to simulate likely trends in the evolution of the vertical suspended sediment concentration profile resulting from wave action, and the corresponding eroded bed depth was calculated through mass balance. Requisite information on characteristic parameters and relationships related to fine sediment erodibility were derived from field sampling of bottom sediment in the lake, and through laboratory experiments using this sediment and lake water. (161pp.

Some considerations on coastal processes relevant to sea level rise

The effects of potential sea level rise on the shoreline and shore environment have been briefly examined by considering the interactions between sea level rise and relevant coastal processes. These interactions have been reviewed beginning with a discussion of the need to reanalyze previous estimates of eustatic sea level rise and compaction effects in water level measurement. This is followed by considerations on sea level effects on coastal and estuarine tidal ranges, storm surge and water level response, and interaction with natural and constructed shoreline features. The desirability to reevaluate the well known Bruun Rule for estimating shoreline recession has been noted. The mechanics of ground and surface water intrusion with reference to sea level rise are then reviewed. This is followed by sedimentary processes in the estuaries including wetland response. Finally comments are included on some probable effects of sea level rise on coastal ecosystems. These interactions are complex and lead to shoreline evolution (under a sea level rise) which is highly site-specific. Models which determine shoreline change on the basis of inundation of terrestrial topography without considering relevant coastal processes are likely to lead to erroneous shoreline scenarios, particularly where the shoreline is composed of erodible sedimentary material. With some exceptions, present day knowledge of shoreline response to hydrodynamic forcing is inadequate for long-term quantitative predictions. A series of interrelated basic and applied research issues must be addressed in the coming decades to determine shoreline response to sea level change with an acceptable degree of confidence. (PDF contains 189 pages.