Assessment of the temporal variability of hydro-physical parameters in the HIROMB model

Comparison between long-term measurements carried out during POLRODEX'97 experiment and results from HIROMB is presented. Analysis based on graphical presentation and statistical measure (reliability index) shows that model reproduces current direction fairly well, while current magnitude is underestimated. Time variability of salinity, temperature and water level variation reproduced by the model indicates discrepancies from observations

Vistula River Mouth - History and Recent Problems

The history of the Vistula River mouth exhibits the development of the hydrographic system of Żuławy lowlands caused by natural phenomena and human intervention. During its history, the Vistula River has changed the location of its direct connection with the Baltic Sea three times; the first (the Gdańsk Vistula) and the second (the Brave Vistula) river outlets were created by nature, while the recent one (the Vistula Cross-Cut) was man-made. Each of these locations faced similar problems, i.e. sedimentation in the river mouth leading to flooding problem in the surrounding region, intensified in winter by ice jams. The recent outlet, made as a short cut of the river reach in 1895, requires permanent maintenance as to diminish a flood risk for the surrounding areas due to sedimentation. Since the opening, its maintenance is carried out by elongation of jetties on both sides of the river mouth, and occasional dredging of sand. Presently, further elongation of jetties is proposed, however new methods to keep the river mouth should be considered

Role of groins in river regulation

Ostrogi są konstrukcjami budowanymi poprzecznie do kierunku przepływu, które stosowane są przy regulacji rzek nizinnych. Zasadniczym celem ich budowy jest ochrona brzegów oraz zwężenie koryta rzecznego, co prowadzi do zwiększenia głębokości w korycie głównym, a w konsekwencji do przedłużenia okresu nawigacyjnego. Analizując wpływ ostróg na hydrodynamikę oraz ruch rumowiska w rzece, należy rozważyć na dwa przypadki: (1) ostrogi niezatopione, kiedy korona konstrukcji znajduje się ponad zwierciadłem wody oraz (2) ostrogi zatopione. W warunkach ostróg niezatopionych obserwuje się zwężenie koryta głównego rzeki, któremu towarzyszy zwiększenie prędkości wody, a w konsekwencji jego pogłębianie. W obszarach między ostrogami ruch wody jest znacznie wolniejszy, co powoduje odkładanie się tam niesionego rumowiska. W przypadku ostróg zatopionych ruch wody odbywa się całym korytem rzeki, jednak zwiększenie oporów ruchu w obszarze ostróg powoduje zmniejszenie przepustowości rzek, co może mieć istotne znaczenie w warunkach powodziowych. W każdym z przypadków ruchowi wody towarzyszy mniej lub bardziej intensywny ruch rumowiska. Stan wiedzy w zakresie mechanizmów wzajemnego oddziaływania rzeki z ostrogami jest nadal niewystarczający, by można było prognozować zmiany denne w korycie rzeki z dużą dokładnością. Ostrogi choć budowane od bardzo dawna, nie zawsze doprowadziły do osiągnięcia zamierzonego celu; często przysparzają dodatkowych trudności (np. wymycia, odkładanie rumowiska). W ostatnim okresie można zauważyć powrót do badań laboratoryjnych; rzadziej wykonywane są pomiary terenowe. Badania na modelach hydraulicznych pozwalają lepiej zrozumieć mechanizmy rządzące ruchem wody i rumowiska w warunkach rzeki regulowanej ostrogami. Dostarczają one również danych dla potrzeb weryfikacji modeli matematycznych, które pozwolą na rozwiązywanie problemów występujących w naturze.Groins are structures often used in lowland river regulation. The main goal of their construction is protection of coast and narrowing of the river channel to increase water depth and prolongation of the navigation period. Analysing the influence of groins on hydrodynamics and sediment transport in rivers it is necessary to consider two cases: (1) non-submerged groins, when the groins top is above the water surface, and (2) submerged groins. In case of nonsubmerged groins the narrowing of the main channel is observed; it is accompanied by increase of water velocity leading to further deepening of the main channel. In the groin fields water flows much slower, supporting sediment deposition. In case of submerged groins water flows in the whole channel, but increase of resistance due to groins causes reduction of its capacity, being an important aspect in flooding periods. Water flow is always accompanied by sediment transport, but the existing knowledge in this respect is still insufficient to allow prediction of morphological changes with high accuracy. Groins are constructed since few centuries but not always the expected results are reached; it is not unique that they create new problems (deepening, sediment deposition). Recently laboratory experiments are carried out to solve simplified problems; less common field measurements are carried out. Tests on hydraulic models allow better understanding the mechanisms governing water and sediment movement in rivers trained by groins. They also support us with data necessary to verify mathematical models. The on-going developments in numerical modelling result in better representation of changeable hydro- and morpho-dynamics; however the results are still far from being able to reproduce all phenomena observed in nature

Oligomannose-rich membranes of dying intestinal epithelial cells promote host colonization by adherent-invasive E. coli

A novel mechanism is revealed by which clinical isolates of adherent-invasive Escherichia coli (AIEC) penetrate into the epithelial cell layer, replicate, and establish biofilms in Crohn's disease. AIEC uses the FimH fimbrial adhesin to bind to oligomannose glycans on the surface of host cells. Oligomannose glycans exposed on early apoptotic cells are the preferred binding targets of AIEC, so apoptotic cells serve as potential entry points for bacteria into the epithelial cell layer. Thereafter, the bacteria propagate laterally in the epithelial intercellular spaces. We demonstrate oligomannosylation at two distinct sites of a glycoprotein receptor for AIEC, carcinoembryonic antigen related cell adhesion molecule 6 (CEACAM6 or CD66c), on human intestinal epithelia. After bacterial binding, FimH interacts with CEACAM6, which then clusters. The presence of the highest-affinity epitope for FimH, oligomannose-5, on CEACAM6 is demonstrated using LC-MS/MS. As mannose-dependent infections are abundant, this mechanism might also be used by other adherent-invasive pathogens

Experimental investigation of the decay from a ship’s propeller

In the present study, an experimental investigation of the decay of the maximum velocity and its turbulent characteristics behind a ship propeller, in “bollard pull” condition (zero speed of advance), is reported. Velocity measurements were performed in laboratory by use of a Laser Doppler Anemometry (LDA) measurement system. Earlier researchers described that the maximum axial velocity is constant at the initial stage of a ship’s propeller jet (Fuehrer and Römisch, 1977; Blaauw and van de Kaa, 1978; Berger et al., 1981; Verhey, 1983) as reported in a pure water jet (Albertson et al., 1950; Lee et al., 2002; Dai, 2005), but a number of researchers disagreed with the constant velocity assumption. The present study found that the maximum axial velocity decays in the zone of flow establishment and the zone of established flow with different rates. The investigation provides an insight into the decays of both the maximum velocity and the maximum turbulent fluctuation in axial, tangential and radial components and the decay of the maximum turbulent kinetic energy. Empirical equations are proposed to allow coastal engineers to estimate the jet characteristics from a ship’s propeller.<br/