On the electromagnetic force on a polarizable body

The force on a macroscopic polarizable body in an inhomogenous electromagnetic field is calculated for three simple exactly solvable situations. Comparing different approaches we pinpoint possible pitfalls and resolve recent confusion about the force density in ferrofluids.Comment: 8 pages, 3 figures, submitted to Am. J. Phy

Role of Li_2B_(12)H_(12) for the Formation and Decomposition of LiBH_4

By in situ X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy, the role of Li_2B_(12)H_(12) for the sorption of LiBH_4 is analyzed. We demonstrate that Li_2B_(12)H_(12) and an amorphous Li_2B_(10)H_(10) phase are formed by the reaction of LiBH_4 with diborane (B_2H_6) at 200 °C. Based on our present results, we propose that the Li -2B - (12)H_(12) formation in the desorption of LiBH_4 can be explained as a result of reaction of diborane and LiBH_4. This reaction of the borohydride with diborane may also be observed for other borohydrides, where B_(12)H_(12) phases are found during decomposition

Meridional circulation in the tropical North Atlantic

A transatlantic CTD/ADCP section nominally located at 11°N was carried out in March 1989. In this paper relative geostrophic velocities are computed from these data via the thermal wind balance, with reference level choices based primarly on water mass distributions. A brief overview of the meridional circulation of the upper waters resulting from these analysis techniques is presented. Schematic circulation patterns of the NADW and AAW are also presented. In both the western and eastern basins these waters are characterized by cyclonic recirculation gyres. A paricularly notable result of the deep western basin analysis is the negligible net flow of middle NADW. Although the horizontal circulation patterns described in this study agree well with results from many previous studies, the meridional overturning cell and net heat flux are considerably lower, while the net freshwater flux is slightly higher than previous estimates. These discrepancies may be attbuted to: (1) differences in methodologies, (2) the increased resolution of this section, and (3) temporal (including decadal, synoptic, and most importantly, seasonal) variability.Funding was provided by the National Science Foundation through Grant Nos. OCE-8716314 and OCE-9101636 and the Office of Naval Research through the American Society for Engineering Education

A data assimilative marine ecosystem model of the central equatorial Pacific: Numerical twin experiments

A five-component, data assimilative marine ecosystem model is developed for the high-nutrient low-chlorophyll region of the central equatorial Pacific (0N, 140W). Identical twin experiments, in which model-generated synthetic \u27data\u27 are assimilated into the model, are employed to determine the feasibility of improving simulation skill by assimilating in situ cruise data (plankton, nutrients and primary production) and remotely-sensed ocean color data. Simple data assimilative schemes such as data insertion or nudging may be insufficient for lower trophic level marine ecosystem models, since they require long time-series of daily to weekly plankton and nutrient data as well as adequate knowledge of the governing ecosystem parameters. In contrast, the variational adjoint technique, which minimizes model-data misfits by optimizing tunable ecosystem parameters, holds much promise for assimilating biological data into marine ecosystem models. Using sampling strategies typical of those employed during the U.S. Joint Global Flux Study (JGOFS) equatorial Pacific process study and the remotely-sensed ocean color data available from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), parameters that characterize processes such as growth, grazing, mortality, and recycling can be estimated. Simulation skill is improved even if synthetic data associated with 40% random noise are assimilated; however, the presence of biases of 10-20% proves to be more detrimental to the assimilation results. Although increasing the length of the assimilated time series improves simulation skill if random errors are present in the data, simulation skill may deteriorate as more biased data are assimilated. As biological data sets, including in situ, satellite and acoustic sources, continue to grow, data assimilative biological-physical models will play an increasingly crucial role in large interdisciplinary oceanographic observational programs

Hypoxia forecasts as a tool for Chesapeake Bay fisheries

The Estuarine Hypoxia component of the U.S. Integrated Ocean Observing System Coastal and Ocean Modeling Testbed (COMT) is evaluating existing hydrodynamic and water quality models used, or likely to be used, for operations in the Chesapeake Bay. As a proof-of-concept, an implementation of the Regional Ocean Modeling System in the Chesapeake Bay (ChesROMS) is linked to a simple respiration model for hypoxia (Hypoxia_SRM). The modeling system is presently being used to produce real-time nowcasts and short-term (3-day) hypoxia forecasts for the Chesapeake Bay, which are currently available on the Virginia Institute of Marine Science (VIMS) website. Workshops with citizen stakeholders have explored potential applications of the estuarine hypoxia nowcast/forecast products in support of recreational and commercial fishing. Interest in this product is high, particularly by recreational fishermen and charter boat captains, since reduced catch per unit effort in the Bay is clearly associated with regions where dissolved oxygen is low. This presentation reviews the insights gained at these stakeholder workshops, including how these stakeholders might apply these products to improve the efficiency and success of their fishing activities and what forecast presentation formats are most useful. Future work involves transporting the hypoxia forecast tool to the Mid-Atlantic Regional Association Coastal Ocean Observing System (MARACOOS), and eventually linking the product with NOAA’s Chesapeake Bay Operational Forecasting System (CBOFS)

Well-posedness of boundary layer equations for time-dependent flow of non-Newtonian fluids

We consider the flow of an upper convected Maxwell fluid in the limit of high Weissenberg and Reynolds number. In this limit, the no-slip condition cannot be imposed on the solutions. We derive equations for the resulting boundary layer and prove the well-posedness of these equations. A transformation to Lagrangian coordinates is crucial in the argument