Random sampling of an AC source: A tool to teach probabilistic observations

An undergraduate level experiment is described to demonstrate the role of probabilistic observations in physics. A capacitor and a DC voltmeter are used to randomly sample an AC voltage source. The resulting probability distribution is analyzed to extract information about the AC source. Different characteristic probability distributions arising from various AC waveforms are calculated and experimentally measured. The reconstruction of the AC waveform is demonstrated from the measured probability distribution under certain restricted circumstances. The results are also compared with a simulated data sample. We propose this as a pedagogical tool to teach probabilistic measurements and their manipulations.Comment: Revtex4 file, 10 pages with 8 figure

Inter- and intra-specific carbon and nitrogen assimilation by dinoflagellate and diatom species

Phytoplankton are key components in primary production and their growth is determined mainly by the availability of nitrogen-nutrients in the ocean. The paradigm that phytoplankton prefer ammonium over nitrate when both substrates are present has been tested using 15N-labelled tracers on cultured diatoms and dinoflagellates isolated from two widespread geographical areas – the Baltic Sea and the Arabian Sea. We found contrary to the paradigm that both taxa preferred nitrate over ammonium and a significant within-species variation in N assimilation. Carbon uptake rates in the same experiments were estimated using 13C-labelled tracer

Role of Cyclonic Eddy in enhancing Primary and New production in the Bay of Bengal

Highlights: • First direct measurements of new production in an eddy in the Bay of Bengal. • 100% increase in nutrient concentrations is seen due to the eddy. • Eddy enhanced new and primary production in the otherwise less productive Bay of Bengal. Abstract: Eddies can be important in sustaining primary production in the tropical oceans, but their role for nutrient cycling is poorly understood in the under-sampled northern Indian Ocean. To assess the role of cyclonic eddies in enhancing primary production, measurements of primary production were carried out at four stations in the northern Bay of Bengal during the early winter 2007, around a cyclonic eddy close to 17.8 °N, 87.5 °E. Shallowing of the thermocline and halocline by 10 m was observed within the eddy compared to the surroundings; mixed layer depth was also reduced within the eddy. The highest surface productivity (2.71 μM C d− 1) and chlorophyll a (0.18 μg L− 1) were found within the eddy, while the lowest, at its outer edge. Further, the eddy supplied nutrients to the surface layers, shallowing the subsurface chlorophyll maximum as well. Integrated production in the euphotic top layers was more than twice within eddy compared to its outer edge, confirming the role of cyclonic eddies in enhancing the primary production in the otherwise less productive Bay of Bengal. Given new nitrogen input via vertical mixing, river discharge or aerosol deposition, the additional primary production due to this new nutrient input and its contribution to the total production (f-ratio, fraction of exportable organic matter) increased significantly from 0.4 to 0.7, and thus the Bay of Bengal can potentially transfer a high fraction of its total production to the deep, assisted by eddies. We suggest possible improvements in experiments for future studies, and the potential for assessing the role of eddies in biogeochemistry

Design Evaluation and Temperature Rise Test of Flameproof Induction Motor

The ignition of flammable gases, vapours or dust in presence of oxygen contained in the surrounding atmosphere may lead to explosion. Flameproof three phase induction motors are the most common and frequently used in the process industries such as oil refineries, oil rigs, petrochemicals, fertilizers, etc. The design of flameproof motor is such that it allows and sustain explosion within the enclosure caused by ignition of hazardous gases without transmitting it to the external flammable atmosphere. The enclosure is mechanically strong enough to withstand the explosion pressure developed inside it. To prevent an explosion due to hot spot on the surface of the motor, flameproof induction motors are subjected to heat run test to determine the maximum surface temperature and temperature class with respect to the ignition temperature of the surrounding flammable gas atmosphere. This paper highlights the design features of flameproof motors and their surface temperature classification for different sizes

Isotopic fractionation in open systems: application to organic matter decomposition in ocean and land

Stable isotopic evolution of a reservoir from which material is continuously removed with isotopic fractionation is generally described by the Rayleigh equa tion, widely used in geochemical research to describe two-component systems. It has been extended to the case of multi-component sources as well. Here we pre sent an equation describing isotopic fractionation in open systems, wherefrom material is not only removed with isotopic fractionation, but fresh material of a dif ferent isotopic composition is added from an external source, at a given rate, and some examples where this equation is applicable