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The article presents methods of forward and backward analysis for real solutions of real quadratic equations. The methods aim to mathematically prove that specific algorithms deliver exact results in spite of all intermediate rounding errors. Applications include the Excess Related Person Indebtedness according to the U.S. corporate tax code, yield-to-maturity of one-year U.S. Treasury bills and calculation of acidity in chemistry.

Abstract: In February 2007, the U.S. Department of Energy, BP Exploration (Alaska), and the U.S. Geological Survey, collected open-hole pressure-response data, as well as gas and water sample collection, in a gas hydrate reservoir (the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well) using Schlumberger''s Modular Dynamics Formation Tester (MDT) wireline tool. Four such MDT tests, ranging from six to twelve hours duration, and including a series of flow, sampling, and shut-in periods of various durations, were conducted. Locations for the testing were selected based on NMR and other log data to assure sufficient isolation from reservoir boundaries and zones of excess free water. Test stages in which pressure was reduced sufficiently to mobilize free water in the formation (yet not cause gas hydrate dissociation) produced readily interpretable pressure build-up profiles. Build-ups following larger drawdowns consistently showed gas-hydrate dissociation and gas release (as confirmed by optical fluid analyzer data), as well as progressive dampening of reservoir pressure build-up during sequential tests at a given MDT test station. History matches of one multi-stage, 12-h test (the C2 test) were accomplished using five different reservoir simulators: CMG-STARS, HydrateResSim, MH21-HYDRES, STOMP-HYD, and TOUGH+HYDRATE. Simulations utilized detailed information collected across the reservoir either obtained or determined from geophysical well logs, including thickness (11.3m, 37 ft.), porosity (35%), hydrate saturation (65%), both mobile and immobile water saturations, intrinsic permeability (1000mD), pore water salinity (5ppt), and formation temperature (3.3–3.9°C). This paper will present the approach and preliminary results of the history-matching efforts, including estimates of initial formation permeability and analyses of the various unique features exhibited by the MDT results. [Copyright &y& Elsevier]

Plasma–particle interactions are explored through the introduction of single microdroplets into laser-induced plasmas. Both spectroscopic analysis and direct imaging of analyte atomic emission are used to provide insight into the various fundamental processes, namely desolvation, atomization, and atomic diffusion. By doping the 50 µm droplets with Lu, Mg or Ca, the analyte excitation temperature and the ion-to-neutral emission ratio are explored as a function of plasma residence time following breakdown. The data suggest a change in the local plasma conditions about the analyte atoms around 15–20 µs following breakdown, which may be interpreted as an overall transition from localized (i.e.perturbed) plasma conditions to the global (i.e.bulk) plasma conditions. A direct assessment of the hydrogen atomic diffusion coefficient following analyte desolvation reveals a value of 1.7 m2s−1in the first 250–500 ns. This value is in good overall agreement with a theoretical analysis and with an analytical treatment of a surface source of hydrogen atoms. In contrast, calcium emission is only observed beyond about 1 µs, with a diffusion coefficient at least an order of magnitude below the hydrogen value. The temporal H and Ca emission data suggest that water vaporizes first, leaving an ever increasing Ca analyte concentration until finally, with nearly all water desorbed, the Ca fraction is vaporized. Overall, the data support the conclusion that finite time-scales of heat and mass transfer play an important role in localized plasma perturbations in the vicinity of the analyte, which has important implications for the LIBS analyte signal. [ABSTRACT FROM AUTHOR]

Abstract: U.S. Environmental Protection Agency (EPA) Method 1623 is designed to detect and determine concentrations of Cryptosporidium oocysts and Giardia cysts in water through concentration, immuno-magnetic separation (IMS), and immuno-fluorescence assay with microscopic examination. A seasonal interference with the method was observed in some municipal source waters collected from reservoirs and as reported to Shaw Environmental, Inc. in the summers of 2005, 2006, and 2007. This interference, which was not confined to a single region of the nation, caused clumping of the IMS beads during the acid dissociation of the IMS procedure in Method 1623. This effect lowered method recoveries for both Cryptosporidium and Giardia; however, the effect was more pronounced for Giardia. A heat dissociation technique (Ware et al., (2003) J. Microbiol. Methods 55, 575–583) was shown to be a viable option for samples which demonstrate the clumping matrix effect and improved Giardia recoveries in partially clumped samples. The heat dissociation application holds promise for fully clumped samples and warrants further investigation. [Copyright &y& Elsevier]

A study has been made of the effects of phenylthiourea on the increases in respiration and ascorbic oxidase activity, and on the growth responses which occur in excised sections of tobacco pith when cultured on agar containing indoleacetic acid. At 5—15X104 M, phenylthiourea acts differentially. usually completely inhibiting ascorbic oxidase activity and the growth while permitting a large respiratory increase on auxin. The demonstration that some of the metabolic changes initiated by auxin are not obligatorily coupled to one another nor to the enlargement process may be useful in the study of the mechanism of action of auxin. [ABSTRACT FROM AUTHOR]

The article presents a study by David Walt and colleagues at the Tufts University wherein they developed a new high-throughput method for measuring single-molecule kinetics in which they trap individual enzymes in microchambers and monitor their substrate turnover in the U.S. The researchers separated a single enzyme in each microchamber and found that each enzyme showed distinct turnover kinetics. Furthermore, they also found that it took time for each enzyme-inhibitor complex to dissociate and for the enzyme to start turning over substrate molecules.